Connection loss difference measuring method, device and program

Abstract

The purpose of the present disclosure is to measure the difference between cores of connection loss at a connecting part by only using measurement from one end, even when non-joined multi-core fibers having different backscatter coefficients are connected.　In order to achieve this purpose, the present invention: inputs an optical pulse to each of a first core and a second core from one end of a non-joined multi-core fiber having a connecting part, and acquires an OTDR waveform for each of the first core and the second core; calculates, on the basis of the acquired OTDR waveform, the ratio between the backscatter intensity for the first core and the backscatter intensity for the second core for at least two points among one point further to the one end side than the connecting part and one point further to the other end side than the connecting part; and calculates the ratio between the calculated ratio at the one end side and the calculated ratio at the other end side.

Description

[Technical field]

[0001] The present disclosure relates to a connection loss difference measuring method, an apparatus, and a program for measuring the difference between cores in connection loss in an uncoupled multicore fiber having a connection portion. [Background technology]

[0002] Decoupled multicore fiber is one of the promising optical fibers for realizing large capacity optical communications in the future.

[0003] In uncoupled multicore fibers, multiple cores act as independent transmission paths for transmission, so crosstalk between the cores is an important characteristic. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] M. Nakazawa et al., “Nondestructive measurement of mode couplings along a multi-core fiber using a synchronous multi-channel OTDR,” Optics Express, vol. 20, no. 11, pp. 12530-12540, 2012. [Non-Patent Document 2] M. Ohashi et al., “Longitudinal fiber parameter measurements of multi-core fiber using OTDR,” Optics Express, vol. 22, no. 24, pp. 30137-30147, 2014. Summary of the Invention [Problem to be solved by the invention]

[0005] Crosstalk is a parameter that indicates the degree of interference between cores. Crosstalk is calculated by taking the ratio between the light intensities of each core of the light output from one end of an uncoupled multicore fiber when light is input from the other end, and expressing it as a logarithm. However, when two or more uncoupled multicore fibers are connected, the light intensity changes due to factors other than interference between cores, such as connection loss that occurs within the multicore fiber, making it impossible to accurately calculate crosstalk. Therefore, it is important to measure the connection loss.

[0006] Optical time domain reflectometry (OTDR) is widely used to measure the loss distribution of optical fibers. OTDR can obtain the splice loss from the change in the OTDR waveform before and after the splice of the optical fibers. Non-Patent Document 1 discloses a method for measuring a multi-core fiber using OTDR.

[0007] On the other hand, if the core diameters or relative refractive index differences between the multi-core fibers to be connected are different, that is, if the backscattering coefficients of the multi-core fibers to be connected are different, it is not possible to obtain the correct connection loss from the OTDR waveform measured from one end.

[0008] Non-Patent Document 2 discloses a method for separating loss components and components of backscattering coefficient differences caused by differences in fiber structure by using OTDR waveforms measured from both ends of a multicore fiber transmission line.

[0009] However, when considering testing when constructing optical fiber transmission lines, testing from both ends of the transmission line is often difficult from an operational standpoint, and there was a need for a method to measure the connection loss at the connection point by testing from one end.

[0010] In addition, since crosstalk is expressed as the logarithm of the optical intensity ratio between cores, even if the connection loss for each core cannot be measured, it is sufficient to calculate crosstalk if the difference in connection loss between cores at the connection can be measured. Therefore, a method for measuring the difference in connection loss between cores at the connection is required to accurately calculate crosstalk.

[0011] In order to solve the above problem, the present disclosure aims to measure the difference in connection loss between cores at a connection portion by measuring from only one end, even when uncoupled multicore fibers with different backscattering coefficients are connected. [Means for solving the problem]

[0012] In order to achieve the above object, the connection loss difference measuring method, device, and program disclosed herein input an optical pulse to one end of each of two cores of a multicore fiber having a connection, acquire an OTDR waveform, and calculate the inter-core loss difference from the backscattered light intensity ratio between the cores before and after the connection.

[0013] Specifically, the connection loss difference measuring method according to the present disclosure includes: inputting an optical pulse into each of a first core and a second core from one end of an uncoupled multicore fiber having a connection portion, and acquiring an OTDR waveform in each of the first core and the second core; Calculating a ratio of a backscattering intensity in the first core to a backscattering intensity in the second core for at least two points, i.e., a point on the one end side of the connection portion and a point on the other end side of the connection portion, based on the acquired OTDR waveform; Calculating a ratio between the calculated ratio at the one end side and the calculated ratio at the other end side; Do the following.

[0014] Specifically, the connection loss difference measuring method according to the present disclosure includes: inputting an optical pulse into each of a first core and a second core from one end of an uncoupled multicore fiber having a connection portion, and acquiring an OTDR waveform in each of the first core and the second core; determining a loss in a splice of backscattered light intensity for each core based on the OTDR waveform; calculating a ratio between the loss of the first core and the loss of the second core; Do the following.

[0015] For example, the connection loss difference measuring method according to the present disclosure includes: The backscattering intensity P in the first core at a distance z from the one end m Using formula (C1) for (z), The backscattering intensity P in the second core at the distance z n Use formula (C2) for (z).

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[0016] Specifically, the connection loss difference measuring device according to the present disclosure comprises: an OTDR measurement unit that acquires OTDR waveforms in a first core and a second core from one end of an uncoupled multicore fiber having a connection portion; a calculation processing unit that calculates a ratio of the backscattering intensity in the first core to the backscattering intensity in the second core for at least two points, i.e., a point on the one end side of the connection portion and a point on the other end side of the connection portion, based on the OTDR waveform acquired by the OTDR measurement unit, and calculates a ratio between the calculated ratio on the one end side and the calculated ratio on the other end side; Equipped with.

[0017] Specifically, the connection loss difference measuring device according to the present disclosure comprises: an OTDR measurement unit that acquires OTDR waveforms in a first core and a second core from one end of an uncoupled multicore fiber having a connection portion; and a calculation processing unit that obtains, for each core, a loss in a connection portion of backscattered light intensity based on the OTDR waveform, and calculates a ratio of the loss in the first core to the loss in the second core.

[0018] For example, in the connection loss difference measuring device according to the present disclosure, The arithmetic processing unit is The backscattering intensity P in the first core at a distance z from the one end m Using formula (C3) for (z), The backscattering intensity P in the second core at the distance z n Use formula (C4) for (z).

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[0019] Specifically, the program according to the present disclosure causes a computer to function as the arithmetic processing unit.

[0020] The above-mentioned inventions can be combined as much as possible. Effect of the Invention

[0021] According to the present disclosure, even when uncoupled multicore fibers with different backscattering coefficients are connected, the difference in connection loss between cores at the connection portion can be measured by measuring from only one end. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating an optical fiber under test according to a first embodiment. [Diagram 2] 1 shows an example of a schematic configuration of a connection loss difference measuring device according to a first embodiment. [Diagram 3] 2 shows an example of a procedure for a connection loss difference measuring method according to the first embodiment. [Figure 4] 2 shows an example of a procedure for a connection loss difference measuring method according to the first embodiment. [Diagram 5] FIG. 2 is a diagram illustrating a program according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings are assumed to indicate the same components.

[0024] (Embodiment 1) The optical fiber under test 20 to be measured by the splice loss difference measuring apparatus 10 according to the present embodiment will be described with reference to Figs. 1(a) and (b). The optical fiber under test 20 is an uncoupled multi-core fiber in which an uncoupled multi-core fiber 20A and an uncoupled multi-core fiber 20B are connected, and has a connection part 21. The optical fiber under test 20 has two or more cores. The optical fiber under test 20 in Fig. 1(a) shows only a first core 20#m and a second core 20#n to be measured among the two or more cores of the optical fiber under test 20. The following embodiments will also be described with the first core 20#m and the second core 20#n. The connection part 21 is at a distance z1 from one end 22 of the optical fiber under test 20 on the uncoupled multi-core fiber 20A side. That is, in the optical fiber under test 20, the distance z≦z1 is the uncoupled multi-core fiber 20A, and the distance z≧z1 is the uncoupled multi-core fiber 20B.

[0025] In this embodiment, as described later, an optical pulse is input from one end 22 to each of the first core 20#m and the second core 20#n to obtain an OTDR waveform. In FIG. 1(a), 23#m represents an example of an OTDR waveform of the first core 20#m when an optical pulse is input from one end 22 to the first core 20#m, and 23#n represents an example of an OTDR waveform of the second core 20#n when an optical pulse is input from one end 22 to the second core 20#n. The OTDR waveforms 23#m and 23#n represent the backscattered light intensity distribution with respect to the distance z on a logarithmic scale. FIG. 1(b) shows the ratio of the backscattered light intensity distribution between the OTDR waveform 23#m and the OTDR waveform 23#n on a logarithmic scale.

[0026] In the OTDR waveforms 23#m and 23#n, the backscattered light intensity distributions of the first core 20#m and the second core 20#n are represented by straight lines with the same slope in the uncoupled multi-core fiber 20A and the uncoupled multi-core fiber 20B. Therefore, in the uncoupled multi-core fiber 20A, the ratio of the backscattered light intensity distributions between the cores is constant. Also, in the uncoupled multi-core fiber 20B, the ratio of the backscattered light intensity distributions between the cores is constant.

[0027] On the other hand, in the OTDR waveforms 23#m and 23#n, at the distance z1 corresponding to the connection portion 21, a sudden increase or decrease (increase in FIG. 1) in the backscattered light intensity occurs in each of the first core 20#m and the second core 20#n. This sudden increase or decrease in the backscattered light intensity is considered to be caused by factors such as the connection loss at the connection portion 21 and the difference in the backscattered coefficient between the uncoupled multi-core fiber 20A and the uncoupled multi-core fiber 20B. In addition, the difference in the backscattered coefficient between the uncoupled multi-core fiber 20A and the uncoupled multi-core fiber 20B is often common between the cores. In such a case, by taking the ratio of the backscattered light intensity distribution between the OTDR waveforms 23#m and 23#n, the difference in the connection loss between the cores at the connection portion 21 can be extracted as shown in FIG. 1(b). Hereinafter, the difference in the connection loss between the cores at the connection portion 21 as shown in FIG. 1(b) is referred to as the connection loss difference. As shown in FIG. 1, the present invention calculates the connection loss difference using the OTDR waveforms of the first core 20#m and the second core 20#n.

[0028] An example of a schematic configuration of a connection loss difference measuring apparatus according to this embodiment is shown in Fig. 2. The connection loss difference measuring apparatus 10 according to this embodiment includes an OTDR measurement section 11 and an arithmetic processing section 15.

[0029] The OTDR measurement unit 11 includes a test light generation unit 12, an input / output unit 13, and a receiving unit 14. The OTDR measurement unit 11 acquires OTDR waveforms from one end of the optical fiber 20 under test to a first core 20#m and a second core 20#n.

[0030] The test light generating section 12 generates a test light pulse. The test light generating section 12 may have any configuration as long as it can generate and output a pulsed light, and may use, for example, a pulsed light source 12-1.

[0031] The input / output unit 13 inputs the test light pulse from the test light generating unit 12 to the optical fiber 20 under test, and outputs backscattered light from the optical fiber 20 under test to the receiving unit 14. The input / output unit 13 is made up of an optical circulator 13-1, an optical switch 13-2, and an input / output device 13-3.

[0032] 2, the first port is connected to the test light generating unit 12, the second port is connected to the optical switch 13-2, and the third port is connected to the receiving unit 14. The optical circulator 13-1 outputs the light input from the test light generating unit 12 connected to the first port to the optical switch 13-2 connected to the second port, and outputs the light input from the optical switch 13-2 connected to the second port to the receiving unit 14 connected to the third port.

[0033] The optical switch 13-2 switches the output destination of the light from the optical circulator 13-1 to the first core 20#m or the second core 20#n. Then, the optical switch 13-2 inputs the backscattered light from the core that is the output destination to the optical circulator 13-1.

[0034] The receiving unit 14 measures the intensity of the backscattered light from the input / output unit 13. As shown in Fig. 2, the receiving unit 14 is composed of a photoelectric converter 14-1 and an AD converter 14-2. The receiving unit 14 converts the backscattered light from the input / output unit 13 into an analog signal representing the intensity of the backscattered light by the photoelectric converter 14-1, and further converts the analog signal into a digital signal by the AD converter 14-2.

[0035] The arithmetic processing unit 15 includes a waveform analysis unit 15-1 and a splice loss difference calculation unit 15-2. The waveform analysis unit 15-1 receives a digital signal from the receiving unit 14. The waveform analysis unit 15-1 acquires an OTDR waveform from the received digital signal representing the backscattered light intensity. Specifically, the waveform analysis unit 15-1 calculates, for each received digital signal, the position in the optical fiber 20 under test where the backscattered light occurs as the distance from one end of the optical fiber 20 under test based on the reception time of the signal. Then, the waveform analysis unit 15-1 acquires an OTDR waveform which is a backscattered light intensity distribution with respect to the distance from one end of the optical fiber 20 under test.

[0036] The connection loss difference calculation unit 15-2 calculates the ratio of the backscattered light intensity in the first core 20#m to the backscattered light intensity in the second core 20#n for at least two points, i.e., one point on the one end side of the connection part 21 and one point on the other end side of the connection part, based on the OTDR waveform acquired by the waveform analysis unit 15-1, and calculates the ratio between the calculated ratio on the one end side and the calculated ratio on the other end side. Note that the connection part 21 may be specified from the OTDR waveform, or the distance z1 of the connection part may be input in advance to the connection loss difference calculation unit 15-2.

[0037] A description will now be given of a connection loss difference measuring method performed by the connection loss difference measuring apparatus 10 according to this embodiment. The connection loss difference measuring method according to this embodiment includes steps S101, S102, and S103.

[0038] (Step S101) The connection loss difference measuring device 10 inputs an optical pulse from the test light generating unit 12 to the first core 20#m via the optical switch 13-2, and obtains an OTDR waveform 23#m for the backscattered light in the first core 20#m. In this embodiment, the backscattered light intensity distribution P m An example of (z) is expressed by equation (1).

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[0039] The connection loss difference measuring device 10 inputs an optical pulse from the test light generating unit 12 to the second core 20#n via the optical switch 13-2, and obtains an OTDR waveform 23#n for the backscattered light in the second core 20#n. In this embodiment, the backscattered light intensity distribution P n An example of (z) is expressed by equation (2).

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[0040] (Step S102) From the OTDR waveform 23#m and the OTDR waveform 23#n, the ratio of the backscattered light intensity between the first core 20#m and the second core 20#n is obtained at least one point where z≦z1 is located on the one end 22 side from the connection part 21. Similarly, the ratio of the backscattered light intensity between the first core 20#m and the second core 20#n is also obtained at least one point where z≧z1 is located on the other end side from the connection part 21. When the backscattered light intensity distribution is known as in equations (1) and (2), the distributions of equations (1) and (2) may be used to obtain the ratio of the backscattered light intensity between the first core 20#m and the second core 20#n at z≦z1 and z≧z1, respectively, as in equation (3).

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[0041] (Step S103) The ratio between the backscattered light intensity ratio between cores at z≦z1 calculated in step S102 and the backscattered light intensity ratio between cores at z≧z1 is calculated. For example, when the backscattered light intensity distribution is known as in equations (1) and (2), the ratio between the first and second terms on the right side of equation (3) is taken. The result is expressed in equation (4).

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[0042] Fig. 4 shows the procedure of a connection loss difference measuring method that replaces the connection loss difference measuring method shown in Fig. 3. In the procedure shown in Fig. 4, step S101 is the same as the procedure shown in Fig. 3, and steps S202 and S203 are performed instead of steps S102 and S103 in Fig. 3.

[0043] (Step S202) From the OTDR waveform 23#m, the ratio of the backscattered light intensity of the first core 20#m at at least one point where z≦z1 is satisfied to the backscattered light intensity of the first core 20#m at at least one point where z ≧z1 is satisfied is calculated. When the backscattered light intensity distribution is known as in equation (1), the ratio of the first and second stages on the right side of equation (1) may be calculated. This gives the connection efficiency η m is required.

[0044] Similarly, from the OTDR waveform 23#n, the ratio of the backscattered light intensity of the second core 20#n at at least one point where z≦z1 is satisfied to the backscattered light intensity of the second core 20#n at at least one point where z ≧z1 is satisfied is calculated. When the backscattered light intensity distribution is known as in equation (2), the ratio of the first and second terms on the right side of equation (2) may be calculated. This gives the connection efficiency η n is required.

[0045] (Step S203) The connection efficiency η calculated in step S202 m and connection efficiency η n The ratio is taken and converted logarithmically to find the difference in connection loss.

[0046] In this embodiment, the Rayleigh scattering coefficient α s Although the backscattered light capture efficiency B is assumed to be common to the uncoupled multi-core fiber 20A and the uncoupled multi-core fiber 20B, the difference in splice loss can be calculated in the same manner even if these are different between the uncoupled multi-core fiber 20A and the uncoupled multi-core fiber 20B. s and the backscattering light capture rate B is the backscattering coefficient.

[0047] As described above, according to the present invention, even when uncoupled multicore fibers having different backscattering coefficients are connected, the difference in connection loss between cores at the connection portion can be measured by measuring from only one end.

[0048] (Embodiment 2) The arithmetic processing unit 15 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. 5 shows a block diagram of a system 100. The system 100 includes a computer 105 connected to a network 135.

[0049] Network 135 is a data communications network. Network 135 may be a private or public network and may include any or all of the following: (a) a personal area network, e.g., covering a room; (b) a local area network, e.g., covering a building; (c) a campus area network, e.g., covering a campus; (d) a metropolitan area network, e.g., covering a city; (e) a wide area network, e.g., covering an area that crosses city, regional, or national boundaries; or (f) the Internet. Communications are conducted by electronic and optical signals over network 135.

[0050] Computer 105 includes a processor 110 and a memory 115 connected to processor 110. Although computer 105 is depicted herein as a stand-alone device, it is not limited to such, but rather may be connected to other devices not shown in a distributed processing system.

[0051] Processor 110 is an electronic device made up of logic circuits that responds to and executes instructions.

[0052] The memory 115 is a tangible computer-readable storage medium in which a computer program is encoded. In this regard, the memory 115 stores data and instructions, i.e., program code, that can be read and executed by the processor 110 to control the operation of the processor 110. The memory 115 can be implemented as a random access memory (RAM), a hard drive, a read-only memory (ROM), or a combination thereof. One component of the memory 115 is a program module 120.

[0053] The program modules 120 include instructions for controlling the processor 110 to perform the processes described herein. Although operations are described herein as being performed by the computer 105 or a method or process or sub-process thereof, those operations are actually performed by the processor 110.

[0054] The term "module" is used herein to refer to a functional operation that may be embodied either as a stand-alone component or as an integrated configuration of multiple subcomponents. Thus, program module 120 may be implemented as a single module or as multiple modules operating in coordination with one another. Furthermore, although program module 120 is described herein as being installed in memory 115 and thus implemented in software, it may be implemented in any of hardware (e.g., electronic circuitry), firmware, software, or a combination thereof.

[0055] Although the program module 120 is shown as already loaded into the memory 115, it may be configured to be located on the storage device 140 for later loading into the memory 115. The storage device 140 is a tangible computer-readable storage medium that stores the program module 120. Examples of the storage device 140 include compact disks, magnetic tapes, read-only memories, optical storage media, memory units consisting of a hard drive or multiple parallel hard drives, and Universal Serial Bus (USB) flash drives. Alternatively, the storage device 140 may be a random access memory or other type of electronic storage device located in a remote storage system not shown and connected to the computer 105 via the network 135.

[0056] System 100 further includes data source 150A and data source 150B, collectively referred to herein as data sources 150, that are communicatively connected to network 135. In practice, data sources 150 may include any number of data sources, i.e., one or more data sources. Data sources 150 may include unstructured data and may include social media.

[0057] The system 100 further includes a user device 130 operated by the user 101 and connected to the computer 105 via a network 135. The user device 130 includes an input device, such as a keyboard or a voice recognition subsystem, to enable the user 101 to communicate information and command selections to the processor 110. The user device 130 further includes an output device, such as a display device or a printer or a voice synthesizer. A cursor control, such as a mouse, trackball, or touch-sensitive screen, enables the user 101 to manipulate a cursor on a display device to communicate further information and command selections to the processor 110.

[0058] The processor 110 outputs the results 122 of the execution of the program modules 120 to a user device 130. Alternatively, the processor 110 can provide the output to a storage device 125, such as a database or memory, or via a network 135 to a remote device, not shown.

[0059] For example, the program module 120 may be a program for acquiring an OTDR waveform based on the measurement result of the backscattered light intensity and performing steps S102 and S103 in Fig. 3 or steps S202 and S203 in Fig. 4. The system 100 may be operated as the arithmetic processing unit 15.

[0060] The term "comprising" or "comprising" is to be interpreted as specifying the presence of the stated features, integers, steps or components, but not excluding the presence of one or more other features, integers, steps or components or groups thereof. The terms "a" and "an" are indefinite articles and therefore do not exclude embodiments having a plurality thereof.

[0061] (Other embodiments) In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. In short, the present invention is not limited to the above-described embodiment, and the components can be modified and embodied without departing from the scope of the present invention at the implementation stage.

[0062] In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components across different embodiments may be appropriately combined. [Industrial Applicability]

[0063] The connection loss difference measuring method, device, and program according to the present disclosure can be applied to the information and communications industry. [Explanation of symbols]

[0064] 10: Connection loss difference measuring device 11: OTDR measurement section 12: Test light generation unit 12-1: Pulsed light source 13: Input / output section 13-1: Optical circulator 13-2: Optical switch 13-3: Input / Output Devices 14: Receiving section 14-1: Photoelectric converter 14-2: AD converter 15: Processing unit 15-1: Waveform analysis section 15-2: Connection loss difference calculation section 20: Optical fiber under test 20A, 20B: Uncoupled multicore fiber 20#m: 1st core 20#n: Second Core 21: Connection 22: One end 23:OTDR waveform 100: System 101:User 105: Computer 110: Processor 115: Memory 120: Program module 122:Result 125: Storage device 130: User device 135: Network 140: Storage device 150: Data source

Claims

1. inputting an optical pulse into each of a first core and a second core from one end of an uncoupled multicore fiber having a connection portion, and acquiring an OTDR waveform in each of the first core and the second core; calculating a ratio of a backscattering intensity in the first core to a backscattering intensity in the second core for at least two points, i.e., a point on the one end side of the connection portion and a point on the other end side of the connection portion, based on the acquired OTDR waveform; Calculating a ratio between the calculated ratio at the one end side and the calculated ratio at the other end side; This is a connection loss difference measurement method.

2. inputting an optical pulse into each of a first core and a second core from one end of an uncoupled multicore fiber having a connection portion, and acquiring an OTDR waveform in each of the first core and the second core; determining a loss in a connection of backscattered light intensity for each core based on the OTDR waveform; calculating a ratio of the loss of the first core to the loss of the second core; This is a connection loss difference measurement method.

3. The backscattering intensity P in the first core at a distance z from the one end ｍ where (z) is represented by formula (C1), The backscattering intensity P in the second core at the distance z ｎ Use formula (C2) for (z) 3. The connection loss difference measuring method according to claim 1 or 2. [Number C1] [Number C2] Here, z １ is the distance from the one end to the connection part, P ｍ０ is the intensity of the optical pulse input to the first core, P ｎ０ is the intensity of the optical pulse input to the second core, α ｓ is the Rayleigh scattering coefficient, B is the backscattered light capture rate, α ｍ is the fiber loss coefficient in the first core, α ｎ is the fiber loss coefficient in the second core, η ｍ is the connection efficiency in the first core, η ｎ represents the connection efficiency in the second core.

4. an OTDR measurement unit that acquires OTDR waveforms in a first core and a second core from one end of an uncoupled multicore fiber having a connection portion; a calculation processing unit that calculates a ratio of a backscattering intensity in the first core to a backscattering intensity in the second core for at least two points, i.e., a point on the one end side of the connection portion and a point on the other end side of the connection portion, based on the OTDR waveform acquired by the OTDR measurement unit, and calculates a ratio between the calculated ratio on the one end side and the calculated ratio on the other end side; A connection loss difference measuring device comprising:

5. an OTDR measurement unit that acquires OTDR waveforms in a first core and a second core from one end of an uncoupled multicore fiber having a connection portion; a processor that calculates a loss of a backscattered light intensity at a connection portion for each core based on the OTDR waveform and calculates a ratio of the loss of the first core to the loss of the second core; A connection loss difference measuring device comprising:

6. The arithmetic processing unit is The backscattering intensity P in the first core at a distance z from the one end ｍ Using formula (C3) as (z), The backscattering intensity P in the second core at the distance z ｎ Using formula (C4) for (z) 6. The connection loss difference measuring device according to claim 4 or 5. [Number C3] [Number C4] Here, z １ is the distance from the one end to the connection part, P ｍ０ is the intensity of the optical pulse input to the first core, P ｎ０ is the intensity of the optical pulse input to the second core, α ｓ is the Rayleigh scattering coefficient, B is the backscattered light capture rate, α ｍ is the fiber loss coefficient in the first core, α ｎ is the fiber loss coefficient in the second core, η ｍ is the connection efficiency in the first core, η ｎ represents the connection efficiency in the second core.

7. A program for causing a computer to function as the arithmetic processing unit according to any one of claims 4 to 6.

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