Performance Evaluation of CPDM 8-QAM for Faster Direct Detection Fiber Optic Communication System under the Effects of Cross-Polarization

This paper presents a proposal to incorporate Circular Polarization Division Multiplexing (CPDM) into the 8-Quadrature Amplitude Modulation (QAM) with direct detection fiber optic communication (FOC) system with a view to octupling the spectral efficiency and accordingly the bandwidth of the system without altering the spectral width of the transmitter. A comprehensive analysis is demonstrated considering the impact of the crosstalk (Xtalk) owing to cross-polarization (XPol) induced crosstalk by arbitrary misalignment of the SOPs to acquire the output expression of the Signal to Cross-talk plus Noise Ratio (SCNR) for a direct detection CPDM 8-QAM receiver. The effects of cross-polarization on the Bit Error Rate (BER) performance is presented considering the Maxwellian distribution of the random misalignment angles. Hence, the system suffers a significant deterioration from the expected results. Furthermore, a detailed comparison between the existing PDM-QPSK and our proposed CPDM 8-QAM model is elucidated where our proposed model is significantly better in terms of system performances.