Demonstration Of An Efficient Cost-Effective Laser Frequency Comb Generator With Digital Signal Processing Algorithm Based High-Speed 256-QAM WDM Coherent Optical Communication System

Over the past thirty years,the capability of commercial fiber optic communication systems has increased the network traffic requirements.The remarkable scalability of wavelength division multiplexing(WDM)technology that has been used effectively to extend optical communication systems spectral efficiency(SE)and meet growing bandwidth(BW)utilization.Nonetheless,the rapid development of network traffic has reversed this situation and the current trends indicate that network traffic is increasing faster than system efficiency.Several breakthroughs have occurred over the last decade to allow more and fast development of the optical fiber communication system capacity.Advanced modulation formats-based WDM coherent optical communication system with the joint digital signal processing very efficient method for the utilization of the available spectral BW.WDM coherent optical communication system based on advanced modulation format combined with digital signal processing technology can effectively improve the SE and B W of the communication system.In these systems,the spectral guard band(G-Band)b/w adj acent channels are minimized at the cost of more stringent requirements on the efficiency of optical,especially the stability of frequency or wavelength.Optical frequency(OF)comb is the most attractive solution for the stability b/w the multiple optical carriers with low cost and low complexity and remains a fruitful and endeavoring field of high data range transmission.OF Comb's outstanding phase-noise efficiency has contributed to a revolution in the WDM optical communications network.This paper is presenting an efficient and novel method for the cost-effective laser frequency comb generator(CE-LFCG)by using the one CW laser,one electro-optical phase modulator(EPM),and one Mech-Zehnder modulator(MZM).The modulators are driven by a single radio frequency(RF)generator without any extra electrical or optical amplifier and filter.CE-LFCG generated the multiple equally space flat lines with acceptable tone to noise ratio in C-Band.All the simulations are completed through Optisystem.The main work of this paper is as follows:(1)A single CW laser-based CE-LFCG is proposed.CE-LFCG successfully generates the equally spaced comb lines in C-Band,and one line represents the one individual laser output.The CW laser-based novel CE-LFCG in this paper can generate the equally spaced comb line at different frequency spectral ratio(FSR)(10,33,50,and 100)GHz,and the number of comb lines varies according to the FSR values.(2)The high SE and high capacity dual-polarization WDM coherent optical communication system for medium and long-haul applications(100*N,N=(5,16,25,35,50)km)are proposed.This system uses CE-LFCG as an optical carrier generator and local oscillator and utilizes the advanced modulation formats 256-QAM.Simulation results show that the transmissions through four different frequencies of the different channels at 320 Gbps bit rate,20Gsymbol/s are realized.All other simulation parameters detail has in table 4-1 in Chapter 4.(3)The digital signal processing(DSP)is introduced at the Rx signal.DSP is an indispensable technology for a modern coherent,optical communication system.The Advanced DSP algorithm is used for the nonlinear impairment's compensation and chromatic dispersion compensation during the propagation.After that the comparison has done for the evaluation of novel CE-LFCG-based DP 256-QAM WDM coherent system in the form of percentage error vector magnitude(EVM%)vs OSNR,EVM%vs launched power,OSNR vs log10BER,launched power vs log10BER over the different length of the transmission link.