ORGANE DE DEPLACEMENT DE FREQUENCE OPTIQUE ET SYSTEME DE TRANSMISSION LE COMPORTANT

摘要

An optical frequency shifter which has no insertion loss polarization dependency and no polarization mode dispersion is formed by: at least one ultrasonic wave generator for generating ultrasonic waves; at least one electric acousto-optic element forming at least one diffraction grating therein upon being applied with the ultrasonic waves generated by the ultrasonic wave generator; at least one polarization rotator for rotating a polarization plane of a first primary diffracted light produced by the diffraction grating, by 90 DEG ; and a light path through which an input light is entered into the electric acousto-optic element at a Bragg angle of the diffraction grating in a prescribed direction side, the prescribed direction being defined as either identical or opposite to a propagation direction of the ultrasonic waves, so that the first primary diffracted light is produced by the diffraction grating from the input light, a polarization plane rotated light produced by the polarization rotator is entered into the electric acousto-optic element at a Bragg angle of the diffraction grating in the prescribed direction side, and a second primary diffracted light produced by the diffraction grating from the polarization plane rotated light is outputted as an output light. An optical soliton-like return-to-zero pulse transmission system using a combination of this optical frequency shifter and a fixed optical filter in an optical amplifier repeater is also disclosed.