Wavelength locking of a laser device

An optical module comprising:

• housing;
• a laser device positioned in the housing and operable to output a divergent light beam;
• an optical fiber output arrangement configured to receive a front portion of the divergent light beam for coupling the front portion of the divergent light beam to an optical fiber;
• and
• a wavelength locking arrangement configured to receive a rear portion of the divergent light beam for locking the operational wavelength of the laser device to a selected frequency, wherein the wavelength locking arrangement does not comprise a collimating lens, wherein the wavelength locking arrangement comprises:
• an etalon device arranged to receive and filter a first portion of the rear portion of the divergent light beam;
• a first monitor photodetector positioned to detect only a central portion of the first portion of the rear portion of the divergent light beam, following filtering by the etalon device and to generate a wavelength-dependent detection signal;
• and
• a second monitor photodetector operable to detect a second portion of the rear portion of the divergent light beam, said second portion travelling from the laser device to the second monitor photodetector without passing through the etalon device and to generate a wavelength-independent detection signal.