Studies of different modulation techniques in the integration of SCM optical communication system

Abstract

Studies considering different modulation techniques used in the integration of subcarrier multiplexing (SCM) optical transmission systems are presented in this paper. The analysis of SCM systems operating in the 1550 nm signal wavelength range involves ASK, QPSK, 16QAM and 64QAM electrical modulations. From experimental results and by numerical simulation, the frequency response of the fibre for the ODSB and OSSB systems is obtained. The simulated results suggest that using dispersion compensating fibre (DCF) it is possible to compensate the dispersive effect in optical fibre for ODSB signals, allowing the system to get OSSB similar frequency response. SCM systems simulations were performed using the commercial software Optisystems from Optiwave, Inc. The system bandwidth increase was analysed in terms of fibre length and dispersion considering different links, subcarrier spacing and number of subcarriers. From experimental results, the intermodulation effect, generated by the optical fibre, is verified and indicated the necessity of using unequal spacing between the subcarriers, which is a factor that limits the SCM systems' performance.