JPH10178387A - Optical inter-connection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit data fast within a computer and an exchange without increasing an optical wiring by superposing and transmitting a clock signal through the use of an optical transmission system for transmitting a frame signal. SOLUTION: A data signal, the frame signal and the clock signal are transmitted from a transmission part 11 to a reception part 12. The data signal is converted to an optical signal from an electric signal by a data optical transmitter 15, inputted to a data optical receiver 18 through an optical fiber 13 and converted to the electric signal again. On the other hand, the clock signal and the frame signal are converted to a signal including both information by a frame clock multiplexing circuit 16, introduced to an optical fiber 14 as an intensity modulated signal by a frame/clock optical transmitter 17, photoelectric- converted by a frame/clock optical receiver 20 and separated into the original frame and clock signals by a separation circuit 21. The reproduced clock signal is inputted to a D flip-flop 19 with the data signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data transmission between electronic circuit boards in a computer or an exchange or between LSI chips. In particular, it relates to data transmission using optical signals.

[0002]

2. Description of the Related Art In order to transmit data at high speed between electronic circuit boards in a computer or an exchange or between LSI chips, data transmission by an optical signal has been conventionally used. In the data transmission in this case, the transmitting side and the receiving side are fixed, and additional information such as an address is not required. In such a case, in order to detect the data timing on the receiving side, the transmitting side transmits a frame signal indicating the existence of data to be transmitted and the period thereof, separately from the data.

FIG. 7 is a block diagram showing a conventional optical interconnection apparatus for performing such data transmission. This optical interconnection device includes a transmission unit 71 and a reception unit 72, which are connected to two optical fibers 73 and 74 for data signals and for frame signals.
The transmitting section 71 includes a data optical transmitter 75 and a frame optical transmitter 76, and the receiving section 72 includes a data optical receiver 77, a self-synchronizing circuit 78, and a frame optical receiver 79.
The data signal is modulated into an optical signal by the data optical transmitter 75 and transmitted to the data optical receiver 77 via the optical fiber 73. The data signal received by the data optical receiver 77 is retimed by the self-synchronizing circuit 78 at the next stage. On the other hand, the frame signal is transmitted from the frame light transmitter 76 and transmitted to the frame light receiver 79 via the optical fiber 74.

[0004]

However, in the prior art, since the clock signal is not transmitted, a self-synchronization circuit for retiming is required in the receiving unit. This circuit becomes a throughput limiting element of the optical interconnection. On the other hand, if a clock signal is to be transmitted, an optical transmission system for that purpose is separately required. It is not desirable that such an optical transmission system be increased in connection between electronic circuit boards or between LSI chips.

[0005] It is an object of the present invention to solve such problems and to provide an optical interconnection apparatus which enables high-speed data transmission inside a computer or an exchange without increasing optical wiring.

[0006]

According to the present invention, an optical transmission system for transmitting a frame signal is used, and a clock signal is superimposed and transmitted.

That is, the optical interconnection device of the present invention comprises a first transmission means for transmitting data by an optical signal, and a frame signal indicating the existence and the period of the data transmitted by the first transmission means. In an optical interconnection device comprising: a second transmission unit that transmits data by another optical signal, the second transmission unit transmits a clock signal synchronized with a clock of data transmitted by the data transmission / reception unit. It is characterized in that it includes means for superimposing and transmitting the frame signal.

Although the first transmission means and the second transmission means may transmit signals by separate optical transmission lines, wavelength multiplex transmission may be performed by a common optical transmission line.

On the transmitting side, a first transmitting means for transmitting data by an optical signal, and transmission of data from the first transmitting means and a frame signal indicating a period thereof are transmitted by an optical signal different from the data. It is preferable that the second transmission unit includes a second transmission unit for transmitting, and the second transmission unit includes a unit for superimposing a clock signal synchronized with a clock of data transmitted by the first transmission unit on the frame signal. Means may be provided for wavelength multiplexing the optical signal transmitted by the first transmitting means and the optical signal transmitted by the second transmitting means.

On the receiving side, a first receiving means for receiving data transmitted by an optical signal, and a signal related to data received by the first receiving means are received by an optical signal different from the data. And a separating circuit for separating the frame signal and the clock signal from the superimposed signal received by the second receiving means. The separation circuit may include a comparator for performing threshold processing on the reception output of the second reception means in order to extract the clock signal. Further, in order to extract a frame signal, a low-pass filter having a time constant longer than a time corresponding to one bit of data received by the first receiving unit, and a unit for performing threshold processing on an output of the low-pass filter may be provided. Means may be provided for synthesizing the reception output of the second reception means and a signal obtained by shifting the phase of the data received by the first reception means by 0.5 bit.

According to the present invention, since a frame signal and a clock signal are superimposed on a high-speed data signal for optical transmission,
Gb / s or more signals over a relatively long distance (10 cm to 100
m). The present invention
A self-synchronous circuit such as clock signal extraction is not required, and can be implemented with a simple configuration.

[0012]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and shows a configuration example of an optical interconnection device. This optical interconnection device includes a transmission unit 11 and a reception unit 12, which are connected via optical fibers 13 and 14. The transmitting unit 11 indicates a data optical transmitter 15 that transmits data to the optical fiber 13 by an optical signal, and shows a clock signal synchronized with a clock of data transmitted by the data optical transmitter 15, the existence of the data, and a period of the data. The frame to be superimposed with the frame signal
A clock multiplexing circuit 16 and a frame / clock optical transmitter 17 for transmitting an output of the frame / clock multiplexing circuit 16 to the optical fiber 14 by an optical signal different from the data optical transmitter 15 are provided. The receiving unit 12 includes a data optical receiver 18 for receiving data transmitted by an optical signal from the optical fiber 13, and a frame / clock optical receiver 20 for receiving a superimposed signal of the frame signal and the clock signal from the optical fiber 14. A separating circuit 21 for separating a frame signal and a clock signal from a superimposed signal received by the frame / clock optical receiver 20, and a D flip-flop for retiming an output of the data optical receiver 18 by the separated clock signal 19 is provided.

As the data light transmitter 15, for example, a 1.55 μm band laser diode (hereinafter referred to as “LD”) driven by a direct modulation method can be used. L
D is driven by a constant current or a constant output, and its output is LiN
Modulation may be performed by a bO ₃ modulator or a semiconductor optical modulator. As the frame / clock multiplexing circuit 16, for example, an AND gate can be used. As the frame clock optical transmitter 17, the same as the data optical transmitter 15 can be used. As the data optical receiver 18, a circuit including a photodiode and a preamplifier can be used.

In this embodiment, a data signal, a frame signal, and a clock signal are transmitted from the transmission unit 11 to the reception unit 12. The data signal is the information itself to be transmitted, the frame signal is a signal indicating the existence of data to be transmitted and the period thereof, and the clock signal is a signal synchronized with the clock of the data signal. Of these, the data signal is converted from an electrical signal to an optical signal by the data optical transmitter 15,
8 and reconverted into an electrical signal. On the other hand, the clock signal and the frame signal are converted into a signal combining both information by the frame / clock multiplexing circuit 16 and introduced into the optical fiber 14 by the frame / clock optical transmitter 17 as an intensity modulation signal. The optical signal is photoelectrically converted by the clock light receiver 20 and separated by the separation circuit 21 into the original frame signal and the clock signal. However, the clock signal is limited to the time during which the frame signal and the data signal are being sent. The reproduced clock signal is input to the D flip-flop 19 together with the data signal, and the data signal is retimed.

FIG. 2 shows a configuration example of the separation circuit 21. In this configuration example, the separation circuit 21 includes an amplifier 22 and a comparator 23 for extracting a clock signal from a frame clock signal which is a reception output of the frame clock optical receiver 18, and a frame signal from the same frame clock signal. , And a low-pass filter 24 and a comparator 25. The frame clock signal contains sufficient information about the clock as it is, and the clock signal can be extracted by simple threshold processing. In the configuration example shown in FIG. 2, first, the frame clock signal is amplified by the amplifier 22, and threshold processing is performed by the comparator 23. As a result, a clock signal whose level has been reproduced is obtained. On the other hand, for the frame signal, the low-pass filter 24 and the comparator 25 remove the clock signal component from the frame clock signal. As the low-pass filter 24, a filter having a time constant longer than the time corresponding to one bit of data is used. For example, if the data signal is 10G
If the clock is 10 GHz and the clock pulse width is 50 ps, the low-pass filter 24
Is suitably about 100 ps.

FIGS. 3A and 3B are diagrams for explaining the operation of the low-pass filter 24 and the comparator 25 for extracting a frame signal. FIG. 3A shows an input signal of the low-pass filter 24, and FIG.
Indicates an output signal of the comparator 25, and (c) indicates an output signal of the comparator 25. The output waveform of the low-pass filter 24 has a sawtooth shape as shown in FIG. Therefore, the level indicated by the broken line in FIG. 3B is used as a reference, and the comparator 25 sets a high level output when the level is higher than this level, and a low level output when the level is lower than this level. Thus, a frame signal is extracted.

FIG. 4 shows another example of the configuration of the separation circuit 21.
In this configuration example, the separation circuit 21 includes a comparator 23 for extracting a clock signal from a frame clock signal which is a reception output of the frame clock optical receiver 20;
Delay circuit 26, comparator 27 and OR gate 2 for extracting a frame signal from the same frame clock signal
8 is provided. The delay circuit 26 is constituted by a 0.5-bit delay line, for example, when the bit rate of the data signal is 10 G
If b / s, the delay of the delay circuit 26 is set to 50 ps. The clock signal is extracted by the threshold processing of the comparator 23 as in the configuration example shown in FIG. With respect to the frame signal, the frame clock signal is delayed by a delay circuit 26, input to a comparator 27, shaped into a waveform, and combined with an output of the comparator 23 by an OR gate 28.

FIGS. 5A and 5B are diagrams for explaining the frame signal extracting operation. FIG. 5A shows the output signal of the comparator 23, FIG. 5B shows the output signal of the comparator 27, and FIG. 5C shows the output signal of the OR gate 28. Is shown. The output signal of the comparator 27 is a clock signal whose phase is shifted by 0.5 bits with respect to the output signal of the comparator 23, and has a positive phase and a negative phase relationship. The frame signal is reproduced by synthesizing these by the OR gate 28. Here, the output of the delay circuit 26 is shaped by the comparator 27, but the output of the comparator 23 or the signal shaped by a comparator different from the comparator 23 may be delayed.

FIG. 6 is a block diagram showing a second embodiment of the present invention, which differs from the first embodiment in that data and a frame clock signal are wavelength-division multiplexed and transmitted by a common optical fiber 13. That is, the transmission unit 11 and the reception unit 12 are connected by the optical fiber 13. Transmission unit 1
1 includes a data optical transmitter 15, a frame clock multiplexing circuit 16, and a frame clock optical transmitter 17, a data signal light output from the data optical transmitter 15, and a frame output from the frame clock optical transmitter 17. An optical coupler 29 for multiplexing the clock signal light is provided. The receiving unit 12 includes a data optical receiver 18, a D flip-flop 1
9. Frame clock optical receiver 20 and separation circuit 2
In addition to the above, a wavelength filter 30 for separating the wavelength multiplexed signal light from the optical fiber 13 into a data signal light and a frame clock signal light is provided. As the optical coupler 29,
A PLC optical circuit can be used. If the LDs of the data optical transmitter 15 and the frame / clock optical transmitter 17 are mounted on an optical coupler of a PLC, the transmission system can be compactly integrated.

Here, for example, a data optical transmitter 15 having an output light wavelength band of 1.55 μm is used, and a frame clock optical transmitter 17 having an output light wavelength of 1.3 μm.
Use a band. These output signal lights are converted into optical couplers 29.
The wavelength multiplexing of the 1.55 μm band data signal light and the 1.3 μm band frame clock signal light is performed. The wavelength-multiplexed signal light is transmitted to the wavelength filter 30 via the optical fiber 13. Wavelength filter 30
Then, the transmitted signal light is divided into a data signal light and a frame clock signal light according to the wavelength, and the data signal light is input to the data light receiver 18 and the frame clock signal light is input to the frame clock light receiver 20. I do. Subsequent processing is the same as that of the first embodiment shown in FIG. 1, and the description is omitted here.

In the first embodiment, two optical fibers are required because the data signal light and the frame / clock signal light are transmitted separately, but in the second embodiment, one optical fiber is used. Data, frame and clock signals can be transmitted, and the transmission system is simple.

[0022]

As described above, according to the present invention,
When connecting between electronic circuit boards or between LSI chips by an optical signal, there is an effect that a high-speed optical interconnection capable of retiming can be performed without using a self-synchronizing circuit on the receiving side.

[Brief description of the drawings]

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

FIG. 2 illustrates a configuration example of a separation circuit.

FIG. 3 is a diagram illustrating the operation of a low-pass filter and a comparator for extracting a frame signal.

FIG. 4 is a diagram showing another configuration example of the separation circuit.

FIG. 5 is a diagram illustrating an operation of extracting a frame signal.

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional optical interconnection device.

[Explanation of symbols]

 11, 71 Transmitter 12, 72 Receiver 13, 14, 73, 74 Optical fiber 15, 75 Data optical transmitter 16 Frame clock multiplexing circuit 17 Frame clock optical transmitter 18, 77 Data optical receiver 19 D flip-flop Reference Signs List 20 frame clock optical receiver 21 separation circuit 22 amplifier 23, 25, 27 comparator 24 low-pass filter 26 delay circuit 28 OR gate 29 optical coupler 30 wavelength filter 76 frame optical transmitter 78 self-synchronous circuit 79 frame optical receiver

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04B 10/06

Claims (8)

[Claims] 1. A first transmission means for transmitting data by an optical signal, and a frame signal indicating the existence and period of data transmitted by the first transmission means is transmitted by an optical signal different from the data. An optical interconnection device comprising: a second transmission unit that performs transmission by superimposing a clock signal synchronized with a clock of data transmitted by the data transmission / reception unit on the frame signal. An optical interconnection device comprising means. 2. The optical interconnection apparatus according to claim 1, further comprising means for performing wavelength division multiplexing transmission by a common optical transmission line between said first transmission means and said second transmission means. 3. A first transmitting means for transmitting data using an optical signal, and a second transmitting means for transmitting a data from the first transmitting means and transmitting a frame signal indicating a period of the data using an optical signal different from the data. An optical interconnection device comprising: a second transmitting unit, wherein the second transmitting unit includes a unit for superimposing a clock signal synchronized with a clock of data transmitted by the first transmitting unit on the frame signal. An optical interconnection device characterized by the above-mentioned. 4. The optical interconnection apparatus according to claim 3, further comprising means for wavelength multiplexing an optical signal transmitted by said first transmitting means and an optical signal transmitted by said second transmitting means. 5. A first receiving means for receiving data transmitted by an optical signal, and a second receiving means for receiving a signal related to data received by the first receiving means by an optical signal different from the data. Wherein the related signal is a superimposed signal of a frame signal indicating data transmission and its period from a transmitting side and a clock signal synchronized with a clock of the data, An optical interconnection device comprising a separating circuit for separating a frame signal and a clock signal from a superimposed signal received by a second receiving means. 6. The optical interconnection device according to claim 5, wherein said demultiplexing circuit includes a comparator for extracting a clock signal by thresholding a reception output of said second receiving means. 7. A low-pass filter having a time constant longer than a time corresponding to one bit of data received by the first receiving means, and an output of the low-pass filter is subjected to threshold processing to extract a frame signal. 7. The optical interconnection device according to claim 5, further comprising: 8. The separation circuit combines the reception output of the second reception unit with a signal of which data received by the first reception unit is shifted by 0.5 bit in phase. 7. The optical interconnection device according to claim 5, further comprising means for extracting a frame signal.