Theoretical analysis of communication systems based on low-coherence interferometry

This paper presents a detailed analysis of crosstalk, dispersion, and the signal-to-noise ratio (SNR) in an optical communication system based on low-coherence interferometry (LCI-Cs). This technique enables the generation of spatially localized carriers through optical path differences using a single central wavelength, introducing what we believe to be a new degree of freedom for data modulation. As a result, both spectral and spatial multiplexing become feasible, substantially increasing the number of transmission channels. The study examines the main factors that affect signal integrity in optical links, including chromatic dispersion, inter-channel crosstalk, interference from other stations, and optical noise-particularly amplified spontaneous emission (ASE) generated by optical amplifiers. The results show that the proposed system exhibits strong resilience to these impairments, primarily due to the partial coherence of the superluminescent source and the architecture of the interferometric setup. From a theoretical standpoint, the influence of the random phase of the optical field on interference formation is analyzed, demonstrating that this phase cancels when the fields originate from the same coherent source. Dispersion effects are modeled using a Taylor expansion of the refractive index as a function of the wavenumber, enabling accurate predictions of pulse broadening and phase shifts introduced by the transmission medium. Finally, a unified noise model is presented, capable of representing both ASE noise from discrete EDFAs and noise arising from distributed amplification schemes such as Raman amplification. The SNR is evaluated in the presence of this noise, and it is shown that when the detection interferometers are properly balanced, the system effectively suppresses common-mode noise and allows robust recovery of the transmitted signal.