Patent ID: 8023829
Filing Date: 2011-09-20
Classification: G01D,H04L

Abstract:
1. Fibre-optic sensing apparatus including apparatus for demodulating a first phase-modulated signal the modulation of which corresponds to a desired signal and noise, the apparatus including a reference sensor arranged to generate a second phase-modulated signal, and further comprising a phase-demodulation unit arranged to receive the first phase-modulated signal and a second phase-modulated signal the modulation of which corresponds to substantially the noise only, said demodulation unit comprising: a quadrature signal generator (QSG) implemented in digital electronics, arranged to receive the second phase modulated signal and to output corresponding I and Q signals; a digital quadrature phase-demodulator (DQPD) adapted to mix said I and Q signals with said first modulated signal to produce an output proportional to said desired signal; and an analog to digital converter (ADC) arranged to digitize the inputs to the DQPD and QSG.