Carrier assisted differential detection with a generalized transfer function.

Direct detection capable of optical field recovery not only enables high-order modulation for high spectral efficiency (SE) but also extends the transmission reach by digital compensation of linear channel impairments such as chromatic dispersion. Recently, to bridge the gap between direct detection and coherent detection, carrier assisted differential detection (CADD) has been proposed for the reception of complex-valued double-sideband signals. In this paper, we extend the concept CADD to a general selection of the transfer functions, beyond the originally-proposed delay interferometer. To validate the proposed CADD approach, we utilize an optical filter based on silicon photonics microring resonator (MRR) as one realization of the generalized transfer functions. With the MRR based optical filter, both the required carrier-to-signal power ratio (CSPR) and the optical signal-to-noise ratio (OSNR) sensitivity are drastically improved over the conventional CADD due to the significantly suppressed signal-signal beating interference (SSBI). In addition, the proposed CADD is resilient to the wavelength offset up to several GHz between the transmitter laser and the center wavelength of the MRR based optical filter. With the proposed transfer function, CADD provides a novel approach for achieving high-SE transmission with superior receiver sensitivity and could be potentially useful for inter-/intra-datacenter or mobile front haul applications.