Enhanced self-phase modulation in tapered fibers.

Fiber tapering reduces the effective area and increases the Kerr nonlinear phase shift of the fundamental mode. A significant nonlinear effect was observed in a micrometer-diameter centimeter-long section of tapered fiber at a wavelength of 1550 nm. The numerical simulation of a second-order soliton entering the taper gives a spectral widening that matches the observed spectrum.