Real-time Fourier transformations performed simultaneously over multiwavelength signals

The real-time Fourier transformation (RTFT) has been previously proposed and demonstrated for a multitude of applications in the areas of optical communications, temporal signal processing, switching, filtering, time-division multiplexing, etc. Here, we present a technique for performing the RTFT simultaneously over all the channels of a multiwavelength (wavelength-division multiplexing) signal traveling in a single optical fiber. The technique only requires the reflection of the original signal in an appropriately designed structure of superimposed chirped fiber gratings. To demonstrate our proposal, we design a real-time optical spectrum analyzer operating on three different wavelength channels. The design is proved to function correctly by means of numerical simulations.