JP2018117210A - Station side device and dispersion compensation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform dispersion compensation in PON.SOLUTION: A TDM-PON or the station device thereof receiving temporary intermittent optical signals transmitted from multiple subscriber devices includes an optical coherent reception unit for receiving an optical signal and converting into an analog signal, an analog-digital conversion unit for converting the analog signal into a digital signal, a digital signal processing unit having an equalization function for equalizing the digital signal by digital signal processing, and a compensation function for compensating various signal deterioration components in the digital signal, and performing dispersion compensation for each optical signal outputted from each subscriber device, and a scheduling unit for scheduling light emission timing of the optical signal in each subscriber device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a station side apparatus and a dispersion compensation method in TDM-PON and TWDM-PON.

  In recent years, for optical access systems, to further increase the capacity of communication lines to cope with the rapid spread of the Internet, and to reduce OPEX (Operating Expense) and CAPEX (Capital Expenditure) There is a need for more economical communication lines to contribute.

  Therefore, research on an PON (Passive Optical Network), which is an economical optical access system, is underway. In the PON, transmission between a center device and an optical passive element is performed by concentrating each transmission path with a plurality of users into a single transmission path by an optical passive element such as an optical power splitter (optical multiplexing / demultiplexing means). The road can be shared by multiple users. Recently, in Japan, GE-PON (Gigabit Ethernet (registered trademark) -PON) that can be shared by up to 32 users by time division multiplexing (TDM) with a 1 Gbps line capacity has been put into practical use. Has been. With the practical application of GE-PON, an economical optical access system, broadband communication services based on FTTH (Fiber To The Home) have come to be offered at a lower price and have rapidly spread.

  On the other hand, research on 10G-EPON (10Gigabit-Ethernet (registered trademark) PON) that can share 10Gbps line capacity as a next-generation optical access system that can meet the needs for higher capacity communication lines Standardization was made in 2009 by IEEE (The Institute of Electrical and Electronics Engineers, Inc.). According to 10G-EPON, it is possible to increase the capacity of a communication line by increasing the bit rate of an optical transceiver while using the same transmission path as that of an existing GE-PON.

  However, for example, it is assumed that a line capacity exceeding 10 Gbps is required for some services such as a high-definition video distribution service. In response to such a request, if the communication line is further increased in capacity by further increasing the bit rate of the optical transceiver (for example, 40 Gbps or 100 Gbps), the significant cost of the optical transceiver is greatly reduced. There is a problem that it is not economical.

  Therefore, as an optical access system for economically increasing the capacity of a communication line, wavelength tunability is provided to the optical transceiver so that the optical transceiver in the station side device can be added in stages according to the bandwidth requirement. Research on TWDM-PON (Time and Wavelength Division Multiplexing-PON), which is a combination of TDM and WDM (Wavelength Division Multiplexing), has been conducted (for example, see Non-Patent Document 1).

S. Kimura, “WDM / TDM-PON Technologies for Future Flexible Optical Access Networks”, 15th OptElectronics and Communications Conference (OECC2010) Technical Digest, July 2010, 6A1-1, pp.14-15

  In the basic configuration of TWDM-PON as shown in FIG. 7, OLTs (Optical Line Terminals installed in a telecommunications carrier's facility) are transmitted / received wavelengths respectively. Are configured to include M OSUs (OSU # 1, OSU # 2,..., OSU # M). Each OSU (Optical Subscriber Unit) includes an optical transmitter that outputs each downlink signal, and an optical receiver that includes a wavelength filter and a light receiver for selectively receiving each uplink burst signal. In general, TWDM-PON has a basic configuration of a system that uses four wavelengths for uplink and downlink signals, and therefore, a configuration in which M = 4 is common.

  On the other hand, in an ONU (Optical Network Unit; optical line terminating device installed on the subscriber side), wavelength tunability is required for transmission of upstream signals and reception of downstream signals. And an optical transceiver having a wavelength variable function including a wavelength tunable optical receiver and wavelength multiplexing / demultiplexing means. As described above, the ONU in the TWDM-PON can realize a function such as wavelength protection when the OSU fails by providing the wavelength variable function.

  As described above, in TWDM-PON, an ONU needs to have an optical transmission / reception function having a wavelength tunable function. Therefore, the ONU needs to have a wavelength tunable optical device or an optical transceiver. Therefore, in the present invention, attention is paid to the upstream burst signal from the ONU to the OLT. ITU-TG, which defines the standard specification of TWDM-PON. In 989.2, the upstream signal wavelength in TWDM-PON is set to the optical communication wavelength band (C band) near 1530 nm. That is, the upstream signal wavelength has been changed from 1300 nm (O band) conventionally used in GE-PON, 10G-EPON and the like to 1530 nm (C band).

  Conventionally, an ONU of a PON generates light by a direct modulation method (a method of generating light by a direct modulation laser inside the ONU) when transmitting a signal to the OLT. In GE-PON, 10G-EPON, and the like, since a wavelength of 1300 nm (O band), which has a strong resistance to chromatic dispersion, is used, an inexpensive direct modulation laser can be used. On the other hand, TWDM-PON uses 1530 nm (C band), which is more susceptible to internal and external factors than 1300 nm (O band), and thus has a problem that it is difficult to use a direct modulation laser.

  Specifically, in a TWDM-PON, when a direct modulation laser that has been used in a conventional PON is used, waveform distortion due to chromatic dispersion as shown in FIG. 8 occurs, and reception sensitivity deteriorates in an OLT receiver. Will occur. The waveform shown in FIG. 8A is an optical signal waveform at the time of laser output, and the waveform shown in FIG. 8B is an optical signal waveform after optical fiber transmission. Therefore, it is difficult to apply these directly modulated lasers in TWDM-PON.

  However, the direct modulation laser has an inexpensive and simple configuration and can easily realize high output of light, so that it is an optimal device as an optical transmission device for ONU that requires high economic efficiency. Therefore, the present invention proposes a configuration of a station side apparatus (OLT) that enables dispersion compensation for each upstream burst frame to which a digital coherent technology is applied for the purpose of applying a direct modulation laser to an ONU in TWDM-PON.

  Digital coherent reception technology combining coherent detection and digital signal processing technology is accelerated by multi-level modulation such as QPSK (Quadrature Phase Shift Keying) and QAM (Quadrature Amplitude Modulation). As a technology capable of realizing a large capacity and capable of compensating optical signal degradation factors such as chromatic dispersion and polarization mode dispersion, and nonlinear optical effect accompanying high speed in the digital signal processing region in recent years. It has been actively researched and developed.

  FIG. 9 shows an example of a digital coherent receiver employed in the long-distance optical transmission system. The digital coherent receiver 2 includes a local oscillation light source (LO) that is a light source serving as a reference light, an optical coherent receiver 21 including an optical receiver, and an AD (Analog / Digital) that converts an analog signal into a digital signal. ) It comprises a converter 22 and a digital signal processing unit 23 for processing a digital signal. Also, the digital signal processing unit 23 includes a fixed equalization unit 232, a polarization compensation unit 233, a clock recovery unit 234, a wavelength offset / phase estimation unit 235, an adaptive equalization unit 236, and a demodulation unit 237 for each functional block. Consists of

  The optical signal input to the digital coherent receiver 2 is coherently detected by the optical coherent receiver 21, and the electrical output signal output from the optical coherent receiver 21 is converted from an analog signal to a digital signal by the AD converter 22. Is done. The digital signal is subjected to various signal processing in the digital signal processing unit 23. The digital signal processing unit 23 has an equalization function for equalizing a digital signal by digital signal processing and a compensation function for compensating for various signal degradation components in the digital signal, and is distributed for each upstream burst signal output by each ONU. Compensate.

  The fixed equalization unit 232 of the digital signal processing unit 23 performs dispersion compensation on the waveform distortion caused by chromatic dispersion accumulated by transmitting the optical signal over a long distance using a fixed dispersion compensation parameter. The polarization compensation unit 233 performs polarization mode dispersion compensation, the clock recovery unit 234 performs clock extraction, and the wavelength offset / phase estimation unit 235 performs wavelength offset compensation and phase estimation of signal light and local light. The adaptive equalization unit 236 performs chromatic dispersion compensation by adaptive filtering in order to perform chromatic dispersion distortion compensation with high accuracy. Finally, the demodulator 237 demodulates the received signal and outputs it as a received electrical signal.

  As described above, by combining optical coherent detection and digital signal processing, dispersion compensation can be performed for distortion components that linearly affect the transmission distance, such as chromatic dispersion and polarization mode dispersion. Become.

  The present invention has been made in view of such circumstances, and proposes a dispersion compensation technique by applying the above-described digital coherent reception technique to a PON and performing dispersion compensation for each burst frame of an upstream burst signal. Objective.

  One aspect of the present invention is a TDM-PON or TWDM-PON station-side device that receives temporally intermittent optical signals transmitted by a plurality of subscriber devices, and that receives the optical signals and converts them into analog signals. An optical coherent receiving unit that converts, an analog-to-digital conversion unit that converts the analog signal into a digital signal, an equalization function that equalizes the digital signal by digital signal processing, and various signal degradation components in the digital signal are compensated A digital signal processing unit that has a compensation function and performs dispersion compensation for each of the optical signals output by each of the subscriber units; a scheduling unit that schedules the light emission timing of the optical signals in each of the subscriber units; It is a station side apparatus characterized by including.

  One aspect of the present invention is the station-side device described above, comprising a user information holding unit that holds accommodation distance information indicating an accommodation distance from each of the subscriber devices, and the digital signal processing unit is fixed A fixed equalization unit that performs dispersion compensation of waveform distortion due to wavelength dispersion in the digital signal using the value of the first dispersion compensation parameter, and a second dispersion compensation parameter based on the accommodation distance information and the light emission timing And an adaptive equalizer that performs dispersion compensation for each optical signal using the value of the second dispersion compensation parameter.

  One aspect of the present invention is the above-mentioned station-side device, comprising: a user information holding unit that holds accommodation distance information indicating an accommodation distance with each of the subscriber devices, wherein the digital signal processing unit is An adaptive equalization unit configured to set a value of a second dispersion compensation parameter based on accommodation distance information and the light emission timing, and to perform dispersion compensation for each of the optical signals using the value of the second dispersion compensation parameter; It is characterized by providing.

  One aspect of the present invention is the above-mentioned station-side device, wherein the digital signal processing unit includes a frame determination unit that determines identification information of a subscriber device, and in the initial communication process, the adaptive equalization unit is And deriving equalization coefficients between the local station apparatus and each of the subscriber apparatuses, and the user information holding unit stores the identification information allocated to each of the subscriber apparatuses in association with the equalization coefficient. In the subsequent communication process, the frame discriminating unit discriminates the identification information of each of the subscriber units when receiving the optical signal from each of the subscriber units, and the adaptive equalization unit discriminates The second dispersion compensation parameter value is set based on the equalization coefficient associated with the identification information.

  One aspect of the present invention is the above-mentioned station-side device, wherein the adaptive equalization unit sets a value of a third dispersion compensation parameter based on information of all connected subscriber devices, and Dispersion compensation is performed on all the optical signals using the value of the third dispersion compensation parameter.

  One aspect of the present invention is the above-mentioned station-side device, wherein the adaptive equalization unit recalculates the value of the third dispersion compensation parameter every time the subscriber device is newly added. Features.

  One aspect of the present invention is a dispersion compensation method by a computer of a TDM-PON or TWDM-PON station-side device that receives temporally intermittent optical signals transmitted by a plurality of subscriber devices, and includes optical coherent reception An optical coherent reception step in which the optical signal is received and converted into an analog signal, an analog-digital conversion unit in an analog-digital conversion step in which the analog signal is converted into a digital signal, and a digital signal processing unit in the digital signal A digital signal having an equalizing function for equalizing the signal by digital signal processing and a compensating function for compensating for various signal deterioration components in the digital signal, and performing dispersion compensation for each optical signal output from each of the subscriber devices A processing step and a scheduling unit for emitting the optical signal in each of the subscriber units; And scheduling step for scheduling the timing, a dispersion compensation method characterized by having a.

  According to the present invention, dispersion compensation can be performed in the PON.

It is a block diagram which shows the function structure of the station side apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the function structure of the station side apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the function structure of the station side apparatus which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the function structure of the station side apparatus which concerns on the 4th Embodiment of this invention. It is a figure which shows the communication process of the station side apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows the communication process of the station side apparatus which concerns on the 6th Embodiment of this invention. It is a figure which shows an example of a structure of the conventional TWDM-PON. It is a figure which shows an example of the waveform distortion resulting from chromatic dispersion. It is a block diagram which shows the function structure of the digital coherent receiver in the conventional long distance optical transmission system.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described.
FIG. 1 is a block diagram showing a functional configuration of a station-side apparatus according to the first embodiment of the present invention. A station apparatus 1a shown in FIG. 1 is a PON station apparatus to which a digital coherent reception technique is applied.

  As shown in the figure, a local apparatus 1a includes a local oscillation light source (LO) that is a light source serving as reference light, an optical coherent receiver 11 (optical coherent receiving unit) including an optical receiver, and an analog signal as a digital signal. AD converter 12 (analog-to-digital converter) for converting to digital signal, digital signal processor 13 for processing digital signals, MAC (Media Access Control) unit 14, a plurality of ONUs (subscriber devices) and OLTs in the PON A communication scheduler unit 15 (scheduling unit) that schedules each communication with the station side device) and a user information holding unit 16 that holds information of each ONU. The digital signal processing unit 13 includes a fixed equalization unit 132, a polarization compensation unit 133, a clock recovery unit 134, a wavelength offset / phase estimation unit 135, an adaptive equalization unit 136, a demodulation unit 137, It is comprised including.

  The optical signal input to the station side device 1a is coherently detected by the optical coherent receiver 11, and then the electrical output signal output from the optical coherent receiver 11 is converted from an analog signal to a digital signal by the AD converter 12. The The digital signal is subjected to various signal processing in the digital signal processing unit 13. The digital signal processing unit 13 has an equalization function for equalizing a digital signal by digital signal processing and a compensation function for compensating for various signal degradation components in the digital signal, and is distributed for each upstream burst signal output by each ONU. Compensate.

  The fixed equalization unit 132 of the digital signal processing unit 13 uses the fixed dispersion compensation parameter (first dispersion compensation parameter) to disperse the waveform distortion caused by chromatic dispersion that is accumulated when the optical signal is transmitted over a long distance. Compensate. The polarization compensation unit 133 compensates for polarization mode dispersion, the clock recovery unit 134 performs clock extraction, and the wavelength offset / phase estimation unit 135 performs wavelength offset compensation and phase estimation of signal light and local light.

  In the PON, when communication between the OLT and each ONU is established, the OLT measures the accommodation distance between each ONU, and the accommodation information indicating the measured accommodation distance is stored in the user information holding unit 16. Save to. The OLT knows the accommodation distances of all the ONUs to be accommodated, so that it does not collide when uplink burst signals (temporarily intermittent optical signals) output from each ONU are combined by the splitter. In addition, the communication scheduler unit 15 instructs the light emission timing in each ONU.

  Thus, in the configuration of the first embodiment, the adaptive equalization unit 136 displays the ONU accommodation distance information held by the user information holding unit 16 and the ONU emission control information based on the instruction from the communication scheduler unit 15. By referencing, it is possible to grasp the transmission distance for each received upstream burst frame. Then, the adaptive equalization unit 136 determines the dispersion compensation parameter value (second dispersion compensation parameter) for each burst frame using these pieces of information, and performs signal processing related to dispersion compensation, so that each burst frame is subjected to signal processing. Dispersion compensation can be performed with high accuracy.

Finally, the demodulator 137 demodulates the received signal and outputs it as a received electrical signal via the MAC unit 14.
As described above, the adaptive equalization unit 136 performs signal processing by combining the accommodation distance information of each ONU, which is information specific to the PON, with respect to the digital coherent reception technique described above, thereby preventing waveform distortion due to wavelength dispersion. Thus, dispersion compensation can be performed for each burst frame.
Note that the functions of the polarization compensator 133, the wavelength offset unit / phase estimator 135, and the like can be appropriately deleted according to the signal format used and the system specifications.
Note that this method is effective for both TDM-PON and TWDM-PON configurations.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described.
FIG. 2 is a block diagram showing a functional configuration of the station side apparatus according to the second embodiment of the present invention. A station apparatus 1b shown in FIG. 2 is a PON station apparatus to which a digital coherent reception technique is applied.

  The configuration of the second embodiment shown in FIG. 2 is characterized in that the fixed equalization unit 132 is deleted from the configuration of the first embodiment (FIG. 1). In general, the fixed equalization unit 132 of the digital signal processing unit 13 copes with the problem that the processing time increases when the adaptive equalization unit 136 performs signal processing on dispersion compensation of an optical signal transmitted over a long distance. Dispersion compensation is performed using a fixed dispersion compensation parameter that can be estimated in advance from system specifications. However, in the optical access system targeted by the present invention, since the transmission distance supported by the standard specification of TWDM-PON is 40 km at the maximum, it can be expected that chromatic dispersion compensation is provided only by the adaptive equalization unit 136. . As a result, the fixed equalization unit 132 can be deleted.

As described above, the adaptive equalization unit 136 performs signal processing by combining the accommodation distance information of each ONU, which is information specific to the PON, with respect to the digital coherent reception technique described above, thereby preventing waveform distortion due to wavelength dispersion. Thus, dispersion compensation can be performed for each burst frame.
Note that the functions of the polarization compensator 133, the wavelength offset unit / phase estimator 135, and the like can be appropriately deleted according to the signal format used and the system specifications.
Note that this method is effective for both TDM-PON and TWDM-PON configurations.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described.
FIG. 3 is a block diagram showing a functional configuration of a station-side apparatus according to the third embodiment of the present invention. A station apparatus 1c shown in FIG. 3 is a PON station apparatus to which a digital coherent reception technique is applied.

  As shown in the figure, a local device 1c includes a local oscillation light source (LO) that is a light source serving as reference light, an optical coherent receiver 11 including an optical receiver, and an AD converter that converts an analog signal into a digital signal. 12, a digital signal processing unit 13 for processing a digital signal, a MAC unit 14, a communication scheduler unit 15 for scheduling communication between a plurality of ONUs and OLTs in the PON, and information on each ONU And a user information holding unit 16. The digital signal processing unit 13 includes a frame determination unit 131, a fixed equalization unit 132, a polarization compensation unit 133, a clock recovery unit 134, a wavelength offset / phase estimation unit 135, and an adaptive equalization unit 136. And a demodulator 137.

  The optical signal input to the station side device 1c is coherently detected by the optical coherent receiver 11, and then the electrical output signal output from the optical coherent receiver 11 is converted from an analog signal to a digital signal by the AD converter 12. The The digital signal is subjected to various signal processing in the digital signal processing unit 13.

  In this embodiment, adaptive equalization is compensated using the dispersion compensation parameter based on the accommodation distance information of each ONU held in the user information holding unit 16 described in the first embodiment and the second embodiment described above. In addition to the part 136, the frame discrimination part 131 is provided.

  In the initial communication process, the adaptive equalization unit 136 derives an equalization coefficient between the local station apparatus 1c and each subscriber apparatus, and associates the identification information with the identification coefficient to be allocated to each subscriber apparatus and the equalization coefficient. It is stored in the user information holding unit 16. In the subsequent communication process, the frame discriminating unit 131 discriminates the identification information of each subscriber device when receiving an upstream burst signal from each subscriber device. Then, the adaptive equalization unit 136 sets the value of the second dispersion compensation parameter based on the equalization coefficient associated with the determined identification information.

  Thereby, in the configuration of the third embodiment, the adaptive equalization unit 136 includes information indicating the head and tail of the upstream burst signal detected by the frame determination unit 131, and each ONU held by the user information holding unit 16. The transmission distance for each received uplink burst frame can be ascertained by referring to the ONU light-emission control information and the ONU light emission control information based on the instruction from the communication scheduler unit 15. Then, the adaptive equalization unit 136 determines dispersion compensation parameter values for each burst frame using these pieces of information, and performs signal processing related to dispersion compensation to perform dispersion compensation for each burst frame with high accuracy. Can do.

  Finally, the demodulator 137 demodulates the received signal and outputs it as a received electrical signal via the MAC unit 14.

As described above, the adaptive equalization unit 136 performs signal processing by combining the accommodation distance information of each ONU, which is information specific to the PON, with respect to the digital coherent reception technique described above, thereby preventing waveform distortion due to wavelength dispersion. Thus, dispersion compensation can be performed for each burst frame.
Note that the functions of the polarization compensator 133, the wavelength offset unit / phase estimator 135, and the like can be appropriately deleted according to the signal format used and the system specifications.
Note that this method is effective for both TDM-PON and TWDM-PON configurations.

[Fourth Embodiment]
The fourth embodiment of the present invention will be described below.
FIG. 4 is a block diagram showing a functional configuration of a station-side apparatus according to the fourth embodiment of the present invention. A station-side device 1d shown in FIG. 4 is a PON station-side device to which a digital coherent reception technique is applied.

  The configuration of the fourth embodiment shown in FIG. 4 is characterized in that the fixed equalization unit 132 is deleted from the configuration of the third embodiment (FIG. 3). In general, the fixed equalization unit 132 of the digital signal processing unit 13 copes with the problem that the processing time increases when the adaptive equalization unit 136 performs signal processing on dispersion compensation of an optical signal transmitted over a long distance. Dispersion compensation is performed using a fixed dispersion compensation parameter that can be estimated in advance from system specifications. However, in the optical access system targeted by the present invention, since the transmission distance supported by the standard specification of TWDM-PON is 40 km at the maximum, it can be expected that chromatic dispersion compensation is provided only by the adaptive equalization unit 136. . As a result, the fixed equalization unit 132 can be deleted.

As described above, the adaptive equalization unit 136 performs signal processing by combining the accommodation distance information of each ONU, which is information specific to the PON, with respect to the digital coherent reception technique described above, thereby preventing waveform distortion due to wavelength dispersion. Thus, dispersion compensation can be performed for each burst frame.
Note that the functions of the polarization compensator 133, the wavelength offset unit / phase estimator 135, and the like can be appropriately deleted according to the signal format used and the system specifications.
Note that this method is effective for both TDM-PON and TWDM-PON configurations.

[Fifth Embodiment]
The fifth embodiment of the present invention will be described below.
FIG. 5 is a diagram showing a communication process of the station side apparatus according to the fifth embodiment of the present invention.
In this communication process, when the OLT registers an ONU with the automatic bandwidth allocation (DBA) function, the accommodation distance information of the newly connected ONU is held as user information in the OLT (that is, The adaptive equalization unit 136 changes the dispersion compensation parameter (third dispersion compensation parameter) for each frame of the uplink burst signal by the OLT holding the accommodation distance information of all ONUs connected thereto. That is, the adaptive equalization unit 136 sets the optimum dispersion compensation parameter for each frame of the uplink burst signal, so that highly accurate dispersion compensation can be applied to all the frames of the received uplink burst signal.
Note that this method is effective for both TDM-PON and TWDM-PON configurations.

[Sixth Embodiment]
The sixth embodiment of the present invention will be described below.
FIG. 6 is a diagram showing a communication process of the station side apparatus according to the sixth embodiment of the present invention.
In the fifth embodiment described above, the adaptive equalization unit 136 changes the dispersion compensation parameter for each uplink burst frame, and enables highly accurate dispersion compensation for each frame. However, the difference in the accommodation distance of each ONU accommodated by the PON is at most several tens km. Therefore, in the communication process in the sixth embodiment, a fixed dispersion compensation parameter derived based on the accommodation distance of all ONUs connected to the OLT is set for all received upstream burst signal frames. The feature is that dispersion compensation is performed.

Further, when a new ONU is added, the fixed dispersion compensation parameter is recalculated only when the accommodation distance of the added ONU is the longest or short distance. Thereby, according to the communication process which concerns on 6th Embodiment, the recalculation frequency of a dispersion compensation parameter and the frequency | count of a change can be reduced, and the load to a signal processing circuit can be reduced.
Note that this method is effective for both TDM-PON and TWDM-PON configurations.

  As described above, the station side apparatus (OLT) according to the present invention can perform dispersion compensation in the PON.

  You may make it implement | achieve at least one part of the station side apparatus in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Station side apparatus, 2 ... Digital coherent receiver, 11 ... Optical coherent receiver, 12 ... AD converter, 13 ... Digital signal processing part, 14 ... MAC part, DESCRIPTION OF SYMBOLS 15 ... Communication scheduler part, 16 ... User information holding part, 21 ... Optical coherent receiver, 22 ... AD converter, 23 ... Digital signal processing part, 131 ... Frame discrimination | determination part , 132... Fixed equalizer, 133... Polarization compensator, 134... Clock recovery unit, 135... Wavelength offset / phase estimator, 136. Demodulator, 232 ... fixed equalizer, 233 ... polarization compensator, 234 ... clock recovery unit, 235 ... wavelength offset / phase estimator, 236 ... adaptive equalizer, 237 ... Demodulator

Claims (7)

A TDM-PON or TWDM-PON station side device that receives temporally intermittent optical signals transmitted by a plurality of subscriber devices,
An optical coherent receiver that receives the optical signal and converts it to an analog signal;
An analog-to-digital converter that converts the analog signal into a digital signal;
It has an equalization function for equalizing the digital signal by digital signal processing, and a compensation function for compensating for various signal degradation components in the digital signal, and dispersion compensation is performed for each optical signal output by each subscriber unit. A digital signal processor to perform;
A scheduling unit that schedules the light emission timing of the optical signal in each of the subscriber devices;
A station-side device comprising: A user information holding unit for holding accommodation distance information indicating an accommodation distance with each of the subscriber devices;
With
The digital signal processor is
A fixed equalizer that performs dispersion compensation of waveform distortion due to wavelength dispersion in the digital signal using a value of a fixed first dispersion compensation parameter;
An adaptive equalization unit that sets a value of a second dispersion compensation parameter based on the accommodation distance information and the light emission timing, and performs dispersion compensation for each optical signal using the value of the second dispersion compensation parameter; ,
The station apparatus according to claim 1, further comprising: A user information holding unit for holding accommodation distance information indicating an accommodation distance with each of the subscriber devices;
With
The digital signal processor is
An adaptive equalization unit that sets a value of a second dispersion compensation parameter based on the accommodation distance information and the light emission timing, and performs dispersion compensation for each optical signal using the value of the second dispersion compensation parameter;
The station apparatus according to claim 1, further comprising: The digital signal processor is
A frame discriminating unit for discriminating identification information of the subscriber unit;
With
In the initial communication process,
The adaptive equalization unit derives an equalization coefficient between its own station side device and each of the subscriber devices,
The user information holding unit stores the identification information assigned to each of the subscriber devices in association with the equalization coefficient,
In the subsequent communication process,
The frame discriminating unit discriminates the identification information of each of the subscriber devices when receiving the optical signal from each of the subscriber devices,
The said adaptive equalization part sets the value of a 2nd dispersion | distribution compensation parameter based on the equalization coefficient matched with the determined said identification information. The Claim 2 or Claim 3 characterized by the above-mentioned. Station side device. The adaptive equalization unit sets a value of a third dispersion compensation parameter based on information of all connected subscriber devices, and uses all the optical signal using the value of the third dispersion compensation parameter. Dispersion compensation is performed for the station side device according to any one of claims 2 to 4. The station-side apparatus according to claim 5, wherein the adaptive equalization unit recalculates the value of the third dispersion compensation parameter every time the subscriber apparatus is newly added. A dispersion compensation method by a computer of a TDM-PON or TWDM-PON station side device that receives temporally intermittent optical signals transmitted by a plurality of subscriber devices,
An optical coherent receiving unit that receives the optical signal and converts it into an analog signal; and
An analog-to-digital conversion unit that converts the analog signal into a digital signal; and
The digital signal processing unit has an equalization function for equalizing the digital signal by digital signal processing, and a compensation function for compensating for various signal degradation components in the digital signal, and the light output by each of the subscriber devices A digital signal processing step for performing dispersion compensation for each signal;
A scheduling step in which a scheduling unit schedules the light emission timing of the optical signal in each of the subscriber devices;
A dispersion compensation method characterized by comprising:

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