Multiple-cavity optical filter using change of cavity length

摘要

This invention describes a tunable optical filter to be used in an optical communication system. The filter of this invention has a pair of resonator cavities (18, 19) which are cascaded. The lengths (X, Y) of each of the cavities (18, 19) change simultaneously with the change in length (X, Y) of a piezoelectric sleeve (1) which contacts a reflective surface (4, 7) of each of the cavities (18, 19) through spacers (3). The sleeves (1) and spacers (3) are set so as to move the reflecting surfaces (4, 7) of the cavities (18, 19) along a single axis in response to a single control signal. When optical signals are passed through the two cavities (18, 19) and when the ratio of the length (X, Y) of the cavities (18, 19) is adjusted to a predetermined ratio of integers, the resonator cavity will resonate at a desired wavelength.