Capacity Enhancement Based on Using Hybrid SCM with SAC-OCDMA Using Different Codes for OFC and FSO Transmission Systems

A new hybrid optical fiber communication (OFC) and free space optics (FSO) communication systems are proposed for enhancing the transmission capacity. It is based on using subcarrier modulation (SCM) with spectral amplitude coding based optical code division multiple access (SAC-OCDMA) technique using three different codes. Permutation vector (PV) code, zero cross correlation (ZCC) code, and fixed right shift (FRS) code are used. The performance is evaluated for various numbers of users, data rate, effective power levels, number of subcarriers, and number of carrier channels. Additionally, the effects under different fog conditions including light fog (LF), medium fog (MF), and heavy fog (HF) are evaluated. Moreover, the proposed FSO system achieves ranges of 1.8 km, 1.05 km, and 0.8 km under LF, MF, and HF conditions respectively. Our results show that the proposed OFC system supports 7, 6, and 5 simultaneous users with PV, ZCC, and FRS codes respectively. Similarly, each user carries 5 channels, and each channel carries 14 subcarriers with 1 Gbps information per subcarrier when PV code is adopted. As for FSO transmission, the proposed hybrid system can support up to 22, 18, and 14 users under LF, MF, and HF respectively. Each user also carries information from 5 channels. All results are obtained at BER less than 3× 10^-3.