Analysis of Beat Noise in Coherent and Incoherent Time-Spreading OCDMA

TLDR

The paper investigates the impact of beat noise and other additive noise on TS‑OCDMA networks and proposes mitigation strategies for coherent and partially coherent systems. By introducing the coherent ratio kt, the authors classify TS‑OCDMA into incoherent, partially coherent, and coherent regimes, derive the corresponding noise distributions and bit‑error rates, and evaluate system performance across these cases. They find that coherent systems are limited by beat noise, whereas increasing kt reduces beat noise in incoherent systems, eventually rendering them beat‑noise‑free.

Abstract

The effect of beat noise and other types of additive noise in time-spreading optical-code-division multiple-access (TS-OCDMA) networks is analyzed in this paper. By defining the coherent ratio kt, the ratio of the chip duration to the coherence time of the light source, TS-OCDMA systems are classified into incoherent, partially coherent, and coherent systems. The noise distributions and the bit-error rates are derived, and system performance is discussed for different cases. The performance of coherent systems is limited by the beat noise. With increasing kt, the effect of beat noise decreases in incoherent systems, and they eventually become free of beat noise. Possible solutions to the beat noise problem in coherent and partially coherent systems are also proposed and discussed.