The Research On Papr Reducing Using Joint Algorithm Based On The Unitary Transformation For CO-OFDM Systems

Optical orthogonal frequency division multiplexing(OOFDM)transmission system is the combination of orthogonal frequency division multiplexing(OFDM)technology and optical communication,it has become a popular research in optical communication field in recent years because of its high-speed,large-capacity,long-haul,and low-cost.OOFDM system can be divided into direct detection OFDM(DDO-OFDM)and coherent optical OFDM(CO-OFDM).CO-OFDM system has been widely used,because it has the dual advantages of coherent detection and OFDM technology.But the inherent shortcoming of OFDM technology,such as higher peak-to-average power ratio(PAPR)is still there.The signals with high PAPR through the light transmission channel,easy to cause severe nonlinear effect,thus affect the transmission performance of the system,so research how to reduce the the PAPR of CO-OFDM system is of great significance.According to the above problem,this paper focus on how to effectively reduce PAPR of CO-OFDM system.1.In view of the traditional companding transform,the repeated companding and filtering method with m to 3 repetitions has been proposed.Through the simulation about PAPR and the bit error rate(BER),the proposed method can undertake joint optimization of PAPR and BER performance.According to the traditional unitary transformation of Hadamard transform and discrete cosine transform(DCT),fast hadamard transform(FHT)and fast DCT are proposed,and the fast algorithm can effectively reduce the computational complexity.According to the partial transmit sequence(PTS)of probability original technology with high computation complexity,iterative partial transmit sequence(IPTS)algorithm with low computation complexity is proposed.2.The combined algorithm based on the above algorithms have been proposed to reduce the PAPR in the CO-OFDM system.First is the combination of FHT with modified ?-law companding transform,the second is the joint fast DCT and modified two-piecewise companding(TPWC)transform method,the two methods by using the unitary transformation to reduce the PAPR,through repeated copanding and filtering to further reduce the PAPR of signal.Finally is a combination of fast DCT with IPTS,IPTS algorithm at the expense of PAPR performance to reduce the computational complexity,but joint after fast DCT can make up for the shortcomings.In addition,PAPR suppression performance,out-of-band power spectrum performance,the BER performance and computational complexity are analyzed by Matlab and Optisystem.The simulation results show that the above three kinds of joint algorithm can guarantee good BER performance under the condition of effective inhibit PAPR.