JP2010032238A - Core wire comparison method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact core wire comparison apparatus for comparing a core wire in an optical fiber excellent in a bending loss property, and improving the working efficiency. <P>SOLUTION: The core wire comparison apparatus includes: an optical fiber bending member 10 having a mechanism for bending the optical fiber 1; a grating forming tool 20 for applying a stress F to the optical fiber 1 through a plurality of protrusions 21, and forming a long-period grating in the optical fiber 1; and a light receiver 30 for detecting a leakage light generated in the optical fiber bending member 10, the grating forming tool 20 or both of them. The grating forming tool 20 is installed in the optical fiber bending member 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for controlling a core used in an optical continuity test in an optical transmission system, and more particularly to a method and apparatus for controlling a core using a long period grating.

  In order to confirm an arbitrary optical fiber core wire during construction and operation of an optical line, it is necessary to be able to find an arbitrary optical fiber core wire at a work site. For this reason, a cord contrast device (see, for example, Patent Document 1) is widely used because it can take out a part of the light propagating through the optical fiber and check whether the optical fiber is a desired optical fiber. . The optical fiber contrast device forms a bent portion in the optical fiber and receives light leaking from the bent portion, thereby determining whether or not the light is propagated in the optical fiber.

Japanese Patent No. 3407812

  However, optical fibers with improved bending loss characteristics, which have been attracting attention recently, have almost no light leaking out even when a bent portion is formed. There was a problem that fiber could not be handled. In addition, since the contrast control is often performed in a work space with a small work space, there is a problem that the contrast control device needs to be as small as possible.

  Accordingly, the present invention has been made in order to solve the above-described problems, and enables the control of the cores even for an optical fiber having excellent bending loss characteristics, and enables the control of the cores to be performed in a small and efficient manner. It is an object to provide a method and apparatus.

The cord control apparatus according to the first invention for solving the above-described problem is:
A bending portion having a mechanism for bending the optical fiber;
A grating forming portion that forms a long-period grating in the optical fiber by applying stress to the optical fiber through a plurality of concave and convex portions;
A light receiving portion for detecting leakage light generated in the bent portion or the grating forming portion or both,
The grating forming portion is installed in the bent portion or adjacent to the bent portion.

The cord control apparatus according to the second invention for solving the above-described problem is as follows.
A cord contrast device according to a first invention,
The bending portion has a bending portion for bending the optical fiber;
The curved portions are provided with the plurality of uneven portions.

The cord control apparatus according to the third invention for solving the above-described problem is as follows.
A cord contrast device according to the first or second invention,
The period of the irregularities in the plurality of irregularities changes along the longitudinal direction of the optical fiber.

The cord control apparatus according to the fourth invention for solving the above-described problem is as follows.
A cord contrast device according to any one of the first to third inventions,
The period of unevenness in the plurality of uneven portions is 0.82 mm or less.

The method for contrasting cores according to the fifth invention for solving the above-described problem is as follows.
A long period grating is formed on the optical fiber by applying a stress to the optical fiber through a plurality of concave and convex portions at a bent portion of the optical fiber or an adjacent portion thereof, and bending the optical fiber. It is confirmed that a light wave is conducted to the optical fiber by detecting the generation of leakage light due to bending of the light, the generation of leakage light due to the formation of the long period grating, or both.

The cord control method according to the sixth invention for solving the above-described problem is as follows.
A cord contrast method according to a fifth invention,
The bending of the optical fiber is performed by a bending portion that bends the optical fiber,
The long-period grating is formed by the plurality of concave and convex portions provided in the curved portion.

The method for contrasting cores according to the seventh invention for solving the above-described problems is as follows.
A cord contrast method according to a fifth or sixth invention,
The period of the irregularities in the plurality of irregularities changes along the longitudinal direction of the optical fiber.

The method of contrasting cores according to the eighth invention for solving the above-described problem is as follows.
A method of contrast control according to any one of the fifth to seventh inventions,
The period of unevenness in the plurality of uneven portions is 0.82 mm or less.

  According to the method and the apparatus for controlling the core wire according to the present invention, the light wave is conducted to the optical fiber by detecting the generation of the leakage light due to the bending of the optical fiber and / or the generation of the leakage light due to the formation of the long period grating. In order to confirm that the optical fiber has been confirmed, it is possible to control the cores even for an optical fiber having excellent bending loss characteristics. Furthermore, it is possible to perform a small and efficient operation.

  Hereinafter, the best mode of the method and apparatus for controlling a core wire according to the present invention will be described in detail in each embodiment.

[First embodiment]
A first embodiment of a method and apparatus for controlling a core wire according to the present invention will be described with reference to FIGS. 1 and 2. In this embodiment, a case where the present invention is applied to an optical fiber with improved bending loss characteristics will be described.
FIG. 1 is a schematic diagram for explaining a first embodiment of a light contrast method and apparatus, and FIG. 2 is a diagram schematically showing a portion where stress is applied to an optical fiber by the light contrast apparatus. . In FIG. 1, λ indicates propagating light propagating to the optical fiber.

  As shown in FIG. 1, the core wire contrast device 100 according to the present embodiment includes an optical fiber bending member 10 (optical fiber bending portion), a grating forming tool 20 (grating forming portion), a light receiver 30 (light receiving portion), and the like. It comprises.

  The optical fiber bending member 10 includes a convex member 11 and a concave member 15. The convex member 11 includes a curved portion 12 including one convex portion formed in an arc shape and two concave portions smoothly connected to both sides of the convex portion. The convex member 11 is slidably disposed with respect to the concave member 15. The recess material 15 includes a first recess material 13 and a second recess material 14. The first recess member 13 and the second recess member 14 include curved portions 13 a and 14 a, respectively, and are formed in a shape capable of sandwiching an optical fiber with the curved portion 12.

  The grating forming tool 20 is a plurality of protrusions 21 (uneven portions) provided on the entrance side bending portion 12a located on the entrance side (left side in the figure) in the light propagation direction in the bending portion 12 of the convex member 11. It is configured. That is, the grating forming tool 20 is installed in the optical fiber bending member 10. The plurality of protrusions 21 are arranged at a predetermined period (interval) Λ. Note that, in the curved portion 12 of the convex member 11, a plurality of protrusions are not provided on the outgoing curved portion 12 b located on the outgoing side (right side in the drawing) in the light propagation direction.

Here, an operation of contrast control for the optical fiber 1 using the core contrast device 100 having the above-described configuration will be described.
First, the optical fiber 1 is disposed between the convex member 11 and the concave member 15. Subsequently, the convex member 11 is slid with respect to the concave member 15, the optical fiber 1 is sandwiched between the convex member 11 and the concave member 15, and stress F is applied to the optical fiber 1 through the convex member 11. At this time, the optical fiber 1 is bent along the curved portion 12 of the convex member 11, the curved portion 13 a of the first concave member 13, and the curved portion 14 a of the second concave member 14, so that bending occurs in the optical fiber 1. Bending loss according to curvature and length occurs. At the same time, as shown in FIG. 2, periodic stress is applied to a predetermined portion 1 a of the optical fiber 1 at a predetermined interval Λ through the plurality of protrusions 21. As a result, a long-period grating with a period Λ is formed in the optical fiber 1, and leakage light is generated if a predetermined condition is satisfied as will be described later. The light leakage due to the bending loss and / or the light leakage due to the formation of the grating are detected by the light receiver 30 to confirm that the light wave is conducted to the optical fiber 1.

  Therefore, according to the core wire contrast device 100 according to the present embodiment, it is possible to perform the core wire contrast by detecting the bending loss with respect to the conventional optical fiber. In addition, the low bending loss optical fiber can be designed to satisfy the condition of the grating period at a desired wavelength, thereby realizing the core contrast of the low bending loss optical fiber. At this time, one optical fiber contrast device 100 can realize two leakage light generation means, ie, leakage light generation due to bending loss and leakage light generation due to the formation of a long period grating, and the grating forming tool 20 can be used for bending an optical fiber. By being installed in the member 10, the two leakage light generating means can be arranged in a small and efficient manner, which is preferable.

  Furthermore, according to the above-described core wire contrast device 100, the plurality of protrusions 21 are provided on the entrance side curved portion 12a of the curved portion 12 of the convex member 11, thereby imparting bending to the optical fiber 1 and the long-period grating. Is preferable because the size of the device itself can be reduced.

[Second Embodiment]
A second embodiment of the cord control method and apparatus according to the present invention will be described with reference to FIG. In this embodiment, a case where the present invention is applied to an optical fiber with improved bending loss characteristics will be described.
FIG. 3 is a schematic diagram for explaining a second embodiment of the method and apparatus for contrasting core wires. In FIG. 3, λ indicates propagating light propagating to the optical fiber.
In this embodiment, the same apparatus (light receiver 30) as that of the core wire contrast device 100 according to the first embodiment described above is denoted by the same reference numeral, and the description thereof is omitted.

  As shown in FIG. 3, the core wire contrast device 200 according to the present embodiment includes an optical fiber bending member 210 (optical fiber bending portion), a grating forming tool 220 (grating forming portion), and the like.

  The optical fiber bending member 210 includes a convex member 211 and a concave member 215. The convex member 211 has a substantially triangular shape in the longitudinal section, and has a curved vertex 211c and inclined portions 211a and 211b extending linearly on both sides of the vertex 211c. The convex member 211 is slidably disposed with respect to the concave member 215.

  The recess material 215 includes a first recess material 213 and a second recess material 214. The first recess member 213 and the second recess member 214 are each formed in a substantially triangular shape in the longitudinal section. The first recessed member 213 is formed with an inclined portion 213a extending linearly. The second recess member 214 is formed with an inclined portion 214a extending linearly. By using the convex member 211 and the concave member 215 having the shapes described above, the optical fiber 1 can be sandwiched between the convex member 211 and the concave member 215.

  The grating forming tool 220 includes a plurality of protrusions 221 (uneven portions) provided on the inclined portion 213a of the first recessed member 213. That is, the grating forming tool 220 is installed in the optical fiber bending member 210. The plurality of protrusions 221 are arranged with a predetermined period Λ. The plurality of protrusions 221 are formed to have the same size.

  Here, an operation of contrast control for the optical fiber 1 using the core contrast device 200 having the above-described configuration will be described. In the case of this work as well as the core wire contrast device 100 according to the first embodiment described above, leakage light can be generated by causing bending loss, and leakage light due to formation of a long-period grating can be generated. Can be generated.

  That is, by sandwiching the optical fiber 1 between the convex member 211 and the concave member 215 and applying a stress F to the optical fiber 1 via the convex member 211, the inclined portions 211a and 211b of the convex member 211, the first concave member Since the optical fiber 1 runs along the inclined portion 213a of 213 and the inclined portion 214a of the second concave member 214, the optical fiber 1 is bent, and bending loss corresponding to the bending curvature and length occurs. At the same time, a periodic stress is applied to the optical fiber 1 through the plurality of protrusions 221 to form a long-period grating with a period Λ in the optical fiber 1. As described later, leakage occurs if a predetermined condition is satisfied. Produce light. The light leakage due to the bending loss and / or the light leakage due to the formation of the grating are detected by the light receiver 30 to confirm that the light wave is conducted to the optical fiber 1.

  Therefore, according to the core wire contrast device 200 according to the present embodiment, the same effects as those of the fiber core contrast device 100 according to the first embodiment described above can be obtained. Further, the inclined portion 211a of the concave member 211 and the inclined portion 213a of the first convex member 213 are linearly formed, and the grating forming tool 220 is formed on these inclined portions 211a and 213a. Therefore, the plurality of protrusions 221 constituting the grating forming tool 220 are formed on the inclined portion 213a formed in a straight line, and the manufacture thereof is easy, and an increase in manufacturing cost can be suppressed.

[Third embodiment]
A third embodiment of the method and device for contrasting cores according to the present invention will be described with reference to FIG. In this embodiment, a case where the present invention is applied to an optical fiber with improved bending loss characteristics will be described.
FIG. 4 is a schematic diagram for explaining a third embodiment of the method and apparatus for contrasting core wires. In FIG. 4, λ indicates propagating light propagating to the optical fiber.
In this embodiment, the same apparatus (light receiver 30) as that of the core wire contrast device 100 according to the first embodiment described above is denoted by the same reference numeral, and the description thereof is omitted.

  As shown in FIG. 4, the core wire contrast device 300 according to the present embodiment includes an optical fiber bending member 310 (optical fiber bending portion), a grating forming tool 320 (grating forming portion), and the like.

  The optical fiber bending member 310 includes a convex member 311 (movable member) and a concave member 313 (support member). The convex member 311 has a rectangular parallelepiped shape and is slidably disposed with respect to the concave member 313. The concave member 313 has a substantially triangular shape in a longitudinal section, and enters the curved portion 313a located on the entrance side (left side in the figure) in the light propagation direction, and extends linearly continuously from the entrance side curved portion 313a. An inclined portion 313b that extends, and an exit-side curved portion 313c that is curved and extends continuously from the inclined portion 313b.

  The grating forming tool 320 includes a plurality of protrusions 321 provided on the bottom surface 311 a of the movable member 311. That is, the grating forming tool 320 is installed in the optical fiber bending member 310. The plurality of protrusions 321 are arranged at a predetermined period (interval) Λ. The plurality of protrusions 321 are formed to have the same size.

  Here, an operation of contrast control for the optical fiber 1 using the core contrast device 300 having the above-described configuration will be described. In the case of this work as well as the core wire contrast device 100 according to the first embodiment described above, leakage light can be generated by causing bending loss, and leakage light due to formation of a long-period grating can be generated. Can be generated.

  That is, the optical fiber 1 is sandwiched between the convex member 311 and the concave member 313, and the optical fiber 1 is taped in a substantially horizontal direction on the upstream and downstream sides in the light propagation direction of the convex member 311 and the concave member 313. Are fixed to a gantry (not shown) with a fixture (not shown), and stress F is applied to the optical fiber 1 via the convex member 311, whereby the bottom surface 311 a of the convex member 311 and the curved portion 313 a of the concave member 313 are formed. , 313c and the inclined portion 313b, the optical fiber 1 is bent, so that the optical fiber 1 is bent, and a bending loss corresponding to the curvature and length of the bending occurs. At the same time, a periodic stress is applied to the optical fiber 1 through the plurality of protrusions 321 to form a long-period grating with a period Λ in the optical fiber 1, and leakage occurs if a predetermined condition is satisfied as described later. Produce light. The light leakage due to the bending loss and / or the light leakage due to the formation of the grating are detected by the light receiver 30 to confirm that the light wave is conducted to the optical fiber 1.

  Therefore, according to the core wire contrast device 300 according to the present embodiment, the same effects as those of the fiber core contrast device 100 according to the first embodiment described above can be obtained. Further, the entrance-side bending portion 313a and the exit-side bending portion 313c of the concave member 313 function as an optical fiber bending portion that imparts bending to the optical fiber 1, and a long period is provided at the inclined portion 313b between the bending portions 313a and 313c. It is a structure in which a grating is formed. In this manner, since the optical fiber 1 can be bent with the single concave member 313, the bending diameters at the entrance side bending portion 313a and the exit side bending portion 313c can be set relatively freely. A plurality of protrusions 321 constituting the grating forming tool 320 are formed on the bottom surface 311a formed in a straight line. Therefore, the structure of the optical fiber bending member 310 and the grating forming tool 320 can be simplified, its manufacture is easy, and an increase in manufacturing cost can be suppressed.

Here, in the long-period grating, when the phase matching condition expressed by the following equation (1) is satisfied, a part of the propagation optical power is converted into a higher order mode. In the following equation (1), β ₀ represents the propagation constant of the propagation light, and β _m represents the propagation constant of the higher-order mode after conversion.

  Higher-order modes generated in the grating leak immediately because propagation loss and bending loss are much larger than those in the propagation mode. Here, FIG. 5 shows a loss spectrum when a long-period grating is formed by the method of the present invention for a hole-assisted optical fiber (HAF) excellent in bending loss characteristics. Here, HAF is used which has a loss of 0.01 dB / turn or less at a wavelength of 1550 nm even at a bending radius of 5 mm, and has a bending loss smaller by 3 digits or more than a conventional optical fiber. In FIG. 5, the dotted line indicates the case where the core wire contrast device in which the period of the plurality of protrusions (distance between adjacent protrusions) is 0.41 mm is used, and the solid line indicates the period of the plurality of protrusions (adjacent This shows a case where a cord contrast device in which the distance between the protrusions is 0.42 mm is used.

  As shown in FIG. 5, in the case of using the core wire contrast device in which the period of the plurality of protrusions is 0.41 mm, a loss of about 0.55 dB peak occurs at the wavelength of about 1360 nm, and the wavelength It can be seen that loss occurs over a range of about 1300 nm to about 1450 nm. Further, in the case of using the cord contrast device in which the period of the plurality of protrusions is 0.42 mm, a loss having a peak of about 0.48 dB occurs at a wavelength of about 1540 nm, and the wavelength is about 1450 nm to about It can be seen that loss occurs over the 1600 nm range. Therefore, it can be confirmed that loss can be generated at a desired wavelength even in HAF. Further, it can be confirmed that the operating wavelength can be changed by changing the grating period (period of unevenness).

Here, a description will be given with reference to FIG. 6 and FIG. 7 showing the relationship between the grating period and the operating wavelength according to the method and apparatus for contrasting core wires of the present invention. FIG. 6 shows the relationship between the grating period and the operating wavelength in the single mode optical fiber (SMF) in the LP ₁₁ mode, the LP ₁₂ mode, and the LP ₁₃ mode (operating conditions of the SMF). It is a graph to show. In FIG. 6, the white circle indicates the case of LP ₁₁ mode, the white square indicates the case of LP ₁₂ mode, and the white triangle indicates the case of LP ₁₃ mode.

FIG. 7 shows the grating period and operating wavelength in the case of HAF (hole-assisted optical fiber), trench A (first trench optical fiber), and trench B (second trench optical fiber). Is a graph showing the relationship (operating conditions of an optical fiber excellent in bending loss characteristics). In FIG. 7, HAF indicates a hole-assisted optical fiber having a loss of 0.01 dB / turn or less at a wavelength of 1550 nm with a bending radius of 5 mm. Trench A improves the bending loss by providing a ring layer having a lower refractive index than the core, the cladding, and the cladding in the cladding, and has a bending radius of 5 mm and a loss of 0.1 dB / turn at a wavelength of 1550 nm. Fiber is shown. Trench B improves the bending loss by providing a ring layer having a lower refractive index than that of the core, the cladding, and the cladding in the cladding, and a trench optical fiber having a bending radius of 5 mm and a loss of 1 dB / turn at a wavelength of 1550 nm. Show. In FIG. 7, the white circle mark indicates the case of HAF, the white square mark indicates the case of the trench A, and the white triangle mark indicates the case of the trench B. The curve in FIG. 7 shows the relationship necessary to convert from the propagation mode to the LP ₁₁ mode.

  When specifying the SMF using the core wire contrast device according to the present embodiment, for example, assuming that the wavelength to be controlled is 1260 to 1650 nm which is the communication wavelength band and the test wavelength band, as shown in FIG. It can be seen that it is necessary to set it to 0.82 mm or less in order to operate at. Further, since the necessary period becomes shorter as the mode order generated in the grating becomes higher, the core contrast of the present invention can be performed on the SMF with the above-described grating period of 0.82 mm or less.

  Further, when the HAF and the trenches A and B are specified using the cord contrast device according to the present embodiment, as shown in FIG. 7, the HAF has a trench type (trench A and B, 0.4 mm to 0.5 mm). ) Requires a grating period of 0.5 mm to 0.8 mm, and it can be seen that the above-described grating period of 0.82 mm or less can be used for HAF or trench type having low bending loss.

Here, it demonstrates with reference to FIG. 8 which shows an example of the arrangement | positioning method of the projection part of a grating formation tool regarding the core wire contrast method and apparatus of this invention.
As shown in FIG. 8, the plurality of protrusions 421 (uneven portions) are arranged so as to change along the longitudinal direction of the optical fiber 1. That is, _one period of the distal end portion 421a of the two projections 421 Λ disposed at the left end in in FIG. 8, the two projections 421 arranged to the right of these protrusions 421 tip 421a Is Λ ₂ (> Λ ₁ ), and the period of the tip portions 421a of the two protrusions 421 arranged at the right end in FIG. 8 is Λ _N (> Λ ₁ , Λ ₂ ). In FIG. 8, it arrange | positions so that the period between the front-end | tip parts 421a of the protrusion part 421 adjacent from the left end side toward the right end side may become large gradually. Thus, by changing the period of the tip part 421a of the protrusion 421 along the longitudinal direction of the optical fiber 1, the period of the grating formed in the optical fiber 1 can be changed in the longitudinal direction. As shown in FIGS. 6 and 7, the required grating period changes when the operating wavelength or the structure of the optical fiber changes. However, the operating wavelength varies or the optical fiber structure varies by changing the grating period in the optical fiber. Is preferable. In FIG. 8, reference numeral 411 indicates a movable member provided with a plurality of protrusions 421, reference numeral 411 a indicates a lower surface of the movable member 411, and reference numeral 423 indicates a fixture for fixing the optical fiber 1.

A description will now be given with reference to FIG. 9 showing the bending loss characteristics of a single-mode optical fiber (SMF) according to the core wire contrast method and apparatus of the present invention.
In the optical fiber bending member provided in the optical fiber contrast device, it is preferable that the curvature of the bent portion is large to some extent, since excessive communication loss may cause communication failure. Here, FIG. 9 shows a case where a conventional SMF is used at a wavelength of 1625 nm as a condition that the bending loss becomes the largest in the communication wavelength band.
For example, when the bending shape in the optical fiber bending member is one 180 ° bend, it can be seen that the bending radius needs to be 8 mm or more in order to reduce the optical loss for communication light to 2 dB or less. Here, the bending shape is assumed to be one 180 ° bending, but the bending shape may be two 90 ° bending, or another bending shape, or a combination of multiple bending radii or bending shapes such as corrugations. Even if it is such a shape, there exists the same effect.

  Here, it demonstrates with reference to FIG. 10 which shows the relationship between the stress to add and the leakage light intensity detected with a light receiver (light-receiving part) regarding the core line contrast method and apparatus of this invention. Here, the fibers to be measured are a single mode optical fiber (SMF) and a hole assist optical fiber (HAF). The total length of the grating is 4 cm, and the grating period is 0.45 mm in accordance with the HAF. HAF shows a hole-assisted optical fiber having a loss of 0.01 dB / turn or less at a wavelength of 1550 nm with a bending radius of 5 mm. In FIG. 10, the white triangle mark indicates the case of SMF, and the white circle mark indicates the case of HAF.

  As shown in FIG. 10, leaking light intensity of about −45 dBm to about −50 dBm is detected over a range of applied stress (load) from ON to about 23 N, and leaked light is detected regardless of the applied stress. As a result, it can be seen that the cord control can be performed. On the other hand, since the bending loss is small in HAF, leakage light cannot be detected when the applied stress (load) is smaller than about 10N. However, as the applied stress becomes larger than about 10N, the effect of the grating It can be seen that the high-order mode that has occurred can be detected to perform the contrast control. From these facts, it can be confirmed that the method and apparatus of the present invention can be applied to optical fibers having conventional SMF and low bending loss characteristics.

  Therefore, according to the cord contrast method and apparatus according to the present embodiment, by detecting the generation of leaked light due to bending of the optical fiber and / or the generation of leaked light due to the formation of a long period grating, an optical wave is applied to the optical fiber. Since it is confirmed that is conducting, it is possible to perform cord contrast even for an optical fiber having excellent bending loss characteristics. Furthermore, it is possible to perform a small and efficient operation.

  In the above description, the grating forming tools 20, 220, and 320 are described using the optical fiber contrast devices 100, 200, and 300 provided in the optical fiber bending members 10, 210, and 310. However, from the light receiving position of the light receiver. Further, on the upstream side, the grating forming device may be a cord contrast device provided adjacent to the optical fiber bending member. Even such a core wire contrast device has the same effects as the above-described core wire contrast devices 100, 200, and 300.

  The light beam contrast method and apparatus according to the present invention can be used for specifying an optical fiber during construction, maintenance, and operation of an optical line.

It is the schematic for demonstrating 1st embodiment of the core line contrast apparatus and method which concern on this invention. It is the figure which showed typically the location where stress is added to an optical fiber by 1st embodiment of the core wire contrast apparatus and method which concern on this invention. It is the schematic for demonstrating 2nd embodiment of the core line contrast apparatus and method which concern on this invention. It is the schematic for demonstrating 3rd embodiment of the core wire contrast apparatus and method which concern on this invention. It is a graph which shows the relationship between a wavelength and a loss at the time of applying to a hole assist optical fiber using 1st embodiment of the core line contrast apparatus and method which concern on this invention. LP ₁₁ mode, LP ₁₂ mode in a single mode optical fiber, and, in the case of LP ₁₃ mode, which is a graph showing the relationship between the grating period and the operating wavelength. It is a graph which shows the relationship between a grating period and an operating wavelength in the case of a hole assist optical fiber (HAF) and a trench type optical fiber (trench A, B). It is a figure which shows typically an example of the arrangement | positioning method of the projection part of the grating formation tool which 1st embodiment of the core wire contrast apparatus and method which concern on this invention comprises. It is a graph showing the bending loss characteristic of SMF concerning the core line contrast apparatus and method of this invention. It is a graph which shows the relationship between the magnitude | size of the stress by 1st embodiment of the core line contrast apparatus and method which concerns on this invention, and the leakage light intensity detected with a light receiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 10,210,310 Optical fiber bending member 11 Convex member 12 Curved part 12a Entering side curved part 15 Recessed material 20,220,320 Grating formation tool 30 Light receiver 100,200,300

Claims (8)

A bending portion having a mechanism for bending the optical fiber;
A grating forming portion that forms a long-period grating in the optical fiber by applying stress to the optical fiber through a plurality of concave and convex portions;
A light receiving portion for detecting leakage light generated in the bent portion or the grating forming portion or both,
The apparatus for contrasting cords, wherein the grating forming part is installed in the bending part or adjacent to the bending part. The bending portion has a bending portion for bending the optical fiber;
The core wire contrast device according to claim 1, wherein the plurality of concave and convex portions are provided in the curved portion. 3. The cord contrast device according to claim 1, wherein the period of the irregularities in the plurality of irregularities changes along the longitudinal direction of the optical fiber. 4. The cord contrast device according to claim 1, wherein a period of irregularities in the plurality of irregularities is 0.82 mm or less. 5. A long period grating is formed on the optical fiber by applying a stress to the optical fiber through a plurality of concave and convex portions at a bent portion of the optical fiber or an adjacent portion thereof, and bending the optical fiber. Detecting the generation of leaked light due to bending of the optical fiber and / or the generation of leaked light due to the formation of the long-period grating, thereby confirming that a light wave is conducted to the optical fiber. Method. The bending of the optical fiber is performed by a bending portion that bends the optical fiber,
6. The method according to claim 5, wherein the long-period grating is formed by the plurality of concave and convex portions provided on the curved portion. The method of contrasting cores according to claim 5 or 6, wherein the period of the irregularities in the plurality of irregularities changes along the longitudinal direction of the optical fiber. The cord contrast method according to any one of claims 5 to 7, wherein a period of irregularities in the plurality of irregularities is 0.82 mm or less.

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