Birefringent active fiber laser sensor

An active laser perturbation sensor, comprising:

• an optical waveguide for receiving and propagating a pump light of a predetermined wavelength launched into said optical waveguide;
• a plurality of lasers, each having a laser cavity, disposed successively along said waveguide, each being pumped by said pump light, at least a portion of at least one of said lasers being exposed to a perturbation;
• at least one of said lasers having a laser cavity with a predetermined birefringence, having lasing light at a first lasing frequency along a first polarization axis and a second lasing frequency along a second polarization axis, said at least one of said lasers emitting an output light having frequencies and polarizations at said first and said second lasing frequencies and polarizations;
• a difference frequency between said first and second lasing frequencies being related to the magnitude of said birefringence and said birefringence varying in response to said perturbation;
• combining means for combining said first and said second polarizations of said output light onto a common polarization as a commonly polarized output light;
• detector means for providing an electrical signal, indicative of said commonly polarized output light, having a frequency component related to said difference frequency between said first and said second lasing frequencies;
• each of said laser cavities having a pair of reflective elements on opposite ends thereof and having a gain medium therebetween, and each of said reflective elements having a reflective wavelength spectrum;
• and
• said reflective wavelength spectrums of said reflective elements of different ones of said lasers being spaced such that there is minimal overlap therebetween over the range of the magnitude of said perturbation being sensed.