Optical waveguide vibration sensor and method

A sensor for measuring parameters of vibrations, comprising:

• an interferometer including a first leg having a first optical path length and a second leg having a second optical path length formed such that the first optical path length is longer than the second optical path length;
• an optical signal generator connected to the interferometer to apply a frequency modulated optical signal input thereto;
• a phase modulator arranged for modulating the phase of optical signals guided by the first leg of the interferometer;
• a piezoelectric crystal arranged to receive vibrations to be measured and produce an electrical signal in response to stresses caused by the ground-borne vibrations, the electrical signal being connected to the first phase modulator such that the optical signals are modulated by a signal having the frequency of the vibrations being measured;
• and
• apparatus for processing optical signals output from the interferometer to determine the velocity and acceleration associated with the vibration.

A sensor for measuring parameters of vibrations, comprising:

• a planar optical waveguide structure;
• means for introducing an optical signal into the optical waveguide;
• means for detecting vibrations due to an external field and producing an electrical signal indicative of the vibrations;
• and
• a phase modulator connected to receive as an input the electrical signal indicative of the vibrations for causing a phase shift in the optical signal guided by the optical waveguide such that the phase shift is a known function of the magnitude of the vibration.

A method for forming a sensor measuring parameters of vibrations, comprising the steps of:

• forming an interferometer including a first leg having a first optical path length and a second leg having a second optical path length formed such that the first optical path length is longer than the second optical path length;
• connecting an optical signal generator to the interferometer to apply a frequency modulated optical signal input thereto;
• placing a first pair of electrodes adjacent one of the legs of the interferometer to form a first phase modulator;
• connecting a coil of wire between the pair of electrodes;
• arranging a magnet to have freedom of motion longitudinally inside the coil in response to externally applied forces, thereby inducing a voltage in the coil, the voltage being applied to the first pair of electrodes, which causes phase modulation of optical signals guided by the leg of the interferometer adjacent the first pair of electrodes;
• and
• processing optical signals output from the interferometer to determine the velocity and acceleration associated with the vibration.

A method for forming a sensor measuring parameters of vibrations, comprising the steps of:

• forming an interferometer including a first leg having a first optical path length and a second leg having a second optical path length formed such that the first optical path length is longer than the second optical path length;
• connecting an optical signal generator to the interferometer to apply a frequency modulated optical signal input thereto;
• arranging a first phase modulator for modulating the phase of optical signals guided by one leg of the interferometer;
• arranging a piezoelectric crystal to receive vibrations to be measured and produce an electrical signal in response to stresses caused by the ground-borne vibrations, the electrical signal being connected to the first phase modulator such that the optical signals are modulated by a signal having the frequency of the vibrations being measured;
• and
• processing optical signals output from the interferometer to determine the velocity and acceleration associated with the vibration.

A method for forming a sensor measuring parameters of vibrations, comprising the steps of:

• forming a planar optical waveguide structure;
• introducing an optical signal into the optical waveguide;
• detecting vibrations due to an external field and producing an electrical signal indicative of the vibrations;
• and
• connecting a phase modulator to receive as an input the electrical signal indicative of the vibrations for causing a phase shift in the optical signal guided by the optical waveguide such that the phase shift is a known function of the magnitude of the vibration.