Method for Measuring Bending Loss of Optical Fiber

Abstract

This optical fiber bending loss measuring method is for calculating an optical fiber bending loss by applying bending to an optical fiber F through use of a plurality of mandrels (e.g., fixed mandrels 55 and movable mandrels 65) that are disposed between a feed-out part 10 and a fixing part (e.g., fiber catcher 70) and that are alternately arranged in the longitudinal direction of the optical fiber. The method includes: a step for fixing, to the fixing part, an optical fiber fed out from the feed-out part without being held between adjacent mandrels; a step for moving the movable mandrels to a forward position and applying bending to the optical fiber by sandwiching the optical fiber between adjacent mandrels so as to bend the optical fiber at a prescribed angle in the longitudinal direction; and a step for calculating an optical fiber bending loss in a state where the bending is applied to the optical fiber.

Description

Technical Field

[0001] The present disclosure relates to a method for measuring bending loss of an optical fiber.

[0002] This application claims priority based on Japanese Patent Application No. 2020-102574 filed on June 12, 2020, and incorporates all the descriptions described in the above Japanese application.

Background Art

[0003] Bending loss characteristics are one of the basic characteristics of an optical fiber. In Recommendation G.652 of the international standard ITU-T (International Telecommunication Union - Telecommunication Standardization sector), the characteristics of a general-purpose single-mode optical fiber (SMF: Single Mode Fiber) are described, and in Recommendation G.657, the characteristics of a low-bending-loss single-mode optical fiber are described. Bending loss is obtained from the attenuation of light with respect to the bent optical fiber. For example, Patent Document 1 discloses a technique for obtaining bending loss over the entire length of an optical fiber.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] A method for measuring the bending loss of an optical fiber according to an aspect of the present disclosure is a method for measuring the bending loss of an optical fiber, which applies bending to the optical fiber by using a plurality of mandrels provided between a feeding portion of the optical fiber and a fixing portion of the optical fiber and arranged alternately in the longitudinal direction of the optical fiber, wherein each adjacent mandrel includes a fixed mandrel that does not move and a moving mandrel configured to be movable between a reference position where no bending is applied to the optical fiber and a forward position where bending is applied to the optical fiber with respect to the fixed mandrel. Composed of pass the optical fiber fed from the feeding portion through between each of the mandrels without sandwiching the optical fiber between adjacent mandrels In a state where no bending is applied a step of fixing the optical fiber to the fixing portion; a step of moving the moving mandrel to the forward position and sandwiching the optical fiber between adjacent mandrels so that the longitudinal direction of the optical fiber is bent at a predetermined angle to apply bending to the optical fiber; and a step of obtaining the bending loss of the optical fiber in a state where bending is applied to the optical fiber.

Brief Description of the Drawings

[0006]

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BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the technique described in Patent Document 1, bending is applied to the optical fiber while the optical fiber is being paid out to obtain the bending loss. In this case, since the position of the optical fiber with respect to the mandrel changes at any time, the measurement variation may become large. Therefore, a measurement method for bending loss that does not cause large measurement variation is desired. In addition, in the technique described in Patent Document 1, an operator needs to hook the optical fiber on the mandrel, and the work is troublesome. For this reason, a measurement method for bending loss that does not make the work troublesome is also desired.

[0008] The present disclosure has been made in view of the above circumstances, and aims to provide a method for measuring the bending loss of an optical fiber that does not cause large measurement variation and Eliminating the need for the operator to hook the optical fiber onto the mandrel, the operator's does not make the work troublesome.

[0009] [Effects of the Present Disclosure] According to the above, it is not necessary to cause large measurement variation. In addition, the work does not become troublesome.

[0010] [Description of Embodiments of the Present Disclosure] First, the content of the embodiment of the present disclosure will be listed and described. The method for measuring the bending loss of an optical fiber according to the present disclosure is a method for measuring the bending loss of an optical fiber, which obtains the bending loss of the optical fiber by applying bending to the optical fiber using a plurality of mandrels provided between the feeding portion of the optical fiber and the fixing portion of the optical fiber and arranged alternately in the longitudinal direction of the optical fiber. Each adjacent mandrel includes a fixed mandrel that does not move and a moving mandrel configured to be movable between a reference position where no bending is applied to the optical fiber and a forward position where bending is applied to the optical fiber with respect to the fixed mandrel. Composed of pass the optical fiber fed from the feeding portion through between each of the mandrels without sandwiching the optical fiber between each adjacent mandrel In a state where no bending is applied a step of fixing the optical fiber to the fixing portion; a step of moving the moving mandrel to the forward position and sandwiching the optical fiber between each adjacent mandrel so that the longitudinal direction of the optical fiber is bent at a predetermined angle to apply bending to the optical fiber; and a step of obtaining the bending loss of the optical fiber in a state where bending is applied to the optical fiber. Since the bending loss is obtained by applying bending to the optical fiber with the mandrel while the optical fiber is fixed to the fixing portion, the measurement variation does not increase. Further, since the moving mandrel is moved to the forward position and sandwiched with the fixed mandrel to apply bending loss to the optical fiber, it is not necessary for the operator to hook the optical fiber on the mandrel, and the work is not troublesome.

[0011] (2) In one aspect of the method for measuring the bending loss of an optical fiber according to the present disclosure, among the plurality of moving mandrels, the moving mandrel located near the fixing portion is moved prior to the moving mandrel located near the feeding portion to apply bending to the optical fiber. Since bending is applied to the optical fiber from the fixing portion side to the feeding portion side, the tension generated in the optical fiber can be evened out and a portion where excessive tension is applied can be eliminated.

[0012] (3) In one aspect of the method for measuring the bending loss of an optical fiber according to the present disclosure, the moving mandrel located near the fixed portion is formed with a larger diameter than the moving mandrel located near the feeding portion. Since the mandrel is configured with two types of diameters and is moved in order from the larger-diameter mandrel to apply bending, it is possible to measure the bending loss for a plurality of bending diameters, and the number of measurement times for the reference can be reduced. As a result, the time required for measuring the bending loss of the optical fiber can be shortened.

[0013] (4) In one aspect of the method for measuring the bending loss of an optical fiber according to the present disclosure, the feeding portions are arranged in parallel along a direction intersecting the longitudinal direction of the optical fiber. Since bending can be simultaneously applied to a plurality of optical fibers using the mandrel, it is possible to improve the efficiency of measuring the bending loss of the optical fiber.

[0014] [Details of Embodiments of the Present Disclosure] Hereinafter, with reference to the accompanying drawings, a specific example of the method for measuring the bending loss of an optical fiber according to the present disclosure will be described. FIG. 1 is a schematic configuration diagram of a bending test apparatus 1 for implementing the method for measuring the bending loss of an optical fiber according to one aspect of the present disclosure. As shown in FIG. 1, the bending test apparatus 1 includes a feeding portion 10, a dancer roller 20, a bending applying device 30, a fiber catcher 70, and a power meter 80. The fiber catcher 70 corresponds to the fixed portion of the present disclosure.

[0015] The optical fiber F is pre-manufactured and is attached to the feeding portion 10 in a state of being wound around a bobbin 11. A light source 12 for inputting light to one end of the optical fiber F is installed in the feeding portion 10. The optical fiber F fed from the bobbin 11 of the feeding portion 10 is sent to the bending applying device 30 while being loaded with tension by the dancer roller 20 and is fixed to the fiber catcher 70.

[0016] In the bending applying device 30, bending can be applied to the optical fiber F using a fixed mandrel 55 and a movable mandrel 65, which will be described later. The optical fiber F fixed to the fiber catcher 70 is connected to the power meter 80. The power meter 80 has, for example, a light receiving unit 81 and a calculation unit 82. In the light receiving unit 81, the power of the light output from the other end of the optical fiber F is measured. The calculation unit 82 obtains the bending loss of the optical fiber F based on the power of the light measured by the light receiving unit 81 and the length of the optical fiber F to which bending is applied by the bending applying device 30.

[0017] In this way, with the optical fiber F fixed to the fiber catcher 70, bending is applied to the optical fiber F by the bending applying device 30 to obtain the bending loss. Therefore, compared with the case of obtaining the bending loss over the entire length of the optical fiber, the measurement variation does not increase. The bending applying device 30 has a guide 31 between the dancer roller 20 and the fixed mandrel 55 and the movable mandrel 65, and also has a guide 36 between the fiber catcher 70. The guide 31 secures the supply height of the optical fiber F toward the bending applying device 30, and the guide 36 secures the discharge height of the optical fiber F away from the bending applying device 30.

[0018] As shown in FIG. 2A, the bending applying device 30 has, for example, a rectangular base plate 51 in a front view. A plurality (for example, five) of through grooves 52 are provided at equal intervals in the base plate 51. Each through groove 52 extends along a direction (the vertical direction shown in the figure) orthogonal to the longitudinal direction (the left - right direction shown in FIG. 2A) of the optical fiber F from the guide 31 to the guide 36 described in FIG. 1, and all of them are formed through the base plate 51.

[0019] The base plate 51 is provided with a plurality (for example, seven) of fixed mandrels 55 at equal intervals. The fixed mandrels 55 are rotatably supported via bearings on a rotating shaft provided on the base plate 51, but the fixed mandrels 55 are fixed on the base plate 51 and do not move in the vertical direction shown in the figure. The fixed mandrels 55 are arranged one by one adjacent to the through groove 52 along the longitudinal direction of the optical fiber F. The diameter (2r) of the fixed mandrel 55 is selected from, for example, 10 mm, 15 mm, 20 mm, 30 mm, and 60 mm.

[0020] Further, as shown in FIG. 2B, the bending applying device 30 has a slide plate 61, for example, on the back side of the base plate 51. The slide plate 61 is provided with a plurality (for example, six) of moving mandrels 65 at equal intervals. In FIG. 2B, an example of two slide plates 61 each mounting three moving mandrels 65 will be described, but it may be configured with one slide plate 61 mounting, for example, six moving mandrels 65.

[0021] Each moving mandrel 65 is rotatably supported via a bearing on a rotating shaft provided on the slide plate 61. Each rotating shaft is disposed in the through groove 52, and each moving mandrel 65 is arranged one by one adjacent to the fixed mandrel 55. The diameter (2r) of the moving mandrel 65 is set to be the same as the diameter of the adjacent fixed mandrel 55 and is selected from, for example, 10 mm, 15 mm, 20 mm, 30 mm, and 60 mm. It should be noted that it is preferable that both the fixed mandrel 55 and the moving mandrel 65 are rotatably supported, but they do not have to rotate if the mandrel surface is slippery and smooth.

[0022] The slide plate 61 is movable in the vertical direction shown in FIG. 2A by a motor 62. The moving mandrel 65 is located at one end of the through groove 52 as shown in FIG. 2A (corresponding to the reference position where no bending is applied to the optical fiber of the present disclosure). When the motor 62 is driven while the optical fiber F is being fed from the guide 31 toward the guide 36, each moving mandrel 65 moves downward along the through groove 52 as shown in FIG. 2C. In the case of FIG. 2C, the outer peripheries of the adjacent fixed mandrels 55 and the moving mandrel 65 are arranged at a predetermined interval so as to face each other without contact. The optical fiber F is wound around the outer periphery of the moving mandrel 65 and bends upward, and is wound around the outer periphery of the adjacent fixed mandrel 55 on its right and bends downward.

[0023] Thereafter, when the moving mandrel 65 moves to the other end of the through groove 52 as shown in FIG. 2D (corresponding to the forward position where bending is applied to the optical fiber of the present disclosure), for example, the adjacent fixed mandrel 55 and the moving mandrel 65 are arranged at a predetermined interval so that their outer peripheries face each other without contact, and the fixed mandrel 55 moves upward and the moving mandrel 65 moves downward in the left - right direction and are arranged alternately. In this case, the optical fiber F is wound around each outer periphery of the moving mandrel 65 and bends upward at an angle close to but not exceeding 180 degrees, for example, and also bends downward at an angle close to 180 degrees at the fixed mandrel 55 adjacent to the right of this moving mandrel 65. Thereby, the optical fiber F is bent by being sandwiched between the adjacent fixed mandrel 55 and the moving mandrel 65.

[0024] In this way, by moving the moving mandrel 65 to the forward position and sandwiching it with the fixed mandrel 55 to apply bending loss to the optical fiber F, it is not necessary for the operator to hook the optical fiber on the mandrel, and the work is not troublesome.

[0025] (Example 1) FIGS. 3 to 5 show a method for measuring the bending loss of an optical fiber according to Example 1. In this Example 1, the diameters (2r) of both the fixed mandrel 55 and the moving mandrel 65 are selected to be, for example, 30 mm.

[0026] First, as shown in FIG. 3, the optical fiber F fed out from the bobbin 11 of the pay - out unit 10 is fed out from the guide 31 toward the guide 36 while a tension is applied by the dancer roller 20, and fixed to the fiber catcher 70 (fiber fixing step). In this case, each moving mandrel 65 is arranged at the reference position, and the optical fiber F is not sandwiched between the adjacent fixed mandrel 55 and the moving mandrel 65, but is passed between the fixed mandrel 55 and the moving mandrel 65 and fixed to the fiber catcher 70. One end of this optical fiber F is connected to the power meter 80.

[0027] Next, for example, without moving each moving mandrel 65 from the reference position, that is, without applying a bend to the optical fiber F, the power of the light emitted from the optical fiber F is measured by the power meter 80 (reference measurement step). Subsequently, as shown in FIG. 4, for example, three moving mandrels 65 located near the fiber catcher 70 are moved to the forward position. As a result, the optical fiber F is bent upward at a predetermined angle (for example, 180 degrees) by the moving mandrel 65 and bent downward at a predetermined angle (for example, 180 degrees) by the adjacent fixed mandrel 55 on the right, and the optical fiber F is sandwiched between the adjacent moving mandrel 65 and fixed mandrel 55 to apply a bend to the optical fiber F (downstream side bend - applying step).

[0028] Thereafter, as shown in FIG. 5, for example, three moving mandrels 65 located near the bobbin 11 are also moved to the forward position, that is, with the optical fiber F bent by all of the fixed mandrel 55 and the moving mandrels 65, the power of the light emitted from the optical fiber F is measured by the power meter 80. Then, the bending loss is obtained from the difference between the power measured in the reference measurement step and the power measured in the bending loss measurement step (bending loss measurement step). In this way, since the bend is applied to the optical fiber F from the fiber catcher 70 side toward the pay - out unit 10 side, the tension generated in the optical fiber F can be evened out, and the location where excessive tension is applied can be eliminated.

[0029] In Example 1, the reference measurement step, the downstream bending application step, and the bending loss measurement step were performed in this order. However, it is also possible to perform them in the order of the downstream bending application step, the bending loss measurement step, and the reference measurement step. The reference measurement step may be performed with the optical fiber F finally returned to a state where no bending is applied. In addition, although an example of a mandrel with bearings has been described, when the moving mandrel 65 is moved in order from the fiber catcher 70 side toward the pay-out section 10 side, it is also applicable to a mandrel without bearings.

[0030] (Example 2) Figs. 6 to 8 show a method for measuring the bending loss of an optical fiber according to Example 2. In this Example 2, the diameters (2r) of the three moving mandrels 65 and the three fixed mandrels 55 located near the fiber catcher 70 are selected to be, for example, 30 mm, while the diameters (2r) of the three moving mandrels 63 and the three fixed mandrels 53 located near the pay-out section 10 are selected to be, for example, 15 mm.

[0031] Also in the case of Example 2, as in Example 1, the optical fiber F fed out from the bobbin 11 is fixed to the fiber catcher 70 while a tension is applied by the dancer roller 20 (fiber fixing step: Fig. 6). Next, with the optical fiber F not being bent, the power of the light emitted from the optical fiber F is measured by the power meter 80 (reference measurement step). Subsequently, as shown in Fig. 7, the large-diameter moving mandrel 65 is moved to the forward position, and the optical fiber F is sandwiched between the adjacent moving mandrel 65 and the fixed mandrel 55 to apply bending to the optical fiber F (downstream bending application step).

[0032] Then, with the large-diameter fixed mandrel 55 and the movable mandrel 65 applying bending, the power meter 80 measures the power of the light emitted from the optical fiber F. Then, the large-diameter bending loss is obtained from the difference between the power measured in the reference measurement step and the power measured in the large-diameter bending loss measurement step (large-diameter bending loss measurement step). Thereafter, as shown in FIG. 8, the small-diameter movable mandrel 63 is also moved to the forward position, and the optical fiber F is bent by all of the fixed mandrel 55, the movable mandrel 65, the fixed mandrel 53, and the movable mandrel 63 (upstream bending application step). In this state, the power meter 80 measures the power of the light emitted from the optical fiber F. In this case, using the power measured in the large-diameter bending loss measurement step as a reference, the small-diameter bending loss can be obtained from the difference between the power measured in the state where bending is applied by the small-diameter fixed mandrel 53 and the movable mandrel 63 (small-diameter bending loss measurement step).

[0033] In this way, by configuring the mandrels with, for example, two diameters and applying bending by moving the large-diameter movable mandrel 65 and the small-diameter movable mandrel 63 in this order, the bending loss for a plurality of bending diameters can be measured, and the number of reference measurements can be reduced. As a result, the time required for measuring the bending loss of the optical fiber F can be shortened.

[0034] (Example 3) In the above Examples 1 and 2, an example in which one optical fiber F is sent from one pay-out unit 10 to the bending device 30 has been described. However, as described above, when a mandrel is used instead of a roller in the bending device 30, a plurality of pay-out units may be arranged in parallel along a direction intersecting the longitudinal direction of the optical fiber F.

[0035] Specifically, as shown in FIG. 9, if the guide 41 is arranged in parallel with the guide 31 and the guide 46 is arranged in parallel with the guide 36, in addition to the optical fiber F going from the guide 31 to the guide 36, for the optical fiber F going from the guide 41 to the guide 46, bending can also be applied using the fixed mandrel 55 and the moving mandrel 65. Therefore, the efficiency of measuring the bending loss of the optical fiber F is improved.

[0036] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is shown not by the above meaning, but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0037] 1... Bending test apparatus, 10... Pay-out unit, 11... Bobbin, 12... Light source, 20... Dancer roller, 30... Bending application device, 31, 36, 41, 46... Guides, 51... Base plate, 52... Through groove, 53, 55... Fixed mandrels, 61... Slide plate, 62... Motor, 63, 65... Moving mandrels, 70... Fiber catcher (fixed part), 80... Power meter, 81... Light receiving part, 82... Calculation part, F... Optical fiber.

Claims

1. A method for measuring the bending loss of an optical fiber, which is provided between the pay-out section of the optical fiber and the fixing section of the optical fiber, and applies bending to the optical fiber by using a plurality of mandrels arranged alternately in the longitudinal direction of the optical fiber, thereby obtaining the bending loss of the optical fiber, comprising: each adjacent pair of said mandrels consists of a fixed mandrel that does not move and a movable mandrel configured to be movable between a reference position where no bending is applied to the optical fiber and a forward position where bending is applied to the optical fiber with respect to the fixed mandrel; a step of fixing the optical fiber fed out from the pay-out section to the fixing section without being sandwiched between each adjacent pair of said mandrels and passing between each of said mandrels in a state where no bending is applied; a step of moving the movable mandrel to the forward position and sandwiching the optical fiber between each adjacent pair of said mandrels so that the longitudinal direction of the optical fiber is bent at a predetermined angle to apply bending to the optical fiber; a step of obtaining the bending loss of the optical fiber in a state where bending is applied to the optical fiber; A method for measuring the bending loss of an optical fiber, comprising the above steps.

2. The method for measuring the bending loss of an optical fiber according to claim 1, wherein among the plurality of movable mandrels, the movable mandrel located near the fixing section is moved prior to the movable mandrel located near the pay-out section to apply bending to the optical fiber.

3. The method for measuring the bending loss of an optical fiber according to claim 2, wherein the movable mandrel located near the fixing section is formed with a larger diameter than the movable mandrel located near the pay-out section.

4. The method for measuring the bending loss of an optical fiber according to any one of claims 1 to 3, wherein the pay-out sections are arranged in parallel along a direction intersecting the longitudinal direction of the optical fiber.

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