JP6227974B2 - Burst signal reception method - Google Patents

Description

  The present invention relates to a method for receiving an upstream burst signal of a PON system using digital coherent optical transmission.

  In an optical transmission system represented by a PON (Passive Optical Network) system, the optical transmission system can be advanced by using digital signal processing. As signal processing technology and integrated circuit technology improve, expectations for optical transmission systems using signal processing technology are increasing.

  In the backbone optical transmission system, studies on large-capacity long-distance transmission using digital coherent technology are in progress. In digital coherent technology, practical coherent detection is realized by signal processing technology such as equalization processing, optical frequency offset compensation processing, and phase estimation processing.

  As a signal processing technology for realizing digital coherent reception, as shown in FIG. 1, a training signal method for performing estimation processing and compensation processing using a regular training signal as a reference, and setting initial parameters using a pull-in signal After that, there is a blind method in which parameters are updated while receiving actual data (for example, Non-Patent Document 1).

  In the training signal system, the training signal PT is transmitted at regular time intervals in addition to the actual data in the multi-level signal transmission device. The digital coherent receiving apparatus determines parameters for estimation processing and compensation processing so as to minimize the error of the training signal PT, and receives data using the parameters. Such a method has the advantage of being easy to implement, but the execution throughput is reduced by the amount of the training signal, synchronization with the training signal is required, delay occurs, and the signal processing parameters are changed until the next training signal is received. There is a drawback that it cannot be changed and cannot follow changes in signal characteristics.

  In the blind method, after setting the initial parameter of the compensation value using the pull-in signal PL, the parameter used for signal processing is continuously updated using the actual data. This eliminates the need for synchronization with the regular training signal PT, and achieves a high effective throughput. On the other hand, the pull-in signal and the data signal need to change continuously, and when the signal characteristics change discontinuously, such as when the transmission path is switched, it is difficult to update parameters using actual data.

  The backbone optical transmission system is a point-to-point connection system, and the transmission path environment rarely changes significantly after the system is constructed. In the backbone optical transmission system, digital coherent technology has been realized by performing estimation processing and compensation processing using a training signal scheme or a blind scheme as shown in FIG. 1 for continuous signals.

  On the other hand, an optical transmission system for access typified by a PON system is a point-to-multipoint connection system comprising a single OLT (Optical Line Terminal) and a plurality of ONUs (Optical Network Units). In the PON system, connection by a plurality of users is realized by time division multiplexing, and the OLT is realized by switching communication with a partner having a different transmission environment at certain time intervals. Therefore, the signal used in the PON system is a burst signal (intermittent signal), and the OLT performs digital coherent reception on the burst signal.

  Both the training signal system and the blind system are based on the application of digital coherent technology to continuous signals. When estimation processing or compensation processing for a continuous signal is applied to a burst signal, for example, there is a possibility that the next burst signal may be received with the signal processing parameters set using the previous burst signal. On the other hand, since the optical offset and the phase information are different for each burst signal, the next burst signal cannot be estimated or compensated using the signal processing parameter of the training signal or the pull-in signal of the previous burst signal.

  In the PON system, the upstream signal from the ONU to the OLT is a burst signal. In order to perform digital coherent reception on a burst signal, it is necessary to switch signal processing parameters for each burst signal. Because the burst signal frame length is not uniform, the training signal method for continuous signals cannot be applied as it is, and the timing of the training signal must be adjusted to use different signal processing parameters for different burst signals. There is. In the blind method, since it is necessary to change the signal processing parameter for each burst signal, it is necessary to perform drawing using the first frame of the burst signal.

Suzuki Ota, Hiroshi Miyamoto, Masato Tomizawa, Koichi Sakano, Koichi Murata, Shinji Shibayama, Makoto Shibuya, Fukuchi Kiyoshi, Hiroshi Hoshida, Kosuke Komaki, Takashi Mizuochi, Kazuo Miyabo, Yoshihide Miyata, Yasuhide Kamio "Research and development of digital coherent signal processing technology", Journal of IEICE Vol. 95, no. 12, 2012

  Therefore, an object of the present invention is to make it possible to apply a training method or a blind method for continuous signals for each burst signal, and to realize digital coherent reception in a PON system.

  The present invention updates a signal processing parameter for each burst signal, thereby enabling application of a training method or a blind method for continuous signals for each burst signal, and realizes digital coherent reception in a PON system.

Specifically, the burst signal receiving device according to the present invention is:
A burst signal receiving apparatus provided in the parent node in a digital coherent optical transmission system in which a single parent node and a plurality of child nodes are connected by time division multiplexing,
For each burst signal transmitted from the child node, a reset signal transmission unit that transmits a reset signal to a signal processing unit for performing coherent detection provided in the parent node ,
The signal processing unit determines a parameter of the coherent detection using a training signal or a pull-in signal of a next burst signal detected after receiving the reset signal .

In the burst signal receiving apparatus according to the present invention further comprises a termination information detection unit for detecting termination information of the burst signal, the reset signal transmitting unit, triggered by the detection of the termination information in the end information detecting unit, the reset signal May be sent .

In the burst signal receiving apparatus according to the present invention, when the termination information detecting section detects the termination information, and change the reception timing of the training signal after the guard time interval elapses in the burst signal, the reception timing of the training signal after the change You may further provide the training signal reception timing estimation part notified to the said signal processing part.

The burst signal receiving apparatus according to the present invention further includes a signal allocation scheduler for creating a user information reference table for storing a reception start time and a reception end time of a burst signal and transmission source information of the burst signal, and the reset signal transmission unit May transmit the reset signal according to the burst signal reception end time in the signal allocation scheduler.

In the burst signal receiving apparatus according to the present invention, the pull-in signal may be a preamble of a burst signal.

Specifically, the burst signal receiving method according to the present invention is:
A burst signal receiving method performed by the parent node in a digital coherent optical transmission system in which a single parent node and a plurality of child nodes are connected by time division multiplexing,
A reset signal transmission unit, for each burst signal transmitted from the child node, a reset signal transmission procedure for transmitting a reset signal to a signal processing unit for performing coherent detection provided in the parent node ;
The signal processing unit executes a parameter setting procedure for determining a parameter of the coherent detection using a training signal or a pull-in signal of a next burst signal detected after receiving the reset signal .

  According to the present invention, it is possible to apply a training method or a blind method for continuous signals for each burst signal, and digital coherent reception can be realized in the PON system.

It is an example of the signal processing technique which implement | achieves digital coherent reception, (a) shows a training system, (b) shows a blind system. 1 is a configuration diagram illustrating an example of a burst signal receiving apparatus according to Embodiment 1. FIG. 6 is a configuration diagram illustrating an example of a burst signal receiving apparatus according to Embodiment 2. FIG. It is a figure which shows the example of a frame structure in the case of setting a signal processing parameter with a training signal system. It is a figure which shows the example of a frame structure in the case of setting a signal processing parameter by a blind system. FIG. 10 is a configuration diagram illustrating an example of a burst signal receiving apparatus according to a third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. These embodiments are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
The invention according to the present embodiment detects end information of a burst signal and initializes parameters used for signal processing of digital coherent reception. The burst signal receiver of this embodiment can be used for an upstream burst signal receiver of a PON system, that is, an OLT.

  As shown in FIG. 2, the burst signal receiving apparatus according to the present embodiment includes an ADC (Analog Digital Converter) 20, an equalization processing unit 21, an optical offset compensation processing unit 22, a phase compensation processing unit 23, a demodulation unit 24, a termination unit An EOB detection unit 25 and a reset signal transmission unit 26 functioning as an information detection unit are provided.

The burst signal receiving method according to the present embodiment includes a termination detection procedure and a parameter setting procedure in order.
In the termination detection procedure, the EOB detection unit 25 detects EOB information of the burst signal and transmits a message to the reset signal transmission unit 26.
In the parameter setting procedure, the reset signal transmission unit 26 resets a signal processing unit that needs to change parameters for each burst signal, such as the equalization processing unit 21, the optical offset compensation processing unit 22, and the phase compensation processing unit 23. A signal is transmitted and each signal processing parameter is initialized.

  In this way, the signal processing parameters are reset for each burst signal, and the same training signal system or blind system as for continuous signals is applied for each burst signal. This makes it possible to apply a signal processing technique similar to estimation processing and compensation processing for a continuous signal to a burst signal, and the digital coherent receiver can receive the burst signal.

  In the burst signal receiving method according to the present embodiment, signal processing parameters are reset using EOB information that is the end of the burst signal. By using the EOB information, it is possible to initialize the signal processing parameter from the reception of the burst signal using the current parameter to the start of reception of the next burst signal.

  That is, the burst signal receiving apparatus may wait until the training signal of the next burst signal is detected after the EOB information is detected, and may transition to waiting for a periodic burst signal after detecting the training signal of the next burst signal. As a result, the burst signal transmission device can control the transmission timing of the training signal without cooperating with other burst signal transmission devices.

  Further, the preamble of the next burst signal may be regarded as a pull-in signal. Thereby, the burst signal can be received without changing the burst signal transmission method.

  By resetting the signal processing unit in this way, it is possible to avoid performing estimation processing or compensation processing using parameters set using other burst signals. Thereby, when switching to another burst signal between training signals by the training signal method, estimation processing or compensation processing using different signal processing parameters can be performed. In the blind method, since the signal processing parameter is changed for each preamble of the burst signal, the estimation process or the compensation process can be performed using the signal processing parameter corresponding to the burst signal.

  In FIG. 2, equalization processing, optical offset compensation processing, and phase compensation processing are performed for digital coherent reception. However, by transmitting a reset signal for signal processing other than the above processing, for each burst signal, Existing signal processing techniques for continuous signals can be applied.

  Further, the reset signal may be transmitted using a preamble that is the tip of the burst signal. When transmitting a reset signal using a preamble, it is necessary to detect the preamble using parameter information adapted to the previous burst signal. However, resetting of signal processing parameters and setting of initial values can be executed only by the preamble. .

(Embodiment 2)
The invention according to the present embodiment refers to the signal allocation scheduler, and initializes parameters used for signal processing of digital coherent reception based on the burst signal reception start time, reception end time, and burst signal transmission source information. . In addition, the burst signal from the same user may be initialized by storing and writing back the signal processing parameter for each burst signal with respect to the signal processing parameter depending on the user information.

  As shown in FIG. 3, the burst signal receiving apparatus according to the present embodiment includes an ADC 30, an equalization processing unit 31, an optical offset compensation processing unit 32, a phase compensation processing unit 33, a demodulation unit 34, a switching control signal transmission unit 35, A reset signal transmission unit 36, a user information reference table 37, and a signal allocation scheduler 38 are provided.

The burst signal receiving method according to this embodiment has a table creation procedure and a parameter setting procedure in this order.
In the table creation procedure, the user information reference table 37 stores the user information reference table using the user information and time information given by the signal allocation scheduler 38.
In the parameter setting procedure, at the burst signal reception start time, the signal processing unit represented by the equalization processing unit 31 and the optical offset compensation processing unit 32 refers to the user information reference table 37 and sets parameters according to the user information reference table. To do.

  The signal allocation scheduler 38 may use a technique used in an existing PON system such as DBA (Dynamic Bandwidth Allocation).

  There are parameters that depend on the ONU and parameters that depend on the burst signal itself. Parameters that depend on the ONU include, for example, intensity information and wavelength information of the received burst signal, and parameters that depend on the burst signal itself include phase information of the received burst signal. A parameter that changes depending on the ONU can be used as an initial setting parameter when a burst signal is received from the same ONU by writing back the parameter at the end of the burst signal in the user information reference table 37. On the other hand, for parameters that depend on the burst signal itself, such as the phase information of the received signal, the parameters are initialized by the reset signal. For example, the reset signal transmission unit 36 refers to time information such as the burst signal reception start time and burst signal reception end time in the user information reference table 37, and resets the phase compensation processing unit 33 according to the burst signal reception end time information. Send a signal.

  As described above, the invention according to the present embodiment makes it possible to digitally coherently receive a burst signal by storing and writing back signal processing parameters or transmitting a reset signal in accordance with signal processing characteristics. . By using signal processing parameter storage and writing back together, it is possible to reduce the bit length of the training signal and the pull-in signal used for setting the signal processing parameter.

  In FIG. 3, time information such as a burst signal reception start time and a burst signal reception end time used for transmission of the reset signal is acquired by referring to the user information reference table 37, but not via the user information reference table 37. You may acquire from the signal allocation scheduler 38. FIG. In addition, the switching control signal transmission unit 35 and the reset signal transmission unit 36 are not PULL types that refer to the user information reference table 37, and the parameter setting signal is transmitted from the user information reference table 37 to the switching control signal transmission unit 35 and the reset signal transmission unit 36. And it is good also as a PUSH type | mold structure which transmits a reset signal transmission message.

  As described above, it is possible to avoid performing estimation processing or compensation processing using parameters set using other burst signals by setting initial parameters or transmitting reset signals. In the training signal system, signal processing using a signal processing parameter set by another burst signal can be avoided by re-receiving the training signal and determining the signal processing parameter. Further, in the blind method, estimation processing or compensation processing according to the burst signal can be performed by using the preamble of the next burst signal as a pull-in signal.

  In FIG. 3, equalization processing, optical offset compensation processing, and phase compensation processing are performed for digital coherent reception. Parameter settings are performed in the equalization processing unit and the optical offset processing unit, and reset signals are output in the phase compensation processing unit. However, parameter setting or reset signals may be transmitted for signal processing other than the above processing. Further, a reset signal may be transmitted to the equalization processing unit and the optical offset compensation processing unit, or a parameter setting signal may be transmitted to the phase compensation processing unit.

(Embodiment 3)
The invention according to the present embodiment is a digital coherent reception for a burst signal in which a signal processing parameter is determined by receiving a training signal at a constant time interval and compensated by signal processing, and the next training signal is received when an EOB signal is detected. The training signal reception timing of burst signal reception is estimated by changing the time after the guard time interval between burst signals.

  As shown in FIG. 6, the burst signal receiving apparatus according to the present embodiment includes an ADC 60, an equalization processing unit 61, an optical offset compensation processing unit 62, a phase compensation processing unit 63, a demodulation unit 64, an EOB detection unit 65, and a reset signal. A transmission unit 66 and a training signal reception timing estimation unit 67 are provided. The EOB detection unit 65 includes an EOB signal detection unit 651 and a timer 652.

  In this embodiment, estimation processing and compensation processing are performed using training signals sent at certain time intervals. In the parameter setting procedure, the training signal reception timing estimation unit 67 estimates the reception timing of the next burst signal on the assumption that a burst signal is sent at regular intervals within a single burst frame, and for each signal processing unit Send information.

  On the other hand, when the EOB signal is detected by the EOB signal detection unit 651, the time until the next burst signal reception timing is acquired by the timer 652 in the parameter setting procedure, and this time is sent to the training signal reception timing estimation unit 67. The training signal reception timing estimation unit 67 estimates that the training signal is received at a constant time interval in the burst signal, but changes the estimated value when the training signal is received after the burst time interval. In the parameter setting procedure, the training signal reception timing estimation unit 67 sends information to each estimation processing and compensation processing unit including the equivalent processing unit 61, the optical offset compensation processing unit 62, and the phase compensation processing unit 63. In this way, by changing the predicted arrival time of the next training signal, it is possible to clarify the training signal reception timing in the burst signal receiving apparatus and facilitate identification of the actual data signal.

  FIG. 4 shows a reception example when the training signal method is applied to the burst signal receiving method by digital coherent optical transmission. FIG. 4 shows an example in which two burst signals are received. A burst signal receiving apparatus in digital coherent optical transmission detects a training signal PT and determines a signal processing parameter. In the training signal method, a training signal PT is inserted at regular time intervals in a burst frame, and estimation processing and compensation processing are performed using signal processing parameters calculated from the training signal PT. The insertion interval of the training signal PT is determined in advance between the burst signal transmitter and the burst signal receiver.

  At the end of the burst signal, the EOB signal detector 651 detects the EOB signal. At this time, the burst signal receiving apparatus initializes the signal processing parameters and transitions to a state of waiting for the training signal of the next burst signal. For example, the reset signal transmission unit 66 outputs a reset signal to the equivalent processing unit 61, the optical offset compensation processing unit 62, and the phase compensation processing unit 63, and initializes the signal processing parameters of each signal processing unit. And the training signal reception timing estimation part 67 changes the estimated value of the time which receives a training signal. By doing so, it is possible to apply digital coherent signal processing for continuous signals for each burst signal without changing the burst signal transmitter.

  Further, the next training signal reception predicted time can be changed by detecting the EOB signal and transitioning to the standby state. Since the training signal is received at regular time intervals within the burst frame, the time when the training signal interval time elapses from the previous training reception time becomes the next training signal reception predicted time. On the other hand, when the EOB detection unit 65 detects an EOB signal, the training signal in the next burst frame is after the guard interval time between burst frames has elapsed since the signal processing unit was reset. By transmitting the reset signal to the signal processing unit and changing the predicted arrival time of the next training signal, it is possible to clarify the training signal reception timing in the burst signal receiving device and facilitate the identification of the actual data signal. it can.

  In this embodiment, the example in which the next training signal reception time is changed after the guard time interval between burst signals when the EOB signal described in the first embodiment is detected has been described, but the present invention is not limited to this. For example, the end of the burst signal may be detected with reference to the signal allocation scheduler described in the second embodiment, and the next training signal reception time may be changed after the guard time interval between burst signals triggered by this detection.

(Embodiment 4)
FIG. 5 shows a reception example when a blind method using a lead-in signal is applied in a burst signal receiving method by digital coherent optical transmission. FIG. 5 shows an example in which two burst signals are received as in FIG.

  In the blind method, the preamble signal is regarded as the pull-in signal PL, initial signal processing parameters are set, and estimation processing and compensation processing are performed by updating the signal processing parameters during actual data transmission. The burst signal receiving apparatus stops updating the parameter when detecting the EOB signal, and transitions to a state of waiting for a pull-in signal. By transitioning to a state of waiting for the pull-in signal PL, it is possible to set the initial compensation value by regarding the preamble of the next burst signal to be received as the pull-in signal. On the other hand, when the state does not transit to the waiting state for the pull-in signal, the next burst signal may be compensated using the signal processing parameter of the previous burst signal.

  By doing so, it is possible to apply digital coherent signal processing for continuous signals for each burst signal without changing the burst signal transmitter.

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

20, 30, 60: ADC
21, 31, 61: equivalent processing units 22, 32, 62: optical offset compensation processing units 23, 33, 63: phase compensation processing units 24, 34, 64: demodulation unit 25, 65: EOB detection units 26, 36, 66 : Reset signal transmission unit 35: Switching control signal transmission unit 37: User information reference table 38: Signal allocation scheduler 651: EOB signal detection unit 652: Timer 67: Training signal reception timing estimation unit

Claims (6)

A burst signal receiving apparatus provided in the parent node in a digital coherent optical transmission system in which a single parent node and a plurality of child nodes are connected by time division multiplexing,
For each burst signal transmitted from the child node, a reset signal transmission unit that transmits a reset signal to a signal processing unit for performing coherent detection provided in the parent node ,
The signal processing unit determines a parameter of the coherent detection using a training signal or a pull-in signal of a next burst signal detected after receiving the reset signal;
Burst signal receiver. It further comprises a termination information detector that detects termination information of the burst signal,
The burst signal receiving apparatus according to claim 1, wherein the reset signal transmission unit transmits the reset signal in response to detection of termination information in the termination information detection unit. When the termination information detecting section detects the termination information, the training signal reception to change the reception timing of the training signal after the guard time interval elapses in the burst signal, and notifies the reception timing of the training signal after the change in the signal processing unit The burst signal receiving apparatus according to claim 2, further comprising a timing estimation unit. A signal allocation scheduler for creating a user information reference table for storing the reception start time and reception end time of the burst signal and the transmission source information of the burst signal;
The reset signal transmitting unit, in accordance with the received end time of the burst signal in the signal allocation scheduler, burst signal receiving apparatus according to claim 1, characterized in that transmitting the reset signal. The burst signal receiving device according to claim 1, wherein the pull-in signal is a preamble of a burst signal. A burst signal receiving method performed by the parent node in a digital coherent optical transmission system in which a single parent node and a plurality of child nodes are connected by time division multiplexing,
A reset signal transmission unit, for each burst signal transmitted from the child node, a reset signal transmission procedure for transmitting a reset signal to a signal processing unit for performing coherent detection provided in the parent node ;
A parameter setting procedure in which the signal processing unit determines a parameter of the coherent detection using a training signal or a pull-in signal of a next burst signal detected after receiving the reset signal ;
Burst signal receiving method, characterized by the execution.

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