Simple Coherent Optical Module
Coherent optical module refers to a typically hot-pluggable coherent optical transceiver that uses coherent modulation (BPSK / QPSK / QAM) rather than amplitude modulation (RZ/ NRZ / PAM4) and is typically used in high-bandwidth data communications applications. This document describes the basic principles of coherent optical modulation schemes used in Dense Wavelength Division Multiplexed (DWDM) networks. A modulation scheme continuously alters the property or properties of a waveform. This technology is the foundation of 10 Gb/s DWDM systems, which were state of the art in the early 2000s. Optical data transport started out like its electronic counterpart, with the simplest and therefore cheapest digital coding schemes: return-to-zero (RZ) or non-return-to-zero (NRZ) on/off-keying (OOK).
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