JP2024068384A - Optical fiber evaluation device and optical fiber evaluation method - Google Patents

Abstract

[Problem] To provide an optical fiber evaluation device and an optical fiber evaluation method that enable individual loss measurement of each core of a multicore fiber and enable identification of defective cores and identification of the positions of defective parts in the multicore fiber. [Solution] The optical fiber evaluation device and the optical fiber evaluation method use a fiber bundle to introduce probe light into a first core at one end of the multicore fiber, and introduce output light from a second core different from the first core into a third core different from the first and second cores, so that the probe light passes through all cores of the multicore fiber having a plurality of cores. A reflector is used to introduce output light from a fourth core into a fifth core different from the fourth core at the other end of the multicore fiber. Then, the optical characteristics of the branching section and the multicore fiber are analyzed based on signal light output from the input/output end when the probe light is introduced from the input/output end into an input/output single mode fiber. [Selected Figure] Figure 1

Description

The present invention relates to an optical fiber evaluation device and an optical fiber evaluation method.

The technology disclosed in Patent Document 1 evaluates the optical characteristics of a coupled multicore fiber having multiple cores and one shared cladding, with one of the multiple cores being disposed at the center of the cladding as the central core. One end of a one-core dummy fiber having one core at the center of a cladding of the same shape and dimensions as the coupled multicore fiber is placed opposite to one end of the coupled multicore fiber, and the two are connected by aligning them based on the outer diameter. Light from a light source is input to the coupled multicore fiber connected to the one-core dummy fiber, and the light that has passed through the one-core dummy fiber and the coupled multicore fiber is measured.

JP 2018-21869 A

However, the technology disclosed in Patent Document 1 does not allow for individual loss measurement of each core in a multicore fiber, and therefore has the problem that it is not possible to identify defective cores in a multicore fiber or to identify the location of defective parts.

The present invention has been made in consideration of the problems inherent in the conventional technology. The object of the present invention is to provide an optical fiber evaluation device and an optical fiber evaluation method that enable individual loss measurement of each core of a multicore fiber and can identify defective cores and the positions of defective parts contained in the multicore fiber.

The optical fiber evaluation device according to the present invention includes a fiber bundle having a plurality of single mode fibers, a branching section installed on one end side of a multicore fiber having a plurality of cores and connecting one of the single mode fibers for each core, a reflector installed on the other end side of the multicore fiber, and a light source and a measuring instrument connected to the input/output end of the input/output single mode fiber among the single mode fibers. At one end side of the multicore fiber, the fiber bundle introduces the probe light into a first core, and introduces the output light from a second core different from the first core into a third core different from the first and second cores so that the probe light output from the light source passes through all the cores of the multicore fiber. At the other end side of the multicore fiber, the reflector introduces the output light from a fourth core into a fifth core different from the fourth core. The measuring instrument analyzes the optical characteristics of the branching section and the multicore fiber based on the signal light output from the input/output end when the probe light is introduced from the input/output end into the input/output single mode fiber.

The optical fiber evaluation method according to the present invention is an optical fiber evaluation method using an optical fiber evaluation device that includes a fiber bundle having a plurality of single mode fibers, a branching section that is installed on one end side of a multicore fiber having a plurality of cores and connects one of the single mode fibers for each core, a reflector that is installed on the other end side of the multicore fiber, and a light source and a measuring instrument that are connected to the input/output end of the input/output single mode fiber among the single mode fibers. Using the fiber bundle, the probe light is introduced into the first core at one end side of the multicore fiber so that the probe light output from the light source passes through all the cores of the multicore fiber, and the output light from the second core different from the first core is introduced into the third core different from the first and second cores. Using the reflector, the output light from the fourth core is introduced into the fifth core different from the fourth core at the other end side of the multicore fiber. Using the measuring instrument, the optical characteristics of the branching section and the multicore fiber are analyzed based on the signal light output from the input/output end when the probe light is introduced from the input/output end into the input/output single mode fiber.

The present invention provides an optical fiber evaluation device and an optical fiber evaluation method that enable individual loss measurement of each core of a multicore fiber and can identify defective cores and the location of defective parts contained in the multicore fiber.

1 is a schematic diagram showing a configuration of an optical fiber evaluation device according to an embodiment of the present invention. FIG. 4 is a schematic diagram showing a configuration of a branching portion. 1 is a schematic diagram showing optical coupling between cores by a reflector. FIG. FIG. 2 is a diagram illustrating a first configuration example of a reflector. FIG. 13 is a diagram illustrating a second configuration example of a reflector. FIG. 11 is a diagram showing an example of measurement data obtained by a measuring device. FIG. 2 is a schematic diagram showing a configuration of an amplifier.

The optical fiber evaluation device and the optical fiber evaluation method according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios. In addition, in the following description of the drawings, the same or similar parts are given the same or similar reference numerals.

[Example of configuration of optical fiber evaluation device]
1 is a schematic diagram showing the configuration of an optical fiber evaluation device according to the present embodiment. The optical fiber evaluation device 1 is a device for evaluating a multicore fiber MF having multiple cores and a branching section 20. Here, the multicore fiber MF is an optical fiber in which multiple cores are arranged in one cladding. In the following, the multicore fiber MF will be described as having four cores CR1, CR2, CR3, and CR4, but the present embodiment is not limited to this. For example, the multicore fiber MF may have any number of cores equal to or greater than two.

As shown in FIG. 1, the optical fiber evaluation device 1 includes a fiber bundle 10, a branching section 20, a reflector 30, a light source 41, and a photodetector 43.

The fiber bundle 10 has a plurality of single mode fibers. In particular, the fiber bundle 10 has single mode fibers corresponding to the number and arrangement of cores in the multicore fiber MF. Each single mode fiber is an optical fiber with one core arranged in one cladding. In this embodiment, the fiber bundle 10 is described as having single mode fibers SF1, SF2, SF3, and SF4, but this embodiment is not limited to this. For example, the fiber bundle 10 may have any number of single mode fibers greater than or equal to two. In addition, the fiber bundle 10 is not limited to only those including single mode fibers, and any form is acceptable as long as it can be coupled to the multicore fiber MF.

The branching unit 20 is installed at one end of the multi-core fiber MF, and connects one of the single mode fibers of the fiber bundle 10 to each core included in the multi-core fiber MF. For example, the branching unit 20 connects single mode fibers SF1, SF2, SF3, and SF4 to cores CR1, CR2, CR3, and CR4 of the multi-core fiber MF, respectively. The configuration of the branching unit 20 will be described in detail later.

The reflector 30 is installed on the other end side of the multi-core fiber MF (the side where the branching section 20 is not installed). The reflector 30 has the function of reflecting output light from one of the cores of the multi-core fiber MF and guiding it to the other cores. The configuration of the reflector 30 will be described in detail later.

The light source 41 and the photodetector 43 are connected to the input/output ends of the input/output single mode fiber among the single mode fibers included in the fiber bundle 10. In this embodiment, the single mode fiber SF1 is assumed to be the input/output single mode fiber, and the light source 41 and the photodetector 43 are assumed to be connected to the single mode fiber SF1.

The light source 41 and the photodetector 43 may be connected to the input/output ends of the input/output single mode fiber via a circulator 45. For example, the circulator 45 may be a non-reversible one-way three-port device.

In this case, the circulator 45 introduces the probe light output from the light source 41 into the input/output single mode fiber via the input/output end. The circulator 45 then introduces the signal light output from the input/output end of the input/output single mode fiber to the photodetector 43. The circulator 45 prevents the probe light output from the light source 41 from proceeding to the photodetector 43, and further prevents the signal light output from the input/output end of the input/output single mode fiber from proceeding to the light source 41.

The probe light output from the light source 41 is introduced into the input/output single mode fiber, and then introduced into each core of the multicore fiber MF via the branching section 20 and the reflector 30. The light scattered or reflected at the branching section 20, the reflector 30, each point in the longitudinal direction of the single mode fibers SF1 to SF4, and each point in the longitudinal direction of the cores CR1 to CR4 is introduced into the photodetector 43 as signal light.

The signal light therefore contains information about the branching unit 20, the single mode fibers SF1 to SF4, and the cores CR1 to CR4. Therefore, by analyzing the signal light, it is possible to obtain information about the individual loss distributions of the branching unit 20, the single mode fibers SF1 to SF4, and the cores CR1 to CR4.

For example, scattering by optical fibers includes Rayleigh scattering. Rayleigh scattering is a phenomenon in which the direction of light changes due to interaction with small particles that are sufficiently small compared to the wavelength of the light. When light is transmitted through an optical fiber, random density fluctuations contained in the optical fiber (density fluctuations of glass, density fluctuations of additives, etc.) cause fluctuations in the refractive index, resulting in Rayleigh scattering. As a result of Rayleigh scattering, losses occur in optical fibers. Losses due to Rayleigh scattering are inversely proportional to the fourth power of the wavelength on the short wavelength side.

For example, the light source 41 is a typical narrow-linewidth fiber laser. In this case, the light source 41 outputs light of a single wavelength as the probe light. The probe light output by the light source 41 may be composed of multiple successive pulsed lights at a predetermined period.

The photodetector 43 analyzes the optical characteristics of the branching section 20 and the multi-core fiber MF based on the signal light output from the input/output end of the input/output single mode fiber when the probe light is introduced into the input/output single mode fiber. For example, the photodetector 43 is an optical time domain reflectometer (OTDR). The photodetector 43 measures and integrates the intensity of the signal light as a function of time or the length of the optical fiber to plot it. Details of the measurement data obtained by the photodetector 43 will be described later.

Here, we will explain the optical path formed by the fiber bundle 10, the branching section 20, the reflector 30, and the multi-core fiber MF. The fiber bundle 10 and the reflector 30 are configured as follows so that the probe light output from the light source 41 passes through all the cores CR1 to CR4 of the multi-core fiber MF.

At one end of the multi-core fiber MF, the fiber bundle 10 introduces probe light into a first core of the multi-core fiber MF, and introduces output light from a second core different from the first core into a third core different from the first and second cores.

For example, the fiber bundle 10 introduces the probe light from the light source 41 into the core CR1, which is the first core, through the single mode fiber SF1, which is an input/output single mode fiber. The single mode fiber SF2 and the single mode fiber SF3 of the fiber bundle 10 are connected to each other on the side to which the branching section 20 is not connected. Then, the fiber bundle 10 introduces the output light from the core CR3, which is the second core, into the core CR2, which is the third core, through the single mode fiber SF3 and the single mode fiber SF2. The single mode fiber SF2 and the single mode fiber SF3 may be directly connected by fusion or the like, or may be connected by a connector or other loopback 50.

In addition, the fiber bundle 10 may introduce the output light from the core CR4 into the terminator 60 via a single mode fiber SF4, which is a single mode fiber for termination. The terminator 60 is connected to one end of the single mode fiber SF4. The terminator 60 attenuates the light introduced into the terminator 60 via the single mode fiber SF4 and suppresses the light returning from the terminator 60 to the single mode fiber SF4. As a result, the noise contained in the signal light can be reduced.

The reflector 30 guides the output light from the fourth core to a fifth core, which is different from the fourth core, at the other end of the multicore fiber MF.

For example, the reflector 30 guides the output light from the fourth core, CR1, to the fifth core, CR3. The reflector 30 also guides the output light from the fourth core, CR2, to the fifth core, CR4.

With the above configuration, the probe light output from the light source 41 passes through the cores CR1, CR3, CR2, and CR4 in that order. More specifically, the probe light passes through the single mode fiber SF1, the branching section 20, the core CR1, the reflector 30, the core CR2, and the branching section 20 in that order. The probe light then passes through the single mode fiber SF2, the loopback 50, the single mode fiber SF3, and the branching section 20 in that order. The probe light then passes through the core CR3, the reflector 30, the core CR4, the single mode fiber SF4, and the terminator 60 in that order.

[Example of branch configuration]
Next, the details of the configuration of the branching unit 20 will be described with reference to FIG. 2. FIG. 2 is a schematic diagram showing the configuration of the branching unit. The branching unit 20 includes a lens array AR, a prism PR, and a single lens LS. Here, the lens array AR is composed of lenses equal in number to the cores CR1 to CR4 of the multicore fiber MF. The prism PR is provided in an area through which light of the central cores of the single mode fibers SF1 to SF4 passes. The single lens LS optically couples the cores CR1 to CR4 of the multicore fiber MF to the central cores of the single mode fibers SF1 to SF4, respectively, via the lens array AR and the prism PR.

The configurations of the lens array AR, prism PR, and single lens LS are changed depending on the number of cores in the multicore fiber MF, the diameter of the cladding of the multicore fiber MF, and the arrangement of the cores within the multicore fiber MF. This makes it possible to optically couple the core of the multicore fiber MF to the central core of the single mode fiber.

For example, FIG. 2 shows how the multicore fiber MF is fixed to the multicore fiber side connector 23 by inserting the multicore fiber MF into the multicore fiber side connector 23 via the multicore fiber holding jig 21. Note that in FIG. 2, the fiber bundle 10 and the multicore fiber MF are in a state of being inserted into a ferrule or the like. Also shown is how the fiber bundle 10 is fixed to the fiber bundle side connector 25 by inserting the fiber bundle 10 into the fiber bundle side connector 25 via the fiber bundle holding jig 27. Here, the fiber bundle side connector 25 includes a lens array AR, a prism PR, and a single lens LS. Then, by attaching the fiber bundle side connector 25 to the multicore fiber side connector 23, the cores CR1 to CR4 of the multicore fiber MF are optically coupled to the central cores of the single mode fibers SF1 to SF4, respectively.

The branching section 20 is not limited to a spatial coupling type, and may be a FIFO (fan-in/fan-out) device of any known type. The multicore fiber holding jig 21 of the multicore fiber side connector 23 may be, for example, an MT ferrule shape, an LC ferrule shape, or a 3D waveguide shape.

In the above example, the lens array AR, prism PR, and single lens LS can be changed by changing the fiber bundle side connector 25 to which the lens array AR, prism PR, and single lens LS are already attached. Therefore, when optically coupling the cores CR1 to CR4 of the multicore fiber MF to the central cores of the single mode fibers SF1 to SF4, respectively, adjustment work such as core alignment is not required.

[Example of reflector configuration]
Next, the details of the configuration of the reflector 30 will be described with reference to Figs. 3, 4A, and 4B. Fig. 3 is a schematic diagram showing the state of optical coupling between cores by the reflector. Fig. 4A is a diagram showing a first configuration example of the reflector. Fig. 4B is a diagram showing a second configuration example of the reflector. The reflector 30 includes a lens 31 and a mirror 33, and the lens 31 and the mirror 33 guide the output light from the fourth core to the fifth core.

In FIG. 3, light output from core CR1, the fourth core, passes through lens 31, is reflected by mirror 33, passes through lens 31 again, and is introduced into core CR3, the fifth core. Also, light output from core CR2, the fourth core, passes through lens 31, is reflected by mirror 33, passes through lens 31 again, and is introduced into core CR4, the fifth core.

The configuration of the lens 31 and mirror 33 is changed according to the number of cores in the multi-core fiber MF, the diameter of the cladding of the multi-core fiber MF, and the arrangement of the cores within the multi-core fiber MF. This makes it possible to reflect output light from one of the cores of the multi-core fiber MF and introduce it into the other cores. This eliminates the need for adjustment work such as aligning the cores.

For example, FIG. 4A shows how the multi-core fiber MF is fixed to the housing 37, which includes the lens 31 and mirror 33, by inserting the multi-core fiber MF into the housing 37 via the split sleeve 35 and the ferrule FR. Here, the configuration of the housing 37 to be attached is changed depending on the multi-core fiber MF.

For example, FIG. 4B shows how the multicore fiber MF is fixed to the multicore fiber side connector 39 by inserting the multicore fiber MF into the multicore fiber side connector 39 via the split sleeve 35 and the ferrule FR. Then, a housing 37 including a lens 31 and a mirror 33 is attached to the multicore fiber side connector 39. Alternatively, a fiber stub FS may be installed in the split sleeve 35. When the housing 37 is attached to the multicore fiber side connector 39, the end face of the core part MFA of the fiber stub FS may abut against the end face of the multicore fiber MF, and the core of the multicore fiber MF and the core part MFA may be optically coupled.

The configuration of the reflector 30 as shown in Figures 4A and 4B improves the reproducibility of the attachment position when attaching and detaching the reflector 30 to the multi-core fiber MF. As a result, it is possible to more reliably reflect output light from one of the cores of the multi-core fiber MF and introduce it into the other cores.

[Example of measurement data]
Fig. 5 is a diagram showing an example of measurement data by the measuring device. The signal light introduced into the photodetector 43 passes through the branching section 20, the reflector 30, the single mode fibers SF1 to SF4, and the cores CR1 to CR4. Therefore, the greater the optical distance from the position where the probe light is scattered or reflected to generate the signal light (hereinafter referred to as the "scattering position") to the photodetector 43, the smaller the light intensity of the signal light becomes. Fig. 5 is a graph in which the horizontal axis represents the distance to the scattering position, and the vertical axis represents the light intensity of the signal light generated at the scattering position.

Area R1 shows the optical intensity of the signal light from the scattering positions in the single mode fiber SF1 of the fiber bundle 10. Area R2 shows the optical intensity of the signal light from the scattering positions in the core CR1, the reflector 30, and the core CR2. Area R3 shows the optical intensity of the signal light from the scattering positions in the single mode fiber SF2, the loopback 50, and the single mode fiber SF3. Area R4 shows the optical intensity of the signal light from the scattering positions in the core CR3, the reflector 30, and the core CR4. Area R5 shows the optical intensity of the signal light from the scattering positions in the single mode fiber SF4.

The optical length of each of the single mode fibers SF1 to SF4 in the fiber bundle 10 is L1, and the optical length of each of the cores CR1 to CR4 in the multi-core fiber MF is L2.

Point DF1 where the light intensity suddenly drops is shown at the boundary between regions R1 to R5. Point DF1 corresponds to the occurrence of loss in the branching section 20. Point DF2 where the light intensity suddenly drops is shown within regions R2 and R4. Point DF2 corresponds to the occurrence of loss in the reflector 30.

It is also shown that in each of the regions R1 to R5, the light intensity decreases as the distance increases. This corresponds to the total loss increasing as the distance traveled by the signal light increases in the single mode fibers SF1 to SF4 and the cores CR1 to CR4.

Therefore, according to this embodiment, the optical characteristics of each core of the multicore fiber MF can be measured all at once without adjusting the optical axis at the branching section 20 or removing and attaching the branching section 20. As a result, the measurement time is reduced to a fraction of the number of cores of the multicore fiber MF. Furthermore, even when performing bidirectional measurements of the multicore fiber MF, this can be achieved by switching the branching section 20 and the reflector 30 between one end and the other end of the multicore fiber MF.

In addition, according to this embodiment, the optical characteristics of the branching section 20 can be measured in a single step in addition to measuring the optical characteristics of each core of the multicore fiber MF.

[Example of amplifier configuration]
6 is a schematic diagram showing the configuration of an amplifier. When the multi-core fiber MF is long or has many cores, the distance that the signal light travels becomes large. Therefore, the signal light that needs to be detected by the photodetector 43 becomes weak. In order to ensure the dynamic range of the photodetector 43, the optical fiber evaluation device 1 may further include an amplifier 70 that amplifies the probe light output from the light source 41.

The light source 41 is connected to the input/output terminals of the input/output single mode fiber via the amplifier 70, and the amplifier 70 introduces the amplified probe light from the input/output terminals into the input/output single mode fiber. For example, the amplifier 70 may include a multiplexer 73, a rare earth doped optical fiber RDF, and an isolator 75. Here, the multiplexer 73 multiplexes the excitation light output from the excitation light source 71 with the probe light output from the light source 41. The rare earth doped optical fiber RDF contains rare earths to amplify the incident light. The isolator 75 extracts the probe light amplified in the rare earth doped optical fiber RDF.

[Effects of the embodiment]
As described above in detail, the optical fiber evaluation device and optical fiber evaluation method according to the present embodiment are an optical fiber evaluation device including a fiber bundle having a plurality of single mode fibers, a branching section installed on one end side of a multicore fiber having a plurality of cores and connecting one of the single mode fibers for each core, a reflector installed on the other end side of the multicore fiber, and a light source and a measuring instrument connected to input/output ends of an input/output single mode fiber among the single mode fibers, and an optical fiber evaluation method using the optical fiber evaluation device.

At one end of the multicore fiber, a fiber bundle introduces the probe light into a first core, and introduces output light from a second core different from the first core into a third core different from the first and second cores, so that the probe light output from the light source passes through all of the cores of the multicore fiber. Furthermore, at the other end of the multicore fiber, a reflector introduces output light from a fourth core into a fifth core different from the fourth core. Then, the measuring instrument analyzes the optical characteristics of the branching section and the multicore fiber based on the signal light output from the input/output end when the probe light is introduced from the input/output end into the input/output single mode fiber.

This enables individual loss measurement of each core of the multicore fiber, and enables identification of defective cores in the multicore fiber and identification of the location of defective parts. In particular, the optical characteristics of each core of the multicore fiber can be measured all at once without adjusting the optical axis or removing and attaching parts. As a result, the measurement time is reduced to a fraction of the number of cores in the multicore fiber. Furthermore, in addition to measuring the optical characteristics of each core of the multicore fiber, the optical characteristics of the branching section can also be measured all at once.

In the optical fiber evaluation device and optical fiber evaluation method according to this embodiment, the branching section may have a lens array consisting of lenses equal to the number of cores in the multicore fiber, a prism provided in an area through which light from the central core of the single mode fiber passes, and a single lens that optically couples the central core of the single mode fiber and the core of the multicore fiber via the lens array and the prism. This improves the reproducibility of the attachment position when attaching and detaching the branching section to the multicore fiber. When optically coupling the core of the multicore fiber to the central core of the single mode fiber, adjustment work such as core alignment is not required.

Furthermore, in the optical fiber evaluation device and optical fiber evaluation method according to this embodiment, the reflector may include a mirror and a lens, and the mirror and lens may guide the output light from the fourth core to the fifth core. This improves the reproducibility of the attachment position when attaching and detaching the reflector to the multicore fiber. As a result, it is possible to more reliably reflect the output light from one of the cores of the multicore fiber and guide it to the other cores. Then, the cores of the multicore fiber can be connected as a single optical path.

In the optical fiber evaluation device and the optical fiber evaluation method according to this embodiment, one single mode fiber connected to the second core via a branching section and another single mode fiber connected to the third core via a branching section may be connected. This allows the cores of the multicore fiber to be connected as one optical path.

Furthermore, the optical fiber evaluation device and the optical fiber evaluation method according to this embodiment may further include a terminator connected to one end of the terminating single mode fiber among the single mode fibers, and the terminator may attenuate the light introduced into the terminator through the terminating single mode fiber and suppress the light returning from the terminator to the terminating single mode fiber. As a result of suppressing the light returning from the end of the single mode fiber into the core of the multicore fiber, the noise contained in the signal light can be reduced.

The optical fiber evaluation device and the optical fiber evaluation method according to this embodiment may further include an amplifier that amplifies the probe light output from the light source, the light source being connected to the input/output terminal via the amplifier, and the amplifier may introduce the amplified probe light from the input/output terminal into the input/output single mode fiber. This ensures the dynamic range of the measuring instrument even when the signal light that needs to be detected by the measuring instrument becomes weak. For example, when the multicore fiber MF is long or has many cores, the distance that the signal light travels becomes large, and the signal light becomes weak. Even in such a case, the signal light can be obtained with high accuracy.

Furthermore, in the optical fiber evaluation device and optical fiber evaluation method according to this embodiment, the measuring instrument may be an optical pulse tester. This allows the optical characteristics of the branching section and the multi-core fiber to be analyzed with high accuracy.

Although the present embodiment has been described above, the present embodiment is not limited to these, and various modifications are possible within the scope of the gist of the present embodiment.

REFERENCE SIGNS LIST 1 Optical fiber evaluation device 10 Fiber bundle 20 Branching section 30 Reflector 31 Lens 33 Mirror 41 Light source 43 Photodetector 45 Circulator 50 Loopback 60 Terminator 70 Amplifier AR Lens array CR1 to CR4 Core LS Single lens MF Multicore fiber PR Prism SF1 to SF4 Single mode fiber

Claims (8)

a fiber bundle having a plurality of single mode fibers;
a branching section that is provided on one end side of a multicore fiber having a plurality of cores and connects one of the single mode fibers to each of the cores;
A reflector provided on the other end side of the multi-core fiber;
a light source and a measuring instrument connected to an input/output end of an input/output single mode fiber among the single mode fibers;
An optical fiber evaluation device comprising:
so that the probe light output from the light source passes through all the cores of the multi-core fiber,
The fiber bundle is provided at one end side of the multicore fiber.
Introducing the probe light into a first core;
Output light from a second core different from the first core is guided into a third core different from the first core and the second core;
The reflector is provided at the other end side of the multi-core fiber.
The output light from the fourth core is guided to a fifth core different from the fourth core;
the measuring instrument analyzes the optical characteristics of the branching section and the multi-core fiber based on signal light output from the input/output end when the probe light is introduced from the input/output end into the input/output single mode fiber. The branch portion is
a lens array including lenses whose number is equal to the number of cores of the multicore fiber;
a prism provided in a region through which light of a central core of the single mode fiber passes;
a single lens that optically couples the central core of the single mode fiber and the cores of the multicore fiber via the lens array and the prism;
The optical fiber evaluation device according to claim 1 , The reflector includes a mirror and a lens.
2. The optical fiber evaluation device according to claim 1, wherein the output light from the fourth core is guided to the fifth core by the mirror and the lens. Among the single mode fibers,
a single mode fiber connected to the second core via the branch portion;
The optical fiber evaluation device according to claim 1 , wherein another single mode fiber is connected to the third core via the branch portion. a terminator connected to one end of a terminating single mode fiber among the single mode fibers,
2. The optical fiber evaluation device according to claim 1, wherein the terminator attenuates light introduced into the terminator through the terminating single mode fiber and suppresses light returning from the terminator to the terminating single mode fiber. an amplifier that amplifies the probe light output from the light source;
the light source is connected to the input/output terminal via the amplifier;
2. The optical fiber evaluation device according to claim 1, wherein the amplifier introduces the amplified probe light from the input/output end into the input/output single mode fiber. The optical fiber evaluation device according to any one of claims 1 to 6, wherein the measuring instrument is an optical pulse tester. a fiber bundle having a plurality of single mode fibers;
a branching section that is provided on one end side of a multicore fiber having a plurality of cores and connects one of the single mode fibers to each of the cores;
A reflector provided on the other end side of the multi-core fiber;
a light source and a measuring instrument connected to an input/output end of an input/output single mode fiber among the single mode fibers;
An optical fiber evaluation method using an optical fiber evaluation device comprising:
so that the probe light output from the light source passes through all the cores of the multi-core fiber,
Using the fiber bundle, at one end side of the multi-core fiber,
Introducing the probe light into a first core;
Output light from a second core different from the first core is guided into a third core different from the first core and the second core;
Using the reflector, at the other end side of the multi-core fiber,
The output light from the fourth core is guided to a fifth core different from the fourth core;
using the measuring instrument, to analyze optical characteristics of the branching section and the multi-core fiber based on signal light output from the input/output end when the probe light is introduced from the input/output end into the input/output single mode fiber.

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