JPH0313036A - Optical receiver for parallel transmission - Google Patents

Abstract

PURPOSE:To regenerate other transmission signal simply with high quality by referencing a threshold level generated from one of plural transmission signals so as to regenerate other transmission signal and using a transmission signal extracting a threshold level as a clock signal. CONSTITUTION:Reception circuits 111-11n-1 among reception circuits receiving reception signals S1-Sn are not provided with an automatic threshold level setting circuit, the reception circuit 11n is provided with an automatic threshold level setting circuit 14 (ATC) together with a photoelectric conversion element 12n, a preamplifier 13n and a comparator 15n, and the automatic threshold level setting circuit 14 supplies an extracted threshold level not only to the comparator 15n but also to comparators 151-15n-1 of other light receiving circuits 111-11n-1. The receiving circuit 11n is so constituted that a system clock is to be received and always a signal input exists during the operation of the system. The clock signal is, in general, a signal having no duty cycle deviation and the threshold level extracted from the clock signal is suitable for the regeneration of other signal sent in parallel with the signal.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an optical receiver for parallel transmission.

More specifically, the present invention relates to a novel configuration of an optical receiver used for parallel transmission of digital optical signals, which can be applied to data transmission between computers.

2. Description of the Related Art In the field of optical communications, it is common practice to multiplex a plurality of signals into one serial signal and transmit this through a medium such as an optical fiber.

However, as the field of application of optical transmission technology expands in response to the adoption of parallel signal transmission methods in combination coater buses and the increase in the amount of transmitted signals, parallel transmission of optical signals Implementation may be considered.

FIG. 3 is a block diagram showing a general configuration of an optical receiver that can be used for parallel transmission of optical signals as described above.

That is, as shown in FIG. 3, the conventional parallel transmission optical receiver receives the parallel transmitted received signal S
It is constituted by a plurality of optical receiving circuits 11 to 17, each of which receives a signal. Each optical receiving circuit 11-1. are photoelectric conversion elements 21 to 2o and preamplifiers 31 to 3, respectively.
．． , the threshold automatic setting circuit 4° to 4o, and the comparator 5
It has the same configuration with □ to 5h. For convenience, in this specification, the entire circuit for receiving parallel signals is referred to as an optical receiver, and a circuit for receiving each bit is referred to as an optical receiver.
The set of photoelectric conversion circuit and signal regeneration circuit will be referred to as an optical reception circuit.

Now, the operation of the optical receiving circuit 11, one of the optical receiving circuits constituting the optical receiver shown in FIG. 3 above, will be explained.

This optical receiving circuit 1. The optical signal input to the optical signal is first converted into an electrical signal by a photoelectric conversion element 2) such as a photodiode, and then amplified by a preamplifier circuit 3°.

Subsequently, the amplified received signal is input to one of the comparators 51 and the automatic threshold setting circuit 41. Here, the threshold automatic setting circuit 41 has a function of extracting a signal threshold level for signal reproduction from a manually input received signal, and usually has a function of extracting a signal threshold level for signal reproduction from a manually inputted received signal. Configured to output a threshold level. That is, the comparator 51 compares the threshold level output from the automatic threshold setting circuit 41 with the human input signal, shapes the waveform of the received signal, and outputs the obtained data DATA1.

The optical receiver shown in FIG. 3 includes a plurality of optical receiving circuits configured as described above, and is configured to waveform-shape each input parallel signal and output the same.

Problems to be Solved by the Invention As mentioned above, conventional optical receivers for parallel transmission are configured such that each receiving circuit functions independently, and each signal is It was working by extracting the threshold level.

By the way, when a signal with a greatly biased duty cycle is received, such as a burst signal, an automatic threshold value setting circuit may not be able to properly set the threshold level of the signal due to a response delay. Playback starts. Therefore, there is a problem that distortion occurs in the pulse width of the obtained data signal.

FIGS. 4(a) and 4(b) are waveform diagrams showing the process in which the above-mentioned pulse width distortion occurs.

That is, when the above-described optical receiving circuit shown in FIG. 3 starts receiving a signal, the received signal S rises with a predetermined amplitude from the signal reference level, as shown in FIG. 4(a). . On the other hand, the threshold level A output by the automatic threshold setting circuit is extracted from the received signal.
As shown in a), the optimum level is gradually reached from the initial level. Therefore, the data signal DA reproduced during the period until the threshold level reaches the appropriate level is shown in Figure 4).
As shown, the signal is reproduced with a pulse width different from the correct signal pulse width shown by the dotted line.

Note that although the explanation has been given here at the start of reception, when pulse width distortion appears most prominently, a similar phenomenon can also occur when the duty cycle of the received signal is uneven.

As mentioned above, conventional optical receivers for parallel transmission are configured by using multiple optical receiver circuits in parallel using automatic threshold setting circuits, and therefore the response of the automatic threshold setting circuits is It is unavoidable that pulse width distortion due to delay occurs in each optical receiving circuit.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a novel parallel transmission optical receiver that can solve the above-mentioned problems of the prior art and can obtain high-quality received signals with a simpler circuit configuration.

Means for Solving the Problems According to the present invention, an optical receiver for parallel transmission is configured to include a plurality of optical receiving circuits including a light receiving element and a waveform shaping circuit and to simultaneously receive a plurality of optical signals. The parallel optical system is characterized in that the signal threshold extracted by one of the optical receiving circuits is configured such that the other optical receiving circuits refer to the signal threshold value extracted by one of the optical receiving circuits to generate a threshold level for each optical receiving circuit. An optical receiver for transmission is provided.

Function: The optical receiver for parallel transmission according to the present invention is configured such that one of the plurality of optical receiving circuits extracts a signal threshold value from a received signal so that the other optical receiving circuits refer to it in their respective signal regeneration processing. Its main feature is that it is structured as follows.

In other words, the signal threshold extraction circuit in the optical receiver is provided to extract an appropriate signal threshold in response to signal levels that differ for each reception condition, and to perform signal reproduction with higher quality. . However, while the received signal level in optical signal transmission generally changes depending on the length of the transmission path and the installation conditions of the transmission path, in parallel transmission, the installation conditions of the transmission path are essentially the same between each bit of the parallel signal. Furthermore, the signal transmission period is also the same.

Therefore, it can be considered that the transmission conditions including the signal level are substantially equal between each bit of the parallel signal.

By the way, among the signals transmitted in parallel, there are signals that are continuously generated without interruption, such as a clock signal for synchronizing between transmitters and receivers.

As mentioned above, a receiver that receives parallel signals is composed of a plurality of optical receiving circuits, and among these optical receiving circuits, the optical receiving circuit that receives the above clock signal always receives the clock signal. ing.

Therefore, this optical receiver circuit constantly extracts the signal threshold. Therefore, by referring to this, other optical receiving circuits that intermittently receive optical signals can immediately generate an appropriate signal threshold.

Hereinafter, the present invention will be described in more detail with reference to the drawings, but the following disclosure is only one example of the present invention and does not limit the technical scope of the present invention in any way.

Embodiment 1 FIG. 1 is a block diagram showing the most basic configuration example of an optical receiver for parallel transmission constructed according to the present invention.

As shown in Figure 1, this optical receiver for parallel transmission also
A receiving circuit 11 receives the received signals 81 to S, respectively.
．． ~11. ．． However, in this receiver, the receiving circuit 11. ~11. ．． is not equipped with an automatic threshold setting circuit, and each of the receiving circuits 111 to 11. ．． ．． are photoelectric conversion elements 12, to 12. ．． −． and preamplifier 131~
13. −.

and comparators 151-15. , is composed of. on the other hand,
Receiving circuit 11. is a photoelectric conversion element 12 and a preamplifier 1
3, and the comparator 15, the threshold automatic setting circuit 1
Furthermore, the automatic threshold setting circuit 14 of the receiving circuit 11 includes not only a comparator 15.
Other optical receiving circuits 111-11. , -, comparators 151~
15, , -, are also configured to supply the extracted threshold values.

In a system including a receiver configured as described above, the receiving circuit 11. , is configured to receive a system clock signal. When the system is in operation, the receiving circuit 11° always has signal power.

Further, the clock signal is generally a signal with no deviation in duty cycle. Furthermore, in general, in parallel optical transmission, the lengths of transmission paths, installation conditions, etc. are substantially the same, and therefore the transmission characteristics are often considered to be substantially the same. Therefore, the threshold value extracted from the clock signal is suitable for the reproduction of other signals transmitted in parallel with this signal;
Since only one threshold automatic setting circuit is required, it is effective in simplifying the system.

Embodiment 2 FIG. 2 is a block diagram showing another example of the configuration of an optical receiver for parallel transmission configured according to the present invention.

In the circuit shown in Figure 1, the threshold level extracted by the optical receiving circuit 11° is supplied directly to the optical receiving circuit, but depending on the system, individual values such as optical transmission power, optical connector loss, etc. There are cases where variations in the transmission path cannot be ignored. The embodiment shown in FIG. 2 deals with such a case.

This optical receiver includes n optical receiving circuits 211 to 21 . The optical receiving circuit 21. , only the power (has a different configuration from other optical receiver circuits).

That is, the optical receiving circuit 21. ~21. ．． are photoelectric conversion elements 221-22. ,, preamplifiers 231-23. -,, comparator 25°~251. −． and threshold automatic setting circuit 24. ~24. −.

(ATC), and further includes threshold initial level setting circuits 261 to 26 . , (A T B C).

On the other hand, the optical receiving circuit 211 includes a photoelectric conversion element 22o, a preamplifier 23. , a comparator 25, and a threshold automatic setting circuit 24h, and does not include a threshold initial level setting circuit. In this optical receiver, an optical receiving circuit 21. The signal open/close level extracted by the threshold automatic setting circuit 24a is the same as that of the other optical receiver circuits 211 to 21.
．． , threshold initial level setting circuits 26° to 26. ．． is configured to be supplied to

More specifically, each optical receiving circuit 21. ~21. .

can be constructed as follows. That is, the photoelectric conversion element 22
1 to 22I are configured with photodiodes, and preamplifiers 231 to 23. Configure the current so that it is manually powered. Preamplifiers 231-23. is a transimpedance type amplifier, and is configured so that the amplifier output voltage is generated on the negative side when a signal is input.

Threshold automatic setting circuit 24□-24. ．． and threshold initial level setting circuit 26. ~26. , is constituted by a negative peak hold circuit, and the threshold automatic setting circuit 24
, ~24. ．． output and threshold initial level setting circuit 26
, ~26. ．． The lower level of the outputs from comparators 25□ to 25. , configure it to be manually powered as a threshold level. Note that the optical receiving circuit 21 is configured to receive the clock signal of this system. Further, as will be described later, the threshold level extracted by the optical receiving circuit 21° is the same as that of the other optical receiving circuits 211 to 21. , is preferably set slightly lower than the threshold level of .

As mentioned above, in the parallel transmission optical receiver shown in FIG. 2, the optical receiving circuit 21. , receives the clock signal and
At this point, an appropriate signal threshold level is extracted for the receiver. This optical receiving circuit 21. As described above, the signal threshold level extracted by the other optical receiving circuits 21. ~21.
．． The signal threshold level of each optical receiving circuit 211-21. .

are supplied to each optical receiving circuit 21. ~21. ．． When the automatic threshold level setting circuits 241 to 24a are not operating due to lack of human power,
1-26. , for each comparator 25. as the initial threshold value. ~25. ．． is supplied to.

FIGS. 4(a) and 4(C) illustrate the optical receiving circuits 21, 21. ．． FIG.

As shown as waveform B in FIG. 4(a), the optical receiving circuit 2
1. ~21. ．． Now, comparators 25, to 25. ．． −． Since the initial value of the signal threshold value supplied to the detector is at a level slightly lower than the appropriate signal threshold level, it maintains a level close to the appropriate value even in a no-signal state (extinguished state). Therefore, even if a burst signal is input to the optical receiving circuits 211 to 21E, the automatic threshold setting circuit responds quickly, and as shown in FIG. Width distortion is significantly reduced.

As described in detail of the invention, the optical receiver for parallel transmission according to the present invention performs signal regeneration of another transmission signal by referring to a threshold value generated from one of a plurality of transmission signals. It is configured. Therefore, by assigning the transmission signal from which the threshold value is extracted to a continuous signal such as a clock signal, it is possible to easily reproduce other transmission signals with high quality.

In other words, even if there is a bias in the duty cycle of the transmission signal, or if a signal suddenly appears after no signal, the threshold value or the initial value of the threshold value is always maintained at an appropriate level. , deterioration of transmission characteristics such as generation of pulse 1'if only does not occur.

Furthermore, the system configuration can be made simpler than that of conventional optical receivers for parallel transmission, which is also advantageous in realizing parallel transmission.

Such an optical receiver for parallel transmission according to the present invention can be advantageously used for data transmission between computers, etc., which requires a large amount of data transfer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a specific configuration example of an optical receiver for parallel transmission constructed according to the present invention, and FIG. 2 is a block diagram showing another example of the optical receiver for parallel transmission constructed according to the present invention. FIG. 3 is a block diagram showing a configuration example of a conventional parallel transmission optical receiver; FIGS. 4(a) to (C) show an automatic threshold setting circuit; FIG. FIG. 3 is a waveform diagram illustrating a process in which pulse width distortion occurs in FIG. [Main reference numbers] 1, ~la, 11. ~11h1 211~21r,... optical receiving circuit, 21~2. ,．． 12. ~12. ．． ．． 221-22,... photoelectric conversion element, 31-3. ,．．
131-13. ,．． 23□~23,..., preamplifier, 41~41. ．． 14. 24, ~24. ．． ...Threshold automatic setting circuit, 5, ~
5. ．． 15+~150. 251-251... comparator, 26, -26. ．．・Threshold initial level setting circuit, 8
1 to S7... Received signal

Claims (4)

[Claims] (1) In an optical receiver for parallel transmission, the optical receiver includes a plurality of parallel optical receiving circuits each including a light receiving element and a waveform shaping circuit, and is configured to receive a parallel signal consisting of a plurality of optical signals. An optical receiver for parallel transmission, characterized in that the signal threshold extracted by one of the optical receivers is referred to by other optical receiver circuits to generate a threshold level for each optical receiver circuit. . (2) The optical receiver for parallel transmission according to claim 1, characterized in that the optical signal received by the optical receiving circuit that supplies the signal threshold level to another optical receiving circuit is a clock signal. Optical receiver for parallel transmission. (3) In the optical receiver for parallel transmission according to claim 1 or 2, the signal threshold extracted by one optical receiving circuit equipped with an automatic signal threshold setting circuit is transmitted to another signal. An optical receiver for parallel transmission, characterized in that a receiving circuit is also configured to be used as a signal threshold. (4) In the optical receiver for parallel transmission according to claim 1 or 2, the signal threshold extracted by one optical receiver circuit equipped with an automatic signal threshold setting circuit is transmitted to another signal receiver circuit. An optical receiver for parallel transmission, characterized in that the optical receiver is configured to use as an initial value of its signal threshold.