Optical waveguide light source coupler

Claim 1

In an optical communication device of the type comprising, an optical waveguide having a core of transparent material and a layer of transparent cladding material disposed upon the surface of said core, a source of optical wave energy, and a light coupler having an input end for receiving light from said source and an output end for emitting light into said waveguide to initiate the propagation of light waves therein, said light coupler being characterized in that it comprises a tapered core of transparent material and a layer of cladding material disposed upon the surface of said core, the refractive index of said core material being greater than that of said cladding material, said core having a large diameter end at the input end of said coupler and a small diameter end at the output end of said coupler, said input end having a polished surface adapted to receive light from said source, said small diameter end of said core being substantially aligned with the core of said optical waveguide, the minimum thickness of said coupler cladding layer being at least ten times the wavelength of the light which said source is adapted to provide, said tapered core and said coupling cladding layer constituting a tapered optical waveguide having a V value at any point along the longitudinal axis thereof determined by the equation V 2 pi a/ lambda square root n12-n22 where a is the radius of the core at said point, lambda is the wavelength of light to be transmitted by said coupler, n1 is the index of refraction of said tapered core at said point, and n2 is the index of refraction of said coupler cladding layer at said point, any change in V value along said longitudinal axis being less than one percent per wavelength- lambda , the V value of said coupler being substantially constant throughout the length thereof.