Crosstalk measurement method and crosstalk measurement device

Abstract

A crosstalk measurement method is provided with: a connection step S1 in which the other end (18) of a core (11) and the other end (18) of a core (12) are optically connected via the core of a first optical fiber (51); a first measurement step (S2) in which pulsed incident light (L) is made to enter from one end (17) of the core (11) by the OTDR (20), and the power of emitted light emitted from the one end (17) of the core (11) is measured by the OTDR (20), the emitted light including pulsed crosstalk light (CL1); the crosstalk light (CL1) is obtained by multiplexing light generated by crosstalk of incident light (L) from the core (11) to the core (12) and light generated by crosstalk of incident light (L) incident from the core (11) to the core (12) from the core (12) to the core (11). And a processing step (S3) in which the magnitude of crosstalk between the core (11) and the core (12) is determined using the measured power of the emitted light.

Description

Technical Field

[0001] The invention relates to a crosstalk measuring method and a crosstalk measuring device. Background Art

[0002] In recent years, due to the increase in the amount of information communication, it is necessary to increase the transmission capacity of optical fibers. Multi-core optical fibers can improve the efficiency of space utilization and can transmit large amounts of information in a limited space, so they have attracted attention. However, since multiple cores are configured in one optical fiber, it is difficult to evaluate the characteristics compared to single-core optical fibers. Therefore, technology for efficiently evaluating multi-core optical fibers is needed. In particular, crosstalk measurement is an important measurement item in multi-core optical fibers, and since it is an item that is not included in the measurement of single-core optical fibers, it is necessary to prepare new measurement equipment, etc.

[0003] As a method for measuring crosstalk, the methods described in the following non-patent documents are known. The following non-patent document 1 shows the PM (Power Meter) method. The PM method is a method of causing light to be incident on a specified core of a multi-core optical fiber from one end of the core, and measuring the power of light emitted from the other end of the core that crosstalks with the core. The following non-patent documents 2 and 3 describe the OTDR (Optical Time Domain Reflectometer) method. In the OTDR method, a multi-channel OTDR is used to cause light to be incident on a specified core, and the backscattered light of the light that crosstalks with the light in other cores is detected to perform crosstalk measurement.

[0004] Non-patent literature 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.

[0005] Non-patent literature 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

[0006] Non-Patent Literature 3: [3] M. Nakazawa, M. Yoshida, and T. Hirooka, “Nondestructive measurement of mode couplings along a multi-core fiber usinga synchronous multi-channel OTDR,” Optics Express, vol. 20, Issue 11, pp. 12530-12540, 2012 Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] In the PM method, it is necessary to make light incident from one end of a multi-core optical fiber and receive light emitted from the other end. In contrast, in the OTDR method, light is made incident from one end of a multi-core optical fiber and light emitted from the one end is received. Therefore, there is a need to use the OTDR method to measure crosstalk. However, regarding the crosstalk measurement methods described in non-patent literature 2 and non-patent literature 3, since the backscattered light of the light that has caused crosstalk is measured, the power of the measured light is small, and it may be difficult to measure the crosstalk. For multi-core optical fibers of the type with less crosstalk, it is even more difficult to measure crosstalk. However, as mentioned above, there is a need to use the OTDR method to measure crosstalk. This need exists not only for multi-core optical fibers, but also for optical devices with multiple optical waveguides where crosstalk may occur.

[0009] Therefore, an object of the present invention is to provide a crosstalk measurement method and a crosstalk measurement device capable of easily performing crosstalk measurement using an OTDR method.

[0010] (II) Technical solution

[0011] In order to solve the above-mentioned problem, a first aspect of the present invention is a crosstalk measurement method, and is a crosstalk measurement method for an optical device, wherein the optical device has a first optical waveguide and a second optical waveguide which include one end and the other end and are arranged in parallel with each other, and the method is characterized in that it comprises: a connecting step, a first measuring step, and a processing step, in which the other end of the first optical waveguide is optically connected to the other end of the second optical waveguide via a first connecting optical waveguide; in the first measuring step, a pulsed incident light emitted from an OTDR is incident from the one end of the first optical waveguide, and a pulsed incident light is incident from the first optical waveguide via a first connecting optical waveguide. The OTDR measures the power of output light emitted from the one end of the first optical waveguide, the output light including pulsed light, the pulsed light being composed of the following optical multiplexes: light generated due to crosstalk of the incident light from the first optical waveguide to the second optical waveguide, and light generated due to crosstalk of the incident light from the second optical waveguide to the first optical waveguide incident from the first optical waveguide to the second optical waveguide via the first connecting optical waveguide; in the processing step, the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide is determined using the measured power of the output light.

[0012] The pulsed incident light propagating from one end of the first optical waveguide to the other end propagates while crosstalking from the first optical waveguide to the second optical waveguide. Therefore, the crosstalk light that crosstalks from the first optical waveguide to the second optical waveguide is also pulsed, and propagates from one end side of the second optical waveguide to the other end while being roughly parallel to the incident light. The incident light that arrives at the other end of the first optical waveguide is incident on the first connecting optical waveguide. In addition, the pulsed crosstalk light that propagates from one end side of the second optical waveguide and arrives at the other end of the second optical waveguide is incident on the first connecting optical waveguide from the side opposite to the incident light. Since the speed of light in the optical device is constant, the propagation speed of the incident light and the propagation speed of the crosstalk light are equal to each other. Therefore, the incident light and the crosstalk light arrive at the other ends of the first optical waveguide and the second optical waveguide respectively and roughly at the same time, and the incident light and the crosstalk light intersect at the approximate midpoint of the first connecting optical waveguide. Furthermore, the incident light is incident from the other end of the second optical waveguide to the second optical waveguide, and the crosstalk light is incident from the other end of the first optical waveguide to the first optical waveguide. At this time, the time when the incident light is incident to the second optical waveguide is approximately the same as the time when the crosstalk light is incident to the first optical waveguide. Therefore, the crosstalk light is propagated from the other end to one end in the first optical waveguide while being approximately parallel to the incident light propagating from the other end to one end in the second optical waveguide. During this period, the incident light propagating in the second optical waveguide is also propagated while crosstalking to the first optical waveguide. Therefore, the light crosstalking from the second optical waveguide to the first optical waveguide is combined with the crosstalk light propagating in the first waveguide. The combined light is pulsed, and the output light emitted from one end of the first optical waveguide includes: pulsed light generated by the crosstalk. The light emitted from the first optical waveguide is received by the OTDR, and the power of the output light is measured. The magnitude of the crosstalk between the first optical waveguide and the second optical waveguide is obtained using the measured power of the output light.

[0013] Thus, according to the crosstalk measurement method of this embodiment, an OTDR is used, and light that crosstalks from light incident on an optical waveguide to another optical waveguide is used, so the power of the crosstalk light is larger than that of the case where backscattered light of the light that has caused the crosstalk is detected as in Patent Documents 2 and 3. In addition, in the crosstalk measurement method of this embodiment, the crosstalk light when the incident light propagates from one end to the other end of the first optical waveguide is combined with the crosstalk light when the incident light propagates from the other end to one end of the second optical waveguide, so there is a tendency that the power of the pulsed light generated by the crosstalk is larger. Therefore, according to the crosstalk measurement method of this embodiment, crosstalk measurement can be easily performed.

[0014] A second aspect of the present invention is the crosstalk measurement method according to the first aspect, wherein the length of the first connecting optical waveguide is longer than the half-value width of the incident light.

[0015] As described above, the incident light and the crosstalk light intersect at the approximate midpoint of the first connecting optical waveguide. Therefore, it can be seen through the OTDR that the pulsed light generated by the crosstalk is generated at the approximate midpoint of the first connecting optical waveguide. In addition, the pulse width of the incident light is approximately the same as the pulse width of the crosstalk light. Therefore, according to the crosstalk measurement method of this mode, the influence of noise such as reflection at the end of the first connecting optical waveguide on the outgoing light containing the pulsed crosstalk light can be suppressed, and the crosstalk can be measured more accurately.

[0016] Mode 3 of the present invention is a crosstalk measurement method according to Mode 1 or 2, characterized in that it also includes a second measurement step, in which pulsed incident light emitted from the OTDR is incident from one end of the second optical waveguide, and the power of output light emitted from the one end of the second optical waveguide is measured by the OTDR, the output light includes pulsed light, and the pulsed light is composed of the following optical multiplexes, namely: light generated by crosstalk of the incident light from the second optical waveguide to the first optical waveguide, and light generated by crosstalk of the incident light from the first optical waveguide to the second optical waveguide caused by the incident light incident from the second optical waveguide to the first optical waveguide via the first connecting optical waveguide, and in the processing step, the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide is calculated using the power of the output light measured by the first measurement step and the power of the output light measured by the second measurement step.

[0017] In this case, since crosstalk light generated by causing incident light to propagate from the first optical waveguide to the second optical waveguide and crosstalk light generated by causing incident light to propagate from the second optical waveguide to the first optical waveguide are used, errors can be suppressed and crosstalk can be calculated more accurately compared to a case where only crosstalk light generated by causing incident light to propagate from the first optical waveguide to the second optical waveguide is used.

[0018] Mode 4 of the present invention is a crosstalk measurement method according to Mode 3, characterized in that, in the processing step, the size of the crosstalk between the first optical waveguide and the second optical waveguide is calculated using the result obtained by averaging the power of the outgoing light measured by the first measuring step and the power of the outgoing light measured by the second measuring step.

[0019] By using such averaging processing, the magnitude of crosstalk can be easily and accurately determined.

[0020] A fifth aspect of the present invention is a crosstalk measurement method according to any one of aspects 1 to 4, characterized in that the wavelength width of the incident light is 1 nm or more.

[0021] In this case, it is possible to reduce the error in the power of the outgoing light measured by the OTDR.

[0022] Mode 6 of the present invention is a crosstalk measurement method according to any one of Modes 1 to 5, characterized in that the OTDR and the first optical waveguide, the first optical waveguide and the first connecting optical waveguide, and the first connecting optical waveguide and the second optical waveguide are optically connected via a fan-in fan-out device, and in the processing step, the size of the crosstalk in the fan-in fan-out device is removed to obtain the size of the crosstalk between the first optical waveguide and the second optical waveguide.

[0023] In this case, when a fan-in fan-out device is used, the influence of crosstalk in the device can be suppressed, and the crosstalk can be obtained more accurately.

[0024] Mode 7 of the present invention is a crosstalk measurement method according to any one of modes 1 to 6, characterized in that the optical device further has a third optical waveguide parallel to the first optical waveguide, and in the processing step, based on the obtained size of the crosstalk between the first optical waveguide and the second optical waveguide, the size of the crosstalk between the first optical waveguide and the third optical waveguide is further obtained.

[0025] In this case, even if the power of light caused by the crosstalk between the first optical waveguide and the third optical waveguide is not measured, the magnitude of the crosstalk between the first optical waveguide and the third optical waveguide can be easily obtained. In addition, in this case, for example, the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide is obtained using a relational expression that represents the relationship between the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide and the magnitude of the crosstalk between the first optical waveguide and the third optical waveguide.

[0026] Mode 8 of the present invention is a crosstalk measurement method according to any one of Modes 1 to 6, characterized in that the optical device further includes a third optical waveguide parallel to the first optical waveguide, and in the connecting step, the other end of the first optical waveguide and the other end of the third optical waveguide are optically connected via a second connecting optical waveguide having a length different from that of the first connecting optical waveguide, and in the first measuring step, the power of the output light emitted from the one end of the first optical waveguide is further measured by the OTDR, the output light includes pulsed light, and the pulsed light The pulsed light is formed by the following optical synthesis, namely: light generated due to crosstalk of the incident light from the first optical waveguide to the third optical waveguide, and light generated due to crosstalk from the third optical waveguide to the first optical waveguide of the incident light incident from the first optical waveguide to the third optical waveguide via the second connecting optical waveguide. In the processing step, the power of the output light including the pulsed light generated due to the crosstalk between the first optical waveguide and the third optical waveguide is used to further calculate the size of the crosstalk between the first optical waveguide and the third optical waveguide.

[0027] In this case, as described in Mode 1, crosstalk occurs between the first optical waveguide and the second optical waveguide, and outgoing light including pulsed light caused by the crosstalk is emitted from one end of the first optical waveguide. Furthermore, in this mode, crosstalk occurs between the first optical waveguide and the third optical waveguide, and outgoing light including pulsed light caused by the crosstalk is emitted from one end of the first optical waveguide. At this time, since the first connecting optical waveguide and the second connecting optical waveguide have different lengths, the pulsed light caused by the crosstalk between the first optical waveguide and the second optical waveguide and the pulsed light caused by the crosstalk between the first optical waveguide and the third optical waveguide are emitted from one end of the first optical waveguide at different times. Therefore, the outgoing light including pulsed light caused by the crosstalk between the first optical waveguide and the second optical waveguide and the outgoing light including pulsed light caused by the crosstalk between the first optical waveguide and the third optical waveguide can be received separately by the OTDR, and the power of each outgoing light can be measured, and the magnitude of each crosstalk can be obtained. Therefore, compared with the case where after measuring the crosstalk between the first optical waveguide and the second optical waveguide, the first optical waveguide and the third optical waveguide are optically connected by a connecting optical waveguide, incident light is injected again from one end of the first optical waveguide, and the crosstalk between the first optical waveguide and the third optical waveguide is measured as in method 1, it is possible to easily measure the crosstalk between the first optical waveguide and the second optical waveguide, and the crosstalk between the first optical waveguide and the third optical waveguide, respectively.

[0028] In the eighth aspect, preferably, a difference between the length of the first connecting optical waveguide and the length of the second connecting optical waveguide is larger than a half-value width of the incident light.

[0029] In this case, interference between pulsed light caused by crosstalk between the first and second optical waveguides and pulsed light caused by crosstalk between the first and third optical waveguides can be suppressed, and the magnitude of the crosstalk can be measured more accurately.

[0030] Mode 9 of the present invention is a crosstalk measurement method according to any one of modes 1, 2, 5, and 6, characterized in that the optical device further includes a third optical waveguide arranged in parallel with the second optical waveguide, and in the connecting step, one end of the second optical waveguide and one end of the third optical waveguide are optically connected via a second connecting optical waveguide, and in the first measuring step, the OTDR further measures: the power of the output light emitted from the one end of the first optical waveguide via the first connecting optical waveguide and the first optical waveguide, the output light including pulsed light, and the pulsed light is composed of the following optical multiplexing , that is, light generated by crosstalk from the second optical waveguide to the third optical waveguide due to the incident light incident from the first optical waveguide to the second optical waveguide via the first connecting optical waveguide, and light generated by crosstalk from the third optical waveguide to the second optical waveguide due to the incident light incident from the second optical waveguide to the third optical waveguide via the second connecting optical waveguide. In the processing step, the power of the output light including the pulsed light generated by the crosstalk between the second optical waveguide and the third optical waveguide is used to further determine the size of the crosstalk between the second optical waveguide and the third optical waveguide.

[0031] In this case, as described in Mode 1, crosstalk occurs between the first optical waveguide and the second optical waveguide, and outgoing light including pulsed light caused by the crosstalk is emitted from one end of the first optical waveguide. Furthermore, in this mode, the pulsed incident light incident from the other end of the second optical waveguide to the second optical waveguide via the first optical waveguide and the first connecting optical waveguide propagates while crosstalking from the second optical waveguide to the third optical waveguide. Therefore, the crosstalk light that crosstalks from the second optical waveguide to the third optical waveguide is also pulsed, and propagates from the other end side to one end of the third optical waveguide while being roughly parallel to the incident light. The incident light that reaches one end of the second optical waveguide is incident to the second connecting optical waveguide. In addition, the crosstalk light that reaches one end of the third optical waveguide is incident to the second connecting optical waveguide from the side opposite to the incident light. As described above, the propagation speed of the incident light and the propagation speed of the crosstalk light are equal to each other, so the incident light and the crosstalk light that arrive at one end roughly at the same time intersect at the approximate midpoint of the second connecting optical waveguide. Furthermore, the incident light is incident from one end of the third optical waveguide to the third optical waveguide, and the crosstalk light is incident from one end of the second optical waveguide to the second optical waveguide. At this time, the moment when the incident light is incident to the third optical waveguide is approximately the same as the moment when the crosstalk light is incident to the second optical waveguide. Therefore, the crosstalk light is propagated from one end to the other end of the second optical waveguide while being approximately parallel to the incident light propagating from one end to the other end in the third optical waveguide. During this period, the incident light propagating in the third optical waveguide is also propagated while crosstalking to the second optical waveguide. Therefore, the light crosstalking from the third optical waveguide to the second optical waveguide is combined with the crosstalk light propagating in the second waveguide. The combined light is pulsed, and the output light emitted from one end of the first optical waveguide via the first connecting optical waveguide and the first optical waveguide includes: the pulsed light generated by the crosstalk between the second optical waveguide and the third optical waveguide. The output light emitted from the first optical waveguide is received by the OTDR, and the power of the output light is measured.

[0032] At this time, the pulsed light caused by the crosstalk between the first optical waveguide and the second optical waveguide and the pulsed light caused by the crosstalk between the second optical waveguide and the third optical waveguide are emitted from one end of the first optical waveguide at different times. Therefore, the emitted light including the light caused by the crosstalk between the first optical waveguide and the second optical waveguide and the emitted light including the light caused by the crosstalk between the second optical waveguide and the third optical waveguide can be received by the OTDR, and the power of each emitted light can be measured, and the magnitude of each crosstalk can be obtained. Therefore, compared with the case where after measuring the crosstalk between the first optical waveguide and the second optical waveguide, the other end of the second optical waveguide and the other end of the third optical waveguide are optically connected by a connecting optical waveguide, the incident light is again incident from one end of the second optical waveguide, and the crosstalk between the second optical waveguide and the third optical waveguide is measured, it is easy to measure the crosstalk between the first optical waveguide and the second optical waveguide and the crosstalk between the second optical waveguide and the third optical waveguide.

[0033] Mode 10 of the present invention is a crosstalk measurement method according to any one of modes 1, 2, 5, and 6, characterized in that the optical device further includes a third optical waveguide parallel to the first optical waveguide, and in the connecting step, one end of the second optical waveguide and the other end of the third optical waveguide are optically connected via a second connecting optical waveguide, and in the first measuring step, the power of the output light emitted from the one end of the first optical waveguide is further measured by the OTDR, the output light includes pulsed light, and the pulsed light is composed of the following optical multiplexing, namely: The processing step further determines the size of the crosstalk between the first optical waveguide and the third optical waveguide by using the power of the output light including the pulsed light generated by the crosstalk between the first optical waveguide and the third optical waveguide, light generated by crosstalk from the first optical waveguide to the third optical waveguide by the incident light incident on the first optical waveguide to the third optical waveguide via the first connecting optical waveguide, the second optical waveguide, and the second connecting optical waveguide.

[0034] In this case, as described in the first embodiment, crosstalk occurs between the first optical waveguide and the second optical waveguide, and outgoing light including pulsed light caused by the crosstalk is emitted from one end of the first optical waveguide. In addition, in this embodiment, the incident light propagating in the first optical waveguide propagates while crosstalking from the first optical waveguide to the third optical waveguide, and the crosstalk light crosstalking from the first optical waveguide to the third optical waveguide is also in a pulsed state, and propagates from one end side to the other end of the third optical waveguide while being roughly parallel to the incident light propagating in the first optical waveguide. The incident light arriving at the other end of the first optical waveguide is incident on the first connecting optical waveguide. The crosstalk light arriving at the other end of the third optical waveguide is incident on the second connecting optical waveguide. As described above, the propagation speed of the incident light and the propagation speed of the crosstalk light are equal to each other, so the incident light and the crosstalk light intersect at the approximate midpoint of the optical waveguide formed by combining the first connecting optical waveguide, the second optical waveguide, and the second connecting optical waveguide. Furthermore, the incident light is incident from the other end of the third optical waveguide to the third optical waveguide via the second connecting optical waveguide, and the crosstalk light is incident from the other end of the first optical waveguide to the first optical waveguide via the first connecting optical waveguide. At this time, the moment when the incident light is incident to the third optical waveguide is substantially the same as the moment when the crosstalk light is incident to the first optical waveguide. Therefore, the crosstalk light propagates from the other end to one end in the first optical waveguide while being substantially parallel to the incident light propagating from the other end to one end in the third optical waveguide. During this period, the incident light propagating in the third optical waveguide also propagates while crosstalking to the first optical waveguide. Therefore, the light crosstalking from the third optical waveguide to the first optical waveguide is combined with the crosstalk light propagating in the first optical waveguide. The combined light is pulsed, and the output light emitted from one end of the first optical waveguide includes: pulsed light generated by the crosstalk between the first optical waveguide and the third optical waveguide. The output light emitted from the first optical waveguide is received by the OTDR, and the power of the output light is measured.

[0035] At this time, the pulsed light caused by the crosstalk between the first optical waveguide and the second optical waveguide and the pulsed light caused by the crosstalk between the first optical waveguide and the third optical waveguide are emitted from one end of the first optical waveguide at different times. Therefore, the emitted light including the light caused by the crosstalk between the first optical waveguide and the second optical waveguide and the emitted light including the light caused by the crosstalk between the first optical waveguide and the third optical waveguide can be received by the OTDR, and the power of each emitted light can be measured, and the magnitude of each crosstalk can be obtained. Therefore, compared with the case where after measuring the crosstalk between the first optical waveguide and the second optical waveguide, the other end of the first optical waveguide and the other end of the third optical waveguide are optically connected by a connecting optical waveguide, the incident light is injected again from one end of the first optical waveguide, and the crosstalk between the first optical waveguide and the third optical waveguide is measured, it is easy to measure the crosstalk between the first optical waveguide and the second optical waveguide and the crosstalk between the first optical waveguide and the third optical waveguide.

[0036] Mode 11 of the present invention is a crosstalk measurement method according to any one of modes 1 to 10, characterized in that in the first measurement step, the OTDR further measures: at least one of the light loss, reflection intensity, bending loss, and broken line in the optical device.

[0037] In this case, since the above-mentioned measurements can be performed in parallel with the crosstalk measurement, it is possible to suppress the time consumption of measurements other than the crosstalk.

[0038] Mode 12 of the present invention is a crosstalk measurement method according to any one of Modes 1 to 11, characterized in that, when the first optical waveguide, the second optical waveguide, and the first connecting optical waveguide are made to propagate light of the same power, the power of the backscattered light per unit length generated in the first connecting optical waveguide is smaller than the power of the backscattered light per unit length generated in the first optical waveguide and the second optical waveguide, respectively.

[0039] In the first connection optical waveguide, since the power of the backscattered light is small, the ratio of the power of the crosstalk light to the power of the backscattered light increases, and the crosstalk light can be easily detected.

[0040] Mode 13 of the present invention is a crosstalk measuring device, and is a crosstalk measuring device for an optical device, wherein the optical device has a first optical waveguide and a second optical waveguide including one end and the other end and arranged in parallel with each other, and the crosstalk measuring device is characterized in that it comprises: a first connecting optical waveguide, which optically connects the other end of the first optical waveguide with the other end of the second optical waveguide; an OTDR, which allows pulsed incident light to be incident from the one end of the first optical waveguide, and measures the power of output light emitted from the one end of the first optical waveguide, the output light including pulsed light, the pulsed light being composed of the following optical multiplexes, namely: light generated due to crosstalk of the incident light from the first optical waveguide to the second optical waveguide, and light generated due to crosstalk of the incident light from the second optical waveguide to the first optical waveguide, which is incident from the first optical waveguide to the second optical waveguide via the first connecting optical waveguide; and a processing unit, which uses the measured power of the output light to obtain the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide.

[0041] According to the crosstalk measurement device of this embodiment, an OTDR is used, and light that crosstalks from light incident to an optical waveguide to another optical waveguide is used, so the power of the crosstalk light is larger than that of the case where backscattered light of the light that has caused the crosstalk is detected as in Patent Documents 2 and 3. In addition, in the crosstalk measurement device of this embodiment, the crosstalk light when the incident light propagates from one end to the other end of the first optical waveguide is combined with the crosstalk light when the incident light propagates from the other end to one end of the second optical waveguide, so there is a tendency that the power of the pulsed light generated by the crosstalk is larger. Therefore, according to the crosstalk measurement device of this embodiment, crosstalk measurement can be easily performed.

[0042] (III) Beneficial effects

[0043] As described above, according to the present invention, it is possible to provide a crosstalk measurement method and a crosstalk measurement device capable of easily performing crosstalk measurement using the OTDR method. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a diagram showing a cross section perpendicular to the longitudinal direction of the multi-core optical fiber according to the first embodiment of the present invention.

[0045] Figure 2 It is a diagram showing a crosstalk measurement device according to the first embodiment.

[0046] Figure 3 1 is a flowchart showing the steps of the crosstalk measurement method according to the first embodiment of the present invention.

[0047] Figure 4 Yes means Figure 3 A diagram of the propagation pattern of light in the crosstalk measurement device.

[0048] Figure 5 It is a diagram showing the measurement results using OTDR.

[0049] Figure 6 yes Figure 5 A magnified view of a portion of .

[0050] Figure 7 This is a diagram showing the power of crosstalk light measured by an OTDR when the length of a multi-core optical fiber is changed.

[0051] Figure 8 This is a diagram showing the relationship between the power of crosstalk light measured in the first embodiment and the power of crosstalk light measured by the PM method.

[0052] Fig. 9 This is a flowchart showing the steps of the crosstalk measurement method according to the second embodiment of the present invention.

[0053] Fig.10This is a diagram showing the state of the crosstalk measurement device in the second measurement step of the second embodiment.

[0054] Fig.11 It is a diagram showing a crosstalk measurement device according to a third embodiment of the present invention.

[0055] Fig.12 It is a diagram showing the measurement results by the OTDR according to the third embodiment.

[0056] Fig.13 It is a diagram showing a crosstalk measurement device according to a fourth embodiment of the present invention.

[0057] Fig.14 It is a diagram showing a crosstalk measurement device according to a fifth embodiment of the present invention.

[0058] Fig.15 It means in Figure 4 3 is a diagram showing measurement results using an OTDR when a hollow core optical fiber is used as the first optical fiber.

[0059] Fig.16 It is a diagram showing a modified example of the crosstalk measurement device of the first embodiment. DETAILED DESCRIPTION

[0060] The following is an illustration of the embodiments of the crosstalk measurement method and the crosstalk measurement device of the present invention in conjunction with the accompanying drawings. The embodiments illustrated below are intended to make the present invention easy to understand, rather than to limit the interpretation of the present invention. The present invention can be changed and improved relative to the following embodiments without departing from the main purpose. In addition, in the drawings referenced below, there are cases where the dimensions of each component are changed for easy understanding.

[0061] (First embodiment)

[0062] Figure 1 1 is a diagram showing a cross section perpendicular to the length direction of a multi-core optical fiber of the present embodiment. The multi-core optical fiber 10 has: a plurality of cores 11 to 14 capable of propagating light, and a cladding 15 surrounding the outer peripheral surface of each core 11 to 14. In addition, the outer peripheral surface of the cladding 15 may also be surrounded by a covering layer composed of resin.

[0063] Each core 11 to 14 has one end and the other end, and is arranged in parallel along the length direction of the multi-core optical fiber 10. The refractive index of the cores 11 to 14 is higher than the refractive index of the cladding 15, and each core 11 to 14 can propagate light. Therefore, each core 11 to 14 can be regarded as a first optical waveguide to a fourth optical waveguide, and the multi-core optical fiber 10 is an optical device having a plurality of optical waveguides arranged in parallel.

[0064] In this embodiment, the cores 11 to 14 are made of silica glass to which a dopant such as germanium (Ge) is added to increase the refractive index, and the cladding 15 is made of silica glass without any additives. Alternatively, for example, the cores 11 to 14 may be made of silica glass without any additives, and the cladding 15 may be made of silica glass to which a dopant such as fluorine (F) is added to decrease the refractive index; or, for example, the cores 11 to 14 may be made of silica glass to which a dopant that increases the refractive index is added, and the cladding 15 may be made of silica glass to which a dopant that decreases the refractive index is added. There are no particular restrictions on the dopant that increases the refractive index and the dopant that decreases the refractive index.

[0065] Next, the optical device crosstalk measurement apparatus according to the present embodiment will be described. Figure 2 is a diagram showing a crosstalk measurement device according to this embodiment. Figure 2 As shown, the crosstalk measuring device 1 of this embodiment includes: OTDR20, processing unit 25 and first optical fiber 51 as main components. The crosstalk measuring device 1 measures the crosstalk in the multi-core optical fiber 10. The multi-core optical fiber 10 has one end 17 and the other end 18. In addition, in the following description, the one end 17 and the other end 18 are sometimes described as the one end 17 and the other end 18 of the cores 11 to 14.

[0066] The OTDR 20 is used in a manner connected to an optical fiber, etc. The OTDR 20 emits pulsed light, and can measure the power of light incident from the multi-core optical fiber 10, and can measure the time from the emission of the pulsed light to the incidence of the measured light, and is a device that can measure the loss of light, that is, the transmission loss, bending loss, connection loss, etc. of the optical fiber, etc., and can detect the broken part of the optical fiber, etc., and can measure the reflection amount of light of the optical fiber, etc. In this embodiment, the OTDR 20 is connected to the fan-in fan-out device 30.

[0067] The fan-in fan-out device 30 includes: a plurality of optical waveguides (not shown) that can be optically connected to the cores 11 to 14 at one end 17 of the multi-core optical fiber 10, and optical fibers 31 to 34 that include cores that are optically connected to the respective optical waveguides. In this example, the core of the optical fiber 31 is connected to the OTDR 20. In addition, in this example, the optical waveguide connected to the core of the optical fiber 31 is connected to the core 11 of the multi-core optical fiber 10. Therefore, the optical fiber 31 is optically connected to the core 11, and the light emitted from the OTDR 20 is incident on the core 11.

[0068] A fan-in fan-out device 40 is connected to the other end 18 of the multi-core optical fiber 10. The fan-in fan-out device 40 has the same structure as the fan-in fan-out device 30, and the cores of optical fibers 41 to 44 are optically connected to a plurality of optical waveguides (not shown) that can be optically connected to the cores 11 to 14 of the multi-core optical fiber 10. In this example, the core 11 is optically connected to the core of the optical fiber 41, and the core 12 is optically connected to the core of the optical fiber 42.

[0069] The first optical fiber 51 is a single-core optical fiber, for example, a single-mode optical fiber. The optical fiber 41 is connected to one end of the first optical fiber 51, and the optical fiber 42 is connected to the other end of the first optical fiber 51. Therefore, the core of the optical fiber 41 and the core of the optical fiber 42 are optically connected via the core of the first optical fiber 51. The core of the first optical fiber 51 can be regarded as a first connecting waveguide, which optically connects the other end of the first optical waveguide as the core 11 and the other end of the second optical waveguide as the core 12.

[0070] The processing unit 25 is connected to the OTDR 20, 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 computing device that uses the power of light measured by the OTDR 20 to find the size of the crosstalk. The processing unit 25 can use, for example: a microcontroller, an IC (Integrated Circuit), an LSI (Large-scale Integrated Circuit), an ASIC (Application Specific Integrated Circuit), and other integrated circuits, and an NC (Numerical Control) device. In addition, when using an NC device, the processing unit 25 may use a machine learning machine or may not use a machine learning machine. When data related to the power of light is input from the OTDR 20, the processing unit 25 calculates the size of the crosstalk between the core 11 and the core 12 based on the data in the manner described below, and outputs data related to the size of the crosstalk calculated. In addition, the processing unit 25 and the OTDR 20 can also be installed in one housing and share some components.

[0071] Next, a method for measuring crosstalk in the optical device according to the present embodiment will be described. Figure 3 FIG. 4 is a flow chart showing the steps of the crosstalk measurement method of this embodiment. Figure 3 As shown, the crosstalk measurement method of this embodiment includes: a connection step S1, a first measurement step S2, and a processing step S3.

[0072] (Connection step S1)

[0073] Prior to this step, a multi-core optical fiber 10 as an optical device to be measured is prepared and set in the crosstalk measurement device 1. The length of the multi-core optical fiber 10 is, for example, 21 km. At this time, in this step, the other end 18 of the core 11 is optically connected to the other end 18 of the core 12 via the core of the first optical fiber 51. The length of the first optical fiber 51 is, for example, 10 km. Specifically, the waveguide connected to the optical fiber 41 in the fan-in fan-out device 40 is connected to the core 11 of the multi-core optical fiber 10, and the waveguide connected to the optical fiber 42 is connected to the core 12. Therefore, in this step, the other end of the first optical waveguide is optically connected to the other end of the second optical waveguide via the first connecting optical waveguide, and after this step, when light is incident from one end 17 of the core 11, the light is incident on the core 12 from the other end 18 of the core 12 via the core of the first optical fiber 51.

[0074] In addition, the OTDR 20 is optically connected to the core 11. Specifically, the waveguide connected to the optical fiber 31 in the fan-in fan-out device 30 is connected to the core 11 of the multi-core optical fiber 10. Therefore, the light emitted from the OTDR 20 enters the core 11 from one end 17 of the core 11.

[0075] In this way, the core 11 of the multi-core optical fiber 10 is optically connected to the OTDR 20, and the core 11 and the core 12 are optically connected via the core of the first optical fiber 51. Figure 2 Status shown.

[0076] (First Measurement Step S2)

[0077] In this step, a pulsed incident light emitted from the OTDR 20 is incident from one end 17 of the core 11 serving as the first optical waveguide, and the power of the output light emitted from the one end 17 of the core 11 is measured by the OTDR 20. The output light includes a pulsed light, which is composed of the following optical multiplexes: light generated by crosstalk of the incident light from the core 11 to the core 12 serving as the second optical waveguide, and light generated by crosstalk from the core 12 to the core 11 of the incident light incident from the core 11 to the core 12 via the core of the first optical fiber 51 serving as the first connecting optical waveguide.

[0078] Figure 4 Yes means Figure 3 The above method is described in detail using this figure. Figure 3In the figure, the fan-in and fan-out devices 30 and 40 are described in a simplified manner. First, pulsed light is emitted from the OTDR 20. In order to stably perform the crosstalk measurement described later, the wavelength width of the light is preferably greater than 1 nm, more preferably greater than 3 nm, and further preferably greater than 5 nm. In addition, in order to measure the crosstalk at a specific wavelength, the wavelength width of the light is preferably less than 30 nm. In addition, regarding the power of the light emitted from the OTDR 20, it is preferred to appropriately adjust the pulse width so that the output light containing the crosstalk light described later is not saturated. In this case, an attenuator can be set between the OTDR 20 and the optical fiber 31.

[0079] The pulsed light emitted from the OTDR 20 is incident on the core 11 from one end 17 of the core 11 as incident light, and propagates from the one end 17 to the other end 18 in the core 11. The pulsed incident light propagating in the core 11 propagates while crosstalking from the core 11 to the core 12. Since the incident light is in a pulsed shape, the crosstalk light CL1 that crosstalks from the core 11 to the core 12 is also in a pulsed shape, and propagates from the one end 17 side of the core 12 to the other end 18 while being approximately parallel to the incident light L. During this period, due to the crosstalk from the core 11 to the core 12, the power of the incident light L decreases according to the distance propagated in the core 11, and the power of the crosstalk light CL1 increases according to the distance propagated in the core 12. Since the speeds of the light propagating in the core 11 and the core 12 are the same, the incident light L and the crosstalk light CL1 arrive at the other end 18 approximately at the same time.

[0080] Next, the incident light L and the crosstalk light CL1 are incident on the core of the first optical fiber 51 substantially at the same time via the fan-in fan-out device 40. At this time, the crosstalk light CL1 is incident from the side opposite to the side where the incident light L is incident on the core of the first optical fiber 51. The incident light L incident on the core of the first optical fiber 51 and the crosstalk light CL1 intersect at the approximate midpoint of the first optical fiber 51. The incident light L and the crosstalk light CL1 arrive at different ends of the first optical fiber 51 substantially at the same time. Furthermore, the incident light L is incident on the core 12 from the other end 18 of the core 12 via the fan-in fan-out device 40, and the crosstalk light CL1 is incident on the core 11 from the other end 18 of the core 11. At this time, the incident light L and the crosstalk light CL1 are incident on the cores 12 and 11 substantially at the same time, respectively. Furthermore, even when the optical fiber 41 and the optical fiber 43 in the fan-in fan-out device 40 have different lengths, the incident light L and the crosstalk light CL1 are incident on the cores 12 and 11 respectively at substantially the same time.

[0081] The incident light L incident on the core 12 and the crosstalk light CL1 incident on the core 11 propagate toward one end 17 in each core 12 and 11 while being roughly parallel. During this period, the incident light L propagating in the core 12 also propagates while crosstalking to the core 11. Therefore, the light crosstalking from the core 12 to the core 11 is combined with the crosstalk light CL1 propagating in the core 11. The combined light is pulsed and propagates while gradually increasing in power. The outgoing light formed by combining the pulsed crosstalk light CL1 and the backscattered light and other light is emitted from the one end 17 of the core 11. Therefore, the outgoing light includes the pulsed crosstalk light CL1.

[0082] The outgoing light emitted from the core 11 is incident on the OTDR 20 via the fan-in fan-out device 30 , is received by the OTDR 20 , and the power thereof is measured by the OTDR 20 .

[0083] Figure 5 FIG. 2 is a diagram showing the measurement results of the outgoing light received by the OTDR 20. Figure 5 In FIG. 1 , the horizontal axis represents the propagation distance of the incident light L, and the vertical axis represents the power of the outgoing light received by the OTDR 20. Figure 5 The vertical axis represents the ratio of the power of the emitted light to the specified power set in the OTDR 20 in decibels. For example, if the specified power is 1 mW, the unit of the vertical axis can be expressed in dBm. Figure 5 As shown, in the interval where the incident light L propagates in the core 11 and the interval where the incident light L propagates in the core 12, backscattered light is measured as outgoing light. The slope of the line representing the outgoing light in these intervals represents the loss of the incident light L per unit length due to backscattering. In addition, at the boundary between the interval of the core 11 and the interval of the first optical fiber 51, and the boundary between the interval of the first optical fiber 51 and the interval of the core 12, pulsed light is measured, which represents reflection in the fan-in fan-out device 40 and the like.

[0084] The pulsed light is measured at the approximate midpoint of the section representing the first optical fiber 51. As described above, the incident light L and the crosstalk light CL1 intersect at the approximate midpoint of the first optical fiber 51, so the pulsed light represents the crosstalk light CL1. In addition, in the section where the incident light L propagates in the first optical fiber 51, the backscattered light is also measured as the outgoing light. Therefore, the power of the outgoing light measured at the approximate midpoint of the first optical fiber 51 includes the power of the crosstalk light CL1 and the power of the backscattered light.

[0085] Thus, a pulse representing the power of the crosstalk light CL1 is shown at the approximate midpoint of the section representing the first optical fiber 51. The pulse width of the incident light L is substantially the same as the pulse width of the crosstalk light CL1. Therefore, in order to prevent the pulse representing the crosstalk light CL1 from reaching the end of the first optical fiber 51, it is preferable that the length of the core of the first optical fiber 51 as the first connecting optical waveguide is longer than the half-value width of the incident light L. That is, when the length of the first optical fiber 51 is set to L SCF , the half-value time width of the incident light L is set to ΔT pulse When the refractive index of the core of the first optical fiber 51 is set to n and the speed of light is set to c, it is preferable that the following formula is satisfied.

[0086] L SCF >ΔT pulse ×c / n

[0087] Furthermore, in order to further suppress the influence of the end of the first optical fiber 51 on the pulse, it is more preferable to satisfy the following formula.

[0088] L SCF >1.2×ΔT pulse ×c / n

[0089] The OTDR 20 outputs data on the measured power of the outgoing light to the processing unit 25 .

[0090] (Processing step S3)

[0091] In this step, the magnitude of the crosstalk between the core 11 and the core 12 is determined using the measured power of the outgoing light. Figure 6 is Figure 5 1 is an enlarged view of the outgoing light measured at the approximate midpoint of the first optical fiber 51 in FIG. As described above, backscattered light is also generated in the first optical fiber 51. Therefore, the power of the backscattered light is measured in the region other than the region showing the pulsed light. Therefore, the processing unit 25 first calculates the power P of the backscattered light in the region showing the pulsed light based on the power of the outgoing light in the region other than the region showing the pulsed light including the crosstalk light CL1, based on the data input from the OTDR 20. BS Specifically, the processing unit 25 performs linear approximation on the power of the emitted light in the region other than the region showing the pulsed light, and obtains the power P of the backscattered light. BS Next, the processing unit 25 obtains the power P of the emitted light in the region showing the pulsed light. OUT The backscattered light power P is obtained BS The difference is the power of the pulsed light. The power of the pulsed light includes: the power P of the crosstalk light CL1 XT_MCF , and the crosstalk power P in the fan-in fan-out device 30 and the fan-in fan-out device 40 XT_FIFOWhen the power P XT_FIFO When the power of the pulsed light is small enough to be ignored, the power of the crosstalk light CL1 can be set to P XT-MCF However, in order to more accurately calculate the power P XT_MCF Preferably, the power P is removed from the power of the pulsed light. XT_FIFO The power of the crosstalk light CL1 is set to P XT_MCF .

[0092] Power XT_FIFO For example, in the crosstalk measurement device 1, the fan-in fan-out device 30 is directly connected to the fan-in fan-out device 40. This makes the length of the multi-core optical fiber 10 zero. If the power of the emitted light is measured in the same manner as in the first measurement step S2, the power P of the pulsed light measured at the approximate midpoint of the first optical fiber 51 is OUT Contains: Power P XT_FIFO and power P BS Therefore, the power P can be obtained in the same way as above. OUT With power P BS The difference between XT_FIFO .

[0093] The processing unit 25 calculates the power P of the crosstalk light CL1. XT_MCF At this time, the processing unit 25 may also convert the size of the crosstalk into decibels representing the ratio of the power of the incident light L emitted from one end 17 of the fiber core 12 and output it. In addition, the processing unit 25 may also convert it into a ratio representing the same as Figure 5 , Figure 6 The decibel ratio of the specified power set in the OTDR 20 is output. In this way, the magnitude of the crosstalk is obtained.

[0094] In addition, in this step, the processing unit 25 may further determine the magnitude of the crosstalk between the core 11 and the core 13 based on the magnitude of the crosstalk between the core 11 and the core 12. In this case, the processing unit 25 determines the magnitude of the crosstalk between the core 11 and the core 13 based on the magnitude of the crosstalk between the core 11 and the core 12, for example, using a relational expression that indicates the relationship between the magnitude of the crosstalk between the core 11 and the core 12 and the magnitude of the crosstalk between the core 11 and the core 13. In this case, the multi-core optical fiber 10 as an optical device has the core 13 as the third optical waveguide arranged in parallel with the core 11 as the first optical waveguide. Therefore, in the processing step S3, based on the magnitude of the crosstalk between the first waveguide and the second waveguide, the magnitude of the crosstalk between the first waveguide and the third waveguide is further determined. In this case, even if the power of light caused by the crosstalk between the core 11 and the core 13 is not measured, the magnitude of the crosstalk between the core 11 and the core 13 can be easily determined. In addition, the magnitude of the crosstalk between the core 11 and the core 14 can be obtained in the same manner as the magnitude of the crosstalk between the core 11 and the core 13 .

[0095] Next, the reliability of the crosstalk measurement according to the present embodiment will be described.

[0096] Figure 7 This is a diagram showing the power of pulsed light composed of crosstalk light CL1 in the multi-core optical fiber 10 and crosstalk light in the fan-in and fan-out devices 30 and 40 measured by the OTDR 20 in the same manner as in the above embodiment, wherein the power of backscattered light is removed from the power of light incident on the OTDR 20. Figure 7 As shown, in this example, the length of the multi-core optical fiber 10 is set to 0 km, 21 km, 42 km, and 84 km. Figure 7 The FIFO shown by the dotted line indicates that the fan-in fan-out device 30 is directly connected to the fan-in fan-out device 40, and the length of the multi-core optical fiber 10 is 0 km. The FIFO is equivalent to the power P XT_FIFO .like Figure 7 As shown, it can be seen that the longer the multi-core optical fiber 10 is, the greater the power of the light generated by the crosstalk is.

[0097] Then, in Figure 7 The fan-in and fan-out devices 30 and 40 are connected to each multi-core optical fiber 10 used for the measurement, and the size of the crosstalk is measured by the PM method. Specifically, the core incident light from the optical fiber 31 of the fan-in and fan-out device 30 optically connected to the core 11 of the multi-core optical fiber 10 is measured for each light emitted from the core of the optical fiber 41 and 42 of the fan-in and fan-out device 40 optically connected to the core 12 of the multi-core optical fiber 10, thereby measuring the size of the crosstalk between the core 11 and the core 12. Therefore, the size of the crosstalk is the ratio of the power of the crosstalk light to the power of the incident light L emitted from one end 17 of the core 12. The above results are shown in the following Table 1.

[0098]

[0099] The peak values ​​in Table 1 are Figure 7 The crosstalk is the power of the pulsed light and the magnitude of the crosstalk is measured by the PM method. Figure 8 TABLE 1 is a graph showing the relationship between the power of the crosstalk light measured in this embodiment and the power of the crosstalk light measured by the PM method. Figure 8 As shown in FIG. 1 , these relationships are linear. Therefore, it is shown that the power of the crosstalk light measured by the crosstalk measurement method of this embodiment and the magnitude of the crosstalk measured by the PM method are roughly correlated. Figure 8 The points shown are approximated by a straight line, and the straight line is expressed by the following equation.

[0100] XT=2.57x-58.9

[0101] R 2 =0.986

[0102] In this formula, XT represents the size of the crosstalk, x represents the power of the crosstalk light, and R 2 is the coefficient of determination. Thus, the coefficient of determination is very close to 1, indicating that the above correlation is high.

[0103] Next, prepare another plurality of multi-core optical fibers 10, and measure the magnitude of the crosstalk in the same manner as in the present embodiment. At this time, similarly to the first measurement step S2, measure the power of the pulsed crosstalk light, substitute the magnitude of the power into x in the above formula, and obtain Figure 8 The vertical axis of the crosstalk is the magnitude of the crosstalk expressed in decibels. In addition, the crosstalk of each multi-core optical fiber 10 was measured by the PM method. The results are shown in Table 2.

[0104]

[0105] In Table 2, the calculated XT value is the magnitude of the crosstalk obtained using the above-mentioned linear approximation formula, and the measured XT value is the magnitude of the crosstalk measured by the PM method. As shown in Table 2, the result of the crosstalk measurement of this embodiment is basically consistent with the result of the crosstalk measurement by the PM method. Therefore, in the processing step S3, when the processing unit 25 converts the magnitude of the crosstalk into decibels representing the ratio of the power of the incident light L output from the one end 17 of the core 12, the power of the pulsed crosstalk light can also be set to x, and the magnitude of the crosstalk XT can be obtained according to the above-mentioned linear approximation formula.

[0106] The above results show that the crosstalk measurement of this embodiment is reliable.

[0107] Next, the crosstalk measurement according to the present embodiment will be described using mathematical formulas.

[0108] The length of the multi-core optical fiber 10 is set to L MCF , the length of the first optical fiber 51 is set to L SCF In addition, the power of the incident light L when it enters the core 11 of the multi-core optical fiber 10 from one end 17 is set to P0, the power of the incident light L when it is emitted from the other end 18 is set to P'0, and the power of the incident light L when it enters the core 12 from the other end 18 and is emitted from the one end 17 of the core 12 is set to P"0. In addition, the power of the crosstalk light that crosstalks from the core 11 to the core 12 and is emitted from the core 12 when the incident light L propagates in the core 11 is set to P XT (L MCF ), when the incident light L propagates in the core 11 and the core 12, that is, when the incident light L travels back and forth in the multi-core optical fiber 10, crosstalk occurs between the core 11 and the core 12 and the power of the crosstalk light emitted from the core 11 is set to P XT (2L MCF ).

[0109] For simplicity, in the following mathematical formula, the multi-core optical fiber 10 is described as a dual-core optical fiber having cores 11 and 12 and not having cores 13 and 14. In addition, the transmission loss of the multi-core optical fiber 10 and the first optical fiber 51 is ignored, and the loss and crosstalk in the fan-in and fan-out devices 30 and 40 are also ignored. In this case, referring to Formula (21a) and Formula (21b) of Non-Patent Document 1, P'0, P"0, P XT (L MCF )、P XT (2L MCF ) is expressed by the following equations (1) to (4).

[0110]

[0111]

[0112]

[0113]

[0114] In the above expression, h is the power coupling coefficient between the core 11 and the core 12 where crosstalk occurs. The unit of the light power here is not converted into decibels, but is expressed in watts, for example.

[0115] In addition, the magnitude of the crosstalk from the core 11 to the core 12 during the propagation of the incident light L in the core 11 is expressed in decibels as a ratio to P'0 and is denoted by XT(L MCF), the magnitude of the crosstalk between the core 11 and the core 12 during the period when the incident light L propagates in the core 11 and the core 12, that is, during the period when the incident light L travels back and forth in the multi-core optical fiber 10, is expressed in decibels as a ratio to P"0 and is set to XT(2L MCF In this case, XT (L MCF )、XT(2L MCF ) is expressed by the following equations (5) and (6).

[0116]

[0117]

[0118] As described above, the OTDR 20 is optically connected to the core 11 at one end 17 of the multi-core optical fiber 10. Therefore, it is impossible to measure P"0 by the OTDR. Therefore, in order to obtain XT (2L) from the power of light measured by the OTDR 20, MCF ), we can use equation (6) to find XT(2L MCF ).

[0119] As described above, the incident light L and the crosstalk light CL1 intersect at approximately the midpoint of the first optical fiber 51. At this time, the distance that the incident light L propagates is the length L of the multi-core optical fiber 10. MCF , and half the length of the first optical fiber 51, namely L SCF / 2. Therefore, the distance from the midpoint of the first optical fiber 51 to the end 17 of the multi-core optical fiber 10 is L MCF +L SCF / 2. If the intensity of the backscattered light from the midpoint of the first optical fiber 51 measured by the OTDR 20 is set to P BS (L MCF +L SCF / 2), then P BS (L MCF +L SCF / 2) is expressed by formula (7).

[0120]

[0121] In formula (7), α S_SCF is the backscattering coefficient of the first optical fiber 51, which indicates the probability that the incident light L will be Rayleigh scattered in the first optical fiber 51, SCF is the capture rate of the first optical fiber 51 , and indicates the probability that the light that has undergone Rayleigh scattering in the core of the first optical fiber 51 propagates toward the core 11 of the multi-core optical fiber 10 .

[0122] Formula (8) is derived based on formula (2) and formula (7).

[0123]

[0124] Calculate P"0 according to formula (8) and substitute it into formula (6), then we get formula (9).

[0125]

[0126] As described in processing step S3, P can be obtained from the power of the emitted light in the region other than the region showing the pulsed crosstalk light based on the data input from the OTDR 20. BS (L MCF +L SCF / 2). In addition, in this description, the crosstalk in the fan-in and fan-out devices 30 and 40 is ignored, so the power P described in the processing step S3 is XT_MCF P XT (2L MCF ). Therefore, P can be obtained as described in processing step S3. XT (2L MCF ). Therefore, by calculating the first term of equation (9) separately in advance, XT(2L) can be obtained from equation (9). MCF In addition, the size of the crosstalk obtained in advance by the PM method and the P measured by the OTDR20 can be used to determine the crosstalk. BS (L MCF +L SCF / 2) and P XT (2L MCF ) to obtain the first term of Formula (9), or the first optical fiber 51 may be measured in advance to obtain the first term of Formula (9).

[0127] As described above, the crosstalk measuring method of the present embodiment comprises: a connection step S1, optically connecting the other end 18 of the core 11 as the first optical waveguide and the other end 18 of the core 12 as the second optical waveguide via the core of the first optical fiber 51 as the first connecting optical waveguide; a first measuring step S2, causing the pulsed incident light L emitted from the OTDR20 to be incident from the one end 17 of the core 11, and measuring the power of the output light emitted from the one end 17 of the core 11 by the OTDR20, the output light including the pulsed crosstalk light CL1, the crosstalk light CL1 being composed of light generated by the crosstalk of the incident light L from the core 11 to the core 12 and light generated by the crosstalk of the incident light L from the core 12 to the core 11 via the core of the first optical fiber 51; and a processing step S3, using the measured power of the output light to determine the magnitude of the crosstalk between the core 11 and the core 12.

[0128] In addition, the crosstalk measuring device of the present embodiment comprises: a core of a first optical fiber 51, which optically connects the other end 18 of the core 11 with the other end 18 of the core 12; an OTDR 20, which allows a pulsed incident light L to be incident from one end 17 of the core 11, and measures the power of an output light emitted from one end 17 of the core 11, the output light including a pulsed crosstalk light CL1, the crosstalk light CL1 being composed of a light generated by crosstalk of the incident light L from the core 11 to the core 12, and a light synthesized wave generated by crosstalk of the incident light L incident from the core 11 to the core 12 via the core of the first optical fiber 51 from the core 11 to the core 12; and a processor 25, which uses the measured power of the output light to determine the magnitude of the crosstalk between the core 11 and the core 12.

[0129] According to such a crosstalk measurement method and crosstalk measurement device, the OTDR 20 is used, and the light incident on the core 11 is used to crosstalk the core 12, so the power of the crosstalk light is larger than the case where the backscattered light of the light that has caused the crosstalk is detected as in Patent Documents 2 and 3. In addition, in the crosstalk measurement method and crosstalk measurement device of the present embodiment, the light that causes the crosstalk when the incident light L propagates from one end 17 to the other end 18 of the core 11 and the light that causes the crosstalk when the incident light L propagates from the other end 18 to the one end 17 of the core 12 are combined, so there is a tendency that the power of the pulse-shaped crosstalk light CL1 generated by the crosstalk is larger. Therefore, according to the crosstalk measurement method and crosstalk measurement device of this embodiment, crosstalk measurement can be easily performed.

[0130] (Second embodiment)

[0131] Next, refer to Fig. 9 , Fig.10 The second embodiment of the present invention will be described in detail. Unless otherwise specified, components identical or equivalent to those of the above embodiment are denoted by the same reference numerals and duplicate descriptions are omitted.

[0132] Fig. 9 FIG. 4 is a flowchart showing the steps of the crosstalk measurement method of this embodiment. Fig. 9 As shown, the crosstalk measuring method of this embodiment is different from the crosstalk measuring method of the first embodiment in that a second measuring step S22 is included. In this embodiment, the connection step S1 and the first measuring step S2 are performed similarly to the crosstalk measuring method of the first embodiment.

[0133] (Second Measurement Step S22)

[0134] In the present embodiment, this step is performed after the first measurement step S2. Fig.10 is a diagram showing the state of the crosstalk measurement device in this step. Fig.10As shown, in this step, the core of the optical fiber 32 of the fan-in fan-out device 30 is connected to the OTDR 20. The optical waveguide connected to the core of the optical fiber 32 is connected to the core 12 of the multi-core optical fiber 10. Therefore, the optical fiber 32 is optically connected to the core 12, and the light emitted from the OTDR 20 is incident on the core 12 from one end 17.

[0135] In this step, the pulsed incident light emitted from the OTDR 20 is made incident from one end 17 of the core 12 as the second optical waveguide. In this case, a multi-channel OTDR may be used. In the first measurement step S2, light may be made incident from one channel of the OTDR 20 to the core 11, and in this step, light may be made incident from another channel of the OTDR 20 to the core 12. In this step, the power of the incident light L from the OTDR 20 to the core 12 is the same as the power of the incident light L from the OTDR 20 to the core 12 in the first measurement step S2. The incident light L incident to the core 12 crosstalks from the core 12 to the core 11 as the first optical waveguide. The incident light L propagating to the other end 18 of the core 12 is made incident from the core 12 to the core 11 via the core of the first optical fiber 51 as the first connecting optical waveguide. The incident light L incident to the core 11 crosstalks from the core 11 to the core 12. Thus, outgoing light including pulsed crosstalk light CL2 formed by combining light generated by crosstalk from the core 12 to the core 11 and light generated by crosstalk from the core 11 to the core 12 is emitted from the one end 17 of the core 12 . The crosstalk light CL2 is formed by combining light generated by crosstalk from the core 12 to the core 11 to the core 12 .

[0136] The OTDR20 measures the power of the outgoing light. The power distribution of the outgoing light measured in this step is similar to that of the Figure 5 The power of the emitted light measured in the first measurement step shown in FIG. Figure 5 The records of core 11 and core 12 are exchanged for interpretation.

[0137] (Processing step S3)

[0138] In the processing step S3 of the present embodiment, first, the processing unit 25 flips the range from the core 12 to the core 11 in the distribution of the power of light measured by the second measurement step S22 along the horizontal axis. In addition, the processing unit 25 obtains: the arithmetic mean of the distribution of the power of light from the core 11 to the core 12 measured by the first measurement step S2 and the distribution of the power of light flipped in this step. Thus, the power of the light backscattered when propagating from one end 17 to the other end 18 in the core 11 and the power of the light backscattered when propagating from the other end 18 to the one end 17 in the core 11 are averaged, and the difference in the power of the light backscattered when propagating from the other end 18 to the one end 17 in the core 11 is substantially eliminated. Figure 5 The slope of the distribution of the optical power within the core 11 is substantially eliminated. Figure 5The slope of the distribution of the light power in the core 12 and the slope of the distribution of the light power in the first optical fiber 51. In addition, at the approximate midpoint of the first optical fiber 51, the crosstalk light averaged by the crosstalk light CL1 and the crosstalk light CL2 appears in a pulse shape.

[0139] Next, in this step, the processing unit 25 obtains the magnitude of the crosstalk light based on the averaged power of the pulsed crosstalk light, similarly to the first embodiment.

[0140] As described above, the crosstalk measuring method of the present embodiment is provided with a second measuring step S22 on the basis of the crosstalk measuring method of the first embodiment. In the second measuring step S22, a pulsed incident light L emitted from the OTDR20 is incident from one end 17 of the core 12, and the power of the output light emitted from the one end 17 of the core 12 is measured by the OTDR20. The output light includes a pulsed light, and the pulsed light is composed of the following optical multiplexes, namely: light generated by crosstalk of the incident light L from the core 12 to the core 11, and light generated by crosstalk of the incident light L from the core 12 to the core 11 via the core of the first optical fiber 51. In the processing step S3, the power of the output light measured by the first measuring step S2 and the power of the output light measured by the second measuring step S22 are used to determine the magnitude of the crosstalk between the core 11 and the core 12.

[0141] In addition, regarding the crosstalk measuring device of the present embodiment, on the basis of the crosstalk measuring device of the first embodiment, the OTDR20 allows a pulsed incident light L to be incident from one end 17 of the core 12, and the power of the output light emitted from the one end 17 of the core 12 is measured by the OTDR20, the output light includes a pulsed light, and the pulsed light is formed by the following optical synthesis, namely: light generated due to crosstalk of the incident light L from the core 12 to the core 11, and light generated due to crosstalk from the core 11 to the core 12 caused by the incident light L incident from the core 12 to the core 11 via the core of the first optical fiber 51. The processing unit 25 uses the power of the output light emitted from the one end 17 of the core 11 due to the incident light L incident from the core 11, and the power of the output light emitted from the one end 17 of the core 12 due to the incident light L incident from the core 12, to calculate the size of the crosstalk between the core 11 and the core 12.

[0142] According to the crosstalk measurement method and the crosstalk measurement device of the present embodiment, the crosstalk light CL1 generated by the incident light L propagating from the fiber core 11 to the fiber core 12 and the crosstalk light CL2 generated by the incident light L propagating from the fiber core 12 to the fiber core 11 are used. Therefore, compared with the case where only the crosstalk light CL1 generated by the incident light L propagating from the fiber core 11 to the fiber core 12 is used, the size of the crosstalk can be calculated more accurately.

[0143] In addition, the power of the incident light L incident on the core 11 in the first measurement step S2 and the power of the incident light L incident on the core 12 in the second measurement step S22 are equal to each other. In the processing step S3, the magnitude of the crosstalk between the core 11 and the core 12 is obtained by averaging the power of the outgoing light measured in the first measurement step S2 and the power of the outgoing light measured in the second measurement step S22. By using such an averaging process, the magnitude of the crosstalk can be easily and accurately obtained. In addition, the power of the incident light L incident on the core 11 in the first measurement step S2 and the power of the incident light L incident on the core 12 in the second measurement step S22 may be different from each other. In this case, in the processing step S3, the processing is performed in consideration of the power of the incident light L. For example, if the power of the incident light L incident on the core 12 in the second measuring step S22 is twice the power of the incident light L incident on the core 11 in the first measuring step S2, the power of the emitted light is halved in the processing step S3 for averaging.

[0144] (Third Embodiment)

[0145] Next, refer to Fig.11 , Fig.12 The third embodiment of the present invention will be described in detail. Unless otherwise specified, the same reference numerals are used for the same or equivalent components as those in the above embodiment, and duplicate descriptions are omitted.

[0146] Fig.11 : is a diagram showing a crosstalk measurement device 1 of the present embodiment. The crosstalk measurement device 1 of the present embodiment is different from the crosstalk measurement device 1 of the first embodiment in that the optical fiber 41 of the fan-in fan-out device 40 is connected to one end of the first optical fiber 51 and the second optical fiber 52 via a coupler 55, and the other end of the second optical fiber 52 is connected to the optical fiber 43 of the fan-in fan-out device 40. The optical waveguide connected to the core of the optical fiber 43 is connected to the core 13 of the multi-core optical fiber 10, and the optical fiber 43 is optically connected to the core 13. Therefore, similarly to the first optical fiber 51 of the first embodiment, the core of the first optical fiber 51 optically connects the core 11 to the core 12, and the core of the second optical fiber 52 optically connects the core 11 to the core 13. The core of the second optical fiber can be regarded as a second connecting waveguide. The length of the second optical fiber 52 is different from that of the first optical fiber 51. In the present embodiment, the case where the second optical fiber 52 is longer than the first optical fiber 51 is described.

[0147] Here, in the present embodiment, the multi-core optical fiber 10 as an optical device further includes a third optical waveguide arranged in parallel with the first optical waveguide as the core 11. In addition, the other end 18 of the first optical waveguide as the core 11 and the other end 18 of the third optical waveguide as the core 13 are optically connected via a second connecting optical waveguide having a length different from that of the first connecting optical waveguide.

[0148] The process of the crosstalk measurement method of this embodiment performed using such a crosstalk measurement device 1 is similar to Figure 3 The flowchart shown is the same. However, each step has the following differences. The following mainly describes the differences.

[0149] (Connection step S1)

[0150] In this step of the present embodiment, the first optical fiber 51 and the second optical fiber 52 are connected to the optical fiber 41 via the coupler 55, and the end of the second optical fiber 52 on the side opposite to the coupler 55 side is connected to the optical fiber 43. That is, in this embodiment, in addition to the connection step S1 of the first embodiment, the other end 18 of the core 11 and the other end 18 of the core 13 are optically connected via the core of the second optical fiber having a different length from the first optical fiber 51. In this way, the core 11 and the core 12 are optically connected, and the core 11 and the core 13 are optically connected.

[0151] (First Measurement Step S2)

[0152] In this step of the present embodiment, incident light L is made incident from the OTDR 20 to the core 11, similarly to the first embodiment. In the present embodiment, in addition to the crosstalk between the core 11 and the core 12 described in the first embodiment, crosstalk is generated and measured as follows. This is described below.

[0153] Regarding the incident light L from the OTDR 20 incident on the core 11, the incident light L propagates from one end 17 to the other end 18 in the core 11, while crosstalking from the core 11 to the core 12 and from the core 11 to the core 13. The light crosstalking from the core 11 to the core 13 is also in a pulsed state, and propagates from the one end 17 side of the core 13 to the other end 18 while being roughly parallel to the incident light L. The power of the crosstalk light CL2 increases according to the distance propagated in the core 13. The crosstalk light CL2 is incident from the optical fiber 43 to the second optical fiber 52 at a time that is roughly the same as the time when the incident light L is incident from the coupler 55 to the second optical fiber 52. The incident light L and the crosstalk light CL2 intersect at the approximate midpoint of the second optical fiber 52. Furthermore, the incident light L is incident on the core 13 at the other end 18 of the multi-core optical fiber 10 via the fan-in and fan-out device 40, and the crosstalk light CL2 is incident on the core 11 at a time substantially the same as the time when the incident light L is incident on the core 13. The incident light L incident on the core 13 and the crosstalk light CL2 incident on the core 11 propagate toward one end 17 in each core 13 and 11 while being substantially parallel. During this period, the incident light L propagating in the core 13 also propagates while crosstalking to the core 11. Therefore, the light crosstalking from the core 13 to the core 11 is combined with the crosstalk light CL2 propagating in the core 11. The combined light is in a pulse shape and propagates while gradually increasing in power. The outgoing light formed by combining the pulsed crosstalk light CL2 with light such as backscattered light is emitted from one end 17 of the core 11. Therefore, the outgoing light contains the pulsed crosstalk light CL2. The outgoing light emitted from the core 11 is incident on the OTDR 20 via the fan-in fan-out device 30 , is received by the OTDR 20 , and the power thereof is measured by the OTDR 20 .

[0154] Fig.12 1 is a diagram showing the measurement results of the OTDR of this embodiment. Since the length of the first optical fiber 51 and the length of the second optical fiber 52 are different from each other, Fig.12 As shown in FIG. 1 , the outgoing light including the crosstalk light CL1 and the outgoing light including the crosstalk light CL2 are incident on the OTDR 20 at different times. In this embodiment, the second optical fiber 52 is longer than the first optical fiber 51, so the outgoing light including the crosstalk light CL2 is incident on the OTDR at a time delayed than the outgoing light including the crosstalk light CL1. Therefore, the OTDR 20 can measure these outgoing lights separately. Therefore, the OTDR 20 performs power measurement of the outgoing light including the pulsed light twice.

[0155] In addition, it is preferable that the difference between the length of the first optical fiber 51 and the length of the second optical fiber 52 is larger than the half-value width of the incident light. In this case, the interference of the pulsed light caused by the crosstalk between the core 11 and the core 12 and the pulsed light caused by the crosstalk between the core 11 and the core 13 can be suppressed, and the magnitude of the crosstalk can be measured more accurately.

[0156] (Processing step S3)

[0157] In this step, the processing unit 25 uses the measured power of the outgoing light to obtain the magnitude of the crosstalk between the core 11 and the core 12, similarly to the first embodiment. In addition, in this step of the present embodiment, the processing unit 25 obtains the magnitude of the crosstalk between the core 11 and the core 13. Since backscattered light is also generated in the first optical fiber 51 and the second optical fiber 52, the power of the backscattered light is measured in an area other than the area showing the pulsed light including the crosstalk light CL2. Therefore, based on the data input from the OTDR 20, the processing unit 25 obtains the power of the backscattered light in the area showing the pulsed light including the crosstalk light CL2, based on the power of the outgoing light in the area other than the area showing the pulsed light including the crosstalk light CL2. Specifically, the processing unit 25 obtains the power P of the backscattered light in the first embodiment. BS Similarly, the power of the backscattered light in the outgoing light including the crosstalk light CL2 is obtained. Next, the processing unit 25 obtains the difference between the power of the outgoing light in the region showing the pulsed light including the crosstalk light CL2 and the obtained power of the backscattered light. The difference is the power of the crosstalk light CL2. In this embodiment, when the power P of the crosstalk in the fan-in fan-out devices 30 and 40 is XT_FIFO If the power is negligible, the power may be ignored. However, in order to more accurately determine the power P of the crosstalk light CL2, it is preferable to remove the power P from the power of the pulsed light to be determined. XT_FIFO The power of is set to the power of the crosstalk light CL2.

[0158] As in the first embodiment, the processing unit 25 converts the power of the crosstalk light CL1 obtained into the magnitude of the crosstalk and outputs it, and converts the power of the crosstalk light CL2 obtained into the magnitude of the crosstalk and outputs it. At this time, the processing unit 25 may convert the magnitude of the crosstalk light CL2 into decibels representing the ratio of the power of the incident light L emitted from one end 17 of the core 13 and output it. In addition, the processing unit 25 may convert it into decibels representing the ratio to the specified power set in the OTDR 20 and output it. In this way, the magnitude of the crosstalk between the core 11 and the core 12 is obtained, and the magnitude of the crosstalk between the core 11 and the core 13 is obtained.

[0159] Regarding the crosstalk measuring method of the present embodiment, on the basis of the crosstalk measuring method of the first embodiment, in the connection step S1, the other end 18 of the core 11 is optically connected to the other end 18 of the core 13 via the core of the second optical fiber 52 having a length different from that of the core of the first optical fiber 51. In the first measuring step S2, the power of the output light emitted from one end 17 of the core 11 is further measured by the OTDR 20. The output light includes pulsed light, which is composed of the following optical multiplexing, namely: light generated by the crosstalk of the incident light L from the core 11 to the core 13, and light generated by the crosstalk from the core 13 to the core 11 due to the incident light L incident from the core 11 to the core 13 via the core of the second optical fiber 52. In the processing step S3, the power of the output light including the pulsed crosstalk light CL2 generated by the crosstalk between the core 11 and the core 13 is used to further calculate the size of the crosstalk between the core 11 and the core 13.

[0160] In addition, regarding the crosstalk measuring device 1 of the present embodiment, on the basis of the crosstalk measuring device 1 of the first embodiment, it also has a core of a second optical fiber 52 whose length is different from the core of the first optical fiber 51, and the core of the second optical fiber 52 optically connects the other end 18 of the core 11 with the other end 18 of the core 13. The OTDR 20 further measures the power of the output light emitted from one end 17 of the core 11, and the output light includes pulsed light, which is formed by the following optical synthesis, namely: light generated by the crosstalk of the incident light L from the core 11 to the core 13, and light generated by the crosstalk from the core 13 to the core 11 due to the incident light L incident from the core 11 to the core 13 via the core of the second optical fiber 52. The processing unit 25 uses the power of the output light including the pulsed crosstalk light CL2 generated by the crosstalk between the core 11 and the core 13 to further calculate the size of the crosstalk between the core 11 and the core 13.

[0161] According to the crosstalk measurement method and the crosstalk measurement device 1 of the present embodiment, the outgoing light including the crosstalk light between the core 11 and the core 12 and the outgoing light including the crosstalk light between the core 11 and the core 13 can be received by the OTDR 20, and the power of each outgoing light can be measured, so that the magnitude of each crosstalk can be obtained. Therefore, compared with the case where the magnitude of the crosstalk between the core 11 and the core 12 is measured, and then the core 11 and the core 13 are optically connected by a connecting optical waveguide, and the incident light is again incident from the one end 17 of the core 11 to measure the magnitude of the crosstalk between the core 11 and the core 13 as in the first embodiment, the magnitude of the crosstalk between the core 11 and the core 12 and the magnitude of the crosstalk between the core 11 and the core 13 can be easily measured.

[0162] In addition, although the second optical fiber 52 is longer than the first optical fiber 51 in the present embodiment, the first optical fiber 51 may be longer than the second optical fiber 52 as long as the length of the first optical fiber 51 is different from the length of the second optical fiber 52 .

[0163] (Fourth Embodiment)

[0164] Next, refer to Fig.13 The fourth embodiment of the present invention will be described in detail. Unless otherwise specified, components identical or equivalent to those of the above-described embodiment are denoted by the same reference numerals and duplicate descriptions are omitted.

[0165] Fig.13 is with Figure 4 The figure of the crosstalk measurement device of this embodiment is similarly described. The crosstalk measurement device 1 of this embodiment is different from the crosstalk measurement device 1 of the first embodiment in that a second optical fiber 52 is provided, and one end 17 of the core 12 as the second optical waveguide and one end of the core 13 as the third optical waveguide are optically connected via the core of the second optical fiber 52 as the second connecting optical waveguide. In this embodiment, the length of the first optical fiber 51 and the length of the second optical fiber 52 may be different from each other or the same.

[0166] The process of the crosstalk measurement method of this embodiment performed using such a crosstalk measurement device 1 is similar to Figure 3 The flowchart shown is the same. However, each step has the following differences. The following mainly describes the differences.

[0167] (Connection step S1)

[0168] In this step of the present embodiment, in addition to the connection step S1 of the first embodiment, one end 17 of the core 12 is optically connected to one end 17 of the core 13 via the core of the second optical fiber 52. Specifically, one end of the second optical fiber 52 is connected to the optical fiber 32 of the fan-in fan-out device 30, and the other end of the second optical fiber 52 is connected to the optical fiber 33 of the fan-in fan-out device 30. In this way, the core 12 and the core 13 are optically connected.

[0169] (First Measurement Step S2)

[0170] In this step of the present embodiment, incident light L is made incident from the OTDR 20 to the core 11, similarly to the first embodiment. In the present embodiment, in addition to the crosstalk between the core 11 and the core 12 described in the first embodiment, crosstalk is generated and measured as follows. This is described below.

[0171] The incident light L from the OTDR 20 that enters the core 11 propagates from the one end 17 to the other end 18 in the core 11, and then enters the core 12 via the first optical fiber 51. The incident light L that propagates from the other end 18 to the one end 17 in the core 12 crosstalks from the core 12 to the core 11, and crosstalks from the core 12 to the core 13, as described in the first embodiment. The light that crosstalks from the core 12 to the core 13 is also in a pulse shape, and propagates from the other end 18 side of the core 13 to the one end 17 while being substantially parallel to the incident light L. The power of the crosstalk light CL2 increases according to the distance propagated in the core 13. The incident light L enters the core 13 from the core 12 via the second optical fiber 52, and the crosstalk light CL2 enters the core 12 from the core 13 via the second optical fiber 52. The incident light L and the crosstalk light CL2 intersect at approximately the midpoint of the second optical fiber 52. Therefore, the moment when the incident light L is incident on the core 13 is approximately the same as the moment when the crosstalk light CL2 is incident on the core 12. The incident light L incident on the core 13 and the crosstalk light CL2 incident on the core 12 propagate from one end 17 to the other end 18 in each core 13 and 12 while being approximately parallel. During this period, the incident light L propagating in the core 13 also propagates while crosstalking to the core 12. Therefore, the light crosstalking from the core 13 to the core 12 is combined with the crosstalk light CL2 propagating in the core 12. The combined light is in a pulse shape and propagates while gradually increasing in power. The pulsed light including the crosstalk light CL2 is incident on the core 11 from the core 12 via the first optical fiber 51, and the outgoing light formed by combining the backscattered light and the crosstalk light CL2 is emitted from one end 17 of the core 11. Therefore, the outgoing light includes the pulsed crosstalk light CL2. The outgoing light emitted from the core 11 is incident on the OTDR 20, is received by the OTDR 20, and the power thereof is measured by the OTDR 20.

[0172] The time when the outgoing light including the crosstalk light CL2 enters the OTDR 20 is delayed by the time when the outgoing light including the crosstalk light CL1 enters the OTDR 20, and the time when the light propagates in the second optical fiber 52, the core 12, the first optical fiber 51, and the core 11. Therefore, the OTDR 20 can measure these outgoing lights separately. Therefore, the OTDR 20 performs power measurement of the pulsed light twice.

[0173] (Processing step S3)

[0174] In this step, the processing unit 25 uses the measured power of the emitted light to obtain the magnitude of the crosstalk between the core 11 and the core 12, similarly to the first embodiment. In this step of the present embodiment, the processing unit 25 obtains the magnitude of the crosstalk between the core 12 and the core 13. The method of obtaining the crosstalk between the core 12 and the core 13 is the same as the method of obtaining the crosstalk between the core 11 and the core 13 of the third embodiment.

[0175] As in the first embodiment, the processing unit 25 converts the power of the crosstalk light CL1 obtained into the magnitude of the crosstalk and outputs it, and converts the power of the crosstalk light CL2 obtained into the magnitude of the crosstalk and outputs it. At this time, the processing unit 25 may convert the magnitude of the crosstalk into decibels representing the ratio of the power of the incident light L emitted from the other end 18 of the core 13 and output it. In addition, the processing unit 25 may convert it into decibels representing the ratio to the specified power set in the OTDR 20 and output it. In this way, the magnitude of the crosstalk between the core 11 and the core 12 is obtained, and the magnitude of the crosstalk between the core 11 and the core 13 is obtained.

[0176] Regarding the crosstalk measurement method of the present embodiment, on the basis of the crosstalk measurement method of the first embodiment, in the connection step S1, one end 17 of the core 12 is optically connected to one end 17 of the core 13 via the core of the second optical fiber 52. In the first measurement step S2, the power of the output light emitted from the one end 17 of the core 11 via the first optical fiber 51 and the core 11 is further measured by the OTDR20. The output light includes pulsed light, which is composed of the following light combinations, namely: light generated due to crosstalk of the incident light L from the core 12 to the core 13, and light generated due to crosstalk of the incident light L from the core 12 to the core 13 via the core of the second optical fiber 52. In the processing step S3, the power of the output light including the pulsed crosstalk light CL2 generated by the crosstalk between the core 12 and the core 13 is used to further determine the size of the crosstalk between the core 12 and the core 13.

[0177] In addition, regarding the crosstalk measuring device 1 of the present embodiment, on the basis of the crosstalk measuring device 1 of the first embodiment, it also has a core of a second optical fiber 52, and the core of the second optical fiber 52 optically connects one end 17 of the core 12 with one end 17 of the core 13. The OTDR 20 further measures: the power of the output light emitted from the one end 17 of the core 11 via the first optical fiber 51 and the core 11, and the output light includes pulsed light, and the pulsed light is formed by the following light synthesis, namely: light generated due to the crosstalk of the incident light L from the core 12 to the core 13, and light generated due to the crosstalk of the incident light L incident from the core 12 to the core 13 via the core of the second optical fiber 52 from the core 12 to the core 13. The processing unit 25 uses the power of the output light including the pulsed crosstalk light CL2 generated by the crosstalk between the core 12 and the core 13 to further calculate the size of the crosstalk between the core 12 and the core 13.

[0178] According to the crosstalk measurement method and the crosstalk measurement device 1 of the present embodiment, the outgoing light including the crosstalk light between the core 11 and the core 12 and the outgoing light including the crosstalk light between the core 12 and the core 13 can be received by the OTDR 20, and the power of each outgoing light can be measured, so that the magnitude of each crosstalk can be obtained. Therefore, compared with the case where the magnitude of the crosstalk between the core 11 and the core 12 is measured, and then the core 12 and the core 13 are optically connected by the connecting optical waveguide, and the incident light is again incident from the one end 17 of the core 11 to measure the magnitude of the crosstalk between the core 12 and the core 13 as in the first embodiment, the magnitude of the crosstalk between the core 11 and the core 12 and the magnitude of the crosstalk between the core 12 and the core 13 can be easily measured.

[0179] In addition, in this embodiment, if Fig. 9 As shown, a second measuring step S22 may be provided after the first measuring step S2. In this case, in the second measuring step S22, the pulsed incident light L emitted from the OTDR 20 is incident from the other end 18 of the core 13. The OTDR 20 measures the power of the output light emitted from the other end 18 of the core 13, the output light including the pulsed light, which is a combination of the light generated by the crosstalk of the incident light L from the core 13 to the core 12 and the light generated by the crosstalk of the incident light L from the core 12 to the core 13 via the second optical fiber 52. In addition, the OTDR 20 measures the power of the outgoing light emitted from the one end 17 of the core 12 through the second optical fiber 52 and the core 13 from the other end 18 of the core 13, the outgoing light including pulsed light obtained by combining the following light: light generated by crosstalk from the core 12 to the core 11 when the incident light L propagates from the one end 17 to the other end 18 in the core 12, and light generated by crosstalk from the core 11 to the core 12 due to the incident light L incident on the core 11 through the first optical fiber 51. In this case, in the processing step S3, the magnitude of the crosstalk between the core 12 and the core 13 is obtained using the power of the outgoing light measured in the first measuring step S2 and the power of the outgoing light measured in the second measuring step S22, as in the second embodiment.

[0180] (Fifth Embodiment)

[0181] Next, refer to Fig.14 The fourth embodiment of the present invention will be described in detail. Unless otherwise specified, components identical or equivalent to those of the above-described embodiment are denoted by the same reference numerals and duplicate descriptions are omitted.

[0182] Fig.14 is with Figure 4The figure of the crosstalk measurement device of this embodiment is similarly described. The crosstalk measurement device 1 of this embodiment is different from the crosstalk measurement device 1 of the first embodiment in that a second optical fiber 52 as a second connecting waveguide is provided, and one end 17 of the core 12 as the second optical waveguide and the other end of the core 13 as the third optical waveguide are optically connected via the second optical fiber 52. In this embodiment, the length of the first optical fiber 51 and the length of the second optical fiber 52 may be different from each other or may be the same.

[0183] The process of the crosstalk measurement method of this embodiment performed using such a crosstalk measurement device 1 is similar to Figure 3 The flowchart shown is the same. However, each step has the following differences. The following mainly describes the differences.

[0184] (Connection step S1)

[0185] In this step of the present embodiment, in addition to the connection step S1 of the first embodiment, one end 17 of the core 12 is optically connected to the other end 18 of the core 13 via the core of the second optical fiber 52. Specifically, one end of the second optical fiber 52 is connected to the optical fiber 32 of the fan-in fan-out device 30, and the other end of the second optical fiber 52 is connected to the optical fiber 43 of the fan-in fan-out device 40. In this way, the core 12 and the core 13 are optically connected.

[0186] (First Measurement Step S2)

[0187] In this step of the present embodiment, incident light L is made incident from the OTDR 20 to the core 11, similarly to the first embodiment. In the present embodiment, in addition to the crosstalk between the core 11 and the core 12 described in the first embodiment, crosstalk is generated and measured as follows. This is described below.

[0188] Regarding the incident light L from the OTDR 20 that enters the core 11, the incident light L propagates from one end 17 to the other end 18 in the core 11, while crosstalking from the core 11 to the core 12 and from the core 11 to the core 13. The light that crosstalks from the core 11 to the core 13 is also in a pulsed state, and propagates from the one end 17 side of the core 13 to the other end 18 while being approximately parallel to the incident light L. The power of the crosstalk light CL2 increases according to the distance propagated in the core 13. The incident light L and the crosstalk light CL2 arrive at the other end 18 at approximately the same time. The incident light L enters the core 13 from the other end 18 of the core 11 via the first optical fiber 51, the core 12, and the second optical fiber 52. In addition, the crosstalk light CL2 enters the core 11 from the other end 18 of the core 13 via the second optical fiber 52, the core 12, and the first optical fiber 51. The incident light L and the crosstalk light CL2 intersect at the approximate midpoint of the waveguide formed by combining the core of the first optical fiber 51, the core 12, and the core of the second optical fiber 52. Therefore, the time when the incident light L enters the core 13 is approximately the same as the time when the crosstalk light CL2 enters the core 11. The incident light L entering the core 13 and the crosstalk light CL2 entering the core 11 propagate from the other end 18 to the one end 17 in each core 13 and 11 while being approximately parallel. During this period, the incident light L propagating in the core 13 also propagates while crosstalking to the core 11. Therefore, the light crosstalking from the core 13 to the core 11 is combined with the crosstalk light CL2 propagating in the core 11. The combined light is in a pulsed shape and propagates while gradually increasing in power. The outgoing light formed by combining the backscattered light and the pulsed crosstalk light CL2 is emitted from one end 17 of the core 11. Therefore, the outgoing light includes the pulsed crosstalk light CL2. The outgoing light emitted from the core 11 is incident on the OTDR 20, received by the OTDR 20, and its power is measured by the OTDR 20.

[0189] The time when the outgoing light including the crosstalk light CL2 enters the OTDR 20 is delayed by the time when the outgoing light including the crosstalk light CL1 enters the OTDR 20, and the time when the light propagates in the second optical fiber 52 and the core 13. Therefore, the OTDR 20 can measure these outgoing lights separately. Therefore, the OTDR 20 performs two power measurements on the pulsed light.

[0190] (Processing step S3)

[0191] In this step, the processing unit 25 uses the measured power of the emitted light to obtain the magnitude of the crosstalk between the core 11 and the core 12, similarly to the first embodiment. In this step of the present embodiment, the processing unit 25 obtains the magnitude of the crosstalk between the core 11 and the core 13. The method of obtaining the crosstalk between the core 11 and the core 13 is the same as the method of obtaining the crosstalk between the core 11 and the core 13 of the third embodiment.

[0192] As in the first embodiment, the processing unit 25 converts the power of the crosstalk light CL1 obtained into the magnitude of the crosstalk and outputs it, and converts the power of the crosstalk light CL2 obtained into the magnitude of the crosstalk and outputs it. At this time, the processing unit 25 may convert the magnitude of the crosstalk into decibels representing the ratio of the power of the incident light L emitted from one end 17 of the core 13 and output it. In addition, the processing unit 25 may convert it into decibels representing the ratio to the specified power set in the OTDR 20 and output it. In this way, the magnitude of the crosstalk between the core 11 and the core 12 is obtained, and the magnitude of the crosstalk between the core 11 and the core 13 is obtained.

[0193] Regarding the crosstalk measurement method of the present embodiment, on the basis of the crosstalk measurement method of the first embodiment, in the connection step S1, one end 17 of the core 12 is optically connected to the other end 18 of the core 13 via the core of the second optical fiber 52. In the first measurement step S2, the power of the output light emitted from the one end 17 of the core 11 is further measured by the OTDR20. The output light includes pulsed light, which is composed of the following optical multiplexing, namely: light generated by the crosstalk of the incident light L from the core 11 to the core 13, and light generated by the crosstalk from the incident light L incident from the core 11 to the core 13 via the core 12 and the core of the second optical fiber 52. In the processing step S3, the power of the output light including the pulsed crosstalk light CL2 generated by the crosstalk between the core 11 and the core 13 is used to further calculate the size of the crosstalk between the core 11 and the core 13.

[0194] In addition, regarding the crosstalk measuring device 1 of the present embodiment, on the basis of the crosstalk measuring device 1 of the first embodiment, it also has a core of a second optical fiber 52, and the core of the second optical fiber 52 optically connects one end 17 of the core 12 with the other end 18 of the core 13. The OTDR 20 further measures the power of the output light emitted from the one end 17 of the core 11, and the output light includes pulsed light, which is formed by the following optical synthesis, namely: light generated by the crosstalk of the incident light L from the core 11 to the core 13, and light generated by the crosstalk from the core 13 to the core 11 due to the incident light L incident from the core 11 to the core 13 via the core 12 and the core of the second optical fiber 52. The processing unit 25 uses the power of the output light including the pulsed crosstalk light CL2 generated by the crosstalk between the core 11 and the core 13 to further calculate the size of the crosstalk between the core 11 and the core 13.

[0195] According to the crosstalk measurement method and the crosstalk measurement device 1 of the present embodiment, the outgoing light including the crosstalk light between the core 11 and the core 12 and the outgoing light including the crosstalk light between the core 11 and the core 13 can be received by the OTDR 20, and the power of each outgoing light can be measured, so that the magnitude of each crosstalk can be obtained. Therefore, compared with the case where the magnitude of the crosstalk between the core 11 and the core 12 is measured, and then the core 11 and the core 13 are optically connected by a connecting optical waveguide, and the incident light is again incident from the one end 17 of the core 11 to measure the magnitude of the crosstalk between the core 11 and the core 13 as in the first embodiment, the magnitude of the crosstalk between the core 11 and the core 12 and the magnitude of the crosstalk between the core 11 and the core 13 can be easily measured.

[0196] In addition, in this embodiment, if Fig. 9As shown, a second measuring step S22 may be provided after the first measuring step S2. In this case, in the second measuring step S22, the pulsed incident light L emitted from the OTDR 20 is incident from one end 17 of the core 13. The OTDR 20 measures the power of the output light emitted from the one end 17 of the core 13, the output light including the pulsed light, which is a combination of the light generated by the crosstalk of the incident light L from the core 13 to the core 11 and the light generated by the crosstalk of the incident light L from the core 11 to the core 13 which is incident from the core 13 to the core 11 via the second optical fiber 52, the core 12, and the first optical fiber 51. In addition, the OTDR 20 measures the power of the outgoing light emitted from the one end 17 of the core 12 via the second optical fiber 52 and the core 13, the outgoing light including pulsed light obtained by combining the light generated by crosstalk from the core 12 to the core 11 when the incident light L propagates from the one end 17 to the other end 18 in the core 12, and the light generated by crosstalk from the core 11 to the core 12 due to the incident light L incident on the core 11 via the first optical fiber 51. In this case, in the processing step S3, the magnitude of the crosstalk between the core 11 and the core 13 is obtained using the power of the outgoing light measured in the first measuring step S2 and the power of the outgoing light measured in the second measuring step S22, as in the second embodiment.

[0197] As mentioned above, although the present invention has been described by taking the above-mentioned embodiment as an example, the present invention is not limited thereto.

[0198] For example, the arrangement and number of cores of the multi-core optical fiber 10 may be different from those in the above-described embodiment.

[0199] In addition, in the above-mentioned embodiment, a multi-core optical 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 optical fiber. For example, it can be applied to the crosstalk measurement of the following optical devices, namely: an optical cable in which a plurality of optical fibers are arranged, an optical fiber ribbon in which a plurality of optical fibers are arranged in a plane, a multi-element optical fiber in which a plurality of bare optical fibers are arranged in a covering layer, and an entire transmission system.

[0200] Furthermore, in at least one of the first measuring step S2 and the second measuring step S22 of the above embodiment, at least one of light loss, reflection intensity, bending loss and disconnection in an optical device such as the multi-core optical fiber 10 may be further measured by the OTDR 20 .

[0201] In addition, the form of the fan-in fan-out devices 30 and 40 is not particularly limited. In addition, the crosstalk measurement device 1 may not include at least one of the fan-in fan-out device 30 and the fan-in fan-out device 40. In this case, for example, the core of the multi-core optical fiber 10 is directly connected to the core of the first optical fiber 51 and the core of the second optical fiber 52. In addition, at least one of the first optical fiber 51 and the second optical fiber 52 may be composed of a connection body of multiple optical fibers.

[0202] In the above embodiment, for example, Figure 5 As shown, the slope of the power of the backscattered light measured by the OTDR 20 is substantially the same in the intervals of the core 11, the core 12, the first optical fiber 51, etc. This means that the loss of the incident light L per unit length caused by backscattering is substantially the same in the intervals of the core 11, the core 12, the first optical fiber 51, etc. Therefore, in the above-mentioned embodiment, when the core 11, the core 12, the first optical fiber 51, etc. propagate light of the same power, the power of the backscattered light per unit length generated in each interval is substantially the same. However, when the core 11, the core 12, the first optical fiber 51, etc. propagate light of the same power, it is preferred that the power of the backscattered light per unit length generated in the first optical fiber 51 is smaller than the power of the backscattered light per unit length generated in the core 11 and the core 12, respectively. As such a first optical fiber 51, for example, a hollow core optical fiber having a hollow core can be cited. Alternatively, the first optical fiber 51 may be an optical fiber in which the relative refractive index difference of the core of the first optical fiber 51 is smaller than that of the light propagating in the core of the multi-core optical fiber 10, and the effective cross-sectional area of ​​the propagating light is larger. This is because the power of the backscattered light is proportional to the numerical aperture (NA) corresponding to the relative refractive index difference. Fig.15 It means in Figure 4 Schematic diagram of the measurement results of OTDR20 when the hollow core fiber is used as the first optical fiber 51. Fig.15 , is a schematic diagram of the measurement results when using a dual-core multi-core optical fiber. Fig.15 As shown, it can be seen that almost no backscattered light is generated in the first optical fiber 51. Therefore, the ratio of the power of the crosstalk light to the power of the backscattered light increases, and the crosstalk light can be easily detected. In addition, for the same reasons as above, it is preferred that the power of the backscattered light per unit length generated in the second optical fiber 52 in the third embodiment to the fifth embodiment is smaller than the power of the backscattered light per unit length generated in the core 11 to the core 13, respectively.

[0203] In addition, in the first embodiment, if Figure 2 , Figure 4 As shown in the figure, the example in which the cores 13 and 14 are not connected to each other by optical fibers is described. However, the present invention is not limited to this. Fig.16 FIG. 2 is a diagram showing a modified example of the crosstalk measurement device of the first embodiment. Fig.16 As shown, the difference between this modification and the first embodiment is that the optical fibers 43 and 44 of the fan-in and fan-out device 40 are connected to the second optical fiber 52, and the other end 18 of the core 13 and the other end 18 of the core 14 are optically connected via the core of the second optical fiber 52. The length of the second optical fiber 52 is the same as that of the first optical fiber 51. Therefore, the distance that the light propagates from the other end 18 of the core 13 to the other end 18 of the core 14 is the same as the distance that the light propagates from the other end 18 of the core 11 to the other end 18 of the core 12. In the first embodiment, the crosstalk light CL1 of the incident light crosstalking from the core 11 to the core 12 and the pulsed light formed by combining the crosstalk light CL1 of the incident light crosstalking from the core 12 to the core 11 are measured. However, the crosstalk light CL1 of the incident light crosstalking from the core 11 to the core 12 also includes the light that crosstalks from the core 11 to the cores 13 and 14 and further crosstalks to the core 12. Similarly, the light that crosstalks from the core 12 to the core 11 also includes the light that crosstalks from the core 12 to the cores 13 and 14 and further crosstalks to the core 11. In the first embodiment, since there is no optical connection between the core 13 and the core 14, the light that does not crosstalk to the core 12 among the light that crosstalks from the core 11 to the core 13 and 14 is emitted from the other end 18. However, according to the present modification, the light that does not crosstalk to the core 12 among the light that crosstalks from the core 11 to the core 13 enters the core 14 via the second optical fiber 52, and the light that does not crosstalk to the core 12 among the light that crosstalks from the core 11 to the core 14 enters the core 13 via the second optical fiber 52. The light that is incident on the cores 13 and 14 via the second optical fiber 52 further crosstalks to the core 12 when propagating from the other end 18 side to the one end 17 side in the cores 13 and 14. Furthermore, as described above, the distance that light propagates from the other end 18 of the core 13 to the other end 18 of the core 14 is the same as the distance that light propagates from the other end 18 of the core 11 to the other end 18 of the core 12. Therefore, the time when the crosstalk light CL1 emitted from the other end of the core 12 enters the other end of the core 11 is substantially the same as the time when the light that crosstalks from the core 11 to the cores 13 and 14 and no longer crosstalks to the core 12 enters the cores 14 and 13 via the second optical fiber 52. According to such a configuration, the light that crosstalks to the core 12 via the cores 13 and 14 is reflected as the crosstalk light CL1 in both the outgoing and returning paths. Therefore, in this variation, the other ends 18 of the core 13 as the third waveguide and the core 14 as the fourth waveguide, which respectively crosstalk with the core 11 as the first optical waveguide and the core 12 as the second optical waveguide, are optically connected via the core of the second optical fiber 52 as the second connecting optical waveguide, so that the size of the crosstalk can be measured more accurately compared to the first embodiment.

[0204] As described above, according to the present invention, there are provided a crosstalk measurement method and a crosstalk measurement device, which can easily perform crosstalk measurement using the OTDR method and can be used in the field of optical fiber communication and the like.

Claims

1. A crosstalk measurement method, which is a crosstalk measurement method for an optical device, wherein the optical device has a first optical waveguide and a second optical waveguide which have one end and the other end and are arranged in parallel with each other, It is characterized in that The method comprises: a connection step, a first measurement step, and a processing step. In the connecting step, the other end of the first optical waveguide is optically connected to the other end of the second optical waveguide via a first connecting optical waveguide; In the first measurement step, a pulsed incident light emitted from an optical time domain reflectometer (OTDR) is made incident from the one end of the first optical waveguide, and the power of the output light emitted from the one end of the first optical waveguide is measured by the OTDR, wherein the output light includes pulsed light, and the pulsed light is a combination of light generated by crosstalk from the first optical waveguide to the second optical waveguide and light generated by crosstalk from the second optical waveguide to the first optical waveguide due to the incident light incident from the first optical waveguide to the second optical waveguide via the first connecting optical waveguide. In the processing step, the magnitude of crosstalk between the first optical waveguide and the second optical waveguide is obtained using the measured power of the outgoing light.

2. The crosstalk measurement method according to claim 1, characterized in that: The length of the first connection optical waveguide is longer than the half-value width of the incident light.

3. The crosstalk measurement method according to claim 1 or 2, characterized in that: The method further comprises a second measuring step, in which a pulsed incident light emitted from the OTDR is incident from one end of the second optical waveguide, and the power of the output light emitted from the one end of the second optical waveguide is measured by the OTDR, wherein the output light includes pulsed light, and the pulsed light is a combination of light generated by crosstalk from the second optical waveguide to the first optical waveguide and light generated by crosstalk from the first optical waveguide to the second optical waveguide due to the incident light incident from the second optical waveguide to the first optical waveguide via the first connecting optical waveguide. In the processing step, the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide is obtained using the power of the outgoing light measured in the first measuring step and the power of the outgoing light measured in the second measuring step.

4. The crosstalk measurement method according to claim 3, characterized in that: In the processing step, the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide is obtained using a result obtained by averaging the power of the outgoing light measured in the first measuring step and the power of the outgoing light measured in the second measuring step.

5. The crosstalk measurement method according to any one of claims 1 to 4, characterized in that: The wavelength width of the incident light is greater than 1 nm.

6. The crosstalk measurement method according to any one of claims 1 to 5, characterized in that: The OTDR and the first optical waveguide, the first optical waveguide and the first connecting optical waveguide, and the first connecting optical waveguide and the second optical waveguide are optically connected via fan-in and fan-out devices. In the processing step, the magnitude of the crosstalk in the fan-in fan-out device is removed to obtain the magnitude of the crosstalk between the first optical waveguide and the second optical waveguide.

7. The crosstalk measurement method according to any one of claims 1 to 6, characterized in that: The optical device further comprises a third optical waveguide arranged in parallel with the first optical waveguide. In the processing step, based on the obtained magnitude of the crosstalk between the first optical waveguide and the second optical waveguide, the magnitude of the crosstalk between the first optical waveguide and the third optical waveguide is further obtained.

8. The crosstalk measurement method according to any one of claims 1, 2, 5 and 6, characterized in that: The optical device further comprises a third optical waveguide arranged in parallel with the first optical waveguide. In the connecting step, the other end of the first optical waveguide and the other end of the third optical waveguide are optically connected via a second connecting optical waveguide having a length different from that of the first connecting optical waveguide. In the first measurement step, the power of the output light emitted from the one end of the first optical waveguide is further measured by the OTDR, the output light including pulsed light, the pulsed light being a combination of light generated by crosstalk from the first optical waveguide to the third optical waveguide and light generated by crosstalk from the third optical waveguide to the first optical waveguide due to the incident light incident from the first optical waveguide to the third optical waveguide via the second connecting optical waveguide, In the processing step, the magnitude of the crosstalk between the first optical waveguide and the third optical waveguide is further obtained using the power of the output light including the pulsed light generated by the crosstalk between the first optical waveguide and the third optical waveguide.

9. The crosstalk measurement method according to any one of claims 1, 2, 5 and 6, characterized in that: The optical device further comprises a third optical waveguide arranged in parallel with the second optical waveguide, In the connecting step, one end of the second optical waveguide and one end of the third optical waveguide are optically connected via a second connecting optical waveguide. In the first measurement step, the power of the output light emitted from the one end of the first optical waveguide via the first connecting optical waveguide and the first optical waveguide is further measured by the OTDR, the output light including pulsed light, the pulsed light being a combination of light generated by crosstalk from the second optical waveguide to the third optical waveguide due to the incident light incident from the first optical waveguide to the second optical waveguide via the first connecting optical waveguide, and light generated by crosstalk from the third optical waveguide to the second optical waveguide due to the incident light incident from the second optical waveguide to the third optical waveguide via the second connecting optical waveguide, In the processing step, the magnitude of the crosstalk between the second optical waveguide and the third optical waveguide is further obtained using the power of the output light including the pulsed light generated by the crosstalk between the second optical waveguide and the third optical waveguide.

10. The crosstalk measurement method according to any one of claims 1, 2, 5 and 6, characterized in that: The optical device further comprises a third optical waveguide arranged in parallel with the first optical waveguide. In the connecting step, one end of the second optical waveguide and the other end of the third optical waveguide are optically connected via a second connecting optical waveguide. In the first measurement step, the power of the output light emitted from the one end of the first optical waveguide is further measured by the OTDR, the output light including pulsed light, the pulsed light being a combination of light generated by crosstalk from the first optical waveguide to the third optical waveguide caused by the incident light incident from the OTDR to the first optical waveguide, and light generated by crosstalk from the third optical waveguide to the first optical waveguide caused by the incident light incident from the first optical waveguide to the third optical waveguide via the first connecting optical waveguide, the second optical waveguide, and the second connecting optical waveguide, In the processing step, the magnitude of the crosstalk between the first optical waveguide and the third optical waveguide is further obtained using the power of the output light including the pulsed light generated by the crosstalk between the first optical waveguide and the third optical waveguide.

11. The crosstalk measurement method according to any one of claims 1 to 10, characterized in that: In the first measurement step, at least one of light loss, reflection intensity, bending loss, and disconnection in the optical device is further measured by the OTDR.

12. The crosstalk measurement method according to any one of claims 1 to 11, characterized in that: When the first optical waveguide, the second optical waveguide, and the first connecting optical waveguide propagate light of the same power, the power of backscattered light per unit length generated in the first connecting optical waveguide is smaller than the power of backscattered light per unit length generated in the first optical waveguide and the second optical waveguide, respectively.

13. A crosstalk measurement device, which is a crosstalk measurement device for an optical device, wherein the optical device has a first optical waveguide and a second optical waveguide which have one end and the other end and are arranged in parallel with each other, It is characterized in that have: a first connecting optical waveguide optically connecting the other end of the first optical waveguide and the other end of the second optical waveguide; an OTDR that causes pulsed incident light to be incident from the one end of the first optical waveguide, and measures power of output light output from the one end of the first optical waveguide, wherein the output light includes pulsed light, the pulsed light being a combination of light generated by crosstalk from the first optical waveguide to the second optical waveguide and light generated by crosstalk from the second optical waveguide to the first optical waveguide due to the incident light incident from the first optical waveguide to the second optical waveguide via the first connecting optical waveguide; as well as A processing unit calculates the magnitude of crosstalk between the first optical waveguide and the second optical waveguide using the measured power of the outgoing light.

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