Coupler for optical communication system
AssigneeThomson-CSF
InventorsGuy de Corlieu, Jean-Claude Reymond
Life of this patent
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Abstract
A coupler for coupling the end of an optical signal transmission line comprising at least one optical waveguide, to a solidstate converter device such as a light emitting diode or a photosensitive diode according to the case, the converter device presenting a refractive index N3 higher than the refractive index N1 of the optical waveguide. The coupler comprises a transparent matching medium having at least a refractive index N4 of value intermediate between the values N1 and N3 and forming a thin parallel faced plate whose maximum thickness is determined on the basis of the numerical aperture of the guide.
Claims10
In an optical communication system having at least one signal transmission line comprising at least one optical waveguide having a core of transparent material having a refractive index N1 surrounded by a layer of transparent cladding material having a refractive index N2 that is lower than N1 and associated by each end to a solid state converter device for light emission and light reception respectively, said converter devices having refractive indices higher than the said core index, optical coupling means for coupling at least one said waveguide end to a said associated device through an optical coupler comprising at least one transparent matching medium having a refractive index N4 intermediate between the said core index N1 and the refractive index N3 of the associated device and forming a thin plate whose maximum thickness along the optical axis direction is given by the relation
- LM = [(D1 + D2)/2] .multidot. [(.sqroot.N4.sup.2 - A.sup.2)/A]
- where A is the numerical aperture of the waveguide, i.e. .sqroot.N1.sup.2 - N2.sup.2 and D1, D2, the diameters of the plane interfaces perpendicular to said axis direction and provided by the core at said waveguide end and the associated device respectively.
An optical coupler for coupling a transmission line to an electro-optical converter device, said transmission line comprising at least one optical waveguide having a core of transparent material surrounded by a layer of transparent cladding material whose refractive index N2 is lower then that of N1 of the core, said converter device having refractive index N3 higher than the said core index N1, said coupler extending between two parallel plane faces presented by the waveguide end and the converter respectively, said plane faces being centered on the optical axis of said waveguide end, said coupler comprising a matching transparent medium whose refractive index N4 is determined intermediate between said values N1 and N3, said medium forming a thin plate between said faces and having a thickness along said optical axis direction determined such that light rays transmitted in the said medium and extending between said two faces present angular deviations with respect to said optical axis whose maximum value .THETA.M is given by N4 sin .theta.M = A where A is the numerical aperture of the waveguide.
Dependencies are inferred from the claim text.