ABSTRACT
Coherent receivers offer far more efficient detection and sensitivity of optical signals under various phase, amplitude, or frequency modulation scheme techniques as compared to simple direct detection. This chapter aims to improve the performance of the optical phase lock loop (OPLL) with the development of a novel FPGA-based loop filter, a digital phase locking state loop. The OPLL and coherent optical reception are not recently demonstrated for digital signal processing-based receivers, but significant development and research related to OPLL has been extensively conducted in the 1980s in the early days of singlemode fiber optical communications. The chapter focuses on the digital LPF, which acts to condition the signal as seen at the photodiode, such that the local oscillator (LO) is driven to match or locking state in frequency and phase of the incoming optical signal. It describes a proposed technique for generating super-LO sources for mixing and betting with superchannels for Tbps coherent optical receivers.
