JP2003198295A - Optical receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of the gain of an AGC (automatic gain control) amplifier increasing gradually, '0' level of the output of the amplifier rises, and the output signal exceeding a determining level of '1'/'0' due to the influence of noises, etc., at reproducing of the data and this causes wrong determination that the level is '1' and the signal is reproduced, if a signal '0' appears continuously in a two-gradation digital optical signal of '1'/'0' to be inputted. <P>SOLUTION: The receiver is provided with a resistor for reducing the gain of the AGC amplifier, a first switch for turning ON/OFF the resistor, and one or more delay devices for making data signals reproduced from the input signal delayed by different times. If '0' appears continuously in the input signals from a plurality of data signals delayed by the delay devices, the switch is turned on, to reduce the gain of the AGC amplifier. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver for receiving an optical signal having two states of high level and low level.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a conventional optical receiver. In the figure, 1 is a photoelectric converter for converting an optical signal represented by a photodiode into a current signal, 2 is a transimpedance amplifier for converting the current output of the photoelectric converter 1 into a voltage signal, and 3 is an output of the transimpedance amplifier 2. Is amplified by changing the gain according to the amplitude voltage,
An AGC amplifier that keeps the output amplitude voltage constant, and a data reproducing circuit 7 that reproduces a digital data signal from the output of the AGC amplifier 3.

The conventional optical receiver is constructed as described above,
It works as follows. In FIG. 7, the optical signal 12 transmitted via the optical fiber is emitted from the end face of the optical fiber and received by the photoelectric converter 1. The signal transmitted through this optical fiber is a pulse signal that has one of two states: high level (hereinafter "1") and low level (hereinafter "0"). A data stream. The photoelectric converter 1 outputs a current signal in response to the reception of the optical signal 12, and is converted into a voltage signal of "1" / "0" in the transimpedance amplifier 2. The output signal of the transimpedance amplifier 2 is adjusted to a voltage signal of a predetermined amplitude by the AGC amplifier 3,
The output signal 6 of the amplifier is input to the data reproduction circuit 7.
The data reproduction circuit 7 compares the output signal 6 of the AGC amplifier with a predetermined judgment level 13 to obtain "1" / ".
It is determined which signal is "0", and the original digital data signal before the optical signal 12 is sent to the optical fiber is reproduced to obtain the "1" / "0" data. Output as signal 8.

[0004]

In the conventional optical receiver,
As shown in FIG. 8 (a), in the input optical signal 12 of "1" / "0" of two digital gradations, "0" is continuous or "0". When the ratio increases, as shown in FIG. 8B, the gain of the AGC amplifier 3 gradually increases, and the "0" level of the output signal 6 of the AGC amplifier rises. When the unnecessary signal such as noise exceeds the judgment level 13 of the data reproducing circuit 7 due to the rise of the "0" level, it is erroneously judged as "1" and is reproduced. There is a problem that a bit error occurs in the data signal as shown in FIG.

The present invention has been made in order to solve the above problems, and it has been proposed that in the input optical signal of digital two gradations of high level ("1") and low level ("0"), Provided is an optical receiver in which a bit error does not occur in a data signal reproduced by a data reproducing circuit even when the level is continuous or the ratio thereof increases.

[0006]

An optical receiver according to the first invention comprises a photoelectric converter for converting an optical signal into a current signal, and a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal. , An AGC amplifier for adjusting the voltage amplitude of the output of the transimpedance amplifier to a predetermined level according to the amplitude voltage, a resistor connected between the input and output terminals of the AGC amplifier, and an output of the AGC amplifier. A data reproducing circuit for reproducing a data signal and whether the connection state of the resistor and the AGC amplifier is ON or OFF based on the number of low level signals in the data signal from the data reproducing circuit within a predetermined time. And a determination device for switching to one side.

An optical receiver according to a second aspect of the present invention includes a photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and the transimpedance amplifier. An AGC amplifier that adjusts the output voltage amplitude to a predetermined level according to the amplitude voltage, a resistor connected between the input and output terminals of the AGC amplifier, and a connection state of the resistor and the AGC amplifier are turned on. A switch for switching to either one of OFF or OFF, a data reproducing circuit for reproducing a data signal from the output of the AGC amplifier, and a plurality of delay circuits for delaying the data signal from the data reproducing circuit by shifting each time. The ratio of the low level signal to the data signal from the data reproduction circuit and the output signal from each of the delay circuits is And a judging device for setting the switch to be ON when the ratio of the low level signal is a predetermined number or more and for setting the switch to be OFF when the ratio of the low level signal is a predetermined number or less. Be prepared.

An optical receiver according to a third aspect of the present invention includes a photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and the transimpedance amplifier. An AGC amplifier that adjusts the output voltage amplitude to a predetermined level according to the amplitude voltage, a resistor connected between the input and output terminals of the AGC amplifier, and a connection state of the resistor and the AGC amplifier are turned on. A switch for switching to either OFF or OFF, a data reproducing circuit for reproducing a data signal from the output of the AGC amplifier, a clock signal reproducing circuit for reproducing a clock signal synchronized with the data signal from the data reproducing circuit, When the data signal is low level, the number of clocks of the clock signal is counted, and the data signal is A counter that clears the counted counter value when the switch is turned on, and the switch is turned on when the counter value of the counter is a certain value or more, and the switch is turned on when the counter value is a certain value or less. And a determiner for setting the switch to off.

An optical receiver according to a fourth aspect of the present invention comprises a photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and the transimpedance amplifier. An AGC amplifier that adjusts the output voltage amplitude to a predetermined level according to the amplitude voltage, a resistor connected between the input and output terminals of the AGC amplifier, and a connection state of the resistor and the AGC amplifier are turned on. A switch that is set to either OFF or OFF, a data reproducing circuit that reproduces a data signal from the output of the AGC amplifier, a clock signal reproducing circuit that reproduces a clock signal synchronized with the data signal from the data reproducing circuit, An integrator that integrates the data signal from the data reproduction circuit, and the switch when the output of the integrator is below a certain value. Set to On Ji, in which a decision unit for setting off otherwise.

In the optical receiver according to the fifth invention, the resistor comprises a plurality of resistors having different resistance values connected in parallel between the input and output terminals of the AGC amplifier, and from the output of the photoelectric converter, An average value monitor for observing the average value of the light quantity of the optical signal, a resistor selection circuit for selecting the resistance to be turned on from the plurality of resistors according to the output value of the average value monitor, and the resistor selection circuit And a second switch for turning on the resistance selected in (4).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a configuration diagram showing a first embodiment of the present invention. In the figure, 1 is a photoelectric converter for converting an optical signal 12 of "1" / "0" transmitted and input from an optical fiber or the like into "1" / "0" of a current, Two
Is a transimpedance amplifier that converts the current output of the photoelectric converter 1 into a voltage signal of "1" / "0", and 3 changes the gain of the output of the transimpedance amplifier 2 according to its amplitude voltage. AGC amplifier that amplifies and amplifies the output amplitude voltage to be constant, and these are equivalent to the conventional optical receiver shown in FIG.

In FIG. 1, reference numeral 4 is a resistor connected between the input and output of the AGC amplifier 3 for reducing the gain of the AGC amplifier 3, and 5 is a first resistor for turning on / off the resistor 4. Switch 7 is a data reproduction circuit for reproducing the original digital data before transmission from the output of the AGC amplifier 3,
Reference numeral 9 is one or more delay circuits for delaying and transmitting the data signal 8 output from the data reproduction circuit 7, and 10 is the data signal 8
And ON / OFF which turns on the first switch 5 when the ratio of "0" of the data signal 8 from the output of one or more delay circuits 9 is a certain value or more, and turns OFF otherwise. It is a data signal judging device for controlling.

In the optical receiver configured as described above,
For example, the delay time τ of the delay circuit 9 is set to 1-bit data length, n delay circuits 9 are used, the delay circuits 9 from 1 to n are connected in series, and the delay circuits 9 from 1 to n−1 are connected. Input to the next delay circuit 9 and the data signal judging device 10, and the output of the n-th delay circuit 9 is the data signal judging device 1
When connected so that only 0 is input, the data signal determiner 1
In 0, n + 1 consecutive data signals 8 are input.
The data signal 8 is composed of data output from the first to nth delay circuits 9 and the data reproduction circuit 7 during the time Δt = τ × (n + 1). The data signal determiner 10 counts the number K of "0" s in the data signal 8 and S
The ratio S of "0" is obtained by calculating = K / (n + 1). This ratio S indicates the ratio of “0” in the data signal during the time Δt, and, for example, when the data reproducing circuit 7 continuously outputs 0 during the time Δt, S = 1. At this time, when the ratio S of "0" is equal to or larger than the constant value Sh, the first switch 5 is turned on, and the other ratio S of "0" in the data signal 8 is a constant value Sh. When it is smaller, the first switch 5 is turned off. For example, the data signal determiner 10 turns ON the first switch 5 when the input signals are all "0", and turns it OFF otherwise.
The F control signal 11 is output.

In the optical receiver thus constructed, as shown in FIG. 3, when the input optical signal 12 is continuously "0", the AGC amplifier 3 outputs the voltage of the AGC amplifier output signal 6. Since the gain is automatically changed so that the amplitude is constant, the AGC amplifier output signal 6 gradually rises to "0" level, but the "0" of the input optical signal 12 is n When +1 consecutive signals are input, all of the n + 1 signals input to the data signal determiner 10 become "0", and the data signal determiner 10 outputs the first signal.
The ON / OFF control signal 11 for turning on the switch 5 is output. Then, the first switch 5 is turned on, and the resistor inside the AGC amplifier 3 and the resistor 4 are connected in parallel. The resistor 4 is effective in determining the gain of the AGC amplifier 3, the gain of the AGC amplifier 3 decreases, and the "0" level of the AGC amplifier output signal 6 decreases.

FIG. 3 is a diagram showing an output signal of the AGC amplifier 3 according to this embodiment. "0" as shown in Fig. 3 (a)
When an optical signal with a continuous level is input, the gain of the AGC amplifier 3 gradually increases as shown in FIG.
The "0" level of the amplifier output signal 6 increases and becomes "1" / "0".
Approach judgment level 13. However, when the ratio S of “0” in the data signal during the time Δt exceeds the constant threshold value Sh, the first switch 5 is turned on and the gain of the AGC amplifier 3 decreases. As a result, as shown in FIG. 3 (b), the "0" level of the AGC amplifier output signal 6 drops, and as a result, as shown in FIG. 3 (c), an output signal without a bit error is generated. Obtainable. As a result, the "0" level of the AGC amplifier output signal 6 rises due to the excessive gain increase of the AGC amplifier 3, and as a result, the "1" / "of the data reproducing circuit 7 is affected by the noise and the like. It is possible to avoid the occurrence of a bit error that exceeds 0 ”determination level 13 and is erroneously determined to be“ 1 ”and reproduction is performed.

As described above, the resistor connected between the input and the output of the AGC amplifier, the first switch for turning the resistor ON / OFF, and the delay signal for transmitting the data signal output from the data reproducing circuit 1 And at least one delay circuit, and when the ratio of "0" of the data signal and the data signal during the time Δt from the output of the one or more delay circuits is a certain value or more, the first switch is turned on. If the ratio of `` 0 '' of the optical signal input by the data signal determiner that performs ON / OFF control is greater than a certain value, turn on the resistor and set the gain of the AGC amplifier Input by lowering it ''
It is possible to provide an optical receiver that does not generate a bit error even if the rate of "0" continues or the ratio increases to a digital 2 gradation optical signal of 1 "/" 0 ". .

As another aspect of this embodiment,
As shown in FIG. 2, n delay circuits 9 having different delay times may be connected in parallel.

Embodiment 2. FIG. 4 is a configuration diagram showing a second embodiment of the present invention.
Instead of the delay circuit 9 and the data signal determiner 10 of FIG. 1, a clock reproduction circuit 14 for reproducing a clock signal 15 synchronized with the data signal 8 output from the data reproduction circuit 7, and the data signal 8 being "0". A counter 16 which counts up the number of clocks of the clock signal 15 and clears the counter value when it is "1";
When the output of is above a certain value, the first switch 5 is turned on.
N, and a counter determiner 17 that performs ON / OFF control to turn OFF in other cases.

In the optical receiver thus constructed, the counter 16 counts up the number of clocks of the clock signal 15 synchronized with the data signal 8 when the data signal 8 is "0". When the value is "1", the value of the counter 16 is cleared, so that the count number of the counter 16 always matches the continuous number of "0" of the data signal 8. Therefore,
By outputting an ON / OFF control signal 11 that turns ON the first switch 5 when the count number of the counter 16 is m or more and turns OFF when the count number is less than m, the same as described in the first embodiment. In addition, it is possible to avoid the occurrence of a bit error when "0" continues in the input optical signal 12.

As described above, the resistor connected between the input and output of the AGC amplifier and the first ON / OFF switch for this resistor
Switch, and a clock reproduction circuit for reproducing a clock signal synchronized with the data signal output from the data reproduction circuit,
A counter that counts up the number of clocks of the clock signal when the data signal is "0" and clears the counter value when the data signal is "1", and the output of the counter is a certain value or more. The first switch is turned on and the resistor is turned on when "0" of the optical signal input by the counter judgment device that performs ON / OFF control that turns it off in other cases continues for a certain value or more. By configuring so as to reduce the gain of the AGC amplifier, `` 0 '' is continuous or proportion to the input digital signal of 2 gradations of `` 1 '' / `` 0 ''. It is possible to provide an optical receiver in which bit errors do not occur even if the number increases. Further, the gain of the AGC amplifier can be reduced with a simpler configuration using a counter without providing a plurality of delay circuits 9 as in the first embodiment.

Embodiment 3. FIG. 5 is a configuration diagram showing a third embodiment of the present invention. Instead of the delay circuit 9 and the data signal judging device 10 of FIG. 1, an integrator 18 for moving and integrating the data signal 8 1 outputted from the data reproducing circuit 7 is provided. And an integration determiner 19 that performs ON / OFF control for turning on the first switch 5 when the output of the integrator 18 is below a certain value and turning it off otherwise.

In the optical receiver configured as described above, for example, the integrator 18 always operates at the current time t0 and the current time t0.
The signal input to the integrator 18 is integrated between the time from and the time before Δt time.
By outputting the ON / OFF control signal 11 that turns ON the first switch 5 when the integrated value of 8 is A or less and turns OFF when the integrated value is larger than A, the same as described in the first embodiment. , It is possible to avoid the occurrence of a bit error when the “0” of the optical signal 12 input during the time Δt exceeds a certain rate.

A resistor connected between the input and output of the AGC amplifier, a first switch for turning the resistor ON / OFF, an integrator for moving and integrating a data signal output from the data reproducing circuit, ON / OF to turn on the first switch when the output of the integrator is below a certain value, and to turn off otherwise.
If the ratio of `` 0 '' during the time Δt of the optical signal input by the integral judgment device that performs F control is a certain value or more,
By configuring so that the gain of the AGC amplifier is reduced by turning it on, `` 0 '' is continuous or ratio to the input digital signal of 2 gradations of `` 1 '' / `` 0 ''. It is possible to provide an optical receiver in which a bit error does not occur even if the number increases. Further, the AG circuit has a simpler configuration using an integrator without providing a plurality of delay circuits 9 as in the first embodiment.
The gain of the C amplifier can be reduced.

Fourth Embodiment 6 is a diagram showing a fourth embodiment of the present invention. In the present embodiment, 1 to 1
1 is the same as the first embodiment. 20 is an average value monitor for monitoring the average value of the output of the photoelectric converter 1, 21 is an average value signal output from the average value monitor 20, 22 is a resistor selection circuit for selecting an optimum resistance from the plurality of resistors 4. , 23
Is a resistor selection signal output from the resistor selection circuit 22,
Reference numeral 24 denotes a second switch that selects an optimum resistance from the plurality of resistors 4 based on the resistor selection signal 23.

In this embodiment, when the "0" level of the optical signal 12 is continuous, the size of the resistor 4 inserted in parallel to the AGC amplifier 3 depends on whether the average value signal 21 is small or large. It is characterized by changing with and.

The operation will be described below. Photoelectric converter 1
The signal output from is input to the average value monitor 20. The average value monitor 20 calculates the average value of the input signals. The calculation of the average value is performed for a sufficiently long time as compared with the gain response speed of the AGC amplifier 3, and also for a sufficiently long time as compared with ΔT shown in the first embodiment. Therefore, the average value signal 21 output from the average value monitor 20
Is a sufficiently long average value of the optical signal 12 in the time direction. The method of calculating the average value may be a general method, for example, a method of charging charges and measuring the amount of charged charges. The details may be appropriately determined by design.

The average value signal 21 output from the average value monitor 20 is input to the resistor selection circuit 22. The resistor selection circuit 22 selects an optimum resistor according to the magnitude of the average value signal 21 and outputs the selection result as a resistor selection signal 23. When the average value signal 21 input is small, the resistor selection circuit 22 outputs the resistor selection signal 23 so as to increase the resistance value of the resistor 4 as compared with the case where the average value signal 21 is large. This is to avoid the fact that when the average value signal 21 is small, the gain of the AGC amplifier 3 is too small due to the resistance value of the resistor 4 and the next input "1" level cannot be recognized as a signal. Is. On the contrary, when the average value signal 21 is large, the gain of the AGC amplifier 3 is excessively increased to prevent the next input "1" level from being saturated. The average value signal 21
The resistance value with respect to the size may be appropriately set according to the design.

The resistor selection signal 23 is applied to the second switch 2
4 is input. In the second switch 24, the resistor 4 corresponding to the signal of the resistor selection signal 23 is connected in parallel with the resistor inside the AGC amplifier 3.

The average value monitor 20 is used in the second embodiment.
It is needless to say that the same is true even if this change is added to the third embodiment.

As described above, when the "0" level of the optical signal 12 is continuous, the size of the resistor 4 inserted in parallel to the AGC amplifier 3 depends on whether the average value signal 21 is small or large. The input high level (''
1 ”) and low level (“ 0 ”) digital 2-gradation optical signals that do not cause bit errors even if the low level (“ 0 ”) continues or the ratio increases It becomes possible to provide a container.

[0031]

As described above, according to the input digital signal of two gradations of the high level ("1") and the low level ("0"), the low level ("0") is added. It is possible to provide an optical receiver in which a bit error does not occur even if ()) increases continuously or in proportion.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment.

FIG. 2 is a configuration diagram showing a first embodiment.

FIG. 3 is a diagram showing a signal waveform according to the first embodiment.

FIG. 4 is a configuration diagram showing a second embodiment.

FIG. 5 is a configuration diagram showing a third embodiment.

FIG. 6 is a configuration diagram showing a fourth embodiment.

FIG. 7 is a configuration diagram showing a conventional technique.

FIG. 8 is a diagram showing a signal waveform of a conventional technique.

[Explanation of symbols]

1 photoelectric converter, 2 transimpedance amplifier, 3 AGC amplifier, 4 resistor, 5 first switch, 6 AGC amplifier output signal, 7 data reproducing circuit, 8 data signal, 9 delay circuit, 10 data signal judging device, 11 ON / OFF control signal, 12 optical signal, 13 `` 1 '' / '' 0 '' judgment level, 14 clock regeneration circuit, 15 clock signal, 16 counter, 17 counter judgment device, 18 integrator, 19
Integral determiner, 20 average value monitor, 21 average value signal, 22 resistor selection circuit, 23 resistor selection signal, 24 second switch.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 10/26 10/28 F term (reference) 5J092 AA01 AA56 CA00 CA41 FA17 FA18 HA19 HA25 HA26 HA38 HA44 KA15 KA31 KA34 KA35 MA11 SA13 TA01 TA06 UL02 5J100 JA01 LA02 LA04 LA10 LA11 LA12 QA01 SA02 5J500 AA01 AA56 AC00 AC41 AF17 AF18 AH19 AH25 AH26 AH38 AH44 AK15 AK31 AK34 AK35 AM11 AS13 AT01 AT06 LU02 5K002 AA03 CA02 CA02 CA02 CA02 CA10

Claims (5)

[Claims] 1. A photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and a voltage amplitude of an output of the transimpedance amplifier. AG that adjusts to a predetermined level according to the voltage
A C amplifier, a resistor connected between the input and output terminals of the AGC amplifier, a data reproducing circuit for reproducing a data signal from the output of the AGC amplifier, and a data signal from the data reproducing circuit within a predetermined time. An optical receiver comprising: a judgment device that switches the connection state of the resistor and the AGC amplifier to either on or off based on the number of low-level signals. 2. A photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and a voltage amplitude of an output of the transimpedance amplifier. AG that adjusts to a predetermined level according to the voltage
A C amplifier, a resistor connected between the input and output terminals of the AGC amplifier, a switch for switching the connection state of the resistor and the AGC amplifier to either ON or OFF, and data output from the AGC amplifier. A data reproduction circuit for reproducing a signal, a plurality of delay circuits for delaying the data signal from the data reproduction circuit by shifting each time, a data signal from the data reproduction circuit and an output signal from each of the delay circuits At a low level signal, the switch is set to ON when the low level signal ratio is a predetermined number or more, and the switch is turned on when the low level signal ratio is a predetermined number or less. An optical receiver having a judging device set to off. 3. A photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and a voltage amplitude of an output of the transimpedance amplifier. AG that adjusts to a predetermined level according to the voltage
A C amplifier, a resistor connected between the input and output terminals of the AGC amplifier, a switch for switching the connection state of the resistor and the AGC amplifier to either ON or OFF, and data output from the AGC amplifier. A data reproduction circuit for reproducing a signal, a clock signal reproduction circuit for reproducing a clock signal synchronized with the data signal from the data reproduction circuit, and counting the number of clocks of the clock signal when the data signal is at a low level, A counter that clears the counted counter value when the data signal is at a low level, and sets the switch to ON when the counter value of the counter is equal to or greater than a certain value, and the counter value is equal to or less than the certain value. In this case, an optical receiver comprising a judging device for setting the switch to off. 4. A photoelectric converter for converting an optical signal into a current signal, a transimpedance amplifier for converting a current signal from the photoelectric converter into a voltage signal, and a voltage amplitude of an output of the transimpedance amplifier. AG that adjusts to a predetermined level according to the voltage
C amplifier, a resistor connected between the input and output terminals of the AGC amplifier, a switch for setting the connection state of the resistor and the AGC amplifier to either ON or OFF, and from the output of the AGC amplifier A data reproducing circuit for reproducing a data signal; a clock signal reproducing circuit for reproducing a clock signal synchronized with the data signal from the data reproducing circuit; an integrator for integrating the data signal from the data reproducing circuit; and an integrator. An optical receiver comprising: a judgment device for setting the switch to be ON when the output of is equal to or less than a constant value, and setting it to be OFF in other cases. 5. The resistor comprises a plurality of resistors having different resistance values connected in parallel between the input and output terminals of the AGC amplifier, and the average value of the light quantity of the optical signal is calculated from the output of the photoelectric converter. An average value monitor to be observed, a resistor selection circuit that selects a resistance to be turned on from the plurality of resistances according to an output value of the average value monitor, and a resistance selected by the resistor selection circuit is turned on. The optical receiver according to any one of claims 1 to 4, further comprising: