RoF using optically equalized RSOA WDM-PON architecture

In this paper Reflective Semiconductor Optical Amplifier (RSOA) based Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) architecture is enhanced to carry radio frequency (RF) signals using an optical offset filtering technique in order to overcome the RF bandwidth limitation of the architecture. Intensity modulation induced chirp of a directly modulated RSOA is exploited to recover back phase information into intensity modulation. This technique eliminates an RF local oscillator part of an intermediate frequency (IF) mixing bank used for RF up and down conversion at the remote Optical Network Unit (ONU). The architecture was experimentally tested by transmitting 64-Quadrature Amplitude Modulation (QAM) OFDM WiFi 802.11g signals at 1 GHz and 6 GHz RF carriers through a 10 km fiber cable. Enhancing the 3dB bandwidth of the architecture from 1 GHz to 8.5 GHz made the RoF architecture stated in this paper capable of transmitting to and from base station of the most popular wireless access radio protocols, GSM, LTE and WiFi, without frequency up and down conversion at the base station. Experimental results indicate that a significant improvement of the received signal quality is achieved. Radio over Fiber (RoF) could be a powerful transmission system able to connect edge of the core network with the wireless access network converging multiple services relaying on an existing WDM-PON technology, replacing the copper cable bottleneck. Therefore, the architecture presented in this paper is a potential candidate to realize cheaper, simpler and colorless RoF transmission system in the access network.