JPH095580A - Inter-board optical interconnection device - Google Patents

Abstract

PURPOSE: To eliminate the need of mechanical alignment, to attain economization, to realize ultra high speed and ultra high density, and to restrain connection loss and crosstalk to an adjacent channel by connecting the end faces of optical fiber array blocks mounted on respective boards, thereby connecting between the boards. CONSTITUTION: After a surface light emitting laser SL-1 is modulated according to an electrical signal inputted from electric components such as an LSI, etc., and made incident on optical fibers constituting the optical fiber array block OA-1, respectively. An optical signal propagated in the optical fiber array block OA-1 is inputted in the optical fiber constituting the optical fiber array block arranged to be opposed through a connection point between the boards. After the optical signal is emitted from the end face of the optical fiber array block, it is made incident on a photodetector, converted into an electrical signal, and guided to the electric components in the board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mounts a board on which an electric circuit is mounted in a bookshelf form,
The present invention relates to an inter-board optical interconnection device that connects ultra-high density and large capacity signals using optical signals.

[0002]

2. Description of the Related Art In order to realize a high speed, wide band communication network,
It is effective to use a large capacity ATM (Asynchronous Transfer Mode) exchange. In order to realize such a large capacity exchange, VLSI (Very Large Scale Integrate)
The challenge is to connect the boards mounted with high-speed switch LSIs, which can be manufactured due to the development of d Citcuits) technology, at high speed and high density. The boards currently in practical use are connected using electrical signals, but when transmitting high-speed signals, it is known that the pin density that can be provided on the boards is limited by EMC noise. ing. However, the signal speed and pin density required for connection between boards tend to increase year by year, which is a bottleneck for realizing a large capacity exchange.

On the other hand, the inter-board optical interconnection, which connects the boards using optical signals, is expected to eliminate the above-mentioned bottleneck due to the high speed and wide band property of light and the EMC noise resistance. There is. In particular, the multi-channel optical interconnection module in which the semiconductor laser array and the photodetector array are connected by an optical fiber is advantageous in module fabrication because the number of channels handled collectively is large, and many high-speed connections are required. Mandatory for broadband channels.

FIG. 6 is a diagram showing the structure of a multi-channel optical interconnection module in which a conventionally proposed semiconductor laser array and an optical detector array are connected by an optical fiber (references: Nishikido, Fujita, Arai, Hino, Akahori, 1993
IEICE Spring National Congress, B-1042). In the figure, TM and RM are a transmission module and a reception module respectively mounted on the board. IN is a group of input signals sent from the LSI on the board, OU is a group of output signals sent to the LSI on the board, MU is a parallel / serial conversion circuit group, DR is a semiconductor laser drive circuit group, and LA is a semiconductor. Laser array, GI is a multimode optical fiber array used to connect between boards, P
D is a photodetector array, PA is a preamplifier group, PO is a postamplifier group, DE is a code discriminator group, and DEM is a serial / parallel conversion circuit group.

In the transmission module TM, the electric signal sent from the LSI or the like is converted into a parallel / serial conversion circuit MU.
Signal is input to the semiconductor laser array LA through the laser drive circuit DR, converted into an optical signal, and then guided to the inter-board connecting multimode optical fiber array GI. In the receiving module, after being converted from an optical signal to an electrical signal by the photodiode,
A signal is amplified using the preamplifier PA and the postamplifier PO. After that, after reproducing the signal with the code discriminator DE,
The signals are separated using the serial / parallel conversion circuit DEM and connected to the LSI on the board.

In an optical interconnection module of the type in which boards are connected using such optical fibers, the length of the optical fiber wiring required to connect the optical fibers depends on the attachment work of the connection mechanism. Generally, several tens of cm or more is required. In addition, since the degree of integration of the optical fiber connection mechanism is generally lower than that of optical devices such as semiconductor laser arrays and photodetector arrays, there is a problem that the size of the entire module becomes large for these reasons. .

In order to solve this drawback, DZTsang et al. Of the Massachusetts Institute of Technology used a light beam for connection between boards, so that the connection between fibers and the dimensional limitation associated with the connection between fibers were eliminated, and therefore, We propose a free-space optical interconnection that can be expected for high-density packaging (Reference: DZTsang, et al., Proceedingsof
IEEE / Laser and Electro-Optics Society 1994 Annual
Meeting, Vol.1, pp.217-218, Paper OP3.3, 1994).

FIG. 7 shows the configuration. In the figure,
TM and RM are a transmission module and a reception module mounted on the board, respectively. IN is a group of input signals sent from the LSI in the board, OU is a group of output signals sent to the LSI in the board, SEL is a surface emitting laser array, and PD is a photodetector array. First, on the transmission module RM side, the lens surface emitting laser array SEL is directly modulated by the input electric signal, and the emitted light from each laser is converted into a light beam by using the microlens array ML2. In the reception module RM, the light beam is condensed on the photodetector array PD by using the microlens array ML2 as well, and after being converted into an electric signal,
Guided to the LSI etc. on the board.

[0009]

However, in the free space optical interconnection in which the light beam is used for connecting the boards, it is necessary to reduce the beam diameter of the light beam propagating between the boards in order to achieve high-density mounting. As the light beam propagates, the tendency for the beam diameter to expand becomes stronger. In this case, if the expanded light beam goes out of the target microlens (or the incident window of the photodetector),
Not only is this a loss, but what leaks into the adjacent microlenses (or the incident window of the photodetector) becomes crosstalk. Further, since the insertion loss of the optical system connecting the boards and the crosstalk depend on the relative positional deviation amount of each component, each component needs to be aligned with high accuracy.

The present invention has been made in view of the above,
The object is to provide an inter-board optical interconnection device which realizes ultra-high speed and ultra-high density while achieving economical efficiency by eliminating the need for mechanical alignment, and which has low connection loss and crosstalk with respect to adjacent channels. Especially.

[0011]

In order to achieve the above object, the present invention according to claim 1 mounts a board on which an electric circuit is mounted in a bookshelf form, and a signal output from each board serves as a backplane. An inter-board optical interconnection device for connection using a connection mechanism, comprising a surface emitting laser for converting an electrical signal into an optical signal, and an optical fiber array in which at least one light input / output end face is obliquely polished into a mirror surface. By providing an optical fiber array block and an optical detector for converting an optical signal into an electric signal for each board, and connecting the boards by directly contacting the end faces of the optical fiber array block provided on each board. The point is to do.

Further, the present invention according to claim 2 is based on claim 1.
In the invention described, each optical entrance and exit end face is provided between the boards an optical fiber array block that is obliquely polished into a mirror surface,
The gist of the invention is that the boards are connected via the optical fiber array block and the board is inserted and removed in one direction.

Further, the present invention according to claim 3 provides the invention according to claim 1.
Alternatively, in the invention described in 2, the gist is that the optical fiber array block is composed of an image fiber.

[0014]

According to the first aspect of the present invention, the light emitted from the surface emitting laser array on each board is incident on the optical fiber array block whose light input / output end faces are mirror-polished. The connection is made by bringing the end faces of the optical fiber array blocks mounted on the boards into contact with each other, so that a special connection mechanism required for connecting the optical fibers to each other is not required, and the degree of integration can be easily increased. Also,
Since at least one of the light input / output end faces of each optical fiber array block is obliquely polished, the light reflection amount at the board connection point can be reduced as compared with the case where the optical input / output end face is planarly polished.

According to the present invention of claim 2,
By providing an optical fiber array block in which each light input / output end face is obliquely polished into a mirror surface between the boards, the board can be inserted and removed in one direction.

Further, according to the invention of claim 3,
By configuring the optical fiber array block with an image fiber, it is possible to achieve economic efficiency.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of an inter-board optical interconnection device according to a first embodiment of the present invention.
The optical signal and the optical beam in the present embodiment described below use light of a certain level or higher as a carrier, and use this as an information signal (basically extendable to digital signals and analog signals) for intensity modulation (others). It can be extended to the modulation system). In order to simplify the description, FIG. 1 is a plan view (side view) of a three-dimensional inter-board optical interconnection device. The thick arrow indicates the board insertion direction.

In FIG. 1, EB-1 to EB-5 are LSs.
LE-1 is an LSI, a board on which electrical components such as I are mounted.
, LS-1 is a surface emitting laser array, PD-
1 is an optical detector array, OA-1 is an optical fiber array block, BP is a backplane into which the board is inserted and removed,
BM1 and BM2 are board lock mechanisms that mechanically hold the board. In this embodiment, unlike the general bookshelf mounting, the adjacent boards are inserted in opposite directions.

In FIG. 1, the surface emitting laser SL-1 is an LSI.
After being modulated by electric signals input from electric components such as the above, they are incident on the optical fibers forming the optical fiber array block OA-1, respectively. The optical signal propagating in the optical fiber array block is input to the optical fibers forming the optical fiber array block, which are also arranged to face each other, through the connection point between the boards. The optical signal is emitted from the end face of the optical fiber array block, is then incident on the photodetector, is converted into an electrical signal, and is guided to electrical components in the board.

In this embodiment, a surface emitting laser array,
And, the optical detector array and the optical fiber array are connected by a direct bonding method (or a butt joint method), but it is expected that the optical coupling efficiency will be improved by adopting a lens coupling method using a microlens array or the like. it can.

FIG. 2 is an enlarged view of the broken line portion in FIG. In the figure, EB-1 to EB-4 are boards, SL is a surface emitting laser array, PD is a photodetector array, OA is an optical fiber array block, BF is a spacer for holding the optical fiber array, and BM1 and B.
M2 is a board lock mechanism that mechanically holds the board. The arrow in the figure indicates the board insertion direction. Similar to FIG. 1, the surface-emitting laser SL enters each of the optical fibers forming the optical fiber array OA after being modulated by an electric signal input from an electric component such as LS1. The optical signal propagating through the optical fiber array OA is input to the optical fibers forming the optical fiber array OA which are also arranged to face each other through the connection point between the boards. The optical signal is emitted from the end face of the optical fiber array OA, then enters the photodetector PD, is converted into an electrical signal, and is guided to electrical components in the board.

Generally, the connection loss between optical fibers largely depends on the amount of misalignment of the optical axes of the fibers, but the extent thereof also differs depending on the type of fiber. For example, the optical connection loss between multimode optical fibers, especially optical fibers with a large core diameter, has a greater tolerance for misalignment of the fiber optical axis than single mode optical fibers, but the signal band that can be propagated due to group velocity delay dispersion is Known to be limited. However, since the distance between the boards mounted on the bookshelf is generally as short as several cm or less, the influence of the group velocity delay dispersion can be neglected. Therefore, a multimode optical fiber is used for the connection between the boards according to the present invention. It is effective to use. As a result, it is possible to reduce the inter-fiber positional displacement accuracy required for the optical fiber array in each optical fiber array block and the mechanical positional displacement tolerance in the board lock mechanism.
The inter-board optical interconnection device according to the present invention can be provided at low cost.

Further, since the surface emitting laser can be easily realized as a two-dimensional array, by using this, higher density can be expected as compared with the conventional optical interconnection device using the edge emitting laser. In this case, the optical fiber used for connecting the boards needs to be a two-dimensional array.

FIG. 3 shows an example of the optical fiber array block. The optical fiber array block is an optical fiber array made up of two-dimensionally arranged optical fibers, with each light input / output end face polished to a mirror surface. FIG. 3 shows a configuration of an optical fiber array using a micro ferrule MF. Examples are given (Reference: Koyabu, Ohira, Yamamoto, "
High-Density Two-Dimensional Fiber Optic Array Collimator Array Module ", 1993 IEICE Fall National Conference, C-25
1). In the figure, OF is an optical fiber, MF is a micro ferrule in which the optical fiber is inserted, GS is an alignment plate for aligning and fixing the micro ferrule, and one of the light input / output end faces is obliquely polished into a mirror surface ( Angle φ), and the other end surface is mirror-polished so as to be perpendicular to the optical axis of the fiber. As described above, by combining the surface emitting laser and the two-dimensional optical fiber array, the two-dimensional arrayed inter-board optical interconnection device according to the present invention can be realized.

FIG. 4 shows a second embodiment according to the present invention. In the figure, EB-1 to EB-3 are boards, SL is a surface emitting laser array, PD is a photodetector array, OA is an optical fiber array whose one end face is obliquely polished, and BF is an optical fiber array. Spacers, TOA-1 and TOA-2 are optical fiber array blocks for relaying between the boards, and BM is a board lock mechanism for mechanically holding the boards. In this embodiment, since the board is inserted in one direction, the optical fiber array T for relay is formed by obliquely polishing the light input / output surface between the boards.
Since OA-1 and TOA-2 are inserted, most of the conventionally used parts for mounting the bookshelf can be used.

FIG. 5 shows a third embodiment according to the present invention. In the figure, EB-1 to EB-3 are boards, SL is a surface emitting laser array, PD is a photodetector array, OA is an image fiber, BF is a spacer for holding the image fiber, TOA-1 and TO.
A-2 is an image fiber that relays between the boards, and BF is a board lock mechanism that mechanically holds the boards. In this embodiment, since the image fiber widely used for the gastroscope, the fiberscope, etc. is used, the cost of the device can be further improved.

[0028]

As described above, according to the present invention,
Light emitted from the surface emitting laser array on each board is incident on the optical fiber array block whose light input / output end faces are mirror-polished, and the end faces of the optical fiber array blocks are brought into contact with each other to connect the boards. Since this is done, a special connection mechanism required to connect the optical fibers to each other is unnecessary, and the degree of integration can be easily increased, and
By polishing at least one of the light input / output end faces of each optical fiber array block at an angle, the amount of light reflected at the board connection point can be reduced compared to the case where the surface is polished. High density optical interconnection can be achieved economically.

Further, according to the present invention, by providing the optical fiber array block in which the respective light input / output end faces are obliquely polished into a mirror surface between the boards, the board can be inserted / removed in one direction. It becomes easy and many conventional parts for mounting bookshelves can be used. Further, by constructing the optical fiber array block with an image fiber, it is possible to achieve economy.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an inter-board optical interconnection device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a broken line portion of the inter-board optical interconnection device of FIG.

3 is a perspective view showing a configuration of an optical fiber array block used in the inter-board optical interconnection device of FIG.

FIG. 4 is a diagram showing a configuration of an inter-board optical interconnection device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of an inter-board optical interconnection device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional inter-board optical interconnection device.

FIG. 7 is a diagram showing another configuration of a conventional inter-board optical interconnection device.

[Explanation of symbols]

 BM board lock mechanism BP backplane EB board OA optical fiber array block PD optical detector array

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H04B 10/12 10/28 10/02 (72) Inventor Kunio Koyabu 1-1 Uchisaiwaicho, Chiyoda-ku, Tokyo No. 6 Nippon Telegraph and Telephone Corp. (72) Inventor Shigeki Hino 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corp.

Claims (3)

[Claims] 1. An inter-board optical interconnection device for mounting a board on which an electric circuit is mounted in a bookshelf shape and connecting signals output from each board by using a connection mechanism which is a backplane. A surface emitting laser for converting to an optical signal, an optical fiber array block composed of an optical fiber array in which at least one of the light incident and emitting end faces is obliquely polished into a mirror surface, and an optical detector for converting an optical signal to an electric signal. An inter-board optical interconnection device, which is provided for each board, and the connections between the boards are made by directly contacting the end faces of the optical fiber array blocks provided on the boards. 2. An optical fiber array block in which each light input / output end face is obliquely polished into a mirror surface is provided between boards, and boards are connected through the optical fiber array block, and the board is inserted / removed in one direction. The inter-board optical interconnection device according to claim 1, wherein 3. The optical fiber array block comprises an image fiber.
Alternatively, the inter-board optical interconnection device described in 2.