Optical spectrally efficient FDM system for electrical and optical bandwidth saving

A newly proposed optical-spectrally efficient frequency division multiplexing (O-SEFDM) system reduces the required communication spectrum by employing non-orthogonal and overlapping sub-carriers. This results in higher spectral efficiency relative to an equivalent optical-orthogonal frequency division multiplexing (O-OFDM) delivering the same data rate. O-SEFDM technique can save spectrums in both the electrical and optical domains. However, due to the loss of orthogonality, detection of O-SEFDM signals becomes more complicated. In this work, we employ a hybrid soft Iterative Detection (ID) together with fixed sphere decoder (FSD), concurrently optimizing performance and complexity. We show that for Bandwidth Compression Factor (BCF) of up to 25 percent, we can achieve the same performance as O-OFDM. This verifies Mazo´s rates of transmission 25 percent faster than the Nyquist rate. We report a 4QAM system occupying approximately the same bandwidth as that of an 8QAM with 1.6 dB improved error performance for the same transmission rate. The same system shows only minor power penalty (1 dB) relative to its 4QAM OFDM bit rate equivalent but with the advantage of 30% bandwidth saving. This study reports¹ optical and electrical bandwidth saving with minor error performance degradation and paves the way for practical.