WO2012100714A1

WO2012100714A1 - Orthogonal frequency division multiplexing passive optical network data transmission method and optical network unit

Info

Publication number: WO2012100714A1
Application number: PCT/CN2012/070588
Authority: WO
Inventors: 朱松林; 郭勇; 张伟良; 耿丹; 陈武
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-01-25
Filing date: 2012-01-19
Publication date: 2012-08-02
Also published as: CN102075823B; CN102075823A

Abstract

The present invention provides an optical network unit (ONU) comprising an optical reception processing unit and a downlink data reception processing unit. The optical reception processing unit receives an optical signal, converts the optical signal into a radio frequency signal, and transmits the radio frequency signal to the downlink data reception processing unit. The downlink data reception processing unit performs wave filtering, demodulation, and demapping on the radio frequency signal, and outputs sub-band data corresponding to the ONU. The present invention also provides a data transmission method. In the present invention, because each ONU only receives current and specific sub-band data, the speed rates required of components therein are reduced, which in turn reduces cost.

Description

Orthogonal frequency division multiplexing passive optical network data transmission method and optical network unit

Technical field

The present invention relates to a communication system, and more particularly to an OFDM (Orthogonal Frequency Division Multiplexing) PON (Passive Optical Network) system data transmission method and an optical network unit.

Background technique

The wide application of Orthogonal Frequency Division Multiplexing (OFDM) technology has injected new vitality into optical communication. OFDM technology dynamically allocates high-speed serial bit information to sub-carriers whose spectra are orthogonal to each other. At the same time, each sub-carrier uses high-order modulation modes such as Quadrature Amplitude Modulation (QAM), which effectively improves the performance. The spectral efficiency of the system. More importantly, the optical signal duration of the optical OFDM symbol on each subcarrier is relatively increased, coupled with the use of cyclic prefix technology, thereby effectively overcoming the chromatic dispersion and polarization mode dispersion in the fiber link. Crosstalk between codes. OFDM PON combines OFDM technology with PON technology, which has many advantages, including: (1) Dynamic allocation of each subcarrier resource: Optical OFDM technology can be used by simple fast Fourier according to the frequency band environment and application scenarios. A transform (FFT) algorithm dynamically modulates the number of bits carried by each subcarrier, the modulation format applied to each subcarrier, and the power of each subcarrier. (2) Convergence access combining wired and wireless can be realized. As a mature technology in wireless communication, OFDM is widely used in WiMax (World Interoperability for Microwave Access), WiFi (Wireless Fidelity, Wireless Protection). True) and LTE (Long Term Evolution) framework. Therefore, the OFDM signal is carried by the OFDM, and the optical network unit (ONU) can realize the convergence access of the wired signal and the wireless signal. (3) The spectrum efficiency of the access network is effectively improved: Due to the orthogonality between the subcarriers of the optical OFDM signal, it not only allows the spectrum of each subcarrier to overlap with each other, but also can be performed by a simple constellation mapping algorithm. High-order modulation such as 16QAM, 8PSK (8 Phase Shift Keying) is implemented on the subcarriers. (4) Excellent anti-dispersion makes it smoothly evolve to the ultra-long-distance access network: In theory, the optical OFDM signal is completely unaffected by the chromatic dispersion and polarization mode dispersion in the link. Therefore, OFDM-PON can realize optical access network to be super long A smooth transition from the access network. (5) Transferring the cost pressure of the optical device to the electric device, the cost of the high-speed optical device is high due to the integration degree and manufacturing process of the optical device, and currently the optical module and the optical device above 10G are very stressful for the access network. . The application of OFDM technology can transfer the cost pressure of optical devices to inexpensive digital signal processing (DSP). The high-speed digital signal processing and the integration and cost advantages of high-frequency microwave devices provide a fast path for access networks to develop and popularize at higher speeds. The proposed OFDM PON solution is mainly used in single-band (Single-band). The network topology is shown in Figure 1, including Optical Line Terminal (OLT), Optical Network Unit (ONU), and Optical Distribution Network. (Optical Distribution Network, ODN). The transmitter structure is as shown in FIG. 2, and includes a data transmission processing unit and an optical transmission processing unit (the laser shown in FIG. 2). The data transmission processing unit includes a digital signal processing (DSP) module, a digital-to-analog conversion module, an IQ modulation, and an Frequency conversion module. The DSP module includes a serial/parallel conversion module, a QAM mapping module, and an inverse fast Fourier transform (IFFT) module. After the high-speed serial data from the upper processing unit enters the DSP module, serial/parallel conversion is first performed to convert the high-speed serial data into multiple parallel low-speed data, and each low-speed data corresponds to one sub-carrier. After serial/parallel conversion, each data is QAM mapped to form a complex point of the constellation, and each complex point is modulated on one subcarrier. After IFFT, the multiplexed parallel data is modulated on the corresponding subcarriers to complete the frequency domain to time domain conversion, and the digital OFDM baseband signal is output, which is divided into two components: In-phase and Quadrature. Corresponds to the real and imaginary parts of the symbol. The digital-to-analog conversion module converts the digital OFDM baseband signal into an analog OFDM baseband signal and sends it to the IQ modulation and up-conversion module. The IQ modulation and up-conversion module separately modulates the in-phase and quadrature components onto the RF carrier to complete the RF modulation. Finally, the RF signal is modulated by the optical transmission processing unit onto the optical carrier and sent to the optical fiber and transmitted to the opposite end. The receiver structure is as shown in FIG. 3, and includes a light receiving processing unit (photodetector shown in FIG. 3) and a data receiving processing unit including a down-conversion and IQ demodulation module, an analog-to-digital conversion module, and a digital Signal Processing (DSP) module. The DSP module includes a Fast Fourier Transform (FFT) module, a QAM demapping module, and a parallel/serial conversion module. The signal from the optical fiber is converted into an analog radio frequency electrical signal by a light receiving processing unit. The analog RF signal is subjected to down-conversion and IQ demodulation to form an analog OFDM baseband signal, which is divided into two components: in-phase and quadrature. The analog OFDM baseband signal is converted into a digital OFDM baseband signal through an analog-to-digital conversion module and sent to the DSP block for processing. The DSP module first performs fast Fourier transform on the digital OFDM baseband signal to complete the time domain to the frequency domain. Converting, recovering the data symbols modulated on each subcarrier, and then recovering the high speed data output to the upper layer receiving processing unit through QAM demapping and parallel/serial conversion. In the downlink direction (OLT ONU), the entire downlink data band is OFDM modulated as a single-band, and is divided into one or more orthogonal sub-carriers. The OFDM-modulated data is transmitted to all ONUs through ODN broadcast, and each ONU must receive OFDM data in the entire frequency band, and then demodulate and receive the sub-carriers allocated to the ONU. This single-band mode requires extremely high requirements for the digital-to-analog conversion module at the transmitting end and the analog-to-digital conversion module at the receiving end. For the downlink rate of 40G bps, even if 16QAM modulation is used, at least 10G bps or more digital-to-analog is required. The analog-to-digital processing module currently requires a high cost of the device. On the other hand, in the uplink direction, since the uplink OFDM signals of the ONUs need to be synthesized in the optical power splitter, in order to avoid signal collision and mutual interference, it is necessary to isolate the uplink signals of the ONUs by using wavelength division multiplexing (WDM). . In this way, not only is the cost higher, but also the structure of the original ODN needs to be changed, and the ONU cannot achieve colorlessness.

Therefore, the current single-band OFDM PON scheme has major problems in terms of device cost, ODN compatibility, and ONU colorlessness.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an orthogonal frequency division multiplexing passive optical network data transmission method and an optical network unit to reduce costs. In order to solve the above problems, the present invention provides an optical network unit, the optical network unit

(ONU) includes a light receiving processing unit and a downlink data receiving processing unit, wherein: the light receiving processing unit is configured to: receive an optical signal, convert the received optical signal into a radio frequency signal, and send the signal to the downlink data receiving processing unit The downlink data receiving processing unit is configured to filter, demodulate and demap the radio frequency signal, and output data of the sub-band corresponding to the ONU. The downlink data receiving and processing unit includes a band pass filter module, a down conversion and IQ demodulation module, an analog to digital conversion module, and a digital signal processing module, where: the band pass filter module is configured to: perform the radio frequency signal Filtering, filtering signals other than the sub-bands corresponding to the ONUs, and And outputting the filtered signal to the down-conversion and IQ demodulation module; the down-conversion and IQ demodulation module is configured to: down-convert the filtered signal into baseband data, demodulate the baseband data, and output an analog signal To the analog to digital conversion module; the analog to digital conversion module is configured to convert the analog signal into a digital signal and output to the digital signal processing module; the digital signal processing module is configured to perform fast Fourier transform on the digital signal Reconciliation mapping. The filter parameters of the band pass filter module and the localization parameters of the down conversion and IQ demodulation module are fixedly configured. The optical network unit further includes an ONU control unit, where: the ONU control unit is configured to: receive a control protocol command sent by the optical line terminal, and configure the configuration carried in the control protocol command to the sub-band of the ONU Sending the parameter to the downlink data receiving processing unit; the downlink data receiving processing unit is further configured to: adjust a filtering parameter of the band pass filter module according to the wavelet band parameter, and/or set the The local oscillator parameters of the frequency conversion and the IQ demodulation module are such that the sub-bands corresponding to the ONUs are sub-bands allocated to the ONUs by the optical line terminals. The optical network unit further includes an uplink data transmission processing unit and an optical burst transmission unit, where: the uplink data transmission processing unit is configured to: map and modulate the data to be transmitted, and output the radio frequency signal to the optical burst transmission unit; The optical burst transmitting unit is configured to convert the radio frequency signal into an optical signal for transmission on a time slot designated by the optical line terminal. The present invention also provides a data transmission method for an orthogonal frequency division multiplexing passive optical network system, comprising: an optical network unit (ONU) receiving an optical signal, converting the received optical signal into a radio frequency signal; and the ONU pair The radio frequency signal is filtered, demodulated and demapped, and the data of the sub-band corresponding to the ONU is output. The step of filtering, demodulating, and demapping the radio frequency signal includes: filtering the radio frequency signal, filtering a signal other than the sub-band corresponding to the ONU, and outputting a filtered signal; and down-converting the filtered signal to Baseband data, demodulating the baseband data, and outputting an analog signal; converting the analog signal into a digital signal; and performing fast Fourier transform and demapping on the digital signal. The sub-wave band corresponding to the ONU is fixed. The method further includes: receiving a control protocol command sent by the optical line terminal, and adjusting a filter parameter of the bandpass filter module of the ONU according to a configuration carried in the control protocol command to a wavelet component parameter of the ONU, And/or, setting the down conversion of the ONU and the local oscillator band of the IQ demodulation module. And the method further includes: mapping, and modulating, by the ONU, the data to be transmitted, obtaining a radio frequency signal, and converting the radio frequency signal into an optical signal, and transmitting the time slot specified by the optical line terminal.

In the present invention, since each ONU receives only the current specific sub-band data, the required device rate is lowered and the cost is also reduced. In addition, the present invention also implements the colorlessness requirement of the ONU by adjusting the bandpass filter or the down-conversion and the local oscillator of the IQ demodulation module through a control protocol.

1 is a network topology; FIG. 2 is a block diagram of a conventional single-band transmitter; FIG. 3 is a block diagram of a conventional single-band receiver; FIG. 4 is a OLT transmitter structure of a multi-band OFDM PON system. Figure 5 is a multi-band OFDM PON system ONU receiver structure; Figure 6 is a multi-band OFDM PON system diagram; Figure 7 is a multi-band OFDM PON downlink frequency division diagram;

Figure 8 is a schematic diagram of the uplink spectrum.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a multi-band OFDM PON scheme, which reduces OFDM PON by combining frequency division multiplexing (FDM) and orthogonal frequency division multiplexing (OFDM) techniques. Deployment costs. In the downlink direction, the entire transmission band is divided into one according to requirements in a fixed manner or a variable manner. One or more wavelet bands. Each sub-band is divided into one or more orthogonal sub-carriers, and each sub-band is independently OFDM-modulated. Multiple ONUs can share a subband bandwidth and implement dynamic bandwidth sharing through subcarrier allocation or statistical multiplexing. The OLT transmitter structure is shown in FIG. 4. The OLT is divided into a plurality of parallel downlink data transmission processing units according to the number of wavelet bands, and each downlink data transmission processing unit processes one wavelet band data. The high-speed data from the upper processing unit is subjected to serial/parallel conversion in the wavelet band, and the data transmitted to each sub-band is respectively associated with the corresponding data transmission processing unit. In each transmission processing unit, serial/parallel conversion is performed on the basis of subcarriers. The OFDM subcarrier modulation is performed by QAM mapping and inverse Fourier transform (IFFT) to form a digital baseband OFDM signal. In the digital to analog conversion module, the in-phase and quadrature components of the digital baseband OFDM signal are converted to in-phase and quadrature components of the analog baseband, respectively. The analog baseband OFDM signal is modulated by the IQ modulation and upconversion module onto the assigned RF frequency. The OFDM radio frequency modulated signals of all sub-bands are synthesized by the combiner module, and then sent to the optical transmission processing unit for modulation onto the optical carrier for transmission through the optical fiber. The structure of the ONU receiver in the downlink direction is as shown in FIG. 5. The photodetection receiving processing unit demodulates the entire downlink spectrum and converts it into an electrical signal. The bandpass filter filters the wavelet band data, and performs down-conversion and IQ demodulation to output an analog OFDM baseband signal, including two components, in-phase and quadrature. The analog OFDM baseband signal is converted to a digital OFDM baseband signal by an analog to digital conversion module. The DSP module performs FFT and QAM demapping operations on the digital OFDM baseband signal, and finally performs current subband OFDM demodulation through parallel/serial conversion. The ONU can be configured to set the fixed parameters of the receiver's bandpass filter and RF (Radio Frequency) local oscillator to enable the ONU to operate in a specific subband; or to dynamically filter the bandpass filter and RF local oscillator parameters. Configure to dynamically configure the subbands of the ONU's operation. The relevant parameters of the receiver processing unit can be dynamically adjusted according to OLT protocol instructions to be able to receive specific sub-band data. The multi-band OFDM PON system uses a multi-band multiplexing technique in the downlink direction, and uses a frequency division multiplexing (FDM) technique to divide the downlink frequency band into a plurality of sub-bands, each of which is independent. Perform OFDM modulation. The bandwidth of each sub-band can be shared by multiple ONUs at the same time. Multiple ONUs can work in the same downlink sub-band simultaneously, and bandwidth sharing is implemented by sub-carrier allocation or statistical multiplexing. The ONU includes an ONU control unit, a light receiving processing unit, and a downlink data receiving processing unit, where: the ONU control unit is configured to receive a protocol command from the OLT control unit in real time, and send the control parameter to the downlink data receiving process in real time. The unit includes: receiving a control protocol command sent by the optical line terminal, and transmitting, to the downlink data receiving and processing unit, a sub-band parameter of the configuration carried in the control protocol command to the ONU; The device is configured to: receive a downlink optical signal, convert it into a radio frequency modulated electrical signal, which is referred to as a radio frequency signal, and send the signal to the downlink data receiving and processing unit; wherein, the optical receiving processing unit may be a photodetector; and the downlink data receiving and processing unit The method is configured to: receive the radio frequency signal, filter, demodulate and demap the radio frequency signal, and output data of a sub-band corresponding to the ONU. The sub-bands corresponding to the ONUs may be fixedly configured or dynamically configured. When the filter parameters of the band pass filter module and the localization parameters of the down-conversion and IQ demodulation module are fixedly configured, the sub-wave band corresponding to the ONU is fixedly configured. When the filter parameters of the band pass filter module and/or the local oscillator parameters of the down-conversion and IQ demodulation module are adjustable, the sub-bands corresponding to the ONU can be dynamically configured. The downlink data receiving and processing unit includes: a band pass filter module, a down conversion and IQ demodulation module, an analog to digital conversion module, and a digital signal processing module, wherein: the band pass filter unit is configured to perform the radio frequency signal Filtering, filtering the out-of-band signal corresponding to the ONU, and outputting the filtered signal to the down-conversion and IQ demodulation module; the down-conversion and IQ demodulation module is configured to down-convert the filtered signal to a baseband Data, demodulating, outputting an analog signal to an analog-to-digital conversion module; the analog-to-digital conversion module is configured to convert the analog signal into a digital signal and output the digital signal processing module; the digital signal processing module is configured to Fast Fourier transform and demapping of the digital signal. The downlink data receiving and processing unit may set a filter parameter of the band pass filter unit according to a wavelet band parameter sent by the ONU control unit, and/or set the down-conversion and IQ demodulation mode. The local oscillator parameter of the block is such that the sub-band corresponding to the ONU is a sub-band of the optical line terminal configured to the ONU. Each ONU can only receive and process data for a particular subband. The downlink data receiving and processing unit may adjust the center frequency of the bandpass filter module to the center frequency of the subband allocated by the ONU according to the parameter sent by the ONU control unit, so that the data of the specified subband can pass the bandpass filter. The module is sent to the next processing unit, and the data outside the specified subband is filtered out. The down-conversion and IQ demodulation module includes a local oscillator and an IQ mixer demodulator module. The downlink data receiving and processing unit may adjust the center frequency of the sub-band allocated by the local oscillator to the ONU according to the parameter sent by the ONU control unit. The adjusted IQ mixer demodulator module can remove the electrical carrier output analog baseband OFDM signal and send it to the analog to digital conversion module for processing. The analog baseband OFDM signal output by the IQ mixer demodulator module includes in-phase and quadrature components. The analog-to-digital conversion module of the ONU is configured to convert the analog baseband OFDM signal output by the down-conversion and IQ demodulation module into a digital baseband OFDM signal and send it to the digital signal processing module. Digital baseband OFDM signals include in-phase and quadrature components. The digital signal processing module of the ONU includes a fast Fourier transform (FFT) processing module,

QAM demapping processing module and parallel/serial conversion processing module.

Uplink direction: In the uplink direction, uplink multiple access can be implemented using a time division multiple access (TDMA) method, or combined with orthogonal frequency division multiple access (OFDMA) or wavelength division multiplexing (WDMA) or Multiple access technology such as code division multiple access (CDMA). The time division multiple access means that each ONU is sequentially transmitted at a time specified by the OLT during uplink transmission, thereby avoiding collision of uplink data. Each ONU must operate under a uniform clock and undergo strict ranging and synchronization to ensure that data can be sent in the correct time slot. In the time division multiple access mode, each ONU uses a burst transmitter to implement time division multiple access, and the ONU has colorlessness. The combination of TDMA and OFDMA means that the ONU can perform OFDM modulation, and multiple ONUs can be based on OFDMA multiple access first, and further based on TDMA on each subcarrier. The combination of TDMA and WDMA means that multiple ONUs can use the same upstream wavelength and further use TDMA. The optical network unit further includes an uplink data transmission processing unit and an optical burst transmission unit, wherein: the uplink data transmission processing unit is configured to map and modulate the data to be transmitted, and output the radio frequency signal to the optical burst transmission unit; The optical burst transmitting unit is configured to convert the radio frequency signal into an optical signal for transmission on a time slot designated by the optical line terminal. The invention provides a data transmission method for an orthogonal frequency division multiplexing passive optical network system, comprising: an optical network unit (ONU) receiving an optical signal, converting the same into a radio frequency signal; and filtering and demodulating the radio frequency signal The solution map outputs data of the wavelet band corresponding to the ONU. The filtering, demodulating, and de-mapping the radio frequency signal includes: filtering the radio frequency signal, filtering a signal outside the sub-band corresponding to the ONU, and outputting a filtering signal;

Downsampling the filtered signal into baseband data, demodulating, outputting an analog signal; converting the analog signal to a digital signal; and performing fast Fourier transform and demapping on the digital signal. The sub-wave band corresponding to the ONU is fixed. The method further includes: receiving a control protocol command sent by the optical line terminal, and adjusting a filtering of the bandpass filter module of the ONU according to a configuration carried in the control protocol command to a wavelet component parameter of the ONU Parameters, and/or, setting the downconversion of the ONU and the wavelet band of the IQ demodulation module.

The ONU further maps and modulates the data to be transmitted, obtains a radio frequency signal, converts the radio frequency signal into an optical signal, and transmits the time slot specified by the optical line terminal. Embodiment System Architecture As shown in FIG. 6, the OLT transmitter includes an OLT control unit and a plurality of parallel downlink data transmission processing units, and each downlink data transmission processing unit correspondingly processes data of one sub-band. The OLT control unit performs parameter configuration and management on each module of each parallel downlink data transmission processing unit of the OLT through an internal control interface, and the OLT control unit performs real-time communication with each ONU control unit through a control protocol command, and the control protocol command passes through the OFDM PON. The public communication channel is sent to each ONU in real time. After receiving the real-time control protocol command sent by the OLT control unit to the ONU, the ONU control unit sends the operation content and parameters to each module of the ONU downlink data receiving and processing unit in real time to realize dynamic real-time control of the ONU. The entire downlink frequency band is F, and the number of wavelet bands is M. In fixed distribution mode, the width of each subband is FM. The radio frequency center frequency f _{c of} each sub-band is separated by F/M. One or more subcarriers are divided in each subband, and OFDM modulation is performed independently. Figure 7 shows the case of five ONUs, where M = 4, where ONU4 and ONU5 share the subcarrier bandwidth in statistical multiplexing. Within each subband, one or more orthogonal subcarriers are divided, and each subband is independently OFDM modulated. Multiple ONUs can share the same subband bandwidth. The OLT dynamically allocates different numbers of subcarriers to each ONU according to user requirements and band quality, as shown in Figure 7 ONUl-ONU4(5). It is also possible to allocate the same subcarriers for multiple ONUs and implement bandwidth sharing by statistical multiplexing, such as ONU4 and ONU5. In the downlink direction, the OLT is divided into M parallel downlink data transmission processing units according to the number of wavelet bands, and each downlink data transmission processing unit processes one wavelet band data, as shown in FIG. 6. The high-speed data from the upper processing unit is subjected to M-way serial/parallel conversion in the wavelet band, and the data transmitted to each sub-band is respectively corresponding to the corresponding downlink data transmission processing unit. In each downlink data transmission processing unit, serial/parallel conversion is performed based on the subcarrier N. The OFDM subcarrier modulation is performed through m-QAM mapping and N-point IFFT to form a digital baseband OFDM signal. In the digital-to-analog conversion unit, the in-phase and quadrature components of the digital baseband OFDM signal are converted into analog in-phase and analog quadrature components, respectively, to obtain an analog baseband OFDM signal. The analog baseband OFDM signal is modulated by the IQ modulation and the up-conversion unit to the RF frequency corresponding to the current sub-band. OFDM radio frequency modulation for all M wavelet bands After the signal is synthesized, it is modulated into an optical carrier and transmitted through the optical fiber. In the downstream direction, the ONU is initialized with the factory default state, and each unit module operates on the default common management channel, such as the first subcarrier of the first subband. The bandpass filter module of the ONU works by default in the subband of the common management channel. The ONU downlink data receiving and processing unit receives the subcarrier where the common management channel is located, and extracts the OLT control protocol broadcast message and sends it to the ONU control unit. When the ONU is initialized in the downlink direction, it operates in the default common management channel, and the OLT control unit establishes a management connection with the ONU control unit through the common management channel. Through the management connection, the OLT control unit can send control protocol commands to the ONU control unit to complete the initialization, registration, and authentication process of the ONU. After the ONU completes the initialization and registration process in the downlink direction, the OLT control unit sends a control protocol command to the ONU control unit through the management connection, and assigns the wavelet band parameters to the registered ONU, including the wavelet band number c, the band center frequency f _e and the wavelet. With information such as the management channel number. After receiving the OLT control protocol command, the ONU control unit extracts the communication channel parameters and sends them to each module of the downlink data receiving and processing unit. First, adjust the center frequency of the bandpass filter module to the center frequency of the wavelet band allocated by the ONU, and then adjust the subcarrier data of the ONU receiving subband management channel. After the adjustment is completed, the radio frequency electric signal formed by the optical signal detected by the photodetector is filtered by the band pass filter, and only the specific sub-band signal allocated to the ONU can enter the downstream data receiving processing unit of the ONU for further processing. After the ONU adjusts the subband of the receiver to the OLT in the downlink direction, the OLT control unit establishes a normal management connection between the subband management channel and the ONU control unit. The OLT control unit can further control the communication of the ONU through a normal management connection. If the normal management connection channel fails to be established, the OLT cannot receive the return message from the ONU within the specified time, and the ONU cannot obtain the control protocol message of the OLT. The two parties return to the public communication channel and perform the initialization process again. The downstream direction ONU adjusts the bandpass filter module so that only the specific subband signals assigned to the ONU can enter the ONU receiver for further processing. If the tunable bandpass filter is not available or the bandpass filter is not adjustable, the subband filtering can be performed by adjusting the downconversion and IQ demodulation module. The local oscillator required for the down-conversion and IQ demodulation module is adjustable, and the local oscillator is adjusted. The frequency is the center frequency f _{e of the} wavelet band, so that the down-conversion and IQ demodulation module can demodulate the data of the specific sub-band, demodulate and remove the electric carrier, and output the analog baseband OFDM signal. After the ONU in the downlink direction completes the receiver adjustment and alignment of the allocated sub-bands, it can receive the specific allocated downlink sub-band data, and complete OFDM demodulation, as shown in FIG. The photodetector demodulates the entire downlink spectrum, and the band pass filter module or the down-conversion and IQ demodulation module realizes filtering of the sub-band data, and outputs the analog OFDM baseband signal, including the in-phase and quadrature components. Converted to a digital OFDM baseband signal by an analog to digital conversion module. The DSP module performs FFT and QAM demapping operations on the digital OFDM baseband signal, and finally performs current subband OFDM demodulation through parallel/serial conversion. Since each ONU receives only the current specific subband data, the required device speed is reduced and the cost is reduced. The colorlessness requirement of the ONU is achieved by adjusting the bandpass filter or downconversion and the local oscillator of the IQ demodulation module through the control protocol. In the uplink direction, Time Division Multiple Access (TDMA) is used. As shown in FIG. 7, ONU 1 - ONU N respectively transmit data in different uplink times. In the uplink direction, the transmission bandwidth can be extended by OFDM modulation in the transmission time of each ONU, as shown in FIG. In the uplink direction, if the TDM+OFDM modulation mode is used, the ONU performs OFDM modulation on the uplink data in the entire uplink frequency band, and transmits the uplink data according to the time slot specified by the OLT, as shown in FIG. The data from the upper layer data processing unit is first N-string/parallel converted according to the sub-carriers, and then converted into a digital baseband OFDM signal by m-QAM mapping and N-point IFFT. In the digital to analog conversion module, the digital baseband OFDM signal is converted into an analog baseband OFDM signal. The OFDM radio frequency modulation is completed by IQ modulation and up-conversion modulation, and finally the radio frequency OFDM signal is transmitted through the optical burst transmission unit in a specified time slot. Since the ONU uplink transmission is based on time division multiple access, it is well compatible with the original ODN network and maintains the colorlessness of the ONU. The uplink OLT internal optical burst receiving unit receives uplink burst data from different ONUs. If the OFDM modulation technique is used in the uplink direction, the data of the optical burst receiving unit of the OLT is subjected to radio frequency down conversion and IQ demodulation by the down-conversion and IQ demodulation module, and the analog OFDM baseband signal is output, including the in-phase and quadrature components. After the analog-to-digital conversion module, the analog OFDM baseband signal is converted into a digital OFDM baseband signal, including in-phase and quadrature components. Digital baseband OFDM signal in number The word signal processing module is demapped by N-point FFT and m-QAM, and finally OFDM demodulation is completed by parallel/serial conversion, and output to the upper layer data processing unit. Since the uplink is based on time division multiple access technology, the OLT uses an optical burst receiving unit, which avoids the use of wavelength division and frequency division devices, maintains compatibility with the original ODN and reduces implementation costs.

Industrial Applicability Compared with the prior art, in the present invention, since each ONU receives only the current specific sub-band data, the required device rate is lowered and the cost is also reduced. In addition, the present invention also implements the colorlessness requirement of the ONU by adjusting the bandpass filter or the downconversion of the bandpass and the local oscillator of the IQ demodulation module by the control protocol.

Claims

Claim

An optical network unit (ONU), comprising: a light receiving processing unit and a downlink data receiving processing unit, wherein: the light receiving processing unit is configured to: receive an optical signal, convert the received optical signal into a radio frequency signal, and send Up to the downlink data receiving processing unit; the downlink data receiving processing unit is configured to filter, demodulate and demap the radio frequency signal, and output data of the sub-band corresponding to the ONU.

The optical network unit according to claim 1, wherein the downlink data receiving processing unit comprises a band pass filter module, a down conversion and IQ demodulation module, an analog to digital conversion module, and a digital signal processing module, wherein: The band pass filter module is configured to: filter the radio frequency signal, filter a signal other than the sub-band corresponding to the ONU, and output a filtered signal to the down-conversion and IQ demodulation module; And the IQ demodulation module is configured to: downconvert the filtered signal to baseband data, demodulate the baseband data, and output an analog signal to an analog to digital conversion module; the analog to digital conversion module is configured to perform the simulation The signal is converted to a digital signal and output to the digital signal processing module; the digital signal processing module is configured to perform fast Fourier transform and demapping on the digital signal.

The optical network unit according to claim 2, wherein the filter parameter of the band pass filter module and the local oscillator parameter of the down-conversion and IQ demodulation module are fixedly configured.

The optical network unit of claim 2, further comprising an ONU control unit, wherein: the ONU control unit is configured to: receive a control protocol command sent by the optical line terminal, and configure the command carried in the control protocol command Transmitting the wavelet band parameters of the ONU to the downlink data receiving processing unit; the downlink data receiving processing unit is further configured to: adjust a filtering parameter of the band pass filter module according to the wavelet band parameter, And/or, setting the local oscillator of the down conversion and IQ demodulation module Wave band.

The optical network unit of claim 1, further comprising an uplink data transmission processing unit and an optical burst transmission unit, wherein: the uplink data transmission processing unit is configured to: map and modulate the data to be transmitted, and output the radio frequency signal to The optical burst transmitting unit is configured to convert the radio frequency signal into an optical signal and transmit the time slot specified by the optical line terminal.

6. A data transmission method for an orthogonal frequency division multiplexing passive optical network system, comprising: an optical network unit (ONU) receiving an optical signal, converting the received optical signal into a radio frequency signal; and the ONU pairing the radio frequency The signal is filtered, demodulated and demapped, and the data of the subband corresponding to the ONU is output.

7. The method according to claim 6, wherein the step of filtering, demodulating and demapping the radio frequency signal comprises: filtering the radio frequency signal, filtering a signal other than the sub-band corresponding to the ONU Outputting a filtered signal; down-converting the filtered signal to baseband data, demodulating the baseband data, and outputting an analog signal; converting the analog signal into a digital signal; and performing fast Fourier transform on the digital signal Reconciliation mapping.

8. The method according to claim 6, wherein the sub-bands corresponding to the ONU are fixed.

The method of claim 6, further comprising: receiving a control protocol command sent by the optical line terminal, and adjusting the band of the ONU to the sub-band parameters of the ONU according to the configuration carried in the control protocol command Filtering parameters of the pass filter module, and/or setting a downconversion of the ONU and a local oscillator parameter of the IQ demodulation module, such that The sub-band corresponding to the ONU is a sub-band of the optical line terminal that is allocated to the ONU.

10. The method of claim 6 further comprising:

The ONU maps and modulates the transmitted data to obtain a radio frequency signal, and converts the radio frequency signal into an optical signal, which is transmitted on a time slot designated by the optical line terminal.