| The work is targeted on designing new sensing devices based on the Sagnac interferometer principle, and improving existing devices. It consists of three major parts.; First, a new all-optical intensity noise subtraction scheme for the Interferometric Fiber-Optic Gyroscope (IFOG) will be described. Although it is very simple compared to electronic noise subtraction schemes reported in the literature, the proposed technique yields similar (or even superior) noise reduction performance.; Second, a novel architecture of the IFOG will be described. A stable phase bias, which is essential for normal operation of a gyroscope, is created in the present scheme via interference of spatial light modes in free space. In comparison, traditional versions of IFOG use the so-called phase modulation-demodulation technique to create the phase bias. Not only is the traditional technique costly, it has also proven to be the major source of errors in the gyro. Performance of the new IFOG design will be studied both theoretically and experimentally. It will be shown that this new gyroscope offers a practical trade-off between performance and cost.; The third (and the major) part of the work deals with developing a prototype of a practical interferometric fiber-optic current and voltage sensor. First, special "spun" fiber, which is used as a sensing element in the sensor, will be analyzed in detail. It will be shown how and why such a fiber greatly improves the accuracy and stability of the device. Then, prototypes of practical current and voltage sensors will be described. The phase bias necessary for measuring current and voltage is again created passively by means of a Faraday rotator. This makes the bandwidth of the sensor much higher compared to standard phase modulation-demodulation signal processing techniques, where the bandwidth is limited to approximately 1/4 of the modulation frequency. Finally, we will demonstrate a new "closed-loop" signal processing scheme for the current sensor. In this scheme, a signal from the current to be measured is exactly compensated by current through a solenoid placed on the sensing fiber coil. In this form, the device acts as a current transformer, potentially capable of operating in the range of frequencies from nearly DC to several tens of kHz. |
