Applications of narrow-filtering based on optical coherent detection

Processing of high-frequency, wide-band signals is conveniently performed in the optical domain due to availability of optical filters which intrinsically have a wide-band response. On the other end, there are several application scenarios where very sharp pass-band filtering is required. In these cases, realizing the processing in the optical domain might not be technically simple, although filters of extremely high Q-factor have been demonstrated. This paper presents the feasibility of signal processing based on very sharp electrical filtering (<; 1 GHz around 193 THz) assisted by optical down-conversion, i.e., by means of optical coherent detection. In particular, we show experimentally two applications where the filtering capability is exploited to perform signal processing: the demodulation of phase-modulated optical signals and the implementation of a chirp-managed transmission link. Other possible applications of this technique will be also discussed at the presentation.