US3891302A
Expired / Lapsed
US
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Method of filtering modes in optical waveguides
Assignee: AT&T Inc
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Filing: 1973-09-28
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Granted: 1975-06-24
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Expires: 1993-09-28
Abstract
Abstract Modes are filtered in an optical waveguide by selecting and providing a periodic variation, such as a surface corrugation or a refractive index variation, in a filter region in the waveguide. The filter region diverts light in an unwanted mode from the propagation axis by scattering or reflection. Both planar waveguide filters and fiber-optic filters are disclosed.
Inventors
- 👤 Franklin Winston Dabby
- 👤 Ami Kestenbaum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:41
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; H04B10/2569; G; G02; G02B; G02B6/00; G02B6/02; G02B6/02057; G02B6/02066; G02B6/10; G02B6/12; G02B6/122; G02B6/124; G02B6/14; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 39
Claim 1
Independent Claim
138 words
A method of mode filtering light of a given frequency propagated through an optical waveguide having a refractive index nf in a first portion of a cross section thereof and a refractive index ns in a second portion of the cross section, where nf > ns, which comprises: selecting and providing variation in a region of the optical waveguide extending along the propagation axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period of the variation being less than lambda /ne - ns, where lambda is the free-space wavelength of the light and ne is the effective refractive index in the waveguide of the unwanted mode, the periodic variation extending to at least a portion of the cross section of the waveguide where the field of the unwanted mode substantially exists.
Claim 2
Independent Claim
138 words
A method of mode filtering light of a given frequency propagated through an optical waveguide having a refractive index nf in a first portion of a cross section thereof and a refractive index ns in a second portion of the cross section, where nf > ns, which comprises: selecting and providing variation in a region of the optical waveguide extending along the propagation axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period of the variation being less than lambda /ne - ns, where lambda is the free-space wavelength of the light and ne is the effective refractive index in the waveguide of the unwanted mode, the periodic variation extending to at least a portion of the cross section of the waveguide where the field of the unwanted mode substantially exists.
Claim 3
Dependent Claim
23 words
The method according to claim 1 wherein said periodic variation comprises a periodic variation in the refractive index of one of the portions.
Claim 4
Dependent Claim
19 words
The method according to claim 1 wherein said periodic variation comprises a corrugation in a surface of the waveguide.
Claim 5
Dependent Claim
27 words
The method according to claim 1 wherein the period d is greater then lambda /ne + ns and the unwanted mode is scattered out of the waveguide.
Claim 6
Dependent Claim
24 words
The method according to claim 1 wherein the period d substantially equals lambda /2ne and the unwanted mode is reflected back along the waveguide.
Claim 7
Independent Claim
104 words
A method of mode filtering light of a given frequency propagated through an optical waveguide having an optical layer supported on a substrate, which comprises selecting and providing a periodic variation in a region of the optical layer along the propagation axis of the waveguide to divert an unwanted mode of light from forward propagation, the period d of the variation being less than lambda /ne - ns where lambda is the free space wavelength of the light, ne is the effective refractive index in the waveguide of the unwanted mode, and ns is the refractive index of the substrate for the unwanted mode.
Claim 8
Independent Claim
104 words
A method of mode filtering light of a given frequency propagated through an optical waveguide having an optical layer supported on a substrate, which comprises selecting and providing a periodic variation in a region of the optical layer along the propagation axis of the waveguide to divert an unwanted mode of light from forward propagation, the period d of the variation being less than lambda /ne - ns where lambda is the free space wavelength of the light, ne is the effective refractive index in the waveguide of the unwanted mode, and ns is the refractive index of the substrate for the unwanted mode.
Claim 9
Dependent Claim
20 words
The method according to claim 6 wherein said periodic variation is comprised in the refractive index of the optical layer.
Claim 10
Dependent Claim
20 words
The method according to claim 6 wherein said periodic variation comprises a corrugation in a surface of the optical layer.
Claim 11
Dependent Claim
27 words
The method according to claim 6 wherein the period d is greater than lambda /ne + ns and the unwanted mode is scattered out of the waveguide.
Claim 12
Dependent Claim
24 words
The method according to claim 6 wherein the period d substantially equals lambda /2ne and the unwanted mode is reflected back along the waveguide.
Claim 13
Independent Claim
108 words
A method of mode filtering light of a given frequency propagated through a fiber optic waveguide comprising a core having a refractive index nf and a cladding having a refractive index ns, where nf > ns, which comprises: selecting and providing a periodic variation in the refractive index of a region of the core along the axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period d of the index variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light, and ne is the effective refractive index in the waveguide of the unwanted mode.
Claim 14
Independent Claim
108 words
A method of mode filtering light of a given frequency propagated through a fiber optic waveguide comprising a core having a refractive index nf and a cladding having a refractive index ns, where nf > ns, which comprises: selecting and providing a periodic variation in the refractive index of a region of the core along the axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period d of the index variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light, and ne is the effective refractive index in the waveguide of the unwanted mode.
Claim 15
Dependent Claim
27 words
The method according to claim 11 wherein the period d is greater than lambda /ne + ns and the unwanted mode is scattered out of the waveguide.
Claim 16
Dependent Claim
24 words
The method according to claim 11 wherein the period d substantially equals lambda /2ne and the unwanted mode is reflected back along the waveguide.
Claim 17
Independent Claim
108 words
A method of mode filtering light of a given frequency propagated through a fiber optic waveguide comprising a core having a refractive index nf and a cladding having a refractive index ns, where nf > ns, which comprises: selecting and providing a periodic variation in the refractive index of a region of the cladding along the axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period d of the index variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light and ne is the effective refractive index in the waveguide of the unwanted mode.
Claim 18
Independent Claim
108 words
A method of mode filtering light of a given frequency propagated through a fiber optic waveguide comprising a core having a refractive index nf and a cladding having a refractive index ns, where nf > ns, which comprises: selecting and providing a periodic variation in the refractive index of a region of the cladding along the axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period d of the index variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light and ne is the effective refractive index in the waveguide of the unwanted mode.
Claim 19
Dependent Claim
27 words
The method according to claim 14 wherein the period d is greater than lambda /ne + ns and the unwanted mode is scattered out of the waveguide.
Claim 20
Dependent Claim
24 words
The method according to claim 14 wherein the period d substantially equals lambda /2ne and the unwanted mode is reflected back along the waveguide.
Claim 21
Independent Claim
136 words
A method of mode filtering light of a given frequency propagated through a fiber optic waveguide having a decreasing radial gradient in refractive index from the axis of the waveguide to the surface of the waveguide, which comprises: selecting and providing a periodic variation in a region of the waveguide along the propagation axis of the waveguide to divert an unwanted mode of light from forward propagation, the period of the variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light, ne is the effective refractive index in the waveguide of the unwanted mode, and ns is the refractive index at the surface of the waveguide, the periodic variation extending to a portion of the cross section of the waveguide where the field of the unwanted mode substantially exists.
Claim 22
Independent Claim
136 words
A method of mode filtering light of a given frequency propagated through a fiber optic waveguide having a decreasing radial gradient in refractive index from the axis of the waveguide to the surface of the waveguide, which comprises: selecting and providing a periodic variation in a region of the waveguide along the propagation axis of the waveguide to divert an unwanted mode of light from forward propagation, the period of the variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light, ne is the effective refractive index in the waveguide of the unwanted mode, and ns is the refractive index at the surface of the waveguide, the periodic variation extending to a portion of the cross section of the waveguide where the field of the unwanted mode substantially exists.
Claim 23
Dependent Claim
19 words
The method according to claim 17 wherein said periodic variation comprises a periodic variation in the index of refraction.
Claim 24
Dependent Claim
19 words
The method according to claim 17 wherein said periodic variation comprises a corrugation in the surface of the waveguide.
Claim 25
Dependent Claim
27 words
The method according to claim 17 wherein the period d is greater than lambda /ne + ns and the unwanted mode is scattered out of the waveguide.
Claim 26
Dependent Claim
24 words
The method according to claim 17 wherein the period d substantially equals lambda /2ne and the unwanted mode is reflected back along the waveguide.
Claim 27
Independent Claim
119 words
A method of filtering TE and TM modes of light transmitted through an optical waveguide having an optical layer supported on a substrate, which comprises selecting and providing a periodic variation in a region of the optical layer along the propagation axis of the waveguide to scatter one of the modes of light out of the waveguide, the period 64 d of the variation being less than lambda /ne - ns and greater than lambda /ne + ns, where lambda is the free-space wavelength of the light propagating through the waveguide, ne is the effective refractive index in the waveguide of the mode to be scattered, and ns is the refractive index of the substrate for the unwanted mode.
Claim 28
Independent Claim
119 words
A method of filtering TE and TM modes of light transmitted through an optical waveguide having an optical layer supported on a substrate, which comprises selecting and providing a periodic variation in a region of the optical layer along the propagation axis of the waveguide to scatter one of the modes of light out of the waveguide, the period 64 d of the variation being less than lambda /ne - ns and greater than lambda /ne + ns, where lambda is the free-space wavelength of the light propagating through the waveguide, ne is the effective refractive index in the waveguide of the mode to be scattered, and ns is the refractive index of the substrate for the unwanted mode.
Claim 29
Dependent Claim
22 words
The method according to claim 22 wherein said periodic variation comprises a periodic variation in the refractive index of said optical layer.
Claim 30
Dependent Claim
20 words
The method according to claim 22 wherein said periodic variation comprises a corrugation in the surface of said optical layer.
Claim 31
Dependent Claim
16 words
The method according to claim 22 wherein both said substrate and said optical layer are isotropic.
Claim 32
Dependent Claim
17 words
The method according to claim 22 wherein said optical layer is isotropic and said substrate is anisotropic.
Claim 33
Dependent Claim
17 words
The method according to claim 22 wherein said optical layer is anisotropic and said substrate is isotropic.
Claim 34
Independent Claim
132 words
A method of mode filtering light propagated substantially along a first surface of a planar optical waveguide having a gradient in the refractive index from nf adjacent the first surface to ns adjacent an opposing second surface, nf > ns, which comprises: selecting and providing a periodic variation in a region of the waveguide along the propagation axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period of the variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light, and ne is the effective refractive index in the waveguide of the unwanted mode, the periodic variation extending to at least a portion of the cross section of the waveguide where the field of the unwanted mode substantially exists.
Claim 35
Independent Claim
132 words
A method of mode filtering light propagated substantially along a first surface of a planar optical waveguide having a gradient in the refractive index from nf adjacent the first surface to ns adjacent an opposing second surface, nf > ns, which comprises: selecting and providing a periodic variation in a region of the waveguide along the propagation axis of the waveguide to divert an unwanted mode of the light from forward propagation, the period of the variation being less than lambda /ne - ns where lambda is the free-space wavelength of the light, and ne is the effective refractive index in the waveguide of the unwanted mode, the periodic variation extending to at least a portion of the cross section of the waveguide where the field of the unwanted mode substantially exists.
Claim 36
Dependent Claim
18 words
The method according to claim 28 wherein said periodic variation comprises a periodic variation in the refractive index.
Claim 37
Dependent Claim
19 words
The method according to claim 28 wherein said periodic variation comprises a corrugation in the surface of the waveguide.
Claim 38
Dependent Claim
24 words
The method according to claim 28 wherein the period d substantially equals lambda /2ne and the unwanted mode is reflected back along the waveguide.
Claim 39
Dependent Claim
27 words
The method according to claim 28 wherein the period d is greater than lambda /ne + ns and the unwanted mode is scattered out of the waveguide.
References Cited (Backward Citations)
US3760292A
Cited
US3723921A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-23 | 1978-12-23 | 1979-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-23 | 1982-12-23 | 1983-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-23 | 1986-12-23 | 1987-06-24 | $7700.00 | Window Closed / Lapsed |