The method and
system operate to calibrate a transmission
laser of the dense
wavelength division
multiplexer (DWDM) and to lock the
laser to a selected transmission
wavelength. In one example, the transmission
laser is a widely
tunable laser (WTL) to be tuned to one of a set of International
Telecommunications Union (ITU) transmission grid lines for transmission through an optic
fiber. To lock the WTL to an ITU grid line, a portion of the output beam from the WTL is routed through the etalon to split the beam into a set of transmission lines for detection by an etalon fringe
detector. Another portion of the beam is routed directly to a laser
wavelength detector. A wavelength-locking controller compares signals from the two detectors and adjusts the temperature of the etalon to align the wavelength of one of the transmission lines of the etalon with the wavelength of the output beam, then controls the WTL in a
feedback loop to lock the laser to the etalon line. The wavelength-locking controller thereafter monitors the temperature of the etalon and keeps the temperature constant to prevent any wavelength drift in the etalon. In one example, the optical components are aligned so that laser wavelength
detector receives a portion of the laser beam directly from the laser so that phase characteristics of the laser beam are not affected by an intervening beamsplitter thereby permitting improved wavelength locking. In another embodiment, an etalon
chirp filter is provided for reducing or eliminating optical frequency
chirp, regardless of the particular ITU channel being used for transmission.