A method for analyzing higher-order dispersion in optical fiber

One of the factors that limit the transmission capacity of the fiber optics communication channel is the chromatic dispersion. Analyzing chromatic dispersion with high accuracy is essential for further improvement in DWDM systems as well as modern dispersion compensation techniques. In this paper, we present a new approach that can be applied for analyzing higher-order chromatic dispersion in SI fibers. In this regard, at first we present a closed formula for finding the exact values of the derivatives of the refractive index with respect to wavelength based on the so-called Sellmeier dispersion formula, in any order and any wavelength. Then we use the Taylor expansion of the propagation constant at the ZMD wavelength, when the second-order dispersion is equal to zero. In fact we use the Taylor expansion for just those terms, which are often ignored, and then we derive a close formula for finding the effects of higher-order dispersion. As an example we investigate the dispersion formula for Gaussian sources.