Abstract: Systems and methods for a transmitter quality metric (TQM) for a standalone estimate of coherent optical transmitter performance include, responsive to defining a reference receiver having known parameters, conducting noise loading on an output signal from a transmitter under test; utilizing the reference receiver and a calculation to determine a transmitter only required signal-to-noise ratio (RSNR) penalty, ?RSNRtx; and providing the ?RSNRtx as a transmitter quality metric (TQM). The transmitter only RSNR penalty is a difference between a RSNR to achieve a required pre-forward error correction (FEC) bit error rate (BER) and a theoretically required RSNR for an ideal modem.

Abstract: A discrete phase shifter and a method for discrete phase shifting in which an input signal is split into two signals. One of the split signals is phase shifted by a first fixed amount by a first fixed phase shifter cell, and the other split signal is phase shifted by a second fixed amount by a second fixed phase shifter cell. A selector is utilized to select at least one of the two split phase shifted signals and to input these to a vector summer. The vector summer synthesizes an output signal that is phase shifted with respect to the input signal. In this manner, the output signal is discretely phase shifted either by the first fixed amount, the second fixed amount, or, by selecting both of the split signals prior to vector summing, the sum of these amounts.