摘要:
A sensor that measures a difference of currents at two locations along a conductor. The sensor uses two fiber optic current sensors. One current sensor at the first location measures current and has a nulling coil about its sensing loop, which carries current to null out the reading of current. Another current sensor at the second location measures current and also has a nulling coil about its sensing loop. The nulling coil of the latter sensor has the same current as the nulling coil of the sensor at the first location. For similar current sensors sensing the same magnitudes of current at their respective locations will have their outputs nulled to zero. However, if the first sensor output is nulled out and the sensor at the second location is sensing a different amount of current than the sensor at the first location, with the same amount of current in its nulling coil, then the output of the second sensor will indicate the difference of currents at the two locations, thereby indicating a loss or a gain of current along the conductor.
摘要:
An interferometric fiber optic gyroscope having compensation electronics to virtually eliminate rotation rate sensing errors caused by Kerr effect in the IFOG due to differing intensities of the counter-propagating beams relative to each other. Compensation accounts for varying intensities of the beams due to all or some changes of: the light beam splitter ratio relative to temperature; fiber coil loss due to temperature and longevity; and the intensity of the light source because of age.
摘要:
A noise reducer for reducing the results in the system output signal of optical noise introduced into an optical subsystem therein, having a phase modulator, by a source through obtaining a noise representation signal used to offset the noise components in the signal obtained from the output of the optical subsystem. This noise representation signal is not delayed in the obtaining thereof by any more than half the delays of the waves emitted from the source in reaching the optical subsystem output. The noise reducer may incorporate a device for adjusting the amplitude of the noise representation signal. It may also include another device for adjusting the phase of the noise representation signal, which may be used to affect the amplitude of the noise representation signal. These adjustments can result in an optimization of the noise representation signal so as to better effectively cancel the optical noise signal at the output of the fiber optic gyro having the noise reducer. The phase adjustment may be accomplished by affecting the phase of the bias modulation signal that goes to demodulate the fiber optic gyroscope system output signal or to demodulate both the fiber optic gyroscope system output signal and the noise representation signal, before the two latter signals are combined. A generator may be used for constructing a periodic signal, such as a triangular wave, having an appropriate amplitude and phase, to be a noise representation signal that is used to offset or cancel the noise components in the output signal from the fiber optic gyroscope system.
摘要:
In accordance with the preset invention, an optical interferometer employed as a current sensor is provided with visibility compensation and scale factor compensation. In accordance with the present invention, the interferometer is constructed so as to propagate a pair of optical beams along a defined optical path, where the optical interferometer includes a pair of optical beams that travel along at least a portion of the defined optical path such that a phase shift is induced between the pair of optical beams in response to a measureand, for example electrical current. At least one photodetector is responsive to at least a portion of the sum of the pair of optical beams and provide a beam output signal indicate thereof. From the beam output signal, a first signal is derived that is indicative of the visibility of the interferometer. A signal processor derives from the beam output signal an output signal indicative of the bias point of the interferometer, where the bias point is indicative of the induced phase shift in response to the measurand. A compensated interferometer output signal indicative of the induced phase shift is derived as a function of the visibility signal and bias point signal. In a specific embodiment of the invention, the visibility signal may simply be the output of a signal averaging circuit which in turn may adjust the gain of the signal processing circuit.
摘要:
A current sensor having an optmized optical fiber coil for sensing the magnetic field of a current of wire passing by or through the coil. The coil is optimally spun such that a particular ratio of the spin rate to the intrinsic polarization beat length is such for best maintenance of the circular polarization state of the light in the coil. The coil fiber may also be Terbium doped for greater sensitivity. The phase or birefringence modulation of the light may be piezoelectric or electro-optic. A Faraday rotator may be used in place of those modulators. The system may be open loop or closed loop. The feedback scheme may be via the modulator or the phase nulling current affecting the sensing coil.
摘要:
An apparatus utilizes a two-mode optical waveguide with a non-circular core to provide stable spatial intensity patterns in both propagation modes for light propagating therein. The light has a wavelength, and the non-circular core has cross-sectional dimensions selected such that (1) the waveguide propagates light at that wavelength in a fundamental mode and a higher order mode, and (2) substantially all of the light in the higher order mode propagates in only a single, stable intensity pattern. Embodiments of the invention include, for example, modal couplers, frequency shifters, mode selectors and interferometers. One of the interferometer embodiments may be used as a strain gauge.
摘要:
A master-slave current sensor system for measuring, for example, differential current on a transmission line is described. The slave current sensor can be periodically recalibrated (or have a compensation value re-calculated) based on the master sensor's average output, and the slave sensor can be unpowered and remote from an electronics box which receives its measurements. Health monitoring and fault location can also be performed using the master-slave optical current sensor system, optionally in conjunction with one or more voltage sensors.
摘要:
A sensor provides an analog sensor output signal that is first converted by a A/D converter, followed by a digital signal processor having a digital signal output that is converted to an analog signal by way of a D/A converter so as to provide an analog information output signal indicative of a parameter quantity intended to be sensed. An analog dither signal and/or a digital dither signal is provided for modulating the A/D converter input signal and/or D/A converter input signal, respectively, separately, or in combination, to enhance dynamic range accuracy of the resultant analog information output signal representative of the quantity of the parameter intended to be sensed.
摘要:
A true dV/dt voltage sensor having no need for a ground reference for measurement. The sensor is connected at two places on the electric line to be measured. The voltage wave has a delay between the two places on the line and the difference is sensed and converted into a voltage measurement. Another approach is to connect the sensor at one place on the electric line. This approach has the second connection through a phase delay circuit that has an input connected to the same place. The delay between the one connection and the output of the phase delay circuit is sensed and converted into a voltage measurement. The sensed difference is a voltage, which is applied across a device, such as an electro-optic crystal, an integrated optic circuit (IOC) or a Mach Zehnder interferometer, which is a light medium that has a birefringence or an index of refraction that varies with changes of applied voltage. The variation of birefringence changes the polarization state of the light going through the device. The intensity of at least one polarization of light is detected and converted to an electrical signal. The intensity of the two interfering light beams from the legs of the Mach Zehnder interferometer is a function of the measured voltage. The electrical signal is integrated into a signal indicative of the magnitude of the voltage being measured on the electric line.
摘要:
An optical fiber is subjected to a series of traveling flexural waves propagating along a length of the fiber. At least a portion of an optical signal propagating within the optical fiber in a first propagation mode is coupled to a second propagation mode. The optical signal in the second propagation mode has a frequency which is equal to either the sum of or the difference between the frequency of the optical signal in the first propagation mode and the frequency of the traveling flexural waves. The frequency of the optical signal in the second propagation mode is shifted upward or downward from the frequency of the optical signal in the first propagation mode as determined by the direction of propagation of the first optical signal with respect to the direction of propagation of the traveling flexural waves, and as also determined by whether the phase propagation velocity of the optical signal in the first propagation mode is greater than or less than the propagation velocity of the optical signal in the second propagation mode.