JP2001318263A - Optical branching/coupling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical branching/coupling device which does not generate malfunction in signal transmission, causing a harmful influence to speeding-up by producing dullness of a signal waveform due to mode dispersion of signal light. SOLUTION: The device is composed of a first laser diode 10a to a fourth laser diode 10d, an optical transmission part 12, and a first photodiode 14a to a fourth photodiode 14d. A spreading angle 2r1 in the lateral direction and a spreading angle 2r2 in the longitudinal direction of signal light which are emitted from respective laser diodes, an angle α in the lateral direction and an angle βin the longitudinal direction of respective photodiodes with respect to the light-emitting part of respective laser diodes, a refractive index of the optical transmission part 12, an NA(numerical aperture), a critical angle (θc) and length n are decided to satisfy Equation (1), where c is the speed of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical branching / coupling device, and more particularly to an optical branching / coupling device used for multi-communication using an optical fiber or the like.

[0002]

2. Description of the Related Art In recent years, with the development of very large scale integrated circuits (VLSI), circuit functions of circuit boards (daughter boards) used in data processing systems have been greatly increased.
Since the number of signal connections to each circuit board increases as the circuit functions of the circuit board increase, the data bus board (mother board) that connects each circuit board (daughter board) with a bus structure has a large number of connectors and connection lines. Have been adopted.

In this parallel architecture, the operation speed of the parallel bus has been improved by increasing the parallelism by increasing the number of connection lines and miniaturizing the connection lines, but the signal delay caused by the capacitance between the connection lines and the resistance of the connection lines has been measured. Therefore, the processing speed of the system may be limited by the operation speed of the parallel bus. Also, the problem of EMI (Electromagnetic Interference) due to the increase in the density of the parallel bus connection wiring is a great constraint on improving the processing speed of the system.

In order to solve such a problem and improve the operation speed of the parallel bus, the use of an optical connection technology in a system called an optical interconnection has been studied.
Various forms of optical interconnection technology have been proposed.

For example, Japanese Patent Application Laid-Open No. 4-134415 discloses a technique for transmitting data between circuit boards using a two-dimensional array device. The technology disclosed herein includes a lens array in which a plurality of lenses having a negative curvature are formed on the surface of a transparent substance having a higher refractive index than air, and a light emitted from the light source. And an optical system for entering from the side surface of the lens array.

However, in the data bus described in Japanese Patent Application Laid-Open No. 4-134415, there is a problem that the intensity of the output signal varies, and light incident from the side passes through the opposite side, resulting in low light efficiency. Furthermore, since it is necessary to dispose the optical input elements of the circuit board at the positions of a plurality of lenses having a negative curvature formed on the surface, there is no flexibility for disposing the circuit board, and the expandability is low. There are also problems.

To solve these problems, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 0-123350 proposes an optical coupling system used for a sheet-like optical data bus. Since this method diffuses and propagates signal light incident on a common signal path, a plurality of circuit boards having a light receiving / emitting section can be securely optically coupled by simple mounting, and precise optical No alignment is required. In addition, the number of circuit boards and the mounting position can be freely changed, and a highly expandable and highly flexible system can be constructed. In addition, since the transmission path is used, it has an environment resistance against dust and the like, and has an advantage that it is resistant to a temperature change and the like because no optical alignment is required.

[0008]

However, in the optical coupling system used for the optical data bus described in Japanese Patent Laid-Open No. Hei 10-123350, since light is diffused in all directions, a plurality of light beams having different propagation angles are used. Is present, and the signal waveform may be distorted due to the mode dispersion of the signal light, which may adversely affect the speeding up.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical branching / coupling device which does not cause a signal transmission failure even when a signal waveform is distorted due to mode dispersion of signal light.

[0010]

According to a first aspect of the present invention, there is provided an optical branching / coupling device for emitting at least one signal light having a predetermined divergence angle; An optical transmission medium that transmits the signal light having a predetermined spread angle emitted from the signal light emitting unit via the optical waveguide, and at least one signal light receiving unit that receives the signal light transmitted by the optical transmission medium; And the propagation time of the signal light propagating the longest propagation distance of the signal light propagating through the optical waveguide, and the propagation time of the signal light propagating the shortest propagation distance of the signal light propagating through the optical waveguide. The signal light emitting means, the optical transmission medium, and the signal light receiving means, and the signal light emitting means so that a signal propagation delay difference, which is a difference between the signal light and the signal light receiving means, is shorter than one cycle of the frequency of the signal light. Means and optical transmission It is characterized in that to determine the body material.

That is, according to the first aspect of the present invention, the signal light emitting means, the optical transmission medium, and the signal light receiving means are arranged so that the signal propagation delay difference is shorter than one cycle of the frequency of the signal light. And the material of the signal light emitting means and the optical transmission medium are determined due to mode dispersion.
It is possible to prevent an adverse effect on the increase in the propagation speed due to the rounding of the signal waveform (due to the difference in the propagation distance of the signal light).

For example, in the signal light emitting means and the light receiving part of the signal light receiving means which are arranged opposite to the opposite surface of the optical transmission medium, the signal light reaching the light receiving part from the light emitting part is as follows. There are two propagation patterns. (1) A first propagation pattern that directly reaches the light receiving unit from the light emitting unit. (2) A second propagation pattern that reflects at least once on at least one of the upper and lower surfaces of the optical transmission medium before reaching the light receiving unit from the light emitting unit and reaches the pattern light receiving unit. (3) A third propagation pattern that reaches the light receiving portion by being reflected at least once on at least one of the left and right side surfaces of the optical transmission medium before reaching the light receiving portion from the light emitting portion. (4) The light is reflected at least once on at least one of the upper surface and the lower surface of the optical transmission medium before reaching the light receiving portion from the light emitting portion, and is reflected at least once on at least one of the left and right side surfaces. The fourth propagation pattern that reaches the part.

In the first propagation pattern, the signal light emitted from the signal light emitting means propagates the shortest propagation distance connecting the light emitting portion and the light receiving portion with a straight line. Therefore, the signal light is propagated to the signal light receiving means at the earliest time. In other words, in the second to fourth propagation patterns, the signal light is reflected and propagated on any one of the upper surface, the lower surface, and the side surface of the optical transmission medium. Therefore, a difference in propagation time (propagation delay) due to a difference in propagation distance occurs.

Since the propagation distance increases as the number of reflections increases in the same type of optical transmission medium, the value obtained by subtracting the propagation time of the shortest distance from the propagation time of the propagation pattern having the largest number of reflections is obtained. As the signal propagation delay difference, shorter than one cycle of the frequency of the signal light,
The spread angle of the signal light emitted by the signal light emitting unit, the arrangement of the light receiving unit of the signal light receiving unit with respect to the light emitting unit,
By determining the length l, the refractive index n, and the critical angle θc of the optical transmission medium, it is possible to prevent adverse effects on high-speed signal propagation due to rounding of the signal waveform due to mode dispersion.

For example, when the signal light is propagated by the first propagation pattern and the second propagation pattern, the shortest propagation distance (referred to as the shortest propagation distance) is the first propagation pattern, and the longest propagation distance. (Referred to as the longest propagation distance) is the second propagation pattern, and the signal propagation delay difference obtained by subtracting the time when the signal light has propagated the shortest propagation distance from the time when the signal light has propagated the longest propagation distance is as follows: You can ask.

Note that the signal propagation delay difference is determined by the spread angle of the signal light emitted from the light emitting portion of the signal light emitting means (note that the angle in the horizontal direction with respect to the optical axis is r as shown in FIG. 2).
₁ , if the vertical angle is r ₂ , the spread angle of the signal light is
(Relatively 2r ₁ degrees in the horizontal direction and 2r ₂ degrees in the vertical direction)
And the critical angle θc of the optical transmission medium, it changes according to the four cases shown in Table 1 below, and can be obtained for each of the four cases.

[0017]

[Table 1]

Here, the relationship between the spread angle of the signal light in the vertical direction and the critical angle of the optical transmission medium, and the relationship between the spread angle of the signal light in the horizontal direction and the critical angle of the optical transmission medium. Also, r
₁ > π / 2−θc is defined by the lateral spread angle r ₁ and the critical angle θc
Is smaller than π / 2, that is, when the lateral spread angle r ₁ is small, and r ₁ ≦ π / 2−θc is the sum of the lateral spread angle r ₁ and the critical angle θc. Is π / 2 or more,
That is, this is the case where the lateral spread angle r ₁ is large.
Similarly, r ₂ > π / 2−θc means that the sum of the vertical divergence angle r ₁ and the critical angle θc is smaller than π / 2, that is, the vertical divergence angle r ₂ is small. r ₂ ≦ π / 2−
θc is the sum of the vertical spread angle r ₂ and the critical angle θc is π /
2 or more, that is, the case where the vertical spread angle r ₂ is large.

In the case of the first propagation pattern, since the propagation distance is the shortest distance that connects the light emitting portion and the light receiving portion with a straight line, r is used in all of the first to fourth cases.
_1, regardless of the magnitude of r ₂ and .theta.c, the propagation distance is represented by a constant distance l / (cosα · cosβ), the propagation time T ₀ can be expressed by the following equation (5). However, as illustrated in FIG. 1, the light receiving section of the signal light receiving section 22 has an angle of α degrees in the horizontal direction and β degrees in the vertical direction relative to the light emitting section of the signal light emitting section 20. assumed to be installed in a position, r ₁ ≧ alpha, and the signal do not adhere to r ₂ ≧ beta can not receive the signal light receiving means r ₁ ≧
α and r ₂ ≧ β. The length of the optical transmission medium 22 is 1, the refractive index is n, and the critical angle is θc. It should be noted that in FIG.
2, a light emitting section of the signal light emitting section 20 and a light receiving section of the signal light receiving section 24 are shown. Of course, the shape of each section is not limited to this.

[0020]

(Equation 5) (However, c is the speed of light.)

Next, the first case, that is, the case where the horizontal divergence angle r ₁ and the vertical divergence angle r ₂ are small (r ₁
> Π / 2−θc, r ₂ > π / 2−θc), the longest propagation distance is the distance over which the signal light emitted from the light emitting portion is reflected by the upper and lower surfaces and reaches the light receiving portion. Therefore, it is represented by 1 / (cos α · sin θc), and its propagation time T ₁₂ can be represented by the following equation (6).

[0022]

(Equation 6)

Therefore, the signal propagation delay difference T ₁₂ -T ₀ when propagating in the second propagation pattern can be expressed by the following equation (7).

[0024]

(Equation 7)

Therefore, the horizontal divergence angle r ₁ , the vertical divergence angle r ₂ , and the criticality of the optical transmission medium are set so that T ₁₂ −T ₀ ≦ 1 / X (where X is the frequency of the signal light). By determining the angle θc, the length l of the optical transmission medium, and the refractive index n of the optical transmission medium, it is possible to prevent the adverse effect on the high-speed signal propagation due to the rounding of the signal waveform due to the mode dispersion. it can.

Next, in the second case, that is, when the horizontal spread angle r ₁ is small and the vertical spread angle r ₂ is large.
In (r ₁ > π / 2−θc, r ₂ ≦ π / 2−θc), the longest propagation distance is represented by 1 / (cos α · sinr ₂ ), and the propagation time T ₂₂ is expressed by the following equation (8). Can be represented by

[0027]

(Equation 8)

Therefore, the signal propagation delay difference T ₂₂ -T ₀ when propagating in the second propagation pattern can be expressed by the following equation (9).

[0029]

(Equation 9)

Therefore, the horizontal divergence angle r ₁ , the vertical divergence angle r ₂ , and the criticality of the optical transmission medium are set so that T ₂₂ −T ₀ ≦ 1 / X (where X is the frequency of the signal light). By determining the angle θc, the length l of the optical transmission medium, and the refractive index n of the optical transmission medium, it is possible to prevent the adverse effect on the high-speed signal propagation due to the rounding of the signal waveform due to the mode dispersion. it can.

In the third case, that is, when the horizontal spread angle r ₁ is large and the vertical spread angle r ₂ is small (r ₁ ≦
In π / 2−θc, r ₂ > π / 2−θc), the longest propagation distance is represented by 1 / (cos α · sin θc), and the propagation time T ₃₂ can be represented by the following equation (10). .

[0032]

(Equation 10)

Therefore, the signal propagation delay difference T ₃₂ -T ₀ when propagating in the second propagation pattern can be expressed by the following equation (11).

[0034]

[Equation 11]

Accordingly, the divergence angle r _{1 in} the horizontal direction, the divergence angle r _{2 in} the vertical direction, and the criticality of the optical transmission medium are set so that T ₃₂ −T ₀ ≦ 1 / X (where X is the frequency of the signal light). By determining the angle θc, the length l of the optical transmission medium, and the refractive index n of the optical transmission medium, it is possible to prevent the adverse effect on the high-speed signal propagation due to the rounding of the signal waveform due to the mode dispersion. it can.

In the fourth case, that is, when the horizontal spread angle r ₁ and the vertical spread angle r ₂ are large (r ₁ ≦ π / 2).
In −θc, r ₂ ≦ π / 2−θc), the longest propagation distance is represented by 1 / (cos α · sinr ₂ ), and the propagation time T ₄₂ can be represented by the following equation (12).

[0037]

(Equation 12)

Therefore, the signal propagation delay difference T ₄₂ -T ₀ when propagating in the second propagation pattern can be expressed by the following equation (13).

[0039]

(Equation 13)

Accordingly, the horizontal divergence angle r ₁ , the vertical divergence angle r ₂ , and the criticality of the optical transmission medium are set so that T ₄₂ −T ₀ ≦ 1 / X (where X is the frequency of the signal light). By determining the angle θc, the length l of the optical transmission medium, and the refractive index n of the optical transmission medium, it is possible to prevent the adverse effect on the high-speed signal propagation due to the rounding of the signal waveform due to the mode dispersion. it can.

The signal light is transmitted between the first propagation pattern and the third propagation pattern.
In the case where the signal is propagated by the first propagation pattern, and when the signal is propagated by all the patterns from the first propagation pattern to the third propagation pattern, the shortest propagation distance is the first propagation pattern, and the longest propagation distance is the first propagation pattern. 3 propagation pattern.

Accordingly, the signal propagation delay difference T _xy −T ₀ obtained by subtracting the time when the signal light has propagated the shortest propagation distance from the time when the signal light has propagated the longest propagation distance is as follows. Note that the signal propagation delay difference T ₁₃ − in the first case is
Since T ₀ and the signal propagation delay difference T ₂₃ -T _{0 in} the second case can be expressed by the same equation, it is shown in equation (14), and the signal propagation delay difference T ₃₃ -T ₀ in the third case and the fourth case The signal propagation delay difference T ₄₃ -T _{0 in} the case of
Shown in equation 5).

[0043]

[Equation 14]

Similarly, when the signal light is propagated by the first propagation pattern and the fourth propagation pattern, and
, The shortest propagation distance is the first propagation pattern, and the longest propagation distance is the fourth propagation pattern.

Therefore, the signal propagation delay difference T _xy −T ₀ obtained by subtracting the time when the signal light has propagated the shortest propagation distance from the time when the signal light has propagated the longest propagation distance is as follows. Expression (16) shows the signal propagation delay difference T ₁₄ -T ₀ in the first case, Expression (17) shows the signal propagation delay difference T ₂₄ -T ₀ in the second case, and Expression (18) indicates the signal propagation delay difference T ₃₄ -T ₀ in the case of the third shows the (19) the signal propagation delay difference T ₄₄ -T ₀ in the case of the fourth.

[0046]

(Equation 15)

The intensity of the light received by the signal light receiving means is
In order to prevent variation, r ₁≦ π / 2−θc,
And r_TwoClaim 4 in the fourth case where ≤π / 2-θc.
As described in the above, the signal is satisfied so as to satisfy the following equation (1).
Horizontal spread angle 2r of signal light from signal light emitting means₁Passing
And vertical divergence angle 2r_TwoThe signal of the signal light receiving means
Angle α in the horizontal direction with respect to the light emitting portion of the light emitting means, vertical direction
, The length l of the optical transmission medium, the refractive index n, the critical angle
It is preferable to configure θc.

[0048]

(Equation 16)

As described above, the signal propagation delay difference, which is the difference between the longest propagation distance and the shortest propagation distance over which the signal light can propagate, is determined by the spread angle of the signal light emitted from the light emitting portion of the signal light emitting means. , The spread angle r _{1 in} the horizontal direction and the spread angle r _{1 in} the vertical direction in accordance with the conditions determined based on the first to fourth cases representing the relationship with the critical angle θc of the optical transmission medium. Divergence angle r ₂ , critical angle θc of optical transmission medium,
By determining the length 1 of the optical transmission medium and the refractive index n of the optical transmission medium, it is possible to prevent signal transmission failure due to a difference in signal propagation time. That is, according to the invention of the present application, it is possible to prevent adverse effects on speeding up of signal propagation due to rounding of a signal waveform due to mode dispersion.

Further, in the optical branching / coupling device according to the first aspect, as described in the third aspect, the signal light having a predetermined divergence angle emitted from one of the signal light emitting means is transmitted to the optical transmission device. When light is received by the plurality of signal light receiving means via the optical waveguide of the medium, and the signal light having a predetermined spread angle emitted from the plurality of signal light emitting means is transmitted through the optical waveguide of the optical transmission medium. In one of the cases where the signal light is received by one of the signal light receiving means, the propagation time of the signal light that has propagated the longest propagation distance of the signal light that propagates in the optical waveguide; Out of the signal light, so that a signal propagation delay difference, which is a difference from a propagation time of the signal light propagating through the shortest propagation distance of the signal light propagating through the signal light, is shorter than a half cycle of the frequency of the signal light. Means, said optical transmission Body, and the arrangement of the signal light receiving means, it is preferable to determine the material of the signal beam emitting unit and an optical transmission medium.

That is, according to the third aspect of the present invention, the signal light emitted from one signal light emitting means is received by the plurality of signal light receiving means, or the signal light emitted from the plurality of signal light emitting means is received. In the case where the signal light is received by one signal light receiving unit, or the signal light emitted from the plurality of signal light emitting units is received by the plurality of signal light receiving units, the signal light is transmitted simultaneously. In the case of transmission, the signal propagation delay difference is set to 1 / frequency of the signal light.
The arrangement of the signal light emitting means, the optical transmission medium, and the signal light receiving means, and the materials of the signal light emitting means and the optical transmission medium are determined so as to be shorter than two periods.

Thus, it is possible to prevent an adverse effect on the increase in the propagation speed due to the rounding of the signal waveform caused by the mode dispersion (difference in the propagation distance of the signal light).

Further, as described in claim 4,
In the signal light emitting means for transferring the signal light propagating over the longest propagation distance and the signal light receiving means, the light receiving part of the signal light receiving means is relatively positioned with respect to the light emitting part of the signal light emitting means. Α ₁ degrees in the horizontal direction, and β ₁ degrees in the vertical direction, and the signal light emitting means and the signal light receiving means for transferring the signal light propagating the shortest propagation distance, receiving portion of the signal light receiving means is relatively laterally alpha ₂ degrees with respect to the light exit portion of the signal light output unit, and,
It is preferable to satisfy the following equation (2) when the camera is installed at a position of β ₂ degrees in the vertical direction.

[0054]

[Equation 17]

For example, when signal light emitted from one signal light emitting means is received by a plurality of signal light receiving means, that is, 1: N (N is the number of signal light receiving means; any positive ) Will be described.

As shown in FIG. 3, of the signal light emitted from the light emitting portion of the signal light emitting device, the light receiving portion a of the signal light receiving device 24 for receiving the signal light having propagated the shortest propagation distance. Is α in the lateral direction relative to the light emitting portion.
_Once, and, in the longitudinal direction it is installed in the beta ₁ degree position, the light receiving portion b of the signal light receiving unit 24 for receiving the signal light propagated through the longest propagation distance relative to the light exit portion It is assumed that it is installed at a position of α ₂ degrees in the horizontal direction and β ₂ degrees in the vertical direction.

Therefore, the distance between the light emitting part of the signal light emitting means 20 and the light receiving part of the signal light receiving means 24a for receiving the signal light having propagated the shortest propagation distance is 1 / (cos α ₁ · sin).
β ₁ ), and the distance between the light emitting part of the signal light emitting means 20 and the light receiving part of the signal light receiving means 24b for receiving the signal light having propagated the longest propagation distance is 1 / (cos α _2.
sin β ₂ ).

Therefore, the signal propagation delay difference ΔT can be expressed by the following equation (20).

[0059]

(Equation 18)

FIG. 3 shows the transmission medium 22,
The signal light emitting means 20, signal light receiving means 24a for receiving the signal light having propagated the shortest propagation distance, and signal light receiving means 24b for receiving the signal light having propagated the longest propagation distance are shown. Is not limited to this.

When the signal light emitted from the plurality of signal light emitting means is received by one signal light receiving means, that is, M: 1 (M is the number of signal light emitting means;
The simultaneous transmission of any positive integer will be described.

As shown in FIG. 4, of the signal light emitted from the light emitting portion of the signal light emitting means, the signal light emitting means 20a for emitting the signal light propagating over the shortest propagation distance.
Is disposed at a position of α ₁ degrees in the horizontal direction and β ₁ degrees in the vertical direction relative to the light receiving portion of the signal light receiving means 24, and the signal propagating through the longest propagation distance The light emitting part of the signal light emitting means 20b for emitting light is α ₂ degrees in the lateral direction relatively to the light receiving part of the signal light receiving means 24, and
It is assumed that it is installed at a position of β ₂ degrees in the vertical direction.

Accordingly, the distance between the light emitting portion of the signal light emitting means 20a for emitting the signal light propagating over the shortest propagation distance and the light receiving portion of the signal light receiving means 24 is 1 / (cos α ₁ · sin).
β ₁ ) and the light emitting portion of the signal light emitting means 20 b for emitting the signal light propagating over the longest propagation distance and the signal light receiving means 2
4 can be expressed by 1 / (cos α ₂ · sin β ₂ ), so the signal propagation delay difference ΔT can be expressed by the above equation (20).

For the sake of explanation in FIG. 4, signal light emitting means 20a for emitting signal light propagating over the shortest propagation distance, signal light emitting means 20b for emitting signal light propagating over the longest propagation distance, transmission medium 22, Also, the signal light receiving means 24 is shown, and of course, the shape of each part is not limited to this.

Further, when the signal light emitted from the plurality of signal light emitting means is received by one signal light receiving means, that is, in the simultaneous transmission of M: N, as shown in FIG. A light emitting portion of the signal light emitting means 20a for emitting the signal light propagating over the shortest propagation distance and the signal light receiving means 2 receiving the signal light propagating over the shortest propagation distance
The distance from the light receiving portion of 4a is 1 / (cos α ₁ · sin β ₁ )
In addition, the light emitting portion of the signal light emitting means 20b for emitting the signal light propagating over the longest propagation distance and the signal light receiving means 2 receiving the signal light propagating over the longest propagation distance
The distance from the light receiving section of 4b is 1 / (cos α ₂ · sin β ₂ )
Therefore, the signal propagation delay difference ΔT can be expressed by the above equation (20).

FIG. 5 shows the signal light emitting means 20a for emitting the signal light propagating over the shortest propagation distance, and the signal light emitting means 2 for emitting the signal light propagating over the longest propagation distance.
0b, a transmission medium 22, a signal light receiving unit 24a for receiving the signal light having propagated the shortest propagation distance, and a signal light receiving unit 24b for receiving the signal light having propagated the longest propagation distance. It is not limited to this.

Therefore, the divergence angle r ₁ in the horizontal direction is set so that ΔT ≦ １ ／ · X (where X is the frequency of the signal light).
By determining the vertical divergence angle r ₂ , the critical angle θc of the optical transmission medium, the length l of the optical transmission medium, and the refractive index n of the optical transmission medium, signal propagation due to rounding of a signal waveform caused by mode dispersion. It is possible to prevent the adverse effect on the high-speed operation from occurring.

Further, the invention described in claim 5 is the first invention.
In the optical branching / coupling device according to (1), light that propagates signal light is provided between the signal light emitting unit and the optical transmission medium and at least one of between the optical transmission medium and the signal light receiving unit. An arrangement of the signal light emitting means, the optical transmission medium, the signal light receiving means, and the optical fiber such that the signal propagation delay difference is shorter than one cycle of the frequency of the signal light. And the material of the signal light emitting means and the optical transmission medium, and the length, the refractive index, and the numerical aperture of the optical fiber are determined.

That is, in the invention of claim 5, optical fibers are provided between at least one of the signal light emitting means and the optical transmission medium and between at least one of the optical transmission medium and the signal light receiving means. The signal light emitting means, the optical transmission medium, and the signal light receiving means, and the signal light emitting means so that the signal propagation delay difference is shorter than one cycle of the frequency of the signal light. And the material of the optical transmission medium, as well as the location of the optical fiber and the length, refractive index, and numerical aperture of the optical fiber are determined. It is possible to prevent adverse effects on speeding up.

That is, as described in claim 1, the signal light arriving at the light receiving portion from the light emitting portion is one of the following four propagation patterns from the first propagation pattern to the fourth propagation pattern. Propagated by

In the case of the first propagation pattern, the signal light emitted from the signal light emitting means does not cause a signal propagation delay difference in the optical transmission medium, but has a propagation time difference during transmission in the optical fiber. In the case of the second to fourth propagation patterns, a difference in propagation time occurs between the signal light emitted from the signal light emitting unit during transmission in the optical transmission medium and in the optical fiber.

The propagation time difference τ of the optical fiber is given by (2)
1) It can be expressed by the following equation. Here, c is the speed of light, l is the length of the optical fiber, n ₁ is the refractive index of the core of the optical fiber, n ₂ is the refractive index of the cladding of the optical fiber, and NA is the numerical aperture of the optical fiber.

[0073]

[Equation 19]

As shown in FIG. 6, a light emitting portion of the signal light emitting means 20 is provided on one end face of the input side optical fiber 26, and the other end face is provided on the optical transmission medium 22.
And transmits the signal light from the light emitting unit 20 to the optical transmission medium 2.
Leading to 2. One end face of the output side optical fiber 28 is provided on the optical transmission medium 22, and the other end face is provided with a light receiving portion of the signal light receiving means 24. The signal light is received from one end face and guided to the light receiving section 24 on the other end face.

The end face of the output side optical fiber 28 on the light receiving side is set at a position α degrees in the horizontal direction and β degrees in the vertical direction relative to the end face on the light emission side of the input side optical fiber 26. The input side optical fiber 26 has a radius r ₁₀ , a length l ₁₀ , a core refractive index n ₁₀ , a numerical aperture NA ₁₀ , a critical angle θc ₁₀ , and the optical transmission medium 22 has a length Is l ₂₀ , the refractive index is n ₂₀ , the numerical aperture is NA ₂₀ , the critical angle is θc ₂₀ , and the output side optical fiber 28 has a length of l ₃₀ , a core refractive index of n ₃₀ , a numerical aperture of NA ₃₀ , The angle is θc ₃₀ .

The propagation time difference occurring during transmission between the optical transmission medium and the optical fiber is determined by the numerical aperture NA of the input side optical fiber.
₁₀ , the following two cases can be considered depending on the relationship between the numerical aperture NA ₃₀ of the output side optical fiber and the numerical aperture NA ₂₀ of the optical transmission medium.

In the first case, NA ₁₀ ≦ NA ₂₀ ≦ NA ₃₀ , N
A ₁₀ > NA ₂₀ ≦ NA _{30 In} the second case; NA ₁₀ > NA ₂₀ > NA ₃₀ , NA ₁₀ ≦ NA ₂₀
> NA _{30 In} the first case, in the first propagation pattern, there is no propagation time difference in the optical transmission medium, so the signal propagation time difference T _f1
Can be expressed only by the signal propagation time difference generated in the fiber. It is shown in equation (22).

[0078]

(Equation 20)

In the second propagation pattern, a propagation time difference occurs due to reflection on the upper and lower surfaces in the optical transmission medium, and a propagation time difference also occurs between the input side optical fiber and the output side optical fiber. _f1 + T _p can be expressed as the sum of the signal propagation time difference caused by the upper and lower surfaces reflection and propagation time difference caused by the fiber. This is shown in equation (23).

[0080]

(Equation 21)

Further, in the third propagation pattern, in the optical transmission medium, a propagation time difference occurs due to left and right side reflections, and
Since there is a propagation time difference between the input side optical fiber and the output side optical fiber, the signal propagation time difference T _f1 + T
_s can be expressed as the sum of the propagation time difference generated in the fiber and the signal propagation time difference due to left and right side reflections.
This is shown in equation (24).

[0082]

(Equation 22)

In the fourth propagation pattern, in the optical transmission medium, a propagation time difference due to upper and lower surface reflections and a propagation time difference due to left and right side reflections occur, and a propagation time difference also occurs between the input side optical fiber and the output side optical fiber. Therefore, the signal propagation time difference T _f1 + T _p + T _s can be expressed as the sum of the propagation time difference generated in the fiber, the propagation time difference due to upper and lower surface reflections, and the propagation time difference due to left and right side reflections. (2
Shown in equation 5).

[0084]

(Equation 23)

In the second case, since the numerical aperture of the output side optical fiber is smaller than that of the optical transmission medium, the light propagating from the optical transmission medium is incident at an angle smaller than the critical angle of the output side optical fiber. Light cannot propagate.

In consideration of the above, in the first propagation pattern, no propagation time difference occurs in the optical transmission medium, so that the signal propagation time difference T _f2 can be expressed only by the propagation time difference generated in the fiber. This is shown in equation (26).

[0087]

(Equation 24)

In the second propagation pattern, a propagation time difference occurs due to reflection on the upper and lower surfaces in the optical transmission medium, and a propagation time difference also occurs between the input side optical fiber and the output side optical fiber. _f2 + T _p can be expressed as the sum of the propagation time difference caused by the upper and lower surfaces reflection and propagation time difference caused by the fiber. This is shown in equation (27).

[0089]

(Equation 25)

Further, in the third propagation pattern, a difference in propagation time occurs due to left and right side reflections in the optical transmission medium, and
Since there is a propagation time difference between the input side optical fiber and the output side optical fiber, the signal propagation time difference T _f2 + T
_s can be expressed as the sum of the propagation time difference generated in the fiber and the propagation time difference due to left and right side reflections. (2
It is shown in equation 8).

[0091]

(Equation 26)

In the fourth propagation pattern, in the optical transmission medium, a propagation time difference due to upper and lower surface reflections and a propagation time difference due to left and right side reflections occur, and a propagation time difference also occurs between the input side optical fiber and the output side optical fiber. Therefore, the signal propagation time difference T _f2 + T _s + T _p can be expressed as the sum of the propagation time difference generated in the fiber, the propagation time difference due to upper and lower surface reflections, and the propagation time difference due to left and right side reflections. (2
It is shown in equation 9).

[0093]

[Equation 27]

The value obtained in all of the above equations (22) to (29) is 1 / X (where X is the frequency of the signal light), that is, the input value is smaller than the period of the signal light. the side optical fiber, the radius r _10, the length l _10, the core refractive index n _10, the numerical aperture NA _10, and .theta.c ₁₀ the critical angle, the optical transmission medium, the length and l _20, the refractive index N ₂₀ , numerical aperture NA ₂₀ , critical angle θc ₂₀ , output optical fiber size, length l ₃₀ , core refractive index n ₃₀ , numerical aperture NA
₃₀ and the critical angle θc ₃₀ , respectively,
It is possible to prevent adverse effects on speeding up of signal propagation due to rounding of a signal waveform due to mode dispersion.

Variation in received light intensity in signal light receiving means
In order to prevent the
6. The optical branching / coupling device according to claim 5, wherein the signal light output is
Input side optical fiber provided between the transmitting means and the optical transmission medium.
Fiber end face, the optical transmission medium and the signal light receiving means
The end face of the output side optical fiber provided between
The output medium is disposed on the opposing surface of the transmission medium, and
The end face of the side optical fiber is connected to the end face of the input side optical fiber.
Relatively α degrees in the horizontal direction and β degrees in the vertical direction.
And the length of the input side optical fiber is l
_Ten, The refractive index n _Ten, The numerical aperture (= sinθ) is NA_Ten, Near
Field angle θc_TenAnd the length of the optical transmission medium is l₂₀,refraction
Rate n₂₀, NA₂₀, The critical angle θc₂₀And said
The length of the output side optical fiber is l₃₀, The refractive index n₃₀, Numerical aperture
To NA₃₀, The critical angle θc₃₀And NA_Ten= NA₃₀≤NA
₂₀When satisfying the relationship of
It is good to satisfy.

[0096]

[Equation 28]

(Where X is the frequency of the signal light and c is the speed of light) Further, in the optical branching / coupling device according to the fifth or sixth aspect, as described in the seventh aspect, the input side optical fiber and When at least one of the output-side optical fibers is provided in a plurality and the signal light is transmitted simultaneously, the propagation time of the signal light that has propagated the longest propagation distance of the signal light propagating in the optical waveguide, and the light guide The signal propagation delay difference, which is the difference from the propagation time of the signal light propagating through the shortest propagation distance of the signal light propagating in the wave path, is 1/1 / frequency of the signal light.
The arrangement of the signal light emitting means, the optical transmission medium, the signal light receiving means, and the optical fiber, the material of the signal light emitting means and the optical transmission medium, and the light The length, refractive index, and numerical aperture of the fiber may be determined.

Thus, it is possible to prevent an adverse effect on the increase in the propagation speed due to the rounding of the signal waveform due to the mode dispersion.

For example, when signal light emitted from one input-side optical fiber is received by a plurality of output-side optical fibers, that is, 1: N (N is the number of output-side optical fibers; ) Will be described. A light emitting portion of the signal light emitting means is provided on one end face of the input side optical fiber, and the other end face is provided on the optical transmission medium, and the signal light from the light emitting section is provided on the optical transmission medium. Leading. One end face of all output side optical fibers is provided on the optical transmission medium, and the other end face is provided with a light receiving portion of the signal light receiving means, and the signal light transmitted through the optical transmission medium is provided. Is received from one end face and guided to a light receiving section on the other end face.

Here, as exemplified in FIG. 7, of the signal light emitted from the end face of the input side optical fiber 26, the end face of the output side optical fiber 28a for receiving the signal light propagating the shortest propagation distance is connected to the input side. An output optical fiber that is installed at a position of α ₁ degrees in the horizontal direction and β ₁ degrees in the vertical direction relative to the end face of the side optical fiber 26 and receives the signal light propagated over the longest propagation distance. It is assumed that the end face of 28 b is disposed at a position of α ₂ degrees in the horizontal direction and β ₂ degrees in the vertical direction relative to the end face of the input side optical fiber 26.

The length of the input side optical fiber 26 is l ₁₀ , the refractive index is n ₁₀ , the numerical aperture is NA ₁₀ = sin θ ₁₀ , the critical angle is θc _10, and the signal light propagating through the shortest propagation distance is received. The length of the output side optical fiber 28a is l ₃₀ , the refractive index is n ₃₀ , the numerical aperture is NA ₃₀ = sin θ ₃₀ , the critical angle is θc ₃₀ , the length of the optical transmission medium 22 is l ₂₀ , the refractive index N ₂₀ , the numerical aperture is NA ₂₀ , and the critical angle is θc ₂₀ , the length of the output side optical fiber 28b that receives the signal light having propagated the longest propagation distance is l ₃₁ , the refractive index is n ₃₁ , and the numerical aperture is n NA ₃₁
= Sin θ ₃₁ , and the critical angle is θc ₃₁ .

Input side optical fiber 2 having the shortest transmission distance
The distance between the other end face of _No. 6 and one end face of the output side optical fiber 28a is l ₁₀ + l ₂₀ / (cos α ₁ · cos β ₁ ) + l
₃₀ and the other end face of the input side optical fiber 26 having the longest transmission distance and the output side optical fiber 2
8 with one end face is l ₁₀ + l ₂₀ / (cos α ₂ ·
cosα ₂ ) + l ₃₁ , so that the signal propagation delay difference ΔT _{1: N} can be expressed by the following equation (30).

[0103]

(Equation 29)

In FIG. 7, for the sake of explanation, the input side optical fiber 26, the optical transmission medium 22, the output side optical fiber 28a for receiving the signal light propagated over the shortest propagation distance, and the output side optical fiber 28a are provided. The figure shows a signal light receiving means 24a, an output optical fiber 28b for receiving signal light having propagated the longest propagation distance, and a signal light receiving means 24b provided on the output optical fiber 28b.

Therefore, when signal light emitted from one input-side optical fiber is received by a plurality of output-side optical fibers, ΔT _{1: N} ≦ 1/2 · X (where X is the frequency of the signal light) ), The input side optical fiber 26 has a length l ₁₀ , a refractive index n ₁₀ , a length l ₂₀ of the optical transmission medium, a refractive index n ₂₀ , and an output side that receives the signal light propagated through the shortest propagation distance. An output side optical fiber 28b for receiving the signal light propagated through the length l ₃₀ , the refractive index n ₃₀ , and the longest propagation distance of the optical fiber 28a.
By determining the length l ₃₁ and the refractive index n ₃₁ , respectively, it is possible to prevent adverse effects on speeding up of signal propagation due to rounding of a signal waveform caused by mode dispersion.

When the signal light emitted from the plurality of input side optical fibers is received by one output side optical fiber, that is, M: 1 (M is the number of input side optical fibers; ) Will be described.

A light emitting portion of the signal light emitting means is provided on one end face of the input side optical fiber, and the other end face is provided on the optical transmission medium so that the signal light from the light emitting portion can be converted to light. Leading to the transmission medium. Also, one end face of all output side optical fibers is provided in the optical transmission medium, and the other end face is provided with a light receiving portion of the signal light receiving means,
The signal light transmitted through the optical transmission medium is received from one end face and guided to a light receiving portion on the other end face.

As illustrated in FIG. 8, the end face of the input side optical fiber 26a for emitting the signal light propagating the shortest propagation distance among the signal lights incident on the end face of the output side optical fiber 28 is connected to the output side optical fiber. The end face of the input side optical fiber 26b which is installed at a position of α ₁ degrees in the horizontal direction and β ₁ degrees in the vertical direction relative to the end face of the input optical fiber 26b and emits the signal light propagating the longest propagation distance. Is set at a position of α ₂ degrees in the horizontal direction and β ₂ degrees in the vertical direction relative to the end face of the output side optical fiber 28.

The length of the input side optical fiber 26a for emitting the signal light propagating through the shortest propagation distance is l ₁₀ , the refractive index is n ₁₀ , the numerical aperture is NA ₁₀ = sin θ ₁₀ , and the critical angle is θc.
₁₀ , the length of the input-side optical fiber 26b that emits the signal light propagating the longest propagation distance is l ₁₁ , the refractive index is n ₁₁ , the numerical aperture is NA ₁₁ = sin θ ₁₀ , and the critical angle is θc ₁₁ , The length of the optical transmission medium 22 is l ₂₀ , the refractive index is n ₂₀ , the length of the output side optical fiber 28 is l ₃₀ , the refractive index is n ₃₀ , the numerical aperture is NA ₃₀ = sin θ ₃₀ , and the critical angle is θc. ₃₀ .

The end face of the input optical fiber 26a for emitting the signal light propagating the shortest propagation distance and the output optical fiber 28
Distance from the end face of l ₁₀ + l ₂₀ / (cos α ₁ · cos
β ₁ ) + l _30, and the distance between the end face of the input side optical fiber 26 b emitting the signal light propagating the longest propagation distance and the end face of the output side optical fiber 28 is l ₁₁ + l
₂₀ / (cos α ₁ · cos β ₁ ) + l ₃₀ , the signal propagation delay difference ΔT _{M: 1} is given by the following (31)
It can be expressed by an equation.

[0111]

[Equation 30]

In FIG. 8, for the sake of explanation, the input side optical fiber 26a for emitting the signal light propagating over the shortest propagation distance,
A signal light emitting means 20a having a light emitting portion provided on one end face of the input optical fiber 26a, an input optical fiber 26b for emitting signal light propagating over the longest propagation distance, and one of the input optical fibers 26b. A signal light emitting unit 20b having a light emitting unit provided on an end surface, an optical transmission medium 22, an output side optical fiber 28, and a signal light receiving unit 24 having a light receiving unit provided on one end surface of the output side optical fiber 28. Is shown.

Therefore, from the plurality of input side optical fibers,
The emitted signal light is transmitted through one output side optical fiber.
ΔT for receiving light_{M: 1}≦ 1/2 · X (where X is signal light
Signal light at the shortest propagation distance so that
Input optical fiber length l_Ten, Refractive index n_Ten, The longest biography
Length of input optical fiber that emits signal light at seeding distance
l ₁₁, Refractive index n₁₁The length l of the optical transmission medium₂₀, Refractive index
n₂₀The length l of the output side optical fiber for receiving the signal light₃₀,
Refractive index n₃₀Modal dispersion by determining
Signal propagation speed due to signal waveform distortion
It is possible to prevent adverse effects from occurring.

Further, in the case where the signal light emitted from the plurality of input side optical fibers is received by the plurality of output side optical fibers, that is, the simultaneous transmission of M: N is performed. Will be described.

As shown in FIG. 9, the input optical fiber 26a for emitting the signal light propagating over the shortest propagation distance and the output optical fiber 28a for receiving the signal light from the input optical fiber 26a have an input Side optical fiber 26a
The end face of the output side optical fiber 28a is disposed at a position relatively α ₁ degrees in the horizontal direction and β ₁ degrees in the vertical direction relative to the end face of the optical fiber 28a. Further, an input optical fiber 26b for emitting signal light propagating over the longest propagation distance, and an output optical fiber 28b for receiving signal light from the input optical fiber 26b
, The end face of the output-side optical fiber 28b is relatively α ₂ degrees in the lateral direction with respect to the end face of the input-side optical fiber 26b,
And it is installed at a position of β ₂ degrees in the vertical direction.

Therefore, the distance between the end face of the input side optical fiber 26a for transferring the signal light propagating the shortest propagation distance and the end face of the output side optical fiber 28a is l ₁₀ + l ₂₀ / (cos α _1).
Cos β ₁ ) + l _30, and the distance between the end face of the input-side optical fiber 26 b for transferring the signal light propagating through the longest propagation distance and the end face of the output-side optical fiber 28 b is l ₁₁ + l ₂₀ / ( cosα ₁ · cosβ ₁ ) + l ₃₁ , so that the signal propagation delay difference ΔT _{M: N} can be expressed by the following equation (32).

[0117]

(Equation 31)

In FIG. 9, for the sake of explanation, the input side optical fiber 26a for emitting the signal light propagating over the shortest propagation distance,
A signal light emitting means 20a having a light emitting portion provided on one end face of the input optical fiber 26a, an input optical fiber 26b for emitting signal light propagating over the longest propagation distance, and one of the input optical fibers 26b. A signal light emitting means 20b having a light emitting portion provided on an end face, an optical transmission medium 22, an output side optical fiber 28a for receiving signal light propagated over the shortest propagation distance,
The signal light receiving means 24a provided on the output side optical fiber 28a, the output side optical fiber 28b receiving the signal light having propagated the longest propagation distance, and the signal light receiving means 24b provided on the output side optical fiber 28b are shown. ing.

Therefore, when the signal light emitted from the plurality of input side optical fibers is received by the plurality of output side optical fibers, the following equation (4) is used, that is, ΔT _{M: N} ≦
The length l ₁₀ of the input side optical fiber that emits the signal light at the longest propagation distance, the refractive index n ₁₀ , and the signal light at the shortest propagation distance so as to be ・ · X (where X is the frequency of the signal light). , The length of the input optical fiber l ₁₁ , the refractive index n ₁₁ , the length of the optical transmission medium l ₂₀ , the refractive index n ₂₀ , the length of the output optical fiber that receives the signal light via the longest propagation distance L ₃₀ , the refractive index n ₃₀ , the length l ₃₁ of the output-side optical fiber that receives the signal light via the shortest propagation distance, and the refractive index n ₃₁ , respectively, to determine the signal waveform caused by the mode dispersion. It is possible to prevent adverse effects on speeding up of signal propagation due to rounding.

[0120]

(Equation 32)

The signal light irradiating means in the first to eighth aspects of the present invention may be, for example, a light emitting element such as a laser diode, and the signal light receiving means may be, for example, a photodiode or the like. Can be used.

The signal light irradiating means may be any one that emits diffused light from the light emitting portion. For example, the signal light irradiating means may be a signal light irradiating means configured to directly emit diffused light, or a light diffusing member such as a diffusing plate may be used. A signal light irradiating unit or the like configured to emit diffused light by emitting parallel light through the light diffusion member provided in the emission unit can be provided.

[0123]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention
As shown in FIG. 10, the optical branching / coupling device according to the embodiment includes first to fourth laser diodes 10a to 10d, an optical transmission unit 12, and first to fourth photodiodes 14a to 14d. I have. The first to fourth laser diodes 10a to 10d correspond to signal light emitting means of the present invention,
The optical transmission unit 12 corresponds to an optical transmission medium of the present invention, and the first to fourth photodiodes 14a to 14d correspond to signal light receiving means of the present invention.

Here, each of the first laser diode 10a to the fourth laser diode 10d is an edge-emitting laser whose signal light emitted from the light emitting surface has a horizontal divergence angle of 28 degrees and a vertical divergence angle of 8 degrees. A diode is used. As such an edge-emitting laser diode, for example, TOLD9441MC (trade name; manufactured by Toshiba Corporation) or the like can be used. In addition, the light emitting surface corresponds to the light irradiation part of the present invention.

Since the space between the laser diode and the optical transmission medium is an air layer, the divergence angle γ ₁ in the horizontal direction in the first embodiment is 18.4 degrees, and the divergence angle γ _{2 in the} horizontal direction. Is 5.4 degrees.

The optical transmission section 12 is a PM formed in a rectangular parallelepiped shape having a width w of 4 mm, a thickness t of 1 mm, and a length 1 of 20 mm.
It is made of a plastic material such as MA (polymethyl methacrylate). The refractive index of the optical transmission unit 12 is 1.49, NA (numerical aperture) is 1, and critical angle (θc) is 4
The first laser diode 10a to the fourth laser diode 10d
On the other hand, a first photodiode 14a to a fourth photodiode 14d are provided, respectively.

As the first to fourth photodiodes 14a to 14d, photodiodes having a light receiving surface with a light receiving diameter of 0.8 mm are used here. As such a photodiode, for example, S5972 (trade name; manufactured by Hamamatsu Photonics) can be used. The light receiving surface corresponds to the light receiving section of the present invention.

Here, the first to fourth laser diodes 10a to 10d and the first to fourth photodiodes 14a to 14d are arranged at 1 mm intervals on the lateral center line of the side surface of the optical transmission unit. ing.

Therefore, for example, the light receiving surface of the first photodiode 14a, which is farthest from the light emitting surface of the fourth laser diode 10d, is 8 laterally relatively to the light emitting surface of the fourth laser diode 10d. .53 degrees (= α
Degrees) and 0 degrees (= β degrees) in the vertical direction.

The configuration of the present embodiment is different from the fourth case (r ₁ ≦
π / 2-θc and, at _{r 2 ≦ π / 2-θc} ), and it is equal to the propagation of signal light in the fourth propagation pattern, the signal propagation delay difference T ₄₄ -T ₀ is the (19) From the formula, 4.7 × 1
0 ⁻¹² (m / s). (However, the speed of light c is 3.0 × 10 ⁸ m
/ S) That is, the driving frequency (frequency of signal light) X is 500 MH
In the case of z, 1 / X = 2 × 10 ⁻⁹ (sec), and the signal propagation delay difference T ₄₄ −T ₀ is smaller than this value.
According to the equation (1), it is possible to obtain an optical branching / coupling device that does not cause a signal transmission failure such as a rounding of a signal waveform due to a mode dispersion of a signal light and a bad effect on high speed operation.

In the first embodiment, an edge-emitting laser diode having a horizontal light emission divergence angle of 28 degrees and a vertical light emission divergence angle of 8 degrees is used. The light emission spread angle in the horizontal direction and the light emission spread angle in the vertical direction are not limited to the values described above.

In the first embodiment, the optical transmission unit 1
Although the first laser diode 10a to the fourth laser diode 10d and the photodiode are disposed facing each other on one set of side surfaces facing each other among the plurality of surfaces, the present invention is not limited to this configuration. It is also possible to adopt a configuration in which the first to fourth laser diodes 10a to 10d and the photodiode are mixedly mounted on a plurality of surfaces. In addition, the light transmission unit 12 has a rectangular parallelepiped shape, but is not limited to this shape, and may have another shape such as a columnar shape or a hexahedral shape.

Further, although the number of laser diodes and photodiodes is four, the present invention is not limited to four, and the number of laser diodes and photodiodes can be changed as needed. It is possible. Further, the number of laser diodes and photodiodes is not limited to the same number, but may be different numbers.

(Second Embodiment) As shown in FIG. 11, an optical branching / coupling device according to a second embodiment of the present invention has a structure similar to that of the above-described first embodiment, and has one light emitting device. This is a case where light from a surface is received by four light receiving surfaces:
4 will be described.

In the second embodiment, the first photo
Of the diodes 14a to 14d,
At the position closest to the light emitting surface of the fourth laser diode 10d
The arranged fourth photodiode 14d has a light receiving surface.
Is relative to the light emitting surface of the fourth laser diode 10d.
8.53 degrees in the horizontal direction (= α₁Degrees), 0 degrees vertically (= β ₁
Degrees).

The first to fourth photodiodes 14a to 14a
Among the photodiodes 14d, the first photodiode 14a, which is arranged farthest from the light emitting surface of the fourth laser diode 10d, has a light receiving surface in a lateral direction relatively to the light emitting surface of the fourth laser diode 10d. 0 degrees (= α ₁
Degrees) is arranged at a position in the vertical direction at 0 ° (= beta ₁ degree).

Therefore, the signal propagation delay difference ΔT is obtained by the above (20)
From the formula, it is 1.1 × 10 ⁻¹² (m / s). (However, the speed of light
c is 3.0 × 10 ⁸ m / s) That is, the driving frequency (frequency of signal light) X is 500 MHz.
In the case of z, 1 / X ・ 1/2 = 1 × 10 ⁻⁹ (sec), and the signal propagation delay difference ΔT is smaller than this value. An optical branching / coupling device that does not cause a signal transmission failure such as a rounding of a waveform of a signal to be generated and a detrimental effect on high speed operation can be obtained.

(Third Embodiment) As shown in FIG. 12, an optical branching / coupling device according to a third embodiment of the present invention includes first to fourth laser diodes 10a to 10d.
d, first emission side fiber 16a to fourth emission side fiber 1
6d, optical transmission unit 12, first light receiving side fiber 18a to fourth light
Light receiving side fiber 18d and first photodiode 14
a to the fourth photodiode 14d.

The first to fourth laser diodes 10a to 10a
The laser diode 10d corresponds to the signal light emitting means of the present invention, the first outgoing fiber 16a to the fourth outgoing fiber 16d correspond to the input optical fiber, and the optical transmission section 12 corresponds to the optical transmission medium of the present invention. And the first light receiving side fiber 18a
The fourth to fourth light receiving fibers 18d correspond to the output optical fibers of the present invention, and the first to fourth photodiodes 14a to 14d correspond to signal light receiving means of the present invention.

The respective structures of the first to fourth laser diodes 10a to 10d, the optical transmission unit 12, and the first to fourth photodiodes 14a to 14d are the same as those in the first embodiment. The description is omitted.

In the third embodiment, in addition to the first laser diode 10a in the first embodiment described above, the first laser diode 10a is provided with one end provided with the first laser diode 10a. An edge is provided.
Since the second laser diode 10b to the fourth laser diode 10d have the same configuration, the description is omitted.

In the third embodiment, the first photodiode 14a is different from the first embodiment.
Instead, the other end of the first light receiving side fiber 18a having the first photodiode 14a provided on one end side is provided. Note that the second to fourth photodiodes 14b to 14d have the same configuration, and a description thereof will be omitted.

The first output side fibers 16a to the fourth
Outgoing side fiber 16d and first light receiving side fiber 18a-
Here, each of the fourth light receiving side fibers 18d has a fiber diameter of 1 mm, a core refractive index of 1.49, and a numerical aperture of 0.4.
5, and a fiber having a length of 30 cm is used. As such a fiber, for example, SH-4001
(Trade name; manufactured by Mitsubishi Rayon Co., Ltd.).

The first output side fibers 16a to the fourth
Outgoing side fiber 16d and first light receiving side fiber 18a-
The fourth light receiving fibers 18d are arranged at 1 mm intervals on the lateral center line of the side surface of the optical transmission unit.

Therefore, for example, the fourth emission side fiber 1
First light receiving side fiber 1 farthest from end face of 6d
The end face of 8a is 8.53 degrees (= α degrees) in the horizontal direction and 0 degrees in the vertical direction relative to the end face of the fourth emission side fiber 16d.
It is arranged at the position of degrees (= β degrees).

The configuration of this embodiment is different from the first case (NA
₁₀ ≦ NA ₂₀ ≦ NA ₃₀ ) and corresponds to the propagation of the signal light in the fourth propagation pattern, so that the signal propagation delay difference T _f1 + T
_p + T _s than above ^{(25), 1.8 × 10 -10 (m /} s)
Becomes (However, the light speed c is 3.0 × 10 ⁸ m / s) That is, the driving frequency (frequency of the signal light) X is 500 MHz.
In the case of z, 1 / X = 2 × 10 ⁻⁹ (sec), and the signal propagation delay difference T _f1 + T _p + T _s is smaller than this value. It is possible to obtain an optical branching / coupling device that does not cause a signal transmission failure such as a rounding of the resulting signal waveform and a detrimental effect on high speed operation.

(Fourth Embodiment) An optical branching / coupling device according to a fourth embodiment of the present invention has a structure similar to that of the third embodiment described above, as shown in FIG. The case of the simultaneous transmission of 1: 4, which is the case where the light from the end face of the side fiber is received by the end face of the four light receiving side fibers, will be described.

In the fourth embodiment, the first light receiving fiber 18a and the fourth light receiving fiber 18b of the first light receiving fiber 18a to the fourth light receiving fiber 18d are used.
Is 50 cm in length l ₃₁ , and the third light receiving side fiber 18
c, The fourth light receiving side fiber 18d has a length l ₃₀ of 30 cm.

In the second embodiment, of the first light-receiving fiber 18a to the fourth light-receiving fiber 18d, the fourth
The fourth light-receiving fiber 18d disposed closest to the end face of the emission fiber 16d has an end face in the lateral direction relative to the light-emitting surface of the fourth emission fiber 16d.
It is arranged at a position of 53 degrees (= α ₁ degree) and 0 degrees (= β ₁ degree) in the vertical direction.

Further, of the first light-receiving fiber 18a to the fourth light-receiving fiber 18d, the fourth light-emitting fiber 16d
The end face of the first light-receiving fiber 18a disposed farthest from the end face of the fourth light-emitting fiber 16d is 0 ° (= α ₁ °) in the horizontal direction relative to the light-emitting surface of the fourth emission-side fiber 16d, and the vertical direction. It is arranged at a position of 0 degrees (= beta ₁ degree) to.

Therefore, the signal propagation delay difference ΔT _{M: N} is equal to (3
From the equation (2), it is 1.0 × 10 ⁻⁹ (m / s). (However, the light speed c is 3.0 × 10 ⁸ m / s) That is, the driving frequency (frequency of the signal light) X is 500 MHz.
In the case of z, 1 / X ・ 1/2 = 1 × 10 ⁻⁹ (sec), and the signal propagation delay difference ΔT _{M: N} is the same value. Therefore, from the above equation (4), the signal light Thus, there is provided an optical branching / coupling device which does not cause a signal transmission failure such as a rounding of a signal waveform caused by the mode dispersion and a bad effect on high speed operation.

It is to be noted that all the numerical values in the first to fourth embodiments are examples, and the present invention provides a condition value which satisfies any of the above expressions (1) to (4). The values are not limited to these values.

[0153]

As described above, according to the first to eighth aspects of the present invention, the signal waveform does not become rounded due to the mode dispersion of the signal light. There is an effect that good diffusion transmission of signal light is possible without causing problems such as adverse effects.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view for explaining the concept of claims 1 and 2 of the present invention, FIG. 1 (A) is a perspective explanatory view,
FIG. 1B is a top view explanatory view, and FIG. 1C is a view seen from the side.

FIG. 2A is an explanatory diagram for explaining a horizontal spread angle of signal light, and FIG. 2B is an explanatory diagram for explaining a vertical spread angle of signal light.

FIG. 3 is a schematic explanatory view for explaining the concept of claim 3 of the present invention, FIG. 3 (A) is a perspective explanatory view, FIG. 3 (B) is a top explanatory view, and FIG. Is an explanatory diagram viewed from the side.

FIG. 4 is a schematic explanatory view for explaining the concept of claims 3 and 4 of the present invention, and FIG. 4 (A) is a perspective explanatory view;
FIG. 4B is a top view explanatory view, and FIG. 4C is a view seen from the side.

5 is another schematic explanatory view for explaining the concept of claim 3 and claim 4 of the present invention, FIG. 5 (A) is a perspective explanatory view, and FIG. 5 (B) is a top explanatory view. FIG. 5C is an explanatory diagram viewed from the side.

6 is a schematic explanatory view for explaining the concept of claim 5 and claim 6 of the present invention, FIG. 6 (A) is a perspective explanatory view,
FIG. 6B is a top view explanatory view, and FIG. 6C is a view seen from the side.

7 is another schematic explanatory view for explaining the concept of claims 5 and 6 of the present invention, FIG. 7 (A) is a perspective explanatory view, and FIG. 7 (B) is a top explanatory view. FIG. 7C is an explanatory diagram viewed from the side.

8 is still another schematic explanatory view for explaining the concept of claims 5 and 6 of the present invention, FIG. 8 (A) is a perspective explanatory view, and FIG. 8 (B) is a top explanatory view. Yes, FIG. 8 (C)
Is an explanatory diagram viewed from the side.

FIG. 9 is a schematic explanatory view for explaining the concept of claims 7 and 8 of the present invention, and FIG. 9 (A) is a perspective explanatory view;
FIG. 9B is a top view explanatory view, and FIG. 9C is a view seen from the side.

FIG. 10A is a perspective view showing a schematic configuration of an optical branching / coupling device according to the first embodiment of the present invention.
10B is a top view of FIG. 10A, and FIG. 10C is a view of FIG. 10A as viewed from the side.

FIG. 11A is a perspective view showing a schematic configuration of an optical branching / coupling device according to a second embodiment of the present invention.
11B is a top view of FIG. 11A, and FIG. 11C is a view of FIG. 11A as viewed from the side.

FIG. 12A is a perspective view showing a schematic configuration of an optical branching / coupling device according to a third embodiment of the present invention.
12B is a top view of FIG. 12A, and FIG. 12C is a view of FIG. 12A as viewed from the side.

FIG. 13A is a perspective view showing a schematic configuration of an optical branching / coupling device according to a fourth embodiment of the present invention.
13B is a top view of FIG. 13A, and FIG. 13C is a view of FIG. 13A as viewed from the side.

[Explanation of symbols]

 10a to 10d Laser diode 12 Optical transmission unit 14a to 14d Photodiode 16a to 16d Emitting fiber 18a to 18d Light receiving fiber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidenori Yamada 430 Nakai-cho, Nakai-machi, Ashigarashimo-gun, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Within (72) Inventor Nori Takanashi 430 Nakai-cho, Nakai-machi, Ashigara-gun, Kanagawa Prefecture Inside Fuji Xerox Fuji Xerox Co., Ltd. Shinya Kyozuka 430 Nakai-cho, Nakai-cho, Ashigara-gun, Kanagawa Prefecture Inside Green Tech Fuji Xerox Co., Ltd. Person Masao Funada 430 Sakai Nakaicho, Ashigara-gun, Kanagawa Prefecture Green Tech Inside Fuji Xerox Co., Ltd. F term (reference) 5F089 AA01 AB03 AC07 AC16 AC17 CA12

Claims (8)

[Claims] At least one signal light emitting means for emitting signal light having a predetermined divergence angle, and optical transmission for transmitting the signal light having a predetermined divergence angle emitted from the signal light emitting means via an optical waveguide. Medium, and at least one signal light receiving means for receiving the signal light transmitted by the optical transmission medium, the propagation time of the signal light having propagated the longest propagation distance of the signal light propagating through the optical waveguide And a signal propagation delay difference that is a difference between a propagation time of the signal light propagating the shortest propagation distance of the signal light propagating through the optical waveguide is shorter than one cycle of the frequency of the signal light. The signal light emitting means,
An optical branching / coupling device, wherein an arrangement of the optical transmission medium and the signal light receiving unit and materials of the signal light emitting unit and the optical transmission medium are determined. 2. A light emitting portion of the signal light emitting device and a light receiving portion of the signal light receiving device are disposed opposite to each other on a surface facing the optical transmission medium. The light emitting unit emits light having a divergence angle of 2r ₁ degrees in the horizontal direction and 2r ₂ degrees in the vertical direction, and the signal light receiving unit is arranged so that α is relatively α with respect to the light emitting unit of the signal light emitting unit. Degrees, and is disposed at a position of β degrees in the vertical direction. The length of the optical transmission medium is 1, the refractive index is n, and the critical angle is θc.
The optical branching / coupling device according to claim 1, wherein the following expression (1) is satisfied when r ₁ ≦ π / 2−θc and r ₂ ≦ π / 2−θc. (Equation 1) (However, X is the frequency of the signal light, c is the speed of light, r ₁ ≧ α, and r ₂ ≧ β) 3. At least one of the signal light emitting means and the signal light receiving means is provided in a plurality, and when transmitting the signal light simultaneously, the longest propagation distance of the signal light propagating in the optical waveguide is determined. The signal propagation delay difference, which is the difference between the propagation time of the propagated signal light and the propagation time of the signal light that has propagated the shortest propagation distance of the signal light propagating in the optical waveguide, is 1/1 of the frequency of the signal light. The arrangement of the signal light emitting means, the optical transmission medium, and the signal light receiving means, and the materials of the signal light emitting means and the optical transmission medium are determined so as to be shorter than two periods. The optical branching and coupling device according to claim 1. 4. The signal light emitting means for delivering the signal light propagating over the longest propagation distance and the signal light receiving means, wherein the signal light receiving means is provided with respect to a light emitting portion of the signal light emitting means. The light receiving section is relatively installed at a position of α ₁ degrees in the horizontal direction, and β ₁ degrees in the vertical direction, and the signal light emitting means and the signal for transferring the signal light propagating over the shortest propagation distance In the light receiving unit, the light receiving unit of the signal light receiving unit is disposed at a position of α ₂ degrees in the horizontal direction and β ₂ degrees in the vertical direction relative to the light emitting unit of the signal light emitting unit. The optical branching / coupling device according to claim 3, wherein the following expression (2) is satisfied. (Equation 2) (However, X is the frequency of the signal light, c is the speed of light) 5. An optical fiber which is provided between said signal light emitting means and said optical transmission medium and at least one between said optical transmission medium and said signal light receiving means and propagates signal light. The signal light emitting means, the optical transmission medium, the signal light receiving means, and the arrangement of the optical fiber; and the signal so that the signal propagation delay difference is shorter than one cycle of the frequency of the signal light. 2. The optical branching / coupling device according to claim 1, wherein the materials of the light emitting means and the optical transmission medium, and the length, the refractive index, and the numerical aperture of the optical fiber are determined. 6. An end face of an input optical fiber provided between said signal light emitting means and said optical transmission medium, and an output light provided between said optical transmission medium and said signal light receiving means. The end face of the fiber is disposed to face the opposing face of the optical transmission medium, and the end face of the output side optical fiber is α degrees in the lateral direction relatively to the end face of the input side optical fiber, and It is installed at a position of β degrees in the vertical direction, the length of the input side optical fiber is l ₁₀ , the refractive index is n ₁₀ , the numerical aperture is NA ₁₀ , the critical angle is θc _10, and the length of the optical transmission medium is l _20, a refractive index n _20, NA ₂₀ and the numerical aperture of the critical angle and .theta.c _{2 0,} the length of the output optical fiber l _30, a refractive index n _30, NA ₃₀ the numerical aperture, the critical the angular and .theta.c _30, when to satisfy the relation _{NA 10 = NA 30 ≦ NA 20} , the following equation (3) Claim 5, characterized in that satisfies
3. The optical branching / coupling device according to 1. (Equation 3) (However, X is the frequency of the signal light, c is the speed of light) 7. When at least one of the input side optical fiber and the output side optical fiber is provided in a plurality and the signal light is transmitted simultaneously, the longest propagation distance of the signal light propagating in the optical waveguide is determined. The signal propagation delay difference, which is the difference between the propagation time of the propagated signal light and the propagation time of the signal light that has propagated the shortest propagation distance of the signal light propagating in the optical waveguide, is 1/1 of the frequency of the signal light. The arrangement of the signal light emitting means, the optical transmission medium, the signal light receiving means, and the optical fiber, the material of the signal light emitting means and the optical transmission medium, and the light 7. The fiber according to claim 5, wherein a length, a refractive index, and a numerical aperture of the fiber are determined.
3. The optical branching / coupling device according to 1. 8. A signal light propagating through the longest propagation distance
The end face of the input side optical fiber to be transferred and the output side optical fiber
And the end face of the input side optical fiber.
On the other hand, the end face of the output side optical fiber
₁Degrees and β in the vertical direction₁Degrees, and the input and output signal light that propagates the shortest propagation distance
The power-side optical fiber and the output-side optical fiber,
Of the output side optical fiber with respect to the end face of the input side optical fiber.
The end face is relatively laterally α_TwoDegrees and β in the vertical direction_TwoDegree
When installed at a position, the input side that emits signal light that propagates the longest propagation distance
The length of the optical fiber is l _Ten, The refractive index n_Ten, NA
_Ten= Sin θ_Ten, The critical angle θc_TenAnd an input side for emitting a signal light propagating through the shortest propagation distance.
The length of the optical fiber is l ₁₁, The refractive index n₁₁, NA
₁₁= Sin θ₁₁, The critical angle θc₁₁And the length of the optical transmission medium is l₂₀, The refractive index n₂₀, Numerical aperture
NA₂₀, The critical angle θc_{Two 0}And an output side for receiving signal light propagating through the longest propagation distance.
The length of the optical fiber is l ₃₀, The refractive index n₃₀, NA
₃₀= Sin θ₃₀, The critical angle θc₃₀And an output side for receiving the signal light propagating over the shortest propagation distance.
The length of the optical fiber is l ₃₁, The refractive index n₃₁, NA
₃₁= Sin θ₃₁, The critical angle θc₃₁And the following
8. The light according to claim 7, wherein the expression (4) is satisfied.
Branch coupling device. (Equation 4)(However, X is the frequency of the signal light, c is the speed of light)