Optical Circuit and Optical Connection Structure

Abstract

Optical alignment between an optical waveguide device and an optical connection part is realized easily and at low cost. An optical circuit in which optical waveguides to be connected to optical fibers are formed includes: an alignment optical waveguide configured to be opposed to, on an optical waveguide edge face to which an optical connection part having guide holes for insertion of core wires of the optical fibers is to be fixed, a guide hole into which an alignment optical fiber is to be inserted; and a light path changing member configured to change a path of light to a vertical direction with respect to the optical axis direction of the core of the alignment optical waveguide.

Claims

1. An optical circuit in which optical waveguides to be connected to optical fibers are formed, comprising: an alignment optical waveguide configured to be opposed to, on an optical waveguide edge face to which an optical connection part having guide holes for insertion of core wires of the optical fibers is to be fixed, a guide hole into which an alignment optical fiber is to be inserted; and a light path changing member configured to change a path of light to a vertical direction with respect to an optical axis direction of a core of the alignment optical waveguide.

2. The optical circuit according to claim 1, wherein the light path changing member is an inclined surface of 45 degrees with respect to the optical axis direction of the core of the alignment optical waveguide.

3. The optical circuit according to claim 1, wherein the light path changing member is a scattering substance connected to the core of the alignment optical waveguide.

4. An optical connection structure for connecting an optical waveguide device and optical fibers, comprising: an optical connection part that has guide holes for insertion of core wires of the optical fibers; and an optical circuit including an alignment optical waveguide that connects an optical waveguide edge face to which the optical connection part is fixed, and a light path changing member configured to change a path of light to a vertical direction with respect to an optical axis direction of a core of the alignment optical waveguide, wherein the alignment optical waveguide is opposed to a guide hole into which an alignment optical fiber is to be inserted, and optical alignment of the optical connection part is performed.

5. An optical connection structure for connecting an optical waveguide device and optical fibers, wherein, on an optical waveguide edge face to which an optical connection part having guide holes for insertion of core wires of the optical fibers is fixed, an alignment optical waveguide that connects the optical waveguide edge face and a light path changing member configured to change a path of light to a vertical direction with respect to an optical axis direction of a core of the alignment optical waveguide is opposed to a guide hole into which an alignment optical fiber is to be inserted, and optical alignment of the optical connection part is performed, and thereby the optical connection part is fixed to the optical waveguide device.

6. The optical connection structure according to claim 4, wherein the light path changing member is an inclined surface of 45 degrees with respect to the optical axis direction of the core of the alignment optical waveguide.

7. The optical connection structure according to claim 4, wherein the light path changing member is a scattering substance connected to the core of the alignment optical waveguide.

8. The optical connection structure according to claim 5, wherein the light path changing member is an inclined surface of 45 degrees with respect to the optical axis direction of the core of the alignment optical waveguide.

9. The optical connection structure according to claim 5, wherein the light path changing member is a scattering substance connected to the core of the alignment optical waveguide.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0016] FIG. 1 is a diagram illustrating a conventional method for connecting an optical waveguide device and optical fibers.

[0017] FIG. 2 is a diagram illustrating a structure of a conventional optical connection part.

[0018] FIG. 3 is a diagram illustrating a conventional method for aligning the optical waveguide device with an optical fiber.

[0019] FIG. 4 is a diagram illustrating a method for connecting an optical waveguide device and optical fibers, according to Embodiment 1 of the present invention.

[0020] FIG. 5 is a diagram illustrating a structure of an alignment optical waveguide according to Embodiment 1.

[0021] FIG. 6 is a diagram illustrating a method for fixing alignment optical fibers to the optical connection part.

[0022] FIG. 7 is a diagram illustrating a method for performing optical alignment by causing light to enter the alignment optical fibers.

[0023] FIG. 8 is a diagram illustrating the optical waveguide device and the optical connection part for which optical alignment is complete.

[0024] FIG. 9 is a diagram illustrating a method for connecting the optical waveguide device and optical fibers, according to Embodiment 2 of the present invention.

[0025] FIG. 10 is a diagram illustrating a method for connecting the optical waveguide device and optical fibers, according to Embodiment 3 of the present invention.

[0026] FIG. 11 is a diagram illustrating a method for connecting the optical waveguide device and optical fibers, according to Embodiment 4 of the present invention.

DESCRIPTION OF EMBODIMENTS

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments, as the optical connection part, an optical connection part as shown in FIG. 1 is used. In the optical connection part, the V groove substrate 11 in which the plurality of V grooves 13 are formed, and the plate lid substrate 12 are fixed to each other using the adhesive 14 with the dummy fibers 15a and 15b interposed therebetween. The V grooves have no limitation to the number and pitch thereof, and are applied in various modes. Also, as an optical fiber to be applied, a single-mode optical fiber whose cladding has an outer diameter of 125 μm is used, for example. However, another optical fiber having any outer diameter, core diameter, and fiber type (such as a multi-mode fiber or a polarization maintaining fiber) may be suitably selected as long as it achieves the same effect. Note that the optical connection part suitably employs, for connection, a housing structure, a guide structure, an adhesive, a spring structure, a protection structure, and the like, but illustrations thereof are omitted in the embodiments. These structures may be suitably added to the embodiments depending on the connection usage.

[0028] The optical waveguide device is not limited to the above-described optical waveguide device as long as it includes a one-dimensional waveguide array. For example, as an light emitting element, an integrated light emitting element may be used in which a plurality of distributed-feedback laser diodes (DFB-LD) made of InP are mounted, and are optically connected to each other by an optical circuit such as a Si waveguide or a glass waveguide. Also, a light emitting element may be used in which a DFB-LD array is bonded to an optical circuit formed on a Si substrate, and is integrated with Si waveguides. Furthermore, an integrated light emitting element may also be used in which an InP material or the like is bonded to a Si substrate to form a laser layer, and waveguides made of Si waveguides, a Si oxide (such as oxide silicon or a silicon oxynitride film), or the like are integrated therewith. Similarly, as a light receiving element, an integrated light receiving element may be used in which a PD made of InGaAs, Ge, or the like is bonded to a substrate, and is optically connected to and integrated with another optical waveguide device.

[0029] Also, an external modulation element or the like may be connected to the light emitting element, or may be made of the same material and integrated on the same substrate, as appropriate. For example, Si waveguides and a modulation element constituted by a thermo-optic switch or an electro-optic switch may also be integrated, or InP waveguides, a modulation element constituted by a thermo-optic switch or an electro-optic switch, and a modulation element made of a ferroelectric such as LN may also be integrated. A structure that has a modulation function due to the electroabsorption effect may also be directly integrated with or formed on the light emitting element. In the embodiments, the modulation elements are omitted. A specific layout of the optical waveguides is also omitted because the present invention is not limited to this.

[0030] The material of the V groove substrate and the lid substrate has no limitation with regard to the material quality as long as the V grooves can be formed therein with accuracy. As a representative example, a glass material can be subjected to cutting work or the like, so that the V grooves are formed. Also, the V groove substrate may also be formed by subjecting a Si substrate or the like to anisotropic etching. Similarly, the V grooves can also be formed by an imprint technique using polymer, or sintering of ceramic, for example.

EMBODIMENT 1

[0031] FIG. 4 shows a method for connecting an optical waveguide device and optical fibers according to Embodiment 1 of the present invention. An optical waveguide device 120 includes, on a Si substrate 121, an optical circuit (PLC) 122 that is constituted by optical waveguides each constituted by a core made of Si and a cladding made of SiO.sub.2. On the PLC 122, a transmitter array 123 and a receiver array 124 are mounted, and a waveguide array 125 extending from an optical waveguide edge face of the optical waveguide device 120 is connected to the transmitter array 123 and the receiver array 124. As a result of the transmitter array 123 and the receiver array 124 being electrically connected to an element or a terminal provided inside a package or on a printed circuit board, a transceiver for optical interconnection is realized.

[0032] An optical connection part 110 is adhered and fixed to the optical waveguide edge face of the optical waveguide device 120, the optical connection part 110 including a V groove substrate 111 with a plurality of V grooves and a plate lid substrate 112 that are joined to each other. Dummy fibers 115a and 115b are inserted into some of the V grooves. Note that illustration of a reinforcing plate arranged on the optical waveguide device 120 is omitted. After the optical connection structure in which the optical waveguide device 120 and the optical connection part 110 are fixed to each other is mounted inside a package or on a printed circuit board, an implementer of the present invention can insert optical fiber core wires of an optical fiber array into guide holes of the optical connection part 110, thereby optically coupling the optical fiber array and the optical waveguide array 125 of the optical waveguide device 120.

[0033] As described above, the light emitting element, the light receiving element, the light modulation element, the optical functional element, and the light amplification element of the optical waveguide device 120 may have any number of channels, any configuration, and any material, and any method such as an integration method may be used for them.

[0034] Conventionally, an alignment optical waveguide for use in optical alignment is a through-type optical waveguide that extends from the optical waveguide edge face of an optical waveguide device to the opposite edge face, so that a monitoring optical fiber for monitoring exiting light can be connected thereto. However, as shown in FIG. 4, the through-type optical waveguide is not preferable depending on the configuration of the optical functional element of the PLC 122 that is connected to the transmitter array 123 or the receiver array 124, because crossing of waveguides, an increase in the dimension of the optical circuit, and the like may occur. Also, in the case of the through-type optical waveguide, when light exiting from the alignment optical waveguide is monitored, light that was not coupled to the optical waveguide, such as a slab mode of the optical functional element formed on the PLC 122 and stray light, is detected from the alignment optical waveguide, resulting in an increase in difficulty in alignment.

[0035] FIG. 5 shows a structure of the alignment optical waveguide according to Embodiment 1. Alignment optical waveguides 126a and 126b of Embodiment 1 are provided at two ends of the optical waveguide array 125, and respectively connect the optical waveguide edge face of the optical waveguide device 120 to a flip-up reflection mirror 127a formed on the PLC 122, and connect the optical waveguide cross-section to a flip-up reflection mirror 127b. The flip-up reflection mirrors 127 have an inclined surface of 45 degrees with respect to the optical axis direction of the cores of the alignment optical waveguides 126, and are formed with a shape of etching performed on the bottom of the PLC 122. Light that has entered the alignment optical waveguides 126 is received on the surface of the optical waveguide device 120, and can be detected by providing, for example, light receiving elements 128. Note that the structure of the reflection mirrors is not limited to that of the mirrors having an inclination of 45 degrees formed with the etching shape as long as they have a structure that can scatter light onto the device surface. The mirrors may have any aspect as long as they have a structure that can emit light in a vertical direction with respect to the device surface.

[0036] As a result of the alignment optical waveguides 126 being provided with the flip-up reflection mirrors 127, it is possible to reflect light upward at appropriate positions on the surface of the optical waveguide device 120, and thus it is not necessary to route the alignment waveguides 126 across the inner area of the PLC 122. Also, there is no need of forming an exit edge face as is common for a through-type optical waveguide, and thus it is possible to realize a reduction in the implementation cost and downsizing of the device.

[0037] The following will describe procedure for optically coupling the optical waveguide device and optical fibers with reference to FIGS. 6 to 8. As shown in FIG. 6, a fiber fixing base 130 is joined to the optical connection part 110 in advance, the core wires of alignment optical fibers 131a and 131b are inserted into predetermined guide holes of the optical connection part 110, and the coverings of the alignment optical fibers 131a and 131b are adhered and fixed to the fiber fixing base 130. The predetermined guide holes refer to guide holes that are opposed to, on the optical waveguide edge face of the optical waveguide device 120, the alignment optical waveguides 126.

[0038] Then, as shown in FIG. 7, light-receiving devices 128a and 128b are placed over the flip-up reflection mirrors 127a and 127b connected to the alignment optical waveguides 126a and 126b. The optical connection part 110 and the fiber fixing base 130 are attached to a holding/operating device, and the fiber edge face of the optical connection part 110 and the waveguide edge face of the optical waveguide device 120 are brought into intimate contact with each other. In this state, the implementer causes light to enter the alignment optical waveguides 126a and 126b from the alignment optical fibers 131a and 131b, and monitors, using the light-receiving devices 128a and 128b, the light intensities of the light exiting from the alignment optical waveguides 126a and 126.

[0039] At a position at which the light intensities detected by the light-receiving devices 128a and 128b are the highest, the optical waveguide device 120 and the optical connection part 110 are adhered and fixed to each other, and the optical alignment is ended. The implementer pulls out or cuts off the alignment optical fibers 131a and 131b, and removes the fiber fixing base 130, as shown in FIG. 8, and thereby completing the coupling between the optical waveguide device 120 and the optical connection part 110. In this way, the optical connection structure is obtained.

[0040] Then, by mounting the optical connection structure inside the package or on the printed circuit board, and then inserting the optical fiber core wires of the optical fiber array into the guide holes of the optical connection part 110, it is possible to optically couple the optical fiber array to the optical waveguide array 125 of the optical waveguide device 120.

[0041] According to the present embodiment, since light from the alignment optical waveguides 126a and 126b has been detected from the surface of the optical waveguide device 120, positioning needs only to be performed on the side on which light is incident, that is, on the optical connection part 110 side. Accordingly, the present embodiment can realize the optical alignment easily and at low cost. Also, as a result of the alignment optical waveguides 126a and 126 being arranged at both ends of the optical waveguide device 120 with the waveguide array 125 interposed therebetween, it is possible to accurately position the optical connection part 110. Furthermore, because, for detection of light from the alignment optical waveguides 126a and 126b, it is sufficient to observe relative light intensities, the flip-up mirrors 127 and the light receiving elements 128 do not need to be positioned with accuracy, and thus it is possible to easily measure the light intensities.

[0042] Note that in the present embodiment, light from the alignment optical waveguides 126a and 126b are detected from the surface of the optical waveguide device 120, but depending on the package structure of the optical transmitter or the optical receiver, the light may also be detected from the reverse side of the optical waveguide device 120 via the substrate 121.

EMBODIMENT 2

[0043] FIG. 9 shows a method for connecting the optical waveguide device and optical fibers according to Embodiment 2 of the present invention. In Embodiment 1, the light receiving elements 128 for use in optical alignment employ a photodiode. Embodiment 2 uses a microscope 140 that can receive light in the range from visible light to infrared light.

[0044] The implementer can monitor the light intensities of light exiting from the alignment optical waveguides 126a and 126b via the flip-up reflection mirrors 127a and 27b, and at the same time, the implementer can view the positions of the guide holes of the optical connection part 110 and the positions of the waveguide array 125 of the optical waveguide device 120. This makes the positioning easy. Furthermore, a reduction in the implementation cost can be expected. Also, even a microscope that can receive only visible light can be used to perform positioning with infrared light, if a fluorescent coating or the like is applied to the surface of the optical waveguide device 120 or the lens of the visible light microscope.

EMBODIMENT 3

[0045] FIG. 10 shows a method for connecting the optical waveguide device and optical fibers according to Embodiment 3 of the present invention. Embodiment 3 uses scattering substances 141a and 141b, instead of the flip-up reflection mirrors 127a and 127b connected to the alignment optical waveguides 126a and 126b. The flip-up reflection mirrors 127a and 127b each constituted by an inclined surface of 45 degrees can reflect light exiting from the alignment waveguides 126a and 126b with low loss, and the light intensities detected by the light receiving elements 128 are high. However, an area in which the light can be received is small, which thus requires adjustment of the positions of the light receiving elements 128. In Embodiment 3, the scattering substances 141a and 141b can extensively scatter light, and thus easy positioning of the light receiving elements 128 is possible.

[0046] The scattering substances 141 need only to emit, from the surface of the optical waveguide device 120, an amount of light such that a change in the light intensity of the light exiting from the alignment optical waveguides 126 can be detected by the light receiving elements 128. As a simplified method for forming the scattering substances 141, it is conceivable to form a hole or a slit in the surface of the optical waveguide device 120 in the vertical direction so that it crosses the core of the alignment optical waveguides 126.

[0047] Therefore, instead of the mirrors or the scattering substances, any light path changing members may be used as long as they can change the path of light from the alignment optical fibers 131 to the vertical direction with respect to the optical axis direction of the cores of the alignment optical waveguides 126.

EMBODIMENT 4

[0048] FIG. 11 shows a method for connecting the optical waveguide device and optical fibers according to Embodiment 4 of the present invention. In Embodiment 4, instead of the light receiving elements 128, light emitting elements 129a and 129b such as laser diodes are arranged above the flip-up reflection mirrors 127a and 127b. When performing optical alignment, the light intensities of light exiting from the alignment optical fibers 131a and 131b are monitored. In Embodiment 1, noise may occur in the light receiving elements 128 due to scattering of light that was not coupled to the waveguides. In Embodiment 4, most components of light that were not coupled to the waveguides are scattered before entering the optical connection part 110, and thus positioning is possible without lowering the accuracy.

REFERENCE SIGNS LIST

[0049] 1, 110 Optical connection part [0050] 2, 120 Optical waveguide device [0051] 3 Guide hole [0052] 4 Optical waveguide [0053] 11, 111 V groove substrate [0054] 12, 112 Lid substrate [0055] 13 V groove [0056] 14 Adhesive [0057] 15, 115 Dummy fiber [0058] 21 Substrate [0059] 22 Optical waveguide [0060] 23 Core [0061] 24 Cladding [0062] 25 Reinforcing plate [0063] 31, 131 Alignment optical fiber [0064] 32 Plug [0065] 121 Si substrate [0066] 122 PLC [0067] 123 Transmitter array [0068] 124 Receiver array [0069] 125 Optical waveguide array [0070] 126 Alignment optical waveguide [0071] 127 Flip-up reflection mirror [0072] 128 Light receiving element [0073] 129 Light emitting element [0074] 130 Fiber fixing base [0075] 140 Microscope [0076] 141 Scattering substance