CAPABILITIES OF LDPC CODES TO IMPROVE THE PRODUCTIVITY OF OPTICAL TELECOMMUNICATIONS WITH OFDM

Abstract

The main prospects for the use of optical electronic communications in the implementation of information channels using OFDM technology are considered. The main differences between optical telecommunications using OFDM technology in comparison with the radio frequency analogue are determined. A general overview of the specifics of signal generation and processing in optical OFDM channels is provided. The factors for increasing the spectral efficiency of optical telecommunications when using OFDM modulation are determined. Circuit solutions for generating and processing signals in optical telecommunications are described. A MATLAB-Simulink designed circuit for studying optical channels is presented. The results of the influence of dispersion phenomena on the shape of multi-position signals in optical channels are presented. The principles of operation of the optical circuit of a QPSK type signal receiver with digital processing units are considered. A method for mathematical description of quasi-cyclic LDPC codes for use in optical telecommunications is presented. The specifics of decoding LDPC codes based on the SPA algorithm are described. Synthesized transmitter and receiver circuit for coherent detection with OFDM and anti-jamming LDPC coding. The specifics of the formation of the OFDM design of optical telecommunication signals for conditions of inter-symbol and inter-channel interference are described. The results of mathematical modeling of the performance of an OFDM optical channel with various designs of noise-resistant codes and their comparison with the proposed LDPC codes are presented. The results obtained unconditionally indicate the advantage in energy gain of coding (EGC) of codes of the G-LDPC type to all considered – current codes. Research shows that the coherent detection scheme provides an EGC improvement of approximately 2.5 dB over the direct detection scheme. Prospects for further research in this direction will be focused on taking into account the rate indicators of information flows with different types of codes as part of optical-OFDM systems, which will make it possible to formulate recommendations regarding the correct choice of channel multiplexing strategy.