JP2009192703A - Optical transmitter and optical path adjustment method thereof - Google Patents

Abstract

An optical transmitter capable of simplifying the alignment process to shorten the process time and correcting an excessive loss generated during mounting and an optical path adjustment method therefor are provided.
An optical transmitter is provided with an optical path adjuster that adjusts the optical path of laser light emitted from an LD chip, and the LD chip, the lens, the optical path adjuster, and the optical fiber are each optically coupled. The optical path of the laser beam is adjusted by the optical path adjuster 7 so that the optical coupling of the laser beam to the optical fiber 1 is maximized after being arranged so that the target center is substantially straight and fixed to the package 3. The
[Selection] Figure 1

Description

  The present invention relates to an optical transmitter and an optical path adjustment method thereof.

  FIG. 10 shows a configuration diagram of a conventional optical transmitter. As shown in FIG. 10, the optical transmitter includes an optical fiber 51, a fiber collar 52, a laser diode (hereinafter abbreviated as LD) module 59 (package 53, lens 54, LD chip 55, submount 56), and the like. Has been. With reference to the optical transmitter shown in FIG. 10, the conventional mounting method of the LD module 59 and the optical fiber 51 used for the conventional optical transmitter (active alignment, see Non-Patent Document 1) will be described below. Explained.

  First, fixing is performed so that the center of the LD chip 55 mounted on the submount 56 and the center of the lens 54 are substantially in the middle of the package opening 58. Next, in a state where the LD chip 55 is energized and emits light, the optical fiber 51 is moved three-dimensionally, and alignment is performed by matching the point where the optical power meter 57 shows the maximum value. Then, the fiber collar 52 and the optical fiber 51, and the fiber collar 52 and the package 53 are fixed by Yttrium Aluminum Garnet pulse laser welding (hereinafter abbreviated as YAG welding). The LD module 59 is mounted (alignment) by such a method.

Atsushi Takai et al., "800Mbit / s / ch x 12ch, True DC-Coupled paralle1 0ptical Interconnects Using Single-Mode Fiber and 1310 nm LD Array", 2000 Electronic Components and Technology Conference, 2000, pp.491-496 Koichiro Nakamura, Masahiro Kajiura, Kazuo Fujiura, “Wide-angle and low-voltage KTN optical beam scanner based on a new operating principle”, 67th JSAP Scientific Lecture, 31a-ZX-4, pp.1087

  In an optical transmitter used in an optical communication system, an important point in mounting (alignment) of the LD module is that the laser light from the LD is optically coupled to the optical fiber with high loss, and Two points are that this mounting process is simplified and the process time is shortened.

  However, the above mounting method has a problem that a relatively long process time of about 20 to 30 minutes is required for alignment because the optical fiber is moved three-dimensionally during alignment. Therefore, even if the aligning device is moved all day, only 50 to 80 aligning units can be aligned. In addition, when the optical fiber is fixed, when the metal melted by YAG welding is cooled and solidified, the optical fiber is slightly shifted from the alignment position (referred to as PWS), resulting in an excessive loss.

  As described above, in the conventional optical transmitter, there is a problem that excessive loss due to PWS occurs in the assembly process of fixing the optical fiber by YAG welding. In addition, since the lens and the optical fiber are fixed by YAG welding, it was not possible to correct the slight shift. In addition, since active alignment is a three-dimensional alignment method, there is a problem that the mounting process time is long.

  The present invention has been made in view of the above problems, and provides an optical transmitter capable of simplifying the alignment process to shorten the process time and correcting excess loss generated during mounting, and an optical path adjustment method thereof. The purpose is to do.

FIG. 1 illustrates an example of the configuration of an optical transmitter according to the present invention.
The optical transmitter according to the present invention includes an optical fiber 1 (optical transmission means), a fiber collar 2, an LD module 9, and the like. The optical fiber 1 is a package opening of a package 3 serving as a casing of the LD module 9. The fiber collar 2 is fixed around the portion 8. Further, inside the package 3 of the LD module 9, a lens 4 (light condensing means) arranged facing the package opening 8 and a lens 4 are arranged, facing the package 3 via the submount 6. A fixed LD chip 5 (light emitting means) is provided.

  In the optical transmitter according to the present invention, at least one optical path adjuster 7 (optical path adjusting means) is inserted between the LD chip 5 and the lens 4, and the laser from the LD chip 5 incident on the optical fiber 1. By adjusting the optical path of light with the optical path adjuster 7, the alignment process between the optical fiber 1 and the LD chip 5 is simplified, and the excess loss caused by PWS is corrected. The optical path adjuster 7 may be inserted not only between the LD chip 5 and the lens 4 but also between the optical fiber 1 and the lens 4. The optical path of the laser beam may be adjusted using a plurality of optical path adjusters 7 provided for each adjustment direction axis.

  The optical path adjuster 7 is constituted by, for example, a MEMS (Micro Electro Mechanical Systems) element made of a semiconductor material having a band gap energy of 1.0 eV or more at room temperature, or a light beam scanner made of an electro-optic element, and by applying a voltage. It has a function of scanning the optical path of the laser light from the LD chip 5 by about 0 to 100 μm. Therefore, if the three components of the LD chip 5, the lens 4, and the optical fiber 1 are fixed with an accuracy of 100 μm or less with respect to the optical axis of the LD module 9 itself, the optical path adjustment is performed so that the optical coupling efficiency is maximized. It becomes possible.

  In an ordinary LD module assembly apparatus, the LD chip 5 can be mounted with an accuracy of −20 μm or more and +20 μm or less, and the processing accuracy of the members of the LD module 9 such as the package 3, the lens 4 and the optical fiber 1 is also −50 μm or more and +50 μm or less. By applying an appropriate voltage to the optical path adjuster 7 after the passive alignment process based on the processing accuracy of the member, an optical coupling efficiency equal to or higher than that of active alignment can be achieved. Further, by driving the optical path adjuster 7 after fixing each member, it is possible to correct excess loss due to a slight positional deviation during the fixing process such as PWS. As a result, the TAT (Turn-around time) of the active alignment process between the LD chip 5 and the optical fiber 1 in the LD module 9 and the occurrence of excessive loss can be avoided, and the economic efficiency and performance of the optical transmitter. Improvement is possible.

  Therefore, the optical transmitter and the optical path adjusting method according to the present invention are characterized as follows.

An optical transmitter according to a first invention for solving the above-mentioned problems is as follows.
One laser beam emitting means for emitting the laser beam;
One condensing means for condensing the laser light emitted from the laser light emitting means;
At least one optical path adjusting means for adjusting the optical path of the laser light emitted from the laser light emitting means or the laser light condensed by the condensing means;
One optical transmission means for transmitting the laser light whose optical path is adjusted by the optical path adjustment means,
After the laser light emitting means, the condensing means, the optical path adjusting means, and the optical transmission means are arranged so that their optical centers are substantially in a straight line and fixed to a housing, the optical transmission means The optical path of the laser beam is adjusted by the optical path adjusting means so that the optical coupling of the laser beam to the laser beam becomes maximum.

An optical transmitter according to a second invention for solving the above-mentioned problems is as follows.
One laser beam emitting means for emitting the laser beam;
One condensing means for condensing the laser light emitted from the laser light emitting means;
At least one optical path adjusting means for adjusting the optical path of the laser light emitted from the laser light emitting means or the laser light condensed by the condensing means;
Having a plurality of sets of one optical transmission means for transmitting the laser light whose optical path is adjusted by the optical path adjustment means,
In each set, after the laser light emitting means, the condensing means, the optical path adjusting means, and the optical transmission means are arranged so that their optical centers are substantially in a straight line and fixed to the housing, The optical path of the laser beam is adjusted by the optical path adjusting unit so that the optical coupling of the laser beam to the optical transmission unit is maximized.

An optical transmitter according to a third invention for solving the above-mentioned problem is as follows.
In the optical transmitter according to the first or second invention,
The optical path adjusting means is configured to adjust the optical path of the laser light by applying a voltage.

An optical transmitter according to a fourth invention for solving the above-mentioned problems is as follows.
In the optical transmitter according to the third invention,
The optical path adjusting means is a MEMS (Micro Electro Mechanical Systems) element made of silicon oxide or a semiconductor material having a band gap energy of 1.0 eV or more at room temperature.

An optical transmitter according to a fifth invention for solving the above-mentioned problem is as follows.
In the optical transmitter according to the fourth invention,
The semiconductor material of the MEMS element is composed of a III-V group compound composed of at least two kinds of elements of silicon or aluminum, gallium, indium, arsenic, phosphorus, and antimony.

An optical transmitter according to a sixth invention for solving the above-mentioned problems is as follows.
In the optical transmitter according to the third invention,
The optical path adjusting means is a light beam scanner made of an electro-optic crystal.

An optical transmitter according to a seventh invention for solving the above-described problem is as follows.
In the optical transmitter according to the sixth invention,
The electro-optic crystal of the light beam scanner is composed of at least two elements selected from lithium, potassium, tantalum, niobium, and oxygen.

An optical path adjustment method for an optical transmitter according to an eighth invention for solving the above-described problems is as follows.
Laser light emitting means for emitting laser light;
Condensing means for condensing the laser light emitted from the laser light emitting means;
At least one optical path adjusting means for adjusting the optical path of the laser light emitted from the laser light emitting means or the laser light condensed by the condensing means;
An optical path adjustment method for an optical transmitter, comprising: an optical transmission unit configured to transmit the laser light whose optical path is adjusted by the optical path adjustment unit,
The laser light emitting means, the condensing means, the light transmission means, and the optical path adjusting means are arranged so that their optical centers are substantially in a straight line, and fixed to the housing,
Emitting laser light from the laser light emitting means,
Measure the intensity of the laser beam output from the optical transmission means,
The optical path of the laser beam is adjusted by the optical path adjusting unit so that the intensity of the laser beam output from the optical transmission unit is maximized.

An optical path adjustment method for an optical transmitter according to a ninth invention for solving the above-mentioned problems is as follows.
In the optical path adjustment method for an optical transmitter according to the eighth invention,
As the optical path adjusting means, one that adjusts the optical path of the laser beam by applying a voltage is used.

  According to the present invention, since the optical path adjuster is provided in the optical transmitter, the alignment process is simplified, the process time is shortened, and the excess loss generated during the mounting is corrected after the mounting, and finally It is possible to avoid the occurrence of excessive loss.

  Hereinafter, some specific embodiments of the present invention will be described with reference to the drawings. In addition, the Example shown below is an illustration of this invention and a various change is possible within the range which does not deviate from the main point of this invention.

<1. Configuration>
FIG. 2 is a configuration diagram illustrating the optical transmitter according to the present embodiment.
As shown in FIG. 2, the optical transmitter of the present embodiment is mainly composed of an optical fiber 11 (optical transmission means) for transmitting light, a fiber collar 12, an LD module 19, and the like. A fiber collar 12 is fixed around the package opening 18 of the package 13 serving as a housing of the LD module 19. Further, the LD module 19 is disposed inside the package 13 so as to face the package opening 18, and is arranged so as to face the lens 14 (light condensing means) for condensing light, and the submount 16. Through the LD chip 15 (laser emitting means) that emits laser light and is inserted between the LD chip 15 and the lens 14 and enters the optical fiber 11. An angle variable MEMS 17 (optical path adjusting means) for adjusting the optical path is provided.

Thus, in the optical transmitter of the present embodiment, the angle variable MEMS 17 is used as the optical path adjuster. The variable-angle MEMS 17 has a movable portion of 0.6 mm square, a movable range of −5 degrees to +5 degrees, and is made of silicon (Si) with a thickness of 150 μm. The MEMS element is composed of a semiconductor material or an oxide such as SiO _2, and it is effective that the semiconductor material has a band gap energy of 1.0 eV or more at room temperature. For example, a compound semiconductor containing at least two elements of silicon (Si) or aluminum (Al), gallium (Ga), indium (In), arsenic (As), phosphorus (P), and antimony (Sb) is preferable. It is.

<2. Principle of operation>
The principle by which excess loss caused by PWS can be corrected by the variable angle MEMS 17 will be described with reference to FIG. FIG. 3 shows an optical component extracted from the optical transmitter shown in FIG. 2 and an optical path of laser light from the LD chip 15 added. FIG. 3 shows a state in which excess loss has occurred due to PWS.

  In a state where no voltage is applied, the variable angle MEMS 17 is at a position perpendicular to the optical path, as indicated by a dotted square. For this reason, after passing through the angle variable MEMS 17 with respect to the optical path of the laser light from the LD chip 15, there is no change in the optical path as shown by the dotted line (there is no change in the vertical direction in FIG. 3). In this state, since the optical path is not adjusted, the laser beam cannot be optically coupled to the optical fiber 11.

  However, when a voltage is applied to the variable angle MEMS 17, the inclination of the variable angle MEMS 17 can be changed as indicated by a solid line. Then, as shown by the solid line, the optical path of the laser beam slides (slids up and down in FIG. 3) after passing through the angle variable MEMS 17 due to the refractive index difference between the MEMS portion and the space system. Is optically coupled to the optical fiber 11. Therefore, it is possible to correct excess loss caused by PWS. In addition, even if a certain amount of deviation occurs in the alignment process, it can be corrected by the angle variable MEMS 17, so that the alignment process can be simplified.

<3. Assembly process>
The assembly process of the optical transmitter of the present embodiment will be described with reference to FIG.

First, the LD chip 15 is mounted on the submount 16.
Next, the optical center of the LD chip 15 on the submount 16, the optical center of the angle variable MEMS 17, and the optical center of the lens 14 are substantially aligned with the center of the package opening 18. , Mounted and fixed in the package 13 with an accuracy of -15 μm or more and +15 μm or less.
Then, the angle variable MEMS 17 and the package 13 and the LD chip 15 and the package 13 are connected by wire bonding.
Finally, the optical fiber 11 and the fiber collar 12, the fiber collar 12 and the package 13 are fixed in this order by YAG welding with an accuracy of −15 μm or more and +15 μm or less so that the optical fiber 11 is substantially at the center of the package opening 18. . That is, the optical center of the LD chip 15, the optical center of the variable angle MEMS 17, the optical center of the lens 14, and the optical center of the optical fiber 11 are arranged and fixed so as to be substantially in a straight line. .
Through the above steps, an optical transmitter as shown in FIG. 2 is completed.

<4. Adjustment using optical path adjuster>
The optical transmitter is completed by the above assembly process, but the optical path may be shifted in this state. Therefore, the angle variable MEMS 17 is used to optically couple the laser light to the optical fiber 11. An experimental system for adjusting the optical path in this embodiment is shown in FIG. In this experimental system, an optical power meter 30 is connected to the optical fiber 11 of the completed optical transmitter, and a constant voltage source 20 is connected to each terminal of the angle variable MEMS 17.

  First, a bias current of 30 mA is passed through the LD chip 15, the optical output from the LD chip 15 is set to +3 dBm, and the output power from the optical fiber 11 when no voltage is applied to the terminal of the angle variable MEMS 17 is output by the optical power meter 30. taking measurement. At this time, the optical output from the optical fiber 11 was −10 dBm.

  Next, without changing the bias current of the LD chip 15, a voltage is applied from the constant voltage source 20 to each of the angle change terminals of the angle variable MEMS 17 in the x direction and the angle change in the y direction, so that the optical power meter 30 reaches the maximum. Adjust the voltage to indicate the value. As an optical path adjustment method, since the angle of the angle variable MEMS 17 changes linearly with respect to the applied voltage, first, the x-axis voltage is gradually applied, and the optical power meter 30 shows the maximum value. Gradually applies the y-axis voltage. When the optical power meter 30 shows the maximum value, the x-axis voltage is applied. When this operation is repeated and the value of the optical power meter 30 does not increase, the optical coupling to the optical fiber 11 is maximized, and the optical path adjustment is completed.

  As a result of applying a voltage of 10 V to the x-axis adjustment terminal and 7 V to the y-axis adjustment terminal, the light output from the optical fiber 11 could be improved to +2 dBm. From this result, it was shown that the optical path can be adjusted by the present invention even after the mounting is completed. From the above, it has been shown that the present invention can simplify the active alignment process between the LD and the optical fiber. Also, the process time can be shortened by simplifying the active alignment process.

  As described above, in the present invention, since the optical path can be adjusted after the completion of mounting, even if the excess loss is increased by YAG welding after the alignment is performed by the active alignment process, the excess loss can be reduced by the present invention. In the end, excessive losses can be avoided.

  In the optical transmitter of this embodiment, the variable angle MEMS 17 is disposed between the LD chip 15 and the lens 14, but may be disposed between the optical fiber 11 and the lens 14. Further, in the optical transmitter of the present embodiment, the optical path adjustment in the x-axis direction and the y-axis direction is performed using one angle variable MEMS 17. For example, two angle variable MEMS are used independently of each other. The optical path adjustment in the x-axis direction and the y-axis direction may be performed.

  In addition, the optical transmitter of the present embodiment can also function as an optical attenuator by changing the optical coupling efficiency by controlling the voltage applied to the angle variable MEMS 17.

<1. Configuration>
FIG. 5 is a configuration diagram illustrating the optical transmitter according to the present embodiment.
As shown in FIG. 5, the optical transmitter of the present embodiment mainly includes an optical fiber 21 (optical transmission means) that transmits light, a fiber collar 22, an LD module 29, and the like. A fiber collar 22 is fixed around the package opening 28 of the package 23 serving as a housing of the LD module 29. In addition, the LD module 29 is disposed inside the package 23 so as to face the package opening 28, and is arranged so as to face the lens 24 (light condensing means) for condensing light and the lens 24. And is inserted between the LD chip 25 (laser light emitting means) that emits laser light and the package opening 28 (optical fiber 21) and the lens 24, passes through the lens 24, A light beam scanner 27 (optical path adjusting means) for adjusting the optical path of the laser light from the LD chip 25 incident on the optical fiber 21 is provided.

  As described above, in the optical transmitter according to the present embodiment, the light beam scanner 27 is used as the optical path adjuster. As the light beam scanner 27, for example, an electro-optic crystal such as a KTN crystal can be applied. The KTN crystal is an optical crystal composed of potassium (K), tantalum (Ta), niobium (Nb), and oxygen (O). In this embodiment, a KTN crystal is used. However, any electro-optic crystal may be used, and at least two of lithium (Li), potassium (K), tantalum (Ta), niobium (Nb) and oxygen (O). Those composed of two or more elements are preferred. For example, lithium niobate (LN) crystal, lithium tantalate (LT) crystal, or the like may be used.

<2. Principle of operation>
The principle that the optical beam scanner 27 can correct excess loss due to PWS will be described with reference to FIG. FIG. 6 shows an optical component extracted from the optical transmitter shown in FIG. 5 and an optical path of laser light from the LD chip 25 added. FIG. 6 shows a state in which excess loss has occurred due to PWS.

  When no electric field is applied to the light beam scanner 27, the light path of the laser beam from the LD chip 25 does not change after passing through the light beam scanner 27 as shown by the dotted line (FIG. 6). There is no change in the vertical direction inside). In this state, since the optical path is not adjusted, the laser beam cannot be optically coupled to the optical fiber 21.

  However, when an electric field is applied to the light beam scanner 27, the optical path of the laser beam can be bent in proportion to the direction and intensity of application of the electric field. Then, as shown by the solid line, the optical path of the laser light passing through the light beam scanner 27 can be changed, so that the laser light is optically coupled to the optical fiber 21 along the path shown by the solid line in the figure. It will be. Therefore, it is possible to correct excess loss caused by PWS. Further, even if a deviation occurs to some extent in the alignment process, it can be corrected by the light beam scanner 27, so that the alignment process can be simplified.

<3. Assembly process>
The assembly process of the optical transmitter of the present embodiment will be described with reference to FIG.

First, the LD chip 25 is mounted on the submount 26.
Next, the optical center of the LD chip 25 on the submount 26, the optical center of the light beam scanner 27, and the optical center of the lens 24 are substantially aligned with the center of the package opening 28. And mounted in the package 23 with an accuracy of −15 μm to +15 μm.
Then, the light beam scanner 27 and the package 23 and the LD chip 25 and the package 23 are connected by wire bonding.
Finally, the optical fiber 21 and the fiber collar 22 and the fiber collar 22 and the package 23 are fixed in this order by YAG welding with an accuracy of −15 μm or more and +15 μm or less so that the optical fiber 21 is substantially at the center of the package opening 28. . That is, the optical center of the LD chip 25, the optical center of the light beam scanner 27, the optical center of the lens 24, and the optical center of the optical fiber 21 are arranged and fixed so as to be substantially in a straight line. Yes.
Through the above steps, an optical transmitter as shown in FIG. 5 is completed.

<4. Adjustment using optical path adjuster>
The optical transmitter is completed by the above assembly process, but the optical path may be shifted in this state. Therefore, a laser beam is optically coupled to the optical fiber 21 using the light beam scanner 27. An experimental system for optical path adjustment in the present embodiment is shown in FIG. In this experimental system, an optical power meter 30 is connected to the optical fiber 21 of the completed optical transmitter, and a constant voltage source 20 is connected to a terminal of the light beam scanner 27. The distance from the light beam scanner 27 to the incident end of the optical fiber 21 is 2 mm.

  First, a bias current of 30 mA is supplied to the LD chip 25, the light output from the LD chip 25 is set to +3 dBm, and the output power from the optical fiber 21 when no voltage is applied to the terminal of the light beam scanner 27 is the optical power meter 30. Measure with At this time, the light output from the optical fiber 21 was −15 dBm.

  Next, without changing the bias current of the LD chip 25, an electric field is applied in the x and y directions of the light beam scanner 27, and the optical power meter 30 adjusts the voltage to a maximum value. As an optical path adjustment method, the angle at which the optical path of the laser beam bends linearly changes with respect to the applied voltage. First, when the voltage in the x-axis direction is gradually applied and the optical power meter 30 shows the maximum value, Next, the voltage in the y direction is gradually applied. When the optical power meter 30 shows the maximum value, a voltage in the x direction is applied. When this operation is repeated and the value of the optical power meter 30 does not increase, the optical coupling to the optical fiber 21 is maximized, and the optical path adjustment is completed.

  When the KTN crystal is the light beam scanner 27, the relationship between the voltage V and the deflection angle θ is expressed as θ = f (V), and the deflection angle θ monotonously increases with respect to the voltage V (see Non-Patent Document 2). . In this embodiment, the deviation is 40 μm in the x-axis direction and 25 μm in the y-axis direction, so that the deflection angle required to match the incident end of the optical fiber 21 is 20 mrad in the x direction and 12.5 mrad in the y direction. Assuming that the correction voltages required at this time are Vx and Vy, respectively, as a result of applying a voltage of Vx [V] to the x-axis adjustment terminal and Vy [V] to the y-axis adjustment terminal, the light output from the optical fiber 21 Was improved to +1.5 dBm. From this result, it was shown that the optical path can be adjusted by the present invention even after the mounting is completed. From the above, it has been shown that the present invention can simplify the active alignment process between the LD and the optical fiber. Also, the process time can be shortened by simplifying the active alignment process.

  As described above, in the present invention, since the optical path can be adjusted after the completion of mounting, even if the excess loss is increased by YAG welding after the alignment is performed by the active alignment process, the excess loss can be reduced by the present invention. In the end, excessive losses can be avoided.

  In the optical transmitter of this embodiment, the light beam scanner 27 is disposed between the optical fiber 21 and the lens 24, but may be disposed between the LD chip 25 and the lens 24. In the optical transmitter of this embodiment, the optical path adjustment in the x-axis direction and the y-axis direction is performed using one optical beam scanner 27. For example, two optical beam scanners are used, and each is independent. Then, the optical path adjustment in the x-axis direction and the y-axis direction may be performed.

  In addition, the optical transmitter of the present embodiment changes the optical coupling efficiency by controlling the voltage applied to the light beam scanner 27 (increasing or decreasing the voltage applied to each adjustment terminal from the correction voltages Vx and Vy), It is also possible to function as a variable optical attenuator.

<1. Configuration>
FIG. 8 is a configuration diagram illustrating the optical transmitter according to the present embodiment.
As shown in FIG. 8, the optical transmitter of the present embodiment includes an optical multiplexer 31 (hereinafter referred to as an optical multiplexer 31) that multiplexes light transmitted through a plurality of optical waveguides (optical transmission means) inside a package 36 serving as a housing. (Referred to as AWG), a microlens array 32 composed of a plurality of microlenses (condensing means), a MEMS array 33 composed of a plurality of angle variable MEMS (optical path adjusting means), and a submount 35 to be fixed to the package 36, A laser array 34 composed of a plurality of LDs (laser beam emitting means) is provided. In the present embodiment, as in the first embodiment, an angle variable MEMS is used as the optical path adjuster. Instead of the variable angle MEMS, a light beam scanner may be used as in the second embodiment.

<2. Principle of operation>
In the present embodiment, a plurality of LDs are arranged in an array, and the AWG 31 on the light receiving side is also composed of a plurality of optical waveguides instead of optical fibers. However, since the angle variable MEMS, the microlens, and the optical waveguide correspond 1: 1 with respect to one channel of the LD, the principle of optical path adjustment using the angle variable MEMS is described in the first embodiment. This is the same as the operation principle described. Therefore, detailed description thereof is omitted here.

<3. Assembly process>
The assembly process of the optical transmitter of the present embodiment will be described with reference to FIG. The laser array 34 used in this example has a channel interval of 400 μm and a channel number of 5 channels. The optical waveguide diameter of the AWG 31 is 12.5 μm, which is the same as that of the single mode optical fiber, and the optical waveguide interval is 400 μm, which is the same as that of the laser array 34.

First, the laser array 34 is mounted on the submount 35.
Next, the optical center of each channel of the laser array 34 on the submount 35, the optical center of each angle variable MEMS of the MEMS array 33, and the optical center of each microlens of the microlens array 32 are substantially aligned. In such a manner, it is mounted and fixed in the package 36 with an accuracy of −15 μm to +15 μm.
Then, the MEMS array 33 and the package 36 and the laser array 34 and the package 36 are connected by wire bonding.
Finally, the optical center of each channel of the AWG 31 is −15 μm so that it is on the extension of the line connecting the optical center of each channel of the laser array 34 and the optical center of each microlens of the microlens array 32. It is fixed with an adhesive with an accuracy of +15 μm or less. That is, the optical center of each channel of the laser array 34, the optical center of each angle variable MEMS of the MEMS array 33, the optical center of each microlens of the microlens array 32, and the optical center of each channel of the AWG 31 Are arranged and fixed so as to be substantially in a straight line.
Through the above steps, an optical transmitter as shown in FIG. 8 is completed.

<4. Adjustment using optical path adjuster>
The optical transmitter is completed by the above assembly process, but the optical path may be shifted in this state. Therefore, each angle variable MEMS of the MEMS array 33 is used to optically couple the laser light from each channel of the laser array 34 to each channel of the AWG 31. An experimental system for adjusting the optical path in this embodiment is shown in FIG. In this experimental system, an optical power meter 37 is placed on the output side of the AWG 31 of the completed optical transmitter, and a constant voltage source 38 is connected to a terminal of the MEMS array 33. In FIG. 9, only the electrical wiring for the angle variable MEMS for one channel of the MEMS array 33 is shown.

  First, a bias current of 30 mA is passed through the uppermost channel 1 of the laser array 34, the optical output from the LD chip 39 is set to +3 dBm, and the voltage from the output end of the AWG 31 is not applied to the terminals of the MEMS array 33. Optical power Measured with an optical power meter 37. At this time, the optical output from the output end of the AWG 31 was −30 dBm.

  Next, in the angle variable MEMS for one channel of the MEMS array 33, without changing the bias current of the LD chip 39, a voltage is applied to each of the angle change terminal in the x direction and the angle change in the y direction, and the optical power The meter 37 adjusts the voltage to the maximum value. As an optical path adjustment method, the angle of the variable angle MEMS changes linearly with respect to the applied voltage. First, when the x-axis voltage is gradually applied and the optical power meter 37 shows the maximum value, Gradually applies the y-axis voltage. When the optical power meter 37 shows the maximum value, an x-axis voltage is applied. When this operation is repeated and the value of the optical power meter 37 does not increase, the optical coupling of the AWG 31 to the optical waveguide is maximized, and the optical path adjustment is completed.

  As a result of applying a voltage of 6V to the x-axis adjustment terminal and 15V to the y-axis adjustment terminal, the optical output from the output end of the AWG 31 could be improved to -4.0 dBm. Considering that the loss in the AWG 31 is about 4.5 dB, this result shows that the optical path adjustment can be performed by the present invention even after the mounting is completed.

  And the above optical path adjustment process was implemented similarly for every channel. As a result, the optical output from the output terminal of the AWG 31 is -23 dBm before adjustment in the channel 2, by applying a voltage of 13V to the x-axis adjustment terminal and 11V to the y-axis adjustment terminal. , And improved to -3.5 dBm. Further, in channel 3, what was -20 dBm before adjustment can be improved to -2.5 dBm by applying a voltage of 8 V to the x-axis adjustment terminal and 6 V to the y-axis adjustment terminal. Further, in channel 4, the voltage before adjustment was -24 dBm, but it was improved to -3.2 dBm by applying a voltage of 7 V to the x-axis adjustment terminal and 8 V to the y-axis adjustment terminal. Moreover, in channel 5, what was -28 dBm before adjustment can be improved to -3.8 dBm by applying a voltage of 11 V to the x-axis adjustment terminal and 13 V to the y-axis adjustment terminal (see Table 5). 1). From the above, it has been shown that the present invention can simplify the active alignment process between the laser array and the AWG. Also, the process time can be shortened by simplifying the active alignment process.

  As described above, in the present invention, since the optical path can be adjusted after the completion of mounting, even if the excess loss is increased by YAG welding after the alignment is performed by the active alignment process, the excess loss can be reduced by the present invention. In the end, excessive losses can be avoided.

  In the optical transmitter of this embodiment, the MEMS array 33 is disposed between the laser array 34 and the microlens array 32, but may be disposed between the AWG 31 and the microlens array 32. In the optical transmitter of this embodiment, the optical path adjustment in the x-axis direction and the y-axis direction is performed for one channel by using one angle variable MEMS. Then, two variable angle MEMS may be used, and the optical path adjustment in the x-axis direction and the y-axis direction may be performed independently.

  In addition, the optical transmitter of the present embodiment can also function as an optical attenuator by changing the optical coupling efficiency by controlling the voltage applied to the MEMS array.

  The present invention is suitable for an optical transmitter and an optical path adjusting method thereof, and can also function as an optical attenuator.

It is a block diagram of an example of the optical transmitter which concerns on this invention. It is a block diagram which shows the optical transmitter of Example 1, and makes the optical path regulator the angle change type MEMS. It is a figure explaining the principle of the optical path adjustment using angle change type MEMS. FIG. 3 is a diagram illustrating an experimental system for performing optical path adjustment in the optical transmitter illustrated in FIG. 2. It is a block diagram which shows the optical transmitter of Example 2, The optical path adjuster is used as the light beam scanner. It is a figure explaining the principle of the optical path adjustment using a light beam scanner. FIG. 5 is a diagram showing an experimental system for performing optical path adjustment in the optical transmitter shown in FIG. 4. It is a block diagram which shows the optical transmitter of Example 3, and uses a laser array and AWG, and makes the optical path adjuster the angle change type MEMS. FIG. 9 is a diagram illustrating an experimental system for performing optical path adjustment in the optical transmitter illustrated in FIG. 8. It is a block diagram of the conventional optical transmitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Fiber color 3 Package 4 Lens 5 LD chip 6 Submount 7 Optical path adjuster 8 Package opening 9 LD module

Claims (9)

One laser beam emitting means for emitting the laser beam;
One condensing means for condensing the laser light emitted from the laser light emitting means;
At least one optical path adjusting means for adjusting the optical path of the laser light emitted from the laser light emitting means or the laser light condensed by the condensing means;
One optical transmission means for transmitting the laser light whose optical path is adjusted by the optical path adjustment means,
After the laser light emitting means, the condensing means, the optical path adjusting means, and the optical transmission means are arranged so that their optical centers are substantially in a straight line and fixed to a housing, the optical transmission means An optical transmitter characterized in that the optical path of the laser beam is adjusted by the optical path adjusting means so that the optical coupling of the laser beam to the laser beam becomes maximum. One laser beam emitting means for emitting the laser beam;
One condensing means for condensing the laser light emitted from the laser light emitting means;
At least one optical path adjusting means for adjusting the optical path of the laser light emitted from the laser light emitting means or the laser light condensed by the condensing means;
Having a plurality of sets of one optical transmission means for transmitting the laser light whose optical path is adjusted by the optical path adjustment means,
In each set, after the laser light emitting means, the condensing means, the optical path adjusting means, and the optical transmission means are arranged so that their optical centers are substantially in a straight line and fixed to the housing, An optical transmitter characterized in that the optical path of the laser light is adjusted by the optical path adjusting means so that the optical coupling of the laser light to the optical transmission means is maximized. The optical transmitter according to claim 1 or 2,
An optical transmitter characterized in that the optical path adjusting means is configured to adjust the optical path of the laser light by applying a voltage. The optical transmitter according to claim 3.
An optical transmitter characterized in that the optical path adjusting means is a micro electro mechanical systems (MEMS) element made of silicon oxide or a semiconductor material having a band gap energy of 1.0 eV or more at room temperature. The optical transmitter according to claim 4, wherein
An optical transmitter characterized in that the semiconductor material of the MEMS element is composed of a III-V group compound composed of at least two kinds of elements of silicon or aluminum, gallium, indium, arsenic, phosphorus, and antimony. The optical transmitter according to claim 3.
An optical transmitter characterized in that the optical path adjusting means is a light beam scanner made of an electro-optic crystal. The optical transmitter according to claim 6.
An optical transmitter, wherein the electro-optic crystal of the light beam scanner is composed of at least two elements of lithium, potassium, tantalum, niobium, and oxygen. Laser light emitting means for emitting laser light;
Condensing means for condensing the laser light emitted from the laser light emitting means;
At least one optical path adjusting means for adjusting the optical path of the laser light emitted from the laser light emitting means or the laser light condensed by the condensing means;
An optical path adjustment method for an optical transmitter, comprising: an optical transmission unit configured to transmit the laser light whose optical path is adjusted by the optical path adjustment unit,
The laser light emitting means, the condensing means, the light transmission means, and the optical path adjusting means are arranged so that their optical centers are substantially in a straight line, and fixed to the housing,
Emitting laser light from the laser light emitting means,
Measure the intensity of the laser beam output from the optical transmission means,
An optical path adjustment method for an optical transmitter, wherein the optical path of the laser light is adjusted by the optical path adjustment means so that the intensity of the laser light output from the optical transmission means is maximized. 9. The optical path adjustment method for an optical transmitter according to claim 8,
An optical path adjustment method for an optical transmitter, wherein the optical path adjustment means adjusts the optical path of the laser beam by applying a voltage.

Images