Method and apparatus for suppression of crosstalk and noise in time-division multiplexed interferometric sensor systems

Abstract

Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal. Modulating the phase difference between the interrogation signal and the leakage light suppresses the interference between the leakage light and the interrogation signal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a continuation of co-pending U.S. patent application Ser. No. 11 / 056,970 filed Feb. 11, 2005, which is herein incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally relates to time division multiplexed interferometric sensors. More specifically, the present invention relates to interrogating interferometric sensors in a manner that improves signal-to-noise ratios. [0004] 2. Description of the Related Art [0005] A interferometric sensor system may comprise a transmitter unit that produces an interrogation signal for the interferometric sensors, a sensor network, and a receiver unit that detects the signals from the sensor network. The sensor network may comprise several optical pathways from its input to its output, and some pairs of optical pathways form sensor interferometers. These optical pathways are called sensor pathways. Each sensor interferometer comp...

AI Technical Summary

Benefits of technology

"The invention aims to reduce crosstalk and noise in time-division multiplexed (TDM) systems by suppressing interference signals from unwanted light components that have propagated noise contributing pathways through the sensor network. The interference signals can lead to crosstalk and noise if they overlap in time with an optical signal received from an interrogated sensor. The invention achieves this by modulating the optical phase in the transmission time slots in such a way that the unwanted interference signals are distributed to frequency bands that do not affect the demodulated sensor signal. The modulation of the optical phase can be divided into a low frequency range and a high frequency range to suppress interference from noise contributing pathways and leakage light. The invention allows for suppression of noise and crosstalk from noise contributing pathways that have a delay that differs with several TDM repetition periods from the delay of the sensor pathways, and a largest possible frequency separation between an optical signal from the interrogated sensor and the unwanted interference signal."

Problems solved by technology

The unwanted light components may lead to crosstalk and noise if they overlap in time with an optical signal received from an interrogated sensor.

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