Bending imparting device for measuring bending loss, bending test device

Abstract

The bending imparting device (30) has at least three or more mandrels (illustrated by a fixed mandrel (55) and a movable mandrel (65)) and imparts a bend to the drawn optical fiber (F) by winding the optical fiber around the mandrels. The diameter of the optical fiber is denoted as D, the radius of the mandrel is denoted as r, the direction connecting the tangent point (T1) on the upstream side at which the optical fiber comes into contact with the mandrel and the tangent point (T2) on the downstream side at which the optical fiber separates from the mandrel is denoted as a first direction (illustrated by the horizontal direction), the interval between adjacent mandrels observed in the first direction is denoted as 2r+d, the direction orthogonal to the first direction is denoted as a second direction (illustrated by the vertical direction), and the interval between adjacent mandrels observed in the second direction is denoted as s. The angle θ formed by the second direction and the common internal tangent line of the adjacent mandrels observed at the center position of the optical fiber is 0 degrees or more and 45 degrees or less, and formula 3 is satisfied.

Description

Technical Field

[0001] This invention relates to a bending induction device and a bending test apparatus for measuring bending loss.

[0002] This application claims priority based on Japanese Application No. 2020-102572, filed on June 12, 2020, and incorporates all the contents of the aforementioned Japanese application. Background Technology

[0003] Bending loss is one of the fundamental characteristics of optical fiber. The characteristics of general single-mode fiber (SMF) are described in ITU-T (International Telecommunication Union-Telecommunication Standardization sector) Recommendation G.652, and the characteristics of low-bending-loss single-mode fiber are described in Recommendation G.657.

[0004] Bending loss is determined based on the attenuation of light in a bent optical fiber. For example, Patent Document 1 discloses a structure in which bending loss is determined by providing multiple sides with different curvatures on a single cylinder.

[0005] Patent Document 1: Japanese Patent Application Publication No. 1-203938 Summary of the Invention

[0006] One aspect of the present invention relates to a bending-imposing device for measuring the bending loss of an optical fiber, comprising at least three mandrels. The drawn optical fiber is bent by winding it around the mandrels. The mandrels are arranged offset from each other at predetermined intervals, such that they are non-contactly opposite each other on the outer periphery of adjacent mandrels along the length direction of the optical fiber. The diameter of the optical fiber is defined as D, and the radius of the mandrels is defined as r. In a plane orthogonal to the rotation axis of the mandrels, a first direction is defined as the direction in which the tangent point upstream of the central mandrel (one of the three mandrels of the same diameter arranged continuously along the length direction of the optical fiber) where the optical fiber wound on the central mandrel begins to contact the central mandrel, and the tangent point downstream of the central mandrel where the optical fiber wound on the central mandrel begins to separate from the central mandrel, connecting to the central mandrel. The interval between adjacent mandrels observed in the first direction is defined as 2r.

[0007] +d, in a plane orthogonal to the axis of rotation of the mandrel, the direction orthogonal to the first direction is designated as the second direction, and the interval between adjacent mandrels observed in the second direction is designated as s. The angle θ formed by the second direction and the common internal tangent of adjacent mandrels observed at the center of the optical fiber is greater than 0 degrees and less than 45 degrees. Wherein, the angle θ satisfies the following equation 3. Attached Figure Description

[0008] Figure 1 This is a schematic structural diagram of a bending test apparatus according to one aspect of the present invention.

[0009] Figure 2A yes Figure 1 The curvature gives the device a front view.

[0010] Figure 2B yes Figure 2A The B-B line sectional view.

[0011] Figure 2C Yes Figure 1 The diagram illustrates the action of the device caused by the bending.

[0012] Figure 2D Yes Figure 1 The diagram illustrates the action of the device caused by the bending.

[0013] Figure 3 This is a diagram representing a computational model configured with a mandrel.

[0014] Figure 4 This is a diagram representing a state where no bending is imposed on the optical fiber.

[0015] Figure 5 It is a diagram that shows how moving a portion of the moving mandrel imparts a bending state to the optical fiber.

[0016] Figure 6 It is a diagram that shows how moving a portion of the moving mandrel imparts a bending state to the optical fiber.

[0017] Figure 7 This diagram illustrates how moving all the moving mandrels causes the optical fiber to bend.

[0018] Figure 8 This is a diagram showing an example of multiple guide sections arranged side by side. Detailed Implementation

[0019] [The problem to be solved by this invention]

[0020] In the structure described in the aforementioned Patent Document 1, the number of optical fiber turns is small, making it difficult to determine the bending loss for low bending loss single-mode optical fiber.

[0021] On the other hand, simply increasing the number of turns of the optical fiber will reduce efficiency. In addition, since the optical fiber is wound in a spiral shape, the winding angle of the optical fiber is easy to become smaller, so sometimes it is impossible to calculate the accurate bending loss.

[0022] Furthermore, when winding optical fibers with a small diameter (e.g., around φ200μm), the bending loss can sometimes not be accurately calculated because the winding angle of the optical fiber tends to become smaller.

[0023] The present invention was proposed in view of the above-mentioned actual situation, and its purpose is to provide a bending induction device and a bending test device for measuring bending loss that are highly efficient and can accurately determine bending loss.

[0024] [Effects of the Invention]

[0025] Based on the above, bending loss can be calculated efficiently and accurately.

[0026] [Description of embodiments of the present invention]

[0027] First, the embodiments of the present invention will be described.

[0028] The bending induction device for measuring bending loss according to the present invention (1) has at least three mandrels, which induce bending in the optical fiber by winding the drawn optical fiber around the mandrels. The mandrels are arranged staggered from each other at a predetermined interval so as to be non-contactly opposite to each other on the outer periphery of adjacent mandrels in the longitudinal direction of the optical fiber. The diameter of the optical fiber is set as D, and the radius of the mandrels is set as r. In a plane orthogonal to the rotation axis of the mandrels, the optical fiber wound on the central mandrel among three mandrels of the same diameter arranged continuously along the longitudinal direction of the optical fiber is connected to the central mandrel. The direction connecting the upstream tangent point where the shaft begins to contact and the downstream tangent point where the optical fiber wound on the central mandrel begins to separate from the central mandrel is defined as the first direction. The interval between adjacent mandrels observed in the first direction is defined as 2r+d. The direction orthogonal to the first direction in a plane orthogonal to the axis of rotation of the mandrel is defined as the second direction. The interval between adjacent mandrels observed in the second direction is defined as s. The angle θ formed by the second direction and the common internal tangent of adjacent mandrels observed at the center of the optical fiber is greater than 0 degrees and less than 45 degrees. The angle θ satisfies the following equation 3.

[0029] If we find the spacing "2r+d" in the first direction and the spacing "s" in the second direction that satisfy Equation 3, we can determine the configuration of each mandrel. Therefore, even if the number of turns of the fiber is increased, the winding angle of the fiber relative to the mandrel will not decrease, thus enabling efficient and accurate determination of bending loss.

[0030] (2) In one embodiment of the bending loss measuring device of the present invention, the bending device has guides for ensuring the supply height of the optical fiber toward the mandrel and the discharge height of the optical fiber separated from the mandrel.

[0031] It can ensure the supply and discharge positions of optical fibers, which helps to accurately measure bending loss.

[0032] (3) In one embodiment of the bending loss measuring device of the present invention, the guide portion is arranged side by side in a direction intersecting the length direction of the optical fiber.

[0033] Using a mandrel allows multiple optical fibers to be bent simultaneously, thus improving the efficiency of optical fiber bending loss measurement.

[0034] (4) In one embodiment of the bending loss measuring device of the present invention, each of the adjacent mandrels is a movable mandrel and a fixed mandrel that does not move. The movable mandrel is configured to move relative to the fixed mandrel between a reference position in which no bending is applied to the optical fiber and a forward position in which bending is applied to the optical fiber. The movable mandrel that is located downstream in the longitudinal direction of the optical fiber moves ahead of the movable mandrel located upstream in order to apply bending to the optical fiber.

[0035] By applying a bend to the optical fiber from the downstream side to the upstream side, the tension generated in the optical fiber can be made uniform, eliminating areas where excessive tension is applied.

[0036] (5) In one embodiment of the bending test apparatus of the present invention, a bending-applying device for measuring bending loss according to any of the above claims has a tension-applying mechanism for applying tension to the optical fiber toward the mandrel.

[0037] It can prevent the optical fiber from loosening when it is wound around the mandrel.

[0038] (6) In one embodiment of the bending test apparatus of the present invention, the bending test apparatus has at least an upstream bending device located on the upstream side when viewed in the longitudinal direction of the optical fiber, and a downstream bending device located on the downstream side compared to the upstream bending device, wherein the mandrel of the downstream bending device is formed to have a larger diameter than the mandrel of the upstream bending device, such that the mandrel of the downstream bending device moves earlier in the second direction than the mandrel of the upstream bending device to impart bending to the optical fiber.

[0039] By using a mandrel with two different diameters, and moving it sequentially from the larger diameter mandrel to induce bending, it is possible to measure bending loss for multiple bending diameters and complete the measurement with fewer reference measurements. This reduces the time required for measuring the bending loss of optical fibers.

[0040] (7) In one embodiment of the bending test apparatus of the present invention, a calculation unit is provided, which calculates the bending loss based on the length of the optical fiber to be bent.

[0041] The length of the fiber that has been bent can be determined, for example by converting it to 1 turn or 10 turns, so that the bending loss can be easily calculated.

[0042] [Detailed Description of Embodiments of the Invention]

[0043] Hereinafter, specific examples of the bending induction device and bending test device for measuring bending loss according to the present invention will be described with reference to the accompanying drawings. Figure 1 This is a schematic structural diagram of a bending test apparatus 1 according to one aspect of the present invention.

[0044] like Figure 1 As shown, the bending test apparatus 1 includes an extraction section 10, a tension adjustment roller 20, a bending induction device 30, an optical fiber catcher 70, and a power meter 80. The tension adjustment roller 20 corresponds to the tension induction mechanism of the present invention, and the bending induction device 30 corresponds to the bending induction device for measuring bending loss of the present invention.

[0045] The optical fiber F is pre-manufactured and mounted on the extraction section 10 in a state of being wound on a spool 11. A light source 12 for inputting light to one end of the optical fiber F is provided in the extraction section 10.

[0046] The optical fiber F extracted from the spool 11 of the extraction section 10 is fed into the bending device 30 under tension applied by the tension adjustment roller 20 and is fixed in the optical fiber catcher 70.

[0047] In the bending device 30, the fixed mandrel 55 and the movable mandrel 65, described later, can be used to bend the optical fiber F.

[0048] An optical fiber F fixed to the optical fiber catcher 70 is connected to a power meter 80. The power meter 80 includes, for example, a light receiving section 81 and a calculation section 82. In the light receiving section 81, the power of the light output from the other end of the optical fiber F is measured. The calculation section 82 calculates the bending loss of the optical fiber F based on the power of the light measured by the light receiving section 81 and the length of the optical fiber F that has been bent by the bending device 30.

[0049] In addition to the fixed spindle 55 and the movable spindle 65, the bending device 30 has a guide portion 31 between itself and the tension adjusting roller 20, and a guide portion 36 between itself and the fiber catcher 70. The guide portion 31 ensures the supply height of the fiber F toward the bending device 30, and the guide portion 36 ensures the discharge height of the fiber F separated from the bending device 30.

[0050] Bending device 30 Figure 2A As shown, for example, a base plate 51 has a rectangular shape when viewed from the front. A plurality of (e.g., 5) through slots 52 are provided at equal intervals on the base plate 51. Each through slot 52 extends along the […]. Figure 1 The described guide portion 31 is oriented along the length direction of the optical fiber F toward the guide portion 36. Figure 2A The left-right direction shown in the figure extends in the orthogonal direction (up-down direction shown in the figure), which is formed by penetrating the base plate 51.

[0051] A plurality of (e.g., seven) fixed mandrels 55 are arranged at equal intervals on the base plate 51. Each fixed mandrel 55 is rotatably supported by a rotation axis provided on the base plate 51 via bearings, but the fixed mandrels 55 are fixed to the base plate 51 and do not move in the vertical direction shown in the figure. One fixed mandrel 55 is arranged next to each through slot 52 along the length direction of the optical fiber F. The diameter (2r) of the fixed mandrel 55 is, for example, any one of 10mm, 15mm, 20mm, 30mm, or 60mm.

[0052] Additionally, the bending device 30, as Figure 2B As shown, a sliding plate 61 is provided on, for example, the back side of the base plate 51. A plurality of (e.g., six) movable spindles 65 are arranged at equal intervals on the sliding plate 61. Furthermore, in this… Figure 2B The example given is two sliding plates 61 with three movable spindles 65 mounted on each of them. However, it is also possible to use a single sliding plate 61 with six movable spindles 65 mounted on each of them.

[0053] Each movable spindle 65 is rotatably supported by a rotating shaft provided on a sliding plate 61 via bearings. Each rotating shaft is disposed within a through groove 52, and one movable spindle 65 is disposed next to each fixed spindle 55. The diameter (2r) of the movable spindle 65 is set to be the same as the diameter of the adjacent fixed spindle 55, for example, any one of 10mm, 15mm, 20mm, 30mm, or 60mm.

[0054] Furthermore, both the fixed spindle 55 and the movable spindle 65 are preferably supported in a way that allows them to rotate freely, but if the surface of the spindle is easy to slide and smooth, they may not rotate.

[0055] The sliding plate 61 is driven by the motor 62 along... Figure 2AIt can move in the up and down directions as shown.

[0056] The movable mandrel 65 is located in Figure 2A One end of the through slot 52 shown (corresponding to the reference position of the present invention where no bending is applied to the optical fiber), when the optical fiber F is pulled out from the guide portion 31 toward the guide portion 36, if the motor 62 is driven, each moving spindle 65 will move as follows: Figure 2C As shown, it moves downwards along the through groove 52. Figure 2C In this case, the outer peripheries of adjacent fixed mandrels 55 and movable mandrels 65 are arranged apart by a predetermined interval in a non-contact manner. At the movable mandrel 65, the optical fiber F is wound around its outer periphery and bent upwards, and at the adjacent fixed mandrel 55 on its right side, it is wound around its outer periphery and bent downwards.

[0057] Then, move the mandrel 65 degrees as follows Figure 2D As shown, for example, when moving to the other end of the through slot 52 (corresponding to the forward position for bending the optical fiber according to the present invention), the adjacent fixed mandrels 55 and movable mandrels 65 are arranged at a predetermined interval with their outer circumferences facing each other in a non-contact manner, and are staggered from each other in the left-right direction, with the fixed mandrels 55 positioned higher and the movable mandrels 65 positioned lower. In this case, the optical fiber F is wound around the outer circumference of the movable mandrels 65, for example, not exceeding 180 degrees, but bent upward at an angle close to 180 degrees, even at the fixed mandrel 55 adjacent to the right side of the movable mandrel 65, it is similarly bent downward at an angle close to 180 degrees. Thus, the optical fiber F is bent by being clamped by the adjacent fixed mandrels 55 and movable mandrels 65.

[0058] As described above, by moving the movable mandrel 65 to the forward position and clamping it with the fixed mandrel 55, bending loss is imparted to the optical fiber F. Therefore, the operator does not need to hook the optical fiber onto the mandrel, and the operation does not become troublesome.

[0059] Here, when the moving spindle 65 is moved to... Figure 2D In the forward position shown, the relationship defined by the fixed mandrel 55 and the movable mandrel 65 wound with the optical fiber F holds.

[0060] In detail, such as Figure 2D The enlarged forward position shown Figure 3 As shown, focus is placed on the centrally located movable spindle 65 among the three continuously arranged fixed spindles 55 and movable spindle 65. The optical fiber F approaches downwards from the adjacent fixed spindle 55 on the left, and after contacting the movable spindle 65 at the upstream tangent point T1, it winds around the outer periphery of the movable spindle 65. Furthermore, it begins to separate from the movable spindle 65 at the downstream tangent point T2, and approaches the adjacent fixed spindle 55 on the right upwards.

[0061] Furthermore, in this specification, the side from which the optical fiber is extracted is designated as the upstream side, and the side from which the optical fiber is fixed by the optical fiber catcher is designated as the downstream side.

[0062] If the radii of both the fixed mandrel 55 and the movable mandrel 65 are set to r and are the same, then Figure 3 The horizontal axial distance between adjacent spindles shown can be represented by 2r + d. Furthermore, this horizontal direction is related to... Figure 2A The same direction as the left and right directions is equivalent to the first direction, which is the direction in which the tangent point T1 on the upstream side where the optical fiber begins to contact the central mandrel and the tangent point T2 on the downstream side where the optical fiber begins to separate from the central mandrel in a plane orthogonal to the rotation axis of the mandrel of the present invention (the plane in which the rotation axis of the mandrel is set as the normal).

[0063] in addition, Figure 3 The interaxial distance between adjacent spindles in the vertical direction can be represented by s. Furthermore, this vertical direction is relative to... Figure 2A The direction that is the same as the vertical direction is equivalent to the second direction, which is a plane orthogonal to the rotation axis of the spindle of the present invention and a direction orthogonal to the first direction.

[0064] Furthermore, when the diameter of the optical fiber F is set to D (D≤d), the distance between the common internal tangents of the fixed mandrel 55 and the movable mandrel 65 observed at the center of the optical fiber F becomes Figure 3 The length of line BC in the right triangle ABC shown. 2 =AB 2 -AC 2 AB 2 (2r+d) 2 +s 2 AC 2 (2r+D) 2 Therefore, the length of line BC can be expressed by Equation 1.

[0065] [Formula 1]

[0066]

[0067] On the other hand, in the Figure 3 When the angle between the vertical direction of the adjacent mandrels shown and the common internal tangent of the fixed mandrel 55 and the movable mandrel 65 observed at the center of the fiber F is set as θ (0°≤θ<90°), the length of the straight line BC becomes the sum of AC*tanθ and s / cosθ, and can therefore be expressed by Equation 2.

[0068] [Equation 2]

[0069]

[0070] Therefore, Equation 3 can be derived from Equations 1 and 2.

[0071] [Formula 3]

[0072]

[0073] As mentioned above, if θ satisfies equation 3, Figure 3 The horizontal axis-to-axis distance 2r+d and the vertical axis-to-axis distance s of the adjacent spindles shown determine the configuration of the fixed spindle 55 and the movable spindle 65. Therefore, even if the number of turns of the fiber F is increased, the winding angle of the fiber F relative to the fixed spindle 55 and the movable spindle 65 will not decrease, thus enabling efficient and accurate calculation of bending loss.

[0074] Furthermore, the winding angle of the optical fiber F relative to the movable mandrel 65 is expressed as 180°–2θ. When θ is 0 degrees, the winding angle of the optical fiber F becomes 180 degrees, which is the ideal winding state. Moreover, when using the bending device 30, the configuration of the fixed mandrel 55 and the movable mandrel 65 can be determined such that the ratio of the difference between the winding length in the ideal winding state and the actual winding length to the winding length in the ideal winding state is, for example, within 50% (2θ / 180°≤0.5), preferably within 10% (2θ / 180°≤0.1), and more preferably within 2% (2θ / 180°≤0.02). That is, the fixed mandrel 55 and the movable mandrel 65 are configured such that θ is 0 degrees or more and 45 degrees or less, preferably such that θ is 0 degrees or more and 9 degrees or less, and more preferably such that θ is 0 degrees or more and 1.8 degrees or less.

[0075] By setting θ within the aforementioned range, the number of fixed mandrels 55 and movable mandrels 65 is not excessively increased, thus ensuring the length of the bent optical fiber F.

[0076] Furthermore, the length of the fiber F bent by the bending device 30 can be determined based on the winding angles of the fixed mandrel 55 and the movable mandrel 65 of the bending device 30. That is, by calculating θ using Equation 3, the lengths of the fiber F bent by the mandrels at both ends of the bending device 30 are rπ(90°―θ) / 180°, and the lengths of the fiber F bent by the mandrels other than the two ends are rπ(180°―2θ) / 180°. Therefore, by summing these lengths, the length of the fiber F bent by the bending device 30 can be determined.

[0077] (Example 1)

[0078] Figures 4-7 This is a diagram illustrating an example of a method for measuring the bending loss of optical fibers. In this embodiment, in... Figure 1 The described extraction section 10 has an upstream bending device 30a near its side, a downstream bending device 30c near its side, and a midstream bending device 30b between the upstream bending device 30a and the downstream bending device 30c.

[0079] The upstream bending device 30a has guide portions 31 and 32, and between guide portions 31 and 32, there is a fixed mandrel 53 and a movable mandrel 63, both with a diameter (2r) of, for example, 15 mm. The midstream bending device 30b has guide portions 33 and 34, and between guide portions 33 and 34, there is a fixed mandrel 54 and a movable mandrel 64, both with a diameter (2r) of, for example, 20 mm. The downstream bending device 30c has guide portions 35 and 36, and between guide portions 35 and 36, there is a fixed mandrel 55 and a movable mandrel 65, both with a diameter (2r) of, for example, 30 mm.

[0080] First, with the optical fiber F extracted from the extraction section 10 under tension applied by the tension adjusting roller 20, it is pulled from the guide section 31 toward the guide section 36 and fixed to the optical fiber catcher 70 (optical fiber fixing process). In this case, as... Figure 4 As shown, each of the movable spindles 63, 64, and 65 is positioned at a reference position. The optical fiber F is not held by adjacent spindles but passes between the spindles and is fixed to the optical fiber catcher 70. One end of the optical fiber F is connected to the power meter 80.

[0081] Next, for example, while keeping each moving spindle 63, 64, 65 in the reference position without moving, that is, without subjecting the fiber F to bending, the bending loss of the fiber F is determined by the power meter 80 (refer to the measurement procedure).

[0082] Next, as Figure 5As shown, the large-diameter movable mandrel 65 involved in the downstream bending device 30c is moved to a forward position. As a result, the optical fiber F bends upward at a predetermined angle (e.g., 180 degrees) at the movable mandrel 65 and downward at a predetermined angle (e.g., 180 degrees) at its adjacent fixed mandrel 55. The adjacent movable mandrel 65 and fixed mandrel 55 clamp the optical fiber F, thus inducing bending. Furthermore, while the optical fiber F is bent by the large-diameter fixed mandrel 55 and movable mandrel 65, the bending loss of the optical fiber F is determined by the power meter 80 (large-diameter bending loss measurement process).

[0083] Next, as Figure 6 As shown, the moving spindle 64 of the mid-diameter involved in the bending device 30b on the mid-side is also moved to a forward position. Thus, the fiber F is clamped by the adjacent moving spindle 64 and fixed spindle 54, thereby inducing bending in the fiber F (mid-side bending induction process). Furthermore, in addition to the large-diameter fixed spindle 55 and moving spindle 65, the bending loss of the fiber F is determined by the power meter 80 while it is bent by the mid-diameter fixed spindle 54 and moving spindle 64. In this case, the bending loss when bending is induced by the mid-diameter fixed spindle 54 and moving spindle 64 can be determined (mid-diameter bending loss measurement process).

[0084] Then, as Figure 7 As shown, the small-diameter movable mandrel 63 involved in the upstream bending device 30a is also moved forward. In addition to the large-diameter fixed mandrel 55, movable mandrel 65, medium-diameter fixed mandrel 54, and movable mandrel 64, the small-diameter fixed mandrel 53 and movable mandrel 63 all apply bending to the fiber F. The bending loss of the fiber F is then determined by the power meter 80. In this case, the bending loss when bending is applied by the small-diameter fixed mandrel 53 and movable mandrel 63 can be determined (small-diameter bending loss measurement process).

[0085] As described above, the fiber F is bent from the downstream side to the upstream side, thus averaging the tension generated in the fiber F and eliminating areas where excessive tension is applied.

[0086] Furthermore, by using a mandrel composed of three diameters, and moving it in the order of the large-diameter moving mandrel 65, the medium-diameter moving mandrel 64, and the small-diameter moving mandrel 63 to impart bending, it is possible to measure bending loss for multiple bending diameters and complete the measurement with fewer reference measurements. This reduces the time required for measuring the bending loss of optical fiber F.

[0087] Furthermore, in Example 1, the process is performed in the order of reference measurement step and bending loss measurement step. However, it is also possible to perform the process in the order of bending loss measurement step and reference measurement step, and the reference measurement step can also be performed after bending is applied.

[0088] In addition, an example of a mandrel with bearings has been given for explanation, but a mandrel without bearings can also be used when the moving mandrel 65 is moved sequentially from the fiber optic capture unit 70 side toward the extraction unit 10 side.

[0089] (Example 2)

[0090] exist Figure 1 An example was given of feeding one optical fiber F from one extraction section 10 to the bending application device 30. However, as described above, if the bending application device 30 uses a mandrel instead of a roller, multiple extraction sections may be arranged side by side in a direction intersecting the length direction of the optical fiber F.

[0091] In detail, such as Figure 8 As shown, if guide section 41 and guide section 31 are arranged side by side, and guide section 46 and guide section 36 are arranged side by side, then in addition to the optical fiber F from guide section 31 to guide section 36, the optical fiber F from guide section 41 to guide section 46 can also be bent using fixed mandrel 55 and movable mandrel 65. Therefore, the efficiency of bending loss measurement of optical fiber F is improved.

[0092] The embodiments disclosed herein should be considered illustrative in all respects, not restrictive. The scope of the invention is defined not by the foregoing meaning, but by the claims, including all modifications within the meaning and scope equivalent to the claims.

[0093] Explanation of the label

[0094] 1… Bending test device, 10… Pull-out section, 11… Bollard, 12… Light source, 20… Tension adjustment roller (tension application mechanism), 30, 30a, 30b, 30c… Bending application device (bending application device for measuring bending loss), 31, 32, 33, 34, 35, 36, 41, 46… Guide section, 51… Base plate, 52… Through groove, 53, 54, 55… Fixed spindle, 61… Sliding plate, 62… Motor, 63, 64, 65… Moving spindle, 70… Fiber optic capture device, 80… Power meter, 81… Light receiving section, 82… Calculation section, F… Fiber optic cable.

Claims

1. A bending induction device for measuring bending loss, comprising at least three mandrels, wherein bending is induced in the optical fiber by winding the drawn optical fiber around the mandrels. The mandrels are staggered from each other by a predetermined interval, positioned so that they are non-contacting relative to each other on the outer periphery of adjacent mandrels along the length of the optical fiber. The diameter of the optical fiber is defined as D, and the radius of the mandrels as r. In a plane orthogonal to the axis of rotation of the mandrels, the direction connecting the upstream tangent point where the fiber wound on the central mandrel (one of three consecutive mandrels of the same diameter arranged along the length of the optical fiber) begins to contact the central mandrel, and the downstream tangent point where the fiber wound on the central mandrel begins to separate from the central mandrel, is defined as a first direction. The interval between adjacent mandrels observed in the first direction is defined as 2r+d. In a plane orthogonal to the axis of rotation of the mandrels, the direction orthogonal to the first direction is defined as a second direction. The interval between adjacent mandrels observed in the second direction is defined as s. The angle θ between the second direction and the common internal tangent of adjacent mandrels observed at the center of the optical fiber is greater than 0 degrees and less than 45 degrees. The angle θ formed satisfies the following equation 3 [Formula 3] Each adjacent mandrel consists of a movable mandrel and a fixed mandrel. The movable mandrel is configured to move relative to the fixed mandrel between a reference position that does not bend the optical fiber and a forward position that bends the optical fiber. The movable mandrel, when viewed along the length of the optical fiber, is positioned downstream and moves earlier than the movable mandrel positioned upstream, thus inducing a bend in the optical fiber.

2. The bending induction device for measuring bending loss according to claim 1, wherein, The bending device has guides for ensuring the supply height of the optical fiber toward the mandrel and the discharge height of the optical fiber separated from the mandrel.

3. The bending induction device for measuring bending loss according to claim 2, wherein, The guide portions are arranged side by side along a direction that intersects the length direction of the optical fiber.

4. A bending test apparatus comprising a bending induction device for measuring bending loss as described in any one of claims 1 to 3. The bending test apparatus has a tension-applying mechanism for applying tension to the optical fiber facing the mandrel.

5. The bending test apparatus according to claim 4, wherein, The bending test apparatus has at least an upstream bending device located on the upstream side when viewed along the length direction of the optical fiber, and a downstream bending device located on the downstream side, wherein the mandrel of the downstream bending device is formed to have a larger diameter than the mandrel of the upstream bending device. The optical fiber is bent by causing the mandrel of the downstream bending device to move earlier in the second direction than the mandrel of the upstream bending device.

6. The bending test apparatus according to claim 4 or 5, wherein, It has a computation unit that calculates the bending loss based on the length of the fiber that has been bent.

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