Measurement of pressure sensitivity of modal birefringence of birefringent optical fibers using a Sagnac interferometer

The paper presents a method of measuring the sensitivity of modal birefringence to pressure in birefringent optical fibers, based on a Sagnac interferometer with a birefringent fiber. In this method, the pressure sensitivity of modal birefringence of the optical fiber is determined on the basis of the measurement of the pressure sensitivity of the Sagnac interferometer including the fiber being measured, and the measurement of the group modal birefringence of that fiber, which is also performed by using the Sagnac interferometer. Utilizing the above method, measurements were performed of the pressure sensitivity of modal birefringence of birefringent optical fibers: a photonic crystal fiber and a bow-tie fiber, in the wavelength range 1460–1600 nm. Presented are the results of these measurements and their comparison with the results obtained by using different methods for the same types of fibers.