The nonlinear refractive index n<sub>2</sub> of silica fiber (24 m) and erbium-doped fiber (10 m) is measured to within an accuracy of 5% by use of time-delayed photorefractive beam coupling of intense 53-ps, 1.064-μm pulses that experience self-phase modulation in the fibers. The resultant induced grating autocorrelation response yields a value of n<sub>2</sub>/A<sub>eff</sub> and a calibration standard for the fiber. A phase shift of the order of 0.19π can be detected and is limited only by laser amplitude fluctuations. A unique advantage of this technique is its ability to measure n<sub>2</sub> accurately in short lengths (z≤25 m) of fiber, whereas other approaches typically use much longer lengths of fiber (z≥100 m) .
© 2003 Optical Society of America
(060.2410) Fiber optics and optical communications : Fibers, erbium
(060.4370) Fiber optics and optical communications : Nonlinear optics, fibers
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(190.5330) Nonlinear optics : Photorefractive optics
Hernando Garcia, Anthony M. Johnson, Ferdinand A. Oguama, and Sudhir Trivedi, "New approach to the measurement of the nonlinear refractive index of short (< 25 m) lengths of silica and erbium-doped fibers," Opt. Lett. 28, 1796-1798 (2003)