The Coherent Optical Orthogonal Frequency Division Multiplexing System (CO-OFDM) is the combination of the OFDM system with the advantages of the coherent detection. The CO-OFDM is mainly used for high-speed data transmission systems like 100 GB/s and 1 Tb/s. In the CO-OFDM implementation scheme, there are two kinds of noise such as the non-linear noise and the linear noise. The linear noise can be defined as the change in phase of the signal in the carrier signal when the carrier is passing through the optical fiber.

In this Thesis, an approach to reduce the linear noise in the CO-OFDM system is studied using the traditional skew detection techniques like Pilot Assisted (PA method) and Maximum Boundary Box (MBB method). The CO-OFDM system with Mach Zehnder Modulator (MZM) is analyzed and simulated in MATLAB and the linear noise is mitigated. The corrected signal is plotted in the form of the Bit Error Rate (BER) versus Signal to Noise Ratio (SNR) graph from high noise to low noise range environment. The BER of the two skew detection methods at SNR of 10 dB is compared under different M-QAM modulations like Binary Phase shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK). These comparisons show that the MBB method at Binary Phase-shift Keying (BPSK) modulation is best suitable to reduce the linear noise compared with PA method.