JP2007147740A - Multimode single core bidirectional device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single core bidirectional device that deals with a multimode fiber having a core diameter of 100-150 μm and that facilitates connection with a multimode fiber as well as having low connection loss. <P>SOLUTION: The device is equipped with: a multimode waveguide 15 which is provided on a substrate 11 and which has one coupling waveguide 12 and two branching waveguides 13, 14 connected in-between; a laser diode 16 connected to the coupling waveguide 12; a photodiode 17 connected to one branching waveguide 13; a multimode fiber 18 connected to the other branching waveguide 14; and a multilayer film filter 22 to be inserted into its exclusive groove 21 formed at a connection 19 between the coupling waveguide 12 and the branching waveguides 13, 14. The two branching waveguides 13, 14 are formed facing the mutually different end faces 23, 24 of the substrate 11 respectively, wherein one end face 23 is connected with the photodiode 17 and the other end face 24 connected with the multimode fiber 18 having a core diameter of 100-150 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a single-core bidirectional device that performs two-way communication by multiplexing transmission light and reception light using a single optical transmission line, and in particular, a multi-mode optical waveguide formed with a multimode optical waveguide. The present invention relates to a mode single core bidirectional device.

  In recent years, with an increase in information capacity, light is used instead of electricity as a communication medium. In optical networks connecting continents and large cities, the amount of information is enormous, so it is possible to transmit a large amount of signals with different wavelengths on a single mode (SM) optical fiber capable of long-distance transmission at 10 Gbps per wavelength. The wavelength division multiplexing (WDM: Wavelength Division Multiplexing) which can increase is used. When a WDM is used in an SM transmission system, a high-density wavelength division multiplexing (DWDM) system with a short wavelength interval has a large number of wavelengths of 8 to 40, and therefore an array capable of demultiplexing multiple wavelengths with one element. A diffraction grating (AWG: Arrayed Waveguide grating) is used. Further, in recent years, in the low-density wavelength division multiplexing (CWDM: Coarse WDM), which has a longer wavelength interval and lower cost than DWDM, the number of demultiplexing is as small as 2 to 8, and thus a system that demultiplexes one wavelength at a time using a plurality of multilayer filters. Is used.

  In the trunk line system, the shift to optical communication is largely advanced, and it is considered that the shift to the optical communication in the downstream such as the access system and the LAN will progress in the future. Downstream costs are likely to be important.

  In relatively short-distance LAN systems, quartz-based multimode optical fibers with a core diameter of 50 to 62.5 μm, which have a high likelihood of connection tolerance, are used, and some are low-density wavelength multiplexing (IEEE802.802). 3ea LX4) is used. The multimode demultiplexer used in this case collimates the propagation light from the optical fiber with a lens or a concave mirror, demultiplexes the collimated light with a multilayer filter, and condenses the light on a light receiver or the like with the lens (for example, Patent Document 1).

  In addition, short-distance home networks and condominium networks require residents to use DIY (Do It Yourself) as in the case of current electrical wiring networks. : Plastic Optical Fibler).

  As a method for transmitting a signal by optical communication, there are a normal single-core bidirectional method using one optical fiber and a dual-core bidirectional method using two optical fibers. In the two-core bidirectional system, two optical transmission lines are used to transmit the transmitting light and the receiving light that are opposed to each other through different lines. By using two optical transmission lines, the cost of the optical transmission line is doubled, and in addition, it is difficult to miniaturize the connector of the optical transmission line and the entire optical transceiver.

  On the other hand, the single-core bidirectional method, that is, the technique of transmitting and receiving transmission light and reception light by multiplexing them on a single optical transmission line, transmits and transmits light having different optical transmission wavelengths to one optical transmission line. It is intended to receive received light. In this system, a single optical transmission line is possible and the cost can be reduced. The single-core bidirectional method has an advantage that the occupied space of the optical fiber can be reduced because the number of fibers is smaller than that of the two-core bidirectional method.

  However, the single-core bidirectional method requires a device that separates and multiplexes the transmission light and the reception light multiplexed into one, and the cost reduction of this device is important. A device using a multilayer filter is generally used as a single-core bidirectional device (see, for example, Patent Document 2).

  For example, as shown in FIG. 8, the single-core bidirectional device 80 is provided with an optical waveguide 85 formed by connecting one coupling waveguide 82 and two branching waveguides 83 and 84 on a substrate 81. A laser diode (LD) 86 is connected to the coupling waveguide 82, a photodiode (PD) 87 is connected to one branch waveguide 83, and a single mode optical fiber 88 is connected to the other branch waveguide 84. It is connected. A multi-layer filter insertion groove 91 is formed in the connection portion 89 between the coupling waveguide 82 and the branch waveguides 83 and 84, and the multi-layer filter 92 is inserted into the multi-layer filter insertion groove 91. The multilayer filter 92 is a wavelength filter that transmits light in a predetermined wavelength band and reflects light in other wavelength bands. Note that a portion surrounded by a dotted line in the figure is a bent portion 93 of the optical waveguide 85.

  In the single-core bidirectional device 80, the light emitted from the LD 86 and propagated through the coupling waveguide 82 passes through the multilayer filter 92 and is transmitted to the optical fiber 88 through the branching waveguide 84. Further, the light incident on the branching waveguide 84 from the optical fiber 88 is reflected by the multilayer filter 92 and is received by the PD 87 through the branching waveguide 83. However, the light incident from the optical fiber 88 and the light emitted from the LD 86 are light having different wavelengths.

  The single-core bidirectional device 80 using such a multilayer filter 92 is mainly for single mode, and it takes time to connect the LD 86 and the optical waveguide 85, the PD 87 and the optical waveguide 85, and the optical waveguide 85 and the optical fiber 88. It was expensive and expensive. In the future, a single-core bidirectional device using a multi-mode fiber that is easy to connect and can be reduced in cost will be required for use in homes, etc., and a multi-mode single-core bidirectional device has been studied. (For example, refer nonpatent literature 1).

JP 2000-162466 A Japanese Patent Laid-Open No. 10-54917 Naruse et al., "Development of 10Gbps single-core full-duplex optical module using polymer waveguide", 2005, IEICE General Conference C-3-133

  However, the conventional multimode single-core bidirectional device is compatible with a fiber having a core diameter of 50 μm, and the core diameter of the optical waveguide formed in the single-core bidirectional device reduces the connection loss with the multimode fiber. Therefore, it is as small as 20 to 40 μm. Therefore, there is a problem that the mounting tolerance of the multi-mode bidirectional device is small and the cost cannot be reduced sufficiently. Further, since the optical fiber connected to the optical waveguide uses an optical fiber formed of glass, there is a problem that it is not suitable for use in the home because it is easily broken and difficult to handle.

  As a method for solving this, a method using a plastic fiber having a core diameter of 100 to 150 μm is conceivable. In the case of a single-core bidirectional device using a multimode fiber of 100 to 150 μm, there is a problem in optical loss and optical crosstalk characteristics because the light spread angle is large.

  Although there is a larger 1 mm multi-mode plastic fiber, it is not possible to use a small-diameter (about 20 μm) photodiode capable of high-speed response because the light receiving diameter is too large.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a single-core bidirectional device that solves the above-described drawbacks, facilitates connection of optical fibers in correspondence with multimode fibers having a core diameter of 100 to 150 μm, and has low loss. is there.

  To achieve the above object, the invention of claim 1 is directed to a multimode waveguide connected to two branch waveguides, a laser diode or a photodiode connected to the coupling waveguide, and one branch. In the multilayer filter insertion groove formed in the connection portion between the photodiode or laser diode connected to the waveguide, the multimode fiber connected to the other branch waveguide, and the coupling waveguide and the branch waveguide In a multimode single-core bidirectional device including a multilayer filter to be inserted, the two branch waveguides are respectively formed facing different end faces of a substrate, and one of the end faces is a photodiode or a laser diode. And a multimode fiber having a core diameter of 100 to 150 μm is connected to the other end face. It is a bi-directional device.

  According to a second aspect of the present invention, there is provided a multimode waveguide provided on a substrate and connected to one coupling waveguide and two branching waveguides; a laser diode connected to the coupling waveguide; Laser diode connected to the branch waveguide, multimode fiber connected to the other branch waveguide, and multilayer filter insertion groove formed at the connection between the coupling waveguide and the branch waveguide In the multimode single-core bidirectional device including the multilayer filter, a first laser diode that outputs light of a predetermined wavelength is connected to the coupling waveguide, and the one branching waveguide is connected to the first branching waveguide. The multimode single-core bidirectional device according to claim 1, wherein a second laser diode that outputs light having a wavelength different from the predetermined wavelength is connected.

  According to a third aspect of the present invention, there is provided a multimode waveguide provided on a substrate and connected to one coupling waveguide and two branching waveguides; a photodiode connected to the coupling waveguide; Inserted into a multilayer filter insertion groove formed at the connection between the photodiode connected to the branch waveguide, the multimode fiber connected to the other branch waveguide, and the coupling waveguide and the branch waveguide In the multimode single-core bidirectional device including the multilayer filter, a first photodiode is connected to the coupling waveguide, and a second photodiode is connected to the one branch waveguide. The multimode single-core bidirectional device according to claim 1.

  According to a fourth aspect of the present invention, when the multilayer filter has a position where the two branching waveguides completely intersect with each other at a position of 0 and a portion where the two branching waveguides begin to intersect with each other at a position of 0, The multi-mode single-core bidirectional device according to any one of claims 1 to 3, which is inserted at a position of 1/5.

  A fifth aspect of the present invention is the multimode single-core bidirectional device according to any one of the first to fourth aspects, wherein the multilayer filter insertion groove is formed in parallel with an end face connecting the multimode fiber.

  A sixth aspect of the present invention is the multimode single-core bidirectional device according to any one of the first to fifth aspects, wherein a branch angle of the connecting portion is 10 ° or less.

  The invention of claim 7 is the multimode single-core bidirectional device according to any one of claims 1 to 6, wherein the NA of the coupling waveguide and the branching waveguide is 0.3 to 0.6.

  According to the present invention, it is possible to achieve an excellent effect of facilitating connection of an optical fiber corresponding to a multimode fiber having a low loss and a core diameter of 100 to 150 μm.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a plan view showing a preferred embodiment of a multimode single-core bidirectional device according to the present invention.

  The multimode single-core bidirectional device 10 includes a multimode waveguide 15 provided on a substrate 11 and connected to one coupling waveguide 12 and two branching waveguides 13 and 14, and the coupling waveguide 12. A connected laser diode (LD) 16, a photodiode (PD) 17 connected to one branch waveguide 13, a multimode fiber 18 connected to the other branch waveguide 14, and a coupling waveguide 12 A multilayer filter 22 is provided which is inserted into a multilayer filter insertion groove 21 formed in a connection part (branch part) 19 with the branch waveguides 13 and 14.

  In the multimode single-core bidirectional device 10 according to the present embodiment, two branching waveguides 13 and 14 are formed facing different end faces 23 and 24 of the substrate 11, respectively, and PD 17 is provided on one end face 23. The multi-mode fiber 18 having a core diameter of 100 to 150 μm is connected to the other end face 24.

  Specifically, the multimode waveguide 15 is formed so that the coupling waveguide 12 and one branching waveguide 14 are substantially linear, and input / output ends (ports 1 and 3) of the respective waveguides 12 and 14. Is formed so as to be located on the end surfaces 25 and 24 (upper and lower sides in the figure) of the substrate 11 facing each other. The other branching waveguide 13 is formed such that its input / output end (port 2) is located on an end face 23 different from the end faces 24 and 25. Each waveguide 12, 13, 14 is formed with a bent portion 26 so as to form an optical path facing a predetermined end face.

  Furthermore, in the multimode single-core bidirectional device 10 of the present embodiment, a multilayer filter insertion groove 21 is formed in parallel to the end face 24, and the multilayer filter 22 is inserted into the multilayer filter insertion groove 21. . The multilayer filter 22 is a wavelength filter that transmits light in a predetermined wavelength band (for example, λ1) and reflects light in other wavelength bands (for example, λ2).

  As the multimode fiber 18 connected to the end face 24, it is desirable to use a plastic fiber that is resistant to bending and is easy to handle.

  The mounting tolerance can be increased by setting the core diameter of the multimode fiber 18 to 100 μm or more. For example, in a home network or a condominium network, it is easy to connect, so that the user can be DIY (Do It Yourself).

  Further, by setting the core diameter to 150 μm or less, it is possible to reduce the connection loss with a PD capable of high-speed response of 2.5 Gbps or more, which has a light receiving diameter of about 100 μm.

  The core diameter of the multimode waveguide 15 is desirably 70 μm when the core diameter of the multimode fiber 18 is 120 μm. This is because the light emitted from the LD 16 is partially reflected by the multilayer filter 22, and the light returns to the LD 16 through the coupling waveguide 12 due to return light or scattered light, but the core diameter is 50 μm or less. If there is, there is a possibility that the stability of laser diode oscillation is hindered by the return light. In this case, an isolator must be provided between the multimode waveguide 15 and the LD 16, and the configuration of the bidirectional device becomes complicated. On the other hand, the larger the core diameter, the smaller the influence of the return light. However, when the core diameter is 100 μm or more, the connection loss between the multimode fiber 18 or PD 17 and the multimode waveguide 15 increases. Because there is.

  The substrate 11 of the multimode waveguide 15 is made of a material such as silicon or quartz. The material for forming the multimode waveguide 15 may be any resin such as acrylic or epoxy.

  The LD 16 is desirably a VCSEL that can be expected to reduce the cost. In addition, a Fabry-Perot laser, a DFB laser, or the like may be used as the LD 16.

  The connection between the LD 16 and the multimode waveguide 15 may be performed by making the optical axis of the LD coincide with the input / output end facing the end face 25. Further, in order to convert the optical path of the multimode waveguide 15 to the substrate side or the overcladding side, a mirror end surface is formed by obliquely cutting the end surface of the core using a dicing saw or the like, and on the surface of the substrate 11 or the overcladding. The LD 16 and the PD 17 may be arranged to connect the LD 16 and the multimode waveguide 15. At this time, it is desirable to use a surface emitting LD (for example, VCSEL) suitable for surface mounting as the LD 16. Further, the multimode fiber 18 may be connected to the multimode waveguide 15 by forming a V-groove or the like in the substrate 11.

  Further, as shown in FIG. 2, in the present embodiment, the multilayer filter 22 has two portions where the two branching waveguides 13 and 14 completely intersect with each other at a position 0 (Y coordinate in the figure). When the portion where the branching waveguides 13 and 14 begin to intersect is assumed to be 1 position, it is inserted at 0 to 1/5 position. Further, the branching angle θ of the branching portion 19 is formed to be 10 ° or less.

  The multimode optical waveguide 15 is preferably formed of a polymer waveguide. The multimode waveguide 15 may be formed of a silica-based waveguide. However, since the silica-based waveguide is manufactured using reactive ion etching (RIE), the waveguide having a large core diameter is manufactured. Takes time. On the other hand, in the case of a polymer waveguide, even a waveguide having a large core diameter can be manufactured in a short time by a direct exposure method, a mold method, or the like, and the cost can be reduced.

  Here, a manufacturing method of the multimode waveguide 15 using the direct exposure method will be described with reference to FIGS. 4A to 4H.

  A substrate 11 shown in FIG. 4A is prepared, and an ultraviolet curable resin is applied as a clad material 41 on the substrate 11 as shown in FIG. 4B. As shown in FIG. 4C, the applied clad material 41 is irradiated with ultraviolet rays UV, and the clad material 41 is cured to form an underclad 42. As shown in FIG. 4D, an ultraviolet curable resin having a refractive index different from that of the clad material 41 is applied on the under clad 42 as the core material 43. As shown in FIG. 4E, a photomask 44 on which a core pattern (waveguide pattern) is drawn is placed above the core material 43, and the core material 43 is irradiated with ultraviolet rays UV through the photomask 44. . As shown in FIG. 4 (f), the core material 43 irradiated with ultraviolet rays is developed with a developer to remove the uncured portion, whereby the core 45 is obtained. As shown in FIG. 4G, a clad material 46 is applied on the core 45 and the under clad 42. Here, the clad material 46 is the same material as the clad material 41 on which the under clad 42 is formed. Finally, as shown in FIG. 4H, the coated clad material 46 is irradiated with ultraviolet rays UV to form an over clad 47, whereby the multimode waveguide 15 is obtained.

  The operation principle of the multimode single-core bidirectional device 10 of the present embodiment will be described. When the light of wavelength λ1 propagating through the multimode fiber 18 is incident from the port 3, the light passes through the branching waveguide 14, is reflected by the multilayer filter 22, and is received by the PD 17 through the branching waveguide 13. . In addition, when light having a wavelength λ 2 oscillated by the LD 16 is incident from the port 1, the light passes through the coupling waveguide 12, passes through the multilayer filter 22, and is transmitted to the multimode fiber 18 through the branching waveguide 14. .

  At this time, the light incident from the port 1 is partially scattered by the substrate end face 25 and the filter insertion groove 21, propagates in the cladding, and travels toward the end face 24.

  Here, according to the multimode single-core bidirectional device 10 of the present embodiment, the two branching waveguides 13 and 14 are respectively formed facing the different end faces 23 and 24 of the substrate 11, and one end face is formed. 23 is connected to the PD 17, and the other end surface 24 is connected to the multi-mode fiber 18 to secure isolation between the multi-mode fiber 18 and the PD 17. There is nothing to do.

  When a PD is connected to the port 1 and light having a wavelength λ2 is incident from the port 3, the light passes through the multilayer filter 22, but partly returns to the end face 24 side. Even in such a case, since the PD and the multimode fiber 18 are connected to different end faces, the return light is not received by the PD.

  Therefore, according to the multimode single-core bidirectional device 10 of the present embodiment, it is possible to prevent the return light or scattered light from the multilayer filter 22 from being received by the PD and to prevent the deterioration of crosstalk. it can.

  Here, FIG. 3 shows the relationship between the insertion position of the multilayer filter 22 and the loss, and the relationship between the filter position and the intensity (dB ratio) of the return light. Here, the return light is incident from port 3 (or port 2) and reflected by the multilayer filter 22 and reflected by the multilayer filter 22 in addition to the light reflected by the multilayer filter 22 on the port 2 side. Indicates the light that returns. In FIG. 3, the filter position on the horizontal axis represents the Y coordinate in FIG. 2, and the vertical axis represents the loss of light emitted to the port 1 and the loss of return light emitted to the end face 24 side.

  As shown in FIG. 3, when the light reflected by the multilayer filter 22 is incident from the port 3, when the filter position is 0 to 1/5, the loss of light propagating through the core is as small as 3 dB or less, And the intensity of the return light is small.

  Therefore, low loss can be achieved by inserting the multilayer filter 22 at a position of 0 to 1/5.

  In the present embodiment, the multilayer filter insertion groove 21 is formed to be parallel to the end face 24 connecting the multimode fiber 18. However, as shown in FIG. 2, the branching portion 19 forms the branching waveguide 14 and the coupling waveguide 12 in a substantially straight line, and the two branching waveguides 13 and 14 are formed with respect to the multilayer filter 22. It forms so that it may have the same incident-reflection angle. By forming the multilayer filter insertion groove 21 and the end face 24 in parallel, the bidirectional device 10 can be cut out from the single wafer and the multilayer filter insertion groove 21 can be collectively formed, thereby reducing the cost. Can be planned.

  The branching angle θ (see FIG. 2) of the branching part 19 is preferably formed to be 10 ° or less. For example, at a branching angle of 10 °, the incident angle to the filter of the lowest order mode is 5 ° or more. In addition, the incident angle of the highest mode of a normal optical fiber formed with NA of 0.2 is a maximum of 12 ° and a minimum of 0 ° in a medium having a refractive index of 1.5. In that case, the multilayer filter 22 must correct the reflection characteristics of p-polarized light and s-polarized light with respect to the incident angle (branching angle). Correction can be made by increasing the wavelength interval, but when the large-diameter multimode fiber 18 is connected to the optical waveguide, the wavelength dependence of loss is large. For example, in an optical waveguide using a fluororesin, the loss at 850 nm is greatly different from 50 dB / km at 650 nm, and it is not suitable to increase the wavelength interval to 100 nm or more. Therefore, if the wavelength interval is 100 nm, the fabrication accuracy of the multilayer filter 22 is ± 10 nm, and the wavelength shift of the LD 16 is ± 5 nm, a transition wavelength interval of 70 nm is required for the multilayer filter 22, and both p-polarized light and s-polarized light are required. This is because the angle width of the incident light to the multilayer filter 22 is 12 ° at the maximum when the reflection characteristics of the polarized light are taken into consideration.

  The NA of the multimode waveguide 15 is preferably 0.3 to 0.6. When the NA is 0.3 or less, the bending radius threshold at which bending loss occurs is as large as about 3 mm, the device size is increased, and this is not preferable for use in a limited space such as a home network. Further, in order to form a multimode waveguide having an NA of 0.6 or more, it is necessary to increase the relative refractive index difference between the core and the clad. Therefore, different materials having greatly different characteristics are used for the core and the clad, which causes a problem in the adhesion between the core and the clad. When NA is 0.6 or more, for example, when an acrylic resin having a refractive index of 1.5 is used for the core, the refractive index of the clad must be 1.37, which is usually a fluorine having a weak adhesive force with other materials. Resin is required. On the other hand, when the refractive index of the core is 1.5 or more, a benzene ring having a large molecular refraction, a halogen-based chlorine, or bromine is used, which is not preferable from an environmental viewpoint.

  Next, a multimode bidirectional device according to a second embodiment will be described.

  As shown in FIG. 5, the basic configuration of the multimode bidirectional device 50 of the present embodiment is the same as that of the multimode single-core bidirectional device 10 of FIG. A difference is that a first LD 17 that outputs light is connected and a second LD 51 that outputs light having a wavelength different from a predetermined wavelength is connected to one branching waveguide 13.

  The operation principle of the multi-mode single-core bidirectional device 50 will be described. The multimode single-core bidirectional device 50 according to the present embodiment is a multiplexing device that combines two different wavelengths of light and transmits them to the multimode fiber 18.

  The light emitted from one LD 51 passes through the branch waveguide 13, is reflected by the multilayer filter 22, propagates through the other branch waveguide 14, and propagates to the multimode fiber 18. On the other hand, light emitted from the LD 16 passes through the coupling waveguide 12, passes through the multilayer filter 22, propagates to the multimode fiber 18 through the other branching waveguide 14. Therefore, the light emitted from the LD 51 and the light emitted from the LD 16 are combined by the multilayer filter 22, and the combined light is transmitted to the multimode fiber 18 through the branching waveguide 14.

  Also in the multimode single-core bidirectional device 50 of the present embodiment, the LD 51 and the multimode fiber 18 are connected to different end faces 23 and 24 of the substrate 11, and the multimode single-core bidirectional device of the previous embodiment. 10 has the same effect.

  Next, a multimode single-core bidirectional device according to a third embodiment will be described.

  As shown in FIG. 6, the basic configuration of the multimode single-core bidirectional device 60 of the present embodiment is the same as that of the multimode single-core bidirectional device 10 of FIG. The difference is that the first PD 17 is connected and the second PD 17 is connected to one branching waveguide 13.

  The operation principle of the multi-mode single-core bidirectional device 60 will be described. The multimode single-core bidirectional device 60 of the present embodiment is a demultiplexing device that demultiplexes two-wavelength multiplexed light incident from the multimode fiber 18 and detects each of the light of each wavelength.

  The wavelength multiplexed light incident from the multimode fiber 18 passes through the branch waveguide 14 and enters the multilayer filter 22. The multilayer filter 22 transmits light of a predetermined wavelength band and reflects light other than the predetermined wavelength band. Therefore, the light of one wavelength passes through the multilayer filter 22 and is received by the first PD 17 through the coupling waveguide 12, and the light of the other wavelength is reflected by the multilayer filter 22 and passes through the branching waveguide 13. The light is received by the second PD 17.

  The multimode single-core bidirectional device 60 of the present embodiment also has the same operational effects as the multimode single-core bidirectional device 10 of FIG.

  Next, embodiments of the present invention will be described based on examples, but the embodiments of the present invention are not limited to these examples.

Example 1
A multi-mode waveguide 15 was formed of a polymer material on the surface of the quartz substrate 11 provided with electrical wiring on the back surface by a direct exposure method. As the polymer material, a photocurable acrylic resin was used, and the refractive index of the core was 1.567 and the refractive index of the cladding was 1.517. The multimode waveguide 15 was formed with an under cladding thickness of 20 μm, a core diameter of 70 μm × 70 μm (width × height), and an over cladding thickness of 20 μm from the top of the core. The pattern of the multimode waveguide 15 has a structure as shown in FIGS. 1 and 2, and the branch angle is 10 degrees. In this embodiment, the branching ratio when light enters from port 1 is port 3: port 2 = 17: 1.

  Further, dicing with a V-shaped blade formed a core on the mirror end face in the vicinity of port 1 and port 2. The device was cut out and the multilayer filter insertion groove 21 having a width of 0.02 mm was collectively formed by dicing. A multilayer filter 22 that reflects at a wavelength of 780 nm and transmits at 850 nm is inserted into the multilayer filter insertion groove 21. In the multilayer filter insertion groove 21, the same material as the core material was dropped and irradiated with ultraviolet rays to fix the multilayer filter 22 while also serving as a matching oil. On the back side of the substrate, a VCSEL having a wavelength of 850 nm is disposed on the mirror end face of port 1, a PD is disposed on the mirror end face of port 2, and a multimode fiber 18 is connected to port 3 to A mode single-core bidirectional device A was produced.

  Furthermore, a single-core bidirectional device B was fabricated by arranging a PD at port 1 and an LD with a wavelength of 780 nm at port 2, and connecting a multimode fiber 18 to port 3. The loss of the single-core bidirectional device was confirmed by connecting LD and PD to the other end of the multimode fiber 18 for each of the devices A and B. The loss of both the devices A and B was 3 dB or less for both transmission and reception. . In addition, when the single-core bidirectional device A and the single-core bidirectional device B are connected using the multi-mode fiber 18 having a length of 100 m and the operation is confirmed, the eye pattern opens even at the operation of 2.5 Gbps. It could be confirmed.

(Example 2)
On a silicon substrate, an acrylic resin having a refractive index of 1.502 is used as a core material, an acrylic resin having a refractive index of 1.452 is used as a cladding material, and a multimode waveguide 15 having an NA of 0.38 is formed by direct exposure Produced. The core diameter of the manufactured multimode waveguide 15 is 70 μm × 70 μm (width × height). The branch angle was 10 °. In the multimode waveguide 15, the multilayer filter insertion groove 21 was formed at a position 20 μm from the position of the Y coordinate 0 in FIG. 2 by a dicing saw having a width of 20 μm. The multilayer filter 22 has a transmission / reflection characteristic shown in FIG. 7 and is produced on a polyimide substrate having a thickness of 12 μm.

  As shown in FIGS. 7A and 7C, the multilayer filter 22 transmits light having a wavelength of 840 nm or more (transmission loss of 0.5 dB or less), and FIGS. 7B and 7D. As shown in FIG. 2, the light has a reflection / reflection characteristic of reflecting light having a wavelength of 790 nm or less (transmission loss of 20 dB or more).

  The multilayer filter 22 was inserted into the multilayer filter insertion groove 21 and fixed with an acrylic ultraviolet curable adhesive having a refractive index of 1.502. Furthermore, the LD 16 having a wavelength of 780 nm is aligned with the coupling waveguide 12 (port 1) at the position where the light emitted from the LD 16 is most efficiently coupled to the coupling waveguide 12 and fixed with an adhesive. An LD 51 having a wavelength of 850 nm was fixed to one branching waveguide 13 (port 2) in the same manner as the LD 16 having a wavelength of 780 nm. In the other branching waveguide 14 (port 3), a GI type plastic optical fiber 18 having a core diameter of 120 μm and NA of 0.19 was fixed at a position where the light emitted from the branching waveguide 14 can be received most efficiently.

  The characteristics of the multimode single-core bidirectional device of this example are as good as 1.7 dB for light loss at a wavelength of 850 nm and 2.9 dB for light loss at a wavelength of 780 nm, including connection loss with a plastic optical fiber. The result was obtained.

(Example 3)
On the silicon substrate 11, an acrylic resin having a refractive index of 1.502 is used as a core material, an acrylic resin having a refractive index of 1.452 is used as a cladding material, and a multimode waveguide 15 having an NA of 0.38 is directly exposed. It was produced by the method. The core diameter of the manufactured multimode waveguide 15 is 70 × 70 (width × height). The branch angle was 10 °. In the multimode waveguide 15, the multilayer filter insertion groove 21 was formed at a position 20 μm from the position of the Y coordinate 0 in FIG. 2 by a dicing saw having a width of 20 μm. The multilayer filter 22 has a transmission / reflection characteristic shown in FIGS. 7A to 7D and is manufactured on a polyimide substrate having a thickness of 12 μm.

  As shown in FIGS. 7A to 7D, the multilayer filter 22 transmits light having a wavelength of 840 nm or more (transmission loss of 0.5 dB or less) and reflects light having a wavelength of 790 nm or less (transmission loss). 20 dB or more) It has transmission and reflection characteristics.

  The multilayer filter 22 was inserted into the multilayer filter insertion groove 21 and fixed with an acrylic ultraviolet curable adhesive having a refractive index of 1.502. Further, the PDs 17 and 17 were aligned with the coupling waveguide 12 (port 1) and the one branching waveguide 13 (port 2) at the position where each port was most efficiently coupled, and fixed with an adhesive. In the other branching waveguide 14 (port 3), a GI type plastic optical fiber having a core diameter of 120 μm and NA of 0.19 was fixed at a position where light can be most efficiently coupled to the other branching waveguide.

  As a result of passing 780 nm and 850 nm wavelength multiplexed light through the connected plastic optical fiber, the 780 nm light can be received by the PD disposed at port 2 and the 850 nm light can be received by the PD disposed at port 1. The loss was 3.0 dB and 3.0 dB, respectively, and good results were obtained.

1 is a top view showing a multimode single-core bidirectional device according to a preferred first embodiment; It is an enlarged plan view of a Y branch part. It is a figure which shows the relationship between the multilayer filter position and loss in the multi-mode single-core bidirectional device of FIG. (A)-(h) is sectional drawing which shows each process of the manufacturing method of the multimode single core bidirectional device of FIG. It is a top view which shows the multimode single core bidirectional device of 2nd Embodiment. It is a top view which shows the multimode single core bidirectional device of 3rd Embodiment. (A), (c) is a figure which shows the permeation | transmission characteristic of a multilayer filter, (b), (d) is a figure which shows the reflective characteristic of a multilayer filter. It is a top view which shows the conventional multimode single core bidirectional device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Multimode single core bidirectional device 11 Substrate 12 Coupling waveguide 13,14 Branching waveguide 15 Multimode waveguide 16 Laser diode 17 Photodiode 18 Multimode fiber 21 Multilayer filter insertion groove 22 Multilayer filter

Claims (7)

A multi-mode waveguide provided on a substrate and connected to one coupling waveguide and two branching waveguides; a laser diode or a photodiode connected to the coupling waveguide; and one branching waveguide Inserted into a multilayer filter insertion groove formed at a connection portion between the connected photodiode or laser diode, the multimode fiber connected to the other branching waveguide, and the coupling waveguide and the branching waveguide In a multimode single-core bidirectional device including a multilayer filter,
The two branched waveguides are respectively formed facing different end surfaces of the substrate, a photodiode or laser diode is connected to one end surface, and a multimode fiber having a core diameter of 100 to 150 μm is connected to the other end surface. Multi-mode single-core bidirectional device characterized by being connected. A multimode waveguide provided on a substrate and connected to one coupling waveguide and two branching waveguides, a laser diode connected to the coupling waveguide, and one branching waveguide A laser diode; a multimode fiber connected to the other branch waveguide; and a multilayer filter inserted in a multilayer filter insertion groove formed at a connection portion between the coupling waveguide and the branch waveguide. Multi-mode single-core bidirectional devices
A first laser diode that outputs light of a predetermined wavelength is connected to the coupling waveguide, and a second laser diode that outputs light of a wavelength different from the predetermined wavelength is connected to the one branch waveguide. The multi-mode single-core bidirectional device according to claim 1, which is connected. A multi-mode waveguide provided on the substrate and connected to one coupling waveguide and two branching waveguides, a photodiode connected to the coupling waveguide, and one branching waveguide A photodiode, a multimode fiber connected to the other branch waveguide, and a multilayer filter inserted into a multilayer filter insertion groove formed at a connection portion between the coupling waveguide and the branch waveguide Multi-mode single-core bidirectional devices
The multimode single-core bidirectional device according to claim 1, wherein a first photodiode is connected to the coupling waveguide, and a second photodiode is connected to the one branch waveguide.   The multilayer filter is inserted at a position of 0 to 1/5, where a position where the two branching waveguides completely intersect is a 0 position and a part where the two branching waveguides start intersecting is a 1 position. The multimode single-core bidirectional device according to any one of claims 1 to 3.   The multimode single-core bidirectional device according to any one of claims 1 to 4, wherein the multilayer filter insertion groove is formed in parallel to an end face connecting the multimode fiber.   The multimode single-core bidirectional device according to any one of claims 1 to 5, wherein a branch angle of the connection portion is 10 ° or less.   The multimode single-core bidirectional device according to claim 1, wherein the NA of the coupling waveguide and the branching waveguide is 0.3 to 0.6.

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