Abstract: A tunable optical filter system receives an optical signal, from an optical fiber. A predetermined wavelength is to be selected from the optical signal. The filter has a first and second aligned collimating lens, each lens having a mirrored surface separated by a gap. The first collimating lens collimates the light beam and outputs a collimated output beam via the its mirrored output surface to the opposing mirrored surface. A diaphragm coupled to a frame has a pair of piezo elements position the diaphragm to adjust the gap to select a predetermined wavelength signal from the collimated beam. A coupler samples a portion of the beam for a servo that responds to an input signal that identifies the wavelength to be selected. The servo provides a pathlength control signal to the piezo elements to coarse select the predetermined wavelength signal from the collimated output beam.