JP2015065613A - Communication system, relay device, communication method and relay method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reset signal with respect to a burst receiver at an accurate timing, when a 3R receiver is used for regenerative relay of an uplink signal in an extention PON system.SOLUTION: The communication system comprises a station side device 12 and a relay device for relaying signal light transmitted/received among a plurality of subscriber side devices. The relay device comprises: a reset signal generation unit which detects uplink signal light and also generates a reset signal, to output the reset signal to an optical receiver; an optical fiber delay unit for, after the reset signal generation unit generates a reset signal, transmitting uplink signal light transmitted from an optical coupler to the optical receiver; and the optical receiver for receiving the uplink signal light transmitted from the optical fiber delay unit and the reset signal output from the reset signal generation unit, performing initial processing for an internal state according to the reset signal, and outputting signal light to an optical transmitter 25.

Description

  The present invention relates to a communication system that performs digital signal transmission in an optical communication system and an optical reception technique of a repeater, and more specifically, after an optical signal is converted into an electrical signal (current signal) by a light receiving element, the current signal is converted into a voltage signal. This is related to the technology of waveform conversion and waveform shaping / amplification. Further, the present invention responds to a bursty data signal input at a plurality of different transmission speeds at a high speed, and can receive signals from a minute signal to a large signal. Regarding technology.

  As a typical network configuration of an optical access system, a single star configuration (Single Star: SS) in which a subscriber side device (ONU: Optical Network Unit) and a station side device (OLT: Optical Line Terminal) are connected one-to-one. ) And a passive optical network (PON) configuration in which a plurality of ONUs are connected to one OLT. The network configuration diagrams of the SS and PON systems are shown in FIGS. 9 and 10, respectively.

  In the SS network shown in FIG. 9, since the ONU 15 can occupy the OLT 12, high-speed communication is possible, but there is a disadvantage that the apparatus cost is high. On the other hand, in the PON system, the PON system is adopted in many optical access systems because a plurality of ONUs 15 share one OLT 12 and optical fiber equipment and are excellent in economic efficiency.

  In the PON system network shown in FIG. 10, downlink transmission is in a continuous mode, and a signal to each ONU 15 is transmitted by time division multiplexing (TDM). The downstream signal is broadcast to all ONUs 15, and each ONU 15 selectively receives only the signal addressed to itself. On the other hand, in uplink transmission, each ONU 15 transmits a signal at a timing designated by the OLT 12 in order to avoid a collision of signals by time division multiple access (TDMA: Time Division Multiple Access). Since the transmission distance between the ONU 15 and the OLT 12 is different for each ONU, the upstream signal from each ONU 15 has the characteristic that it is intermittent with different strength and phase, and the upstream signal is called a burst mode.

  In general, an optical receiver is a photodiode (PD) that is a light receiving element, an impedance conversion amplifier (TIA), an amplitude limiting amplifier (LIA), a clock data regenerator (CDR). (Recovery). A configuration of a general optical receiver 30 is shown in FIG.

  The PD 31 converts an optical signal that has propagated through the optical fiber into a current signal, and the TIA 32 at the subsequent stage converts and amplifies the current signal into a voltage signal. The LIA 33 further amplifies the voltage signal input from the TIA 32 to a voltage signal having a constant amplitude, and outputs the amplified voltage signal to the CDR 34. The CDR 34 in the subsequent stage performs clock extraction based on the input signal, and uses the reproduced clock to identify and reproduce the signal whose amplitude has been limited by the LIA 33.

  In the PON system, since the upstream signal is in a burst mode, the TIA 32 and LIA 33 constituting the optical receiver 30 of the OLT 12 amplify burst signals having significantly different intensities without distortion, and the CDR 34 generates a clock signal from burst signals having different phases. Need to be extracted. In this case, each receiving circuit needs to be optimized for each burst signal, but each circuit requires a certain response time.

  From the viewpoint of providing an uplink communication service, it is necessary to support a large transmission line loss for wide-area accommodation, and therefore, an equalization amplifier is required to have a high sensitivity and a wide dynamic range reception performance. In addition, from the viewpoint of realizing high uplink transmission efficiency, it is necessary to shorten the physical overhead such as guard time and preamble length between uplink burst signals, so that instantaneous response performance is required for TIA32, LIA33, and CDR34. The In order to realize a high-speed PON system, establishment of a high-speed burst signal receiving technique as described above plays an extremely important role.

  In order to achieve both high-sensitivity reception and wide dynamic range reception in an amplifier such as TIA32, a technique is used in which the gain of the amplifier is controlled according to the input signal strength by automatic gain control (AGC). That is, when the input signal strength is small, high-sensitivity reception is enabled by increasing the gain of the amplifier, and when the input signal strength is large, the input overload is increased by decreasing the gain of the amplifier.

  In general, a differential interface is often used in an electric circuit. The reason is that the voltage amplitude may be halved as compared with the single-phase interface, and the common-mode noise resistance is high. In order to use a differential interface in the optical receiver 30, there is a configuration in which a single-phase / differential converter (S / BS) is provided after the TIA 32.

  Next, as a means for controlling the gain, as described in Non-Patent Document 1, the output amplitude of the amplifier is monitored, and a signal for setting the amplifier gain to a desired value is fed back and given to the amplifier. There is a way to control. Similarly, during single-phase / differential conversion, there is a method of monitoring the DC potential difference between differential pairs at the latter stage of S / B output and performing feedback control. A circuit diagram that can be considered in this case is shown in FIG.

  However, since such feedback control requires a long time for the gain of TIA 32 and single-phase / differential conversion, there is a problem that the uplink transmission efficiency may be degraded when used in the PON system.

  As means for speeding up the gain control in the TIA 32 and the single-phase / differential conversion of the transmission circuit within the optical receiver, there is a technique as described in Non-Patent Document 2. High-speed level detection by the hysteresis comparator 37 is used for gain control and single-phase / differential conversion. A circuit diagram that can be considered in this case is shown in FIG.

  The TIA has two TIA core circuits, a TIA 48 functioning as a main and a TIA 49 functioning as a replica, and the circuit constants are completely the same. Those outputs are connected to a single-phase differential converter (S / B) 46. An automatic threshold controller (ATC: Automatic threshold controller) is connected to the subsequent stage of the single-phase / differential converter. The operation of the TIA core and hysteresis comparator 37 is shown in FIG. The hysteresis comparator 37 receives two TIA outputs (main and replica).

  Since the TIA 49 functioning as a replica core has an open input terminal and no input signal, the output voltage basically maintains a constant value. Therefore, the DC component is canceled and the main TIA core output amplitude is input to the hysteresis comparator 37 as it is.

Although depending on the TIA core output amplitude, SW1 is turned ON when the TIA core output amplitude output from the single-phase / differential converter 46 and input to the hysteresis comparator 37 exceeds a certain threshold. FIG. 15 shows a circuit diagram of the TIA core circuit. It has two variable resistors R _L and R _f , and a MOSFET type switch is used.

The output destination of the output amplitude output from the hysteresis comparator 37, that is, SW1, is connected to the MOSFET of the TIA core circuit, and thereby the two resistance values R _L and R _f are controlled. As a result, by setting a high impedance conversion gain Z _H is relative to the input optical signal intensity is low light, achieving high sensitivity. By setting a low impedance conversion gain Z _L with respect to the input optical signal strength is greater light, increasing the input overload resistance, to achieve a wide dynamic range.

  FIG. 16 shows an example of an ATC circuit diagram. A high-speed peak hold circuit 43 is connected to each differential pair, and a control voltage is generated by detecting and holding the peak voltage to realize high-speed single-phase differential conversion. It has a function of detecting and holding a voltage corresponding to the input signal voltage to the ATC 47 at high speed.

  In the PON system in which the above gain control and single-phase differential conversion have different upstream signal strengths for each ONU, it is necessary to reset the circuit for each upstream signal so as to operate optimally for each upstream signal. Such an external reset signal is generally given to the optical receiver 30 of the OLT 12 from the MAC_LSI in the subsequent stage outside the optical receiver 30.

  By the way, from the viewpoint of reducing the operation cost of the optical access system, widening the PON system is one of the effective means. As shown in FIG. 1, a configuration example in which the repeater 13 is arranged between the ONU 15 and the OLT 12 can be given. Although the configuration of the repeater 13 is various, regarding the regenerative repeater of the uplink signal, the method using an optical amplifier and the 3R having a 3R function (Reshaping, Retiming, Regenerating) using a burst receiver as described above. There are two means of regenerative relay.

  However, when the 3R receiver is used for the regenerative relay of the upstream signal, it is difficult to give an external reset signal to the burst receiver at an accurate timing because the repeater 13 is located far from the OLT 12. .

Masaki Noda, Satoshi Yoshima, Masamichi Nogami, Jun-ichi Nakagawa, “A Study on Fast Burst Reception Time for 10G-EPON OLT TIA”, IEICE Electronics Society Conference, C-3-72, September 2012. Susumu Nishihara, Makoto Nakamura, Tsuyoshi Ito, Takeshi Kurosaki, Yusuke Ohtomo, and Akira Okada, "A SiGe BiCMOS Burst-mode Transimpedance Amplifier Using Fast and Accurate Automatic Offset Compensation Technique for 1G / 10G Dual-rate Transceiver", in Proc BCTM 2010 , Paper 10.2, September 2009. Susumu Nishihara, Makoto Nakamura, Kazuyoshi Nishimura, Keiji Kishine, Shunji Kimura, and Kazutoshi Kato, "10.3 Gbit / s burst-mode PIN-TIA module with high sensitivity, wide dynamic range and quick response", IET Electronics Letters, Vol . 44, no. 3, 31st January 2008.

  When a 3R receiver is used for regenerative relay of an upstream signal in a long-length PON system, it is difficult to give a reset signal to the burst receiver at an accurate timing.

  In order to solve the above-described problems, an object of the present invention is to provide a reset signal to a burst receiver at an accurate timing when a 3R receiver is used for regenerative relay of an uplink signal in a long-length PON system.

  To achieve the above object, the present invention has a function of generating a reset signal by providing a delay line to an uplink repeater and detecting the start of a burst signal at high speed.

A communication system according to the present invention includes:
Receiving a downstream signal light transmitted from the station side device, receiving a plurality of subscriber side devices transmitting the upstream signal light to the station side device, and receiving the upstream signal light transmitted from the subscriber side device; A communication system comprising: the station side device that transmits the downlink signal light; and the relay device that relays the uplink signal light and the downlink signal light transmitted and received between the subscriber side device and the station side device. There,
The relay device is
An optical coupler that branches the upstream signal light output from the subscriber side device to be sent to a reset signal generation unit and an optical fiber delay unit;
Generating a reset signal by detecting the upstream signal light, and outputting the reset signal to an optical receiver located in a subsequent stage; and
The optical fiber delay unit that delays the upstream signal light transmitted from the optical coupler by a reset signal generation time during which the reset signal generation unit generates the reset signal, and transmits the delayed signal light to the optical receiver located at a subsequent stage. When,
The upstream signal light transmitted from the optical fiber delay unit and the reset signal output from the reset signal generation unit are received, an internal state is initialized according to the reset signal, and the upstream signal light is electrically The optical receiver that outputs an upstream electrical signal converted into a signal to an optical transmitter;
And an optical transmitter that converts the upstream electrical signal into electro-optic light and transmits the electrical signal converted upstream signal light to the station side device.

The relay device according to the present invention is
A relay device for relaying upstream signal light and downstream signal light transmitted and received between a station side device and a plurality of subscriber side devices,
An optical coupler that branches the upstream signal light output from the subscriber side device to be sent to a reset signal generation unit and an optical fiber delay unit;
Generating a reset signal by detecting the upstream signal light, and outputting the reset signal to an optical receiver located in a subsequent stage; and
The optical fiber delay unit that delays the upstream signal light transmitted from the optical coupler by a reset signal generation time during which the reset signal generation unit generates the reset signal, and transmits the delayed signal light to the optical receiver located at a subsequent stage. When,
The upstream signal light transmitted from the optical fiber delay unit and the reset signal output from the reset signal generation unit are received, the upstream signal light is converted into an electrical signal, and the internal state is changed according to the reset signal. The optical receiver that performs initialization processing and outputs the upstream electrical signal obtained by converting the upstream signal light into an electrical signal to an optical transmitter;
And an optical transmitter that converts the upstream electrical signal into electro-optic light and transmits the electrical signal converted upstream signal light to the station side device.

In the relay device according to the present invention,
The reset signal generator is
The upstream signal light output from the optical coupler is detected, a reset signal is generated according to a pre-assigned identification pattern of the upstream signal light, and the reset signal is output to an optical receiver located at a subsequent stage. Good.

In the relay device according to the present invention,
The reset signal generator is
The upstream signal light output from the optical coupler may be detected, a reset signal may be generated according to the intensity of the upstream signal light, and the reset signal may be output to an optical receiver located at a subsequent stage.

A communication method according to the present invention includes:
A relay apparatus communication method for relaying uplink signal light and downlink signal light transmitted and received between a station side device and a plurality of subscriber side devices,
The relay device is
An optical coupler that branches the upstream signal light output from the subscriber side device to be sent to a reset signal generation procedure and an optical fiber delay procedure;
The reset signal generation procedure for detecting the upstream signal light and generating a reset signal and outputting the reset signal to an optical receiver located in a subsequent stage;
After the reset signal is generated in the reset signal generation procedure, the optical fiber delay procedure for transmitting the upstream signal light transmitted from the optical coupler to the optical receiver located in the subsequent stage;
Receiving the upstream signal light transmitted in the optical fiber delay procedure and the reset signal output in the reset signal generation procedure, converting the upstream signal light into an electrical signal, and receiving an optical receiver in response to the reset signal; The optical receiver that initializes the internal state of the output signal and outputs an upstream electrical signal obtained by converting the upstream signal light into an electrical signal;
The optical transmitter for converting the upstream electrical signal into electro-optic light and transmitting the upstream signal light subjected to electro-optic conversion to the station side device.

The relay method according to the present invention is:
A relay method for relaying uplink signal light and downlink signal light transmitted and received between a station side device and a plurality of subscriber side devices,
An optical coupler for branching the upstream signal light output from the subscriber side device to be sent to the reset signal generation procedure and the optical fiber delay procedure;
In the reset signal generation procedure, the upstream signal light is detected and a reset signal is generated, and the reset signal is output to an optical receiver located in a subsequent stage,
After the reset signal generation procedure generates a reset signal in the optical fiber delay procedure, the upstream signal light transmitted from the optical coupler is transmitted to the optical receiver located at a subsequent stage,
The optical receiver receives the upstream signal light transmitted from the optical fiber delay procedure and the reset signal output from the reset signal generation procedure, initializes an internal state according to the reset signal, and Output upstream electrical signal that is converted upstream signal light into electrical signal,
The upstream electrical signal is subjected to electro-optical conversion, and the upstream optical signal subjected to electro-optical conversion is transmitted to the station side device.

In the relay method according to the present invention,
The reset signal generation procedure includes:
The upstream signal light output from the optical coupler is detected, a reset signal is generated according to a pre-assigned identification pattern of the upstream signal light, and the reset signal is output to an optical receiver located at a subsequent stage. Good.

In the relay method according to the present invention,
The reset signal generation procedure includes:
The upstream signal light output from the optical coupler may be detected, a reset signal may be generated according to the intensity of the upstream signal light, and the reset signal may be output to an optical receiver located at a subsequent stage.

  The above inventions can be combined as much as possible.

  According to the present invention, when a 3R receiver is used for regenerative relay of an uplink signal in a long PON system, a reset signal for a burst receiver can be given at an accurate timing. As a result, it becomes easy to realize a long-lengthened PON system.

2 shows a configuration example of a network according to the present embodiment. The structural example of the repeater which concerns on this embodiment is shown. The structural example of the uplink repeater which concerns on this embodiment is shown. The structural example which used the hysteresis comparator in the reset signal generator which concerns on this embodiment is shown. It is a figure explaining the input-output characteristic of the hysteresis comparator which concerns on this embodiment. It is a figure explaining the time-sequential operation | movement which concerns on this embodiment. The structural example which used the pattern discriminator in the reset signal generator which concerns on this embodiment is shown. The structural example which used the input optical signal intensity | strength monitor part in the reset signal generator which concerns on this embodiment is shown. The structural example of SS system network which concerns on related technology is shown. The structural example of the PON system network which concerns on related technology is shown. The structural example of the optical receiver which concerns on related technology is shown. The structural example of the feedback type AGC / ATC circuit which concerns on related technology is shown. The structural example of the feedforward type GC / ATC circuit which concerns on related technology is shown. It is a figure explaining the operating characteristic of the hysteresis comparator which concerns on related technology. The structural example of the TIA core circuit which concerns on related technology is shown. The structural example of ATC which concerns on related technology is shown.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(First embodiment)
A first embodiment of the present invention will be described.
FIG. 1 shows an example of a communication system according to the present embodiment. The communication system according to the present embodiment includes a repeater 13 that functions as a relay device for relaying optical signals of uplink signal light and downlink signal light transmitted and received between the station side device 12 and a plurality of subscriber side devices. . The repeater also includes a reset signal generator 26 that functions as a reset signal generation unit, an optical fiber delay line 27 that functions as an optical fiber delay unit, and an optical receiver and an optical transmitter 25 that have a 3R function.

The network configuration is as shown in FIG. 1, and a bidirectional repeater 13 is arranged between the OLT 12 and the splitter 14 functioning as an optical splitter. The bidirectional repeater 13 is a burst-compatible 3R optical receiver. Have.

The optical access network configuration assumed in this embodiment is 10G-EPON (IEEE Std 802.3av) where downlink communication is time division multiplexing (TDM) and uplink communication is time division multiple access (TDMA). -2009). In 10G-EPON, a wavelength of 1.577 μm band is used for downlink communication and a 1.27 μm band is used for uplink communication.

  As shown in FIG. 2, the repeater 13 includes a wavelength multiplexing / demultiplexing filter A, a wavelength multiplexing / demultiplexing filter B, an optical amplifier 18, and an uplink 3R repeater 20. The wavelength multiplexing / demultiplexing filter A is connected to the ONU 15 via the splitter 14 that functions as a passive optical splitter.

  The wavelength multiplexing / demultiplexing filter A sends a downstream 1.577 μm band signal transmitted from the optical amplifier 18 included in the repeater 13 in the ONU direction, while an upstream 1.27 μm signal transmitted from the ONU 15. This is a passive component that transmits a band optical signal to the 3R receiver built in the repeater 13.

  The wavelength multiplexing / demultiplexing filter B sends a signal in the downstream 1.577 μm band transmitted from the OLT 12 to the optical amplifier 18 built in the repeater 13, while being sent from the 3R receiver built in the repeater 13. This is a passive component that transmits an upstream 1.27 μm band signal to the OLT 12. The optical amplifier 18 has a function of amplifying the downstream signal intensity transmitted from the OLT 12 via the wavelength filter 19-B and regenerating and transmitting it to the ONU 15 via the wavelength filter 19-A.

  Next, the configuration of the uplink 3R repeater 20 will be described with reference to FIG. The upstream 3R repeater 20 includes a 3R optical receiver 24, an optical transmitter 25, a reset signal generator 26, an optical fiber delay line 27, and an optical coupler 28.

  The configuration and operation of the 3R optical receiver 24 in this embodiment are the same as those described in the related art, and it is assumed that the 3R optical receiver 24 includes an external reset type burst receiver. The optical fiber delay line 27 is for gaining time until the reset signal generator 26 generates a reset signal by giving a delay at a time t.

  The reset signal generator 26 taps a part of the upstream optical signal by the optical coupler 28, and detects the input of the upstream burst signal to give a reset signal to the burst receiver. The internal state of the 3R optical receiver 24 can be initialized according to the reset signal. Although the external reset type burst receiver has an instantaneous response performance, the response time needs to some extent, for example, about 100 ns according to Non-Patent Document 3, so the length of the optical fiber delay line 27 is about 20 m, for example. Can be a reasonable choice.

  Next, the operation of the reset signal generator 26 will be described in detail with reference to FIG. The reset signal generator 26 includes a PD 31, two TIAs having exactly the same characteristics (referred to as TIA 32-1 and TIA 32-2, respectively), a hysteresis comparator 37, and a reset signal output circuit 38. The TIA 32-1 is connected to the PD 31, and an input optical signal to the reset signal generator 26 is input. Since the input of the TIA 32-2 is open and the output voltage is always a constant value, the differential input to the hysteresis comparator 37 changes only when an upstream burst optical signal exists.

The input / output characteristics of the hysteresis comparator 37 are shown in FIG. V_H is output when the input voltage exceeds Vth_2, and V_L is output when the input voltage falls below Vth_1. In general, in the case of a signal format that expresses a signal with binary values of “1” and “0”, for example, NRZ, an optical signal that expresses “0” also has a certain intensity. This is because the optical signal has a finite extinction ratio. For example, an upstream optical signal of 10G-EPON has an extinction ratio of 6 dB. The average input current I _in to the TIA 32-1 and the extinction ratio _Er can be expressed as the following formula (1).

、Ｐ_ｉｎ、Ｉ_Ｈ、Ｉ_ＬはそれぞれＰＤ３１の変換効率、平均入力光信号強度、「１」レベルでの入力電流、「０」レベルでの入力電流を表す。次に、ＴＩＡ３２−１への入力電流は、消光比を考慮すると以下式（２）のように表すことが出来る。 here,

Represents _{P in,} I H, the conversion efficiency of _{I L} each PD 31, the average input optical signal intensity, the input current at "1" level, the input current at "0" level. Next, the input current to the TIA 32-1 can be expressed as the following formula (2) in consideration of the extinction ratio.

  Therefore, the output voltage of the TIA 32-1 can be expressed as the following formula (3).

Here, R _f and V _ave are the impedance conversion gain and the TIA32-1 average output voltage, respectively. When the uplink signal is present, the output voltage of considering the finite extinction ratio at least TIA32-1 is more V _L. In addition, it does not exceed the _{V H, V ave} is more than sure. Accordingly, the threshold value of the hysteresis comparator 37 included in the reset signal generator 26 can generate a reset signal by setting V _L for Vth_1 and V _ave for Vth_2.

  In other words, when an upstream signal from any ONU 15 enters, the output voltage of the hysteresis comparator 37 becomes V_H, thereby resetting the burst receiver in the 3R optical receiver 24. On the other hand, when the upstream signal from the ONU 15 disappears, the input voltage to the hysteresis comparator 37 falls below Vth_1, so the output voltage of the hysteresis comparator 37 becomes V_L, which is an initial state.

  The reset signal output circuit 38 has a function of outputting a reset pulse to the 3R receiver with a rising edge at which the output voltage of the hysteresis comparator 37 changes from V_L to V_H as a trigger.

  Calculate parameters using specific numbers. For example, the input optical signal intensity from any ONU 15 to the upstream repeater 20 is −28 dBm, the extinction ratio is 6 dB, the insertion loss of the wavelength filter 19-A is 1 dB, the optical coupler 28 is 2 to 2, and the branching ratio is 50%. Suppose that Then, the input optical signal intensity to the reset signal generator 26 is −32 dBm.

Next, it is assumed that the conversion efficiency of the PD 31 included in the reset signal generator 26 is 0.9, and the impedance conversion gain of the TIA 32-1 is 5 kΩ. Then, from Expression (3), V _L and V _ave are 1.1 mV and 4.5 mV, respectively. Therefore, Vth_1 and Vth_2 may be set to 1.1 mV and 4.5 mV, respectively.

  In an electronic circuit, characteristics vary to some extent at the time of manufacture. Therefore, in consideration of an actual margin, these values may be set slightly lower than the above values. Next, the operation in the time domain of the present invention will be described in detail with reference to FIG.

  The TIA 32 and LIA 33 included in the upstream 3R optical receiver 24 include a TIA 32 and a high-speed peak hold circuit 43 of a type in which the gain is switched between two values using an external reset signal in FIGS. 13 to 16 described in the related art.

Specifically, assuming that upstream signals having different optical signal strengths from one different ONU and the other ONU are input to the repeater 20, each input optical signal strength has a relationship of P ₁ > P ₂ , Let P ₁ be stronger.

Optical signal from one ONU is inputted to the reset signal generator 26 at time t _1. On the other hand, the upstream optical signal is input to the 3R receiver 24 due to the delay by the optical fiber delay line 27 at time t ₂ after the delay of time t.

Since the output voltage of the hysteresis comparator 37 inside the reset signal generator instantaneously becomes the voltage V _H , the reset signal generator 26 outputs a reset pulse to the 3R receiver 24. In response to the input of the reset signal, the gain of the TIA 32 is reset. Since the input optical signal strength is high, after a certain response time, the time _{t 3} the impedance conversion gain of TIA32 switches to _{Z H.}

On the other hand, when the value of the peak hold circuit 43 of the ATC circuit 47 is the initial value was _{V Hold_0,} is cleared to 0 once receives the reset signal. Thereafter, the value converges to the value V _{hold — 1} corresponding to the input signal voltage by time t ₄ . The reset signal generator 26, signals from one ONU to time t ₅ are inputted. When there is no signal, the output voltage of the hysteresis comparator 37 instantaneously changes to _VL .

Next, an optical signal having a weak optical signal intensity from the other ONU is input. The reset signal generator 26 is input to the time t _6. The upstream optical signal is input to the 3R receiver 24 due to the delay by the optical fiber delay line 27 at time t ₇ after the delay of time t.

Since the output voltage output of the hysteresis comparator 37 inside the reset signal generator instantaneously becomes the voltage V _H , the reset signal generator 26 outputs a reset pulse to the 3R receiver 24. In response to the input of the reset signal, the gain of the TIA 32 is reset. Since the input optical signal strength is small, after a certain response time, the time _{t 8} the impedance conversion gain of TIA32 is switched to _{Z L.}

On the other hand, if the value of the peak hold circuit 43 of the ATC circuit 47 is held at the previous value and is V _{hold —} 1, it is once cleared to 0 upon receiving the input of the reset signal. Thereafter, the value converges to the value V _{hold — 2} corresponding to the input signal voltage by time t ₉ . The reset signal generator 26, signals from the other ONU is input to the time _{t 10.}

  In this embodiment, the presence or absence of an input optical signal is detected by a circuit that focuses on the fact that the extinction ratio of the optical signal is finite. However, the present invention is not limited to such a specific input optical signal detection circuit. In addition, the present invention is not limited to a specific TIA or ATC circuit 47, and can be applied to a burst optical receiver using an external reset signal.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings. The configuration of the reset signal generator 26 is different from that of the first embodiment, and the rest is the same. As shown in FIG. 7, the reset signal generator 26 according to the second embodiment includes a PD 31, a TIA 32, a pattern identifier 40, and a reset signal output circuit 38. The pattern discriminator 40 detects a specific pattern in the PON system.

  For example, in upstream communication of the PON system, each signal has a redundant pattern section used as an identification pattern called “preamble”. Although the main signal is not included in this preamble section, gain control of the TIA 32 and clock extraction / data reproduction in the CDR 34 are performed using this section.

  For example, in 10G-EPON, the following values are defined in binary numbers such as 10 1111 1101 0000 0010 0001 1000 1010 0111 1010 0011 1001 0010 1101 1101 1001 1010 as a synchronization pattern which is a preamble section pattern.

  The above pattern is repeatedly transmitted over the preamble period. The pattern discriminator 40 instantaneously detects that the above pattern has been input, and immediately outputs a reset signal to the 3R receiver 24 when detecting the input of the synchronization pattern. Thereby, the internal state of the 3R receiver 24 is initialized according to the reset signal. Since other operations are the same as those in the first embodiment, description thereof is omitted.

(Third embodiment)
A third embodiment of the present invention will be described with reference to the drawings. The configuration of the reset signal generator 26 is different from the first embodiment and the second embodiment, and the others are not changed. As shown in FIG. 8, the reset signal generator 26 of the present embodiment has an input optical signal intensity monitor unit 42, and detects the input optical signal intensity with high accuracy.

  For example, the input optical signal intensity monitor unit 42 samples the input optical signal intensity at regular intervals / time periods, and outputs the average value to the subsequent reset signal output circuit 38 at regular intervals. The reset signal output circuit 38 according to the present embodiment has a comparator inside, and when the set threshold value is exceeded, it is determined that an input optical signal exists and outputs a reset signal to the 3R receiver 24. Thereby, the internal state of the 3R receiver 24 is initialized according to the reset signal. Since other operations are the same as those in the first embodiment, description thereof is omitted.

  The present invention can be applied to the information communication industry.

12: OLT
13: Repeater 14: Splitter 15: ONU
16: HGW
18: Optical amplifier 19-A, 19-B: Wavelength filter 20: Uplink 3R repeater 24: 3R optical receiver 25: Optical transmitter 26: Reset signal generator 27: Optical fiber delay line 28: Optical coupler 30: Optical Receiver 31: PD
32, 32-1, 32-2: TIA
33: LIA
34: CDR
35: LDD
36: LD
37: Hysteresis comparator 38: Reset signal output circuit 40: Pattern discriminator 42: Input optical signal intensity monitor unit 43: Peak hold circuit 44: BUF
45: AGC
46: S / B (single phase / differential converter)
47: ATC
48: TIA core (main)
49: TIA Core (Replica)
51, 52: SW1

Claims (8)

Receiving a downstream signal light transmitted from the station side device, receiving a plurality of subscriber side devices transmitting the upstream signal light to the station side device, and receiving the upstream signal light transmitted from the subscriber side device; A communication system comprising: the station side device that transmits the downlink signal light; and the relay device that relays the uplink signal light and the downlink signal light transmitted and received between the subscriber side device and the station side device. There,
The relay device is
An optical coupler that branches the upstream signal light output from the subscriber side device to be sent to a reset signal generation unit and an optical fiber delay unit;
Generating a reset signal by detecting the upstream signal light, and outputting the reset signal to an optical receiver located in a subsequent stage; and
The optical fiber delay unit that delays the upstream signal light transmitted from the optical coupler by a reset signal generation time during which the reset signal generation unit generates the reset signal, and transmits the delayed signal light to the optical receiver located at a subsequent stage. When,
The upstream signal light transmitted from the optical fiber delay unit and the reset signal output from the reset signal generation unit are received, an internal state is initialized according to the reset signal, and the upstream signal light is electrically The optical receiver that outputs an upstream electrical signal converted into a signal to an optical transmitter;
The optical transmitter that converts the upstream electrical signal into electro-optic light, and transmits the upstream signal light subjected to electro-optic conversion to the station side device; and
A communication system comprising: A relay device for relaying upstream signal light and downstream signal light transmitted and received between a station side device and a plurality of subscriber side devices,
An optical coupler that branches the upstream signal light output from the subscriber side device to be sent to a reset signal generation unit and an optical fiber delay unit;
Generating a reset signal by detecting the upstream signal light, and outputting the reset signal to an optical receiver located in a subsequent stage; and
The optical fiber delay unit that delays the upstream signal light transmitted from the optical coupler by a reset signal generation time during which the reset signal generation unit generates the reset signal, and transmits the delayed signal light to the optical receiver located at a subsequent stage. When,
The upstream signal light transmitted from the optical fiber delay unit and the reset signal output from the reset signal generation unit are received, the upstream signal light is converted into an electrical signal, and the internal state is changed according to the reset signal. The optical receiver that performs initialization processing and outputs the upstream electrical signal obtained by converting the upstream signal light into an electrical signal to an optical transmitter;
The optical transmitter that converts the upstream electrical signal into electro-optic light, and transmits the upstream signal light subjected to electro-optic conversion to the station side device; and
A relay device comprising: The reset signal generator is
Detecting upstream signal light output from the optical coupler, generating a reset signal according to a pre-assigned identification pattern of the upstream signal light, and outputting the reset signal to an optical receiver located at a subsequent stage; The relay apparatus according to claim 2, wherein the relay apparatus is characterized in that: The reset signal generator is
The upstream signal light output from the optical coupler is detected, a reset signal is generated according to the intensity of the upstream signal light, and the reset signal is output to an optical receiver located at a subsequent stage. 2. The relay device according to 2. A relay apparatus communication method for relaying uplink signal light and downlink signal light transmitted and received between a station side device and a plurality of subscriber side devices,
The relay device is
An optical coupler that branches the upstream signal light output from the subscriber side device to be sent to a reset signal generation procedure and an optical fiber delay procedure;
The reset signal generation procedure for detecting the upstream signal light and generating a reset signal and outputting the reset signal to an optical receiver located in a subsequent stage;
After the reset signal is generated in the reset signal generation procedure, the optical fiber delay procedure for transmitting the upstream signal light transmitted from the optical coupler to the optical receiver located in the subsequent stage;
Receiving the upstream signal light transmitted in the optical fiber delay procedure and the reset signal output in the reset signal generation procedure, converting the upstream signal light into an electrical signal, and receiving an optical receiver in response to the reset signal; The optical receiver that initializes the internal state of the output signal and outputs an upstream electrical signal obtained by converting the upstream signal light into an electrical signal;
The optical transmitter that converts the upstream electrical signal into electro-optic light, and transmits the upstream signal light subjected to electro-optic conversion to the station side device; and
A communication method comprising: A relay method for relaying uplink signal light and downlink signal light transmitted and received between a station side device and a plurality of subscriber side devices,
An optical coupler for branching the upstream signal light output from the subscriber side device to be sent to the reset signal generation procedure and the optical fiber delay procedure;
In the reset signal generation procedure, the upstream signal light is detected and a reset signal is generated, and the reset signal is output to an optical receiver located in a subsequent stage,
After the reset signal generation procedure generates a reset signal in the optical fiber delay procedure, the upstream signal light transmitted from the optical coupler is transmitted to the optical receiver located at a subsequent stage,
The optical receiver receives the upstream signal light transmitted from the optical fiber delay procedure and the reset signal output from the reset signal generation procedure, initializes an internal state according to the reset signal, and Output upstream electrical signal that is converted upstream signal light into electrical signal,
The upstream electrical signal is electro-optically converted, and the electro-optically converted upstream signal light is transmitted to the station side device,
A relay method characterized by the above. The reset signal generation procedure includes:
Detecting upstream signal light output from the optical coupler, generating a reset signal according to a pre-assigned identification pattern of the upstream signal light, and outputting the reset signal to an optical receiver located at a subsequent stage; The relay method according to claim 6. The reset signal generation procedure includes:
The upstream signal light output from the optical coupler is detected, a reset signal is generated according to the intensity of the upstream signal light, and the reset signal is output to an optical receiver located at a subsequent stage. 6. The relay method according to 6.

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