JP2008064869A - Optical branching apparatus, optical module, and optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical branching apparatus capable of reducing coupling loss between an optical fiber and a translucent medium, and also to obtain an optical module and an optical transmission system with the same. <P>SOLUTION: An optical signal made incident on the incident part 40 of the translucent medium 22 is reflected to six emitting parts 42 by a slope 40A. Also, the reflected optical signal is reflected by a slope 42A installed on each emitting part 42. Reflection by the slopes 40A, 42A scatters part of the optical signal. The numerical aperture (NA3) of the exiting optical fiber 46, however, is prepared larger than the numerical aperture (NA1) of the incident optical fiber 24. As a result, this way can reduce coupling loss between the incident optical fiber 24 or the exiting optical fiber 46 and the translucent medium 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical branching device that branches an optical signal, an optical module including the optical branching device, and an optical transmission system.

When an optical signal is incident on a light-transmitting medium and branched into a plurality of outputs, a plate-shaped light-transmitting medium is formed in a staircase shape, and each step portion is provided with an inclined surface that reflects the light signal. There has been proposed an optical branching device that splits an optical signal into a plurality of optical fibers and emits it by forming a signal emitting portion. (Patent Document 1)
This optical branching device is characterized in that the size of the output portion of the optical signal formed on the translucent medium is approximately equal to the core diameter of the optical fiber that receives the optical signal output from the output portion. Thus, the coupling loss at the connection portion between the translucent medium and the optical fiber is improved.
Japanese Patent Laid-Open No. 2003-4972

  However, an ideal surface cannot be created on the inclined surface that reflects the optical signal provided at each step portion, and subtle irregularities and waviness are added to the inclined surface.

  As described above, the unevenness or the like is added to the inclined surface, so that an optical signal incident on the translucent medium is diffused when reflected by the inclined surface. In such a case, in an optical fiber having only a large core diameter, an optical signal may be transmitted through the optical fiber and cause coupling loss.

  An object of the present invention is to reduce the coupling loss between an optical fiber and a translucent medium in consideration of the above facts.

  An optical branching device according to claim 1 of the present invention has a plurality of step portions at one end, and causes an optical signal to enter or exit from the translucent medium at least at one end or the other end. A plate-like translucent medium having an inclined surface for coupling, an incident optical fiber coupled to an incident portion and entering the optical signal into the translucent medium, and a translucent segment coupled to the output portion. An optical branching device including an output optical fiber that emits signal light from a medium, wherein the numerical aperture of the output optical fiber is larger than the numerical aperture of the incident optical fiber.

  According to the above configuration, for example, the translucent medium reflects the optical signal incident from the incident optical fiber on the inclined surface, branches the optical signal through the plurality of emitting portions, and enters the outgoing optical fiber.

  On the other hand, since fine irregularities and undulations are added to the inclined surface in production, the optical signal that is incident on the translucent medium and reflected by the inclined surface is diffused.

  However, since the numerical aperture of the outgoing optical fiber is as large as the numerical aperture of the incident optical fiber, the optical signal incident on the outgoing optical fiber from the translucent medium does not pass outside the outgoing optical fiber. In this way, the coupling loss between the optical fiber and the translucent medium can be reduced.

  The optical branching device according to claim 2 of the present invention is characterized in that, in claim 1, the core diameter of the outgoing optical fiber is larger than the core diameter of the incident optical fiber.

  According to the above configuration, since the core diameter of the outgoing optical fiber is larger than the core diameter of the incident optical fiber, many optical signals can be received.

An optical branching device according to a third aspect of the present invention is the optical branching device according to the first or second aspect, wherein the numerical aperture (NA1) of the incident optical fiber, the numerical aperture (NA2) of the translucent medium, and the outgoing optical fiber. The numerical aperture (NA3) satisfies the following relational expression.
NA1 = NA2 <NA3
Or NA1 <NA2> NA3 and NA1 <NA3
・ Or NA1 <NA2 ≦ NA3
According to the above configuration, the numerical aperture (NA1) of the incident optical fiber, the numerical aperture (NA2) of the translucent medium, and the numerical aperture (NA3) of the outgoing optical fiber are NA1 = NA2 <NA3 or NA1 <NA2 Since the relationship of> NA3 and NA1 <NA3 or NA1 <NA2 ≦ NA3 is satisfied, the coupling loss can be reduced even if the optical signal is diffused by the reflection of the inclined surface.

  An optical branching device according to a fourth aspect of the present invention is the connector according to any one of the first to third aspects, wherein both end faces of the plurality of incident optical fibers and both end faces of the plurality of outgoing optical fibers have the same specifications. And optically coupled to a plurality of light emitting portions for the optical signal, a plurality of the translucent media, and a plurality of light receiving portions for the optical signal.

  According to the above configuration, since the connectors having the same specifications are used, it is possible to reduce the cost by sharing the parts.

  An optical branching device according to a fifth aspect of the present invention is the optical branching device according to the fourth aspect, wherein end surfaces of the incident optical fiber and the outgoing optical fiber on the light transmitting medium side are inserted into an optical fiber insertion hole of the connector, The pitch connected to the translucent medium is different from the pitch at which the end face on the light emitting part side of the incident optical fiber and the end face on the light receiving part side of the outgoing optical fiber are connected.

  According to the said structure, the difference in the pitch of each fiber is coped with by using the optical fiber insertion hole of a connector properly. As a result, a connector having the same specification can be used, and there is no need to create a new connector.

  An optical module according to a sixth aspect of the present invention includes the optical branching device according to any one of the first to fifth aspects, a light emitting element that transmits an optical signal corresponding to information to the optical branching device, and the light emission. And a light receiving element that receives an optical signal emitted from the element through the optical branching device.

  According to the above configuration, the optical branching device according to any one of claims 1 to 5 branches the optical signal transmitted by the light emitting element, and the light receiving element receives the optical signal branched by the optical branching device. To do.

  As described above, since the optical module includes the optical branching device according to any one of claims 1 to 5, it is possible to reduce the coupling loss between the optical fiber and the translucent medium and efficiently. An optical signal can be transmitted.

  An optical transmission system according to a seventh aspect of the present invention includes an electrical interface through which an electrical signal is transmitted from an external input device, a photoelectric conversion circuit that converts the electrical signal from the electrical interface into an optical signal, and the optical signal being branched And a photoelectric conversion circuit that converts an optical signal branched by the branching device into an electrical signal, and outputs the electrical signal from the electrical interface to an external output. It transmits to a device.

  According to the above configuration, the photoelectric conversion circuit converts the electrical signal transmitted by the electrical interface into an optical signal, and the optical branching device according to any one of claims 1 to 5 branches the optical signal. . Further, the photoelectric conversion circuit converts the branched optical signal into electrical communication. Further, the electric signal is transmitted from the electric interface to the external output device.

  As described above, since the optical transmission system includes the optical branching device according to any one of claims 1 to 5, the coupling loss between the optical fiber and the translucent medium can be reduced. Signals can be transmitted to a plurality of external output devices.

  An optical transmission system according to an eighth aspect of the present invention is the optical transmission system according to the seventh aspect, wherein the external output device is a plurality of image display devices that display images.

  According to the above configuration, signals can be transmitted to a plurality of image display devices at the same time.

  According to the present invention, it is possible to reduce the coupling loss between the optical fiber and the translucent medium.

  An embodiment of an optical module 20 in which an optical branching device 18 according to the present invention is employed will be described with reference to FIGS.

  As shown in FIGS. 8A and 8B, the optical module 20 includes an optical branch device 18 that branches an optical signal, a light emitting element 26 that transmits an optical signal corresponding to information to the optical branch device 18, and light emission. A light receiving element 60 that receives an optical signal transmitted from the element 26 through the optical branching device 18 is provided.

  The light emitting element 26 is attached to a light emitting element base 34. The light emitting element 26 includes a 4-bit VCSEL array composed of four surface emitting lasers (VCSELs) having a light emitting point pitch of 250 μm. It is used. The light receiving element 60 uses a 4-bit PD array, and includes six light receiving elements 60 in FIG.

  As shown in FIG. 7, an incident first connector 28 to which one end of four incident optical fibers 24 for transmitting optical signals is attached is provided at a position facing the light emitting surface of the light emitting element 26. As the incident first connector 28, a commercially available 8-core type MT connector having a connection hole pitch of 250 μm is employed. The incident optical fibers 24 are connected to the four connection holes on the center side of the incident first connector 28, respectively. That is, the incident optical fibers 24 are connected to the incident first connector 28 at a pitch of 250 μm so as to correspond to the light emitting points of the light emitting elements 26. In addition, the dotted line in the incident 1st connector 28 shown in FIG. 7 shows the connection hole which is not used.

  Further, as shown in FIG. 5, guide pins 30 are provided toward the light emitting element base 34 on both sides of the rectangular mounting surface that is long in the horizontal direction of the incident first connector 28. The incident first connector 28 is fixed to the light emitting element base 34 by fitting the guide pins 30 into mounting holes (not shown) of the light emitting element base 34 (see FIG. 7).

  Further, as the incident optical fiber 24 attached to the incident first connector 28 shown in FIG. 7, in this embodiment, BF04433 (manufactured by Furukawa Electric, numerical aperture (NA1) = 0.2, core diameter / cladding diameter = 50/125 μm) is used.

  The other end of each of the four incident optical fibers 24 is provided with an incident second connector 32 having the same specifications as the incident first connector 28, and is incident on every other 8 connection holes having a pitch of 250 μm. An optical fiber 24 is connected. That is, the incident optical fiber 24 is connected to the incident second connector 32 at a pitch of 500 μm. In addition, the dotted line in the incident 2nd connector 32 shown in FIG. 7 shows the connection hole which is not used.

  Further, like the incident first connector 28, guide pins 38 are provided on both sides of the mounting surface of the incident second connector 32 toward the mounting base 36 of the translucent medium 22 described later. The incident second connector 32 is fixed by fitting the guide pin 38 into a mounting hole (not shown) of the mounting base 36.

  In addition, four plate-like translucent media 22 on which optical signals from the four incident optical fibers 24 are incident are provided to face the attachment surface of the incident second connector 32.

  Specifically, as shown in FIG. 2, the optical signal incident by the incident optical fiber 24 is reflected at one end portion of the translucent medium 22 to guide the optical signal to the translucent medium 22. , An incident portion 40 having a 45 ° inclined surface 40A is provided. At the other end of the translucent medium 22, there is provided an emitting portion 42 having a 45 ° inclined surface 42 </ b> A formed at six step portions. In the present embodiment, the translucent medium 22 has a thickness of 50 μm, a width (light signal incident portion) of 300 μm, a stepped portion having a width and pitch of 50 μm, and a length of 30050 μm, as shown in FIG. The optical signal incident on the incident portion 40 is reflected by the inclined surface 40A of the incident portion 40, and further reflected by the inclined surface 42A of the emitting portion 42, so that the optical signal can be branched into six. Further, as shown in FIG. 3, the area of each emitting portion 42 (area of the projection surface of the inclined surface 42A) is a square with one side of 50 μm.

  Note that the translucent medium 22 shown in FIGS. 2 and 3 is illustrated with the width direction of the translucent medium 22 enlarged to facilitate understanding of the shape of the translucent medium 22.

  Further, as shown in FIG. 1, the four optically transmissive media 22 are configured so that each optical fiber is arranged at a pitch of 500 μm along the connection hole direction of the incident second connector 32.

  For example, the material of the translucent medium 22 may be a cycloolefin polymer (refractive index: 1.52) as a core material and a fluororesin (trade name Cytop, refractive index: 1.34) manufactured by Asahi Glass. Is possible. The translucent medium 22 is formed by injection molding or the like, and is formed on the upper and lower surfaces of the translucent medium 22 by a clad material (not shown). The numerical aperture (NA2) of the translucent medium 22 is set larger than the numerical aperture (NA1) of the incident optical fiber 24. Here, the numerical aperture (NA2) of the translucent medium 22 is defined by the core refractive index and the refractive index of the clad formed on the upper and lower surfaces of the translucent medium 22.

  Moreover, since the translucent medium 22 does not necessarily require a clad material, when there is no clad material, an air layer (refractive index: 1) is defined as a clad layer.

  Furthermore, when the translucent medium 22 is formed integrally with a glass substrate or the like on which the translucent medium 22 is mounted (when there is no air layer between the translucent medium 22 and the mounted glass substrate). The numerical aperture (NA2) is defined by the refractive index of the glass substrate and the like and the refractive index of the translucent medium 22.

  Further, the translucent medium 22 is attached to a flat fixed substrate 44 shown in FIG. 7 in order to fix its shape. The fixed substrate 44 can be formed using, for example, an ABS (styrene / butadiene / acrylonitrile copolymer) resin or a glass substrate. Further, on the back surface of the fixed substrate 44, a mounting base 36 that supports the above-described fixed substrate 44 is provided.

  Further, as shown in FIG. 8B, one end of the outgoing optical fiber 46 into which the optical signal emitted from the emitting part 42 is incident is attached, and the outgoing first connector 48 having the same specifications as the incoming first connector 28 is provided. Six pieces are arranged on the emission part 42.

  As shown in FIG. 6, four outgoing optical fibers 46 are attached to each outgoing first connector 48, and every other outgoing optical fiber 46 is connected to eight connection holes with a pitch of 250 μm. Has been. That is, the outgoing optical fiber 46 is attached to the outgoing first connector 48 at a pitch of 500 μm, and the outgoing optical fiber 46 is disposed so as to correspond to the outgoing part 42 as shown in FIG.

  That is, by using every other connection hole provided in the outgoing first connector 48 and considering the arrangement of the translucent medium 22, a standardized connector such as an MT connector is used. Thus, an inexpensive optical branching device 18 and an optical module 20 are realized.

  Furthermore, in the present embodiment, BF04434 (manufactured by Furukawa Electric Co., Ltd., numerical aperture (NA3) = 0.275, core diameter / cladding diameter = 62.5 / 125 μm) is used as the outgoing optical fiber 46.

  That is, the numerical aperture (NA3) of the outgoing optical fiber 46 is set larger than the numerical aperture (NA1) of the incident optical fiber 24.

  Further, as shown in FIG. 3, all the reflected light having a square shape of 50 μm on one side reflected by the emitting portion 42 enters the core shape of the outgoing optical fiber 46, and the use of the optical signal Efficiency has been improved.

  Further, as shown in FIG. 6, guide pins 70 are provided on both sides of the rectangular mounting surface of the emission first connector 48 toward the mounting base 36, and the guide pins 70 are attached to the mounting base 36. The first output connector 48 is fixed by being fitted into a mounting hole (not shown).

  Further, at the other end of the outgoing optical fiber 46, six outgoing second connectors 50 having the same specifications as the incoming first connector 28 are arranged with respect to the outgoing first connector 48. The outgoing optical fiber 46 is attached to four connection holes on the center side among the eight connection holes of the outgoing second connector 50. That is, the outgoing optical fibers 46 are attached to the outgoing second connector 50 at a pitch of 250 μm. Further, guide pins 62 are provided on both sides of the rectangular mounting surface of the emission second connector 50 toward a light receiving element base 64 to which a light receiving element 60 described later is attached. The second emission connector 50 is fixed by being fitted into a mounting hole (not shown) of the element base 64.

  A light receiving element 60 for receiving an optical signal is provided at a position facing the four outgoing optical fibers 46 attached to the outgoing second connector 50. This light receiving element 60 employs a 4-bit PD array (light receiving diameter of 80 μm) having an element pitch of 250 μm, and this element faces the outgoing optical fiber 46 attached to the outgoing second connector 50. is doing.

  With the above configuration, as shown in FIG. 8, the optical signal transmitted from the light emitting element 26 is incident from one end of the four incident optical fibers 24 attached to the incident first connector 28 and is incident second. The light is emitted in the horizontal direction from the other end attached to the connector 32 toward the incident portions 40 of the four translucent media 22.

  Further, as shown in FIG. 1, the optical signal that has entered the incident portion 40 of the translucent medium 22 from the horizontal direction is reflected toward the six emitting portions 42 by the inclined surface 40A. Further, the reflected optical signal is reflected by the inclined surface 42A provided in each emitting portion 42 and enters one end of the outgoing optical fiber 46 attached to the outgoing first connector 48 arranged side by side.

  Further, as shown in FIG. 6, the optical signal incident from one end of the outgoing optical fiber 46 attached to the outgoing first connector 48 is emitted from the other end of the outgoing optical fiber 46 attached to the outgoing second connector 50. Then, it is received by the light receiving element 60.

  Here, on the inclined surfaces 40A and 42A of the translucent medium 22 shown in FIG. 2, fine irregularities and undulations are added in production, and the optical signal incident on the translucent medium 22 is inclined. The optical signal is diffused by reflection at 40A and 42A. However, the numerical aperture (NA3) of the outgoing optical fiber 46 is larger than the numerical aperture (NA2) of the translucent medium 22, and the numerical aperture (NA2) of the translucent medium 22 is greater than the incident optical fiber. The numerical aperture is larger than 24 (NA1). For this reason, even if the optical signal is scattered by the reflection on the inclined surfaces 40A and 42A, the coupling loss between the incident optical fiber 24 and the outgoing optical fiber 46 and the translucent medium 22 can be reduced.

  Moreover, since the connector of the same specification is employ | adopted for all the connectors, the number of parts is reduced.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It is clear to the contractor. For example, in the above-described embodiment, a cycloolefin polymer is used as the material of the translucent medium 22. However, the material is not limited to this material, and a translucent plastic material or an inorganic material such as glass can be used. .

  Next, an embodiment of an image display system 80 employing the optical branching device 18 according to the present invention will be described with reference to FIG.

  As shown in FIG. 9, an image display system 80 according to the present embodiment includes a personal computer 82 that transmits video as an electrical signal, and photoelectric conversion that receives an electrical signal from the personal computer 82 and converts the electrical signal into an optical signal. A circuit (not shown) and an optical branching device 18 are provided. Further, the image display system 80 connects the optical signal branched by the optical branching device 18 to a plurality of cable-like optical fibers 92 and each optical fiber 92, and converts the optical signal from the optical fiber 92 into an electrical signal. A plurality of receivers (photoelectric conversion circuits) 88 for conversion, and a plurality of monitors (image display devices) 90 for displaying images using electric signals from the receivers 88 are provided. The personal computer 82 is connected to, for example, an electrical interface unit of a photoelectric conversion circuit (not shown) by a DVI cable, and similarly, the receiver 88 and the monitor 90 are connected by a DVI cable.

  A video signal (electrical signal) from the personal computer 82 is EO-converted by a photoelectric conversion circuit connected to the optical branching device 18, and the converted optical signal passes through a plurality of optical fibers 92 and a plurality of receivers 88. Is transmitted. In the receiver 88, the OE-converted electrical signal is transmitted to the monitor 90, and an image is displayed on the monitor 90.

  According to the present embodiment, by adopting the optical branching device 18, the coupling loss between the incident optical fiber 24, the outgoing optical fiber 46, and the translucent medium 22 can be reduced, and a plurality of signals for displaying an image are obtained. It is possible to efficiently distribute and display on the monitor 90.

It is the perspective view which showed the translucent medium, incident 2nd connector, output 1st connector, etc. of the optical branching device concerning embodiment of this invention. It is the perspective view which showed the translucent medium of the optical branching apparatus which concerns on embodiment of this invention. It is the front view which looked at the translucent medium of the optical branching device concerning the embodiment of the present invention from the direction of an optical fiber. It is the side view which showed the translucent medium of the optical branching apparatus which concerns on embodiment of this invention, an incident optical fiber, an output optical fiber, etc. FIG. It is the perspective view which showed the incident 1st connector of the optical branching apparatus which concerns on embodiment of this invention. It is the top view which showed the output optical fiber etc. of the optical module which concerns on embodiment of this invention. It is the top view which showed the incident optical fiber etc. of the optical module which concerns on embodiment of this invention. 1 is a schematic configuration diagram illustrating an optical module according to an embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image display system according to an embodiment of the present invention.

Explanation of symbols

18 optical branching device 20 optical module 22 translucent medium 24 incident optical fiber 26 light emitting element 28 incident first connector 32 incident second connector 40A inclined surface 40 incident portion 42A inclined surface 42 emitting portion 46 outgoing optical fiber 48 outgoing first connector 50 Output second connector 60 Light receiving element 80 Image display system (optical transmission system)
84 Electrical interface 88 Receiver (photoelectric conversion circuit)
90 Monitor (image display device)

Claims (8)

A plate-like light-transmitting property having a plurality of step portions at one end and an inclined surface for causing an optical signal to enter or exit from the light-transmitting medium at least at one end or the other end A medium, an incident optical fiber coupled to the incident part and entering the optical signal into the translucent medium, and an output optical fiber coupled to the output part and emitting signal light from the translucent medium; In an optical branching device comprising:
An optical branching device characterized in that the numerical aperture of the outgoing optical fiber is larger than the numerical aperture of the incident optical fiber.   2. The optical branching device according to claim 1, wherein a core diameter of the outgoing optical fiber is larger than a core diameter of the incident optical fiber. 2. The numerical aperture (NA1) of the incident optical fiber, the numerical aperture (NA2) of the translucent medium, and the numerical aperture (NA3) of the outgoing optical fiber satisfy the following relational expression. Or the optical branching apparatus of 2.
NA1 = NA2 <NA3
Or NA1 <NA2> NA3 and NA1 <NA3
・ Or NA1 <NA2 ≦ NA3   The both end faces of the plurality of incident optical fibers and the both end faces of the plurality of outgoing optical fibers are bundled with connectors of the same specification, the plurality of light emitting portions of the optical signal, the plurality of translucent media, and the optical signal 4. The optical branching device according to claim 1, wherein the optical branching device is optically coupled to a plurality of light receiving units.   The end surfaces of the incident optical fiber and the outgoing optical fiber on the light transmitting medium side are inserted into the optical fiber insertion holes of the connector, and the pitch connected to the light transmitting medium is determined by the light emitting portion of the incident optical fiber. The optical branching device according to claim 4, wherein the pitch is different from the pitch at which the end face on the side and the end face on the light receiving part side of the outgoing optical fiber are connected. An optical branching device according to any one of claims 1 to 5,
A light emitting element for transmitting an optical signal according to information to the optical branching device;
A light receiving element for receiving an optical signal emitted from the light emitting element through the optical branching device;
An optical module comprising: An electrical interface through which an electrical signal is transmitted from an external input device;
A photoelectric conversion circuit that converts an electrical signal from the electrical interface into an optical signal;
A branching device according to any one of claims 1 to 5, which branches the optical signal;
A photoelectric conversion circuit for converting an optical signal branched by the branching device into an electrical signal;
With
An optical transmission system, wherein an electrical signal is transmitted from the electrical interface to an external output device.   8. The optical transmission system according to claim 7, wherein the external output device is a plurality of image display devices that display images.

Images