Patent ID: 6278657
Filing Date: 2001-08-21
Classification: G01H,G01S

Abstract:
An acoustic sensor comprising:a source of light pulses;a first coupler which couples said light pulses to a first optical path having a first optical length and to an array of sensors, said array of sensors comprising at least a first sensor, said first sensor being in a second optical path having a second optical length different from said first optical length;an optical delay path;a polarization dependent second coupler, which couples light pulses received from said first optical path in a first polarization to said optical delay path and which couples light pulses received from said array in a second polarization to said optical delay path, said light pulses coupled to said optical delay path in said first polarization returning from said optical delay path to said second coupler in said second polarization, said light pulses coupled to said optical delay path in said second polarization returning from said optical delay path to said second coupler in said first polarization, said second coupler coupling said light pulses returning to said second coupler from said optical delay path in said first polarization to said first optical path to propagate therein to said first coupler, said second coupler coupling light pulses returning to said second coupler from said optical delay path in said second polarization to said array to propagate therein to said first coupler, said first coupler combining said light pulses from said first optical path and said light pulses from said array to cause light pulses traveling equal distances through said first optical path and said array to interfere and to generate a detectable output signal, said detectable output signal varying in response to acoustic energy impinging on said first sensor; andat least one detector which detects said detectable output signals to generate a detector output signal responsive to variations in said detectable output signal from said first coupler.