Method and apparatus for control of dpsk and dqpsk receivers and transmitters

Abstract

An optical communication device such as a transmitter or receiver has a control loop for controlling relative phase of two related optical signals based on signal peak intensity. An optical transmitter measures the signal peak intensity of a combined optical signal representing two data channels to adjust relative phase as desired. An optical receiver measures the signal peak intensity of combined electrical signals, single electrical signals or single optical signals to adjust relative phase as desired. Signal peak intensity is minimized or maximized by adjusting the relative phase, depending upon the modulation configuration used. The feedback control provides a consistent and robust control to stabilize the optical communication device in the presence of variables such as temperature changes, aging and manufacturing tolerances.

1 . A method for controlling an optical communication device having two or more optical paths, each for carrying an optical data signal, comprising:
 combining two or more optical data signals to produce one or more resultant signals;   monitoring peak intensities of the one or more resultant signals; and   adjusting a phase difference between the two or more optical data signals to influence the peak intensity of the one or more resultant signals to achieve a predetermined characteristic.