Method for facile and accurate measurement of optical fiber dispersion maps

There is a great need for accurate and convenient measurement of the chromatic dispersion parameter, D, as a function of distance along a span of dispersion-shifted fiber. While other methods have been proposed and tested for the determination of such dispersion maps, those methods really measure λ₀, the wavelength of zero dispersion, rather than D itself. They further require extensive data-taking over a considerable wavelength range, so that the measurements for just one map tend to take a long time. By contrast, the method we describe measures the map D(λ_i,z) directly, where λ_i is the wavelength of one of the two fixed-wavelength sources used, and the data for a given map can be taken (including many repetitions for signal-averaging), processed, and displayed, in just a few seconds. The method also requires access to only one end of the fiber. Our method for measuring D is based on either of the two strongest four-wave mixing (FWM) processes. The method thus involves launching, simultaneously, strong, submicrosecond pulses at two pump wavelengths into the fiber, so that they may generate FWM product fields at Stokes and anti-Stokes wavelengths, sequentially in each part of the fiber