Optical Fiber Gain Medium with Modal Discrimination of Amplification

摘要

An active multimode optical fiber consisting of a first core section ( 11 ), a thin barrier layer ( 12 ) material having a thickness (d 2 ) and a lower refractive index than that of the first core section by an index difference (Deltan), a second core section ( 13 ) having a refrective index equal or higher than that of the first core section, and a cladding ( 14 ) having an index lower than that of the first core section. Said index difference and said thickness are selected so that a fundamental core mode couples less strongly with said cladding modes than higher order core modes. A scheme of changing the symmetry of the fiber for reduced sensitivity of the fundamental mode of the first core section to resonance effects.