Consistent with the present disclosure, an apparatus for producing a control signal for a laser source is provided, comprising an etalon configured to receive light from the laser source and control circuitry that provides the control signal, wherein the control signal is indicative of a comparison of (a) a difference between a forward transmission signal of the etalon and a backward reflection signal of the etalon and (b) the light received by the etalon from the laser source. Alternatively, the control signal is indicative of a comparison of (a) a difference between a forward transmission signal of the etalon and a backward reflection signal of the etalon and (b) a combination of the forward transmission signal of the etalon and the backward reflection signal of the etalon. Also consistent with the present disclosure, a method of aligning an etalon-based wavelength locking apparatus is provided, wherein the etalon of the apparatus is aligned with an optical axis along a direction of propagation of the output of the laser source by monitoring the signals indicative of the forward transmission signal and the backward reflection signal of the etalon.