All-optical Frequency Up-conversion Technique using Four-wave Mixing in Semiconductor Optical Amplifiers for Radio-over-fiber Applications

An all-optical frequency up-conversion technique based on a four-wave mixing (FWM) effect in semiconductor optical amplifiers (SOAs) was utilized for conversion of an optical intermediate frequency (IF) signal (2.5 GHz) to an optical radio frequency (RF) signal (40 GHz) by mixing with an optical local oscillator (LO) signal (37.5 GHz). This scheme provides positive conversion efficiency of 5.77 dB for the optical IF power of -22 dBm and the optical LO power of -13 dBm. The conversion efficiency was almost flat for the LO frequency range from 20 GHz to 47.5 GHz. The phase noise at the LO frequency of 37.5 GHz was -84.5 dBc/Hz (at 10 kHz offset) after the frequency up-conversion.

I Introduction

Recently, radio-over-fiber (RoF) systems are attracting much attention for broadband wireless access applications including wireless backbone networks, remote medical applications, and multimedia broadcasting. The RoF system is attractive especially for microwave and millimeter-wave frequency bands since the optical fiber has advantages including ultra-low loss and ultra-wide bandwidth. The RoF system has an inherent compatibility with the wavelength division multiplexing (WDM) technique that is suitable for wireless networks based on microcell or picocell configuration where numerous remote antenna stations are required [1].