We present a new technique for measuring the intermodal beat length of a two-mode optical fiber. We formed a Fabry–Perot fiber cavity by depositing reflective mirrors on the fiber tips. As the fiber is stretched, two series of resonance peaks are observed. One series is due to the resonance of LP01q modes and the other is due to the LP11q modes. From the separation of resonance peaks as a function of cavity length, we deduce the intermodal beat length of the fiber. The measurement principle and the experimental confirmation are discussed.
© 1997 Optical Society of America
Original Manuscript: January 2, 1996
Revised Manuscript: October 21, 1996
Published: May 20, 1997
Masoud Vaziri and Chin-Lin Chen, "Intermodal beat length measurement with Fabry–Perot optical fiber cavities," Appl. Opt. 36, 3439-3443 (1997)