FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1. Title of the Invention:-
AN OPTICAL FIBER WITH MORE THAN ONE DOPED REGION AND A
METHOD OF SPLICING THE SAME
2. Applicant(s):-
(a) Name: STERLITE TECHNOLOGIES LTD.
(b) Nationality: An Indian Company
(c) Address: E1/E2/E3, MIDC, Waluj, Aurangabad -431136
Maharashtra, INDIA
3. Preamble to the Description:-
Complete Specification:
The following specification particularly describes the invention and the manner in which it is to be performed.

AN OPTICAL FIBER WITH MORE THAN ONE DOPED REGION AND A
METHOD OF SPLICING THE SAME
FIELD OF THE INVENTION
[0001] Embodiments herein generally relate to an optical fiber with more than one doped region and method of splicing the same. In particular, the embodiments are directed to an optical fiber with a core region doped with a dopant, a clad region including a moat and/or a trench region which are doped with said dopant or a different dopant, wherein the optical fiber is provided with at least one element that substantially prevents diffusion of dopants to and from said doped regions, during the process of splicing of said optical fiber with another optical fiber, resulting in a spliced region, wherein said spliced region between said optical fiber and another optical fiber exhibits an average value of splicing loss that is less than or equal to 0.04 dB.
BACKGROUND OF THE INVENTION
[0002] Optical fiber plays a significant role in the field of communications. A momentous increase in usage of optical fiber is being observed. It is expected that the use of optical fiber will continue to increase in order to deliver greater amount of information in the form of data, audio, and video signals to residential and commercial users. [0003] A typical optical fiber comprises a core and a cladding surrounding the core. The refractive index of core is higher as compared to the refractive index of the cladding in order to achieve satisfactory transmission of light (or an optical signal) inside the optical fiber, by a, phenomenon known as total internal reflection. Most of the transmitted

light (or optical signal) passes through the core region, whereas the cladding confines the light. Generally, either the refractive index of the core is substantially uniform across its diameter (also called step index optical fiber) or the refractive index of the core has a maximum at the center and decrease in parabolic fashion (also called graded index optical fiber). Depending on specific requirements other geometric shape and profile of the refractive index of the core is possible.
[0004] Optical fibers are generally divided into two classes' namely single mode optical fiber and multimode optical fiber. In single mode optical fiber the core diameter is small (for example, the core diameter is in the range of 8 urn to 10 urn) allowing only a single mode to propagate whereas in multimode optical fiber the core diameter is large (for example the core diameter is in the range of 40 µm to 70 urn) allowing multiple modes to propagate through the fiber. Generally, the overall diameter of both the single mode and multimode optical fibers is about 125 µm.
[0005] Single mode optical fiber is widely used in transmission lines due to its high bandwidth and low attenuation. In addition to high bandwidth and low attenuation, single mode optical fiber also exhibits chromatic dispersion and a chromatic dispersion slope, wherein both the chromatic dispersion and chromatic dispersion slope meets particular standards. [0006] Another type of optical fiber known as the non-zero dispersion shifted fiber [NZDSF] is also used in the optical fiber communication networks. This optical fiber has a chromatic dispersion tailored to a small value at the operating wavelength. The NZDSF comprises of a

central core region, a cladding region and a moat region doped with an up dopant such as germanium similar to that of the core region. [0007] Recently, bend insensitive optical fibers have been developed which are less sensitive to bends as compared to single mode fibers and are useful in offices, homes and other places where bends in the optical fiber are inevitable. Bend insensitive optical fiber comprises of a central core region, a cladding region and a trench region which is down doped with dopants such as fluorine or boron. Bend insensitive fibers have been categorized under ITU-T specifications under the G657 group. [0008] In an optical fiber communication network it is often required to splice or join the optical fibers of same or different types. Splicing is done by using a splicing machine called a splicer through a fusion splicing process, wherein the ends of the two optical fibers to be spliced are brought in close proximity of each other. The splicing machine is provided with an electric arc that heats the ends of the optical fibers to melt the glass and heat fuse them. The region where the ends of the two optical fibers are heat fused is referred to as the spliced region hereinafter.
[0009] Various types of splicers are available commercially operating on different principles. One of the splicing methods employs the principle of matching the cladding of the optical fiber, wherein the claddings of the optical fibers to be spliced are matched and then heat fused. In another splicing method core regions of two fibers are matched and fused. Some splicers are provided with suitable hardware and software to recognize the type of optical fiber and optical fiber refractive index profile. In this case the splicer matches the core region of both the fibers

to be spliced and then heat fuses them. Optionally the splicing devices may be provided with camera along with display screen for real time visualization and control of the splicing process.
[00010] One important aspect of the splicing is to have the optical fibers spliced such that the splicing loss due to the splice, in particular, in and around the spliced region is as low as possible.
[0001 1] It is observed that splicing of the one type of Fiber to another, in particular optical fibers having one or more doped regions as in case of the NZDSF and the G657 optical fibers, wherein there are two or more doped regions which may lie in close proximity to each other, there are chances of diffusion of the dopants from one region to another region during the splicing process owing to the generated heat. This diffusion of dopants from one region to another may lead to distorted refractive index profile at and around said spliced region which in-turn may lead to high splicing loss or loss of signal which is undesirable. [00012] In G657 optical fibers, wherein the core region is doped with germanium and the trench region is doped with fluorine, the trench region and the core region are separated from one another by an inner cladding region (which may be un-doped silica). To improve on the optica! parameters such as mode field diameter and the cutoff wavelength there is a trend of having the trench region closer and closer to the core region. However, if the trench region is positioned near to the core region, the germanium from the core region may diffuse into the trench region and the fluorine in the trench region may diffuse into the core region, thereby leading to distorted refractive index profile at and around the spliced region. A similar argument may be applied to the

NZDS fibers also or to any other optical fiber with similar refractive index profiles.
[00013] It is also observed that the splicing devices are unable to recognize the core correctly if the core and the moat/trench region are in very close proximity to each other. This may lead to ill-aligned splicing which in turn may lead to very high splicing loss.
[00014] From the above it is evident that the prior art optical fibers, especially the ITU-T G657 (doped with fluorine as down dopant) and the NZDSF are prone to diffusion of the dopants from one region to another owing to the heat generated during splicing. This leads to increased splicing loss owing to the distorted refractive index profile at and around the spliced region.
NEED OF THE PRESENT INVENTION
[00015] Therefore, there is a need to have optical fibers such that the diffusion of the dopants from one region to another at and around the spliced region owing to the heat generated during splicing is reduced or prevented.
OBJECTS OF THE PRESENT INVENTION
[00016] Accordingly, an object is to provide an optical fiber.
[00017] Another object is to provide an optical fiber with more than one
doped region and with reduced splicing loss.
[00018] Still another object is to provide an optical fiber with more than
one doped region such that the diffusion of the dopants from one region
to another during splicing is reduced.

[00019] Still another object is to provide an optical fiber with more than
one doped region such that the diffusion of the dopants from one region
to another during splicing is prevented.
[00020] Still another object is to provide an optical fiber with more than
one doped region such that the diffusion of the dopants from one region
to another is prevented.
[00021] Another object is to provide an optical fiber with more than one
doped region such that the distortion of the refractive index profile due
to diffusion of the dopants from one region to another does not occur.
[00022] Yet another object is to provide an optical fiber with more than
one doped region such that in case even if the diffusion of the dopants
occurs the effect of diffusion is nullified
[00023] Another object is to provide a method for splicing the optical
fiber with more than one doped region.
[00024] Other objects, advantages and preferred embodiments of the
present invention will be apparent from the following description when
read in conjunction with the accompanying figures, which are not
intended to limit the scope of the present invention, but incorporated
merely for illustrating the present invention.
SUMMARY OF THE PRESENT INVENTION
[00025] Accordingly, the present invention solves one or more problems associated with the prior art.
[00026] In accordance with the present invention, an optical fiber with more than one doped region and method of splicing the same is disclosed wherein the optical fiber comprises a core region doped with a

dopant, a clad region including a moat and/or a trench region which are doped with the same dopant as used in the core or may be doped with a different dopant, wherein the optical fiber is provided with at least one element that substantially prevents diffusion of dopants to and from the doped regions, during the process of splicing of the optical fiber with another optical fiber, resulting in a spliced region, wherein the spliced region between the two optical fibers that exhibits an average value of splicing loss of less than or equal to 0.04 dB.
[00027] In accordance with one embodiment the element is distance or separation between doped regions which is enough to prevent inter-diffusion of dopants from one region to another.
[00028] In accordance with one embodiment the element includes provision of barrier layers at and around doped regions to avert diffusion of dopants to and from said doped regions.
[00029] In accordance with one embodiment the element includes provision of a dopant in and around the periphery of said doped regions that nullifies the effect of diffused dopant from the doped regions. [00030] In accordance with one embodiment the optical fiber may be provided with one or more elements in combinations, for example, the optical fiber may include optimum separation between the core region and the moat and/or trench region along with barrier layers in and around the periphery of the core region and the moat and/or trench region.
[00031] In accordance with one embodiment the optical fiber may be provided with one or more elements in combinations, for example, the optical fiber may include optimum separation between the core region

and the moat and/or trench region along with a dopant in and around the periphery of the core region and the moat and/or trench region that nullifies the effect of diffused dopant from the doped regions. [00032] In accordance with one embodiment the optical fiber may be provided with one or more elements in combinations, for example, the optical fiber may include barrier layers in and around the periphery of the core region and the moat and/or trench region along with a dopant in and around the periphery of the core region and the moat and/or trench region that nullifies the effect of diffused dopant from the doped regions. [00033] In accordance with one embodiment the optical fiber may be provided with all three elements, namely, the optimum separation between the core region, the moat and/or trench region, the provision of barrier layers and provision of a dopant that nullifies the effect of diffused dopants from the core region and the moat and/or the trench region.
[00034]These and other embodiments of the present invention will be apparent from the following description when read in conjunction with the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description of the embodiments of the present invention, are intended to provide an overview for understanding the nature and character of the invention as it is claimed.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIG URES
[00035] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate

corresponding parts in the various figures. The embodiments
herein will be better understood from the following description
with reference to the drawings, in which:
[00036] FIG. 1 illustrates an optical fiber with a moat and barrier
layers in accordance with one embodiment of the present
invention; and
[00037] FIG. 2 illustrates an optical fiber with a trench and barrier
layers in accordance with one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[00038] The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[00039] The present invention overcomes the limitations of the prior art by providing an optical fiber with more than one doped region and method of splicing the same and in particular by providing an optical fiber with a core region doped with a dopant, a clad region including a

moat and/or a trench region which are doped with the same dopant or different dopant, wherein the optical fiber is provided with at least one element that substantially prevents diffusion of dopants to and from said doped regions, during the process of splicing of the optical fiber with another optical fiber, resulting in a spliced region, wherein the spliced region between the optical fiber and another optical fiber that exhibits an average value of splicing loss of less than or equal to 0.04 dB. [00040] In accordance with the present invention, the term "element" includes any means by which the diffusion of dopants to and from the doped regions may be prevented.
[00041] The present invention is explained with reference to two types of fibers. Referring to FIG. 1, that illustrates an optical fiber 100 with a moat 103 and barrier layers [indicated by numeral 105] in accordance with one embodiment of the present invention, the first optical fiber 100 comprises a central core region 101 doped with a dopant that increases the refractive index of the core region, an inner cladding region 102 which may or may not be doped, a moat region 103 doped with the same or different dopant as that of the core region and an outer cladding region 104 which is substantially un-doped.
[00042] In accordance with the present invention the relative refractive index ∆1MAX of the core region 101 is greater than the relative refractive index of the moat 103 region ∆3MAX-MOAT, which in-turn is greater than the relative refractive index of the inner cladding region 102 A2MAX and ∆2MAX is greater than or equal to ∆4MAX, which is the relative refractive index of the outer cladding region 104.

[00043] In accordance with the present invention the separation (d) between the core region 101 and the moat region 103 is chosen such that even though the dopants from the core region 101 and the moat region 103 may diffuse out during the process of splicing of the optical fiber
100 with another fiber, but they do not mix up in the inner cladding
region 102.
[00044] In accordance with the present invention the separation (d) is determined by the diffusion coefficients of the dopants of the core region
101 and the moat region 103 under consideration. The more the dopants
are mobile the more the distance or separation (d) between the two
regions.
[00045] Referring to FIG. 2, which illustrates an optical fiber 201 with a trench 203 and barrier layers 205 in accordance with one embodiment of the present invention, the optical fiber 200 comprises a central core region 201 doped with a dopant that increases the refractive index of the core region, an inner cladding region 202 which may or may not be doped, a trench region 203 doped with a refractive index decreasing dopant and an outer cladding region 204 which is substantially un-doped.
[00046] In accordance with the present invention the relative refractive index ∆1MAX of the core region 201 is greater than the relative refractive index of any of the three regions and the relative refractive index ∆3_ TRENCH of the trench region 203 being the lowest. The inner cladding region 202 and the outer cladding region 204 may or may not be doped with a dopant.

[00047] In accordance with the present invention the separation (d) between the core region 201 and the trench region 203 is chosen such that even though the dopants from the core region 201 and the moat region 203 may diffuse out during the process of splicing of the optical fiber 200 with another fiber, but they do not mix up in the inner cladding region 202.
[00048] In accordance with the present invention the separation (d) is determined by the diffusion coefficients of the dopants of the core region 201 and the trench region 203 under consideration. The more the dopants are mobile the more the distance or separation (d) between the two regions.
[00049] In accordance with one embodiment of the present invention the periphery of the core region 101/201 and the moat region 103 or the trench region 203 may be provided with barrier layers 105/205. [00050] In accordance with one embodiment the barrier layers may comprise of a dopant that may be different from the dopant utilized in the core region 101/201 and the moat region 103 or the trench region 203. The function of the barrier layers is to prevent the diffusion of the dopants in the regions 101/201, 103/203 to surrounding regions. [00051] In accordance with one embodiment the barrier layers may comprise of material that has high density as compared to the layers of glass in the core region 101/201 or the moat region 103 or the trench region 203.
[00052] In accordance with one embodiment of the present invention the periphery of the core region 101/201, the moat region 103 and the trench region 203 may be provided with dopant which nullifies effect of

diffusion of the dopants from the core region 101/201, the moat region 103 and the trench region 203.
[00053] In accordance with an exemplary embodiment the core region 101/201 might be doped with Ge02 which increases the refractive index. The periphery of the core region 101/201 might be doped with a dopant such as fluorine or boron. Similarly, the periphery of the moat region 103 may be doped with fluorine or boron whereas the periphery of the trench region may be doped with Ge02.
[00054] In accordance with one embodiment of the present invention the elements, namely, the separation between the regions, the provision of barrier layers in and around the periphery of various regions and the use of nullifying dopants in and around the periphery of the various regions may be used in combinations.
[00055] In accordance with one embodiment of the present invention the optical fiber may be provided with an optimum separation (d) between the core region 101/201 and the moat region 103 or the trench region 203 along with the periphery of the core region 101/201 and the moat region 103 or the trench region 203 provided with barrier layers. [00056] In accordance with another embodiment of the present invention the optical fiber may be provided with an optimum separation (d) between the core region 101/201 and the moat region 103 or the trench region 203 along with the periphery of the core region 101/201 and the moat region 103 or the trench region 203 provided with dopants that nullifies the effect of the dopants that diffuse out of the respective regions.

[00057] In accordance with still another embodiment of the present invention the optical fiber may be provided with barrier layers in and around the periphery of the core region 101/201, the moat region 103 and the trench region 203 along with the periphery of the core region 101/201 and the moat region 103 or the trench region 203 provided with dopants that nullifies the effect of the dopants that diffuse out of the respective regions.
[00058] [n accordance with yet another embodiment of the present invention the optical fiber may be provided with all the three elements, namely, the optimum separation between the various regions, the barrier layers and the nullifying dopants in and around the periphery of the various regions.
[00059] In accordance with the present invention, a standard single-mode optical fiber which comprises simply one core and a cladding surrounding the core region may be provided with the barrier layers in and around the periphery of the core region which averts the diffusion of the dopant in the core region.
[00060] In an alternate embodiment, the standard single mode optical fiber core region may be provided with a dopant, in and around the periphery that nullifies the effect of the diffused dopant from the core region.
[00061] In still another embodiment the standard single mode optical fiber core region may be provided with combination of both the barrier layers to prevent diffusion of the dopants from the core region and the dopant nullifying the diffused dopant from the core region, in and around the periphery of the core region.

[00062] In accordance with one embodiment a method for splicing optical fibers is provided, with at least one optical fiber comprising a core region and a cladding region including a trench region and/or a moat region, the method comprising the steps of providing two optical fibers to be spliced, at least one of the two optical fibers comprises a core region and a cladding region including a trench region and/or a moat region, providing a suitable splicing machine for splicing the two optical fibers, splicing the two optical fibers resulting in a spliced region, wherein the optical fiber with the trench region and/or the moat region included within the cladding region satisfies at least one of the following conditions, namely, the separation between the core region and trench and/or moat region is such that diffusion of dopants to and from the core region and trench /moat region is prevented, in and around the periphery of the core region and trench and/or moat region is provided a barrier layer which averts diffusion of dopants from and to the core region and trench and/or moat region and in and around the periphery of the core region and trench and/or moat region is provided a dopant that nullifies the effect of diffused dopant, wherein the spliced region between the optical fiber and another optical fiber that exhibits an average value of splicing loss of less than or equal to 0.04 dB.
[00063] It is observed that the optical fiber with more than one doped region and with reduced splicing loss as the diffusion of the dopants from one region into another is prevented or reduced substantially during the splicing. This in turn leads to a reduced distortion of the refractive index profile in and around said spliced region, thereby reducing the splicing loss.

[00064] In accordance with the present invention it is observed that the optical fiber with one or more of the above mentioned elements, the spliced region that exhibits an average value of splicing loss of less than about 0.04 dB and preferably less than about 0.03 dB. [00065] Further, since the core region and the trench region or the moat region is now separated and that the diffusion is minimized, the splicing machine is able to recognize the core and the trench region or the moat region, thereby reducing the risk of ill-alignment of the optical fibers during the splicing process.
[00066] Example 1 [in accordance with the prior art]: In this experiment a standard single mode fiber and a trenched optical fiber [essentially a bend insensitive optical fiber] were spliced using a Nanjing Jilong Splicer model no. KL-280. The trenched optical fiber was provided with a separation (d) between the core region and the trench region, d = 6 urn. The ends of both the fibers were cleaved to obtain surfaces perpendicular to the longitudinal axis of the optical fibers. The optical fibers were spliced by heat fusing the ends using the splicing machine. The splice loss at the spliced region of the spliced optical fibers was measured using EXFO model no. FTB150 Optical Time Domain Reflectometer [OTDR]. The splicing and measurement was repeated for about 15 similar samples. It was found that the average splicing loss of the 15 samples was about 0.0441 dB.
[00067] Example 2 [in accordance with the present invention]: In this experiment a standard single mode fiber and a trenched optical fiber [essentially a bend insensitive optical fiber] were spliced using Nanjing Jilong Splicer model no. KL-280. The trenched optical fiber was

provided with a separation (d) between the core region and the trench region, d = 3.4 µm, about 1 µm greater than that in example 1. The ends of both the fibers were cleaved to obtain surfaces perpendicular to the longitudinal axis of the optical fibers. The optical fibers were spliced by heat fusing the ends using the splicing machine. The splice loss at the spliced region of the spliced optical fibers was measured using the Optical Time Domain Reflectometer [OTDR] from EXFO with the model no. FTB150. The splicing and measurement was repeated for about 15 similar samples. It was found that the average splicing loss of the 15 samples was about 0.0294 dB.
[00068] It is to be noted that though the present invention was disclosed using optical fibers with trench/moat and four regions at most the teachings of the present invention can be extended to optical fibers with more complex refractive index profiles and more than four regions. [00069] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be

practiced with modification within the spirit and scope of the embodiments as described herein.

We Claim:
1. An optical fiber with more than one doped regions, wherein said optical fiber is provided with at least one element that substantially prevents diffusion of dopants from one doped region to another, during the process of splicing of said optical fiber with another optical fiber, resulting in a spliced region.
2. The optical fiber as claimed in claim 1, wherein said element is separation between doped regions, wherein the separation is enough to prevent the diffusion of dopants from one doped region to another.
3. The optical fiber as claimed in claim 1, wherein said element includes provision of barrier layers at and around doped regions to avert diffusion of dopants from one doped region to another, wherein said barrier layers are layers of high density.
4. The optical fiber as claimed in claim 1, wherein said element includes provision of a dopant in and around the periphery of said doped regions that nullifies the effect of diffused dopant from said doped regions.
5. An optical fiber with more than one doped regions, said optical fiber
comprises doped regions separated by a predetermined distance and
provided with barriers at and around a periphery of said doped regions to
avert diffusion of dopants to and from said doped regions, during the
process of splicing of said optical fiber with another optical fiber,
resulting in a spliced region.
6. An optical fiber with reduced splicing loss, said optical fiber comprising:
a central core region doped with at least a dopant and featuring a
refractive index profile;

an inner cladding region having a refractive index profile surrounding
said central core region;
a moat region doped with a dopant and featuring a refractive index
profile surrounding said inner cladding region; and
an outer cladding region having a refractive index profile surrounding
said moat region;
wherein separation between said core region and said moat region is
chosen such that diffusion of dopants to and from said core region and
said moat region is prevented during the process of splicing of said
optical fiber with another optical fiber, resulting in a spliced region.
7. An optical fiber with reduced splicing loss, said optical fiber comprising:
a central core region doped with a suitable dopant and featuring a
refractive index profile;
an inner cladding region having a refractive index profile surrounding
said central core region;
a moat region doped with a dopant and featuring a refractive index
profile surrounding said inner cladding region; and
an outer cladding region having a refractive index profile surrounding
said moat region;
wherein said core region and said moat region are provided with barrier
region in and around periphery of said core region and said moat regions
such that diffusion of dopants to and from said core region and said moat
region is prevented during the process of splicing of said optical fiber
with another optical fiber, resulting in a spliced region.
8. An optical fiber with reduced splicing loss, said optical fiber comprising:

a central core region doped with a suitable dopant and featuring a refractive index profile;
an inner cladding region having a refractive index profile surrounding said central core region;
a moat region doped with a dopant and featuring a refractive index profile surrounding said inner cladding region; and
an outer cladding region having a refractive index profile surrounding said moat region;
wherein said core region and said moat region are provided with barrier regions in and around periphery of said core region and said moat regions and separation between said core region and said moat region is chosen such that diffusion of dopants to and from said core region and said moat region is prevented during the process of splicing of said optical fiber with another optical fiber, resulting in a spliced region. 9. An optical fiber with reduced splicing loss, said optical fiber comprising: a central core region doped with a suitable dopant and featuring a refractive index profile;
an inner cladding region having a refractive index profile surrounding said central core region;
a trench region doped with a dopant and featuring a refractive index profile surrounding said inner cladding region; and
an outer cladding region having a refractive index profile surrounding said trench region;
wherein separation between said core region and said trench region is chosen such that diffusion of dopants to and from said core region and

said trench region is prevented during the process of splicing of said
optica] fiber with another optical fiber, resulting in a spliced region. 10. An optical fiber with reduced splicing loss, said optical fiber comprising:
a central core region doped with a suitable dopant and featuring a
refractive index profile;
an inner cladding region having a refractive index profile surrounding
said central core region;
a trench region doped with a dopant and featuring a refractive index
profile surrounding said inner cladding region; and
an outer cladding region having a refractive index profile surrounding
said trench region;
wherein said core region and said trench region are provided with barrier
region in and around periphery of said core region and said trench
regions such that diffusion of dopants to and from said core region and
said trench region is prevented during the process of splicing of said
optical fiber with another optical fiber, resulting in a spliced region. 1 1. An optical fiber with reduced splicing loss, said optical fiber comprising:
a central core region doped with a suitable dopant and featuring a
refractive index profile;
an inner cladding region having a refractive index profile surrounding
said central core region;
a trench region doped with a dopant and featuring a refractive index
profile surrounding said inner cladding region; and
an outer cladding region having a refractive index profile surrounding
said trench region;

wherein said core region and said trench region are provided with barrier regions in and around periphery of said core region and said trench regions and separation between said core region and said trench region is chosen such that diffusion of dopants to and from said core region and said trench region is prevented during the process of splicing of said optical fiber with another optical fiber, resulting in a spliced region.
12. A method of splicing an optical fiber, wherein said method comprises:
providing two optical fibers to be spliced;
at least one of the two optical fibers comprising a core region and
a cladding region including a trench region and/or a moat region;
providing a suitable splicing machine for splicing said two optical fibers,
splicing said tow optical fibers resulting in a spliced region;
wherein said optical fiber with the trench region and/or the moat region
included within the cladding region satisfies at least one of the following
conditions:
the separation between said core region and trench and/or moat region is
such that diffusion of dopants to and from the core region and trench
/moat region is prevented;
in and around the periphery of said core region and trench and/or moat
region is provided a barrier layer which averts diffusion of dopants from
and to said core region and trench and/or moat region; and
in and around the periphery of said core region and trench and/or moat
region is provided a dopant that nullifies the effect of diffused dopant.
13. The optical fiber as claimed in any of the preceding claims, wherein said
core region and moat region is doped with germanium and said trench
region is doped with at least one of fluorine and boron.

14. The optical fiber spliced region as claimed in any of the preceding claims, wherein said spliced region exhibits said an average value of splice loss of less than or equal to 0.04 dB.
15. The optical fiber as claimed in claim any of the preceding claims, wherein said spliced region between said optical fiber and another optical fiber exhibits an average value of splicing loss of less than or equal to 0.03 dB.