U.S. patent application number 11/399009 was filed with the patent office on 2007-10-11 for highly dispersive dispersion compensating fiber for transmission fiber and transmission system utilizing same.
Invention is credited to William Allen Wood.
Application Number | 20070237477 11/399009 |
Document ID | / |
Family ID | 38575380 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070237477 |
Kind Code |
A1 |
Wood; William Allen |
October 11, 2007 |
HIGHLY DISPERSIVE DISPERSION COMPENSATING FIBER FOR TRANSMISSION
FIBER AND TRANSMISSION SYSTEM UTILIZING SAME
Abstract
A dispersion compensating optical fiber is disclosed which is
highly dispersive and which has a low effective area. The
dispersion compensating optical fiber is suited for use with
transmission optical fiber such as conventional single mode fiber.
An optical transmission fiber and optical transmission system are
also disclosed.
Inventors: |
Wood; William Allen;
(Painted Post, NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
US
|
Family ID: |
38575380 |
Appl. No.: |
11/399009 |
Filed: |
April 5, 2006 |
Current U.S.
Class: |
385/126 ;
385/123 |
Current CPC
Class: |
G02B 6/02028 20130101;
G02B 6/03644 20130101; G02B 6/03677 20130101; G02B 6/02261
20130101 |
Class at
Publication: |
385/126 ;
385/123 |
International
Class: |
G02B 6/036 20060101
G02B006/036; G02B 6/02 20060101 G02B006/02 |
Claims
1. An optical fiber comprising: a core disposed about a centerline;
and a cladding surrounding the core; wherein the core and cladding
define a relative refractive index profile; wherein the core
comprises: a central segment extending radially outward from the
centerline; a first annular segment surrounding the central
segment; and a second annular segment surrounding the first annular
segment; wherein the refractive index profile provides an effective
area at 1550 nm less than or equal to 15.0 .mu.m.sup.2, a
dispersion at 1550 nm more negative than -150 ps/nm/km, and a kappa
at 1550 nm greater than 100 nm, wherein kappa is dispersion at 1550
nm divided by dispersion slope at 1550 nm, and wherein the relative
refractive index profile of the central segment has an alpha shape
with an alpha greater than 10.
2. (canceled)
3. The optical fiber of claim 1 wherein the optical fiber exhibits
a pin array bend loss at 1550 nm of less than 10 dB.
4. The optical fiber of claim 1 wherein the kappa at 1550 nm is
greater than 200 nm.
5. The optical fiber of claim 1 wherein the central segment
comprises a maximum relative refractive index .DELTA..sub.1MAX
greater than 1.8%.
6. The optical fiber of claim 1 wherein the first annular segment
comprises a minimum relative refractive index .DELTA.1.sub.MIN more
negative than -0.35%.
7. The optical fiber of claim 1 wherein the central segment extends
to a radius, R1, between 0.7 and 1.5 .mu.m.
8. The optical fiber of claim 1 wherein the first annular segment
extends to a radius, R2, between 3.0 and 4.5 .mu.m.
9. The optical fiber of claim 1 wherein the first annular segment
extends for a radial width, W.sub.2, between 2.0 and 3.0 .mu.m.
10. The optical fiber of claim 1 wherein the first annular segment
has a midpoint, R2.sub.MID, between 2.1 and 2.7 .mu.m.
11. The optical fiber of claim 1 wherein the second annular segment
comprises a maximum relative refractive index .DELTA.3.sub.MAX
greater than 0.25%.
12. The optical fiber of claim 1 wherein the second annular segment
has half-height peak width, HHPW3, between 0.5 and 1.2 .mu.m.
13. The optical fiber of claim 1 wherein the second annular segment
has half-height peak midpoint, R3.sub.HHMID, between 4.0 and 6.0
.mu.m.
14. The optical fiber of claim 1 wherein the second annular segment
has a midpoint, R3.sub.MID, between 4.0 and 6.0 .mu.m.
15. The optical fiber of claim 1 wherein the second annular segment
has a width, W3, between 0.5 and 4.0 .mu.m.
16. The optical fiber of claim 1 wherein the refractive index
profile provides a mode field diameter at 1550 nm of between 3.90
and 4.20 .mu.m.
17. The optical fiber of claim 1 wherein the refractive index
profile provides a theoretical cutoff of less than 1570 nm.
18. The optical fiber of claim 1 wherein the product of the
effective area at 1550 nm and the absolute magnitude of the
dispersion at 1550 nm is greater than 2000 attoseconds.
19. The optical fiber of claim 1 wherein the refractive index
profile provides a dispersion slope at 1550 nm of between -0.5 and
-1.0 ps/nm.sup.2/nm
20. An optical fiber transmission line comprising: a transmission
optical fiber having a dispersion at 1550 nm between 14 and 22
ps/nm-km and a dispersion slope at 1550 nm less than 0.08
ps/nm.sup.2-km; and the dispersion compensating fiber of claim 1
optically coupled to the transmission optical fiber.
21. An optical fiber comprising: a core disposed about a
centerline; and a cladding surrounding the core; wherein the core
and cladding define a relative refractive index profile; wherein
the core comprises: a central segment extending radially outward
from the centerline; a first annular segment surrounding the
central segment; and a second annular segment surrounding the first
annular segment; wherein the refractive index profile provides an
effective area at 1550 nm less than or equal to 15.0 .mu.m.sup.2, a
dispersion at 1550 nm more negative than -150 ps/nm/km, and a kappa
at 1550 nm greater than 100 nm, wherein kappa is dispersion at 1550
nm divided by dispersion slope at 1550 nm, and wherein the central
segment extends to a radius, R1, between 0.7 and 1.5 .mu.m, and
wherein the optical fiber exhibits a pin array bend loss at 1550 nm
of less than 10 dB.
22. An optical fiber comprising: a core disposed about a
centerline; and a cladding surrounding the core; wherein the core
and cladding define a relative refractive index profile; wherein
the core comprises: a central segment extending radially outward
from the centerline; a first annular segment surrounding the
central segment; and a second annular segment surrounding the first
annular segment; wherein the refractive index profile provides an
effective area at 1550 nm less than or equal to 15.0 .mu.m.sup.2, a
dispersion at 1550 nm more negative than -150 ps/nm/km, and a kappa
at 1550 nm greater than 100 nm, wherein kappa is dispersion at 1550
nm divided by dispersion slope at 1550 nm, and wherein the
refractive index profile provides a theoretical cutoff of less than
1570 nm.
Description
BACKGROUND OF THE INVENTION
[0001] 1 Field of the Invention
[0002] The present invention relates generally to optical fiber,
and particularly to dispersion compensating optical fibers and
systems employing same.
[0003] 2. Technical Background
[0004] While some optical transmission systems can tolerate fairly
large amounts of residual dispersion at 10 Gbit/second, these
systems can tolerate only small amounts of residual dispersion at
higher transmission rates of about 40 Gbit/second without causing
unwanted signal distortion. Dispersion in such high bit-rate
optical transmission systems needs to be controlled at the
wavelength, or wavelengths, or interest. Various solutions have
been proposed to achieve dispersion, and dispersion slope, values
required for compensating transmission fibers. One approach
involves housing a dispersion compensating fiber in a dispersion
compensating module wherein the dispersion compensating fiber
compensates for the accumulated dispersion of the transmission
fiber at a location where the fiber end is accessible. Such modules
include a length of dispersion compensating fiber wound onto a
spool or reel.
[0005] Wavelength division multiplexing (WDM) systems have operated
around the 1550 nm wavelength region, defined herein as including
the C-band, which includes wavelengths between about 1525 nm to
about 1565, and the L-band, which includes wavelengths between
about 1565 nm to about 1625 nm
SUMMARY OF THE INVENTION
[0006] Dispersion compensating optical fiber ("DCF") disclosed
herein comprises highly negative dispersion and low effective area
for operating wavelengths in the C-band, the L-band, or both the
C-band and L-band. The DCF also comprises a kappa that provides
dispersion compensation for an optical transmission fiber
("transmission fiber") at a plurality of wavelengths within a
wavelength band. Also disclosed herein are optical fiber
transmission lines which comprise transmission fiber and such DCF.
Some embodiments of the DCF disclosed herein are particularly well
suited for compensating the dispersion of transmission fiber having
a dispersion at 1550 nm between 14 and 22 ps/nm-km, such as SMF-28e
optical fiber manufactured and sold by Coming Incorporated. The
transmission fiber may have a dispersion slope at 1550 nm of less
than 0.07 ps/nm 2-km, or less than 0.07 ps/nm.sup.2-km and greater
than 0.05 ps/nm.sup.2-km, such as SMF-28e optical fiber. In some
embodiments, an optical fiber transmission line is disclosed herein
comprising a transmission optical fiber having a dispersion at 1550
nm between 14 and 22 ps/nm-km and a dispersion slope at 1550 nm
less than 0.07 ps/nm.sup.2-km optically coupled to at least one DCF
disclosed herein.
[0007] The DCF disclosed herein comprises a core disposed about a
centerline, and a cladding surrounding the core. The core comprises
a central segment extending radially outward from the centerline, a
first annular segment surrounding the central segment, and a second
annular segment surrounding the first annular segment.
[0008] In some embodiments, the core and cladding define a relative
refractive index profile which provides an effective area at 1550
nm less than or equal to 15.0 .mu.m , a dispersion at 1550 nm more
negative than -150 ps/nm/km, and a kappa at 1550 nm greater than
100 nm, wherein kappa is dispersion at 1550 nm divided by
dispersion slope at 1550 nm.
[0009] The relative refractive index profile of the central segment
of the DCF disclosed herein preferably has an alpha shape with an
alpha greater than 10, more preferably greater than 15, for
improved bending performance. In some embodiments, the profile of
the central segment has a step shape, or slightly rounded step.
[0010] In some embodiments, the DCF exhibits a pin array bend loss
at 1550 nm of less than 10 dB.
[0011] In some embodiments, kappa at 1550 nm is greater than 200
nm.
[0012] In some embodiments, the central segment comprises a maximum
relative refractive index .DELTA..sub.1MAX greater than 1.8%.
[0013] In some embodiments, the first annular segment comprises a
minimum relative refractive index .DELTA.2.sub.MIN more negative
than -0.35%.
[0014] In some embodiments, the central segment extends to a
radius, R1, between 0.7 and 1.5 .mu.gm.
[0015] In some embodiments, the first annular segment extends to a
radius, R2, between 3.0 and 4.5 .mu.m.
[0016] In some embodiments, the first annular segment extends for a
radial width, W.sub.2, between 2.0 and 3.0 .mu.m.
[0017] In some embodiments, the first annular segment has a
midpoint, R2.sub.MID, between 2.1 and 2.7 .mu.m.
[0018] In some embodiments, the second annular segment comprises a
maximum relative refractive index .DELTA.3.sub.MAX greater than
0.25%.
[0019] In some embodiments, the second annular segment has
half-height peak width, HHPW3, between 0.5 and 1.2 .mu.m.
[0020] In some embodiments, the second annular segment has
half-height peak midpoint, R3.sub.HHMID, between 4.0 and 6.0
.mu.m.
[0021] In some embodiments, the second annular segment has a
midpoint, R3.sub.MID, between 4.0 and 6.0 .mu.m.
[0022] In some embodiments, the second annular segment has a width,
W3, between 0.5 and 4.0 .mu.m.
[0023] In some embodiments, the refractive index profile provides a
mode field diameter at 1550 nm of between 3.90 and 4.20 .mu.m.
[0024] In some embodiments, the refractive index profile provides a
theoretical cutoff of less than 1570 nm.
[0025] In some embodiments, the product of the effective area at
1550 nm and the absolute magnitude of the dispersion at 1550 nm is
greater than 2000 attoseconds.
[0026] In some embodiments, the refractive index profile provides a
dispersion slope at 1550 nm of between -0.5 and -1.0
ps/nm.sup.2/nm.
[0027] In one aspect, an optical fiber transmission line is
disclosed herein comprising a transmission optical fiber having a
dispersion at 1550 nm between 14 and 22 ps/nm-km and a dispersion
slope at 1550 nm less than 0.08 ps/nm.sup.2-km and a dispersion
compensating fiber of claim 1 optically coupled to the transmission
optical fiber. In another aspect, an optical fiber transmission
system incorporating such transmission line is also disclosed
herein.
[0028] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 shows a relative refractive index profile
corresponding to a first embodiment of optical waveguide fiber as
disclosed herein.
[0030] FIG. 2 shows a relative refractive index profile
corresponding to a second embodiment of optical waveguide fiber as
disclosed herein.
[0031] FIG. 3 shows respective dispersion vs. wavelength curves for
the optical fiber embodiments of FIGS. 1-2 and five other
embodiments.
[0032] FIG. 4 shows an isometric cutaway representation of an
embodiment of an optical waveguide fiber as disclosed herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] Additional features and advantages of the invention will be
set forth in the detailed description which follows and will be
apparent to those skilled in the art from the description or
recognized by practicing the invention as described in the
following description together with the claims and appended
drawings.
[0034] The "refractive index profile" is the relationship between
refractive index or relative refractive index and waveguide fiber
radius.
[0035] The "relative refractive index percent" is defined as
.DELTA.%=100.times.(n.sub.i.sup.2-n.sub.c.sup.2)/2n.sub.c.sup.2,
where n.sub.i is the maximum refractive index in region i, unless
otherwise specified, and n.sub.c is the average refractive index of
the cladding region. As used herein, the relative refractive index
is represented by .DELTA. and its values are given in units of "%",
unless otherwise specified. In cases where the refractive index of
a region is less than the average refractive index of the cladding
region, the relative index percent is negative and is referred to
as having a depressed region or depressed index, and is calculated
at the point at which the relative index is most negative unless
otherwise specified. In cases where the refractive index of a
region is greater than the average refractive index of the cladding
region, the relative index percent is positive and the region can
be said to be raised or to have a positive index. An "updopant" is
herein considered to be a dopant which has a propensity to raise
the refractive index relative to pure undoped SiO.sub.2. A
"downdopant" is herein considered to be a dopant which has a
propensity to lower the refractive index relative to pure undoped
SiO.sub.2. An updopant may be present in a region of an optical
fiber having a negative relative refractive index when accompanied
by one or more other dopants which are not updopants. Likewise, one
or more other dopants which are not updopants may be present in a
region of an optical fiber having a positive relative refractive
index. A downdopant may be present in a region of an optical fiber
having a positive relative refractive index when accompanied by one
or more other dopants which are not downdopants. Likewise, one or
more other dopants which are not downdopants may be present in a
region of an optical fiber having a negative relative refractive
index.
[0036] "Chromatic dispersion", herein referred to as "dispersion"
unless otherwise noted, of a waveguide fiber is the sum of the
material dispersion, the waveguide dispersion, and the inter-modal
dispersion. In the case of single mode waveguide fibers the
inter-modal dispersion is zero. Dispersion slope is the rate of
change of dispersion with respect to wavelength.
[0037] "Effective area" is defined as: A.sub.eff=2.pi.
(.intg.f.sup.2r dr).sup.2/(.intg.f.sup.4 r dr), where the
integration limits are 0 to .infin., and f is the transverse
component of the electric field associated with light propagated in
the waveguide. As used herein, "effective area" or "A.sub.eff"
refers to optical effective area at a wavelength of 1550 nm unless
otherwise noted.
[0038] The term ".alpha.-profile" or "alpha profile" refers to a
relative refractive index profile, expressed in terms of .DELTA.(r)
which is in units of "%", where r is radius, which follows the
equation,
.DELTA.(r)=.DELTA.(r.sub.o)(1-[|r-r.sub.o|/(r.sub.1-r.sub.o)].sup..alpha.-
), where r.sub.o is the point at which .DELTA.(r) is maximum,
r.sub.1 is the point at which .DELTA.(r)% is zero, and r is in the
range r.sub.i.ltoreq.r.ltoreq.r.sub.f, where .DELTA. is defined
above, r.sub.i is the initial point of the .alpha.-profile, r.sub.f
is the final point of the .alpha.-profile, and .alpha. is an
exponent which is a real number.
[0039] The mode field diameter (MFD) is measured using the Peterman
II method wherein, 2w=MFD, and w.sup.2=(2.intg.f.sup.2 r
dr/.intg.[df/dr].sup.2 r dr), the integral limits being 0 to
.infin..
[0040] The bend resistance of a waveguide fiber can be gauged by
induced attenuation under prescribed test conditions.
[0041] One type of bend test is the lateral load microbend test. In
this so-called "lateral load" test, a prescribed length of
waveguide fiber is placed between two flat plates. A #70 wire mesh
is attached to one of the plates. A known length of waveguide fiber
is sandwiched between the plates and a reference attenuation is
measured while the plates are pressed together with a force of 30
newtons. A 70 newton force is then applied tot he plates and the
increase in attenuation in dB/m is measured. The increase in
attenuation is the lateral load attenuation of the waveguide.
[0042] The "pin array" bend test is used to compare relative
resistance of waveguide fiber to bending. To perform this test,
attenuation loss is measured for a waveguide fiber with essentially
no induced bending loss. The waveguide fiber is then woven about
the pin array and attenuation again measured. The loss induced by
bending is the difference between the two measured attenuations.
The pin array is a set of ten cylindrical pins arranged in a single
row and held in a fixed vertical position on a flat surface. The
pin spacing is 5 mm, center to center. The pin diameter is 0.67 mm.
During testing, sufficient tension is applied to make the waveguide
fiber conform to a portion of the pin surface.
[0043] The theoretical fiber cutoff wavelength, or "theoretical
fiber cutoff", or "theoretical cutoff", for a given mode, is the
wavelength above which guided light cannot propagate in that mode.
A mathematical definition can be found in Single Mode Fiber Optics,
Jeunhomme, pp. 39-44, Marcel Dekker, New York, 1990 wherein the
theoretical fiber cutoff is described as the wavelength at which
the mode propagation constant becomes equal to the plane wave
propagation constant in the outer cladding. This theoretical
wavelength is appropriate for an infinitely long, perfectly
straight fiber that has no diameter variations.
[0044] Unless otherwise noted herein, optical properties (such as
dispersion, dispersion slope, etc.) are reported for the LP01
mode.
[0045] An optical transmission line as used herein includes a
length of optical fiber, or a plurality of optical fibers fused
together serially, extending between optical devices, for example
between two optical amplifiers, or between a multiplexing device
and an optical amplifier. The optical transmission line may
comprise transmission fiber and dispersion compensating fiber,
wherein the dispersion compensating fiber may be deployed in a
module (DC module) or laid out lengthwise, or both, as selected to
achieve a desired system performance or parameter such as residual
dispersion at the end of an optical transmission line.
[0046] Various wavelength bands, or operating wavelength ranges, or
wavelength windows, can be defined as follows: "1310 nm band" is
1260 to 1360 nm; "E-band" is 1360 to 1460 nm; "S-band" is 1460 to
1530 nm; "C-band" is 1525 to 1565 nm; "L-band" is 1565 to 1625 nm;
and "U-band" is 1625 to 1675 nm.
[0047] The optical fiber 10 disclosed herein comprises a core 100
and a cladding layer (or cladding) 200 surrounding and directly
adjacent the core. The cladding 200 has a refractive index profile,
.DELTA..sub.CLAD (r). Preferably, .DELTA..sub.CLAD(r)=0 throughout
the cladding 200.
[0048] The core 100 preferably comprises silica doped with
germanium, i.e. germania doped silica. Dopants other than
germanium, singly or in combination, may be employed within the
core, and particularly at or near the centerline, of the optical
fiber disclosed herein to obtain the desired refractive index and
density. The core 100 of the optical fiber disclosed herein
comprises a relative refractive index profile with both positive
and negative segments. The core 100 is surrounded by and directly
adjacent to a cladding layer 200.
[0049] Dispersion compensating optical fiber 10 disclosed herein
comprises a core 100, disposed about a centerline and comprising a
refractive index profile, and a cladding 200 surrounding the core.
The core 100 comprises a central segment 20 extending radially
outwardly from the centerline, a first annular segment 30
surrounding the central segment 20, and a second annular segment 50
surrounding the first annular segment 30. The central segment 20
has a relative refractive index profile, .DELTA..sub.1(r), having a
maximum relative refractive index .DELTA..sub.1MAX, wherein
.DELTA..sub.1(r) is positive. The first annular segment 30 has a
relative refractive index profile, .DELTA..sub.2(r) wherein
.DELTA..sub.2(r) is negative. The second annular segment 50 has a
relative refractive index profile, .DELTA..sub.3(r), having a
maximum relative refractive index .DELTA..sub.3MAX, wherein
.DELTA..sub.3(r) is non-negative, and wherein .DELTA..sub.3(r) is
positive in at least a portion of the second annular segment.
[0050] The central segment 20 extends from the centerline to a
radius R1 where .DELTA.=0%, i.e. where the relative refractive
index profile crosses the .DELTA.=0% axis and goes from positive in
the central segment 20 to negative in the first annular segment
30.
[0051] First annular segment (or moat) 30 surrounds the central
segment 20 and is directly adjacent thereto, extending radially
outwardly to a first annular segment outer radius, R.sub.2, where
.DELTA. first reaches 0%, i.e. where the relative refractive index
profile reaches the .DELTA.=0% axis i.e. goes from negative in the
first annular segment 30 to non-negative in the second annular
segment 50. First annular segment 30 has a width W.sub.2 (=R2-R1)
disposed at a midpoint R.sub.2MID (=(R1+R2)/2) and has a relative
refractive index percent, .DELTA..sub.2 %(r). The first annular
segment 30 is directly adjacent the central core segment 20.
[0052] Second annular segment (or ring) 50 surrounds the first
annular segment 30 and preferably directly adjacent thereto and
extends to a second annular segment outer radius R3 where the
relative refractive index profile first reaches .DELTA.=0.03% at a
radial location greater than the radius where .DELTA..sub.3MAX
occurs. Segment 50 has a width W.sub.3 (=R3-R2) disposed at a
midpoint R.sub.3MID (=(R2+R3)/2), and has a positive relative
refractive index percent, .DELTA..sub.3 %(r)>0, wherein
preferably .DELTA..sub.1MAX>.DELTA..sub.3MAX>0. The second
annular segment 50 has a non-negative relative refractive index
profile wherein at least a portion of the segment 50 has a positive
relative refractive index profile with a "peak" or a maximum
relative refractive index percent, .DELTA..sub.3MAX. R.sub.3HHi
marks the first radially inward, or centermost, occurrence of the
half-height of .DELTA..sub.3MAX. R.sub.3HHj marks the first
radially outward occurrence of the half-height of
.DELTA..sub.3,MAX. The ring half-height peak width HHPW.sub.3 is
bounded by inner and outer radii, R.sub.3HHi and R.sub.3HHj,
respectively. The midpoint of the ring half-height peak width
HHPW.sub.3 occurs at a radius R.sub.3HHMID which is half the radial
distance between R.sub.3HHi and R.sub.3HHj. .DELTA..sub.3MAX may
occur at R.sub.3HHMID. In some embodiments, R.sub.3HHMID coincides
with the middle of the segment 50, R.sub.3MID, between R.sub.2 and
R.sub.3. The second annular segment 50 is directly adjacent the
first annular segment 30.
[0053] Cladding 200 surrounds the second annular segment 50 and is
preferably adjacent thereto and has a relative refractive index
percent, .DELTA..sub.c %(r). Cladding 200 constitutes the outermost
silica part of the fiber. The core ends and the cladding begins at
a radius R.sub.CORE.
[0054] In some embodiments, the core comprises a relative
refractive index profile having a so-called centerline dip which
may occur as a result of one or more optical fiber manufacturing
techniques. However, the centerline dip in any of the refractive
index profiles disclosed herein is optional.
[0055] In some embodiments, the effective area at 1550 nm is
greater than 10 .mu.m.sup.2 and less than or equal to 15.0
.mu.m.sup.2.
[0056] Preferably, the DCF exhibits a pin array bend loss at 1550
nm of less than 10 dB. In some embodiments, the DCF exhibits a pin
array bend loss at 1550 nm of less than 5 dB.
[0057] In some embodiments, the kappa of the DCF at 1550 nm is
greater than 200 nm, and in other embodiments, between 250 and 350
nm.
[0058] In some embodiments, the dispersion of the DCF at 1550 nm is
more negative than -150 ps/nm/km and less negative than -250
ps/nm/km. In other embodiments, the dispersion at 1550 nm is more
negative than -200 ps/nm/km.
[0059] In some embodiments, .DELTA..sub.1MAX is greater than 1.8%.
In other embodiments, .DELTA..sub.1MAX is greater than or equal to
2.0%. In other embodiments, .DELTA..sub.1MAX is greater than 1.8%
and less than 2.5%.
[0060] In some embodiments, .DELTA.2.sub.MIN is more negative than
-0.35%. In other embodiments, .DELTA.2.sub.MIN is more negative
than -0.35% and more positive than -0.70%.
[0061] In some embodiments, the central segment extends to a
radius, R1, between 0.7 and 1.5 .mu.m, and in other embodiments
between 0.9 and 1.3 .mu.m.
[0062] In some embodiments, the first annular segment extends to a
radius, R2, between 3.0 and 4.5 .mu.m, and in other embodiments
between 3.0 and 4.0 .mu.m.
[0063] In some embodiments, W.sub.2 is between 2.0 and 3.0
.mu.m.
[0064] In some embodiments, R2.sub.MID is between 2.1 and 2.7
.mu.m, and in other embodiments between 2.2 and 2.6 .mu.m.
[0065] In some embodiments, .DELTA.3.sub.MAX is greater than 0.25%,
and in other embodiments greater than 0.30%. In other embodiments,
.DELTA.3.sub.MAX is between 0.25% and 0.8%. In other embodiments,
.DELTA.3.sub.MAX is between 0.30% and 0.70%.
[0066] In some embodiments, the second annular segment has
half-height peak width, HHPW3, between 0.5 and 1.2 .mu.m.
[0067] In some embodiments, the second annular segment has
half-height peak midpoint, R3.sub.HHMID, between 4.0 and 6.0
.mu.m.
[0068] In some embodiments, the second annular segment has a
midpoint, R3.sub.MID, between 4.0 and 6.0 .mu.m. In some
embodiments, the second annular segment has a width, W3, between
0.5 and 4.0 .mu.m.
[0069] In some embodiments, the refractive index profile provides a
mode field diameter at 1550 nm of between 3.90 and 4.20 .mu.m.
[0070] In some embodiments, the refractive index profile provides a
theoretical cutoff of less than 1570 .mu.m, and in other
embodiments, less than 1500 nm.
[0071] In some embodiments, the product of the effective area at
1550 nm and the absolute magnitude of the dispersion at 1550 nm is
greater than 2000 attoseconds, and in other embodiments between
2000 and 3500 attoseconds.
[0072] In some embodiments, the refractive index profile provides a
dispersion slope at 1550 nm of between -0.5 and -1.0
ps/nm.sup.2/nm.
[0073] Tables 1-2 list an illustrative set of embodiments, Examples
1-8. FIG. 1 shows the corresponding relative refractive index
profile of Example 1 in curve 1, and FIG. 2 shows the corresponding
relative refractive index profile of Example 2 in curve 2. FIG. 2
is also representative of the relative refractive index profiles of
Examples 3-8 as further defined in Table 1. The alpha's of the
relative refractive index profiles of the central segments of all
of the Examples are greater than about 15. TABLE-US-00001 TABLE 1
Example 1 2 3 4 5 6 7 8 .DELTA..sub.1MAX % 1.96 2.24 2.24 2.31 2.35
2.31 2.39 2.46 .alpha..sub.1 (step) 15 15 15 15 15 15 15 R1 .mu.m
1.2 1.2 1.25 1.1 1.1 1.1 1.1 1.1 .DELTA..sub.2MIN % -0.61 -0.64
-0.58 -0.57 -0.52 -0.57 -0.42 -0.62 R2 .mu.m 3.9 3.3 3.5 3.5 3.6
3.5 3.9 3.3 W.sub.2 .mu.m 2.7 2.1 2.25 2.4 2.5 2.4 2.8 2.2
R2.sub.MID .mu.m 2.6 2.3 2.4 2.3 2.4 2.3 2.5 2.2 .DELTA..sub.3MAX %
0.68 0.37 0.49 0.51 0.52 0.51 0.49 0.61 R3.sub.HHi .mu.m 3.9 4.5
4.8 4.7 4.96 4.7 5.2 4.7 R3.sub.HHJ .mu.m 4.8 5.2 5.5 5.3 5.6 5.3
5.8 5.3 HHPW3 .mu.m 0.9 0.7 0.7 0.6 0.64 0.6 0.6 0.6 R3.sub.HHMID
.mu.m 4.35 4.85 5.15 5 5.28 5 5.5 5 R.sub.3 = .mu.m 4.8 5.8 6.2 6.0
6.3 6.0 6.0 6 R.sub.CORE W.sub.3 .mu.m 0.9 2.5 2.7 2.5 2.7 2.5 2.1
2.7 R.sub.3MID .mu.m 4.35 4.55 4.85 4.75 4.95 4.75 4.95 4.65
[0074] TABLE-US-00002 TABLE 2 Example 1 2 3 4 5 6 7 8 Dispersion
@1500 nm ps/nm-km -138 -139 -138 -181 -181 -180 -166 -165 @1525 nm
ps/nm-km -152 -152 -152 -200 -200 -200 -182 -182 @1550 nm ps/nm-km
-167 -167 -167 -220 -220 -220 -200 -200 @1575 nm ps/nm-km -182 -182
-182 -239 -239 -239 -218 -218 @1600 nm ps/nm-km -195 -196 -195 -252
-251 -254 -233 -234 @1625 nm ps/nm-km -205 -209 -204 -257 -255 -261
-243 -246 D. Slope ps/nm.sup.2-km -0.60 -0.59 -0.605 -0.783 -0.786
-0.800 -0.730 -0.735 @1550 nm Kappa 1550 nm 278 283 276 281 280 275
274 272 Aeff 1550 nm .mu.m.sup.2 14.7 12.4 14.1 14.3 14.3 12.5 14.1
12.0 MFD 1550 nm .mu.m 4.11 3.95 4.19 4.15 4.15 3.92 4.17 3.86 Pin
Array dB 8.2 1.0 3.1 10 7.9 1.1 9.3 0.6 @1550 nm Theoretical nm
1384 1446 1514 1482 1521 1557 1504 1547 Cutoff |D| .times. Aeff
attosec 2455 2071 2355 3146 3146 2750 2820 2400 (@1550 nm)
[0075] Embodiments of the DCF disclosed herein are suitable for
incorporation into an optical fiber transmission line that also
comprises a transmission optical fiber having a dispersion at 1550
nm between 14 and 22 ps/nm-km and a dispersion slope at 1550 nm
less than 0.080 ps/nm 2-km, and in some embodiments between 0.055
and 0.070 ps/nm 2-km, and in other embodiments between 0.058 and
0.065 ps/nm.sup.2-km.
[0076] FIG. 3 shows the corresponding dispersion curves (versus
wavelength) of embodiments represented by Examples 1-8 in curves
1-8, respectively. Examples 5 and 6 have substantially similar
dispersion curves 5 and 6. Curve A in FIG. 3 shows the dispersion
curve of one representative transmission optical fiber having a
dispersion at 1550 nm of about 16.7 ps/nm-km and a dispersion slope
at 1550 nm of about 0.06 ps/nm.sup.2-km, wherein the dispersion has
been multiplied by a factor of -10 for purposes of illustrating the
positive dispersion and the negative dispersions in one chart. The
overlap of Curves 1 and 2 with Curve A shows that Examples 1 and 2
are well suited to compensate the dispersion of such transmission
fiber, particularly at wavelengths between 1525 and 1565 nm. The
overlap of Curve 3 with Curve A shows that Example 3 is well suited
to compensate the dispersion of such transmission fiber,
particularly at wavelengths between 1525 and 1625 nm. Similarly,
FIG. 3 shows that Examples 4, 5 and 6 are well suited to compensate
the dispersion of a transmission fiber having a dispersion at 1550
nm of about 22 ps/nm-km and a dispersion slope at 1550 nm of about
0.078 ps/nm.sup.2-km, particularly at wavelengths between 1525 and
1565 nm, and also into the L-band (from 1565 nm to about 1590 nm)
and Examples 7 and 8 are well suited to compensate the dispersion
of a transmission fiber having a dispersion at 1550 nm of about 20
ps/nm-km and a dispersion slope at 1550 nm of about 0.073
ps/nm.sup.2-km, particularly at wavelengths between 1525 and 1565
nm, and also into the L-band (from 1565 nm to about 1600 nm).
[0077] In one aspect, an optical fiber transmission system is
disclosed herein comprising an optical source for transmitting
optical signals through a transmission optical fiber and a
dispersion compensating fiber disclosed herein, wherein the
transmission optical fiber has a first length, the dispersion
compensating fiber has a second length, and wherein, for all
wavelengths between 1525 and 1565 nm, the optical signals
transmitted through the transmission optical fiber and the
dispersion compensating fiber exhibit a residual dispersion of less
than 10 ps/nm per 100 km of the transmission optical fiber,
preferably less than 2 ps/nm per 100km of the transmission optical
fiber. In some embodiments, for all wavelengths between 1525 and
1625 nm, the optical signals transmitted through the transmission
optical fiber and the dispersion compensating fiber exhibit a
residual dispersion of less than 10 ps/nm per 100 km of the
transmission optical fiber, preferably less than 5 ps/nm per 100 km
of the transmission optical fiber. The transmission fiber and the
DCF are optically coupled into an optical transmission line.
[0078] A selected length of DCF made in accordance with Example 1
or Example 2 can be optically coupled with a transmission optical
fiber having a dispersion at 1550 nm between 16 and 17 ps/nm-km and
a dispersion slope at 1550 nm of about 0.06 ps/nm.sup.2-km in an
optical fiber transmission line which has a residual dispersion
with magnitude less than 0.02 ps/nm per km of the transmission
optical fiber at every wavelength between 1525 and 1565 nm. A
selected length of DCF made in accordance with Example 3 can be
optically coupled with a transmission optical fiber having a
dispersion at 1550 nm between 16 and 17 ps/nm-km and a dispersion
slope at 1550 nm of about 0.06 ps/nm.sup.2-km in an optical fiber
transmission line which has a residual dispersion with magnitude
less than 0.05 ps/nm per km of the transmission optical fiber at
every wavelength between 1525 and 1625 nm.
[0079] The optical fibers disclosed herein can be made by a vapor
deposition process, such as outside vapor deposition (OVD) process.
Thus, for example, known OVD laydown, consolidation, and draw
techniques may be advantageously used to produce the optical
waveguide fiber disclosed herein. Other processes may be used, for
example but in no way limited to, modified chemical vapor
deposition (MCVD) or vapor axial deposition (VAD) or plasma
chemical vapor deposition (PCVD).
[0080] 0.4 is a schematic representation (not to scale) of an
optical waveguide fiber 10 as disclosed herein having core 100 and
a cladding 200 directly adjacent and surrounding the core 100. The
core comprises central segment 20, first annular segment 30 and
second annular segment 50. The cladding 200 may be comprised of a
cladding material which was deposited, for example during a laydown
process, or which was provided in the form of a jacketing, such as
a tube in a rod-in-tube optical preform arrangement, or a
combination of deposited material and a jacket. The clad layer 200
is surrounded by a primary coating P and a secondary coating S. The
refractive index of the cladding 200 is used to calculate the
relative refractive index percentage as discussed elsewhere herein.
Referring to the Figures, the cladding 200 has a refractive index
of n.sub.c surrounding the core which is defined to have a
.DELTA.(r)=0%, which is used to calculate the refractive index
percentage of the various portions or regions of an optical fiber
or optical fiber preform.
[0081] In some embodiments, the optical fiber disclosed herein has
a silica-based core 100 and cladding 200. In some embodiments, the
cladding 200 has an outer diameter, 2*R,max, of about 125 .mu.m. In
some embodiments, the outer diameter of the cladding 200 has a
constant diameter along the length of the optical fiber. In some
embodiments, the refractive index of the optical fiber has radial
symmetry. In some embodiments, the outer diameter of the core 100
has a constant diameter along the length of the optical fiber. In
some embodiments, one or more coatings surround and are in contact
with the cladding. The coating may be a polymer coating such as
acrylate. In some embodiments, the coating has a constant diameter,
radially and along the length of the fiber.
[0082] In some embodiments, the optical fibers disclosed herein
have a low water content having an attenuation curve which exhibits
a relatively low, or no, water peak in a particular wavelength
region, especially around 1380 nm. Methods of producing low water
peak optical fiber can be found in PCT Application Publication
Numbers WO00/64825, WO01/47822, and WO 02/051761, the contents of
each being hereby incorporated by reference.
[0083] The dispersion compensating optical fiber disclosed herein
is thus highly dispersive, allowing shorter lengths of the DCF to
be optically coupled with transmission fiber, such as conventional
single mode fiber, thereby reducing insertion losses and package
sizes. The product of the effective area and dispersion is
sufficiently high to reduce nonlinear impairments.
[0084] It is to be understood that the foregoing description is
exemplary of the invention only and is intended to provide an
overview for the understanding of the nature and character of the
invention as it is defined by the claims. The accompanying drawings
are included to provide a further understanding of the invention
and are incorporated and constitute part of this specification. The
drawings illustrate various features and embodiments of the
invention which, together with their description, serve to explain
the principals and operation of the invention. It will become
apparent to those skilled in the art that various modifications to
the preferred embodiment of the invention as described herein can
be made without departing from the spirit or scope of the invention
as defined by the appended claims.
* * * * *