JPH05341143A - Surface mounting type two-way transmitting module - Google Patents

Abstract

PURPOSE:To make a device compact, and reduce cost, and enable a high speed modulation by housing a light emitting element chip for sending and a light receiving element chip for receiving in a grove provided in a silicon substrate so as to be optically coupled with an optical waveguide. CONSTITUTION:In a waveguide element 1, a quarts glass is laminated on a silicon substrate 12 to form an optical waveguide 62, which consists of a core and a clad. The silicon substrate 12 is formed with a mounting groove 21 at a predetermined depth, and a stem 2 with a lens.LD (laser diode) and a stem 3 with monitor PD (photo-diode) and a stem 4 with signal detecting PD are arranged on the mounting groove 21. The stem 2 is formed with a rectangular base made of silicon, and an LD chip 34 as a light emitting element chip for sending and a spherical lens 31 are placed on this base. The stem 4 is formed with a base, which is provided with a reflecting end surface opposite to the waveguide 62, and a signal detecting PD chip as a light receiving element chip for receiving is placed on this base. These chips are optically coupled with the waveguide 62.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional transmission module capable of bidirectional optical communication, and more particularly to a surface-mounted bidirectional module which is small in size, low in price, capable of high-speed modulation and has little crosstalk. The present invention relates to a transmission module.

[0002]

2. Description of the Related Art In recent years, bidirectional transmission has been performed in which a transmission signal and a reception signal are passed through a single optical fiber for transmission and reception. A bidirectional transmission module capable of bidirectional optical communication is connected to the optical fiber. A bidirectional transmission module capable of bidirectional optical communication has conventionally been configured by accommodating a light emitting element and a light receiving element which are independent of each other in one package. Specifically, as shown in FIG. 5, the box-type package 13
In one, three lenses are combined in a T-shape and arranged so that demultiplexing and multiplexing are possible, and a can-sealed laser diode (hereinafter LD) 135 and a can-sealed photodiode (hereinafter PD) 136 are provided. Are optically coupled to the above lens.

First lens 132 and second lens 133
Are coaxially cemented with each other, and the third lens 134 is arranged at a right angle to the axis at this cemented portion. The cemented surface between the first lens 132 and the second lens 133 is arranged by cutting the respective lenses at an inclination of 45 ° so that the cut surfaces overlap each other, and the optical wavelength filter 137 is interposed between the cemented surfaces. It is set up. And the third lens 13
4 is joined to the side surface of the first lens 132 so as to face this inclined surface.

An optical fiber 117 from the outside of the box-type package 131 is connected to the end surface of the first lens 132, and the LD 1
35 is arranged so as to face the end surface of the second lens 133,
The PD 136 is arranged so as to face the end surface of the third lens 134. Wavelength 1.3 incident from optical fiber 117
The μm light is collimated by the first lens, reflected by the light wavelength filter 137, and received by the PD 136. On the other hand, the wavelength emitted from the LD135 is 1.55 μm
Is collimated by the second lens 133, passes through the optical wavelength filter 137, and enters the optical fiber 117. By optically coupling the LD, PD and optical fiber to the T-shaped lens with the optical wavelength filter sandwiched in this way, bidirectional transmission can be performed with one package.

[0005]

However, the above-mentioned conventional bidirectional transmission module has the following drawbacks.

First, the light emitting element and the light receiving element are of a can-sealing type. LDs and PDs with cans sealed have large cans despite their small chips.
It is not possible to reduce the size of the box package that houses this. Therefore, the bidirectional transmission module cannot be downsized.

High accuracy is required for the axis alignment between the optical fiber and the LD or PD, but the dimensional accuracy of the box-type package determines the axis alignment accuracy. Alignment accuracy affects optical characteristics. However, since the box-type package is machined, the size of the box-type package is greatly varied. Therefore, many of the box-type packages have poor optical characteristics at the time of manufacturing, and the yield is reduced.

Further, the light emitted from the LD is partially reflected by the optical fiber, and the reflected light returns to the LD, which makes the operation of the LD unstable. If the operation of the LD is unstable, high speed modulation becomes impossible. Therefore, the communication speed cannot be increased.

Further, since the stray light derived from the light emitted from the LD is easily received by the PD, the optical crosstalk between the transmission and the reception becomes large. Therefore, it cannot be used in a system that requires highly reliable transmission. That is, the range of application to the system is limited.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above problems and provide a surface-mount type bidirectional transmission module which is small in size, low in price, capable of high-speed modulation, and has less crosstalk.

[0011]

In order to achieve the above object, the present invention provides a silicon-based glass laminated on a silicon substrate to form an optical waveguide consisting of a core and a clad, and to form a groove in the silicon substrate. A light emitting element chip for transmission and a light receiving element chip for reception, which are combined with an optical lens, are housed in the groove by being optically coupled to the optical waveguide.

An airtight lid that covers the groove is placed on the silicon substrate to hermetically seal it.

A prism with an optical wavelength filter for guiding desired receiving light to the light receiving element chip is provided between the light receiving element chip and the optical waveguide.

Further, an electronic circuit chip for a light emitting / receiving element chip is mounted in the groove.

[0015]

With the above structure, since the light emitting element chip and the light receiving element chip are accommodated on one silicon substrate and the optical waveguide is formed on this silicon substrate, bidirectional transmission is possible through the optical waveguide. ..

Since the lid for airtightness is placed in the groove on the silicon substrate and hermetically sealed, the light emitting element chip and the light receiving element chip are shielded from the outside air and can be prevented from deterioration.

The prism with the optical wavelength filter reflects only the receiving light on the light receiving element chip. Therefore, the light for transmission does not enter the light-receiving element chip and crosstalk is reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a surface mount type bidirectional transmission module according to the present invention. In this embodiment, 1.3 μ
m / 1.5 μm bi-directional transmission module application example, 1.3 μm TX / 1.5 μm RX module,
That is, it shows a module that transmits a wavelength signal of 1.3 μm and receives a wavelength signal of 1.5 μm. This module is mainly composed of a waveguide element 1, a stem 2 with a lens / LD, a stem 3 with a monitor PD, a stem 4 with a signal detection PD,
The sealing lid 5 and the optical fiber terminal block 6 are composed of six parts.

The waveguide element 2 has an optical waveguide and serves as a base body of a bidirectional transmission module, and is formed by laminating silica glass on a silicon substrate. In FIG. 1, one waveguide element 2 is shown.

FIG. 2 shows aa-aa of the waveguide device 1 of FIG.
A sectional view is shown. The waveguide element 1 is 8 × 8 μm on the silicon substrate 12 on which the buffer layer 11 having a thickness of about 20 μm is formed.
m of rectangular core 13 is formed, and about 15 μm
A thick clad 14 is formed to form a buried waveguide. The core 13 is made of TiO ₂ —SiO ₂ glass, and the clad 14 is made of P ₂ O ₅ —B ₂ O ₃ —SiO ₂ glass.

A waveguide 62 composed of the core of the waveguide element 1.
Is configured as an optical multiplexer / demultiplexer 61. That is, a-
The core 13 is gradually widened on both sides of the aa cross section, the first port 15 is formed at one end contacting the optical fiber terminal block 6, and the second port is formed at the other end facing the mounting groove 21 described later. Three ports 16 and 17 are formed. In the optical multiplexer / demultiplexer 61, the 1.3 μm light incident from the second port 16 is combined and emitted to the first port 15, and the 1.5 μm light incident from the first port 15 is demultiplexed. And is emitted to the third port 17.

Silicon substrate 12 constituting the waveguide device 1
Has a mounting groove 21 having a predetermined depth, and a cross section of the waveguide 62 appears on the side surface of the mounting groove 21. The waveguide 62 has a cross section of the second and third ports 1.
6 and 17 are formed. Au is metallized on the bottom surface of the mounting groove 21. This mounting groove 2
A lens / LD stem 2, a monitor PD stem 3, and a signal detection PD stem 4 are arranged on the display unit 1. In this arrangement, the lens / LD stem 2 faces the second port 16, the monitor PD stem 3 is linearly aligned with the lens / LD stem 2, and the signal detection PD stem 4 is the third port 1.
It is arranged so as to face 7. These stems 2, 3, 4
Are heated and fixed to their respective positions by Au-Sn solder. A through hole 22 communicating with the opposite surface of the silicon substrate 12 is formed on the bottom surface of the mounting groove 21. An electrode rod 23 is inserted into the through hole 22, and a drive current of the LD is injected through the electrode rod 23,
The lightning current of PD can be taken out.

Next, in order to explain the stem 2 with lens / LD and the stem 3 with monitor PD, FIG.
The sectional view in bb is shown.

The lens / LD stem 2 is a waveguide element 1
A rectangular base is formed of the same silicon as the above, and the LD chip 34 and the spherical lens 31 are mounted on the base. The LD chip 34 is a Fabry-Perot type semiconductor laser that emits a 1.3 μm wavelength signal, and is integrated on the heat sink submount 32 by using Au—Sn solder. Is fixed on the stem with lens and LD 2. Au-Sn solder is also used in this fixing. Au-S
The reason for using n solder is that it has a proven track record in terms of reliability. The ball lens 31 is a YIG ball lens having a diameter of 1 mm, and is arranged so as to face the light emitting surface of the LD chip 34.
It is fixed by u-Sn solder. A non-reflective coating film 33 for preventing light reflection is formed on both side surfaces of the spherical lens 31 for entering and exiting light, so that return light to the LD chip 34 side can be cut. The optical axes of the LD chip 34 and the spherical lens 31 are fixed at a position where they can enter the waveguide 62, that is, at a height facing the cross section of the core 13.

The stem 3 with monitor PD is the LD chip 34.
A monitor P for monitoring backward emission light is provided on a table having a reflection film 36 facing the light emitting surface on the opposite side of the substrate at an angle of about 45 °.
The D chip 37 is mounted. The monitor PD chip 37 is attached to the electrode 38 formed on the upper surface of the stem 3 with monitor PD, and the light receiving surface thereof is projected on the reflection film 36. The electrode 38 is connected to the electrode rod 23 by a bonding wire 39 and is connected to an external circuit of the bidirectional module.

The stem with signal detection PD 4 is shown in detail in FIG. FIG. 4 is a sectional view taken along line c-cc in FIG. The signal detecting PD-attached stem 4 is formed on a table provided with a reflecting end face facing the waveguide 62 at an angle of about 45 °.
The signal detection PD chip 44 such as a pin photodiode for receiving a 5 μm wavelength signal is mounted. A multi-layer film filter 42 is attached to the reflecting end face to reflect only light of a desired wavelength (here, 1.5 μm) and pass light of other wavelengths. The signal detection PD chip 44 is attached to the electrode 38 formed on the upper surface of the signal detection PD-equipped stem 4, and its light-receiving surface is projected onto the reflection end face to which the multilayer filter 42 is attached. The electrode 38 is connected to the electrode rod 23 by a bonding wire 39 and is connected to an external circuit of the bidirectional module.
Reflection end face with multilayer filter 42 attached and waveguide 62
A pinhole plate 43 having a pinhole on the optical axis and for cutting off stray light incident from outside the optical axis is provided between and.

The LD chip 34 and the PD chip 44 are easily deteriorated by moisture in the air or the like and must be hermetically sealed in order to improve reliability. In the present invention, however, the mounting groove 21 is not formed. A sealing lid 5 is provided so as to cover the opening. As shown in FIG. 4, the sealing lid 5 is formed so as to rise from the periphery of the opening of the mounting groove 21 and to cover the above-described stems 2, 3, and 4 above. The joint between the sealing lid 5 and the waveguide element 1 is hermetically sealed using Sn-Pb solder.
Electrode rod 23 and waveguide element 1 in each through hole 22
The space between and is hermetically sealed by filling the low melting point glass 40. The sealing lid 5 is preferably made of the same silicon as the substrate 12.

Next, in the optical fiber terminal block 6 shown in FIG. 1, two silicon substrates provided with V-shaped grooves face each other, and the optical fiber 45 is sandwiched between the V-shaped grooves.
It is fixed with resin. Optical fiber terminal block 6
Are joined to the first port 15 side of the waveguide element 1. The joint surface between the waveguide element 1 and the optical fiber terminal block 6 is fixed by an optical adhesive.

Next, the operation of the embodiment will be described.

The 1.3 μm light emitted from the LD chip 34 is condensed by the spherical lens 31 and the second port 1 of the waveguide is used.
It is incident on 6. The light is merged by the optical multiplexer / demultiplexer 61, and then output to the first port 15 of the waveguide 62 and incident on the optical fiber 45. The light emitted from the LD chip 34 is condensed by the spherical lens 31 and efficiently enters the core 13 of the waveguide 62. At this time, the antireflection coating films 33 on both side surfaces of the spherical lens 31 cut off the returning light to the LD chip 34 side. Since the LD chip 34 is not affected by the returning light, the operation becomes stable.

The backward output light emitted from the LD chip 34 is reflected by the reflection film 36 formed on the end face of the stem 3 with monitor PD, enters the monitor PD 37, and is converted into an electric signal. The electric signal generated by the rear output light is transmitted to the LD chip 34.
It is used for APC (Automatic Power Control) and so on.

On the other hand, 1.5 μm from the optical fiber 45
Light is incident on the first port 15 of the waveguide 62, demultiplexed by the optical multiplexer / demultiplexer 61, and then emitted from the third port 17. The light emitted from the third port 17 passes through the pinhole of the plate with pinhole 43. At this time, stray light is cut off by the pinhole plate 43. The light passing through the pinhole is reflected by the multilayer filter 42 formed on the end surface of the stem 4 with the signal detection PD. Since the multilayer filter 42 reflects only the light of 1.5 μm, the signal detection P
Only light of 1.5 μm coming from the optical fiber 45 is received by D44. This light is the signal detection PD44
Is converted into an electric signal by. The pinhole-equipped plate 43 and the multilayer filter 42 block 1.3 μm stray light and the like derived from the LD chip 34, so that optical crosstalk is reduced.

As described above, the surface mount type bidirectional transmission module according to the present invention has a size of 1.3 μm / 1.5 μm.
Bidirectional transmission of m is possible. Since this module can mount a chip component of about 1 mm directly on the waveguide element substrate, it can be miniaturized. Furthermore, the main components are the waveguide element 1, lens and L
The number of parts is 6 including the stem 2 with D, the stem 3 with monitor PD, the stem 4 with signal detection PD, the lid 5 for sealing, and the optical fiber terminal block 6, and the assembly man-hours can be significantly shortened and the cost is reduced. .. Further, since the groove for accommodating the light emitting element chip and the light receiving element chip is hermetically sealed by the airtight lid, these light emitting and light receiving element chips are not deteriorated.

In the embodiment of FIG. 1, the electric signals for the LD, PD, and monitor PD are input and output from the outside of the module through the electrode rod 23, but an electronic circuit chip such as a preamplifier is mounted on the mounting groove 21. A surface-mounted bidirectional transmission module including an electronic circuit may be provided inside the module.

As a spherical lens, 1 mmφ YIG
A spherical lens was used, but the lens material is TaF ₃ , TiO 2.
₂ or the like may be used, and the diameter of the spherical lens is 0.5 to 2 mm.
You may use the thing of.

[0037]

The present invention exerts the following excellent effects.

(1) Since the light emitting element chip and the light receiving element chip are housed on one silicon substrate and the optical waveguide is formed on this silicon substrate, the bidirectional transmission module is miniaturized.

(2) Since the light-emitting / light-receiving element chips are mounted in the groove on the silicon substrate, the manufacturing is simple, the yield is improved, and the price can be reduced.

(3) Since the influence of the returning light is eliminated, the operation becomes stable. Therefore, high speed modulation becomes possible.

(4) Since the optical crosstalk can be greatly improved, it can be applied to a system that requires highly reliable transmission.

(5) Since electronic circuits such as a preamplifier can be mounted, new functions can be added. Therefore, hybridization is possible.

(6) Since many bidirectional transmission modules can be formed on one wafer, the price of one module becomes low.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a cross section taken along the line aa of FIG.

FIG. 3 is a partially enlarged cross-sectional view showing a b-bb cross section of FIG. 1.

4 is a partially enlarged cross-sectional view showing a c-cc cross section of FIG. 1. FIG.

FIG. 5 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 12 silicon substrate 13 core 14 clad 21 groove 34 light emitting element chip 44 light receiving element chip for reception 62 optical waveguide

Claims (4)

[Claims] 1. A light emitting element for transmission in which quartz glass is laminated on a silicon substrate to form an optical waveguide consisting of a core and a clad, and a groove is formed in the silicon substrate, and an optical lens is combined in the groove. A surface-mount type bidirectional transmission module, characterized in that a chip and a light-receiving element chip for reception are optically coupled to and housed in the optical waveguide. 2. The surface mounting type bidirectional transmission module according to claim 1, wherein an airtight cover that covers the groove is placed on the silicon substrate and hermetically sealed. 3. The surface mount type according to claim 1, wherein a prism with an optical wavelength filter for guiding desired receiving light to the light receiving element is provided between the light receiving element chip and the optical waveguide. Bidirectional transmission module. 4. The surface-mounted bidirectional transmission module according to claim 1, wherein an electronic circuit chip for a light emitting / receiving element chip is mounted in the groove.