Patent ID: 7986878
Filing Date: 2011-07-26
Classification: H04B

Abstract:
1. A method for optical communications, the method comprising: operating a programmable optical transmitter to provide a plurality of different quadrature amplitude modulation (QAM) constellations with different data bit rates in controlling signal modulation of an optical channel signal with a variable data bit rate selected from the QAM constellations; operating the optical transmitter to select one of the QAM constellations to control the signal modulation based on a condition of an optical transmission link that transmits the optical channel signal; and operating the optical transmitter to select another one of the QAM constellations to control the signal modulation when the condition of the optical transmission link changes, wherein after a period of time in operating the optical transmitter under the selected QAM constellation, the method comprises operating the optical transmitter to perform another test to measure performance of the optical transmission link; using measured performance of the optical link to determine whether the selected QAM constellation currently in use for the signal modulation in the optical transmitter is adequate; and operating the optical transmitter to select a different QAM constellation in transmitting the optical channel signal over the optical transmission link when the previously selected QAM constellation currently in use for the signal modulation is not adequate based on the measured performance.