JP2013195773A - Light reception module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reception module capable of facilitating alignment in a mounted-height direction of optical elements.SOLUTION: An optical module according to the present invention includes: a carrier substrate 1; an optical waveguide substrate 2 mounted on the carrier substrate 1; and a subcarrier 3 mounted on the carrier substrate 1. The subcarrier 3 includes a direction converter 4 and a light receiving element 5. The direction converter 4 reflects light emitted from the optical waveguide substrate 2 toward a mounting surface of the subcarrier 3 mounted on the carrier substrate 1 in a vertical downward direction. The light receiving element 5 receives the light reflected by the direction converter 4. The carrier substrate 1 includes a position selecting part 6. The position selecting part 6 can select a mounting position of the subcarrier 3 in a vertical direction with respect to a substrate upper surface of the carrier substrate 1.

Description

  The present invention relates to a light receiving module.

In the light receiving module, an optical waveguide element that guides or branches received light, a PD (Photo Diode) element, or the like is integrated on a carrier substrate, and a structure that is reduced in size and cost is often used. For example, a configuration is known in which light emitted from an optical waveguide element is bent and light is incident on a PD mounted on the same carrier as a TIA (Trans Impedance Amplifier) or a ceramic wiring board. Such a configuration is particularly effective for downsizing a multi-channel light receiving module. In recent years, it has been applied to a light-receiving module for ultra-high-speed optical communication such as a digital coherent receiver.

  FIG. 5 is a diagram showing a configuration of a general light receiving module used for light reception for optical communication. In the module, an optical waveguide substrate 2000 and a subcarrier substrate 7000 are mounted on a carrier substrate 1000. Subcarrier substrate 7000 mounts prism 4000 and PD 6000 supported by pedestal 5000. The collimator lens 3000 has a structure in which output light from the optical waveguide substrate 1000 is collimated light, and the prism 4000 has a structure that bends the collimated light by 90 degrees. In addition, it is possible to reduce the number of parts and facilitate the optical axis adjustment by using a prism 1000 that integrates the functions of the lens and the prism.

By accumulating on the subcarrier, the accuracy of the positional relationship between the prism and the PD can be sufficiently secured in practice. On the other hand, the processing accuracy of the carrier substrate and the subcarrier substrate is not sufficiently ensured with respect to the allowable value of the optical axis deviation. Therefore, in order for the light emitted from the waveguide substrate to be accurately received by the light receiving element, it is necessary to devise alignment when mounting the subcarrier substrate 7000 in order to sufficiently increase the accuracy of the mounting position.

In Patent Document 1, an optical waveguide array is brought close to an optical element array placed on a substrate, and an optical axis between the optical waveguide array and the optical element array is set while monitoring an optical signal output through an optical path conversion mirror. A method of aligning and fixing the optical waveguide array on the substrate at a position where the output of the optical signal becomes a desired value is described.

However, adjusting and fixing the horizontal direction, the vertical direction, and the element angle while monitoring the optical signal has a problem in terms of manufacturing cost. On the other hand, in Patent Document 2, an element marker is formed on a semiconductor laser, a mounting marker is formed on a quartz substrate, and alignment is performed so that the element marker and the mounting marker are on the same straight line. A method of mounting on a substrate is described. Such a method is advantageous in terms of cost because it can be implemented without monitoring the optical signal.

JP 2009-288614 A JP 2002-062447 A

  However, the methods described in Patent Documents 1 and 2 are methods for mounting an optical element on a substrate, and are not directly applicable to mounting on a carrier substrate of a subcarrier substrate that is difficult to ensure processing accuracy. . In addition, since the invention described in Patent Document 2 is not considered to ensure the positional accuracy in the height direction, it has not necessarily been able to ensure practically sufficient positional accuracy.

An object of the present invention is to provide a light receiving module that solves the above problems.

According to the present invention, a carrier substrate;
An optical waveguide substrate mounted on the carrier substrate;
A subcarrier mounted on the carrier substrate,
The subcarrier is:
A direction changer that converts the direction of light emitted from the optical waveguide substrate into a direction perpendicular to the upper surface of the carrier substrate;
A light receiving element for receiving the light whose direction has been converted,
The carrier substrate is
There is provided a light receiving module including a position selection unit formed so that a mounting position of the subcarrier in a direction perpendicular to the upper surface of the carrier substrate can be selected.

  ADVANTAGE OF THE INVENTION According to this invention, the light receiving module which improved the precision of the mounting position on the carrier substrate of the subcarrier which has a light receiving element can be provided.

It is a figure which shows the structure of the light reception module which concerns on 1st Embodiment. It is a figure which shows the structure of the light reception module which concerns on 2nd Embodiment. It is (a) top view and (b) side surface sectional drawing which show the specific example of a structure of the light reception module which concerns on 2nd Embodiment. It is a figure which shows the structure of the light reception module which concerns on 3rd Embodiment. It is a figure which shows the structure of the general light receiving module used for the light reception for optical communications.

(First embodiment)
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a light receiving module according to the first embodiment of the present invention. The light receiving module of FIG. 1 includes a carrier substrate 1, an optical waveguide substrate 2 mounted on the carrier substrate 1, and a subcarrier 3 mounted on the carrier substrate 1. The subcarrier 3 includes a direction changer 4 and a light receiving element 5. The direction changer 4 reflects light emitted from the optical waveguide substrate 2 vertically downward with respect to the mounting surface of the subcarrier 3 mounted on the carrier substrate 1. The light receiving element 5 receives the light reflected by the direction changer 4. The carrier substrate 1 includes a position selection unit 6. The position selection unit 6 can select a mounting position in the direction perpendicular to the upper surface of the carrier substrate 1 of the subcarrier 3.

  According to the present embodiment, since the position selection unit 6 can select the mounting position in the height direction after the formation of the substrate module and the carrier substrate, the accuracy of the mounting position of the subcarrier on the carrier substrate is further improved. It becomes possible. Moreover, since it can be adjusted by selecting the mounting position, the mounting position of the subcarrier on the carrier substrate can be easily adjusted.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 2 is a diagram illustrating a configuration of an optical module according to the second embodiment. The light receiving module of FIG. 2 includes a carrier substrate 40, collimating lens arrays 90-1 and 90-2, and a PLC 80 and a subcarrier substrate 140 mounted on the carrier substrate 40. Here, the PLC 80 corresponds to the optical waveguide substrate 2 in FIG. The subcarrier substrate 140 mounts the prism 100 and the PD array 110 supported by the pedestal 150. Here, the carrier substrate 40 and the subcarrier substrate 140 are substrates obtained by processing, for example, metal or ceramic. The subcarrier substrate 140 corresponds to the subcarrier 3 in FIG. The PD array 110 corresponds to the light receiving element 5. The prism 100 corresponds to the direction changer 4. The carrier substrate 40 has a staircase structure 160 in a portion where the subcarrier substrate 140 is mounted. Here, the staircase structure 160 corresponds to the position selection unit 6 in FIG.

  The prism 100, the pedestal 150, and the PD array 110 are mounted in advance on the subcarrier substrate 140, and the subcarrier substrate 140 on which these are mounted is mounted on the carrier substrate 40. Here, when the subcarrier substrate 140 is mounted on the carrier substrate 40, one of the steps of the staircase structure 160 is selected and mounted. Each step of the staircase structure 160 has a slight height difference that is about the error caused by the processing tolerances described above. Therefore, by selecting any step of the staircase structure 160 and mounting the subcarrier substrate 140, the mounting height position can be finely adjusted. Specifically, a stage is selected such that the optical axis 200 of the light output from the collimating lens arrays 90-1 and 90-2 matches the input part of the prism 100. Note that the distance between the collimating lens arrays 90-1 and 90-2 and the prism 100 differs depending on the stage selected, but the light output from the collimating lens arrays 90-1 and 90-2 is collimated light, which affects the characteristics. Is insignificant.

3A is a plan view and FIG. 3B is a side sectional view showing a specific example of the light receiving module according to the present embodiment. As an example of the light receiving module in the present embodiment, a light receiving module used for a digital coherent receiver compatible with polarization multiplexed quadrature phase shift keying (DP-QPSK) will be described.

As shown in FIG. 3, in the light receiving module according to the present embodiment, an optical fiber 20-1 that inputs signal light into the package 10 and an optical fiber 20-2 that inputs local light into the package 10. It is fixed. Here, the package 10 is obtained by processing a material such as metal or ceramic. Collimating lenses 30-1 and 30-2 are installed at the input portion of the package 10.

Inside the package 10, the carrier substrate 40 is mounted with the tap prism 50, the PD 60, the condenser lenses 70-1 and 70-2, the PLC 80, and the subcarrier substrate 140. The subcarrier substrate 140 carries the prism 100 supported by the PD array 110, TIAs 120-1 to 4, the wiring substrate 130, and the pedestal 150.

The collimating lenses 30-1 and 30-2 output the input light from the optical fibers 20-1 and 20-2 as collimated light to the condensing lenses 70-1 and 70-2 in the package. The tap prism 50 branches a part of the collimated light output from the collimating lens 30-1 to the PD 60, and the PD 60 receives the collimated light branched by the tap prism 50 and monitors the optical power of the signal light. The condensing lenses 70-1 and 70-2 collect the collimated light input from the collimating lenses 30-1 and 30-2 on the input unit of the PLC 80.

The PLC 80 is a coherent mixer configured by a 90 ° hybrid interferometer. In the digital coherent light receiving module, the TE polarized light component and TM polarized light component of the signal light are branched and interfered with the local light, so that each polarized light 4 port outputs 8 ports in total. Each of the collimating lens arrays 90-1 and 90-2 includes four collimating lenses, and outputs the light output from the eight output ports of the PLC 80 to the prism 100 as collimated light. The prism 100 reflects a plurality of collimated lights input from the collimating lens arrays 90-1 and 90-2 in the direction toward the bottom surface of the package 10. The PD array 110 includes eight PDs, and receives light reflected from the prism 100 on the upper surface.

The TIAs 120-1 to 120-4 convert currents output from the eight PDs of the PD array 110 into voltages and output the voltages to the wiring board 140. Since the differential signal output from two adjacent PDs in the PD array 110 is voltage-converted by one TIA, there are four TIAs. In addition, since the reception characteristics deteriorate as the distance between the PD and the TIA increases, it is preferable that the PD array 110 and the TIAs 120-1 to 4 are as close as possible. The wiring board 140 and the package 10 are electrically wired by a wire bonding technique or the like, and an electric signal is output outside the package.

According to the present embodiment, in addition to the same effects as those of the first embodiment, it is possible to absorb an error caused by a processing intersection of components by simply selecting any step of the staircase structure 160 of the carrier substrate 40. Alignment in the height direction can be facilitated.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 4 is an enlarged view showing a main part of the configuration of the optical module according to the present embodiment. In the present embodiment, the other configuration of FIG. 4 is the same as the configuration of FIG. 2 in the second embodiment, and thus description thereof is omitted.

  The optical module in this embodiment has a spacer 170 between the subcarrier substrate 140 and the carrier substrate 40 as shown in FIG. Here, the spacer 170 is a substrate obtained by processing a material such as metal or ceramic, and corresponds to the position selection unit 6 in FIG.

When the subcarrier 140 is mounted on the carrier substrate 40, the spacer 170 is selected to have such a height that the optical axis 200 of the light output from the collimating lens arrays 90-1 and 90-2 matches the input portion of the prism 100. .

  According to this embodiment, in addition to the same effects as those of the first and second embodiments, the carrier substrate 40 does not need to be processed in advance and can be realized with a simple component configuration. Is possible.

A plurality of types of spacers 170 having a slight height difference of an error caused by the processing tolerance described above may be prepared in advance. Further, only one spacer 170 may be used, or a plurality of different types or the same type may be used in combination.

  Instead of the spacer 170 in the present embodiment, a resin such as a thermosetting resin may be inserted between the subcarrier substrate 140 and the carrier substrate 40.

  The embodiments described above are examples of the present invention, and various configurations other than those shown in the embodiments can be taken in the present invention.

(Other expressions of the embodiment)
Some or all of the embodiments described above can be described as in the following supplementary notes, but are not limited thereto.

(Appendix)
(Appendix 1)
A carrier substrate;
An optical waveguide substrate mounted on the carrier substrate;
A subcarrier mounted on the carrier substrate,
The subcarrier is:
A direction changer that converts the direction of light emitted from the optical waveguide substrate into a direction perpendicular to the upper surface of the carrier substrate;
A light receiving element for receiving the light whose direction has been converted,
The carrier substrate is
A light receiving module, comprising: a position selection unit formed so that a mounting position of the subcarrier in a direction perpendicular to the upper surface of the carrier substrate can be selected.
(Appendix 2)
The position selection part is formed integrally with the carrier substrate,
The light receiving module according to appendix 1.
(Appendix 3)
The position selection unit is provided with a step whose height decreases according to a horizontal distance from the optical waveguide substrate.
The light receiving module according to appendix 1 or 2.
(Appendix 4)
A collimating lens that emits light output from the optical waveguide substrate to the direction changer as collimated light is provided.
The light receiving module according to any one of appendices 1 to 3.
(Appendix 5)
The position selection unit is one or more spacers,
The light receiving module according to appendix 1.
(Appendix 6)
The position adjustment unit is a cured resin,
The light receiving module according to appendix 1.

DESCRIPTION OF SYMBOLS 1 Carrier board | substrate 2 Optical waveguide board | substrate 3 Subcarrier 4 Direction change device 5 Light receiving element 6 Position selection part 10 Package 20-1, 2 Optical fiber 30-1, 2 Collimating lens 40 Carrier board 50 Tap prism 60 PD
70-1, 2 condenser lens 80 PLC
90-1, Collimating lens array 100 Prism 110 PD array 120-1-4 TIA
130 Wiring board 140 Subcarrier board 150 Pedestal 160 Staircase structure 170 Spacer 200 Optical axis 1000 Carrier board 2000 Optical waveguide board 3000 Collimator lens 4000 Prism 5000 Pedestal 6000 PD
7000 Subcarrier substrate

Claims (5)

A carrier substrate;
An optical waveguide substrate mounted on the carrier substrate;
A subcarrier mounted on the carrier substrate,
The subcarrier is:
A direction changer that converts the direction of light emitted from the optical waveguide substrate into a direction perpendicular to the upper surface of the carrier substrate;
A light receiving element for receiving the light whose direction has been converted,
The carrier substrate is
A light receiving module, comprising: a position selection unit formed so that a mounting position of the subcarrier in a direction perpendicular to the upper surface of the carrier substrate can be selected. The position selection part is formed integrally with the carrier substrate,
The light receiving module according to claim 1. The position selection unit is provided with a step whose height decreases according to a horizontal distance from the optical waveguide substrate.
The light receiving module according to claim 1 or 2. A collimating lens that emits light output from the optical waveguide substrate to the direction changer as collimated light is provided.
The light receiving module according to claim 1. The position selection unit is one or more spacers,
The light receiving module according to claim 1.

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