We report the realization of a three-path Mach–Zehnder interferometer using single-mode fibers and two integrated 3 × 3 fiber couplers. We observed enhanced phase sensitivity, as compared with two-path interferometers, with a visibility of the interference pattern of more than 97%. This interferometer has an analog in two-photon interferometry, and we believe it to be the first nontrivial example of N × N multiport interferometers.
© 1996 Optical Society of America
Original Manuscript: August 14, 1995
Published: February 15, 1996
Gregor Weihs, Michael Reck, Harald Weinfurter, and Anton Zeilinger, "All-fiber three-path Mach–Zehnder interferometer," Opt. Lett. 21, 302-304 (1996)