Experimental Investigation Of A Linewidth-insensitive Coherent AM Optical Link

Video delivery and antenna remoting are two important applications of analog optical links [l]. High dynamic range is needed for both applications. At low signal power, the dynamic range of coherent systems is larger than that of direct detection systems [2]. In many applications, semiconductor lasers have to be used as light sources to make the system compact. However, laser diodes have relatively large linewidth (due to phase noise) that may cause signal degradation. To reduce the impact of phase noise, some kind of phase noise cancellation is required. Theoretical investigation of one cancellation technique - AM-WIRNA (WIRNA stands for the receiver structure: Wide bandpass filter - Rectifier - NArrow lowpass filter) heterodyne system - has been reported in [2]. That theory predicts that, with WIRNA detection, distortion is quite small.