Research On Digitalized Radio Over Fiber(D-RoF) Transmission System And Its Related Algorithms

With the development of 5G wireless transmission technology,digitalized radio-over-fiber(D-RoF)technology has attracted more and more attention in order to meet users' terminal problems such as large amount of information data,wired wireless coexistence,and large mobile communication demand.Compared to analog radio-over-fiber(A-RoF),D-RoF technology has stable fiber link performance,nonlinearity and dispersion have little influence on it and easy to compensate.It also has great advantages in network installation,operation and maintenance management.Higher-order quadrature amplitude modulation(QAM)and orthogonal frequency division multiplexing(OFDM)are usually used to ensure the transmission quality of signal and to save the spectrum resource in D-RoF system.However,the main factor that restricts the development of D-RoF technology is the high bit rate of digital signal.The main contents and results of this research are as follows:1.The research background and development status of radio-over-fiber(RoF)technology,sampling frequency offset and polarization division multiplexing technology are introduced.The advantages and disadvantages of A-RoF and D-RoF are compared and the key technologies in D-RoF and polarization demultiplexing technology are expounded.And the simulation implemention of D-RoF system is introduced.2.In D-RoF system,the modulation method of baseband signal adopts OFDM technology,which can improve the spectrum utilization rate,but it will also bring some problems that commonly existing in OFDM system,including the problem of sampling frequency offset.Therefore,this article describes the causes of sampling frequency offset and analyzes its impact on the system,and then a pilot-aided algorithm is adopted for estimation and compensation of sampling frequency offset to improve the system's performance.The simulation results show that the algorithm has good compensation effect and is suitable for D-RoF system.3.Considering the high bit rate problem that existing in D-RoF system,a polarization division multiplexing technology is applied in D-RoF system to improve the transmission capacity of single wavelength channel from the perspective of improving the optical fiber transmission capacity.Polarization demultiplexing has been realized by using one-way tracking vector(OTV)algorithm and two-way tracking vector(TTV)digital signal processing(DSP)algorithm respectively in traditional Stokes analyzer and simplified Stokes analyzer.The simulation results have proved that two-way tracking vector algorithm can reduce power budget effectively in the orthogonal polarization division demultiplexing system,the needed optical power of two-way tracking vector algorithm is 2dBm less than that of one-way tracking vector algorithm for reaching the best bit error rate(BER)performance.Meanwhile,the polarization demultiplexing has been realized in a non-orthogonal polarization division demultiplexing system with a minimum polarization division multiplexing angle of 76 degree by using two-way tracking vector algorithm and traditional Stokes analyzer,which enriches the dimension of polarization division multiplexing greatly and significantly enhance system flexibility without increasing cost and complexity.