IMPROVEMENT OF EXTINCTION RATIO OF OPTICAL FIBER AND COMMUNICATION EQUIPMENT UTILIZING SAID FIBER

摘要

PURPOSE:To improve the extinction ratio of the signal light inputted to an optical fiber having the diffenct refractive indices in orthogonal optical main axis directions in such a manner that the polarization plane thereof coincides with the short axis by making pump light incident on said optica fiber while making the plane of polarization thereof coincident with the long axis. CONSTITUTION:A signal light source 1 outputs polarized signal light to the short axis of a polarization maintaining optical fiber 6 and a pump light source 2 outputs polarized pump light to the long axis of the fiber 6. The mode of the pump light is preferably the waveguide mode of the lowest order propagating in the fiber 6. The wavelengths mode of the lowest order propagating in the fiber 6. The wavelengths of the signal light and pump light may be equal or different. The signal light is transmitted through a dichroic reflecting mirror 4 an is made incident on the fiber 6. The pump light is reflected by a total reflecting mirror 3 and the mirror 4 and is made incident on the fiber 6. The pump light component is separated and removed by a polarizer 7 at the output end of the fiber 6.