Tunable optical filter and tunable optical filter module

A tunable optical filter module, comprising:

• a tunable optical filter, having an optical axis, wherein an input light field moves forward from an upstream end to a downstream end of the optical axis, and passes through the tunable optical filter to form an output light field, the input light field has a main frequency range and a sub-frequency range, the output light field has the main frequency range, and the tunable optical filter comprises:
• an optical filtering element, having a lens body, a first coating film and a second coating film, wherein the first coating film and the second coating film are respectively disposed on a first surface and a second surface of the lens body opposite to each other, and a resonant cavity with a cavity length is formed inside the lens body;
• and
• a temperature controlling assembly, thermally connected with the optical filtering element, wherein the temperature controlling assembly controls a temperature of the optical filtering element to adjust the cavity length, so as to select the main frequency range;
• a light incident assembly, disposed on the optical axis, and guiding the input light field to enter the tunable optical filter;
• and
• a light receiving assembly, disposed on the optical axis, and receiving the output light field from the tunable optical filter.