Description:TECHNICAL FIELD
[0001] The present disclosure relates to optical fibers and more
particularly, relates to a reduced diameter optical fiber with improved
macro-bending and micro-bending performance.
BACKGROUND
[0002] Optical fiber cables are a critical component of a modern
communications network across the globe. As the data and data rate requirement
increases, more optical fibers are required in the network to support higher
capacity and speed. Data centers are continuously trying to meet the challenges of
delivering more bandwidth networks. However, attributes such as attenuation and
bend loss are a few significant factors aiding the degradation of signals and
channel capacity.
[0003] One way to improve the channel capacity is to increase the number
of optical fibers in the network, which can be done by reducing the diameter of
the optical fibers. However, as the diameter of the optical fibers decreases,
attributes like micro-bending sensitivity, attenuation, and residual and applied
stress may increase. To overcome the aforesaid drawbacks, a fiber clad diameter
can be reduced by changing glass material composition of the optical fibers. In the
same context, a prior art reference “US8200057B2” discloses an optical fiber with
a core, an inner cladding, and an outer cladding. The inner cladding surrounds the
core, and an outer cladding with a deep trench surrounds the inner cladding. The
fiber with both core and inner cladding is doped with an up-dopant (Germanium)
and a down-dopant (Fluorine). The outer cladding deep trench is doped with
fluorine material. When both the core and the inner cladding are doped with
Germanium, the fiber results more density fluctuations in the core and the inner
cladding, an increased Rayleigh scattering which leads to high attenuation losses.
Since both the core and inner cladding are doped with Germanium, the usage of
Germanium is high which is not cost-effective way to manufacture the fiber and it
also leads to an increased viscosity mismatch in the cladding interfaces of fiber.
Another prior art reference “US10094975B2” describes an optical fiber having a core doped with the up dopant such as chlorine. An inner cladding surrounds the
core that is doped with down-dopant such as fluorine and an outer cladding
surrounds the inner cladding that is down-doped with fluorine. When the inner
cladding of the optical fiber is doped with down-dopant such as fluorine, the
viscosity of inner cladding is increased and hence viscosity mismatch also
increase, which further increases the structural relaxation time during fiber draw
process leads to increase in scattering losses and attenuation losses in the optical
fiber. Yet another prior art reference “US11125937B2” describes an optical fiber
that has a core that is doped with Germanium, an inner cladding surrounding the
core, and an outer cladding surrounding the inner cladding. The outer cladding is
chlorine-doped such that the relative refractive index varies as a function of
radius. The radially varying relative refractive index profile of the outer cladding
reduces excess stress in the core and inner cladding, which helps lower fiber
attenuation while also reducing macro bend and micro bend loss. When the outer
cladding of the optical fiber is chlorine-doped, the outer glass of the optical fiber
become less viscous and soft which leads to increased draw tension in the core
during the optical fiber draw process. The increased draw tension in the core is
not desirable as this increase density fluctuations and scattering losses in the
optical fiber.
[0004] While the prior arts cover various solutions to increase channel
capacity, however, there still remains a scope for improvement.
OBJECT OF THE DISCLOSURE
[0005] A principal object of the present disclosure is to provide a reduced
diameter optical fiber with improved macro-bending and micro-bending
performance.
[0006] Another object of the present disclosure is to provide a reduced
diameter optical fiber with low attenuation losses.
[0007] Another object of the present disclosure is to provide a novel
refractive index (RI) profile of an optical fiber with an immediate fluorine trench
surrounding an up-doped inner clad and an up-doped core region, wherein the inner clad is doped with chlorine surrounding the up-doped core region and the
core region is doped with germanium and chlorine. The enhanced design of the RI
profile of the optical fiber reduces macro-bending and micro-bending sensitivity.
SUMMARY
[0008] Accordingly, the present disclosure provides an optical fiber. The
optical fiber comprises a core extending along a central axis of the optical fiber,
wherein the core comprises at least a first up-dopant (e.g., Germanium) and a
second up-dopant (e.g., Chlorine). The optical fiber further comprises a cladding
surrounding the core. The cladding comprises a first cladding surrounding the
core, a second cladding surrounding the first cladding, and a third cladding
surrounding the second cladding. The first cladding has at least the second
up-dopant, the second cladding has at least one down-dopant (e.g., Fluorine), and
the third cladding is undoped (e.g., pure silica). The first cladding may have traces
of the first up-dopant and the at least one down-dopant, the second cladding may
have traces of the second up-dopant, and the third cladding may have traces of the
at least one down-dopant. The third cladding is covered/surrounded by a first
coating followed by a second coating.
[0009] The core is defined by a core refractive index ?1, the first cladding
is defined by a first cladding refractive index ?2, the second cladding is defined
by a second cladding refractive index ?3 and the third cladding is defined by a
third cladding refractive index ?4 such that ?1 > ?2 > ?3 and ?3 < ?4.
[0010] The optical fiber has (i) an attenuation less than 0.324 dB/km at
1310 nm wavelength and less than 0.19 dB/km at 1550 nm wavelength, (ii) a
macro bend loss of 0.02 dB at 1turn, 10 mm bend radius, 1550 nm wavelength
and, 0.07 dB at 1 turn, 10 mm bend radius, 1625 nm wavelength, and, 0.01 dB at
10 turns, 15 mm bend radius, 1550 nm wavelength and 0.09 dB at 10 turns, 15
mm bend radius, 1625 nm wavelength (iii), a micro bending loss of 1.08 dB/km at
1550 nm wavelength and 1.379 dB/km at 1625 nm wavelength, and (iv) a MAC
number less than 6.8.The optical fiber has a clad diameter between 79.3 µm and
125.7 µm. The optical fiber has a coating diameter of 158 µm to 200 µm.
[0011] These and other aspects herein will be better appreciated and
understood when considered in conjunction with the following description and the
accompanying drawings. It should be understood, however, that the following
descriptions are given by way of illustration and not of limitation. Many changes
and modifications may be made within the scope of the invention herein without
departing from the spirit thereof.
BRIEF DESCRIPTION OF FIGURES
[0012] The invention is illustrated in the accompanying drawings,
throughout which like reference letters indicate corresponding parts in the
drawings. The invention herein will be better understood from the following
description with reference to the drawings, in which:
[0013] FIG. 1 illustrates a cross-sectional view of an optical fiber
according to the present disclosure.
[0014] FIG. 2 is an example refractive index (RI) profile of the optical
fiber.
[0015] FIG. 3 illustrates concentration profiles of a core, a first cladding, a
second cladding and a third cladding of the optical fiber.
[0016] FIG. 4 illustrates a graph showing variation of concentration of
dopants in the RI profile including diffusion.
[0017] FIG. 5 is the RI profile of first cladding of the optical fiber.
[0018] FIG. 6 is the RI profile of second cladding of the optical fiber.
[0019] FIG. 7 illustrates a cross-sectional view of an optical fiber having
coating.
[0020] FIG. 8 illustrates a cross-sectional view of an optical fiber having
multiple cores.
DETAILED DESCRIPTION
[0021] In the following detailed description of the invention, numerous
specific details are set forth in order to provide a thorough understanding of the
invention. However, it will be obvious to a person skilled in the art that the invention may be practiced with or without these specific details. In other
instances, well known methods, procedures and components have not been
described in detail so as not to unnecessarily obscure aspects of the invention.
[0022] Furthermore, it will be clear that the invention is not limited to
these alternatives only. Numerous modifications, changes, variations, substitutions
and equivalents will be apparent to those skilled in the art, without parting from
the scope of the invention.
[0023] The accompanying drawings are used to help easily understand
various technical features and it should be understood that the alternatives
presented herein are not limited by the accompanying drawings. As such, the
present disclosure should be construed to extend to any alterations, equivalents
and substitutes in addition to those which are particularly set out in the
accompanying drawings. Although the terms first, second, etc. may be used herein
to describe various elements, these elements should not be limited by these terms.
These terms are generally only used to distinguish one element from another.
[0024] Unlike existing optical fibers, the present disclosure provides a
novel refractive index (RI) profile of an optical fiber with an immediate fluorine
trench (down-doped outer cladding) surrounding an up-doped inner cladding and
an up-doped core, wherein the inner clad is doped with chlorine surrounding the
up-doped core and the core is doped with germanium and chlorine.
[0025] The up-doping of the core and the inner cladding and down-doping
of the outer cladding result in enhanced design of the RI profile of the optical
fiber and help in reducing attenuation, macro-bending and micro-bending losses
in the optical fiber. The proposed combination of up-doping and down-doping
provides excellent optical fiber properties. Advantageously, the proposed optical
fiber increases the channel capacity to fulfil the requirement of data centers.
[0026] FIG. 1 illustrates a cross-sectional view of an optical fiber (100)
according to the present disclosure and FIG. 2 is an example refractive index (RI)
profile (200) of the optical fiber (100).
[0027] Generally, an optical fiber refers to a medium associated with
transmission of information over long distances in the form of light pulses. The optical fiber uses light to transmit voice and data communications over long
distances when encapsulated in a jacket/sheath. The optical fiber may be of ITU.T
G.657.A2 category. Alternatively, the optical fiber may be of ITU.T G.657.A1 or
G.657.B3 or G.652.D or other suitable category or the optical fiber may be a
multi-core optical fiber. The ITU.T, stands for International Telecommunication
Union-Telecommunication Standardization Sector, is one of the three sectors of
the ITU. The ITU is the United Nations specialized agency in the field of
telecommunications and is responsible for studying technical, operating and tariff
questions and issuing recommendations on them with a view to standardizing
telecommunications on a worldwide basis. The optical fiber may be a bend
insensitive fiber that has less degradation in optical properties or less increment in
optical attenuation during multiple winding/unwinding operations of an optical
fiber cable. The optical fiber comprises one or more cores, one or more clads or
claddings and/or one or more coating layers, where a core is a light-carrying
portion of the optical fiber using total internal reflection in which optical signal is
confined and a cladding is a region that prevents loss of signal by preventing any
signal leakage from the core. The refractive index of the cladding is lower than
the refractive index of core in order to cause reflection within the core so that light
waves are transmitted through the optical fiber. The coating protects the optical
fiber from moisture and physical damage and also improves the strength in terms
of heat and cold resistance.
[0028] Further, the term “refractive index” as used herein is referred to as
the measure of change of speed of light from one medium to another and is
particularly measured in reference to speed of light in vacuum. More specifically,
the refractive index facilitates measurement of bending of light from one medium
to another medium. The term refractive index profile” of the optical fiber as used
herein is referred to as the distribution of refractive indexes in the optical fiber
from the core to the outmost cladding layer of the optical fiber. Based on the
refractive index profile, the optical fiber may be configured as a step index fiber.
The refractive index of the core of the optical fiber is constant throughout the fiber
and is higher than the refractive index of the cladding. Further, the optical fiber may be configured as a graded index fiber, wherein the refractive index of the
core gradually varies as a function of the radial distance from the center of the
core.
[0029] Referring to FIG. 1, the optical fiber (100) comprises a core (102)
extending along a central axis (112) of the optical fiber (100). The term “core” of
the optical fiber (100) as used herein is referred to as an inner most cylindrical
structure present in the center of the optical fiber (100), that is configured to guide
the light rays inside the optical fiber (100). The core (102) may be a glass core.
The core (102) comprises at least a first up-dopant and a second up-dopant. In
general, up-doping is referred to as adding doping materials to facilitate increase
in the refractive index of a particular layer or part of the optical fiber. The
materials configured to facilitate up-doping are known as up-dopants. The first
up-dopant may be germanium, for example and the second up-dopant may be
chlorine, for example. Addition of germanium increases the refractive index in the
core (102). Germanium may be present in a range of 2500 to 3200 ppm,
preferably 3000 ppm and chlorine may be present in a range of 1850 to 2100 ppm
in the core (102). Further, germanium may be present in a range of 3.5 to 4.5%
(mol%), preferably 4% (mol%) If chlorine and germanium are doped beyond the
given range, bubbles may be generated in the core (102) and below the given
range, viscosity matching at a core-cladding interface may be impacted.
[0030] The core (102) is defined by a core radius R1 and a core refractive
index ?1. The core radius R1 is in a range of 3.6 to 4.1 µm and the core refractive
index ?1 is in a range of 4.9 to 5.5. Further, ?1% is in a range of 0.34 to 0.38. The
core (102) is further defined by a core thickness T1 as shown in FIG. 2, which is
in a range of 3.6 to 4.1 µm.
[0031] The optical fiber (100) further comprises a cladding (104). The
cladding (104) surrounds the core (102). The term “cladding” of the optical fiber
(100) as used herein is referred to as one or more layered structure covering the
core (102) of the optical fiber (100) from the outside, that is configured to possess
a lower refractive index than the refractive index of the core (102) to facilitate
total internal reflection of light rays inside the optical fiber (100).
[0032] Particularly, the cladding (104) comprises a first cladding (106)
surrounding the core (102), a second cladding (108) surrounding the first cladding
(106), and a third cladding (110) surrounding the second cladding (108). The first
cladding (106) comprises of silica glass doped with the second up-dopant, the
second cladding (108) has at least one down-dopant, and the third cladding (110)
is undoped. That is, the first cladding (106) is up-doped with chlorine, the second
cladding (108) is down-doped with fluorine, for example, forming an immediate
trench to the first cladding (106) and the third cladding (110) is pure silica. In
general, a trench is referred as a down doped region with a higher down dopant
concentration to decrease the refractive index of the down doped region with
respect to pure silica and increase the relative refractive index of the core region.
In general, down-doping is referred to as adding doping materials to facilitate the
decrease in the refractive index of a particular layer or part of the optical fiber.
The materials configured to facilitate down-doping are known as down-dopants.
In general, the undoped means a region of the optical fiber contains a dopant not
intentionally added to the region during fabrication, but the term does not exclude
low levels of background doping that may be inherently incorporated during the
fabrication process. Such background doping levels are very low in amount that
does not have an insignificant effect on the refractive index of the undoped region.
Chlorine may be present in a range of 2490 to 2800 ppm, preferably 2680 ppm in
the first cladding (106) and fluorine may be present in a range of 0.8 to 1%
(mol%) in the second cladding (108).If chlorine and fluorine are doped beyond
the given range, bubbles may be formed in the cladding (104) and below the given
range, viscosity matching at the core-cladding interface may be impacted.
[0033] Further, the first cladding (106) may have traces of the first
up-dopant and the at least one down-dopant, the second cladding (108) may have
traces of the second up-dopant, and the third cladding (110) may have traces of
the at least one down-dopant. In an aspect of the present disclosure, the first
cladding (106) may have traces of the first up-dopant in 7.1% to 16.1% region of
a total region of the first cladding (106) and the traces of at least one down-dopant
in 8.9% to 17.9% region of the total region of the first cladding (106). In another aspect of the present disclosure, the third cladding (110) may have traces of the at
least one down-dopant in 1.1% to 4.3% region of a total region of the third
cladding (110). In an aspect of the present disclosure, when the diameter of the
cladding (104) of the optical fiber (100) is equal to 80 + 0.7, the third cladding
(110) may have traces of the at least one down-dopant in 2.1% to 4.3% region of
the total region of the third cladding (110) and when the diameter of the cladding
(104) of the optical fiber (100) is equal to 125 + 0.7, the third cladding (110) may
have traces of the at least one down-dopant in 1.1% to 2.2% region of the total
region of the third cladding (110).
[0034] The traces of dopants may be induced in another region through
the diffusion process during Outside Vapor Deposition (OVD) process. These
traces are negligible and it is difficult to be quantified. There is no measurable
impact of these traces even though they have a minute role in viscosity matching
between different glass regions during the OVD process.
[0035] Advantageously, the up-doping, in the aforesaid ranges, reduces the
viscosity mismatch between the core (102) and the first cladding (106) i.e., the
core-cladding interface and also helps in reducing viscosity mismatch between the
first cladding (106) and the second cladding (108), which further reduces
structural relaxation time during fiber draw and hence scattering and attenuation
losses. Generally, viscosity is the measure of resistance to flow. Herein, the
concentration of the first up-dopant in the core (102), the concentration of the
second up-dopant in the first cladding (106) and the concentration of the
down-dopant in the second cladding (108) is used to match the viscosity.
Mismatch of the viscosity in the optical fiber leads to displacement of the core
(102) to the first cladding (106) at a given temperature, such as temperatures
between the softening points of the core (102) to the first cladding (106) and the
displacement causes interfacial fluctuations that become permanent when the
glass is cooled and, thereby, increases attenuation. Matching the viscosity of the
core (102), the first cladding (106) and the second cladding (108) reduces
interfacial fluctuation.
[0036] The addition of chlorine in the first cladding (106) reduces residual
stress between the core (102) and the first cladding (106), wherein the residual
stress is a stress that develops over the entire length from thermal expansion
mismatch between the core (102) and the first cladding (106) as well as draw
induced stress. Further, down-doping with fluorine in the second cladding (108)
reduces RI as well as viscosity and creates trench which helps in increasing mode
confinement (i.e., leaking loss due to bending and stress) and hence reduces
macro-bending and micro-bending losses, which is very critical as bend loss
sensitivity increase as we move towards lower diameter optical fibers i.e., < 125
µm. Typically, the bending loss in an optical fiber under pressure is related
linearly to the resulting lateral pressure, and the pressure on the core can be
minimized by providing a cushion in the core region, which is done by coating
thickness changes and providing a trench between the core and an outer cladding
of the optical fiber. When the external force is applied to the optical fiber, the
trench protects the core from deformation.
[0037] Combination of both up-doping and down-doping helps in
reducing viscosity mismatch between the core (102), the first cladding (106), the
second cladding (108) and the third cladding (110), which provides benefit in
attenuation, macro-bend, and micro-bend losses in lower-diameter optical fibers.
The aforesaid combination also reduces losses due to applied stress that is
imparted to the optical fiber (100) by bending, pulling or twisting during
processing, handling and deployment. In a reduced diameter optical fiber (100),
the aforesaid ranges of radius, thickness and refractive index are important to
achieve the characteristics and properties of the optical fiber (100) of the present
disclosure.
[0038] The first cladding (106) is defined by a first cladding radius R2 and
a first cladding refractive index ?2, the second cladding (108) is defined by a
second cladding radius R3 and a second cladding refractive index ?3 and the third
cladding (110) is defined by a third cladding radius R4 and a third cladding
refractive index ?4 such that ?1 > ?2 > ?3 and ?3 < ?4. The below table 2 represents peak and average values of ?1, ?2, ?3 with reference to a horizontal
axis (202) representing pure silica:
Peak Avg.
?1 5.5 5.1
?2 0.04 0.025
?3 -5.3 -4.4
Table 2
[0039] The first cladding radius R2 is in a range of 9 to 10 µm, the second
cladding radius R3 is in a range of 15 to 16 µm, and the third cladding radius R4
is in a range of 39 to 40 µm such that a final clad diameter of the optical fiber
(100) is in a range of 80 to 125 µm with a tolerance of + 0.7 µm. Further, the first
cladding refractive index ?2 is in a range of 0.2 to 0.4, the second cladding
refractive index ?3 is in a range of -3.9 to -5.3, and the third cladding refractive
index ?4 is in a range of 0 to 0.02. Further, ?2% is in a range of 0.02 to 0.04,
?3% is in a range of -0.27 to -0.34 and ?4% is in a range of 0 to 0.002. In an
aspect of the present disclosure, an absolute difference between absolute value of
a first cladding refractive index percentage ?2% and a second cladding refractive
index percentage ?3% may be in a range of 0.26 to 0.30. A refractive index ?i
and a refractive index percentage ?i % of the core (102), first cladding (106),
second cladding (108) and third cladding (110) is determined using below
equations.
??? = (???? - ??) ?? 1000
??? % = ????-??
?? ?? 100
where, ???? is refractive index of ith region of the optical fiber (100).
i = 1 for core region
i = 2 for first cladding region
i = 1 for second cladding region
i = 1 for third cladding region
?? is refractive index of pure silica.
[0040] The first cladding (106) is further defined by a first cladding
thickness T2, the second cladding (108) is further defined by a second cladding
thickness T3 and the third cladding (110) is further defined by a third cladding thickness T4 as depicted in FIG. 2. The first cladding thickness T2 is in a range of
5.4 to 5.8 µm, the second cladding thickness T3 is in a range of 6 to 7 µm, and the
third cladding thickness T4 is in range of 23 to 45.6 µm such that T2 is greater
than T1 and less than T3.
[0041] The cladding (104) has a diameter (i.e., clad diameter) between
79.3 µm and 125.7 µm. In an aspect of the present disclosure, the cladding (104)
of the optical fiber (100) may have a diameter that is equal to 80 + 0.7 µm such
that the third cladding thickness T4 is in range of 23 to 24 µm. In a reduced
diameter optical fiber (100), the aforesaid ranges of radius, thickness and
refractive index are important to achieve the characteristics and properties of the
optical fiber (100) of the present disclosure.
[0042] FIG. 3 illustrates concentration profiles (300) of the core (102), the
first cladding (aka “inner cladding”) (106), the second cladding (aka “outer
cladding with a trench”) (108) and the third cladding (aka “outer cladding
undoped”) (110).
[0043] FIG. 4 illustrates a graph (400) showing variation of concentration
of dopants in the RI profile (300) including diffusion. FIG. 5 is the RI profile
(500) with an up-doped first cladding. FIG. 6 is the RI profile (600) with a
down-doped second cladding.
[0044] Referring back to FIG. 1, the optical fiber (100) may have coatings,
where the third cladding (110) is covered by a first coating (114) followed by a
second coating (116) as shown in FIG. 7. The first coating (114) is a protective
primary coating around the third cladding (110) acting as a soft layer and the
second coating is a protective secondary coating around the primary coating
acting as a hard layer. The first coating (114) is defined by a first coating thickness
having a range of 15 to 43.5 µm and the second coating (116) is defined by a
second coating thickness having a range of 9 to 42.5 µm. The second coating
(116) may be a coloured coating. A coating thickness ratio may be in a range of
0.5 and 3. The coating thickness ratio is defined as a ratio of the first coating
thickness to the second coating thickness. The optical fiber (100) has a coating
diameter of about 158 µm to 250 µm. In an aspect of the present disclosure, the cladding (104) of the optical fiber (100) may have a diameter that is equal to 80 +
0.7 µm such that the first coating thickness may be in a range of 15 to 30 µm and
the second coating thickness may be in a range of 9 to 20 µm. In an aspect of the
present disclosure, the cladding (104) of the optical fiber (100) may have a
diameter that is equal to 125 + 0.7 µm such that the first coating thickness may be
in a range of 20 to 43.5 µm and the second coating thickness may be in a range of
19 to 42.5 µm.
[0045] Referring back to FIG. 1, the optical fiber (100) may have a
plurality of cores (102) of which first through fourth cores (102a-102d) are shown
in Fig. 8. The plurality of cores (102) may be a glass core. The plurality of cores
(102) comprises at least a first up-dopant and a second up-dopant. The optical
fiber (100) comprising the plurality of cores (102) may be termed as a multi-core
optical fiber. The term multi-core optical fiber as used herein defines an optical
fiber that includes multiple core regions, each capable of communicating the
optical signals between transceivers including transmitters and receivers which
may allow for parallel processing of multiple optical signals. The plurality of
cores (102) may be arranged in a predefined lattice on the cross-section of the
optical fiber (100) that is perpendicular to an axis extending parallelly along the
central axis (112) of the optical fiber (100). As illustrated, the predefined lattice is
a square lattice. Alternatively, the predefined lattice may be a hexagonal lattice. It
will be apparent to a person skilled in the art that the plurality of cores (102) are
shown to be arranged in the square lattice to make the illustrations concise and
clear and should not be considered as a limitation of the present disclosure. In
various alternate aspects, the plurality of cores (102) may be arranged in any type
of the predefined lattice, without deviating from the scope of the present
disclosure. In some aspects of the present disclosure, each core of the plurality of
cores (102) may have a core radius. The core radius is measured from a central
axis of the core (not shown). Specifically, the first through fourth cores
(102a-102d) may have the core radius. In one aspect of the present disclosure, the
core radius of each core of the plurality of cores (102) may be equal. In another aspect of the present disclosure, the core radius of each core of the plurality of
cores (102) may be different.
[0046] The optical fiber (100) further comprises a cladding (104). The
cladding (104) surrounds the plurality of cores (102). The cladding (104)
comprises a first cladding (106) surrounding the core (102), a second cladding
(108) surrounding the first cladding (106), and a third cladding (110) surrounding
the second cladding (108). The first cladding (106) comprises of silica glass
doped with the second up-dopant, the second cladding (108) has at least one
down-dopant, and the third cladding (110) is undoped. That is, the first cladding
(106) is up-doped with chlorine, the second cladding (108) is down-doped with
fluorine, for example, forming an immediate trench adjacent to the first cladding
(106) and the third cladding (110) is pure silica. The cladding (104) of the optical
fiber (100) may have a cladding diameter D less than or equal to 125 + 0.7 µm.
[0047] The proposed optical fiber (100) has low attenuation and low
macro bending loss and micro bending loss. In general, the attenuation measures
the amount of light/signal lost between input and output. Further, the micro
bending loss refers to small-scale "bends" in the optical fiber, often from pressure
exerted on the optical fiber itself as when it is cabled and the other elements in the
cable press on it and the macro bending loss refers to a loss caused by bending the
optical fiber at a predetermined curvature. The optical fiber (100) has an
attenuation less than 0.324 dB/km at 1310 nm wavelength and less than 0.19
dB/km at 1550 nm wavelength. The optical fiber (100) has a macro bend loss of
0.02 dB at 1 turn, 10 mm bend radius and 1550 nm wavelength, 0.07 dB at 1 turn,
10 mm bend radius and 1625 nm wavelength, 0.01 dB at 10 turns, 15 mm bend
radius and 1550 nm wavelength and 0.09 dB at 10 turns, 15 mm bend radius and
1625 nm wavelength. Further, the optical fiber (100) has a micro bending loss of
1.08 dB/km at 1550 nm wavelength and 1.379 dB/km at 1625 nm wavelength.
Further, when the diameter of the cladding (104) of the optical fiber (100) is equal
to 125 + 0.7 µm, the optical fiber (100) has a micro bending loss of 0.3 dB/km at
1550 nm wavelength and 0.35 dB/km at 1625 nm wavelength Furthermore, the
optical fiber (100) has a MAC number is less than 6.8. The MAC number refers to mode field diameter (MFD) divided by cut-off wavelength, wherein the mode
field diameter describes the distribution of light intensity observed at the
cross-section of a single-mode optical fiber and the cut-off wavelength is defined
as a wavelength above which a single-mode fiber will support and propagate only
one mode of light.
[0048] It will be apparent to those skilled in the art that other
embodiments of the invention will be apparent to those skilled in the art from
consideration of the specification and practice of the invention. While the
foregoing written description of the invention enables one of ordinary skill to
make and use what is considered presently to be the best mode thereof, those of
ordinary skill will understand and appreciate the existence of variations,
combinations, and equivalents of the specific embodiment, method, and examples
herein. The invention should therefore not be limited by the above-described
embodiment, method, and examples, but by all embodiments and methods within
the scope of the invention. It is intended that the specification and examples be
considered as exemplary, with the true scope of the invention being indicated by
the claims.
[0049] Conditional language used herein, such as, among others, “can”,
“may”, “might”, “may”, “e.g.”, and the like, unless specifically stated otherwise,
or otherwise understood within the context as used, is generally intended to
convey that certain alternatives include, while other alternatives do not include,
certain features, elements and/or steps. Thus, such conditional language is not
generally intended to imply that features, elements and/or steps are in any way
required for one or more alternatives or that one or more alternatives necessarily
include logic for deciding, with or without other input or prompting, whether
these features, elements and/or steps are included or are to be performed in any
particular alternative. The terms “comprising,” “including,” “having,” and the like
are synonymous and are used inclusively, in an open-ended fashion, and do not
exclude additional elements, features, acts, operations, and so forth. Also, the term
“or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or
all of the elements in the list.
[0050] Disjunctive language such as the phrase “at least one of X, Y, Z,”
unless specifically stated otherwise, is otherwise understood with the context as
used in general to present that an item, term, etc., may be either X, Y, or Z, or any
combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not
generally intended to, and should not, imply that certain alternatives require at
least one of X, at least one of Y, or at least one of Z to each be present.
While the detailed description has shown, described, and pointed out novel
features as applied to various alternatives, it can be understood that various
omissions, substitutions, and changes in the form and details of the devices or
algorithms illustrated can be made without departing from the scope of the
disclosure. As can be recognized, certain alternatives described herein can be
embodied within a form that does not provide all of the features and benefits set
forth herein, as some features can be used or practiced separately from others. , Claims:I/We Claim:
1. An optical fiber (100) comprising:
one or more core (102) extending along a central axis (112) of the optical
fiber (100), wherein the one or more core (102) comprises at least a first
up-dopant and a second up-dopant; and
a cladding (104) surrounding the one or more core (102), wherein the
cladding (104) has at least the second up-dopant, at least one down-dopant, and an
undoped region,
wherein the optical fiber (100) has (i) an attenuation less than 0.324
dB/km at 1310 nm wavelength and less than 0.19 dB/km at 1550 nm wavelength,
and (ii) a MAC number less than 6.8.
2. The optical fiber (100) as claimed in claim 1, wherein the cladding (104)
comprises a first cladding (106) surrounding the one or more core (102), a second
cladding (108) surrounding the first cladding (106), and a third cladding (110)
surrounding the second cladding (108), wherein the first cladding (106) has at
least the second up-dopant, wherein the second cladding (108) has at least one
down-dopant, and wherein the third cladding (110) is undoped.
3. The optical fiber (100) as claimed in claim 1, wherein the first up-dopant
is Germanium (Ge), the second up-dopant is Chlorine (Cl), and at least one
down-dopant is Fluorine (F).
4. The optical fiber (100) as claimed in claim 1, wherein the optical fiber
(100) has (i) a macro bend loss of 0.02 dB at 1turn, 10 mm bend radius, 1550 nm
wavelength, (ii) a macro bend loss of 0.07 dB at 1 turn, 10 mm bend radius, 1625
nm wavelength and 0.01 dB at 10 turns, 15 mm bend radius, 1550 nm wavelength,
(iii) a macro bend loss of 0.09 dB at 10 turns, 15 mm bend radius, 1625 nm wavelength, (iv) a micro bending loss of 1.08 dB/km at 1550 nm wavelength and
(v) a micro bending loss of 1.379 dB/km at 1625 nm wavelength.
5. The optical fiber (100) as claimed in claim 1, wherein the first cladding
(106) has traces of the first up-dopant and the at least one down-dopant, and the
third cladding (110) has traces of the at least one down-dopant.
6. The optical fiber (100) as claimed in claim 1, wherein the core (102) is
defined by a core refractive index ?1, the first cladding (106) is defined by a first
cladding refractive index ?2, the second cladding (108) is defined by a second
cladding refractive index ?3 and the third cladding (110) is defined by a third
cladding refractive index ?4 such that ?1 > ?2 > ?3 and ?3 < ?4.
7. The optical fiber (100) as claimed in claim 1, wherein a core refractive
index ?1 is in a range of 4.9 to 5.5, a first cladding refractive index ?2 is in a
range of 0.2 to 0.4, a second cladding refractive index ?3 is in a range of -3.9 to
-5.3, and a third cladding refractive index ?4 is in a range of 0 to 0.02.
8. The optical fiber (100) as claimed in claim 1, wherein the optical fiber
(100) has a clad diameter between 79.3 µm and 125.7 µm.
9. The optical fiber (100) as claimed in claim 1, wherein an absolute
difference between absolute value of a first cladding refractive index percentage
?2% and a second cladding refractive index percentage ?3% is in a range of 0.26
to 0.30.
10. The optical fiber (100) as claimed in claim 1, wherein the core (102) is
defined by a core thickness T1 in a range of 3.6 to 4.1 µm, the first cladding (106)
is defined by a first cladding thickness T2 in a range of 5.4 to 5.8 µm, the second
cladding (108) is defined by a second cladding thickness T3 in a range of 6 to 7
µm and the third cladding (110) is defined by a third cladding thickness T4 in
range of 23 to 45.6 such that T2 is greater than T1 and less than T3.
11. The optical fiber (100) as claimed in claim 1, wherein the core (102) is
defined by a core radius R1 in a range of 3.6 to 4.1 µm, the first cladding (106) is defined by a first cladding radius R2 in a range of 9 to 10 µm, the second cladding
(108) is defined by a second cladding radius R3 in a range of 15 to 16 µm and the
third cladding (110) is defined by a third cladding radius R4 in a range of 39.5 to
63 µm such that a final clad diameter of the optical fiber (100) is in a range of 79
to 126 µm .
12. The optical fiber (100) as claimed in claim 1, wherein the third cladding
(110) is covered by a first coating (114) followed by a second coating (116),
wherein the first coating (114) is defined by a first coating thickness in a range of
15 to 43.5 µm and the second coating (116) is defined by a second coating
thickness in a range of 9 to 42.5 µm, wherein the second coating (116) is a
coloured coating.
13. The optical fiber (100) as claimed in claim 1, wherein the optical fiber
(100) has a ratio of the first coating thickness to the second coating thickness in a
range of 0.5 and 3.