Influence of ASE noise on the signal OSNR and error vector magnitude in coherent optical communications

The effect of amplified spontaneous emission (ASE) noise on the optical signal quality of coherent optical communications, characterized by optical signal to noise ratio (OSNR) and error vector magnitude (EVM), is investigated numerically. The influences of ASE noise only and the interaction of ASE noise, dispersion and nonlinear optical effect on the signal OSNR and EVM are investigated. Moreover, the relationship between OSNR and EVM is derived theoretically, for systems with ASE noise only and with ASE noise and nonlinearity.