JP2004336200A - Burst signal start detection circuit, optical receiver, and optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burst signal start detection circuit for detecting a stage of a burst signal reaching a duty ratio at which the burst signal can accurately be identified / recovered and transmitting the result to an identification recovery section as a control signal so as to enable the accurate identification / recovery of the burst signal. <P>SOLUTION: An optical receiver 12 receives an optical signal from an optical transmitter 10 via an optical transmission line 11, and an photoelectric conversion section 13 applies photoelectric conversion to the optical signal and gives the result to an amplifier 14. The amplifier amplifies the received electric signal. When the duty ratio of an output signal from the amplifier reaches a specified value on the basis of the output signal from the amplifier, the burst signal start detection circuit 16 generates the control signal and gives the control signal to the identification recovery section 15. A CLK generating section 17 generates a CLK on the basis of the signal received from the amplifier and thereafter transmits the CLK signal to the identification recovery section. While receiving the control signal from the burst signal start detection circuit, the identification recovery section identifies / recovers the signal transmitted from the amplifier on the basis of the CLK transmitted from the CLK generating section. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a burst signal start time detection circuit, an optical receiving device including the burst signal start time detection circuit, and an optical transmission system.
[0002]
[Prior art]
FIG. 4 is a block diagram showing a configuration of a conventional optical receiving device. The optical receiver illustrated in FIG. 4 includes a photoelectric conversion unit 30 that performs optical-to-electric conversion of a burst signal, an amplification unit 31 that amplifies an electric signal output from the photoelectric conversion unit 30, and an output that is output from the amplification unit 31. A peak detector 32 for detecting a peak value of the signal; a comparator 33 for comparing the output signal from the peak detector 32 with the reference voltage Vref and sending the comparison result as a control signal to the identification and reproduction unit 35; A CLK generator 34 for generating a clock signal (hereinafter, the clock is referred to as CLK) from the electric signal output from the controller 31, and an amplifier 31 based on the CLK signal from the CLK generator 34 and the control signal from the comparator 33. And an identification / reproduction unit 35 for identifying / reproducing an electric signal from the apparatus. In this example, it is possible to instruct the identification / reproduction unit 35 to start identification / reproduction of the electric signal output from the amplification unit 31 by the control signal sent from the comparison unit 33 to the identification / reproduction unit 35.
[0003]
However, in the above-described conventional optical receiving device, the duty ratio of the electric signal output from the amplification unit 31 greatly deviates from 50%, and the identification / reproduction unit 35 can accurately identify and reproduce. However, there is a problem that a signal for instructing accurate start of identification / reproduction cannot be sent out.
[0004]
Further, as a conventional technique for identifying and reproducing a burst signal, a first level determination circuit for determining whether or not the amplitude of received data is within a linear range of a preamplifier, and an input terminal at both ends for receiving data of the received data are provided to input terminals at both ends. A high-level voltage and a low-level voltage are supplied, a first voltage dividing circuit having a variable resistor is provided, and the first level determining circuit determines that the amplitude of the received data is a linear value of the preamplifier. When it is determined that the output voltage is within the range, the output voltage of the first voltage divider circuit is controlled at the center of the amplitude of the reception data, and the first level determination circuit determines that the amplitude of the reception data is When it is determined that the output voltage is in the non-linear range, the output voltage of the first voltage divider circuit is controlled to be higher than the center of the amplitude of the received data, and the output voltage of the first voltage divider circuit is supplied to the main amplifier as a threshold. Also supplied as voltage There has been disclosed (e.g., see Patent Document 1 below).
[0005]
In the above configuration, even if an offset voltage for preventing malfunction due to noise is applied, the threshold value is controlled to be equal to the average value of the high level and the low level of the received data, and the non-linear characteristic of the preamplifier is used. Even if the duty ratio of the received data is degraded, an automatic threshold control circuit that corrects the duty ratio is realized, whereby the performance of the optical receiver in the local optical communication system can be improved.
[0006]
[Patent Document 1]
JP-A-9-270755
[Problems to be solved by the invention]
However, in such a configuration, when the duty ratio of the burst signal whose transmission speed is high is shifted, it is not possible to control the threshold voltage to the optimum threshold voltage at high speed, and as a result, accurate identification and reproduction cannot be performed. There is a problem that the possibility is large.
[0008]
The present invention has been made in order to solve the above-described problems of the conventional example, and detects a stage at which a duty ratio of a burst signal reaches a duty ratio at which identification and reproduction can be accurately performed. An object of the present invention is to provide a burst signal start time detection circuit capable of realizing identification and reproduction, an optical receiving device including the burst signal start time detection circuit, and an optical transmission system.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the burst signal start detection circuit according to the present invention, after a burst signal is subjected to optical-electrical conversion and amplification, a delay unit for delaying an input signal to be input for a predetermined time, An EX-OR unit for obtaining an exclusive OR with the output signal of the delay unit; an average voltage generation unit for generating an average voltage of the output signal of the EX-OR unit; and a peak detection unit for detecting a peak of the input signal A reference voltage generator that generates a reference voltage based on a detection signal of the peak detector, and a comparator that compares an output signal of the average voltage generator with a reference voltage output from the reference voltage generator. It is provided with. With this configuration, when the duty ratio of a burst signal with a high transmission speed is shifted, it is possible to control the threshold voltage to an optimum threshold value at high speed, and the duty ratio of the burst signal can be accurately identified and reproduced. A certain stage can be detected, and accurate identification and reproduction can be realized based on the detection.
[0010]
The delay section is configured to delay the input signal by an arbitrary time. With this configuration, the EX-OR unit can notify the average voltage generation unit of the accurate duty ratio of the amplification unit output signal as a signal.
[0011]
Further, the reference voltage generation unit is configured to generate a reference voltage when the level of the detection signal of the peak detection unit reaches a certain prescribed value, and to send the reference voltage to the comparison unit. With this configuration, it is possible to notify the comparing section of the time when the output signal of the amplifier section reaches the duty ratio at which identification and reproduction can be performed accurately.
[0012]
Further, the comparison unit compares the output signal of the average voltage generation unit with the reference voltage output from the reference voltage generation unit, and when the duty ratio of the input signal becomes a certain prescribed value, It is configured to send a control signal to the device. With this configuration, it is possible to perform control for starting identification / reproduction in a subsequent device from the stage when the output signal of the amplification unit reaches a duty ratio that allows accurate identification / reproduction.
[0013]
Further, the optical receiving device according to the present invention is a photoelectric conversion unit that converts an input optical signal into an electric signal, an amplification unit that amplifies an output signal of the photoelectric conversion unit, and an output signal of the amplification unit. A burst signal start-time detection circuit for generating a control signal when the duty ratio reaches a predetermined value; a clock generation unit for generating a clock based on an output signal of the amplification unit; and a burst signal start-time detection. An identification reproducing section for identifying and reproducing an output signal of the amplifying section based on a detection signal of a circuit and an output signal of the clock generating section. With this configuration, when the duty ratio of a burst signal with a high transmission speed is shifted, the optimum threshold voltage is controlled at a high speed, and the duty ratio at which the output signal of the amplifier section can be accurately identified and reproduced is reached. From the stage, it is possible to realize an optical receiving device that starts identification / reproduction in the identification / reproduction unit.
[0014]
Further, the amplification unit, the delay unit, the EX-OR unit, the average voltage generation unit, and the comparison unit are configured to be integrated on one IC. With this configuration, it is possible to reduce the size and cost of the burst signal start detection circuit, the optical receiver, and the optical transmission system.
[0015]
Further, the optical transmission system according to the present invention is an optical transmission device that transmits an optical signal, an optical transmission line that transmits an optical signal from the optical transmission device, and an optical signal that has propagated through the optical transmission line. , And the above-described optical receiver. With this configuration, when the duty ratio of the high-speed optical burst signal transmitted from the optical transmission device and propagated through the optical transmission path is shifted, the optical receiving device converts the optical burst signal into an electric burst signal, In addition, it is possible to realize an optical transmission system that controls the threshold voltage at an optimum value at a high speed and starts identification / reproduction at a stage when the output signal of the amplifier reaches a duty ratio at which identification / reproduction can be accurately performed.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram illustrating a configuration of an optical transmission system according to an embodiment of the present invention. The optical transmission system shown in FIG. 1 generates and transmits an optical signal, an optical transmission line 11 that transmits an optical signal from the optical transmission device 10, and an optical signal transmitted through the optical transmission line 11. And an optical receiving device 12 for receiving the received optical signal. The optical receiving device 12 includes a photoelectric conversion unit 13, an amplification unit 14, an identification reproduction unit 15, a burst signal start time detection circuit 16, and a CLK generation unit 17. You.
[0017]
Here, in the optical receiving device 12, the optical signal input in the photoelectric conversion unit 13 is converted into an electric signal and transmitted to the amplification unit 14. The amplifying unit 14 amplifies the input electric signal, and sends the amplified electric signal to the identification reproducing unit 15, the burst signal start time detection circuit 16 and the CLK generation unit 17, respectively. The burst signal start detection circuit 16 generates a control signal based on the output signal of the amplifier 14 when the duty ratio of the output signal of the amplifier 14 reaches a certain specified value, and sends the control signal to the discrimination / reproduction unit 15. The CLK generation unit 17 generates a CLK based on the signal transmitted from the amplification unit 14, and then transmits the CLK signal to the identification reproduction unit 15. The identification reproducing unit 15 identifies and reproduces the signal transmitted from the amplifying unit 14 based on the CLK signal transmitted from the CLK generating unit 17 while receiving the control signal from the burst signal start time detection circuit 16. I do.
[0018]
Hereinafter, the configuration of the burst signal start detection circuit 16 will be described. FIG. 2 is a block diagram showing the configuration of the burst signal start time detection circuit 16 in the optical receiver 12 and its surroundings. As shown in FIG. 2, the burst signal start detection circuit 16 comprises a delay unit 16a for amplifying the burst signal by optical-to-electric conversion and delaying the input signal to be input for a predetermined time, an input signal and a delay unit 16a. EX-OR unit 16b for obtaining an exclusive OR with the output signal of EX-OR (hereinafter, the exclusive OR is referred to as EX-OR), and an average voltage generating unit for generating an average voltage of the output signal of the EX-OR unit 16b 16c, a peak detector 16d for detecting a peak of the input signal, a reference voltage generator 16e for generating a reference voltage based on a detection signal of the peak detector 16d, an output signal of the average voltage generator 16c and a reference voltage generator. And a comparison unit 16f for comparing the reference voltage output from the unit 16e.
[0019]
Next, an operation according to the configuration shown in FIG. 2 will be described. The photoelectric conversion unit 13 converts the input optical signal into an electric signal and sends the signal to the amplification unit 14. The amplification unit 14 amplifies the input electric signal, and the amplified electric signal is sent to the burst signal start time detection circuit 16, the CLK generation unit 17, and the identification reproduction unit 15, respectively. The electric signal input to the burst signal start detection circuit 16 is branched and sent to the delay unit 16a, the EX-OR unit 16b, and the peak detection unit 16d.
[0020]
3 (corresponding to waveforms A to G in the burst signal start detection circuit 16 shown in FIG. 2) (FIGS. 3A and 3B are collectively referred to as FIG. 3). The operation will be described. The delay unit 16a delays the input electric signal (waveform A in FIG. 3) by an arbitrary fixed time, and then sends the signal to the EX-OR unit 16b. In FIG. 3, the delay amount is 1 bit (waveform B in FIG. 3). The EX-OR unit 16b performs an EX-OR operation on the electric signal transmitted from the amplifying unit 14 (waveform A in FIG. 3) and the electric signal transmitted from the delay unit 16a (waveform B in FIG. 3). The output signal (waveform C in FIG. 3) is sent to the average voltage generator 16c.
[0021]
The average voltage generation unit 16c calculates the average value of the input electric signal, and sends the averaged signal (waveform D in FIG. 3, hereinafter referred to as Vave) to the comparison unit 16f. For example, in the case of the burst signal 1 shown in FIG. 3A, at the start of the signal, the value approaches the value of “1” from the intermediate value of the alternating “1” and “0” of the electric signal.
[0022]
On the other hand, the peak detector 16d detects the peak value of the electric signal sent from the amplifier 14, and sends the result (waveform E in FIG. 3) to the reference voltage generator 16e. The reference voltage generator 16e generates a reference voltage based on the signal transmitted from the peak detector 16d (waveform F in FIG. 3, hereinafter referred to as Vr). Here, the reference voltage generation unit 16e has a specified value of the reference voltage (hereinafter, referred to as Vr1) to be compared with the signal sent from the peak detection unit 16d, and the output signal of the peak detection unit 16d is Vr1 ( Vr is generated when it exceeds the dotted line in the waveform E in FIG. 3 and is sent to the comparison unit 16f.
[0023]
The comparison unit 16f generates a control signal (waveform G in FIG. 3, hereinafter referred to as Vstat) based on the signal (hereinafter, Vave) and Vr sent from the average voltage generation unit 16c, and sends it to the identification reproduction unit 15. Here, the comparison unit 16f includes a voltage for comparison with Vave (hereinafter, Vr2) and a voltage for comparison with Vr (hereinafter, Vr3), and Vave becomes Vr2 or more (Vave ≧ Vr2). At the stage when Vr becomes equal to or higher than Vr3 (Vr ≧ Vr3), a control signal is generated and sent to the identification reproducing unit 15. The state of Vave ≧ Vr2 means that the duty ratio of the output signal of the amplification unit 14 has a value that allows the identification and reproduction unit 15 to accurately identify and reproduce. Further, the state of Vr ≧ Vr3 means that the amplitude of the burst signal is at a level at which the identification and reproduction unit 15 can accurately identify and reproduce.
[0024]
The CLK generation unit 17 generates a CLK based on the electric signal transmitted from the amplification unit 14, and then transmits the CLK signal to the identification reproduction unit 15. When the Vstat changes from “0” to “1”, the identification reproducing unit 15 starts identification and reproduction of the electric signal transmitted from the amplification unit 14 based on the CLK signal transmitted from the CLK generation unit 17. .
[0025]
Thereby, when the duty ratio at the start of the burst signal reaches 50% from a value larger than 50%, the electric signal output from the amplification unit is branched into two, one of which is delayed by an arbitrary time, and both of the EX-ORs are delayed. Then, after averaging, a control signal is generated by comparison with a reference voltage, and the control signal is sent to the identification reproducing unit 15 so that the identification reproducing unit 15 can accurately identify and reproduce the output signal of the amplification unit. it can. In addition, by integrating the amplifying unit 14, the delay unit 16a, the EX-OR unit 16b, and the average voltage generating unit 16c into one IC, it is possible to reduce the size and cost of the device and system.
[0026]
The case where the duty ratio at the start of the burst signal reaches 50% from a value larger than 50% has been described above. The case where the duty ratio at the start of the burst signal reaches 50% from a value smaller than 50%. Performs the same operation. Also in the case of the burst signal 2 shown in FIG. 3B, the waveform C in FIG. 3 is an intermediate value of the alternating “1” and “0” of the electric signal at the start of the signal, but the value of “1” gradually increases. Approach. The operation of the other blocks is omitted because it is the same as “when the duty ratio at the start of the burst signal reaches 50% from a value larger than 50%” shown in FIG.
[0027]
Thus, when the duty ratio at the start of the burst signal reaches 50% from a value smaller than 50%, the electric signal output from the amplifier is branched into two, one of which is delayed by an arbitrary time, and both of the EX-ORs are delayed. Then, after averaging, a control signal is generated by comparison with a reference voltage, and the control signal is sent to the identification reproducing unit 15 so that the identification reproducing unit 15 can accurately identify and reproduce the output signal of the amplification unit. it can.
[0028]
As described above, in this embodiment, in the burst signal start detection circuit, the EX-OR of the electrical signal, the averaging of the EX-OR output, the generation of the control signal by comparing the averaged voltage with the reference voltage, and the control thereof By transmitting the signal to the identification and reproduction unit 15, even when the duty ratio of the output signal of the amplification unit at the start of the burst signal does not reach a value that can be accurately identified and reproduced by the identification and reproduction unit 15 at the subsequent stage of the amplification unit. In the case where the duty ratio at which the identification / reproduction unit 15 can accurately identify / reproduce the data does not reach the duty ratio, the identification / reproduction unit 15 does not perform the identification. Can transmit a control signal for causing the identification reproducing section 15 to execute the identification. As a result, the identification / reproduction unit 15 can accurately identify and reproduce the amplification unit signal. In addition, by integrating the amplifying unit 14, the delay unit 16a, the EX-OR unit 16b, and the average voltage generating unit 16c into one IC, it is possible to reduce the size and cost of the device and system.
[0029]
Note that FIGS. 1 and 2 are only schematically shown to the extent that this embodiment can be understood, and therefore, the present invention is not limited to the configurations and operations of FIGS.
[0030]
【The invention's effect】
As described above, according to the present invention, the stage at which the duty ratio of the burst signal can be accurately identified and reproduced is detected, and based on the detection, the burst signal start which can realize accurate identification and reproduction can be realized. Provided are an optical receiving device and an optical transmission system including a time detection circuit, a burst signal start time detection circuit.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an optical transmission system according to an embodiment of the present invention. FIG. 2 is an optical receiving device according to an embodiment of the present invention, a burst signal start detection circuit in the receiving device, and a peripheral circuit thereof. FIG. 3 is a block diagram showing a configuration; FIG. 3 is a waveform diagram corresponding to waveforms A to G in a burst signal start detection circuit 16 shown in FIG. 2; FIG. 3 (a) is a waveform diagram for burst signal 1; FIG. 4 is a block diagram showing a configuration of a conventional optical receiving apparatus.
Reference Signs List 10 optical transmission device 11 optical transmission line 12 optical reception device 13 photoelectric conversion unit 14 amplification unit 15 identification reproduction unit 16 detection circuit 16a at start of burst signal delay unit 16b EX-OR unit 16c average voltage generation unit 16d peak detection unit 16e reference Voltage generation unit 16f Comparison unit 17 CLK generation unit

Claims (7)

After a burst signal is subjected to optical-electrical conversion and amplification, a delay unit for delaying an input signal to be input for a predetermined time,
An EX-OR unit that obtains an exclusive OR of the input signal and the output signal of the delay unit;
An average voltage generator that generates an average voltage of the output signal of the EX-OR unit;
A peak detection unit that detects a peak of the input signal,
A reference voltage generator that generates a reference voltage based on the detection signal of the peak detector;
A comparison unit that compares an output signal of the average voltage generation unit and a reference voltage output from the reference voltage generation unit,
Burst signal start detection circuit provided. 2. The burst signal start time detection circuit according to claim 1, wherein the delay section is configured to delay the input signal by an arbitrary time. 2. The reference voltage generator is configured to generate a reference voltage when the level of the detection signal of the peak detector reaches a predetermined value, and send the reference voltage to the comparator. 3. Or the burst signal start detection circuit according to 2. The comparison unit compares the output signal of the average voltage generation unit with the reference voltage output from the reference voltage generation unit, and when the duty ratio of the input signal becomes a certain specified value, the comparison unit outputs 4. The burst signal start time detection circuit according to claim 1, wherein the circuit is configured to transmit a control signal. A photoelectric conversion unit for converting an input optical signal into an electric signal,
An amplification unit that amplifies an output signal of the photoelectric conversion unit,
The burst signal start detection circuit according to any one of claims 1 to 4, wherein the control signal is generated when a duty ratio of an output signal of the amplification unit reaches a predetermined value.
A clock generation unit that generates a clock based on an output signal of the amplification unit;
An identification reproduction unit that identifies and reproduces the output signal of the amplification unit based on the detection signal of the burst signal start detection circuit and the output signal of the clock generation unit,
Optical receiver provided. The optical receiver according to claim 5, wherein the amplification unit, the delay unit, the EX-OR unit, the average voltage generation unit, and the comparison unit are integrated in one IC. An optical transmission device for transmitting an optical signal;
An optical transmission line for transmitting an optical signal from the optical transmitter,
The optical receiver according to claim 5 or 6, which receives an optical signal that has propagated through the optical transmission line.
Optical transmission system equipped.

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