CN105578316B - OCDMA and OFDM mixed passive optical network system - Google Patents
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Abstract
Description
技术领域technical field
本发明属于光纤通信技术领域，具体涉及一种OCDMA(正交频分复用)和OFDM(光码分多址)混合的无源光网络系统。The invention belongs to the technical field of optical fiber communication, and in particular relates to a passive optical network system mixed with OCDMA (orthogonal frequency division multiplexing) and OFDM (optical code division multiple access).
背景技术Background technique
随着各种新业务的出现和人们日益增长的带宽需求，“最后一公里”已经成为接入网的瓶颈。作为解决宽带光接入需求的最好方法，无源光网络(PON)技术以带宽高、成本低、结构简单、可靠性好等优点，已经在全球范围内的相当多地区有了一定规模的实施。当前的PON技术中，有很多种实现方法，主要包括波分复用无源光网络(WDM-PON)、时分复用无源光网络(TDM-PON)、EPON(以太网无源光网络)和GPON(吉比特无源光网络)等实现方案。With the emergence of various new services and people's increasing demand for bandwidth, "the last mile" has become the bottleneck of the access network. As the best way to solve the demand for broadband optical access, the passive optical network (PON) technology has the advantages of high bandwidth, low cost, simple structure, and good reliability. implement. In the current PON technology, there are many implementation methods, mainly including wavelength division multiplexing passive optical network (WDM-PON), time division multiplexing passive optical network (TDM-PON), EPON (Ethernet passive optical network) And GPON (Gigabit Passive Optical Network) and other implementation schemes.
WDM-PON虽然可以提供较高的带宽容量，但是需要通过追加波长的方法来增加用户的数量。TDM-PON技术已经逐渐成熟而且已经进入商业阶段，但由于在TDM-PON采用时分复用，突发接收的传输方式，这些特点决定了只靠提高设备性能不能满足更高的速率要求，比如40Gb/s或者更高速率的无源光网络。这主要是因为在TDM-PON中器件成本和光纤色散等因素，限制了系统传输的速率。现阶段10Gbit/s的EPON和GPON技术标准已经出台，各大运营商也推出了相应的产品。40Gbit/s的GPON乃至100Gbit/s的EPON技术也组件被研究领域和工业界广泛关注。但是，由于目前的接入网是多种业务网络的融合，以及各种新业务的出现。目前的EPON和GPON技术也逐渐变得难以维持，需要寻找更佳的解决方案。Although WDM-PON can provide higher bandwidth capacity, it needs to increase the number of users by adding wavelengths. TDM-PON technology has gradually matured and entered the commercial stage, but because TDM-PON adopts time division multiplexing and burst reception transmission mode, these characteristics determine that only by improving equipment performance cannot meet higher rate requirements, such as 40Gb /s or higher rate passive optical network. This is mainly because factors such as device cost and fiber dispersion limit the transmission rate of the system in TDM-PON. At this stage, 10Gbit/s EPON and GPON technical standards have been issued, and major operators have also launched corresponding products. The GPON of 40Gbit/s and even the EPON technology of 100Gbit/s are also widely concerned by the research field and the industry. However, because the current access network is the integration of multiple service networks, and the emergence of various new services. The current EPON and GPON technologies have gradually become difficult to maintain, and a better solution needs to be found.
发明内容Contents of the invention
本发明所要解决的技术问题是现有PON的实现方法难以满足日益增长的多种业务网络需求的不足，提供一种OCDMA和OFDM混合的无源光网络系统。The technical problem to be solved by the present invention is that it is difficult for the existing PON implementation method to meet the growing requirements of various service networks, and a passive optical network system mixed with OCDMA and OFDM is provided.
为解决上述问题，本发明是通过以下技术方案实现的：In order to solve the above problems, the present invention is achieved through the following technical solutions:
一种OCDMA和OFDM混合的无源光网络系统，包括发送端和接收端，发送端和接收端通过光纤连接。所述发送端由OCDMA编码模块、OFDM信号生成器和发送外调制器组成；输入数据送入OFDM信号生成器的输入端，OFDM信号生成器的输出端连接发送外调制器的一个输入端，OCDMA编码模块的输出端连接发送外调制器的另一个输入端，发送外调制器的输出端与光纤的一端连接。所述接收端由OCDMA解码模块、OFDM信号解码器和接收外调制器组成；光纤的另一端连接接收外调制器的一个输入端，OCDMA解码模块的输出端连接接收外调制器的另一个输入端，接收外调制器的输出端与OFDM信号解码器的输入端连接，OFDM信号解码器的输出端送出输出数据。A passive optical network system mixed with OCDMA and OFDM, including a sending end and a receiving end, which are connected through optical fibers. Described sending end is made up of OCDMA encoding module, OFDM signal generator and sending external modulator; Input data is sent into the input end of OFDM signal generator, and the output end of OFDM signal generator is connected and sends an input end of external modulator, OCDMA The output end of the encoding module is connected to the other input end of the sending external modulator, and the output end of the sending external modulator is connected to one end of the optical fiber. Described receiving end is made up of OCDMA decoding module, OFDM signal decoder and receiving external modulator; The other end of optical fiber connects an input end of receiving external modulator, and the output end of OCDMA decoding module connects receiving another input end of external modulator , the output end of the receiving external modulator is connected to the input end of the OFDM signal decoder, and the output end of the OFDM signal decoder sends output data.
上述OCDMA编码模块包括编码光源和编码波分复用器；编码光源输出端连接编码波分复用器的输入端，编码波分复用器的输出端连接发送外调制器。The above-mentioned OCDMA coding module includes a coded light source and a coded wavelength division multiplexer; the output end of the coded light source is connected to the input end of the coded wavelength division multiplexer, and the output end of the coded wavelength division multiplexer is connected to the sending external modulator.
上述OFDM信号生成器包括信道编码模块、发送串并转换模块、星座映射模块、共轭对称模块、导频插入模块、训练序列模块、IFFT模块、循环前缀模块、发送并串转换模块和数模转换模块；信道编码模块的输入端接入输入数据，信道编码模块的输出端经发送串并转换模块连接星座映射模块的输入端；星座映射模块的输出端经共轭对称模块连接导频插入模块的输入端；导频插入模块的输出放在训练序列模块之后，一起送入IFFT模块；IFFT模块的输出端经循环前缀模块连接发送并串转换模块的输入端；发送并串转换模块的输出端连接数模转换模块的输入端，数模转换模块的输出端与发送外调制器的输入端相连。The above-mentioned OFDM signal generator includes a channel coding module, a sending serial-parallel conversion module, a constellation mapping module, a conjugate symmetry module, a pilot insertion module, a training sequence module, an IFFT module, a cyclic prefix module, a sending parallel-serial conversion module and a digital-to-analog conversion module; the input end of the channel coding module is connected to the input data, and the output end of the channel coding module is connected to the input end of the constellation mapping module through the sending serial-to-parallel conversion module; the output end of the constellation mapping module is connected to the pilot insertion module through the conjugate symmetry module Input terminal; the output of the pilot insertion module is placed after the training sequence module and sent to the IFFT module together; the output terminal of the IFFT module is connected to the input terminal of the sending parallel-serial conversion module through the cyclic prefix module; the output terminal of the sending parallel-serial conversion module is connected The input end of the digital-to-analog conversion module, and the output end of the digital-to-analog conversion module are connected to the input end of the sending external modulator.
上述OCDMA解码模块包括解码光源和解码波分复用器；解码光源输出端连接解码波分复用器的输入端，解码波分复用器的输出端连接接收外调制器。The above-mentioned OCDMA decoding module includes a decoding light source and a decoding wavelength division multiplexer; the output end of the decoding light source is connected to the input end of the decoding wavelength division multiplexer, and the output end of the decoding wavelength division multiplexer is connected to the receiving external modulator.
上述OFDM信号解码器包括模数转换模块、接收串并转换模块、去循环前缀模块、FFT模块、信道均衡模块、去对称共轭模块、星座解映射模块和信道编码模块；模数转换模块的输入端连接接收外调制器的输出端，模数转换模块的输出端连接接收串并转换模块的输入端；接收串并转换模块的输出端经去循环前缀模块与FFT模块的输入端连接；FFT模块的输出端经信道均衡模块连接去对称共轭模块的输入端，去对称共轭模块的输出端经星座解映射模块与信道编码模块的输入端连接；信道编码模块的送出输出数据。The above-mentioned OFDM signal decoder includes an analog-to-digital conversion module, a receiving serial-to-parallel conversion module, a cyclic prefix module, an FFT module, a channel equalization module, a symmetrical conjugate module, a constellation demapping module and a channel coding module; the input of the analog-to-digital conversion module The terminal is connected to the output terminal of the receiving external modulator, and the output terminal of the analog-to-digital conversion module is connected to the input terminal of the receiving serial-parallel conversion module; the output terminal of the receiving serial-parallel conversion module is connected to the input terminal of the FFT module through the decyclic prefix module; the FFT module The output end of the channel equalization module is connected to the input end of the symmetrical conjugate module, and the output end of the symmetrical conjugate module is connected to the input end of the channel coding module through the constellation demapping module; the channel coding module sends output data.
与现有技术相比，本发明主要有以下优势：Compared with the prior art, the present invention mainly has the following advantages:
1、本发明采用的是光码分多址(OCDMA)和正交频分复用(OFDM)混合的无源光网络，充分利用了OFDM技术和OCDMA技术在PON系统中的优点，如频带利用率的提高、抗色散和偏振模色散的能力，如异步传输、传输安全性能高等特点，与相同用户数传统的其他无源光网络相比，系统价格更加低廉；1, what the present invention adopted is the passive optical network that optical code division multiple access (OCDMA) and orthogonal frequency division multiplexing (OFDM) mix, has fully utilized the advantage of OFDM technology and OCDMA technology in PON system, as frequency band utilization Compared with traditional passive optical networks with the same number of users, the system price is lower;
2、本发明发送端输出的OFDM电信号，频谱只包含实部部分，同时在接收端生成的OCDMA地址码序列采用直接检测技术解调出OFDM电信号，降低的系统的复杂度同时节约了成本；2. The frequency spectrum of the OFDM electrical signal output by the sending end of the present invention only includes the real part, and the OCDMA address code sequence generated at the receiving end adopts direct detection technology to demodulate the OFDM electrical signal, which reduces the complexity of the system and saves the cost ;
3、本发明针对不同用户的需求，可以提供动态资源分配的FFT点，充分利用数据带宽。3. According to the needs of different users, the present invention can provide FFT points for dynamic resource allocation and fully utilize the data bandwidth.
附图说明Description of drawings
图1为一种OCDMA和OFDM混合的无源光网络系统的整体框图。FIG. 1 is an overall block diagram of a passive optical network system in which OCDMA and OFDM are mixed.
图2为OCDMA编码模块的框图。Fig. 2 is the block diagram of OCDMA encoding module.
图3为OFDM信号生成器框图。Figure 3 is a block diagram of the OFDM signal generator.
图4为OCDMA解码模块的框图。Fig. 4 is a block diagram of the OCDMA decoding module.
图5为OFDM信号解码器框图。Fig. 5 is a block diagram of an OFDM signal decoder.
具体实施方式detailed description
一种OCDMA和OFDM混合的无源光网络系统，如图1所示，包括发送端和接收端，发送端和接收端通过光纤连接。A passive optical network system mixed with OCDMA and OFDM, as shown in Figure 1, includes a sending end and a receiving end, and the sending end and the receiving end are connected through optical fibers.
所述发送端由OCDMA编码模块、OFDM信号生成器和发送外调制器组成。输入数据送入OFDM信号生成器的输入端，OFDM信号生成器的输出端连接发送外调制器的一个输入端，OCDMA编码模块的输出端连接发送外调制器的另一个输入端，发送外调制器的输出端与光纤的一端连接。The sending end is composed of an OCDMA coding module, an OFDM signal generator and a sending external modulator. The input data is sent to the input end of the OFDM signal generator, the output end of the OFDM signal generator is connected to one input end of the sending external modulator, the output end of the OCDMA encoding module is connected to the other input end of the sending external modulator, and the sending external modulator The output end is connected to one end of the optical fiber.
上述OCDMA编码模块包括编码光源和编码波分复用器，编码光源输出端连接编码波分复用器的输入端，编码波分复用器的输出端连接发送外调制器。在本发明优选实施例中，编码光源为放大自发射ASE宽带光源，编码波分复用器采用光纤光栅(FBGs)或者光子光波电路(PLCs)实现。参见图2。The above-mentioned OCDMA encoding module includes an encoding light source and an encoding wavelength division multiplexer, the output end of the encoding light source is connected to the input end of the encoding wavelength division multiplexer, and the output end of the encoding wavelength division multiplexer is connected to the transmitting external modulator. In a preferred embodiment of the present invention, the coded light source is an amplified self-emissive ASE broadband light source, and the coded wavelength division multiplexer is realized by fiber gratings (FBGs) or photonic lightwave circuits (PLCs). See Figure 2.
在OCDMA编码模块中，编码光源产生稳定的光信号，连接后级的编码波分复用器。经过编码波分复用器的宽谱光源，能够滤出多个波长的光信号，即产生特定序列的OCDMA地址码编码序列，然后送入发送外调制器中。在发送外调制器中，已调的OFDM信号被OCDMA地址码编码序列进行编码被送入光纤信道。如(7,3,1,1)OOC码集中的(1101000)地址码，编码波分复用器为1550.0nm到1552.4nm，各波长间隔为0.4nm，即经过波分复用器输出的光信号波长分别为1550.0nm、1550.4nm、1550.8nm、1551.2nm、1551.6nm、1552.0nm、1552.4nm。上述OFDM信号生成器包括信道编码模块、发送串并转换模块、星座映射模块、共轭对称模块、导频插入模块、训练序列模块、IFFT(傅里叶逆变换)模块、循环前缀模块、发送并串转换模块和数模转换模块。信道编码模块的输入端接入输入数据，信道编码模块的输出端经发送串并转换模块连接星座映射模块的输入端。星座映射模块的输出端经共轭对称模块连接导频插入模块的输入端。导频插入模块的输出放在训练序列模块之后，一起送入IFFT模块。IFFT模块的输出端经循环前缀模块连接发送并串转换模块的输入端。发送并串转换模块的输出端连接数模转换模块的输入端，数模转换模块的输出端与发送外调制器的输入端相连。参见图3。In the OCDMA encoding module, the encoding light source generates a stable optical signal, which is connected to the subsequent encoding wavelength division multiplexer. The wide-spectrum light source through the coded wavelength division multiplexer can filter out optical signals of multiple wavelengths, that is, generate a specific sequence of OCDMA address code coded sequences, and then send them to the external modulator. In the sending external modulator, the modulated OFDM signal is encoded by the OCDMA address code sequence and sent to the optical fiber channel. For example, the (1101000) address code in the (7,3,1,1) OOC code set, the encoding wavelength division multiplexer is 1550.0nm to 1552.4nm, and the wavelength interval is 0.4nm, that is, the light output by the wavelength division multiplexer The signal wavelengths are 1550.0nm, 1550.4nm, 1550.8nm, 1551.2nm, 1551.6nm, 1552.0nm, 1552.4nm, respectively. The above-mentioned OFDM signal generator includes a channel coding module, a sending serial-to-parallel conversion module, a constellation mapping module, a conjugate symmetry module, a pilot insertion module, a training sequence module, an IFFT (inverse Fourier transform) module, a cyclic prefix module, a sending parallel Serial conversion module and digital-to-analog conversion module. The input end of the channel coding module is connected to the input data, and the output end of the channel coding module is connected to the input end of the constellation mapping module through the sending serial-to-parallel conversion module. The output end of the constellation mapping module is connected to the input end of the pilot insertion module via the conjugate symmetry module. The output of the pilot insertion module is placed after the training sequence module and sent to the IFFT module together. The output end of the IFFT module is connected to the input end of the sending parallel-serial conversion module through the cyclic prefix module. The output end of the sending parallel-serial conversion module is connected to the input end of the digital-to-analog conversion module, and the output end of the digital-to-analog conversion module is connected to the input end of the sending external modulator. See Figure 3.
OFDM信号生成器主要为了产生频谱仅为OFDM电信号的实部信号。具体工作原理为：信道编码模块对输入的信号进行一系列的信道编码，如交织，卷积，RS码等技术，增加输入信号的抗干扰性。经过信道编码的输入信号送入发送串并转换模块，将串行数据流转换为一定比特的并行数据流，用于后级星座映射。经过星座映射模块的并行数据流映射在星座图的特定坐标点上。导频插入模块对一定数目的经过星座映射后的数据插入导频信息，其中插入导频信息的数目根据后级IFFT模块的点数确定。若做N点IFFT，根据傅里叶变换的共轭对称性，为得到频谱仅实部信号有效的OFDM信号。对IFFT前N/2个点加载数据，后N/2个点的数据为前N/2数据的共轭对称，输出的复数数据虚部为0，即实部信号。训练序列模块对IFFT后的实部信号头部添加经过IFFT的本地训练序列。循环前缀模块对添加本地训练序列的经过IFFT变换的实部数据加入循环前缀，以防止码间串扰。发送并串转换模块和数模转换模块分别对添加循环前缀后的数据进行并串转换和数模转换，然后送入发送外调制器。The OFDM signal generator is mainly for generating the real part signal whose frequency spectrum is only the OFDM electrical signal. The specific working principle is: the channel coding module performs a series of channel coding on the input signal, such as interleaving, convolution, RS code and other technologies, to increase the anti-interference of the input signal. The channel-coded input signal is sent to the sending serial-to-parallel conversion module, which converts the serial data stream into a parallel data stream with certain bits, which is used for subsequent constellation mapping. The parallel data streams passing through the constellation mapping module are mapped on specific coordinate points of the constellation diagram. The pilot insertion module inserts pilot information into a certain number of constellation-mapped data, wherein the number of inserted pilot information is determined according to the number of points of the subsequent IFFT module. If N-point IFFT is performed, according to the conjugate symmetry of Fourier transform, in order to obtain an OFDM signal whose spectrum is only valid for the real part signal. Load data to the first N/2 points of IFFT, and the data of the last N/2 points is the conjugate symmetry of the first N/2 data, and the imaginary part of the output complex data is 0, that is, the real part signal. The training sequence module adds an IFFT-processed local training sequence to the head of the real part signal after IFFT. The cyclic prefix module adds a cyclic prefix to the IFFT-transformed real part data added with the local training sequence to prevent intersymbol interference. The sending parallel-to-serial conversion module and the digital-to-analog conversion module respectively perform parallel-to-serial conversion and digital-to-analog conversion on the data added with the cyclic prefix, and then send it to the sending external modulator.
所述接收端由OCDMA解码模块、OFDM信号解码器和接收外调制器组成。光纤的另一端连接接收外调制器的一个输入端，OCDMA解码模块的输出端连接接收外调制器的另一个输入端，接收外调制器的输出端与OFDM信号解码器的输入端连接，OFDM信号解码器的输出端送出输出数据。The receiving end is composed of an OCDMA decoding module, an OFDM signal decoder and a receiving external modulator. The other end of the optical fiber is connected to one input end of the receiving external modulator, the output end of the OCDMA decoding module is connected to the other input end of the receiving external modulator, the output end of the receiving external modulator is connected to the input end of the OFDM signal decoder, and the OFDM signal The output of the decoder sends out the output data.
上述OCDMA解码模块与OCDMA编码模块的结构相一致，包括解码光源和解码波分复用器，解码光源输出端连接解码波分复用器的输入端，解码波分复用器的输出端连接接收外调制器。在本发明优选实施例中，解码光源为放大自发射ASE宽带光源，解码波分复用器采用光纤光栅(FBGs)或者光子光波电路(PLCs)实现。参见图4。The above-mentioned OCDMA decoding module is consistent with the structure of the OCDMA encoding module, including a decoding light source and a decoding wavelength division multiplexer, the output end of the decoding light source is connected to the input end of the decoding wavelength division multiplexer, and the output end of the decoding wavelength division multiplexer is connected to the receiver external modulator. In a preferred embodiment of the present invention, the decoding light source is an amplified self-emission ASE broadband light source, and the decoding wavelength division multiplexer is realized by using fiber gratings (FBGs) or photonic lightwave circuits (PLCs). See Figure 4.
在OCDMA解码模块中，解码光源产生稳定的光信号，连接后级的解码波分解复用器。经过解码波分解复用器的宽谱光源，滤出多个波长的光信号，产生与发送端严格一致的OCDMA地址码解码序列，然后送入接收外调制器中。在接收外调制器中，已调的OFDM信号被OCDMA地址码解码序列进行编码被送入光纤信道。In the OCDMA decoding module, the decoding light source generates a stable optical signal, which is connected to the subsequent decoding wave demultiplexer. After the wide-spectrum light source of the decoding wave decomposition multiplexer, the optical signals of multiple wavelengths are filtered out, and the OCDMA address code decoding sequence that is strictly consistent with the sending end is generated, and then sent to the receiving external modulator. In the receiving external modulator, the modulated OFDM signal is encoded by the OCDMA address code decoding sequence and sent to the optical fiber channel.
上述OFDM信号解码器包括模数转换模块、接收串并转换模块、去循环前缀模块、FFT(傅里叶变换)模块、信道均衡模块、去对称共轭模块、星座解映射模块和信道编码模块。模数转换模块的输入端连接接收外调制器的输出端，模数转换模块的输出端连接接收串并转换模块的输入端。接收串并转换模块的输出端经去循环前缀模块与FFT模块的输入端连接。FFT模块的输出端经信道均衡模块连接去对称共轭模块的输入端，去对称共轭模块的输出端经星座解映射模块与信道编码模块的输入端连接。信道编码模块的送出输出数据。参见图5。由于训练序列是发送端和接收端都已知的序列。在接收端对接收到的已知序列进行同步和均衡。即用信道估计的方法来跟踪信道相应的变化，从而对接收到的数据进行校正和恢复。The above-mentioned OFDM signal decoder includes an analog-to-digital conversion module, a receiving serial-to-parallel conversion module, a cyclic prefix removal module, an FFT (Fourier transform) module, a channel equalization module, a symmetrical conjugate removal module, a constellation demapping module and a channel coding module. The input end of the analog-to-digital conversion module is connected to the output end of the receiving external modulator, and the output end of the analog-to-digital conversion module is connected to the input end of the receiving serial-to-parallel conversion module. The output end of the receiving serial-to-parallel conversion module is connected with the input end of the FFT module through the decyclic prefix module. The output end of the FFT module is connected to the input end of the desymmetric conjugate module through the channel equalization module, and the output end of the desymmetric conjugate module is connected to the input end of the channel coding module through the constellation demapping module. The output data sent by the channel coding module. See Figure 5. Since the training sequence is a sequence known to both the sending end and the receiving end. The received known sequence is synchronized and equalized at the receiving end. That is, channel estimation is used to track the corresponding changes of the channel, so as to correct and restore the received data.
OFDM信号解码器主要为了还原用户信号。具体工作原理为：将经过接收外调制器产生的仅实部信号有效的OFDM电信号接入模数转换模块。模数转换模块对其进行模数转换后输出的数字信号送入接收串并转换模块，对其进行串并转换。去循环前缀模块对并行数据进行去循环前缀，去除循环前缀的数据包含已知的训练序列和输入数据后IFFT后的数据。FFT模块分别对这两个部分的数据做相应点的FFT运算。信道均衡模块根据已知训练序列经过FFT后的数据进行信道均衡。信道均衡的结果经过去共轭对称后送入星座解映射模块，对星座图的阈值进行动态调整，同时对FFT后除去训练序列的数据进行解映射。根据傅里叶变换实部信号频谱的对称共轭性，星座解映射的前N/2个数据即为有效数据，后N/2个数据为有效数据的共轭。输出的后N/2个数据不做处理即可，输出的前N/2有效数据即为经过发送端信道编码后的数据。对该部分数据进行信道解码后送出输出数据，信道解码模块包括解交织、Viterbi译码、RS码等。分别对应发送端信道编码的交织、卷积、RS码等模块。The OFDM signal decoder is mainly to restore the user signal. The specific working principle is: the OFDM electrical signal, which is only valid for the real part signal generated by the receiving external modulator, is connected to the analog-to-digital conversion module. The digital signal output by the analog-to-digital conversion module after performing analog-to-digital conversion is sent to the receiving serial-to-parallel conversion module for serial-to-parallel conversion. The cyclic prefix removal module removes the cyclic prefix from the parallel data, and the data without the cyclic prefix includes the known training sequence and the IFFT data after the input data. The FFT module performs the FFT operation on the corresponding points of the data of these two parts respectively. The channel equalization module performs channel equalization according to the FFT data of the known training sequence. The result of channel equalization is sent to the constellation demapping module after deconjugation and symmetry, and the threshold of the constellation diagram is dynamically adjusted, and at the same time, the data removed from the training sequence after FFT is demapped. According to the symmetric conjugation of the real part signal spectrum of the Fourier transform, the first N/2 data of the constellation demapping is the effective data, and the last N/2 data are the conjugate of the effective data. The last N/2 pieces of data that are output need not be processed, and the first N/2 valid data that are output are data after channel coding at the sending end. The part of the data is channel-decoded and then the output data is sent out. The channel decoding module includes de-interleaving, Viterbi decoding, RS code and so on. Corresponding to the interleaving, convolution, RS code and other modules of the channel coding at the sending end.
OFDM技术来源于射频传输领域，运用于PON技术中不仅可以实现更高的频谱利用率，而且还具有抗色散和偏振模色散的能力。OCDMA技术是将码分多址(CDMA)技术与光纤通信相结合的通信方式，具有支持异步传输，传输协议透明，用户共享信道的特点。本发明充分利用OFDM与OCDMA的突出优点，将OFDM技术与OCDMA技术有效结合所实现的一种混合的无源光网络，具有频谱利用率高，抗色散和偏振模色散，传输系统兼容性和扩展性好，优良的带宽分配机制，异步传输，系统安全性能高等特点。OFDM technology originates from the field of radio frequency transmission. When applied to PON technology, it can not only achieve higher spectrum utilization, but also has the ability to resist dispersion and polarization mode dispersion. OCDMA technology is a communication method that combines Code Division Multiple Access (CDMA) technology with optical fiber communication. It has the characteristics of supporting asynchronous transmission, transparent transmission protocol, and user-shared channels. The present invention fully utilizes the outstanding advantages of OFDM and OCDMA, and effectively combines OFDM technology and OCDMA technology to realize a hybrid passive optical network, which has high spectrum utilization rate, anti-chromatic dispersion and polarization mode dispersion, transmission system compatibility and expansion Good performance, excellent bandwidth allocation mechanism, asynchronous transmission, and high system security performance.
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