METHOD FOR MEASURING EXTINCTION RATIO OF CONSTANT POLARIZATION FIBER

摘要

PURPOSE:To measure accurately an extinction ratio of a constant polarization fiber by taking out a light polarized in a certain direction from the light discharged from a single mode fiber and receiving the taken-out light by a fiber which has a function to eliminate the clad mode. CONSTITUTION:The light discharged from a single mode fiber 1 is converted to a parallel light by a lens 2 and is projected to an analyzer 3. Only a certain polarized component is taken out by the analyzer 3 and is condensed by a lens 4 and is received by a light receiving fiber 6. This fiber 6 has a mode field diameter smaller than that of the fiber 1 and has a function to eliminate the clad mode. Consequently, the light propagated in a part other than the mode field part of the fiber 1 is not made incident on the mode field part of the fiber 6. Thus, a power meter provided in the exit of the fiber 6 can measure the optical power of only the fundamental mode light of the fiber 1.