Crosstalk measurement method, crosstalk measurement device, light loss measurement method, and light loss measurement device

Abstract

To provide a crosstalk measurement method and cross-talk measurement device that can measure crosstalk, using an OTDR, and to provide a light loss measurement method and light loss measurement device that can measure a loss of light of a waveguide having an impact of the crosstalk suppressed, using the OTDR.SOLUTION: A crosstalk measurement method comprises: a first measurement step of making first incidence light incident from one end of a first waveguide, and almost simultaneously making second incidence light incident from one end of a second waveguide, and measuring power of emitting light emitted from one end 17 of a first light waveguide by an OTDR 20; a second measurement step of making the first incidence light from the one end 17 of the first light waveguide, making light from the OTDR 20 non-incident upon the second light waveguide, and measuring power of emitting light emitted from the one end 17 of the first light waveguide by the OTDR 20; and a processing step of using the power of the emitting light measured in the first measurement step and second measurement step to obtain crosstalk of the first light waveguide.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a crosstalk measurement method, a crosstalk measurement device, an optical loss measurement method, and an optical loss measurement device. [Background technology]

[0002] In response to the recent increase in the amount of information and communication, there is a demand to expand the transmission capacity of optical fibers. Multicore fibers have attracted attention because they can improve spatial utilization efficiency and transmit large amounts of information in a limited space. However, because multiple cores are arranged in one optical fiber, it is more difficult to evaluate the characteristics of multicore fibers than single-core fibers. Therefore, technology to efficiently evaluate multicore fibers is required. In particular, crosstalk measurement is an important measurement item for multicore fibers, but is not included in the measurement items for single-core fibers, so new measurement equipment must be prepared.

[0003] The methods described in the following non-patent documents are known as crosstalk measurement methods. Non-patent document 1 below describes a PM (Power Meter) method. The PM method is a method in which light is made incident on one end of a specific core of a multi-core fiber, and the power of light emitted from the other end of a core that crosstalks with the core is measured. Non-patent documents 2 and 3 below describe an OTDR (Optical Time Domain Reflectometer) method. In the OTDR method, a multi-channel OTDR is used to make light incident on a specific core, and light that crosstalks with other cores is detected as backscattered light of the light, thereby measuring crosstalk. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] [1] K. Takenaga, Y. Arakawa, S. Tanigawa, N. Guan, S. Matsuo, K. Saitoh and M. Koshiba, “An Investigation on Crosstalk in Multi-Core Fibers by Introducing Random Fluctuation along Longitudinal Direction,” IEICE TRAN. COMMUN., Vol.E94-B, No.2, 2011. [Non-Patent Document 2] [2] M. Ohashi, K. Kawazu, A. Nakamura, and Y. Miyoshi, “Simple backscattered power technique for measuring crosstalk of multi-core fibers,” OptoElectronics and Communications Conference, Busan, South Korea, P1-25, 2012, DOI: https: / / doi.org / 10.1109 / OECC.2012.6276724 [Non-Patent Document 3] [3] M. Nakazawa, M. Yoshida, and T. Hirooka, “Nondestructive measurement of mode couplings along a multi-core fiber using a synchronous multi-channel OTDR,” Optics Express, vol. 20, Issue 11, pp. 12530-12540, 2012 Summary of the Invention [Problem to be solved by the invention]

[0005] In the PM method, it is necessary to input light from one end of a multicore fiber and receive the light output from the other end. In contrast, in the OTDR method, light is input from one end of a multicore fiber and the light output from the one end is received. For this reason, there is a need to measure crosstalk using an OTDR. However, in the crosstalk measurement methods described in Non-Patent Documents 2 and 3, since the backscattered light of the light after crosstalk is measured, there is a concern that the power of the measured light is small and it is difficult to measure crosstalk. In a multicore fiber with less crosstalk, it is even more difficult to measure crosstalk. However, as described above, there is a need to measure crosstalk using an OTDR. Such a need may arise not only for multicore fibers but also for optical devices having multiple optical waveguides in which crosstalk may occur.

[0006] There is also a need to measure the loss with the effect of crosstalk of light propagating through the cores of a multicore fiber suppressed. In this case, there is also a need to measure the loss using an OTDR. However, in a multicore fiber, when trying to measure the loss of light in a specific core, the loss of light caused by the core, such as Rayleigh scattering, and the loss caused by crosstalk between the core and other cores are combined, making it difficult to measure the loss of light caused by the core with an OTDR. Such measurements are difficult not only in multicore fibers but also in optical devices having multiple optical waveguides in which crosstalk may occur.

[0007] Therefore, an object of the present invention is to provide a crosstalk measurement method and crosstalk measurement device capable of measuring crosstalk using an OTDR, and an optical loss measurement method and optical loss measurement device capable of measuring optical loss in an optical waveguide in which the effects of crosstalk are suppressed using an OTDR. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, a first aspect of the present invention is a method for measuring crosstalk in an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at the shortest distance, the method comprising: separating light output from an OTDR into a first incident light and a second incident light, the number of which is the same as the number of the second optical waveguides and which has a predetermined power ratio with respect to the first incident light; making the first incident light incident from one end of the first optical waveguide, and making the second incident light incident from one end of each of the second optical waveguides at approximately the same timing as the timing at which the first incident light is incident from one end of the first optical waveguide; a first measurement step of measuring a power of output light output from the one end of a first optical waveguide with the OTDR; a second measurement step of measuring a power of output light output from the one end of the first optical waveguide with the OTDR while making the light output from the OTDR incident as a first incident light from the one end of the first optical waveguide and not making the light from the OTDR incident on the second optical waveguide; and a processing step of determining crosstalk of the first optical waveguide using the power of the output light measured in the first measurement step and the power of the output light measured in the second measurement step.

[0009] In the first measurement step, the first incident light propagating through the first optical waveguide crosstalks into the second optical waveguide, and the second incident light propagating through the second optical waveguide crosstalks into the first optical waveguide. Meanwhile, in the second measurement step, the first incident light propagating through the first optical waveguide crosstalks into the second optical waveguide, but the second incident light does not crosstalk into the first optical waveguide because the second incident light does not propagate through the second optical waveguide. Therefore, the power of the light propagating through the first optical waveguide in the first measurement step and the power of the light propagating through the first optical waveguide in the second measurement step differ by the power of the light crosstalking from the second optical waveguide to the first optical waveguide. Therefore, the power of the light emitted from the first optical waveguide in the first measurement step and the power of the light emitted from the first optical waveguide in the second measurement step differ only by the power of the light propagating to one end of the first optical waveguide by Rayleigh scattering or the like among the light crosstalking from the second optical waveguide to the first optical waveguide. Also, the ratio of the power of the light of the first incident light crosstalking to the second optical waveguide and the power of the light of the second incident light crosstalking to the first optical waveguide is based on the ratio of the power of the first incident light to the power of the second incident light. Therefore, the crosstalk of the first optical waveguide can be obtained by using the power of the emitted light measured in the first measurement step and the power of the emitted light measured in the second measurement step as described above. In this way, according to the crosstalk measurement method of this embodiment, the crosstalk can be measured using an OTDR. Note that the first step may precede the second step, and the second step may precede the first step. Furthermore, the first incident light in the first measurement step and the first incident light in the second measurement step may have different powers.

[0010] A second aspect of the present invention is the crosstalk measuring method according to the first aspect, characterized in that the power of the first incident light and the power of the second incident light in the first measuring step are approximately equal to each other.

[0011] In this case, in the first measurement step, the power of the light that the first incident light crosstalks into the second optical waveguide is approximately equal to the power of the light that the second incident light crosstalks into the first optical waveguide, so that the calculation for determining the crosstalk of the first optical waveguide can be simplified and the crosstalk can be easily determined.

[0012] A third aspect of the present invention is the crosstalk measuring method according to the first aspect, wherein the predetermined power ratio is 0.5 or more and 2 or less.

[0013] If the power of the second incident light relative to the power of the first incident light is 0.5 or more and 2 or less, the crosstalk can be calculated with a sufficiently acceptable error even using the simple calculation in which the power of the first incident light and the power of the second incident light are approximately equal to each other.

[0014] A fourth aspect of the present invention is a crosstalk measurement method according to any one of the first to third aspects, characterized in that the power of the first incident light in the first measurement step and the power of the first incident light in the second measurement step are 0.5 to 2 times each other.

[0015] The crosstalk per unit length can be found from the difference between the slope of the OTDR waveform obtained in the first measurement step and the slope of the OTDR waveform obtained in the second measurement step. Therefore, the first incident light in the first measurement step and the first incident light in the second measurement step may have different powers, but it is preferable that the power of the first incident light in the first measurement step and the power of the first incident light in the second measurement step are 0.5 to 2 times, since this makes it easier to compare the OTDR waveforms compared to when the ratio of the respective powers is outside this range.

[0016] A fifth aspect of the present invention is the crosstalk measurement method according to any one of the first to fourth aspects, characterized in that the optical device has at least one third optical waveguide other than the first optical waveguide and the second optical waveguide, and in the first measurement step, in addition to the first incident light and the second incident light, the light output from the OTDR is separated into third incident lights, the number of which is the same as the number of the third optical waveguides and which have a predetermined power ratio to the first incident light, and the third incident light is made incident from one end side of each of the third optical waveguides at approximately the same timing as the timing at which the first incident light is made incident from the one end of the first optical waveguide.

[0017] The crosstalk between the first optical waveguide and the third optical waveguide is smaller than the crosstalk between the first optical waveguide and the second optical waveguide. Therefore, even if no light is incident on the third optical waveguide in the first measurement step, the crosstalk of the first optical waveguide can be measured with a sufficiently tolerable error. In the fifth aspect, the third incident light having a predetermined power ratio to the first incident light is incident on the third optical waveguide, thereby canceling at least a part of the crosstalk between the first optical waveguide and the third optical waveguide. Therefore, according to this configuration, the crosstalk of the first optical waveguide can be obtained more accurately.

[0018] In order to solve the above-mentioned problems, a sixth aspect of the present invention provides a crosstalk measurement device for an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at the shortest distance, the crosstalk measurement device comprising: an OTDR; and a second incident light optically connected to the OTDR and the optical device, the first incident light being incident on one end of the first optical waveguide and the second incident light being the same in number as the number of the second optical waveguides and having a predetermined power ratio to the first incident light, the second incident light being incident on one end of each of the second optical waveguides at approximately the same timing as the timing at which the first incident light is incident on one end of the first optical waveguide, and the second incident light being incident on one end of each of the second optical waveguides at approximately the same timing as the timing at which the first incident light is incident on one end of the first optical waveguide, and a processing unit that determines crosstalk of the first optical waveguide using the power of the output light measured by the OTDR in the first measurement state and the power of the output light measured by the OTDR in the second measurement state.

[0019] In the first measurement state, the first incident light propagating through the first optical waveguide crosstalks into the second optical waveguide, and the second incident light propagating through the second optical waveguide crosstalks into the first optical waveguide. On the other hand, in the second measurement state, the first incident light propagating through the first optical waveguide crosstalks into the second optical waveguide, but since the second incident light does not propagate through the second optical waveguide, the second incident light does not crosstalk into the first optical waveguide. Therefore, the processing unit can obtain the crosstalk of the first optical waveguide using the power of the emitted light measured in the first measurement state and the power of the emitted light measured in the second measurement state, in the same manner as in the above-mentioned crosstalk measurement method, using the OTDR.

[0020] In a seventh aspect of the present invention, the light separation input / output unit includes a separation unit that separates light output from the OTDR into the first incident light and each of the second incident lights, a first optical connection unit that optically connects the separation unit to the first optical waveguide and propagates the first incident light toward the first optical waveguide and propagates the output light toward the OTDR, and a second optical connection unit that optically connects the separation unit to each of the second optical waveguides in the first measurement state and optically disconnects the separation unit from each of the second optical waveguides in the second measurement state. and a second optical connection section having an optical component that propagates the second incident light toward each of the second optical waveguides in the first measurement state and suppresses the light output from the one end of the second optical waveguide from propagating toward the OTDR side, wherein an optical path length from the separation section to the one end of the first optical waveguide via the first optical connection section is approximately equal to an optical path length from the separation section to the one end of the second optical waveguide via the second optical connection section.

[0021] Furthermore, aspect 8 of the present invention is a crosstalk measuring device according to aspect 7, characterized in that the first optical connection portion has a loss portion that generates an optical loss approximately equal to the optical loss in the optical component and the optical switch when light of equal power is incident on the first optical connection portion and the second optical connection portion.

[0022] Since the first optical connection portion has the loss portion, the ratio between the power of the first incident light entering the first optical waveguide and the power of the second incident light entering the second optical waveguide can be prevented from fluctuating from a predetermined power ratio due to optical loss in the optical components and the optical switch.

[0023] In order to solve the above-mentioned problems, a ninth aspect of the present invention is an optical loss measurement method for measuring optical loss in a first optical waveguide in an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at the shortest distance, the optical loss measurement method comprising: a measuring step of separating light output from an OTDR into a first incident light and a second incident light, the number of which is the same as the number of the second optical waveguides and the power of which is approximately equal to that of the first incident light, causing the first incident light to be input from one end of the first optical waveguide and causing the second incident light to be input from one end of each of the second optical waveguides at approximately the same timing as that of causing the first incident light to be input from one end of the first optical waveguide, and measuring the power of the output light output from the one end of the first optical waveguide with the OTDR; and a processing step of determining optical loss in the first optical waveguide using the power of the output light measured in the measuring step.

[0024] In this optical loss measurement method, the power of the first incident light incident on the first optical waveguide is approximately equal to the power of the second incident light incident on the second optical waveguide. Therefore, in the measurement step, the power of the light crosstalked by the first incident light to the second optical waveguide is approximately equal to the power of the light crosstalked by the second incident light to the first optical waveguide. Therefore, the power of the output light measured by the OTDR reflects the loss of the first incident light due to Rayleigh scattering or the like when the first incident light propagates through the first optical waveguide in a state where crosstalk is not substantially generated. Therefore, the processing step can obtain the loss in which the influence of crosstalk of the first incident light is suppressed. Therefore, according to the optical loss measurement method of this aspect, the loss of the first optical waveguide in which the influence of crosstalk is suppressed can be measured using the OTDR.

[0025] A tenth aspect of the present invention is the optical loss measurement method of aspect 9, characterized in that the optical device has at least one third optical waveguide other than the first optical waveguide and the second optical waveguide, and in the measuring step, in addition to the first incident light and the second incident light, the light output from the OTDR is separated into third incident lights, the number of which is the same as the number of the third optical waveguides and the power of which is approximately equal to that of the first incident lights, and the third incident lights are made incident from one end side of each of the third optical waveguides at approximately the same timing as the timing at which the first incident light is made incident from the one end of the first optical waveguide.

[0026] The crosstalk between the first optical waveguide and the third optical waveguide is smaller than the crosstalk between the first optical waveguide and the second optical waveguide. Therefore, even if no light is incident on the third optical waveguide in the measurement step, the loss of the first optical waveguide in which the influence of crosstalk is suppressed can be measured with a sufficiently tolerable error. However, by incident a third incident light having a power approximately equal to that of the first incident light on the third optical waveguide, the crosstalk between the first optical waveguide and the third optical waveguide can be almost cancelled. Therefore, according to this configuration, the loss of the first optical waveguide in which the influence of crosstalk is suppressed can be measured more accurately.

[0027] In order to solve the above-mentioned problems, an eleventh aspect of the present invention is an optical loss measurement device for measuring an optical loss in a first optical waveguide in an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at the shortest distance, the optical loss measurement device comprising: an OTDR; and an optical device optically connected to the OTDR and the optical device, the optical loss measurement device splitting light output from the OTDR into a first incident light and a second incident light having the same number as the number of the second optical waveguides and approximately equal power to the first incident light, and inputting the first incident light to one end of the first optical waveguide. and a light separation input / output section that causes one end of the first optical waveguide to be input to the OTDR and causes the second input light to be input to one end of each of the second optical waveguides at approximately the same timing as the first input light is input from one end of the first optical waveguide, and that propagates output light output from the one end of the first optical waveguide to the OTDR and suppresses light output from the one end of the second optical waveguide from propagating to the OTDR, and a processing section that determines the optical loss in the first optical waveguide using the power of the output light measured by the OTDR.

[0028] In this optical loss measurement device, the power of the first incident light entering the first optical waveguide from the optical separation input / output unit is approximately equal to the power of the second incident light entering the second optical waveguide. In the same manner as in the optical loss measurement method described above, the power of the output light measured by the OTDR reflects the loss of the first incident light due to Rayleigh scattering or the like when the first incident light propagates through the first optical waveguide in a state where crosstalk is not substantially generated. Therefore, the processing unit can determine the loss of the first incident light in which the influence of crosstalk in the first optical waveguide is suppressed. Therefore, according to the optical loss measurement device of this aspect, the OTDR can be used to measure the loss in which the influence of crosstalk in the first optical waveguide is suppressed.

[0029] A twelfth aspect of the present invention is the optical loss measurement device of Aspect 11, characterized in that the optical separation input / output unit includes a separation unit that separates the light output from the OTDR into the first incident light and each second incident light, a first optical connection unit that optically connects the separation unit and the first optical waveguide and propagates the first incident light toward the first optical waveguide and propagates the output light toward the OTDR, and a second optical connection unit that is optically connected to the separation unit and each of the second optical waveguides and has an optical component that propagates the second incident light to each of the second optical waveguides and suppresses the light output from the one end of the second optical waveguide from propagating toward the OTDR side, and an optical path length from the separation unit to the one end of the first optical waveguide via the first optical connection unit is approximately equal to an optical path length from the separation unit to the one end of the second optical waveguide via the second optical connection unit.

[0030] In addition, aspect 13 of the present invention is the optical loss measurement device of aspect 12, characterized in that the first optical connection portion has a loss portion that generates an optical loss approximately equal to the optical loss in the optical component when light of equal power is incident on the first optical connection portion and the second optical connection portion.

[0031] By having the first optical connection portion have the above-mentioned loss portion, it is possible to prevent the power of the first incident light entering the first optical waveguide and the power of the second incident light entering the second optical waveguide from fluctuating from approximately equal power due to optical loss in the optical component. Effect of the Invention

[0032] As described above, according to the present invention, there are provided a crosstalk measurement method and a crosstalk measurement device capable of measuring crosstalk using an OTDR, and an optical loss measurement method and an optical loss measurement device capable of measuring the optical loss of an optical waveguide in which the effects of crosstalk are suppressed using an OTDR. [Brief description of the drawings]

[0033] [Figure 1] 1 is a diagram showing a cross section perpendicular to the longitudinal direction of a multi-core fiber according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram showing a crosstalk measuring device in a first embodiment. [Diagram 3] 4 is a flowchart showing the procedure of a crosstalk measuring method in the first embodiment. [Figure 4] 10A to 10C are diagrams illustrating crosstalk in a multicore fiber in a first measurement step. [Diagram 5] 13A to 13C are diagrams illustrating the state of crosstalk in a multicore fiber in a second measurement step. [Figure 6] FIG. 13 is a diagram showing the measurement results by an OTDR. [Figure 7] 5 is a diagram showing a measurement result of crosstalk according to the first embodiment and a measurement result of crosstalk by a PM method. FIG. [Figure 8] 4 is a diagram showing a cross section perpendicular to the longitudinal direction of a multi-core fiber according to a modified example of the first embodiment. FIG. [Figure 9] FIG. 13 is a diagram showing a crosstalk measuring device in a modified example of the first embodiment. [Figure 10] FIG. 13 is a diagram illustrating an optical loss measurement apparatus in a second embodiment. [Figure 11] 10 is a flowchart showing the procedure of an optical loss measurement method in a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, embodiments for carrying out the crosstalk measurement method, crosstalk measurement device, optical loss measurement method, and optical loss measurement device according to the present invention will be illustrated with reference to the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention, and are not intended to limit the interpretation of the present invention. The present invention can be modified and improved from the following embodiments without departing from the spirit of the present invention. Note that in the drawings referred to below, the dimensions of each component may be changed to facilitate understanding.

[0035] (First embodiment) FIG. 1 is a diagram showing a cross section perpendicular to the longitudinal direction of the multicore fiber of this embodiment. The multicore fiber 10 has a plurality of cores 11, 12 capable of propagating light, and a clad 15 surrounding the outer peripheral surfaces of the cores 11, 12. The clad 15 is a common clad for the cores 11 and 12 that surrounds the outer peripheral surfaces of the cores 11 and 12, and may be called a common clad. The outer peripheral surface of the clad 15 may be surrounded by a coating layer made of resin. The only core adjacent to the core 11 is the core 12. Therefore, the core 12 is the core adjacent to the core 11 at the shortest distance. The length of the multicore fiber 10 is a length at which measurable crosstalk occurs between the cores 11 and 12, and is, for example, several hundred meters or more.

[0036] Each of the cores 11, 12 has one end and the other end, and is arranged parallel to each other along the longitudinal direction of the multicore fiber 10. The refractive index of the cores 11, 12 is higher than the refractive index of the cladding 15, and each of the cores 11, 12 is capable of propagating light. Therefore, the core 11 is a first optical waveguide and the core 12 is a second optical waveguide, so that the multicore fiber 10 is an optical device having a plurality of optical waveguides arranged parallel to each other. The cores 11 and 12 may be formed in a spiral shape and arranged parallel to each other, or the cores 11, 12 may be formed in a straight line and arranged parallel to each other.

[0037] In this embodiment, the cores 11 and 12 are made of silica glass doped with a dopant such as germanium (Ge) that increases the refractive index, and the clad 15 is made of silica glass without any dopant. For example, the cores 11 and 12 may be made of silica glass without any dopant, and the clad 15 may be made of silica glass doped with a dopant such as fluorine (F) that decreases the refractive index, or the cores 11 and 12 may be made of silica glass doped with a dopant that increases the refractive index, and the clad 15 may be made of silica glass doped with a dopant that decreases the refractive index. In addition, the dopant that increases the refractive index and the dopant that decreases the refractive index are not particularly limited.

[0038] Next, a crosstalk measuring device for an optical device according to this embodiment will be described. Fig. 2 is a diagram showing the crosstalk measuring device according to this embodiment. As shown in Fig. 2, the crosstalk measuring device 1 according to this embodiment mainly comprises an OTDR 20, a processing unit 25, and a light separation input / output unit 30, and measures crosstalk in a multi-core fiber 10. The multi-core fiber 10 has one end 17 and the other end. In the following description, the one end 17 and the other end may also be described as the one end 17 and the other end of the cores 11, 12.

[0039] The OTDR 20 is used by being connected to an optical fiber or the like, and is capable of emitting pulsed light, measuring the power of light incident from the optical fiber, and measuring the time from when the pulsed light is emitted until the measured light is incident, and is capable of measuring light losses such as transmission loss, bending loss, connection loss, etc. of the optical fiber, detecting broken parts of the optical fiber, etc., measuring the amount of light reflection, etc. In this embodiment, an optical fiber 21 is connected to the OTDR 20.

[0040] The processing unit 25 is electrically connected to the OTDR, and data related to the power of light received by the OTDR 20 is output to the processing unit 25. The processing unit 25 is a calculation device that calculates crosstalk using the power of light measured by the OTDR 20. The processing unit 25 can be, for example, a microcontroller, an integrated circuit such as an IC (Integrated Circuit), an LSI (Large-scale Integrated Circuit), or an ASIC (Application Specific Integrated Circuit), or an NC (Numerical Control) device. The processing unit 25 may use a machine learning device, or may not use a machine learning device. When data related to the power of light is input from the OTDR 20, the processing unit 25 calculates the crosstalk of the core 11 based on the data, as described later, and outputs data related to the calculated crosstalk. The processing unit 25 and the OTDR 20 may be housed in one housing, and some of the components may be shared.

[0041] The light separation input / output section 30 mainly comprises a separation section 31, a first optical connection section 311, and a second optical connection section 322.

[0042] The separation unit 31 is connected to the optical fiber 21, and the light emitted from the OTDR 20 is incident on the separation unit 31. The separation unit 31 separates the light emitted from the OTDR 20 into a plurality of lights. In this embodiment, since the multi-core fiber 10 has two cores 11 and 12, the separation unit 31 separates the light emitted from the OTDR 20 into a first incident light and a second incident light. An example of the separation unit 31 is an optical coupler that optically couples the cores of two parallel optical fibers. In this embodiment, the light incident from the optical fiber 21 is separated into two first incident lights and a second incident light having approximately equal powers. Such an optical coupler may be called a 3 dB coupler. The separation unit 31 is connected to the optical fibers 35 and 36, and the separated first incident light is incident on the optical fiber 35, and the separated second incident light is incident on the optical fiber 36.

[0043] The first optical connection section 311 mainly comprises a loss section 32 and a part of a fan-in-fan-out device 39, and the second optical connection section 322 mainly comprises an optical component 33, an optical switch 34 and another part of the fan-in-fan-out device 39.

[0044] The loss section 32 is formed by bending a section of the optical fiber 35 connected to the separation section 31 at a predetermined diameter. In this section, a part of the light propagating through the optical fiber 35 leaks from the core and is lost.

[0045] The optical component 33 is connected to the optical fiber 36 and the optical fiber 37. The optical component 33 outputs the light incident from the optical fiber 36 to the optical fiber 37, and suppresses the light incident from the optical fiber 37 from propagating to the optical fiber 36. Examples of the optical component 33 include an isolator and a circulator. When the optical component 33 is an isolator, the forward direction of the isolator is the direction from the optical fiber 36 side to the optical fiber 37 side. In this case, the isolator transmits the light from the optical fiber 36 side to the optical fiber 37 side, and attenuates the power of the light from the optical fiber 37 side to the optical fiber 36 side. The isolator may block the light from the optical fiber 37 side to the optical fiber 36 side. When the optical component 33 is a circulator, the circulator includes, for example, a first port connected to the optical fiber 36, a second port connected to the optical fiber 37 and outputting the light incident on the first port, and a third port outputting the light incident on the second port. In this case, it is preferable that an optical fiber provided with a non-reflection termination is connected to the third port in order to prevent reflected light from propagating to the first port.

[0046] The optical switch 34 is connected to the optical fiber 37 and the optical fiber 38. The optical switch 34 can be switched between a state in which the optical fiber 37 and the optical fiber 38 are optically connected and a state in which the optical fiber 37 and the optical fiber 38 are optically disconnected. The optical switch 34 can be a mechanical optical switch or an electronic optical switch. The mechanical optical switch can be an optical switch configured to mechanically move a prism, a mirror, or an optical fiber. The mirror can be an MEMS mirror. The electronic optical switch can be an optical switch configured to utilize an electro-optic effect, a magneto-optic effect, an acousto-optic effect, a thermo-optic effect, or a semiconductor gate. The optical switch 34 can also be configured to connect or fusion-splice the optical fiber 37 and the optical fiber 38 with a single-core connector.

[0047] Note that when light passes through the optical component 33 and the optical switch 34, the light is lost to a certain extent. For this reason, when light of equal power is incident on the first optical connection section 311 and the second optical connection section 322, it is preferable that the power of the light lost in the loss section 32 is approximately equal to the power of the light lost in the optical component 33 and the optical switch 34, since this can prevent the power of the light lost in the first optical connection section 311 from differing from the power of the light lost in the second optical connection section 322.

[0048] The optical fiber 35 and the optical fiber 38 are each connected to a fan-in-fan-out device 39. The fan-in-fan-out device 39 has a plurality of optical waveguides (not shown) that can be optically connected to the cores 11 and 12 individually at one end 17 of the multicore fiber 10, and a pair of optical fibers including cores that are optically connected individually to the respective optical waveguides. This pair of optical fibers is connected to the optical fibers 35 and 36. Note that the optical fibers 35 and 36 may be this pair of optical fibers. The fan-in-fan-out device 39 optically connects the core of the optical fiber 35 to the core 11, and optically connects the core of the optical fiber 38 to the core 12.

[0049] The optical path length from the separation unit 31 to one end 17 of the core 11 via the first optical connection unit 311 is approximately equal to the optical path length from the separation unit 31 to one end 17 of the core 12 via the second optical connection unit 322. "Approximately equal" optical path lengths means that the difference in optical path lengths is equal to or less than the pulse width of the light emitted from the OTDR 20. The difference in optical path lengths is preferably equal to or less than 1 / 2 of the pulse width, more preferably equal to or less than 1 / 3 of the pulse width, and even more preferably equal to or less than 1 / 5 of the pulse width, and most preferably these optical path lengths are equal to each other.

[0050] Next, a crosstalk measuring method for an optical device according to this embodiment will be described. Fig. 3 is a flowchart showing the procedure of the crosstalk measuring method according to this embodiment. As shown in Fig. 3, the crosstalk measuring method according to this embodiment includes a first measuring step S11, a second measuring step S12, and a processing step S13.

[0051] (First measurement step S11) This step is to separate the light output from OTDR 20 into a first incident light and a second incident light, to make the first incident light incident from one end of core 11, which is the first optical waveguide, and to make the second incident light incident from one end 17 of each core 12 at approximately the same timing as the first incident light is incident from one end 17 of core 11, and to measure the power of the output light output from one end 17 of core 11 with OTDR 20.

[0052] Prior to this step, the optical switch 34 is set to a state in which the core of the optical fiber 37 and the core of the optical fiber 38 are optically connected to each other. Thus, the light separating input / output unit 30 is in the first measurement state.

[0053] In this embodiment, as described above, there is one core 12. Therefore, in the separation unit 31, the light incident from the optical fiber 21 is separated into two lights, one of which is output to the optical fiber 35 as a first incident light, and the other is output to the optical fiber 36 as a second incident light. That is, in this embodiment, the separation unit 31 separates the incident light into the first incident light and the same number of second incident lights as the number of cores 12. In this embodiment, the power of the first incident light and the power of the second incident light are approximately equal to each other.

[0054] The first incident light entering the optical fiber 35 leaks a part of the light at the loss section 32 and enters the fan-in-fan-out device 39. As described above, in this step, the optical switch 34 optically connects the core of the optical fiber 37 and the core of the optical fiber 38. Therefore, the second incident light entering the optical fiber 36 enters the fan-in-fan-out device 39 from the optical fiber 38 via the optical component 33 and the optical switch 34. The power of the first incident light lost at the loss section 32 is approximately equal to the power of the second incident light lost at the optical component 33 and the optical switch 34. Therefore, the power of the first incident light entering the fan-in-fan-out device 39 and the power of the second incident light are approximately equal to each other.

[0055] The first incident light entering the fan-in-fan-out device 39 enters the core 11, which is the first optical waveguide, from one end 17 and propagates through the core 11. The second incident light entering the fan-in-fan-out device 39 enters the core 12, which is the second optical waveguide, from one end 17 and propagates through the core 12. As described above, the power of the first incident light and the power of the second incident light entering the fan-in-fan-out device 39 are approximately equal, so the power of the first incident light entering the core 11 and the power of the second incident light entering the core 12 are approximately equal. Also, as described above, the optical path length from the separation unit 31 to the one end 17 of the core 11 via the first optical connection unit 311 is approximately equal to the optical path length from the separation unit 31 to the one end 17 of the core 12 via the second optical connection unit 322. Therefore, the timing when the first incident light enters one end 17 of the core 11 and the timing when the second incident light enters one end 17 of the core 12 are substantially the same.

[0056] FIG. 4 is a diagram showing the state of crosstalk in the multi-core fiber 10 in this step. As shown in FIG. 4, a part of the first incident light crosstalks from the core 11 to the core 12, and a part of the second incident light crosstalks from the core 12 to the core 11. In FIG. 4, the light that crosstalks from the core 11 to the core 12 is indicated by CL12, and the light that crosstalks from the core 12 to the core 11 is indicated by CL21. In this embodiment, the power of the first incident light and the power of the second incident light are approximately equal, so that the power of the light CL12 that crosstalks from the core 11 to the core 12 and the power of the light CL21 that crosstalks from the core 12 to the core 11 are approximately equal to each other. Therefore, the loss of light due to the crosstalk of the first incident light is suppressed. In addition, the first incident light propagates through the core 11 while losing power due to Rayleigh scattering, etc., and the second incident light propagates through the core 12 while losing power due to Rayleigh scattering, etc.

[0057] Light returning from the core 11 to the one end 17 side due to Rayleigh scattering or the like enters the optical fiber 35 from the one end 17 of the core 11 via the fan-in-fan-out device 39, and enters the OTDR 20 from the optical fiber 35 via the separation unit 31 and the optical fiber 21. On the other hand, light returning from the core 12 to the one end 17 side due to Rayleigh scattering or the like enters the optical fiber 38 from the one end 17 of the core 12 via the fan-in-fan-out device 39, and enters the optical fiber 38 from the optical fiber 38 via the optical switch 34 and the optical fiber 37 into the optical component 33. However, the optical component 33 propagates the light entering from the optical fiber 36 to the optical fiber 37, but suppresses the propagation of the light entering from the optical fiber 37 to the optical fiber 36, so that the light returning from the core 11 enters the OTDR 20, and the entrance of the light returning from the core 12 into the OTDR 20 is suppressed.

[0058] Therefore, the OTDR 20 measures the power of the light that is emitted from one end 17 of the core 11 and enters the OTDR 20. The OTDR 20 outputs to the processing unit 25 information related to the measured light power.

[0059] (Second measurement step S12) In this step, the light output from OTDR 20 is input as the first incident light from one end 17 of core 11, while the light from OTDR 20 is not input to core 12, and the power of the output light output from one end 17 of core 11 is measured by OTDR 20.

[0060] Prior to this step, the optical switch 34 is set to a state in which the core of the optical fiber 37 and the core of the optical fiber 38 are optically disconnected from each other. Thus, the light separation input / output unit 30 is in the second measurement state.

[0061] In this embodiment, light having a power equal to that of the light output from the OTDR 20 in the first measurement step S11 is output from the OTDR 20. Since the separator 31 does not change between the first measurement step S11 and this step, in this step of the present embodiment, first incident light having a power equal to that of the first incident light output from the separator 31 in the first measurement step S11 is output from the separator 31 to the optical fiber 35. Also, second incident light having a power equal to that of the second incident light output from the separator 31 in the first measurement step S11 is output from the separator 31 to the optical fiber 36.

[0062] The first incident light entering the optical fiber 35 leaks a part of the light at the loss section 32, similarly to the first measurement step S11, and enters the core 11 from one end 17 via the fan-in-fan-out device 39. Also, as described above, in this step, the optical switch 34 optically disconnects the core of the optical fiber 37 from the core of the optical fiber 38. Therefore, the second incident light entering the optical fiber 36 enters the optical switch 34 via the optical component 33 and the optical fiber 37, but does not propagate to the optical fiber 38. Therefore, in this step, the second incident light, which is a part of the light from the OTDR 20, does not enter the core 12. The first incident light entering the core 11 propagates through the core 11.

[0063] Fig. 5 is a diagram showing the state of crosstalk in the multi-core fiber 10 in this step. In Fig. 4, light that crosstalks from the core 11 to the core 12 is indicated by CL12. As shown in Fig. 5, a part of the first incident light crosstalks from the core 11 to the core 12, but since the second incident light does not enter the core 12, a part of the second incident light does not crosstalk from the core 12 to the core 11. Also, similar to the first measurement step S11, the first incident light propagates through the core 11 while losing power due to Rayleigh scattering or the like.

[0064] Light returning to one end of the core 11 due to Rayleigh scattering or the like is incident on the OTDR from the core 11 via the fan-in-fan-out device 39, the optical fiber 35, the separator 31, and the optical fiber 21, in the same manner as in the first measurement step S11. On the other hand, almost no light is emitted from one end 17 of the core 12. Even if light is emitted from one end 17 of the core 12, the light is not propagated to the optical fiber 36 due to optical components 33 such as the optical switch 34 and the isolator.

[0065] The OTDR 20 measures the power of the light that is emitted from one end 17 of the core 11 and enters the OTDR 20. The OTDR 20 outputs to the processing unit 25 information related to the measured light power.

[0066] Fig. 6 is a diagram showing the measurement results by the OTDR 20. This measurement was performed using light with a wavelength of 1625 nm and a pulse width of 500 ns, with an averaging time of 60 seconds. In Fig. 6, the non-linear solid line shows the measurement result by the OTDR 20 in the first measurement step S11, the dashed line shows the measurement result by the OTDR 20 in the second measurement step S12, and the dotted line shows the difference between the measurement result by the OTDR 20 in the first measurement step S11 and the measurement result by the OTDR 20 in the second measurement step S12.

[0067] In Fig. 6, the slope of the solid line reflects the light loss per unit length of the core 11 in the first measurement step S11. The slope here is, for example, the slope of the straight line when the solid line is averaged and linearized. As described above, in the first measurement step S11, the first incident light propagating through the core 11 crosstalks to the core 12, and the second incident light propagating through the core 12 crosstalks to the core 11. For this reason, the light loss due to the crosstalk of the first incident light is suppressed. Therefore, the slope of the solid line reflects the loss per unit length in which the influence of the crosstalk of the core 11 is suppressed.

[0068] Even if the power of the first incident light entering the core 11 differs from the power of the second incident light entering the core 12 by 10%, the loss of the first incident light in the core 11 differs by only about 0.001 dB / km. This is within a range that is fully acceptable as a measurement result of light loss. Therefore, in this specification, when the power of the first incident light and the power of the second incident light are approximately equal to each other, this includes a case where the power of the first incident light and the power of the second incident light differ by 10% or less. However, it is preferable that the power of the first incident light and the power of the second incident light differ by 5% or less, more preferably by 2% or less, and even more preferably that they are equal.

[0069] In FIG. 6, the inclination of the dashed line reflects the loss of light per unit length of the core 11 in the second measurement step S12. The inclination here is, for example, the inclination of the straight line when the dashed line is averaged and straightened. As described above, in the second measurement step S12, the first incident light propagating through the core 11 crosstalks to the core 12, but the second incident light does not enter the core 12, so crosstalk from the core 12 to the core 11 does not occur. For this reason, the first incident light loses light due to crosstalk. Therefore, the inclination of the dashed line reflects the sum of the loss per unit length when the influence of the crosstalk of the core 11 is suppressed and the loss per unit length due to crosstalk. Note that the power of the light measured by the OTDR 20 changes significantly near the distances of 1.7 km and 3.7 km in FIG. 6, and this portion corresponds to the end of the multi-core fiber 10. Therefore, the measurement results at such singular points are not used in the solid and dashed lines.

[0070] 6, the slope of the dotted line indicating the difference between the measurement result of the OTDR 20 in the first measurement step and the measurement result of the OTDR 20 in the second measurement step is shown by a straight solid line. The slope of this line reflects the crosstalk per unit length of the core 11. Therefore, the crosstalk of the core 11 may be obtained from this line. However, it is preferable to perform processing as in the next processing step S13 using the following formula.

[0071] (Processing step S13) This step is a step of determining crosstalk using the power of the output light emitted from the core 11 measured by the OTDR 20 in the first measurement step S11 and the power of the output light emitted from the core 11 measured by the OTDR 20 in the second measurement step S12.

[0072] From the theory of coupled power of light in a multicore fiber having two cores, the power of light propagating through the cores 11 and 12 can be expressed by the following differential equations (1) and (2). TIFF2025002425000002.tif12170TIFF2025002425000003.tif12170z is the distance from one end 17 of the cores 11 and 12, P1(z) and P2(z) are the powers of the light propagating through the cores 11 and 12 at the point z from the one end 17. α1 and α2 are the loss coefficients in the cores 11 and 12, and h 12 ,h 21 is the intercore coupling constant between core 11 and core 12, and h 12 =h 21 =h. P'1(z) is dP1(z) / dz, and P'2(z) is dP2(z) / dz. Generally, in a multicore fiber, the loss coefficient of each core is roughly equal, and the effect on the coupling constant can be ignored, so α1 = α2 = α.

[0073] Therefore, the above formulas (1) and (2) become differential equations shown in the following formulas (3) and (4). TIFF2025002425000004.tif12170TIFF2025002425000005.tif12170

[0074] The general solutions of equations (3) and (4) can be written as the following equations (5) and (6) using constants C1 and C2. TIFF2025002425000006.tif12170TIFF2025002425000007.tif12170

[0075] In the first measurement step S11, the power of the first incident light entering the core 11 and the power of the second incident light entering the core 12 are approximately equal. If the power of the first incident light and the second incident light entering from one end 17 of the cores 11 and 12 is P0, then P1(0)=P2(0)=P0. In this case, C1=P0 and C2=0, and equations (5) and (6) become the following equation (7). TIFF2025002425000008.tif12170

[0076] Furthermore, in the second measurement step S12, the power of the first incident light entering core 11 from one end 17 is equal to the power of the first incident light entering core 11 from one end 17 in the first measurement step S11, that is, P0. Furthermore, the power of the second incident light entering core 12 from one end 17 is 0. Therefore, P1(0)=P0, P2(0)=0. In this case, C1=C2=(1 / 2)P0, and equations (5) and (6) become the following equations (8) and (9). TIFF2025002425000009.tif16170TIFF2025002425000010.tif16170

[0077] Here, the power of the light propagating through the cores 11 and 12 in the first measurement step S11 is P 1,a (z), P 2,a (z), and the power of the light propagating through the cores 11 and 12 in the second measurement step S12 is P 1,b (z), P 2,b In this case, P1(z) and P2(z) in equation (7) are 1,a (z), P 2,a (z), and P1(z) and P2(z) in equations (8) and (9) are 1,b (z), P 2,b (z). In this case, equation (9) becomes equation (10). TIFF2025002425000011.tif12170

[0078] Here, if the length of the multi-core fiber 10 is L, and z=L, the crosstalk X(L) of the core 11 is P 2,b (L) / P1,b Since the crosstalk X(L) can be expressed as (L), the crosstalk X(L) is given by the following formula (11). Note that the power of core 11 and core 12 measured by OTDR 20 is a value obtained by multiplying the power in each formula by the backscattering coefficient, which is the probability of Rayleigh scattering, and the capture rate, which is the proportion of Rayleigh scattered light that propagates toward one end, but these are almost common to cores 11 and 12 and are cancelled out in the numerator and denominator, so they are not included in this calculation formula. TIFF2025002425000012.tif30170

[0079] P 1,b (L) / P 1,a (L) can be replaced with a value obtained by dividing the power of the light measured by the OTDR 20 in the second measurement step S12 by the power of the light measured by the OTDR 20 in the first measurement step S11. Therefore, the processing unit 25 calculates the value obtained by dividing the power of the light measured by the OTDR 20 in the second measurement step S12 by the power of the light measured by the OTDR 20 in the first measurement step S11 as P 1,b (L) / P 1,a As (L), the crosstalk of core 11 is calculated from equation (11).

[0080] In this manner, the crosstalk of the core 11 is measured using the OTDR 20 .

[0081] Next, the accuracy of the above measurement will be verified.

[0082] First, the accuracy of the measurement of the optical loss in the core 11 will be described. As described above, the slope of the solid line in Fig. 6 reflects the optical loss per unit length of the core 11 in the first measurement step S11, and the slope of the dashed line reflects the optical loss per unit length of the core 11 in the second measurement step S12. Therefore, under the same conditions as those used for the measurement in Fig. 6, the optical loss of the core 11 in the first measurement step S11 and the second measurement step S12 was measured at wavelengths of 1625 nm and 1650 nm based on the power of the emitted light measured by the OTDR 20. In addition, the loss of the core 11 was measured at each wavelength by the cutback method. The results are shown in Table 1 below. TIFF2025002425000013.tif64170

[0083] The cut-back method in Table 1 is a method in which light from both cores 11 and 12 is received at the other end so that the light loss of core 11 with the effects of crosstalk suppressed can be measured. As shown in Table 1, the light loss of core 11 measured in the first measurement step S11 was roughly consistent with the light loss of core 11 measured by the cut-back method.

[0084] Next, the accuracy of the measurement of the crosstalk of the core 11 will be described. Under the same conditions as in the measurement of FIG. 6, the crosstalk of the core 11 was measured at wavelengths of 1625 nm and 1650 nm according to the crosstalk measurement method of this embodiment. Moreover, the crosstalk of the core 11 was measured by the PM method at the same wavelengths. The results are shown in FIG. 7. In FIG. 7, △ indicates the measurement result according to this embodiment, and ◯ indicates the measurement result by the PM method. As shown in FIG. 7, the crosstalk of the core 11 measured by this embodiment and the crosstalk of the core 11 measured by the PM method were roughly consistent.

[0085] In the above embodiment, the separation unit 31 separates the light from the OTDR 20 into two so that the power of the first incident light and the power of the second incident light are equal. For this reason, the crosstalk X(z) is shown by the above formula (11). Next, consider a case where the separation unit 31 separates the light from the OTDR 20 into two so that the power of the first incident light and the power of the second incident light have a predetermined power ratio. In this case, the separation unit 31 separates the light from the OTDR 20 into the first incident light and the second incident light so that the power ratio is a predetermined power ratio.

[0086] The predetermined power ratio between the first incident light and the second incident light output from the separation unit 31 is set to 1:η. If the power of the first incident light incident from one end 17 of the core 11 is set to P1(0)=P0 as above, the power of the second incident light incident from one end 17 of the core 12 is P2(0)=ηP0. In this case, the constants C1 and C2 are C1={(1+η) / 2}P0 and C2={(1-η) / 2}P0. Therefore, equations (5) and (6) become the following equations (12) and (13). TIFF2025002425000014.tif16170TIFF2025002425000015.tif16170

[0087] In this case, P in Eq. (11) 1,b (L) / P 1,a (L) is expressed as follows: (14) TIFF2025002425000016.tif37170

[0088] When hL is sufficiently smaller than 1, tanh(hL) ≒ hL. Therefore, equation (11) becomes the following equation (15). TIFF2025002425000017.tif16170

[0089] As mentioned above, P 1,b (z) / P 1,a (z) can be replaced with a value obtained by dividing the power of the light measured by the OTDR 20 in the second measurement step S12 by the power of the light measured by the OTDR 20 in the first measurement step S11. Therefore, in this example, the processing unit 25 calculates the value obtained by dividing the power of the light measured by the OTDR 20 in the second measurement step S12 by the power of the light measured by the OTDR 20 in the first measurement step S11 as P 1,b (z) / P 1,a As (z), the crosstalk of core 11 is calculated from equation (15).

[0090] In this manner, in the separator 31, the crosstalk of the core 11 is measured using the OTDR 20 when the first incident light and the second incident light have a predetermined power ratio of 1:η.

[0091] Incidentally, the crosstalk of the core 11 calculated by formula (11) differs by only about 3 dB between the case where the power of the first incident light and the power of the second incident light are approximately equal and the case where the power ratio of the power of the first incident light and the power of the second incident light is 1:0.5. This difference is comparable to the variation in crosstalk measurement in measurement methods such as the PM method, and is within the acceptable range for the crosstalk measurement result. Therefore, if the predetermined power ratio of the power of the first incident light and the power of the second incident light is 0.5:1 to 1:0.5, that is, if the predetermined power ratio is 0.5 or more and 2 or less, the crosstalk of the core 11 can be measured within the acceptable error even when formula (11) is used.

[0092] It should be noted that the first measurement step S11 may precede the second measurement step S12, and the second measurement step S12 may precede the first measurement step S11.

[0093] As described above, the crosstalk measurement method of this embodiment includes a first measurement step S11 in which light output from the OTDR 20 is separated into a first incident light and a second incident light, the first incident light is made incident from one end 17 of the core 11 and the second incident light is made incident from one end 17 of the core 12, and the power of the output light output from the one end 17 of the core 11 is measured by the OTDR 20; a second measurement step S12 in which the light output from the OTDR 20 is made incident from the one end 17 of the core 11 as the first incident light having a power approximately equal to the power of the first incident light made incident into the core 11 in the first measurement step S11, and the light from the OTDR 20 is not made incident into the core 12, and the power of the output light output from the one end 17 of the core 11 is measured by the OTDR 20; and a processing step S13 in which the crosstalk of the core 11 is obtained using the power of the output light measured in the first measurement step S11 and the power of the output light measured in the second measurement step S12.

[0094] According to such a crosstalk measuring method and crosstalk measuring device, in the first measurement step S11, the first incident light propagating through the core 11 crosstalks to the core 12, and the second incident light propagating through the core 12 crosstalks to the core 11. On the other hand, in the second measurement step S12, the first incident light propagating through the core 11 crosstalks to the core 12, but the second incident light does not crosstalk to the core 11. Therefore, the power of the light propagating through the core 11 in the first measurement step S11 and the power of the light propagating through the core 11 in the second measurement step differ by the power of the light crosstalking from the core 12 to the first optical waveguide. Therefore, the power of the light emitted from the core 11 in the first measurement step S11 and the power of the light emitted from the core 11 in the second measurement step S12 differ by the power of the light propagating to one end 17 of the core 11 by Rayleigh scattering or the like, among the light crosstalking from the core 12 to the core 11. Furthermore, the ratio between the power of the light that crosstalks from the first incident light to the core 12 and the power of the light that crosstalks from the second incident light to the core 11 is based on the ratio between the power of the first incident light and the power of the second incident light. Therefore, by using the power of the exit light measured in the first measurement step S11 and the power of the exit light measured in the second measurement step S12 as described above, the crosstalk of the core 11 can be obtained using the OTDR20 method.

[0095] The crosstalk measuring device 1 of the present embodiment is optically connected to the OTDR 20 and the multi-core fiber 10, and separates light output from the OTDR 20 into a first incident light and a second incident light, and has a first measurement state in which the first incident light is input from one end 17 of the core 11 and the second incident light is input from one end 17 of the core 12, and the output light output from the one end 17 of the core 11 is propagated to the OTDR 20 and the light output from the one end 17 of the core 12 is suppressed from propagating to the OTDR; and a second measurement state in which first incident light of power approximately equal to the power of the first incident light to be incident on the core 11 in the first measurement state is input from one end 17 of the core 11, while preventing light from the OTDR 20 from entering the core 12, and propagating output light output from the one end 17 of the core 11 to the OTDR 20. The optical separation input / output section 30 is switchable between this state and a second measurement state in which first incident light of power approximately equal to the power of the first incident light to be input to the core 11 in the first measurement state is input from one end 17 of the core 11, while preventing light from the OTDR 20 from entering the core 12, and propagating output light output from the one end 17 of the core 11 to the OTDR 20.

[0096] In the same manner as in the above-described crosstalk measurement method, the processing unit 25 can use the power of the emitted light measured in the first measurement state and the power of the emitted light measured in the second measurement state to determine the crosstalk of the core 11 using an OTDR.

[0097] In this embodiment, the power of the first incident light in the first measurement step S11 and the power of the first incident light in the second measurement step S12 are assumed to be equal to each other. However, the power of the first incident light in the first measurement step S11 and the power of the first incident light in the second measurement step S12 may be different from each other. In this case, for example, the crosstalk per unit length of the core 11 can be obtained from the difference between the gradient of the power of the light measured by the OTDR 20 in the first measurement step S11 and the gradient of the power of the light measured by the OTDR 20 in the second measurement step S12. In this way, the crosstalk of the core 11 can be obtained from the gradient of the power of the light measured by the OTDR 20, so the power of the light incident on the core 11 in the second measurement step S12 may be any power. However, it is preferable that the power of the first incident light in the first measurement step S11 is 0.1 to 10 times the power of the first incident light in the second measurement step S12, and more preferably 0.5 to 2 times, since this makes it easier to compare the waveforms output from the OTDR 20 in each step, and it is more preferable that the power of the first incident light in each step is equal to each other as in the above embodiment.

[0098] (Modification) Next, a modified example of this embodiment will be described in detail with reference to Figures 8 and 9. Note that components that are the same as or equivalent to those in the above embodiment will be given the same reference numerals and duplicated descriptions will be omitted unless otherwise specified.

[0099] FIG. 8 is a diagram showing a cross section perpendicular to the longitudinal direction of the multicore fiber according to this modification. As shown in FIG. 8, the multicore fiber 10 of this modification is different from the multicore fiber 10 of the above embodiment in that it has cores 11 to 14. The cores 11 to 14 are arranged at equal intervals on a circumference centered on the center of the cladding 15. Therefore, the cores 11 to 14 are located on the vertices of a square. The cores 12 and 13 are adjacent to the core 11 at the closest point. The cores 12 and 13 are second optical waveguides adjacent to the core 11 as the first optical waveguide at the closest point, and the core 14 is a third optical waveguide other than the second optical waveguide adjacent to the core 11 as the first optical waveguide at the closest point. The configuration of the cores 13 and 14 is the same as the configuration of the cores 11 and 12. Note that the inter-core distance between the cores 11 and 12 does not have to strictly match the inter-core distance between the cores 11 and 13. For example, even if the inter-core distance between cores 11 and 12 and the inter-core distance between cores 11 and 13 differ by approximately the diameter of core 11, cores 12 and 13 are each the closest cores to core 11.

[0100] 9 is a diagram showing a crosstalk measurement device in this modified example. The crosstalk measurement device 1 in this modified example is mainly different from the crosstalk measurement device 1 in the above embodiment in that the light separation input / output section 30 includes a second optical connection section 323 and a third optical connection section 334 having the same configuration as the second optical connection section 322.

[0101] In this modification, the separation unit 31 is further connected to the optical fiber 36 of the second optical connection unit 323 and the third optical connection unit 334. The separation unit 31 separates the light incident from the OTDR 20 through the optical fiber 21 into a first incident light, two second incident lights, and one third incident light. In this modification, the powers of the first incident light, the second incident light, and the third incident light are equal to each other. The separation unit 31 causes the second incident light to enter the optical fiber 35 in the same manner as in the above embodiment, and causes one of the second incident lights to enter the optical fiber 36 of the second optical connection unit 322. The separation unit 31 also causes the other second incident light to enter the optical fiber 36 of the second optical connection unit 323, and causes it to enter the optical fiber 36 of the third optical connection unit 334.

[0102] Moreover, the fan-in-fan-out device 39 of this modification has a plurality of optical waveguides (not shown) that can be optically connected individually to the cores 11 to 14 at one end 17 of the multicore fiber 10, and four optical fibers including cores that are optically connected individually to the respective optical waveguides. These four optical fibers are connected to the optical fiber 35, the optical fibers 38 of the second optical connection parts 322 and 323, and the optical fiber 38 of the third optical connection part 334. Note that the optical fiber 35 and each of the optical fibers 38 may be the above four optical fibers. As in the above embodiment, the fan-in-fan-out device 39 optically connects the core of the optical fiber 35 to the core 11, and optically connects the core of the optical fiber 38 of the second optical connection part 322 to the core 12. Furthermore, the fan-in-fan-out device 39 optically connects the core of the optical fiber 38 of the second optical connection unit 323 to the core 13, and optically connects the core of the optical fiber 38 of the third optical connection unit 334 to the core 14.

[0103] In addition, the optical path length from the separation unit 31 to one end 17 of core 11 via the first optical connection unit 311, the optical path length from the separation unit 31 to one end 17 of core 12 via the second optical connection unit 322, the optical path length from the separation unit 31 to one end 17 of core 13 via the second optical connection unit 323, and the optical path length from the separation unit 31 to one end 17 of core 14 via the third optical connection unit 334 are approximately equal.

[0104] In this modification, prior to the first measurement step S11, the optical switches 34 of the second optical connection units 322, 323 and the third optical connection unit 334 are set to a state in which the core of the optical fiber 37 and the core of the optical fiber 38 are optically connected. In this way, the light separation input / output unit 30 is in the first measurement state.

[0105] In the first measurement step, the light output from the OTDR 20 is separated by the separation unit 31 into a first incident light, a pair of second incident light, and a third incident light, each having equal power, and in the same manner as in the above embodiment, the first incident light is incident on the core 11, and one of the second incident light is incident on the core 12. The other second incident light is incident on the core 13 from the second optical connection unit 323 via the fan-in-fan-out device 39, and the third incident light is incident on the core 14 from the third optical connection unit 334 via the fan-in-fan-out device 39. The powers of the first to third incident light incident on the cores 11 to 14 are approximately equal to each other. In addition, the timing at which the first incident light is incident from one end 17 of core 11, the timing at which the second incident light is incident from one end 17 of core 12, the timing at which the second incident light is incident from one end 17 of core 13, and the timing at which the third incident light is incident from one end 17 of core 14 are generally the same.

[0106] In this step of the present modification, a part of the first incident light crosstalks from the core 11 to the cores 12 to 14, and a part of each of the second incident light and the third incident light crosstalks from the cores 12 to 14 to the core 11. In this modification, the power of the first incident light is approximately equal to the power of each of the second incident light and the third incident light, so that the power of the light crosstalking from the core 11 to the cores 12 to 14 and the power of the light crosstalking from the cores 12 to 14 to the core 11 are approximately equal to each other. Therefore, the loss of light due to the crosstalk of the first incident light is suppressed as in the above embodiment. The light returning from the core 11 to the one end 17 side is incident on the OTDR as in the first embodiment. On the other hand, the incidence of the light returning from the cores 12 to 14 to the OTDR 20 is suppressed as in the above embodiment. Therefore, in the OTDR 20, the power of the light emitted from the one end 17 of the core 11 and incident on the OTDR 20 is measured, and information related to the measured power of the light is output to the processing unit 25.

[0107] In this modification, prior to the second measurement step S12, the optical switches 34 of the second optical connection units 322, 323 and the third optical connection unit 334 are set to a state in which the core of the optical fiber 37 and the core of the optical fiber 38 are optically disconnected from each other. In this way, the light separation input / output unit 30 is in the second measurement state.

[0108] For this reason, in this modification, the first incident light is incident on core 11 in the same manner as in the second measurement step S12 in the above embodiment, and no light is incident on cores 12 to 14. For this reason, a part of the first incident light crosstalks from core 11 to cores 12 to 14, but no light crosstalks from cores 12 to 14 to core 11. The light returning to one end side of core 11 is incident on OTDR 20 in the same manner as in the above embodiment, and information related to the power of the measured light is output from OTDR 20 to processing unit 25.

[0109] Also in this modification, in processing step S13, the processing unit 25 obtains the crosstalk of the core 11 by using an equation obtained by modifying equation (11) for a four-core multicore fiber.

[0110] In this manner, the crosstalk of the core 11 is measured using the OTDR 20 even in cases other than the case where there are two cores, as in this modified example.

[0111] The crosstalk from core 11 to core 14 is much smaller than the crosstalk from core 11 to the closest adjacent cores 12 and 13. Therefore, the crosstalk of core 11 can be measured using OTDR 20 without incidenting the third incident light to core 14. However, it is preferable to incident the third incident light to core 14, since this makes it possible to measure the crosstalk of core 11 with a smaller measurement error.

[0112] Furthermore, when the first incident light incident on the core 11 and the second incident light incident on the cores 12 and 13 have a predetermined power ratio of 1:η, the processing unit 25 can calculate the crosstalk by using an equation or the like applicable to the case of a four-core multicore fiber.

[0113] In the present embodiment and the modified example, the third incident light having a power approximately equal to that of the first incident light is incident on the core 14, which is the third optical waveguide. However, the first incident light incident on the core 11 and the third incident light incident on the core 14 may have a predetermined power ratio. In this case, the power of the third incident light may be different from the power of the second incident light.

[0114] Also in the modified example, the first measurement step S11 may precede the second measurement step S12, and the second measurement step S12 may precede the first measurement step S11.

[0115] In the above embodiment and modified examples, in the process step S13, the crosstalk of the core 11 may be obtained by other formulas or algorithms as long as the power of the emitted light measured in the first measurement step S11 and the power of the emitted light measured in the second measurement step S12 are used. For example, the crosstalk of the core 11 may be obtained from the slope of the solid line and the slope of the dashed line in FIG.

[0116] Second embodiment Next, a second embodiment of the present invention will be described in detail with reference to Figures 10 and 11. Note that components that are the same as or equivalent to those in the above embodiment will be given the same reference numerals and will not be described again unless otherwise specified. This embodiment relates to an optical loss measurement method and an optical loss measurement device.

[0117] In this embodiment, the loss of light in which the influence of crosstalk in the cores 11 of the multi-core fiber 10 in FIG. 1 is suppressed is measured.

[0118] Fig. 10 is a diagram showing the optical loss measurement device of this embodiment. As shown in Fig. 10, the optical loss measurement device 2 of this embodiment differs from the crosstalk measurement device 1 of the first embodiment in that the light separation input / output unit 30 does not include an optical switch. Therefore, an optical fiber 38 is connected to an optical component 33. Note that even if the light separation input / output unit 30 includes an optical switch, the optical loss measurement device 2 can be used as long as the optical switch 34 in Fig. 2 is in a state in which the core of the optical fiber 37 and the core of the optical fiber 38 are optically connected, that is, in the first measurement state of the first embodiment.

[0119] Next, a method for measuring optical loss in the multi-core fiber 10 according to the present embodiment will be described. Fig. 11 is a flowchart showing the procedure of the method for measuring optical loss in the present embodiment. The method for measuring optical loss in the present embodiment includes a measuring step S21 and a processing step S22.

[0120] (Measurement step S21) The measurement step S21 of this embodiment is a step of splitting the light emitted from the OTDR 20 into a first incident light and a second incident light, making the first incident light incident from one end 17 of the core 11 and the second incident light incident from one end 17 of the core 12, and measuring the power of the light emitted from the one end 17 of the core 11 by the OTDR 20. Therefore, the measurement step S21 of this embodiment is generally similar to the first measurement step S11 of the first embodiment. However, in this embodiment, the light splitting input / output unit 30 does not include an optical switch, so the measurement step S21 of this embodiment is different from the first measurement step S11 of the first embodiment in that it does not include a procedure related to an optical switch. Therefore, in this step, the measurement result shown by the solid line in FIG. 6 is obtained.

[0121] (Processing step S22) Processing step S22 in this embodiment is a step of determining the light loss in the core 11 using the power of the output light measured in measurement step S21. In this step, for example, the light loss per unit length of the core 11 is determined from the slope of the measurement result shown by the solid line in FIG. 6. By determining the loss of the first incident light in the core 11 in this manner, it is possible to measure the loss with the influence of crosstalk suppressed. The accuracy of the light loss in the core 11 determined in this embodiment is roughly consistent with the case of measuring the light loss in the core 11 using the cutback method, as explained in the first embodiment using Table 1.

[0122] In this way, the optical loss in the core 11 with the effects of crosstalk suppressed is measured using the OTDR.

[0123] When the multicore fiber 10 has the cores 11 to 14 as in the modification of the first embodiment, the crosstalk measurement device 1 shown in Fig. 9 can be made into an optical loss measurement device by removing the optical switch 34 and connecting the optical fiber 38 to the optical component 33, or by setting the optical switch 34 to a state in which the cores of the optical fiber 37 and the cores of the optical fiber 38 are all optically connected. In this case, similarly to the first measurement step S11 in the modification of the first embodiment, light is made incident on the cores 11 to 14, and the power of the light exiting from one end 17 of the core 11 is measured by the OTDR 20. The optical loss in the core 11 is calculated using the measurement result.

[0124] Although the present invention has been described above using the above-mentioned embodiments as examples, the present invention is not limited to these.

[0125] For example, the arrangement and number of cores in the multi-core fiber 10 may be different from those in the above embodiment.

[0126] In the above embodiment, a multi-core fiber is used as an example of an optical device in which waveguides are arranged in parallel, but the optical device of the present invention is not limited to a multi-core fiber as long as crosstalk occurs between the waveguides. For example, the optical device of the present invention may be applied to an optical fiber cable in which multiple optical fibers are arranged in an array, an optical fiber tape in which multiple optical fibers are arranged in a planar array, a multi-element fiber in which multiple bare optical fibers are arranged in one coating layer, and crosstalk measurement in the waveguides of an entire transmission system. Therefore, the distance between the parallel waveguides does not need to be constant.

[0127] In addition, in at least one of the first measuring step S11, the second measuring step S12, and the measuring step S21 in the above embodiment, the OTDR 20 may further measure at least one of the reflection intensity and the breakage in an optical device such as the multi-core fiber 10.

[0128] Furthermore, there is no particular limitation on the form of the fan-in-fan-out device 39. Furthermore, the crosstalk measurement device 1 does not need to include the fan-in-fan-out device 39. In this case, for example, the core 11 of the multicore fiber 10 and the optical fiber 35 are directly connected, and the core 12 of the multicore fiber 10 and the optical fiber 38 are directly connected.

[0129] In the above embodiment and modified example, the separation unit 31 separates the light incident from the OTDR 20 into the same number of lights as the optical fibers 35, 36 connected to the separation unit 31. However, the separation unit 31 may separate and output the light incident from the OTDR 20 in addition to the same number of lights as the optical fibers 35, 36. However, from the viewpoint of effectively using the light from the OTDR 20, it is preferable that the separation unit 31 separates the light incident from the OTDR 20 into the same number of lights as the optical fibers 35, 36.

[0130] In the above embodiment, the positions of the optical component 33 and the optical switch 34 may be interchanged.

[0131] Moreover, the loss section 32 is not essential. However, when the optical loss of the first optical connection section 311 and the second optical connection section 322 is to be matched, it is preferable that the loss section 21 is provided in the first optical connection section 311. [Industrial Applicability]

[0132] As described above, according to the present invention, there are provided a crosstalk measurement method and crosstalk measurement device capable of measuring crosstalk using an OTDR, and an optical loss measurement method and optical loss measurement device capable of measuring optical loss in an optical waveguide in which the effects of crosstalk are suppressed using an OTDR, and it is expected that these will be used in fields such as optical fiber communications. [Explanation of symbols]

[0133] 1. Crosstalk measurement device 10. Multicore fiber (optical device) 11... Core (first optical waveguide) 12... Core (second optical waveguide) 13 Core (second optical waveguide) 14... Core (third optical waveguide) 20...OTDR 25 Processing section 30...Light separation input / output section 31... Separation section 32...Loss section 33 Optical components 34 Optical switch 39 Fan-in-fan-out devices S11: First measurement step S12: Second measurement step S13 Processing step S21 Measurement step S22 Processing step

Claims

1. 1. A method for measuring crosstalk in an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at a nearest position, comprising the steps of: a first measuring step of separating light emitted from an OTDR (Optical Time Domain Reflectometer) into a first incident light and a second incident light, the number of which is equal to the number of the second optical waveguides and which has a predetermined power ratio to the first incident light, making the first incident light incident from one end of the first optical waveguide and making the second incident light incident from one end of each of the second optical waveguides at approximately the same timing as the timing at which the first incident light is incident from one end of the first optical waveguide, and measuring the power of the output light output from the one end of the first optical waveguide by the OTDR; a second measuring step of making the light output from the OTDR input as a first incident light from the one end of the first optical waveguide, while making the light from the OTDR not input to the second optical waveguide, and measuring the power of the output light output from the one end of the first optical waveguide with the OTDR; a processing step of determining crosstalk of the first optical waveguide using the power of the emitted light measured in the first measuring step and the power of the emitted light measured in the second measuring step; Equipped 13. A crosstalk measuring method comprising:

2. The power of the first incident light and the power of the second incident light in the first measuring step are approximately equal to each other.

2. The crosstalk measuring method according to claim 1 .

3. The predetermined power ratio is equal to or greater than 0.5 and equal to or less than 2.

2. The crosstalk measuring method according to claim 1 .

4. The power of the first incident light in the first measurement step is 0.5 to 2 times the power of the first incident light in the second measurement step.

2. The crosstalk measuring method according to claim 1 .

5. The optical device has at least one third optical waveguide other than the first optical waveguide and the second optical waveguide, and in the first measurement step, in addition to the first incident light and the second incident light, the light output from the OTDR is separated into third incident lights, the number of which is the same as the number of the third optical waveguides and which have a predetermined power ratio to the first incident light, and the third incident light is made incident from one end side of each of the third optical waveguides at approximately the same timing as the timing at which the first incident light is made incident from the one end of the first optical waveguide.

5. The crosstalk measuring method according to claim 1, wherein the crosstalk measuring means is a first measuring means.

6. 1. An apparatus for measuring crosstalk of an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at the shortest distance, OTDR and a first input light source connected to the OTDR and the optical device, which separates light output from the OTDR into a first input light source and a second input light source having the same number as the number of the second optical waveguides and a predetermined power ratio to the first input light source, which inputs the first input light source from one end of the first optical waveguide and inputs the second input light source from one end of each of the second optical waveguides at approximately the same timing as the timing at which the first input light source is input from one end of the first optical waveguide, a light splitting input / output unit switchable between a first measurement state in which the light output from the one end is propagated to the OTDR and the light output from the one end of the second optical waveguide is suppressed from propagating to the OTDR, and a second measurement state in which the light output from the OTDR is input as a first input light to the one end of the first optical waveguide, the light from the OTDR is prevented from being input to the second optical waveguide, and the output light output from the one end of the first optical waveguide is propagated to the OTDR; a processing unit that obtains crosstalk of the first optical waveguide using the power of the output light measured by the OTDR in the first measurement state and the power of the output light measured by the OTDR in the second measurement state; Equipped A crosstalk measuring device comprising:

7. The light separation input / output unit includes: a splitter that splits the light emitted from the OTDR into the first incident light and each of the second incident lights; a first optical connection section that optically connects the separation section and the first optical waveguide and propagates the first incident light toward the first optical waveguide and propagates the outgoing light toward the OTDR; an optical switch that optically connects the separation unit and each of the second optical waveguides in the first measurement state and optically disconnects the separation unit and each of the second optical waveguides in the second measurement state; and a second optical connection unit having an optical component that propagates the second incident light toward each of the second optical waveguides and suppresses the light output from the one end of the second optical waveguide from propagating toward the OTDR side in the first measurement state; Equipped with An optical path length from the separation portion to the one end of the first optical waveguide via the first optical connection portion is approximately equal to an optical path length from the separation portion to the one end of the second optical waveguide via the second optical connection portion.

7. The crosstalk measuring device according to claim 6.

8. The first optical connection portion has a loss portion that generates an optical loss approximately equal to an optical loss in the optical component and the optical switch when light of equal power is incident on the first optical connection portion and the second optical connection portion.

8. The crosstalk measuring device according to claim 7.

9. 1. An optical loss measurement method for measuring optical loss in a first optical waveguide in an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at a closest position, the method comprising: a measuring step of separating light output from an OTDR into a first incident light and a second incident light, the number of which is equal to the number of the second optical waveguides and having a power approximately equal to that of the first incident light, causing the first incident light to be input from one end of the first optical waveguide, and causing the second incident light to be input from one end of each of the second optical waveguides at approximately the same timing as the timing at which the first incident light is input from one end of the first optical waveguide, and measuring the power of the output light output from the one end of the first optical waveguide with the OTDR; a processing step of determining a loss of light in the first optical waveguide using the power of the emitted light measured in the measuring step; Equipped 13. An optical loss measuring method comprising:

10. The optical device has at least one third optical waveguide other than the first optical waveguide and the second optical waveguide, and in the measuring step, in addition to the first incident light and the second incident light, the light output from the OTDR is separated into third incident lights, the number of which is the same as the number of the third optical waveguides and which have a power approximately equal to that of the first incident lights, and the third incident lights are made incident from one end side of each of the third optical waveguides at approximately the same timing as the timing at which the first incident lights are made incident from the one end of the first optical waveguide.

10. The optical loss measuring method according to claim 9.

11. 1. An optical loss measurement apparatus for measuring optical loss in a first optical waveguide in an optical device having a plurality of optical waveguides including a first optical waveguide arranged in parallel with each other and at least one second optical waveguide adjacent to the first optical waveguide at a closest position, the apparatus comprising: OTDR and a light separation input / output section that is optically connected to the OTDR and the optical device, that separates light output from the OTDR into a first incident light and a second incident light, the number of which is the same as the number of the second optical waveguides and which has approximately the same power as the first incident light, that causes the first incident light to be input from one end of the first optical waveguide, and that causes the second incident light to be input from one end of each of the second optical waveguides at approximately the same timing as the timing at which the first incident light is input from the one end of the first optical waveguide, and that propagates the output light output from the one end of the first optical waveguide to the OTDR and suppresses the light output from the one end of the second optical waveguide from propagating to the OTDR; a processing unit that determines an optical loss in the first optical waveguide using the power of the emitted light measured by the OTDR; Equipped 1. An optical loss measuring device comprising:

12. The light separation input / output unit includes: a splitter that splits the light emitted from the OTDR into the first incident light and each of the second incident lights; a first optical connection section that optically connects the separation section and the first optical waveguide and propagates the first incident light toward the first optical waveguide and propagates the outgoing light toward the OTDR; a second optical connection unit having an optical component that is optically connected to the separation unit and each of the second optical waveguides, and that propagates the second incident light to each of the second optical waveguides and suppresses the light output from the one end of the second optical waveguide from propagating to the OTDR side; Equipped with An optical path length from the separation portion to the one end of the first optical waveguide via the first optical connection portion is approximately equal to an optical path length from the separation portion to the one end of the second optical waveguide via the second optical connection portion.

12. The optical loss measuring device according to claim 11.

13. The first optical connection portion has a loss portion that generates a loss of light approximately equal to the loss of light in the optical component when light of equal power is incident on the first optical connection portion and the second optical connection portion.

13. The optical loss measuring device according to claim 12.

Images