EP0055822A1
Expired / Lapsed
EP
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Optical transmission line and its method of manufacture
Assignee: Nortel Networks Ltd
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Filing: 1981-11-09
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Granted: —
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Expires: 2001-11-09
Abstract
Abstract A preform (25) for an optical fiber is produced with a graded index core, the core forming material being formed, or deposited, at high rates with a small number of layers, relative to conventional methods. The preform (25) is drawn to form a fiber, and the profile of the refractive index of the fiber has a very "coarse" or stepped form. While the modal dispersion can be larger than a conventional fiber, the overall modal dispersion of a transmission line composed of a plurality of lengths joined together does not increase at such a rate as with a conventional fiber. Also the fiber can be less sensitive to wavelength. As a result fiber, preforms, and transmission lines and cables, can be produced cheaper and yet still meet specification standards.
Inventors
- 👤 Koichi Abe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 03:55
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/02; G02B6/036; G02B6/03616; G02B6/03622; G02B6/03627; C; C03; C03B; C03B37/00; C03B37/01; C03B37/012; C03B37/01205; C03B37/01211; C03B37/014; C03B37/018; C03B37/01807; C03B37/01861; C03B37/02; C03B37/025; C03B37/027; C03B2201/00; C03B2201/06; C03B2201/20; C03B2201/28; C03B2201/30; C03B2201/31; C03B2203/00; C03B2203/10; C03B2203/22; C03B2203/26; C03B2207/00; C03B2207/80; C03B2207/85; C03B2207/86; G02B6/028; G02B6/0281
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
77 words
An optical fiber having a graded index core composed of a plurality of individual layers of silica glass, the refractive index of the layers increasing from the outer layer to the center of the core, characterized by the radial profile (18) of the refractive index of the core (15) being of stepped form departing significantly from a smooth profile of optimum, approximately parabolic, form, the mean refractive index profile of the layers closely following the smooth profile.
Claim 2
Dependent Claim
77 words
An optical fiber having a graded index core composed of a plurality of individual layers of silica glass, the refractive index of the layers increasing from the outer layer to the center of the core, characterized by the radial profile (18) of the refractive index of the core (15) being of stepped form departing significantly from a smooth profile of optimum, approximately parabolic, form, the mean refractive index profile of the layers closely following the smooth profile.
Claim 3
Dependent Claim
20 words
An optical fiber as claimed in claim 1, characterized by the plurality of layers being a maximum of about thirty.
Claim 4
Dependent Claim
20 words
An optical fiber as claimed in claim 1, characterized by the plurality of layers being a maximum of about twenty-five.
Claim 5
Dependent Claim
20 words
An optical fiber as claimed in claim 1, characterized by the plurality of layers being a maximum of about twenty.
Claim 6
Dependent Claim
17 words
An optical fiber as claimed in claim 1, characterized by the plurality of layers being about fifteen.
Claim 7
Dependent Claim
17 words
An optical fiber as claimed in claim 1, characterized by a cladding layer (16) of fused silica.
Claim 8
Dependent Claim
91 words
A preform for use in forming an optical fiber having a graded index core, comprising: a tube of fused silica and a plurality of layers of silica glass on an inside wall of the tube, the refractive index of the layers increasing from the outer layer to the inner layer, characterized by the radial profile (18) of the refractive index of the core (15) being of stepped form departing significantly from a smooth profile of optimum, approximately parabolic, form, the mean refractive index of the layers closely following said smooth profile.
Claim 9
Dependent Claim
91 words
A preform for use in forming an optical fiber having a graded index core, comprising: a tube of fused silica and a plurality of layers of silica glass on an inside wall of the tube, the refractive index of the layers increasing from the outer layer to the inner layer, characterized by the radial profile (18) of the refractive index of the core (15) being of stepped form departing significantly from a smooth profile of optimum, approximately parabolic, form, the mean refractive index of the layers closely following said smooth profile.
Claim 10
Dependent Claim
20 words
A preform as claimed in claim 7, characterized by the plurality of layers being from about fifteen to about thirty.
Claim 11
Independent Claim
87 words
A method of making a preform for the manufacture of an optical fiber, comprising: forming a plurality of layers of glass on an inside wall of a fused silica tube, the refractive index of the layers increasing from the outer layer to the inner layer, characterized by the radial profile (18) of the refractive index of the plurality of layers being of stepped form departing significantly from a smooth profile of optimum, approximately parabolic, form, the mean refractive index of the layers closely following said smooth profile.
Claim 12
Independent Claim
87 words
A method of making a preform for the manufacture of an optical fiber, comprising: forming a plurality of layers of glass on an inside wall of a fused silica tube, the refractive index of the layers increasing from the outer layer to the inner layer, characterized by the radial profile (18) of the refractive index of the plurality of layers being of stepped form departing significantly from a smooth profile of optimum, approximately parabolic, form, the mean refractive index of the layers closely following said smooth profile.
Claim 13
Dependent Claim
112 words
A method as claimed in claim 9, characterized by mounting a tube (11, 25) of fused silica for rotation about a longitudinal axis; rotating the tube (11, 25), feeding a mixture of vapour and gases through the tube (25) the mixture being of oxygen, and a vapour containing a dopant, traversing a heating zone (40) relative to the tube (25) to react the mixture and form a fused layer (12) on the inner wall of the tube (11, 25), varying the amount of dopant supplied to the mixture to provide the increase in refractive index, repeating the traverse of the heating zone (-40) a predetermined number of times less than about thirty.
Claim 14
Dependent Claim
37 words
A method as claimed in claim 10, characterized by the mixture reacting to form a particulate deposit on the inner wall downstream of the heating zone, the heating zone (40) fusing the deposit to form a layer.
Claim 15
Dependent Claim
22 words
A method as claimed in claim 11, characterized by the vapour containing silica being formed by bubbling oxygen through SiCl 4 .
Claim 16
Dependent Claim
23 words
A method as claimed in claim 12, characterized by the vapour containing a dopant being formed by bubbling oxygen through GeCl 4 .
Claim 17
Dependent Claim
22 words
A method as claimed in claim 13, characterized by the mixture including a further vapour formed by bubbling oxygen through phosphorus oxychloride.
Claim 18
Dependent Claim
23 words
15, A method as claimed in claim 13, characterized by increasing the flow of germanium containing vapour in accordance with a predetermined programme.
Claim 19
Independent Claim
36 words
A method as claimed in any one of claims 10 to 15 characterized by increasing the temperature of the heating zone (40) to collapse the tube (11, 25) and formed layers (12) to a solid rod.
Claim 20
Dependent Claim
17 words
A method as claimed in claim 14, characterized by the flow of vapour containing phosphorus maintained constant.
Claim 21
Dependent Claim
25 words
A method as claimed in claim 16, characterized by the tube (11, 25) and layers (12) being collapsed by traversing the heat zone (40) twice.
Claim 22
Dependent Claim
23 words
A method as claimed in claim 16, characterized by maintaining a flow of oxygen through the tube (11, 25) until it is collapsed.
Claim 23
Dependent Claim
30 words
A method as claimed in claim 10, characterized by the heating zone being formed by a burner (40) including feeding hydrogen and oxygen to the burner (40) at predetermined rates.
Claim 24
Dependent Claim
33 words
A method of forming an optical fiber characterized by the steps of forming a preform as claimed in claim 16, inserting the rod into a furnace and drawing the preform into a fiber.
Claim 25
Dependent Claim
64 words
22, A method of forming an optical fiber characterized by the steps of forming a preform as claimed in claim 16, inserting the rod into a tube of fused silica which is a close fit on the rod, inserting the rod and tube into a furnace and drawing the rod and tube to collapse the tube on to the rod and produce a fiber.
Claim 26
Dependent Claim
15 words
An optical fiber characterized by the method as claimed in claim 21 or claim 22.
Claim 27
Dependent Claim
17 words
A transmission line characterized by a plurality of lengths of optical fiber as claimed in claim 1.
Claim 28
Dependent Claim
30 words
A cable for optical transmission of signals comprisinq a plurality of transmission lines, each transmission line characterized by a plurality of lengths of optical fiber as claimed in claim 1.
Claim 29
Dependent Claim
16 words
An optical transmission line characterized by a plurality of optical fibers as claimed in claim 23.
Claim 30
Independent Claim
86 words
A method of making a preform for an optical fiber, the preform having a composite layer of doped silica glass on an inside wall of a fused silica tube, characterized by forming between about fifteen and about thirty separate layers of doped silica glass to a total thickness of about .55mm, the doping of the layers being varied to give a stepped refractive index which increases radially inward, the mean refractive index profile of the layers closely following a smooth profile of optimum, approximately parabolic, form.
Claim 31
Independent Claim
86 words
A method of making a preform for an optical fiber, the preform having a composite layer of doped silica glass on an inside wall of a fused silica tube, characterized by forming between about fifteen and about thirty separate layers of doped silica glass to a total thickness of about .55mm, the doping of the layers being varied to give a stepped refractive index which increases radially inward, the mean refractive index profile of the layers closely following a smooth profile of optimum, approximately parabolic, form.
Claim 32
Dependent Claim
14 words
A method as claimed in claim 27, characterized by collapsing to a solid rod.
Claim 33
Dependent Claim
25 words
A method of making an optical fiber characterized by the steps of making a preform as claimed in claim 28 and drawing into a fiber.
Claim 34
Dependent Claim
46 words
A method of making an optical fiber characterized by the steps of making a preform as claimed in claim 28, inserting the rod into a tube of fused silica which is a close fit on the rod, and drawing the tube and rod into a fiber.
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