Contributions to the acoustic signal sensitivity of fiber distributed-feedback (DFB) lasers in air are investigated both theoretically and experimentally. The theoretical results show that the dominant contribution to the laser frequency shift comes from adiabatic temperature shifts in the surrounding air at lower frequencies and from pressure at higher frequencies. The transition frequency was found to be between 5 and 20 kHz, depending on the elastic boundary conditions of the fiber laser. The acoustically induced frequency shifts of two fiber DFB lasers were measured, and the sensitivities varied from 0.61 MHz/Pa at a 100-Hz acoustic frequency to 0.34 kHz/Pa at a 15-kHz acoustic frequency.
© 1999 Optical Society of America
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.6810) Instrumentation, measurement, and metrology : Thermal effects
(140.3490) Lasers and laser optics : Lasers, distributed-feedback
(140.3510) Lasers and laser optics : Lasers, fiber
Sigurd Weidemann Løvseth, Jon Thomas Kringlebotn, Erlend Rønnekleiv, and Kjell Bløtekjær, "Fiber Distributed-Feedback Lasers Used as Acoustic Sensors in Air," Appl. Opt. 38, 4821-4830 (1999)