Wavelength reuse in UWB-over-fiber networks

Wavelength reuse techniques for bidirectional ultra-wide band (UWB) over fiber (UWBoF) networks are presented. The downstream optical signal from the central station (CS) is reused for upstream data transmission with the original data erased at the base station (BS). Two wavelength reuse schemes for the generation of a clear optical carrier at the BS are theoretically analyzed and experimentally demonstrated. In the first scheme, the wavelength reuse is based on phase-modulation to intensity-modulation (PM-IM) conversion and destructive interferencing using a polarization modulator (PolM) and a fiber Bragg grating (FBG). A theoretical analysis is performed which is verified by an experiment. In the second scheme, the wavelength reuse is based on injection locking of a Fabry--Perot laser diode (FP-LD) and polarization multiplexing. The UWB injection signal contributes to better BERs of both downstream and upstream services and a lower power penalty cause by the wavelength reuse of the whole system than the baseband signal. A bidirectional point-to-point transmission of over a 25-km single-mode fiber (SMF) using a single wavelength from the CS in each scheme is demonstrated.