Optical pulse multiplication and temporal coding using true time delay achieved by long-period fiber gratings in dispersion compensating fiber

Abstract

We present an optical pulse multiplication and temporal coding method for OCDMA systems. The true time delay among the pulses was obtained by utilizing the difference in the propagation speeds of the core mode and a co-propagating cladding mode coupled by a long-period fiber grating. By cascading gratings we could get an equally spaced 40-GHz pulse train from a 10-GHz input train. The dispersion compensating fiber having an inner cladding structure enabled us to have the gratings that were not sensitive to the polymer jacket on the cladding surface, and also allowed shortening the device length. Various coding and decoding of a pulse train are possible by controlling the separations among the gratings. (C) 2004 Optical Society of America.