Patent ID: 7251023

Claim:
A fiber-optical sensor for measuring a quantity to be measured, comprising a pumping light source, a fiber laser and a detection and evaluation unit, wherein the fiber laser comprises (a) a birefringent first end reflector and a second end reflector, (b) a laser-amplifying fiber and a sensor fiber and (c) a means for mode coupling, wherein (d) the laser-amplifying fiber, the sensor fiber and the means for mode coupling are arranged between the first end reflector and the second end reflector, and wherein (e) in the fiber laser, light is capable of propagating in two optical states which are orthogonal to one another due to their polarization or their transversal space structure, wherein (f) the mutually orthogonal optical states can be coupled to one another by the means for mode coupling, and wherein (g) a number of longitudinal modes are capable of oscillating in each of the two orthogonal optical states in the fiber laser, and wherein (h) a change in the birefringence first end reflector can be achieved for the two orthogonal optical states in the sensor fiber by interaction of the quantity to be measured with the sensor fiber, characterized in that (i) the first end reflector is detuned with respect to the second end reflector.