Optical Phase Conjugation Technology In Optical Fiber Communication System

With the development of fiber amplifier, the loss of optical fibers is no longer the main factor influencing of the performance in high-speed and long distance optic-fiber communication, but the capacity of communication systems is still restricted by the dispersion and nonlinearity effect. Optical phase conjugation is one of the research hotspot in optical communication systems because it can compensate dispersion and nonlinearity effect. It is the accurate reverse of the transmission and the phase factor around of light wave by the use of an optical nonlinear phenomenon. It is widely used because of its natural correct in phase interference and its property of reverse transmission.This article elaborates the foreign and domestic studies of optical phase conjugation first, then introduces the two general methods which can cause optical phase conjugation. Next, a basic equation which governs propagation of optical pulse in single mode fibers is obtained on the basis of the Maxwell's Equations, and analyses the dispersion and nonlinearity effect which can influence the propagation of light pulse in optical fibers, and make resolution and verification by the use of the split-step Fourier method. We also study the dispersion and nonlinearity effect compensation principle of temporal phase conjugation and spectral phase conjugation. Then make theoretical analysis and numerical calculation for two technologies under two cases:one is single pulse transmission, the other is dual pulse transmission. The results showed that:temporal phase conjugation can compensate signal distortion caused by group velocity dispersion and self-phase modulation and intrapulse Raman scattering, but not for odd-order dispersion and self-steepening, while spectral phase conjugation can compensate group velocity dispersion and third-order dispersion and self-phase modulation and self-steepening, but not for signal distortion caused by intrapulse Raman scattering. If we put the two technologies together, then the performance of the communication systems is greatly improved, and it resolves a problem of optic-fiber communication system towards high-speed, large capacity and long distance.