In both civil and military applications it is important to minimize the cost of surveillance and to cover large areas without patrolling. The sensor described in this thesis is designed to be a robust alternative to traditional surveillance systems by both being inexpensive and able to cover considerable distances. The sensor is using the change of polarization as a measure of the external mechanical and geometrical perturbation on a standard optical fiber. Multiple test signals with different polarization are used to collect enough information to fully describe the fibers effect on the state of polarization. By comparing several of these descriptions the external perturbation can be quantified. The polarimetric signal processing to extract this information is formulated in this thesis. A laboratory set up of the sensor has been evaluated. A characterization of the components used in the sensor has been made and the results are presented in the report. The sensor was tested tested both with a controlled mechanical strain and in a field trial. After evaluating the results it is evident that the evolution of the test signals polarization state can be monitored and that the Mueller matrix describing the fibers effect on the state of polarization can be formulated.