Performance Comparison of Coherent versus Incoherent Direct Sequence Optical Code Division Multiple Access System

In this paper, we consider the case of a Direct-Detection Direct Sequence Optical Code Division Multiple Access (DSOCDMA) system using Superstructured Fiber Bragg Grating (S-FBG) as encoder/decoder to implement unipolar codes such as Prime Sequence (PS) and Extended Quadratic Codes (EQC) codes. We use the Importance Sampling (IS) technique, which is a variant of the known Monte-Carlo (MC) method, to evaluate the Bit Error Rate (BER). We compare performances of the coherent and incoherent DS-OCDMA system and we validate our simulation results by experimental measure. Our simulation results depict a BER floor due the beat noise of the incoherent source. We show that increasing bit rate leads to a deterioration of the BER behavior and requiring an increase of the optical bandwidth of the signal.