Patent EP0212815A2 successfully refreshed from Google Patents.
EP0212815A2
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Optical fiber evanescent grating reflector
Assignee: Leland Stanford Junior University
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Filing: 1986-07-02
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Granted: —
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Expires: 2006-07-02
Abstract
Abstract A periodic grating structure (150,152,162,164) is plaed on a facing surface (140) formed on an optical fiber (120) so that the grating structure (150, 152, 162, 164) is within a portion of the evanescent field of an optical signal propagating through the optical fiber (120). The optical fiber 120 has at least two propagation modes, and the spatial periodicity of the grating structure (150, 152, 162, 164) cause the optical signal to be reflected and coupled between the two modes.
Inventors
- 👤 Wayne V. Sorin
- 👤 Herbert J. Shaw
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 17:13
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/10; G02B6/24; G02B6/26; G02B6/28; G02B6/293; G02B6/29331; G02B6/29332; G02B6/29334; G02B6/14
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
152 words
An intermode coupling apparatus (100) for coupling an optical signal travelling in a first mode of a multimode optical fiber to a second mode of said fiber, said optical signal having a vacuum wavelength (λg), said apparatus characterized by: a length of multimode optical fiber (120) having an inner core (122) and an outer cladding (124) and having a portion of said cladding (124) removed to form a facing surface (140) on said fiber (120); and a periodic grating structure (150,152,162,164) on said facing surface (140) within the evanescent field of said optical signal propagating in said first mode, said grating structure (152) having a periodicity A in accordance with the following expression: wherein n m1 is the effective refractive index of the optical fiber (120) for light propagating in said first mode and n m2 is the effective refractive index of the optical fiber for light propagating in said second mode.
Claim 2
Dependent Claim
152 words
An intermode coupling apparatus (100) for coupling an optical signal travelling in a first mode of a multimode optical fiber to a second mode of said fiber, said optical signal having a vacuum wavelength (λg), said apparatus characterized by: a length of multimode optical fiber (120) having an inner core (122) and an outer cladding (124) and having a portion of said cladding (124) removed to form a facing surface (140) on said fiber (120); and a periodic grating structure (150,152,162,164) on said facing surface (140) within the evanescent field of said optical signal propagating in said first mode, said grating structure (152) having a periodicity A in accordance with the following expression: wherein n m1 is the effective refractive index of the optical fiber (120) for light propagating in said first mode and n m2 is the effective refractive index of the optical fiber for light propagating in said second mode.
Claim 3
Dependent Claim
25 words
The intermode coupling apparatus (100) as defined in Claim 1, characterized in that said grating structure (150,152,162,164) comprises grooves (162) formed in said cladding (124).
Claim 4
Dependent Claim
32 words
The intermode coupling apparatus (100) as defined in Claim 2, characterized in that said grooves (162) have a width in the direction of propagation of said optical signal substantially equal to A/2.
Claim 5
Dependent Claim
38 words
The intermode coupling apparatus (100) as defined in Claim 3 characterized in that the grooves (162) are spaced apart by ridges (164) having a width in the direction of propagation of said optical signal substantially equal to A/2.
Claim 6
Dependent Claim
27 words
The intermode coupling apparatus (100) as defined in Claim 2, characterized in that said grooves (162) are formed in said cladding (124) by etching said cladding (124).
Claim 7
Dependent Claim
36 words
The intermode coupling apparatus (100) as defined in Claim 1, characterized in that said grating structure (150,152,162,164) comprises a holographic reflection grating (150) having a plurality of parallel ridges (152) positioned on said facing surface (140).
Claim 8
Dependent Claim
26 words
The intermode coupling apparatus (100) as defined in Claim 6, characterized in that said ridges (152) are periodically spaced from each other by said distance A.
Claim 9
Dependent Claim
29 words
The intermode coupling apparatus (100) as defined by Claim 6, characterized by comprising an index matching oil applied between said facing surface (140) and said holographic reflection grating (150).
Claim 10
Dependent Claim
34 words
The intermode coupling apparatus (100) as defined by Claim 8, characterized in that pressure is applied to said holographic reflection grating (150) to ensure contact between said ridges (152) and said facing surface (140).
Claim 11
Independent Claim
162 words
A method of manufacturing an apparatus (100) for coupling optical energy between a first optical propagation mode and a second optical propagation mode characterized by the steps of: forming a facing surface (140) on the cladding (124) of an optical fiber (120) having an inner core (122) and an outer cladding by removing a portion of the cladding (124) from the optical fiber (120) to expose the evanescent field of an optical signal propagating therein; and placing a periodic grating structure (150,152,162,164) on said cladding (124) at said facing surface (140), said periodic grating structure having a periodicity A in accordance with the following expression: where n m1 is the effective refractive index of the optical fiber (120) for optical energy propagating in said first propagation mode, n m2 is the effective refractive index of the optical fiber (120) for optical energy propagating in said second propagation mode, and x 0 is the vacuum wavelength of the optical signal to be coupled.
Claim 12
Independent Claim
162 words
A method of manufacturing an apparatus (100) for coupling optical energy between a first optical propagation mode and a second optical propagation mode characterized by the steps of: forming a facing surface (140) on the cladding (124) of an optical fiber (120) having an inner core (122) and an outer cladding by removing a portion of the cladding (124) from the optical fiber (120) to expose the evanescent field of an optical signal propagating therein; and placing a periodic grating structure (150,152,162,164) on said cladding (124) at said facing surface (140), said periodic grating structure having a periodicity A in accordance with the following expression: where n m1 is the effective refractive index of the optical fiber (120) for optical energy propagating in said first propagation mode, n m2 is the effective refractive index of the optical fiber (120) for optical energy propagating in said second propagation mode, and x 0 is the vacuum wavelength of the optical signal to be coupled.
Claim 13
Dependent Claim
52 words
The method as defined in Claim 10, characterized in that said placing step comprises the step of by positioning a holographic grating reflector (150) on said facing surface (140), said holographic grating reflector (150) having a spatially periodic series of ridges (152) that are positioned in contact with said facing surface (140).
Claim 14
Dependent Claim
36 words
The method as defined in Claim 11, characterized by comprising the step of placing an index matching oil on said facing surface (140) prior to placing said holographic grating reflector (150) on said facing surface (140).
Claim 15
Dependent Claim
34 words
The method as defined in Claim 11, characterized by comprising the step of applying pressure to the holographic grating reflector (152) to ensure contact between said holographic grating reflector and said facing surface (140).
Claim 16
Dependent Claim
47 words
The method as defined in Claim 10, characterized in that said placing step comprises the step of etching said facing surface (148) to form a series of grooves (162) thereon, spaced apart by a series of ridges (164), said grooves and ridges having a periodicity of A.
References Cited (Backward Citations)
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