Apparatus for detecting wavelength drift and method therefor

摘要

In an optical communications network employing a wavelength division multiplexing (WDM) system, different wavelengths of electromagnetic radiation are used to transmit different signals. Because the wavelength of electromagnetic radiation that a laser device emits can drift as the temperature of the laser device changes, channels can overlap causing cross-talk. Consequently, the present invention provides a laser wavelength locking control loop apparatus (5) comprising a wavelength selective device (9) and a photodector (11), coupled to a feedback controller circuit (13). Electromagnetic radiation emitted by the laser device (7) is provided to the wavelength selective device (9) which provides a first output signal at a first wavelength and a second output signal at a second wavelength. The first and second output signals are directed to the photodetector (11) so as to coincide when incident thereupon. A beat signal results from the coincidence of the first and second output signals and this is used to measure wavelength drift.