# US 5,703,986 A · Monomode optical fiber

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- Number: US 5,703,986 A
- Document ID: US5703986A
- Status: Granted
- Kind: A
- Application number: 08/687,370
- Filed: 1996-08-02
- Granted: 1997-12-30
- Earliest claimed: 1994-12-23
- Assignees: Alcatel
- Inventors: Claude Brehm; Jean-Yves Boniort; Pascale Nouchi; Jacques Auge
- Web page: https://patentgrep.com/patent/US5703986A

## CPC

- G02B 6/02: Optical fibres with cladding {with or without a coating}
- G02B 6/02028: {Small effective area or mode field radius, e.g. for allowing nonlinear effects (non-linear optical waveguide devices G02F1/365)}
- G02B 6/02395: {Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture (G02B6/02052, G02B6/02057, G02B6/024, G02B6/032, G02B6/105, G02B6/14 take precedence; coating on fibre gratings G02B6/02104; multilayer core or cladding G02B6/036; reinforcing splice joints G02B6/2558; optical cables, i.e. comprising protective structures external to the protective coating such as a jacket or plural coated optical fibres G02B6/44; coating of glass to obtain optical fibres C03C25/104)}
- G02B 6/0281: {Graded index region forming part of the central core segment, e.g. alpha profile, triangular, trapezoidal core (G02B6/0288, G02B6/0286 take precedence)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

The present invention concerns a monomode optical fiber comprising an optical core for guiding the majority of light waves, surrounded by an optical sheath, the difference between the maximum refraction coefficient of the core and that of the optical sheath being indicated as .DELTA.n and the radius of the core being indicated as a, characterized in that: a .epsilon.›0.6a.sub.c :1.1a.sub.c !, a.sub.c being provided, in .mu.m, by the formula: ##EQU1## where k=2.pi./.lambda., .lambda. being (in .mu.m) the wavelength of the transmission, and where n.sub.g is the coefficient of said optical sheath, equal within 10.sup.-3 to that of pure silica, .DELTA.n is greater than or equal to 0.01, and in that, .phi. being the diameter of said optical sheath, in .mu.m: .phi..epsilon.›.phi..sub.min :100!, .phi..sub.min being provided, in .mu.m, by the formula: ##EQU2## where ##EQU3##

## Claims

### Claim 1

A monomode optical fiber comprising an optical core for guiding light waves, surrounded by an optical sheath, the difference between the maximum refraction coefficient of said core and that of said optical sheath being indicated as .DELTA.n and the radius of said core being indicated as a, characterised in that:
a .epsilon.›0.6a.sub.c :1.1a.sub.c !, a.sub.c being provided, in .mu.m, by the formula: ##EQU10## where k=2.pi./.lambda., .lambda. being, in .mu.m, the wavelength of the transmission, and where n.sub.g is the refraction coefficient of said optical sheath, equal within 10.sup.-3 to that of pure silica,
.DELTA.n is greater than or equal to 0.01,
and in that, .phi. being the diameter of said optical sheath, in .mu.m: .phi..epsilon.›.phi..sub.min :100!, .phi..sub.min being provided, in .mu.m, by the formula: ##EQU11## where ##EQU12##

### Claim 2 (depends on 1)

An optical fiber according to claim 1, characterized in that it displays a step, trapezoid or triangle-type profile.

### Claim 3 (depends on 1)

An optical fiber according to claim 1, characterized in that said optical sheath is surrounded by a protective coating made of a synthetic material.

### Claim 4 (depends on 3)

An optical fiber according to claim 3, characterized in that said protective coating has a thickness which neighbours 50 .mu.m.