Optical coupling device for optical waveguides

Claim 1

An improved optical multiplexing/demultiplexing device for coupling an end face of a first optical waveguide which transmits a plurality N of signals of different wavelengths with the end faces of N further optical waveguides which each transmit one of such signals, such device comprising means for spectrally separating said signals, such spectral separating means comprising a plurality N of interference filters respectively having a wavelength-selective reflective spherical surface and means for spatially separating the wavelengths respectively reflected by such surfaces, whereby the N signals can be multiplexed/demultiplexed between said first optical waveguide and said N further optical waveguides; such improvement being characterized in that: the end faces of all of said optical waveguides are disposed in the same plane P; each of said filters comprises a pair of lenses which are planoconvex and planoconcave, respectively, the curved faces of which have a common optical axis which is perpendicular to the plane P and which are in contact over a common surface which constitutes said reflective spherical surface of such filter; each such pair of contacting planoconvex and planoconcave lenses thereby forming a plate having planar surfaces which are parallel to the plane P, such plates being arranged successively one after another with respect to the plane P, the planar surfaces of successive plates being in contact with each other; the centers of curvature of the reflective spherical surfaces of such plates being situated in the plane P and respectively located midway between the end face of said first optical waveguide and the end faces of respective ones of said further optical waveguides; each of said plates having the same refractive index n, and the radius of curvature R N of the spherical surface of the Nth plate being given by the relationship: R.sub.N =(n/n.sub.o)l.sub.o +(E.sub.1 +E.sub.2 +E.sub.N-1 +l.sub.N) where E 1 , E 2 . . . E N-1 are the thicknesses of the respective plates, .sub. N is the thickness of the planoconcave lens of the N th plate measured along the optical axis thereof, 1 O is the distance between the plane P and the front face of the first plate, and n O is the refractive index of the medium between the plane P and the front face of the first plate.