About this calculator

This calculator computes the polarization beat length of a polarization maintaining (PM) optical fiber. Beat length is the distance after which the polarization state has made one rotation, i.e. the phase shift between the two polarization modes is . Beat length is one way to define a PM fiber's birefringence, the other two being the index difference or the propagation constant difference between the polarization modes.

Either or (in ) can be given as input to the calculator along with the wavelength of the signal. is related to the index difference as follows

so the calculator first calculates (if necessary)

and then the beat length as