WO2007082490A1 - A passive optical network, equipment and method for supporting the multicast service - Google Patents

A passive optical network, equipment and method for supporting the multicast service Download PDF

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Publication number
WO2007082490A1
WO2007082490A1 PCT/CN2007/000233 CN2007000233W WO2007082490A1 WO 2007082490 A1 WO2007082490 A1 WO 2007082490A1 CN 2007000233 W CN2007000233 W CN 2007000233W WO 2007082490 A1 WO2007082490 A1 WO 2007082490A1
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WIPO (PCT)
Prior art keywords
optical
onu
optical signal
data
olt
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Ceased
Application number
PCT/CN2007/000233
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English (en)
French (fr)
Inventor
Wei Huang
Huafeng Lin
Jun Zhao
Feng Wang
Tao Jiang
Jun Chen
Yuntao Wang
Guo Wei
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Priority to EP07702163.2A priority Critical patent/EP1981196B1/en
Publication of WO2007082490A1 publication Critical patent/WO2007082490A1/zh
Priority to US12/177,803 priority patent/US20080304830A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0226—Fixed carrier allocation, e.g. according to service
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0228—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths
    • H04J14/023—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths in WDM passive optical networks [WDM-PON]
    • H04J14/0232—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths in WDM passive optical networks [WDM-PON] for downstream transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0238—Wavelength allocation for communications one-to-many, e.g. multicasting wavelengths
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
    • H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
    • H04J14/0245—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU
    • H04J14/0246—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU using one wavelength per ONU
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
    • H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
    • H04J14/0249—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for upstream transmission, e.g. ONU-to-OLT or ONU-to-ONU
    • H04J14/025—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for upstream transmission, e.g. ONU-to-OLT or ONU-to-ONU using one wavelength per ONU, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0282—WDM tree architectures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation

Definitions

  • the present invention relates to a Passive Optical Network (PON) technology, and in particular to a Wavelength Division Multiplexed Passive Optical Network (WDM-PON) supporting a multicast service.
  • PON Passive Optical Network
  • WDM-PON Wavelength Division Multiplexed Passive Optical Network
  • ONT Optical line terminal
  • ONU Optical Line Terminal
  • ONU Optical network unit
  • multiplexer/demultiplexer multiplexer/demultiplexer
  • the PON mainly includes: a central office - an OLT, an Optical Distribution Network (ODN), and a number of ONUs.
  • the ODN is typically composed of a multiplexer/demultiplexer and an optical fiber connecting the multiplexer/demultiplexer to the OLT and the ONU, the multiplexer/demultiplexer being used on the one hand to
  • the optical signal of the OLT is demultiplexed, and the demultiplexed optical signals are respectively sent to the respective ONUs.
  • the optical signals from the respective ONUs are multiplexed, and the multiplexed optical signals are output to the optical signals.
  • OLT Optical Distribution Network
  • PON can be divided into many different types according to the implementation mechanism, for example: ATM-PON based on Asynchronous Transfer Mode (ATM), EPON (Ethernet Over PON) based on Ethernet (Ethernet), with thousands Gigabit PON (Gigabit PON), WDM-PON combined with wavelength division multiplexing (WDM) technology, and optical code division multiple access passive optical network combined with code division multiple access (CDMA) OCMDA-PON, Optical Code Division Multiple Access Passive Optical Network) and the like.
  • WDM-PON is a peer-to-peer network structure.
  • a peer-to-peer network usually uses intra-band multi-copy to transmit multicast service data.
  • the OLT has high processing power and requires complex multicast protocols to support it.
  • the multicast service especially when many users order the same program, the processing capability of the OLT will become the bottleneck of the WDM-PON system; on the other hand, 'the same data should be copied separately on multiple wavelengths. , respectively transmitted to different ONUs, thus wasting the bandwidth resources of the system. Summary of the invention
  • the embodiment of the invention provides a WDM-PON, which can save bandwidth resources of the system and reduce requirements for processing capability of the OLT.
  • the embodiment of the invention further provides an OLT, a multiplexing/demultiplexing device and an ONU.
  • the embodiment of the invention further provides a method for implementing multicast service and CATV broadcast, which has low requirements on the processing capability of the OLT and can greatly save bandwidth resources of the WDM-PON system.
  • a WDM-PON comprising: an optical line terminal OLT, a multiplexing/demultiplexing device, and n optical network units ONU;
  • the OLT is configured to carry downlink unicast data respectively sent to the n ONUs to optical signals of different wavelengths, and divide one or more multicast service data into one or more channels.
  • the C signal is carried on one or more optical signals of a specific wavelength, and the optical signals of the different wavelengths and the optical signals of the specific wavelength are multiplexed into one optical signal, and then sent to the multiplexing/demultiplexing Device
  • the multiplexer/demultiplexer is configured to separate optical signals of different wavelengths from the OLT, perform power allocation on optical signals of specific wavelengths carrying the multicast-type services, and carry the downlinks of the n ONUs.
  • the optical signal of the broadcast data is wavelength-selectively output;
  • the n ONUs are respectively used to process the signals from the corresponding output end of the multiplexing/demultiplexing device, and respectively obtain the multicast type service data and the downlink unicast data corresponding to the multicast type.
  • An OLT includes: an OLT-side downlink processing module, configured to carry downlink unicast data respectively sent to the n ONUs to optical signals of different wavelengths, and respectively carry one or more multicast service data To the optical signal of one or more specific wavelengths, the optical signals of the different wavelengths and the optical signals of the specific wavelength are multiplexed into one optical signal, and then sent to the multiplexer/demultiplexer.
  • an OLT-side downlink processing module configured to carry downlink unicast data respectively sent to the n ONUs to optical signals of different wavelengths, and respectively carry one or more multicast service data
  • the optical signals of the different wavelengths and the optical signals of the specific wavelength are multiplexed into one optical signal, and then sent to the multiplexer/demultiplexer.
  • the multiplexing/demultiplexing device includes:
  • a coarse wavelength divider configured to separate, from the received optical signal, one or more optical signals having a specific wavelength for carrying the multicast-type service, and an optical signal for carrying downlink unicast data of each ONU;
  • the n:n waveguide array optical filter is configured to separate optical signals from the coarse wavelength division for carrying downlink unicast data of each ONU, and obtain n optical signals having different wavelengths, and respectively route to n output ports of the waveguide array optical filter;
  • a branching device having a branching ratio of l:a, for distributing power of a light signal having a specific wavelength from the coarse wavelength division, dividing into a parts, and outputting to a combined multiplexer respectively;
  • the ONU of the embodiment of the present invention includes: an ONU downlink processing module, configured to process signals from the corresponding output end of the multiplexing/demultiplexing device, respectively, to obtain downlink unicast data and/or corresponding to them respectively.
  • the multicast class service data is configured to process signals from the corresponding output end of the multiplexing/demultiplexing device, respectively, to obtain downlink unicast data and/or corresponding to them respectively.
  • a method for implementing a multicast service using a WDM-PON system includes:
  • the OLT separates the multicast service data and the downlink unicast data sent to the at least one ONU from the downlink data from the upper layer device;
  • the OLT carries the multicast service data by using an optical signal having a specific wavelength, and the downlink unicast data of the at least one ONU is respectively carried on at least one optical signal having a preset wavelength;
  • the OLT multiplexes the optical signal of the specific wavelength and the optical signal carrying the downlink unicast data of each ONU, and sends the optical signal to the multiplexing/demultiplexing device;
  • the multiplexer/demultiplexer separates, according to the wavelength, the optical signal with a specific wavelength that carries the multicast service data and at least one optical signal that carries downlink unicast data of each ONU from the received optical signal. And outputting, at the same time, the optical signal of the specific wavelength that carries the multicast service data to all or part of the ONUs in the at least one ONU, and outputting at least one optical signal that carries the ONU downlink unicast data to its corresponding
  • the ONU separates, from the received optical signal, an optical signal having a specific wavelength that carries the multicast service data and an optical signal that carries its own downlink unicast data, and performs optical/electrical conversion and demodulation processing respectively. Obtaining the multicast service data and its own downlink unicast data, and transmitting the multicast service data to the next layer device for further processing.
  • a method for implementing cable TV CATV broadcasting in a wavelength division multiplexing-passive optical network includes:
  • the OLT optically amplifies the received optical signal of a specific wavelength carrying the CATV broadcast signal through an optical amplifier
  • the OLT multiplexes the optical signal of the specific wavelength of the CATV broadcast signal that is optically amplified and the optical signal that carries the downlink unicast data of each ONU, and sends the optical signal to the multiplexer/demultiplexer;
  • the multiplexer/demultiplexer separates the optical signal of the specific wavelength carrying the CATV broadcast signal and the at least one optical signal carrying the downlink unicast data of each ONU from the received optical signal according to the wavelength,
  • the optical signal of the specific wavelength carrying the CATV broadcast signal is simultaneously output to all or part of the ONUs in the ONU, and one or more optical signals carrying the downlink unicast data of the ONU are respectively output to their corresponding ONUs;
  • the ONU separates, from the received optical signal, the optical signal of a specific wavelength carrying a CATV broadcast signal and an optical signal carrying its own downlink unicast data, wherein the optical signal of a specific wavelength carrying the CATV broadcast signal is lighted
  • the CATV broadcast signal of the electric domain is obtained and transmitted to the next layer device for further processing, and the optical signal carrying the downlink unicast data is subjected to optical/electrical conversion and demodulation, and then the downlink unicast of the ONU is obtained.
  • the data is transmitted to the next layer of equipment for processing.
  • the multicast service may be used for one or More than one optical signal with a specific wavelength is carried, so that the problem of waste of bandwidth resources caused by the in-band multi-copy transmission mode in the prior art can be effectively solved, the bandwidth resource of the system is effectively saved, and since the WDM is The OLT does not need to support complex multicast protocols in the PON system, thus reducing the complexity of the OLT.
  • FIG. 1 is a schematic diagram of the basic structure of an existing PON system
  • FIG. 2 is a schematic diagram showing the functions of a multiplexing/demultiplexing device used in a WDM-PON according to a preferred embodiment of the present invention
  • FIG. 3 is a schematic diagram showing the basic structure of a WDM-PON system according to a preferred embodiment of the present invention.
  • FIG. 4 is a schematic structural diagram of a system when a multicast service is implemented in a WDM-PON according to another preferred embodiment of the present invention.
  • FIG. 5 is a schematic structural diagram of a system for implementing a CATV service and a multicast service in a WDM-PON according to another preferred embodiment of the present invention
  • FIG. 6 is a schematic diagram showing the internal structure of a multiplexing/demultiplexing device according to a preferred embodiment of the present invention.
  • FIG. 7 is a schematic diagram showing the internal structure of a multiplexing/demultiplexing device according to another preferred embodiment of the present invention.
  • FIG. 8 is a flowchart of a method for implementing the multicast service according to a preferred embodiment of the present invention. Mode for carrying out the invention
  • a preferred embodiment of the present invention provides a WDM-PON system that can support multicast-type services, such as supporting multicast services and/or broadcast services and/or cable television.
  • CATV cable television.
  • FIG. 3 shows the basic structure of the WDM-PON system according to this embodiment. As shown in FIG. 3, the method mainly includes: an OLT, a multiplexing/demultiplexing device, n ONUs, and the OLT, and the multiplexing. /demultiplexer and the fibers of the n ONUs. Where n is a natural number.
  • the OLT is configured to carry, in the downlink direction, n downlink unicast data respectively sent to the n ONUs to n optical signals with different wavelengths, and one or more multicast services.
  • the data is respectively carried on the optical signals of one or more specific wavelengths, and the optical signals of the different wavelengths and the optical signals of the one or more specific wavelengths are multiplexed into one optical signal, and then output to the multiplexing/
  • the OLT removes the uplink optical signals from the respective ONUs in the uplink direction, and further detects and demodulates the uplink data of each user, and outputs the uplink data to the upper-level device.
  • the function of the multiplexer/demultiplexer is as shown in FIG. 2, which mainly includes: separating, in a downlink direction, optical signals of different wavelengths received from the OLT, for using a specific wavelength for carrying the multicast service.
  • the optical signal for example, an optical signal of wavelength m , performs power distribution, that is, simultaneously outputs the optical signal of the specific wavelength on the plurality of output ports or all the output ports thereof, and n other wavelengths for carrying the unicast data of each ONU.
  • the optical signals are wavelength-selectively outputted, that is, optical signals of different wavelengths are respectively outputted on predetermined corresponding output ports; and in the uplink direction, n different signals of different wavelengths from different ONUs are multiplexed to obtain one
  • the optical signal is output to the OLT.
  • the ONU is configured to process the signal from the output end of the multiplexing/demultiplexing device in the downlink direction to obtain the multicast service data and the downlink unicast data corresponding to the ONU respectively; Upward, the uplink data of the ONU is carried on an optical signal having a predetermined wavelength, and output to the multiplexing/demultiplexing device.
  • the OLT further includes three parts: an OLT-side downlink processing module, an OLT-side uplink processing module, and a first optical circulator (Circulator):
  • the first optical circulator is connected to the OLT downlink processing module, the OLT uplink processing module, and the multiplexing/demultiplexing device, and is configured to output a downlink optical signal from the OLT downlink processing module.
  • the multiplexer/demultiplexer and output an uplink optical signal from the multiplexer/demultiplexer to the OLT-side uplink processing module.
  • the OLT-side downlink processing module includes:
  • a downlink data separator configured to separate the multicast service data from the downlink service data and the downlink unicast data that are sent to the n ONUs respectively;
  • a pre-processing module for transmitting a multicast service data, for receiving broadcast data (for example, a CATV signal) from a higher-level device and/or multicast-type service data from the downlink data separator, and processing and amplifying the data Obtaining optical signals of one or more specific wavelengths carrying one or more multicast type service data;
  • broadcast data for example, a CATV signal
  • multicast-type service data from the downlink data separator
  • the multicast data pre-processing module directly optically amplifies the optical signal carrying the broadcast data from the upper-level device through the optical amplifier; and one or more channels from the downstream data splitter
  • the multicast type service data is separately modulated onto one or more optical signals having a specific wavelength, and the modulated optical signal is subjected to other related processing; therefore, the multicast type data transmission pre-processing module It should further comprise: an optical amplifier for optically amplifying the broadcast data, and/or one or more lasers for generating a particular wavelength of optical signal and one or more of the multicast-type service data modulated to said a modulator in an optical signal of a particular wavelength, wherein the function of the laser and the modulator can be performed simultaneously by a Direct Modulation Laser (DML);
  • DML Direct Modulation Laser
  • a main broad spectrum laser source for generating a broad spectrum optical signal
  • the WDM-PON may further comprise a prepared wide spectrum laser source for providing an alternate wide spectrum optical signal when the main broad spectrum laser source fails; the first waveguide array optical filter (AWG) for the main broad spectrum laser source or The broad-spectrum optical signal outputted by the spectral laser source is processed to generate n optical signals of wavelengths ⁇ , respectively, to provide laser sources of different wavelengths for the optical modulator array;
  • AMG waveguide array optical filter
  • a light modulator array comprising n modulators for respectively modulating downlink unicast data of the corresponding n ONUs from the downlink data separator to wavelengths ⁇ , ⁇ output by the first AWG ⁇ road light signal;
  • a multiplexer configured to carry one or more optical signals having a specific wavelength (for example, ⁇ 1 ⁇ b, etc.) and the downlink unicast data carrying n ONUs carrying the multicast-type service data, respectively, having a wavelength of ⁇
  • the ⁇ n optical signals are multiplexed into one optical signal and output to the first optical circulator.
  • the multiplexer can be a coupler or a wavelength array optical filter (AWG) or other multiplexing device.
  • the uplink processing module of the OLT includes:
  • a second AWG configured to separate wavelengths from the upstream optical signals from the first optical circulator ⁇ road light signal
  • a photodiode or photodetector (PD) array that is, a photodetector array, comprising n PDs for converting an upstream optical signal from the second AWG into an electrical signal;
  • the demodulator array includes n demodulators for demodulating the electrical signals output by the photodiode or the photodetector array, respectively, and recovering the uplink data of each ONU.
  • the 0NU in the WDM-P0N shown in Figure 3 also includes the 0NU-side downlink processing module and the 0NU-side uplink processing module and a second optical circulator:
  • the second optical circulator is connected to the ONU uplink processing module, the 0NU terminal downlink processing module, and the multiplexing/demultiplexing device, and is configured to output an uplink optical signal from the ONU uplink processing module. Going to the multiplexing/demultiplexing device, and outputting the downlink optical signal from the multiplexer/demultiplexer to the ONU downlink processing module;
  • the 0NU end downlink processing module includes: a coarse wavelength divider, configured to separate optical signals of different wavelengths from the optical signals from the multiplexing/demultiplexing device, including optical signals with a wavelength of ⁇ for carrying downlink unicast data corresponding to the ONU And an optical signal having a specific wavelength optical signal, such as a wavelength of and/or 1) , for carrying the multicast-type service;
  • the number of PDs included in the PD array is determined according to the number of multicast services. If the X-way multicast service is carried, the PD array will contain x+1 PDs, one of which will be used for the PD.
  • the optical signal carrying the downlink unicast data corresponding to the ONU in the optical signal of the wavelength division of ⁇ ! ⁇ ⁇ is converted into an electrical signal; the remaining X PDs are respectively used to The specific wavelength optical signal of the splitter for carrying each multicast service is converted into an electrical signal;
  • a demodulator array the number of demodulators included corresponding to the number of PDs in the PD array, wherein a demodulator is configured to demodulate an electrical signal carrying downlink unicast data of the ONU to obtain a downlink of the ONU Unicast data; the remaining demodulator is used to demodulate the electrical signals carrying the multicast service data outputted by the PD array to obtain the multicast service data.
  • the 0NU-end uplink processing module includes: a modulator for modulating uplink data of the ONU into an optical signal.
  • the optical signal is required by the ONU to transmit uplink data, and may be generated by the OLT or by the ONU itself. If the optical signal is generated by the ONU itself, the ONU uplink processing module further needs to include a light source, as shown in FIG.
  • the downlink data splitter extracts the multicast service from the data stream from the upper-level device. Data; then the extracted multicast service data is modulated by the modulator to The optical signal of the wavelength m is outputted by the fixed-wavelength laser, and after being amplified by the optical amplifier, the multiplexer transmits the optical signal of the wavelength m of the multicast service data and the bearer.
  • a multi-wavelength optical signal having a wavelength including ⁇ wide and X m is obtained, and the optical signal is transmitted to the complex via the first optical circulator.
  • the above-mentioned specific wavelength laser, modulator and optical amplifier constitute the multicast type service data transmission pre-processing module in FIG.
  • the multiplexer/demultiplexer separates optical signals of different wavelengths from the received optical signals, and simultaneously outputs the optical signals of the wavelengths carrying the multicast service data from the n output ends thereof, and The n- channel optical signals of the wavelengths of ⁇ n carrying the downlink unicast data of each ONU are respectively output to their corresponding output ends.
  • the optical signal outputted on each output end of the multiplexer/demultiplexer includes at least the optical signal carrying the multicast service and the wavelength of the downlink unicast data of each ONU.
  • the optical signal output from output 1 will contain two wavelengths into 111 and the output of output 2 will contain two wavelengths.
  • the optical signal outputted by the output ⁇ will contain two wavelengths remind 1 and ⁇ ⁇ . Subsequently, the n output signals will be transmitted to the n ONUs of the WDM-PON system, respectively.
  • the ONU terminal downlink processing module separates the optical signal from the multiplexing/demultiplexing device into an optical signal of a wavelength ⁇ ⁇ carrying the multicast service and a wavelength carrying the downlink unicast data of each ONU.
  • the optical signals for carrying the ONU downlink unicast data in ⁇ ! ⁇ ⁇ are respectively converted into electrical signals, and then respectively demodulated to obtain the multicast service data.
  • the downlink unicast data corresponding to the ONU are respectively converted into electrical signals, and then respectively demodulated to obtain the multicast service data.
  • the OLT should also be able to capture the request from the ONU to join the multicast group, on the one hand to complete the multicast proxy function, and on the other hand, according to the authentication returned by the upper layer multicast server.
  • determining whether the ONU has the right to request the multicast group data, and sending a multicast service control message to the ONU according to the judgment result Based on the multicast service control packet from the OLT, the ONU filters out the multicast group data that the OLT allows to receive, and directly discards the multicast group data that is not allowed by the OLT. After the ONU filters out the multicast group data allowed by the OLT, it sends it to the corresponding next-level device for further processing.
  • FIG. 5 is a schematic diagram showing the structure of a WDM-PON system capable of simultaneously providing CATV services and multicast services according to still another preferred embodiment of the present invention.
  • the WDM-PON which can provide both CATV services and multicast services for ONUs, has the following improvements based on the structure shown in Figure 4:
  • an optical amplifier is connected to the multiplexer for optically amplifying the optical signal of the wavelength ⁇ from the outside carrying the CATV signal.
  • the specific wavelength laser, the modulator, the optical amplifier connected to the modulator, and the optical amplifier for amplifying the CATV signal shown in Fig. 5 constitute the multicast-type service data transmission pre-processing module in Fig. 3.
  • the multiplexer/demultiplexer in the downlink direction, the multiplexer/demultiplexer further performs power on a specific signal, that is, an optical signal carrying the CATV signal in an optical signal from the OLT. Assignment, that is, simultaneously outputting the optical signal of the specific wavelength ⁇ on each of its output ports.
  • the optical signal outputted by each output of the multiplexer/demultiplexer includes an optical signal of wavelength m carrying the multicast data and an optical signal of wavelength b carrying the CATV signal.
  • the optical signals carrying the downlink unicast data of each ONU are respectively one of 4 n .
  • the coarse wavelength division multiplexer further separates the optical signal of the wavelength b that carries the CATV signal
  • the PD array and the demodulator array further include a pair of bearers.
  • the optical signal of the wavelength B of the CATV signal is optically/electrically converted and demodulated by a PD and a demodulator, so that the CATV data can be obtained at each ONU.
  • the OLT can also realize controlled viewing of the CATV service in a manner similar to the implementation of the multicast service, for example, by transmitting a broadcast control message.
  • the above-mentioned WDM-PON system can implement multicast or broadcast services, and at the same time, since only one or more separate wavelength carriers are used in the above WDM-PON system or Multi-channel multicast service data, which can effectively avoid the number of users to be sent to the multicast service data in the prior art, and how many copies are to be copied, thereby greatly saving the bandwidth resources of the WDM-PON system. It can also reduce the load of OLT scheduling. The OLT does not need to support complex multicast scheduling protocols, thus reducing the complexity of the system.
  • the multiplexer/demultiplexer used in the above WDM-PON system is different from the multiplexer/demultiplexer used in the existing WDM-PON system, in order to realize the above WDM-PON system, in a preferred embodiment of the present invention, specifically provides a new type of multiplexing/resolving of optical signals having both AWG functions and certain specific wavelengths applied in the above WDM-PON system. Use the device.
  • Figure 6 shows the structure of this multiplexer/demultiplexer.
  • the multiplexing/demultiplexing device described in this embodiment includes:
  • a coarse wavelength division configured to separate, from the received optical signal, an optical signal having a specific wavelength (for example, 13 and/or constructive 1 and/or other specific wavelengths) for carrying the multicast-type service, and An optical signal carrying unicast data of each ONU;
  • An AWG of l:n is used for separating the optical signal of the wavelength ⁇ ⁇ ⁇ from the coarse wavelength division to obtain an optical signal with ⁇ wavelengths of ⁇ , respectively, and routing to the n output ports of the AWG respectively
  • ⁇ corresponds to the number of ONUs in the WDM-PON system
  • a branching device having a branching ratio of 1:n for distributing power of a specific wavelength (for example, a wavelength of b and/or and/or other specific wavelengths) from the coarse wavelength divider to ⁇ copies, And output to ⁇ combiners respectively; n combiners, wherein each combiner is coupled to an output of the AWG and an output of the splitter for coupling an optical signal of a particular wavelength from the splitter to the AWG Go to each output branch.
  • a specific wavelength for example, a wavelength of b and/or and/or other specific wavelengths
  • the n outputs of the multiplexer/demultiplexer as shown in FIG. 6 can be obtained with a specific wavelength (for example, b and/or notice 1 and/or The optical signals of other specific wavelengths, and the n optical signals carrying the downlink unicast data of the respective ONUs, can be applied to the WDM-PON system.
  • a specific wavelength for example, b and/or consult 1 and/or
  • the optical signals of other specific wavelengths, and the n optical signals carrying the downlink unicast data of the respective ONUs, can be applied to the WDM-PON system.
  • the n outputs of the multiplexer/demultiplexer shown in FIG. 6 described above each include an optical signal having a specific wavelength for carrying the multicast-type service, and in some special cases. Certain ONUs in the WDM-PON system may not support the multicast service. In this case, it is not necessary to simultaneously output the multicast service to all output ports of the multiplexing/demultiplexing device.
  • another preferred embodiment of the present invention also provides a simplified multiplexer/demultiplexer. As shown in FIG. 7, the multiplexer/demultiplexer includes:
  • a coarse wavelength divider configured to separate, from the received optical signal, an optical signal having a specific wavelength (eg, and/or Weg 1 and/or other specific wavelengths) for carrying the multicast-type service and for An optical signal carrying downlink unicast data of each ONU;
  • An AWG of l:n is used for separating the wavelength-containing optical signals from the coarse wavelength division, and obtaining n optical signals of wavelengths ⁇ , respectively, and routing them to the n output ports of the AWG, where n corresponds to The number of ONUs in the WDM-PON system;
  • a branching device having a branching ratio of l:a for using a specific wavelength from the coarse wavelength division (example) If the optical signals of wavelengths b and/or are distributed, they are divided into a parts and output to a combiner respectively; wherein a is a natural number greater than or equal to 1 and less than n, corresponding to the WDM-PON system The number of ONUs supporting the multicast service;
  • each combiner is coupled to an output of the AWG and an output of the splitter for coupling an optical signal of a particular wavelength from the splitter to the AWG Go to the output branch.
  • the above multiplexer/demultiplexer can simultaneously transmit the optical signals carrying the multicast-type service data to the respective ONUs of the WDM-PON system by means of power allocation, so that the wavelengths are on separate wavelengths. It is possible to transmit multicast or broadcast data, which can greatly save the bandwidth resources of the system.
  • a preferred embodiment of the present invention also provides a method of implementing the multicast class service using the WDM-PON system described above. As shown in FIG. 8, the method mainly includes the following steps:
  • Step A The OLT separates the multicast service data from the downlink data from the upper layer device and the downlink unicast data sent to each ONU in the WDM-PON system;
  • Step B The OLT carries the multicast service data by using an optical signal having a specific wavelength, and the downlink unicast data of each ONU is respectively carried on an optical signal having a downlink wavelength set in advance for each ONU;
  • Step C multiplexing the optical signal of the specific wavelength and each optical signal carrying the downlink unicast data of each ONU to the multiplexing/demultiplexing device in the ODN;
  • Step D The multiplexer/demultiplexer separates the optical signal of the specific wavelength and the optical signals of each unicast data of each ONU from the received optical signal according to the wavelength, where the specific The optical signals of the wavelength are simultaneously output to all or part of the ONUs, and the optical signals of the downlink unicast data of the ONU are respectively output to their corresponding ONUs;
  • Step E Each ONU in the WDM-PON system is separated from the received optical signal An optical signal having a specific wavelength and an optical signal carrying its own downlink unicast data are respectively subjected to optical/electrical conversion and demodulation processing, and then the multicast service data and its own downlink unicast data are obtained, and the multicast is obtained.
  • the service data is transmitted to the next layer of equipment for further processing.
  • the OLT can control whether the ONU can receive multicast service data by sending a corresponding control message to the ONU.
  • the foregoing multicast service may be an ordinary multicast or broadcast service, or may be a CATV service.
  • the OLT will also send a broadcast control message for prohibiting or allowing the ONU to receive the CATV broadcast signal to the ONU as needed; after the ONU receives the broadcast control message, if the broadcast control message is prohibited
  • the ONU will turn off the reception of the CATV broadcast signal by the optical/electrical converter; if the broadcast control message allows the ONU to receive the CATV broadcast signal, the ONU will enable the optical/electrical converter to broadcast the CATV. Signal reception.
  • multicast or broadcast can be implemented in the WDM-PON system, and since the multicast service is transmitted only once on a specific wavelength in the above WDM-PON system,
  • the invention solves the problem of waste of bandwidth resources caused by adopting the in-band multi-copy transmission mode in the prior art, effectively saves the bandwidth resources of the system, and reduces the complexity of the OLT because the OLT side does not need to adopt a complicated multicast protocol. degree.

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Description

支持组播类业务的无源光网络、 设备及方法
技术领域
本发明涉及无源光网络（PON, Passive Optical Network )技术， 特 别涉及一种支持组播类业务的波分复用无源光网络 （ WDM-PON , Wavelength Division Multiplexed Passive Optical Network ) , 在该 WDM-PON中使用的光线路终端（OLT, Optical Line Terminal ), 光网络 单元 （ONU , Optical Network Unit )、 复用 /解复用器以及利用上述 WDM-PON实现组播类业务的方法。 发明背景
随着诸如高质量的视频信息业务、 视频点播 （VoD , Video on Demand )等高速数据业务的发展，用户对接入网数据接入带宽的需求将 达到 100 兆比特 /秒 ( Mbps )左右， 利用现有的例如拨号上网、 非对称 数字用户线 （ADSL )等接入方式无法满足用户对接入带宽的需求， 因 此， 使用光纤铺设接入网的需求正在迅速增长， PON正是能够满足上述 高速数据业务的带宽需求的用户接入网， 并且既经济又方便运营和维 护。
现有 PON的基本结构如图 1所示。 一般而言， PON主要包括： 中 心局—— OLT、 光分配网 （ODN, Optical Distribution Network )和若干 个 ONU。 所述 ODN通常由复用 /解复用器以及连接所述复用 /解复用器 与所述 OLT及所述 ONU的光纤构成，所述复用 /解复用器一方面用于将 来自 OLT 的光信号解复用， 并将解复用后的光信号分别发送到各个 ONU, 另一方面， 用于将来自各个 ONU的光信号复用， 并将复用后的 光信号输出到所述 OLT。 根据实现机制的不同， PON可以划分为多种不同的类型， 例如： 基 于异步转移模式（ ATM, Asynchronous Transfer Mode ) 的 ATM-PON, 基于以太网 （Ethernet ) 的 EPON ( Ethernet Over PON ), 具有千兆比特 速率的 GPON( Gigabit PON ),结合波分复用（ WDM )技术的 WDM-PON, 以及结合码分多址（ CDMA, Code Division Multiple Access )技术的光 码分多址无源光网络 （OCMDA-PON, Optical Code Division Multiple Access Passive Optical Network )等等。
WDM-PON是一种点对点的网络结构， 点对点结构的网络通常采用 带内多拷贝的方式传输组播类业务数据： 一方面，对 OLT的处理能力要 求很高， 需要复杂的多播协议来支持所述组播类业务， 尤其是在许多用 户点播同样的节目时， OLT的处理能力将成为 WDM-PON系统的瓶颈； 另一方面， '同样一份数据要在多个波长上分别拷贝一份， 分别传输到不 同的 ONU, 因而浪费了系统的带宽资源。 发明内容
本发明实施例提供一种 WDM-PON, 可以节约系统的带宽资源， 降 低对 OLT处理能力的要求。
本发明实施例还提供了一种 OLT、 复用 /解复用器以及 ONU。
本发明实施例还提供了一种实现组播业务及 CATV广播的方法， 该 方法对 OLT的处理能力要求较低， 并且可以极大地节省 WDM-PON系 统的带宽资源。
一种 WDM-PON, 包括： 光线路终端 OLT、 复用 /解复用器及 n个光 网络单元 ONU;
其中， 所述 OLT用于将分别发送到 n个 ONU的下行单播数据分别 承载到不同波长的光信号上， 而将一路或一路以上的组播类业务数据分 别^ C载到一个或一个以上特定波长的光信号上， 并将上述不同波长的光 信号以及所述特定波长的光信号复用成一个光信号， 然后发送到所述复 用 /解复用器；
所述复用 /解复用器用于分离来自所述 OLT的不同波长的光信号， 对承载所逑组播类业务的特定波长的光信号进行功率分配， 而对承载所 述 n个 ONU下行单播数据的光信号进行波长选择性输出；
所述 n个 ONU分别用于对来自所述复用 /解复用器对应输出端的信 号进行处理， 分别得到所述组播类业务数据以及自身所对应的下行单播 数据。
一种 OLT, 包括： OLT端下行处理模块， 用于将分别发送到 n个 ONU的下行单播数据分别承载到不同波长的光信号上，而将一路或一路 以上的組播类业务数据分别承载到一个或一个以上特定波长的光信号 上， 并将上述不同波长的光信号以及所述特定波长的光信号复用成一个 光信号， 然后发送到复用 /解复用器。
本发明实施例所述的复用 /解复用器包括：
粗波分器， 用于从所接收的光信号中分离出用于承载所述组播类业 务的一路或一路以上具有特定波长的光信号以及用于承载各个 ONU下 行单播数据的光信号；
l:n的波导阵列光滤波器，用于对来自所述粗波分器的用于承载各个 ONU下行单播数据的光信号进行分离， 得到 n路具有不同波长的光信 号， 并分别路由到所述波导阵列光滤波器的 n个输出端口；
分支比为 l:a的分支器， 用于将来自所述粗波分器的具有特定波长 的光信号进行功率分配， 分成 a份， 并分别输出到 a个合波器；
a个合波器， 其中每个合波器连接到所述波导阵列光滤波器的一个 输出端及所述分支器的一个输出端， 用于将来自所述分支器的特定波长 的光信号耦合到所述波导阵列光滤波器的 a个输出支路中去； 其中， n为自然数； a为大于或等于 1且小于或等于 n的自然数。 而本发明实施例所述的 ONU包括： ONU端下行处理模块， 用于对 来自所述复用 /解复用器对应输出端的信号进行处理，分别得到自身所对 应的下行单播数据和 /或所述组播类业务数据。
一种利用 WDM-PON系统实现组播业务的方法包括：
所述 OLT从来自上一层设备的下行数据中分离出组播业务数据以 及发送到至少一个 ONU的各路下行单播数据；
所述 OLT将所述组播业务数据用具有特定波长的光信号承载，而将 所述至少一个 ONU的下行单播数据分别承载于具有预先设定波长的至 少一个光信号上；
所述 OLT将所述特定波长的光信号以及承载各个 ONU下行单播数 据的光信号复用在一起， 并发送到所述复用 /解复用器；
所述复用 /解复用器根据波长，从所接收的光信号中分离出承载所述 组播业务数据的所述具有特定波长的光信号以及至少一个承载各个 ONU下行单播数据的光信号，将其中承载所述组播业务数据的所述特定 波长的光信号同时输出到至少一个 ONU中的全部或部分 ONU, 而将承 载 ONU下行单播数据的至少一个光信号分别输出到其对应的 ONU; 所述 ONU从所接收的光信号中分离出承载所述组播业务数据的具 有特定波长的光信号以及承载自身下行单播数据的光信号， 分别进行光 /电变换以及解调处理后，得到所述组播业务数据以及自身的下行单播数 据， 并将組播业务数据传输给下一层设备作进一步处理。
一种在波分复用-无源光网络中实现有线电视 CATV 广播的方法包 括：
所述 OLT从上一层设备接收承载 CATV广播信号的具有特定波长的 , 光信号；
所述 OLT通过光放大器对所接收的承载 CATV广播信号的特定波长 的光信号进行光放大；
所述 OLT将所述经过光放大的承载 CATV广播信号的特定波长的光 信号和承载各个 ONU下行单播数据的光信号复用在一起， 并发送到所 述复用 /解复用器；
戶斤述复用 /解复用器根据波长，从所接收的光信号中分离出所述承载 CATV广播信号的特定波长的光信号以及至少一个承载各个 ONU下行 单播数据的光信号， 将其中所述承载了 CATV广播信号的特定波长的光 信号同时输出到所述 ONU中的全部或部分 ONU, 而将承载 ONU下行 单播数据的一个以上光信号分别输出到其对应的 ONU;
所述 ONU从所接收的光信号中分离出所述承载 CATV广播信号的 特定波长的光信号以及承载自身下行单播数据的光信号， 其中所述承载 CATV 广播信号的特定波长的光信号进行光 /电变换后， 得到电域的 CATV广播信号并传输给下一层设备作进一步处理， 而承载自身下行单 播数据的光信号给光 /电变换及解调后， 得到本 ONU的下行单播数据并 传输给下一层设备处理。
由此可以看出，在利用本发明实施例所述的 WDM-PON系统以及通 过本发明实施例所述方法实现所述组播类业务的过程中， 可以将所述组 播类业务用一个或一个以上具有特定波长的光信号来承载， 因而可以有 效解决现有技术中采用带内多拷贝传输方式所带来的带宽资源浪费的 问题，有效地节约了系统的带宽资源， 并且由于在该 WDM-PON系统中 OLT不需要支持复杂的多播协议， 因而降低了 OLT的复杂度。
另夕卜， .由于组播类业务的数据流量一般都比较大， 而且优先级比较 高， 因此， 将所述组播类业务分离出来使用单独的波长传输， 可以更好 _ 地确保其它实时业务（例如 VOIP ) 的服务质量， 因而， 可以更好地保 证 WDM-PON系统的服务质量。 附图简要说明
图 1为现有 PON系统的基本结构示意图；
图 2为本发明一个优选实施例所述 WDM-PON中所使用的复用 /解 复用器的功能示意图；
图 3为本发明一个优选实施例所述 WDM-PON系统的基本结构示意 图；
图 4为才艮据本发明另一个优选实施例所述的在 WDM-PON中实现组 播业务时的系统结构示意图；
图 5为根据本发明又一个优选实施例所述的在 WDM-PON中实现 CATV业务和组播业务时的系统结构示意图；
图 6 为本发明一个优选实施例所述的复用 /解复用器内部结构示意 图；
图 7为本发明另一个优选实施例所述的复用 /解复用器内部结构示意 图；
图 8为本发明一个优选实施例所述的实现所述组播类业务的方法流 程图。 实施本发明的方式
为使发明的目的、 技术方案及优点更加清楚明白， 以下参照附图对 本发明的实施例作进一步详细说明。
本发明的一个优选实施例提供了一种可以支持组播类业务的 WDM-PON 系统， 例如支持组播业务和 /或广播业务和 /或有线电视 ( CATV ) 业务的 WDM-PON 系统。 图 3 显示了本实施例所述的 WDM-PON系统的基本结构， 如图 3所示， 主要包括： OLT、 复用 /解复 用器、 n个 ONU以及连接所述 OLT、所述复用 /解复用器及所述 n个 ONU 的光纤。 其中， n为自然数。
其中， 所述 OLT在下行方向上用于将分别发送到所述 n个 ONU的 n路下行单播数据分别承载到 n个具有不同波长的光信号上， 而将一路 或一路以上的组播类业务数据分别承载到一个或一个以上特定波长的 光信号上， 并将上述不同波长的光信号以及所述一个或一个以上特定波 长的光信号复用成一个光信号， 然后输出到所述复用 /解复用器； 所述 OLT在上行方向上， 分离出来自各个 ONU的上行光信号， 并经进一步 的检测和解调， 恢复出各个用户的上行数据， 并输出到上一级设备。
所述复用 /解复用器的功能如图 2所示， 主要包括： 在下行方向上， 分离从所述 OLT接收的不同波长的光信号，对用于承载所述组播类业务 的特定波长的光信号，例如波长为 m的光信号进行功率分配， 即在其多 个输出端口或所有输出端口上同时输出该特定波长的光信号， 而对承载 各个 ONU下行单播数据的 n路其它波长的光信号进行波长选择性输出， 即将不同波长的光信号分别在预先确定的对应输出端口上输出； 而在上 行方向上， 将来自不同 ONU的 n路不同波长的上行信号进行复用， 得 到一个光信号， 并输出到所述 OLT。
所述 ONU在下行方向上用于对来自所述复用 /解复用器一个输出端 的信号进行处理， 分别得到所述组播类业务数据以及该 ONU所对应的 下行单播数据； 而在上行方向上， 将该 ONU的上行数据承载到具有预 先确定波长的光信号上， 并输出到所述复用 /解复用器。
仍参见图 3， 所述 OLT进一步包括 OLT端下行处理模块、 OLT端 上行处理模块以及第一光环形器（Circulator )三个部分： 其中，所述第一光环形器连接所述 OLT端下行处理模块、 OLT端上 行处理模块以及所述复用 /解复用器， 用于将来自所述 OLT端下行处理 模块的下行光信号输出到所述复用 /解复用器， 并将来自所述复用 /解复 用器的上行的光信号输出到所述 OLT端上行处理模块。
所述 OLT端下行处理模块包括：
下行数据分离器， 用于从下行业务数据中分离出组播类业务数据以 及 n路分别发送到 n个 ONU的下行单播数据；
组播类业务数据传输前处理模块， 用于接收来自上一级设备的广播 数据 (例如 CATV信号）和 /或来自所述下行数据分离器的組播类业务数 据， 并进行处理和放大后， 得到一个或一个以上特定波长的承载一路或 一路以上的组播类业务数据的光信号；
-其中， 所述组播类数据传输前处理模块对来自上一级设备的承载广 播数据的光信号将直接通过光放大器进行光放大处理； 而对来自所述下 行数据分离器的一路或一路以上的组播类业务数据， 则将其分别调制到 一个或一个以上具有特定波长的光信号上， 并对调制过后的光信号进行 相关的其它处理； 因此， 所述组播类数据传输前处理模块应当进一步包 括： 一个用于对广播数据进行光放大的光放大器， 和 /或一个或一个以上 用于产生特定波长光信号的激光器以及一个或一个以上将所迷组播类 业务数据调制到所述特定波长的光信号中的调制器， 其中激光器和调制 器的功能可以由一个直接调制激光器（Direct Modulation Laser, DML ) 同时完成；
主宽谱激光源， 用于生成一宽谱光信号；
为了保证系统的可靠性，所述 WDM-PON还可以进一步包括一个备 宽谱激光源，用于在所述主宽谱激光源失效时，提供备用的宽谱光信号； 第一波导阵列光滤波器 （AWG ), 用于对所述主宽谱激光源或备宽 谱激光源输出的宽谱光信号进行处理， 生成波长分别为 ~ 的 n路光 信号， 为光调制器阵列提供不同波长的激光源；
光调制器阵列， 包含 n个调制器， 用于将来自所述下行数据分离器 的、 对应 n个 ONU的下行单播数据分别调制到由所述第一 AWG输出 的波长分别为 λ, λη的 η路光信号中；
复用器， 用于将承载有所述组播类业务数据的具有特定波长（例如 λ1Ώ b等）一个或一个以上光信号以及承载有 n个 ONU下行单播数据 的、 波长分別为 λ^λ^^ n路光信号复用为一个光信号， 并输出到所述 第一光环形器。 复用器可以是耦合器， 也可以是波长阵列光滤波器 ( AWG )或其它复用器件。
所述 OLT端上行处理模块包括：
第二 AWG, 用于从来自所述第一光环形器的上行光信号中分离出 波长分别为
Figure imgf000011_0001
的 η路光信号；
光电二极管或光检测器（PD, Photodiode or Photo Detector ) 阵列， 即光检测器阵列， 包含 η个 PD，分別用于将来自所述第二 AWG的一路 上行光信号转换成电信号；
解调器阵列， 包含 η个解调器， 分别用于解调由所述光电二极管或 光检测器阵列输出的电信号， 恢复各个 ONU的上行数据。
图 3中所示 WDM-P0N中的 0NU也包括 0NU端下行处理模块和 0NU端上行处理模块两个部分以及一个第二光环形器:
其中所述第二光环形器连接到所述 0NU端上行处理模块、 0NU端 下行处理模块以及所述复用 /解复用器， 用于将来自所述 0NU端上行处 理模块的上行光信号输出到所述复用 /解复用器， 并将来自所复用 /解复 用器的下行的光信号输出到所述 0NU端下行处理模块；
所迷 0NU端下行处理模块包括： 粗波分器， 用于从来自所述复用 /解复用器的光信号中， 分离出不同 波长的光信号， 包括波长为 〜 的光信号中用于承载本 ONU所对应下 行单播数据的光信号以及用于承载所述组播类业务的具有特定波长光 信号， 例如波长为 和/或 1)的光信号；
PD阵列， 所包含的 PD数量根据所述组播类业务的数目而定， 若承 载有 X路组播类业务， 则该 PD阵列中将包含 x+1个 PD, 其中一个 PD 用于将来自所述粗波分器的波长为 λ!〜λη的光信号中承载本 ONU所对应 的下行单播数据的光信号转换成电信号； 余下的 X个 PD分别用于将来 自所述粗波分器的用于承载各路组播类业务的特定波长光信号转换成 电信号；
解调器阵列， 所包含的解调器数量与所述 PD阵列中的 PD数量对 应， 其中一个解调器用于对承载本 ONU的下行单播数据的电信号进行 解调，得到本 ONU的下行单播数据；余下的解调器分别用于对 PD阵列 输出的承载各路组播类业务数据的电信号进行解调 , 得到各路组播类业 务数据。
所述 0NU端上行处理模块包括：用于将该 ONU的上行数据调制到 一光信号中的调制器。
所述光信号是本 ONU传输上行数据所需要的、 既可来源于 OLT也 可由 ONU自己产生。如果该光信号是由 ONU自己产生的，则所述 ONU 端上行处理模块还需要进一步包括一个光源， 如图 3中所示。
下面结合图 4， 通过本发明的另一个优选实施例详细说明所述 WDM-PON实现组播业务的动态工作过程。
'如图 4所示，在利用所述的 WDM-PON系统实现组播业务的过程中， 首先，在 OLT中， 由下行数据分离器从来自上一级设备的数据流中提取 出组播业务数据； 然后将所提取的组播业务数据通过调制器调制到由特 定波长激光器所输出的波长为 m的光信号中， 并经过光放大器的放大 后，由复用器将承载所述组播业务数据的波长为 m的光信号与承载各个
ONU的下行单播数据的波长分别为 4n的 η路光信号进行复用后 , 得 到波长包括 λ广 以及 Xm的多波长光信号， 该光信号将经由第一光环形 器， 传输到复用 /解复用器。 上述特定波长激光器、 调制器以及光放大器 构成了图 3中的組播类业务数据传输前处理模块。
所述复用 /解复用器从所接收的光信号中分离出不同波长的光信号， 并将承载所述组播业务数据的波长为 的光信号同时从其 n个输出端输 出，而将承载各个 ONU下行单播数据的波长分别为 〜 n的 η路光信号 分别输出到其对应输出端。 这样，在所述复用 /解复用器的每个输出端上 输出的光信号中，将至少包含承载所述组播业务的波长为 的光信号以 及承载各个 ONU下行单播数据的波长分別为 〜 中的一路光信号，例 如，输出端 1输出的光信号将包含两个波长入111和 ，输出端 2输出的光 信号将包含两个波长
Figure imgf000013_0001
λ2， ... ...，输出端 η输出的光信号将包含两个 波长 „1和 λη。 随后， 这 η个输出信号将被分别传输到 WDM-PON系统 的 η个 ONU上。
在各个 ONU中， ONU端下行处理模块将来自所述复用 /解复用器的 光信号分离为承载所述组播业务的波长为 λ∞的光信号以及承载各个 ONU下行单播数据的波长分别为 λ!〜λη中用于承载本 ONU下行单播数 据的一路光信号， 分别将这两路光信号变换为电信号后， 再分别进行解 调， 即可得到所述组播业务数据以及本 ONU对应的下行单播数据。
与此同时，为了实现所述组播业务， OLT还应当能够捕获来自 ONU 的加入组播组的请求， 一方面完成组播代理功能， 另一方面， 根据上一 层組播服务器返回的鉴权结果， 判断该 ONU是否有权限所请求的组播 组数据， 并根据判断结果发送一个组播业务控制报文给该 ONU, 所述 ONU根据来自 OLT的组播业务控制报文， 滤出 OLT允许其接收的组播 组数据， 而直接丟弃 OLT不允许的组播组数据。 ONU滤出 OLT允许的 组播组数据后， 将发送给相应的下一级设备作进一步处理。
通过图 3所示的 WDM-PON系统还可以进一步提供 CATV业务，图 5显示了根据本发明又一个优选实施例的， 能够同时提供 CATV业务以 及组播业务的 WDM-PON系统结构示意图。
如图 5 所示， 可以同时为 ONU提供 CATV业务以及组播业务的 WDM-PON在图 4所示结构的基础之上进行了如下的改进：
对 OLT而言， 增加了一个将输出端连接到所述复用器的光放大器， 用于对来自外部的承载着 CATV信号的波长为 λ^ 光信号进行光放大。 此时， 图 5·中所示的特定波长激光器、 调制器、 连接到调制器的光放大 器以及用于放大 CATV信号的光放大器构成了图 3中的组播类业务数据 传输前处理模块。
对所述复用 /解复用器而言， 在下行方向上， 所述复用 /解复用器还 将进一步对来自 OLT的光信号中承载所述 CATV信号的特定波长即 的光信号进行功率分配 , 即在其各个输出端口上同时输出该特定波长 ^ 的光信号。 这样， 所述复用 /解复用器每个输出端所输出的光信号中， 将 包含承载所述组播数据的波长为 m的光信号、 承载所述 CATV信号的 波长为 b的光信号以及承载各个 ONU下行单播数据的波长分别为 4n 中的一路光信号。
另外， 对所述 ONU而言， 所述粗波分复用器将进一步分离出承载 所述 CATV信号的波长为 b的光信号， 所述 PD阵列和解调器阵列中还 将进一步包含对承载所述 CATV信号的波长为 b的光信号进行光 /电变 换以及解调的 PD和解调器， 从而就可以在每个 ONU得到所述 CATV 数据。 在 CATV业务的实现过程中， OLT也可以通过与实现组播业务相类 似的方式， 例如通过发送广播控制报文， 实现 CATV业务的受控收看。
从上述实现组播业务的过程可以看出，利用上述的 WDM-PON系统 可以实现组播或广播业务， 同时， 由于在上述 WDM-PON系统中仅使用 了一个或多个单独的波长承载一路或多路组播类业务数据， 从而可以有 效避免现有技术中组播类业务数据要发送给多少个用户， 就要拷贝多少 份的问题， 从而可以大大节省 WDM-PON系统的带宽资源， 另外， 还可 以减少 OLT调度的负荷度， OLT不需要支持复杂的组播调度协议，从而 降低系统的复杂度。
从上述实施例可以看出， 上述 WDM-PON 系统所使用的复用 /解复 用器与现有 WDM-PON系统所使用的复用 /解复用器是不相同的， 为了 实现所述的 WDM-PON系统，在本发明的一个优选实施例中，具体给出 了应用在上述 WDM-PON系统中的、既具有 AWG功能又可广播某些特 定波长的光信号的新型复用 /解复用器。 图 6显示了这种复用 /解复用器 的结构。
如图 6所示， 本实施例所述的复用 /解复用器包括：
粗波分器， 用于从所接收的光信号中分离出用于承载所述组播类业 务的具有特定波长（例如 13和/或 „1和/或其他特定的波长）的光信号以 及用于承载各个 ONU下行单播数据的光信号；
l:n的 AWG, 用于对来自所述粗波分器的波长包含 λ λη的光信号 进行分离， 得到 η路波长分别为 〜 的光信号， 并分别路由到该 AWG 的 η个输出端口， 其中 η对应于 WDM-PON系统中的 ONU数目；
分支比为 l:n的分支器， 用于将来自所述粗波分器的特定波长（例 如波长为 b和 /或 和 /或其他特定的波长）的光信号进行功率分配， 分 成 η份， 并分别输出到 η个合波器； n个合波器， 其中每个合波器连接到所述 AWG的一个输出端及所 述分支器的一个输出端， 用于将来自所述分支器的特定波长的光信号耦 合到所述 AWG的各个输出支路中去。
由此可以看出，在如图 6所示的复用 /解复用器的 n个输出端均可以 得到承载所述组播类业务的具有特定波长（例如 b和 /或 „1和/或其他特 定的波长）的光信号， 以及承载各个 ONU下行单播数据的 n路光信号， 从而可以应用到所述的 WDM-PON系统中。
熟悉本领域的技术人员可以理解， 还可以有其它各种替代方案来实 现本实施例所述的复用 /解复用器， 例如可以将上述粗波分器、分支器以 及合波器的功能集成到一个 AWG中实现，还可利用粗波分器、分支器、 合波器以及 N:N的波导光栅路由器（WGR, waveguide grating router ) 来实现等等。
如前所述，在上述图 6所示的复用 /解复用器的 n个输出端均包含用 于承载所述组播类业务的具有特定波长的光信号， 而在某些特殊的情况 下， WDM-PON系统中的某些 ONU可能不支持所述组播类业务， 此时， 将所述组播类业务同时输出到所述复用 /解复用器的所有输出端口并不 是必须的， 为此， 本发明的另一个优选实施例还给出了一种简化的复用 /解复用器， 如图 7所示， 所述复用 /解复用器包括：
粗波分器， 用于从所接收的光信号中分离出用于承载所述组播类业 务的具有特定波长（例如 和 /或 „1和/或其他特定的波长）的光信号以 及用于承载各个 ONU下行单播数据的光信号；
l:n的 AWG, 用于对来自所述粗波分器的波长包含 光信号 进行分离， 得到 n路波长分别为 ~ 的光信号， 并分别路由到该 AWG 的 n个输出端口， 其中 n对应于 WDM-PON系统中的 ONU数目；
分支比为 l:a的分支器， 用于将来自所述粗波分器的特定波长（例 如波长为 b和 /或 的光信号进行功率分配， 分成 a份， 并分别输出 到 a个合波器； 其中， a为大于或等于 1而小于 n的自然数， 对应于所 述 WDM-PON系统中支持所述组播类业务的 ONU的数目；
a个合波器，其中每个合波器连接到所述 AWG的一个输出端及所述 分支器的一个输出端， 用于将来自所述分支器的特定波长的光信号耦合 到所述 AWG的 a个输出支路中去。
由此可以看出， 由于上述复用 /解复用器可以通过功率分配的方式将 承载所述组播类业务数据的光信号同时传输到 WDM-PON 系统的各个 ONU, 使得在单独的波长上传输组播或广播的数据成为可能， 从而可以 大大节省系统的带宽资源。
除上述 WDM-PON系统以及复用 /解复用器之外， 本发明的一个优 选实施例还提供了一种利用上述 WDM-PON 系统实现所述组播类业务 的方法。 如图 8所示， 该方法主要包括以下步骤：
步骤 A: OLT从来自上一层设备的下行数据分离出组播类业务数据 以及发送到 WDM-PON系统中各个 ONU的各路下行单播数据；
步骤 B: OLT将所述组播类业务数据用具有特定波长的光信号承载， 而将所述各个 ONU的下行单播数据分别承载于具有预先为各个 ONU设 定的下行波长的光信号上；
步骤 C: 将所述特定波长的光信号以及承载各个 ONU下行单播数 据的各路光信号复用在一起发送到 ODN中的复用 /解复用器；
步骤 D: 所述复用 /解复用器根据波长， 从所接收的光信号中分离出 所述特定波长的光信号以及承载各个 ONU下行单播数据的各路光信号， 将其中所述特定波长的光信号同时输出到所有或部分 ONU, 而将承载 ONU下行单播数据的各路光信号分别输出到其对应的 ONU;
步骤 E: WDM-PON系统中的各个 ONU从所接收的光信号中分离 出具有特定波长的光信号以及承载自身下行单播数据的光信号， 分别进 行光 /电变换以及解调处理后，得到所述组播类业务数据以及自身的下行 单播数据， 并将组播业务数据传输给下一层设备作进一步处理。
另外， 如前所述， OLT可以通过发送相应的控制报文给所述 ONU, 实现对 ONU能否接收组播类业务数据的控制。
上述組播类业务可以是普通的组播或广播业务， 也可以是 CATV业 务。 特别地， 对于 CATV业务， OLT还将根据需要发送用于禁止或允许 ONU接收 CATV广播信号的广播控制报文给所述 ONU; ONU接收到广 播控制报文后， 如果所述广播控制报文禁止该 ONU接收 CATV广播信 号， 则 ONU将关闭光 /电变换器对 CATV广播信号的接收； 如果所述广 播控制报文允许该 ONU接收 CATV广播信号， 则 ONU将启用光 /电变 换器对 CATV广播信号的接收。
由此可以看出， 通过上述方法， 可以在 WDM-PON系统中实现组播 或广播，并且， 由于组播类业务在上述 WDM-PON系统中仅在一个特定 的波长上传输了一次， 因此可以解决现有技术中采用带内多拷贝传输方 式所带来的带宽资源浪费的问题， 有效地节约了系统的带宽资源， 并且 由于 OLT侧不需要采用复杂的多播协议， 因而降低了 OLT的复杂度。

Claims

权利要求书
1、 一种波分复用 -无源光网络系统， 其特征在于， 包括： 光线路终 端 OLT、 复用 /解复用器和 n个光网络单元 ONU, 其中 n为自然数； 所述 OLT用于将组播类业务数据承载到特定波长光信号上，并发送 到所述复用 /解复用器；
所述复用 /解复用器用于从来自 OLT的光信号中分离出所述特定波 长光信号， 进行功率分配后分别输出到所述 n个 ONU;
所述 n个 ONU分别用于接收所述复用 /解复用器对应输出端输出的 所述组播类业务数据。
2、根据权利要求 1所述的波分复用 -无源光网络系统， 其特征在于， 所述 OLT进一步用于将分别发送到 n个 O U的下行单播数据分别 承载到不同波长的光信号上， 将所述不同波长的光信号以及所述特定波 长光信号复用成一个光信号，并将复用后的光信号发送到所述复用 /解复 用器；
所述复用 /解复用器进一步用于从接收的光信号中分离出分别承载 所述 n个 ONU下行单播数据的光信号， 并进行波长选择性输出；
所述 ONU进一步用于接收所述复用 /解复用器对应输出端输出的自 身所对应的下行单播数据。
3、 一种光线路终端 OLT, 其特征在于， 包括：
OLT端下行处理模块， 用于将组播类业务数据承载到特定波长的光 信号上， 并输出。
4、 根据权利要求 3所述的 OLT, 其特征在于， 所迷 OLT端下行处 理模块进一步用于将分别发送到 n个光网络单元 ONU的下行单播数据 分別承载到不同波长的光信号上， 将上述不同波长的光信号以及所述特 定波长光信号复用成一个光信号后， 输出。
•5、 居权利要求 3或 4所述的 OLT, 其特征在于， 进一步包括： 第一光环形器以及 OLT端上行处理模块；
其中， 所述第一光环形器连接所述 OLT端下行处理模块、 OLT端上 行处理模块和所述复用 /解复用器， 用于将来自所述 OLT端下行处理模 块的下行光信号输出到所述复用 /解复用器； 并将来自所述复用 /解复用 器的上行光信号输出到所述 OLT端上行处理模块；
所述上 OLT端上行处理模块接收来自所述第一光环形器的上行光 信号， 并从中恢复出所述 n个光网络单元 ONU的上行数据。
6、 才艮据权利要求 4所述的 OLT, 其特征在于， 所述下行处理模块 包括：
下行数据分离器， 用于从下行业务数据中分离出需要进行广播或组 播的组播类业务数据以及 n路分别发送到所述 n个 ONU的下行单播数 据；
组播类数据传输前处理模块， 用于接收来自所述下行数据分离器的 或来自其它传输通道的一路或一路以上的组播类业务数据， 对所述组播 类业务数据进行处理后， 输出承载有所述组播类业务数据的一个或一个 · 以上具有特定波长的光信号；
主宽镨激光源， 用于生成一宽谱光信号；
第一波导阵列光滤波器， 用于根据所述主宽谱激光源输出的宽谱光 信号， 生成 n路具有不同波长的光信号， 为光调制器阵列提供不同波长 的激光源；
光调制器阵列， 包含 n个调制器， 用于将来自所述下行数据分离器 的、 对应 n个 ONU的下行单播数据分别调制到由所述第一波导阵列光 滤波器输出的 n路具有不同波长的光信号中； 复用器， 用于将来自所述组播类数据传输前处理模块的承载有组播 类业务数据的具有特定波长的光信号以及承载有 n个 ONU的下行单播 数据的、 具有不同波长的 n路光信号复用为一个光信号， 并输出到所述 第一光环形器。
7、 根据权利要求 6所述的 OLT, 其特征在于， 所述组播类数据传 输前处理模块进一步包括：
至少一个激光器， 分别用于产生至少一路特定波长的光信号； 至少一个调制器， 分别用于接收所述下行数据分离器输出的所述至 少一路组播类业务数据， 将所述组播类业务数据分別调制到所述激光器 输出的所述特定波长的光信号中。
8、 根据权利要求 7所述的 OLT, 其特征在于： 激光器和调制器的 功能由同一个设备同时实现。
9、 根据权利要求 7或 8所述的 OLT, 其特征在于， 所述组播类数 据传输前处理模块进一步包括：
一个或一个以上光放大器， 用于对承载所述组播类业务数据的所述 特定波长的光信号进行光放大。
10、 根据权利要求 6或 7或 8或 9所述的 OLT, 其特征在于， 所述 组播类数据传输前处理模块进一步包括： 用于接收来自上一级设备的广 播业务光信号， 并对该广播业务光信号进行光放大的光放大器。
11、 根据权利要求 6所述的 OLT, 其特征在于， 所述下行处理模块 进一步包括： 一个连接到所述第一波导阵列光滤波器的备宽谱激光源， 用于在所述主宽谱激光源失效时， 为所述第一波导阵列光滤波器提供备 用的宽语光信号。
12、根据权利要求 5所述的 OLT, 其特征在于， 所述 OLT端上行处 理模块包括： 第二波导阵列光滤波器， 用于将来自所述第一光环形器的上行光信 号分离为具有不同波长的 n路光信号；
光电二极管或光检测器 PD阵列， 包含 n个 PD, 分别用于将来自所 述第二波导阵列光滤波器的一路上行光信号转换成电信号；
解调器阵列， 包含 n个解调器， 分别用于解调由所述 PD阵列输出 的电信号， 生成一个 ONU的上行数据。
13、 一种复用 /解复用器， 其特征在于， 包括：
粗波分器， 用于从所接收的光信号中分离出特定波长光信号及其他 波长光信号；
分支比为 l:a的分支器， 用于将来自所述粗波分器的特定波长光信 号进行功率分配， 分成 a份， 并分别输出到 a个合波器；
a个合波器， 用于将来自所述分支器的特定波长的光信号耦合到所 述粗波分器输出的其他波长光信号中；
其中， a为大于或等于 1 自然数。
14、 根据权利要求 13所述的复用 /解复用器， 其特征在于， 进一步 包括：
1 :n的第三波导阵列光滤波器，用于分离来自所述粗波分器的其他波 长光信号， 得到 n路具有不同波长的光信号， 并将其中 a路不同波长的 光信号分別输出到所述 a个合波器；
其中， n为大于或等于 a的自然数。
15、 根据权利要求 14所述的复用 /解复用器， 其特征在于， 所述粗 波分器、 所述分支器以及所述合波器与所述第三波导阵列光滤波器的功 能集成在一个设备中， 完成所述复用 /解复用器的功能。
.16、 一种光网络单元 ONU, 其特征在于， 包括：
ONU端下行处理模块， 用于对来自复用 /解复用器对应输出端的信 号进行处理， 分别得到自身所对应的下行单播数据和所述组播类业务数 据。
17、 根据权利要求 16所述的 ONU, 其特征在于， 进一步包括： 第 二光环形器以及 ONU端上行处理模块；
其中， 所述第二光环形器连接所述复用 /解复用器、 ONU端下行处 理模块和 ONU端上行处理模块， 用于将来自所述复用 /解复用器的下行 光信号输出到所述 ONU端下行处理模块；并将来自所述 ONU端上行处 理模块的上行的光信号输出到所述复用 /解复用器；
所述 ONU端上行处理模块把用户的上行数据调制到相应波长的激 光中， 并传输到所述第二光环形器。
18、 根据权利要求 16所述的 ONU, 其特征在于， 所述 O U端下 行处理模块包括：
粗波分器， 用于从来自所述第二光环形器的下行光信号中， 分离出 不同波长的光信号；
光电二极管或光检测器 PD阵列， 包括至少两个： PD, 其中一个 PD 用于将来自所述粗波分器的、 用以承载本 ONU所对应的下行单播数据 的光信号转换成电信号； 余下的 PD分别用于将来自所述粗波分器的一 路或一路以上承载所述组播类业务数据的具有特定波长光信号转换成 电信号；
解调器阵列， 包括至少两个调制器， 其中一个用于对承载本 ONU 的下行单播数据的电信号进行解调， 得到本 ONU的下行单播数据； 余 下的解调器分别用于对余下 PD阵列输出的承载所述组播类业务数据的 电信号进行解调， 得到所述组播类业务数据。
19、 根据权利要求 16所述的 ONU, 其特征在于， 所述 ONU端上 行处理模块包括： 调制器， 用于将该 ONU的上行数据调制到一未调制 光信号中。
20、 一种在波分复用-无源光网络中实现组播业务的方法， 其特征在 于， 包括：
OLT从下行数据中分离出组播业务数据， 承载于特定波长光信号上 后， 发送到复用 /解复用器；
所述复用 /解复用器根据波长，从所接收的光信号中分离出所述特定 波长光信号， 并通过功率分配将所述特定波长光信号输出到至少一个 ONU;
所述至少一个 ONU分别从所接收的光信号中分离出所述特定波长 光信号， 进行光 /电变换以及解调处理后， 得到所述组播业务数据。
21、根据权利要求 20所述的实现组播业务的方法， 其特征在于， 进 一步包括：
OLT从下行数据中分离出所述至少一个 ONU的下行单播数据， 分 别承载于至少一个光信号上后， 与所述特定波长光信号复用在一起发送 到所述复用 /解复用器；
所述复用 /解复用器根据波长，从所接收的光信号中分离出至少一个 承载 ONU下行单播数据的光信号， 并分别输出到其对应的 ONU; 所述 ONU从所接收的光信号中分离出承载自身下行单播数据的光 信号， 进行光 /电变换以及解调处理后， 得到自身的下行单播数据。 ..
22、 根据权利要求 20或 21所述的实现组播业务的方法， 其特征在 于， 所述方法进一步包括：
所述 OLT捕获来自 ONU的加入组播组的请求， 一方面完成组播代 理功能， 另一方面进行鉴权并根据鉴权结果， 判断该 ONU是否有权限 接收所请求的组播组数据， 并根据判断结果发送一个组播业务控制报文 给所述 ONU; 所述 ONU根据来自所述 OLT的所述组播业务控制报文， 滤出所述 OLT允许其接收的组播组数据，而直接丟弃所述 OLT不允许的组播组数 据。
23、 一种在波分复用-无源光网络中实现有线电视 CATV广播的方 法， 其特征在于， 包括：
OLT从上一层设备接收承载 CATV广播信号的特定波长光信号， 通 过光放大器对所接收的特定波长光信号进行光放大， 并将所述经过光放 大的特定波长光信号发送到所述复用 /解复用器；
所述复用 /解复用器根据波长，从所接收的光信号中分离出所述承载 CATV 广播信号的特定波长光信号， 并通过功率分配输出到至少一个 ONU;
所述至少一个 ONU 分別从所接收的光信号中分离出所述承载 CATV广播信号的特定波长光信号，进行光 /电变换后，得到电域的 CATV 广播信号并传输给下一层设备作进一步处理。
24、 根据权利要求 23所述的实现 CATV广播的方法， 其特征在于， 进一包括： ' 所述 OLT将承载各个 ONU下行单播数据的光信号和所述特定波长 光信号复用在一起发送到所述复用 /解复用器；
所述复用 /解复用器根据波长，从所接收的光信号中分离出至少一个 承载 ONU下行单播数据的光信号， 并分别输出到其对应的 ONU;
所述 ONU从所接收的光信号中分离出承载自身下行单播数据的光 信号， 进行光 /电变换及解调， 得到本 O U的下行单播数据后， 传输给 下一层设备处理。
■25、 根据权利要求 23或 24所述的实现 CATV广播的方法， 其特征 在于， 所述方法进一步包括： 所述 OLT根据需要发送广播控制报文给所述 ONU, 所述广播控制 报文用于禁止或允许 ONU接收 CATV广播信号；
所述 ONU接收到广播控制报文后， 如果所述广播控制报文禁止该 ONU接收 CATV广播信号， 则 ONU将关闭光 /电变换器对 CATV广播 信号的接收；如果所述广播控制报文允许该 ONU接收 CATV广播信号， 则 ONU将启用光 /电变换器对 CATV广播信号的接收。
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CN101009530A (zh) 2007-08-01
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US20080304830A1 (en) 2008-12-11
CN101009530B (zh) 2012-02-15
EP1981196A1 (en) 2008-10-15

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