JP4206517B2 - Receiving apparatus and receiving method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital optical receiving system, and in particular, when receiving burst optical signals having different powers, an automatic threshold capable of reproducing a normal optical OFF DC level even if the 0 level in a cell differs depending on the extinction ratio. The present invention relates to a receiving device with a control function (hereinafter referred to as a receiving device with an ATC function).
[0002]
[Prior art]
In recent years, optical fiber transmission technology capable of high-speed transmission is being introduced to subscriber networks in order to meet the increasing demand for broadband services centered on images. In order to introduce the optical fiber transmission technology into the subscriber network, not only the cost of the transmission device on the subscriber side but also the cost of the station side device and the optical fiber line are essential. An optical subscriber transmission system devised from such a requirement is a PDS (Passive Double Star) transmission system. In the PDS transmission system, a subscriber and a station are connected to an optical branch circuit by an optical fiber, and data transmitted from the subscriber to the station is transmitted as a burst optical signal called a cell. Thus, each cell is time-division multiplexed so as not to overlap, and then received by the station apparatus.
[0003]
In order to regenerate the burst optical signal received by the station equipment, a level difference of about 30 dB occurs due to variations in the insertion loss of the optical fiber and the optical branch circuit between each subscriber and the station. The device has a function of converting to a constant amplitude for each received burst. In addition, since each cell received has a small extinction ratio of about 10 dB, there is a difference between the 0 level and the light OFF level in the cell. Is required to have a function to reproduce the image accurately.
[0004]
As this type of conventional receiving device with ATC function, for example, there are those shown in IEICE Technical Report IDC97-104, P73-80 (issued in 1997), and FIG. 8 shows the conventional ATC shown in the above document. FIG. 9 is a diagram illustrating the configuration of the function receiving device, and FIG. 9 is an operation explanatory diagram. In FIG. 8, 101 is a light receiving element, 102 is a preamplifier, 103 is a limiter amplifier, 104 is an output buffer, 105 is a peak detection circuit, 106 is a 1/2 circuit, 107 is a DC feedback circuit, and 108 is a reset circuit.
[0005]
The operation will be described. The optical signal as shown in FIG. 9-S1 is photoelectrically converted by the light receiving element 101 and then amplified with low noise by the preamplifier 102 and converted into a voltage signal as shown in FIG. 9-S2 (a), (b). The signal is sent to the amplifier 103 and the peak detection circuit 105.
The peak detection circuit 105 detects and holds a voltage equal to the amplitude peak value (negative voltage) at high speed to obtain a waveform as shown by the solid line in FIG. 9-S4, but it is detected by a reset signal as shown in FIG. 9-S3.・ Restore the held voltage to the initial value. On the other hand, the DC feedback circuit 107 generates a DC feedback voltage equal to the DC voltage of the preamplifier 102 (corresponding to {circle around (0)} in FIG. 9-S5) as indicated by the solid line in FIG. 9-S5.
[0006]
Here, the 1/2 circuit 106 generates a voltage that is 1/2 of the output voltage of the peak detection circuit 105 and the DC feedback voltage from the DC feedback circuit 107, and the limiter amplifier uses the waveform as a threshold as shown in FIG. 9-S6. 103 is applied.
By this operation, the limiter amplifier 103 amplifies the data with a constant amplitude around the threshold, and the identification waveform shown in FIG. 9-S7 is obtained as the positive phase output of the limiter amplifier 103.
[0007]
The above operation is an operation when the input signal light has no extinction ratio. However, in general, the input signal light always has an extinction ratio, and when there are many cells having a small extinction ratio, the output potential of the DC feedback circuit 107 depends on the extinction ratio.
FIG. 10 is a diagram showing the operation in this case. S1 is an input signal of the preamplifier 102, S2 (a) is an input signal of the limiter amplifier 103, and S2 (b) is an enlarged waveform of the input signal of the limiter amplifier 103. , S3 is a reset pulse waveform, S4 is an output voltage of the peak detection circuit 105, a solid line of S5 (a) is a DC feedback voltage from the DC feedback circuit 107, a solid line of S5 (b) is an enlarged waveform of the cells 6 and 7, S6 Is a threshold waveform applied to the limiter amplifier 103.
[0008]
When there are a large number of cells having a small extinction ratio, the DC feedback voltage from the DC feedback circuit 107 is composed of an integrating circuit having a large response time constant, and the detection level is lowered due to the sink current of the next stage circuit. Follow the 0 level of other cells. As a result of this operation, the threshold waveform applied to the limiter amplifier 103 shown in S6 generates a threshold waveform that cannot follow the {circle around (0)} level with respect to the cell 6, causing an error during limiter reproduction. Further, when all the cells having a small extinction ratio do not exist, a control response to follow the 0 level of the cell 6 occurs, and the DC feedback control becomes unstable.
[0009]
[Problems to be solved by the invention]
As described above, the conventional receiver with the ATC function has a problem that the DC feedback voltage from the DC feedback circuit cannot accurately generate the optical OFF level of the input signal when there are many cells having a small extinction ratio. It was.
[0010]
[Means for Solving the Problems]
A receiving apparatus according to the present invention includes an amplifier that amplifies a difference between an input signal and a threshold value and outputs a positive-phase signal and a reverse-phase signal, an amplitude detector that detects an amplitude voltage of the input signal, and the input signal An inter-cell voltage detecting means for detecting a voltage between the cells of the input signal based on an inter-cell signal indicating between the cells of the cell and a signal of a positive phase and a reverse phase by the amplifier; and A threshold generator that generates the threshold based on the amplitude voltage detected by the amplitude detector and the voltage detected by the inter-cell voltage detection means; and the inter-cell voltage detection means outputs a signal in reverse phase by the amplifier. Peak detection between cells using the inter-cell signal, a gate control peak detection circuit that holds and outputs the voltage detected in the cell in the cell, and an average of a positive phase signal and a negative phase signal by the amplifier Detect the voltage, The difference between the output voltage of the detected average voltage and the gate control peak detector circuit is one having a DC feedback circuit for amplifying.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a receiver with an ATC function according to the present embodiment, in which 1 is a light receiving element, 2 is a preamplifier, 3 is an amplifier, 4 is an amplitude detector, 5 is a threshold generator, 6 is a gate control holding circuit, and 7 is a DC feedback circuit.
Next, the operation will be described. The input signal photoelectrically converted by the light receiving element 1 is amplified with low noise by the preamplifier 2 and further amplified and output by the amplifier 3. The negative phase input voltage and the threshold generation 5 output voltage of the amplifier 3 are controlled by the amplitude detector 4 and the DC feedback circuit 7, respectively. In the DC feedback circuit 7, a voltage is generated such that the difference between the low level of the positive phase output Q of the amplifier 3 and the high level of the negative phase output Q bar (corresponding to the optical input signal OFF) is zero.
[0017]
The gate control holding circuit 6 detects and holds the output voltage of the DC feedback circuit 7 only between the cells (light OFF level) by the inter-cell signal. By this operation, the negative phase input voltage of the amplifier 3 follows only the light OFF level, so that DC feedback control can be performed regardless of the extinction ratio in the cell. When a cell is input, a voltage that is approximately half of the input amplitude is generated by the threshold generation 5 based on the output of the amplitude detector 4 and the output of the gate control holding circuit 6, and becomes the reverse phase input voltage of the amplifier 3. Since the input waveform is discriminated and amplified by this voltage, a correct threshold voltage can be generated even for a cell with small received light power.
[0018]
FIG. 2 is a diagram showing the waveforms of each part of the receiving apparatus with an ATC function according to the first embodiment. S1 is a preamplifier input waveform, S2 (a) is a preamplifier output waveform, and S2 (b) is a preamplifier. Enlarged view of cell 6 and cell 7 of the amplifier output waveform, S3 is the inter-cell signal, S4 is the amplitude detector output, S5 (a) is the gate control holding circuit output, and S5 (b) is the cell 6 of the gate control holding circuit output. The enlarged view of the cell 7, S6 is the amplifier normal phase output and negative phase output, and S7 is the threshold generator output. As described above, the gate control holding circuit detects and holds the voltage only between the cells (light OFF level), and is controlled so that ΔVo of S6 becomes zero. When there are many cells with a small extinction ratio, it is possible to suppress the operation in which the DC feedback voltage from the DC feedback circuit follows the level of the cells other than the cell 6. Playback can be performed correctly.
In the above example, a cell has been described, but the same applies to a packet.
In addition, the amplifier can be obtained not only by a linear amplifier but also by a limiter amplifier.
[0019]
Embodiment 2. FIG.
FIG. 3 is a diagram showing the configuration of the receiving device with an ATC function according to the present embodiment. In FIG. 3, 8 is a gate control peak detection circuit, and 9 is a storage capacitor. Others are the same as those of the first embodiment and will not be described.
Next, the operation will be described. The gate control peak detection circuit 8 and the storage capacitor 9 detect the peak of the light OFF level of the reverse phase output of the amplifier 3 only between the cells (light OFF level), and hold it in the cell. The DC feedback circuit operates so as to follow the optical OFF level of the input signal as described above. However, by using this peak detection value as a comparison value, the same operation as in the first embodiment is performed, and the same effect is obtained. It is done. In the above example, the cell is described, but the same applies to the packet.
[0020]
Embodiment 3 FIG.
4 is a diagram showing the configuration of the amplitude detector 4 in FIG. 1 and the amplitude detector 4 in FIG. 3. In FIG. 4, 11 is a peak detection circuit, 12 is a reset circuit, and 13 is a peak detection capacitor.
An amplitude detection circuit 4 includes a peak detection circuit 11, a reset circuit 12, and a peak detection capacitor 13. Others are the same as those of the first embodiment and will not be described.
The amplitude detector detects the peak of the input signal and holds the peak detection and holding means, and the reset circuit resets the peak value by the inter-cell signal.
Since the amplitude detector is configured as described above, the amplitude can be detected with a simple circuit.
[0021]
Embodiment 4 FIG.
FIG. 5 is a diagram showing the configuration of the DC feedback circuit 7 of the receiver with an ATC function according to the second embodiment, and shows a first configuration example of the DC feedback circuit 7 of FIG.
In FIG. 5, 10 is an average value detector, 11 is a comparator, 7 is a DC feedback circuit, and comprises an average value detector 10 and a comparator 11.
Next, the operation will be described. The average value detector 10 detects the average voltage (light OFF level) from the positive phase and negative phase outputs of the amplifier 3.
The peak control only between the cells (light OFF level) is performed by the gate control peak detection circuit 8 and the storage capacitor 9, and the differential voltage between the average value detector 10 and the gate control peak detection circuit 8 is amplified by the comparator 11. . The potential of the signal corresponding to the optical signal “light OFF” of the normal phase and the reverse phase output of the amplifier 3 can be stabilized with high accuracy by the amplification degree of the comparator 11.
[0022]
Embodiment 5 FIG.
FIG. 6 shows a second configuration example of the DC feedback circuit 7 of the receiving device with an ATC function in the second embodiment.
In FIG. 6, 14 is a first differential amplifier, 15 is a second differential amplifier, 16 is a first resistor, 17 is a second resistor, and 18 is a third differential amplifier.
The operation will be described. The first differential amplifier 14 amplifies the negative phase signal from the positive phase and negative phase outputs of the amplifier 3. By connecting first and second resistors of the same value in the positive and negative phases of the output of the second differential amplifier 15, the average voltage is amplified and output with the positive and negative phase outputs of the amplifier 3 as inputs. Further, by amplifying the differential voltage between the negative phase output of the first differential amplifier 14 and the average voltage output from the connection point of the first and second resistors, as shown above, The potential of the signal corresponding to the optical signal “light OFF” of the positive and negative phase outputs of the amplifier 3 can be stabilized with high accuracy by the second and third amplification degrees.
[0023]
Embodiment 6 FIG.
FIG. 7 is a diagram showing a configuration of the gate control peak detection circuit 8 constituting the receiving device with the ATC function according to the present embodiment.
In FIG. 7, 19 is a signal input terminal, 20 is an inter-cell signal terminal, 21 is a holding voltage output terminal, 9 is a holding capacitor, 23 is a reference voltage (Vref) terminal, 24 is a first NPN transistor, and 25 is a second. NPN transistor 26, a third NPN transistor 26, a current source 26, a positive power supply 28, a negative power supply 29, and a bias voltage 30 of a storage capacitor.
[0024]
The operation will be described. The differential circuit composed of the second and third NPN transistors 25 and 26 has the voltage applied to the reference voltage 23 as a threshold voltage, and the second NPN transistor 25 is turned on by the inter-cell signal at the inter-cell signal terminal 20. Thus, a current determined by the current source 27 flows through the first and second NPN transistors 24 and 25. During this time, the capacitor 9 is charged. When the inter-cell signal becomes lower than the reference voltage (Vref) terminal 23, the second NPN transistor 25 is turned off, and the current of the first NPN transistor 24 is also turned off. At this time, the capacitor 9 that stores the input voltage only while it is turned on by the inter-cell signal does not have a discharge path, and therefore operates to efficiently hold the input voltage.
[0025]
【The invention's effect】
As described above, according to the present invention, the optical OFF level of the output signal of the amplifier can be stabilized regardless of the extinction ratio in the cell, and a stable reception signal can be reproduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a receiving apparatus with an ATC function according to a first embodiment.
FIG. 2 is a diagram showing waveforms of respective parts of the receiving device with an ATC function according to the first embodiment.
FIG. 3 is a diagram illustrating a configuration of a receiving device with an ATC function according to a second embodiment.
4 is a diagram showing a configuration of an amplitude detector of the receiving device with an ATC function according to Embodiment 1 or 2. FIG.
FIG. 5 is a diagram showing a configuration of a first DC feedback circuit of a receiving device with an ATC function according to a second embodiment.
FIG. 6 is a diagram showing a configuration of a second DC feedback circuit of the receiving device with an ATC function according to the second embodiment.
FIG. 7 is a diagram illustrating a configuration of a gate control peak detection circuit of a receiving device with an ATC function according to a second embodiment.
FIG. 8 is a diagram showing a configuration of a conventional example.
FIG. 9 is a diagram showing a waveform of each part of a conventional example.
FIG. 10 is a diagram showing waveforms at various points of a problem in the conventional example.
[Explanation of symbols]
1: light receiving element 2: preamplifier 3: amplifier 4: amplitude detection 5: threshold generation 6: gate control holding 7: DC feedback circuit 8: gate control peak detection circuit 9: holding capacitor 10: average value detector 11: comparison Unit 12: Reset circuit 13: Peak detection capacitor 14: First differential amplifier 15: Second differential amplifier 16: First resistor 17: Second resistor 18: Third differential amplifier 19: Signal input terminal 20: Inter-cell signal terminal 21: Holding voltage output terminal 23: Reference voltage terminal (Vref)
24: First NPN transistor 25: Second NPN transistor 26: Third NPN transistor 27: Current source 28: Positive power supply terminal 29: Negative power supply terminal

Claims (4)

An amplifier that amplifies the difference between the input signal and the threshold value and outputs a normal phase signal and a negative phase signal;
An amplitude detector for detecting the amplitude voltage of the input signal;
An inter-cell voltage detecting means for detecting a voltage between the cells of the input signal based on an inter-cell signal indicating between the cells of the input signal and a signal having a phase opposite to that of the normal signal by the amplifier. When,
A threshold generator for generating the threshold based on the amplitude voltage detected by the amplitude detector and the voltage detected by the inter-cell voltage detector ;
The inter-cell voltage detecting means detects a peak of a signal having a reverse phase by the amplifier between the cells based on the inter-cell signal, and holds and outputs the peak detected voltage in the cell. And a DC feedback circuit for detecting an average voltage of a positive phase signal and a negative phase signal by the amplifier and amplifying a difference between the detected average voltage and an output voltage of the gate control peak detection circuit. A receiving device. The DC feedback circuit includes an average value detection circuit that detects and outputs an average voltage of a positive phase signal and a negative phase signal by the amplifier, an output voltage of the average value detection circuit, and an output of the gate control peak detection circuit The receiving apparatus according to claim 1 , further comprising a comparison unit that amplifies a difference from the voltage.   2. The amplitude detector according to claim 1, further comprising: a peak detection holding unit that detects and holds a peak value of the input signal; and a reset circuit that releases the held peak value by the inter-cell signal. The receiving device described. An amplification step of amplifying the difference between the input signal and the threshold value and outputting a normal phase signal and a reverse phase signal;
An amplitude detection step for detecting an amplitude voltage of the input signal;
Inter-cell voltage detection for detecting the voltage between the cells of the input signal based on the inter-cell signal indicating between the cells of the input signal and the signal of the positive phase and the reverse phase of the amplification step. Steps,
A threshold generation step for generating the threshold based on the amplitude voltage detected in the amplitude detection step and the voltage detected in the inter-cell voltage detection step ;
In the inter-cell voltage detection step, a gate-controlled peak detection is performed by detecting a peak of a signal having a reverse phase in the amplification step between cells by the inter-cell signal, and holding and outputting the detected voltage in the cell. And a DC feedback step for detecting an average voltage of the positive phase signal and the negative phase signal by the amplification step and amplifying a difference between the detected average voltage and the output voltage by the gate control peak detection step. And a receiving method.

Images