JPH1098439A - Optical signal transmitter, optical signal receiver and optical signal transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent phase difference mutually between data and clocks by modulating respectively allocated carrier waves with plural pieces of digital data, multiplexing the frequencies of provided plural modulated waves with clocks and sending them through a light emitting element to one transmission line. SOLUTION: At an optical transmission submodule 11(1), data modulation circuits A1-AN respectively modulate prescribed subcarriers F1-FN with parallel digital data f1-fn inputted to input terminals and output them through respectively correspondent filters FIL and delay elements TT1-TTN to a frequency multiplexer circuit 11A. A clock signal fCLK inputted to the input terminal is sent through the filter FIL and a delay element TTCLK to the frequency multiplexer circuit 11A. The frequency multiplexer circuit 11A multiplexes the frequencies of these inputs, drives a light emitting diode LD1 of an LD array 12 through an LD driver 11B and sends out a signal to an optical fiber 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal transmitting device and an optical signal receiving device, and can be applied to, for example, devices interconnected via an optical fiber. Further, the present invention relates to an optical signal transmitting / receiving apparatus, and can be applied to, for example, an apparatus having an integrated transmitting / receiving unit for transmitting / receiving an optical signal via an optical fiber.

[0002]

2. Description of the Related Art Today, there is an increasing demand for higher speed / larger capacity transmission systems. Along with this,
Research and development in each institution is further intensified, and, for example, a technique for connecting between boards of a computer or a frame of an electronic exchange via an optical fiber to perform multi-channel optical transmission has been developed. Related documents are shown below.

Document name: 1994 IEICE Spring Conference B-1102 Evaluation of transmission module for multi-channel optical transmission B-1103 Evaluation of reception module for multi-channel optical transmission Discloses a method of transmitting / receiving a plurality of data multiplexed / encoded or demultiplexed / decoded and a clock in parallel via a plurality of optical fibers.

[0004]

However, in order to avoid the influence of skew (mainly, the propagation delay difference between optical fibers), it is required to transmit a plurality of parallel signals and clocks without signal conversion as they are. In some cases, parallel data transmitted between a plurality of optical fibers cannot be overshot by the same clock. In the apparatus having the above configuration, the input parallel data is multiplexed / encoded and the output data is separated / composited. However, both the electronic circuit and the power consumption increase, and depending on the amount of skew, serial (one fiber) is used. However, there is a drawback that the same electronic circuit and power consumption as those for transmitting the data are required.

In transmitting data, if a pattern of 0 or 1 is continuous, it is necessary to widen the band of the transmission module or encode the transmission module. For this reason, when the pattern continuity cannot be predicted, there is a disadvantage that the bandwidth of the transmission module must be designed from DC or an electronic circuit for encoding such as data scrambling is required. Was.

[0006]

According to the present invention, there is provided an optical signal transmitting apparatus for transmitting a clock and a plurality of digital data, which comprises the following means.

That is, (1) a plurality of data modulating means corresponding to each of a plurality of digital data and modulating a carrier wave assigned to each digital data with the digital data and outputting, and (2) a plurality of data modulating means. It is characterized by comprising: frequency multiplexing means for frequency-multiplexing and outputting a modulated carrier wave and a clock; and (3) a light emitting element driven based on the output of the frequency multiplexing means.

As described above, in the optical signal transmitting apparatus according to the present invention, the carrier wave modulated by the digital data and the clock are frequency-multiplexed and transmitted to one transmission line. It is possible to prevent a phase difference from occurring between the data and between the data and the clock.

An optical signal receiving apparatus for demodulating a clock and a plurality of digital data from a received optical signal is characterized by including the following means.

That is, (1) light receiving means for receiving an optical signal obtained by frequency-multiplexing a clock and a plurality of modulated waves and converting the signal into an electric signal; and (2) an electric signal output from the light receiving means based on a frequency band. Frequency separating means for separating a clock and a plurality of modulated waves, and (3) a plurality of demodulating and outputting the original digital data used for modulating the modulated wave from each modulated wave corresponding to each of the plurality of modulated waves. And data demodulating means.

As described above, in the optical signal receiving apparatus of the present invention, the clock and a plurality of modulated waves are separated from the frequency multiplexed signal transmitted through one transmission line, and the original digital data is demodulated therefrom. By doing so, it is possible to eliminate the influence of the transmission delay difference between the transmission paths as in the case where a plurality of transmission paths are used and the skew between the data and the clock.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) First Embodiment Hereinafter, a first embodiment in which the present invention is applied to an optical parallel transmission apparatus that transmits and receives an optical signal via an optical fiber will be described with reference to the drawings.

(A-1) Configuration of First Embodiment (A-1-1) Overall Configuration FIG. 2 shows a basic configuration of an optical parallel transmission apparatus according to the first embodiment. As shown in FIG. 2, the optical parallel transmission device includes an optical transmission module 10 and an optical reception module 20, and a tape optical fiber 30 connecting these modules.

First, the configuration of the optical transmission module 10 of the two optical modules will be described with reference to the block diagram of FIG. The optical transmission module 10 is characterized in that parallel digital data and a clock signal, which have been conventionally transmitted separately, are frequency-multiplexed and transmitted.

As shown in FIG. 1, the optical transmission module 10
Are N optical transmission submodules 11 (1) to 11 (1) to 11
(N) and the LD array 12. Each of the N optical transmission sub-modules 11 (i) (i = 1 to N) has an input terminal for inputting parallel digital data f1 to fN and a clock signal fCLK.

The optical transmission sub-module 11 (i) inputs the parallel digital data f1 to fN input to these input terminals to the corresponding data modulation circuits A1 to AN, respectively, and outputs the clock signal fCLK to the corresponding filter FIL.
To enter. Note that each of the data modulation circuits A1 to AN includes:
Predetermined subcarriers F1 to FN are input from corresponding subcarrier generation circuits F1 to FN. Each of the data modulation circuits A1 to AN modulates the subcarriers F1 to FN with each digital data, and modulates the subcarriers F1 to FN with the corresponding filter FI.
Output to L.

The filter FIL includes subcarriers F1 to F1.
The outputs corresponding to FN are respectively output to delay elements TT1 to TT
The signal is output to the frequency multiplexing circuit 11A through N and TTCLK.

The frequency multiplexing circuit 11A includes a delay element TT1
To TTN and TTCLK are frequency-multiplexed and supplied to the LD driver 11B to drive the LD driver. The output of this LD driver 11B is used as the output of each optical transmission sub-module 11 (i) as the LD array 12B.
Is output to

As the LD array 12, an array of a plurality of N light emitting diodes LD1 to LDN corresponding to the respective optical transmission submodules 11 (1) to 11 (N) is used. Note that a collection of individual LDs may be used. In any case, each of the light emitting diodes LD1 to LDN is driven by the output of each of the optical transmission submodules 11 (1) to 11 (N). The light outputs of the light emitting diodes LD1 to LDN are input from one end of the tape optical fiber 30 and transmitted to the other end. Although a tape optical fiber is used here, an individual fiber may of course be used.

Next, the configuration of the optical receiving module 20 will be described. As shown in FIG. 3, the optical receiving module includes a plurality of optical receiving sub-modules 21 (1) to 21 (N),
And a D array 22.

The PD array 22 is formed by integrally integrating a plurality of photodiodes PD1 to PDN, and is connected to the other end of the tape optical fiber 30. Of course, the photodiodes PD1 to PDN may be a collection of individual photodiodes. In any case,
The photodiodes PD1 to PDN photoelectrically convert an optical signal transmitted via the tape optical fiber 30 and supply the optical signal to an input terminal of a corresponding optical receiving submodule 21 (i) (i = 1 to N).

The optical receiving submodule 21 (i) (1
N) are the corresponding photodiodes PD1 to PD
The output of the DN is input to the PD driver 21A. here,
The PD driver 21A includes photodiodes PD1 to PD
N is a circuit that supplies power to N and amplifies and outputs only the AC signal component of the photoelectrically converted signal. The PD driver 21A supplies the amplified signal to the frequency separation circuit 21B and to a DC level detection circuit 21C described later.

The frequency separation circuit 21B separates the input signal into a signal component corresponding to parallel digital data and a signal component corresponding to a clock signal. The signal component corresponding to the parallel digital data is a data demodulation circuit B1.
To BN, and a signal component corresponding to the clock signal is directly supplied to the limiter amplifier LAMP.
Given to AMP. The data demodulation circuits B1 to BN
Operates to demodulate digital data by comparing the input signal with a predetermined threshold.

The output of the limiter amplifier LAMP is delayed by the corresponding delay elements TR1 to TRN and TRCLK, and then output from the output terminal as parallel digital data f1 to fN and a clock signal fCLK.

The above-described DC level detection circuit 21C
In this example, the DC level included in the output of the PD driver 21A is detected.
Has been given to. Further, the threshold generation circuit 21D
A threshold value corresponding to the detected DC level is generated and applied to each of the data demodulation circuits B1 to BN.

(A-1-2) Detailed Configuration of Each Part Next, a specific detailed configuration of the optical transmission sub-optical transmission sub-module 11 (i) and the optical reception sub-module 21 (i) will be described.

First, the optical transmission sub-optical transmission sub-module 1
The configuration of 1 (i) will be described with reference to FIG. This figure 4
Are data modulation circuits A1 to AN, frequency multiplexing circuit 11A
4 shows the circuit configuration and connection configuration of the LD driver 11B in detail. In FIG. 4, only two of the N data modulation circuits A1 to AN are shown.

The data modulation circuit A comprises a source-grounded field effect transistor FET. Here, predetermined frequency-multiplied signals (represented by frequency multiplications 1 and 2 in the figure) are applied to the drain of the field-effect transistor FET from the corresponding subcarrier generation circuit F, respectively. Receive data modulation.

This modulation is realized by the impedance change of the field effect transistor FET according to the digital data. That is, 0 [V] to -4 [V] are applied to the gate.
Is applied, the impedance of the field effect transistor FET changes from approximately 0 to approximately infinity. This change in impedance appears as a change in drain current. When the drain current is 0, the frequency-multiplied signal remains unchanged, and when the drain current flows, a signal attenuated by the voltage drop generated in the resistor R1 is used as the filter FIL and the delay circuit T. Is applied to

The LD driver 11B includes a light emitting diode L
A resistor R3 and an inductance L connected in series with D
1 and a current source I1, a resistor R3 and an inductance L
At the connection midpoint of No. 1, the modulation signal is frequency-multiplexed from each frequency multiplexing circuit 11A. That is, this connection midpoint functions as the frequency multiplexing circuit 11A. The above is the configuration of the optical transmission sub-optical transmission sub-module 11 (i).

Next, the configuration of the optical receiving sub-module 21 (i) will be described. The configuration of the optical receiving sub-module 21 (i) will be described with reference to FIG. FIG. 5 shows a detailed circuit configuration and connection configuration of the PD driver 21A, the data demodulation circuits B1 to BN, the DC level detection circuit 21C, and the threshold value generation circuit 21D. In FIG. 5, N
Only two of the data demodulation circuits B1 to BN are shown.

The PD driver 21A has an input terminal connected to the anode of the photodiode PDC. One electrode of the capacitor CC1 and one end of the resistor RC1 are connected to the input. A signal current corresponding to the amount of light received by the photodiode PDC flows through the resistor RC1, and a signal corresponding to the current is applied to the operational amplifier circuit AMP via the capacitor CC1. Note that the output of the operational amplifier circuit AMP is provided to the input terminal of the frequency separation circuit 21B.

The frequency separation circuit 21B is configured by connecting in parallel the number of band-pass filters BPF corresponding to the number of parallel receptions (N in this example), and a PD driver 21A provided to an input terminal.
Is input to each band-pass filter BPF in parallel, thereby separating a frequency signal component corresponding to each subcarrier F. Each band-pass filter BPF may be made of a combination of a plurality of resistors, capacitors, and inductances, or may be a band-pass filter such as a saw filter. In any case, each bandpass filter B
The signal separated by the PF is supplied to the input terminal of the corresponding data demodulation circuit B.

The data demodulation circuit B comprises a detection circuit comprising a diode PC1, a smoothing circuit comprising a capacitor CC2 and a resistor RC6, and a comparison circuit. The diode PC1 inputs the input from the previous stage to the anode. One end of the capacitor CC2 and one end of the resistor RC6 are connected to the cathode of the diode PC1, and a half-wave rectified output is applied.

The smoothed output is input to a comparison circuit having a differential amplifier circuit configuration. Here, the smoothed signal is input to the base of the NPN transistor TR5.
On the other hand, a reference K serving as a reference for data demodulation is input from the threshold value generation circuit 21D to the base of an NPN transistor TR6 forming a differential pair with the transistor TR5.
The differential pair performs a switching operation in accordance with the magnitude relationship between the reference K and the smoothed signal. When the smoothed signal is larger, a current flows through the load resistor RC7.
8 so as to flow a current. That is, when the smoothed signal is larger than the reference K, the transistor TRC
4 outputs an “H” level signal, and the transistor TRC3 outputs an “L” level signal.

The DC level detection circuit 21C includes a low-pass filter (a resistor RC2, a transistor TRC1, a resistor RC3, and a capacitor CC3) for detecting a DC component of the converted current received from the cathode of the photodiode PDC, and outputs the detected DC current. A current mirror circuit (transistors TRC1, TRC1
C2, resistors RC3 and RC4).

The threshold value generating circuit 21D comprises a resistor RC5 for converting a current turned back by the current mirror circuit constituting the DC level detecting circuit 21C into a voltage. Note that one end of the resistor RC5 is connected to the collector of the PNP transistor TRC2, and the other end is grounded.

(A-2) Operation of the First Embodiment Before describing the transmission operation by the optical parallel transmission apparatus having the above configuration, the effect of the transmission delay will be described.

In general, the electric processing in the apparatus is often a multiple of 8, such as 8 bits, 16 bits, 32 bits, and the like. Further, since data has a meaning as a unit of a multiple of 8 bits, a falling edge of a signal having a frequency twice as high as that of data, which is generally called a clock, is adjusted to approximately the center of the data to determine High / Low of the data.

For this reason, if there is a transmission delay difference between the data and the clock, and between the data and the data, the data may be erroneously read. The transmission delay difference is caused not only by the delay difference of the electric element and the optical element itself, but also by the difference in the line length of the electric wire or the optical fiber, and the slight difference in the permittivity and the magnetic permeability due to the difference in production. There is a delay difference. Incidentally, since the delay difference is proportional to the distance, it is difficult to compensate for the difference by the transmission / reception device.

FIG. 6 shows an example of the input digital data f1 to fN, and the effect of the delay difference occurring in the input digital data f1 to fN will be described. For example, as shown in the upper part of FIG. 6, even when the relationship between the data and the clock is uniform at the time of input, if there is a shift as shown in the lower part of FIG. Cannot be recognized.

That is, the digital data f1 having the data “1” at the place where the data “1” should be read can be read, but the digital data f2 can be read.
With regard to, the correct data cannot be read because the data of "2" exists in the place where the data of "l" should be read. In addition, the digital data fN cannot recognize the digital data fN because the clock falls at the data break.

It is a feature of the optical parallel transmission apparatus according to the present embodiment that such a situation can be effectively avoided. Here, the digital data inputs f1 to fN of FIG.
The case where the digital data input is input will be described as an example.

The clock signal fCLK input together with the digital data inputs f1 to fN is applied to the filter FIL, and is converted into only a clock signal component (sine wave).
On the other hand, the digital data inputs f1 to fN are input to the corresponding data modulation circuits A1 to AN, respectively, and are used for modulating the corresponding subcarriers F1 to FN. Here, the subcarriers F1 to FN are signals (carriers) for transmitting data, and are generated by individual transmitters or multiplied by the clock frequency. The data modulation circuits A1 to AN are field-effect transistors FET
The digital data input to one of the gates modulates the subcarrier applied to the drain.

In this modulation, when the potential of the digital data input is lowered, the impedance of the field-effect transistor FET increases and the drain current decreases. On the other hand, when the potential of the digital data input is increased, the potential of the field-effect transistor FET increases. A characteristic in which the impedance is reduced and the drain current increases is used. That is, when the drain current is small, the amplitude of the subcarrier signal is output almost as it is, and when the drain current is large, it is attenuated and output by the resistor R1.

Accordingly, a subcarrier signal amplitude-modulated by the digital data signal appears at the drain of the field effect transistor FET1. Note that an extra signal included in the subcarrier signal, that is, a low frequency component (particularly, a DC component) is removed by the capacitor CB1.

This signal is frequency-multiplexed through a filter FIL and a delay element T for correcting a delay difference between the time when the digital data is input to the input terminal and the time when the signal is frequency-multiplexed. Of course, this is not necessary if there is no delay difference due to routing or the like. Here, assuming that the frequency of the amplitude modulation is F and the frequency of the subcarrier is F, and the modulation frequency is f, the relationship between the amplitude and time of the subcarrier and the modulated wave can be expressed by the following equations (1) and (2).

Y = acos2πFt (1) y = bcos2πft (2) Here, the amplitude modulation of the subcarrier by the modulation wave is as follows.
Since the amplitude of the subcarrier is shown as a + bcos 2πft, this is replaced with a in equation (1), and the following equation (3) is obtained.

Y = (a + bcos2πft) cos2πFt = acos2πFt + bcos2πftcos2πFt = acos2πFt + b / 2 (cos2π (F + f) + cos2π (F-f) t (3) Equation (3) is shown only for the relationship between frequency and amplitude. Here, the modulation frequency is f
Therefore, a band of F ± f is required. By the way, the actual modulation wave frequency f is a rectangular wave,
Although a harmonic component is included, only a sine wave component is transmitted. This sine wave can be made closer to the original rectangular wave if the rising of the waveform is made faster and the level is made constant by a limiter amplifier after data demodulation described later.

Next, an example of band allocation after frequency multiplexing by the frequency multiplexing circuit 11A designed based on the above-described amplitude modulation will be described. First, FIG. 8 shows a first band allocation example. Here, F1, F2,... FN indicate the subcarrier frequencies, fCLK indicates the clock frequency, and x2, x3.
The frequency is twice, three times,... N times. Also, FI
L1, FIL2... FILN indicate the band of the band-pass filter assigned to each channel. FIG.
Actually describes the band of the filter, so in practice, a frequency width is required between each filter.

Next, FIG. 9 shows a second band allocation example. This band allocation example is an example in which only one sideband of amplitude modulation is transmitted. By transmitting only one sideband in this way, it is possible to effectively use the frequency.

FIG. 10 shows a third band allocation example. This band allocation example is an example in which a clock signal is transmitted at a half frequency. In this case, on the receiving side, the exclusive OR (EX-O) of the transmission signal and the signal delayed by the clock width is used.
If R) is obtained, not only can the clock signal be reproduced, but also the frequency separation between the clock frequency and the first carrier can be made large, so that frequency separation becomes easy.

In any case, a multiplexed signal of a clock and a plurality of data generated in each optical transmission sub-module is subjected to electro-optical conversion by each of the laser diodes LD1 to LDN and output to the tape optical fiber 30. . The above is the operation of the optical transmission module 10.

Next, this optical signal is transmitted to the tape optical fiber 3.
The operation of the optical receiving module 20 for receiving the signal via the “0” will be described. The optical signal is transmitted to each of the photodiodes PD1 to PD of the PD array 22 provided at the input stage of the optical receiving module 20.
After being photoelectrically converted by N, it is input to each of the corresponding optical receiving sub-modules 21 (i).

Each of the optical receiving sub-modules 21 (i) converts the AC signal component of the input signal into a PD driver 21 (i).
A is amplified at A and output to the frequency separation circuit 21B, while the DC signal component of the input signal is detected at the DC level detection circuit 21C, and is supplied to the threshold value generation circuit 21D, thereby performing the following. Generate a threshold voltage (reference K).

The frequency separation circuit 21B (having a band as shown in FIGS. 8 to 10) receives an AC signal from the PD driver 21A and converts the AC signal into a clock signal component and each data by a plurality of band-pass filters. Separate into signal components. The separated data signal components are input to data demodulation circuits B1 to BN, respectively.

The data demodulation circuits B1 to BN half-wave rectify the data-modulated and transmitted carrier with the diode DC1, and then shape the waveform with a smoothing circuit including the capacitor CC2 and the resistor RC6. The magnitude of the input signal level is determined by comparing the input signal level with a reference K by a comparator having a differential amplifier circuit configuration including TR6, resistors RC7, RC8, and a current source IC1. Here, when the input signal level is higher than the threshold voltage (reference K) generated by threshold generation circuit 21D, a signal of "H" level is output, and when it is lower, the signal of "L" level is output. Output a signal.

After that, the limiter amplifier LAMP shapes the waveform of the rising output data, and converts the output data into rectangular wave data with sharp rising. Then, delay circuits TR1 to TR provided at the subsequent stage of each limiter amplifier LAMP
The transmission skew in the optical receiving module is corrected by RN and TCLK. Needless to say, TR1 and the like are not required if no delay difference occurs due to wiring routing or wiring routing. In addition, it is also possible to omit the limiter and the delay circuit TR for each data by preparing a limiter amplifier only for the clock signal component and retiming each data.

The above is the operation content of the optical receiving module 20.

Finally, the relationship between the modulation factor and the threshold will be described with reference to FIG. Optical transmission module 1
As shown in FIG. 11, the signal transmitted from 0 is superimposed on a carrier modulated to a DC level. By the way, D
The C level and the degree of modulation of the carrier and the carrier are 1: a:
b.

After the optical signal thus modulated is attenuated in the transmission line, it enters the photodiode PD and is converted into a signal current. As described above, this signal current is supplied to the DC level detection circuit 21C and the PD driver 21A at the same level. If the transfer coefficient from the resistor RC1 to the transistor TR5 is set to 1, the reference K is set to the resistor RC5 so as to be between ab and a. In addition, when the transfer coefficient is n, it is set to be n times.

Here, from the DC level detection circuit 21C,
Since the distance from the PD driver 21A to the base of the transistor TR5 is linear between the reference K and the transistor TR5, even if the signal fluctuates according to the transmission distance, the reference K and the transistor TR5
The ratio of coming to the base does not change. That is, there is no need to adjust the reference level according to the transmission distance.

(A-3) Effects of the First Embodiment As described above, according to the first embodiment, a signal obtained by frequency-multiplexing a clock and data bundle as one unit is applied to one optical fiber. Input and transmit the signal, the transmission time difference between the optical fibers, which has been a problem when transmitting these signals through a plurality of optical fibers, especially the skew that increases in proportion to the transmission distance. It can be done without consideration.

Further, by setting the frequency band from the carrier wave to the modulation signal, the modulation signal can be transmitted from the DC level to the modulation frequency, so that it is not necessary to use a method of narrowing the band such as a scrambler. , Can greatly reduce the hardware.

Further, since the DC level to be transmitted is set as the threshold value, H / L can be determined regardless of the transmission distance. Even if the optical power fluctuates, the H / L can be determined within the time during which the threshold value follows (the time of the time constant of the DC filter). There is no need to control the temperature, and it is expected that the automatic optical power adjustment and the temperature control circuit will be eliminated.

Further, by transmitting the carrier wave to only one side, the frequency band can be saved, the frequency band of the laser, the photodiode, and the electronic circuit can be lowered, and inexpensive elements can be used. Of course, since the frequency band of one channel can be narrowed, the number of data channels can be increased accordingly.

(B) Second Embodiment Hereinafter, a first embodiment in which the present invention is applied to an optical parallel transmission apparatus for transmitting and receiving an optical signal via an optical fiber will be described with reference to the drawings.

(B-1) Configuration of the Second Embodiment The difference between the first embodiment and the second embodiment is that the amplitude modulation of subcarriers by digital data is multi-level modulation, and the frequency band is This is the point at which the efficiency was increased.
The multi-valued conversion is 4-valued for 2-bit data, 9-valued for 3-bit data, 16-valued for 4-bit data, and ideally infinitely possible. Will be described. FIG. 12 shows an example of multi-value conversion using two bits.

The possible values of the 2-bit data are A, B,
Place C and D. The 2-bit data may be converted into 2-bit data by serial-to-parallel conversion of one data, or any two pieces of parallel data may be used. FIG.
FIG. 1 shows an example of an implementation circuit for obtaining the multi-value data. Here, when the threshold values of a, b, and c are as shown in FIG. 14, A, B, C, and D have the relationship shown in the table of the output data realizing circuit of FIG.

From this, the input circuit can be constituted by a logical product (AND) circuit and an inverting (knot) circuit, and the output circuit is formed by a logical product (AND) circuit, an inverting (knot) circuit and a logical sum (OR) circuit. It turns out that it is composed. Since the output is in the same state as the output of A in the normal state, the circuit that outputs A among the output circuits can be deleted here.

The optical signal transmission using these circuits is the optical parallel transmission apparatus according to the present embodiment. Note that the configuration of the optical parallel transmission device is basically the same as the case of FIGS. 1 and 3 used in the description of the first embodiment. here,
Only different parts of the configuration will be described with reference to FIGS.

FIG. 15 shows a part of the configuration of the optical transmission sub-module according to the second embodiment.
(I), frequency multiplexing circuit 11A and LD driver 11B
FIG. On the other hand, FIG. 16 shows a part of the configuration of the optical receiving submodule according to the second embodiment, and includes a data demodulation circuit B (i) and a DC level detection circuit 2
1C shows a circuit example of a threshold generation circuit 21D. Note that the case of FIG. 16 differs from that of the first embodiment in that the circuits in the portion surrounded by the thick line are configured in parallel by the number of multi-values minus one.

(B-2) Operation of the Second Embodiment A transmission operation by the optical parallel transmission apparatus having the above configuration will be described.

First, the operation of the optical transmission module 10 will be described. First, 2-bit data is converted into a multi-level signal by the input circuit of FIG. For example, if both data 1 and data 2 are 1, A is converted, if data 1 is 1 and data 2 is 0, B is converted, and so on / off signals are applied to switches SW1 to SW4 in FIG. Is entered.

Note that one end of each of the switches SW1 to SW4 is connected to a power source V11 to V14 (V21) of -1 [V].
To V24), and a voltage corresponding to the number of closed switches is applied to the field effect transistor FET1 (FET1).
2) is applied to the gate.

That is, -1 [V] if the number of closed switches is one, -2 [V] if two, and -4 if four.
[V]. In this example, when the converted data is A, only one switch is closed and B
In the case of, only two switches are closed, and in the case of... D, only four switches are closed.

Accordingly, the current flowing through the field effect transistor FET1 (FET2) is increased or decreased according to the value of the multi-level signal, and a signal subjected to multi-level amplitude modulation appears at the drain as shown in FIG. . If this signal is frequency-multiplexed and applied to the laser diode LD (i), the first
As in the case of the first embodiment, transmission can be performed with a bundle of data and a clock signal as one unit.

Next, the operation of the optical receiving module 20 will be described. The optical receiving module 20 has three (= 4 value-1) circuit stages X each having a threshold value generating circuit 21D for generating different threshold values a, b, and c and a data demodulating circuit B (i). The signal current photoelectrically converted by the PD diode is input to Y and Z.

Here, the three circuit stages X, Y, and Z compare each signal current with threshold values a, b, and c, and output three outputs. The output circuit shown in FIG. 13 obtains four values of A, B, C, and D from these three outputs according to the conversion table of FIG. Note that the three thresholds represented by a, b, and c have the relationship shown in FIG.

As described above, according to the second embodiment,
Binary data multiplex transmission can be realized. This method is the same in the case of ternary, quaternary,..., And can be realized by increasing the number of circuits described above.

(B-3) Effects of Second Embodiment As described above, according to the second embodiment, in addition to the effects of the first embodiment, it is possible to further save the frequency band. This also reduces the burden of speeding up the element,
In addition, an increase in the number of data channels can be expected.

(C) Other Embodiments (C-1) In the above embodiments, the case of AM modulation has been described as a modulation method, but the present invention is not limited to this, and a carrier is used. For modulation, FM modulation, P
The present invention can be applied to various modulation schemes such as M modulation, QPSK modulation, and QAM modulation.

(C-2) In the above embodiment,
Although the data modulation circuit is constituted by a single-stage single-gate field-effect transistor, it can be applied to other types of field-effect transistors and other connections. For example, a multi-gate field effect transistor may be used, or two or more stages of field effect transistors may be connected in cascade.

(C-3) Further, in the above-described embodiment, the optical transmitting module and the optical receiving module connected via the optical fiber have been described. However, the transmitting / receiving module having these two modules in one housing is described. It can also be applied to devices.

(C-4) Furthermore, in the above-described embodiment, a general device for transmitting an optical signal in parallel via an optical fiber has been described. However, this includes a device such as a computer or an electronic exchange, or a device between these devices. And the case where the processing data is transmitted as is between the internal substrates.

[0086]

As described above, according to the present invention, a frequency multiplexed signal obtained by frequency multiplexing a modulated wave modulated by digital data and a clock is transmitted or received via one transmission line. By doing so, it is possible to prevent a phase difference from occurring between data used for modulating each modulated wave or between data and clock during transmission.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a functional configuration of an optical transmission module according to a first embodiment.

FIG. 2 is a block diagram illustrating an overall configuration of the optical parallel transmission device.

FIG. 3 is a block diagram illustrating a functional configuration of the optical receiving module according to the first embodiment.

FIG. 4 is a block diagram illustrating a main circuit configuration of the optical transmission submodule according to the first embodiment.

FIG. 5 is a block diagram illustrating a main circuit configuration of the optical receiving sub-module according to the first embodiment.

FIG. 6 is an explanatory diagram illustrating an example of digital data including a transmission skew.

FIG. 7 is an explanatory diagram illustrating a relationship between a subcarrier and a modulation frequency.

FIG. 8 is an explanatory diagram showing a first frequency allocation example after frequency multiplexing.

FIG. 9 is an explanatory diagram showing a second frequency allocation example after frequency multiplexing.

FIG. 10 is an explanatory diagram showing a third frequency allocation example after frequency multiplexing.

FIG. 11 is a signal waveform diagram illustrating a relationship between a modulation factor and a threshold value.

FIG. 12 is a chart showing a relationship between input data and multi-value output.

FIG. 13 is a logic block illustrating an input circuit and an output circuit of digital data.

FIG. 14 is a chart showing a relationship between input data and multi-value output.

FIG. 15 is a block diagram illustrating a main circuit configuration of an optical transmission sub-module according to a second embodiment.

FIG. 16 is a block diagram illustrating a main circuit configuration of an optical receiving sub-module according to a second embodiment.

[Explanation of symbols]

10 optical transmission module, 11 (1) to 11 (N) optical transmission submodule, 11A frequency multiplexing circuit, 11B
... LD driver, 12 LD array, A1 to AN data modulation circuit, FIL filter, TT1 to TTN, TT
CLK: delay circuit, 20: optical receiving module, 21
(1) to 21 (N) ... optical receiving sub-module, 21B ...
Frequency separation circuit, 21C DC level detection circuit, 21D
... Threshold value generation circuit, B1-BN ... Data demodulation circuit, L
AMP: Limiter amplifier, TR1 to TRN, TRCLK
... Delay circuit, 30 ... Tape optical fiber.

Claims (10)

[Claims] 1. An optical signal transmitting apparatus for transmitting a clock and a plurality of digital data, wherein a plurality of carrier waves respectively corresponding to the plurality of digital data and modulating a carrier wave assigned to each digital data with the digital data are output. Data modulating means, frequency multiplexing means for frequency-multiplexing and outputting the carrier wave modulated by the plurality of data modulating means and the clock, and a light emitting element driven based on the output of the frequency multiplexing means. An optical signal transmission device characterized by the above-mentioned. 2. The optical signal transmitting apparatus according to claim 1, further comprising a plurality of circuit units each of which includes the plurality of data modulating units, the frequency multiplexing unit, and the light emitting unit. 3. The optical signal transmitting apparatus according to claim 1, wherein the data modulating means uses an amplitude modulation method for modulating a carrier wave and transmits only one sideband of the carrier wave. 4. The optical signal transmitting apparatus according to claim 1, wherein said data modulating means uses a multi-level amplitude modulation method for modulating a carrier wave. 5. An optical signal receiving apparatus for demodulating a clock and a plurality of digital data from a received optical signal, comprising: a light receiving means for receiving an optical signal obtained by frequency-multiplexing a clock and a plurality of modulated waves and converting the signal into an electric signal. Frequency separating means for separating an electric signal output from the light receiving means into a clock and a plurality of modulated waves based on a frequency band; and a modulated wave corresponding to each of the plurality of modulated waves. And a plurality of data demodulating means for demodulating and outputting the original digital data used for the modulation. 6. The optical signal transmitting apparatus according to claim 5, further comprising a plurality of circuit units each of which includes the light receiving unit, the frequency separating unit, and the plurality of data demodulating units. 7. The optical signal according to claim 5, wherein the data demodulating means performs a demodulation operation using a threshold generated based on a DC level of the received optical signal. Receiver. 8. The light according to claim 5, wherein the plurality of modulated waves are amplitude-modulated signal waves, of which only one sideband is extracted. Signal receiver. 9. The optical signal receiving apparatus according to claim 5, wherein the plurality of modulated waves are multi-level amplitude modulated signal waves. 10. An optical signal comprising: the optical signal transmitting device according to any one of claims 1 to 4; and the optical signal receiving device according to any one of claims 5 to 9. Signal transmitting and receiving device.