Impact of Laser Relative Intensity Noise on a Multiband OFDM Ultrawideband Wireless Signal Over Fiber System

We experimentally investigate and theoretically analyze the performance of a multiband orthogonal frequency division multiplexing (MB-OFDM) ultrawideband (UWB) wireless signal over fiber system considering the impact of laser relative intensity noise (RIN). Two types of RIN are considered: laser intrinsic RIN and laser phase-noise-converted RIN due to fiber dispersion. To reduce the impact of intrinsic RIN, laser output power of 2 dBm and beyond should be used. With the increase of fiber length and/or laser linewidth, UWB wireless signal over fiber is more degraded due to the converted RIN. For a given 0.6 dB degradation of error vector magnitude (EVM), the allowed laser linewidth is 30 MHz for 20 km of standard single-mode fiber for the first three bands. However, the converted RIN has much greater impact on higher-frequency UWB channels, depending on fiber length. A laser with a linewidth of less than 1 MHz will ensure that the EVM penalty due to the converted RIN is less than 1 dB for all 14 bands of MB-OFDM UWB.