Abstract: A method is provided for sensing an environmental effect upon a sensing element and includes exposing the sensing element into the environmental effect, producing a light signal in the sensing element, modulating the light signal with a modulation signal, and determining a path length of the light signal as a function of the modulation signal. A fiber optic sensor is provided that includes a light source producing a light, a sensing element optically coupled to the light source such that the light propagates through the sensing element, a detector optically coupled to the sensing element. The detector detects light intensity propagating in the sensing element. An electronics processor receives the detector output and produces a modulation signal for the light. The processor further produces an output signal indicative of the environmental effect as a function of the modulation signal.

Abstract: An exemplary WDM coupling device may include optical fibers. The coupling device may also include region(s) having varying coefficients of thermal expansion. During a temperature variation, one or more of the region(s) may alter in size to substantially cancel temperature-dependent changes associated with the WDM coupling device.

Abstract: A method is provided for sensing an environmental effect upon a sensing element and includes exposing the sensing element into the environmental effect, producing a light signal in the sensing element, modulating the light signal with a modulation signal, and determining a path length of the light signal as a function of the modulation signal. A fiber optic sensor is provided that includes a light source producing a light, a sensing element optically coupled to the light source such that the light propagates through the sensing element, a detector optically coupled to the sensing element. The detector detects light intensity propagating in the sensing element. An electronics processor receives the detector output and produces a modulation signal for the light. The processor further produces an output signal indicative of the environmental effect as a function of the modulation signal.

Abstract: A fiber optic gyroscope with counter-propagating electromagnetic waves in a fiber-optic coil senses rotation about the coil. Such a fiber-optic gyroscope uses a bias modulation to bias the gyroscope on a rate sensitivity portion of the interferogram. Using a saw-tooth waveform as the bias modulation results in a system with many advantages over a system modulated by square waves or sinusoidal wave. For example, the system is less sensitive to cross coupling because the drive is significantly different than the detected signal. In addition, the saw-tooth waveform can be used in a closed loop scheme with the advantage of a frequency output proportional to the rate and a reduction or elimination of the known causes of dead band in a closed loop gyro.

Abstract: A fiber optic gyroscope (FOG) including a depolarizer having substantially equal first and second fiber segments of polarization maintaining (PM) fiber coupled to a single mode (SM) fiber loop. The first PM fiber segment includes sections of fiber connected together via a splice having an angle from about 35° to 55° between major axes of polarization of the sections which it connects. Similarly, the second PM fiber segment includes sections of fiber connected together via a splice having an angle from about 35° to 55° between major axes of polarization of the sections which it connects. The length of each fiber section is chosen to maintain the thermal and mechanical symmetry of the SM fiber loop.

Abstract: A fiber optic fault detector and generic fiber optic sensor system for detecting breaks in an optical fiber using a low coherence interferometric technique. The system comprises a light source configured to produce light traveling along the optical path, a modulator optically coupled to the light source configured to modulate at least a portion of the light as a function of a modulation signal, a detector optically coupled to the modulator configured to produce a detector output based upon a sensed intensity of the light, and an electronic array configured to receive the detector output and determine the optical fault. The low coherence interferometric technique allows for detection of a fault in the fiber with a minimal amount of test equipment and with higher measurement sensitivity and resolution. The system may alternatively include a transducer, positioned in place of the fiber under test, having a response which changes in reflective or optical path length.