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

Abstract

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 of the fiber nonlinearity. In the coherent optical OFDM with index modulation system (CO-OFDM-IM), the information is conveyed not only through activated subcarriers but also by indices of the active subcarrier that are dynamically updated at the transmitted symbol rates. Unlike the conventional coherent optical OFDM (CO-OFDM) system, adjusting the number of the active subcarriers in the CO-OFDM-IM system provides improved BER performance and reduction the signal peak-to-averageratios, when the fiber nonlinearity becomes significant. The simulation results illustrate that the proposed CO-OFDM-IM system has better BER performance when the proposed CO-OFDM-IM system and the CO-OFDM system have similar spectral efficiency. Also, the CO-OFDM-IM system can provide better spectral efficiency than the CO-OFDM system at the low-to-medium order modulation such as BPSK, QPSK, and 16QAM.INDEX TERMS Coherent optical communications, OFDM, OFDM with index modulation, spectral efficiency.

Highly Accurate Technique for CO-OFDM Channel Estimation Technique Using Extreme Learning Machine (ELM)

“…It indicates that the effect of different wavelengths is much less than that of the same wavelength. [31] illustrate that the proposed CO-OFDM-IM system has better BER performance when the proposed CO-OFDM-IM system and the CO-OFDM system have similar spectral efficiency. Also, the CO-OFDM-IM system can provide better spectral efficiency than the CO-OFDM system at low-tomedium order modulation such as BPSK, QPSK, and 16QAM.…”

“…To avoid this problem, calculations are done by minimizing the final weights 𝛽 𝐸𝐿𝑀 with the inclusion or a regularization parameter. In other words, the mean square error is given by equations (31,32). min 𝛽 𝐸𝐿𝑀 ,𝑒…”

“…Where, 𝛽 𝐸𝐿𝑀 * signifies the optimal solution of ELM. Thus to improve the accuracy of the predictions model, the expressions for 𝛽 𝐸𝐿𝑀 shown above are obtained when modifying the problem on equation (31)…”

High-Bandwidth Coherent OFDM-Nyquist-TDM Transceiver With Low-Bandwidth Electronics

“…With the steady introduction of new applications, technologies, and services, global traffic has been experiencing exponential growth. Over the past decade, the need for high-speed data communication and advanced signal processing has fueled numerous research efforts [1], [2], [3], [4], [5], [6], [7], [8]. Among other multi-carrier modulation techniques, orthogonal frequency division multiplexing (OFDM) has been extensively studied in communication systems as one possibility to meet the exponential rise of internet traffic requirements [1], [2], [3], [4], [5], [6], [7], [8], [9].…”

“…Over the past decade, the need for high-speed data communication and advanced signal processing has fueled numerous research efforts [1], [2], [3], [4], [5], [6], [7], [8]. Among other multi-carrier modulation techniques, orthogonal frequency division multiplexing (OFDM) has been extensively studied in communication systems as one possibility to meet the exponential rise of internet traffic requirements [1], [2], [3], [4], [5], [6], [7], [8], [9]. OFDM is well known for its many advantages such as subcarrier flexibility, and high spectral efficiency [1], [2], [3], [4], [5], [6], [7], [8], [9].…”