JPH10341207A - Optical concentrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the concentrator to have an optical bus in terms of the hardware in common and to suppress contention between optical transmitters by providing separately plural logic paths to connect plural nodes, a physical optical fiber connecting an optical transmitter to one optical receiver and a control signal line that avoids contention of transferred optical signals at a receiver side. SOLUTION: Respective nodes 501-503 transfer data with each other through an optical bus 2001. An idle state of an optical receiver of the node 502 is confirmed by an arbiter 1001 of the node 501 through a control signal generator 301. If the optical receiver of the node 502 is in the idle state, the arbiter permits transfer to the control signal generator 301, data are subject to time multiplexing by a time multiplexer 1 and converted into an optical signal by an optical transmitter 11, and the converted signal is given to an optical switch 21. Only the optical gate connecting to the node 502 passes the optical signal by the optical switch 21. The signal is given to a concentrator 42 and then an optical fiber 602 and led to the optical receiver of the node 502.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data bus for transferring data between a plurality of nodes. In particular, the present invention relates to a data communication bus in a computer or a bus used for backboard wiring, wiring between frames, etc. of a communication device.

[0002]

2. Description of the Related Art A bus for data communication uses a plurality of logical paths for sharing a logical data transfer path connecting between frames, boards, and electric ICs corresponding to nodes. A configuration in which the number of internal wirings (the number of physical paths) is reduced is used. Here, the data transfer path configured in this manner is called a bus.

In a computer, a bus is generally used to connect a CPU, a memory, and an input / output device. In the current technology, an electric wiring is used as the bus. For example, as a bus connecting electric ICs, a pattern wiring on a board on which ICs are mounted, and as a bus connecting boards, a backboard wiring mounted on a backboard is used for transfer between frames. Uses an electric wiring in which a plurality of electric wirings are bundled.

However, in recent computers, C
With an improvement in PU capability and an increase in operating speed, it has become indispensable to increase the capacity of data transferred by these electric wires. Also, in recent computers, in order to achieve higher performance, research and studies on a configuration in which a plurality of processors are implemented in the computer and connected in parallel by a bus or a network are being actively studied and studied, and the transfer capacity of the bus is being studied. Is a major issue. To cope with this, buses are currently mounted using a large number of electrical wirings. However, with the increase in the number of coupling devices and the capacity, the bus driver's fan-out limit (bus drive capability) Area), the area (size) required when mounting a large number of electrical wiring
The problem has emerged. In fact, at present, 1
Since transfer at about 50 Mbps per wiring is the limit, 160 or more electrical wirings are required to obtain a bus width (transfer capacity) of about 1 GB / s (control lines are also required for transfer). Therefore, electrical wiring is required in addition to data transfer).

[0005] Further, with the increase in the required throughput of the switching equipment and the required throughput of the cross-connect equipment, the demand for increasing the capacity of the transfer path for transferring between boards in the communication equipment or between the communication equipments has increased. Is coming. In order to cope with such an increase in capacity, optical interconnection has been studied. In practice, this optical interconnection has been used in communication devices to reduce the size of electrical wiring and save space. As such an optical interconnection, a technique using an optical fiber as a transmission medium is known, and a parallel optical module and the like are being studied.

However, communication devices such as exchanges and cross-connect devices originally need to transfer data between the devices constituting the communication device. It is necessary to arrange optical interconnections on each of the transfer paths corresponding to the devices.

[0007] Further, since the switching equipment and the cross-connect device originally have a switch function as a device, if a bus configuration including the switch function can be taken, the switch function can be realized by using the broadcast-select function of the bus. The transfer path can be shared, and a significant reduction in the device itself is expected. However, with the increase in communication capacity in recent years, it has become difficult to realize this bus by electric wiring technology, as with a bus in a computer.

As an optical bus technology using an optical technology, a technology for sharing a data transfer path using a wavelength multiplexing technology as disclosed in Japanese Patent Application Laid-Open No. 64-11431 has been studied. This technology employs a configuration in which the same transmission medium is shared by transferring data within the same optical transmission medium at different wavelengths. For this reason, the cost is increased due to the necessity of a light source having a wavelength which is essentially different. In addition, since the signal light is distributed in order to realize the broadcast function required to fulfill the function of the bus, the number of fan-outs as a bus is limited by the loss due to light distribution or optical branching. Due to these two factors, the number of nodes connected by the bus is currently limited to about ten at most.

[0009]

As described above, if an attempt is made to respond to the expansion of the transfer capacity with an electric bus using current electric wiring, a large cost is required to construct the electric bus. There is a problem that it is difficult to implement in terms of size when trying to implement.

For example, when a bus in a computer is constituted by a conventional electric bus technology, there are two points of a total cost (cost required for improving the bus driving capability and cost required for mounting) and an actual mounting problem. Is difficult to achieve.

In a communication device, an optical interconnection technology has been introduced in place of electric wiring for data transfer in the device. However, since optical interconnection for performing point-to-point data transfer between devices is used, an optical interconnection technology is used. Optical interconnections corresponding to all transfer paths are required. For this reason, when the number of devices to be coupled increases, the number of optical interconnections increases by the square of the number of devices, which causes a serious problem in mounting.

Further, if a wavelength-division multiplexing bus using optical technology is used to solve these mounting problems, the number of nodes that can be connected to the bus is limited by the cost and distribution loss of the transfer path, and the number of nodes increases. There was a problem that it could not cope or the cost of configuring the bus increased.

[0013]

Means for Solving the Problems A first invention of the present invention is:
It comprises a physical optical data bus shared by a plurality of logical paths connecting a plurality of nodes, and a bus control wiring for preventing transfer data transferred on the optical data bus from conflicting on the optical bus. It is an optical bus.

According to a second aspect of the present invention, in an optical data bus connecting a plurality of (n: n is an integer) nodes, data transferred to another node generated within the node or to its own node is stored in the node. Multiplexing circuit for time multiplexing, an electrical-optical signal converter for converting the output of the time multiplexing circuit into an optical signal sequence, and a plurality (n) of optical signal sequences output from the electrical-optical signal converter. An optical switch selectively connected to each of the waveguide arrays 1 to n; and an m-th (m) of the plurality of optical waveguide arrays output from a plurality of nodes connected to the optical data bus.
N is an integer from 1 to n), an optical waveguide for transferring the output of the optical concentrator to the m-th node, and a light for converting the transferred optical signal into an electric signal train.
An optical data bus comprising an electrical converter.

According to a third aspect of the present invention, in an optical data bus connecting a plurality of (n: n is an integer) nodes, time-multiplexed transfer data generated in the node to another node is transmitted in the node. A time multiplexing circuit, an electric switch for selectively connecting the output of the time multiplexing circuit to a plurality of (n) signal paths, and an electric switch for converting the n electric output signals of the electric switch into optical signal trains. A plurality of optical signal array converters and a plurality of (n) optical waveguide arrays 1 to n for coupling the outputs of the electro-optical signal array converters, the plurality of optical waveguide arrays being output from a plurality of nodes connected to the optical data bus. N optical concentrators for concentrating the m-th optical waveguide array (m is an integer from 1 to n), an optical waveguide for transmitting the output of the optical concentrator to the m-th node, and the transmitted optical signal -To-electric conversion that converts light into an electric signal sequence An optical data bus which is characterized in that it is composed of a.

According to a fourth aspect of the present invention, in the optical data bus according to the third or fourth aspect, the data transfer capacity is increased by preparing a plurality of the optical data buses in parallel. Data bus.

According to a fifth aspect of the present invention, there is provided the optical data bus according to the second, third, or fourth aspect, wherein the optical waveguide is formed of an optical fiber.

The sixth invention of the present invention is directed to the second, third, fourth and fifth aspects.
In the optical data bus according to the present invention, as the optical concentrator,
When the outputs from the plurality of waveguides are coupled to one waveguide, the number of excitation spatial modes of the plurality of waveguides on the input side is set to 1
The optical data bus is characterized in that (1 is an integer of 1 or more) is smaller than the number k (k is an integer) of the excitation spatial mode of the waveguide on the output side.

A seventh aspect of the present invention is an optical concentrator that couples signal lights output from a plurality of single mode optical fibers to one multimode optical fiber.

[0020]

According to a first aspect of the present invention, there are provided a plurality of logical paths for connecting a plurality of nodes, a physical optical fiber for connecting a plurality of optical transmitters and one optical receiver, and a transfer of the optical fiber. The received optical signal has another control signal line for preventing competition on the receiver side. With such a configuration, the optical bus can be shared in hardware, and contention between optical transmission and reception can be suppressed.

According to a second aspect of the present invention, the number of optical signal outputs is reduced by time-multiplexing signals generated from a plurality of nodes, and when transferring the optical signal outputs to a plurality of receivers,
First, the optical bus configuration includes a 1 * n optical switch for selecting a transfer destination optical receiver, and an optical signal output is transferred only to the optical receiver selected by the optical switch.

Further, when data is transferred from a plurality of nodes to one receiver at the same time, interference occurs on the receiving side. To avoid this, the control signal line shown in the first invention of the present invention is used. And control this conflict.

With such a configuration, the size of the entire bus itself can be reduced, and the cost can be significantly reduced as compared with the conventional bus.

According to a third aspect of the present invention, in place of the optical switch for selecting the receiving side according to the second aspect of the invention, optical transmitters are prepared by the number of receivers, and the optical transmitters are connected to the electric 1 * n. This is an optical bus configured to be selected by a switch.

In this configuration, a plurality of optical transmitters are required. For example, if an array type optical transmission module is used,
An optical bus can be configured in combination with a conventional electric switch.

A fourth aspect of the present invention is to spatially multiplex a plurality of buses as a method for improving the data transfer capability of an optical transmitter.

The fifth invention of the present invention is to improve the mounting flexibility by using an optical fiber as the optical waveguide.

According to the sixth and seventh aspects of the present invention, as an optical waveguide for connecting the optical transmitter and the optical receiver of the present invention, the outputs from the plurality of optical transmitters are connected to the optical receiver by reducing the loss. To provide a configuration that can be used.

Here, the technique used is that, when a plurality of optical waveguides with a small number of excitation modes are guided to one optical waveguide with a large number of excitation modes, the light can be guided for each excitation mode. It uses that lossless coupling is possible. Conventionally, as described in Japanese Patent Application Laid-Open No. 1-264323, the coupling between a single-mode (1 excitation mode) optical fiber and a multi-mode (a plurality of excitation modes) optical fiber is connected with almost zero loss. The connection loss is reduced by connecting the outputs of a plurality of single-mode fibers (optical fibers with a small number of excitation modes) to multi-mode optical fibers (an optical fiber with a large number of excitation modes). That was not known.

By adopting such a configuration, an optical waveguide loss such as an optical coupler conventionally used for guiding the output of the optical transmitter to the optical receiver (in the case of the n * 1 coupler, almost equal to the transmission). 1 / n times when combined), and can be ideally reduced to zero. For this reason, it is possible to eliminate the limit of the number of nodes (the number of optical transceivers that can be connected to the optical bus) that has been conventionally determined by the loss limit between optical transmission and reception, and to provide a technology that can theoretically be expanded to infinity.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows a configuration diagram of a first embodiment of the present invention.

A plurality of nodes 501, 502, 503
The signals generated at the nodes 501, 502, and 503, which are connected to the optical data bus 2001, are time-multiplexed by the time multiplexing circuits 1, 2, and 3 to be 4 Gb / s.
The optical transmitters 11 and 1 convert the signals into optical signal trains.
2, 13 are input. Here, an inexpensive Fabry-Perot laser that outputs light at a wavelength of 1.3 microns was used for the optical transmitter. The output of this optical transmitter is divided into an optical splitter 151 that divides each optical output into eight, and an optical amplifier gate 152 (when an injection current is injected into the optical amplifier, a signal passes therethrough; 1 * 8 with integrated operation that does not pass signals)
Optical switches 21, 22, and 2 (the configuration diagram is shown in FIG. 3)
3 and the optical switches 21, 22, and 23 are connected to eight-core optical fiber arrays 31, 32, and 33, respectively.
These eight-core optical fiber arrays have a first core, a second core,.
.. Each bundle is bundled and converged by optical fiber couplers 41, 42, and 43 which are optical concentrators, and the output of the concentrator 41 is transmitted to the optical receiver 51 of the node 501 through the optical fiber 601.
The output of the concentrator 42 is connected to the node 5 through the optical fiber 602.
02 is connected to the optical receiver 52. In this embodiment, first, single-mode fibers are used as the optical fiber arrays 31, 32, and 33, and the optical fibers 601 and 602, and single-mode optical fiber couplers are used as the concentrators 41 and. For this reason, in the concentrator 41, the signal power is attenuated to about ８ and input to the optical fiber 601. The outputs of the optical receivers 51, 52, and 53 are time-separated by time separators 61, 62, and 63 so as to correspond to the transmission signals.
Converted to 03. In transmitting data, each node uses control signal generators 301, 302, and 303 for generating optical bus control signals, and an arbiter 1001 connected thereto. It controls contention for data transfer on the optical bus.

Next, a specific operation of this embodiment will be described.

As described above, the nodes 501, 502, and 503 are connected via the optical bus 2001, and transfer data via the optical bus 2001. For example, an operation in which the node 501 transfers the data 101 to the node 502 will be described. In the node 501, first, the arbiter 100
In step 1, the idle state of the optical receiver of the node 502 which is the transfer destination node is confirmed. If the optical receiver of the node 502 is performing data transfer with another node, the arbiter feeds back this information to the control signal generator 301 to temporarily stop the transfer, and Control to avoid contention. If the optical receiver at node 502 is idle, the arbiter grants transfer to control signal generator 301 and the data is time multiplexed by time multiplexer 1 and then transmitted by optical transmitter 11 to the 1.3 micron optical signal. Is converted to
Input to the optical switch 21. The optical switch is at node 5
The optical signal is passed by applying an injection current only to the optical gate connected to 02. Here, 2 of the optical fiber array 31
An optical signal is introduced only at the core. At this time, the optical transmitter and the optical switch are operated synchronously so that the output light from the optical transmitter 11 is not blocked by the optical switch. In this configuration, since the optical transmitter and the optical switch are installed in the same node (in this embodiment, on the same board), the synchronization state can be easily adjusted with an accuracy of several tens ps or less. This signal is input to the optical fiber 602 after being input to the concentrator 42, and is guided to the optical receiver 52 of the node 502. By performing the above operation, data transfer can be performed while avoiding data transfer competition on the optical bus. After the end of the transfer, the control signal generator 301 informs the arbiter 1001 of the end of the signal transfer and the idle state of the node 502.

Further, in this embodiment, when the empty state of the other receiver is confirmed, the plurality of optical gates of the optical switch are transmitted to the plurality of receivers simultaneously with the data transfer from the node 501 to the node 502. By setting it in the transparent state, it was possible to perform multicast operation. Also, this node 5
At the same time as the data transfer from 01 to the node 502, the transfer from the node 502 to the node 503 can be performed using the contention control in the arbiter, and the data transfer capacity of the bus can be increased as a whole.

As described above, when this embodiment is used, a large-capacity data transfer, which is difficult to realize by the conventional electric technology, can be realized by using a low-cost optical device such as a Fabry-Perot laser. Was. Further, the number of coupled optical fiber wirings can be significantly reduced as compared with the conventional optical interconnection based on point-to-point communication using an optical switch.

(Embodiment 2) Next, as a second embodiment,
A case where the sixth and seventh aspects of the present invention are applied to the first example of the present invention will be described.

The structure is the same as that of FIG.
The first point is that the optical fibers 31, 32, and 33 are single mode fibers having a small number of modes (the number of modes is 1), and the multimode fibers (a plurality of modes are multiple) are used as the optical fibers 602 and 603. Is different from the embodiment. The configuration diagram is shown in FIG.

With such a configuration, the loss of about 1/8 of the concentrators 41 and 42 described in the first embodiment can be reduced.
Almost eliminated. Also in this example, the loss in the concentrator was 1 dB or less.

As described above, in the first embodiment, as the number of nodes connected to the optical bus increases, the loss in the concentrator increases, and the number of nodes that can be accommodated in the optical bus is limited. In the embodiment, even if the number of nodes is increased, the loss in the concentrator does not change, the limitation on the number of nodes that can be connected to the optical bus is eliminated, and the number of nodes can be expanded to 16 or 32.

(Embodiment 3) Next, as a third embodiment,
The case where the third invention of the present invention is applied will be described.

This embodiment is different from the first embodiment in that
The outputs of the time multiplexers 1, 2, and 3 are input to 1: 8 electric switches 111, 112, and 113, and the laser array modules 121, 122, and
The point is that a signal is obtained by modulating 123. here,
Instead of using an optical switch, an optical switch is selected by an electric switch to generate an optical transmission signal, an output from the optical transmission signal is introduced to an optical bus 2001, and data is transferred to a receiving node. . The operation is the same as in the first embodiment, and a description thereof will be omitted.

(Modifications of the Present Invention) There are various other modifications in the first embodiment of the present invention.

The optical data bus itself is not always constituted by an optical fiber, but is constituted by an optical waveguide, and may take a shape such as a backboard wiring. The data rate of the time-multiplexed signal is not limited to 4 Gb / s,
Gb / s or 10 Gb / s may be higher or lower. The configuration of the optical transmitter is not limited to the Fabry-Perot rate of 1.3 μm, the wavelength may be 1.5 μm, 0.8 μm, long wavelength or short wavelength, and the laser configuration may be a multi-mode laser such as a Fabry-Perot laser. However, a single mode laser such as a distributed feedback laser may be used. If the transfer capacity is insufficient, it can be handled by using a plurality of time multiplexers, optical transmitters, optical switches, and optical buses. The modulation method may be a method of directly modulating the injection current or a method of modulating using an external modulator. As an optical switch,
This function is not limited to the optical switch in which the optical branch and the optical gate are integrated, but may be realized by a lithium niobate switch or a combination of a plurality of non-integrated switches. Further, in the present embodiment, the simple bus contention control is used. However, in addition to this, the contention status at the receiver is inquired to the receiver itself, or when the receiver becomes idle, the receiver becomes idle. Control such as a control method for transmitting the state to the arbiter is also conceivable.

In this embodiment, these two elements are mounted in the same node in order to easily synchronize the optical transmitter and the optical switch. However, if the configuration is the same as that of this embodiment,
Instead of mounting the optical transmitter and the optical switch in the same node, the switches of the respective nodes can be integrated and installed.

The second embodiment of the present invention has the same modification as the first embodiment.

In this embodiment, a concentrator for coupling a plurality of single-mode optical fibers to one multimode optical fiber is used as an optical concentrator. Optical concentrators that couple to fibers can also be used. Also, the number of connected nodes is not limited to 8, 16, and 32 shown in the present embodiment, and may be 3 or less, or 50 or more, and any number of nodes less than this. it can.

As for the third embodiment of the present invention, the first,
There are modifications similar to the second embodiment.

[0049]

According to the present invention, when an attempt is made to respond to an increase in transfer capacity with an electric bus using current electric wiring, a problem that a large cost is required for the configuration, and a case where an actual mounting is attempted. The problem that the implementation was difficult due to the size was solved. For example, in the case of a bus in a computer, if it is configured by the conventional electric bus technology, the overall cost (the cost required for improving the bus driving capability and the cost required for mounting) and a solution for the actual mounting problem can be solved. Gave.

In a communication device, an optical interconnection technology has been introduced in place of electric wiring for data transfer in the device. However, since an optical interconnection for performing point-to-point data transfer between devices is used, an optical interconnection technology is used. Optical interconnections corresponding to all transfer paths are required. Therefore, a solution has been provided to reduce the number of optical interconnections when the number of devices to be coupled increases.

Furthermore, if a wavelength multiplexing bus using optical technology is used to solve these mounting problems, the number of nodes that can be connected to the bus is limited by cost and distribution loss of a transfer path, and the number of nodes increases. It also provided a solution to the problem of not being able to handle or increasing the cost of configuring the bus.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a 1 * 8 optical switch.

FIG. 4 is a configuration diagram of an optical concentrator used in a second embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3 time multiplexers 11, 12, 13 optical transmitters 21, 22, 23 optical switches 31, 32, 33 optical fiber arrays 41, 42, 43 optical concentrators 51, 52, 53 optical receivers 61, 62, 63 Time separator 101, 102, 103 Transmit signal 201, 202, 203 Receive signal 301, 302, 303 Control signal generator 501, 502, 503 Node 1001 Arbiter 2001 Optical bus 111, 112, 113 Electrical switch 121, 122, 123 Laser array module

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Claims (4)

[Claims] 1. An optical concentrator, wherein signal light input from a plurality of single-mode optical waveguides is coupled to one multi-mode optical waveguide. 2. An optical concentrator for coupling signal light input from a plurality of single mode optical fibers to one multimode optical fiber. 3. An optical concentrator wherein signal light input from three or more single-mode optical waveguides is coupled to one multi-mode optical waveguide. 4. An optical concentrator for coupling signal light input from three or more single mode optical fibers to one multimode optical fiber.