Tunable optical filter - US 20020149850 A1
A tunable optical notch filter employing a Fabry-Perot etalon has a first partially reflective mirror and a second mirror with variable effective reflectivity. Both the gap of the etalon and the effective reflectivity of the second mirror can be controlled, e.g. by TAB actuators, enabling a control of the central wavelength and the depth (loss) of the notch of the spectral response of the filter.