An actuator mechanism for a tunable optical filter unit that filters a selected wavelength band of the input light from a DWDM input light. The input light comprises a plurality of wavelength bands or optical channels of light, each of which are centered at a respective channel wavelength. The actuator mechanism exerts a substantially linear force to strain or stress a tunable optical filter element to a desire reflection wavelength(s). A controller, in accordance with a control algorithm, provides a drive signal to the actuator mechanism in response to a command signal and a feedback signal indicative of the center wavelength of the desired optical channel(s) to be filtered. The actuator mechanism includes a drive mechanism that translates linearly a slide in response to the drive signal. The linear slide includes a sloped engagement surface for engaging a flexure arm assembly that provides a substantially linear force in a direction of displacement, which is substantially perpendicular to the direction of translation of the slide, to the optical filter unit for tuning the Bragg grating of the optical filter element.