| A novel method and apparatus for sensing AC and DC electric fields incorporating a fiber-optic transducer mounted directly on the tip of an optical fiber waveguide has been demonstrated. The transducer employs a conductive Fabry-Perot microcavity bounded by a conductive, thin and corrugated silicon diaphragm. When the conductive microcavity is placed into an electric field, the electric field is excluded from within the equipotential cavity, which acts as a Faraday cage, and a net electrostatic force exerted on the surface of the diaphragm. The diaphragm deflects linearly and uniformly under the influence of the extremely low electrostatic pressures which are induced. The diaphragm deflection modulates the reflectance within the optical fiber by varying the gap of the cavity. The change in reflected light is measured and correlated to the field strength using and improved dual-wavelength referencing technique which compensates for bending and transmission losses in the optical fiber.; Electric fields in the range of 0 to 300KV/m were successfully measured. The minimum intensity detected was of the order of 40KV/m. This relatively low intensity is due to the high boron-diffusion of the fabricated silicon diaphragms. However, higher sensitivities are possible by thinning the diaphragm, increasing its radius, reducing the boss ratio or decreasing the corrugation depth.; No corona or discharge effects were noticed and a good repeatability was observed in the measurements. |
