Optical characteristic measuring method and optical characteristic measuring system

Abstract

An optical characteristic measuring method according to the present disclosure includes: a step of connecting a first input / output device to a first end surface of an optical fiber; a step of connecting a second input / output device to a second end surface of the optical fiber; a step of connecting the first input / output device and the second input / output device to an optical switch and connecting a first measuring instrument and a second measuring instrument to the optical switch; a step of measuring a first optical characteristic of the optical fiber by causing first measurement light to be incident on the optical fiber in a first connection state in which the first input / output device and the second input / output device are connected to the first measuring instrument by the optical switch; and a step of measuring a second optical characteristic of the optical fiber by causing second measurement light to be incident on the optical fiber in a second connection state in which the first input / output device and the second input / output device are connected to the second measuring instrument by the optical switch.

Description

Optical Property Measurement Method and Optical Property Measurement System

[0001] The present disclosure relates to an optical property measurement method and an optical property measurement system. This application claims priority based on Japanese Application No. 2024-161944 filed on September 19, 2024, and incorporates all the descriptions set forth in the above-mentioned Japanese application.

[0002] Patent Document 1 discloses a method for measuring the optical properties of a multi-core optical fiber. In the method described in Patent Document 1, measurement light is incident on the first end of the multi-core optical fiber, and based on the measurement light emitted from the second end of the multi-core optical fiber, the cut-off wavelength of each core of the multi-core optical fiber is measured.

[0003] Japanese Unexamined Patent Application Publication No. 2018-138910

[0004] An optical property measurement method according to one aspect of the present disclosure includes connecting a first input / output device to a first end face of an optical fiber including a first end face, a second end face located opposite to the first end face, and a plurality of cores; connecting a second input / output device to the second end face of the optical fiber; connecting the first input / output device and the second input / output device to an optical switch and connecting a first measuring device and a second measuring device to the optical switch; measuring a first optical property of the optical fiber by causing first measurement light to be incident on the optical fiber through the first input / output device or the second input / output device in a first connection state in which the optical switch connects the first input / output device and the second input / output device to the first measuring device; and measuring a second optical property of the optical fiber by causing second measurement light to be incident on the optical fiber through the first input / output device or the second input / output device in a second connection state in which the optical switch connects the first input / output device and the second input / output device to the second measuring device.

[0005] Figure 1 is a diagram showing the configuration of an optical properties measurement system according to one embodiment. Figure 2 is a diagram showing the first and second end faces of the optical fiber in Figure 1. Figure 3 is a diagram showing the configuration of the FIFO in Figure 1. Figure 4 is a flowchart showing an optical properties measurement method according to one embodiment. Figure 5 is a diagram illustrating step S12 in Figure 4. Figure 6 is a diagram illustrating step S14 in Figure 4. Figure 7 is a diagram illustrating step S17 in Figure 4. Figure 8 is a diagram illustrating step S18 in Figure 4. Figure 9 is a diagram illustrating step S19 in Figure 4.

[0006] As described above, multicore optical fibers require different optical properties to be measured for each required test. These optical properties are measured using measuring instruments prepared for each measurement item. The measuring instrument is optically connected to the multicore optical fiber and measures the optical properties according to the measurement item based on the measurement light passing through the multicore optical fiber. When determining the optical properties according to a second measurement item, a second measuring instrument corresponding to the second measurement item is connected to the multicore optical fiber, and then the optical properties according to the measurement item are measured using a second measuring instrument. The need to switch measuring instruments for each measurement item can lead to an increase in the effort and time required to measure the optical properties.

[0007] This disclosure provides an optical properties measurement method and an optical properties measurement system that can easily measure the optical properties of optical fibers.

[0008] According to this disclosure, it is possible to provide an optical properties measurement method and an optical properties measurement system that can easily measure the optical properties of optical fibers.

[0009] The contents of this disclosed embodiment will be explained.

[0010] [1] An optical property measurement method according to one aspect of the present disclosure comprises the steps of: connecting a first input / output device to a first end face of an optical fiber including a first end face, a second end face located opposite to the first end face, and a plurality of cores; connecting a second input / output device to a second end face of the optical fiber; connecting the first input / output device and the second input / output device to an optical switch and connecting a first measuring instrument and a second measuring instrument to the optical switch; measuring a first optical property of an optical fiber by irradiating the optical fiber with a first measurement light through the first input / output device or the second input / output device in a first connection state in which the first input / output device and the second input / output device are connected to the first measuring instrument by the optical switch; and measuring a second optical property of an optical fiber by irradiating the optical fiber with a second measurement light through the first input / output device or the second input / output device in a second connection state in which the first input / output device and the second input / output device are connected to the second measuring instrument by the optical switch.

[0011] In the optical properties measurement method described in [1] above, by pre-connecting the number of measuring instruments corresponding to the required number of measurement items to the optical switch, it becomes possible to automatically switch the measuring instruments to the optical fiber. In this case, compared to the case where manual switching of measuring instruments is required for each measurement item, it becomes possible to measure all optical properties corresponding to the measurement items efficiently in a short time. Therefore, according to the optical properties measurement method described in [1] above, the optical properties of an optical fiber can be easily measured.

[0012] [2] In the optical properties measurement method of [1] above, the step of connecting the first input / output device to the first end face of the optical fiber may include the steps of: connecting a measuring instrument capable of measuring test light incident on the first end face and returning to the first end face to the first input / output device, and causing test light from the measuring instrument to be incident on one of the multiple cores of the optical fiber through the first input / output device; and performing rotational alignment of the first input / output device with respect to the optical fiber such that the measuring instrument detects the test light emitted from all but one of the multiple cores as a result of the incidence of test light on one core. In this case, a simple rotational alignment of the optical fiber and the first input / output device can be performed by using a measuring instrument connected to the first input / output device to confirm whether or not the test light has passed through all the cores of the optical fiber. Normally, when connecting the first input / output device to an optical fiber, precise rotational alignment of the optical fiber and the first input / output device is performed, for example, by observing the first end face of the optical fiber using a fusion splicer. As with the optical properties measurement method described in [1] above, when the purpose is to measure the optical properties of an optical fiber, precise rotational alignment between the optical fiber and the first input / output device is not required. Therefore, by performing the simple rotational alignment described above, the connection work of the first input / output device to the first end face of the optical fiber can be easily carried out.

[0013] [3] In the optical property measurement method of [1] or [2] above, the step of connecting the second input / output device to the second end face of the optical fiber may include the steps of: connecting a measuring instrument capable of measuring test light incident on the second end face and returning to the second end face to the second input / output device, causing test light from the measuring instrument to be incident on one of the multiple cores of the optical fiber through the second input / output device; and rotating the second input / output device relative to the optical fiber so that the measuring instrument detects the test light emitted from all but one of the multiple cores as a result of the incident of test light on one core through the second input / output device. In this case, a simple rotational alignment of the optical fiber and the second input / output device can be performed by checking whether or not the test light has passed through all the cores of the optical fiber using the measuring instrument connected to the second input / output device. This makes it easy to connect the second input / output device to the second end face of the optical fiber.

[0014] [4] In the optical property measurement method described in any of [1] to [3] above, after the step of connecting the first input / output device to the first end face of the optical fiber and before the step of connecting the second input / output device to the second end face of the optical fiber, the method may further include the step of identifying the correspondence between the multiple first input / output ports of the first input / output device and the multiple cores by observing the arrangement of the multiple cores on the second end face while the first input / output device is rotationally aligned with respect to the optical fiber. Normally, when connecting the first input / output device to an optical fiber using a fusion splicer, the first input / output device is connected to the first end face after observing the first end face of the optical fiber. When performing simple rotational alignment between the optical fiber and the first input / output device using the measuring instrument described above, it is difficult to directly observe the first end face of the optical fiber after connecting it to the first input / output device. The second end face, which is located opposite the first end face, can be directly observed, and if the arrangement of the multiple cores on the second end face can be confirmed, the correspondence between the multiple cores and the multiple first input / output ports of the first input / output device can be identified. Therefore, in the method described in [4] above, after connecting the first end face of the optical fiber to the first input / output device, the arrangement of multiple cores on the second end face is observed to determine the correspondence between multiple cores and multiple first input / output ports. This makes it possible to accurately measure the optical properties of the optical fiber.

[0015] [5] In the optical property measurement method described in [4] above, after the step of connecting the second input / output device to the second end face of the optical fiber, the method may further include the step of identifying the correspondence between the plurality of first input / output ports of the first input / output device and the plurality of second input / output ports of the second input / output device, with the second input / output device rotated and aligned with respect to the optical fiber. In this case, by identifying the correspondence between the plurality of first input / output ports of the first input / output device and the plurality of second input / output ports of the second input / output device, the optical properties of the optical fiber can be measured with greater accuracy.

[0016] [6] An optical property measurement system according to one aspect of the present disclosure includes an optical fiber having a first end face, a second end face located opposite the first end face, and a plurality of cores; a first input / output device connected to the first end face of the optical fiber; a second input / output device connected to the second end face of the optical fiber; a first measuring instrument capable of measuring a first optical property of the optical fiber by irradiating the optical fiber with a first measurement light through the first input / output device or the second input / output device; a second measuring instrument capable of measuring a second optical property of the optical fiber by irradiating the optical fiber with a second measurement light through the first input / output device or the second input / output device; and an optical switch disposed between the first input / output device and the second input / output device and the first measuring instrument and the second measuring instrument, which can switch between a first connection state in which the first input / output device and the second input / output device are connected to the first measuring instrument and a second connection state in which the first input / output device and the second input / output device are connected to the second measuring instrument. With this optical property measurement system, as described above, the optical properties of the optical fiber can be easily measured.

[0017] [7] The optical property measurement system described in [6] above may further include a control device that is communicatively connected to the first measuring instrument, the second measuring instrument, and the optical switch, and controls the switching operation from the first connection state to the second connection state by the optical switch, the measurement operation of the first optical property by the first measuring instrument, and the measurement operation of the second optical property by the second measuring instrument, respectively. In this case, the optical properties of the optical fiber can be measured even more easily using the control device.

[0018] [8] In the optical property measurement system described in [6] or [7] above, the first measuring instrument includes a plurality of first input / output units connected to an optical switch for emitting a first measurement light and detecting the first measurement light, and the second measuring instrument includes a plurality of second input / output units connected to an optical switch for emitting a second measurement light and detecting the second measurement light, the number of the plurality of second input / output units may differ from the number of the plurality of first input / output units. By using a plurality of measuring instruments with different numbers of input / output units, a variety of optical properties such as wavelength dispersion, polarization mode dispersion, and crosstalk can be measured.

[0019] [Details of Embodiments of the Disclosure] Specific examples of the optical property measurement method and optical property measurement system of this embodiment will be described with reference to the drawings. This disclosure is not limited to these examples and is intended to include all changes in the meaning and scope equivalent to the claims, as indicated by the claims. In the following description, the same elements in the description of the drawings will be denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate.

[0020] Figure 1 shows the configuration of the optical properties measurement system 1 of this embodiment. The optical properties measurement system 1 is a system for measuring the optical properties of an optical fiber 10. The configuration of the optical fiber 10 will be described below. The optical fiber 10 includes a first end face 10a and a second end face 10b located opposite to the first end face 10a.

[0021] Figure 2 shows the first end face 10a and the second end face 10b of the optical fiber 10. As shown in Figure 2, the optical fiber 10 is a multicore optical fiber having N cores (where N is an integer of 2 or more). In the example shown in Figure 2, the optical fiber 10 has four cores C1, C2, C3, and C4. In Figure 2, the cores C1, C2, C3, and C4 are numbered. The optical fiber 10 has a cladding 13 and a marker 14. The cores C1, C2, C3, and C4 are arranged at equal intervals on concentric circles centered on the central axis L10 of the optical fiber 10, for example. The cladding 13 is a common cladding surrounding the cores C1, C2, C3, C4 and the marker 14. The marker 14 has a different refractive index than the cladding 13.

[0022] The optical properties measurement system 1 shown in Figure 1 comprises measuring instruments 20A, 20B, and 20C, an optical switch 30, fan-in / fan-out (FIFO) units 40A and 40B, and a control device 50.

[0023] Each of the measuring instruments 20A, 20B, and 20C measures the optical properties of the optical fiber 10 by irradiating measurement light onto one of the cores C1, C2, C3, or C4 of the optical fiber 10. The optical switch 30 is positioned between the measuring instruments 20A, 20B, and 20C and the optical fiber 10, and switches the connection between the measuring instruments 20A, 20B, and 20C and the optical fiber 10. The FIFO 40A (first input / output device) is positioned between the optical switch 30 and the first end face 10a of the optical fiber 10, and connects the optical switch 30 and the optical fiber 10. The FIFO 40B (second input / output device) is positioned between the optical switch 30 and the second end face 10b of the optical fiber 10, and connects the optical switch 30 and the optical fiber 10.

[0024] The optical switch 30 includes the same number of ports P1, P2, P3, and P4 as the cores C1, C2, C3, and C4 (i.e., N ports), and the same number of ports P5, P6, P7, and P8 as the cores C1, C2, C3, and C4 (i.e., N ports). Figure 1 shows the ports of the optical switch 30 numbered. Ports P1, P2, P3, and P4 are optically connected to the cores C1, C2, C3, and C4 on the first end face 10a by FIFO 40A. Ports P5, P6, P7, and P8 are optically connected to the cores C1, C2, C3, and C4 on the second end face 10b by FIFO 40B. In this specification, "connecting" two elements includes both directly linking two elements and indirectly linking two elements by inserting another element between them.

[0025] Figure 3 shows the configurations of FIFOs 40A and 40B. As shown in Figure 3, FIFO 40A optically connects the cores C1, C2, C3, and C4 of the first end face 10a of the optical fiber 10 to the ports P1, P2, P3, and P4 of the optical switch 30. FIFO 40A includes the same number of input / output ports 41a, 42a, 43a, and 44a (first input / output ports) as the cores C1, C2, C3, and C4, and the same number of input / output ports 45a, 46a, 47a, and 48a as the input / output ports 41a, 42a, 43a, and 44a.

[0026] The input / output ports 41a, 42a, 43a, and 44a of the FIFO 40A are formed, for example, by etching the tips of the same number of single-core fibers as the cores C1, C2, C3, and C4 of the optical fiber 10 to reduce their diameter, and then bundling these tips together. In this bundle of tips, the spacing between the cores of the single-core fibers is the same as the spacing between the cores C1, C2, C3, and C4. By fixing this bundle of tips against the first end face 10a of the optical fiber 10, the first end of each single-core fiber is optically connected to the cores C1, C2, C3, and C4, respectively. The second end of each single-core fiber is an input / output port 45a, 46a, 47a, and 48a, respectively, and is optically connected to the ports P1, P2, P3, and P4 of the optical switch 30, respectively.

[0027] The FIFO 40B optically connects the cores C1, C2, C3, and C4 of the second end face 10b of the optical fiber 10 to the ports P5, P6, P7, and P8 of the optical switch 30. The FIFO 40B includes the same number of input / output ports 41b, 42b, 43b, and 44b (second input / output ports) as the cores C1, C2, C3, and C4, and the same number of input / output ports 45b, 46b, 47b, and 48b as the input / output ports 41b, 42b, 43b, and 44b.

[0028] The input / output ports 41b, 42b, 43b, and 44b of the FIFO 40B are formed, for example, by etching the tips of the same number of single-core fibers as the cores C1, C2, C3, and C4 of the optical fiber 10 to reduce their diameter, and then bundling these tips together. By fixing this bundle of tips against the second end face 10b of the optical fiber 10, the first end of each single-core fiber is optically connected to the cores C1, C2, C3, and C4, respectively. The second end of each single-core fiber is the input / output port 45b, 46b, 47b, and 48b, respectively, and is optically connected to the ports P5, P6, P7, and P8 of the optical switch 30, respectively.

[0029] Refer to Figure 1 again. The optical switch 30 includes ports P9 to P24. In Figure 1, ports P1 to P24 are numbered "1" to "24". Ports P13 and P14 are optically connected to measuring instrument 20A (first measuring instrument). Ports P15 and P16 are optically connected to measuring instrument 20B. Ports P17 to P24 are optically connected to measuring instrument 20C (second measuring instrument). Ports P9 to P12 are spare ports that are not optically connected to the optical fiber 10 or any of the measuring instruments 20A, 20B, or 20C. The optical switch 30 is, for example, a cross-connect type optical switch, and any port among ports P1 to P24 can be connected to any other port.

[0030] Measuring instrument 20A includes input / output units 21a and 22a (first input / output units) optically connected to ports P13 and P14 of the optical switch 30, respectively. Measuring instrument 20B includes input / output units 21b and 22b optically connected to ports P15 and P16 of the optical switch 30, respectively. The number of input / output units 21b and 22b in measuring instrument 20B is the same as the number of input / output units 21a and 22a in measuring instrument 20A. Measuring instrument 20C includes input / output units 21c to 28c (second input / output units) optically connected to ports P17 to P24 of the optical switch 30. Input / output unit 29c in measuring instrument 20C is a spare input / output unit not connected to the optical switch 30. The number of input / output units 21c to 28c in measuring instrument 20C is greater than the number of input / output units 21a and 22a in measuring instrument 20A, and the number of input / output units 21b and 22b in measuring instrument 20B. The number of input / output sections 21c to 28c is the same as the number of ports P1 to P8 of the optical switch 30 (i.e., 2N).

[0031] The measuring instrument 20A directs measurement light from the input / output unit 21a through the optical switch 30 into the optical fiber 10 and detects the measurement light that enters the input / output unit 22a from the optical fiber 10 through the optical switch 30. The measuring instrument 20A then calculates the optical properties of the optical fiber 10 based on the detected measurement light. Examples of optical properties of the optical fiber 10 include wavelength dispersion, polarization mode dispersion (PMD), crosstalk, and bending loss. In this embodiment, the measuring instrument 20A calculates the wavelength dispersion (first optical property) as an optical property of the optical fiber 10.

[0032] The measuring instrument 20B directs measurement light from the input / output unit 21b through the optical switch 30 into the optical fiber 10 and detects the measurement light that enters the input / output unit 22b from the optical fiber 10 through the optical switch 30. Then, the measuring instrument 20B calculates the optical properties of the optical fiber 10 based on the detected measurement light. The measuring instrument 20B calculates optical properties that are different from those calculated by the measuring instrument 20A. In this embodiment, the measuring instrument 20B calculates PMD (second optical properties) as the optical properties of the optical fiber 10.

[0033] The measuring instrument 20C directs measurement light from the input / output unit 21c through the optical switch 30 into the optical fiber 10, and detects the measurement light that enters from the optical fiber 10 through the optical switch 30 to the input / output unit 22c and 28c. Then, the measuring instrument 20C calculates the optical characteristics of the optical fiber 10 based on the detected measurement light. The measuring instrument 20C calculates optical characteristics that are different from those calculated by the measuring instrument 20A and the measuring instrument 20B. In this embodiment, the measuring instrument 20C calculates the crosstalk between the cores C1, C2, C3, and C4 of the optical fiber 10 as an optical characteristic of the optical fiber 10.

[0034] Thus, each of the measuring instruments 20A, 20B, and 20C calculates different optical characteristics from each other. The measurement light emitted from each of the measuring instruments 20A, 20B, and 20C may be continuous light, chopped light, or pulsed light.

[0035] The optical switch 30 switches between connection mode M1 (first connection state) in which the optical fiber 10 is optically connected to the measuring instrument 20A, connection mode M2 ​​in which the optical fiber 10 is optically connected to the measuring instrument 20B, and connection mode M3 (second connection state) in which the optical fiber 10 is optically connected to the measuring instrument 20C.

[0036] In connection mode M1 (see Figure 7), the optical switch 30 selectively optically connects one of ports P1, P2, P3, or P4 to port P13, and selectively optically connects one of ports P5, P6, P7, or P8 to port P14. This allows one of the cores C1, C2, C3, or C4 on the first end face 10a of the optical fiber 10 to be selectively optically connected to the input / output section 21a of the measuring instrument 20A. Furthermore, one of the cores C1, C2, C3, or C4 on the second end face 10b of the optical fiber 10 can be selectively optically connected to the input / output section 22a of the measuring instrument 20A. In this state, the measuring instrument 20A can calculate the wavelength dispersion of the optical fiber 10 by irradiating one of the cores C1, C2, C3, or C4 with measurement light.

[0037] In connection mode M2 ​​(see Figure 8), the optical switch 30 selectively optically connects one of ports P1, P2, P3, or P4 to port P15, and selectively optically connects one of ports P5, P6, P7, or P8 to port P16. This allows one of the cores C1, C2, C3, or C4 on the first end face 10a of the optical fiber 10 to be selectively optically connected to the input / output section 21b of the measuring instrument 20B. Furthermore, one of the cores C1, C2, C3, or C4 on the second end face 10b of the optical fiber 10 can be selectively optically connected to the input / output section 22b of the measuring instrument 20B. In this state, the measuring instrument 20B can calculate the PMD of the optical fiber 10 by irradiating one of the cores C1, C2, C3, or C4 with measurement light.

[0038] In connection mode M3 (see Figure 9), the optical switch 30 selectively optically connects one of ports P1, P2, P3, or P4 to port P17, and optically connects all ports P1 through P8 that are not optically connected to port P17 to ports P18 through P24. This allows one of the cores C1, C2, C3, or C4 of the first end face 10a of the optical fiber 10 to be selectively optically connected to the input / output section 21c of the measuring instrument 20C. The cores that are not optically connected to the input / output section 21c can be optically connected to the input / output sections 22c through 28c of the measuring instrument 20C, respectively. In this state, the measuring instrument 20C can calculate the crosstalk between the cores C1, C2, C3, and C4 of the optical fiber 10 by irradiating one of the cores C1, C2, C3, or C4 with measurement light.

[0039] The control device 50 is, for example, one or more computers including a CPU, memory, and storage device. The control device 50 is communicatively connected to the optical switch 30 and the measuring instruments 20A, 20B, and 20C, respectively, and controls the operation of the optical switch 30 and the measuring instruments 20A, 20B, and 20C, respectively. The optical switch 30 switches between connection modes M1, M2, and M3 according to instruction signals from the control device 50. Each of the measuring instruments 20A, 20B, and 20C measures the optical properties of the optical fiber 10 according to instruction signals from the control device 50.

[0040] The operation of the optical properties measurement system 1 of this embodiment and the optical properties measurement method of this embodiment using the optical properties measurement system 1 will be described.

[0041] Figure 4 is a flowchart illustrating the optical properties measurement method of this embodiment. Figure 5 is a diagram illustrating step S12 in Figure 4. Figure 6 is a diagram illustrating step S14 in Figure 4. Figure 7 is a diagram illustrating step S17 in Figure 4. Figure 8 is a diagram illustrating step S18 in Figure 4. Figure 9 is a diagram illustrating step S19 in Figure 4.

[0042] As shown in FIG. 4, first, prepare the above-described optical switch 30, optical fiber 10, FIFOs 40A and 40B, and measuring devices 20A, 20B, and 20C (step S11).

[0043] Next, use an OTDR (Optical Time Domain Reflectometer) device 60 (measuring device) to connect the FIFO 40A to the first end face 10a of the optical fiber 10 (step S12). The OTDR device 60 is a device that injects a test light into one end of the optical fiber 10 and measures the light that returns to that end by backscattering and reflection. In the present embodiment, the OTDR device 60 is used for rotational alignment of the optical fiber 10 and the FIFOs 40A and 40B.

[0044] Specifically, with the input / output ports 61, 62, 63, and 64 of the OTDR device 60 connected to the input / output ports 45a, 46a, 47a, and 48a of the FIFO 40A, respectively, inject a test light L6A from the OTDR device 60 into any one of the input / output ports 45a, 46a, 47a, and 48a. For example, the OTDR device 60 injects the test light L6A from the input / output port 61 into the input / output port 45a. The test light L6A incident on the input / output port 45a passes through the FIFO 40A and is incident on the core C1 of the first end face 10a of the optical fiber 10.

[0045] Then, adjust the rotational position of the FIFO 40A with respect to the first end face 10a of the optical fiber 10 so that the OTDR device 60 detects the test light L6B that has returned from the cores C2, C3, and C4 to the first end face 10a among the test lights L6A incident on the core C1. When the test light L6B that has returned to the first end face 10a is incident on the input / output ports 62, 63, and 64 of the OTDR device 60 through the input / output ports 46a, 47a, and 48a of the FIFO 40A, it can be said that the cores C1, C2, C3, and C4 of the first end face 10a of the optical fiber 10 are optically connected to the input / output ports 41a, 42a, 43a, and 44a of the FIFO 40A, respectively. This state is a state in which the FIFO 40A is simply rotationally aligned with respect to the optical fiber 10. With the FIFO 40A rotationally aligned with respect to the optical fiber 10, connect the FIFO 40A to the first end face 10a of the optical fiber 10.

[0046] Next, by observing the arrangement of the cores C1, C2, C3, and C4 on the second end face 10b of the optical fiber 10 to which the FIFO 40A is not connected, the correspondence between the cores C1, C2, C3, and C4 and the input / output ports 41a, 42a, 43a, and 44a of the FIFO 40A is specified (step S13). Since the first end face 10a of the optical fiber 10 is connected to the FIFO 40A, the first end face 10a cannot be directly observed. Since the arrangement of the cores C1, C2, C3, and C4 is the same at the first end face 10a and the second end face 10b, in order to confirm the arrangement of the cores C1, C2, C3, and C4, it is not necessary to directly observe the first end face 10a, and it is only necessary to be able to observe the second end face 10b.

[0047] When observing the second end face 10b, for example, by using a microscope and confirming the correspondence between the cores C1, C2, C3, and C4 and the input / output ports 41a, 42a, 43a, and 44a based on the position of the marker 14 (see FIG. 2), the cores C1, C2, C3, and C4 are associated with the input / output ports 41a, 42a, 43a, and 44a. Thereby, it can be determined which of the cores C1, C2, C3, and C4 each of the input / output ports 41a, 42a, 43a, and 44a of the FIFO 40A is optically connected to. When observing the second end face 10b, the cores C1, C2, C3, and C4 are identified, and the arrangement of the cores C1, C2, C3, and C4 is confirmed.

[0048] As a method for identifying the cores C1, C2, C3, and C4, a method of providing the marker 14 shown in FIG. 2 is known. In the example of FIG. 2, the core C1 closest to the marker 14 is designated as "1", and the cores C2, C3, and C4 arranged clockwise from the core C1 are numbered "2", "3", and "4", respectively. At this time, as shown in FIG. 2, the core arrangements at the first end face 10a and the second end face 10b are mirror-symmetric arrangements. Therefore, in order to connect cores with the same numbers, it is important to confirm the core arrangements of each of the first end face 10a and the second end face 10b before connecting the FIFO 40A to the first end face 10a.

[0049] Next, the OTDR device 60 is used to connect the FIFO 40B to the second end face 10b of the optical fiber 10 (step S14). Specifically, with the input / output ports 61, 62, 63, and 64 of the OTDR device 60 connected to the input / output ports 45b, 46b, 47b, and 48b of the FIFO 40B, respectively, the OTDR device 60 is used to inject test light L6A into one of the input / output ports 45b, 46b, 47b, or 48b. For example, the OTDR device 60 injects test light L6A from input / output port 61 into input / output port 45b. The test light L6A injected into input / output port 45b passes through the FIFO 40B and is injected into the core C1 of the second end face 10b of the optical fiber 10.

[0050] Then, the rotational position of the FIFO 40B relative to the second end face 10b of the optical fiber 10 is adjusted so that the OTDR device 60 detects the test light L6B that returns to the second end face 10b from cores C2, C3, and C4 of the test light L6A that was incident on core C1. When the test light L6B that has returned to the second end face 10b is incident on the input / output ports 62, 63, and 64 of the OTDR device 60 through the input / output ports 46b, 47b, and 48b of the FIFO 40B, it can be said that the cores C1, C2, C3, and C4 of the second end face 10b of the optical fiber 10 are optically connected to the input / output ports 41b, 42b, 43b, and 44b of the FIFO 40B, respectively. This state is defined as the state in which the FIFO 40B is simply rotated and centered relative to the optical fiber 10. With the FIFO 40B rotated and aligned with the optical fiber 10, the FIFO 40B is connected to the second end face 10b of the optical fiber 10. For the simplified rotational alignment of the FIFO 40B with respect to the optical fiber 10, a different OTDR device than the one used for the simplified rotational alignment of the FIFO 40A with respect to the optical fiber 10 (OTDR device 60) may be used. In other words, multiple OTDR devices may be prepared. A multi-channel OTDR device may also be prepared.

[0051] Next, the correspondence between the input / output ports 41a, 42a, 43a, and 44a of FIFO 40A connected to the first end face 10a of the optical fiber 10 and the input / output ports 41b, 42b, 43b, and 44b of FIFO 40B connected to the second end face 10b of the optical fiber 10 is identified (step S15). This makes it possible to identify which of the input / output ports 41a, 42a, 43a, and 44a of FIFO 40A each of the input / output ports 41b, 42a, 43a, and 44b of FIFO 40B are optically connected to. This makes it possible to associate the input / output ports 41b, 42b, 43a, and 44b of FIFO 40B with the input / output ports 41a, 42a, 43a, and 44a of FIFO 40A, respectively. The correspondence between input / output ports 41a, 42a, 43a, and 44a and input / output ports 41b, 42b, 43b, and 44b may be confirmed using a light source and a power meter, or using an optical switch.

[0052] Next, the FIFOs 40A and 40B and the measuring instruments 20A, 20B, and 20C are connected to the optical switch 30 (step S16). Specifically, as shown in Figure 3, the input / output ports 45a, 46a, 47a, and 48a of the FIFO 40A, and the input / output ports 45b, 46b, 47b, and 48b of the FIFO 40B are optically connected to ports P1 through P8 of the optical switch 30, respectively. As shown in Figure 1, the input / output sections 21a and 22a of the measuring instrument 20A are optically connected to ports P13 and P14 of the optical switch 30, respectively. The input / output sections 21b and 22b of the measuring instrument 20B are optically connected to ports P15 and P16 of the optical switch 30, respectively. The input / output sections 21c through 28c of the measuring instrument 20C are optically connected to ports P17 through P24 of the optical switch 30, respectively.

[0053] Next, the optical switch 30 is set to connection mode M1, which optically connects the optical fiber 10 and the measuring instrument 20A (step S17). In connection mode M1, for example, as shown in Figure 7, the optical switch 30 optically connects port P1 to port P13 and port P5 to port P14. In this state, the measuring instrument 20A causes measurement light L1A to be incident on the core C1 of the first end face 10a of the optical fiber 10 through ports P13 and P1 from the input / output unit 21a. Of the measurement light L1A incident on the core C1 of the first end face 10a, measurement light L1B emitted from the core C1 of the second end face 10b is incident on the input / output unit 22a of the measuring instrument 20A through ports P5 and P14. The measuring instrument 20A calculates the wavelength dispersion of the optical fiber 10 as an optical characteristic based on the measurement light L1A and L1B. Step S17 is repeated sequentially, with cores C2, C3, and C4 being the cores into which the measurement light L1A is incident.

[0054] Next, the optical switch 30 switches to connection mode M2, which optically connects the optical fiber 10 and the measuring instrument 20B (step S18). In connection mode M2, for example, as shown in Figure 8, the optical switch 30 optically connects port P1 to port P15 and port P5 to port P16. In this state, the measuring instrument 20B causes measurement light L2A to be incident on the core C1 of the first end face 10a of the optical fiber 10 through ports P15 and P1 from the input / output unit 21b. Of the measurement light L2A incident on the core C1 of the first end face 10a, the measurement light L2B that is emitted from the core C1 of the second end face 10b is incident on the input / output unit 22b of the measuring instrument 20B through ports P5 and P16. The measuring instrument 20B calculates the PMD of the optical fiber 10 as an optical characteristic based on the measurement light L2A and L2B. Step S18 is repeated sequentially, with cores C2, C3, and C4 being the cores into which the measurement light L2A is incident.

[0055] Next, the optical switch 30 switches to connection mode M3, which optically connects the optical fiber 10 and the measuring instrument 20C (step S19). In connection mode M3, for example, as shown in Figure 9, the optical switch 30 optically connects port P1 to port P17, and optically connects ports P2 to P8 to ports P18 to P24. In this state, the measuring instrument 20C causes measurement light L3A to be incident on the core C1 of the first end face 10a of the optical fiber 10 through ports P17 and P1 from the input / output unit 21c. Of the measurement light L3A incident on the core C1 of the first end face 10a, the measurement light L3B emitted from the cores C1, C2, C3, and C4 of the second end face 10b is incident on the input / output unit 21c to 28c of the measuring instrument 20C through ports P1 to P8 and ports P17 to P24. The measuring instrument 20C calculates the crosstalk of the optical fiber 10 as an optical characteristic based on the measurement light L3A and L3B. Step S19 is repeated sequentially with cores C2, C3, and C4 into which the measurement light L3A is incident.

[0056] The measuring instrument 20C can calculate parallel crosstalk and opposing crosstalk in a single measurement by detecting the measurement light L3B from all cores C1, C2, C3, and C4. If the number of input / output units in the measuring instrument 20C is limited, it is also possible to measure crosstalk by sequentially changing the cores connected to those input / output units.

[0057] The effects obtained by the optical property measurement method and optical property measurement system 1 according to this embodiment, as described above, will be explained together with the problems of the prior art.

[0058] To measure the optical properties of an optical fiber, it is necessary to inject light into the core of the optical fiber and detect the emitted light from that core or another core. In single-core optical fibers, the cladding diameter is constant and the core is centrally located, so the optical properties can be measured relatively easily by butt jointing. In multi-core optical fibers, rotational alignment is required to inject light into each core.

[0059] One possible method for irradiating each core of a multicore optical fiber is to rotate and center the fiber while observing its end face. However, when measuring the optical properties of an optical fiber, it is usually required to measure multiple optical properties corresponding to multiple measurement items. In the above method, rotation and centering for irradiating each core is required for each measurement item and each core, which can increase the time required to measure all optical properties. Therefore, such a method is not suitable for measuring optical properties in mass production.

[0060] As an alternative to individually aligning each core of a multicore optical fiber, an input / output device called a FIFO (First-Input / Output Focuser) can be considered. The first end of the FIFO has the same core configuration as the multicore optical fiber, and the second end of the FIFO has the same core configuration as the bundled single-core optical fibers. If the core spacing between a pre-prepared FIFO and a multicore optical fiber differs significantly, it becomes difficult to connect the FIFO to the multicore optical fiber. In mass production, the core configuration of multicore optical fibers is basically limited, so FIFOs are effective as input / output devices.

[0061] FIFOs and multicore optical fibers are typically connected using a fusion splicer. Specifically, the end face of the multicore optical fiber is observed, and the correspondence between the core of the multicore optical fiber and the input / output port of the FIFO is established. Then, optical properties are measured using measuring instruments that perform various optical property measurements. When connecting FIFOs and multicore optical fibers using a fusion splicer, rotational alignment takes time. Since measuring instruments for optical properties are prepared individually for each measurement item, switching between instruments is necessary when measuring optical properties according to the next measurement item. Therefore, this can lead to an increase in the effort and time required for measuring optical properties.

[0062] In contrast, in this embodiment, the number of measuring instruments 20A, 20B, and 20C corresponding to the required measurement items are pre-connected to the optical switch 30. This makes it possible to automatically switch the connections of the measuring instruments 20A, 20B, and 20C to the optical fiber 10. In this case, compared to the case where manual switching of the measuring instruments 20A, 20B, and 20C is required for each measurement item, it becomes possible to efficiently measure all optical characteristics corresponding to the measurement items in a short amount of time. Therefore, according to this embodiment, the optical characteristics of the optical fiber 10 can be easily measured.

[0063] As in this embodiment, step S12 of connecting the FIFO 40A to the first end face 10a of the optical fiber 10 may include the steps of: connecting an OTDR device 60 capable of measuring test light L6B that is incident on the first end face 10a and returns to the first end face 10a to the FIFO 40A, and injecting test light L6A from the OTDR device 60 into the core C1 of the optical fiber 10 through the FIFO 40A; and rotating the FIFO 40A relative to the optical fiber 10 so that the OTDR device 60 can detect test light L6B emitted from cores C2, C3, and C4 as the test light L6A is incident on core C1 through the FIFO 40A. In this case, by using the OTDR device 60 connected to the FIFO 40A to confirm whether the test light L6A and L6B have passed through all the cores C1, C2, C3, and C4 of the optical fiber 10, a simple rotational alignment of the optical fiber 10 and the FIFO 40A can be performed. Normally, when connecting the FIFO 40A to the optical fiber 10, precise rotational alignment of the optical fiber 10 and the FIFO 40A is performed, for example, by observing the first end face 10a of the optical fiber 10 using a fusion splicer. In this embodiment, when the purpose is to measure the optical properties of the optical fiber 10, precise rotational alignment of the optical fiber 10 and the FIFO 40A is unnecessary, so by performing the simple rotational alignment described above, the connection work of the FIFO 40A to the first end face 10a of the optical fiber 10 can be easily performed. There is no need to prepare an expensive fusion splicer.

[0064] As in this embodiment, step S14, which connects the FIFO 40B to the second end face 10b of the optical fiber 10, may include the steps of: connecting an OTDR device 60 capable of measuring the test light L6A that is incident on the second end face 10b and returns to the second end face 10b to the FIFO 40B, and injecting the test light L6A from the OTDR device 60 into the core C1 of the optical fiber 10 through the FIFO 40B; and rotating the FIFO 40B relative to the optical fiber 10 so that the OTDR device 60 can detect the test light L6A emitted from cores C2, C3, and C4 as the test light L6A is incident on core C1 through the FIFO 40B. In this case, by using the OTDR device 60 connected to the FIFO 40B to confirm whether or not the test light L6A and L6B have passed through all the cores C1, C2, C3, and C4 of the optical fiber 10, a simple rotational alignment of the optical fiber 10 and the FIFO 40B can be performed. This makes it easy to connect the FIFO 40B to the second end face 10b of the optical fiber 10.

[0065] As in this embodiment, the optical characteristic measurement method may include a step S13 in which, after step S12 in which FIFO 40A is connected to the first end face 10a of the optical fiber 10, and before step S14 in which FIFO 40B is connected to the second end face 10b of the optical fiber 10, the arrangement of cores C1, C2, C3, C4 on the second end face 10b is observed with respect to the optical fiber 10, thereby identifying the correspondence between the input / output ports 41a, 42a, 43a, 44a of FIFO 40A and cores C1, C2, C3, C4. Normally, when connecting FIFO 40A to the optical fiber 10 using a fusion splicer, the FIFO 40A is connected to the first end face 10a of the optical fiber 10 after observing the first end face 10a. When performing a simple rotational alignment between the optical fiber 10 and the FIFO 40A using the OTDR device 60 described above, it is difficult to directly observe the first end face 10a of the optical fiber 10 after connecting it to the FIFO 40A. The second end face 10b, which is located opposite the first end face 10a, can be directly observed, and if the arrangement of cores C1, C2, C3, and C4 on the second end face 10b can be confirmed, the correspondence between cores C1, C2, C3, and C4 and the input / output ports 41a, 42a, 43a, and 44a of the FIFO 40A can be identified. Therefore, in this embodiment, after connecting the first end face 10a of the optical fiber 10 to the FIFO 40A, the arrangement of cores C1, C2, C3, and C4 on the second end face 10b is observed to determine the correspondence between cores C1, C2, C3, and C4 and the input / output ports 41a, 42a, 43a, and 44a of the FIFO 40A. This makes it possible to accurately measure the optical characteristics of the optical fiber 10.

[0066] As in this embodiment, the optical characteristics measurement method may include, after step S14 of connecting the FIFO 40B to the second end face 10b of the optical fiber 10, step S15 of identifying the correspondence between the input / output ports 41a, 42a, 43a, 44a of the FIFO 40A and the input / output ports 41b, 42b, 43b, 44b of the FIFO 40B, while the FIFO 40B is rotationally aligned with respect to the optical fiber 10. In this case, by identifying the correspondence between the input / output ports 41a, 42a, 43a, 44a of the FIFO 40A and the input / output ports 41b, 42b, 43b, 44b of the FIFO 40B, the optical characteristics of the optical fiber 10 can be measured with greater accuracy.

[0067] As in this embodiment, the optical properties measurement system 1 may include a control device 50 that controls the switching operation of connection modes M1, M2, and M3 by the optical switch 30, and the measurement operation of optical properties by measuring instruments 20A, 20B, and 20C, respectively. In this case, the optical properties of the optical fiber 10 can be measured even more easily using the control device 50.

[0068] As in this embodiment, the number of input / output units 21c to 28c of the measuring instrument 20C may be greater than the number of input / output units 21a and 22a of the measuring instrument 20A. By using measuring instruments 20A and 20C with different numbers of input / output units, various optical properties such as wavelength dispersion, PMD, and crosstalk can be measured.

[0069] The optical property measurement method and optical property measurement system of this disclosure are not limited to the embodiments described above, and various other modifications are possible. For example, in the embodiments described above, a case was described in which the optical property measurement system 1 is equipped with three measuring instruments 20A, 20B, and 20C. The optical property measurement system of this disclosure may be equipped with two measuring instruments, or with four or more measuring instruments. In the embodiments described above, a case was described in which the optical switch 30 has spare ports P9 to P12. The optical switch does not have spare ports. The optical switch may be an optical switch other than a cross-connect type.

[0070] 1…Optical properties measurement system 10…Optical fiber 10a…First end face 10b…Second end face 13…Cladding 14…Marker 20A…Measuring instrument (first measuring instrument) 20B…Measuring instrument 20C…Measuring instrument (second measuring instrument) 21a, 22a, 21b, 22b, 21c, 22c, 23c, 24c, 25c, 26c, 27c, 28c, 29c…Input / output section 30…Optical switch 40A…FIFO (first input / output device) 40B…FIFO (second input / output device) 41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b, 45a, 45b, 46a, 46b, 47a, 47b, 48a, 48b, 61, 62, 63, 64…Input / output port 50...Control device 60...OTDR device (measuring instrument) C1, C2, C3, C4...Core L1A, L1B, L2A, L2B, L3A, L3B...Measurement light L6A, L6B...Test light L10...Central axis M1...Connection mode (first connection state) M2...Connection mode M3...Connection mode (second connection state) P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12, P13, P14, P15, P16, P17, P18, P19, P20, P21, P22, P23, P24...Port S11, S12, S13, S14, S15, S16, S17, S18, S19...Step

Claims

1. An optical characteristic measurement method comprising: connecting a first input / output device to a first end face of an optical fiber including a first end face, a second end face located opposite to the first end face, and a plurality of cores; connecting a second input / output device to the second end face of the optical fiber; connecting the first input / output device and the second input / output device to an optical switch, and connecting a first measuring instrument and a second measuring instrument to the optical switch; measuring a first optical characteristic of the optical fiber by injecting a first measurement light into the optical fiber through the first input / output device or the second input / output device in a first connection state in which the first input / output device and the second input / output device are connected to the first measuring instrument by the optical switch; and measuring a second optical characteristic of the optical fiber by injecting a second measurement light into the optical fiber through the first input / output device or the second input / output device in a second connection state in which the first input / output device and the second input / output device are connected to the second measuring instrument by the optical switch.

2. The optical property measurement method according to claim 1, wherein the step of connecting the first input / output device to the first end face of the optical fiber includes: connecting a measuring instrument capable of measuring the test light that is incident on the first end face and returning to the first end face to the first input / output device, and causing the test light from the measuring instrument to be incident on one of the plurality of cores of the optical fiber through the first input / output device; and rotating the first input / output device relative to the optical fiber so that the measuring instrument detects the test light emitted from all of the plurality of cores except the one core as a result of the incidence of the test light on the one core.

3. The optical property measurement method according to claim 1 or 2, wherein the step of connecting the second input / output device to the second end face of the optical fiber includes: connecting a measuring instrument capable of measuring the test light that is incident on the second end face and returning to the second end face to the second input / output device, and causing the test light from the measuring instrument to be incident on one of the plurality of cores of the optical fiber through the second input / output device; and rotating the second input / output device relative to the optical fiber so that the measuring instrument detects the test light emitted from all of the plurality of cores except the one core as a result of the incident of the test light on the one core.

4. The optical property measurement method according to any one of claims 1 to 3, further comprising the step of determining the correspondence between a plurality of first input / output ports provided on the first input / output device and the plurality of cores by observing the arrangement of the plurality of cores on the second end face of the optical fiber, after the step of connecting the first input / output device to the first end face of the optical fiber and before the step of connecting the second input / output device to the second end face of the optical fiber, with the first input / output device rotated and aligned with the optical fiber.

5. The optical characteristic measurement method according to claim 4, further comprising the step of connecting the second input / output device to the second end face of the optical fiber, and then, with the second input / output device rotated and aligned with respect to the optical fiber, determining the correspondence between a plurality of first input / output ports provided by the first input / output device and a plurality of second input / output ports provided by the second input / output device.

6. An optical property measurement system comprising: an optical fiber having a first end face, a second end face located opposite the first end face, and a plurality of cores; a first input / output device connected to the first end face of the optical fiber; a second input / output device connected to the second end face of the optical fiber; a first measuring instrument capable of measuring a first optical property of the optical fiber by irradiating the optical fiber with a first measurement light through the first input / output device or the second input / output device; a second measuring instrument capable of measuring a second optical property of the optical fiber by irradiating the optical fiber with a second measurement light through the first input / output device or the second input / output device; and an optical switch disposed between the first input / output device and the second input / output device and the first measuring instrument and the second measuring instrument, which can switch between a first connection state in which the first input / output device and the second input / output device are connected to the first measuring instrument and a second connection state in which the first input / output device and the second input / output device are connected to the second measuring instrument.

7. The optical property measurement system according to claim 6, further comprising a control device that is communicably connected to the first measuring instrument, the second measuring instrument, and the optical switch, and controls the switching operation of the optical switch from the first connection state to the second connection state, the measurement operation of the first optical property by the first measuring instrument, and the measurement operation of the second optical property by the second measuring instrument, respectively.

8. The optical property measurement system according to claim 6 or 7, wherein the first measuring instrument is connected to the optical switch and includes a plurality of first input / output units for emitting and detecting the first measuring light, and the second measuring instrument is connected to the optical switch and includes a plurality of second input / output units for emitting and detecting the second measuring light, the number of the plurality of second input / output units being different from the number of the plurality of first input / output units.

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