Coherence selective sensor system

A method of optically sensing dynamic displacements over a large dynamic range with high linearity comprising the steps of:

• (a) using an optical source of low coherent light having a given polarization to generate optical signals non-coherent to small pathlength differences;
• (b) propagating said low coherent light through a fiber optic to a remotely located fiber sensor;
• (c) rotating the polarization of said low coherent light, producing a reflected light signal by reflecting a first portion of the light, rotating said first portion of the light, and producing a transmitted light signal by transmitting a second portion of the light through the sensor, such that the reflected light signal and the transmitted light signal are propagated back towards the source through the fiber optic, in a manner which provides a phase displacement without coherence between the reflected and transmitted light signals with information of interest;
• and
• (d) propagating phase displaced signals to a reference transducer and repropagating the phase displaced signals to produce a coherent interferometric optical signal by matching pathlength difference between repropagated signals from the transducer and the signals from the sensor to within an arbitrary difference of (2n+1).pi./2 radians, n.pi. radians or any angle therebetween.

A method of optically sensing optical propagation variations over a large dynamic range with high linearity comprising the steps of:

• (a) using an optical source of low coherent light to generate linearly polarized optical signals non-coherent to small pathlength differences;
• (b) propagating said low coherent light through a fiber optic to a remotely located fiber sensor;
• (c) linearly polarizing said light by an angle of 45 degrees;
• (d) reflecting a first portion of the light back towards said source and rotating said first light portion again by an angle of 45 degrees to produce a reflected signal, and transmitting a second portion of the light through the sensor and fiber coupler in a manner which rotates said transmitted light by 90 degrees and produces a transmitted signal, such that the reflected signal and the transmitted signal are propagated back towards the source through the fiber optic, in a manner which provides a phase displacement without coherence between the signals, said phase displacement containing information of interest;
• and
• (e) propagating the phase displaced signals to a reference transducer and repropagating the signals to produce a coherent interferometric optical signal by matching pathlength differences between the repropagated signals from the transducer and the reflected and transmitted signals from the sensor to within an arbitrary difference of (2n+1).pi./2 radians, n.pi. radians or any angle therebetween.

A method of optically transmitting information, comprising:

• (a) using an optical source of low coherent light to generate a linearly polarized optical probe beam non-coherent to small pathlength differences;
• (b) splitting said probe beam into first and second optical beams;
• (c) passing said first beam through an integrated optics phase modulator wherein said phase modulator is operable to inscribe electrical information onto said first beam, and passing said second beam through an optical fiber, in a manner which provides a phase displacement without coherence between said first and second beams, said phase displacement containing information of interest;
• (d) coupling said first and second beams into a common transmission fiber;
• and
• (e) propagating the phase displaced first and second beams to a receiver which includes a reference transducer operable to produce a coherent interferometric optical signal therefrom.