DIRECTIONAL COUPLER FOR POLARIZATION PLANE MAINTAINING OPTICAL FIBER APPLIED WITH EXTERNAL FORCE

摘要

PURPOSE:To improve polarization maintainability, i.e. a quenching ratio greatly by providing the 1st and the 2nd quartz substrates with a means which applies elliptic jacket type polarization plane maintaining optical fibers embedded in the substrate respectively with force at right angles to their elliptic jackets from both sides. CONSTITUTION:An SPF1 is embedded fixedly in a quartz substrate 2 so that the long axis direction of its elliptic jacket 13 is at right angles to the surface of the quartz substrate 2. The surface of the quartz substrate 2 is polished together with the SPF1 and then a pressure clamp 20 for applying a 1-1,000kg/cm<2> (normally 2kg/cm<2>) to the SPF1 at right angles to the long axis direction of the elliptic jacket 13 from both side is added to the quartz substrate 2. Two quartz substrates 2 manufactured as mentioned above are stacked one over another across a refractive index matching liquid 3 so that polished surfaces face each other, and the cores 11 of SPFs 1 in surfaces of the two quartz substrate 2 are coupled closely so that evanescent coupling is caused, thus obtaining a polarization plane maintaining optical fiber direction coupler which provides 1:1 branching.