JP2007173908A - Burst optical signal receiver and gain setting method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burst optical signal receiver capable of eliminating a signal uncertain interval in a head field of a signal frame of a burst optical signal, eliminating a limit of a data interval, and transmitting the burst optical signal without degrading the effective throughput even at high speed communication and to provide a gain setting method thereof. <P>SOLUTION: In an initial stage when each slave station is connected to a PON system, the burst optical signal receiver measures delays of burst optical signal frames (#1, #2, #3,...#n) from the slave stations, sets a gain level of an amplifier for amplifying an optical detection signal of the optical burst signal in the order of "small", "medium", and "large", identifies at which level the signal frames from each slave station can be received, and stores a result of the identification to a memory. In an actual operation, the burst optical signal receiver reads the gain level stored in the memory in matching with the received burst optical signal frame by each slave station, and further, controls a voltage applied to an avalanche photodiode for detecting the optical signal according to the gain level. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a burst optical signal receiving apparatus and a gain setting method thereof, and more particularly, in a PON (Passive Optical Network) optical transmission network system, a master station side that optimally converts a burst optical signal of a wide range of optical levels into an optical / electrical signal. The present invention relates to a burst optical signal receiving apparatus applied to an optical receiver and a gain setting method thereof.

  The PON optical transmission network system is a mainstream network system of FTTH (Fiber To The Home), which is a data communication service for homes using optical fibers. As shown in FIG. An optical branching device 5-3 called a star coupler (optical splitter) is inserted in the middle of an optical fiber 5-2 extending to a slave station (subscriber's house), and further an optical branching device 5-3 is further inserted and branched. Then, the optical fiber 5-2 is drawn into a plurality of slave stations (subscriber premises) 5-4.

  For the downstream optical signal from the master station 5-1 to each slave station 5-4, each slave station 5-4 receives a transmission signal from the optical transmitter 5-11 of one master station 5-1, The reception level of each signal is constant, but for the upstream burst optical signal from each slave station 5-4 to the master station 5-1, optical signals transmitted from a plurality of slave stations 5-4 having different distances are used. Since the optical receiver 5-12 of the master station 5-1 receives the optical signal, the optical receiver 5-12 of the master station 5-1 receives optical signals having different reception levels over a wide range.

  FIG. 6 shows a configuration example of a conventional optical receiver that receives optical signals having a wide range of reception levels. In FIG. 6, 6-1 is a photodetector (PD) such as a photodiode, 6-2 is a current-voltage (I / V) converter that converts current into voltage, and 6-3 is a preamplifier (Pre-AMP). ), 6-4 is a peak (or average) detector, and 6-5 is a main amplifier (Main-AMP).

  In the optical receiver having the above-described configuration, when burst optical signals from a plurality of slave stations are input, the burst optical signal level is detected by the photodetector (PD) 6-1 and converted into a current level. The current level is converted to a voltage level by a voltage (I / V) converter 6-2, and the voltage level is amplified by a preamplifier (Pre-AMP) 6-3.

  The output of the preamplifier (Pre-AMP) 6-3 is input to a peak (or average) detector 6-4, and the peak (or average) detector 6-4 receives a peak value from a received signal over a predetermined period. (Or average value) is detected, and the gain of the preamplifier (Pre-AMP) 6-3 is controlled according to the peak value (or average value), and is constant from the preamplifier (Pre-AMP) 6-3. Feedback control is performed so that a level output voltage signal is obtained.

In receiving a burst optical signal with a wide range of optical levels, a burst optical receiving circuit that performs gain control according to the peak value (or average value) of the input level of the received signal as described above by feedback control is disclosed in, for example, the following patent document 1 and 2 etc.
JP-A-8-102716 Japanese Patent No. 2616480

  Since the conventional optical receiver as shown in FIG. 6 performs feedback control for switching the gain of the preamplifier (Pre-AMP) 6-3 according to the optical input level for each frame of the burst optical signal, It is possible to regenerate the electrical output by receiving and sensing the peak value or average value of the level and performing optimum gain control according to the light input level.

  However, it takes a predetermined time to detect the peak value or average value of the optical reception input level, and a feedback time constant (delay time of feedback control) is generated. Then, the signal indefinite section is inevitably generated, and there is a problem that the data section is limited when realizing high-speed communication, and the effective throughput is lowered.

  A specific example of signal indefinite interval generation by the above feedback control is shown in FIG. As shown in the figure, for the setting of the gain (b) of the preamplifier (Pre-AMP) for each signal frame of the optical signal input (a), a gain control section is provided at the head of each signal frame. In the gain control interval, the telegraph signal output (c) of the preamplifier (Pre-AMP) becomes a signal indefinite interval.

  In the case of low-speed communication, the signal indefinite period is not affected without reaching the data period of the signal frame as shown in FIG. 7D. However, in the case of high-speed communication, the signal indefinite period is as shown in FIG. As shown, since the data section of the signal frame is reached and the data in the data section is deleted, the data section must be reduced, and the effective throughput is reduced.

  The present invention eliminates a signal indefinite section in the head area of a signal frame of a burst optical signal, eliminates a data section restriction, and can transmit a burst optical signal without reducing effective throughput even in high-speed communication. An object of the present invention is to provide a device and a gain setting method thereof.

  The burst optical signal receiving apparatus according to the present invention includes (1) a photodetector that outputs a current signal according to an input light level, and a current-voltage conversion that outputs a voltage signal by converting the current signal output by the photodetector. And an amplifier for amplifying the output voltage of the current-voltage conversion means, for a wide range of input optical levels from each slave station that transmits the burst optical signal, from the amplifier. As a gain level at which a substantially constant voltage level is output, a gain level storage means for storing in memory a gain level optimum for each slave station from among a plurality of gain levels, and for each input slave station Means for reading the gain level stored in the gain level storage means in accordance with the burst optical signal frame and setting the read gain level as the gain of the amplifier. It is characterized in.

  (2) an avalanche photodiode that outputs a current signal according to an input light level, a current-voltage conversion unit that converts a current signal output from the avalanche photodiode and outputs a voltage signal, and the current-voltage conversion unit In a burst optical signal receiving device comprising: an amplifier that amplifies the output voltage of the output signal, a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits the burst optical signal. As the gain level, the gain level storing means for storing the optimum gain level corresponding to each slave station from among the gain levels in a plurality of stages in advance in the memory, and matching the burst optical signal frame for each input slave station The gain level stored in the gain level storage means is read, and the voltage level corresponding to the read gain level is It means for applying a voltage applied Chez photodiode, and further comprising a.

  (3) an avalanche photodiode that outputs a current signal according to an input light level, a current-voltage conversion unit that converts a current signal output from the avalanche photodiode and outputs a voltage signal, and the current-voltage conversion unit In a burst optical signal receiving device comprising: an amplifier that amplifies the output voltage of the output signal, a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits the burst optical signal. As the gain level, the gain level storing means for storing the optimum gain level corresponding to each slave station from among the gain levels in a plurality of stages in advance in the memory, and matching the burst optical signal frame for each input slave station Reading the gain level stored in the gain level storage means, and setting the read gain level as the gain of the amplifier. Moni, a voltage level corresponding to the read-out gain level, characterized by comprising a means for applying a voltage applied to the avalanche photodiode.

  The burst optical signal receiving apparatus gain setting method according to the present invention includes (4) a photodetector that outputs a current signal corresponding to an input optical level, and a voltage signal obtained by converting the current signal output from the photodetector. In a gain setting method of a burst optical signal receiving device comprising a current-voltage conversion means for outputting a current, and an amplifier for amplifying the output voltage of the current-voltage conversion means, a wide range from each slave station that transmits a burst optical signal As the gain level at which a substantially constant voltage level is output from the amplifier with respect to the input optical level, an optimum gain level corresponding to each slave station is selected from among a plurality of stages of gain levels. The process of measuring the delay with each step and storing it in the memory in advance, and reading the gain level stored in the memory in accordance with the burst optical signal frame inputted for each slave station. Characterized in that the gain levels including the steps of setting a gain of the amplifier.

  (5) an avalanche photodiode that outputs a current signal according to an input light level; a current-voltage conversion unit that converts a current signal output from the avalanche photodiode and outputs a voltage signal; and the current-voltage conversion unit And a gain setting method for a burst optical signal receiving apparatus comprising: an amplifier that amplifies the output voltage of the burst optical signal; and a substantially constant voltage from the amplifier with respect to a wide range of input optical levels from each slave station that transmits the burst optical signal. As a gain level at which a level is output, an optimum gain level corresponding to each slave station is measured from among a plurality of gain levels at the initial stage when the slave station is connected and stored in advance in a memory. The gain level stored in the memory is read out in accordance with the process and the burst optical signal frame for each slave station to be inputted, Sets the level as the gain of the amplifier, a voltage level corresponding to the read-out gain level, characterized in that it comprises a the steps of applying a voltage applied to the avalanche photodiode.

  According to the present invention, by using the delay measurement time of the burst optical signal frame for each slave station that is always performed in the initial stage of the PON network connection, the gain level for each burst optical signal frame of each slave station is measured and the memory is measured. Feed-forward that reads and sets the gain level stored and stored in accordance with the reception of burst optical signal frames of each slave station, instead of the conventional feedback control for the gain control of the optical receiver. By performing the control, it is possible to eliminate the indefinite section of the burst optical signal in the frame start area, eliminate the restriction of the data section, and enable transmission of the burst optical signal without reducing the effective throughput even in high-speed communication. .

  In a one-to-n PON network system in which n slave stations are connected to one master station as shown in FIG. 5, since n slave stations with different distances are connected, the optical receiver of the master station In this case, it is necessary to perform photoelectric conversion on a burst optical signal in a wide range of light levels and reproduce a waveform at a certain level.

  For this reason, in the present invention, at the initial stage when each slave station is connected to the network, it is predetermined for each identification section (discovery window) for measuring the delay time of the burst optical signal frame from each slave station. The gain level (3 or more levels) is set while increasing in order, and the measurement of the delay time of burst optical signal frames from each slave station and the optimum gain level are simultaneously identified by repeating the reception measurement in this identification section. To do. The identification result is stored in the memory in a table format.

  And, in actual operation, based on the gain level identification result information stored in this memory, by performing feedforward control for instructing the gain level for each received frame from the control unit, all the signals inputted to the optical receiving unit The burst optical signal frame is amplified at the optimum gain level from the first bit, and the output waveform at a substantially constant level can be reproduced.

  FIG. 1 shows a specific example of the reception gain level measurement at the initial stage according to the present invention. FIG. 4A shows the input waveform of burst optical signal frames from each of the slave stations (# 1 to #n), and FIG. 4B shows the gain level of the preamplifier (Pre-AMP). (C) shows the electrical signal output of the preamplifier (Pre-AMP).

  As shown in FIG. 1, the gain level of the preamplifier (Pre-AMP) is set to “low” in the first slave station frame identification period, and in the second slave station frame identification period that follows, The gain level of the amplifier (Pre-AMP) is set to “medium”, and the gain level of the preamplifier (Pre-AMP) is set to “high” in the subsequent third slave station frame identification period. In this way, the reception gain level is set while increasing in order for each identification section.

  In the example shown in FIG. 1, in the first slave station frame identification section in which the gain level is set to “low”, the frame signals received from the slave stations # 1 to #n are received from the slave station # 1. Accordingly, as shown in FIG. 6D, the gain level “small” is stored in the identification result table together with the delayed transmission “T1 (s)” as the identification result of the slave station # 1, as shown in FIG.

  Similarly, in the second slave station frame identification section in which the gain level is set to “medium”, the slave stations # 1, # 2, and # 3 are received by the frame signals from the slave stations # 1 to #n. Accordingly, the gain level “medium” is stored and held in the identification result table together with the delayed transmissions “T2 (s)” and “T3 (s)” as the identification results of the slave stations # 2 and # 3, respectively. . Note that the identification result of the slave station # 1 is already stored and held, and the identification result is not written in this identification section for the slave station that is already stored and held.

  Similarly, in the third slave station frame identification section in which the gain level is set to “large”, the frame signals received from the slave stations # 1 to #n are received from the slave stations # 1 to #n. Accordingly, the gain level “large” is stored and held in the identification result table together with the delayed transmissions “T4 (s)” to “Tn (s)” as the identification results of the slave stations # 4 to #n. Also in this case, the identification results of the slave stations # 1 to # 3 are already stored and retained, and the identification results are not written in the section according to this formula for the slave stations that are already stored and retained.

  FIG. 2 shows a first embodiment of an optical receiver for receiving burst optical signals according to the present invention. In the figure, a photodiode (PD) 2-1 that outputs a current signal according to the received optical input level, and a current voltage (I / I) that converts the current output from the photodiode (PD) 2-1 into a voltage. V) A signal converter 2-2, a preamplifier (Pre-AMP) 2-3 whose gain is changed by changing a feedback resistance value, and a preamplifier (Pre-AMP) 2 by a gain control signal from the control unit. -3, the variable resistor 2-4 for changing the feedback resistance value, the main amplifier (Main-AMP) 2-5 for amplifying the output voltage of the preamplifier (Pre-AMP) 2-3, and the input light level. And a signal discriminator 2-6 for identifying whether or not reception is possible.

  In the initial stage of connecting the slave station to the network, as described above, the gain control signal instructed from the control unit (not shown) is set so that the gain level gradually increases in the first to third slave station frame identification sections. Accordingly, the resistance value of the variable resistor 2-4 is changed. Then, in the first to third slave station frame identification sections, the signal discriminator 2-6 discriminates whether or not a burst optical signal from each slave station has been received, and the identification result is shown in an identification result table (not shown). Keep it in memory.

  Also, during normal operation, the control unit (not shown) reads the gain level corresponding to each slave station stored in the above-described identification result table and sends the gain control signal corresponding to the gain level to the variable resistor 2-4. Send it out. The variable resistor 2-4 changes the feedback resistance value of the preamplifier (Pre-AMP) 2-3 in real time according to the gain control signal, and controls the gain of the preamplifier (Pre-AMP) 2-3. .

  FIG. 3 shows a second embodiment of an optical receiver for receiving burst optical signals according to the present invention. In the second embodiment, an avalanche photodiode (APD) 3-1 having an amplifying action is used as the photodiode (PD) 2-1 in the first embodiment, and an avalanche photodiode (APD) 3 is used. The voltage value applied to -1 is changed simultaneously with the gain control of the preamplifier (Pre-AMP) 2-3, and burst light reception with a larger dynamic range is made possible.

  Note that the amplification factor of the avalanche photodiode (APD) 3-1 changes according to the voltage value to be applied. A gain control signal from a control unit (not shown) is input to the variable resistor 2-4 and also input to a D / A converter 3-2 that converts a digital signal into an analog voltage signal. -2 is applied to the high voltage circuit 3-3 of the avalanche photodiode (APD) 3-1, so that a voltage corresponding to the gain control signal from the control unit is applied to the avalanche photodiode (APD) 3-1. Apply to.

  When controlling the voltage applied to the avalanche photodiode (APD) 3-1, if a received signal having a large light level is input with a high voltage applied, the avalanche photodiode (APD) 3-1 is broken. Therefore, when identifying the frame signal delay and the gain level performed at the initial stage of the network connection of the slave stations, it is necessary to set the gain level in ascending order.

  FIG. 4 shows a specific example of gain level setting during actual operation according to the present invention. In the figure, (a) shows the input of the received burst optical signal, (b) shows the gain level of the preamplifier (Pre-AMP), and (c) shows the preamplifier (Pre-AMP). Electric signal output is shown.

  As shown in the figure, for the optical signal input of signal frames # 2 and # 3 having a medium input level, the “medium” gain level stored and held in advance is read from the identification result table and set, and the input level For the optical signal input of the signal frame # 1 having a large value, the “small” gain level stored and held in advance is read from the identification result table and set, so that the optical signal input of the signal frames # 4 and #n having the small input level is set. On the other hand, the “large” gain level stored and held in advance is read from the identification result table and set.

  As a result, an optimum gain level is set from the beginning of the burst optical signal frame, and a signal waveform having a substantially constant output level can be reproduced as shown in FIG. As shown in FIG. 4, there is no signal indefinite section in the data section, and an optical burst signal can be transmitted without reducing the execution throughput even during high-speed communication.

It is a figure which shows the specific example of the reception gain level measurement of the initial stage by this invention. It is a figure which shows 1st Embodiment of the optical receiver which receives the burst optical signal by this invention. It is a figure which shows 2nd Embodiment of the optical receiver which receives the burst optical signal by this invention. It is a figure which shows the specific example of the gain level setting in actual operation by this invention. It is a figure which shows the structural example of a PON optical transmission network system. It is a figure which shows the structural example of the conventional optical receiver. It is a figure which shows the specific example of signal indefinite area generation | occurrence | production by feedback control.

Explanation of symbols

2-1 Photodiode (PD)
2-2 Current-voltage (I / V) signal converter 2-3 Preamplifier (Pre-AMP)
2-4 Variable resistor 2-5 Main amplifier (Main-AMP)
2-6 Signal identifier 3-1 Avalanche photodiode (APD)
3-2 D / A converter 3-3 High voltage circuit

Claims (5)

A photodetector that outputs a current signal according to the input light level, a current-voltage converter that converts the current signal output from the photodetector and outputs a voltage signal, and amplifies the output voltage of the current-voltage converter A burst optical signal receiving device comprising:
As a gain level at which a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits a burst optical signal, it corresponds to each slave station from among a plurality of gain levels. Gain level storage means for storing and holding the optimum gain level in the memory in advance;
Means for reading out the gain level stored in the gain level storage means in accordance with the burst optical signal frame for each slave station to be inputted, and setting the read gain level as the gain of the amplifier;
A burst optical signal receiving apparatus comprising: An avalanche photodiode that outputs a current signal according to the input light level, a current-voltage conversion unit that converts a current signal output from the avalanche photodiode and outputs a voltage signal, and amplifies the output voltage of the current-voltage conversion unit A burst optical signal receiving device comprising:
As a gain level at which a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits a burst optical signal, it corresponds to each slave station from among a plurality of gain levels. Gain level storage means for storing and holding the optimum gain level in the memory in advance;
The gain level stored in the gain level storage means is read in accordance with the frame of the burst optical signal for each input slave station, and the voltage level corresponding to the read gain level is applied as the voltage applied to the avalanche photodiode. Means for applying;
A burst optical signal receiving apparatus comprising: An avalanche photodiode that outputs a current signal according to the input light level, a current-voltage conversion unit that converts a current signal output from the avalanche photodiode and outputs a voltage signal, and amplifies the output voltage of the current-voltage conversion unit A burst optical signal receiving device comprising:
As a gain level at which a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits a burst optical signal, it corresponds to each slave station from among a plurality of gain levels. Gain level storage means for storing and holding the optimum gain level in the memory in advance;
The gain level stored in the gain level storage means is read out in accordance with the frame of the burst optical signal inputted for each slave station, and the read gain level is set as the gain of the amplifier. Means for applying a voltage level corresponding to a voltage applied to the avalanche photodiode;
A burst optical signal receiving apparatus comprising: A photodetector that outputs a current signal according to the input light level, a current-voltage converter that converts the current signal output from the photodetector and outputs a voltage signal, and amplifies the output voltage of the current-voltage converter And a gain setting method for a burst optical signal receiving device comprising:
As a gain level at which a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits a burst optical signal, it corresponds to each slave station from among a plurality of gain levels. Measuring the optimum gain level together with the initial delay measurement to which the slave station is connected and pre-stored in the memory;
In accordance with the input burst optical signal frame for each slave station, reading the gain level stored in the memory, and setting the read gain level as the gain of the amplifier;
A method for setting a gain of a burst optical signal receiving apparatus. An avalanche photodiode that outputs a current signal according to the input light level, a current-voltage conversion unit that converts a current signal output from the avalanche photodiode and outputs a voltage signal, and amplifies the output voltage of the current-voltage conversion unit And a gain setting method for a burst optical signal receiving device comprising:
As a gain level at which a substantially constant voltage level is output from the amplifier with respect to a wide range of input optical levels from each slave station that transmits a burst optical signal, it corresponds to each slave station from among a plurality of gain levels. Measuring the optimum gain level together with the initial delay measurement to which the slave station is connected and pre-stored in the memory;
The gain level stored in the memory is read out in accordance with the burst optical signal frame for each input slave station, the read gain level is set as the gain of the amplifier, and the read gain level is supported. Applying the applied voltage level as an applied voltage of the avalanche photodiode;
A method for setting a gain of a burst optical signal receiving apparatus.

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