Fiber laser sensor

A fiber laser sensor for sensing the magnitude of a variable, said sensor comprising,

• a first fiber laser oscillator,
• a second fiber laser oscillator, said fiber oscillators being spatially arranged parallel to each other,
• an optical fiber optically coupled to said first oscillator and to said second oscillator to allow energy transfer between said first oscillator and said fiber and between said second oscillator and said fiber, said fiber constituting a loss element for all net energy transferred to said fiber from energy transfers between said fiber and said first and second oscillators, said coupling causing said oscillators to oscillate at one of a plurality of a common frequencies,
• means for making the optical path length of one said oscillators longer than the optical path length of the other of said oscillators so that both of said oscillators have sufficient gain to sustain oscillation at only one of said plurality of common frequencies, and
• means for changing the optical path length of at least one of said oscillators in accordance with the magnitude of said variable.

A fiber laser sensor for sensing the magnitude of a variable, said sensor comprising,

• a first fiber laser oscillator comprised of a first glass birefringent fiber core doped with a laser-active dopant, said fiber having mirrors at each end and sustaining oscillations along one of two axes of polarization,
• a second fiber laser oscillator comprised of a second glass birefringent fiber core doped with a laser-active dopant, said fiber having mirrors at each end and sustaining oscillations along one of said two axes of polarization, said fiber oscillators being spatially arranged parallel to each other and rotated angularly with respect to each other so that the axes of polarization of each fiber are aligned,
• a third glass fiber core spatially aligned parallel to said fiber laser cores and spaced from each fiber laser core a distance which is less than one core diameter, said third fiber being optically coupled to said first oscillator and to said second oscillator to allow energy transfer between said first oscillator and said fiber and between said second oscillator and said fiber, said fiber said third fiber having optically transparent ends and constituting a loss element for all net energy transferred to said fiber from energy transfers between said fiber and said first and second oscillators, said coupling causing said oscillators to oscillate at one of a plurality of a common frequencies,
• a common cladding surrounding said first, said second and said third cores, said fibers and said cladding being cut at an angle with respect to the longitudinal axis so that the optical path length of one said oscillator fibers is longer than the optical path length of the other of said oscillator fibers so that both of said oscillators have sufficient gain to sustain oscillation at only one of said plurality of common frequencies, and
• means for changing the optical path length of at least one of said oscillators in accordance with the magnitude of said variable.

A differential fiber laser sensor for sensing the magnitude of a variable, said sensor comprising,

• two fiber laser sensor units, each of said units comprising,
• a first fiber laser oscillator,
• a second fiber laser oscillator, and
• a first energy transfer element optically coupled to said first oscillator and to said second oscillator to allow energy transfer between said first oscillator and said element and between said second oscillator and said element, said element constituting a loss element for all net energy remaining in said element from energy transfers between said element and said first and second oscillators,
• means for extracting energy from said first sensor unit,
• means for extracting energy from said second sensor unit, and
• means for mixing the energy extracted from said first sensor unit with the energy extracted from said second sensor unit to form output energy having a frequency which is the difference between the frequency of energy extracted from said first sensor unit and the frequency of energy extracted from said second sensor unit.