JPH1154788A - Two-way optical communication module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-way optical communication module which is easily assembled, manufactured at a low cost, and kept stable in characteristics, by a method wherein receiving signal light is detected after it is reflected from a light emitting part so as to improve coupling efficiency between the light emitting part, a photodetcting part and a light transmission path, and the light emitting part and the photodetecting part are so structured as to be easily die-bonded or wire-bonded. SOLUTION: This module is composed of a light emitting part 1 which emits transmission signal light, a condensing lens 4 which couples the transmission signal light emitted from the light emitting part 1 to a transmission path, a photodetecting part 2 which receives receiving signal light R1 transmitted through the light transmission path, and leads 8 electrically connected to the light emitting part 1 and photodetecting part 2 by wire bonding respectively. In this case, the photodetecting part 2 is so located as to receive reflected light R2 which is the receiving signal light R1 transmitted through the light transmission path and then reflected from the light emitting part 1, and to detect the reflected light R2 through its side opposite to its other side where wires are bonded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-division bidirectional optical communication module used for optical communication using an optical fiber. More specifically, the present invention relates to a bidirectional optical communication module having a structure in which a received signal light is reflected by a light emitting element and received by a light receiving element, and can be easily assembled.

[0002]

2. Description of the Related Art A conventional bidirectional optical communication module receives a light-emitting element 21 such as a semiconductor laser for generating a transmission signal light and a reception signal light via a half mirror 23 as shown in FIG. A light receiving element 22 composed of a photodiode, a phototransistor, etc., a condensing lens 24 for coupling transmission signal light to an optical transmission path 25 such as an optical fiber, an optical transmission path 25 for transmitting condensed light, A light condensing lens 26 condenses the received signal light emitted from the path 25 and reflected by the half mirror 23 to the light receiving element 22. With this configuration, the transmission signal light from the light emitting element 21 enters the optical transmission path 25 via the half mirror 23 and is sent to the other party. When a signal sent from the other party is received, the received signal light from the optical transmission line 25 can be received by being reflected by the half mirror 23 and converted into an electric signal by the light receiving element 22. Is performed. In this case, transmission and reception are alternately switched by time division, and no mutual interference occurs.

In this configuration, the light emitting element 21 and the light receiving element 22 must be independently assembled via the half mirror so as to be aligned with the optical axis of the condenser lens, and it is very difficult to assemble with high accuracy. Therefore, as shown in FIG. 5, the light receiving surface of the light receiving element 22 is received as a reflection surface by about half without using a half mirror, and the light emitting element 2
1 is coupled to the condenser lens 24 or an optical transmission line (not shown) by reflecting light from
No. 14,726, and the like.

In the optical communication module having these configurations,
Attenuation by the reflection surface of the half mirror or light receiving element, attenuation by tilting the light emitting surface or light receiving surface of the light emitting element or light receiving element with respect to the axis of the light beam so that the return light does not enter the optical transmission path. For this reason, the coupling efficiency between the light emitting element or the light receiving element and the optical transmission line is reduced, and a light emitting element having a large output or a light receiving element having high sensitivity must be used, which causes an increase in cost.

[0005]

To improve the coupling efficiency between the light emitting element or the light receiving element and the optical transmission line, the present inventors have disclosed a light emitting element in Japanese Patent Application No. 9-92006. Discloses a structure in which light from a light source is coupled directly to an optical transmission path via a condenser lens, and a light receiving element is provided at a position where the light reflected by the light emitting element of the signal light received from the optical transmission path can be received. . That is, as shown in FIG. 3, the light emitting element 1 is mounted on the header 6 in which the inclined surface on which the light emitting element 1 is mounted and the inclined surface on which the light receiving element 2 is mounted so as to face the light emitting surface A of the light emitting element are integrally formed. By mounting the light receiving element 2, an optical module that is accurately positioned is obtained. The light emitting element 1 is formed by die bonding a laser diode chip 1a to a submount 1b made of silicon.
Is formed integrally with the stem 7 to which the lead 8 is fixed. The periphery thereof is sealed with a cap (not shown) or the like, so that the condenser lens 4 and the optical transmission path 5 are attached so that their optical axes coincide with each other.

However, in this structure, since the mounting surface of the light receiving element is downward, the shape is complicated, and the surface on which the light receiving element is mounted has a reverse taper. Can not. Furthermore, after the light emitting element and the light receiving element are die-bonded to the header, the header must be fixed to the stem, and then each electrode of the light emitting element and the light receiving element must be wire-bonded to the lead of the stem, but the light receiving element faces downward. Therefore, the work of die bonding and wire bonding of the light receiving element is very difficult. For this reason, a bonding failure is likely to occur, and a long working time is required.
There is a problem that it becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and the receiving efficiency is obtained by reflecting a received signal light on a light emitting unit and receiving the reflected signal light, thereby coupling efficiency between the light emitting unit or the light receiving unit and the optical transmission line. It is an object of the present invention to provide an inexpensive and stable characteristic bidirectional optical communication module which has a structure in which die bonding and wire bonding of a light emitting unit and a light receiving unit can be easily performed while improving the characteristics.

[0008]

According to the present invention, there is provided a bidirectional optical communication module comprising: a light emitting unit for generating a transmission signal light;
A condenser lens for coupling the transmission signal light from the light emitting section to the optical transmission path; a light receiving section for receiving the reception signal light from the optical transmission path; The light receiving unit is located at a position capable of receiving reflected light of the signal light received from the optical transmission line by the light emitting unit, and a surface of the light receiving unit on which the wire bonding is performed. It is provided so as to be able to receive the reflected light from the opposite side.

With this configuration, the received signal light reflected by the light emitting unit can be received without the wire bonding surface of the light receiving unit facing the light emitting unit, so that the light receiving element can be improved while improving the optical coupling efficiency. Die bonding and wire bonding operations can be easily performed.

[0010] More specifically, a light receiving section is provided by bonding both ends of the light receiving section to the upper surface of two protruding sections having a gap, so that this type of optical communication module is used. InP of light receiving element chip substrate
Is the 1.3 μm band or 1.55 band used for the optical communication.
Since light in the μm band is transmitted, reflected light from the light emitting unit passing through the gap can be received from the back surface (the surface opposite to the surface to be wire-bonded) of the light receiving unit.

More specifically, the light receiving portion is formed of a light receiving element chip, and both ends of the light receiving element chip are bonded to the two projecting portions, respectively, or the light receiving portion transmits the received signal light. And a light receiving element chip die-bonded on the submount, and both ends of the submount are bonded to the two protrusions, respectively. In addition, it is possible to receive the received signal light reflected by the light emitting unit from the back surface side of the light receiving unit.

When the light receiving element chip is bonded on the submount, if the light receiving element chip is die-bonded to the submount with bumps facing down, it is not necessary to perform direct wire bonding to the light receiving element chip, which is fragile. There is no risk of damaging the light receiving element chip. Further, since the receiving amplifier is formed on the submount, the length of the lead from the light receiving element chip to the amplifier and the stray capacitance, which are likely to cause noise, can be extremely reduced, and a high-performance optical communication module can be obtained. Becomes

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a bidirectional optical communication module according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of one embodiment of the optical communication module according to the present invention. As shown in FIG. 1, a light emitting section 1 for generating a transmission signal, and a transmission signal light from the light emitting section 1 are optically transmitted. A condensing lens (rod lens 4) coupled to a light path (not shown), a light receiving section 2 for receiving a signal light received from the optical transmission path, a light emitting section 1 and a light receiving section 2, and a gold wire 3 and the like. And a lead 8 electrically connected by wire bonding. The light receiving section 2 is located at a position where it can receive the reflected light R2 of the received signal light R1 from the light transmission path by the light emitting section 1, and Surface opposite to the surface of the light receiving section 2 on which wire bonding is performed (hereinafter referred to as the back surface)
It is provided so as to be able to receive the reflected light R2 reflected by the light emitting unit 1 from. In the example shown in FIG. 1, the light receiving unit 2 is bonded to the upper surfaces of the protrusions 6 a and 6 b of the header 6 in which the protrusions 6 a and 6 b are formed so that the gap G is formed, at both end surfaces thereof. I have. The light emitting section 1 is mounted on the inclined surface 6c of the side wall of the header 6 inclined with respect to the vertical plane so that the emitted light travels upward, and the received signal light transmitted from the optical transmission path via the rod lens 4 is received. The light-emitting unit 1 and the light-receiving unit 2 are provided so that R1 reflects on the light-emitting surface A of the light-emitting unit 1 and receives the reflected reception signal light R2 traveling to the gap G from the back side of the light-receiving unit 2.

The light emitting section 1 is, for example, a semiconductor laser chip 1 for emitting a laser beam from a light emitting surface A which is an end face thereof.
a is fixed to a submount 1b made of a silicon substrate or the like. Reference numeral 1c denotes a drive circuit portion for driving the laser chip 1a formed on the submount 1b. A semiconductor laser has an end face, which is a light emitting surface, made a mirror surface by cleavage or the like, and an amorphous S
By forming a multilayer film made of an inorganic substance such as i or Al ₂ O ₃ , the reflectance with respect to the oscillation wavelength is appropriately set, and a resonator is formed by the light emitting layer and the multilayer film on the end face. Thus, it is possible to oscillate in the resonator. Accordingly, the reflectance can be adjusted by adjusting the multilayer film, the oscillation intensity in the resonator can be adjusted, and the reflectance of the received signal light can also be adjusted by the multilayer film. In a laser chip used as a normal optical communication module, the multilayer film is adjusted so that the reflectance at this end face is about 30%. Although the ratio of the light emitted from the light source becomes small, it oscillates sufficiently and its intensity increases, so that the total light intensity does not decrease.
The amount of light received by the light receiving element can be increased. This reflectance is adjusted to preferably about 50 to 90%, more preferably about 60 to 90%.

By fixing the submount 1b of the light emitting portion 1 to the header 6 with a low melting point metal such as In or the like, the light emitting surface A is inclined at a predetermined angle with respect to the optical axis of the rod lens 4 and positioned on the optical axis. It is attached to be. The reason that the light emitting surface A is inclined with respect to the optical axis is that the received signal light from the optical transmission line is reflected by the light emitting surface A so as not to return to the optical transmission line again, and the reflected light is received. This is because the light can be received by the unit 2. Therefore, it is sufficient if the reflected light is tilted so as not to enter the condenser lens.

In the example shown in FIG. 1, the light receiving section 2 is formed by bonding a light receiving element chip 2a composed of a photodiode or the like to the center of a submount 2b made of a material such as silicon which transmits a received signal light. ing. The central portion is positioned on the gap G and bonded at both ends so that the back surface of the central portion can receive the reflected reception signal light R2 reflected by the light emitting surface A of the light emitting portion 1. As described above, the protrusion 6a of the header 6
6b. Light receiving element chip 2a
Since the wavelength of light used for optical communication is in a 1.3 μm band or a 1.55 μm band, a semiconductor material that absorbs light in the above-mentioned wavelength band is usually pn on a semiconductor substrate made of InP.
They are stacked to form a bond. However, not limited to the photodiode, a phototransistor, a photocell, or the like can be used. Since this InP does not absorb the reception signal light in the above-mentioned wavelength band, even if it is received from the back side of the substrate, it can be received without attenuation.

On the other hand, as the submount 2b, a substrate such as a glass plate or a silicon substrate that transmits the received signal light is used, but the silicon substrate is easy and convenient to handle. By using the silicon substrate, as shown in FIG. 1, the light receiving element chip 2a is turned upside down and directly connected to a wiring (not shown) formed on the submount 2b by a bump (not shown) or the like. can do. as a result,
Wire bonding of the gold wire 3 or the like can be performed on the silicon substrate of the submount 2b. Further, by using the silicon substrate as the submount 2b,
The amplifier circuit 2c can be formed on the submount 2b, and can amplify a signal received near the light receiving element chip.

If the back surface of the light receiving section 2 is provided in a direction perpendicular to the reception signal light R2 reflected from the light emitting surface,
The received signal light reflected by the light receiving unit 2 is further reflected by the light emitting surface, enters the optical transmission path, interferes, and becomes noise. Therefore, it is necessary to tilt the light receiving unit 2 so as not to be perpendicular to the reflected signal light. However, according to the present invention, the tilted light emitting unit 1 receives the reflected received signal light R2 traveling obliquely upward. As shown in (2), the light receiving section 2 is provided in the horizontal direction, so that the reflected reception signal light R2 and the back surface of the light reception section 2 are in an oblique direction, and the reception signal light reflected by the light reception section 2 emits more light. It proceeds in a direction different from that of the unit 1. Therefore,
The light receiving unit 2 can be horizontally bonded to the upper surfaces of the protrusions 6a and 6b formed so as to have the gap G.

The header 6 is made of, for example, iron or copper alloy, and is formed with protrusions 6a and 6b so as to have gaps G at intervals such that the light receiving portion at the center of the light receiving portion 2 is exposed. At the same time, the heights of the protrusions 6a and 6b are set such that the reflected reception signal light R2 reflected on the light emitting surface A of the light emitting unit 1 is directed to the back surface of the light receiving unit 2 mounted on the protrusions 6a and 6b. You. Also, an inclined surface 6 on which the light emitting unit 1 is mounted.
c is formed so that the received signal light R1 from the optical transmission line is reflected and does not return directly to the optical transmission line, for example, at an angle of about 15 ° with the vertical direction. The header 6 has, for example, heights of the protruding portions 6a and 6b of about 1.5 mm, an area of about 1 mm × 0.5 mm, and a width of the gap G of 0.5 mm.
Degree, the height of the inclined surface 6c is as small as about 1 mm,
It is easily manufactured by preparing a mold of this shape and press-forming an iron plate or the like. Therefore, only by mounting the light emitting unit 1 on the inclined surface 6c and mounting the light receiving unit 2 on the protruding portions 6a and 6b, the received signal light R1 from the optical transmission line is not returned to the optical transmission line, and A module that satisfies the positional relationship between the light emitting unit 1 and the light receiving unit 2 so as to receive the reflected reception signal light R2 from the light emitting surface can be easily assembled.

The stem 7 is formed, for example, by press molding integrally with the header 6 described above, and a lead 8 is fixed to a through hole of the stem 7 by a glass material 9 or the like, and then the lead 8 is plated with Au. The electrodes of the light emitting unit 1 and the light receiving unit 2 mounted on the header 6 are wire-bonded to the leads 8 with the gold wires 3 and further covered with a cap (not shown), thereby obtaining the optical communication module of the present invention.

In the example shown in FIG. 1, the light receiving section 2 has a structure in which the light receiving element chip 2a is die-bonded on a submount 2b made of silicon. It is sufficient that the light receiving portion 2 has a structure for receiving light from the opposite side), and the structure of the light receiving portion 2 is not limited to this example. FIG. 2 shows a modification of the light receiving section 2.

In the example shown in FIG. 2A, the light receiving element chip 2a is directly connected to the projections 6a, 6a without providing a submount.
This is an example in which the end portion is mounted on the b. so that its end is fixed to the protruding portions 6a and 6b. Also in this case, the center of the light receiving element chip 2a is exposed above the gap G, and the reflected reception signal light R2 passing through the gap G is received from the back surface of the light receiving element chip 2a. In this case, each electrode pad 2d of the light receiving element chip 2a is directly wire-bonded to the lead 8 by the gold wire 3.

In the example shown in FIG. 2B, the light receiving element 2 is formed by die-bonding the light receiving element chip 2a on the submount 2b, and the light receiving element chip 2a has the electrode pads 2d facing up. The electrode pad 2d and the lead 8 are directly wire-bonded as in FIG. 2A. With this structure, an expensive light-receiving element chip can be reduced in size.

In the example shown in FIG. 2C, the light receiving element chip 2a is facing down (the surface on which the electrode pads are provided is facing down).
This is an example of bonding on the submount 2b so that With this structure, the submount 2
b, each electrode pad of the light receiving element chip 2a is electrically connected to a wiring 2e provided beforehand via a bump (not shown), and a gold wire 3 is provided between the electrode pad 2f provided on the submount 2b and the lead 8. Performs wire bonding. This structure eliminates the need for wire bonding to a brittle light-receiving element chip made of InP or the like and allows wire bonding to a silicon substrate, thereby improving the reliability of wire bonding and improving the wire bonding work. It will be easier.

The example shown in FIG. 2D is an example in which an amplifier circuit 2c is formed on the submount 2b in the example of FIG. 2C, and has the structure shown in FIG. When the submount 2b is made of silicon, such an amplifier circuit and wiring can be easily formed. On the other hand, if the amplifier circuit 2c is formed on the submount 2b,
The signal a can be immediately amplified by the signal a, so that a structure in which external noise is hardly picked up is obtained. As a result, S
The N ratio is improved, and the optical communication module has excellent characteristics.

According to the optical communication module of the present invention, the received signal light reflected by the light emitting surface of the light emitting unit is not received with the wire bonding surface of the light receiving unit facing the light emitting unit, but is received by the light receiving unit. Since light is received from the back surface, the wire bonding surface of the light receiving unit can be set to the upper surface. As a result, the shape of the header for mounting the light emitting unit and the light receiving unit does not need to form a downward inclined surface, so that the shape is simplified, and the header can be easily formed by press molding. Furthermore, since the light-emitting portion and the light-receiving portion need only be mounted on the inclined surface and the upper surface of the projecting portion of the header formed by press molding, there is no work such as mounting on the back side of the concave portion, so that assembly is very easy. it can. Therefore, it can be assembled by a general automatic machine. Further, since the light emitting unit and the light receiving unit are not mounted downward and the surface to be wire-bonded is on the upper surface side, the wire bonding can be performed very easily.

On the other hand, the reflected reception signal light reflected on the light emitting surface hardly passes through the light receiving element chip and the submount and is not absorbed. Therefore, the receiving sensitivity does not decrease. Further, when bonding a light receiving element chip to a submount made of silicon, an expensive light receiving element chip can be reduced in size, an amplifier circuit can be easily formed on the submount, and leads (gold wires) from the light receiving element can be formed. , Etc.), the signal can be increased before noise enters, and a received signal with a high SN ratio can be obtained.

Since the transmission and the reception are performed in a time-division manner, the transmission and the reception are performed in a time-division manner, the reception signal light from the optical transmission line is incident on the light emitting unit and causes the light emitting unit to oscillate. It has no effect.

[0030]

According to the present invention, while the coupling efficiency between the light emitting unit and the light receiving unit and the optical transmission line is greatly improved,
Assembling of the light emitting section and the light receiving section becomes very easy. Furthermore, the shape of the header for mounting the light emitting unit and the light receiving unit is simplified, and the header can be easily formed by press molding. In addition, by using a submount for the light receiving section, the light receiving element chip can be reduced in size, the material of expensive components can be reduced, and it is not necessary to use wire bonding for the light receiving element chip, and the chip is chipped. Therefore, the yield and the reliability are not reduced. As a result, a highly reliable bidirectional optical communication module with high characteristics can be obtained at very low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of a module for bidirectional optical communication of the present invention.

FIG. 2 is a diagram showing a modification of the light receiving unit of FIG.

FIG. 3 is an explanatory diagram of a structure example in which a received signal light is reflected by a light emitting unit and received by a light receiving unit.

FIG. 4 is an explanatory diagram of an example of a conventional bidirectional optical communication module.

FIG. 5 is an explanatory diagram of another example of a conventional bidirectional optical communication module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-emitting part 2 Light-receiving part 2a Light-receiving element chip 2b Submount 4 Rod lens 6a Projection 6b Projection 8 Lead

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/02

Claims (6)

[Claims] A light-emitting unit for generating a transmission signal light; a condenser lens for coupling the transmission signal light from the light-emitting unit to an optical transmission line; and a light-receiving unit for receiving a reception signal light from the optical transmission line. , The light emitting unit and the light receiving unit and a lead that is respectively wire-bonded and electrically connected,
The light receiving unit is configured to receive the reflected light from the light transmission unit at a position capable of receiving the reflected light from the light emitting unit and receive the reflected light from the surface of the light receiving unit opposite to the surface on which the wire bonding is performed. A bidirectional optical communication module provided so as to be capable of being used. 2. The light receiving section, wherein both ends of the light receiving section are respectively bonded to upper surfaces of two projecting portions having a gap, and receive light reflected by the light emitting section via the gap. Item 2. An optical communication module according to Item 1. 3. The light receiving section comprises a light receiving element chip,
3. The optical communication module according to claim 2, wherein both ends of the light receiving element chip are bonded to the two protruding portions, respectively, and the wire bonding is performed between a surface side of the light receiving element chip and the lead. 4. The light-receiving section includes a submount made of a material that transmits the received signal light, and a light-receiving element chip die-bonded on the submount. 3. The optical communication module according to claim 2, wherein the optical communication module is bonded to the projecting portions. 5. The optical communication module according to claim 4, wherein said light receiving element chip is die-bonded to said submount with bumps facing down. 6. The optical communication module according to claim 4, wherein a receiving amplifier is formed on the submount.