Proceedings PaperFibre Optic Two Polarization Interferometer With Unambiguous Digital Readout And Its Application As Remote Strain Sensor
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For overcoming the ambiguity of fringe counting in fibre optic interferometers with remote readout two phase shifted (π/2) interference signals are produced employing the residual birefringence of non-ideal monomode fibres. A simple logic circuit determines the sign of the measurand change corresponding to the sign of the phase shift and feeds the counting pulses into an up-down counter. The method is tested by strain measurements with jacketed as well as bare sections of fibre employing a Mach-Zehnder setup.