System and method for optical heterodyne detection of an optical signal including optical preselection that is adjusted to accurately track a local oscillator signal

摘要

An optical heterodyne detection system includes a tunable optical pre-selector (514; 914; 1514; 1714) that is adjusted to track the frequency of a swept local oscillator signal. The tunable optical pre-selector is adjusted in response to a measure of the frequency of the swept local oscillator signal and in response to a measure of a portion of the swept local oscillator signal after the portion of the swept local oscillator signal has optically interacted with the optical pre-selector. In an embodiment, at least some portion of the swept local oscillator signal is modulated (2014) before it interacts with the optical pre-selector. In another embodiment, the optical pre-selector is dithered such that a dither (2016) is imparted on the portion of the swept local oscillator signal that interacts with the optical pre-selector. Whether the local oscillator signal is modulated or the optical pre-selector is dithered, the portion of the swept local oscillator signal that interacts with the pre-selector is detected and used in a feedback control circuit (730; 1530) to generate a control signal which causes the error between the center frequency of the pre-selector and the frequency of the swept local oscillator signal to be small. <IMAGE>