Spectral-domain measurement of the strain sensitivity of phase modal birefringence of polarization-maintaining optical fibers

•New method of measuring strain sensitivity of phase modal birefringence is proposed.•New procedure for determining the sign of group modal birefringence is introduced.•New procedure for identifying the sign of phase modal birefringence is given.•The proposed measurement method was validated experimentally.

The paper presents a new and simple method of measuring the strain sensitivity of phase modal birefringence (dΔn/dε) of polarization maintaining fibers (PMFs). The method is based on measuring the spectral strain sensitivity of a strain sensor in the configuration of a Sagnac interferometer with a PMF. The measured spectral strain sensitivity of the sensor is used to determine the strain sensitivity of phase modal birefringence and the polarimetric strain sensitivity of the PMF. In addition, a new procedure for determining the sign of the strain sensitivity of phase and group modal birefringence of a PMF. Using this method, measurements of the strain sensitivity of modal birefringence of PMFs were performed: a PM-PCF and a Bow-Tie fiber, in the wavelength range 1460–1600 nm. A comparison of the results of these measurements with results obtained using other methods for the same types of fibers is presented.