The effect of phase noise and spurs on coherent communications performance

The effect of the stochastic properties of oscillator and frequency synthesizer (frequency source) phase noise and spurious frequencies (spectral purity) on coherent communications performance is measured and compared to the theoretical work. The stochastic properties are investigated; flicker-of-phase (1/f) and flicker-of-frequency (1/f ³) are non-Gaussian, while white phase (1/f⁰) and white frequency (1/f²) are Gaussian. Spurious frequencies (spurs) are Gaussian only if the conditions of the central limit theorem (CLT) apply, as is any summation of spurs and phase noise. A well-calibrated BER measurement on an otherwise-ideal BPSK link was repeated for two non-Gaussian sources, a 1/f³ phase noise and a single-spur, low phase noise source, both with a σ_φ high enough to induce noticable implementation loss. Compared to five different theoretical probability-of-error (P_e) equations all presuming Gaussian spectral purity, the measured BER for both sources were in the middle and close to each other