Optical Generation and Distribution of OFDM Ultrawideband Signals Over Fiber

Abstract

In this paper is presented an architecture aiming the distribution of orthogonal frequency division multiplexing (OFDM) signals, compatible with ultra-wide band (UWB) standards, in wavelength division multiplexing (WDM) radio-over-fiber (RoF) scenario. The suggested WDM architecture allows unicast and multicast transmission of OFDM signals within the standard millimeter-wave (mm-wave) UWB bands, from 3.1 to 10.6 GHz and from 57 to 64 GHz, respectively 8 GHz and 60 GHz. The generation of the OFDM-UWB signals with the desired mm-wave carriers' frequencies is made using an optical frequency-quadrupling technique, thus with lower bandwidth requirements for the optical modulator, and allowing the use of a lower frequency electrical drive signal. The OFDM-UWB signals distribution is fully passive, recurring to a cyclic AWG (Arrayed Waveguide Grating). Two types of modulation are used, double side band (DSB) for up-/down-link unicast transmission and DSB with carrier suppression for down-link multicast. In this later case, we avoid the need for high precision filtering, to remove the optical carrier at the receiver, providing a system with greater tolerance to frequency variations. The system's performance is evaluated for different bit rates, input powers and transmission distances, allowing transmission up to 12 km over single mode fiber (SMF), with a maximum EVM below the maximum permissible relative constellation error which is set to a root mean square (RMS) EVM of 14.13% ECMA-368 International Standard: High rate ultra wide-band PHY and MAC Standard, 2007.