Toward 100 Terabit per Second All-Optical Frequency-Division Multiplexing System

Abstract

The conventional optical orthogonal frequency-division multiplexing (O-OFDM) systems use electrical (digital) fast Fourier transform (FFT) to generate the OFDM signal in the electrical domain by embedding the data on the different radio frequency subcarriers. The resultant OFDM signal then modulates the optical carrier. To overcome the speed limitation of electrical FFT, an optical FFT (OFFT) may be used to generate directly an optical OFDM signal where the data are embedded on different optical subcarriers. This leads to all-optical OFDM (AO-OFDM) systems which are characterized by terabit per second (Tbps) transmission data rate while keeping the features behind OFDM signaling such as reducing the effect of fiber group-velocity dispersion and polarization dispersion. In this paper, the transmission performance of AO-OFDM fiber communication systems is investigated for different operating parameters and link impairments.The work in this paper is divided into two main parts. The first part covers the design and test of N-OFFT where the number of bins N varies from 4 to 64. The proposed configuration is based on 3 dB directional couplers, optical phase shifters, and optical time delays. In the second part, the designed OFFTs are used to implement AO-OFDM communication systems operating with different numbers of optical subcarriers N_sc, symbol rates R_s, and modulation formats. The systems are implemented in VPIphotonics 9.8 software environment to assess its transmission performance. The system performance is recorded for different dual-polarization (DP) M-quadrature amplitude modulation (QAM) formats (16-, 32-, 64-, 128-, and 256-QAM), different numbers of optical subcarriers N_sc (8, 16, 32, and 64), and different symbol rates R_s (25, 50, and 100 GBd). The simulation results indicate that 100 Tbps total data rate transmission can be achieved over 400 km standard single mode fiber using DP 256-QAM system operates with 64 optical subcarriers and 100 GBd symbol rate.