Abstract: An optical switch operating on thermooptic effects has a branching section heater for heating a branching section of a core and a branched core heater for heating a branched core. The heaters are controlled separately so that the branching section and the branched core can be heated to respective temperatures so as to minimize insertion loss of inputted light and to prevent outputting light from a port not intended for light output.

Abstract: An optical switch operating on thermooptic effects has a branching section heater for heating a branching section of a core and a branched core heater for heating a branched core. The heaters are controlled separately so that the branching section and the branched core can be heated to respective temperatures so as to minimize insertion loss of inputted light and to prevent outputting light from a port not intended for light output.

Abstract: The optical filter is comprised of a thin film having a multi-layered structure free of a substrate. The multi-layered structure is composed of alternately superposed high refractivity layers and low refractivity layers with one another. Each layer has a dense composition effective to prevent absorption of water and exhibiting substantially the same internal stress. In production of the thin film, there is utilized a substrate soluble to a certain solvent. An optical material of high refractive index and another optical material of low refractive index are alternately deposited by accelerated energy particles on the substrate surface to form a thin film of multi-layered structure. Lastly, the substrate is dissolved into the solvent to separate the thin film to form the optical filter free of the substrate.