JP6013953B2 - Multi-core fiber connection fan-in / fan-out device, optical connection device, and optical connection method - Google Patents

Description

  The present invention relates to a fan-in / fan-out device, an optical connection device, and an optical connection method in the field of optical communication, and particularly suitable for high-efficiency connection between a multi-core optical fiber that performs large-capacity signal transmission and an optical element. Connection structure.

In recent years, the amount of information transmitted by optical communication has been increasing year by year. In particular, in trunk line communication systems, the information transmission capacity of existing optical fibers approaches the saturation limit, and various new transmission methods that exceed this limit have been devised. Transmission methods using multi-core fibers have been in the limelight since 2000 as a leading fundamental technology that breaks the limits of transmission capacity. Here, when a multi-core fiber is used as an optical signal transmission path, an element that connects a plurality of optical transmission paths at an optical signal input to the multi-core fiber or an optical signal output from the multi-core fiber, or a connection Parts for are needed. As prior arts related to such connection elements and connection parts, there are known documents described below.
In Patent Document 1, a refractive index distribution type lens array is inserted into a connection part between multi-core fiber end faces having seven cores to reduce a divergence angle of light emitted from the core of the multi-core fiber, and to face each other. In this structure, a light beam incident on the core of the fiber end face is focused.

  Patent Document 2 describes a device that converts an optical arrangement when connecting an end face of a multicore fiber and an end face of each optical fiber in a configuration in which a plurality of single core optical fibers are arranged and arranged.

  Patent Document 3 describes a structure of a flat plate element that connects a multi-core fiber and a plurality of single-core fibers. Two optical waveguides are formed in this flat element, and one end of these optical waveguides can be connected to a multi-core fiber, and the other end can be connected to two single-core fibers. A guide groove is formed so that

  Non-Patent Document 1 describes an optical path system in which light passes through two lenses placed between a multicore fiber and a single core fiber when connecting one multicore fiber and a plurality of single core fibers. Has been. Non-Patent Document 2 describes a method of using a confocal lens system using two convex lenses when connecting multi-core fibers.

  Non-Patent Document 3 describes a method of three-dimensionally forming a plurality of optical waveguides in a flat plate, and optical connection with the end surfaces of a multi-core fiber having seven cores at the formed end surfaces of the plurality of optical waveguides. The three-dimensional configuration of the optical waveguide is determined so as to be possible.

  In Non-Patent Document 4, as a method of forming an optical waveguide in a substrate, there is a method of forming an optical waveguide by squeezing a laser beam and irradiating the surface of the substrate and increasing the optical refractive index of the laser irradiation portion. It has been described.

JP 2010-286718 A JP 2010-286697 A Japanese Patent Laid-Open No. 62-118310

2012 IEICE Electronics Society Conference Electronics Electronics Proceedings 1 C-3-82, September 11-14, 2012 Toyama 2012 IEICE Electronics Society Annual Conference 1 C-3-83, September 11-14, 2012 Toyama City 2012 IEICE Electronics Society Conference Electronics Electronics Proceedings 1 B-10-12, September 11-14, 2012 Toyama City Technical Digest 9th Optoelectronics and Communications Conference, 3rd International Conference on Optical Internet, July 12-16, 2004, Yokohama, Japan, pp. 88-89 (Technical Digest Ninth optoelectronics and communications conference, Third international conference on optical internet, July 12-16, 2004, Yokohama, Japan, pp.88-89.)

  The structure disclosed in Patent Document 1 is based on the premise that the seven cores of the multi-core fiber are formed symmetrically at equal intervals. However, when any one of the cores is manufactured out of the center symmetrical position due to dimensional variation in the manufacturing process of the multi-core fiber, the connection loss when connecting the end faces of the multi-core fiber increases. There is a problem.

  In the optical array conversion device disclosed in Patent Document 2 described above, when any one of the cores of the multi-core fiber is manufactured out of position with respect to the design arrangement / dimension, the misaligned core is optically connected. There is a problem that loss increases.

  Even in the flat plate element disclosed in Patent Document 3, when the core position is shifted from the design due to manufacturing variations during the production of the multi-core fiber, between the optical waveguide in the flat plate element and the core of the multi-core fiber. There is a problem that connection loss increases.

  Also, in both cases of Non-Patent Document 1 and Non-Patent Document 2, if the core position or arrangement deviates from the design value due to the finished dimensional variation in the multi-core fiber manufacturing process, There exists a subject that the connection loss of the optical fiber which opposes increases.

  Accordingly, an object of the present invention is to provide an optical connection that can construct a highly reliable optical communication system by reducing connection loss when connecting a plurality of optical waveguides simultaneously in parallel and by increasing the signal-to-noise ratio of an optical signal. It is to provide a device and an optical connection method.

  Furthermore, by applying the configuration of the present invention, it is possible to operate in a low power consumption state in which the light output is suppressed, and therefore it is to provide a system capable of energy saving operation.

  As a means for solving the above-described problems, the first lens system and the second lens system are inserted into the connection portion between the FI / FO and the multi-core fiber. In the first lens system, the FI / In this configuration, a collimator lens and a convex lens are provided on the end face side of the FO. On the other hand, in a 2nd lens system, it is set as the structure which provided the collimator lens and the convex lens in the multi-core fiber end surface.

  Further, in the first lens system of this configuration, the convex lens has a focal length equal to the distance between the convex lens and the collimator lens. In the second lens system, the convex lens has a focal length that is the same as that of the convex lens. The arrangement is such that the distance from the collimator lens at the end of the multicore fiber is equal.

  Here, a device that connects one multi-core fiber and a plurality of single-core optical fibers is referred to as a fan-in / fan-out device (hereinafter, fan-in / fan-out device is abbreviated as FI / FO). . The FI / FO has a structure having a plurality of optical waveguides therein, and the optical waveguide in the FI / FO is disposed on the end surface on the side connected to the multicore fiber in a cross section perpendicular to the optical axis direction of the multicore fiber. On the other hand, at the end connected to a single core optical fiber, the arrangement and interval of the optical waveguides in the FI / FO are arranged side by side in a plane or in a multilayer structure, The spacing between the waveguides can be reduced, for example, to a dimension equal to the cladding diameter of a single core optical fiber.

  By adopting the configuration of the present invention, it is possible to construct a highly reliable optical communication system by reducing the connection loss when simultaneously connecting a plurality of optical waveguides in parallel and by increasing the signal-to-noise ratio of the optical signal. It is possible to provide a connection device and an optical connection method.

  Furthermore, by applying the configuration of the present invention, it is possible to operate in a state of low power consumption with suppressed light output, and thus it is possible to provide a system capable of energy saving operation.

The perspective view which shows embodiment of this invention. The side surface schematic diagram which shows embodiment of this invention. The side surface schematic diagram which shows embodiment of this invention. The graph which compared the change of the connection loss with respect to the optical axis offset by the optical connection structure to which this invention is applied, and the conventional optical connection structure. The schematic diagram which shows another embodiment of this invention. The schematic diagram which shows another embodiment of this invention. The schematic diagram which shows the formation process of the optical waveguide and lens in Embodiment 1 of this invention. The schematic diagram which shows the formation process of the lens in Embodiment 1 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

The present Example 1 is demonstrated in detail using FIG. 1 and FIG.
In FIG. 1, seven multi-core fibers 3 having seven cores and seven single-core optical fibers 4 are arranged via a fan-in / fan-out device (abbreviated as FI / FO) 2 provided on the mount 1. It is a perspective view which shows the structure to connect.

  For example, the multi-core fiber 3 is aligned and fixed in a V-groove provided on the surface of the mount 1. In addition, a second lens system, which will be described later, is disposed between the multi-core fiber 3 and the FI / FO 2. In addition, the first lens system is provided in the FI / FO 2 on the side facing the second lens system.

  When the light input to one of the cores of the multi-core fiber 3 is output from the multi-core fiber 3, the light passes through the second lens system and enters the position corresponding to the position of the one core of the first lens system. To do. The incident light propagates through the optical waveguide in the FI / FO 2 corresponding to the position and is output to the optical fiber 4. Light input to the other core of the multicore fiber 3 also propagates in the same way.

  In the multi-core fiber 3, one core is arranged at the center, and six cores are arranged in a regular hexagon around the center core. The thickness of each core disposed in the multi-core fiber 3 (here, the core refers to a portion where the refractive index of light is higher than the surrounding and includes almost 90% or more of the energy distribution of propagating light). For example, it is about 10 μm in the single mode transmission with a wavelength of 1.5 μm. The interval between adjacent cores is in the range of 20 μm to 125 μm, and the crosstalk of the optical transmission signal between the adjacent cores is ensured to be 30 dB or more.

  FIG. 2 shows a structure in which a connection portion between the FI / FO 2 and the multi-core fiber 3 is viewed from a direction (lateral direction) perpendicular to the traveling direction of transmitted light. At the connection end A of the FI / FO 2, each end of the optical waveguides 8, 9, 10 faces the multi-core fiber 3 through a collimator lens 11 and a convex lens 12 as a first lens system.

  In addition, in this figure, although the optical waveguide 8, 9, 10 is shown, since the optical waveguide of this figure is arranged in each vertex and center part of a regular hexagon, the figure seen from the horizontal direction is Only the optical waveguides 8, 9, 10 are visible. Accordingly, since the optical waveguides are arranged in the back direction so as to overlap each of the optical waveguides 8, 9, and 10, the optical waveguides 8, 9, and 10 are described as representatives. The same treatment is applied to each core of a multicore fiber 3 to be described later.

On the other hand, on the end face of the multi-core fiber 3, a collimator lens 13 and a convex lens 14 are arranged as second lens systems in the respective cores of 5, 6, and 7. Here, in the first lens system, the distance between the collimator lens 11 and the convex lens 12 is equal to the focal length f ₅ of the convex lens 12. In the second lens system, the distance between the collimator lens 13 and the convex lens 14 is the focal length of the convex lens 14. It has become equal disposed f _3. Here, the diameters of the convex lenses 12 and 14 need to be equal to or less than the interval between adjacent cores in the multi-core fiber, and are in the range of 20 μm to 125 μm. The lower limit of 20 μm is determined from the restriction of crosstalk with the adjacent core. On the other hand, the upper limit value of 125 μm is determined because the minimum interval at which the optical fibers are arranged in parallel is defined as 125 μm.

In addition, the focal lengths f ₅ and f ₃ can be selected within a range of, for example, 100 μm to several mm. Thus, it is desirable to be about several mm.

  FIG. 3 shows a configuration in which end portions of the convex lens 21, the collimator lens 20, and the multi-core fiber 25 constituting the second lens system are integrally stored in the ferrule 26. With such a configuration, in the mounting process in the connection between the FI / FO 30 and the multi-core fiber 25, it is not necessary to adjust the position of the lens itself, and the working time can be greatly reduced.

  FIG. 4 shows how the connection loss when the present invention is applied in the connection between the FI / FO and the multi-core fiber with respect to the optical axis lateral shift of the core (optical waveguide) (position shift in the direction perpendicular to the light traveling direction). It is the graph which measured how it changed. When the present invention is applied, even if the optical axis lateral deviation of the optical waveguide increases from 0 μm to 10 μm, the connection loss is about 0.1 dB, which can be ignored in practice. Here, the connection loss is an amount proportional to the ratio between the input optical power and the output optical power.

  The reason why the connection loss can be significantly reduced with respect to the lateral deviation of the optical axis depends on the configuration of the collimator lens 11, the convex lens 12, the collimator lens 13, and the convex lens 14. That is, the light output from the multi-core fiber 3 is output as parallel light by the collimator lens 13 and is provided on the incident surface of the FI / FO 2 via the convex lens 13 while holding the parallel light by the convex lens 14. The light enters the collimator lens 11. At this time, the optical system is designed so that the incident light is focused on the collimator lens 11 even if the convex lens 14 and the convex lens 13 are displaced within a predetermined range. In addition, it turns out that the shift | offset | difference in a predetermined range is at least within 10 micrometers as the measurement result of FIG. 4 shows. Such a deviation is a practically sufficient allowable range.

  Here, the collimator lens has a function of maintaining the straightness of the light beam and is structurally a distributed lens in which the refractive index is inclined inside the lens. The collimator lens may be built in one end of the optical waveguide or externally attached to one end thereof. The built-in will be described later.

  On the other hand, in the conventional connection configuration using no lens, it can be seen that as the optical axis lateral deviation of the core increases from 0 μm, the connection loss increases rapidly. For example, when the optical axis lateral deviation is 5 μm, the connection loss increases to about 2 dB.

  The process concept for manufacturing FI / FO will be described with reference to FIG. In FIG. 7, when laser light 41 having a wavelength of 805 nm from the top and a light output of several tens of mW to several W is repeatedly irradiated with a single pulse time width of about femtoseconds toward the upper surface of the quartz substrate 40, the laser light is focused vertically and horizontally. A minute part of about 1 μm is locally heated and reaches around 1000 ° C. near the melting temperature of quartz. As a result, the refractive index of the overheated quartz locally increases, and a portion having a refractive index of about 0.003 larger than the refractive index of 1.455 in the peripheral portion not subjected to heating is formed.

  By adjusting the focal position of the laser light applied to the quartz, it is possible to focus on a position 100 μm deep from the outermost surface of the quartz. The optical waveguide 42 and the bent waveguide 43 can be formed. In addition, when the laser beam 44 is irradiated from the end face of the quartz 40, the laser beam scanning method is made into a coaxial cylindrical shape, and the focal position is changed from the end face of the quartz in the depth direction, an optical waveguide is formed in the depth direction. can do. Furthermore, if the laser beam is scanned concentrically near the end face of quartz, a convex lens 45 or a refractive index distribution type structure in which the refractive index is decreased concentrically from the central axis toward the periphery can be produced. A collimator lens 46 can be formed.

  FIG. 8 focuses on the end face of the multi-core fiber 50, and when the above-described laser light 52 is repeatedly irradiated with a single pulse time of femtosecond, the refractive index increases coaxially in a part of the core, and the collimator lens 53 can be formed. .

Example 2 will be described in detail with reference to FIGS. 5 and 6.
FIG. 5A is a perspective view of an FI / FO 61 configured using seven single core optical fibers 62. The FI / FO 61 is formed by bundling and fusing seven optical fibers so that the end A can be connected to a multi-core fiber having seven cores. It is provided on each optical fiber end face and integrated with the FI / FO 61 as shown in FIG. The plano-convex lens 60 may be prepared by, for example, molding an acrylic resin containing polymethyl methacrylate (PMMA), a vinyl resin, an ethylene resin, or the like by nanoimprint technology, or by processing synthetic quartz. You may do it. A plano-convex lens provided by adhering to the end A of the FI / FO has a function of taking out the emitted light from the end face of each optical fiber as a parallel beam.

  FIG. 6 is a schematic cross-sectional view of the main part of the configuration in which the FI / FO 61 is connected to the multi-core fiber 65. When connecting the FI / FO 61 and the multi-core fiber 65 having seven cores on the mount 58, seven convex lenses 64 are provided on the FI / FO 61 side according to the configuration of the present invention, as in the above-described embodiment. Also, seven convex lenses 67 are provided on the multi-core fiber side. The FI / FO 61 and the convex lens 64 are arranged so that the optical axes of the respective cores coincide in the ferrule 63, and the interval between the plano-convex lens 60 and the convex lens 64 is equal to the focal length of the convex lens 64. On the other hand, the distance between the convex lens 67 and the plano-convex lens 66 is arranged to be equal to the focal length of the convex lens 67.

  With the configuration of the present invention, in mounting and assembling the FI / FO 61 and the multi-core fiber 65, the distance S between the ferrule 63 and the ferrule 68 and the rotation angle adjustment in the direction perpendicular to the optical axis can be adjusted to the V groove on the mount 58. Achieved by adjusting along.

  In addition, the present Example 2 has the effect that the stand which mounts FI / FO61 is unnecessary, or the attachment dimension of a connection part can be made small and can be reduced in size.

  In the first and second embodiments of the present invention, the case where the number of cores of the multi-core fiber is 7 is described. However, the number of cores is not limited to 7, and the number of cores is not less than 2 and not more than 6, or not less than 8. It is clear that the configuration of the invention can be applied.

  The product to which the present invention is applied is an FI / FO device having the first and second lens systems, or an FI / FO device to which an extra length of a multicore fiber and a single core optical fiber may be attached. And

1,58 ... Mount,
2, 30, 61 ... Fan-in / fan-out device (FI / FO),
3, 25, 50, 65 ... multi-core fiber,
4, 62 ... optical fiber,
5,6,7,51 ... core,
8, 9, 10, 42 ... optical waveguide,
11, 13, 20, 22, 46, 53 ... Collimator lens,
12, 14, 21, 23, 45, 64, 67 ... convex lens,
26, 63, 68 ... Ferrule,
40 ... quartz,
41, 44, 52 ... laser light,
43 ... Bent waveguide,
60, 66: Plano-convex lens.

Claims (8)

A light input / output end capable of inputting / outputting a light beam from both ends and a plurality of optical waveguides,
One end of the light input / output end includes a first light input / output end connectable to a multi-core fiber,
The other end of the light input / output end includes a second light input / output end connectable to an optical fiber having a plurality of single cores,
A convex lens having the same optical axis as each of the plurality of optical waveguides and provided at the first light input / output end;
A refractive index gradient distribution type lens that maintains a straight distance of the light beam provided on a side of the plurality of optical waveguides facing the convex lens while maintaining a predetermined distance between the convex lens ,
The fan-in / fan-out device , wherein the predetermined interval is a focal length of the convex lens . A light input / output end capable of inputting / outputting a light beam from both ends and a plurality of optical waveguides,
One end of the light input / output end includes a first light input / output end connectable to a multi-core fiber,
The other end of the light input / output end includes a second light input / output end connectable to an optical fiber having a plurality of single cores,
A first convex lens having the same optical axis as each of the plurality of optical waveguides and provided at the first light input / output end;
A first gradient index gradient lens that maintains a first distance from the first convex lens and that maintains the straightness of the light beam provided on the side of the plurality of optical waveguides facing the first convex lens;
A second gradient index type lens provided at an input / output end of the multi-core fiber facing the first convex lens;
Between the first convex lens and the front Stories second refractive index gradient distribution type lens, and a second convex lens provided to hold the second distance from said second refractive index gradient distribution type lens,
The first interval is a focal length of the first convex lens;
The optical connection device, wherein the second interval is a focal length of the second convex lens. A fan-in fan-out device according to claim 1, optical device and the optical fiber shall be the being provided integrally on a substrate having a multi-core fiber and a plurality of single cores. The optical connection device according to claim 2 , wherein the optical waveguides are spaced apart by 125 μm or more.   The optical connecting device according to claim 2, wherein an interval between adjacent cores of the multi-core fiber is arranged symmetrically within a range of 20 μm to 125 μm. The optical connection device according to claim 2 , wherein the first gradient index gradient lens is built in or externally attached. Light having a multi-core fiber connected to one end of a fan-in / fan-out device having a light input / output end capable of inputting / outputting light beams from both ends and a plurality of optical waveguides, and having a plurality of single cores at the other end Connect the fiber,
A refractive index gradient distribution type lens that maintains straightness of the light beam is provided at one end of the plurality of optical waveguides,
An optical connection method, wherein a convex lens having the same optical axis as each of the plurality of optical waveguides is provided, and the gradient index gradient lens is disposed at a focal length of the convex lens. Another gradient index distribution lens provided at the input / output end of the multi-core fiber facing the convex lens;
Between the convex lens and the front Symbol another refractive index gradient distribution type lens, and a separate lens that is provided to hold a predetermined distance from said other of the refractive index gradient distribution type lens,
The optical connection method according to claim 7 , wherein the predetermined interval is a focal length of the another convex lens.

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