Alignment of a birefringent fiber Sagnac interferometer by fiber twist

We have shown that the Sagnac interferometer (SI) consisting of a coupler with output ports connected by high-birefringent fiber can be ideally adjusted by twisting the fiber at the output ports even though the coupler has birefringence. We used numerical simulations and experiments on a coupler with weak birefringence to show that the SI can be adjusted for any mutual orientation of the high-birefringent fiber and coupler port principal axes. This provides the simplest and the cheapest procedure of fabrication and adjustment of wavelength-division multiplexers and sensors based on the SI fabricated from a high-birefringent fiber and a non-polarization preserving directional coupler. (C) 1999 Published by Elsevier Science B.V. All rights reserved.