Contents 1. Introduction
With the advent of broadband wireless systems operating at microwave frequency bands, and with the entailed shrinkage of cell coverage for high capacity wireless access, the simplification of the antenna stations becomes crucial to reduce access infrastructure cost, and to deploy the access-points at the most accurate locations according to the optimal network plan. For this purpose, radio-over-fiber (RoF) distribution antenna systems are an attractive option for the transparent delivery of wireless data signals from a central controller location (CS) to remote antenna sites (AS) via optical fiber. In this way, the entire wireless signal processing load is confined at the CS whereas the simplified ASs contain the RF modules. Among many other RoF techniques, the Optical Frequency Multiplication (OFM) principle proposed in [1] is a cost-effective and dispersion-tolerant method to optically generate microwave frequencies and deliver wireless signals to a remote AS. Based on the generation of harmonics by frequency modulation of a light source, it has proved the up-conversion and transparent delivery of QAM signals in the 17GHz band over several kilometers of multimode fiber [3]–[4]. This was achieved by sweeping the wavelength of a continuous wave laser with an external phase modulator to obtain a wide optical frequency deviation.
