Radio-over-fiber transport systems with an innovative phase modulation to intensity modulation converter

Abstract. Robust optical phase modulation (PM) schemes have been widely employed in the development of radio-over-fiber (RoF) transport systems. However, the signals produced by these PM schemes require a delay line interferometer (DI), a fiber Bragg grating (FBG), an optical band-pass filter (OBPF), or dedicated dispersive devices to convert them back into the intensity modulation (IM) signal format prior to detection by a photodetector (PD). Inserting a costly DI into a transport link can significantly increase overall cost, and the use of a fixed working window OBPF, FBG, or dedicated dispersive devices to achieve the conversion is inflexible. To overcome these problems in PM-based RoF transport systems, a long-reach RoF link with an innovative PM-to-IM converter is proposed and experimentally demonstrated. Compared with the published PM schemes, the proposed architecture can utilize a vertical-cavity surface-emitting laser (VCSEL) to achieve the same performance of the published PM-to-IM converter at a lower cost. In addition, by adjusting the VCSEL driving current, a tunable range exceeding 350 GHz is experimentally obtained for the converter working window. The proposed long-reach RoF transport system is the first to achieve such PM-to-IM conversion by using a VCSEL and can contribute to the development of RoF transport systems.