Fiber dispersion induced nonlinearity in fiber-optic links with multimode laser diodes

In analog RF fiber-optic (FO) links with directly modulated multimode laser diodes (LD's), nonlinear distortions of the received modulation signal occur due to fiber dispersion. Using a simple analytical two mode model, we show that the mutual compensation of strong nonlinearities between particular modes breaks down at high-modulation frequencies. The effect can be observed even in 1300-nm links with single-mode (SM) standard fibers. Simulations as well as measurements of intermodulation (IM) illustrate this argument.