A variable optical amplifier mounts a fiber coupler within a flexure that provides for deflecting one section of the coupler with respect to another about a tapered intermediate section for controlling transmissions through the coupler. The flexure has a free portion suspended by a pair of resilient arms for relatively deflecting the coupler sections while minimizing friction and maintaining a fixed angular orientation with an actuator. A kinematic link between the flexure and the actuator is thermally compensated not only at a given deflection position but throughout the entire intended range of operation.