MCF connection system and MCF connection method

Abstract

An MCF connection system according to the present invention comprises: MCF transmission path (10) that has cores (11)-(14) of a quantity of N; a first FIFO (100); a light source (500) that outputs, to one end of the first FIFO, a quantity of N inspection lights having mutually different characteristics; a connection device (800) that optically connects a first end part forming one end of the MCF transmission path and the other end of the first FIFO; an identification device (610) that identifies a characteristic of an inspection light output from a second end part forming the other end of the MCF transmission path; and a measurement device (620) that measures, for each core of the MCF transmission path, a first optical power, which is the optical power of the inspection light output from the second end part, in correspondence with the characteristic. The light source inputs the inspection light into each of the plurality of cores at one end of the first FIFO, and the connection device (800) adjusts, for each core, an optical axis between the other end of the first FIFO and the first end part such that the value of each first optical power is within a prescribed range, and fixes the connection between the other end of the first FIFO and the first end part after the optical axis between the other end of the first FIFO and the first end part has been adjusted.

Description

[Technical Field]

[0001] The present invention relates to an MCF connection system for connecting multi-core fibers used in an optical fiber transmission system. [Background technology]

[0002] In recent years, with the expansion of demand for international data communications, the importance of submarine cable systems, which are capable of large-capacity and high-speed communications, has been increasing. Research and development of multi-core fiber (MCF) is underway as one means of increasing transmission capacity without changing the outer diameter of the submarine cable. MCF is an optical fiber with multiple cores in a single optical fiber.

[0003] Single-core fiber (Single-Core Fiber, S) has one core in one optical fiber. Fan-In / Fan-Out (FIFO) is used to connect general optical devices with SCF interfaces to optical transmission lines including MCFs. General optical devices include optical repeaters and optical components. A FIFO is an optical component with multiple SCFs on one end and MCFs on the other end, and the cores of these SCFs are connected to each core of the MCF inside the FIFO. Therefore, a FIFO can connect optical devices with SCF interfaces to MCFs.

[0004] In relation to the present invention, Patent Document 1 describes a method for axial alignment of a coupled multi-core optical fiber, and Patent Document 2 describes an MCF provided with markers for aligning cores with each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 217539 [Patent Document 2] International Publication No. 2012 / 121027 Summary of the Invention [Problem to be solved by the invention]

[0006] When connecting a FIFO and an MCF, it is preferable to connect each core of the FIFO to each core of the MCF with low loss. Furthermore, it is also preferable that the variation in connection loss between each core of the FIFO and each core in the MCF is small. Meanwhile, in a typical procedure for connecting a FIFO and an MCF, multiple beams of light distributed from a single light source are input to one end of the MCF via the FIFO. Then, optical axis adjustment is performed between one end of the FIFO and one end of the MCF so that the sum of the optical powers output from all cores at the other end of the MCF is maximized.

[0007] However, this procedure has the problem that it is not easy to know whether each core of the MCF is connected to the FIFO with low loss. The reason is that it is not possible to know the connection status of each core at the connection point between one end of the FIFO and one end of the MCF. Therefore, in order to connect the MCF and the FIFO (hereinafter referred to as the "first FIFO") while suppressing the variation in connection loss between cores, the following steps (a) to (d) are required. (a) Connect a FIFO (first FIFO) to one end of the MCF (first optical axis adjustment). (b) To optimize the connection of the first FIFO, the test light is input from the first FIFO and another FIFO (second FIFO) is connected to the other end of the MCF. (c) Input the test light for each core from the second FIFO. (d) The connection between the first FIFO and one end of the MCF is disconnected, and a second optical axis adjustment is performed between the first FIFO and one end of the MCF so as to reduce the variation in connection loss for each core.

[0008] In other words, the general procedure requires steps (b)-(d) of connecting the first FIFO and MCF, then disconnecting the connection and adjusting the optical axis using the test light in the opposite direction. For this reason, it has been difficult to connect the MCF and FIFO simply and with high quality using the general procedure.

[0009] (Object of the invention) An object of the present invention is to provide a technique for simply connecting an MCF and a FIFO with high quality. [Means for solving the problem]

[0010] The MCF connection system of the present invention comprises: MCF (Multi-Core Fiber) transmission line with N cores, The first FIFO (Fan-In / Fan-Out), a light source that outputs N test lights having different characteristics to one end of the first FIFO; a connection means for optically connecting a first end portion of the MCF transmission line to the other end of the first FIFO; an identification means for identifying a characteristic of the test light output from a second end portion that constitutes the other end of the MCF transmission line; a measuring means for measuring a first optical power indicating an optical power of each core of the test light output from the second end portion for each core of the MCF transmission line in correspondence with the characteristics; Equipped with N is an integer equal to or greater than 2, the light source inputs the test light to each of a plurality of cores at one end of the first FIFO; The connection means adjusts the optical axis between the other end of the first FIFO and the first end for each core so that each value of the first optical power falls within a predetermined range, and after adjusting the optical axis between the other end of the first FIFO and the first end, fixes the connection between the other end of the first FIFO and the first end.

[0011] The MCF connection method of the present invention includes: An MCF connection method including a first procedure for optically connecting an MCF transmission line having N cores and a first FIFO, N is an integer equal to or greater than 2, The first step comprises: inputting test light having different characteristics into each of a plurality of cores at one end of the first FIFO; optically connecting the other end of the first FIFO and a first end forming one end of the MCF transmission line for each core; Identifying a characteristic of the test light output from a second end portion of the MCF transmission line; measuring a first optical power indicating an optical power of each core of the test light output from the second end portion for each core of the MCF transmission line in correspondence with the characteristics; adjusting an optical axis between the other end of the first FIFO and the first end so that each value of the first optical power falls within a predetermined range; fixing the connection between the other end of the first FIFO and the first end; Includes instructions. [Effects of the Invention]

[0012] The present invention allows a simple and high-quality connection between a FIFO and an MCF. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating an MCF connection system. [Figure 2] 10A and 10B are diagrams illustrating optical axis adjustment of an MCF. [Figure 3] 10 is an example of a flowchart of a first procedure. [Figure 4] FIG. 1 is a diagram illustrating an MCF connection system. [Figure 5] 10 is an example of a flowchart of a second procedure. [Figure 6] FIG. 1 is a diagram illustrating an MCF connection system. [Figure 7] FIG. 1 is a diagram illustrating an MCF connection system. [Figure 8]FIG. 2 is a block diagram showing an example of the configuration of a light source. DETAILED DESCRIPTION OF THE INVENTION

[0014] Embodiments of the present invention will be described below. Arrows in each drawing are provided as examples to explain the direction of signals in the embodiments, and are not intended to limit the direction. Furthermore, unless otherwise specified, intersections of lines do not represent the connection of signals with different directions. Elements already mentioned are given the same names and reference symbols, and duplicate descriptions in each embodiment will be omitted.

[0015] (First embodiment) In this embodiment, an MCF connection system and an MCF connection method will be described for connecting a FIFO 100 to one end of an MCF transmission line 10. Fig. 1 is a diagram for explaining an MCF connection system 1 according to a first embodiment of the present invention.

[0016] The MCF transmission line 10 is an optical transmission line made of MCF. In the MCF transmission line 10, multiple cores are formed inside a single optical fiber. The MCF transmission line 10 is an uncoupled MCF in which each core can transmit light independently. The FIFO 100 is a fan-in / fan-out (FIFO) for connecting the MCF transmission line 10 to multiple SCFs. One end of the FIFO 100 is an MCF (MCF 101), and the other end is SCFs (SCFs 111-114). In the FIFO 100, each core of the MCF 101 is connected to a core of each of the SCFs 111-114 in a one-to-one relationship. In other words, the FIFO 100 can connect optical equipment with an MCF interface to optical equipment with multiple SCF interfaces. By connecting a FIFO 100 to one end of the MCF transmission line 10, in an optical transmission system in which the MCF transmission line 10 is used as an optical transmission line, the MCF transmission line 10 can be connected to optical equipment (e.g., an optical repeater and optical components provided in the optical repeater) that uses an SCF as an interface.

[0017] The MCF connection method described in this embodiment is hereinafter referred to as the first procedure. In the first procedure, a FIFO 100 is connected to an MCF transmission line 10. In this embodiment, a case will be described in which the MCF transmission line 10 is a four-core MCF (an MCF having four cores 11-14). The MCF 101 at one end of the FIFO 100 is also a four-core MCF, and the SCFs 111-114 are SCFs. However, the following procedure can also be applied to a case in which the MCF transmission line 10 is an N-core MCF, where N is a natural number equal to or greater than 2.

[0018] 1, the MCF connection system 1 includes an MCF transmission line 10, a FIFO 100, a light source 500, an optical switch 600, an optical wavelength meter 610, an optical power meter 620, and a connection device 800. The MCF connection system 1 may also include a control device 900. The control device 900 controls the light source 500, the optical switch 600, the optical wavelength meter 610, and the optical power meter 620 to execute the first procedure. The control device 900 is one form of control means.

[0019] The light source 500 can output one of four test lights with mutually different characteristics. In this embodiment, a case will be described in which the characteristic is the wavelength of the test light. That is, the light source 500 outputs four test lights with mutually different wavelengths. The number of wavelengths is the number of cores in the MCF transmission line 10. The light source 500 includes laser diodes (LD) 501-504. The LDs 501-504 are, for example, semiconductor laser diodes. The test light having wavelength λ1 output from the LD 501 is input to the SCF 111 of the FIFO 100. Similarly, the test light having wavelengths λ2, λ3, and λ4 output from the LDs 502, 503, and 504 are input to the SCFs 112, 113, and 114, respectively. Because the test light having wavelengths λ1-λ4 input to the SCFs 111-114 of the FIFO 100 are different from one another, the test light having wavelengths λ1-λ4 output from each core of the MCF 101 of the FIFO 100 is also different from one another. The light source 500 of this embodiment simultaneously outputs only one test light among the four test light having wavelengths λ1-λ4. That is, the light source 500 outputs the test light to one of the SCFs 111-114. The FIFO 100 and the MCF transmission line 10 are optically connected so that test light of wavelength λ1 is input to core 11 of the MCF transmission line 10, wavelength λ2 to core 12, wavelength λ3 to core 13, and wavelength λ4 to core 14.

[0020] The splicing device 800 has the function of adjusting the positional relationship between two MCFs and fixing the connection between them by fusion. Specifically, the splicing device 800 adjusts the optical axis between the MCF 101 and the MCF transmission line 10 so that the cores of both are optically coupled. The cores of the MCF 101 and the MCF transmission line 10 are connected by a butt joint during the optical axis adjustment, and are fusion-spliced ​​after the optical axis adjustment is complete. A general fusion splicer for fusion-splicing two MCFs may be used as the splicing device 800.

[0021] 1 illustrates an example in which only the LD 501 emits light. When the wavelength of the inspection light is λ1, the LDs 502 to 504 are not involved in the optical axis adjustment, and therefore these blocks are indicated by dashed lines.

[0022] In the procedure of this embodiment, the MCF 101 of the FIFO 100 is optically connected to a first end (end 21) that forms one end of the MCF transmission line 10 for each of the four cores 11-14. Then, at end 21, test light having different wavelengths is input from the light source 500 to each of the cores 11-14. As a result, the cores 11-14 of the MCF transmission line 10 transmit test light of different wavelengths. The four test light beams are output from the cores 11-14 at end 22 that forms the other end of the MCF transmission line 10.

[0023] The test light output from the cores 11-14 at the end 22 is input to the optical switch 600. The optical switch 600 outputs the input test light to an optical wavelength meter 610 or an optical power meter 620. The optical switch 600 is a 1×2 optical switch that can output light input from a bare fiber of the MCF transmission line 10 to either of two SCFs.

[0024] The optical wavelength meter 610 measures the wavelength of the test light input from the optical switch 600 and outputs the measurement result. An optical spectrum analyzer may be used instead of the optical wavelength meter 610. The optical power meter 620 measures the power of the light input from the optical switch 600 and outputs the measurement result. An optical coupler may be used instead of the optical switch 600. The optical coupler instead of the optical switch 600 distributes the test light output from the end 22 to the optical wavelength meter 610 and the optical power meter 620. By using such an optical coupler, the wavelength and optical power of the input test light can be measured simultaneously.

[0025] Because the light source 500 outputs test light to one of the SCFs 111-114, test light of only one wavelength is input to the optical wavelength meter 610 and the optical power meter 620 at a time. Therefore, the optical wavelength meter 610 and the optical power meter 620 measure the wavelength and optical power of the test light of one wavelength output by the light source 500. The method for outputting the measurement results of the wavelength and optical power is arbitrary. These measurement results may be displayed on a display or transmitted as data to another device (e.g., the control device 900). The optical switch 600 outputs the light input from the end 22 to the optical wavelength meter 610 or the optical power meter 620. By controlling the optical switch 600 while switching the wavelength of the test light in the light source 500, the wavelength and optical power of the test light propagating through the MCF transmission line 10 can be measured for each core of the MCF transmission line 10.

[0026] Here, the optical axis is adjusted for each core between the FIFO 100 and the MCF transmission line 10 so that the optical power values ​​of the four cores measured by the optical power meter 620 fall within a predetermined range. For example, when only the LD 501 is emitting light in the light source 500 and test light of wavelength λ1 is input to the core 11 of the MCF transmission line 10, the optical wavelength meter 610 can detect that the wavelength of the test light is λ1. This indicates that the test light output from the LD 501 is propagating through the core 11 of the MCF transmission line 10 via the SCF 111 and MCF 101 of the FIFO 100. In other words, the SCF 111 and the core 11 are associated with each other. Then, the optical switch 600 switches the output destination of the test light from the optical wavelength meter 610 to the optical power meter 620. This allows the optical power meter 620 to measure the optical power of the test light of wavelength λ1 that has propagated through the core 11. Furthermore, the loss of the path from the SCF 111 to the end 22 via the core 11 can also be calculated from the power of the inspection light output by the light source 500 .

[0027] When the LD that outputs the test light in light source 500 is changed from LD 501 to LD 502, LD 503, and LD 504, the core of MCF transmission line 10 through which the test light propagates also changes to core 12, core 13, and core 14, respectively. After the wavelength of the test light is identified by optical wavelength meter 610, the output destination of the test light is switched from optical wavelength meter 610 to optical power meter 620. As a result, the optical power of each of the test lights output from cores 12-14 and the loss of the path through cores 12-14 can be measured by optical power meter 620 in the same manner as for core 11. For example, when the light source of the test light is switched from LD 501 to LD 502, test light of wavelength λ2 is output from the second core of end portion 22. Therefore, when test light of wavelength λ2 is detected by the optical wavelength meter 610, it can be determined that the wavelength of the test light output by the light source 500 has been switched to λ2, and as a result, it has become possible to measure the optical power, etc. of the test light propagated through the core 12 connected to the SCF 112.

[0028] 2 is a diagram illustrating optical axis adjustment of an MCF in a splicing device 800. The splicing device 800 can independently hold the MCF 101 and the MCF transmission line 10. The splicing device 800 brings the end of the MCF 101 and the end 21 of the MCF transmission line 10 close to each other. The splicing device 800 then performs optical axis adjustment by adjusting the relative positions of the X-axis, Y-axis, Z-axis, and the rotation angle θ around the central axis of the MCF 101 and the MCF transmission line 10. By performing optical axis adjustment between the MCF 101 and the MCF transmission line 10 for each core according to the optical power of the test light measured by the optical power meter 620, the FIFO 100 and the MCF transmission line 10 can be optically connected with low loss while suppressing variations between the cores. When the optical power of the test light output from the MCF 101 of the FIFO 100 can be considered to be equal, the difference in optical power between the wavelengths of the test light measured by the optical power meter 620 indicates the difference in loss between the cores from the SCFs 111-114 to the end 22. It is preferable that these differences are small. It is also preferable that the connection loss between the FIFO 100 and the MCF transmission line 10 is small. That is, it is preferable that the optical axis adjustment is performed so that the optical power of the test light of each wavelength measured by the optical power meter 620 is large. Furthermore, when the optical power of the test light of each wavelength output from the MCF 101 and the loss at each wavelength in the cores 11-14 of the MCF transmission line 10 are both known, these known values ​​may be used to perform the above-mentioned optical axis adjustment.

[0029] For example, first, the light source 500 is caused to output an inspection light beam having a wavelength of λ1. Then, optical axis adjustment is performed between the MCF 101 and the core 11 at the end 21 so that the optical power of the inspection light beam is increased. After that, the wavelength of the inspection light beam output by the light source 500 is switched, and optical axis adjustment is performed between the MCF 101 and the cores 12-14 for each of the inspection light beams having wavelengths of λ2, λ3, and λ4. In the optical axis adjustment, for example, the positional relationship between the cores is adjusted between the cross section of the MCF 101 and the cross section of the end 21. In the optical axis adjustment, the rotation angle around the central axis of the MCF 101 and the MCF transmission line 10 may be adjusted.

[0030] The optical axis adjustment described above is performed on the test light beams with wavelengths λ1 to λ4 so as to suppress variations in the optical power among the test light beams with wavelengths λ1 to λ4 measured by the optical power meter 620. As a result, variations in the connection loss between the cores of the MCF 101 and the end 21 can be suppressed. That is, the first procedure described in this embodiment has the effect of enabling a simple and high-quality connection between the FIFO 100 and the MCF transmission line 10. This is because, in this procedure, the optical power of the test light beam is measured for each of the cores 11 to 14 of the MCF transmission line 10 in accordance with the characteristics of the test light beam. As a result, unlike typical procedures, the first procedure can be completed after the first optical axis adjustment between the FIFO 100 and the end 21 without disconnecting the connection and performing a second optical axis adjustment (i.e., with just one optical axis adjustment).

[0031] In this case, a lower limit (first threshold) of the optical power of the test light may be defined for each of the wavelengths λ1-λ4 (i.e., each core), and the optical axis adjustment between the MCF 101 and the end 21 may be terminated when the optical power measured for all cores is equal to or greater than the first threshold. Alternatively, an upper limit (second threshold) of the optical power may be defined for each core, and the optical axis adjustment between the MCF 101 and the end 21 may be terminated when the optical power measured for all cores is equal to or greater than the first threshold and equal to or less than the second threshold.

[0032] After the optical axis adjustment, the FIFO 100 and the MCF transmission line 10 are fusion-spliced ​​using a splicing device 800. Fusion-splicing the FIFO 100 and the MCF transmission line 10 allows the FIFO 100 and the MCF transmission line 10 to be integrated. This makes it possible to improve the reliability of the portion where the FIFO 100 and the MCF transmission line 10 are connected. Note that methods other than fusion may be used to connect these two MCFs. For example, the MCF 101 and the MCF transmission line 10 can be fixed together using an adhesive that uses ultraviolet-curing resin after the optical axis adjustment is complete.

[0033] By following the above procedure, the FIFO 100 and the MCF transmission line 10 can be connected so as to satisfy a predetermined loss condition with only one optical axis adjustment. That is, the MCF connection system 1 of this embodiment can easily connect the FIFO and the MCF with high quality. Furthermore, during this connection, the optical power of the test light can be measured while identifying the cores 11-14 of the MCF connected to the FIFO 100, and the loss of the MCF transmission line 10 can be calculated.

[0034] (Another expression of the first embodiment) The above-described effects of the MCF connection system 1 can also be achieved by the following configuration. The reference symbols in Figure 1 are given in parentheses. That is, the MCF connection system (1) comprises an MCF transmission line (10) having N cores (N is an integer of 2 or more), a first FIFO (100), a light source (500), a connection means (800), an identification means (610), and a measurement means (620).

[0035] A light source (500) outputs N test lights having different characteristics to one end (SCFs 111-114) of the first FIFO (100). A connection means (800) optically connects a first end (21) constituting one end of the MCF transmission line (10) to the other end (101) of the first FIFO (100). An identification means (610) identifies the characteristics (wavelength in the first embodiment) of the test lights output from the second end (22). A measurement means (620) measures the first optical power, which is the optical power of the test lights output from the second end (22), for each core (11-14) of the MCF transmission line (10) in correspondence with the characteristics of the test lights.

[0036] Furthermore, the light source (500) inputs test light to each of the multiple cores (SCF111-114) at one end of the first FIFO (100). The connection means (800) adjusts the optical axis between the other end (MCF101) of the first FIFO and the first end (21) for each core so that each value of the first optical power falls within a predetermined range.

[0037] FIG. 3 is an example flowchart of the first step in the above-described expression. In the first step, first, test light is input to each of the multiple cores at one end of the first FIFO (S01 in FIG. 3). Each test light has different characteristics. Then, the other end of the first FIFO is optically connected to the first end for each core (S02). The characteristics of the test light output from the second end are identified (S03), and the first optical power is measured in accordance with the characteristics (S04). Furthermore, the optical axis between the one end of the first FIFO and the first end is adjusted so that each value of the first optical power falls within a predetermined range (S05). Finally, the one end of the first FIFO and the first end are fusion-spliced ​​(S06).

[0038] The MCF connection system 1 described above and the MCF connection method used therein also have the effect of enabling a simple and high-quality connection between a FIFO and an MCF.

[0039] (Second embodiment) 4 is a diagram illustrating an MCF connection system 2 according to a second embodiment. In the second embodiment, the other end (end 22) of the MCF transmission line 10 and the MCF 201 of the FIFO 200 are optically connected for each core. In the second embodiment, the MCF transmission line 10 is also a four-core MCF. However, the number of cores in the MCF transmission line 10 is not limited to four.

[0040] FIFO200 is a fan-in / fan-out interface for connecting an MCF and four SCFs. One end of FIFO200 is MCF201, and the other end is SCF211-214. In FIFO200, each core of MCF201 is connected to each core of SCF211-214 in a one-to-one relationship. In other words, FIFO200 can connect optical devices with an MCF interface to optical devices with multiple SCF interfaces.

[0041] In FIG. 4, the optical axis adjustment between the FIFO 100 and the MCF transmission line 10 is completed. The procedure described in the first embodiment can be applied to this optical axis adjustment. The MCF connection method described in this embodiment is hereinafter referred to as the second procedure. In the second procedure, the optical axes of the end portion 22 and the MCF 201 are adjusted by the connecting device 801 so that the cores of both are optically coupled at their cross sections. For example, the four cores of the MCF 201 and the four cores 11-14 of the MCF transmission line 10 are optically connected by butt joints at the end portion 22. The function of the connecting device 801 is similar to that of the connecting device 800 described in FIG. 2. That is, the connecting device 801 can adjust the optical axis between the MCF 201 and the MCF transmission line 10 so that the cores of both are optically coupled, and can fix the connection between them by fusion splicing after the optical axis adjustment is completed.

[0042] The SCFs 211-214 of the FIFO 200 are input to optical power meters (OPMs) 621-624 via optical band pass filters (OBPFs) 631-634, respectively. , 633, and 634 are optical filters that transmit only light of wavelengths λ1, λ2, λ3, and λ4, respectively. Optical power meters 621-624 measure the optical power of light that has passed through the optical bandpass filters 631-634, respectively. With this configuration, unlike the first embodiment, the MCF connection system 2 can measure the optical power of each of the test lights of wavelengths λ1-λ4 using the optical power meters 621-624 without using the optical switch 600.

[0043] As in the first embodiment, the light source 500 outputs test light of one of wavelengths λ1-λ4. FIG. 4 illustrates a case in which only the LD 501 emits light and the power of the test light of wavelength λ1 is measured by the optical power meter 621. When the wavelength of the test light is λ1, the LDs 502-504, the optical bandpass filters 632-634, and the optical power meters 622-624 are not involved in the optical axis adjustment, and these blocks are indicated by dashed lines. Then, the optical axes between the end 22 and the SCFs 211-214 are adjusted so that the optical power values ​​output from the cores 11-14 measured by the optical power meters 621-624 fall within a predetermined range. That is, the optical axes of each core between the MCF 201 and the end 22 are adjusted according to the optical power of the test light measured by the optical power meters 621-624. This allows each core of the MCF 201 to be optically connected to the cores 11-14 of the MCF transmission line 10 with low loss while suppressing variations in connection loss between the cores. For example, by observing the measurements of the optical power meters 621-624 while changing the wavelength of the test light and repeatedly adjusting the optical axis between the MCF 201 and the end 22 for each core, the optical axis between the cores 11-14 and the MCF 201 can be adjusted for each core. The optical axis adjustment procedure between the MCF 101 and the end 21 can be applied to the optical axis adjustment between the MCF 201 and the end 22. That is, the light source 500 is caused to output test light with a wavelength λ1. Then, the optical axis adjustment between the core 11 and the MCF 201 is performed at the end 22 so that the optical power of the test light is increased. Thereafter, the wavelength of the test light output by the light source 500 is switched, and optical axis adjustment is performed between the MCF 201 and the cores 12-14 for each of the test light with wavelengths λ2, λ3, and λ4. In the optical axis adjustment, for example, the positional relationship between the cores is adjusted between the cross section of the MCF 201 and the cross section of the end portion 22. In the optical axis adjustment, the rotation angles of the MCF 201 and the MCF transmission line 10 around the central axis may be adjusted.

[0044] By performing optical axis adjustment between the MCF transmission line 10 and the MCF 201 for each of the wavelengths λ1-λ4, it is possible to suppress variations in connection loss for each core. In this case, a lower limit (third threshold) of the optical power of the test light may be specified for each core, and the optical axis adjustment between the MCF 201 and the end 22 may be terminated when the optical power measured for all cores is equal to or greater than the third threshold. Alternatively, an upper limit (fourth threshold) of the optical power may be specified for each core, and the optical axis adjustment between the MCF 201 and the end 22 may be terminated when the optical power measured for all cores is equal to or greater than the third threshold and equal to or less than the fourth threshold.

[0045] By following the above procedure, each core of the FIFO 200 can be connected to each core of the MCF transmission line 10 so as to satisfy a predetermined loss condition. This connection can be performed by identifying the cores of the FIFO 100 and the MCF transmission line 10. The reason for this is that the cores to be connected can be managed based on the wavelength of the test light when adjusting the optical axis between the end portion 22 and the MCF 201. For example, by setting the transmission wavelength of the optical bandpass filter 631 connected to the SCF 211 to wavelength λ1, the SCF 211 can be connected to a path passing through the SCF 111 and the core 11.

[0046] After adjusting the coupling between the MCF 201 and the MCF transmission line 10, the connection between them is fixed using a splicing device 801. Fusion splicing between the MCF 201 and the MCF transmission line 10 allows the FIFO 200 and the MCF transmission line 10 to be integrated while maintaining the loss during optical axis adjustment. This improves the reliability of the spliced ​​portion. Furthermore, by performing the procedure of the second embodiment following the procedure of the first embodiment, the FIFO 100, the MCF transmission line 10, and the FIFO 200 can be integrated. This allows optical devices that use SCF as an interface to be easily connected to both ends of the MCF transmission line 10. Note that methods other than fusion splicing may be used to connect these two MCFs. For example, the MCF 201 and the MCF transmission line 10 can be fixed using an adhesive that uses a UV-curable resin after optical axis adjustment is complete.

[0047] The MCF connection systems 1 and 2 described in the first and second embodiments and the first and second procedures applicable thereto have the effect of enabling FIFOs to be connected to both ends of an MCF simply and with high quality. The reason for this is that, because the wavelength of the test light differs for each core, it is possible to adjust the optical axis while checking the connection loss for each core when connecting one end (end 21) of the MCF transmission line 10 to the FIFO 100 and when connecting the other end (end 22) of the MCF transmission line 10 to the FIFO 200. This allows the connection between the FIFO 100 and the end 21 and the connection between the end 22 and the FIFO 200 to be completed with a single optical axis adjustment, without having to disconnect the connection after the optical axis adjustment.

[0048] Note that MCFs equipped with markers that serve as references for core position when splicing MCFs together are also known (e.g., Patent Document 2). The markers are used to identify the positions of multiple cores included in the MCF at both ends of the MCF. However, connecting such an MCF to a FIFO requires a special fusion splicer equipped with a camera for visually recognizing the markers. Furthermore, when the MCF has a large number of cores, identifying the cores can be difficult even with the markers. However, the MCF connection systems 1 and 2 described in the first and second embodiments adjust the optical axis between the FIFO 100 and the MCF transmission line 10 while identifying each core at both ends (ends 21 and 22) of the MCF transmission line 10 using the wavelength of the inspection light, and then connect the two. Therefore, the MCF transmission line 10 does not require a marker. Furthermore, the connection devices 800 and 801 do not require a special function for visually recognizing the markers on the MCF transmission line.

[0049] (Another way of saying the second step) Fig. 5 is an example of a flowchart of the second procedure. The second procedure described above can also be written as shown in Fig. 5. The reference numerals of Fig. 4 are added in parentheses.

[0050] The second procedure is an MCF connection method performed after the first procedure. In the second procedure, first, similar to the first procedure, test light is input to each of the multiple cores (SCFs 111-114) at one end of the first FIFO (100) (S11 in FIG. 5). Each test light has different characteristics. Next, one end (MCF 201) of the second FIFO (200) is optically connected to the second end (22) for each core (S12). Then, the characteristics of the test light output from the other end (SCFs 211-214) of the second FIFO (200) are identified (S13). In addition, the second optical power, which is the optical power of the test light output from the other end (SCFs 211-214) of the second FIFO, is measured for each core of the MCF transmission line (10) in correspondence with the characteristics of the test light (S14). In this way, the optical axis between the second end (22) and one end (MCF201) of the second FIFO is adjusted so that each value of the second optical power falls within a predetermined range (S15). After the optical axis adjustment is completed, the second end (22) and one end (MCF201) of the second FIFO are fusion-spliced ​​(S16).

[0051] (Modification of the second embodiment) A description will be given of a modified example of the above-mentioned MCF connection system 2. Fig. 6 is a block diagram showing an example of the configuration of an MCF connection system 2A. In the MCF connection system 2A, a light source 500A is used instead of the light source 500 of the MCF connection system 2.

[0052] The light source 500A includes an LD 510, an optical coupler 511, and optical bandpass filters 512-515. The LD 510 is a typical tunable laser diode with a tunable oscillation wavelength. The LD 510 outputs light of any one of wavelengths λ1-λ4 as test light under external control. That is, the light source 500A can output test light of any one of wavelengths λ1-λ4. The optical coupler 511 distributes the test light output by the LD 510 to each core of the FIFO 100. If the FIFO 100 and the MCF transmission line 10 have four cores, the optical coupler 511 is, for example, a 1×4 coupler. If the FIFO 100 and the MCF transmission line 10 have N cores, the optical coupler 511 is, for example, a 1×N coupler. The optical bandpass filters 512, 513, 514, and 515 transmit only light of wavelengths λ1, λ2, λ3, and λ4, respectively. As a result, test light of different wavelengths is input to the SCFs 111-114 of the FIFO 100. Therefore, even when the light source 500A is used, the test light output from each core of the MCF 101 of the FIFO 100 all has a different wavelength. Even when the light source 500A having such a configuration is used, the connection procedure between the FIFO 100 and the MCF transmission line 10 and the connection procedure between the MCF transmission line 10 and the FIFO 200 described with reference to FIGS. 1 to 5 can be performed.

[0053] 6 illustrates a case where LD 510 emits light at wavelength λ1, and the power of the test light of wavelength λ1 is measured by optical power meter 631. When the wavelength of the test light is λ1, optical bandpass filters 513-515, optical bandpass filters 632-634, and optical power meters 622-624 are not involved in the optical axis adjustment, and therefore these blocks are indicated by dashed lines.

[0054] (Third embodiment) 7 is a diagram illustrating an MCF connection system 3 according to a third embodiment of the present invention. In this embodiment, a procedure for connecting an end 22 of the MCF transmission line 10 to a FIFO 200 after an end 21 of the MCF transmission line 10 is connected to a FIFO 100 will be described. The procedure of this embodiment may be implemented instead of the procedure described in the second embodiment. Furthermore, the procedure of the first embodiment may be used to connect the MCF transmission line 10 to a FIFO 100.

[0055] In the following description, as in the previous embodiments, the MCF transmission line 10 has four cores, but the following steps and configurations can also be applied to the case where the MCF has N cores.

[0056] 7, the MCF connection system 3 includes an MCF transmission line 10, FIFOs 100 and 200, a light source 550, an optical switch 601, an optical coupler 651, an optical spectrum analyzer (OSA) 611, and an optical power meter 620.

[0057] The light source 550 includes LDs 501-504. The LDs 501-504 are, for example, semiconductor laser diodes. The LDs 501, 502, 503, and 504 output inspection light beams with wavelengths λ1, λ2, λ3, and λ4, respectively. The wavelengths λ1-λ4 are different from one another. That is, the light source 550 can simultaneously output inspection light beams with wavelengths λ1-λ4. However, the light source 550 may output inspection light beams with three or fewer wavelengths among the wavelengths λ1-λ4. Therefore, the light source 550 may be used in place of the light sources 500 and 500A described in the first and second embodiments.

[0058] Prior to the procedure of this embodiment, the MCF 101 of the FIFO 100 and the end 21 of the MCF transmission line 10 are optically connected for every four cores. As a result, at the end 21, test light beams having different wavelengths are input from the light source 500 to each of the four cores 11-14 of the MCF transmission line 10. As a result, the test light beams having different wavelengths propagate simultaneously through the cores 11-14 of the MCF transmission line 10. The four test light beams are output from the cores 11-14 at the end 22 that forms the other end of the MCF transmission line 10.

[0059] The cores of the MCF 201 and the cores 11-14 of the MCF transmission line 10 are optically connected by butt joints. Light output from the four SCFs 211-214 of the FIFO 200 is input to an optical spectrum analyzer 611 and an optical power meter 620 via an optical switch 601 and an optical coupler 651. The optical switch 601 is a 4×1 optical switch that connects one SCF selected from the SCFs 211-214 to the optical coupler 651. The optical coupler 651 is a 1×2 optical coupler that distributes the light input from the optical switch 601 to the optical spectrum analyzer 611 and the optical power meter 620. The optical spectrum analyzer 611 measures the wavelength of the test light for the core selected by the optical switch 601. That is, the optical switch 601 selects the core for which the wavelength and optical power of the test light are to be measured. The optical power meter 620 measures the optical power of the test light for the core selected by the optical switch 601.

[0060] With this configuration, one of the test lights output from the four SCFs 211 - 214 of the FIFO 200 is input to the optical spectrum analyzer 611 and the optical power meter 620 via the optical switch 601 and the optical coupler 651 .

[0061] The procedure of the second embodiment can be applied to the optical axis adjustment between the end 22 of the MCF transmission line 10 and the MCF 201 of the FIFO 200. That is, the optical axis adjustment is performed between the end 22 and the MCF 201 so that the optical power values ​​measured by the optical power meter 620 are within a predetermined range for each of the wavelengths λ1 to λ4. By setting the light source 550 to simultaneously output test light of wavelengths λ1 to λ4, the wavelengths and optical powers of the test light of wavelengths λ1 to λ4 can be easily and repeatedly measured using the optical spectrum analyzer 611 and the optical power meter 620. Here, the wavelength of the test light is switched simply by switching the optical switch 601. Then, by repeatedly performing the optical axis adjustment between the MCF 201 and the end 22 for each core, the optical axes of the FIFO 200 and the MCF transmission line 10 for each of the cores 11 to 14 can be suitably adjusted for each core. In the procedure of this embodiment, as in the second embodiment, the cores 11-14 of the MCF transmission line 10 and each core of the MCF 201 can be optically connected with low loss while suppressing variations in connection loss between the cores.

[0062] (Modification of the third embodiment) A description will be given of a modified example of the above-described MCF connection system 3. Fig. 8 is a block diagram showing an example of the configuration of a light source 550A that can be used in place of the light source 550 of the MCF connection system 3.

[0063] The light source 550A is composed of an ASE (Amplified Spontaneous Emission) light source 520 and an optical coupler 5 21 and optical bandpass filters 522-525. The ASE light source 520 outputs broadband light (ASE light) with a nearly flat spectrum. The ASE light can be generated by injecting pump light into an optical amplification medium. The wavelength band of the ASE light includes the wavelengths λ1-λ4 of the test light.

[0064] The optical coupler 521 distributes the ASE light output from the ASE light source 520 to each core of the FIFO 100. If the FIFO 100 and the MCF transmission line 10 have four cores, the optical coupler 521 is a 1x4 coupler. If the FIFO 100 and the MCF transmission line 10 have N cores, the optical coupler 521 is a 1xN coupler. The optical bandpass filters 522, 523, 524, and 525 transmit only light of wavelengths λ1, λ2, λ3, and λ4, respectively. This allows test light of wavelengths λ1, λ2, λ3, and λ4 to be simultaneously generated from the ASE light. When the SCFs 111-114 of the FIFO 100 are connected to the light source 550A, the test light of wavelengths λ1-λ4 is input to the SCFs 111-114, respectively. Optical attenuators may be connected in series with the optical bandpass filters 522-525. The attenuation amount of the optical attenuator may be set so that the optical power of the inspection light of each wavelength output from the light source 550 is equal.

[0065] Light source 550A generates inspection light using the ASE generated by ASE light source 520 and optical bandpass filters 522-525. Therefore, when changing the wavelength of the inspection light, it is sufficient to change the transmission bands of optical bandpass filters 522, 523, 524, and 525, and there is no need to change expensive components such as laser diodes.

[0066] Even when the light source 550A is used, the wavelengths of the test lights output from the cores of the MCF 101 of the FIFO 100 are all different. Even when the light source 500A having such a configuration is used, the first procedure and the second procedure described in the above embodiment can be executed.

[0067] (Fourth embodiment) In the first to third embodiments, the cores of the MCF transmission line 10 through which the test light propagates can be identified based on the wavelength of the test light. However, the characteristic of the test light used to identify the cores is not limited to wavelength. For example, the four test light beams input to the SCFs 111-114 of the FIFO 100 may be pulse-width modulated to different widths. For example, the test light beams input to the four cores 11-14 of the MCF transmission line 10 may be modulated to have different pulse widths W1-W4, and an optical receiver capable of identifying the pulse width of an optical signal may be used instead of the optical wavelength meter 610 and the optical spectrum analyzer 611. The optical receiver can then identify the core through which the test light propagates by determining whether the pulse width of the received test light is W1-W4. In other words, even when the characteristic of the test light is the pulse width of the test light, the core can be identified in the same way as when the characteristic of the test light is the wavelength.

[0068] Alternatively, the test light may be pulsed light, and the transmission interval of the pulsed light may be changed for each core. For example, the test light may be a pulse train, and test light with different pulse intervals T1-T4 may propagate through each core. In this case, an optical receiver capable of identifying the reception interval of optical pulses is used instead of an optical wavelength meter and an optical spectrum analyzer. Such an optical receiver can identify the core through which the test light has propagated by determining whether the reception interval of the pulses of the test light being received is T1-T4. In other words, even when the characteristic of the test light is the pulse interval of the test light, the core can be identified in the same way as when the characteristic of the test light is the wavelength or pulse width.

[0069] The modulation method of the inspection light is not limited to the pulse width or pulse interval. For example, the pulse light may be amplitude-modulated with a low-frequency signal of 10 kHz to 1 MHz. The modulation frequency may be changed for each core, and the core through which the inspection light has propagated may be identified by detecting the frequency of the low-frequency signal with an optical receiver.

[0070] When the inspection light is pulsed, it is preferable to modulate the inspection light so that the duty ratio of each inspection light propagating through the cores 11 to 14 is the same, which prevents the difference in optical power of the inspection light between the cores 11 to 14 from being affected by the duty ratio when measuring the optical power.

[0071] Note that part or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0072] (Appendix 1) MCF (Multi-Core Fiber) transmission line with N cores, The first FIFO (Fan-In / Fan-Out), a light source that outputs N test lights having different characteristics to one end of the first FIFO; a connection means for optically connecting a first end portion of the MCF transmission line to the other end of the first FIFO; an identification means for identifying a characteristic of the test light output from a second end portion that constitutes the other end of the MCF transmission line; a measuring means for measuring a first optical power indicating an optical power of each of the N cores of the test light output from the second end portion for each of the cores of the MCF transmission line in correspondence with the characteristics; 1. An MCF connection system comprising: N is an integer equal to or greater than 2, the light source inputs the test light to each of a plurality of cores at one end of the first FIFO; the connection means adjusts an optical axis between the other end of the first FIFO and the first end for each core so that each value of the first optical power falls within a predetermined range, and after adjusting the optical axis between the other end of the first FIFO and the first end, fixes the connection between the other end of the first FIFO and the first end. MCF connection system.

[0073] (Appendix 2) One end of the first FIFO is a plurality of SCFs (Single Core Fibers) included in the first FIFO, The other end of the first FIFO is an MCF included in the first FIFO. MCF connection system as described in Appendix 1.

[0074] (Appendix 3) a second FIFO; the connecting means optically connects the second end and one end of the second FIFO; the measuring means measures second optical powers, which are optical powers of the plurality of test lights output from the other end of the second FIFO, for each core of the MCF transmission line in correspondence with the characteristics; the connecting means adjusts an optical axis between the second end and one end of the second FIFO so that each value of the second optical power falls within a predetermined range. MCF connection system as described in Appendix 2.

[0075] (Appendix 4) one end of the second FIFO is an MCF included in the second FIFO; The other end of the second FIFO is a plurality of SCFs provided in the second FIFO. MCF connection system as described in Appendix 3.

[0076] (Appendix 5) 5. The MCF connection system according to any one of claims 1 to 4, further comprising a control means for controlling the light source, the connection means, the identification means, and the measurement means.

[0077] (Appendix 6) 6. The MCF connection system according to any one of claims 1 to 5, wherein the characteristic is the wavelength of the test light.

[0078] (Appendix 7) 6. The MCF connection system according to any one of claims 1 to 5, wherein the characteristic is a pulse width of the test light.

[0079] (Appendix 8) 6. An MCF connection system according to any one of claims 1 to 5, wherein the characteristic is a duty ratio of a pulse of the inspection light.

[0080] (Appendix 9) An MCF connection method including a first procedure for optically connecting an MCF transmission line having N cores and a first FIFO, N is an integer equal to or greater than 2, The first step comprises: inputting test light having different characteristics into each of a plurality of cores at one end of the first FIFO; optically connecting the other end of the first FIFO and a first end forming one end of the MCF transmission line for each core; Identifying a characteristic of the test light output from a second end portion of the MCF transmission line; measuring a first optical power indicating an optical power for each of the N cores of the test light output from the second end portion for each of the cores of the MCF transmission line in correspondence with the characteristics; adjusting an optical axis between the other end of the first FIFO and the first end so that each value of the first optical power falls within a predetermined range; fixing the connection between the other end of the first FIFO and the first end; How to connect to MCF.

[0081] (Appendix 10) One end of the first FIFO is a plurality of SCFs (Single Core Fibers) included in the first FIFO, The other end of the first FIFO is an MCF included in the first FIFO. MCF connection method described in Appendix 10.

[0082] (Appendix 11) An MCF connection method including a second step executed after the first step, The second step comprises: optically connecting one end of the second FIFO to the second end for each core; identifying the characteristic of the test light output from the other end of the second FIFO; measuring a second optical power, which is the optical power of the test light output from the other end of the second FIFO, for each core of the MCF transmission line in correspondence with the characteristics; adjusting an optical axis between the second end and one end of the second FIFO so that each value of the second optical power falls within a predetermined range; fixing a connection between the second end and one end of the second FIFO; 11. The MCF connection method according to claim 9 or 10,

[0083] (Appendix 12) one end of the second FIFO is an MCF included in the second FIFO; The other end of the second FIFO is a plurality of SCFs provided in the second FIFO. MCF connection method described in Appendix 11.

[0084] (Appendix 13) 13. The MCF connection method according to claim 11, wherein at least one of the first procedure and the second procedure is controlled by a control means.

[0085] (Appendix 14) 14. The MCF connection method according to any one of claims 9 to 13, wherein the characteristic is the wavelength of the inspection light.

[0086] (Appendix 15) 14. The MCF connection method according to any one of claims 9 to 13, wherein the characteristic is a pulse width of the inspection light.

[0087] (Appendix 16) 14. The MCF connection method according to any one of claims 1 to 13, wherein the characteristic is a duty ratio of a pulse of the inspection light.

[0088] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0089] For example, some or all of the operations of the MCF connection system of each embodiment may be programmed. The MCF connection system of each embodiment may include a computer that executes this program. The computer may implement some or all of the functions of the MCF connection system of each embodiment by executing the program. The computer may be, for example, a logic device, a central processing unit, or a digital signal processing unit. The control device 900 described in the embodiments may also include a computer. At least one of the first procedure and the second procedure may be controlled by the control unit 900. The program may also be recorded on a computer-readable, fixed, non-transitory recording medium. The recording medium may be, for example, a flexible disk, a fixed magnetic disk, or a non-volatile semiconductor memory. The program may also be distributed via a network.

[0090] Furthermore, the configurations described in the respective embodiments are not necessarily mutually exclusive, and the functions and effects of the present invention may be achieved by a configuration that combines all or part of the above-described embodiments. [Explanation of symbols]

[0091] 1, 2, 2A, 3 MCF connection system 10 MCF transmission line 11-14 Core 21, 22 End 100, 200 FIFO 101, 201 MCF 500, 500A, 550, 550A light source 501-504 Laser Diode (LD) 511, 521 Optical Coupler 512-515, 522-525 Optical Bandpass Filters (OBPF) 520 ASE light source 600, 601 Optical switch 610 Optical wavelength meter 611 Optical Spectrum Analyzer (OSA) 620-624 Optical Power Meter (OPM) 631-634 Optical bandpass filter 651 Optical Coupler 800, 801 connection devices 900 Control device

Claims

1. an MCF (Multi-Core Fiber) transmission line having N cores; a first FIFO (Fan-In / Fan-Out); a light source that outputs N test lights having different characteristics to one end of the first FIFO at different timings; a connecting means for optically connecting a first end portion of the MCF transmission line to the other end of the first FIFO; an identification means for identifying a characteristic of the test light output from a second end portion of the MCF transmission line; a measuring means for measuring a first optical power indicating an optical power of each of the N cores of the test light output from the second end portion for each of the cores of the MCF transmission line in correspondence with the characteristics; N is an integer of 2 or more, the light source inputs the test light to each of a plurality of cores at one end of the first FIFO; the connection means adjusts the optical axis between the other end of the first FIFO and the first end for each core so that each value of the first optical power falls within a predetermined range, and fixes the connection between the other end of the first FIFO and the first end after adjusting the optical axis between the other end of the first FIFO and the first end.

2. One end of the first FIFO is a plurality of SCFs (Single Core Fibers) provided in the first FIFO; The other end of the first FIFO is an MCF included in the first FIFO.

10. The MCF connection system of claim 1.

3. Further comprising a second FIFO; the connecting means optically connects the second end and one end of the second FIFO; the measuring means measures a second optical power, which is the optical power of the test light output from the other end of the second FIFO, for each core of the MCF transmission line in correspondence with the characteristics; the connecting means adjusts an optical axis between the second end and one end of the second FIFO so that each value of the second optical power falls within a predetermined range, and fixes the connection between the second end and one end of the second FIFO after adjusting the optical axis between the second end and one end of the second FIFO.

3. The MCF connection system of claim 2.

4. one end of the second FIFO is an MCF included in the second FIFO, The other end of the second FIFO is provided with a plurality of SCFs.

4. The MCF connection system of claim 3.

5. The MCF connection system according to claim 1 , further comprising a control means for controlling the light source, the connection means, the identification means, and the measurement means.

6. 6. The MCF connection system according to claim 1, wherein the characteristic is a wavelength of the test light.

7. 6. The MCF connection system according to claim 1, wherein the characteristic is a pulse width of the test light.

8. 6. The MCF connection system according to claim 1, wherein the characteristic is a duty ratio of a pulse of the inspection light.

9. 1. An MCF connection method including a first step for optically connecting an MCF transmission line having N cores to a first FIFO, the first step comprising: N is an integer of 2 or more, The first step comprises: inputting test lights having different characteristics to each of the plurality of cores at one end of the first FIFO at different timings; the other end of the first FIFO is optically connected to a first end forming one end of the MCF transmission line for each core; identifying a characteristic of the test light output from a second end portion of the MCF transmission line; measuring a first optical power indicating an optical power for each of the N cores of the test light output from the second end portion for each core of the MCF transmission line in correspondence with the characteristics; adjusting an optical axis between the other end of the first FIFO and the first end so that each value of the first optical power falls within a predetermined range; fixing the connection between the other end of the first FIFO and the first end; MCF connection method.

10. One end of the first FIFO is a plurality of SCFs (Single Core Fibers) provided in the first FIFO; The other end of the first FIFO is an MCF included in the first FIFO.

10. The MCF connection method according to claim 9.

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