JP2008275943A - Optical fiber bending head and optical fiber collating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber bending head and an optical fiber collating device capable of obtaining sufficient leaked light without depending on types of optical fibers. <P>SOLUTION: The optical fiber bending head 10 bends an optical fiber 30 to allow detectable light to leak. The head comprises a convex head member 2 having a main curved convex portion 1 and a concave head member 4 having a main curved concave portion 3, with the convex and concave head members 2, 4 defining a bending portion 5 that presses and bends the optical fiber 30 between the main curved convex portion 1 and the main curved concave portion 3. A protruding portion 7 is formed in the main curved convex portion 1, and the ends 7a, 7b of the protruding portion produce steps 7c, 7d having discontinuously varied height. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical fiber bending head used for an optical fiber contrast device and the like, and an optical fiber contrast device using the same.

As a method of optical fiber contrast (for example, optical fiber core wire contrast) in an optical line, a leakage light is generated by bending the optical fiber while maintaining a conductive state, and this leaked light is converted into a core wire contrast machine (so-called A technique of detecting (detecting) an optical fiber by detecting it with a photodetector of an optical fiber contrast device such as an ID tester has become widespread.
For example, Patent Documents 1 to 3 are known as techniques related to the optical fiber reference device.
JP 2004-347528 A JP 2006-235362 A JP 2007-40911 A

In recent years, optical fibers that can reduce bending loss have been developed. For example, it is known that the bending loss can be reduced by optimizing the mode field diameter, the core-cladding relative refractive index, the core diameter, and the like.
Since this type of bending-resistant optical fiber is unlikely to generate leaked light, the coupling efficiency between the leaked light and the photodetector becomes low during a control inspection or the like.
Increasing the curvature of bending can increase the leakage light, but in general, increasing the curvature increases bending loss. Therefore, when this curvature is applied to general optical fibers, the bending loss increases and communication is interrupted. Problems occur.
By using different optical fiber bending heads depending on the type of optical fiber, it is possible to apply a curvature suitable for the optical fiber. There are problems in terms of work efficiency and cost.
The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical fiber bending head and an optical fiber reference device capable of obtaining sufficient leakage light regardless of the type of optical fiber.

An optical fiber bending head according to a first aspect of the present invention is an optical fiber bending head that bends an optical fiber to leak detectable light, and includes a convex head member having a curved convex portion and a concave portion. A concave head member, and the convex and concave head members define a bending imparting portion that presses the optical fiber with the curved convex portion and the concave portion to impart a bend to leak light, and the curved portion The protrusion is formed with a protrusion that protrudes in the protruding direction of the curved protrusion and presses the optical fiber, and the end of the protrusion forms a step that changes discontinuously. To do.
An optical fiber bending head according to a second aspect of the present invention is the optical fiber bending head according to the first aspect, wherein the bending imparting portion is a main bending portion that applies the bending to the optical fiber at the bending convex portion and the concave portion, and one end of the main bending portion. And a sub-bending portion formed on the side and the other end side for bending the optical fiber in a direction opposite to the main bending portion, and an end portion of the protruding portion is formed between the main bending portion and the sub-bending portion. It is located at or near the boundary.
An optical fiber bending head according to a third aspect of the present invention is the optical fiber bending head according to the first or second aspect, wherein the protrusion is formed to extend in a bending direction of the curved convex portion.
An optical fiber bending head according to a fourth aspect of the present invention is the optical fiber bending head according to any one of the first to third aspects, wherein an opening for guiding the leaked light to a photodetector is formed in the concave portion of the concave head member. The projecting portion is formed to project the optical fiber toward the opening.
An optical fiber bending head according to a fifth aspect of the present invention is the optical fiber bending head according to any one of the first to fourth aspects, wherein the protruding portion outer surface and the concave portion are formed in a substantially arcuate shape, and the protruding portion outer surface is formed. The radius of curvature of is larger than the radius of curvature of the recess.
An optical fiber bending head according to a sixth aspect of the present invention is the optical fiber bending head according to the fifth aspect, wherein the curved convex portion and the outer surface of the protruding portion are formed in a concentric substantially circular arc shape.
An optical fiber reference device according to a seventh aspect of the present invention is the optical fiber bending head according to any one of the first to sixth aspects, a transmission unit for allowing test light to enter the optical fiber, and the optical fiber. It has a photodetector for detecting the leaked light obtained by the bending head, and a receiver for judging the optical fiber as a control based on a detection signal obtained by the photodetector.

According to the optical fiber bending head of the present invention, the protruding portion is formed on the curved convex portion, and the end portion thereof forms a step portion. In this step portion, the optical fiber is locally bent, and in this portion, Light leakage is likely to occur.
Therefore, even when applied to a type of optical fiber having a small allowable bending radius, sufficient leakage light can be obtained, and the coupling efficiency between the leakage light and the photodetector can be increased.

FIG. 1 is a front view showing an optical fiber contrast device (optical fiber core wire contrast device) using an optical fiber bending head 10 according to a first embodiment of the present invention.
This optical fiber reference device includes an optical fiber bending head 10, a transmitter 40 that makes test light incident on the optical fiber 30, a photodetector 50 that detects leaked light obtained by the optical fiber bending head 10, and a light detection And a receiving unit 60 that determines the optical fiber 30 as a control based on a detection signal from the detector 50.

The optical fiber bending head 10 has a convex head member 2 having a main curved convex portion 1 and a concave head member 4 having a main curved concave portion 3.
The convex head member 2 includes a main curved convex portion 1, sub-curved concave portions 6, 6 which are on one end side and the other end side of the main curved convex portion 1 and are curved in a direction opposite to the main curved convex portion 1, And a protrusion 7 formed on the main curved protrusion 1.
The main curved convex part 1 can be substantially arc-shaped. The curvature or the like of the main curved convex portion 1 can be determined so that, for example, bending that causes light leakage in a general optical fiber can be given. In the illustrated example, the main curved convex part 1 is formed so as to be line symmetric with respect to a center line C1 passing through the lowermost part 1c and the center of curvature 1d.

The sub-curved concave portions 6 and 6 can be formed in a substantially arc shape, and can be formed starting from the one end 1a and the other end 1b of the main curved convex portion 1. The sub-curved concave portions 6 and 6 are preferably formed so as to be smoothly continuous with the main curved convex portion 1, that is, so that the tangential direction at the end portions 1 a and 1 b coincides with the tangential direction of the main curved convex portion 1. .
The main curved convex portion 1 is not limited to a shape that is line symmetric with respect to the center line C1, but may be a shape that is asymmetric with respect to the center line C1. The shapes of the main curved convex portion 1 and the sub curved concave portions 6 and 6 may be curves other than an arc.

The projecting portion 7 is for projecting leakage light even in an optical fiber having a small bending loss, and is formed so as to project in the projecting direction of the main curved projecting portion 1.
The protruding portion 7 is formed to extend in the bending direction of the main curved convex portion 1. In the illustrated example, the protruding portion 7 has an arc shape along the main curved convex portion 1, that is, an arc shape concentric with the main curved convex portion 1. The protruding portion 7 is formed to be line symmetric with respect to the center line C1 as an axis of symmetry.
The horizontal distances α1 and α2 from the center line C1 of the one end 7a and the other end 7b of the protrusion 7 are preferably 10 mm or less. By setting the distances α1 and α2 in this range, it becomes easy to detect the leaked light from the optical fiber 30 with the photodetector 50.

The one end portion 7a and the other end portion 7b are shaped to form stepped portions 7c and 7d whose height changes discontinuously with respect to the main curved convex portion 1. That is, in the one end portion 7a and the other end portion 7b, the height with respect to the main curved convex portion 1 is discontinuously increased.
The shape of the one end portion 7a and the other end portion 7b may be any shape as long as it gives local bending to the optical fiber 30 and promotes light leakage, and the end surface may be a curved surface. It may be flat. For example, it may be a flat end surface substantially along the center line C1. Even when the end surface is a curved surface, it is preferable that the tangential direction of the outer surface is discontinuously changed with respect to the main curved convex portion 1.

If the thickness of the protruding portion 7, that is, the height of the stepped portions 7c and 7d, is too small, the leakage light is insufficiently emitted, and if it is too large, the bending loss increases. For this reason, the thickness of the protrusion 7 is preferably equal to or smaller than the outer diameter of the optical fiber 30, and can be set to, for example, 1/4 to 1 with respect to the outer diameter of the optical fiber 30. Specifically, the thickness of the protrusion 7 can be set to, for example, 0.05 to 1 mm, preferably 0.1 to 0.5 mm.
Although the protrusion 7 in the illustrated example has a constant thickness, the thickness of the protrusion 7 may not be constant.
The formation positions of the one end portion 7a and the other end portion 7b can be the end portions 1a, 1b of the main curved convex portion 1 or the vicinity thereof. In the illustrated example, the end portions 7a and 7b are located in the vicinity of the end portions 1a and 1b, more specifically, slightly closer to the sub-curved concave portions 6 and 6 than the end portions 1a and 1b.

The protruding portion 7 can be formed of synthetic resin, metal, or the like. In the case of using a synthetic resin, an elastic material may be used, or an inelastic material may be used. For example, ABS resin can be used.
The protruding portion 7 may be a separate member from the convex head member 2 or may be formed integrally with the convex head member 2.
When the protrusion 7 is a separate member from the convex head member 2, the protrusion 7 can be formed by fixing the protrusion 7 formed separately from the convex head member 2 to the main curved protrusion 1. When the protrusion 7 is integrated with the convex head member 2, the convex head member 2 with the protrusion 7 integrally formed can be formed by, for example, a well-known resin molding method.

The curvature radius of the outer surface of the protruding portion 7 may be the same as or different from the curvature radius of the main curved convex portion 1.
In the illustrated example, the outer surface of the projecting portion 7 has a substantially arc shape concentric with the main curved convex portion 1, and therefore the radius of curvature of the outer surface of the projecting portion 7 is larger than the radius of curvature of the main curved convex portion 1. Is thicker than When the curvature of the curved concave portion 3 is substantially equal to the curvature of the main curved convex portion 1, the curvature radius of the outer surface of the protruding portion 7 is slightly larger than the curvature radius of the main curved concave portion 3, so that the optical fiber 30 is a convex head member. When the optical fiber 30 is bent between 2 and the concave head member 4, force is easily applied to the optical fiber 30 by the end portions 7 a and 7 b of the protruding portion 7. For this reason, local bending tends to occur at the end portions 7 a and 7 b of the protruding portion 7.
The convex head member 2 can be moved in a direction toward and away from the concave head member 4.

The concave head member 4 has a main curved concave portion 3, and sub-curved convex portions 9, 9 which are on one end side and the other end side of the main curved concave portion 3 and are curved in a direction opposite to the main curved concave portion 3.
The main curved concave portion 3 can have a shape curved in a substantially arc shape along the main curved convex portion 1. The curvature of the main curved concave portion 3 can be substantially equal to or slightly larger than the curvature of the main curved convex portion 1.
The sub-curved convex portions 9, 9 can be formed in a shape that is curved in a substantially arc shape along the sub-curved concave portions 6, 6. The curvature of the sub-curved convex portions 9 and 9 can be substantially equal to or slightly smaller than the curvature of the sub-curved concave portions 6 and 6.
The sub-curved convex portions 9 are preferably formed so as to be smoothly continuous with the main curved concave portion 3 starting from one end and the other end of the main curved concave portion 3.
In the concave head member 4, an opening 8 is formed at the center of the main curved recess 3, and leakage light can be guided to the photodetector 50 through the opening 8.
The convex head member 2 and the concave head member 4 can be formed of synthetic resin, metal, or the like.

By disposing the convex head member 2 on the concave head member 4 so that the main curved convex portion 1 faces the main curved concave portion 3, the gap between the convex head member 2 and the concave head member 4 is as follows. Defined as a bend imparting portion 5.
The sub-curved concave portions 6 and 6 of the convex head member 2 face the sub-curved convex portions 9 and 9 of the concave head member 4.
For this reason, the bending imparting portion 5 includes a main curved portion 11 defined by the main curved convex portion 1 and the main curved concave portion 3, and a sub curved portion defined by the sub curved concave portions 6, 6 and the sub curved convex portions 9, 9. 12 and 12.
Since the sub-curved portions 12 and 12 are defined by the sub-curved concave portions 6 and 6 and the sub-curved convex portions 9 and 9, the sub-curved portions 12 and 12 are curved in a direction opposite to the main curved portion 11, and one end of the main curved portion 11 is formed. It has a shape that is smoothly continuous from the part and the other end.

When the formation positions of the one end portion 7a and the other end portion 7b of the protruding portion 7 are the one end portion 1a and the other end portion 1b of the main curved convex portion 1 or the vicinity thereof, the positions of the end portions 7a and 7b are as follows: This is the boundary between the main bending portion 11 and the sub bending portions 12, 12, or the vicinity thereof.
By forming the end portions 7a and 7b at this position, the leaked light emitted from the optical fiber 30 at the end portions 7a and 7b can easily reach the photodetector 50.

  The transmission unit 40 includes a light source 41 and a control unit 42 that controls light emission of the light source 41, and allows test light to enter the optical fiber 30 through an optical coupler (not shown).

The light detector 50 can detect leak light from the optical fiber 30 and output a detection signal. For example, a photodiode can be used.
The photodetector 50 is preferably installed so that the center portion thereof is located on the center line C1 of the main curved convex portion 1.

  Examples of the receiving unit 60 include an amplifier circuit that amplifies a detection signal from the photodetector 50, a comparator that compares the obtained signal with a communication signal, and a determination circuit that determines a comparison result. .

Examples of the optical fiber 30 include an optical fiber core wire and an optical fiber cord.
As the optical fiber 30, a type having a small bending loss (with an allowable bending radius of, for example, 15 mm or less) can be used, and an optical fiber having an allowable bending radius exceeding the above range can also be used.
For example, in the single mode (SM) type optical fiber core wire, the allowable bending is larger than that of a general one (for example, mode field diameter 9.2 ± 0.4 μm, cutoff wavelength 1.27 μm or less, allowable bending radius about 30 mm). Those having a small radius are known (for example, a mode field diameter of 8.6 ± 0.4 μm, a cutoff wavelength of 1.27 μm or less, and an allowable bending radius of about 15 mm).
As the optical fiber 30, a multimode type can also be used.

Next, a method of performing a comparison test using this optical fiber comparison apparatus will be described.
As shown in FIG. 1, the optical fiber 30 is disposed on the concave head member 4, the convex head member 2 is lowered, and the optical fiber 30 is pressed by the main curved convex portion 1.
As a result, the optical fiber 30 is bent between the main curved convex portion 1 and the main curved concave portion 3 at the bending portion 11 of the bending applying portion 5.
Since the optical fiber 30 is pressed by the protruding portion 7 and protrudes toward the opening portion 8, the optical fiber 30 is disposed closer to the photodetector 50.

The optical fiber 30 is pressed downward by the projecting portion 7, and an upward force is applied to the sub-curved portion 12 by the sub-curved convex portions 9, 9 of the concave head member 4. The one end portion 7a and the other end portion 7b (step portions 7c and 7d) are locally bent along the shape of the step portions 7c and 7d, and light leakage easily occurs at these portions.
Therefore, even when applied to the optical fiber 30 having a small allowable bending radius, sufficient leakage light can be obtained and the coupling efficiency between the leakage light and the photodetector 50 can be increased.
Since the optical fiber 30 is disposed at a position close to the photodetector 50 by the protruding portion 7, the leaked light easily reaches the photodetector 50 and high coupling efficiency is obtained.

  Further, in the optical fiber bending head 10, the allowable bending can be achieved by adjusting the pressing force when the optical fiber 30 is sandwiched between the convex head member 2 and the concave head member 4 or by optimizing the height of the protrusion 7. Even when applied to an optical fiber 30 having a relatively large radius, bending loss can be suppressed.

The leaked light is detected by the photodetector 50, and the photodetector 50 outputs a detection signal.
In the receiving unit 60, for example, the detection signal is amplified by an amplifier circuit, compared with a communication signal having the same frequency component by a comparator, and the determination circuit determines whether or not the frequency components match. Thereby, it can be determined whether or not the optical fiber 30 is the target optical fiber.

Note that the shape and number of the protrusions are not limited to the illustrated example as long as they can bend the optical fiber minutely and promote the emission of leaked light. For example, you may form a some protrusion part intermittently along the main curve convex part 1. FIG. Further, the recesses 3 and 6 may be non-curved.
The optical fiber bending head of the present invention is not limited to the illustrated example, and can also be applied to a live line discrimination device. In this case, it is possible to determine whether or not the optical fiber is live by entering the signal light into the optical fiber and detecting it as leakage light.

Example 1
When attempting to detect leaked light using the optical fiber bending head 10 shown in FIG. 1, the minimum value of optical power for obtaining detectable leaked light was examined.
The curvature radius of the main curved convex part 1 was 10.0 mm. The protrusion 7 is made of an inelastic ABS resin and has a thickness of 0.25 mm. The curvature radius of the protrusion 7 was 10.25 mm. The wavelength of the test light was 1.55 μm.
The used optical fiber 30 is an SM type optical fiber single core wire (outer diameter 0.5 mm, mode field diameter 8.6 ± 0.4 μm, cutoff wavelength 1.27 μm or less, allowable bending radius 15 mm).
The results are shown in FIG. Moreover, the result of having measured the bending loss is shown in FIG.

(Comparative Example 1)
FIG. 2 shows the result of examining the minimum detectable optical power using an optical fiber bending head similar to the optical fiber bending head 10 shown in FIG. 1 except that the protruding portion 7 is not formed. Moreover, the result of having measured the bending loss is shown in FIG. Other test conditions were in accordance with Example 1.

2 and FIG. 3, in Example 1, the minimum optical power enabling the control test is improved by about 3.2 dB, although the increase in loss is very small compared to Comparative Example 1.
From this, it can be seen that in Example 1, the coupling efficiency between the leaked light and the photodetector was greatly improved.
Also, using a general SM type optical fiber single core wire (mode field diameter 9.2 ± 0.4 μm, cutoff wavelength 1.27 μm or less, allowable bending radius 30 mm) having a relatively large allowable bending radius As a result of conducting a leakage light detection test according to Example 1, it was confirmed that no significant increase in bending loss was observed.

(Comparative Example 2)
An optical fiber bending head similar to the optical fiber bending head 10 is used except that the protruding portion 7 is not formed and the curvature of the main curved convex portion 1 is relatively large. Examined. The curvature radius of the main curved convex part 1 was 9.7 mm.
The results are shown in FIG. Moreover, the result of having measured the bending loss is shown in FIG. Other test conditions were in accordance with Example 1.

(Comparative Example 3)
An optical fiber bending head similar to that of Comparative Example 2 was used except that the curvature of the main curved convex portion 1 was relatively small, and the minimum value of detectable optical power was examined. The curvature radius of the main curved convex part 1 was 10.0 mm.
The results are shown in FIG. Moreover, the result of having measured the bending loss is shown in FIG. Other test conditions were in accordance with Example 1.

  4 and 5, the difference in the minimum optical power between Comparative Example 2 and Comparative Example 3 is about 0.7 dB. From this, even if the curvature of the main curved convex portion 1 is changed within a range where the bending loss does not increase greatly, it is determined that it is difficult to significantly improve the minimum optical power.

It is a block diagram which shows typically an example of the optical fiber contrast apparatus of this invention. It is a graph which shows a test result. It is a graph which shows a test result. It is a graph which shows a test result. It is a graph which shows a test result.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main curve convex part, 2 ... Convex head member, 3 ... Main curve recessed part, 4 ... Concave head member, 5 ... Bending provision part, 7 ... Projection part, 7a, 7b: end of the projecting portion, 7c, 7d: stepped portion, 10 ... optical fiber bending head, 11 ... main bending portion, 12 ... sub bending portion, 30 ... Optical fiber, 40... Transmitter, 50... Photodetector, 60.

Claims (7)

An optical fiber bending head that bends an optical fiber to leak detectable light,
A convex head member having a curved convex portion and a concave head member having a concave portion, and these convex shape and concave head member press the optical fiber at the curved convex portion and the concave portion to impart bending. A bend imparting section that leaks light,
The curved convex portion is formed with a protruding portion that protrudes in the protruding direction of the curved convex portion and presses the optical fiber, and an end portion of the protruding portion forms a step portion whose height changes discontinuously. An optical fiber bending head characterized by The bending imparting portion is formed on the one end side and the other end side of the main bending portion to bend the optical fiber by the bending convex portion and the concave portion, and is opposite to the main bending portion in the optical fiber. A sub-curved portion for applying a bending in the direction,
2. The optical fiber bending head according to claim 1, wherein an end of the protruding portion is located at or near a boundary between the main bending portion and the sub-curving portion.   The optical fiber bending head according to claim 1, wherein the protruding portion is formed to extend in a bending direction of the curved convex portion. The concave portion of the concave head member is formed with an opening that guides the leaked light to a photodetector,
The optical fiber bending head according to any one of claims 1 to 3, wherein the protrusion is formed to protrude the optical fiber toward the opening. The protrusion outer surface and the recess are formed to be curved in a substantially arc shape,
The optical fiber bending head according to any one of claims 1 to 4, wherein a radius of curvature of the outer surface of the protruding portion is larger than a radius of curvature of the concave portion.   6. The optical fiber bending head according to claim 5, wherein the curved convex portion and the outer surface of the protruding portion are formed to be curved in a concentric substantially arc shape. The optical fiber bending head according to any one of claims 1 to 6,
A transmitter for making test light incident on the optical fiber;
A photodetector for detecting the leakage light obtained by the optical fiber bending head;
And a receiving unit that determines whether or not the optical fiber is a target optical fiber based on a detection signal obtained by the photodetector.

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