JP2013068891A - Method of manufacturing multi-core interface, and multi-core interface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a multi-core interface, which is capable of coping with even core intervals of 40 μm or less in a multi-core fiber, suppressing optical loss, and uniformly processing a plurality of optical fibers, and to provide a multi-core interface.SOLUTION: A front end part of an optical fiber 7 has a coating layer 2c removed therefrom and is immersed in an etching liquid S and is etched while being drawn up at a prescribed speed, to form a taper portion 8 which has a tapered front end and has a front end outer diameter equal to core intervals of a multi-core fiber 10, and then the optical fiber 7 is drawn up from the etching liquid S at a breath to form a straight portion 9 having a constant outer diameter equal to core intervals of the multi-core fiber 10, on the front end side of the taper portion 8, whereby a processed optical fiber 2 is prepared. Front end parts of a plurality of prepared processed optical fibers 2 are bundled and inserted to a through hole 4 of a ferrule 3.

Description

  The present invention relates to a manufacturing method of a multi-core interface and a multi-core interface that are connected to an end of a multi-core fiber and individually input light to a plurality of cores or individually extract light propagating through a plurality of cores. .

  With the recent increase in transmission capacity, research and development of optical communication using Space Division Multiplexing (SDM) and Mode Division Multiplexing (MDM) has been promoted and used in the past. Attempts have been made to drastically improve the transmission capacity of optical communication by combining with wavelength division multiplexing (WDM).

  In the space division multiplexing method, it is necessary to prepare a plurality of optical transmission paths. As an optical cable used for this space division multiplexing system, for example, a cable in which a number of optical fibers are bundled to form a single optical cable can be considered. However, such an optical cable is expensive and has a problem that it cannot be used as a submarine optical cable laid on the seabed with a high static pressure because of the large outer diameter of the entire optical cable.

  Therefore, a multi-core fiber (MCF) in which a plurality of cores are formed in a common clad has been proposed (see, for example, Patent Documents 1 and 2).

  In a multi-core fiber, since a plurality of cores are formed in a common cladding, the cost is lower than the case where a plurality of optical fibers are bundled into one optical cable, and the outer diameter of the entire optical cable can be reduced. It can also be used on the seabed with high static pressure.

  By realizing a space division multiplexing system using such a multi-core fiber and applying a wavelength division multiplexing system to an optical signal propagating through each core, the transmission capacity can be further improved.

  By the way, in the multi-core transmission system using the multi-core fiber, an optical functional component having a fan-out function from the transmitter to the multi-core fiber and from the multi-core fiber to the receiver is required.

  In other words, when trying to realize the space division multiplexing method using multi-core fibers, it is necessary to have optical functional components that individually input light to multiple cores of multi-core fibers, or to individually extract light propagating through multiple cores. It becomes. Such an optical functional component is referred to as a multi-core interface (MCI).

  In particular, when a multi-core fiber is used for an optical cable for long-distance transmission, it is necessary to insert an optical amplifier (repeater) in the middle of the transmission path, but an optical amplifier that amplifies the light propagating through a plurality of cores at once. It is difficult to realize, and even if realized, it becomes very expensive. Therefore, the light propagating through the multiple cores of the multi-core fiber is taken out and individually input to an optical amplifier such as an EDFA (Erbium Doped Fiber Amplifier), and the light amplified by each optical amplifier is individually incident on the multiple cores again A multi-core interface is required. However, current optical fiber couplers cannot handle multi-core fibers and cannot be used as multi-core interfaces.

  Furthermore, when using a multi-core fiber for a submarine optical cable, it is required to make the diameter of the multi-core fiber as small as possible in order to withstand high static pressure at the sea bottom. It is desirable to make the diameter of the multi-core fiber as small as possible because the smaller the diameter is, the more the fracture due to bending can be suppressed. Therefore, a multi-core interface capable of handling such a small-diameter multi-core fiber is desired.

  Therefore, the present inventors use a plurality of small-diameter optical fibers in which the outer diameter of the clad is formed to be equal to the core interval of the multi-core fiber, and bundle the tips of the plurality of small-diameter optical fibers into a ferrule. A multi-core interface is being proposed.

JP-A-5-341147 JP 2010-55028 A JP 2005-134622 A

  However, the proposed multicore interface has a problem that it is difficult to cope with the case where the core interval of the multicore fiber to be connected is 40 μm or less. It is technically difficult to manufacture a small-diameter optical fiber having a cladding outer diameter of 40 μm or less and a uniform cladding outer diameter. This is because the loss increases.

  Further, since the proposed multi-core interface uses a very thin optical fiber, there is a problem in that transmission loss due to microbending increases due to the influence of side pressure or the like.

  Therefore, the present inventors use a general optical fiber having an outer diameter of 125 μm, which is easy to manufacture, and taper the tip of the optical fiber to reduce the outer diameter of the cladding at the tip of the optical fiber. I thought to match the core spacing of the multi-core fiber to be connected.

  As a technique for processing the tip of the optical fiber into a tapered shape, for example, there is Patent Document 3.

  In Patent Document 3, the tip of the optical fiber is brought into contact with a rotating grinding plate, whereby the tip of the optical fiber is scraped off to produce a plurality of tapered tapered optical fibers, and the produced plurality of processed optical fibers are emitted. An optical fiber bundle in which ends are assembled is disclosed.

  However, in the optical fiber bundle of Patent Document 3, as shown in FIG. 5A, the optical axes of the cores 52 of the processed optical fibers 51 at the exit end are not parallel to each other. Therefore, the optical fiber bundle 50 cannot be directly connected to the multicore fiber as a multicore interface.

  Further, when used as a multi-core interface, it is necessary to insert the end portion (outgoing end portion) of each processed optical fiber 51 into a ferrule and perform polishing processing so that the end faces coincide with each other, but the optical fiber bundle of FIG. When polishing is applied to 50, as shown in FIG. 5 (b), the core 52 is polished in an oblique state, so that the core diameter of the core 52 at the end face changes and the MFD (mode field diameter) changes. As a result, there arises a problem that the optical loss at the connection portion increases. Further, when the polishing depth is changed, the interval between the cores 52 is changed, so that there is a problem that the misalignment with respect to the core of the multi-core fiber to be connected is generated and the optical loss at the connection portion is increased.

  Furthermore, since the grinding process of Patent Document 3 needs to be performed on each optical fiber, it is difficult to perform uniform processing on a plurality of optical fibers, and mass production is difficult. is there.

  Therefore, the object of the present invention is to solve the above-mentioned problems, can cope with the case where the core interval of the multi-core fiber is 40 μm or less, can suppress the optical loss, and is uniform for a plurality of optical fibers. It is an object to provide a multicore interface manufacturing method and a multicore interface that can be easily processed.

  The present invention was devised to achieve the above object, and has a plurality of cores and a common clad covering the periphery of the plurality of cores, and the plurality of cores form a triangular lattice at equal intervals. A multi-core interface manufacturing method for individually inputting light to the plurality of cores or for individually extracting light propagating through the plurality of cores. By removing the coating layer at the tip of the fiber and immersing the tip of the optical fiber from which the coating layer has been removed in an etching solution and performing the etching process while pulling up the optical fiber at a predetermined speed, the tip is tapered. And a tapered portion having an outer diameter equal to the core interval of the multi-core fiber is formed, and then the optical fiber is pulled up from the etching solution all at once. By forming a straight portion having the same outer diameter and the same core interval as the multi-core fiber on the distal end side of the tapered portion, a processed optical fiber is manufactured, and the plurality of manufactured processing The end portions of the optical fibers are bundled and inserted into the through-holes of the ferrule, the end surfaces of the bundled processed optical fibers and the end surfaces of the ferrules are matched by polishing, and the processed optical fibers are attached to the ferrule. This is a manufacturing method of a fixed multi-core interface.

  The plurality of optical fibers may be simultaneously manufactured by performing the etching process simultaneously on the plurality of optical fibers.

  The tapered portion may be formed with an inclination angle of less than 1 °.

  As the optical fiber, an optical fiber having an outer diameter of 125 μm may be used.

  Further, the present invention includes a plurality of cores and a common clad covering the periphery of the plurality of cores, and the plurality of cores are connected to end portions of multicore fibers formed at equal intervals so as to form a triangular lattice. A multi-core interface for individually entering light into the plurality of cores or individually extracting light propagating through the plurality of cores, wherein the coating layer is removed from the tip of the optical fiber, and the coating layer Forming a tapered portion having a tapered tip and an outer diameter equal to the core interval of the multi-core fiber at the tip end of the optical fiber, and the core interval of the multi-core fiber on the tip side of the tapered portion. A plurality of processed optical fibers formed with straight portions having the same outer diameter and a constant outer diameter, and ferrules formed with through holes into which the processed optical fibers are inserted. A plurality of processed optical fibers are bundled and inserted into the through-holes of the ferrules, and the end surfaces of the bundled processed optical fibers and the end surfaces of the ferrules are polished by polishing. A multi-core interface in which the plurality of processing optical fibers are matched and fixed to the ferrule.

  According to the present invention, it is possible to cope with the case where the core interval of the multi-core fiber is 40 μm or less, the optical loss can be suppressed, and the multi-core interface capable of uniformly processing a plurality of optical fibers. A manufacturing method and a multi-core interface can be provided.

It is a figure which shows the multi-core interface which concerns on one embodiment of this invention, (a) is a sectional side view, (b) is the 1B-1B sectional view taken on the line, (c) is a sectional side view of a processing optical fiber, d) is an enlarged cross-sectional view of the tip of each processed optical fiber when a plurality of processed optical fibers are bundled. (A) is a cross-sectional view of the multi-core fiber to be connected, and (b) is a side view when the multi-core interface is connected to the multi-core fiber. (A)-(c) is a figure explaining the manufacturing method of the multi-core interface which concerns on one embodiment of this invention. It is a schematic block diagram of the multi-core transmission system using the multi-core interface of FIG. (A), (b) is a figure explaining the problem at the time of using the conventional optical fiber bundle as a multi-core interface.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the multi-core interface manufactured by the multi-core interface manufacturing method according to the present embodiment will be described.

  1A and 1B are diagrams showing a multi-core interface according to the present embodiment, where FIG. 1A is a side sectional view, FIG. 1B is a sectional view taken along line 1B-1B, and FIG. 1C is a side sectional view of a processed optical fiber. (D) is an expanded sectional view of the tip of each processed optical fiber when a plurality of processed optical fibers are bundled. 2A is a cross-sectional view of a multicore fiber to be connected, and FIG. 2B is a side view when a multicore interface is connected to the multicore fiber.

  As shown in FIGS. 1 and 2, the multi-core interface 1 is connected to the end of the multi-core fiber 10, and individually enters light into the plurality of cores 11 of the multi-core fiber 10, or transmits light that propagates through the plurality of cores 11. It is for taking out individually.

As shown in FIG. 2A, the multi-core fiber 10 includes a plurality of cores 11 and a common clad 12 covering the periphery of the plurality of cores 11, so that the plurality of cores 11 form a triangular lattice. It is formed at intervals. Here, one core 11 is formed at the center of the clad 12, and the six cores 11 are formed at equal intervals so that the centers are positioned on a coaxial circle with the center of the core 11 as an axis. The case of using will be described. These seven cores 11 are formed such that the intervals (core intervals) d ₁ between adjacent cores 11 are all equal. The clad diameter D ₁ of the multicore fiber 10 is, for example, about 125 μm, and the core interval d ₁ is, for example, about 42 μm.

  The multi-core interface 1 has seven processed optical fibers 2 corresponding to the seven cores 11 of the multi-core fiber 10 and a ferrule 3 in which a through hole 4 into which the processed optical fiber 2 is inserted is formed. Here, the case where seven processed optical fibers 2 are used corresponding to the seven cores 11 of the multi-core fiber 10 will be described. However, the number of processed optical fibers 2 is the same as the number of cores 11 of the multi-core fiber 10. The number.

  In the present embodiment, the processed optical fiber 2 has one core 2a, a clad 2b that covers the periphery of the core 2a, and a coating layer 2c that covers the clad 2b, and the outer diameter of the clad 2b is 125 μm in general. A typical optical fiber 7 is used. The optical fiber 7 having the outer diameter of the clad 2b of 125 μm is easy to manufacture and low in cost, and the outer diameter of the clad 2b can be uniformly manufactured as compared with the thin optical fiber. Note that the outer diameter of the clad 2b is not limited to 125 μm, and the transmission loss due to the microbend is not larger than the allowable range due to the influence of the side pressure or the like, and may be any outer diameter that can be uniformly manufactured. What is necessary is just about 125 micrometers.

  As the optical fiber 7 used for the processed optical fiber 2, it is desirable to use a fiber whose core 2 a is formed to have a core diameter substantially the same as the core diameter of the multi-core fiber 10 to be optically coupled. Here, the case where all the seven cores 11 of the multi-core fiber 10 have the same core diameter and the cores 2a of the optical fibers 7 used for the seven processed optical fibers 2 all have the same core diameter will be described. When the ten cores 11 are formed with different core diameters, the core diameter of the optical fiber 7 used for each processed optical fiber 2 is set so as to be substantially equal to the core diameter of the core 11 of the multi-core fiber 10 to be optically coupled. It is good to set.

The processed optical fiber 2 removes the coating layer 2c at the tip of the optical fiber 7, and the tip of the optical fiber 7 from which the coating layer 2c has been removed has a tapered tip and an outer diameter at the tip of the multi-core fiber 10. A taper portion 8 equal to the core interval d ₁ is formed, and a straight portion 9 having the same core interval d ₁ and outer diameter d ₂ of the multi-core fiber 10 and a constant outer diameter d ₂ is formed on the tip end side of the taper portion 8. Formed. A method for producing the processed optical fiber 2 will be described later.

  In the processed optical fiber 2, the tapered portion 8 and the straight portion 9 are formed at the distal end portion of the optical fiber 7. However, in the tapered portion 8 and the straight portion 9, only the outer diameter of the cladding 2 b changes, and the core 2 a The core diameter is formed so as not to change.

  The multi-core interface 1 is formed by bundling the end portions of the processed optical fibers 2 and inserting them into the through-holes 4 of the ferrule 3, the end surfaces of the bundled processed optical fibers 2 (the front end surfaces of the straight portions 9), the end surfaces of the ferrules 3 Are matched by polishing and each processed optical fiber 2 is fixed to a ferrule 3.

  When bundling the distal end portions of the respective processed optical fibers 2, as shown in FIG. 1 (d), the surfaces of the tapered portions 8 are aligned with each other (the overall diameter when bundling gradually toward the distal end side. Each processed optical fiber 2 is bundled so that the diameter of the processed optical fiber 2 is reduced. Then, the straight portion 9 of the processed optical fiber 2 disposed on the outside is slightly bent at the base end portion thereof, and approaches the straight portion 9 of the processed optical fiber 2 disposed at the center, and the straight portion of each processed optical fiber 2 9 are arranged in parallel. As a result, the optical axes of the cores 2a of the straight portions 9 are parallel to each other.

At this time, since the straight portion 9 may be damaged if the bending at the base end portion of the straight portion 9 is increased, it is desirable to make the inclination angle of the tapered portion 8 as small as possible, and to be less than 1 °. Is desirable. In other words, the angle θ of the tapered portion 8 with respect to the radial direction of the processed optical fiber 2 (left and right direction in FIG. 1C) is desirably 89 ° <θ <90 °. In this case, for example, when the outer diameter of the clad 2b of the optical fiber 7 is 125 μm and the outer diameter d ₂ of the straight portion 9 is ₂₀ to 60 μm, the length L ₁ of the taper portion 8 is 3010 μm or more. In FIG. 1C and FIG. 1D, for easy understanding, the inclination angle of the taper portion 8 is larger than the actual _one, and the length L ₁ of the taper portion 8 is shorter than the actual _one . .

The length L ₂ of the straight portion 9 may be not less than the polishing depth of the polishing process, and may be 30 μm or more (for example, 100 μm).

Further, the outer diameter D ₂ of the distal end portion (straight portion 9) when the seven processed optical fibers 2 are bundled is made to be substantially the same as the cladding diameter D ₁ of the multicore fiber 10. When the outer diameter d ₂ of the straight portion 9 is about 42 μm, the outer diameter D ₂ of the tip when the seven processed optical fibers 2 are bundled is about 126 μm (≈125 μm).

The through-hole 4 of the ferrule 3 is formed in a circular shape in a cross-sectional view, and is gradually contracted toward the tip so as to be along each processed optical fiber 2 when each processed optical fiber 2 is inserted into the through-hole 4. It is formed in a tapered shape with a diameter. Diameter of the distal end portion of the through-hole 4 (the portion for accommodating the straight portion 9) is substantially the same form as the outer diameter D ₂ of the entire straight portion 9 which bundles. As the ferrule 3, any material may be used, for example, a metal, glass, or resin may be used.

  On the insertion side of the processed optical fiber 2 in the through-hole 4, a concave groove 5 is formed for accommodating a portion having the coating layer 2 c of each processed optical fiber 2, and the ferrule 3 is formed from the tip of each processed optical fiber 2. , And so as to cover up to the portion having the coating layer 2c. In the present embodiment, the concave groove 5c having a constant diameter is formed, but the concave groove 5c may be formed in a tapered shape that gradually decreases in diameter toward the distal end side.

  The through holes 4 and the concave grooves 5 are filled with an adhesive 6 so that the processed optical fibers 2 and the ferrule 3 are bonded and fixed. As the adhesive 6, for example, a thermosetting resin, a room temperature curable resin, an ultraviolet curable resin, or the like can be used.

  When connecting the multi-core interface 1 to the end of the multi-core fiber 10, as shown in FIG. 2B, a multi-core fiber ferrule 13 is provided at the end of the multi-core fiber 10, and the end face of the multi-core fiber ferrule 13 is provided. And the end face of the ferrule 3 of the multi-core interface 1 may be brought into contact with each other to optically couple each core 11 of the multi-core fiber 10 and the core 2a of each processed optical fiber 2. At this time, it is desirable to interpose a refractive index matching material having a refractive index equivalent to that of the cores 11 and 2a between the ferrules 13 and 3 so as to reduce the optical loss at the connection portion.

  Next, a method for manufacturing the multi-core interface according to the present embodiment will be described.

  In the manufacturing method of the multi-core interface according to the present embodiment, first, the processed optical fiber 2 is manufactured by etching the optical fiber 7 with hydrofluoric acid (HF). By performing the etching process while pulling up the optical fiber 7, the portion staying in the etching solution becomes longer as the portion is closer to the tip of the optical fiber 7, and the etching is further performed, and the outer shape of the clad 2 b is tapered. Can be formed.

Specifically, as shown in FIG. 3 (a), the coating layer 2c at the tip of the optical fiber 7 is removed, and the tip of the optical fiber 7 from which the coating layer 2c has been removed is removed with an etching solution (here, a fluorine). Acid) Soak in S. At this time, the length of the optical fiber 7 immersed in the etching solution S is determined by considering the length L ₁ of the taper portion 8 and the length L of the straight portion 9 in consideration of polishing in the polishing step described later, the etching amount, and the like. Make it longer than the sum of _two .

Thereafter, as shown in FIG. 3B, etching is performed while pulling up the optical fiber 7 at a predetermined speed v ₁ , so that the tip is tapered and the outer diameter of the tip is equal to the core interval d _{1 of the} multicore fiber 10. An equal taper portion 8 is formed. The speed v ₁ for pulling up the optical fiber 7 may be set as appropriate according to the etching speed, the desired inclination angle of the tapered portion 8, and the like. The pulling time t _{1 at} this time is L ₁ / v ₁ .

After the tapered portion 8 is formed, as shown in FIG. 3C, the optical fiber 7 is pulled up from the etching solution S all at once, so that the core interval d ₁ and the outer diameter of the multicore fiber 10 are formed on the distal end side of the tapered portion 8. d ₂ are equal, and the outer diameter d ₂ to form a straight portion 9 is constant. Thereby, the processing optical fiber 2 is obtained. At this time, the speed v ₂ when pulling up the optical fiber 7 from the etching solution S is larger than the above-described speed v ₁ , and the optical fiber 7 is pulled up from the etching solution S as quickly as possible, so that the etching amount in the straight portion 9 is reduced. It is desirable to be the same.

  Here, the case where one processed optical fiber 2 is manufactured has been described, but in practice, a plurality of optical fibers 7 are simultaneously etched to manufacture a plurality of processed optical fibers 2 at once. Is desirable. As a result, it is possible to produce a processed optical fiber 2 that is uniformly processed under the same conditions (that is, in which the uniform tapered portion 8 and the straight portion 9 are formed), and a plurality of processed optical fibers 2 are formed. At the same time, it is possible to improve mass productivity.

  After producing the processed optical fiber 2, the tip ends of the produced processed optical fibers 2 are bundled and inserted into the through holes 4 of the ferrule 3, and the end face of each bundled processed optical fiber 2 and the end face of the ferrule 3 are polished. Each processed optical fiber 2 is fixed to the ferrule 3 by matching.

  At this time, in order to make it easy to insert the processed optical fiber 2 into the through hole 4, before inserting the processed optical fiber 2 into the through hole 4, the bundled processed optical fibers 2 are integrated by applying ultrasonic vibration to the distal end portion thereof. The integrated processing optical fiber 2 may be inserted into the through hole 4.

  Further, when performing the polishing process, each processed optical fiber 2 and the ferrule 3 are bonded and fixed in a state where the tip end portion (straight portion 9) of each bundled processed optical fiber 2 is slightly protruded from the end face of the ferrule 3. Then, it is preferable to polish the protruding portion so that the end face of each processed optical fiber 2 coincides with the end face of the ferrule 3. As described above, the multi-core interface 1 is obtained.

  Next, a multi-core transmission system using the multi-core interface 1 of the present invention will be described. Here, a multi-core transmission system using both space division multiplexing and wavelength division multiplexing will be described.

  As shown in FIG. 3, the multi-core transmission system 21 includes a transmitter 22, EDFAs 23a and 23b as optical amplifiers, and a receiver 24. The transmitter 22 and the EDFA 23a are connected to the multi-core fiber 10a and the multi-core. It is connected via a dispersion compensating fiber (MC-DCF (Multi Core Dispersion Compensating Fiber)) 25, and an EDFA 23a and an EDFA 23b installed in front of the receiver 24 are connected via a multi-core fiber 10b. is there. The multicore fiber 10a and the multicore dispersion compensating fiber 25 are connected by fusion splicing or connector connection.

  The transmitter 22 and the multi-core fiber 10a are connected via the multi-core interface 1a, and the multi-core dispersion compensating fiber 25 and the EDFA 23a are connected via the multi-core interface 1b. The EDFA 23a and the multi-core fiber 10b are connected via a multi-core interface 1c, and the multi-core fiber 10b and the EDFA 23b installed in the previous stage of the receiver 24 are connected via a multi-core interface 1d. These multi-core interfaces 1a to 1d are all multi-core interfaces of the present invention.

  The transmitter 22 has a transmission having n LDs (Laser Diodes) 22a that emit light of different wavelengths and AWGs (Arrayed Waveguide Gratings) 22b that combine the light from the LDs 22a. A plurality of portions 22c are provided. In FIG. 3, only three transmitters 22c are shown for simplification of the drawing, but the number of transmitters 22c is the same as the number of cores 11 of the multicore fibers 10a and 10b.

  The optical fiber extending from the AWG 22b of each transmitter 22c is connected to the processed optical fiber 2 of the multi-core interface 1a by fusion connection or connector connection. Thereby, each transmission part 22c of the transmitter 22 is each optically coupled with each core 11 of the multi-core fiber 10a via the multi-core interface 1a.

  In the present invention, since a general optical fiber 7 having a cladding diameter of 125 μm is used for the processing optical fiber 2, an optical fiber extending from the processing optical fiber 2 and the AWG 22b (a general optical fiber having a cladding diameter of 125 μm) The fusion splicing is easy. For example, it is technically very difficult to connect a thin optical fiber having a cladding diameter of 40 μm and a general optical fiber having a cladding diameter of 125 μm with a low loss, and a thin optical fiber having a cladding diameter of 40 μm is clad with a diameter of 80 μm. And connecting the optical fiber having a cladding diameter of 80 μm to the optical fiber having a cladding diameter of 125 μm.

  In the present invention, a thin optical fiber is not used, and the processed optical fiber 2 having a clad diameter of 125 μm from the thin straight portion 9 through the taper portion 8 is used. There is no need to go through a fiber connection, and it is possible to greatly improve the optical loss generated at the connection.

  Each processed optical fiber 2 of the multi-core interface 1b is connected to an optical fiber extending from the input side of the EDFA 23a by fusion connection or connector connection. Thereby, each core of the multi-core dispersion compensating fiber 25 is optically coupled to each EDFA 23a via the multi-core interface 1b. In addition, since the core diameter of the multi-core dispersion compensating fiber 25 is generally smaller than the core diameter of the normal multi-core fibers 10a and 10b, an optical fiber 7 having a small core diameter is used as each processed optical fiber 2 of the multi-core interface 1b. It is desirable to use what was used.

  The optical fiber extending from the output side of the EDFA 23a is connected to the processed optical fiber 2 of the multi-core interface 1c by fusion connection or connector connection. Thereby, each EDFA 23a is optically coupled to each core 11 of the multi-core fiber 10b via the multi-core interface 1c.

  Each processed optical fiber 2 of the multi-core interface 1d is connected to an optical fiber extending from the input side of the EDFA 23b by fusion connection or connector connection. Thereby, each core 11 of the multi-core fiber 10b is optically coupled to each EDFA 23b via the multi-core interface 1d.

  The receiver 24 includes a plurality of receiving units 24c each having an AWG 24b that demultiplexes light output from the EDFA 23b for each wavelength and n PDs (Photo Diodes) 24a that receive the light demultiplexed by the AWG 24b. Yes. Each receiving unit 24c is optically connected to the EDFA 23b via an optical fiber or the like. In FIG. 3, for the sake of simplification, the number of receiving units 24c is three, but the number of receiving units 24c is the same as the number of cores 11 of the multicore fibers 10a and 10b.

  In the multi-core transmission system 21, the light emitted from each LD 22a is multiplexed by the AWG 22b and enters the core 11 of the multi-core fiber 10a via the multi-core interface 1a. The light incident on the core of the multicore fiber 10a passes through the multicore fiber 10a and the multicore dispersion compensation fiber 25, enters the EDFA 23a via the multicore interface 1b, and is amplified by the EDFA 23a.

  The light amplified by the EDFA 23a enters the core 11 of the multicore fiber 10b through the multicore interface 1c, passes through the multicore fiber 10b, and enters the EDFA 23b through the multicore interface 1d. The light incident on the EDFA 23b is amplified by the EDFA 23b, and the amplified light is incident on the receiving unit 24c of the receiver 24. The light incident on the receiving unit 24c is demultiplexed by the AWG 24b and received by each PD 24a.

  In this multi-core transmission system 21, if the number of LDs 22a and PDs 24a is n, and the number of cores of the multi-core fibers 10a and 10b (that is, the number of transmitters 22c, receivers 24c, and EDFAs 23a and 23b) is m, then n × m The optical signal of the channel can be transmitted and received, and the transmission capacity can be dramatically improved.

As described above, in the manufacturing method of the multi-core interface according to the present embodiment, the coating layer 2c at the tip of the optical fiber 7 is removed, and the tip of the optical fiber 7 from which the coating layer 2c has been removed is etched. Etching is performed while dipping in S and pulling up the optical fiber 7 at a predetermined speed v ₁ , thereby forming a tapered portion 8 having a tapered tip and an outer diameter equal to the core interval d ₁ of the multicore fiber 10. Thereafter, the optical fiber 7 is pulled up from the etching solution S all at once, so that the core interval d ₁ and the outer diameter d ₂ of the multi-core fiber 10 are equal and the outer diameter d ₂ is constant at the tip side of the tapered portion 8. The processed optical fiber 2 is manufactured by forming the portion 9, and the tips of the manufactured processed optical fibers 2 are bundled and inserted into the through-hole 4 of the ferrule 3. The end surface of the processing optical fiber 2 and the end surface of the ferrule 3 are matched by polishing, and the plurality of processing optical fibers 2 are fixed to the ferrule 3.

The outer diameter d ₂ of the straight portion 9 can be adjusted as appropriate according to the etching amount (residence time in the etching solution S), and can be set to 40 μm or less, so that the core interval d ₁ of the multicore fiber 10 is 40 μm or less. It becomes possible to cope with this.

  That is, according to the present invention, even if the core 11 has a small diameter and a high density, the multi-core fiber 10 can individually enter and exit the core 11 of the multi-core fiber 10. The multi-core fiber 10 in which the core 11 is formed with such a small diameter and high density can withstand high static pressure on the seabed and is resistant to bending, and thus is suitable as a submarine optical cable. Therefore, the present invention greatly contributes to the improvement of the transmission capacity of the submarine optical transmission system.

  Further, since the thin straight portion 9 and the tapered portion 8 are accommodated in the ferrule 3 and only the optical fiber 7 having a large diameter (here, a clad diameter of 125 μm) is extended from the ferrule 3, a microbend caused by a lateral pressure is used. It is possible to suppress transmission loss due to the transmission.

  Further, by forming the straight portion 9 at the distal end of the processed optical fiber 2, changes in MFD due to polishing and changes in the core interval are eliminated, and the optical axes of the cores 2 a are parallel to each other at the distal end portion of each processed optical fiber 2. Thus, the optical loss at the connection portion when connected to the multi-core fiber 10 can be significantly suppressed.

  Furthermore, according to the present invention, a plurality of optical fibers 7 can be etched at the same time, and a plurality of optical fibers 2 can be manufactured at once. And mass production is easy.

  Further, according to the present invention, it is possible to use an optical fiber having a clad diameter of 125 μm that is easy to manufacture and low in cost, and whose outer shape can be easily manufactured uniformly. Since the uniformity of the outer diameter is not impaired by the etching process, the processed optical fiber 2 having a uniform process can be manufactured with higher accuracy, which contributes to further reduction of the optical loss at the connection portion.

  Furthermore, according to the present invention, since the multi-core interface 1 is configured using the processed optical fiber 2 having a large diameter (here, a cladding diameter of 125 μm) from the thin straight portion 9 through the taper portion 8, the small diameter Compared to the case where an optical fiber is used, it is easy to connect to another general optical fiber (optical fiber having a clad diameter of 125 μm), and connection with low optical loss is possible.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, the optical fiber 7 is pulled up at a constant speed v ₁ when the tapered portion 8 is formed. However, the present invention is not limited to this, and includes, for example, an outer diameter measuring means such as a laser. While measuring the outer diameter, the pulling speed of the optical fiber 7 may be controlled so that the tapered portion 8 has a desired shape.

  In the above embodiment, the multi-core interface 1 is formed using seven processed optical fibers 2. However, the number of processed optical fibers 2 can be set as appropriate according to the number of cores 11 of the multi-core fibers 10 to be connected. It is. However, as the number of the processing optical fibers 2 increases, the bending at the base end portion of the straight portion 9 of the processing optical fiber 2 disposed on the outside increases, and in this case, the inclination angle of the taper portion 8 is further reduced. Therefore, it is desirable to make the bending at the base end portion of the straight portion 9 as small as possible.

  Furthermore, in the said embodiment, although the through-hole 4 of the ferrule 3 was formed in circular shape by sectional view, it is not restricted to this, You may form the through-hole 4 of the ferrule 3 in hexagonal shape by sectional view. . Thereby, the processing optical fiber 2 can be easily aligned.

  Furthermore, in the above embodiment, the bundled processed optical fiber 2 is inserted into the ferrule 3 in which the through-hole 4 is formed. However, the present invention is not limited to this, and a tape material is wound around the tip of the bundled processed optical fiber 2. It is also possible to form a ferrule 3. Further, instead of using the ferrule 3, a resin shrinkable tube is used, and after the processed optical fiber 2 is inserted into the shrinkable tube, the shrinkable tube is heated and contracted to hold the processed optical fiber 2. Good.

DESCRIPTION OF SYMBOLS 1 Multi-core interface 2 Processed optical fiber 2a Core 2b Clad 2c Coating layer 3 Ferrule 4 Through-hole 5 Groove 6 Adhesive 7 Optical fiber 8 Tapered part 9 Straight part

Claims (5)

A plurality of cores and a common clad covering the periphery of the plurality of cores, wherein the plurality of cores are connected to end portions of a multicore fiber formed at equal intervals so as to form a triangular lattice; A method of manufacturing a multi-core interface for individually entering light, or individually extracting light propagating through the plurality of cores,
By removing the coating layer at the tip of the optical fiber and immersing the tip of the optical fiber from which the coating layer has been removed in an etching solution and performing the etching process while pulling up the optical fiber at a predetermined speed, A tapered portion that is tapered and has an outer diameter equal to the core interval of the multi-core fiber is formed, and then the optical fiber is pulled up from the etching solution at a stretch, so that the multi-core fiber is formed on the distal end side of the tapered portion. Fabricate a processed optical fiber by forming a straight section where the core interval and the outer diameter are equal and the outer diameter is constant,
The plurality of fabricated optical fibers are bundled and inserted into a through-hole of a ferrule, and the end surfaces of the bundled plural processed optical fibers and the end surfaces of the ferrule are matched by polishing, and the plurality of processed An optical fiber is fixed to the ferrule. A method for manufacturing a multi-core interface. The method of manufacturing a multi-core interface according to claim 1, wherein the etching process is simultaneously performed on a plurality of the optical fibers, and the plurality of processed optical fibers are collectively manufactured. The method of manufacturing a multi-core interface according to claim 1, wherein the tapered portion is formed with an inclination angle of less than 1 °. The method for manufacturing a multi-core interface according to any one of claims 1 to 3, wherein an optical fiber having an outer diameter of 125 µm is used as the optical fiber. A plurality of cores and a common clad covering the periphery of the plurality of cores, wherein the plurality of cores are connected to end portions of a multicore fiber formed at equal intervals so as to form a triangular lattice; A multi-core interface for individually entering light or individually extracting light propagating through the plurality of cores,
In addition to removing the coating layer at the tip of the optical fiber, a tapered portion having a tapered tip and an outer diameter equal to the core interval of the multi-core fiber is formed at the tip of the optical fiber from which the coating layer has been removed. A plurality of processed optical fibers having a straight portion on the distal end side of the tapered portion, in which the core interval and the outer diameter of the multi-core fiber are equal and the outer diameter is constant, and
A ferrule having a through hole into which the plurality of processed optical fibers are inserted, and
The end portions of the plurality of processing optical fibers are bundled and inserted into the through-holes of the ferrules, and the end surfaces of the bundled processing optical fibers and the end surfaces of the ferrules are matched by polishing, and the plurality of processing A multi-core interface characterized in that an optical fiber is fixed to the ferrule.