Group delay time measurement system of optical fiber

Abstract

To provide a measurement method, a measurement system, an arithmetic processing unit, and a program capable of measuring group delay time and wavelength dispersion regardless of time resolution of a measuring device.SOLUTION: A measurement system comprises an optical pulse testing device 11 and an arithmetic processing unit 12, the optical pulse testing device 11 applies optical pulses to both the ends of an optical fiber transmission line 50 in which a tested optical fiber 53, and at least two reference fibers (51, 52) having known group delay time are cascaded, and measures a waveform of backscattering light generated by the respective optical pulses, and the arithmetic processing unit 12 calculates a structure asymmetric loss value from each backscattering light from an optional position of the optical fiber transmission line 50, and calculates group delay time for the tested optical fiber 53 from known group delay time of the reference fibers (51, 52) and the structure asymmetric loss values of the reference fibers and the tested optical fiber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a measurement system for measuring the group delay time of an optical fiber. [Background technology]

[0002] Chromatic dispersion in optical fibers is an important parameter related to transmission rate. Therefore, it is essential to measure chromatic dispersion when manufacturing optical fibers. Non-Patent Document 1 discloses a method for obtaining chromatic dispersion of optical fibers using an optical time domain reflectometer (OTDR). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] DR Anderson et al., “Troubleshooting optical-fiber networks, understanding and using your optical time-domain reflectometer,” second edition, Elsevier Academic Press, 2004. Summary of the Invention [Problem to be solved by the invention]

[0004] The method in Non-Patent Document 1 involves injecting an optical pulse into an optical fiber under test and measuring the optical pulse that is reflected back from the far end of the optical fiber under test. The group delay time in the optical fiber can be directly obtained from the round-trip time of the optical pulse. This group delay time is measured at multiple wavelengths, and chromatic dispersion is obtained through numerical processing. However, this method requires direct acquisition of the group delay time, which poses a problem in that the accuracy of chromatic dispersion measurement is limited by the time resolution of the measurement device.

[0005] Therefore, in order to solve the above problem, an object of the present invention is to provide a measurement method, a measurement system, a processing device, and a program that can measure group delay time and chromatic dispersion regardless of the time resolution of the measurement device. [Means for solving the problem]

[0006] To achieve the above object, a measurement method according to the present invention uses a reference fiber with a known group delay time to obtain the group delay time of the optical fiber under test based on the group delay time of the reference fiber, and obtains chromatic dispersion from the obtained group delay time.

[0007] Specifically, the measurement method according to the present invention is a method for measuring the group delay time of an optical fiber under test, comprising the steps of: an optical pulse is input to both ends of an optical fiber transmission line in which the optical fiber under test and two or more reference fibers having known group delay times are cascade-connected; measuring the waveform of backscattered light generated by each of said light pulses; calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line; and Calculating the group delay time of the optical fiber under test from the known group delay time of the reference fiber, a structural imperfection loss value in one of the reference fibers, and a structural imperfection loss value in the optical fiber under test. It is characterized by:

[0008] A measurement system according to the present invention includes an optical pulse tester and a processor, and measures the group delay time of an optical fiber under test, and comprises: The optical pulse tester comprises: an optical pulse is input to both ends of an optical fiber transmission line in which the optical fiber under test and two or more reference fibers with known group delay times are cascade-connected, and the waveform of backscattered light generated by each of the optical pulses is measured; The arithmetic processing device calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line; and Calculating the group delay time of the optical fiber under test from the known group delay time of the reference fiber, a structural imperfection loss value in one of the reference fibers, and a structural imperfection loss value in the optical fiber under test. It is characterized by:

[0009] Furthermore, a processing device according to the present invention is a processing device that calculates a group delay time of an optical fiber under test from waveforms of backscattered light generated by each optical pulse measured by an optical pulse testing device that cascade-connects an optical fiber under test and two or more reference fibers with known group delay times, and calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line; and Calculating the group delay time of the optical fiber under test from the known group delay time of the reference fiber, a structural imperfection loss value in one of the reference fibers, and a structural imperfection loss value in the optical fiber under test. It is characterized by:

[0010] The present invention is characterized in that the arithmetic processing device calculates the group delay time for each of the optical pulses of three wavelengths, and calculates chromatic dispersion for the optical fiber under test from the group delay times calculated for the optical pulses of the three wavelengths.

[0011] The measurement method according to the present invention uses an optical fiber transmission line in which an optical fiber under test and two reference fibers with known group delay times are cascaded, and calculates the group delay time of the optical fiber under test from the waveform of backscattered light of optical pulses incident from both ends of the optical fiber transmission line and the group delay time of the reference fibers. Then, in this measurement method, the chromatic dispersion of the optical fiber under test is calculated based on the wavelength dependency of the group delay time of the optical fiber under test.

[0012] In this way, in this measurement method, the group delay time is not directly acquired but is calculated based on the group delay time of the reference fiber, so the measurement accuracy is not limited by the time resolution of the measurement device. Therefore, the present invention can provide a measurement method, measurement system, and processing device that can measure group delay time and chromatic dispersion regardless of the time resolution of the measurement device.

[0013] Here, the optical fiber under test may be not only a single-mode fiber but also a spatially multiplexed optical fiber such as a multicore fiber or a few-mode fiber. In this case, the optical fiber under test and the reference fiber constituting the optical fiber transmission line are both spatially multiplexed optical fibers having multiple spatial channels. In this case, the measurement system according to the present invention further includes an input / output device that inputs the optical pulse from the optical pulse test apparatus into each spatial channel of the optical fiber transmission line and inputs the backscattered light from the spatial channel into the optical pulse test apparatus. The arithmetic processing unit then calculates the group delay time for each spatial channel.

[0014] In another case, the optical fiber under test that constitutes the optical fiber transmission line may be a spatially multiplexed optical fiber having a plurality of spatial channels, and the reference fiber may be a single-mode fiber. In this case, the measurement system according to the present invention further comprises an input / output device that inputs the optical pulse from the optical pulse test apparatus into each spatial channel of the optical fiber under test and inputs the backscattered light from the spatial channel into the optical pulse test apparatus. The arithmetic processing unit then calculates the group delay time for each spatial channel.

[0015] The present invention also provides a program for causing a computer to function as the arithmetic processing device. The arithmetic processing device of the present invention can be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0016] The above inventions can be combined as much as possible. [Effects of the Invention]

[0017] The present invention can provide a measurement method, a measurement system, a processing device, and a program that can measure group delay time and chromatic dispersion regardless of the time resolution of the measurement device. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 2] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 3] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 4] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 5] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 6] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 7] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 8] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 9] 1 is a diagram illustrating a system for measuring group delay time of an optical fiber according to the present invention. [Figure 10] 1 is a diagram illustrating a method for measuring a group delay time of an optical fiber according to the present invention. [Figure 11] FIG. 1 is a diagram illustrating a processing device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following description of the preferred embodiments of the present invention will be given with reference to the accompanying drawings. The preferred embodiments described below are examples of the present invention, and the present invention is not limited to the preferred embodiments. In this specification and the drawings, components having the same reference numerals are intended to represent the same components.

[0020] (Embodiment 1) FIG. 1 is a diagram illustrating the measurement system of this embodiment. Two reference fibers (51, 52) with known parameters and an optical fiber 53 under test are cascade-connected to form an optical fiber transmission line 50. The measurement device 10 has an optical pulse tester (OTDR) 11 and a processing unit 12. The OTDR 11 is connected to one end (end A) of the optical fiber transmission line 50, and an optical pulse is incident thereon to measure the backscattered light waveform. Subsequently, the OTDR 11 is connected to the other end (end B) of the optical fiber transmission line 50, and an optical pulse is incident thereon to measure the backscattered light waveform. In other words, the measurement system of FIG. 1 is a system in which the OTDR is alternately connected to ends A and B of the optical fiber transmission line 50 to measure the backscattered light.

[0021] The measurement system of this embodiment is a measurement system that includes an optical pulse tester 11 and a processing unit 12, and measures the group delay time of an optical fiber 53 under test, The optical pulse test equipment 11 includes: an optical fiber transmission line 50 in which an optical fiber 53 under test and two or more reference fibers (51, 52) with known group delay times are cascade-connected, and an optical pulse is input to both ends of the optical fiber transmission line 50, and the waveform of backscattered light generated by each of the optical pulses is measured; The processing unit 12 Calculating a structural imperfection loss value by averaging the light intensity of each of the backscattered lights from any position on the optical fiber transmission line 50; and Calculating the group delay time of the optical fiber under test 53 from the known group delay times of the reference fibers (51, 52), the structural imperfection loss value of one of the reference fibers, and the structural imperfection loss value of the optical fiber under test 53. It is characterized by:

[0022] Furthermore, the processing unit 12 calculating the group delay time for each of the optical pulses of three wavelengths; and Calculating chromatic dispersion for the optical fiber 53 under test from the group delay times calculated using the optical pulses of the three wavelengths. It is characterized by: The arithmetic processing of the arithmetic processing unit 12 will be described later.

[0023] (Embodiment 2) 2 is a diagram illustrating the configuration of a measurement system when the reference fibers (51, 52) and the optical fiber under test 53 constituting the optical fiber transmission line 50 are few-mode fibers of spatial multiplexing optical fibers. In this case, compared to the measurement system of the first embodiment, this measurement system further includes an input / output device (mode converter 14) that inputs optical pulses from the optical pulse test apparatus 11 into each spatial channel (transmission mode) of the optical fiber transmission line 50 and inputs the backscattered light from the corresponding spatial channel to the optical pulse test apparatus 11. The mode converter 14 converts the optical pulses from the optical pulse test apparatus 11 from their fundamental mode to the propagation mode of the measurement target in the few-mode fiber, and converts the backscattered light from the few-mode fiber from the propagation mode of the measurement target to the fundamental mode. In this configuration, the mode converter 14 is placed between the measurement apparatus 10 and end A or B of the optical fiber transmission line 50.

[0024] (Embodiment 3) 3 is a diagram illustrating the configuration of a measurement system when the reference fibers (51, 52) constituting the optical fiber transmission line 50 are single-mode fibers and the optical fiber under test 53 is a few-mode fiber of a spatially multiplexed optical fiber. In this case, compared to the measurement system of the first embodiment, this measurement system further comprises an input / output device (mode converter 14) that inputs optical pulses from the optical pulse test apparatus 11 into each spatial channel (transmission mode) of the optical fiber under test 53 and inputs the backscattered light from the corresponding spatial channel to the optical pulse test apparatus 11. The function of the mode converter 14 is as described above. In this configuration, the mode converter 14 is placed between the reference fiber 52 and the optical fiber under test 53, or between the measurement apparatus 10 and end B of the optical fiber transmission line 50.

[0025] (Embodiment 4) 4 is a diagram illustrating the configuration of a measurement system when the reference fibers (51, 52) and the optical fiber under test 53 constituting the optical fiber transmission line 50 are multi-core fibers of spatial multiplexing optical fibers. In this case, compared to the measurement system of the first embodiment, this measurement system further comprises an input / output device 15 that inputs optical pulses from the optical pulse test apparatus 11 to each spatial channel (core) of the optical fiber transmission line 50 and inputs the backscattered light from the corresponding spatial channel to the optical pulse test apparatus 11. The input / output device 15 inputs optical pulses from the optical pulse test apparatus 11 to a core to be measured in the multi-core fiber and inputs the backscattered light from the corresponding core to the optical pulse test apparatus 11. In this configuration, the input / output device 15 is disposed between the measurement apparatus 10 and end A or end B of the optical fiber transmission line 50.

[0026] (Embodiment 5) 5 is a diagram illustrating the configuration of a measurement system when the reference fibers (51, 52) constituting the optical fiber transmission line 50 are single-mode fibers and the optical fiber under test 53 is a multi-core fiber of a spatial multiplexing optical fiber. In this case, compared to the measurement system of the first embodiment, this measurement system further comprises an input / output device 15 that inputs optical pulses from the optical pulse test apparatus 11 into each spatial channel (core) of the optical fiber under test 53 and inputs the backscattered light from the corresponding spatial channel to the optical pulse test apparatus 11. The function of the input / output device 15 is as described above. In this configuration, the input / output device 15 is placed between the reference fiber 52 and the optical fiber under test 53, or between the measurement apparatus 10 and end B of the optical fiber transmission line 50.

[0027] (Embodiment 6) 6 is also a diagram illustrating the measurement system of this embodiment. The measurement device 20 of this measurement system has an OTDR 11, a processing unit 12, and an optical switch 13. Ends A and B of an optical fiber transmission line 50 are connected to the optical switch 13. By switching the optical switch 13, the OTDR 11 can measure the waveforms of backscattered light from both ends of the optical fiber transmission line 50. The arithmetic processing of the arithmetic processing unit 12 will be described later.

[0028] (Embodiment 7) 7 is a diagram illustrating a measurement system in which the optical fiber transmission line 50 is a spatial multiplexing optical fiber. In contrast to the measurement system in FIG. 6, this measurement system has a device 16, which is a mode converter or an input / output device, placed between the optical switch 13 and terminals A and B. As explained in the second and fourth embodiments, this measurement system can measure the backscattered light waveform for each spatial channel (core or propagation mode).

[0029] (Embodiment 8) Figure 8 is also a diagram illustrating the measurement system of this embodiment. The measurement device 30 of this measurement system includes an OTDR 11, a processing unit 12, an optical switch 13, and reference fibers (51, 52). The only difference between the measurement systems of Figures 2 and 3 is whether or not the reference fibers (51, 52) are included in the measurement device; the basic operations are the same. The arithmetic processing of the arithmetic processing unit 12 will be described later.

[0030] (Embodiment 9) 9 is a diagram illustrating a measurement system in which the optical fiber under test 53 is a spatial multiplexing optical fiber. In contrast to the measurement system in FIG. 8, this measurement system has a device 16, which is a mode converter or an input / output device, placed between the reference fiber 52 and end A and between the optical switch 13 and end B. As explained in the third and fifth embodiments, this measurement system can measure the backscattered light waveform for each spatial channel (core or propagation mode).

[0031] (Embodiment 4) FIG. 4 is a flowchart illustrating the measurement method of this embodiment. This measurement method is a method for measuring the group delay time of the optical fiber under test 53, forming an optical fiber transmission line 50 by cascading an optical fiber 53 under test and two or more reference fibers (51, 52) having known group delay times, injecting optical pulses into both ends of the optical fiber transmission line 50, and measuring the waveforms of backscattered light generated by each of the optical pulses (steps S02, S03); Calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line 50, and calculating a group delay time for the optical fiber under test 53 from the known group delay time of the reference fibers (51, 52), the structural imperfection loss value in one of the reference fibers (51 or 52), and the structural imperfection loss value in the optical fiber under test 53 (step S04). It is characterized by:

[0032] Furthermore, this measurement method Calculating the group delay time for each of the optical pulses of three wavelengths (step S05); and Calculating chromatic dispersion for the optical fiber 53 under test from the group delay times calculated for the optical pulses of the three wavelengths (step S06). It is characterized by:

[0033] First, two reference fibers (51, 52) with known group delay times are cascade-connected to an optical fiber 53 to be measured. Then, in step S02, the OTDR 11 measures the waveform of the backscattered light from the end A of the optical fiber transmission line 50. Next, in step S03, the waveform of backscattered light from end B of the optical fiber transmission line 50 is measured. Then, in step S04, a calculation to be described later is performed to calculate the group delay time of the optical fiber 53 under test using the two acquired backscattered light waveforms. To calculate the chromatic dispersion of the optical fiber under test 53, it is necessary to acquire the group delay time using three or more optical pulses. Therefore, if the acquired group delay time is determined to be less than three wavelengths in the chromatic dispersion step S05, the wavelength of the optical pulse is changed and steps S02 to S04 are repeated. On the other hand, if the acquired group delay time is three or more wavelengths, the chromatic dispersion is calculated using the calculation described below.

[0034] [supplement] The group delay times of the two reference fibers (51, 52) are different from each other. The wavelength of the optical pulse that the OTDR 11 inputs into the optical fiber transmission line 50 means the central value (central wavelength) of the wavelengths contained in the optical pulse. If the optical fiber under test 53 is a spatial multiplexing optical fiber, steps S02 to S06 are performed for each spatial channel to be measured using the mode converter 14 and the input / output device 15. [End of supplement]

[0035] (arithmetic processing) Here, the calculations performed by the calculation processing unit 12 will be explained. The light intensity waveforms S1(z) and S2(Lz) of the backscattered light output from the A end and the B end of the optical fiber transmission line 50 by the OTDR 11 can be described by the following equations.

number

number

[0036] The capture rate B(z) can be expressed as follows:

number

[0037] Using the optical intensity waveforms S1(z) and S2(Lz) of the backscattered light, the structural imperfection loss I(z) due to structural fluctuations in the optical fiber, which is the average value of S1(z) and S2(Lz), can be described by the following equation:

number

number

[0038] Here, if we assume that the change in the Rayleigh scattering coefficient is small over the entire length of the optical fiber transmission line, the following equation is obtained:

number

number

[0039] Similarly, the normalized structural imperfection loss at a position z=z1 of the second reference fiber 52 can be expressed by the following equation:

number

[0040] Here, n1(z) can be considered constant in the longitudinal direction, so that the mode field diameter at distance z can be calculated from equations (7) and (8) using the known mode field diameters and structural imperfection loss waveforms of the two reference fibers (51, 52) as follows:

number

[0041] Next, the group velocity v g and group delay τ g Consider the group delay τ g can be approximately expressed by the following equation:

number

number

number

[0042] Next, let us consider chromatic dispersion. Chromatic dispersion D is defined by the following equation:

number

number

[0043] Next, the coefficients a(z), b(z), and c(z) at position z are calculated using the group delays at the three wavelengths. The chromatic dispersion can be calculated from equations (13) and (14) as follows:

number

[0044] The approximation function of the group delay with respect to the wavelength may be changed depending on the wavelength used in the test. For example, the following equation may be used instead of equation (14):

number

number

[0045] As described above, in step S04 of FIG. 4, the arithmetic processing unit 12 Using equation (4), the light intensities (S1(z), S2(Lz)) of the backscattered light from an arbitrary position z (position on the optical fiber 53 under test) of the optical fiber transmission line 50 are averaged to obtain the structural imperfection loss value I n (z), and The optical intensities (S1(z1), S2(L-z1)) of the backscattered light from an arbitrary position z1 (position on the reference fiber 52) of the optical fiber transmission line 50 are averaged to obtain a structural imperfection loss value I n (z1). Furthermore, the calculation processing unit 12 calculates, using equation (12), The known group delay time τ of the reference fiber 51 g (z0) and the known group delay time τ of the reference fiber 52. g (z1) and the structural imperfection loss value I in the reference fiber 52 n (z1) and the structural imperfection loss value I in the optical fiber under test. n (z) and the group delay time τ g Calculate (z).

[0046] Then, in step S06 of FIG. 4, the arithmetic processing unit 12 The group delay time (τ g (λ1, z), τ g (λ2, z), τ g After calculating (λ3, z), These are substituted into equation (14) to calculate the respective coefficients (a(z), b(z), c(z)), which are then substituted into equation (15) to determine the chromatic dispersion of the optical fiber 53 under test.

[0047] (Embodiment 5) The arithmetic processing unit 12 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.

[0048] 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 spanning city, region, or country boundaries; or (f) the Internet. Communications are conducted over network 135 by electronic and optical signals.

[0049] Computer 105 includes a processor 110 and 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.

[0050] Processor 110 is an electronic device made up of logic circuits that responds to and carries out instructions.

[0051] The memory 115 is a tangible computer-readable storage medium on 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 its operation. 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.

[0052] The program modules 120 contain 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.

[0053] The term "module" is used herein to refer to a functional operation that may be embodied as either a stand-alone component or 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, while 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.

[0054] Although program module 120 is shown as already loaded into memory 115, it may also be configured to reside on storage device 140 for later loading into memory 115. Storage device 140 is a tangible, computer-readable storage medium that stores program module 120. Examples of storage device 140 include compact discs, magnetic tape, read-only memory, optical storage media, a memory unit consisting of a hard drive or multiple parallel hard drives, and a universal serial bus (USB) flash drive. Alternatively, storage device 140 may be random access memory or another type of electronic storage device located in a remote storage system (not shown) and connected to computer 105 via network 135.

[0055] 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.

[0056] 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, that allows the user 101 to communicate information and command selections to the processor 110. The user device 130 also 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, allows the user 101 to manipulate a cursor on the display device to communicate further information and command selections to the processor 110.

[0057] The processor 110 outputs the results 122 of the execution of the program modules 120 to the 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.

[0058] 4 may be the program module 120. The system 100 can be operated as the arithmetic processing device 12.

[0059] The terms "comprising" or "comprising" should 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.

[0060] (Other embodiments) It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. In short, the present invention is not limited to the above-described embodiments, and the components can be modified and embodied in the implementation stage without departing from the spirit of the present invention. For example, in the above-described embodiments, three optical fibers (an optical fiber under test and two reference fibers) are cascade-connected as the optical fiber transmission line, but two or more reference fibers connected in cascade to the optical fiber under test can also be used as the optical fiber transmission line for testing.

[0061] Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

[0062] (Effects of the Invention) The measurement system according to the present invention can measure the group delay time and chromatic dispersion with high accuracy without being restricted by the time resolution of the measurement device. [Explanation of symbols]

[0063] 10, 20, 30: Measuring equipment 11: Optical Time Domain Reflectometer (OTDR) 12: Processing unit 13: Optical switch 14: Mode converter 15: Input / output devices 16: Device 50: Optical fiber transmission line 51, 52: Reference fiber 53: Optical fiber under test 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. A measurement system for measuring the group delay time of an optical fiber under test, comprising an optical pulse tester and a processing unit, The optical pulse tester comprises: an optical pulse is input to both ends of an optical fiber transmission line in which the optical fiber under test and two or more reference fibers with known group delay times are cascade-connected, and the waveform of backscattered light generated by each of the optical pulses is measured; The arithmetic processing device calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line; and Calculating the group delay time of the optical fiber under test from the known group delay time of the reference fiber, a structural imperfection loss value in one of the reference fibers, and a structural imperfection loss value in the optical fiber under test. A measurement system characterized by:

2. the optical fiber under test and the reference fiber constituting the optical fiber transmission line are both spatially multiplexed optical fibers having a plurality of spatial channels, an input / output device that inputs the optical pulses from the optical pulse testing apparatus to each of the spatial channels of the optical fiber transmission line and inputs the backscattered light from each of the spatial channels to the optical pulse testing apparatus; The arithmetic processing device calculates the group delay time for each of the spatial channels.

2. The measurement system according to claim 1, wherein:

3. the optical fiber under test is a spatial multiplexing optical fiber having a plurality of spatial channels, and the reference fiber is a single-mode fiber, both of which constitute the optical fiber transmission line; an input / output device that inputs the optical pulses from the optical pulse testing apparatus into each of the spatial channels of the optical fiber under test and inputs the backscattered light from the spatial channels into the optical pulse testing apparatus; The arithmetic processing device calculates the group delay time for each of the spatial channels.

2. The measurement system according to claim 1, wherein:

4. The arithmetic processing device calculating the group delay time for each of the optical pulses of three wavelengths; and Calculating chromatic dispersion for the optical fiber under test from the group delay times calculated using the optical pulses of three wavelengths.

4. The measurement system according to claim 1, wherein:

5. A method for measuring a group delay time of an optical fiber under test, comprising the steps of: an optical pulse is input to both ends of an optical fiber transmission line in which the optical fiber under test and two or more reference fibers having known group delay times are cascade-connected; measuring the waveform of backscattered light generated by each of said light pulses; calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line; and Calculating the group delay time of the optical fiber under test from the known group delay time of the reference fiber, a structural imperfection loss value in one of the reference fibers, and a structural imperfection loss value in the optical fiber under test. A measurement method characterized by:

6. An arithmetic processing device that calculates the group delay time of an optical fiber under test from the waveform of backscattered light generated by each optical pulse measured by an optical pulse testing device that cascade-connects an optical fiber under test and two or more reference fibers with known group delay times, comprising: calculating a structural imperfection loss value by averaging the light intensities of the backscattered light from any position on the optical fiber transmission line; and Calculating the group delay time of the optical fiber under test from the known group delay time of the reference fiber, a structural imperfection loss value in one of the reference fibers, and a structural imperfection loss value in the optical fiber under test. A processing unit characterized by:

7. A program for causing a computer to function as the arithmetic processing device according to claim 6.

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