New Optical Modulation Formats In WDM Ultra-long-haul Systems

Because of the rapid growth of capacity requirement on long distance transmission, fiber-optic telecommunications are advancing into high data rate and wavelength division multiplexing (WDM). In order to maximize the system capacity and minimize the performance degradation caused by transmission impairments, system design and optimization are important. Similar to other communication systems, signal modulation format is a key issue, which determines transmission quality and spectral efficiency.This paper gave a description about the conceptions of optical modulation format, and classified them by carrier mode. Through constructing simulation systems on WDM Ultra-long-haul transmission, we studied and discussed the two main kinds: amplitude-shift keying (ASK) and Differential Phase-Shift-Keying (DPSK). We analyzed the principle, the structures of transmitter and receiver, and the Bit Error Rate (BER) on every optical modulation formats: Non-Return-to-Zero (NRZ), half frequency modulated RZ (HRZ), full frequency modulated RZ (FRZ), Carrier Suppressed RZ (CSRZ), Single Sideband RZ (SSB), Duobinary Amplitude Modulated Phase Shift Keying Modulation (AM-PSK), Phase-Shaped Binary (PSBT), HRZ-DPSK, FRZ-DPSK, CSRZ-DPSK, Differential Quadrature Phase Shift Keying Modulation (DQPSK).In order to solve the problem about the channel allocation of WDM system, particle swarm optimization (PSO) algorithm was introduced. Although the original PSO algorithm is easy to trap into sub-optima, we proposed a new modified PSO to avoid sub-optima but keep the simplicity at the same time. This is the first time to introduce the conception of collision into PSO arithmetic, so it is called collision PSO.