In modern communication networks, Orthogonal Frequency Division Multiplexing (OFDM) combined with Cognitive Radio (CR) has the potential to combat with the spectrum scarcity problem by efficiently utilizing the frequency bandwidth of the network. OFDM is a subset of frequency division multiplexing that realizes the Multi-Carrier Modulation (MCM) technique through a single channel, and has many advantages that are critical for high-speed CR networks. This paper carries out a performance analysis based on the Bit Error Rate (BER), Q-factor, input power, and link distances of the Coherent Optical OFDM (CO-OFDM) system using a 512-subcarrier 16 Quadrature Amplitude Modulation (16QAM) technique for the transmission of optical signals at a data rate of 10 Gbps. The results indicate that the possible reliable transmission distance is up to 150 Km without using any compensation scheme in relation to the link distance and input power.