This Standard is applicable to single sections of PM fiber, to cascaded PM fibers, and to PM fibers interconnected with optical devices. It is also applicable to polarization-maintaining components that lack PM fiber pigtails, in which case the measurement is performed on a PM fiber jumper connected to the output of the component. The method requires gently stretching or heating approximately 0.1- 0.3 meters of PM fiber in order to generate at least a fraction of a cycle of phase shift between the fast and slow waves. Measurement applications are described in Annex C. In all applications of this method, the measured crosstalk value represents the accumulated crosstalk at the location along the PM fiber where the stretching or heating is applied, irrespective of the optical fibers and components that follow it.

Hereafter the test device is referred to as the "sample". The sample must include a section of PM fiber along which the polarization crosstalk is to be measured.

This Standard complements FOTP-193, which describes the measurement of polarization crosstalk at a plane beyond the output interface of the sample.

The polarization crosstalk of PM itself, without connectors, tends to be proportional to fiber length. In such cases the proportionality constant, commonly referred to as the "h-parameter," is another measure of PM fiber performance. A test method for h-parameter is the subject of FOTP-192.

This method is restricted to wavelengths greater than or equal to that at which the fiber is effectively single-mode. The cutoff wavelength of an uncabled fiber may be determined by FOTP-80.