PHOTO COUPLER AND METHOD FOR OPTICALLY COUPLING GRIN LENS-ATTACHED OPTICAL FIBERS

摘要

In an optical coupler in which optical fibers with GRIN lenses are disposed to face each other coaxially with a predetermined inter-lens distance being provided, even in the case where light with different wavelengths is transmitted, an appropriate coupling efficiency is obtained with each wavelength without changing the setting of the inter-lens distance for each wavelength,.;In an optical coupler 1 in which optical fibers with GRIN lenses 10, each having an optical fiber 11 and a GRIN lens 12 joined coaxially, are disposed to face each other coaxially, with a preset inter-lens distance WD being provided, and to couple transmission light of one of the optical fibers with GRIN lenses 10 to the other one of the optical fibers with GRIN lens 10, an intermediate position of the inter-lens distance WD is set to match a beam waist position of light with a shortest wavelength λ_m out of the transmission light, and a lens length z along an optical axis direction of the GRIN lens 12 is set in accordance with a bottom of a coupling loss due to a distance-shift D of a beam waist position of light with a wavelength λ_i different from the λ_m out of the transmission light.