Measurement device and measurement method

Abstract

A measurement device 1 comprises a processing unit 11 that: employs a value obtained by dividing an effective non-linear coefficient of a coupled multi-core fiber by a non-linear reduction coefficient of the coupled multi-core fiber, which decreases non-linearly as the number of cores increases, as a non-linear coefficient for when the multi-core of the coupled multi-core fiber is assumed to be a single core; and calculates the effective cross-sectional area when the multi-core of a coupled multi-core fiber is assumed to be a single core, as the effective cross-sectional area of the coupled multi-core fiber, using the non-linear coefficient.

Description

Measuring device and measuring method

[0001] The present disclosure relates to a measurement device and a measurement method.

[0002] In optical fiber communication systems, the transmission capacity of optical fibers is limited by nonlinear effects that occur within the optical fiber. To alleviate this limitation, spatial multiplexing technologies are available, such as parallel transmission using a multicore fiber with multiple cores in one optical fiber, and mode multiplexing transmission using a multimode fiber with multiple modes (carrier modes) in one core (see Non-Patent Documents 1 to 4).

[0003] For example, in a single-mode multicore fiber in which each structure of multiple cores propagates a single mode, studies have been conducted on coupled multicore fibers in which the core structure and core spacing are adjusted so that the transmitted light propagating through each core is coupled to each other and random coupling is induced between the modes of each core (see Non-Patent Document 5).

[0004] It is known that coupled multicore fibers have lower nonlinearity than uncoupled multicore fibers in which the transmitted light from each core is not coupled to each other in optical transmission experiments (see Non-Patent Document 6). It is also known that coupled multicore fibers have low nonlinearity theoretically (see Non-Patent Document 7). Furthermore, a method for measuring the effective nonlinear coefficient of a coupled multicore fiber is also known (see Non-Patent Document 8).

[0005] H. Takara, 18 others, "1.01-Pb / s (12 SDM / 222 WDM / 456 Gb / s) Crosstalk-managed Transmission with 91.4-b / s / Hz Aggregate Spectral Efficiency", ECOC2012, Th.3.C.1.pdf T. Sakamoto, 3 others, "Differential Mode Delay Managed Transmission Line for WDM-MIMO System Using Multi-Step Index Fiber", Journal of Lightwave Technology, Vol.30, No.17, September 1, 2012, p.2783-p.2787 Y. Sasaki, 5 others, "Large-effective-Area Uncoupled Few-Mode Multi-Core Fiber", ECOC2012, Tu.1.F.3.pdf T. Ohara, 6 others, "Over-1000-Channel Ultradense WDM Transmission With Supercontinuum Multicarrier Source", Journal of Lightwave Technology, Vol.24, No.6, June 2006, p.2311-p.2317 T. Sakamoto, 5 others, "Fiber Twisting- and Bending-Induced Adiabatic / Nonadiabatic Super-Mode Transition in Coupled Multicore Fiber", Journal of Lightwave Technology, Vol.34, No.4, February 15, 2016, p.1228-p.1237 R. Ryf, 14 others, "Long-Haul Transmission over Multi-Core Fibers with Coupled Cores", Proc. of ECOC2017, M.2.E.1S.Mumtaz et al., “Nonlinear Propagation in Multimode and Multicore Fibers: Generalization of the Manakov Equations”, Journal of Lightwave Technology, Vol.31, No.3, February 1, 2013, p.398-p.406T. Sakamoto et al., “Characterization of Coupled Multi-core Fiber Nonlinearity using Modified CW-SPM Method”, OFC2023, W1C.2.

[0006] However, the effective area, which is an important design parameter of coupled multicore fibers, changes depending on the bending and twisting of the coupled multicore fiber, and therefore the calculation load for determining the effective area is high, making it difficult to accurately grasp it.

[0007] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a technique capable of calculating the effective area of ​​a coupled multi-core fiber.

[0008] A measurement device according to one aspect of the present disclosure includes a processing unit that defines a nonlinear coefficient when the multiple cores of the coupled multicore fiber are assumed to be single cores as a result of dividing an effective nonlinear coefficient of the coupled multicore fiber by a nonlinear reduction coefficient of the coupled multicore fiber, which nonlinearly reduces as the number of cores increases, and that uses the nonlinear coefficient to calculate an effective cross-sectional area when the multiple cores of the coupled multicore fiber are assumed to be single cores as the effective cross-sectional area of ​​the coupled multicore fiber.

[0009] A measurement device according to an aspect of the present disclosure measures γ, which indicates an effective nonlinear coefficient of a coupled multicore fiber, by k=1.0259×M, which indicates a nonlinear reduction coefficient of the coupled multicore fiber. －０．９１５９５ (M is the number of cores) is divided by γ, which indicates the nonlinear coefficient when the multiple cores of the coupled multicore fiber are assumed to be a single core. ０ and A represents the effective cross-sectional area when the multiple cores of the coupled multi-core fiber are assumed to be single cores. ０ｅｆｆ A ０ ｅｆｆ = (n ２ ω ０ ) / (cγ ０ ) (n ２ is the nonlinear refractive index, ω ０ is the angular frequency of light, and c is the speed of light in vacuum), and a processing unit for calculating the effective cross-sectional area of ​​the coupled multi-core fiber.

[0010] In a measurement method according to one aspect of the present disclosure, a measurement is performed using a measurement device, in which the effective nonlinear coefficient of a coupled multicore fiber is divided by a nonlinear reduction coefficient of the coupled multicore fiber, which nonlinearly reduces as the number of cores increases, to obtain a nonlinear coefficient when the multiple cores of the coupled multicore fiber are assumed to be single cores, and the effective cross-sectional area of ​​the coupled multicore fiber is calculated using the nonlinear coefficient to obtain the effective cross-sectional area when the multiple cores of the coupled multicore fiber are assumed to be single cores.

[0011] According to the present disclosure, it is possible to provide a technique capable of calculating the effective cross-sectional area of ​​a coupled multi-core fiber.

[0012] FIG. 1 is a diagram showing the configuration of a measurement device according to the first embodiment. ｋｌ ｅｆｆ 3 is a diagram showing the calculation results of the effective cross-sectional area A and the effective nonlinear coefficient γ. ０ ｅｆｆ 4 is a diagram showing the nonlinear reduction coefficient k relative to the number of cores M. FIG. 5 is a diagram showing the nonlinear reduction coefficient k relative to the number of cores M. FIG. 6 is a diagram showing the nonlinear reduction coefficient k relative to the number of cores M. FIG. 7 is a diagram showing the nonlinear reduction coefficient k relative to the number of cores M. ０ ｅｆｆ 7 is a diagram showing the configuration of a measurement system according to the second embodiment. FIG. 8 is a flowchart showing a method for calculating the effective cross-sectional area A ０ ｅｆｆ FIG. 1 is a flow chart showing a calculation method of

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same parts are designated by the same reference numerals and the description thereof will be omitted.

[0014] [Summary of the Present Disclosure] The present disclosure discloses a technique for measuring the effective cross-sectional area of ​​a coupled multi-core fiber (hereinafter, coupled MCF (Multi-Core Fiber)). Specifically, the effective cross-sectional area is calculated assuming that the multiple cores of the coupled MCF are a single core.

[0015] In this way, the effective area is calculated assuming that the multi-cores of a coupled MCF are a single core, so that the effective area is a value independent of bending or twisting. Therefore, the effective area, which is an important design parameter of a coupled MCF, can be calculated accurately and efficiently. As a result, it becomes possible to appropriately design optical fiber communication systems using coupled MCFs, and to provide users with communication networks with high transmission speeds and high-quality communication services.

[0016] 1 is a diagram showing the configuration of a measurement apparatus 1 according to the first embodiment. The measurement apparatus 1 is a measurement apparatus that measures (calculates) the effective cross-sectional area of ​​a coupled MCF.

[0017] A coupled MCF is an optical fiber in which light passing through each core in the MCF is coupled to each other and propagates. The effective area is an index that represents the effective distribution of optical power within the MCF. Specifically, the effective area is the area when the optical power of the fundamental mode propagating through the MCF is equalized within the cross section of the MCF.

[0018] The measurement device 1 includes a processing unit 11 , a display unit 12 , and a storage unit 13 .

[0019] The processing unit 11 has a function of calculating a value obtained by dividing an effective nonlinear coefficient of the coupled MCF (hereinafter referred to as the effective nonlinear coefficient) by a nonlinear reduction coefficient of the coupled MCF that nonlinearly reduces as the number of cores increases, and setting the value as the nonlinear coefficient when the multi-core of the coupled MCF is assumed to be a single core. The processing unit 11 also has a function of using the nonlinear coefficient to calculate an effective cross-sectional area when the multi-core of the coupled MCF is assumed to be a single core, and setting the effective cross-sectional area as the effective cross-sectional area of ​​the coupled MCF.

[0020] For example, the processing unit 11 converts γ, which indicates the effective nonlinear coefficient of the coupled MCF, into k=1.0259×M, which indicates the nonlinear reduction coefficient of the coupled MCF.－０．９１５９５ (M is the number of cores) is divided by γ, which indicates the nonlinear coefficient when the multi-core of the coupled MCF is assumed to be a single core. ０ (=γ / k). The processing unit 11 calculates A, which indicates the effective cross-sectional area when the multi-core of the coupled MCF is assumed to be a single core. ０ ｅｆｆ A ０ ｅｆｆ = (n ２ ω ０ ) / (cγ ０ ) (n ２ is the nonlinear refractive index, ω ０ is the angular frequency of light, c is the speed of light in a vacuum), and ０ ｅｆｆ is the effective cross-sectional area of ​​the coupled MCF.

[0021] The display unit 12 has a function of displaying the effective cross-sectional area of ​​the coupled MCF.

[0022] The storage unit 13 has a function of storing the effective cross-sectional area of ​​the coupled MCF and the like.

[0023] The measuring device 1 may be a measuring instrument for measuring the effective cross-sectional area of ​​a coupled MCF, or may be a computer equipped with a CPU, memory, storage, a communication device, an input device, an output device, and the like.

[0024] Next, the function of the processing unit 11 will be described in detail.

[0025] The nonlinear characteristics of coupled MCFs have been theoretically investigated based on the nonlinear Manakov equation (see Non-Patent Document 7).

[0026] First, the definition of the effective nonlinear coefficient in a coupled MCF will be explained. The equation describing multimode propagation with random coupling between modes is expressed by equation (1) (see equation (1) in Non-Patent Document 8).

[0027]

[0028] In equation (1), nonlinear effects other than fiber loss, higher-order chromatic dispersion, and self-phase modulation are ignored, and γ is the effective nonlinear coefficient of the coupled MCF.

[0029] In particular, the effective nonlinear coefficient γ of the coupled MCF is expressed as ｋｌ ｅｆｆ (See equation (3) in Non-Patent Document 8)

[0030]

[0031] M is the number of modes (= number of cores). ２ is the nonlinear refractive index. ０ is the central angular frequency of the propagating light, and c is the speed of light in a vacuum.

[0032] Effective cross-sectional area A of coupled MCF ｋｌ ｅｆｆ is expressed by equation (3).

[0033]

[0034] When k = l, the effective area of ​​the kth mode (intra-modal A ｅｆｆ When k≠l, the mutual effective cross section (inter-modal A) indicates the magnitude of the nonlinear effect between the kth mode and the lth mode. ｅｆｆ ) is shown.

[0035] Here, calculations have shown that the electric field distribution of a coupled MCF varies greatly depending on the bending diameter and bending direction (see Non-Patent Document 5). Therefore, when examining the nonlinear characteristics of a coupled MCF, the effective cross-sectional area A ｋｌ ｅｆｆ needs to be calculated.

[0036] FIG. 2 shows the effective cross-sectional area A of a two-core fiber coupled MCF. ｋｌ ｅｆｆ The core radius a is 4.5 μm, the relative refractive index difference Δ is 0.35%, the core spacing Λ is 20 μm, and the bending radius R is 80 mm. The bending angle θ is as shown in the figure.

[0037] In a two-core fiber coupled MCF, the fundamental mode (even mode) and the first higher-order mode (odd mode) exist as spatial modes (propagation modes). The effective cross-sectional area of ​​each mode is defined as A. １１ｅｆｆ , A ２２ ｅｆｆ In addition, the effective cross section between the two modes is A １２ ｅｆｆ , A ２１ ｅｆｆ Let's say.

[0038] The solid line shows the effective cross-sectional area A of the fundamental mode １１ ｅｆｆ The effective cross section A of the first higher mode ２２ ｅｆｆ is the effective cross-sectional area A of the fundamental mode １１ ｅｆｆ The dotted line indicates the effective cross-sectional area A １２ ｅｆｆ The effective cross-sectional area A between the other modes ２１ ｅｆｆ is the effective cross-sectional area A between one mode １２ ｅｆｆ is not shown in the figure.

[0039] Effective cross-sectional area A of the fundamental mode １１ ｅｆｆ is constant when the bending angle θ is between 0 and 80 degrees. On the other hand, the effective cross-sectional area A １２ ｅｆｆ decreases as the bending angle θ increases. １１ ｅｆｆ , A １２ ｅｆｆ When comparing these, it can be seen that there is a large deviation in the range of θ=0 to 80 degrees.

[0040] Next, the above two effective cross-sectional areas A １１ ｅｆｆ , A １２ ｅｆｆ The effective nonlinear coefficient γ was calculated for each bending angle θ using the formula: In FIG. 2, the calculation results of the effective nonlinear coefficient γ for each bending angle θ are shown by the dashed line. The effective nonlinear coefficient γ remains constant even when the bending angle θ increases. Therefore, it can be seen that the effective nonlinear coefficient γ does not depend on the bending direction.

[0041] The effective cross-sectional area A of the four-core fiber coupled MCF is also ｋｌ ｅｆｆThe bending direction dependence of the effective nonlinear coefficient γ was calculated, and the calculation results were similar to those of the two-core coupled MCF.

[0042] From the above, the effective nonlinear coefficient γ of the coupled MCF does not depend on the bending direction, so it is sufficient to use a value calculated at a specific bending angle. ｋｌ ｅｆｆ It is necessary to take bending and twisting into account when calculating.

[0043] However, the effective cross-sectional area A of the coupled MCF ｋｌ ｅｆｆ As can be seen from equation (3), a complex overlap integral calculation is required. Also, as can be seen from equation (2), calculations for each mode are required. In other words, the conventional method of rewriting equation (1) into equations (2) and (3) requires a high calculation load for the effective cross-sectional area of ​​the coupled MCF, making it difficult to calculate.

[0044] Therefore, in this embodiment, the effective nonlinear coefficient γ of the coupled MCF included in the formula (1) is expressed as kγ ０ and this is transformed into equation (4).

[0045]

[0046] k is the nonlinear reduction coefficient of the coupled MCF and is defined as in equation (5). That is, the conventional nonlinear reduction coefficient k (=Σ （ｋ≦ｌ） Ｍ (32 / 2 δｋｌ ) (1 / (6M(2M+1)))) for (A ０ ｅｆｆ / A ｋｌ ｅｆｆ ) multiplied by .

[0047]

[0048] gamma ０ is a nonlinear coefficient when the multi-core of the coupled MCF is assumed to be a single core, and is expressed by equation (6). ｋｌ ｅｆｆ The nonlinear coefficient γ (= (n ２ ω ０ ) / (cA ｋｌｅｆｆ )) instead of A ０ ｅｆｆ The nonlinear coefficient γ when the multi-core of the coupled MCF is assumed to be a single core is calculated using ０ is used.

[0049]

[0050] A ０ ｅｆｆ is the effective cross-sectional area when the coupled MCF is assumed to be a single core. ０ ｅｆｆ is the effective area calculated for a single-core fiber, and can be calculated using a simple calculation method that has been used for conventional single-mode fibers. ２ , ω ０ , c can also be easily obtained, so γ ０ As a result, the nonlinearity of the coupled MCF can be divided into two factors: the design of each core structure and the nonlinearity reduction coefficient k. In particular, in this embodiment, the nonlinearity reduction coefficient k is considered.

[0051] Here, the effective cross-sectional area A ０ ｅｆｆ The relationship between the nonlinear reduction coefficient k and the number of cores M will be explained.

[0052] FIG. 3(a) shows the effective cross-sectional area A of a 2-core fiber coupled MCF and a 4-core fiber coupled MCF when the optical power V is fixed at 2.21 and the core radius a is variable. ０ ｅｆｆ The core spacing Λ is set to 20 μm, and the bending radius R is set to 80 mm. ０ ｅｆｆ Although the nonlinearity reduction coefficient k varies greatly, it can be seen that a constant value is obtained for each number of cores M even if the core radius a changes.

[0053] FIG. 3(b) shows the effective cross-sectional area A when the core radius a is fixed at 4.5 μm and the optical power V value is changed. ０ ｅｆｆand the nonlinear reduction coefficient k. ０ ｅｆｆ Although the value of V changes significantly, it can be seen that the nonlinear reduction coefficient k has a constant value for each number of cores M even if the value of V changes.

[0054] We also varied the core arrangement, bending radius, and core-to-core distance, but confirmed that a constant value for the nonlinear reduction coefficient k was obtained for each number of cores, similar to the results shown in Figure 3.

[0055] 4 is a diagram showing the nonlinear reduction coefficient k versus the number of cores M. It can be seen that the k value decreases nonlinearly as the number of cores M increases. Approximating the curve of the nonlinear reduction coefficient k versus the number of cores M results in, for example, equation (7).

[0056]

[0057] 5 is a diagram showing specific values ​​of the nonlinear reduction coefficient k corresponding to a predetermined number of cores M. These are the values ​​of the plotted points shown in FIG. 4. For the coupled MCF described in Non-Patent Document 8, the effective cross-sectional area of ​​the coupled MCF calculated using Equations (2) and (3) is ｋｌ ｅｆｆ The calculated value of and the effective cross-sectional area A ０ ｅｆｆ and the effective cross-sectional area of ​​the coupled MCF calculated using the value of the nonlinear reduction coefficient k in FIG. ｋｌ ｅｆｆ As a result of comparing the calculated value of with, it was confirmed that the error was 0.3% or less.

[0058] From the above results, the effective cross-sectional area A when the multi-core of the coupled MCF is assumed to be a single core can be calculated by the procedure shown in FIG. ０ ｅｆｆ can be calculated from the effective nonlinear coefficient γ of the coupled MCF.

[0059] First, the processing unit 11 calculates the effective nonlinear coefficient γ of the coupled MCF to be measured using the method described in Non-Patent Document 8 (step S101).

[0060] Next, the processing unit 11 substitutes the number of cores M of the coupled MCF to be measured into the above formula (7) to calculate the nonlinearity reduction coefficient k of the coupled MCF to be measured.Then, the processing unit 11 calculates a value obtained by dividing the effective nonlinearity coefficient γ of the coupled MCF to be measured by the nonlinearity reduction coefficient k using the following formula (8), and calculates the nonlinearity coefficient γ when the multi-core of the coupled MCF to be measured is assumed to be a single core. ０ (step S102).

[0061]

[0062] Next, the processing unit 11 calculates the nonlinear coefficient γ of the coupled MCF to be measured. ０ is substituted into the following equation (9), and the effective cross-sectional area A is calculated when the multi-core of the coupled MCF to be measured is assumed to be a single core. ０ ｅｆｆ is calculated (step S103).

[0063]

[0064] Finally, the processing unit 11 calculates the effective cross-sectional area A ０ ｅｆｆ is output to the display unit 12 as the effective cross-sectional area of ​​the coupled MCF to be measured, and the effective cross-sectional area is stored in the storage unit 13 (step S104).

[0065] The effective cross-sectional area A of the thus obtained coupled MCF is ０ ｅｆｆ is a value that indicates the structure of each core of a coupled MCF that is independent of bending and twisting, and is a useful parameter in designing a coupled MCF.

[0066] The effective cross-sectional area A of the coupled MCF is ０ ｅｆｆ Another method for determining the effective cross-sectional area A is to measure the two-dimensional refractive index distribution and calculate it using the core radius and the refractive index difference. However, this method requires measuring the refractive index distribution, and the measurement results contain errors. Since the measurement results contain measurement errors, ０ ｅｆｆ It can be said that the accuracy of the calculation results is low.

[0067] There is also a method of obtaining the near-field pattern using a CCD camera, etc. However, since the dynamic range of the CCD camera is not sufficient, the effective cross-sectional area A ０ ｅｆｆ Therefore, the calculation result of the effective cross section A is highly accurate. ０ ｅｆｆ There is thought to be no alternative to measuring this.

[0068] According to this embodiment, the nonlinear coefficient γ when the multi-core of the coupled MCF is assumed to be a single core is calculated by dividing the effective nonlinear coefficient γ of the coupled MCF by the nonlinear reduction coefficient k of the coupled MCF, which reduces the nonlinearity as the number of cores increases. ０ and its nonlinear coefficient γ ０ The effective cross-sectional area A when the multi-core of the coupled MCF is assumed to be a single core using ０ ｅｆｆ is calculated as the effective cross-sectional area of ​​the coupled MCF, the effective cross-sectional area is a value independent of bending or twisting. Therefore, the effective cross-sectional area, which is an important design parameter of the coupled MCF, can be calculated accurately and efficiently.

[0069] According to this embodiment, γ, which indicates the effective nonlinear coefficient of the coupled MCF, is expressed as k=1.0259×M －０．９１５９５ (M is the number of cores) is divided by γ, which indicates the nonlinear coefficient when the multi-core of the coupled MCF is assumed to be a single core. ０ and A is the effective cross section when the multi-core of the coupled MCF is assumed to be a single core. ０ ｅｆｆ A ０ ｅｆｆ = (n ２ ω ０ ) / (cγ ０ ) (n ２ is the nonlinear refractive index, ω ０ Since the effective cross-sectional area of ​​the coupled MCF is calculated from the angular frequency of light (where ω is the angular frequency of light and c is the speed of light in a vacuum), the effective cross-sectional area is a value independent of bending or twisting. Therefore, the effective cross-sectional area, which is an important design parameter of the coupled MCF, can be calculated accurately and efficiently.

[0070] As a result of the above, it becomes possible to appropriately design an optical fiber communication system using coupled MCF, and it becomes possible to provide users with a communication network with high transmission speeds and high-quality communication services.

[0071] Second Embodiment In the first embodiment, a method for calculating the effective nonlinear coefficient γ of a coupled MCF in step S101 using the method described in Non-Patent Document 8. In the second embodiment, a method for calculating the effective nonlinear coefficient γ by utilizing self-phase modulation occurring in an optical fiber (CW-SPM method) will be described.

[0072] 7 is a diagram showing the configuration of a measurement system 100 according to the second embodiment. The measurement device 1 described in the first embodiment is a component of the measurement system 100.

[0073] Two continuous light beams with slightly different wavelengths (e.g., 1550.00 nm continuous light and 1550.28 nm continuous light) are output from two wavelength-tunable laser light sources 2 a and 2 b. These two continuous light beams are amplified by a pair of optical amplifiers 3 a and 3 b, respectively, combined by an optical fiber coupler 4, and then passed through an optical bandpass filter 5 and a first variable optical attenuator 6 to enter the coupled MCF 200 under measurement from an optical output port 7.

[0074] The spectrum transmitted through the coupled MCF 200 is received by an optical input port 8 and then by an optical spectrum analyzer 10 via a second variable optical attenuator 9. The optical spectrum analyzer 10 measures the amount of phase rotation of the waveform from the spectrum, and the measuring device 1 calculates the effective nonlinear coefficient γ of the coupled MCF 200 based on the measurement results. Note that the method of calculating the nonlinear coefficient γ from the measurement results of the amount of phase rotation of the waveform can be realized by an existing method (see, for example, Non-Patent Document 8).

[0075] FIG. 8 shows the effective cross-sectional area A of the coupled MCF according to the second embodiment. ０ ｅｆｆ FIG. 1 is a flow chart showing a calculation method of

[0076] First, the processing unit 11 acquires the spectrum of light transmitted through the coupled MCF 200 to be measured from the optical spectrum analyzer 10 (step S201).

[0077] Next, the processing unit 11 calculates the effective nonlinear coefficient γ of the coupled MCF 200 under measurement from the acquired spectrum based on the measurement result of the amount of phase rotation of the waveform measured by the optical spectrum analyzer 10 (step S202).

[0078] Finally, the processing unit 11 calculates the effective cross-sectional area A when the multi-core of the coupled MCF 200 to be measured is assumed to be a single core, from the effective nonlinear coefficient γ of the coupled MCF 200 to be measured, in the same manner as in steps S102 to S104 of the first embodiment. ０ ｅｆｆ Calculate the effective cross section A ０ ｅｆｆ is output to the display unit 12 as the effective cross-sectional area of ​​the coupled MCF to be measured, and the effective cross-sectional area is stored in the storage unit 13 (step S203).

[0079] REFERENCE SIGNS LIST 1 Measuring device 11 Processing unit 12 Display unit 13 Storage unit 2a, 2b Wavelength tunable laser light source 3a, 3b Optical amplifier 4 Optical fiber coupler 5 Optical bandpass filter 6 First variable optical attenuator 7 Optical output port 8 Optical input port 9 Second variable optical attenuator 10 Optical spectrum analyzer 100 Measurement system 200 Coupled MCF

Claims

1. A measuring device comprising: a processing unit that calculates an effective cross-sectional area of the combined multi-core fiber as the effective cross-sectional area of the combined multi-core fiber by using the non-linear coefficient, where the non-linear coefficient is a value obtained by dividing a value obtained by dividing the effective non-linear coefficient of the combined multi-core fiber by a non-linear reduction coefficient that non-linearly reduces as the number of cores increases, assuming that the multi-core of the combined multi-core fiber is a single core.

2. Let γ represent the effective nonlinear coefficient of the coupled multi-core fiber, and divide it by k = 1.0259×M －０．９１５９５ (where M is the number of cores) to obtain the nonlinear coefficient γ when the multi-core of the coupled multi-core fiber is assumed to be a single core. ０ Let A represent the effective cross-sectional area when the multi-core of the coupled multi-core fiber is assumed to be a single core. ０ ｅｆｆ Let A ０ ｅｆｆ = (n ２ ω ０ ) / (cγ ０ ) (where n ２ is the nonlinear refractive index, ω ０ is the angular frequency of light, and c is the speed of light in vacuum), and a processing unit that calculates the effective cross-sectional area of the coupled multi-core fiber. A measuring device comprising the processing unit.

3. The measuring device according to claim 1 or 2, wherein the processing unit obtains a spectrum that has passed through the combined multi-core fiber from an optical spectrum analyzer, calculates the effective non-linear coefficient of the combined multi-core fiber from the spectrum, and calculates the effective cross-sectional area of the combined multi-core fiber by using the calculated effective non-linear coefficient.

4. A measuring method performed by a measuring device, the method comprising: calculating, as a non-linear coefficient when assuming that the multi-core of the combined multi-core fiber is a single core, a value obtained by dividing the effective non-linear coefficient of the combined multi-core fiber by a non-linear reduction coefficient that non-linearly reduces as the number of cores increases; and calculating an effective cross-sectional area of the combined multi-core fiber as the effective cross-sectional area of the combined multi-core fiber by using the non-linear coefficient.

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