JP2001053223A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module of small size, large capacity, and low skew wherein the limit on the width of the optical module due to the width of an electric circuit is resolved while an inter-channel equidistant wiring zs provided between an optical element array and electric circuit. SOLUTION: An optical element array where optical elements are monolithic- integrated in 1-dimension, and an electric circuit connected to the optical element array are provided. Here, the electric circuit is divided into a plurality of sections which are arranged in orientation different from the optical element array. For example, it is divided into two electric circuits 4a and 4b which face each other with the optical element array 3 in between.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module for connecting an information processing device and a communication device or an electrical signal terminal in the device by an optical signal wiring.

[0002]

2. Description of the Related Art In recent years, in high-speed and large-capacity information processing devices and communication devices, the transmission capacity of electric signal wiring used for signal transmission between devices or within a device has reached a limit.
Parallel optical interconnection technology for replacing these electrical signal wirings with broadband optical signal wirings has been developed. In order to realize this parallel optical interconnection, it is necessary to develop a compact, high-speed and large-capacity optical module.

FIG. 12 shows a basic configuration of a conventional multi-channel optical module for parallel optical interconnection.
In the figure, an optical module 1 has an optical element array 3 disposed on a wiring board 2, an electric circuit 4 for processing (for example, transmitting or receiving) electric signals disposed on one side thereof, and an optical element array 3 on the opposite side. This is a configuration in which an optical coupling system component 5 that connects the optical fiber ribbon 3 and the optical fiber ribbon 7 is arranged. The optical element array 3 and the electric circuit 4 are connected by a signal wiring 6.

The optical element array 3 has a structure in which a plurality of optical elements are monolithically integrated one-dimensionally at the same pitch as the inter-fiber pitch of the optical fiber ribbon 7 of 250 μm. This optical element array 3 usually has a width of about pitch × the number of channels (for example, 12 × 25 in the case of a 12-channel array).
0 μm = 3 mm).

On the other hand, since the electric circuit 4 is usually connected to the coplanar wiring of the differential signal,
The number of bonding pads (ground, normal phase signal, reverse phase signal) is required. The pitch of these bonding pads is narrowed in order to match the pitch between channels of the optical element array 3. However, the trade-off is a trade-off between an increase in crosstalk between channels and a reduction in yield due to a short circuit between bonding wires. So the pitch between pads is
About 150 μm was the limit of narrowing. That is, the pitch between the pads is equivalent to 450 μm between the channels,
The pitch of the optical element array 3 was about twice as large, and the width of the electric circuit 4 was about twice as large as that of the optical element array 3.

[0006]

As described above, the current electric circuit 4 has a width approximately twice as large as the optical fiber ribbon 7 and the optical element array 3, and this determines the width of the optical module itself. Here, even if the optical coupling system and the optical fiber connector were downsized, there was a factor that the downsizing of the optical module did not progress.

On the other hand, if the electric circuit 4 is forcibly reduced in size in accordance with the optical element array 3, an increase in electric crosstalk in the circuit and a thermal runaway due to an increase in heat generation density will cause the performance of the optical module. And reliability may be reduced.

Further, since the channel pitch of the electric circuit 4 corresponding to each channel of the optical element array 3 is different, the signal wiring 6 has to be radial as shown in FIG. For this reason, it is difficult to connect the channels by equidistant wiring, and this has been a factor of increasing the skew between the channels.

The present invention eliminates the limitation of the width of an optical module caused by the width of an electric circuit, realizes equidistant wiring between channels between an optical element array and an electric circuit, and reduces the size and size of the optical module.
An object is to provide a large-capacity and low-skew optical module.

[0010]

FIG. 1 shows a basic structure of an optical module according to the first and second aspects of the present invention. In the figure, an electric circuit having a width about twice as large as the optical element array 3 per channel is divided into two electric circuits 4a and 4b having the same width as the optical element array 3, and opposing each other with the optical element array 3 interposed therebetween. Deploy. Thereby, the limitation of the width of the optical module caused by the width of the electric circuit is eliminated, and the equidistant signal wires 6a, 6
b becomes possible.

The signal wiring 6a for connecting the electric circuit 4a and the optical element array 3 and the electric circuit 4b and the optical element array 3
Are formed so that they are alternately connected, the length of each signal wiring can be made equal and shortest.

In this case, the signal wiring 6a passes under the optical element array 3 so that signal pads (● in the figure) for connection with the optical element array 3 are aligned on one side of the optical element array 3. However, the signal pads of each signal wiring may be arranged on both sides of the optical element array 3 respectively. The signal wires 6a and 6b are formed in parallel with the edge of the wiring board 2 as shown in FIG. 1A, or are formed at a predetermined angle with respect to the edge of the wiring board 2 as shown in FIG. They may be formed in parallel. Further, the optical coupling system component 5 for connecting the optical element array 3 and the optical fiber ribbon 7 is disposed so as to overlap with one of the electric circuits 4a.

FIG. 2 shows the basic structure of the optical module according to the third aspect. In the figure, two optical element arrays 3a, 3b
The electric circuits 4a and 4b to be connected respectively to the optical element arrays 3a and 3b are opposed to each other. Thus, the limitation on the width of the optical module due to the width of the electric circuit can be eliminated.

In FIG. 2, the electric circuits 4a and 4b are arranged obliquely with respect to the optical element arrays 3a and 3b, respectively. , Electric circuit 4b and optical element array 3b
This is to make the signal wirings 6b connecting them as equal in length as possible.

FIG. 3 shows the basic structure of the optical module according to the fourth aspect. In the figure, the electric circuit connected to the optical element array 3a is divided into two electric circuits 4a1, 4a2, and the electric circuit connected to the optical element array 3b is divided into two electric circuits 4b1,
4b2, and each of the divided electric circuits is divided into an optical element array 3
a and 3b are arranged to face each other. Thus, the limitation on the width of the optical module due to the width of the electric circuit can be eliminated.

[0016]

(First Embodiment) FIG. 4 shows a first embodiment of the optical module of the present invention. This embodiment shows a configuration in the case of using the optical transmission module or the optical reception module. 4A is a top view, and FIG. 4B is a side view. Here, the arrangement on the wiring board 2 is shown.

In the figure, one (two in total) electric circuit mounting parts 12a and 12b are formed on the wiring board 2 on both sides of the optical element array mounting part 11, respectively. The electric circuit mounting portions 12a and 12b have a depth called a cavity.
0.5mm concave shape, electric circuit 4
The heights of the upper surfaces of the a and 4b and the surface of the wiring board 2 substantially match.

Each of the electric circuits 4a and 4b to be mounted is 6
It has a channel configuration, and the signal lines 6a and 6b connected to the 12-channel optical element array 3 are alternated. Each of the signal wirings 6a and 6b passes from the surface of the wiring board 2 to the lower part of the optical element array mounting part 11 and
Is drawn out to the upper surface of the electric circuit 4b side to form a signal pad. Here, in order to distinguish the signal pads corresponding to each of the signal wirings 6a and 6b on the optical element array mounting portion 11, ■ and ● are alternately arranged in the top view of FIG.

Further, signal wiring and power supply terminals 13 for connecting the electric circuits 4a and 4b to external circuits are formed around the electric circuit mounting portions 12a and 12b. Although not shown, the ground line of the optical element array 3 is
1 to penetrate from the back surface of the wiring board 2.

The 12-channel optical element array 3 has individual optical elements formed at a pitch of 250 μm, and the size of one chip is 3.2 mm in width, 0.5 mm in length, and 0.3 mm in height.
On the other hand, the size of the electric circuits 4a and 4b of each of the six channels is 4 mm in width, 3 mm in length, and 0.5 mm in height. As described above, the electric circuit for 12 channels is divided into two chips for 6 channels, and the chips are arranged to face each other with the optical element array 3 interposed therebetween.
And the width of the electric circuits 4a and 4b can be made substantially equal, and the width of the wiring board 2, which is a determining factor of the module size, can be reduced to 5.5 mm. Furthermore, since the widths of the optical element array 3 and the electric circuits 4a and 4b are substantially the same, the signal wirings 6a and 6b can be made straight with a short distance and low loss, and the wiring length between channels can be easily made equal. And the skew between channels can be reduced.

When the configuration shown in FIG. 4 is used as an optical transmission module, for example, a surface emitting laser diode array is used as the optical element array 3, and transmission circuits are used as the electric circuits 4a and 4b. In the case of an optical receiving module, for example, a planar pin photodiode array is used as the optical element array 3, and receiving circuits are used as the electric circuits 4a and 4b. However, although the pitch of both optical element arrays and the size of the array chip are almost the same, there is a slight difference in the wiring pattern of both modules.

(Module Assembly) FIGS. 5 to 8 show a module assembly process in the first embodiment. here,
2 are denoted by the same reference numerals, and the optical element array 3
Shall be surface type.

FIG. 5 shows a die bonding process for chip components. Optical element array 3 and electric circuits 4a and 4b
Are fixed by soldering at predetermined positions on the wiring board 2 by die bonding. Further, the optical element array mounting section 11
At the position aligned with the optical element array 3 on the upper surface of the electric circuit 4a side of
The spacer 21 is fixed by soldering. This spacer 21
A silicon plate having a height of 0.32 mm (> 0.3 mm height of the optical element array 3) is a member for supporting the optical coupling system component 5 disposed on the electric circuit 4a.

FIG. 6 shows a wire bonding step.
The signal pads on the optical element array 3 and the signal pads of the signal wirings 6a and 6b (which appear to overlap here) are connected by wire bonding. The signal and power supply pads on the electric circuits 4a and 4b are connected to the signal wirings 6a and 6b and the signal wiring and power supply terminal 13 by wire bonding. Note that, instead of the wire bonding, the connection may be made by using another method such as a solder bump or a through hole.

FIG. 7 shows a module case insertion step. The wiring board 2 is fixed in the module case 22 by soldering. FIG. 8 shows a mounting process of the optical coupling system component and the cover. The optical coupling system component 5 is an MT type optical fiber connector 31.
The organic waveguide film 32 is attached to one end of
This is a configuration in which a 90 ° optical path conversion mirror 33 is arranged at the other end of 2. This optical coupling system component 5 is inserted from above the electric circuit 4a, and is positioned on the spacer 21 so that the optical element array 3 comes under the 90 ° optical path conversion mirror 33.
Fix with UV-curable resin. In this way, by utilizing the empty space above the electric circuit 4a for incorporating the optical coupling system, the space utilization efficiency can be increased and the module can be downsized.

Further, the receptacle of the MT type optical fiber connector 31 is fixed to the module case 22 with an adhesive. After that, the mounted components in the module case 22 are sealed with resin, and the cover 23 is attached to the module case 22 to complete the optical module.

(Module Characteristics) The size (excluding the signal wiring and power supply terminal 13) of the optical module assembled as described above is 7 mm wide, 23 mm long, and 7.5 mm high (volume
1.2 ml). The size of a conventional optical module (with 12-channel electrical circuit) is 11 mm wide, 25 mm long,
Since the height is 7.5 mm (volume 2.1 ml), the size of the optical module can be reduced by 36% and the volume by 43%.

Further, according to the optical module of the present invention, the signal wiring between the optical element array and the electric circuit can be made equal in length, short in distance,
Since loss can be easily reduced, improvement in signal transmission characteristics can be expected. Actually, the optical transmission module and the optical reception module according to the configuration of the present embodiment are opposed to each other, and the signal transmission (1.25G
bit / s, NRZ-PRBS 2 ²³ -1) When comparing the bit error rate characteristics measured by using the conventional optical module and the result of performing similar measurements, the minimum receiving sensitivity was improved by about 3 dB. It was confirmed. Also, the skew between channels was reduced from about 120 ps in the past to 10 ps or less (below the measurement limit).

(Second Embodiment) FIG. 9 shows a second embodiment of the optical module of the present invention. This embodiment shows a configuration (transceiver configuration) when used as an optical transceiver module. That is, the optical element array includes both a six-channel Fabry-Perot type laser diode (FP-LD) array for transmission and a six-channel waveguide photodiode (WG-PD) array for reception, for example. 9A is a top view, and FIG. 9B is a side view. Here, the arrangement on the wiring board 2 is shown.

In the drawing, a transmitting circuit mounting pad 42 and a receiving circuit mounting pad 43 are formed on both sides of an optical sub-module mounting portion 41 on the wiring board 2. No cavity is formed in this transmitting / receiving circuit mounting portion. A six-channel transmitting circuit 44 is fixed to the transmitting circuit mounting pad 42 by soldering, and a six-channel receiving circuit 45 is fixed to the receiving circuit mounting pad 43 by soldering.

An optical submount 51 is mounted on the optical sub-module mounting section 41, and an FP-LD
The array 46 and the WG-PD array 47 are mounted in a line. Therefore, the FP-LD array 46 and the transmission circuit 4
4 and a signal wiring 6b connecting the WG-PD array 47 and the receiving circuit 45, each of which becomes radial due to a difference in width between the optical element array and the electric circuit. To make them approximately equal in length,
The transmission circuit 44 and the reception circuit 45 are arranged diagonally.

Further, around the transmission circuit mounting pad 42 and the receiving circuit mounting pad 43, a signal wiring / power supply terminal 13 for connecting the transmission circuit 44 and the receiving circuit 45 to an external circuit is formed. Although not shown, FP-LD
The ground lines of the array 46 and the WG-PD array 47 are formed to penetrate from the optical submount 51 to the back surface of the wiring board 2.

Each of the six-channel FP-LD array 46 and WG-PD array 47 incorporates individual optical elements at a pitch of 250 μm.
It is 3.2mm, 0.5mm long and 0.3mm high. On the other hand, the transmission circuit 44 and the reception circuit 45 of each of the six channels are used.
The size of each is 4mm wide, 3mm long, 0.5m high
m. By arranging the transmitting circuit 44 and the receiving circuit 45 to face each other, the width of the wiring board 2 can be reduced to 5.5 mm.

(Assembly of Optical Sub-Module) FIG. 10 shows an assembly process of the optical sub-module. Here, parts corresponding to those in FIG. 9 are denoted by the same reference numerals.

In the figure, an optical submount 51 has V groove portions 52a and 52b in which two sets of six V grooves for aligning six optical fibers on a silicon substrate at a pitch of 250 μm are arranged.
And a terrace portion 53 for mounting the FP-LD array 46 and the WG-PD array 47. The distance between the V-shaped grooves 52a and 52b is 0.5 mm. Terrace 5
3, signal wirings 6a, 6b formed on the wiring board 2;
And an FP-LD array 46 and a WG-PD array 47
Are formed, and signal wirings 54a and 54b for connecting are formed. Here, the FP-LD array 46 and the WG-PD array 47 are connected to the signal wiring 54 of the terrace 53 by a predetermined positioning mechanism using, for example, an alignment marker.
a, 54b.

Next, the length 15 m exposed from the MT connector
The coating of the 5 mm distal end of the 12-fiber optical fiber ribbon 7 is removed, and the optical fiber ribbon 7 is arranged in the V-grooves 52a and 52b and inserted to a predetermined position specified by a marker line, for example.
The optical fiber holder 55 is placed and fixed with an ultraviolet curing resin. Further, the tip of the optical fiber ribbon 7 and the FP-L
In the gap between the D array 46 and the WG-PD array 47,
A transparent ultraviolet curable resin having a refractive index substantially equal to the refractive index of the core of the optical fiber is filled and cured. At this time, F
If the P-LD array 46 and the WG-PD array 47 are mounted at predetermined positions, the V-groove 52 is formed so that the alignment with the optical fiber ribbon 7 is automatically completed.
a, 52b and the terrace 53 are processed.

(Assembly of Optical Module) FIG. 11 shows an assembly process of an optical module according to the second embodiment. Here, components corresponding to those in FIGS. 9 and 10 are denoted by the same reference numerals.

In the figure, a transmitting circuit 44 is provided on a wiring board 2.
When the receiving circuit 45 is mounted, the signal and power supply pads on each circuit chip are connected to the signal wirings 6a and 6b and the signal wiring and power supply terminal 13 by wire bonding. Next, the wiring board 2 is fixed in a module case 60 with electric input / output terminals (PGA),
The terminal pad 62 connected to the PGA connection terminal 61 of 0 and the signal wiring / power supply terminal 13 are connected by wire bonding.

Subsequently, the assembled optical sub-module is mounted on the module case 60. At this time, the stat pins 64 provided on the MT connector section 63 of the optical sub-module are set in the pin receiving holes 65 of the module case 60, and the stat pins 64 are fixed to the module case 60 by soldering. Each component of the optical submount 51 is designed to be mounted on the optical submodule mounting portion 41 on the wiring board 2. Further, the signal wires 54a and 54b on the terrace 53 of the optical submount 51 are connected to the signal wires 6a and 6b on the wiring board 2 by wire bonding. Finally, the mounted components in the module case 60 are sealed with a resin, and a cover is attached to the module case 60 to complete the optical module.

(Module Characteristics) The size of the optical module assembled as described above (excluding the PGA connection terminal 61) is 7 mm wide, 25 mm long and 8 mm high (volume 1.4 m).
l). The size of the conventional optical module (with a 6-channel transmitting circuit and a 6-channel receiving circuit mounted in parallel) is 11 mm in width, 24 mm in height, and 8 mm in height (2.1 ml in volume). 33% reduction in volume is achieved.

Further, in the optical module of the present invention, compared with the case where the 6-channel transmitting circuit and the 6-channel receiving circuit are arranged in parallel, the signal wiring between the transmitting / receiving circuit and the optical element array can be made equal in length, shorter, and shorter. Since loss can be easily reduced, improvement in signal transmission characteristics can be expected. Actually, the optical transmission and reception module according to the configuration of the present embodiment is opposed to each other, and the signal transmission (1.
Comparing the bit error rate characteristic measured by performing 25 Gbit / s, NRZ-PRBS 2 ²³ -1) with the result of performing the same measurement using the conventional optical module, the minimum receiving sensitivity is 2.5
It was confirmed that it was improved by about dB. Further, the improvement of the skew between channels was the same as in the first embodiment.

[0042]

As described above, in the optical module of the present invention, the electric circuit connected to the optical element array is divided and arranged in a different direction (for example, opposed to the optical element array). In addition, the limitation of the width of the optical module due to the width of the electric circuit can be eliminated, and the size can be reduced to 30 to 40% of the conventional size.

Further, the electric circuit and the optical element array can be easily wired at the same distance, the skew between channels can be reduced, and the transmission characteristics can be improved. As a result, the intended use can be expanded, and the restrictions on the use environment conditions can be relaxed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an optical module according to claims 1 and 2;

FIG. 2 is a diagram showing a basic configuration of an optical module according to claim 3;

FIG. 3 is a diagram showing a basic configuration of an optical module according to claim 4;

FIG. 4 is a diagram showing a first embodiment of the optical module of the present invention.

FIG. 5 is a view showing a die bonding step of a chip component.

FIG. 6 is a view showing a wire bonding step.

FIG. 7 is a view showing a module case insertion step.

FIG. 8 is a view showing a mounting process of an optical coupling system component and a cover.

FIG. 9 is a diagram showing an optical module according to a second embodiment of the present invention.

FIG. 10 is a diagram showing an assembly process of the optical sub-module.

FIG. 11 is a diagram showing an assembling process of the optical module according to the second embodiment.

FIG. 12 is a diagram showing a basic configuration of a conventional multi-channel optical module.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical module 2 Wiring board 3 Optical element array 4 Electric circuit 5 Optical coupling system component 6 Signal wiring 7 Optical fiber ribbon 11 Optical element array mounting part 12 Electric circuit mounting part 13 Signal wiring and power supply terminal 21 Spacer 22 Module case 23 Cover 31 MT type optical fiber connector 32 Organic waveguide film 33 90 ° optical path conversion mirror 41 Optical submodule mounting part 42 Transmitting circuit mounting pad 43 Receiving circuit mounting pad 44 Transmitting circuit 45 Receiving circuit 46 Fabry-Perot type laser diode (FP-LD)
Array 47 Waveguide photodiode (WG-PD) array 51 Optical submount 52 V-groove 53 Terrace 54 Signal wiring 60 Module case 61 PGA connection terminal 62 Terminal pad 63 MT connector 64 Stat pin 65 Pin receiving hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01L 27/14 J (72) Inventor Mitsuo Usui 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Within Telephone Co., Ltd. (72) Inventor Kosuke Katsura 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yasuhiro Ando 2-3-1 Otemachi, Chiyoda-ku, Tokyo Sun F-term (Reference) in the Telegraph and Telephone Corporation 4M118 AA10 AB05 CA05 GA09 HA20 HA23 HA24 HA25 HA30 5F073 AB02 AB16 EA29 FA23 5F089 AA01 AC07 AC10 CA20 FA10

Claims (4)

[Claims] An optical module including an optical element array in which optical elements are monolithically integrated in one dimension and an electric circuit connected to the optical element array, wherein the electric circuit is divided into a plurality, and each of the divided electric circuits is An optical module having a configuration arranged in different directions with respect to the optical element array. 2. An optical module comprising: an optical element array in which optical elements are monolithically integrated in one dimension; and an optical module including an electric circuit connected to the optical element array, wherein the electric circuit is divided into a plurality of electric circuits. An optical module having a configuration in which the optical elements are opposed to each other with the optical element array interposed therebetween, and the electric circuits connected to the optical elements and the signal wiring connecting the optical element array are formed alternately. 3. An optical module comprising a plurality of optical element arrays in which optical elements are monolithically integrated one-dimensionally and a plurality of electric circuits respectively connected to the respective optical element arrays, wherein an electric circuit connected to an adjacent optical element array is provided. An optical module characterized in that are arranged in different directions with respect to the optical element array. 4. An optical module comprising: a plurality of optical element arrays in which optical elements are monolithically integrated one-dimensionally; and a plurality of electric circuits connected to the respective optical element arrays, wherein the electric circuits connected to the respective optical element arrays An optical module, wherein each of the optical modules is divided into a plurality of parts, and the divided electric circuits are arranged in different directions with respect to the optical element array.