JP4052107B2 - Burst optical receiver and burst optical signal receiving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical receiver applied to an optical communication network, and more particularly to a burst optical receiver in which signal light is transmitted in bursts.
[0002]
[Prior art]
FIG. 10 is a configuration diagram of a conventional PON (Passive Optical Network). In the PON uplink, the signal lights 51 to 53 output from the subscriber stations 104 to 106 are multiplexed by the optical multiplexer 103 and received by the burst optical receiver 102 of the center station 101.
[0003]
Different signal light transmission timings are assigned to the respective subscribers 104 to 106, and the signal lights 51 to 53 are output in bursts in units of predetermined signal cells according to the respective signal light transmission timings. In the signal light after the multiplexing process output from the optical multiplexer 103, the signal lights 51 to 53 from the subscriber stations 104 to 106 are time-division multiplexed in signal cell units.
[0004]
Here, since the transmission distances from the subscriber stations 104 to 106 to the optical multiplexer 103 are different, the intensity of the signal light input to the burst optical receiver 102 is different for each signal cell. For example, the light intensity of the signal cell of the signal light 51 transmitted from the subscriber station 104 having the shortest transmission distance among the subscriber stations 104 to 106 is larger than the light intensity of the signal cells of the other signal lights 52 and 53. Become.
Accordingly, the burst optical receiver 102 needs to appropriately receive and process signal cells having different optical intensities.
[0005]
FIG. 6 is a configuration diagram of a conventional burst optical receiver (see, for example, Non-Patent Document 1). In FIG. 6, a PD (Photo Diode) 1 converts input signal light into an electric signal and outputs it to the burst preamplifier 4.
[0006]
FIG. 7 is a configuration diagram of the burst preamplifier 4 (see, for example, Patent Document 1). In the burst preamplifier 4, when the voltage of the electric signal is higher than a predetermined reference voltage V1, the preamplifier gain is switched by turning on the transistor Tr1 or Tr2 connected in parallel to the transimpedance amplifier 10.
[0007]
The burst preamplifier 4 measures the signal light transmission timing of the signal cells of each of the subscriber stations 104 to 106, and within the reception time of the first bit of each signal cell with reference to the signal light transmission timing, Gain switching control is performed.
[0008]
The “H” level holding circuit 3 monitors the electric signal after the amplification process output from the burst preamplifier 4, detects the High / Low level of the electric signal corresponding to On / Off of the input signal optical pulse, and A high level voltage of the signal (hereinafter referred to as “H” level signal ”) is output. The “H” level signal is held at a constant value over the reception time of one signal cell.
[0009]
Next, the threshold generation circuit 5 multiplies the “H” level signal by a predetermined coefficient to calculate an “H” level determination threshold. The limiter amplifier 6 compares the electric signal after the amplification processing with the “H” level determination threshold value and reproduces and outputs (Vout) a digital signal pulse.
[0010]
FIG. 8 is an explanatory diagram showing a time chart of input / output signals of the conventional burst preamplifier. When the voltage of the electric signal input to the burst preamplifier 4 is equal to or higher than the reference voltage V1, the second bit is changed because the gain of the burst preamplifier 4 is reduced during reception of the first bit of each signal cell. Thereafter, the voltage of the electric signal after the amplification process becomes small.
[0011]
With such a configuration, even when signal light having different light intensity is input for each signal cell, a signal pulse without distortion can be reproduced.
[0012]
[Patent Document 1]
JP 2000-315923 A (FIG. 4, paragraphs 0049 to 0064)
[Non-Patent Document 1]
“CMOS Instantaneous Response Gain Control Amplifier IC for PDS Optical Subscriber System”, Nakamura et al., Proceedings of the IEICE Autumn Meeting, B-897, 495, September 1994 [0013]
[Problems to be solved by the invention]
In the conventional burst optical receiver, an “H” level signal is generated based on the first bit before gain switching, and an “H” level determination threshold is calculated. Therefore, as shown in FIG. 9, when the voltage of the electric signal of the first bit is significantly higher than the reference voltage V1, an inappropriate “H” level determination threshold is determined based on the electric signal of the first bit. Is calculated.
In this case, when the signal pulse is reproduced based on the “H” level determination threshold for the second and subsequent bits after the gain switching, there is a problem that an erroneous digital signal pulse is generated.
[0014]
The present invention has been made to solve the above problems, and a burst optical receiver and a burst optical signal receiving method capable of reproducing digital signal pulses without error even when the gain of the burst preamplifier is switched. The purpose is to provide.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, a burst optical receiver according to the present invention switches a light-receiving element that converts received signal light into an electric signal, an amplification gain according to the intensity of the electric signal, and the electric signal. A burst preamplifier for amplifying and outputting the signal, an “H” level holding circuit for detecting an “H” level signal value of the amplified electric signal and outputting it as an “H” level signal, and the “H” level signal And a threshold value generation circuit for calculating an “H” level determination threshold value for reproducing a digital signal pulse, and a “H” level holding circuit ”for a predetermined time required for gain switching control of the burst preamplifier. A mask generation circuit that suppresses the H ”level signal generation process, and the electric signal after the amplification process is compared with the“ H ”level determination threshold value, and the digital signal pulse is And a limiter amplifier that.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a burst optical receiver according to the first embodiment. In FIG. 1, a PD 1 converts input signal light into an electric signal, a timing control circuit 7 regenerates signal light transmission timing of each signal cell, and a burst preamplifier 4 amplifies gain according to the signal level of the electric signal. And the electric signal is amplified with a predetermined gain, the “H” level holding circuit 3 outputs an “H” level signal having a voltage equal to the High level of the electric signal, and the mask generating circuit 2 A control signal for suppressing the generation processing of the “H” level signal is generated, the threshold generation circuit 5 calculates the “H” level determination threshold based on the “H” level signal, and the limiter amplifier 6 Compared with the “H” level determination threshold value, a digital signal pulse is reproduced and output from Vout.
[0017]
The operation of the burst optical receiver according to the first embodiment configured as described above will be described.
The input signal light is converted into an electric signal by the PD 1. The timing control circuit 7 stores the time division multiplex transmission timing of the PON in advance, reproduces the signal light transmission timing of each subscriber station based on the electric signal, and continues after the transmission of one signal cell is completed. A reset pulse signal is output before the reception of the signal cell to be received. Here, the output timing of the reset pulse signal is set to an appropriate timing according to the transmission margin time between the signal cells.
[0018]
The electric signal is input to the burst preamplifier 4. The burst preamplifier 4 has the same configuration as that shown in FIG. In the burst preamplifier 4, when the voltage of the electric signal is larger than a predetermined reference voltage V1, a gain of the preamplifier is switched by turning on the transistor Tr1 or Tr2 connected in parallel to the transimpedance amplifier 10. The burst preamplifier 4 performs gain switching control of the preamplifier within the reception time of the first bit of each signal cell with reference to the reset pulse signal generated by the timing control circuit 7.
The burst preamplifier 4 amplifies the electric signal with the switching-controlled gain and outputs it.
[0019]
The mask generation circuit 2 generates a control signal for suppressing the operation of the “H” level holding circuit 3 based on the electric signal after the amplification process.
FIG. 2 is an explanatory diagram showing a control signal generation method in the mask generation circuit 2. The mask generation circuit 2 stores a signal determination value V2 for detecting the rise / fall of the electrical signal. The signal determination value V2 is set to an appropriate value in advance according to the signal strength of each signal cell and the signal conversion performance of the PD1 based on preliminary experiments and computer simulation.
[0020]
When the mask generation circuit 2 detects the reception start of the signal cell based on the reset pulse signal output from the timing control circuit 7, the mask generation circuit 2 compares the electric signal after the amplification process with the signal determination value V2, and A rising / falling change point (indicated by a cross in FIG. 2) is detected.
After the reset pulse signal is input, the mask generation circuit 2 turns the control signal On (High level in FIG. 2) when a rising change point at which the voltage of the electric signal after amplification exceeds the signal determination value V2 is detected. Set to. Next, the rising / falling change point of the electrical signal is started, and when the count value N = 1, the control signal is set to Off (Low level in FIG. 2). As shown in the lower part of FIG. 2, the control signal generated in this way becomes On over the first bit reception time of the signal cell.
[0021]
Next, the “H” level holding circuit 3 sets the “H” level signal to the initial value 0 when the reset pulse signal is input, detects the point where the control signal has changed to Off, and then performs the amplification process. Monitoring of the electric signal of the electric signal, the High / Low level of the electric signal corresponding to the On / Off of the input signal light pulse is detected, and the voltage value of the high level of the electric signal (hereinafter ““ H ”level signal”) Is called). The “H” level signal is held at a constant value over the reception time of the signal cell being received.
Here, since the control signal is On for the first bit of the signal cell, the generation of the “H” level signal is performed after the second bit of the signal cell.
[0022]
The threshold generation circuit 5 multiplies the “H” level signal by a predetermined coefficient α to calculate an “H” level determination threshold. As the coefficient α, an appropriate value (for example, α = 0.5) is selected in advance in order to reproduce a digital signal pulse to be described later.
[0023]
The limiter amplifier 6 compares the electric signal after the amplification processing with the “H” level determination threshold value and reproduces and outputs (Vout) a digital signal pulse.
[0024]
FIG. 3 is an explanatory diagram showing an operation timing chart of the burst optical receiver according to the first embodiment.
The first bit of the signal cell is before the gain switching control of the burst preamplifier 4 is performed, and the high level voltage of the electric signal after the amplification processing is larger than that of the second and subsequent bits.
[0025]
In the first bit of the signal cell, since the mask generation circuit 2 sets the control signal to On, the “H” level signal generation processing of the “H” level holding circuit 3 is suppressed, and the initial value 0 is output. Yes. Therefore, the threshold value generation circuit 5 calculates the “H” level determination threshold value (= 0) by multiplying the initial value 0 of the “H” level signal by the coefficient α, and the limiter amplifier 6 calculates the electric signal after amplification processing and the “H” level signal. “Comparing with the level judgment threshold value, the digital signal pulse is reproduced and output (Vout).
[0026]
On the other hand, in the second bit of the signal cell, when the mask generation circuit 2 switches the control signal to Off, the “H” level holding circuit 3 generates an “H” level signal based on the electric signal after the amplification process. The threshold generation circuit 5 calculates the “H” level determination threshold by multiplying the “H” level signal by the coefficient α, and the limiter amplifier 6 compares the amplified electric signal with the “H” level determination threshold. A digital signal pulse is reproduced and output (Vout).
[0027]
With the configuration as described above, in the burst optical receiver according to the first embodiment, “H” appropriate for the electric signal after the gain switching control of the burst preamplifier 4 (after the second bit of each signal cell) is generated. “A level determination threshold can be calculated. Therefore, it is possible to provide a burst optical receiver capable of reproducing a digital signal pulse without error even if each signal cell has a different PON.
[0028]
In the first embodiment, the mask generation circuit 2 sets the control signal to OFF when the count value N = 1 of the rising / falling change point of the electric signal after the amplification process, and the first bit of the signal cell. Although the generation processing of the “H” level signal is suppressed, the count value N for setting the control signal Off is not limited to 1, and an appropriate value is set according to the time required for the gain switching of the burst preamplifier 4. Is done.
[0029]
For example, as shown in FIG. 4, when N bits are required for switching the gain of the burst preamplifier 4, after inputting the reset pulse signal, the mask generation circuit 2 sends the control signal On over the N-bit reception time before the gain switching. Set to. By operating in this way, the “H” level signal is generated for the N + 1th bit and after of the electric signal, and the electric power after the gain switching control of the burst preamplifier 4 is generated (after the second bit of each signal cell). An appropriate “H” level determination threshold value for the signal can be calculated.
Here, the number N of bits required for the gain switching of the burst preamplifier is measured by a preliminary experiment.
[0030]
The “H” level holding circuit 3 sets the “H” level signal to the initial value 0 when the reset pulse signal is input. However, the initial value of the “H” level signal is not limited to 0. In the PON, the voltage value of the electric signal of the signal cell having the lowest light intensity at the time of reception is set to the initial value, or another initial value appropriate for reproducing the signal pulse is set. May be.
[0031]
Embodiment 2. FIG.
In the first embodiment, the mask generation circuit generates the control signal based on the detection result of the rising / falling change point of the electric signal after the amplification process, but in the second embodiment, the mask generation circuit performs a burst. A timer for measuring the time required to switch the gain of the preamplifier is provided, and a control signal is generated based on the timer.
The second embodiment is different from the first embodiment in that a timer is provided in the mask generation circuit, and the other configurations are the same. Accordingly, the corresponding components are denoted by the same reference numerals. The description is omitted.
[0032]
FIG. 5 is an explanatory diagram showing an operation timing chart of the burst optical receiver according to the second embodiment.
When the mask generation circuit 2 detects the reception start of the signal cell based on the reset pulse signal output from the timing control circuit 7, the mask generation circuit 2 compares the electric signal after the amplification process with the signal determination value V <b> 2, and the rise of the electric signal is detected. A change point (indicated by a cross in FIG. 5) is detected.
[0033]
After the reset pulse signal is input, the mask generation circuit 2 turns the control signal On (High level in FIG. 2) when a rising change point at which the voltage of the electric signal after amplification exceeds the signal determination value V2 is detected. Set to.
[0034]
Next, the mask generation circuit 2 starts a timer in which the time ΔT required for gain switching control of the burst preamplifier 4 is set, and sets the control signal to Off (Low level in FIG. 5) when a timer timeout is detected. The control signal generated in this way becomes On over the ΔT as shown in the lower part of FIG. Here, the time ΔT set in the timer is set to an appropriate value according to the gain switching time of the burst preamplifier 4.
[0035]
By adopting such a configuration, the burst optical receiver according to the second embodiment can calculate an appropriate “H” level determination threshold for the electrical signal after the gain switching control of the burst preamplifier 4 is generated. Therefore, it is possible to provide a burst optical receiver capable of reproducing a digital signal pulse without error even if each signal cell has a different PON.
[0036]
In the second embodiment, the mask generation circuit 2 detects the change point of the rising edge of the electric signal after the amplification process after inputting the reset pulse signal, and starts the timer. However, this is limited to such a method. Instead, the control signal may be turned on when the reset pulse signal is input, the timer is started, and the control signal may be switched off when the timer detects a timeout. In this case, the timer of the mask generation circuit 2 includes a signal cell reception start margin time from the reset pulse signal input to the start of reception of the first bit of the signal cell, and a time ΔT required for switching the gain control of the burst preamplifier 4. The added waiting time is set.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to calculate an appropriate “H” level determination threshold for an electric signal after occurrence of gain switching control of a burst preamplifier. Therefore, it is possible to provide a burst optical receiver capable of reproducing digital signal pulses without error even if the signal cells have different optical intensities.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a burst optical receiver according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a control signal generation method in the mask generation circuit according to the first embodiment of the present invention;
FIG. 3 is an explanatory diagram showing an operation timing chart of the burst optical receiver according to the first embodiment of the present invention.
FIG. 4 is an explanatory diagram showing an operation timing chart of another burst optical receiver according to the first embodiment of the present invention;
FIG. 5 is an explanatory diagram showing a control signal generation method in a mask generation circuit according to a second embodiment of the present invention;
FIG. 6 is a configuration diagram of a conventional burst optical receiver.
FIG. 7 is a configuration diagram of a burst preamplifier.
FIG. 8 is an explanatory diagram showing a time chart of input / output signals of a burst preamplifier in a conventional burst optical receiver.
FIG. 9 is an explanatory diagram showing an operation timing chart of a conventional burst optical receiver.
FIG. 10 is a configuration diagram of a subscriber system in a conventional PON.
[Explanation of symbols]
1 Light receiving element (PD)
2 Mask generation circuit 3 “H” level holding circuit 4 Burst preamplifier 5 Threshold generation circuit 6 Limiter amplifier 7 Timing control circuit 10 Transimpedance amplifier 15 Diodes 18 and 19 Comparator 20 and 21 Flip-flops R1 to R4 Resistors Tr1 and Tr2 Transistor 51 ~ 53 Signal light 101 Center station 102 Burst optical receiver 103 Optical multiplexer 104 ~ 106 Subscriber station

Claims (4)

A light receiving element that converts received signal light into an electrical signal;
A burst preamplifier that amplifies and outputs the electrical signal while switching the amplification gain according to the strength of the electrical signal;
An “H” level holding circuit for detecting an “H” level signal value of the amplified electric signal and outputting it as an “H” level signal;
A threshold generation circuit for calculating an “H” level determination threshold for reproducing a digital signal pulse based on the “H” level signal;
A mask generation circuit that suppresses the “H” level signal generation processing of the “H” level holding circuit for a predetermined time required for gain switching control of the burst preamplifier;
A limiter amplifier that compares the electric signal after the amplification process with the “H” level determination threshold value and reproduces a digital signal pulse ;
The mask generation circuit detects and counts the rising and falling change points of the electric signal after amplification in accordance with a predetermined signal determination value, and based on the count value, “H” of the “H” level holding circuit. A burst optical receiver characterized in that the level signal generation processing is activated . A light receiving element that converts received signal light into an electrical signal;
A burst preamplifier that amplifies the electrical signal and outputs it while switching the amplification gain according to the strength of the electrical signal,
An “H” level holding circuit for detecting an “H” level signal value of the amplified electric signal and outputting it as an “H” level signal;
A threshold generation circuit for calculating an “H” level determination threshold for reproducing a digital signal pulse based on the “H” level signal;
A mask generation circuit that suppresses the “H” level signal generation processing of the “H” level holding circuit for a predetermined time required for gain switching control of the burst preamplifier;
A limiter amplifier that compares the electric signal after the amplification process with the “H” level determination threshold value and reproduces a digital signal pulse;
The mask generation circuit has a timer for measuring a predetermined time required for gain switching control of the burst preamplifier, and activates the “H” level signal generation processing of the “H” level holding circuit upon detection of the timer timeout. A burst optical receiver characterized in that it is configured . A photoelectric conversion process for converting the received signal light into an electrical signal;
  Amplifying step of amplifying and outputting the electrical signal while switching the amplification gain according to the strength of the electrical signal,
  An “H” level detection step of detecting an “H” level signal value of the electric signal after amplification processing and outputting it as an “H” level signal;
  A threshold generation step of calculating an “H” level determination threshold for reproducing a digital signal pulse based on the “H” level signal;
  A mask generation step of suppressing the “H” level signal generation processing over a predetermined time required for gain switching control in the amplification step;
  A digital signal reproduction step of reproducing the digital signal pulse by comparing the electric signal after the amplification process with the “H” level determination threshold value;
  The mask generation step detects and counts the rising and falling change points of the electric signal after amplification processing according to a predetermined signal determination value, and based on the count value, “H” in the “H” level detection step. A burst optical signal receiving method, wherein level signal generation processing is started. A photoelectric conversion process for converting the received signal light into an electrical signal;
Amplifying step of amplifying and outputting the electrical signal while switching the amplification gain according to the strength of the electrical signal,
An “H” level detection step of detecting an “H” level signal value of the electric signal after amplification processing and outputting it as an “H” level signal;
A threshold generation step of calculating an “H” level determination threshold for reproducing a digital signal pulse based on the “H” level signal;
A mask generation step of suppressing the “H” level signal generation processing over a predetermined time required for gain switching control in the amplification step ;
A digital signal reproduction step of reproducing the digital signal pulse by comparing the electric signal after the amplification process with the “H” level determination threshold value ;
In the mask generation step, a predetermined time required for gain switching control in the amplification step is measured by a timer, and “H” level signal generation processing in the “H” level detection step is started by detecting the timer timeout. A method of receiving a burst optical signal.

Images