Coherent Optical OFDM With Index Modulation for Long-Haul Transmission in Optical Communication Systems

In this paper, it is proposed to enhance coherent optical orthogonal frequency-division multiplexing (OFDM) system by using index modulation in terms of bit error rate (BER) and spectral efficiency for different levels the fiber nonlinearity. OFDM with (CO-OFDM-IM), information conveyed not only through activated subcarriers but also indices active subcarrier that are dynamically updated at transmitted symbol rates. Unlike conventional (CO-OFDM) system, adjusting number CO-OFDM-IM provides improved BER performance reduction signal peak-to-average-ratios, when nonlinearity becomes significant. The simulation results illustrate has better CO-OFDM have similar efficiency. Also, can provide than low-to-medium order such as BPSK, QPSK, 16QAM.