JPH09200121A - Optical transmission method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain an optical transmission without the need for a clock recovery circuit requiring a large circuit scale. SOLUTION: In the transmission system, a optical transmission circuit 15 uses a drive current obtained by summing a modulation current in response to an input data signal DI and a modulation current in response to an input clock signal CI to drive a laser diode 14, an optical signal of which is sent via an optical fiber 16. In the reception system, the transmitted optical signal via the optical fiber 16 is received by a photo diode 17 and an optical reception circuit 18 is used to extract a data component Vod and a clock component Voc from the received output and the data component Vod is fed to a D input of a D F/F 19 and the clock component Voc is fed to a CK input of the D F/F 19, which reproduces a data signal DO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission method and apparatus for transmitting optical digital signals, and more particularly to an optical transmission method and apparatus suitable for interconnection parallel optical transmission between digital electronic exchanges. It is a thing.

[0002]

2. Description of the Related Art Generally, as a conventional optical digital signal transmission system, a system shown in FIG. 9 is known. FIG.
In the LD drive circuit (T) 91, the input data signal D
The laser diode (LD) 92 is driven based on I. At this time, in the laser diode 92, an optical signal is generated by the intensity modulation method based on the characteristics of the drive current (I) versus the emission power (L) shown in FIG. This optical signal is
It is transmitted to the receiving system via the optical fiber 93. The transmitted optical signal is received by the photodiode 94.
The photodiode 94 converts the received optical signal into a current signal. This current signal is supplied to the optical receiving circuit (R) 95.

The optical receiving circuit 95, as shown in FIG.
Current-voltage conversion amplifier 111 and AGC (Automatic Gain)
Control) amplifier 112 and comparator 113 having a predetermined threshold voltage Vth.
The data signal output from the optical receiving circuit 95 becomes a data (D) input of a D-type flip-flop (hereinafter referred to as DF / F) 96 and is also supplied to the clock recovery circuit 97. The clock recovery circuit 97 generates (reproduces) a clock pulse signal based on the input data.
I do. This clock pulse signal is output as it is as the clock pulse signal CO, and the DF / F9
6 clock (CK) input. The inverted output Qb of the DF / F 96 becomes the output data signal DO.

As the clock recovery circuit 97,
As shown in FIG. 12, a differential rectifier circuit 121, a tank circuit 122, and an amplifier 123 (97 A) are used, and as shown in FIG.
1 and a PLL (Phase Locked Loop) circuit 132 (97B). Regarding the circuit configurations of these clock recovery circuits 97A and 97B,
The details will be described below.

First, in the clock recovery circuit 97A, the differential rectification circuit 121 differentiates the change point of the data from the input data signal to generate the frequency fo component of the clock and rectifies it. The tank circuit 122 is a kind of tuning circuit, and has a performance in which the pass bandwidth is extremely narrow around the frequency fo, and by inputting the output signal of the differential rectification circuit 121, the frequency fo
The sine wave signal of is output. The amplifier 123 clamps the sine wave signal output from the tank circuit 122 and shapes the waveform into a clock pulse signal.

Next, in the clock recovery circuit 97B, the differential rectification circuit 131 generates the frequency fo component of the clock from the input data signal, as in the case of the differential rectification circuit 121 of the clock recovery circuit 97A. Differentiate the change point of data and rectify it. The PLL circuit 132 is composed of a voltage controlled oscillator (VCO) whose oscillation frequency is near fo, a phase comparator and an operational amplifier, and outputs the differential rectification circuit 131 and the VCO.
Of the oscillation frequency of the VCO is controlled by the output of the operational amplifier according to the amount of change, and a clock pulse signal synchronized with the input data is generated.

[0007]

However, in the optical digital signal transmission system having the above configuration, it is necessary to have the clock recovery circuit 97 having the complicated circuit configuration as described above as a circuit for reproducing the clock pulse signal CO. Therefore, there is a problem in terms of economy. In particular, when it is desired to transmit a large amount of data between devices, several transmission systems having this clock recovery circuit 97 are required.

On the other hand, another conventional optical digital signal transmission system for transmitting a large amount of data between devices is a parallel optical transmission system shown in FIG. This parallel optical transmission method is based on N transmission systems 141-1 to 141-1 having the same configuration as the transmission system of FIG.
141-n and N receiving systems 142-1 to 142-n, which are obtained by removing the clock recovery circuit 97 from the receiving system in FIG. 9, and receive N data signals DI1 to DIn from N optical fibers 143. -1 to 143-n for parallel transmission and further another transmission system 144, optical fiber 145 and reception system 14
At 6, the clock signal CK is transmitted. FIG. 15 shows the optical signals P1 to Pn + 1 and the optical receiver circuit output voltage V.
Waveforms of O1 to VOn + 1, output data signals DO1 to DOn, and output clock signal CKO are shown.

However, in the above-mentioned conventional parallel optical transmission system, N optical fibers 143-1 to 14-1 for parallel transmission are used.
There is a problem that the transmission distance is limited due to the problem of skew caused by the 43-n delay variation. Here, the skew caused by the delay variation will be described in detail. The optical fibers 143-1 to 143-n, which are transmission lines, have respective lengths L
Is different (including the bending of the fiber), the arrival time from the input to the output of the optical fibers 143-1 to 143-n is different for each channel. Also, the optical fibers 143-1 to 1
The refractive index n of the material forming 43-n also varies.

Since the propagation time T of the optical signal in the optical fibers 143-1 to 143-n is proportional to the value of L × n (the amount called the optical path length), the optical fibers 143-1 to 14-1 of the respective channels.
Even if they are input to 43-n at the same time, the data on the output side will have different phases. Such a phase shift is generally called skew. When performing parallel transmission, each channel data may be independent on the time axis or may be related to each other on the time axis.
At the receiving point after transmission, the former needs to be in phase with each data and the clock, and the latter needs to be in phase with each other between data and clocks. In the method, since the phase difference between the channels needs to be 1 bit or less, the transmission distance is limited.

[0011]

In the optical transmission method according to the present invention, a light emitting element is driven by a drive current obtained by adding a modulation current according to a data signal and a modulation current according to a clock signal, and this light emission is performed. The optical signal emitted from the element is transmitted through the optical transmission line, while the optical signal passing through the optical transmission line is received by the light receiving element, and the data component and the clock component are extracted from the output signal of the light receiving element. A data signal is reproduced based on the data component and the clock component.

The optical transmission device according to the present invention includes an optical transmission circuit for driving a light emitting element by a drive current obtained by adding a modulation current according to a data signal and a modulation current according to a clock signal, and a light emitting element for emitting light. And an optical receiving circuit for receiving an optical signal transmitted through the optical transmission line by a light receiving element and extracting a data component and a clock component from an output signal of the light receiving element. , And a data reproducing circuit for reproducing a data signal based on the data component and the clock component extracted by the optical receiving circuit.

In the above-described optical transmission method and device thereof, first, in the transmission system, the modulation current according to the data signal and the modulation current according to the clock signal are added, and the light emitting element is driven by using the added current as a drive current. . The optical signal emitted from this light emitting element is transmitted to the receiving system via the optical transmission line. On the other hand, in the receiving system, the optical signal transmitted through the optical transmission line is received by the light receiving element, and the data component and the clock component are extracted from the output signal of the light receiving element. Then, the data signal is reproduced based on the extracted data component and clock component.

In another optical transmission method according to the present invention, a reference frame signal is inserted into each of a plurality of data signals, and a modulation current and a reference clock signal according to the plurality of data signals into which the reference frame signal is inserted are provided. Driving a plurality of light emitting elements by each of the drive currents obtained by adding the modulation currents, and transmitting the optical signals emitted from the plurality of light emitting elements via a plurality of optical transmission lines, and The light emitting element is driven by the drive current obtained by adding the modulation current according to the clock signal and the modulation signal according to the reference frame signal, and the optical signal emitted from this light emitting element is separated from the plurality of optical transmission lines. While transmitting via the optical transmission line,
A plurality of light receiving elements receive an optical signal that has passed through a plurality of optical transmission lines, a data component and a clock component are extracted from each output signal of the plurality of light receiving elements, and a plurality of data components and clock components are extracted based on the data components and the clock components. While reproducing the data signal, the light receiving element receives the optical signal that has passed through another optical transmission line,
A clock component and a frame component are extracted from the output signal of the light receiving element, a reference clock signal and a reference frame signal are reproduced based on the clock component and the frame component, and based on the reproduced reference clock signal and the reference frame signal. , The bit synchronization and phase synchronization of a plurality of reproduced data signals are performed.

Another optical transmission apparatus according to the present invention is a frame generation circuit for generating a reference frame signal, a plurality of frame insertion circuits for inserting a reference frame signal into each of a plurality of data signals, and a reference frame signal. A plurality of driving currents obtained by adding a modulation current according to a plurality of inserted data signals and a modulation current according to a reference clock signal. 1 optical transmission circuit, and a plurality of optical transmission lines that respectively transmit the optical signals emitted from the plurality of first light emitting elements,
A second optical transmission circuit for driving the second light emitting element by a drive current obtained by adding a modulation current according to the reference clock signal and a modulation current according to the reference frame signal, and from the second light emitting element A plurality of optical transmission lines that are different from the multiple optical transmission lines that transmit the emitted optical signals, and each optical signal that has passed through the multiple optical transmission lines is received by a plurality of light receiving elements, and from each output signal of these light receiving elements A plurality of first optical receiving circuits for extracting the data component and the clock component, and reproducing a plurality of data signals based on the data component and the clock component extracted by each of the plurality of first optical receiving circuits , A plurality of data recovery circuits that separate the frame signal from each data signal and the optical signal that has passed through another optical transmission line are received by the light receiving element, and the clock component and the frame component are extracted from the output signal of this light receiving element. A second optical receiving circuit, a signal reproducing circuit for reproducing the reference clock signal and the reference frame signal based on the clock component and the frame component extracted by the second optical receiving circuit, and the signal reproducing circuit for reproducing the reference clock signal and the reference frame signal. And a plurality of synchronization circuits for performing bit synchronization and phase synchronization of the plurality of data signals reproduced by the plurality of data reproduction circuits based on the reference clock signal and the reference frame signal.

In performing the parallel optical transmission in the above other optical transmission method and apparatus, first, in the transmission system, a reference frame signal is inserted into each of a plurality of data signals, and a plurality of the reference frame signals are inserted. Of the data signal and the modulation current according to the reference clock signal are added, and the plurality of light emitting elements are respectively driven by using the added current as a drive current. The optical signals emitted from the plurality of light emitting elements are transmitted to the receiving system via the plurality of optical transmission lines. At the same time, the modulation current according to the reference clock signal and the modulation signal according to the reference frame signal are added, the light emitting element is driven by using the added current as a drive current, and the optical signal emitted from the light emitting element is It is transmitted to the receiving system via an optical transmission line different from the optical transmission line.

On the other hand, in the receiving system, each optical signal transmitted through the plurality of optical transmission lines is received by the plurality of light receiving elements,
A data component and a clock component are extracted from each output signal of the plurality of light receiving elements, and a plurality of data signals are reproduced based on the data component and the clock component. At the same time, an optical signal that has passed through another optical transmission line is received by the light receiving element, the clock component and the frame component are extracted from the output signal of this light receiving element, and the reference clock signal and the reference frame signal are extracted based on this clock component and the frame component. To play. Then, in order to achieve skew-free, bit synchronization and phase synchronization are performed for the plurality of reproduced data signals based on the reproduced reference clock signal and reference frame signal.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the present invention. In FIG. 1, the transmission system includes a first drive circuit (T11) 11 that outputs a modulation current Io according to the input data signal DI and a second drive circuit that outputs a modulation current 2Io according to the input clock signal CI. (T12) 12, an adder 13 that adds both drive currents Io and 2Io, and an optical transmission circuit 15 including a laser diode (LD) 14 that is a light emitting element that is modulated and driven by the added current. . In this optical transmission circuit 15, the modulation current of the second drive circuit 12 is the first
It is not necessary that the modulation current Io of the drive circuit 11 is twice as large as the modulation current Io, and any amount of current that can discriminate the clock signal CI from the data signal DI on the receiving side may be used.

FIG. 2 shows an example of a concrete circuit configuration of the optical transmission circuit 15. In FIG. 2, the first drive circuit 11 is
Differential pair transistors Q1 and Q2 whose emitters are commonly connected and whose input is the input data signal DI and its opposite phase signal, a current source transistor Q3 whose collector is connected to a common connection point of the emitters, and its emitter And a resistor R1 connected between the ground and the ground. The current Io flows through the current source transistor Q3.

The second drive circuit 12 has differential emitter transistors Q4 and Q5 whose emitters are commonly connected and whose input is the input clock signal CI and its opposite phase signal.
, Current source transistors Q6 and Q7 having collectors connected to their common emitter connection points, and resistors R2 and R3 connected between the emitters and the ground. The same current Io as that of the current source transistor Q3 flows through each of the current source transistors Q6 and Q7. The collectors of the transistors Q2 and Q5 in the drive circuits 11 and 12 are commonly connected to form an adder 13, and the common connection point is connected to the cathode of the laser diode 14.

The anode of the laser diode 14 is a power source V
cc, and its cathode is grounded via the current source 21. This current source 21 has a bias current Ib.
Is flowing. By the way, since the current-to-light output characteristic of the laser diode 14 generally has a large temperature characteristic, it is necessary to perform some temperature compensation in order to stabilize the optical output power with respect to temperature. In order to perform this temperature compensation, the optical transmission circuit 15 uses an APC (Autom) to automatically stabilize the optical output power against fluctuations in temperature and the like.
atic Power Control) 22 is built in.

A more general method of temperature compensation is APC by negative feedback control. In order to perform the negative feedback control, it is necessary to detect the optical output of the laser diode 14. Therefore, by utilizing the feature that the laser diode 14 outputs the forward light (transmitted to the transmission line) and the backward light, the backward light is received by the monitor photodiode 23 and the optical output of the laser diode 14 is detected. Monitor photodiode 2
3 is generally integrally mounted in the same package as the laser diode 14.

The light receiving current from the monitoring photodiode 23 is current-voltage converted by the preamplifier 24, passes through the inverter 25, and the peak of the voltage amplitude is detected by the peak detection circuit 26. The detection voltage of the peak detection circuit 26 is supplied to the operational amplifier 27. Operational amplifier 27
Are current source transistors Q3, Q6, Q7 so that the detection voltage of the peak detection circuit 26 becomes the same value as the reference voltage Vp.
Control each base input of. As a result, the drive current (Io + 2Io) of the laser diode 14 is controlled, and the optical output of the laser diode 14 is stabilized.

Referring again to FIG. 1, laser diode 14
Then, an optical signal is generated by the intensity modulation method based on the characteristics of the drive current and the emission power shown in FIG. This optical signal is transmitted to the receiving system via the optical fiber 16 forming the optical transmission path. In the receiving system, the transmitted optical signal is received by the photodiode 17, which is a light receiving element. The photodiode 17 converts the received optical signal into a current signal. This current signal is sent to the optical receiver circuit (RA) 1
8 is supplied. The optical receiving circuit 18 is the photodiode 1
This is for obtaining the data component Vod and the clock component Voc based on the current signal from 7.

FIG. 4 shows an example of a concrete circuit configuration of the light receiving circuit 18. In FIG. 4, the optical receiving circuit 18 includes a preamplifier 41 for converting a current signal from the photodiode 17 into a current-voltage, and an AGC amplifier 42 having a predetermined time constant.
A comparator 43 for comparing the output voltage vo of the AGC amplifier 42 with the voltage discrimination level Vth2, and the AGC amplifier 4
2 and the comparator 44 for comparing the output voltage vo of the second output with the voltage discrimination level Vth3. Voltage identification level Vt
h2 and Vth3 are set so as to have the relationship shown in FIG. 5A with respect to the output voltage vo of the AGC amplifier 42.

Consequently, the comparator 43 extracts the clock component Voc by comparing the output voltage vo of the AGC amplifier 42 with the voltage discrimination level Vth2. Also,
The comparator 44 extracts the data component Vod by comparing the output voltage vo of the AGC amplifier 42 with the voltage discrimination level Vth3. Waveforms of the clock component Voc and the data component Vod are shown in FIG. On the other hand, in the AGC amplifier 42, when the data component Vod is extracted by the comparator 44, it is necessary to hold the peak value of the received data output of the AGC amplifier 42 for a long time, so that the time constant is set large. .

The data component Vod output from the optical receiving circuit 18 becomes the data (D) input of the DF / F 19 as the data reproducing circuit, and the clock component Voc is delayed by the delay circuit 20 for a predetermined time. DF / F19
The clock (CK) is input, and is directly output as a clock signal CO to the outside. DF / F19
Is a clock component Voc slightly delayed by the delay circuit 20.
The original data signal is reproduced by setting up / holding the data component Vod in synchronization with, and its Q output is used as the data signal DO. Waveforms of the clock signal CO and the data signal DO are shown in FIG.

Now, the necessity of giving a slight delay to the clock component Voc by the delay circuit 20 will be described. The original data signal is reproduced on the time axis by the DF / F19. At this time, the setup time and the hold time of the DF / F19 are required to properly distinguish the input data with the clock component. It is necessary to give a time margin to. Therefore, a time margin is given to the clock component Voc by passing it through the delay circuit 20. Assuming a general DF / F, the delay amount is T / 4, where T is one clock length, the optimum delay amount.

As described above, the drive current (Io + 2I) obtained by adding the modulation current Io corresponding to the input data signal DI and the modulation current 2Io corresponding to the input clock signal CI.
The laser diode 14 is driven by o) and the optical signal emitted from the laser diode 14 is transmitted to the optical fiber 1
While transmitting via 6, the photodiode 17 receives the optical signal, the optical receiving circuit 18 extracts the data component Vod and the clock component Voc from the received output, and the data signal DO is output based on the clock component Voc. By reproducing the data, data can be reproduced without using a clock recovery circuit having a complicated circuit configuration as in the past.

Next, an application example in the case of being adopted for inter-device parallel optical transmission such as interconnection parallel optical transmission between digital electronic exchanges will be described. When performing parallel optical transmission, each channel data may be independent on the time axis or may have a relationship on the time axis between the channels. FIG. 6 is a block diagram showing another embodiment of the present invention applied when each channel data is independent on the time axis.

In this parallel optical transmission system, as is apparent from FIG. 6, N transmission systems and reception systems of FIG. 1 are arranged in parallel as they are, and N input data signals DI1 to DIn are input clock signals CI1. .About.CIn are transmitted via N optical fibers 16-1 to 16-n. The parallel number N (N is an integer) at this time is N ≧ 1, and it is applicable to single transmission. However, when N = 1, the configuration itself is as shown in FIG. As described above, by adopting a configuration in which N transmission systems and reception systems in FIG. 1 are arranged in parallel as they are, a large amount of data can be transmitted between the devices with a simple circuit configuration.

FIGS. 7 and 8 are configuration diagrams showing still another embodiment of the present invention applied when the respective channel data have a relationship on the time axis between the respective channels,
FIG. 7 shows the configuration of the transmission system, and FIG. 8 shows the configuration of the reception system.

First, in the transmission system of FIG. 7, the frame generation circuit 71 generates the reference frame signal F0 based on the reference clock signal CK0, and the reference frame signal F0 is supplied to the frame insertion circuits 72-1 to 72-n. The input data signals D1 to Dn are inserted at the same timing. Each input data signal D1 to Dn in which the reference frame signal F0 is inserted
Is the first drive circuit (T11 to Tn1) 11-1 to 11-n
Is supplied to. Further, the reference transmission clock signal CK0 ′ based on the reference clock signal CK0 is supplied to the second drive circuit (T
12-Tn2) 12-1 to 12-n.

Subsequent circuit configurations and circuit operations are similar to those in the embodiment of FIG. That is, the reference frame signal F0 is inserted and the modulation current corresponding to each of the input data signals D1 to Dn and the modulation current corresponding to the reference transmission clock signal CK0 'are added by the adders 13-1 to 13-n. The laser diode 14-1 is driven by the driving current which is the addition current
~ 14-n are driven. Then, the laser diode 14
-1 to 14-n, the optical signals emitted from each optical fiber 16
It is transmitted to the receiving system via -1 to 16-n.

A clock transmission system is provided in addition to the N data transmission systems. That is, the reference transmission clock signal CK0 'is the first drive circuit (T01) 11-0.
Then, the reference frame signal F0 is changed to the second drive circuit (T02).
12-0 are supplied to the respective input data signals D1 to D
The reference frame signal F0 is inserted into the reference transmission clock signal CK0 'together with n at the same timing.
That is, the modulation current according to the reference transmission clock signal CK0 'and the modulation current according to the reference frame signal F0 are added by the adder 13-0, and the laser diode 14-0 is driven by the driving current which is the addition current. To be done. And
The optical signal emitted from the laser diode 14-0 is transmitted to the receiving system via the optical fiber 16-0.

Next, the circuit configuration of the receiving system will be described. In the receiving system, the optical fibers 16-1 to 16-n, 16
Each optical signal transmitted via -0 is a photodiode 17
Light is received at -1 to 17-n and 17-0. Photodiode 17
The output signals of -1 to 17-n and 17-0 are output to the optical receiving circuit (RA
1 to RAn) 18-1 to 18-n, 18-0, and further DF / F 19-1 to 19-n, 19-0 and delay circuit 2
The data signal including the frame signal F0 and the clock signal are reproduced by passing through 0-1 to 20-n and 20-0. The regenerated data signal and clock signal are
It is supplied to the frame separation circuits 81-1 to 81-n, 81-0.

The frame separating circuits 81-1 to 81-n are a synchronizing circuit for separating the frame signal F0 from the received data signal and separating the data signal, the clock signal and the frame signal from which the frame signal F0 is separated. It is supplied to elastic stores (hereinafter, abbreviated as ES) 82-1 to 82-n. On the other hand, the clock signal separated by the frame separation circuit 81-0 is output as it is to the outside as the clock signal CK0 and further ES82-1 together with the reference frame signal F0.
~ 82-n.

Here, a specific configuration of the ESs 82-1 to 82-n will be described. Since all ESs 82-1 to 82-n have the same configuration, ES82-1 will be described below as an example. This ES82-1 is a serial / parallel (S / S) that converts serial data into parallel data.
P) conversion circuit 83, parallel / serial (P / S) conversion circuit 84 for converting parallel data into serial data again,
A memory (MEM) 85 for temporarily storing data and a write address counter (WA
C) 86 and a read address counter (RCA) 87 which controls reading.

The serial / parallel conversion circuit 83 operates in synchronization with the clock signal CK1 transmitted by being superimposed on the data signal, and the parallel / serial conversion circuit 84 synchronizes with the clock signal CK0 transmitted separately from each data signal. And work. Further, the write address counter 86 operates in synchronization with the frame signal F1 inserted into the data signal and transmitted,
The read address counter 87 operates in synchronization with the reference frame signal F0 transmitted by being superimposed on the clock signal CK0.

In ESs 82-1 to 82-n having the above structure,
It is necessary to establish bit synchronization (change points of each data and reference clock are aligned) in order to prevent bit error due to double reading or data loss with respect to transmission delay variation of each data signal transmitted in parallel. is there. Therefore, the serial / parallel conversion circuit 83 serially / parallel converts each data to relatively suppress the transmission delay variation and perform the timing identification with the reference transmission clock signal CK0 with the phase margin increased. After that, the parallel / serial conversion circuit 84 is again used.
Parallel / serial conversion is carried out, and each parallel data is restored to establish bit synchronization.

Next, in each ES 82-1 to 82-n, the write address counter 86 is operated by the frame signals F1 to Fn separated from the data signals transmitted in parallel, while being transmitted together with the reference transmission clock signal CK0. The read address counter 87 with the reference frame signal F0
Is operated to write / read each data signal in the memories 82-1 to 82-n. Thereby, the phase synchronization of the data signals transmitted in parallel is established according to the reference frame signal F0. That is, the arrangement relationship of the data on the time axis is uniform among the channels.

As described above, in the inter-device parallel optical transmission system, the reference frame signal F is added to each of the data signals D1 to Dn.
While inserting 0, the reference transmission clock signal CK0 is superposed and transmitted, while the reference frame signal F0 is superposed on the reference transmission clock signal CK0 and transmitted in another system, and the receiving system includes ES82-1 to 82-n. By providing the bit synchronization and the phase synchronization of the data of each channel, skew-free parallel optical transmission can be performed regardless of the transmission distance.

[0043]

As described above, according to the optical transmission method and device of the present invention, light is emitted by the drive current obtained by adding the modulation current according to the data signal and the modulation current according to the clock signal. While driving the element and transmitting the optical signal emitted from this light emitting element via the optical transmission line, the optical signal passing through the optical transmission line is received by the light receiving element, and the data component and the clock are output from the output signal of this light receiving element. By extracting the component and reproducing the data signal based on this data component and clock component, it is possible to reproduce the data signal without using a clock recovery circuit with a complicated circuit configuration as in the past Optical transmission becomes possible with various circuit configurations.

Further, according to another optical transmission method and apparatus according to the present invention, a reference frame signal is inserted into each of a plurality of data signals, and a reference clock signal is further superimposed to be passed through a plurality of optical transmission lines. The reference clock signal is superimposed on the reference clock signal through a different optical transmission line and transmitted, while the optical signals that have passed through the multiple optical transmission lines are received by multiple light receiving elements A data component and a clock component are extracted from the output, a plurality of data signals are reproduced based on the data component and the clock component, and an optical signal that has passed through another optical transmission path is received by a light receiving element,
A clock component and a frame component are extracted from the received light output, a reference clock signal and a reference frame signal are reproduced based on the clock component and the frame component, and reproduced based on the reproduced reference clock signal and the reference frame signal. Moreover, since the bit synchronization and the phase synchronization of the plurality of data signals are achieved, skew-free parallel optical transmission can be performed regardless of the transmission distance.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing an example of an optical transmission circuit.

FIG. 3 is a characteristic diagram of drive current vs. emission power of a laser diode.

FIG. 4 is a circuit diagram showing an example of a light receiving circuit.

FIG. 5 is a waveform diagram of each part of the reception system.

FIG. 6 is a configuration diagram showing another embodiment of the present invention.

FIG. 7 is a configuration diagram (1) showing still another embodiment of the present invention.

FIG. 8 is a configuration diagram (2) showing still another embodiment of the present invention.

FIG. 9 is a configuration diagram showing a conventional example.

FIG. 10 is a characteristic diagram of drive current vs. emission power of a laser diode.

FIG. 11 is a block diagram showing an example of an optical receiving circuit.

FIG. 12 is a block diagram showing an example of a clock recovery circuit.

FIG. 13 is a block diagram showing another example of the clock recovery circuit.

FIG. 14 is a configuration diagram showing another conventional example.

FIG. 15 is a waveform chart of each part of FIG.

[Explanation of symbols]

 11, 11-0 to 11-n First drive circuit 12, 12-0 to 12-n Second drive circuit 14, 14-0 to 14-n Laser diode 15 Optical transmission circuit 16, 16-0 to 16 -n optical fiber 17, 17-0 to 17-n photodiode 18, 18-0 to 18-n optical receiver circuit 19, 19-0 to 19-n D-type flip-flop 20, 20-0 to 20-n delay circuit 71 frame generation circuit 72-1 to 72-n frame insertion circuit 81-0 to 81-n frame separation circuit 82-1 to 82-n elastic store

Claims (8)

[Claims] 1. A light emitting element is driven by a drive current obtained by adding a modulation current according to a data signal and a modulation current according to a clock signal, and an optical signal emitted from this light emitting element is passed through an optical transmission line. While transmitting the optical signal through the optical transmission line, the optical signal is received by the light receiving element, the data component and the clock component are extracted from the output signal of the light receiving element, and the data signal is reproduced based on the data component and the clock component. An optical transmission method comprising: 2. An optical transmission method, wherein a plurality of data signals are transmitted in parallel by using the optical transmission method according to claim 1. 3. A reference frame signal is inserted into each of a plurality of data signals, and a modulation current according to the plurality of data signals in which the reference frame signal is inserted and a modulation current according to a reference clock signal are added. The plurality of light emitting elements are driven by each of the drive currents obtained by the above, the optical signals emitted from the plurality of light emitting elements are transmitted through the plurality of optical transmission lines, and the modulation is performed according to the reference clock signal. A light emitting element is driven by a drive current obtained by adding a current and a modulation signal corresponding to the reference frame signal, and an optical signal emitted from the light emitting element is transmitted through an optical transmission path different from the plurality of optical transmission paths. On the other hand, each optical signal transmitted through the plurality of optical transmission lines is received by a plurality of light receiving elements, and a data component and a clock component are extracted from each output signal of the plurality of light receiving elements. Output, reproduces a plurality of data signals based on the data component and the clock component, receives the optical signal that has passed through the other optical transmission line by the light receiving element, and outputs the clock component and the frame component from the output signal of the light receiving element. Extract and reproduce the reference clock signal and the reference frame signal based on the clock component and the frame component, and the bit synchronization and the phase of the reproduced data signals based on the reproduced reference clock signal and the reference frame signal. An optical transmission method characterized by synchronization. 4. An optical transmission circuit for driving a light emitting element by a drive current obtained by adding a modulation current according to a data signal and a modulation current according to a clock signal, and transmitting an optical signal emitted from the light emitting element. And an optical receiving circuit that receives an optical signal transmitted through the optical transmission line with a light receiving element and extracts a data component and a clock component from an output signal of the light receiving element, the optical receiving circuit An optical transmission device, comprising: a data reproduction circuit that reproduces a data signal based on the data component and the clock component extracted in. 5. The optical transmission device according to claim 4, further comprising a delay circuit that delays the clock component extracted by the optical receiving circuit by a predetermined time and applies the delayed clock component to the data reproducing circuit. 6. An optical transmission device comprising a plurality of the optical transmission devices according to claim 4 or 5 arranged in parallel. 7. A frame generation circuit for generating a reference frame signal, a plurality of frame insertion circuits for inserting the reference frame signal into each of a plurality of data signals, and a plurality of the plurality of reference frame signals inserted therein. A plurality of first optical transmission circuits for driving a plurality of first light emitting elements by each of drive currents obtained by adding a modulation current corresponding to each data signal and a modulation current corresponding to a reference clock signal A plurality of optical transmission lines for respectively transmitting the respective optical signals emitted from the plurality of first light emitting elements, a modulation current according to the reference clock signal and a modulation current according to the reference frame signal. A second optical transmission circuit that drives a second light emitting element by a drive current obtained by adding and a plurality of optical transmission lines that transmit the optical signal emitted from the second light emitting element are separated. An optical transmission line and a plurality of first optical receivers for receiving each optical signal passing through the plurality of optical transmission lines by a plurality of light receiving elements and extracting a data component and a clock component from each output signal of these light receiving elements. Circuit, and a plurality of data reproductions for reproducing a plurality of data signals based on the data component and the clock component extracted by each of the plurality of first optical receiving circuits and separating a frame signal from each data signal. A circuit, a second optical receiving circuit that receives an optical signal that has passed through the other optical transmission line with a light receiving element, and extracts a clock component and a frame component from an output signal of the light receiving element; and the second optical receiving circuit A signal reproduction circuit for reproducing the reference clock signal and the reference frame signal based on the clock component and the frame component extracted in 1., and the reference clock reproduced by the signal reproduction circuit An optical transmission device comprising: a plurality of synchronizing circuits for performing bit synchronization and phase synchronization of a plurality of data signals reproduced by the plurality of data reproducing circuits based on a signal and a reference frame signal. 8. A serial / serial converter for serially / parallel-converting the data signal reproduced by the data reproducing circuit in synchronization with the clock component extracted by the first optical receiving circuit. A parallel conversion circuit, a parallel / serial conversion circuit for converting output data of the serial / parallel conversion circuit into parallel / serial conversion in synchronization with the reference clock signal reproduced by the signal reproduction circuit, and the parallel / serial conversion circuit Memory for storing the data, a write control circuit for controlling the writing of the memory in synchronization with the frame signal separated by the data reproducing circuit, and the memory for synchronizing with the reference frame signal reproduced by the signal reproducing circuit. 8. The optical transmission device according to claim 7, further comprising a read control circuit for performing read control of the.