Single Photodiode, Single Wavelength, and Single Polarization 65 Gb/s 16-QAM and QPSK Coherent Transmission

This paper presents an investigation of an optical transmission scheme using a single photodetector (PD) which, as in conventional coherent detection systems, allows the linear transfer of the amplitude and phase information of the optical field into the electrical domain. This is possible by means of optical heterodyne detection and the adjustment of the carrier-to-signal power ratio (CSPR), thus the undesired signal-to-signal beating products (SSBP) due to the PD square-law, can be considered negligible. Through simulation, the CSPR impact on this scheme is determined. Then, its experimental validation is done for a single wavelength and single polarization transmission with a total bitrate of 65 Gb/s over 10 km of standard single-mode fiber (SSMF).