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Embedded multicore hollow fiber with high birefringence.

We fabricate and demonstrate a hollow fiber with multiple embedded cores (MCHF) based on a modified "suspended core-in-tube" preform technique. Its birefringence properties are controlled by the MCHF core's ovality, which could be controlled by the applied pressure and drawing temperature in the MCHF preform. An in-fiber Mach-Zehnder interferometer with 90.38% visibility is built by fuse-tapering a single-mode fiber to the MCHF, and the splice loss is less than 2 dB. We expect that the proposed MCHF has some potential applications in in-fiber interferometers without the polarization-induced fading problem and in the biosensing area.