Research On High Order Coded Modulation In Optical Networks With Short Distance Transmission

In recent years,with the vigorous development of the Internet industry,the demand for network traffic from social media,big data centers,cloud computing service providers and other forms of Internet applications has increased rapidly.The increasing demand for optical network interconnection applications has put forward higher and higher requirements for optical network transmission rate and transmission bandwidth.Ethernet standard is also constantly upgrading to adapt to the rapid growth of the Internet.In the Internet age,the wide adoption of bandwidth intensive services and cloud computing services makes the data communication links need higher and higher data transmission rates.In optical network communication systems,high order modulation formats can be used to increase the frequency efficiency by increasing the data rate in a system with a given transmission bandwidth.In the study of optical network for short distance transmission with high order modulation encoding technology,considering the system cost,complexity and power consumption and other aspects,this paper focuses on the high order modulation optical network system that combines related encoding with frequency transformation technology,and strive to reduce the channel interference while maintaining low system costs and enhancing the channel capacity.The main innovation and completion of this paper are as follows:(1)A multidimensional iterative encoding high order modulation schemes for short distance optical network is proposed,which is based on cyclic iterative coding model and a QAM modulation scheme for sub constellation allocation based on this scheme is proposed.By processing the data of input adjacent bits,it can change the distribution characteristics of output signals,so that the signal is more suitable for transmission channel characteristics to improve system performance.At the same time,the scheme can be adjusted flexibly according to the specific modulation technology to suit the different transmission scenes.The QAM modulation scheme based on multi-dimensional cyclic iterative coding for sub constellation allocation can reduce the system power and improve the anti-jamming ability of transmission signals by changing the distribution characteristics of sub constellation signals.Compared with the traditional scheme,the new scheme has about 0.9dB optical signal to noise ratio gain when the bit error rate is 10-3 in the fiber channel.(2)An APPM scheme based on two-dimensional iterative encoding for short distance optical network is proposed.The APPM used in the scheme can get better balance in transmission rate and power efficiency spectrum.By the iterative encoding of signals in the two dimensions of pulse amplitude and position,the APPM symbols distribution and probability have been changed,enhancing the transmission performance of the system under the influence of noise and dispersion effect in the fiber channel.Compared with the traditional scheme,the new scheme achieves about 1dB SNR gain mainly under the influence of noise effect in the fiber channel while the BER is 10-3,and the BER performance is beyond one order of magnitude in the dispersion coefficient D=17ps/nm/km of the optical fiber mainly under the influence of dispersion effect.(3)An adaptive discrete wavelet transform and two-dimensional iterative encoding scheme based on APPM-OFDM in short distance optical network is proposed.The APPM encoding modulation scheme based on two-dimensional iterative encoding scheme is used in OFDM system,which replaces the FFT with DWT as signal processing technology.Not only spectrum efficiency and power efficiency of the system have become more balanced,and also the transmission performance of the communication system in the fiber channel has been improved.Compared with the traditional FFT-OFDM scheme,the DWT-OFDM scheme using cyclic iterative coding has about 5dB SNR gain while the BER is 10-3 in the fiber channel.