Time domain response of an optically frequency swept Fabry-Perot interferometer

Time domain techniques are used to analyze the response of a Fabry-Perot interferometer to an optically swept carrier. A technique which increases the sensitivity or dynamic range of a fiber-optic sensor Fabry-Perot interferometer is analyzed. At slow optical sweep rates, classical Fabry-Perot fringes are produced when a linearly swept optical carrier interrogates a Fabry-Perot sensor interferometer. As the optical sweep rate is increased, the finesse of the Fabry-Perot fringes begins to decrease. Fringe finesse continues to deteriorate with increasing sweep rates until the fringes are destroyed, unless certain discrete sweep rates are selected. The analysis shows how the discrete sweep rates are selected. The sensitivity or dynamic range of a Fabry-Perot sensor system is increased by placing a second Fabry-Perot of appropriate length in series with the sensor Fabry-Perot. The phase information of the sensor interferometer is preserved in time domain multiplication in a manner that is analogous to the radio frequency processing of phase information.