JP2007027819A - Method of controlling light output in passive optical network system, and subscriber premises communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the effect of tailing in incoming burst light signal reception in a station communication device, and to prevent a trouble, where the abnormal continuous luminous output of a subscriber premises communication device affects other subscriber premises communication devices. <P>SOLUTION: A station communication device OLT monitors a light reception level from each subscriber premises communication device ONU by a reception level monitor 1-15, and transmits an instruction signal for increasing or decreasing the amplitude of the incoming burst light signal to each subscriber premises communication device ONU by a light output instruction signal transmitter 1-16 to set the light reception level to a fixed range. Each subscriber premises communication device ONU extracts the instruction signal by a light output instruction signal extractor 1-27. A light output control unit 1-28 follows the instruction signal, and controls a light output setting section 1-22 so that the amplitude of the incoming burst light signal is increased or decreased. In abnormal continuous emission, infinite losses are given to the light output setting section 1-22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical output control method and a subscriber home side communication device in a passive optical network system, and more specifically, a station side communication device (OLT: Optical Line Terminator) and a plurality of subscriber home side communication devices (ONU: Optical). In a passive optical network (PON) system in which a network unit is connected by an optical transmission line branched by an optical star coupler / splitter, the amplitude of an upstream burst optical signal output from a customer premises communication device (ONU) The present invention relates to a light output control method and a subscriber home side communication device that can be suitably applied to the adjustment of the above and the stop of abnormal light emission output in the subscriber home side communication device (ONU).

  FIG. 4 shows a configuration of a general passive optical network (PON) system. The passive optical network (PON) system branches an optical signal transmitted through one optical fiber connected to a station side communication device (OLT) 4-1 by an optical star coupler / splitter 4-3, and allows a plurality of users. Is a transmission system in which a single optical fiber is shared by a plurality of users by drawing an optical fiber into the subscriber's home side communication devices (ONU # 1 to # 3) 4-2, and a station side communication device (OLT) 4-1 Sharing and optical fiber laying costs can be kept low. 983 series B-PON and G. It is recommended and standardized as 984 series G-PON.

  In addition, with the spread of high-speed Internet services, the IEEE 802.3 working group has been recommended as IEEE 802.3ah for home-use data communication services (FTTH: Fiber To The Home) using optical fiber, and GE-PON (Gigabit Ethernet (registered) As a means for providing a more economical and faster FTTH system as a trademark (trademark) -PON), it has been introduced in the Japanese market from the end of 2004.

  However, the passive optical network (PON) system has an absolute signal level loss due to the optical star coupler / splitter 4-3 at the branch point. This increases as the number of branches increases. For example, in the case of 32 branches, the fixed loss is about 17 dB. In this case, the telecommunications carrier must design the device in consideration of this fixed loss.

  For this reason, it is necessary to use an optical signal receiving circuit of a station-side communication device (OLT) installed in a telecommunications carrier station building having a wide dynamic range with respect to the reception level. Generally, an avalanche photodiode ( It is necessary to secure a wide dynamic range by amplifying a weak signal detected by an avalanche photodiode (APD) using APD (Avalanche Photodiode). That is, it is necessary to cope with reception of both an optical burst signal with a low loss and an optical burst signal with a high loss.

  Also, if one of the plurality of subscriber premises communication devices (ONUs) connected to the passive optical network (PON) continues to emit abnormal light due to a failure, it is connected to the same passive optical network (PON). In addition, this abnormal light emission continuous output is superimposed on the burst optical signal transmitted by another subscriber premises communication unit (ONU), and the other subscriber premises communication unit (ONU) cannot communicate or the communication quality deteriorates. To do. It is also required to solve such countermeasures against abnormal light emission.

  In a passive optical network (PON) system, burst optical signals transmitted from a plurality of subscriber home side communication units (ONU) 4-2 installed on a user home side are transmitted at time-divisionally assigned to each station. Uplink data transmission is realized by receiving at the side communication device (OLT) 4-1.

  Each burst optical signal transmitted from the subscriber home side communication device (ONU) 4-2 is transmitted between the station side communication device (OLT) 4-1 and each subscriber home side communication device (ONU) 4-2. The optical signal reception circuit of the local communication apparatus (OLT) 4-1 receives individual bursts because the optical star coupler / splitter 4-3 is received at different amplitudes and phases. Advanced reception processing techniques such as amplitude correction and phase synchronization establishment are required for each optical signal. Particularly in a gigabit class passive optical network (PON) such as GE-PON, it is necessary to establish phase synchronization for each high-speed optical burst signal.

  As described above, the station side communication device (OLT) 4-1 needs to receive burst optical signals from the respective subscriber premises side communication devices (ONU) 4-2 having different amplitudes with high sensitivity and high quality. However, when a high-sensitivity avalanche photodiode (APD) is used in the receiving circuit, it takes a long time to discharge after receiving a burst optical signal having a large amplitude, and it cannot be ignored from the output end even after the burst optical signal disappears. There is a characteristic (trailing) in which the output of the level appears, and this causes a phenomenon that the subsequent small amplitude burst optical signal cannot be received correctly. This is the same even if a PIN photodiode is used.

  In a conventional passive optical network (PON) system, a PIN diode or an avalanche photodiode (APD) with little tailing that satisfies the system requirements is selected for an optical signal receiving circuit of a station side communication device (OLT), or an optical signal is received. Since a circuit for removing tailing has been added by improving the signal receiving circuit, it is a significant cost increase factor for the station side communication device (OLT) and the entire system.

  FIG. 5 shows an example of a trailing method when a burst optical signal having a large amplitude is inputted and an example of a conventional method for compensating (cancelling) the current. In the figure, (a) is an optical signal receiving unit having a trailing compensation function, (b) is each output waveform in the optical signal receiving unit, and (c) is an output waveform with and without trailing compensation. Show.

  As shown in FIG. 5B, the tailing of the output of the photodetector PD (APD, PIN) due to the reception of the burst optical signal Burst1 having a large amplitude overlaps the subsequent burst optical signal Burst2 having a small amplitude, thereby The burst optical signal Burst2 having a small amplitude cannot be received with high accuracy.

Therefore, as shown in FIG. 6A, the output voltage of the photo detector PD (APD, PIN) is input to the voltage follower, and the output current (I _E ) of the voltage follower is used as the trailing elimination current to output the photo detector PD. By adding to the input of the preamplifier PRE, a burst optical signal (waveform shown as “compensated” in (c) of FIG. 5) is output.

  FIG. 6 shows an optical signal receiving circuit and gain control characteristics of the station side communication apparatus (OLT). (A) of the figure shows the optical signal receiving circuit of the station side communication device (OLT), and (b) shows the relative gain of the optical signal receiving circuit with respect to the input optical signal. The burst optical signal input from the optical fiber 6-1 is output as an electrical signal by the photodetector 6-2, amplified by the preamplifier 6-3, and then amplified by the main amplifier 6-4.

  The output signal of the main amplifier 6-4 is input to the peak detection circuit 6-5, and the peak detection circuit 6-5 outputs the peak level of the received signal to the gain control circuit 6-6. The gain control circuit 6-6 controls the light multiplication factor of the photodetector 6-2 and the gain of the main amplifier 6-4 according to the peak level input from the peak detection circuit 6-5.

  The light multiplication factor of the photodetector 6-2 controlled by the gain control circuit 6-6 is shown as a curve A in FIG. 6B, and the gain of the main amplifier 6-4 is shown as a curve B in FIG. As shown in the figure, the optical multiplication factor of the photodetector 6-2 and the gain of the main amplifier 6-4 are reduced for an input signal with a large amplitude, and the optical amplification of the photodetector 6-2 for an input signal with a small amplitude. By increasing the magnification and the gain of the main amplifier 6-4, the dynamic range for the received burst optical signal is expanded.

  As a countermeasure against the trailing by the large-amplitude burst optical signal, the ITU-T recommendation G.A. 984.2 describes in the appendix the case where the burst optical signal output of the subscriber premises communication unit (ONU) is down 3 dB and 6 dB, but does not describe a specific implementation method.

  Further, the following patent documents 1 to 3 describe the prior art of measures against the constant output of optical signals due to the failure / abnormality of the subscriber premises communication unit (ONU) in the passive optical network (PON). . In Patent Literature 1, in an optical burst signal transmission system in which a transmission path is configured by optical branching (1: n), when the terminal device abnormally emits light, the terminal device itself stops the optical output, and the failure affects the entire system. An optical signal output monitoring circuit of an optical transmission device for preventing this is described.

  In addition, Patent Document 2 adds a circuit for detecting the continuous light emission of the laser in order to prevent the failure of the optical transmission module of one subscriber from spreading to the entire system, and automatically emits light when the continuous light emission is detected. An optical transmission circuit is described in which a transmission interval allocated to itself is obtained, and light emission is forcibly stopped regardless of the presence or absence of a failure in the optical transmission module except for this transmission interval.

  Further, Patent Document 3 monitors the abnormality of the optical burst signal transmitted from the slave station device in the master station device, identifies a specific slave station device emitting abnormal light of the optical burst signal, By transmitting an optical burst stop signal instructing the slave station device to stop the optical burst signal, and receiving the optical burst stop signal in the slave station device, by blocking transmission of the optical burst signal to the master station device, An optical burst transmission / reception control system and method for identifying a slave station device that performs abnormal output of an optical burst signal and blocking the optical output of the optical burst signal from the slave station device are described.

The above-mentioned patent documents 1 to 3 are listed below.
JP-A-10-224299 JP-A-8-84119 JP 2002-217929 A

  As described above, in a passive optical network (PON) of a gigabit class such as GE-PON, an avalanche photodiode (APD) or the like is used to amplify a weak received signal, thereby ensuring a wide dynamic range and reducing loss. It is necessary to accurately receive both a small burst optical signal and a lossy burst optical signal.

  Further, in an optical receiver circuit using an avalanche photodiode (APD) or the like, when a burst optical signal having a large amplitude is received, there is a characteristic (soaking) in which an output level appears even after completion of reception, and the subsequent burst optical signal Measures are required to correctly receive the signals without being affected by the snooping, and measures against abnormal continuous light emission due to a failure of the customer premises communication device (ONU) connected to the passive optical network (PON) It is necessary to take it together.

  The present invention can reduce the dynamic range required for reception of burst optical signals transmitted from each subscriber premises communication unit (ONU) in a passive optical network (PON) system, and An optical output control method in a passive optical network system that can eliminate the influence of tailing on the reception of a burst optical signal and does not affect other users on the trouble of abnormal continuous light emission of a subscriber premises communication unit (ONU) And a subscriber premises communication device.

  An optical output control method in a passive optical network system according to the present invention includes (1) each subscriber home in a passive optical network system comprising a plurality of subscriber home side communication devices and a station side communication device connected via an optical fiber. A method of controlling an optical output of an upstream burst optical signal of a side communication device, the step of monitoring an optical reception level of an upstream burst optical signal from each subscriber home side communication device in the station side communication device; An instruction signal instructing each subscriber's home apparatus to increase or decrease the amplitude of the upstream burst optical signal is transmitted so that the optical reception level of the upstream burst optical signal from the home side communication apparatus is within a certain range. A step of controlling the subscriber's home side communication device to increase or decrease the amplitude of the upstream burst optical signal in accordance with the instruction signal received from the station side communication device; Monitoring the output level of the optical burst signal, and setting the increase or decrease of the amplitude of the upstream burst optical signal so that the upstream burst optical signal is output at a predetermined output level. .

  (2) As an instruction signal for instructing an increase or decrease in the amplitude of the upstream burst optical signal, a difference in optical reception level between consecutive upstream burst optical signals sequentially received by the station side communication device is within a predetermined range. Thus, a signal instructing to increase or decrease the amplitude of the upstream burst optical signal is transmitted.

  (3) As an instruction signal for instructing an increase or decrease in the amplitude of the upstream burst optical signal, a difference between the maximum value and the minimum value of the optical reception level of the upstream burst optical signal received by the station side communication device is a predetermined value. A signal instructing an increase or decrease in the amplitude of the upstream burst optical signal is transmitted so as to fall within the range.

  Further, the subscriber premises communication device in the passive optical network system of the present invention is (4) a subscriber premises communication device connected to the station side communication device via an optical fiber and constituting the passive optical network system. Optical output instruction signal extraction means for extracting an instruction signal for instructing increase or decrease of the amplitude of the upstream burst optical signal notified from the station side communication device, and increasing or decreasing the amplitude of the upstream burst optical signal according to the instruction signal An optical output control means for controlling the output, an optical output monitoring means for monitoring the output level of the upstream burst optical signal, and an upstream burst according to an instruction of the optical output control means so that the upstream burst optical signal is output at a predetermined output level. And optical output setting means for setting an increase amount or a decrease amount of the amplitude of the optical signal.

  (5) The optical output level of the amplitude of the upstream burst optical signal is simply increased from a zero level with a predetermined time constant when the power is turned on, and is controlled to reach a predetermined level. .

  Further, (6) an abnormal light emission state in which the light emitting element emits light during a period other than the transmission timing of the upstream burst optical signal assigned from the station side communication device, from the output signal from the optical output monitor means or the station side communication device An abnormality detection means for detecting based on the signal to be notified, and when the abnormal light emission state is detected by the abnormality detection means, the light output control means forcibly increases the light output with respect to the light output setting means. The light output is stopped by controlling to give a quantity.

  (7) For the optical output setting means, a waveguide type optical switch in which a waveguide is formed on an electro-optic effect crystal substrate is used as an optical attenuator, and the optical signal is monotonously adjusted by adjusting the attenuation amount of the optical attenuator. It is characterized by increasing or decreasing.

  According to the present invention, the subscriber premises communication apparatus (ONU) in the station side communication apparatus (OLT) is configured so that the optical reception level of the upstream burst optical signal from each subscriber premises communication apparatus is within a certain range. By controlling the output of the amplitude of the upstream burst optical signal, the avalanche photodiode (APD) or PIN diode of any characteristic of the optical receiver circuit of the station side communication device (OLT) is not affected by the tailing. Therefore, it is possible to receive an upstream burst optical signal with high accuracy, and the requirements of the dynamic range of the optical receiving circuit are relaxed, and a passive optical network (PON) system can be constructed at low cost.

  Further, the optical output setting means used for the output control of the amplitude of the upstream burst optical signal in the subscriber premises communication device (ONU) can also be used as the optical output suppressing means at the time of abnormal light emission of the optical transmitter, It is possible to eliminate the adverse effect on other subscriber premises communication devices (ONUs) due to abnormal light emission of the optical transmitter.

  FIG. 1 shows the configuration of a passive optical network (PON) system according to the present invention. As shown in the figure, a passive optical network (PON) system includes a station side communication device (OLT) 1-1, and an optical fiber and an optical star coupler / splitter 1- 1 connected to the station side communication device (OLT) 1-1. 3 and a plurality of users' subscriber premises side communication devices (ONU) 1-2 connected via the network.

  The station side communication device (OLT) 1-1 receives each subscriber home side communication device (ON) so that the upstream burst optical signal transmitted from the plurality of subscriber home side communication devices (ONU) 1-2 is received without collision. ONU) 1-2, an upstream bandwidth setting control unit 1-11 for instructing transmission timing control, and an optical transmission unit 1-12 for transmitting a signal to each subscriber home side communication device (ONU) 1-2 as an optical signal. And an optical multiplexer / demultiplexer 1-13 for transmitting an optical transmission signal from the optical transmission unit 1-12 to the optical fiber and an optical reception signal from the optical fiber to the optical reception unit 1-14, and each subscriber An optical receiver 1-14 that receives an optical signal from the home side communication device (ONU) 1-2, and a reception level monitor unit that monitors an optical reception level from each subscriber home side communication device (ONU) 1-2. 1-15 and the amplitude of each subscriber premises communication unit (ONU) 1-2 In order to make the optical signal to be an amplitude within a certain range, an optical output instruction signal transmission unit that instructs each subscriber premises communication unit (ONU) 1-2 to increase or decrease the amplitude of the upstream burst optical signal 1-16.

  Each subscriber premises communication device (ONU) 1-2 includes an optical transmission unit 1-21 that transmits a signal to the optical station communication device (OLT) 1-1 as an optical signal, and an output level of the optical signal ( Optical output setting unit 1-22 for setting (amplitude), optical output monitor unit 1-23 for monitoring the output level (amplitude) of the optical signal, and light transmitted to the optical station side communication device (OLT) 1-1. An optical multiplexer / demultiplexer 1-24 that transmits a transmission signal to an optical fiber and transmits an optical reception signal from the optical fiber to an optical reception unit 1-25, and an optical station side communication apparatus (OLT) 1-1. Abnormal light emission is detected based on the optical receiver 1-25 that receives the optical signal and the received signal from the optical station side communication device (OLT) 1-1 or the output signal from the optical output monitor 1-23. The uplink bar notified from the abnormality detection unit 1-26 and the optical station side communication device (OLT) 1-1. The optical output instruction signal extraction unit 1-27 that detects the amplitude instruction signal of the strike optical signal and the input signals from the abnormality detection unit 1-26, the optical output instruction signal extraction unit 1-27, or the optical output monitor unit 1-23. The optical output control unit 1-28 controls the increase / decrease of the output level (amplitude) of the optical signal and notifies the optical output setting unit 1-22 of the output level (amplitude).

  The station side communication device (OLT) 1-1 monitors the optical reception level from each subscriber home side communication device (ONU) 1-2 by the reception level monitoring unit 1-15, and the amplitude is measured for each subscriber side device. In order to set different optical signals to an optical reception level within a certain range, each subscriber premises communication unit (ONU) 1-2 receives an instruction signal for increasing or decreasing the amplitude of the upstream burst optical signal as an optical output instruction signal. The data is sent from the sending unit 1-16.

  Each subscriber home side communication device (ONU) 1-2 extracts the instruction signal received from the station side communication device (OLT) 1-1 by the light output instruction signal extraction unit 1-27, and the light output control unit 1- 28 controls the setting of the optical output setting unit 1-22 to increase or decrease the amplitude of the upstream burst optical signal in accordance with the instruction signal. Each subscriber premises communication unit (ONU) 1-2 monitors its own optical output level by the optical output monitor unit 1-23 and sends the monitor output to the optical output control unit 1-28. Thus, the subscriber premises communication unit (ONU) 1-2 itself controls to transmit an optical signal having a predetermined optical output level.

  FIG. 2 shows a specific example of the amplitude control of the upstream burst optical signal according to the present invention. Here, a plurality of subscriber home side communication devices including the first and second subscriber home side communication devices (ONU # 1, # 2) are already connected to the passive optical network (PON), and the nth It is assumed that the subscriber premises communication device (ONU # n) is newly connected.

  At this time, the nth subscriber home side communication device (ONU # n) is connected to the second subscriber home side communication device (ONU # 2) and the first subscriber home side communication device as shown in FIG. It is assumed that the transmission timing is assigned to transmit the upstream burst optical signal at a transmission timing adjacent to each transmission timing of (ONU # 1).

  The station side communication device (OLT) 1-1 transmits the light of the upstream burst optical signal of the continuous second subscriber home side communication device (ONU # 2) and the nth subscriber home side communication device (ONU # n). The level difference M1 and the optical level difference M2 of the upstream burst optical signal between the nth subscriber home side communication device (ONU # n) and the first subscriber home side communication device (ONU # 1) are a predetermined level difference. The amplitude instruction of the upstream burst optical signal is given to the nth subscriber home side communication device (ONU # n) so that it becomes L1 or less.

  In this way, by controlling the amplitude of the upstream burst optical signal from the subscriber premises communication device (ONU), the reception level of the continuous upstream burst optical signal in the station side communication device (OLT) 1-1 is large. This eliminates the difference, prevents reception deterioration due to tailing when burst optical signals are continuously input, and eliminates or simplifies a circuit that compensates (cancels) the tailing current. Further, the difference in reception level of the upstream burst optical signal from each subscriber premises communication unit (ONU) is reduced, and the dynamic range required for the optical reception circuit of the station side communication unit (OLT) can be reduced. .

  In addition, each subscriber home side communication device (ONU) received by the station side communication device (OLT) as an upstream burst optical signal amplitude instruction signal from the station side communication device (OLT) to the subscriber home side communication device (ONU). Each of the subscriber premises communication devices (so that the difference between the maximum value and the minimum value of the reception level of the burst optical signal from is smaller than a certain default value L2 (predetermined predetermined value range). ONU).

  Even with such a configuration, the difference in the reception level of the upstream burst optical signal from each subscriber premises communication unit (ONU) can be reduced, and reception degradation due to the influence of tailing can be prevented. The dynamic range required for the OLT optical receiver circuit can be reduced.

  In this way, the optical level information for each subscriber home side communication device (ONU) obtained by delay measurement or the like in the passive optical network (PON) connection performed at the time of new registration of the subscriber home side communication device (ONU) is used. Thus, the reception level difference of the upstream burst optical signal from each subscriber premises communication unit (ONU) can be suppressed within a certain range.

  In addition, the monitor information of the optical reception level for each subscriber premises communication device (ONU) in the station side communication device (OLT) is not limited to the newly registered connection of the subscriber premises communication device (ONU). It is good also as a structure to update. Further, as a control of the optical output of the subscriber premises side communication device (ONU), it is possible to adopt a configuration in which the optical output is shut down by giving an infinite optical loss to cope with an abnormal light emission failure.

  The optical output control of each subscriber premises communication unit (ONU) 1-2 is performed with a certain default value L3 (predetermined predetermined value) in an initial state where there is no instruction from the station side communication unit (OLT) 1-1. Output at an amplitude level close to the value range. In the initial state, each subscriber premises communication unit (ONU) 1-2 optical transmitter 1-21 is set with a bias current and a pulse current of the light emitting element so as to output an optical signal with a certain default amplitude, The output level monitored by the light output monitor unit 1-23 is input to the light output control unit 1-28, and the light output control unit 1-28 determines the output level of the light output setting unit 1-22 according to the monitor output level. The optical attenuation is adjusted and control is performed so that an optical signal having a level close to a predetermined default value L3 is output.

  Further, as the optical output control in each subscriber premises communication unit (ONU) 1-2, the optical output level is simply increased from the zero level when the power is turned on to the above-mentioned default value L3 with a predetermined time constant. It can be set as the structure controlled so that (a some fluctuation | variation is accept | permitted). That is, immediately after the power is turned on, the attenuation amount of the optical attenuator in the optical output setting unit 1-22 is set to an infinite state (extremely large attenuation amount), and the attenuation amount of the optical attenuator is gradually decreased from this state. The light output level can be controlled to simply increase to the level of the default value L3.

  Further, as the optical output control in each subscriber premises communication device (ONU) 1-2, the optical transmission unit 1-21 emits light during a period that is not the transmission timing instructed from the station communication device (OLT) 1-1. In the abnormal light emitting state, the optical output setting unit is determined by the determination process of the subscriber home side communication device (ONU) 1-2 itself or by receiving the optical output stop instruction signal from the station side communication device (OLT) 1-1. The optical attenuator at 1-22 is forcibly set to have a sufficiently large attenuation, and the optical output is stopped.

  That is, the abnormality detection unit 1-26 detects an abnormal light emission state in a period not at the transmission timing instructed from the station side communication device (OLT) 1-1, and an input signal from the light output monitor unit 1-23. Based on this, the abnormality detection unit 1-16 detects the abnormal light emission state and notifies the light output control unit 1-28 of the abnormal light emission state. The light output control unit 1-28 forcibly sets a large light attenuation amount in the abnormal light emission state. The optical output setting unit 1-22 is controlled to stop the optical output.

  Further, the abnormal light emission state of the subscriber's home side communication device (ONU) 1-2 is detected by some method such as detecting communication abnormality based on the received data in the station side communication device (OLT) 1-1, and the station Side communication device (OLT) 1-1 transmits an optical output stop instruction signal to the subscriber premises communication device (ONU) 1-2, and the subscriber premises communication device (ONU) 1-2 The instruction signal is detected by the abnormality detection unit 1-26, and the light output control unit 1-28 controls to forcibly set a large light attenuation amount according to the instruction signal and stops the light output.

As an optical output setting unit 1-22 for optical output control in the customer premises communication unit (ONU) 1-2, Ti (titanium) is applied to an electro-optic effect crystal substrate such as LiNbO ₃ (lithium nayobate, lithium niobate) ) Etc. can be applied to realize a configuration that monotonously increases or decreases the optical output.

FIG. 3 shows a configuration example of the light output setting unit 1-22 in the present invention. As shown in the figure, in the light output setting unit 1-22, an intersecting waveguide 3-2 is formed on the electro-optic effect crystal substrate 3-1 such as LiNbO ₃ by diffusion of Ti (titanium), A waveguide type optical switch in which electrodes 3-3 and 3-4 are formed at the intersection can be used.

  Corresponding to the voltage applied between the electrodes 3-3 and 3-4 at the intersection of the waveguide 3-2, the optical signal incident on the port P1 from the optical transmitter 1-21 is distributed to the ports P3 and P4. Therefore, for example, when the input optical signal level to the light receiving element arranged at the port P3 is not excessive, the optical signal incident from the port P1 is directly emitted from the port P3 and incident on the light receiving element. By dispersing the optical signal incident from the port P1 to the ports P3 and P4, the output level from the port P3 can be reduced and the optical signal level can be suppressed.

  By controlling the voltage applied to the electrodes 3-3 and 3-4 at the intersection of the waveguide 3-2, the level of the optical signal emitted from the port P3 can be attenuated, and the attenuation amount is from zero to infinite. Adjustable to large. In addition to the waveguide type optical switch, the optical output setting unit 1-22 may be configured by an optical switch using a Bragg diffraction phenomenon, a distributed coupling type optical switch, or the like.

  In order to adjust the light output level, conventionally, the bias current and pulse current of the light emitting element are changed. For example, the pulse current is halved in order to halve the light output level. However, in such a method, only the peak level is lowered, so that the extinction ratio is deteriorated. On the other hand, as a means for increasing or decreasing the amplitude of the optical signal, the optical output level is made variable without deteriorating the extinction ratio by passing through an optical attenuator whose attenuation is adjustable from zero to infinity. be able to. Note that the negative attenuation in the optical attenuator means an increase in the optical output level. Also, in the event of abnormal light emission due to a failure of the subscriber premises communication unit (ONU) 1-2, it is possible to eliminate the influence on the entire passive optical network (PON) system by giving virtually infinite optical loss. It becomes.

It is a figure which shows the structure of the passive optical network (PON) system by this invention. It is a figure which shows the specific example of the amplitude control of the upstream burst optical signal by this invention. It is a figure which shows the structural example of the light output setting part in this invention. It is a figure which shows the structure of a general passive optical network (PON) system. It is a figure which shows an example of the conventional method which compensates (cancels) the mode of the tailing when the burst optical signal with a large amplitude is input, and its electric current. It is a figure which shows the optical signal receiving circuit and gain control characteristic of a station side communication apparatus (OLT).

Explanation of symbols

1-1 Station side communication equipment (OLT)
1-11 Upband setting control unit 1-12 Optical transmission unit 1-13 Optical multiplexer / demultiplexer 1-14 Optical reception unit 1-15 Reception level monitoring unit 1-16 Optical output instruction signal transmission unit 1-2 User subscriber Home side communication device (ONU)
1-21 Optical transmission unit 1-22 Optical output setting unit 1-23 Optical output monitoring unit 1-24 Optical multiplexer / demultiplexer 1-25 Optical reception unit 1-26 Abnormality detection unit 1-27 Optical output instruction signal extraction unit 1- 27 28 Optical output controller 1-3 Optical star coupler / splitter

Claims (7)

An optical output control method of an upstream burst optical signal of each subscriber home side communication device in a passive optical network system comprising a plurality of subscriber home side communication devices and a station side communication device connected via an optical fiber,
In the station side communication device, the step of monitoring the optical reception level of the upstream burst optical signal from each subscriber home side communication device, and the optical reception level of the upstream burst optical signal from each subscriber home side communication device are constant Transmitting an instruction signal instructing increase or decrease of the amplitude of the upstream burst optical signal to each subscriber premises apparatus so as to be within the range;
In the subscriber premises communication device, in accordance with the instruction signal received from the station communication device, controlling to increase or decrease the amplitude of the upstream burst optical signal, monitoring the output level of the upstream burst optical signal, Setting the amount of increase or decrease of the amplitude of the upstream burst optical signal so that the upstream burst optical signal is output at the output level;
An optical output control method in a passive optical network system, comprising:   As an instruction signal for instructing an increase or decrease in the amplitude of the upstream burst optical signal, the upstream optical signal level difference between successive upstream burst optical signals that are sequentially received by the station side communication device is within a predetermined range. 2. The optical output control method in a passive optical network system according to claim 1, wherein a signal instructing an increase or decrease in the amplitude of the burst optical signal is transmitted.   The difference between the maximum value and the minimum value of the optical reception level of the upstream burst optical signal received by the station side communication device is within a predetermined range as the instruction signal for instructing the increase or decrease of the amplitude of the upstream burst optical signal. 2. The optical output control method in a passive optical network system according to claim 1, wherein a signal instructing an increase or decrease in the amplitude of the upstream burst optical signal is transmitted. In the subscriber premises side communication device that is connected to the station side communication device via an optical fiber and constitutes a passive optical network system,
An optical output instruction signal extracting means for extracting an instruction signal for instructing an increase or decrease in the amplitude of the upstream burst optical signal notified from the station side communication device;
Optical output control means for controlling to increase or decrease the amplitude of the upstream burst optical signal according to the instruction signal;
Optical output monitoring means for monitoring the output level of the upstream burst optical signal;
An optical output setting means for setting an increase amount or a decrease amount of the amplitude of the upstream burst optical signal in accordance with an instruction of the optical output control means so that the upstream burst optical signal is output at a predetermined output level;
A subscriber premises side communication apparatus in a passive optical network system comprising:   5. The means for controlling the optical output level of the amplitude of the upstream burst optical signal to be simply increased from a zero level with a predetermined time constant when the power is turned on to reach a predetermined level. Subscriber-side communication device in the passive optical network system of Japan. An abnormal light emission state in which the light emitting element emits light during a period other than the transmission timing of the upstream burst optical signal assigned from the station side communication device, an output signal from the optical output monitor means or a signal notified from the station side communication device An anomaly detection means to detect based on;
When an abnormal light emission state is detected by the abnormality detection means, the light output control means controls the light output setting means to forcibly give a large light attenuation amount to stop the light output. 6. The subscriber premises side communication device in the passive optical network system according to claim 4 or 5.   As the optical output setting means, a waveguide type optical switch in which a waveguide is formed on an electro-optic effect crystal substrate is used as an optical attenuator, and the optical signal is monotonously increased or attenuated by adjusting the attenuation amount of the optical attenuator. The subscriber premises side communication apparatus in the passive optical network system according to claim 4, 5 or 6.

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