JPH01101504A - Method for pair identification of optical fiber - Google Patents

Abstract

PURPOSE:To suppress the application of residual distortion to the coat of an optical fiber without exerting influence to optical transmission characteristics upon an active line by using a light source in a wavelength area increasing an optical loss for bend as compared with the wavelength of a light source used for optical transmission for reference light. CONSTITUTION:A reference light source 3 having wavelength generating a loss larger than the increment of an optical loss for the bend 4 of an optical fiber in the wavelength area of the light source used for optical transmission and having a loss almost equal or less to/than the optical transmission loss of the optical fiber is used. A fiber 2-1 is bent, a photodetecting sensor 5 is arranged on a position in the range where a bent angle along the optical fiber 2-1 from the start of bend of the fiber 2-1 on the incident end side of the reference light source 3 in the direction reverse to the incident side of the light source 3 is pi/4-3 and pi/4 radian to identify the core 2-1 about the sensor 5. Consequently, the optical fiber can be identified without exerting influence to optical transmission characteristics upon an active line and without generating an extremely small bend such that residual distortion is applied to the coat of the optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical fiber comparison method for comparing optical fibers in an optical fiber cable.

Conventional techniques and problems to be solved by the invention Conventional optical core line contrasters attempt to contrast optical signals in the same wavelength range (for example, 1.3 μm) as the wavelength range used for optical transmission. The reference light enters the optical fiber from one end, and then the optical fiber to be compared is given an extremely small bend, and the leakage of the reference light from the bend is detected. We are conducting a comparison of However, in this case, the curvature of the bent portion is large, so when focusing on the optical signal propagating in the optical fiber, the bending causes a very large increase in optical loss. Therefore, if you accidentally bend the core wire used for transmitting commercial signals (hereinafter referred to as the live line), there is a risk that the optical transmission characteristics of the live line may be affected and code errors may occur. was there. In particular, when comparing an 8M type optical fiber coated wire with a large transmission capacity, it cannot be detected unless it is bent more than a GI type optical fiber coated wire in order to increase the leakage light due to the difference in guide structure. Furthermore, since the curvature given to the optical fiber during fiber comparison is very large, there is also a drawback that residual strain is applied to the optical fiber coating after fiber comparison due to bending.

In order to eliminate these drawbacks, the present invention applies an extremely small bend to the live line of an optical fiber cable without affecting the optical transmission characteristics and which causes residual strain to be added to the optical fiber sheathing. An object of the present invention is to provide a method for comparing optical fiber cores without any trouble.

Means for Solving the Problems The present invention provides an optical fiber core comparison method for comparing optical fiber cores in an optical fiber cable consisting of a plurality of cores. A reference optical fiber core wire having a wavelength that causes a larger loss than the increase in optical loss due to bending, and the optical transmission loss of the optical fiber is approximately equal to or less than that, is bent, and the reference light source input end side is bent. ° of the optical fiber core wire
A light receiving sensor is disposed at a position where the bending angle is in the range of π/4 to 3, π/4 radian along the optical fiber from the beginning of bending in the direction opposite to the reference light source incident side, and the optical fiber is To contrast.

Effect of the Invention The present invention uses the above-mentioned configuration to provide a live line of an optical fiber cable without affecting the optical transmission characteristics and without subjecting the optical fiber cable to extremely small bends that would add residual strain to the coated optical fiber. can.

Embodiment FIG. 1 shows a principle diagram of an embodiment of the optical fiber core comparison method of the present invention.

In the figure, l is the optical fiber cable, 2 is the optical fiber core, 2-/ is the control core, 2-2 is the active line, 3 is the reference light source, ≠ is the bent part of the optical fiber, and j is the leakage light. Detection unit,
A shows the symmetrical position of the optical fiber.

FIG. 2 is a typical example of the optical loss wavelength characteristics of an 8M type optical fiber with respect to bending (when the bending diameter is 20 w x ψ).

As shown in FIG. 1, a reference beam 3 is incident on a plurality of optical fibers in an optical fiber table/ from one end of a reference fiber 2-/, and a reference beam 3 is inputted at a reference position A of the optical fiber 2-/. bends the optical fiber core, and directs the leakage light of the reference beam 3 from the bending section to the optical fiber core ≠
It is detected by a light receiving sensor j provided nearby and the optical fiber core wire 2-/ is compared.

Conventionally, this reference light 3 uses the same wavelength as the wavelength used for optical transmission of the active cycle @2-2.

On the other hand, as shown in Fig. 2, 8
The optical loss wavelength characteristics for bending of M-type optical fiber are as follows:
At 1 to 3 μm, which is used for normal optical transmission, there is almost no increase in optical loss.

However, in a wavelength range of 1.1 μm or less or 1.4 μm or more, an increase in optical loss due to bending is observed.

Therefore, in the present invention, a light source having a wavelength range within these ranges is used as the reference light 3 to perform comparison of the optical fiber cores. As a result, even if an attempt is made to compare the optical fiber core wire of the active line 2-2 by mistake, the optical transmission characteristics will not be affected at all.

That is, an example in which an optical fiber cable using a wavelength of 1.3 μm is used for optical transmission will be specifically described below.

As shown in Figure 2, the SM type optical fiber core is 20+A
When bent at +ψ, at a wavelength of 1.55 μm, it is approximately several d
B's optical loss increases. However, at 1.3 μm, no increase in optical loss occurs at all. Therefore, if a light source with a wavelength of 1.55 μm is used as the reference light 3, the leakage light of the reference light 3 can be detected from the bent part of the optical fiber at the reference position A of the optical fiber by the leakage light detection j. The comparison of the control core wire 2-/ can be easily performed.

Therefore, if the optical fiber core wires are compared under the above conditions, even if the live line 2-2 is erroneously bent for the purpose of comparison, there is no problem at all since there is no increase in optical loss at 1.3 μm.

Furthermore, if a low-loss region of an optical fiber near 1.55 μm is used as the light source wavelength of the reference light, the optical loss characteristics of recent optical fibers are lower than 1.3 μm, so the possible transmission distance of the reference light is Since the length is longer, the distance from the reference light input end of the optical fiber to the optical fiber core comparison position can be increased, which has the advantage of facilitating fiber core comparison over a long distance.

FIG. 3 shows a bending angle dependence measurement system for the amount of leaked light, where B is the original fiber core bending jig and θ is the light receiving sensor position.

FIG. 4 shows the dependence of the amount of leaked light on the position of the light receiving sensor. Fourth
It can be seen from the figure that the peak value of the leakage light amount detection power exists when the light receiving sensor position θ is around π/2 radians.

Therefore, since the power level that can be compared with the optical center line is higher than the dotted line level in Figure 4, the position of the light receiving sensor is adjusted from π/4 to
It becomes clear that the value should be set to 3.π/4 radians.

In order to improve the sensitivity of the leakage light of the reference light 3, various measures may be taken such as synchronizing the light source side and the light receiving section side with a signal, providing a plurality of bending sections, etc.

Also, within the allowable optical loss variation of the active recovery 2-2 (range in which AGC operates), the larger the curvature of the optical fiber, the more
Furthermore, since the S/N ratio can be improved, the bending diameter is approximately 1
It is possible to reduce it to 5■ψ.

FIG. 5 shows a perspective view of an embodiment of a bending device for optical fiber according to the present invention.

In the figure, 7 is a convex bent portion, and ♂ is a concave bent portion.

The configuration of the optical fiber bending device will be explained. The convex bending portion 7 has a U-shaped cross section that projects perpendicularly from the center of the rectangular base 7A to the side surface of the long side, and has a semicircular lower portion. The semi-cylindrical body 7B is integrally constructed, and an optical fiber core storage groove 7- is formed on the entire outer circumference of the semi-cylindrical body 7B at right angles to the axial direction thereof.
/ and circular holes 7C penetrating downward in both wing parts of the base 7A.The concave bent part t is formed into a rectangular plate-like body, and has a semicircular cross section with an opening at one end in the center of the upper surface part. A groove rh is formed, and sliding columns lrB are planted on the left and right sides of the base of the groove FA. The sliding column fB of the concave bent part g is inserted into the hole 7c of the convex bent part 7, and the semi-cylindrical body 7BIJ'' can be fitted into the groove part FA.

FIG. 6 is a cross-sectional view of the optical fiber when it is being spun.
-/ is a light receiving sensor.

In this example, the bending angle of the optical fiber is π radian,
Also, the case where the light receiving sensor j-/ is attached at a position approximately in the center (π/2 radian) of the concave bending portion where the leakage light is maximum is shown. Therefore, by making the bending portions symmetrical in this way, the bending portions can be symmetrical regardless of the direction of the reference light incident end of the optical fiber core.

Effects of the Invention In the optical fiber core comparison method of the present invention, a light source in a wavelength region where the amount of optical loss due to bending is larger than the wavelength of the light source used for optical transmission is used as a reference, so the bending diameter cannot be set to an extreme value. There's no need to make it smaller.

Therefore, even if the live line is erroneously compared (bent), there is no risk of affecting the optical transmission characteristics.

Furthermore, since the position of the light receiving sensor in the bending portion of the optical fiber is defined in the range of π/4 to 3π/4 where the leakage light is maximum, it is possible to efficiently detect the leakage light. Furthermore, by making the structure of the optical fiber core part symmetrical with respect to the light receiving sensor position 2, it is possible to compare the optical fiber cores regardless of the incident end direction of the reference light source.

Furthermore, the method of the present invention produces the effect that reference can be made without imparting residual strain such as bending of the optical fiber coating.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of an embodiment of the optical fiber comparison method of the present invention, Fig. 2 is a typical example of optical loss wavelength characteristics with respect to bending of an 8M type optical fiber (when the bending diameter is 20wψ), and Fig. 3
The figure shows a measurement system for the bending angle dependence of the amount of leaked light, FIG. 4 shows the dependence of the amount of leaked light on the position of the leakage light detection part, FIG. FIG. 2 shows a cross-sectional view of the optical fiber when it is being spun. l: Optical fiber table, 2: Optical fiber core, core/
: Reference fiber, λ-2=live line, 3: Reference light, lA: Optical fiber core, ! = leakage light detection unit, j-/: light receiving sensor, A: contrast position of optical fiber coated wire, 6: optical fiber coated wire bending jig, θ: optical fiber coated wire bending angle, 7: convex bent portion, 7-/: Optical fiber core storage groove, lr
: Concave bend. Patent applicant: Nippon Telegraph and Telephone Corporation Representative Patent Attorney Isao Abe 4: :L7y('+-t4Jh f4F r
"kl" 6p Figure 1 Figure 2 ft9L4-y4! ft 61 (hadn Figure 4 7) 6-inch boat 11°! Figure 5- Figure 6

Claims (1)

[Claims] In an optical fiber comparison method that compares optical fibers in an optical fiber cable consisting of multiple fibers, the loss is greater than the increase in optical loss due to bending of the optical fiber in the wavelength range of the light source used for transmission. arise,
A reference optical fiber having a wavelength at which the optical transmission loss of the optical fiber is approximately the same or less is bent, and from the beginning of bending the optical fiber on the reference light source input end side to the reference light source input side. An optical fiber coated wire comparison method in which a light receiving sensor is disposed at a position where the bending angle along the optical fiber coated wire is in the range of π/4 to 3, π/4 radians in the opposite direction to the optical fiber coated wire, and the optical fiber coated wire is compared. .