ACOUSTO-OPTIC FIBER-OPTIC FREQUENCY SHIFTER USING PERIODIC CONTACT WITH A SURFACE ACOUSTIC WAVE

摘要

ACOUSTO-OPTIC FIBER-OPTIC FREQUENCY SHIFTERUSING PERIODIC CONTACT WITH A SURFACE ACOUSTIC WAVEAbstract of the DisclosureAn acoustic wave is propagated colinearly with theoptical signals in an optical fiber to cause coupling ofan optical signal in one propagation mode of the opticalfiber to the other propagation mode in the opticalfiber. The acoustic wave is selected to have an acousticwave length which is shorter in the direction of opticalpropagation than the optical beat length between the twopropagation modes of the fiber. In order to causephase-matching between the two optical propagation modes,a periodic structure is used to cause the acoustic wave tocontact the optical fiber at periodic locations so thatthe coupling between the two propagation modes isperiodically enabled and disabled. The periodic contactof the acoustic wave with the optical fiber has the effectof adding a spatial propagation constant. The periodicityof the periodic structure is selected so that the spatialpropagation constant of the periodic structure is equal tothe mismatch in the propagation constants of the twooptical propagation modes and the acoustic wave. Thepresent invention thereby provides a means of obtaininggreater shifts in the optical frequency while using acolinearly propagating acoustic wave.