Coherent Optical OFDM System or Long-Haul Transmission

In this paper, the coherent optical – orthogonal frequency division modulation (CO-OFDM) technique for transmission of optical signal at 10Gbps data rate has been investigated. The CO-OFDM technique has been evaluated using quadrature phase shift keying (QPSK) modulation technique. The use of Dispersion compensation fiber (DCF) in various compensation schemes, i.e., post, pre and symmetrical configuration along with Single mode fiber (SMF) has been studied. The effect of variation in input power values and various compensation schemes has been investigated in terms of Q-factor, bit error rate (BER). Q-factor has been calculated from the constellation diagram. The overall observation shows that the faithful transmission distance can be increased by using DCF and the better performance is observed in using DCF in post compensation scheme in QPSK when the input laser power is 5dBm. It is determined that faithful transmission without using compensation scheme is possible for 100km. As we shift above 100km compensation scheme are required for realistic transmission and the best choice is post compensation scheme for transmission up to 145km.