Optical wavelength demultiplexer

Claim 1

An optical wavelength demultiplexer which comprises a first substrate which has a top surface and an elongated groove extending therein from said top surface, said elongated groove having a floor which is convexly curved in the elongated dimension of said groove, the shallowest depth of said convexly curved floor in said first substrate being less than a distance r, a single-mode optical fiber having a radius r positioned in said elongated groove in said first substrate, said optical fiber including an inner core and an outer cladding, a portion of said outer cladding which would otherwise extend above said top surface of said first substrate being removed to provide a generally flat, mirror-polished surface, said generally flat, mirror-polished surface being near said inner core of said single-mode optical fiber, said optical fiber being capable of carrying light having differing wavelengths therethrough, and a diffraction grating in direct contact with said generally flat, mirror-polished surface of said outer cladding of said optical fiber so as to separate a portion of the light that is passing through said optical fiber and reflect said light portion back into said optical fiber in the direction from which it came, said light portion comprising of certain wavelengths, said diffraction grating having a pitch of λ/2n f , where λ is the wavelength light to be separated and n f the effective refractive index of said optical fiber, said diffraction grating being oriented with respect to said optical fiber that the direction of its pitch is coincident with the elongation direction of said groove.