US5351325A — Narrow band Mach-Zehnder filter

Claim 1

Independent Claim 94 words

A Mach-Zehnder filter for passing a signal, the wavelength spectrum of which is centered about a wavelength λ f , said filter comprising input coupler means for splitting an input signal into N equal simultaneously propagating output signals, where N>2, combining means for combining N optical signals into a single output signal, N optical waveguide paths for connecting said N outputs to said combining means, each of said N waveguides subjecting the light propagating therethrough to a delay that is different from the delay experienced by light propagating through each of the other waveguides.

Claim 2

Dependent Claim 94 words

A Mach-Zehnder filter for passing a signal, the wavelength spectrum of which is centered about a wavelength λ f , said filter comprising input coupler means for splitting an input signal into N equal simultaneously propagating output signals, where N>2, combining means for combining N optical signals into a single output signal, N optical waveguide paths for connecting said N outputs to said combining means, each of said N waveguides subjecting the light propagating therethrough to a delay that is different from the delay experienced by light propagating through each of the other waveguides.

Claim 3

Dependent Claim 21 words

A filter in accordance with claim 1 wherein said waveguide paths have the same length and have different refractive index profiles.

Claim 4

Dependent Claim 105 words

A filter in accordance with claim 2 wherein each of said waveguide paths comprises a core region of refractive index n 1 surrounded by a cladding of refractive index n 2 , the relative refractive index difference between the core and cladding of a waveguide path being characterized by a Δ-value that is equal to (n 1 2 -n 2 2 /(2n 1 2 ), the Δ-values of a first path and a second path being Δ 1 and Δ 2 , respectively, and Δ i , the Δ-value of the ith path satisfying the relationship Δ i =Δ 1 +(i-1)(Δ 2 -Δ 1 ).

Claim 5

Dependent Claim 23 words

A filter in accordance with claim 1 wherein said waveguide paths comprise optical fibers having the same length and having different core diameters.

Claim 6

Dependent Claim 14 words

A filter in accordance with claim 1 wherein said waveguide paths have different lengths.

Claim 7

Dependent Claim 114 words

A filter in accordance with claim 5 wherein each of said waveguide paths comprises a core region of refractive index n 1 surrounded by a cladding of refractive index n 2 , the relative refractive index difference between the core and cladding of a waveguide path being characterized by a Δ-value that is equal to (n 2 2 -n 2 2 )/(2n 1 2 ), the Δ-values all of said paths being equal, the length of a first and a second of said paths being L 1 and L 2 , respectively, and L i , the length of the ith path satisfying the relationship L i =L 1 +(i-1)(L 2 -L 2 ).

Claim 8

Dependent Claim 70 words

A filter in accordance with claim 1 wherein said input coupler means comprises a fused fiber coupler in which an input fiber is surrounded by N equally-spaced output fibers, said input fiber and said output fibers being fused together and tapered in a coupling region, the characteristics of which are such that light of said wavelength λ f propagating in said input fiber substantially completely couples to said output fibers.

Claim 9

Dependent Claim 71 words

A filter in accordance with claim 1 wherein said input coupler means comprises a fused fiber coupler in which an input fiber is surrounded by N equally-spaced output fibers, said input fiber and said output fibers being fused together and tapered in a coupling region, the characteristics of which are such that light of said wavelength λ f propagating in said input fiber does not completely couple to said output fibers.

Claim 10

Dependent Claim 59 words

A filter in accordance with claim 1 wherein said input coupler means comprises a fused fiber coupler in which an input fiber is surrounded by N equally-spaced output fibers, said input fiber and said output fibers being fused together and tapered in a coupling region, said coupler including means for preventing coupling between adjacent ones of said output fibers.

Claim 11

Dependent Claim 28 words

A filter in accordance with claim 9 wherein said means for preventing coupling comprises a glass region having a refractive index lower that that of said fiber claddings.

Claim 12

Dependent Claim 17 words

A filter in accordance with claim 9 wherein said means for preventing coupling comprises an air gap.

Claim 13

Dependent Claim 115 words

A Mach-Zehnder filter for passing a signal, the wavelength spectrum of which is centered about a wavelength λ f , said filter comprising an elongated body of matrix glass, at least first and second and third dissimilar optical fibers extending longitudinally through said body, a phase shift region in said body in which all of said fibers have different propagation constants, whereby optical signals propagate through said optical fibers at different velocities in said phase shift region, two spaced coupler regions in said body at opposite ends of said phase shift region, the diameter of said body and the diameters of said fibers being smaller in said coupler regions than in said phase shift region.

Claim 14

Dependent Claim 115 words

A Mach-Zehnder filter for passing a signal, the wavelength spectrum of which is centered about a wavelength λ f , said filter comprising an elongated body of matrix glass, at least first and second and third dissimilar optical fibers extending longitudinally through said body, a phase shift region in said body in which all of said fibers have different propagation constants, whereby optical signals propagate through said optical fibers at different velocities in said phase shift region, two spaced coupler regions in said body at opposite ends of said phase shift region, the diameter of said body and the diameters of said fibers being smaller in said coupler regions than in said phase shift region.

Claim 15

Dependent Claim 17 words

A filter in accordance with claim 12 wherein all of said fibers have different refractive index profiles.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-09-26	1998-03-28	1998-09-27	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-09-26	2002-03-28	2002-09-27	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-09-26	2006-03-28	2006-09-27	$7700.00	Window Closed / Lapsed

Narrow band Mach-Zehnder filter

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag