Performance analysis of crosstalk effects in subcarrier multiplexing and wave division multiplexing in optical communication systems

In traditional optical communication, duplexity is achieved by using two fibers, each with a transmitter and a receiver. Economically, bidirectional wavelength division multiplexing (WDM) transmission systems utilizing a single mode fiber (SMF) are more attractive, not only reducing fiber usage by a factor of two but also minimizing the number of components. Duplex transmissions over a SMF can double the capacity of an installed unidirectional link. This paper aims to explore an alternative approach using subcarrier multiplexing (SCM)-based optical networks. It evaluates the physical transmission quality of analog and digital signals using the SCM approach, considering fiber nonlinear crosstalk such as stimulated Raman scattering, cross-phase modulation, and four-wave mixing in the SCM externally modulated optical link. A suitable bandwidth of 890–960 MHz is chosen for subcarriers with a channel bandwidth of 200 kHz per carrier. The study investigates the optical beat interference (OBI) performance limitations of the subcarrier multiplexing WDM optical transmission system. OBI for 10 channels at an input power of 1 dB is − 40 dB, whereas for 110 channels with a separation of 250 kHz, the OBI is −20 dB.