Wavelength Reuse for Two-Direction Transmissions of Optical CDMA Signals on Radio-Over-Fiber Application

In this paper, we propose a radio over fiber (RoF) system based on optical code-division multiple access (OCDMA) with the wavelength reuse technique. The proposed network supports two-direction transmissions between a central office (CO) and base stations (BSs). Wavelength reuse reduces the system complexity by using a part of optical spectrum for downlink signals as the light source for uplink signals. Therefore, the BSs have a simple structure since the light sources are centralized at the CO. Spectral-amplitude coding (SAC), encoding signals on the user's spectrum, is used to identify the desired user without multiple access interference (MAI). We demonstrate a two-direction transmission of binary phase-shift keying (BPSK) signals over an OCDMA network to show the system practicability. The SAC codes with a low cross-correlation value are used to transmit OCDMA signals to reduce the system bit-error rate (BER).