JP2001168843A - Optical burst transmission reception circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical burst transmission reception circuit, where the need for the selection of a light-emitting element (LD) that takes characteristic fluctuations in the forward output light and backward output light of the LD affected by a coupling state between the LD and a monitor PD into account for optical transmission output constant control is eliminated and the circuit configuration of using a function block in common can be simplified. SOLUTION: A light-receiving element (PD) 22 and a preamplifier circuit 23 having already been prepared for an optical reception section 11 are used in common to detect a light emission output from the light-emitting element (LD) 18 of an optical transmission section 5 and to control the output to be a constant value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical burst transmission / reception circuit, and more particularly, to a PON in which a master station and a slave station are connected via a star coupler in a 1: n configuration in an optical subscriber system.
The present invention relates to an optical transmitting and receiving circuit used in a system.

[0002]

2. Description of the Related Art The prior art of such an optical transmission / reception circuit is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-9626 (Japanese Patent No. 2502750), "Level control method of optical repeater" and Japanese Patent Application Laid-Open No. 3-2.
No. 83927, “Optical repeater” and the like.
In the former, as shown in FIG. 5, an optical transmitting terminal 40, optical repeaters (hereinafter referred to as optical amplifiers) 51a to 51n, optical beam splitters (hereinafter referred to as optical splitters) 52a to 52n,
It is composed of APC control circuits 53a to 53n and optical fibers 50a to 50n connecting these circuits.

Next, the operation of the "level control method of the optical repeater" according to the prior art shown in FIG. 5 will be described. Optical transmitting terminal 4
0 is amplified by the optical amplifiers 51a to 51n each time the amplitude-modulated optical signal is transmitted and transmitted through the optical fibers 50a to 50n of the optical transmission line. Part of the power is split by the optical splitters 52a to 52n.
Then, the level of the low-frequency signal is detected by APC control circuits 53a to 53n including an O / E (optical-electrical) converter, a filter, a level comparator, and an amplification current source so that the level becomes constant. And the output gains of the optical amplifiers 51a to 51n are controlled. Thereby, the amplification degree of the optical repeater is remotely controlled based on the extracted information on the modulation degree of the low frequency signal. The existing optical amplifier is controlled by adding APC control circuits 53a to 53n each including an O / E converter, a filter, a level comparator, and an amplified current source for the purpose of constant level control.

FIG. 6 shows a configuration example of a general PON system used for an optical subscriber system. Referring to FIG. 6, this type of optical burst transmission and reception will be described. This PON
In the system, the master station and the slave stations (1) to (3) are radially connected via an optical star coupler. The distance between the master station and each slave station usually varies. In the example of FIG. 6, the distance between each slave station and the master station has a relationship of slave station (1)> slave station (2)> slave station (3), where slave station (1) is the most distant from the master station. It is far away. Normally, both the slave station and the master station have a pair of optical transmission / reception circuits.

In an optical subscriber system, upstream signal transmission is performed by:
The TD to which the band and timing are assigned to each slave station and transmitted so that signals from a plurality of slave stations do not collide with each other.
The MA (time division multiple access) method is used.
In downlink signal transmission, an uplink signal and a downlink signal are divided in one frame and distributed to slave stations by a TDM (time division multiplex) method. In addition, since the uplink signal and the downlink signal move on one transmission path, a TCM scheme in which the transmission time is divided so as not to interfere with each other is used.

FIG. 7 shows an input / output state of each station in an optical subscriber system including a master station and slave stations (1) to (3). In FIG. 8, (a) shows the input / output state of the master station. (B) shows the input / output state of the slave station (1). (C)
Indicates the input / output state of the slave station (2). (D)
This shows the input / output state of the slave station (3). In (a) to (d), a down signal is shown on both the left and right sides, and an up signal is shown in the center.

FIG. 8 is a block diagram showing a conventional optical burst transmission / reception circuit. FIG. 9 is an example of a detailed configuration diagram of the optical burst transmission / reception circuit according to the prior art shown in FIG. Optical transmitting / receiving unit or optical burst transmitting / receiving circuit 1
Is an electric transmission input terminal 2, an APC initial value setting terminal 3,
Signal detection circuit 4, light transmission unit 5, delay circuit A6, APC control circuit 7, light transmission output terminal 9, light reception input terminal 10, light reception unit 11, inversion circuit 13, electric reception output terminal 15, and backward light conversion. It is composed of a section 16. As shown in FIG. 9, the optical transmission unit 5 includes a drive circuit 17 and a light emitting element (for example, a laser diode, hereinafter, referred to as an LD) 18. The light receiving unit 11 includes a light receiving element (for example, a photodiode, hereinafter referred to as PD) 22, a preamplifier circuit 23, an automatic gain control (AGC) circuit 24, an automatic threshold control (ATC) circuit 25, and a limiter (LIM) circuit 26. Contains.
Further, the backward light conversion unit 16 includes a monitoring light receiving element (monitor PD) 27 and a preamplifier circuit 28.

On the other hand, FIG. 10 shows the APC of FIGS.
FIG. 3 is a block diagram illustrating a detailed configuration of a control circuit 7. This A
The PC control circuit 7 receives a peak hold circuit 29 receiving an output of the preamplifier circuit 28 in the backward optical conversion circuit 16, and inputs an output of the peak hold circuit 29 and an initial setting value from the APC initial value setting terminal 3. Differential voltage detection circuit 30
And a comparison circuit 33, and a constant current control circuit 32 which receives the outputs of the difference voltage detection circuit 30 and the comparison circuit 33 as inputs.
And a holding circuit 34. This holding circuit 34
The output signal from the delay circuit A6 is input to the peak hold circuit 29.

Next, the operation of the conventional optical burst transmitting / receiving section 1 shown in FIGS. 8 to 10 will be briefly described. When an electric digital data input signal is input from the electric transmission input terminal 2, the drive circuit 17 in the optical transmission unit 5 drives the LD 18 connected to the positive power supply, and outputs forward output light to the optical transmission output terminal 9. . The rear output light of the driven LD 18 is received by the monitor PD 27 in the rear light conversion unit 16, amplified by the preamplifier 28 after current / voltage conversion, and input to the APC control circuit 7. The input signal is supplied to a peak hold circuit 29 in the APC control circuit 7.
Is detected and held. A difference between the held voltage value and an initial setting value preset from the APC initial value setting terminal 3 is detected by a difference voltage detecting circuit 30, and separately from the difference voltage detecting circuit 30, Compare with

The result of the comparison by the comparison circuit 33 and the information on the difference voltage from the difference voltage detection circuit 30 are used as the constant current control circuit 3.
2 to provide a control signal to the drive circuit 17 of the optical transmitter 5 via the holding circuit 34. With this control, the optical transmission output from the LD 18 operates so as to be constantly maintained within one burst of data. Here, it is necessary to reset the information of the APC control every time the burst data is transmitted. The signal detection circuit 4 detects the input of the electric signal and inverts it by the inversion circuit 13.
A signal obtained by delaying the delay time caused by the delay circuit 6 by the delay circuit A6 is supplied to the peak hold circuit 29 and the hold circuit 34 in the APC control circuit 7 as a reset signal.

Next, an optical receiving circuit will be described. When a digital optical signal is received by the optical receiving input terminal 10, it is converted into an electric signal by the PD 22 connected to the positive power supply electrode,
The current / voltage conversion and amplification are performed by the preamplifier circuit 23. The gain of the amplified electric signal is switched so that the gain can be switched even at the optical input of the minimum light receiving level so that the signal can be stably received.
It is input to the GC circuit 24. After that, the identification value is optimized according to the input level, the signal passes through the ATC circuit 25 for identification, the upper part of the waveform is limited (restricted), and the signal passes through the LIM circuit 26 for performing waveform correction (or shaping). Then, it is output to the electric reception output terminal 15 as an electric signal having a predetermined electric level.

[0012]

The prior art described above is
There are some problems described below. First, in the optical transmission output constant control, it is necessary to adjust each optical element individually.
The reason is that the coupling loss between the LD 18 and the monitor PD 27 is usually not stable. Therefore, even if the power of the forward output light is the same, the monitor current obtained from the backward output light varies. The dynamic range of the preamplifier circuit 28 that performs current / voltage conversion is limited at the time of design, and the circuit is complicated to design to have a wide dynamic range. Under these restrictions, it is necessary to select optical elements and adjust circuit constants. This variation in the monitor current makes it difficult to perform initial adjustment of the APC control and A
This causes a PC error and hinders stabilization of transmission power. It is not impossible to adjust the coupling loss between the LD 18 and the monitor PD 27 by adjusting the optical axis, etc.
This leads to an increase in the number of manufacturing steps and a decrease in quality.

Second, when the photocurrent of the monitor PD 27 is kept constant, there is always a maximum fluctuation (hereinafter referred to as tracking error) of the optical output power of the LD 18 due to a change in ambient temperature. Power stabilization. The reason is that a tracking error occurs due to the deviation of the monitor current-light output characteristic of the element used from the linearity and the temperature characteristic of the coupling efficiency of the optical system such as a lens and a connector. In general, it is necessary to consider at least about ± 1 dB of temperature fluctuation at the time of temperature.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to perform tracking control of optical transmission output without affecting the variation of the monitor current of the backward output light caused by the variation of the coupling loss between the LD and the monitor PD. It is an object of the present invention to provide an optical burst transmitting / receiving circuit capable of reducing the number of circuits and using a part of an existing receiving circuit to reduce unnecessary circuits.

[0015]

SUMMARY OF THE INVENTION The present invention converts an input signal from an electrical transmission input terminal into an optical signal and receives an optical signal from an optical transmission output terminal and an optical reception input terminal. An optical burst transmission / reception circuit for an optical subscriber system having an optical receiving unit for outputting from an electrical signal output terminal. And an optical distributor including an optical splitter and an optical coupler is provided on the output side of the optical transmitter and the input side of the optical receiver, respectively.
A part of the output of the optical transmitter is input to the optical coupler via the optical splitter. With this configuration, it is possible to eliminate the backward light conversion unit and the like of the LD of the light transmission unit, which are conventionally required.

According to a preferred embodiment of the present invention, an optical attenuator is provided between the optical splitter and the optical coupler of the optical distribution unit. In addition, an optical mask circuit is arranged on the output side of the light receiving unit, and controls an electric reception signal output from the light receiving unit to an electric reception output terminal. This optical mask circuit controls the output of a signal detection circuit that detects an input signal from an electric transmission input terminal with a signal delayed by a delay circuit. Further, the optical transmission unit may
It is controlled by the output of the APC control circuit which receives the initial set value from the C initial value setting terminal and the output of the optical receiver.

That is, in the optical burst transmission / reception circuit according to the present invention, transmission and reception used in each station of the optical subscriber system operate in a time-division manner, and an optical distribution unit including an optical splitter and an optical distributor is added and transmitted. By providing a function of branching a part of the light and returning it to its own reception input, one function of its own reception unit is shared, and the monitor current of the backward output light caused by the coupling loss variation between the LD and the monitor PD is reduced. The tracking error can be reduced without being affected by the variation, and the optical transmission output constant control can be realized. In addition, unnecessary circuits can be reduced by diverting a part of the existing receiving circuit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of a preferred embodiment of an optical burst transmission / reception circuit according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an external force configuration of an optical burst transmitting / receiving circuit according to a first embodiment of the present invention. FIG. 2 shows a detailed configuration of the optical burst transmission / reception circuit of FIG. Note that, for convenience, the same reference numerals are used for components corresponding to the above-described related art. The optical burst transmission / reception circuit or optical transmission / reception unit 1 includes an electric transmission input terminal 2, an APC initial value setting terminal 3, a signal detection circuit 4,
Optical transmission unit 5, delay circuit A6, APC control circuit 7, optical distribution unit 8, optical transmission output terminal 9, optical reception input terminal 10, optical reception unit 11, mask circuit 12, inversion circuit 13, delay circuit B1
4. Electric reception output terminal 15 and optical fibers 36 and 37
It is composed of The optical fiber 36 couples between the light transmitting unit 5 and the light distribution unit 8. On the other hand, the optical fiber 37 couples between the light distribution unit 8 and the light reception unit 11. Here, as shown in FIG. 2, the optical transmission unit 5 includes a drive circuit 17 and a light emitting element (LD) 18. The optical distributor 8 includes an optical splitter 19 and an optical coupler 20. Optical receiver 11
Includes a light receiving element (PD) 22 connected to a positive power supply 21, a preamplifier 23, an AGC circuit 24, an ATC circuit 25, and a LIM circuit 26. The APC control circuit 7 can be the same as the circuit of FIG. 10 described above.

The optical transmission unit 5 drives the LD 18 via the drive circuit 14 with the digital electric signal input from the electric transmission input terminal 2, and outputs the transmitted optical signal to the optical distributor 8.
Is output to the optical splitter 19 in the inside. The optical splitter 19 outputs to the optical transmission output terminal 9 and also to one input terminal of the optical coupler 20. The optical coupler 20 couples the optical reception signal from the optical reception input terminal 10 with the optical signal from the optical splitter 19 described above. The PD 22 of the optical receiver 11 receives the optical signal from the optical coupler 20 and converts it into a predetermined electric signal. The output of the PD 22 is supplied to the front-end amplifier 23, AG
The data is input to the mask circuit 12 via the C circuit 24, the ATC circuit 25, and the LIM circuit 26. In addition, preamplifier 2
The output of 3 is the peak hold circuit 2 of the APC control circuit 7.
9 is also input. On the other hand, the signal detection circuit 4 detects the presence or absence of a digital electric signal input from the electric transmission input terminal 2. The output of the signal detection circuit 4 supplies a reset signal to the peak hold circuit 29 and the hold circuit 34 of the ATC control circuit 7 via the inversion circuit 13 and the delay circuit A6 (see FIG. 10). The output of the signal detection circuit 4 is input to the mask circuit 12 via the delay circuit B14. The mask circuit 12 masks and controls the electric reception signal output from the LIM circuit 26 of the optical receiver 11. The delay circuit B14 sets the timing at which the mask circuit 12 masks. As shown in FIG. 10, the APC control circuit 7 includes a peak hold circuit 29, a difference voltage detection circuit 30, a comparison circuit 33, a constant current control circuit 32, and a holding circuit 34.
It consists of.

Next, the operation of the optical burst transmitting / receiving circuit shown in FIGS. 1 and 2 will be described with reference to the timing chart of FIG. The optical burst transmission / reception circuits shown in FIGS. 1 and 2 are also used, for example, in the PON system configuration shown in FIG. 6 and operate as shown in FIG. That is, the downstream signals (D1 to D3)
Is sent from the master station to each slave station. Since there is a difference in the distance between each slave station and the master station, the slave stations (1) to (3) receive power in different forms. Next, an uplink signal is transmitted from each slave station in a time-division manner at a certain timing so as not to be affected by data collision and reflection between uplink and downlink (D11 to D31). Here, since there is a difference in the distance between each of the slave stations and the master station, the master station receives burst-shaped data with different powers. Normally, as described above, uplink and downlink ping-pong transmissions are performed, and each station
The C control circuit 7 and the like are provided with a function of canceling a variation amount with respect to a temperature variation.

The operation when a signal is transmitted from the master station to the slave station (2) as the transmission state of the downlink signal will be described. FIG.
(A) to (n) are timing charts for explaining the operation of the optical burst transmission / reception circuit according to the present invention.
First, at the master station, as shown in FIG. 3A, data signals (D1 to D1) which are digital electric signals are input to the electric transmission input terminal 2.
3) is input. The LD 18 is driven by the drive circuit 17 in the optical transmitter 5. Therefore, the output of the optical transmission unit 5 is output at the output power Po11 as shown in FIG.
It is assumed that the drive current is initially set so that the output power of the LD 18 becomes Po10. It is also assumed that the output power of the optical transmission unit 5 has been initially set to Po10 and has been reduced to Po11 due to a change in ambient temperature.

The optical signal having the output power Po11 of the optical transmitter 5 is transmitted to the optical splitter 19 in the optical distributor 8 via an optical fiber.
Sent to Here, the branching ratio of the optical branching device 19 is, for example, 1:10, and the input of the optical branching device 19 has a relationship of 9/10 for the optical transmission output terminal 9 and 1/10 for the optical coupler 20. It is assumed that the optical signal is branched and transmitted. Accordingly, an optical signal of the power level Po21 reduced by the excess loss (0.3 dB) and the branch loss (3 dB) is output to the optical transmission output terminal 9 (see FIG. 3C). Next, the branching ratio of the optical coupler 20 is 1:10, the input of the optical coupler 20 is 9/10 from the optical receiving input terminal 10 to the output of the optical coupler 20, and the optical splitter 19 is Output from the optical coupler 2
It is assumed that the optical signal is combined and transmitted with respect to the output of 0 in a relation of 1/10. Therefore, the optical coupler 20 is
The optical signal is output at the power level P31 reduced by the excess loss (3 dB) and the branch loss (3 dB), and the signal is transmitted to the PD 22 in the optical receiver 11 (see FIG. 3E).

Here, assuming that the optical power level transmitted from the optical transmission unit 5 is +0 dBm, the output of the optical transmission output terminal 9 by the optical splitter 19 is: +0 dBm− (0.46 dB + 3 dB + 0.3 dB) =
-3.76 dBm. Further, the optical coupler 20 has +0 dBm− (10 dB + 3 dB + 0.3 dB) = −
A signal of 13.3 dBm is transmitted. The optical receiving unit 1 is provided by the optical splitter 19.
The received power level of the PD 22 in the unit 1 is −13.3 dBm− (10 dB + 3 dB + 0.3 dB).
= −26.6 dBm.

From the relationship with the dynamic range of the preamplifier 23 in the optical receiver 11, the optical splitter 19 is initialized at the time of initialization.
It is necessary that the preamplifier 23 does not saturate and the reception power level can be controlled linearly with a margin with respect to the branching ratio of the optical coupler 20. The received optical signal is subjected to current / voltage conversion by the preamplifier 23 in the optical receiver 11, and is amplified to the amplitude Vp1. Upon receiving this signal, the peak hold circuit 29 in the APC control circuit 7 detects and holds the peak. Next, the retained result is
It is transmitted to the negative input of the difference voltage detection circuit 30 and the comparison circuit 33. Then, a comparison is made with the voltage potential Vt preset in the APC initial value setting terminal 3 to detect a difference. Here, there is a relationship of Vt = Vp1 + Vs1, and the constant current control circuit 32 increases the drive current for the potential Vs1.
And a holding circuit 34 sends a control signal to the control input of the drive current 14. With this control, the output power level of the optical transmission unit 5 shifts from Po11 to Po10. The power level of the optical transmission output terminal 9 also shifts from Po21 to Po20. Further, the output power level of the optical coupler 20 also shifts from P31 to P30. In this state, a change in the transmission power due to a change in the ambient temperature is corrected, and the state returns to the initial setting state.

This correction operation is held by the peak hold circuit 29 and the holding circuit 34 while transmitting the downlink signals D1 to D3. Further, after D3 transmission, the correction information is reset. Next, when D4 and D5 are input as downlink signals, new correction information is detected and control is performed. Here, the reset signal is given at a timing obtained by inverting the output of the signal detection circuit 4 by the inversion circuit 13 and delaying the output by the delay circuit A13. The amount of delay depends on whether the signal is LD1.
8, the light passes through the light distribution unit 8, and is converted into an electric signal by the PD 22. Further, a time ta generated by passing through the preamplifier circuit 23, the peak hold circuit 29, the comparison circuit 33, and the constant current control circuit 32 is set in advance.

At the time of transmission transmission, the gain of the signal from the optical distribution unit 8 output from the preceding value amplifier circuit 23 is controlled by the AGC circuit 24. The signal is identified by the ATC circuit 25 based on the optimum threshold value, the waveform is corrected by the LIM circuit 26, and output at a predetermined level (Vo). This signal is masked by the mask circuit 12. The control of the mask circuit 12 is performed at a timing delayed by the delay circuit B14 based on the signal of the signal detection circuit 4. Here, as the delay amount, a time tb from the input of the drive circuit 17 through the light distribution unit 8 to the time when the output is obtained in the light reception unit 11 is set in advance.

Next, D11 and D1 are sent to the master station as uplink signals.
The operation when the data No. 3 is sent from the slave station will be described. The signals of D11 and D13 received by the master station are input to the optical reception input terminal 10 and are transmitted to the optical coupler 20.
Is input to At the output of the optical coupler 20, a power level further reduced by the excess loss and the coupling loss from the power value of 9/10 is obtained and sent to the PD 22 of the optical receiver 11. The input light receiving signal is supplied to the preceding value amplification circuit 23 and the AGC circuit 2
4. The signal is output as an electric signal having a predetermined level (Vo) via the ATC circuit 25 and the LIM circuit 26. Here, the information of the signal detection circuit 4 determines the APC control circuit 7
Is in a reset state. Since the mask circuit 12 is in the non-mask state, the electric reception output terminal 15 is directly connected to L
The output signal of the IM circuit 26 is transmitted.

Next, the operation when new down signals D4 and D5 are input will be described. This time, it is assumed that the light transmission power level is higher than the voltage potential Vt set at the APC initial value setting terminal 3 due to a change in ambient temperature. Therefore, the detected potential Vp2 of the peak hold circuit 29 is Vp2 = Vt +
Vs2. This time, a control signal is sent to the control input of the drive circuit 17 by the constant current control circuit 32 and the holding circuit 34 so as to reduce the drive current for the potential Vs2. With this control, the output power level of the optical transmitter 5 shifts from Po12 to Po10. The power level of the optical transmission output terminal 9 also shifts from Po22 to Po20. Further, the output power level of the optical coupler 20 also shifts from P32 to P30. In this state, a change in the transmission power due to a change in the ambient temperature is corrected, and the state returns to the initial setting state. The timing of data to be transmitted when transmission from the slave station to the master station and reception from the master station to the slave station with respect to the slave station are different, but the operation of the optical burst transmission / reception circuit is the same.

[0030]

Next, a second embodiment of the optical burst transmitting / receiving circuit according to the present invention will be described with reference to the block diagram of FIG. In FIG. 4, the same reference numerals are used for components corresponding to the components in FIGS. 1 and 2. The optical burst transmission / reception circuit includes a signal detection circuit 4, an optical transmission unit 5, a delay circuit A6, an APC control circuit 7, an optical distributor 8, an optical reception unit 11, a mask circuit 12, and an inversion circuit 1.
3 and a delay circuit B14. Optical transmitter 5, APC
The control unit 7 and the light receiving unit 11 are the same as those in the first embodiment of FIG. However, the optical distributor 8 includes an optical attenuator 35 in addition to the optical splitter 19 and the optical coupler 20.
9 and the optical coupler 20.

As described above in relation to the first embodiment, the branching ratio between the optical splitter 19 and the optical coupler 20 is linearly controlled with a margin without the preamplifier 23 in the optical receiver 11 being saturated. It is necessary to set such that a light receiving level that can be input is input. However, the type of the branching ratio between the optical branching device 19 and the optical coupler 20 is limited, and P
It cannot be set in consideration of the conversion efficiency of D22 and the dynamic range of the preamplifier circuit 23. Therefore, when the reception input level is not suitable, it is avoided by adjusting and setting the attenuation by the optical attenuator 35 inserted at the time of the initial setting.

The preferred embodiment of the optical burst transmitting / receiving circuit according to the present invention has been described in detail. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention in any way.

[0033]

As is apparent from the above description, the optical burst transmission / reception circuit according to the present invention has the following remarkable effects in practical use. First, in performing the optical transmission power constant control, it is not necessary to select an LD in consideration of the variation of the backward output light caused by the variation of the coupling loss between the used monitor PD and the LD, that is, the variation of the monitor current. The reason is that only when the transmitting unit operates, the output power constant control of the transmitting unit shares one function of its own receiving unit, and the monitor PD is not used.
This is because control is performed using a PD provided in the receiving unit in advance as a monitor PD.

Second, in performing the optical transmission power constant control,
The transmission power loss distribution can be set without considering the tracking error caused by the coupling of the monitor PD to be used with the LD. Thereby, stable control can be realized.
The reason is that only during the operation of the transmitting unit, the output constant control of the transmitting unit is controlled by using the PD provided in the receiving unit as the monitor PD without using the monitor PD, sharing one function of the own receiving unit. Because it does.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of an optical burst transmission / reception circuit according to the present invention.

FIG. 2 is a detailed configuration diagram of the optical burst transmission / reception circuit of FIG. 1;

FIG. 3 is a timing chart for explaining the operation of the optical burst transmission / reception circuit of FIGS. 1 and 2;

FIG. 4 is a detailed configuration diagram of an optical burst transmission / reception circuit according to a second embodiment of the present invention;

FIG. 5 is an explanatory diagram of a conventional optical repeater level control method.

FIG. 6 is a configuration example of a general PON system using the present invention.

FIG. 7 is an explanatory diagram of a signal transmission state of the PON system of FIG. 6;

FIG. 8 is a schematic configuration diagram of an APC control circuit of a conventional optical burst transmission / reception circuit.

FIG. 9 is a detailed configuration diagram of FIG. 8;

FIG. 10 is a specific configuration diagram of an APC control circuit.

[Explanation of symbols]

 Reference Signs List 1 optical transmission / reception unit 2 electric transmission input terminal 3 APC initial value setting terminal 4 signal detection circuit 5 optical transmission unit 6, 14 delay circuit 7 APC control circuit 8 optical distribution unit 9 optical transmission output terminal 10 optical reception input terminal 11 optical reception Unit 12 Mask circuit 15 Electric reception output terminal 17 Drive circuit 18 Light emitting element (LD) 19 Optical splitter 20 Optical coupler 22 Light receiving element (PD) 35 Optical attenuator 36, 37 Optical fiber

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04B 10/04 10/06

Claims (5)

[Claims] 1. An optical transmitter for converting an input signal from an electric transmission input terminal into an optical signal and outputting the signal from an optical transmission output terminal, and receiving an optical signal from the optical reception input terminal and outputting the signal from the electric reception output terminal. An optical burst transmission / reception circuit for an optical subscriber system having an optical receiving unit, wherein an optical distribution unit including an optical splitter and an optical coupler is provided on an output side of the optical transmitting unit and an input side of the optical receiving unit, respectively. An optical burst transmission / reception circuit, wherein a part of an output of a transmission unit is input to the optical coupler via the optical splitter. 2. An optical attenuator is provided between the optical splitter and the optical coupler of the optical distribution unit.
3. The optical burst transmitting / receiving circuit according to claim 1. 3. An optical receiving circuit according to claim 1, wherein an optical mask circuit is arranged on an output side of said optical receiving section, and an electric receiving signal output from said optical receiving section to an electric receiving output terminal is mask-controlled. 3. The optical burst transmitting / receiving circuit according to claim 1. 4. The optical mask circuit according to claim 3, wherein the optical mask circuit is controlled by a signal obtained by delaying an output of a signal detection circuit for detecting the input signal from the electric transmission input terminal by a delay circuit. An optical burst transmission / reception circuit as described in the above. 5. The optical transmitter according to claim 1, wherein said optical transmitter receives an initial setting value from an APC initial value setting terminal and an output of said optical receiving unit.
5. The optical burst transmitting / receiving circuit according to claim 1, wherein the optical burst transmitting / receiving circuit is controlled by an output of a PC control circuit.