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EP0143583A2
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Fiber optic modal coupler
Assignee: Leland Stanford Junior University
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Filing: 1984-11-15
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Granted: —
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Expires: 2004-11-15
Abstract
Abstract A modal coupler, for coupling between modes of an optical er, such as between first and second order modes or be- een orthogonal polarization modes, comprises a single ntinuous strand of optical fiber (24), and a device (14) cluding a plurality of coupling surfaces (18) for applying ess to the optical fiber at spaced intervals along the fiber. le stress deforms the fiber and abruptly changes the fiber ometry at the beginning and end of each stressed region. The ange in fiber geometry causes coupling of light from the damental mode to the second order mode or between po- ization modes. Under certain conditions with nonbirefrin- nt fiber the coupler exhibits polarization dependence, and ds, may be utilized as a fiber optic polarizer. In addition, e device couples coherently, and may be used in interfero- etric systems.
Inventors
- 👤 Herbert John Shaw
- 👤 Robert C. Youngquist
- 👤 Janet L. Brooks
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 09:33
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/27; G02B6/2726; G02B6/274; G02B6/2753; G02B6/2773; G02B6/28; G02B6/2804; G02B6/2821; G02B6/293; G02B6/29302; G02B6/42; G02B6/4201; G02B6/4246; G02F; G02F1/00; G02F1/01; G02F1/0128; G02F1/0131; G02F1/0134
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
136 words
A directional coupler characterized by: an optical fiber (24) having two modes of propagation, each of said modes of propagation having a different effective index of refraction, so that light propagating in one of said modes has a different propagation velocity than light propagating in the other of said modes: a light source (66) for introducing a lightwave into said optical fiber (24); . a support structure (10), having a surface for supporting one side of said optical fiber (24); and a structure (14) having a plurality of surfaces (18) spaced along said optical fiber, for pressing against another side of said fiber, such that said fiber (24) is squeezed between said surfaces (18) and said support structure (10) to provide a series of alternating stressed and unstressed regions (32, 34, 36) along said optical fiber.
Claim 2
Dependent Claim
136 words
A directional coupler characterized by: an optical fiber (24) having two modes of propagation, each of said modes of propagation having a different effective index of refraction, so that light propagating in one of said modes has a different propagation velocity than light propagating in the other of said modes: a light source (66) for introducing a lightwave into said optical fiber (24); . a support structure (10), having a surface for supporting one side of said optical fiber (24); and a structure (14) having a plurality of surfaces (18) spaced along said optical fiber, for pressing against another side of said fiber, such that said fiber (24) is squeezed between said surfaces (18) and said support structure (10) to provide a series of alternating stressed and unstressed regions (32, 34, 36) along said optical fiber.
Claim 3
Dependent Claim
37 words
The directional coupler defined in Claim '1 wherein each of said surfaces (18) has abrupt edges to provide abrupt changes in the geometry of said fiber at the beginning and end of each stressed region (32, 36).
Claim 4
Dependent Claim
68 words
The directional coupler defined in either of Claims 1 or 2, wherein the width (W) of each surface (18) in the direction of the fiber axis is approximately-equal to an odd multiple of one half the fiber beat length and the spacing (S) between adjacent surfaces (18) in the direction of the fiber axis is approximately equal to an odd multiple of one half the fiber beat length.
Claim 5
Dependent Claim
66 words
The directional coupler defined in any of Claims 1 through 3, wherein (i) said lightwave has a wavelength selected to cause only the fundamental (LP 01 ) set of modes to propagate in said fiber, (ii) said optical fiber (24) is a monomode, birefringent fiber, and (iii) said two modes of propagation are the two orthogonal polarization modes of the fundamental LP 01 set of modes.
Claim 6
Dependent Claim
48 words
The directional coupler defined in Claim 4, further characterized by an orientation device (26, 28) for holding said fiber (24) on said support structure (10) so that the axes of birefringence of said fiber are in a selected angular orientation relative to said surface of said support structure.
Claim 7
Dependent Claim
33 words
The directional coupler defined in Claim 5, wherein said orientation device is characterized by fiber holding plates (26) rotatable relative to said support structure (10) to rotate said fiber about its longitudinal axis.
Claim 8
Dependent Claim
86 words
The directional coupler defined in any of Claims 1 through 3, wherein: said fiber is substantially nonbirefringent; said modes of propagation are the fundamental (LP 01 ) set of modes and the second order (LP 11 ) set of .- modes of said fiber (24); and said lightwave has a wavelength shorter than-the cutoff wavelength of said fiber so that said lightwave propagates through said fiber only in the fundamental (LP 01 ) set of modes and the second order (LP 11 ) set of modes.
Claim 9
Dependent Claim
29 words
The directional-coupler defined in any of Claims 1 through 7, wherein said surfaces (18) are on a ridged block (14), and said support structure comprises a flat plate (10).
Claim 10
Dependent Claim
81 words
The directional coupler defined in .Claim 8, wherein the coupler is further characterized by a plurality of pins (22) projecting from said support structure (10), and a plurality of holes (20) in said ridged block (14), wherein said holes (20) and said pins (22) are correspondingly arranged so each of said pins is aligned with and fits into one of said holes, so said ridged block (14) can be slid toward and away from said flat plate (10) on said pins.
Claim 11
Dependent Claim
49 words
The coupler defined in any of Claims 1 through 9, further characterized by a modulating driver (158) for oscillating said surfaces (18) relative to said support structure (10) in accordance with a modulating signal to vary the stress applied to said fiber (24) in said stressed regions (32, 36).
References Cited (Backward Citations)
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