Optical coherent receivers operate on the principle of mixing an incoming optical field (information channel) with a high power local oscillator (LO) signal prior to detection by the photodetector. tion assisted by digital signal processing (DSP). The objective of this tutorial chapter is to briefly review the operating principles of state-of-the-art ong-haul coherent optical communications systems. We review detection methods, including noncoherent, differentially coherent, and coherent detection, as well as a hybrid method. It allows the coherent detection of polarization-multiplexed optical signals in the C-Band by mixing the test signal with a built-in local laser. • Optical coherent receiver in a compact 19"-chassis • Coherent detection of high-speed optical dual-polarization m-PAM and m-QAM signals > 40, > 70 and 110 GHz versions available Applications • Test and measurement • Development of multi-terabit transmission systems and components • Polarization.
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