Litton Systems, Inc.

James D Green

Lawrence J Hershman

Eugene L Ferraro

Kevin R Wagg

A calibration technique for a signal processing system, wherein a digital down converter is selected by a system controller for calibration. The digital down converter's settings are copied into a calibration digital down converter which mimics the operation of the selected digital down converter. A best polarization diversity detector signal path, an optimal phase offset value for an in-phase data signal, an optimal phase offset value for a quadrature phase data signal, and a normalized gain value for the in-phase and quadrature phase signals of the selected digital down converter are determined. The system controller updates the selected digital down converter with the determined optimal settings. This procedure is repeated for each digital down converter in the signal processing system, while the signal processing occurs simultaneously.

Method and apparatus for calibration of a signal processing system

A calibration technique for lasers of a data acquisition module in a signal processing system, wherein an optimal value of a phase modulation coefficient is calculated for each laser and used as the amplitude of a cosine wave signal for the laser module carrier frequency for phase modulation of the laser output signal. The phase modulation coefficient is determined from a global average I/Q ratio, calculated for all channels of the selected laser module, as an average of all I/Q ratios of in-phase and quadrature phase angle components of the signals returned from the sensors. The phase modulation coefficient for the selected laser module is determined empirically or by dividing the previously determined phase modulation coefficient by the previously determined global average I/Q ratio.

Method and apparatus for calibration of a multi-channel fiber optic

A technique for interrogation of fiber optic interferometric sensors wherein an optical signal is modulated by an array of fiber optic sensors in response to acoustic pressure. Modulated signals (channels) from each sensor are multiplexed onto a single fiber optic cable and the multiplexed signal is input to a polarization diversity detector having at least two outputs. The optical signal is converted into a digital, electrical signal. A plurality of digital down converters demultiplex and demodulate the separate channels and output in-phase data and quadrature phase data for each of the signal channels. A system controller connects to the digital down converters and to a calibration digital down converter. The calibration digital down converter, controlled by the system controller, mimics an operation of each digital down converter in turn in order to determine optimal digital down converter settings for each digital down converter. The system controller updates the optimal settings for each digital down converter such that the digital down converters are dynamically calibrated according to the optimal settings. The in-phase and quadrature phase data output of the digital down converters are then processed with an acoustic signal processor.

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Newbury Park, CA, United States of America

James D Green