JPH11163803A - Optical signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent occurrence of a reception error in the case of receiving an input optical signal from an optical switch whose on/off is selected at a high speed by controlling a photoelectric conversion gain to be converged at a high speed into an amplitude value (amplification factor) optimum to data identification in open loop automatic gain control when an input optical signal is subjected to photoelectric conversion and in closed/open loop automatic gain control with respect to a photoelectric conversion signal. SOLUTION: A transmitted input optical signal is photoelectrically converted, a gain of the photoelectrically converted signal is controlled and a data signal is identified and recovered with a recovered clock signal. An open loop automatic gain control means (photocoupler 11, PIN-PD 15, current/voltage conversion circuit 16, discrimination device 17, and APD bias voltage control section 18) controls a photoelectric conversion gain of the input optical signal at the APD 12 corresponding to a level of a branched input optical signal to be a prescribed amplification factor. Furthermore, a closed loop automatic gain control means (AGC amplifier 14, gain control section 19, and peak detector 20) applies automatic gain control AGC to a voltage signal (input optical signal) from a preamplifier 13 to be a prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system, and performs open-loop automatic gain control when photoelectrically converting an input optical signal, and performs closed / open-loop automatic gain control for the photoelectrically converted signal. In addition, the present invention relates to an optical signal receiving device that identifies and reproduces a data signal with a reproduced clock signal.

[0002]

2. Description of the Related Art Conventionally, in an optical communication system, an optical signal receiver using an avalanche photodiode (APD) has been used. FIG. 5 is a block diagram showing a configuration of a conventional optical signal receiver using an APD. In this optical signal receiver, an input optical signal is photoelectrically converted by the APD 2, and the converted current signal is converted into a voltage signal by the preamplifier 3. This voltage signal is variably amplified by an automatic gain control (AGC) amplifier 4 to an amplitude value suitable for data identification. AGC amplifier 4
In, automatic gain control for setting the output signal to a constant level is performed.

In this automatic gain control, the peak value of the output signal from the AGC amplifier 4 is detected by a peak detector 10 and
This detection signal is input to the APD bias voltage controller 8 and the gain controller 9. Control of the amplification factor M of the APD 2 and variable gain control of the AGC amplifier 4 are performed in accordance with the level of the detection signal.

In this gain control, closed loop control is performed so that the gains of the APD 2 and the AGC amplifier 4 become small when the amplitude value of the output signal of the AGC amplifier 4 is large. That is, the closed loop control is repeated until the level of the output signal of the AGC amplifier 4 reaches a predetermined amplitude value. Conversely, when the output signal of the AGC amplifier 4 has a small amplitude value, the closed loop control is performed so that the gains of the APD 2 and the AGC amplifier 4 become large. That is, the closed loop control is repeated until the level of the output signal of the AGC amplifier 4 reaches a predetermined amplitude value.

As described above, in the conventional optical signal receiver, the AP
The data discrimination is performed by adjusting the amplification factor M of D2 and the gain of the AGC amplifier 4 to optimize the amplitude value of a signal input to a discrimination reproduction circuit and a timing extraction circuit (not shown).

[0006]

However, the above conventional example has a disadvantage that it is difficult to optimize the gain M of the APD 2 and the gain of the AGC amplifier 4 with respect to a steep change of the input optical signal. For example, optical cross connect and optical AD
Like M (Add Drop Mux), turn on the input optical signal at high speed.
When receiving an input optical signal from an optical switch that is turned off,
The adjustment of the gain M of the APD 2 and the gain of the AGC amplifier 4 could not be optimized at high speed with respect to a steep change of the input optical signal.

This is because when the input optical signal changes from off to on, the amplification factor M of the APD 2 does not change until a detection signal generated from the output signal of the AGC amplifier 4 is input. Further, the speed of the closed loop control system for controlling the amplification factor M cannot be increased so much as to prevent oscillation. Therefore, when the output signal of the AGC amplifier 4 is input to the discrimination reproduction circuit and the timing extraction circuit, the optimum amplitude value cannot be set at high speed, and a reception error occurs.

The present invention has been made to solve the above-mentioned problems in the prior art, and has an open-loop automatic gain control for photoelectrically converting an input optical signal and a closed / open-loop automatic gain control for the photoelectrically converted signal. Can be quickly converged to the optimum amplitude value (amplification factor) for data identification, and it is possible to reliably prevent the occurrence of a reception error even when receiving an input optical signal from an optical switch that switches on and off at a high speed. An object of the present invention is to provide an optical signal receiving device.

[0009]

According to a first aspect of the present invention, there is provided an apparatus for controlling a gain of a signal obtained by photoelectrically converting an input optical signal transmitted optically, and for controlling a gain of a reproduced clock signal. In an optical signal receiving apparatus for discriminating and reproducing a signal, an open-loop automatic gain control means for performing gain control when photoelectrically converting the input optical signal in accordance with the level of the input optical signal obtained by branching the input optical signal; , A current / voltage converter for converting a current signal converted by the photoelectric converter into a voltage signal, and a closed loop automatic gain controller for controlling a voltage signal from the current / voltage converter to a predetermined value. This is a configuration including:

According to a second aspect of the present invention, the gain of a signal obtained by photoelectrically converting an optically transmitted input optical signal is controlled.
In an optical signal receiving apparatus that identifies and reproduces a data signal with a reproduced clock signal, a first open-loop automatic control that performs gain control when photoelectrically converting the input optical signal in accordance with the level of the input optical signal obtained by splitting the input optical signal. Gain control means, a photoelectric conversion element for photoelectrically converting an input optical signal, current / voltage conversion means for converting a current signal converted by the photoelectric conversion element into a voltage signal, and a voltage signal from the current / voltage conversion means for converting the voltage signal from the current / voltage conversion means to a predetermined value. And a second open loop automatic gain control means for controlling and outputting the output.

According to a third aspect of the present invention, in the optical signal receiving apparatus, an automatic gain control (AGC) amplifier circuit that performs variable amplification control by closed loop control is used as the closed loop automatic gain control means.

According to a fourth aspect of the present invention, in the optical signal receiving apparatus, a superlattice avalanche photodiode is used as the photoelectric conversion element.

According to a fifth aspect of the present invention, in the optical signal receiving apparatus, a preamplifier circuit is used as the current / voltage conversion means.

According to a sixth aspect of the present invention, the open-loop automatic gain control means photoelectrically converts the branched input optical signal, converts the current signal into a voltage signal, and determines the voltage signal in advance. An open-loop control circuit is used to control and determine the gain in the photoelectric conversion by the photoelectric conversion element to a predetermined value by comparing and judging with the level.

According to a seventh aspect of the present invention, as the closed loop automatic gain control (AGC) amplifier circuit, an AGC amplifier for variably amplifying and outputting a voltage signal from a current / voltage conversion means and an AGC amplifier. And a gain controller that controls the amplification output of the AGC amplifier to a predetermined value based on the peak value detected by the peak detector.

In the optical signal receiving apparatus according to the present invention, as the open-loop control circuit, an optical coupler for supplying one main signal obtained by branching an input optical signal to a photoelectric conversion element, and the other input branching by the optical coupler. A PIN photodiode that photoelectrically converts an optical signal, a current / voltage conversion circuit that converts a current signal from the PIN photodiode into a voltage signal, and a discriminator that determines an input optical signal level from the voltage signal of the current / voltage conversion circuit. A photoelectric conversion element bias voltage control unit that sets a bias voltage for controlling the gain in photoelectric conversion of the photoelectric conversion element to a predetermined value based on the input optical signal level determined by the discriminator in the photoelectric conversion element. is there.

According to a ninth aspect of the present invention, in the optical signal receiving apparatus, as the first and second open-loop automatic gain control means, an optical coupler for supplying one main signal obtained by branching an input optical signal to a photoelectric conversion element; A PIN photodiode for photoelectrically converting the other input optical signal branched by the coupler, and a current / current for converting a current signal from the PIN photodiode to a voltage signal
A voltage conversion circuit, a CPU for transmitting a control signal for controlling a gain in photoelectric conversion of the photoelectric conversion element to a predetermined value based on a voltage signal corresponding to an input optical signal level from the current / voltage conversion circuit, and control from the CPU A photoelectric conversion element bias voltage control unit for setting a bias voltage for controlling a gain in photoelectric conversion to a predetermined value based on a signal to the photoelectric conversion element, an AGC amplifier for variably amplifying a voltage signal from the current / voltage conversion unit; And a gain control unit that controls the AGC amplifier based on a control signal from the CPU and controls the output signal of the AGC amplifier to a predetermined value.

An optical signal receiving apparatus according to a tenth aspect is configured to further include a removing unit for removing a noise component between the current / voltage conversion circuit and the discriminator.

An optical signal receiving apparatus according to an eleventh aspect of the present invention is configured to further include a removing unit for removing a noise component between the current / voltage conversion circuit and the CPU.

According to a twelfth aspect of the present invention, in the optical signal receiving apparatus, as a removing unit for removing the noise component, a band-pass filter or an input / output unit that passes a frequency band of a data signal in a voltage signal from the current / voltage conversion circuit. And an amplifier circuit having a resonance circuit corresponding to the frequency band of the data signal.

According to a thirteenth aspect of the present invention, in the optical signal receiving apparatus, the discriminator determines whether or not the input optical signal branched by the optical coupler is interrupted / continued, and outputs an alarm signal when the input optical signal is interrupted.

According to a fourteenth aspect of the present invention, in the optical signal receiving apparatus, the CPU determines whether or not the input optical signal split by the optical coupler is interrupted / continued, and outputs an alarm signal when the input optical signal is interrupted.

According to a fifteenth aspect of the present invention, there is provided the optical signal receiving apparatus, wherein the plurality of input optical signals are plural, and one input optical signal is selected from the plurality of input optical signals, or each of the plurality of input optical signals is inputted. It is configured to further include an optical switch for switching outputs.

An optical signal receiving apparatus according to claim 16, wherein a clock extraction circuit for reproducing a clock signal from an output signal of the closed loop automatic gain control means and the second open loop automatic gain control means, and a clock signal from the timing extraction circuit. And a discrimination and reproduction circuit for discriminating and reproducing the data signal based on the data and transmitting the data signal.

[0025] Claims 1, 3 to 8, 1 having such a configuration.
The optical signal receivers 3, 15, and 16 perform open-loop automatic gain control of the photoelectric conversion gain of the input optical signal in accordance with the level of the input optical signal obtained by splitting the input optical signal. In addition, the current signal obtained by converting the input optical signal signal by the photoelectric conversion element,
The signal is converted into a voltage signal, and the voltage signal is set to a predetermined value by closed loop automatic gain control and output.

As a result, the open-loop automatic gain control for photoelectrically converting the input optical signal and the closed-loop automatic gain control for the photoelectrically converted signal can be quickly converged to an optimum amplitude value (amplification factor) for data identification. Become. That is, for example, when receiving an input optical signal from an optical switch that turns on and off an input optical signal at high speed, such as an optical cross-connect or an optical ADM, the photoelectric conversion element is not affected by a sharp change in the input optical signal. The gain adjustment and the gain adjustment of the AGC amplifier can be speeded up. Further, unnecessary oscillation in a closed loop control system for controlling the amplification factor is effectively prevented, and as a result, a reception error does not occur.

The optical signal receiving apparatus according to the second, fourth, fifth, ninth, and thirteenth to sixteenth aspects of the present invention provides an open-loop automatic gain for the photoelectric conversion gain of an input optical signal in accordance with the level of the input optical signal obtained by branching the input optical signal. The current signal obtained by controlling the input optical signal signal by the photoelectric conversion element is further controlled, and the converted voltage signal is set to a predetermined value level by open loop automatic gain control and output.

As a result, the gain in the photoelectric conversion element is controlled by the open-loop automatic gain control in accordance with the level of the input optical signal. The control can be speeded up as compared with the closed loop automatic gain control.

In the optical signal receiving apparatus according to the present invention, since the noise component of the input optical signal is removed, even when the noise component is not negligible compared to the input optical signal, The level of the input optical signal can be accurately determined.

[0030]

Next, an embodiment of an optical signal receiving apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an optical signal receiving apparatus according to an embodiment of the present invention. The optical signal receiving apparatus shown in FIG. 1 passes an input optical signal as it is and, for example, splits an optical coupler 11 at a 10: 1 level, and photoelectrically converts an input optical signal (main signal) from the optical coupler 11. And an avalanche photodiode (APD) 12 whose amplification factor is controlled by a bias voltage.

Further, the optical signal receiving apparatus is provided with an APD 12
Preamplifier 1 for converting the current signal into a voltage signal and outputting the voltage signal
3 and an AGC amplifier that amplifies the voltage signal (input optical signal) from the preamplifier 13 to an amplitude value necessary for data identification by a discrimination reproduction circuit and a timing extraction circuit (not shown) by closed loop automatic gain control (AGC). 14, a PIN photodiode (PD) 15 for photoelectrically converting an input optical signal branched by the optical coupler 11, and a current / voltage conversion circuit for converting a current signal from the PIN-PD 15 into a voltage signal 16.

In the optical signal receiving apparatus, the discriminator 17 for discriminating the level of the voltage signal from the current / voltage conversion circuit 16 and the input / output signal branched by the optical coupler 11 are used by the current / voltage conversion circuit 16. An APD bias voltage control unit 18 for generating a bias voltage for controlling the amplification factor M of the APD 12 in accordance with the level of the converted voltage signal and transmitting the generated bias voltage to the APD 12; It has a gain control section 19 for generating a bias voltage for controlling the amplification factor M of the APD 12 at the level of the input optical signal, and a peak detector 20 for detecting a peak value of an output signal from the AGC amplifier 14.

Next, the operation of this embodiment will be described. In this optical signal receiving apparatus, an input optical signal is transmitted to an optical coupler 1.
1 is input to the APD 12 as a main signal. In the optical coupler 11, the input optical signal is branched, for example, at a ratio of 10: 1, and the branched input optical signal is input to the PIN-PD 15 as a level monitor signal. In APD12,
The input optical signal is photoelectrically converted, and this current signal is converted to the preamplifier 1
3 and converted into a voltage signal, which is then input to the AGC amplifier 14. The AGC amplifier 14 amplifies the voltage signal (input optical signal) to an amplitude value necessary for data identification by an identification reproducing circuit and a timing extracting circuit (not shown) by closed loop automatic gain control (AGC).

The input optical signal branched by the optical coupler 11 is photoelectrically converted, and a voltage signal obtained by converting the current signal into a voltage by the current / voltage conversion circuit 16 is input to the discriminator 17. The discriminator 17 discriminates the level of the voltage signal from the current / voltage conversion circuit 16 and outputs a voltage signal indicating this level to A
The signal is sent to the PD bias voltage control unit 18. The APD bias voltage controller 18 controls the amplification factor M of the APD 12 according to the level of the input optical signal branched by the optical coupler 11, that is, the level of the voltage signal from the current / voltage conversion circuit 16.
Is generated and transmitted to the APD 12.

In the closed loop automatic gain control (AGC) for the AGC amplifier 14, an output signal from the AGC amplifier 14 is input to a peak detector 20, where a peak value is detected and sent to a gain controller 19. The gain control unit 19 performs closed-loop automatic gain control (AGC) for the AGC amplifier 14 based on the level of the peak value. As a result, A
The voltage signal (input optical signal) from the GC amplifier 14 is amplified to an amplitude value necessary for data identification in a later-stage identification reproduction circuit and timing extraction circuit (not shown).

As described above, the main signal (input optical signal) input to the AGC amplifier 14 has an amplification factor M at the PIN-PD 15 which is equal to the current / voltage conversion circuit 16, the discriminator 17, and the APD.
The open-loop automatic gain control through the bias voltage control unit 18 is controlled according to the level of the input optical signal.
As a result, the AGC amplifier 14 performs variable amplification by closed-loop automatic gain control (AGC) that converges to a voltage signal (input optical signal) having an optimum amplitude value at a high speed in a subsequent stage.

Therefore, for example, when receiving an input optical signal from an optical switch that turns on and off the input optical signal at a high speed, such as an optical cross-connect or an optical ADM, the APD 12 responds to a sharp change in the input optical signal. Amplification Factor M and AGC
The gain adjustment (AGC) of the amplifier 14 can be speeded up. Further, oscillation in a closed loop control system for controlling the amplification factor M is effectively prevented, and as a result, a reception error does not occur.

[0038]

FIG. 2 is a block diagram showing the configuration of the first embodiment. The optical signal receiving apparatus according to the first embodiment includes an optical coupler 11, a preamplifier 13, an AGC amplifier 14,
PIN-PD15, current / voltage conversion circuit 16, discriminator 1
7, an APD bias voltage controller 18, a gain controller 19, and a peak detector 20.

Further, the optical signal receiving apparatus has a 2 × 2 optical switch 10 for switching two input optical signals so as to be switched to the optical coupler 11, photoelectrically converts the input optical signal from the optical coupler 11, and A superlattice APD 12a whose amplification factor is controlled by a bias voltage, and an AGC amplifier 14
1p-p reproduced from the output signal (input optical signal) from
And identified and reproduced based on a clock signal having a frequency of 9.95328 GHz, reproduced at 1 Vpp and having a transmission rate of 9.95.
Discrimination / reproduction circuit 2 for transmitting 328 Gb / s data signal
1 and a timing extraction circuit 22 that generates a clock signal of 1 Vp-p and a frequency of 9.95328 GHz reproduced from the output signal (input optical signal) of the AGC amplifier 14 and sends the clock signal to the identification reproduction circuit 21.

Next, the operation of the first embodiment will be described. The optical signal receiving apparatus of the first embodiment is an optical switch 1
Input optical signal from 0 (STM64 standard, wavelength 1.55μ)
m) is input to the optical coupler 11 which branches at 10: 1. An input optical signal of a non-branched main signal from the optical coupler 11 is input to the superlattice APD 12a, and the branched input optical signal is used as a level monitor signal as a PIN-PD15.
Is input to Here, the input optical signal is switched from off to on at high speed (steep) by the optical switch 10, and
An input optical signal of 9.6 dBm is input.

The superlattice APD 12a receives an input optical signal of -10 dBm, and the PIN-PD 15 receives
An input optical signal of −20 dBm branched at 10: 1 is input. The input optical signal input to the PIN-PD 15 is photoelectrically converted, and the current signal is converted into a voltage signal by the current / voltage conversion circuit 16 and input to the discriminator 17. The determiner 17 determines that an input optical signal of −10 dBm has been input to the superlattice APD 12 a based on the level of the voltage signal input here.

The discriminator 17 controls the APD bias voltage controller 18 so that the superlattice APD 12a has a predetermined amplification factor M in accordance with the level, or the APD bias voltage is controlled by a discrimination signal from the discriminator 17. The voltage controller 18 controls the superlattice APD 12a to have a predetermined amplification factor M. Here, the input optical signal input to the superlattice APD 12a is controlled to an amplification factor M = 10 by the control of the APD bias voltage control unit 18.

The photoelectrically converted current signal is converted by the preamplifier 13 into a voltage signal. This preamplifier 1
The voltage signal output from the AGC amplifier 3 is about 600 mVp-p and is input to the AGC amplifier 14 having a maximum gain of 20 dB. The output signal of the AGC amplifier 14 is input to the peak detector 20. The peak detector 20 detects a peak value (amplitude value), and compares the difference with a predetermined value of 600 mVp-p, which is optimal for data discrimination in the discrimination reproduction circuit 21 and the timing extraction circuit 22, and detects the difference.

A signal having a level corresponding to this detection is sent to the gain control unit 19. The gain control unit 19 includes the peak detector 2
AGC voltage corresponding to the detection signal at 0
4 to perform closed loop gain control (AGC). In this case, since the output signal of the AGC amplifier 14 matches the predetermined optimum 600 mVp-p for data identification, A
The closed loop gain control in the GC amplifier 14 converges at high speed. The output signal from the AGC amplifier 14 is input to the identification reproduction circuit 21 and the timing extraction circuit 22.

The timing extracting circuit 22 generates a clock signal of 1 Vpp and a frequency of 9.95328 GHz, and outputs the clock signal to the identification reproducing circuit 21. The identification and reproduction circuit 21 performs identification and reproduction on the basis of the clock signal from the timing extraction circuit 22, and reproduces 1 Vp-p and the transmission speed of 9.95328G.
b / s data signal is transmitted. The optical switch 10
When the input optical signal, which is the output of the optical switch, is switched from on to off, the PIN-PD 15
The discriminator 17 determines that the input optical signal is in the OFF state (input optical signal is disconnected) by the level monitor signal of the input optical signal branched to the input optical signal, and the input optical signal disconnection when the input optical signal is disconnected / continued. Outputs an alarm signal.

The discriminator 17 controls the APD bias voltage controller 18 so that the superlattice APD 12a has a predetermined amplification factor M = 4 corresponding to the level determined here. APD by the discrimination signal from
The bias voltage control unit 18 controls the superlattice APD 12a so that a predetermined amplification factor M = 4.

As a result, as in the first embodiment, for example, an optical cross-connect or an optical AD
When receiving an input optical signal from an optical switch that turns on and off the input optical signal at a high speed, such as M, adjustment of the APD 12 to the amplification factor M for a steep change of the input optical signal, and an AGC amplifier 14 can be speeded up. Further, oscillation of the closed loop control system for controlling the amplification factor M is also effectively prevented, so that no reception error occurs.

FIG. 3 is a block diagram showing the configuration of the second embodiment. In the second embodiment, an optical switch 10, an optical coupler 11, and a superlattice A having the same configuration as the first embodiment shown in FIG.
PD 12a, preamplifier 13, AGC amplifier 14, PI
N-PD 15, current / voltage conversion circuit 16, discriminator 17,
An APD bias voltage control unit 18, a gain control unit 19, a peak detector 20, an identification reproduction circuit 21, and a timing extraction circuit 22 are provided. Furthermore, a band-pass filter (BPF) 25 having a center frequency f0 = 8 kHz for extracting an 8 kHz signal in the STM64 standard and removing a noise component (ASE) as a configuration corresponding to the second embodiment.
Is provided. The BPF 25 is, for example,
An amplifier circuit having a resonance circuit with a frequency of 8 kHz in the input / output unit may be used.

Next, the operation of the second embodiment will be described. In the optical signal receiving apparatus of the second embodiment, the input optical signal (STM64 standard, wavelength 1.5
5 μm) is input to an optical coupler 11 that branches off 10: 1. The input optical signal of the main signal from the optical coupler 11 is input to the superlattice APD 12a, and the branched input optical signal is input to the PIN-PD 15 as a level monitor signal. Here, the input optical signal is switched from off to on at high speed (steep) by the optical switch 10, and an input optical signal of -9.6 dBm is input.

The superlattice APD 12a receives an input optical signal of -10 dBm, and the PIN-PD 15 receives
An input optical signal of −20 dBm is input. PIN-PD
The input optical signal input to 15 is photoelectrically converted, and the current signal is converted to a voltage signal by current / voltage conversion circuit 16 and input to BPF 25. The BPF 25 removes a noise component (ASE) and extracts an 8 kHz signal of the STM64 standard. That is, since the input optical signal is transmitted through the optical signal amplifier of several stages on the optical signal transmission line,
Noise component (ASE) level is large and superlattice APD1
The noise component (ASE) is removed by the BPF 25 because it cannot be ignored as compared with the level of the main signal (input optical signal) to 2a.

The signal from the BPF 25 is input to the discriminator 17. In the discriminator 17, in the same manner as in the first embodiment, the superlattice AP
It is determined that an input optical signal of -10 dBm has been input to D12a. In this discriminator 17, the superlattice APD 12a corresponding to the discriminated level has a predetermined amplification factor M
APD bias voltage controller 18 is controlled so that
Alternatively, the APD bias voltage control unit 18 controls the superlattice APD 12a to have a predetermined amplification factor M according to a discrimination signal from the discriminator 17.

The input optical signal to the superlattice APD 12a is A
The amplification factor M is controlled by the control of the PD bias voltage controller 18.
= 10, and the photoelectrically converted current signal is converted into a voltage signal by the preamplifier 13 in the same manner as in the first embodiment. The voltage signal output from the preamplifier 13 is about 600 mVp-p, and the maximum gain is 20 mVp-p.
The signal is input to a dB AGC amplifier 14. The output signal of the AGC amplifier 14 is input to the peak detector 20. The peak detector 20 detects a peak value (amplitude value), and a predetermined identification and reproduction circuit 21 and a timing extraction circuit 22
The difference is compared with 600 mVp-p, which is optimal for data discrimination, and the detection is performed.

A signal having a level corresponding to this detection is sent to the gain control unit 19. The gain control unit 19 includes the peak detector 2
AGC voltage corresponding to the detection signal at 0
4 to perform closed loop gain control. In this case, AG
Since the output signal of the C amplifier 14 matches 600 mVp-p which is optimal for predetermined data identification, the closed-loop automatic gain control (AGC) in the AGC amplifier 14 converges at high speed. The output signal from the AGC amplifier 14 is input to the identification reproduction circuit 21 and the timing extraction circuit 22.

The timing extracting circuit 22 generates a clock signal of 1 Vp-p and a frequency of 9.95328 GHz, and outputs it to the identification reproducing circuit 21. The identification and reproduction circuit 21 performs identification and reproduction based on the clock signal from the timing extraction circuit 22 and reproduces 1 Vp-p and a transmission rate of 9.95328 G
b / s data signal is transmitted. The optical switch 10
When the input optical signal, which is the output of the optical switch, is switched from on to off, the PIN-PD 15
The discriminator 17 determines that the input optical signal is in the OFF state (input optical signal is disconnected) by the level monitor signal of the input optical signal branched to the input optical signal, and the input optical signal disconnection when the input optical signal is disconnected / continued. Outputs an alarm signal.

In the discriminator 17, the superlattice APD 12a determines the amplification factor M according to the level determined here.
= 4, or the APD bias voltage controller 18 controls the superlattice APD 12a to have a predetermined amplification factor M = 4 according to a discrimination signal from the discriminator 17. I do.

As a result, in the second embodiment, the BPF2
5, the noise component (ASE) is removed and the 8 kHz signal in the STM64 standard is extracted. Therefore, even when the noise component (ASE) is at a level that is not negligible compared to the input optical signal, the input optical signal Level can be accurately determined. Therefore, the same advantage as that of the first embodiment, that is, the APD against a sharp change of the input optical signal is obtained.
The adjustment of the gain 12 to the amplification factor M and the gain adjustment of the AGC amplifier 14 can be more reliably speeded up. Also,
Oscillation of the closed loop control system is more effectively prevented, and also in this case, no reception error occurs.

FIG. 4 is a block diagram showing the configuration of the third embodiment. The third embodiment has the same optical switch 10, optical coupler 11, superlattice APD 12a, preamplifier 13, AGC amplifier 14, PIN-PD 15, current / voltage conversion circuit 16, and APD bias voltage control as in the first embodiment. Part 1
8, a gain control unit 19, an identification reproduction circuit 21, and a timing extraction circuit 22.

Further, as a configuration corresponding to the third embodiment, a center frequency f0 for extracting an 8 kHz signal in the STM64 standard and removing a noise component (ASE) is 8 kHz.
z bandpass filter (BPF) 25 and super lattice AP
A CPU 26 is provided for controlling the gain of the D12a during photoelectric conversion according to the level of the input optical signal, and controlling the amplification gain of the AGC amplifier 14 according to the level of the input optical signal. In this configuration, the amplification gain control (AGC) of the AGC amplifier 14 corresponds to the embodiment shown in FIG.
Unlike the closed-loop automatic gain control of the first and second embodiments shown in FIG.

Next, the operation of the third embodiment will be described. In the optical signal receiving apparatus according to the third embodiment, similarly to the first embodiment, the input optical signal (STM6
4 standard, wavelength 1.55 μm) is input to the optical coupler 11 which branches 10 to 1. The unbranched main signal (input optical signal) from the optical coupler 11 is input to the superlattice APD 12a, and the branched input optical signal is input to the PIN-PD 15 as a level monitor signal. Here, the input optical signal is switched at high speed (steep) from off to on by the optical switch 10, and an input optical signal of -9.6 dBm is input.

The superlattice APD 12a receives an input optical signal of -10 dBm, and the PIN-PD 15 receives
An input optical signal of −20 dBm is input. PIN-PD
The input optical signal to the input / output 15 is photoelectrically converted, and the current signal is converted to a voltage signal by a current / voltage conversion circuit 16 to be converted to a BPF2.
5 is input. In the BPF 25, the noise component (AS
E) is removed, and an 8 kHz signal of the STM64 standard is extracted. That is, since the input optical signal is transmitted through several stages of optical signal amplifiers on the optical signal transmission line, the noise component (ASE) level is large and compared with the main signal (input optical signal) level to the superlattice APD 12a. Therefore, the noise component (ASE) is removed by the BPF 25.

The signal from the BPF 25 is input to the CPU 26. In the CPU 26, as in the first embodiment, the superlattice AP is determined based on the level of the voltage signal input thereto.
It is determined that an input optical signal of -10 dBm has been input to D12a. The CPU 26 controls the APD bias voltage control unit 18 so that the superlattice APD 12a has a predetermined amplification factor M according to the determined level, or the APD bias voltage control unit 18 The superlattice APD 12a is controlled to have a predetermined amplification factor M.

The input optical signal input to the superlattice APD 12 a is controlled by the APD bias voltage controller 18 to
The amplification factor is controlled to M = 10, and the current signal obtained by the photoelectric conversion is converted into a voltage signal by the preamplifier 13 in the same manner as in the first embodiment. The voltage signal output from the preamplifier 13 is about 600 mVp-p, and is input to the AGC amplifier 14 having a maximum gain of 20 dB. This AGC amplifier 14
The open loop automatic gain control is performed under the control of the CPU 26 through the gain control unit 19.

In this automatic gain control, for example, the superlattice A
From the relationship between the input optical signal (main signal) from the optical coupler 11 input to the PD 12a and the amplification factor M in the superlattice APD 12a, the gain is set to 0 dB in order to set the amplitude value of the output signal of the AGC amplifier 14 to a predetermined value. Control. The output signal from the AGC amplifier 14 is input to the identification reproduction circuit 21 and the timing extraction circuit 22.

The timing extraction circuit 22 generates a clock signal of 1 Vp-p and a frequency of 9.95328 GHz, and outputs it to the identification reproduction circuit 21. The identification and reproduction circuit 21 performs identification and reproduction based on the clock signal from the timing extraction circuit 22 and reproduces 1 Vp-p and a transmission rate of 9.95328 G
b / s data signal is transmitted. The optical switch 10
When the input optical signal, which is the output of the optical switch, is switched from on to off, the PIN-PD 15
The discriminator 17 determines that the input optical signal is in the OFF state (input optical signal is disconnected) by the level monitor signal of the input optical signal branched to the input optical signal, and the input optical signal disconnection when the input optical signal is disconnected / continued. Outputs an alarm signal.

In the discriminator 17, the superlattice APD 12a determines the amplification factor M =
The APD bias voltage control unit 18 is controlled so as to be equal to 4, or the APD bias voltage control unit 18 is controlled by the discrimination signal from the discriminator 17 so that the superlattice APD 12a has a predetermined amplification factor M = 4. The APD 12a is controlled. Also, the AGC amplifier 14 is controlled to a predetermined gain.

As a result, even in the third embodiment, the BPF2
5, the noise component (ASE) is removed, and the 8 kHz signal in the STM64 standard is extracted. Therefore, even if the noise component (ASE) is at a level that is not negligible compared to the input optical signal, the input light branched off. The signal can be determined more accurately. Also, since the open-loop automatic gain control of the superlattice APD 12a is performed in accordance with the level of the input optical signal, the gain control in photoelectric conversion in the superlattice APD 12a can be performed at a higher speed than in the closed-loop automatic gain control. Become.

Therefore, the third embodiment has the same advantages as the first and second embodiments. That is, the amplification factor M of the APD 12 and the AGC
The speed of the gain adjustment of the amplifier 14 can be further increased, the oscillation of the closed loop control system for controlling the amplification factor M is effectively prevented, and as a result, no reception error occurs.

[0068]

As is apparent from the above description, according to the optical signal receiving apparatus according to the first, third to eighth, thirteenth, fifteenth, and sixteenth aspects, the level of the input optical signal corresponding to the level of the input optical signal obtained by branching the input optical signal is obtained. The photoelectric conversion gain of the input optical signal is controlled by open-loop automatic gain control, and the current signal obtained by converting the input optical signal signal by the photoelectric conversion element is further set by the closed-loop automatic gain control to the converted voltage signal to a predetermined value. Output.

As a result, the open-loop automatic gain control for photoelectrically converting the input optical signal and the closed-loop automatic gain control for the photoelectrically converted signal can be quickly converged to an amplitude value (amplification factor) optimum for data identification. Become. Oscillation of the closed loop control system for controlling the amplification factor is also effectively prevented, and no reception error occurs.

According to the optical signal receiving apparatus of the second, fourth, fifth, ninth, and thirteenth to sixteenth aspects, the photoelectric conversion gain of the input optical signal is increased in accordance with the level of the input optical signal obtained by branching the input optical signal. Automatic gain control is performed, a current signal obtained by converting an input optical signal signal by a photoelectric conversion element, and a converted voltage signal are set to a predetermined value by open-loop automatic gain control. As a result, the gain control at the time of photoelectrically converting the input optical signal signal by the photoelectric conversion element can be performed at a higher speed as compared with the closed loop automatic gain control.

According to the optical signal receiving apparatus of the present invention, since the noise component of the input optical signal is removed, the noise component has a large level that cannot be ignored compared to the input optical signal. Also, the level of the input optical signal can be accurately determined.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical signal receiving apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a first embodiment.

FIG. 3 is a block diagram showing a configuration of a second embodiment.

FIG. 4 is a block diagram showing a configuration of a third embodiment.

FIG. 5 is a block diagram illustrating a configuration of a conventional optical signal receiver.

[Explanation of symbols]

 Reference Signs List 10 optical switch 11 optical coupler 12 avalanche photodiode (APD) 12a superlattice APD 13 preamplifier 14 AGC amplifier 15 PIN photodiode (PD) 16 current / voltage conversion circuit 17 discriminator 18 APD bias voltage controller 19 gain controller Reference Signs List 20 peak detector 21 discrimination reproduction circuit 22 timing extraction circuit 25 bandpass filter (BPF) 26 CPU

Claims (16)

[Claims] 1. An optical signal receiving apparatus for controlling the gain of a signal obtained by photoelectrically converting an optically transmitted input optical signal, and identifying and reproducing a data signal with a reproduced clock signal. Open loop automatic gain control means for performing gain control when photoelectrically converting an input optical signal corresponding to a signal level; a photoelectric conversion element for photoelectrically converting the input optical signal; and a current signal converted by the photoelectric conversion element An optical signal receiving apparatus comprising: current / voltage conversion means for converting a voltage signal into a voltage signal; and closed loop automatic gain control means for controlling a voltage signal from the current / voltage conversion means to a predetermined value. 2. An optical signal receiving apparatus for controlling a gain of a signal obtained by photoelectrically converting an optically transmitted input optical signal, and identifying and reproducing a data signal with a reproduced clock signal. First open-loop automatic gain control means for performing gain control when photoelectrically converting an input optical signal in accordance with a signal level; photoelectric conversion element for photoelectrically converting the input optical signal; and conversion by the photoelectric conversion element Current / voltage conversion means for converting a current signal into a voltage signal; and second open loop automatic gain control means for controlling and outputting a voltage signal from the current / voltage conversion means to a predetermined value. Optical signal receiving device. 3. An automatic gain control (AGC) amplifier circuit for performing variable amplification control by closed loop control as said closed loop automatic gain control means.
The optical signal receiving device as described in the above. 4. The optical signal receiving apparatus according to claim 1, wherein a superlattice avalanche photodiode is used as the photoelectric conversion element. 5. The method according to claim 1, wherein a preamplifier circuit is used as said current / voltage conversion means.
The optical signal receiving device as described in the above. 6. The open-loop automatic gain control means photoelectrically converts a branched input optical signal, converts a current signal into a voltage signal, and compares and determines the voltage signal with a predetermined level to perform photoelectric conversion. 2. An optical signal receiving apparatus according to claim 1, wherein an open-loop control circuit for controlling a gain in photoelectric conversion in said step to a predetermined value is used. 7. The closed loop automatic gain control (AGC).
As an amplifier circuit, an AGC amplifier that variably amplifies and outputs a voltage signal from a current / voltage converter, a peak detector that detects a peak value of an output signal from the AGC amplifier, and a peak that is detected by the peak detector. A based on the value
The optical signal receiving device according to claim 3, further comprising: a gain control unit configured to perform control for setting an amplification output of the GC amplifier to a predetermined value. 8. An open-loop control circuit comprising: an optical coupler for supplying one main signal obtained by branching an input optical signal to a photoelectric conversion element; and a PIN photo for photoelectrically converting the other input optical signal branched by the optical coupler. A diode; a current / voltage conversion circuit for converting a current signal from the PIN photodiode into a voltage signal; a discriminator for discriminating an input optical signal level from a voltage signal of the current / voltage conversion circuit; And a photoelectric conversion element bias voltage control unit that sets a bias voltage for controlling the gain in photoelectric conversion of the photoelectric conversion element to a predetermined value based on the input optical signal level set in the photoelectric conversion element. Item 7. The optical signal receiving device according to Item 6. 9. An optical coupler for supplying one main signal obtained by splitting an input optical signal to a photoelectric conversion element as first and second open loop automatic gain control means, and the other input optical signal split by the optical coupler. A photoelectric conversion circuit, a current / voltage conversion circuit for converting a current signal from the PIN photodiode into a voltage signal, and a voltage signal corresponding to an input optical signal level from the current / voltage conversion circuit. CPU for transmitting a control signal for controlling a gain in photoelectric conversion of a photoelectric conversion element to a predetermined value
A photoelectric conversion element bias voltage control unit that sets a bias voltage for controlling a gain in photoelectric conversion to a predetermined value based on a control signal from the CPU in the photoelectric conversion element; and a voltage signal from a current / voltage conversion unit. That variably amplifies
A C amplifier; and a gain controller for controlling the AGC amplifier based on a control signal from the CPU and performing control to set an output signal of the AGC amplifier to a predetermined value. The optical signal receiving device according to claim 2. 10. The optical signal receiving apparatus according to claim 8, further comprising a removing unit for removing a noise component between the current / voltage conversion circuit and the discriminator. 11. The optical signal receiving apparatus according to claim 9, further comprising a removing unit for removing a noise component between the current / voltage conversion circuit and the CPU. 12. A band-pass filter that passes a frequency band of a data signal in a voltage signal from the current / voltage conversion circuit or an input / output unit corresponding to a frequency band of the data signal as the removing unit that removes the noise component. 11. An amplifier circuit having a resonance circuit is used.
The optical signal receiving device as described in the above. 13. The optical signal receiving apparatus according to claim 8, wherein the discriminator determines whether or not the input optical signal branched by the optical coupler is interrupted / continued, and outputs an alarm signal when the input optical signal is interrupted. apparatus. 14. The optical signal receiving apparatus according to claim 9, wherein the CPU determines whether or not the input optical signal branched by the optical coupler is interrupted / continued, and outputs an alarm signal when the input optical signal is interrupted. apparatus. 15. The input optical signal is plural, and one input optical signal is selected from the plurality of input optical signals, or
3. The optical signal receiving device according to claim 1, further comprising an optical switch for switching input and output of each of the plurality of input optical signals. 16. A timing extraction circuit for reproducing a clock signal from output signals of the closed loop automatic gain control means and the second open loop automatic gain control means, and a data signal is identified based on the clock signal from the timing extraction circuit. The optical signal receiving device according to claim 1, further comprising: an identification reproducing circuit that reproduces and transmits the signal.