US 5,058,976 AGranted

System comprising Er-doped optical fiber

AssigneeAT&T Bell Laboratories

InventorsDavid J. DiGiovanni, Kenneth L. Walker

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Abstract

The inventive optical fiber communication system comprises Si-based amplifier fiber whose core comprises Ge, Al, and Er. The amplifier fiber has an effective index difference (.DELTA.n) greater than 0.03, an effective core diameter a less than 3.5 .mu.m, a maximum Al concentration in the core of at least 6 mole %, a mode field diameter at the pump wavelength that is less than 5 .mu.m, a V-number at the pump wavelength in the range 1.4-2.0, a cut-off wavelength less than 1.4 .mu.m, and an Er distribution whose effective diameter is less than that of the Ge distribution. The fiber has advantageous properties including low amplification threshold and noise. Disclosed is also a method of making optical fiber that can be used to produce fiber having characteristics (e.g., .DELTA.n>0.03, high Al concentration) not generally obtainable with prior art methods. In a particular embodiment the method comprises a partial collapse of a tubular preform prior to completion of core material deposition, completion of core material deposition, and final collapse.

Claims14

Dependent claims

Optical fiber communication system comprising a length of optical fiber signal-transmissively connecting signal-generating means at a first location to signal-detecting means at a second location spaced from the first location;

the length of optical fiber comprising a length of transmission fiber and a length of Er-doped amplifier fiber;
the communication system further comprising means for generating pump radiation and means for coupling pump radiation into the length of optical fiber at a location intermediate the first and second locations;
the signal-generating means adapted for generating signal radiation of wavelength .lambda..sub.s (.lambda..sub.s .about.1.5 .mu.m), the means for generating pump radiation adapted for generating radiation of wavelength .lambda..sub.p less than .lambda..sub.s ;
the amplifier fiber comprising a first region of relatively high refractive index and a second region, contactingly surrounding the first region, of relatively low refractive index;
the first region comprising Ge and Al, and further comprising Er, associated with the amplifier fiber being refractive index difference .DELTA.n=(n.sub.c -n.sub.cl), where n.sub.c is an effective refractive index associated with the first region and n.sub.cl is a refractive index associated with the second region, an effective core diameter a, a mode field diameter at wavelength .lambda..sub.p, an Er distribution, an Al distribution, and a Ge distribution, with each of said distributions being associated an effective diameter;
CHARACTERIZED IN THAT
a) .DELTA.n>0.03 and a is less than 3.5 .mu.m;
b) the maximum Al concentration in the first region is at least 6 mole %;
c) .DELTA.n and a are chosen such that the mode field diameter for the pump radiation is less than 5 .mu.m, such that the V-number at .lambda..sub.p is in the range 1.4-2.0, and such that the amplifier fiber has a cut-off wavelength (.lambda..sub.co) that is less than 1.4 .mu.m;
and
d) the effective diameter associated with the Er distribution is less than that associated with the Ge distribution, and the effective diameter associated with the Al distribution is not substantially larger than that associated with the Er distribution.

8 more elements

Method of making a silica-based Er-doped optical fiber comprising a core and a cladding and adapted for use as an amplifier fiber for radiation of wavelength in the range 1.5-1.6 .mu.m;

the method comprising
a) providing a silica-based substrate tube;
b) forming a vitreous deposit on the inner surface of the tube;
c) collapsing at least a portion of the tube such that a rod-like preform results;
the preform comprising core material and cladding material;
and
d) drawing the optical fiber from the rod-like preform;
CHARACTERIZED IN THAT step b) and c) comprise
e) forming a first quantity of vitreous deposit on the inner surface, the first quantity comprising a portion of the core material, whereby a tubular preform is produced
f) partially collapsing at least a portion of the tubular preform such that the inner diameter of the at least portion of the tubular preform is reduced;
g) forming a second quantity of vitreous deposit on the inner surface of the partially collapsed at least portion of the tubular preform, the second quantity comprising the remainder of the core material;
h) collapsing at least a part of the partially collapsed at least portion of the tubular preform, such that the rod-like preform results.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/562,770Filed 3 Aug 1990
Granted: 22 Oct 1991
Term ends: Not estimatedThe source records don’t support an estimate.

Classification11 codes

H04B 10/2935
Considering the whole optical path: with a cascade of amplifiers
C03B 37/01838
Reactant delivery systems, e.g. reactant deposition burners: for delivering and depositing additional reactants as liquids or solutions, e.g. for…
H01S 3/06708
Fibre lasers: constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
H04B 10/2912
In which processing or amplification is carried out without conversion of the main signal from optical form: characterised by the medium used for…