Generating higher-level quadrature amplitude modulation (QAM) using a delay line interferometer and systems and methods incorporating same

摘要

In general, optical communication systems and methods may generate higher-level nmQAM from nQAM signals using one or more delay line interferometers (DLIs) arranged in various configurations. The nQAM signals may be generated by a lower-level modulator, such as a BPSK modulator, QPSK modulator or lower-level QAM modulator, with binary driving signals. Different parameters of the DLIs, such as free spectral range (FSR), phase shift, and amplitude imbalance, may be selected to accomplish the desired higher-level nmQAM depending upon the nQAM signal.

主权项

1. An optical communication method comprising:
modulating at least one optical carrier at a channel wavelength with a binary data stream using at least one nQAM modulator to provide at least one nQAM signal, where n is an integer greater than one (1); and coupling the at least one nQAM signal into at least one delay line interferometer (DLI) to generate at least one nmQAM signal, where m is an integer greater than 1, wherein the DLI splits the nQAM signal into at least first and second nQAM signals on at least first and second DLI arms, and wherein at least one of the first and second DLI arms provides a time delay sufficient for a one symbol shift such that at least one of the at least first and second nQAM signals is shifted by one symbol relative to another of the at least first and second nQAM signals; and transmitting the at least one nmQAM signal over an optical transmission path.