Phase-Insensitive RF Envelope Detection Allows Optical Heterodyning of MHz-Linewidth Signals

We demonstrate the insensitivity of the envelope detection based mobile terminal to phase fluctuations of the RF signal. This property enables the generation of radio over fiber (RoF) signals heterodyning non-narrow linewidth laser signals and using direct modulation. We report the experimental generation of up to 2-Gb/s orthogonal frequency division multiplexing (OFDM) signals and their transmission over a 25-km long fiber span using direct modulation and DFB lasers with a combined linewidth of 2.1 MHz with a resulting BER below 10(-3).