The nonlinear change of the dielectric constant (Kerr effect) in a glass fiber can be utilized to self-confine optical pulses in a multimode fiber at wavelengths longer than 1.3 μm. The range of the deviation in the group velocity Δνg of the different modes to be confined is given by Δνg2/νg2 ≤ 2(∂νg/∂f × f/νg)n2/n0|E|2, where f and νg are the frequency and the group velocity, respectively, of the mode; n0 and n2 (= 3 × 10−22 m2/V2) are the linear and nonlinear indices of refraction; and E is the peak electric field averaged over the cross sections of the fiber.
© 1980 Optical Society of America
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