US4723828A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bandwidth enhancement of multimode optical transmisson lines
Assignee: Nortel Networks Ltd
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Filing: 1984-11-09
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Granted: 1988-02-09
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Expires: 2004-11-09
Abstract
Abstract To improve pulse dispersion of a multimode fiber transmission line, it is spliced to a short length of fiber adapted to strongly attenuate mode groups propagating near the core center.
Inventors
- 👤 Philip-Michael Garel-Jones
- 👤 Richard S. Lowe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:52
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/02; G02B6/028; G02B6/0288; G02B6/02214; G02B6/02285; G02B6/036; G02B6/03605; G02B6/03611; G02B6/03616; G02B6/03622; G02B6/03627; G02B6/10; G02B6/14; G02B6/24; H; H04; H04B; H04B10/00; H04B10/25; H04B10/2581; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
83 words
An apparatus, comprising: a multimode optical fiber transmission line having a light input end, and a short length of fiber having the characteristic of strongly attenuating at least one light mode group passed through said fiber without attenuating other mode groups of different order, said short length of fiber having a low refractive index central core region for attenuating an axially propagating mode group and having a light output end coupled to said light input end of said multimode optical fiber transmission line.
Claim 2
Independent Claim
83 words
An apparatus, comprising: a multimode optical fiber transmission line having a light input end, and a short length of fiber having the characteristic of strongly attenuating at least one light mode group passed through said fiber without attenuating other mode groups of different order, said short length of fiber having a low refractive index central core region for attenuating an axially propagating mode group and having a light output end coupled to said light input end of said multimode optical fiber transmission line.
Claim 3
Dependent Claim
29 words
An apparatus as claimed in claim 1 in which the low refractive index central core region of the short length of fiber occupies a diameter of about 12 microns.
Claim 4
Dependent Claim
62 words
An apparatus as claimed in claim 1 in which the short length of fiber has a refractive index profile which is substantially parabolic increasing from a minimum at an outer part of the core to a maximum at a region about 5 microns from the center of the core, the parabolic refractive index profile being modified by a low index central region.
Claim 5
Dependent Claim
43 words
An apparatus as claimed in claim 3 in which the low index central region is silica doped with an index depressing material and the part of the core immediately around said central low index region is silica doped with an index raising material.
Claim 6
Dependent Claim
21 words
An apparatus as claimed in claim 1 in which the central region of the short length of fiber is strongly absorbing.
Claim 7
Dependent Claim
19 words
an apparatus as claimed in claim 5 in which the absorbing region comprises silica containing a light absorbing dopant.
Claim 8
Dependent Claim
24 words
An apparatus as claimed in claim 3 wherein said multimode optical transmission line has a substantially parabolic refractive index which dips at the center.
Claim 9
Independent Claim
60 words
A method, comprising: providing a multimode optical fiber transmission line; and coupling to said line a short length of fiber having the characteristic of strongly attenuating at least one light mode group passed through said fiber without attenuating other mode groups of different order and having a low refractive index central core region for attenuating an axially propagating mode group.
Claim 10
Independent Claim
60 words
A method, comprising: providing a multimode optical fiber transmission line; and coupling to said line a short length of fiber having the characteristic of strongly attenuating at least one light mode group passed through said fiber without attenuating other mode groups of different order and having a low refractive index central core region for attenuating an axially propagating mode group.
Claim 11
Dependent Claim
77 words
A method as claimed in claim 8, including the steps of forming said short length of fiber with a core and a cladding, forming the core with a generally parabolic refractive index profile which dips at the center of the short length of fiber and has a central low refractive index region with a diameter of at least 12 microns and a refractive index substantially lower than the index of an immediately adjacent part of the core.
Claim 12
Dependent Claim
33 words
A method as claimed in claim 9, including the steps of forming said multimode optical transmission line using an MCVD process to have a substantially parabolic refractive index which dips at the center.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-02-08 | 1991-08-10 | 1992-02-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-02-08 | 1995-08-10 | 1996-02-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-02-08 | 1999-08-10 | 2000-02-09 | $7700.00 | Window Closed / Lapsed |