Real-time restoration method for image transmission in a multimode optical fiber.

A new restoration method for a distorted image transmitted through a single step-index multimode fiber is presented. The transmission of the reference beam along with the image enables one to compensate on a real-time basis for the distortion caused by the fiber modal phase dispersion. At the receiver end the interference between the Fourier-transformed image and the reference beam creates gratings in a photorefractive crystal. It is theoretically shown that, owing to the spatial segregation characteristic of the Fourier-transformed mode distribution of the step-index fiber, the phase conjugation of thetransmitted image through four-wave mixing obtained from the crystal reconstructs the original image.