The JDS Uniphase WL1000 Series Wavelength Locker module is designed for detecting and locking DFB laser wavelengths in DWDM systems. By using a high precision Etalon, two photodetectors, and two splitters, it is capable of locking a wavelength range from 191.8THz to 196.2THz. The wavelength accuracy of +/-2.5GHz is achieved by temperature control built within the module.