| 摘要 |
PURPOSE:To obtain an inexpensive and stable variable wavelength optical filter which suits to a communication device using an optical fiber by causing Fabry- Perot effect in an optical fiber which has a reflecting film on both end surfaces to transmit part of light energy. CONSTITUTION:The reflecting film is formed of a dielectric multilayered film which reflects 90-99% of light energy on both end surfaces of the optical fiber 2. A piezoelectric element 3 and a plate 4 of ceramic are stacked one over another and pressure is applied by using a vise 5 to press the plate 4 against a base. When light is made incident on the optical fiber 2, resonance is caused by the Fabry-Perot effect in the optical fiber 2 to such wavelength lambda that the lens L of the optical path between both end surfaces is mlambda/N (m: natural number, N: refractive index of waveguide part of optical fiber), so that light with the wavelength lambda is transmitted. Further, no resonance occurs to light wavelength lambda' slightly different from the wavelength lambda, so the light with the wavelength lambda' is not transmitted. When the voltage of a power source 6 is varied, the piezoelectric element deforms to vary the pressure, the refractive index becomes N+DELTAN, and the resonance wavelength lambda varies, thus obtaining the optical filter which varies in transmission wavelength lambda. |
