| abstract |
A low loss fiber optic coupler is fabricated by forming a coupler preform (10) having a plurality of spaced glass cores (12,13) extending longitudinally through a matrix of glass having a refractive index lower than that of the cores. The preform is heated and stretched to form a glass rod (20) which is then severed into a plurality of units (21). Heat is applied to the central region (23) of each unit while the ends of the unit are pulled apart to elongate the taper inwardly the heated central region. The unit is then provided with a plurality of optical fibers (69, 70, 75, 76°, 82, 83; 89), one of which extends from each of the cores at the endfaces of the unit. A preferred method of providing the optical fibers involves forming the coupler preform of a matrix glass (46) that is easily dissolves in a solvent. Each of the fiber cores within the matrix is surrounded by a layer of cladding glass (54) that is relatively resistant to disolving by the solvent. |