PM fiber based sensing tapes with automated 45° birefringence axis alignment for distributed force/pressure sensing.

Polarization maintaining (PM) fibers can be used for distributed force/pressure sensing in which the birefringence axis of the PM fiber should preferably be oriented 45° from the direction of the force/pressure for the maximum sensitivity. However, it is a challenge to achieve such 45° axis orientation for a long length of PM fiber in practice. In this paper, we report the development of what we believe the first equipment and process for making PM fiber based sensing tapes, capable of automatically adjusting the fiber axis orientation 45° with respect to the tape surface.

Accurate method for measuring the thermal coefficient of group birefringence of polarization-maintaining fibers.

We present a method to accurately measure the group birefringence variation with temperature in high-birefringence polarization-maintaining (PM) fibers using a distributed polarization analyzer. By analyzing polarization cross-talk peaks purposely induced at both ends of a PM fiber, the temperature coefficient of group birefringence can be accurately obtained. We confirm the theoretical prediction that the group birefringence of PANDA and TIGER PM fibers decrease linearly with temperature from -40 °C to 80 °C, and find that the temperature coefficients are -5.