| 摘要 |
A low loss fiber optic coupler is fabricated by forming a coupler preform having a plurality of spaced glass cores extending longitudinally through a matrix of glass having a refractive index lower than that of the cores. The coupler preform is formed by inserting a plurality of coated optical fiber preform rods into an aperture extending axially through an elongated boule of relatively etchable matrix glass. The cladding portion of the rods, which is relatively etch-resistant, is coated with a layer of etchable glass. The coupler preform is heated and stretched to form a glass rod which is then severed into a plurality of units. Heat is applied to the central region of each unit, and the central region is elongated and tapered inwardly. When an end of the unit is immersed in acid, the matrix glass dissolves, thereby leaving the unit cores and surrounding etch-resistant cladding glass protruding from the newly formed endface of the unit. |
