US4852968A — Optical fiber comprising a refractive index trench

Claim 1

Independent Claim 306 words

An optical fiber, adapted for single mode operation at an operating wavelength λ op , that comprises (a) a core having a refractive index n 1 (a), and a radius a 1 , where a is the radial fiber coordinate; (b) a cladding that contactingly surrounds the core and extends outward from a 1 , at least the part of the cladding between a 1 and a radius a d consists of relatively low optical loss first cladding material having a refractive index that nowhere exceeds the maximum value of n 1 (a); associated with the fiber are fiber characteristics comprising: (i) a curve of chromatic dispersion vs wavelength, the curve having a slope and a zero at least at one zero dispersion wavelength λ o ; (ii) a dependence of λ o on a 1 ; (iii) a spectral range in which the absolute value of the curve of chromatic dispersion vs. wavelength is less than a predetermined value; (iv) a curve of integrated mode power vs. radius; (v) a bending loss at a given bend radius; and (vi) a maximum core doping level and, associated therewith, a Rayleigh scattering loss; (c) the cladding comprises a first cladding region that extends from a 1 to radius a 2 and has a refractive index n 2 (a), an index trench that extends from a 2 to a radius a 3 and has a refractive index n 3 (a), and a second cladding region that extends outward from a 3 and has a refractive index n 4 (a), with a 1 <a 2 <a 3 ≦a d , and with the maximum value of n 3 (a) being less than the minimum value of n 2 (a) and also less than n 4 (a=a 3 ), the refractive index of the second cladding at a 3 .

Claim 2

Dependent Claim 306 words

An optical fiber, adapted for single mode operation at an operating wavelength λ op , that comprises (a) a core having a refractive index n 1 (a), and a radius a 1 , where a is the radial fiber coordinate; (b) a cladding that contactingly surrounds the core and extends outward from a 1 , at least the part of the cladding between a 1 and a radius a d consists of relatively low optical loss first cladding material having a refractive index that nowhere exceeds the maximum value of n 1 (a); associated with the fiber are fiber characteristics comprising: (i) a curve of chromatic dispersion vs wavelength, the curve having a slope and a zero at least at one zero dispersion wavelength λ o ; (ii) a dependence of λ o on a 1 ; (iii) a spectral range in which the absolute value of the curve of chromatic dispersion vs. wavelength is less than a predetermined value; (iv) a curve of integrated mode power vs. radius; (v) a bending loss at a given bend radius; and (vi) a maximum core doping level and, associated therewith, a Rayleigh scattering loss; (c) the cladding comprises a first cladding region that extends from a 1 to radius a 2 and has a refractive index n 2 (a), an index trench that extends from a 2 to a radius a 3 and has a refractive index n 3 (a), and a second cladding region that extends outward from a 3 and has a refractive index n 4 (a), with a 1 <a 2 <a 3 ≦a d , and with the maximum value of n 3 (a) being less than the minimum value of n 2 (a) and also less than n 4 (a=a 3 ), the refractive index of the second cladding at a 3 .

Claim 3

Dependent Claim 65 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the slope of the curve of chromatic dispersion vs. wavelength at λ o is substantially reduced, relative to a second fiber that is identical to the first fiber except that in the second fiber n 3 (a)=n 2 (a=a 2 ).

Claim 4

Dependent Claim 61 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the integrated mode power at any radius a≧a 3 is substantially reduced, relative to a second fiber that is identical to the first fiber except that in the second fiber n 3 (a)=n 2 (a=a 2 ).

Claim 5

Dependent Claim 85 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the integrated mode power at any radius a≧a 3 is substantially reduced and such that a d is substantially reduced, substantially without increase in the bending loss, all relative to a second fiber that is identical to the first fiber except that the second fiber, in addition to having greater a d , has n 3 (a)=n 2 (a=a 2 ).

Claim 6

Dependent Claim 83 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the integrated mode power at any radius a≧a 3 is substantially reduced and such that the bending loss at a given bend radius is substantially reduced, all relative to a second fiber that is identical to the first fiber except that the second fiber, in addition to having greater bending loss, has n 3 (a)=n 2 (a=a 2 ).

Claim 7

Dependent Claim 131 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the integrated mode power at any radius a≧a 3 is substantially reduced, relative to a second fiber, the first fiber comprising a relatively high optical loss second cladding material extending outward from a d , associated with the second cladding material being a loss at λ op , the material of the first fiber second cladding region having substantially higher loss at λ op than the corresponding material of the second cladding region of the second fiber, the second fiber being identical to the first except that the second fiber, in addition to having lower loss second cladding material, has n 3 (a)=n 2 a=a 2 ).

Claim 8

Dependent Claim 72 words

The optical fiber of claim 1 constituting a first fiber, wherein the maximum core doping level is substantially reduced, relative to a second optical fiber that is identical to the first fiber except that the second fiber, in addition to having a greater core doping level and therefore greater Rayleigh scattering loss, has n 2 (a)=n 3 (a=a 2 ), with n 3 (a) being constant for a 2 <a<a 3 .

Claim 9

Dependent Claim 12 words

The fiber of claim 1, wherein n 3 (a) is substantially constant.

Claim 10

Dependent Claim 16 words

The first fiber of claim 4, wherein a d is substantially equal to a 3 .

Claim 11

Dependent Claim 16 words

The first fiber of claim 5, wherein a d is substantially equal to a 3 .

Claim 12

Dependent Claim 16 words

The first fiber of claim 2, wherein a d is substantially greater than a 3 .

Claim 13

Dependent Claim 30 words

The first fiber of claim 7, wherein a 1 and a 2 are chosen such that (a 2 -a 1 ) is from 0.1 to 20 times a 1 .

Claim 14

Dependent Claim 60 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the dependence of λ o on a 1 is substantially reduced, relative to a second fiber that is identical to the first fiber except that in the second fiber n 3 (a)=n 2 (a=a 2 ).

Claim 15

Dependent Claim 77 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the extent of the spectral region in which the absolute value of the curve of chromatic dispersion vs. wavelength is less than a predetermined value is substantially increased, relative to a second fiber that is identical to the first fiber except that in the second fiber n 3 9a)=n 2 (a=a 2 ).

Claim 16

Dependent Claim 67 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that the maximum absolute value of the chromatic dispersion in a spectral region of predetermined extent is substantially reduced, relative to a second fiber that is identical to the first fiber except that in the second fiber n 3 (a)=n 2 (a=a 2 ).

Claim 17

Dependent Claim 57 words

The fiber of claim 1 constituting a first fiber, wherein a 2 , a 3 , and n 3 (a) are chosen such that λ o is moved to a shorter wavelength, relative to a second fiber that is identical to the first fiber except that in the second fiber n 3 (a)=n 2 (a=a 2 ).

Claim 18

Dependent Claim 168 words

An optical communication system comprising a light source and a detector, further comprising single-mode optical fiber comprising: (a) a core of transparent material having a refractive index n 1 (a) (where a is the radial fiber coordinate) and a radius a 1 ; (b) a first cladding region of transparent material, contactingly surrounding said core region, with index of refraction n 2 (a) and extending to a radius a 2 ; (c) a trench region of transparent material, contactingly surrounding the first cladding region, with index n 3 (a) and extending to a radius a 3 ; and (d) a second cladding region with index n 4 (a) contactingly surrounding the trench region, wherein; (e) the maximum value of n 1 (a) is larger than any of n 2 (a) and n 3 (a), and is greater than or equal to n 4 (a); and (f) the maximum value of n 3 (a) is less than the minimum values of n 2 (a) and n 4 (a), respectively.

Claim 19

Dependent Claim 168 words

An optical communication system comprising a light source and a detector, further comprising single-mode optical fiber comprising: (a) a core of transparent material having a refractive index n 1 (a) (where a is the radial fiber coordinate) and a radius a 1 ; (b) a first cladding region of transparent material, contactingly surrounding said core region, with index of refraction n 2 (a) and extending to a radius a 2 ; (c) a trench region of transparent material, contactingly surrounding the first cladding region, with index n 3 (a) and extending to a radius a 3 ; and (d) a second cladding region with index n 4 (a) contactingly surrounding the trench region, wherein; (e) the maximum value of n 1 (a) is larger than any of n 2 (a) and n 3 (a), and is greater than or equal to n 4 (a); and (f) the maximum value of n 3 (a) is less than the minimum values of n 2 (a) and n 4 (a), respectively.

Claim 20

Dependent Claim 22 words

The optical communication system of claim 17 in which the radius of the core a 1 is between 2.5 and 5 μm.

Claim 21

Dependent Claim 26 words

The optical communication system of claim 18 in which (a 2 -a 1 ) is between 1/2 and 10 times the core radius a 1 .

Claim 22

Dependent Claim 26 words

The optical communication system of claim 19 in which (a 3 -a 2 ) is between one and five times the core radius a 1 .

Claim 23

Dependent Claim 58 words

The optical communication system of claim 17 in which the core index profile is nominally triangular, with a 1 between 2.5 and 3.5 μm and the maximum value of Δ 1 is between 0.5 and 1.5%, where Δ 1 =(n 2 1 -n 2 o )/2n 2 o , with n o being the refractive index of silica.

Claim 24

Dependent Claim 18 words

The optical communication system of claim 21 in which a 2 /a 1 is between 1.5 and 3.5.

Claim 25

Dependent Claim 42 words

The optical communication system of claim 21 in which (a 3 -a 2 ) is between 6 and 18 μm and Δ 3 is between -0.1 and -0.6%, where Δ 3 is (n 2 3 -n 2 o )/2n 2 o .

Claim 26

Dependent Claim 44 words

The optical communication system of claim 17 in which the core index profile is nominally triangular and the refractive index of the first cladding region and of at least a part of the second cladding region is less than the refractive index of silica.

Claim 27

Dependent Claim 18 words

The optical communication system of claim 17 where there are additional trench regions within the second cladding region.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1992-07-31	1993-01-30	1993-08-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1996-07-31	1997-01-30	1997-08-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2000-07-31	2001-01-30	2001-08-01	$7700.00	Window Closed / Lapsed

Optical fiber comprising a refractive index trench

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