WO2011130995A1

WO2011130995A1 - Optical code division multiple access-passive optical network (ocdma-pon) system, optical distribution network device (odn) and optical line terminal (olt)

Info

Publication number: WO2011130995A1
Application number: PCT/CN2010/077912
Authority: WO
Inventors: 朱松林; 耿丹; 陈彪; 王大伟; 成亮
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-04-23
Filing date: 2010-10-20
Publication date: 2011-10-27
Also published as: CN101902666A

Abstract

An Optical Code Division Multiple Access-Passive Optical Network (OCDMA-PON) system, an Optical Distribution Network (ODN) device and an Optical Line Terminal (OLT) are provided in the present invention. The system includes: an OLT and an ODN, wherein the OLT dense-wavelength-division-multiplexes the multiple path modulated downstream data into one path of signal, and then encodes the signal, outputs the encoded one path of signal to said ODN; the ODN decodes the received one path of signal, dense-wavelength-division-demultiplexes the signal into a plurality of signals, and then ouputs the signals. Application of the present invention can expand the capacity of access subscribers in the existing OCDMA-PON.

Description

Optical code division multiple access passive optical network system, optical distribution network device and optical line terminal

The present invention relates to the field of optical fiber communication technologies, and in particular, to an optical code division multiple access passive optical network system, an optical distribution network device, and an optical line terminal based on optical code division multiple access multiplexing technology. Background technique

With the rapid development of computer, communication and video technologies, the demand for broadband services such as video, high-speed data and digital TV is increasing, and the traditional copper access network can not meet this demand, which makes it have high bandwidth. The fiber access network has developed rapidly and become one of the research hotspots of communication technology.

In the access network, the Passive Optical Network (PON) basically uses a point-to-multipoint tree network structure, an optical line terminal (OLT, Optical Line Terminal) and multiple optical network units (ONUs, The Optical Network Unit is connected, and the Optical Distribution Network (ODN) is composed of passive components such as optical splitters and optical couplers. It does not require any active electronic devices and devices, so the transmission performance and performance are A certain balance can be achieved between costs. The main parts and functions are as follows:

Optical line terminal: mainly provides the optical interface between the network and the optical distribution network, and can separate the switched and non-switched services, manage the signaling and monitoring information from the ONU, and provide maintenance and supply functions for itself and the ONU.

Optical Distribution Network: The power distribution of optical signals is accomplished using passive component optical splitters/couplers, connectors, and single-mode fibers, often using a tree-like branching structure.

Optical network unit: The optical network unit provides an interface between user data, video, telephone network and optical network, converts the received optical signal into a signal required by the user, and cooperates with an optical network terminal (ONT, Optical Network Termination). Thereby forming a network terminal. Adaptation Function (AF): It can be included in the ONU or it can be completely independent. It mainly provides adaptation functions for ONUs and user equipments.

There are three main types of PONs based on different multiple access technologies: time-division multiplexed passive optical network (TDM-PON), wavelength division multiplexing based passive optical network (WDM-PON), and optical code-based multi-division Address multiplexed passive optical network (OCDM-PON).

OCDMA is a multiple access multiplexing technology that combines the large bandwidth of optical fiber media with the flexibility of CDMA. It is an application and extension of CDMA technology in the field of optical fiber communication. It has the advantages of asynchronous access, shared channel, and good security. An OCDMA-PON structure is shown in Fig. 1. It includes an optical line terminal and an optical network unit based on optical code division multiple access technology, and the optical line terminal is connected to one or more optical network units based on optical code division multiple access technology. Of course, an optical distribution network may also be included, and the optical line terminal is connected to one or more optical network units through an optical distribution network, and the optical distribution network may be a coupler, a spectrometer or the like.

Each user in the OCDMA-PON is assigned a unique address code or a codec carrying a unique address code in the ONU. After the user data stream is modulated onto the optical carrier, it is encoded by the optical encoder, and the encoded user data stream is transmitted to the OLT through the optical distribution network. In the OLT, the encoded optical signal is decoded by an optical decoder. The decoded data stream is then uploaded to other core networks through transmitters in the OLT to implement mutual communication between different ONUs between different PONs. The data stream transmitted from the core network is modulated at the OLT end, and then encoded by the optical encoder, and then the encoded data stream is downlinked to the optical distribution network through the Fibre Channel, and then transmitted to each ONU or ONT through the ONU. After decoding, the decoder recovers the original data and implements reception.

The application of OCDMA-PON to the access network has the following advantages: It can realize direct multiplexing and exchange of optical signals, dynamically allocate bandwidth, and expand the network easily, and the network management is simple, so it is suitable for real-time, high burst, high rate. And confidential communication services. By assigning a codeword to a user to achieve multiple access, the user can access immediately and asynchronously, and the delay is also small; the security performance is good. In time division multiplexing (TDM) and wavelength division multiplexing (WDM) networks, as long as the fiber is slightly bent, use The optical language analyzer analyzes the leaked light to obtain and crack each signal. After using the OCDMA technology, the eavesdropper obtains only the pseudo-random optical signal without obtaining the coding scheme and the corresponding code group sequence. The probability of each signal is low; the optical signal processing is simple. There is no strict wavelength requirement like WDM. On the other hand, it does not require strict clock synchronization like TDM, which greatly reduces the cost of transceiver equipment; has soft capacity; OCDMA network control management is convenient; OCDMA network can realize different users Random asynchronous access; the node unit in the network is easy to implement all-optical processing, and the service transparency is high; different users distinguished by different codes can easily provide different quality of service and flexible network management. Although the existing OCDMA-PON has the above advantages, the inventors have found that the existing OCDMA-PON system still has the following disadvantages:

1) The number of code multiplexing is limited, which limits the number of access users of the system;

2) As the number of multiplexing increases, the crosstalk between users increases gradually, which limits the number of access users of the system to a certain extent;

3) OCDMA is a spread spectrum technology that requires a large bandwidth, and the inherent defect of the BER caused by the interference between users (MUI) limits the number of access users of the system.

WDM-PON multiplexes wavelength resources, and divides the same fiber into many channels according to different wavelengths. It is divided into coarse wavelength division multiplexing (CWDM, Coarse Wavelength Division Multiple) and dense wavelength division multiplexing (DWDM, Dense Wavelength Division). Multiple ), CWDM has a channel spacing of 20 nanometers, and DWDM has a channel spacing of 0.2 nanometers to 1.2 nanometers. The number of wavelengths that DWDM can provide relative to CWDM is greatly improved, but the number of users supporting a single channel is still limited. The limited wavelength resources result in a single channel being expensive, and the capacity of the entire PON structure is limited. Summary of the invention

The object of the present invention is to provide a dense code division multiplexing compatible optical code division multiple access passive optical network system, an optical distribution network device and an optical line terminal based on optical code division multiple access multiplexing technology, to expand the prior art. The access user capacity of the optical code division multiple access passive optical network. In order to achieve the above object, the present invention provides an optical code division multiple access passive optical network system, the system comprising:

The optical line terminal includes: an optical sending module, configured to modulate multiple downlink data to a single wavelength or broadband optical carrier of different wavelengths, and divide the multiple modulated downlink data into dense wavelength division multiplexer Dense Waves The Dense Wavelength Division Multiplexed signal outputted by the Dense Wavelength Division Multiplexer is encoded by a signal, and the encoded downlink signals are combined into one output, wherein different Dense Wavelength Division Multiplexers are densely outputted. The wavelength division multiplexing signal is different in coding; the optical receiving module is configured to receive the uplink signal, decode the received uplink signal, and perform the wavelength division multiplexing output of the decrypted set; the optical distribution network includes: the first coupler And receiving the downlink signal output by the optical sending module, dividing the downlink signal into multiple channels and outputting the same; and combining the received multiple uplink signals into one channel; and outputting multiple first signal processing modules, each The first signal processing module is connected to a port of the first coupler, and is configured to decode a downlink signal output by the first coupler The decoded downlink signal decryption set is wavelength-multiplexed into a plurality of single-wavelength downlink signals, and then outputted; the uplink signal is received, and the received uplink signal is densely wavelength-division multiplexed and encoded, and is encoded by the first The coupler outputs to the optical receiving module, and different first signal processing modules use different encodings when encoding the received uplink signal;

a plurality of optical network unit groups, each of the optical network unit groups being connected to one of the first signal processing modules, for receiving a downlink signal output by the connected first signal processing module; receiving uplink data, The uplink signal obtained after the received uplink data modulation is output to the connected first signal processing module.

Preferably, the optical code division multiple access passive optical network system, wherein the optical transmission module includes a plurality of modulation and coding modules and a second coupler,

Each of the modulation and coding modules includes:

a plurality of downlink modulation modules, each of the downlink modulation modules configured to modulate downlink data to a single wavelength or broadband optical carrier of different wavelengths; The first dense wavelength division multiplexer includes: a plurality of input ports and an output port; wherein each of the input ports is connected to one of the downlink modulation modules, and configured to output the connected downlink modulation module The modulated downlink data is densely wavelength division multiplexed into one channel and output through the output port;

a first encoder, connected to an output port of the first DWDM, configured to encode and output a downlink signal output by the first DWDM;

The second coupler is configured to combine the downlink signals output by each of the modulation and coding modules into one channel and output the signals to the optical distribution network.

Preferably, the optical code division multiple access passive optical network system, wherein the optical receiving module comprises:

a third coupler, configured to divide the uplink signal output by the optical distribution network into multiple channels and output; a plurality of first decoders, each of the first decoders and an output port of the third coupler Connecting, configured to decode one of the multiple uplink signals output by the third coupler and output the same;

a plurality of second dense wavelength division multiplexers, each of the second dense wavelength division multiplexers being connected to each of the first decoders for decoding an uplink signal output by the first decoder The demultiplexed wavelength division multiplexing is multi-channel output.

Preferably, the optical code division multiple access passive optical network system, wherein the first signal processing module in the optical distribution network comprises:

a second codec module, configured to decode one of the multiple downlink signals output by the first coupler, and output the received uplink signal to the first coupler; the third dense wave a sub-multiplexer, configured to perform wavelength division multiplexing of the downlink signal decryption set output by the second codec module into a plurality of single-wavelength downlink signals, and output the signals to a corresponding plurality of optical network units; The signal is densely wavelength division multiplexed and output to the second codec module.

Preferably, the optical code division multiple access passive optical network system, wherein The optical network unit includes:

a fourth coupler, configured to divide the downlink signal output by the first signal processing module into two paths and output the same;

An optical receiving link, configured to receive a downlink signal output by the fourth coupler, and recover original downlink data;

And a reflective semiconductor optical amplifier, configured to receive another downlink signal output by the fourth coupler, and erase data in the downlink signal to serve as a carrier light source for uplink data.

Preferably, the passive optical network system, wherein the optical line terminal and/or optical distribution network uses an encoder and/or codec based on a super-structured fiber Bragg grating for encoding and/or codec .

In another aspect, an optical distribution network device is provided, including:

a first coupler, configured to divide the downlink signal output by the optical line terminal into multiple channels and output the same, and combine the received multiple uplink signals into one channel and output the same;

a plurality of first signal processing modules, each of the first signal processing modules being connected to a port of the first coupler for decoding a downlink signal output by the first coupler, and decoding The downlink signal decryption set is wavelength division multiplexed into a plurality of single-wavelength downlink signals, and is output; receiving the uplink signal, performing the densely wavelength division multiplexing coding on the received uplink signal, and outputting through the first coupler after encoding Different first signal processing modules use different encodings when encoding the received uplink signals.

Preferably, the optical distribution network device, wherein the first signal processing module comprises: a second codec module, configured to decode one of the multiple downlink signals output by the first coupler, and output the same Transmitting the received uplink signal to the first coupler; the third dense wavelength division multiplexer is configured to perform wavelength division multiplexing of the downlink signal decryption set output by the second codec module into multiple After the single-wavelength downlink signal is output to the corresponding multiple optical network units; The received multiple uplink signals are Densely Wavelength Division Multiplexed and output to the second codec module. Preferably, the optical distribution network device, wherein the second codec module comprises: an encoder, a decoder, and/or a codec based on a super-structured fiber Bragg grating.

In another aspect, an optical line terminal is provided, including: an optical sending module and a light receiving module, where the optical transmitting module includes a plurality of modulation and coding modules and a second coupler,

Each of the modulation and coding modules includes:

a plurality of downlink modulation modules, each of the downlink modulation modules configured to modulate downlink data to a single wavelength or broadband optical carrier of different wavelengths;

The first dense wavelength division multiplexer includes: a plurality of input ports and an output port; wherein each of the input ports is connected to one of the downlink modulation modules, and configured to output the connected downlink modulation module The modulated downlink data is densely wavelength division multiplexed into one channel and output through the output port;

The second coupler is configured to combine the downlink signals output by each of the modulation and coding modules into one channel and output the signals.

Preferably, the optical line terminal, wherein the light receiving module comprises:

a plurality of second dense wavelength division multiplexers, each of the second dense wavelength division multiplexers being connected to each of the first decoders for decoding an uplink signal output by the first decoder The demultiplexed WDM is divided into multiple outputs.

The technical effects of the present invention are: The optical code division multiple access downlink signal is obtained by densely wavelength-multiplexing the multiple downlink signals into one channel in the optical line terminal, and the multiple optical code division multiple access downlink signals are coupled together and output to the light. a first signal processing module in the distribution network, each of the encoded signals corresponding to a first signal processing module, which is decoded by the first signal processing module and decrypted and integrated after the wavelength division multiplexing, so that the light is shattered by dense wavelength division multiplexing technology The address codes are multiplexed, and the number of accessible users is greatly increased corresponding to the prior art optical code division multiple access passive network system, which greatly expands the access user capacity of the system. DRAWINGS

1 is a schematic structural diagram of a prior art optical code division multiple access passive optical network;

2 is a schematic structural diagram of an optical code division multiple access passive optical network according to an embodiment of the present invention; FIG. 3A is a schematic structural diagram of an optical transmission module of an optical line terminal according to an embodiment of the present invention; FIG. 3B is another implementation of the present invention; FIG. 3C is a schematic structural diagram of an optical transmission module of an optical line terminal according to another embodiment of the present invention; FIG. 4 is a schematic diagram of an optical receiving terminal of an optical line terminal according to an embodiment of the present invention; FIG. 5 is a schematic structural diagram of an optical distribution network according to an embodiment of the present invention;

6 is a schematic structural diagram of an optical network unit according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a pulse modulation scheme with a limited extinction ratio according to an embodiment of the present invention. detailed description

The present invention will be described in detail below with reference to the drawings and specific embodiments.

The inventors of the present invention have found that the combination of OCDMA technology and DWDM technology can increase the user capacity of the system in the process of solving the technical problem of the present invention, because the OCDMA technology encodes and decodes user data in the code space, and can be superimposed on the wavelength. In terms of space, the number of multiplexes can be increased. 2 is a schematic structural diagram of an optical code division multiple access passive optical network system according to an embodiment of the present invention. As shown in FIG. 2, the passive optical network system of this embodiment includes:

The optical line terminal includes an optical transmitting module and a light receiving module. The optical transmitting module is configured to modulate multiple downlink data to a single wavelength or broadband optical carrier of different wavelengths, and multiplex the modulated downlink data into a single signal through a dense wavelength division multiplexer to divide the dense wave into multiple signals. The dense wavelength division multiplexing signal output by the device is encoded, and the encoded downlink signals are combined into one output, wherein the code of the dense wavelength division multiplexing signal output by the dense wavelength division multiplexer of different channels is used. different. The optical receiving module is configured to receive an uplink signal, and decode the received uplink signal and decrypt the set wave and then output the signal.

The optical distribution network includes a first coupler and a plurality of first signal processing modules. The first coupler is configured to receive the downlink signal output by the optical transmitting module, divide the downlink signal into multiple channels, and output the received multiple uplink signals into one channel. Each of the plurality of first signal processing modules is respectively connected to a port of the first coupler for decoding a downlink signal output by the first coupler, and decoding The downlink signal decryption set is wavelength-division multiplexed into a plurality of single-wavelength downlink signals, and then received, and the received uplink signal is densely wavelength-division multiplexed, encoded, and passed through the first coupler after encoding. And outputting to the optical receiving module to be decrypted by the optical receiving module to obtain a wavelength division multiplexing output, wherein different first signal processing modules use different encodings when encoding the received uplink signal.

Each of the plurality of optical network unit groups is respectively connected to a first signal processing module for receiving the downlink signal output by the connected first signal processing module, and receiving the uplink data, and receiving The uplink signal obtained after the uplink data modulation is output to the connected first signal processing module.

As shown in FIG. 2, the N first signal processing modules and the N optical network unit groups are taken as the first signal processing module 1 to the first signal processing module N, and the optical network unit group 1 to the optical network. The network element group N, N is a natural number, and each optical network unit group includes at least one optical network unit. In this example, the optical line terminal is coupled to the first coupler of the optical distribution network by a circulator (second circulator, not shown). The downlink signal output by the optical transceiver module is input to the first coupler through the port 1 of the second circulator, and the uplink signal output by the first coupler is input to the light receiving module through the port 3 of the second circulator, and the first coupler of the optical distribution network It is connected to the second circulator through port 2 of the second circulator.

In the passive network system of the embodiment of the present invention, the dense wavelength division multiplexing technology is used, such as by using a dense wavelength division multiplexer to multiplex signals of different wavelength channels to share the OCDMA encoder code, thereby increasing the available channels. number.

Preferably, in the passive optical network system of the embodiment of the present invention, the optical line terminal and/or the optical distribution network are performed by using an encoder and/or codec based on Superstructured Fiber Bragg Grating (SSFBG). coding. Utilizing the spectral cut characteristics of SSFBG, the operating bandwidth of an SSFBG-based encoder is broad-spectrum relative to the bandwidth of a single channel of a dense wavelength division multiplexer, so that the same codeword can be reused in different wavelength channels, and By using a special optical distribution network structure, one codec corresponds to a group of wavelength division multiplexed users, which saves the codec and increases the capacity of the system. In addition, the structure of the ONU and the OLT can be simplified, and the number of codecs in the OLT can be reduced. The codec is not needed in the ONU, so that the user does not have to maintain a relatively expensive codec by himself, but maintains the codec in the ODN. Device.

FIG. 3A is a schematic structural diagram of an optical transmitting module of an optical line terminal according to an embodiment of the present invention. As shown in FIG. 3A, the optical transmitting module includes a plurality of modulation and coding modules and a second coupler;

Each modulation and coding module includes: a plurality of downlink modulation modules, each of which is configured to modulate downlink data to a broadband optical carrier. In this example, the downlink modulation module is a modulator.

The first Dense Wavelength Division Multiplexer comprises: a plurality of input ports and an output port, each input port being connected to a downlink modulation module, configured to input the connected downlink modulation module The modulated downlink data is densely wavelength-division multiplexed into one channel and output through the output port.

The first encoder is connected to the output port of the first Dense Wavelength Division Multiplexer, and is configured to encode and output the downlink signal of the output of the first Dense Wavelength Division Multiplexer; in this example, to include N An encoder is taken as an example, and is a first encoder 1 to a first encoder N. The different wavelength modulation multiplexers included in different modulation and coding modules correspond to different first encoders to realize output to different dense wavelength division multiplexers. The multiplexed signal is encoded differently to obtain the downlink code of the optical code division multiple access; preferably, the first encoder is a wide spectrum coder with respect to each channel of the first dense wavelength division multiplexer; preferably, The first encoder is an SSFBG based optical encoder.

The second coupler is configured to combine the downlink signals output by each modulation and coding module, that is, the downlink signals output by the first encoder included in each modulation and coding module, into one channel, and output the signals to the optical distribution network.

As shown in Fig. 3A, in this example, different modulation and coding modules use different modulated laser sources. As shown in Fig. 3A, in this example, N laser sources are used, which are laser source 1 to laser source N, respectively, and N is a natural number. Illustratively, the laser source used is a pulse light source. The source of the optical source generated by the pulsed light source is a broad spectrum source relative to each channel of the first dense wavelength division multiplexer. In other embodiments of the present invention, a plurality of modulation and coding modules may be corresponding to one laser source; or all of the modulation and coding modules correspond to one laser source, as shown in FIG. 3B; or each downstream modulation module corresponds to one laser. Source, in this case, the number of laser sources is large and the cost is high.

In other embodiments of the present invention, the optical sending module may be further configured to modulate multiple downlink data to a single wavelength optical carrier of different wavelengths, as shown in FIG. 3C, each downstream modulation module, in this case, a modulator corresponding to a single wavelength. The laser source is configured to modulate the downlink data onto the corresponding single-wavelength optical carrier. In this example, each wavelength channel of the first DWDM corresponds to a single-wavelength laser source having a corresponding wavelength.

Preferably, the optical transmitting module further includes a first optical amplifier, and the signal output by the second coupler is amplified by the first optical amplifier and then output to the optical distribution network through the port 1. In the optical transmitting module, each The transmission fibers are used to connect between devices. Preferably, the signal output by the third coupler is sent to the first optical amplifier through the dispersion compensating fiber.

FIG. 4 is a schematic structural diagram of an optical receiving module of an optical line terminal according to an embodiment of the present invention. As shown in FIG. 4, the light receiving module includes:

And a third coupler, configured to divide the uplink signal output by the optical distribution network into multiple channels and output the signals. a plurality of first decoders, in this example, a first decoder 1 to a second decoder N, where N is a natural number, in this example, the number of first decoders corresponds to the number of first encoders, each The first decoder is connected to an output port of the third coupler, and is configured to decode one of the multiple uplink signals output by the third coupler and output the same.

a plurality of second dense wavelength division multiplexers, one of each of the second dense wavelength division multiplexers being coupled to one of the first decoders for decoding the output of the first decoder The signal decryption set is wavelength division multiplexed into multiple channels and output. The number of second dense wavelength division multiplexers corresponds to the number of first decoders. The first decoder 1 to the first decoder N correspond to the second Dense Wavelength Division Multiplexer 1 to the second Dense Wavelength Division Multiplexer N, respectively.

Preferably, in this example, the light receiving module further includes: a second optical amplifier, configured to amplify the uplink signal received from the optical distribution network and then input the third coupler; and the photoelectric conversion module used as the data stream receiver A charged limiting amplifier, a photodetector (PD) that converts an optical signal into an electrical signal, and a decision circuit (DE) for clock extraction and setting of a decision level and outputting a digital signal. Preferably, the signal is transmitted between the second optical amplifier and the optical distribution network through the dispersion compensation fiber DCF, and the signal output from the optical distribution network is input to the second optical amplifier through the port 3 and then split by the third coupler.

In the embodiment of the present invention, an optical amplifier is used to improve the transmission power or the receiving end power, but in order to ensure a good signal-to-noise ratio performance of the link, the types of optical amplifiers used for transmitting and receiving are different, and the high-saturation for transmitting is high. Power amplifiers for receiving low noise preamplifiers.

FIG. 5 is a schematic structural diagram of an optical distribution network according to an embodiment of the present invention. Figure 5, in this example, the light division The distribution network includes: a first coupler and N first signal processing modules, N is a natural number, and each first signal processing module constitutes a codec and dense wavelength division multiplexing demultiplexing link, including a second codec module And a third dense wavelength division multiplexer. Each of the second codec modules is configured to decode one of the multiple downlink signals output by the first coupler, and output the received uplink signal to the first coupler. Each third dense wavelength division multiplexer is configured to perform wavelength division multiplexing of the downlink signal decryption set output by the second codec module into a plurality of single wavelength downlink signals, and output to a corresponding plurality of optical network units, and The received multiple uplink signals are densely wavelength-division multiplexed and output to the second codec module. In this example, a third dense wavelength division multiplexer corresponds to M optical network units, where M is a natural number and M is not Greater than the number of available channels of the third Dense Wavelength Division Multiplexer. The second codec module implements the encoding function through a separate encoder, the decoding function is implemented by a separate decoder, or functions as a decoder by the codec when the encoded signal is input, and functions as an encoder when the original signal passes. . The number of second codec modules in this example corresponds to the number of first encoders and the number of first decoders. In this example, in order to make different encodings corresponding to different first signal processing modules, different second codec modules corresponding to different first signal processing modules are different. In this example, N first signal processing modules correspond to the first The second codec module is: the second codec module 1 to the second codec module N, and the corresponding third dense wavelength division multiplexer is the third dense wavelength division multiplexer 1 to the third dense wavelength division multiplexing N. In the embodiment of the present invention, the number of the first dense wavelength division multiplexers in the optical transmitting module in the OLT and the number of the second dense wavelength division multiplexers in the optical receiving module and the third dense wavelength division in the optical distribution network The number of multiplexers corresponds.

In the passive optical network system of the embodiment of the present invention, the OLT is connected to multiple optical network units through the optical distribution network, as shown in FIG. 5, each dense wavelength division multiplexer in the optical distribution network (the third dense wavelength division multiplexer) Each output port of the ) corresponds to an ONU, assuming that there are N dense wavelength division multiplexers in the optical distribution network, such as the third dense wavelength division multiplexer 1 to the third dense wavelength division multiplexer N in the figure. Each Dense Wavelength Division Multiplexer has M output ports, so that the total number of connectable optical network units becomes M x N. However, since the second codec module 1 to the second codec module N work in the same band Therefore, M x N users only use M wavelength channels, because different DWDMs are multiplexed with optical address codes, compared to pure OCDM-PON or DWDM-PON. The maximum number of users that can be accessed has increased significantly.

In this example, the second codec module is implemented as: a second codec. In the OCDMA-PON of this embodiment, each of the second codecs corresponds to a third dense wavelength division multiplexer, thereby corresponding to a group of ONUs, in this case, M ONUs. After the user's upstream data stream is modulated onto the optical carrier wave, it is multiplexed by the Dense Wavelength Division Multiplexer and then passed through the optical encoder, and the encoded user data is uplinked to the OLT through the coupler. In the OLT, the encoded data stream is inversely processed by the optical decoder through the optical decoder, that is, the inverse processing of the optical encoding process, to achieve optical decoding. The decoded data stream is then decomposed and demodulated by the decrypted set wavelength division multiplexing process of the dense wavelength division multiplexer, and uploaded to other core networks to realize mutual transmission of information between different PONs. The data stream transmitted from the core network is modulated at the OLT end, and then encoded by the first encoder, and then the encoded data stream is transmitted to each ONU through the Fibre Channel, and the data stream encoded by the ONU end passes through the light. The decoder implements decoding and recovers the transmitted data for the reception of user data. In other embodiments of the invention, the second codec module can also be implemented by separate encoders and decoders.

Briefly, the optical code division multiple access downlink data or downlink signal output by the optical line terminal enters the optical distribution network from port 2, and the optical code division multiple access signal is divided into N channels of DWDM multiplexed signals by the first coupler; each signal After decoding, the second codec is decoded by a third dense wavelength division multiplexer, and then the data is sent to each ONU. The uplink data or the uplink signal of each ONU is densely divided by the third dense wavelength division multiplexer. After multiplexing, it is encoded and coupled and then uplinked from port 2 to the OLT.

FIG. 6 is a schematic structural diagram of an ONU according to an embodiment of the present invention. In the embodiment of the present invention, the ONU can be greatly simplified due to the special ODN structure, and no codec module is needed in the ONU. As shown in FIG. 6, the ONU of this example mainly includes: a first circulator 601, a fourth coupler 602, an optical receiving link, and a reflective semiconductor optical amplifier (RSOA); in this example, the optical receiving link is composed of a photodetector and The judger consists of. The fourth coupler is configured to output the first signal processing module in the optical distribution network The downstream signal is split into two channels and output. As shown in FIG. 6, port 1 of the first circulator is connected to a channel port of the third dense wavelength division multiplexer in the ODN, and receives the OCDMA decoded signal. After the fourth coupler, the signal is divided into two paths, and one path is photoelectric. The detector and the decider recover the original data; the other can be injected into the reflective semiconductor optical amplifier for data erasure to provide a carrier light source for the uplink data. To achieve this function, the data in the OLT is modulated with a finite extinction ratio. The way, that is, the data '0' retains a part of the light. Preferably, the Mach-Zehnder modulator is used in the OLT to modulate the data onto the optical pulse, the data "0" corresponds to a low pulse; the data "1" corresponds to a high pulse. The RSOA is connected to the first circulator through the port 2 of the first circulator, and the reflected upstream data is input to the optical distribution network through the port 3 of the circulator.

The use of the gain saturation effect of the reflective semiconductor optical amplifier can achieve the erasure of the downlink data. The main working principle is: When the incident light intensity or gain coefficient is increased to cause the semiconductor optical amplifier to be saturated, the output is a constant continuous light. , can be used as the carrier of the uplink signal. It should be noted that when the extinction ratio of the downlink optical signal is large, it is difficult to achieve gain saturation when the optical signal is weak, so that the formed carrier is obviously not ideal, and excessively increasing the gain coefficient leads to a decrease in efficiency, so For the downlink signal, a suitable extinction ratio should be set to achieve the gain saturation while making full use of the downstream light source. The finite extinction ratio modulation technique can well satisfy this point, especially when the uplink and downlink rates are the same, this modulation mode will effectively improve the erasure effect of RSOA on downlink data.

In the OCDMA-PON system according to an embodiment of the present invention, a pulse modulation technique using a finite extinction ratio is used to electrically modulate digital data by using different "high and low" optical pulses, and a specific finite extinction ratio pulse modulation scheme is shown in FIG. When the bias voltage of the modulator and the voltage peak-to-peak value of the signal are set at appropriate positions, the electro-optic modulated laser pulse will exhibit the pattern of "high and low" pulses as shown. In this example, "1" and "0" in the original data are represented by pulses of different light intensities. According to the principle of OCDMA, the user is assigned a unique optical orthogonal code, so "1" and "0" in the data. Both are encoded by an OCDMA encoder. Specifically, after the downlink data enters the optical distribution network, after being decoded by the optical codec in the optical distribution network and restored to the "high and low" pulse form, after the dense wavelength division multiplexing, the first circulator is input to the optical receiving link. And reflective semiconductor optical amplifiers. The part of the signal input to the optical receiving link is converted into an electrical signal by the photodetector, and finally the clock is recovered by the decision circuit, and an appropriate threshold level D is set (as shown in FIG. 7), and the data above the threshold D is "1", the data below D is "0". The other part of the input ONU signal is erased by the amplification of the reflective semiconductor optical amplifier, and then used as the modulated light of the uplink data. In this example, preferably, the ONU uses a two-fiber bidirectional structure. Preferably, the connections between the above devices are all connected using a transmission fiber.

Preferably, the passive optical network system of the embodiment of the present invention further includes an optical terminal, and one or more optical network terminals are connected to one or more optical network units as specific users of the optical network unit.

In the embodiment of the present invention, in the channel, the data stream is modulated onto the optical carrier sent by the laser source, and the modulated data of the different wavelength channels are multiplexed by the dense wavelength division multiplexer, encoded by the optical encoder, and the like. The signals multiplexed and encoded by the Dense Wavelength Division Multiplexer are coupled together for transmission. According to the principle of OCDMA, the user is assigned a unique optical orthogonal code. In this example, not every ONU is assigned an address code, but each dense wavelength division multiplexer in the ODN is assigned a unique address code. . In this example, the encoding used is not limited to the optical orthogonal code, but may be other types of encoding, and it is only necessary to ensure that the encodings of different dense wavelength division multiplexers in the ODN are different. In this example, the second codec corresponding to the different dense wavelength division multiplexers in the ODN is different. After the encoded signal is recovered by the corresponding decoder in the ODN, the data is sent to different optical network units through different wavelength channels by demultiplexing of the dense wavelength division multiplexer. In the passive optical network of the embodiment of the present invention, no codec needs to be placed in the ONU, and the codec work is performed uniformly in the ODN.

The above-mentioned dense wavelength division multiplexer of the present invention is a dense wavelength division multiplexing demultiplexer capable of implementing dense wavelength division multiplexing and demultiplexing.

The passive optical network system of the embodiment of the present invention utilizes the spectrum cutting of the OCDMA codec Sex, such as the spectrum cutting feature of the SSFBG codec, simultaneously encodes and decodes multiple wavelength channels with one codec, which saves wavelength and codec on the basis of significantly increasing system capacity; each codec corresponds to In a wavelength multiplexer; the total number of users is equal to N (number of address codes) M (number of wavelengths corresponding to each address code); and further, by using a reflective semiconductor amplifier at the ONU end to erase downlink data as uplink data Providing a light source provides significant cost savings. The invention utilizes the dense wavelength division multiplexing technology, and the wavelength division is finer than the coarse wavelength division multiplexing technology, and the number of available channels is also more.

The technical solution of the embodiment of the present invention combines DWDM and traditional OCDMA-PON with a special ODN structure, which can greatly increase the number of users while saving the number of wavelengths and the number of codecs; 调制 modulation method with limited extinction ratio, The ONU uses RSOA to extract the upstream light source, which saves the light source at the ONU end and reduces the cost of the system design. The colorless nature of RSOA makes the ONU have a colorless structure, which is beneficial to reduce cost and improve reliability, and reduces the complexity of ONU construction. Degree, and because the ONU does not contain codecs, improves the maintainability of the ONU, making further integration of OCDMA-PON and WDM-PON possible; due to the application of code division multiple access technology, avoiding accurate measurement of OLT to ONU Distance problem; flexible rate, OCDMA technology can support high-speed data stream, its codec is transparent to the highest rate that can be supported and any rate below. At the same time, OCDMA technology is transparent to the protocol applied in the network.

The embodiment of the present invention further provides an optical distribution network device, including: a first coupler, configured to divide a downlink signal output by an optical line terminal into multiple channels and output the same, and combine the received multiple uplink signals into one channel and output the same. a plurality of first signal processing modules, each of the first signal processing modules being coupled to a port of the first coupler for decoding a downlink signal output by the first coupler, and decoding After the downlink signal decryption set is wavelength division multiplexed into a plurality of single-wavelength downlink signals, the uplink signal is received, and the received uplink signal is densely wavelength-division multiplexed and encoded, and the first coupling is performed after encoding. The output of the device is different when different first signal processing modules encode the received uplink signal. Preferably, in the optical distribution network device of the embodiment, the first signal processing module includes: a second codec module, configured to decode one of the multiple downlink signals output by the first coupler, and output the same, and The received uplink signal is encoded and output to the first coupler; the third dense wavelength division multiplexer is configured to perform wavelength division multiplexing of the downlink signal decryption set output by the second codec module into multiple After the wavelength downlink signal, the signal is output to the corresponding plurality of optical network units, and the received multiple uplink signals are densely wavelength-multiplexed and output to the second codec module.

Preferably, in the optical distribution network device of this embodiment, the second codec module comprises: an encoder, a decoder, and/or a codec based on a super-structured fiber Bragg grating.

The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It is considered as the scope of protection of the present invention.

Claims

Claim

An optical code division multiple access passive optical network system, characterized in that the system comprises a light path terminal and an optical distribution network;

The optical line terminal is configured to perform wavelength division multiplexing of the modulated modulated downlink data into one channel, and output the encoded one channel signal to the optical distribution network;

The optical distribution network is configured to decode the received signal and decrypt the set wavelength division multiplexing into multiple signals for output.

The optical CDMA passive optical network system according to claim 1, wherein the optical line terminal further comprises: an optical sending module, configured to modulate the multiple downlink data to a single wavelength a wavelength or wideband optical carrier, multiplexed modulated modulated downlink data into a signal by a dense wavelength division multiplexer, and encodes the dense wavelength division multiplexed signal output by the dense wavelength division multiplexer, and The encoded downlink signals are combined into one output, wherein the codes of the dense wavelength division multiplexing signals output by different dense wavelength division multiplexers are different;

The optical distribution network further includes: a first coupler and a plurality of first signal processing modules; wherein

a first coupler, configured to receive a downlink signal output by the optical transmitting module, divide the downlink signal into multiple channels, and output the same; and combine the received multiple uplink signals into one channel and output the same;

a plurality of first signal processing modules, each of the first signal processing modules being connected to a port of the first coupler for decoding a downlink signal output by the first coupler, and decoding The downlink signal decryption set is wavelength division multiplexed into a plurality of single wavelength downlink signals and output.

The optical CDMA passive optical network system according to claim 2, wherein the optical line terminal further comprises: an optical receiving module, configured to receive an uplink signal, and receive the received uplink signal Decoding, and decrypting the set after wavelength division multiplexing;

The plurality of first signal processing modules are configured to receive an uplink signal, perform the densely wavelength division multiplexed coding on the received uplink signal, and output the code to the The optical receiving module uses different encoding codes when encoding the received uplink signals by different first signal processing modules.

The optical CDMA passive optical network system according to claim 3, wherein the system further comprises: a plurality of optical network unit groups, each of the optical network unit groups and one of the a signal processing module is connected to receive the downlink signal output by the connected first signal processing module, and receive the uplink data, and output the uplink signal obtained by the modulated uplink data to the connected first signal processing. Module.

The optical code division multiple access passive optical network system according to claim 4, wherein the optical transmission module comprises a plurality of modulation and coding modules and a second coupler;

Each of the modulation and coding modules includes: a plurality of downlink modulation modules, a first Dense Wavelength Division Multiplexer, and a first encoder;

The optical CDMA passive optical network system according to claim 5, wherein the optical receiving module comprises a third coupler, a plurality of first decoders, and a plurality of second dense wave splitting User; among them,

a third coupler, configured to divide the uplink signal output by the optical distribution network into multiple channels and output the signals; a plurality of first decoders, each of the first decoders being connected to an output port of the third coupler for decoding one of the plurality of uplink signals output by the third coupler ;

The optical code division multiple access passive optical network system according to any one of claims 4 to 6, wherein the first signal processing module in the optical distribution network comprises a second codec module and a third dense wavelength division multiplexer; wherein

The optical CDMA passive optical network system according to any one of claims 4 to 6, which is

The optical network unit includes a fourth coupler, a light receiving link, and a reflective semiconductor optical amplifier; wherein

The reflective semiconductor optical amplifier is configured to receive another downlink signal output by the fourth coupler, and erase data in the downlink signal to serve as a carrier light source for uplink data.

The passive optical network system according to any one of claims 4 to 6, characterized in that the optical line terminal and/or the optical distribution network utilizes an encoder and/or code based on a super-structured fiber Bragg grating The decoder is used for encoding and/or encoding and decoding.

An optical distribution network device, comprising: a first coupler and a plurality of first signal processing modules; wherein

a first coupler, configured to divide the downlink signal output by the optical line terminal into multiple channels and output the same; and combine the received multiple uplink signals into one channel and output the same;

The optical distribution network device according to claim 10, wherein the first signal processing module comprises a second codec module and a third dense wavelength division multiplexer;

The optical distribution network device according to claim 11, wherein the second codec module comprises: an encoder, a decoder, and/or a codec based on a super-structured fiber Bragg grating.

An optical line terminal, comprising: an optical transmitting module and a light receiving module, wherein the optical transmitting module includes a plurality of modulation and coding modules and a second coupler; Each of the modulation and coding modules includes a plurality of downlink modulation modules, a first Dense Wavelength Division Multiplexer, and a first encoder;

The optical line terminal according to claim 13, wherein the light receiving module comprises a third coupler, a plurality of first decoders, and a plurality of second dense wavelength division multiplexers; wherein, the third a coupler, configured to divide the uplink signal output by the optical distribution network into multiple channels and output; a plurality of first decoders, each of the first decoders being connected to an output port of the third coupler, Decoding one output of the multiple uplink signals output by the third coupler;