Optical fiber mode revolver, full-fiber mode multiplexer and demultiplexer

The invention discloses an optical fiber mode revolver, a full-fiber mode multiplexer and a demultiplexer. The optical fiber mode revolver comprises two inner cores which are symmetrically distributed, and the distances between the fiber core of the optical fiber and the two inner cores are preset distances; the angle between the connection line between the inner cores and the optical axis of the guided mode is the preset angle; the refractive index of the fiber core and the refractive indexes of two inner cores are different; the length of the optical fiber mode revolver is the beat length of two propagation constants of two guided modes which realize the mode conversion. Because the two inner cores are symmetrically arranged on two sides of the fiber core of the optical fiber, the refractive index of the inner core is different from that of the fiber core, and the incident guided mode can be rotated for 90 degrees. As a result, the mode conversion can be realized on the basis of the optical fiber, and the reusing of the mode can be realized. Besides, the mode revolver is based on the optical fiber, which prevents the insertion loss and effectively improves the performance of the communication system.