Description:TECHNICAL FIELD
The present disclosure relates generally to optical fibers, and more particularly to an optical fiber and an optical fiber cable.
BACKGROUND
Increasing demand of high-speed optical fiber communication has subsequently increased the density of optical fiber networks, which has led to a larger problem of accommodation of the optical fiber cables. Attenuation of optical signals and micro-bending losses in the optical fibers have a huge impact on range and quality of optical signal communicated in the network.
Prior art reference “WO2023009103A1” discloses an optical fiber with a relative refractive index (RRI) profile having a triangular or trapezoidal shaped trench which is difficult to manufacture. A variation in refractive index due to such trench shape is very difficult to control practically.
Prior art reference “US11506835B2” discloses an optical fiber that exhibits low macro-bend loss at 1550 nm at bend diameters greater than 40 mm. The RRI profile of the optical fiber includes a trench cladding region such that the volume of the trench is controlled to minimize macro-bend loss at large bend diameters.
The existing ITU-T G.657.A2 compliant optical fibers with RI profile having a buffer clad region between a core region and a trench region fail to provide enhanced optical properties to reduce bending losses. Further, the buffer region increases the manufacturing cost and makes fiber manufacturing process tedious and time taking. A variation in micro-bending loss (in decibel per kilometer) with respect to a variation in wavelength (in nanometer) for known G.657.A2 optical fibers is illustrated in FIG. 3 as 302.
Thus, there is a need to develop an optical fiber that is inexpensive, easy to manufacture, reduced in diameter, and provides ultra-low bend losses as well as optimized mode field diameter (MFD) values.
SUMMARY
In an aspect of the present disclosure, an optical fiber has an up-doped core, and a cladding that surrounds the core. The cladding has a first cladding that is defined by a first relative refractive index difference, and is a continuous region adjacent to the core such that a relative refractive index profile of the first cladding is an alpha profile. A mode field diameter of the optical fiber is in a range of 8.2 micrometers (µm) to 9.0 µm at a wavelength of 1310 nanometers (nm), and a cable cut-off wavelength of the optical fiber is less than or equal to 1260 nm.
BRIEF DESCRIPTION OF DRAWINGS
The following detailed description of the preferred aspects of the present disclosure will be better understood when read in conjunction with the appended drawings. The present disclosure is illustrated by way of example, and not limited by the accompanying figures, in which, like references indicate similar elements.
FIG. 1 illustrates an optical fiber.
FIG. 2 illustrates a refractive index profile of the optical fiber of FIG. 1.
FIG. 3 illustrates a graph that represents a comparison of micro-bending loss with respect to wavelength of the optical fiber with G.657.A2 (prior art).
FIG. 4 illustrates an optical fiber cable.
DEFINITIONS
The term “sheath” as used herein is referred to as an outermost layer or an outermost layer of the optical fiber cable that holds and protects the contents of the optical fiber cable.
The term “strength member” as used herein is referred to as a cable element made up of filaments or yarns that provides strength to the optical fiber cable.
The term “ribbon bundle” as used herein is referred to as a bundle of optical fiber ribbons.
The term “intermittently bonded fiber (IBR)” as used herein refers to an optical fiber ribbon having a plurality of optical fibers such that the plurality of optical fibers is intermittently bonded to each other by a plurality of bonded portions that are placed along the length of the plurality of optical fibers. The plurality of bonded portions is separated by a plurality of unbonded portions. An intermittently bonded ribbon fiber cable consists of fibers bonded using matrix material. As such, they lack a flat structure. The rollable ribbons in an intermittently bonded ribbon fiber are bundled together and have the appearance of a spider’s web. Hence, they are also called spider web ribbon fiber. Due to their loose fiber bundling, intermittently bonded ribbon cables are perfect for making optic fiber cables with higher packing density.
The term “core” as used herein refers to an inner most cylindrical structure present in the center of the optical fiber, that is configured to guide the light rays inside the optical fiber.
The term “cladding” as used herein refers to one or more layered structure covering the core of an optical fiber from the outside, that is configured to possess a lower refractive index than the refractive index of the core to facilitate total internal reflection of light rays inside the optical fiber. Further, the cladding of the optical fiber may include an inner cladding layer coupled to the outer surface of the core of the optical fiber and an outer cladding layer coupled to the inner cladding from the outside.
The term “trench” as used herein is referred to 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.
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 “relative refractive index difference” as used herein is referred to as a measure of the relative difference in refractive index between two optical materials. As used herein, the relative refractive index difference is represented by ? and its values are given in units of “%”, unless otherwise specified. In some cases where the refractive index of a region is less than the average refractive index of an undoped region, the relative refractive index percentage is negative, and the region is referred as a trench region.
The term “reduced diameter optical fiber” as used herein is referred to as an optical fiber as disclosed in the present disclosure having a diameter range of 60 micrometers (µm) to 125 µm with a tolerance of + 0.7 µm. Such optical fibers have very less peripheral clad thickness. The reduced diameter optical fiber significantly increases the packing density of the optical fiber cables.
The term “refractive index profile” (also termed as relative refractive index profile ?(r)) of the optical fiber as used herein is referred to as a 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.
The term “down doped” as used herein is referred to as addition of doping materials to facilitate decrease in the refractive index of a particular layer or part of optical fiber. The materials configured to facilitate down-doping are known as down-dopants. Specifically, at least one down dopant as used herein is Fluorine.
The term “Up doped” as used herein is referred to as addition of doping materials to facilitate increase in the refractive index of a particular layer or part of optical fiber. The materials configured to facilitate up-doping are known as up-dopants. Specifically, the up dopant as used herein is one of Germanium and Chlorine.
The term “un doped” as used herein is referred to as a material that is not intentionally doped, or which is pure silica. However, there are always chances of some diffusion of dopants in the region which is negligible.
The term “core volume” as used herein is defined as a volume acquired by the core with respect to the core radius Rcore. The core volume may have a magnitude in micrometers square (µm2) that may be determined by the following equation: = R0Rcore? r rdr
wherein Rcore is radius of core.
The term “trench volume” as used herein is referred to as a volume (surface integral volume) acquired by region between the core radius ‘Rcore’ and the trench radius ‘R1’ may have a trench volume with a magnitude in µm2 that may be determined by the following equation: = RcoreR1? r rdr
wherein Rcore is radius of core,
R1 is the trench radius.
The term “Mode Field Diameter (MFD)” as used herein is referred to as the size of the light-carrying portion of the optical fiber. For single-mode optical fibers, this region includes the optical fiber core as well as a small portion of the surrounding cladding glass of the optical fiber. The selection of desired MFD helps to describe the size of the light-carrying portion of the optical fiber.
The term “macro bend loss” as used herein is referred to as the losses induced in bends around mandrels (or corners in installations), generally more at the cable level or for fibers. The macro bend loss occurs when the fiber cable is subjected to a significant amount of bending above a critical value of curvature. The macro bend loss is also called as large radius loss.
The term “micro bend loss” as used herein is referred to as a loss in an optical fiber that relates to a light signal loss associated with lateral stresses along a length of the optical fiber. The micro bend loss is due to coupling from the optical fiber’s guided fundamental mode to lossy modes or cladding modes.
The term “Zero Dispersion Wavelength (ZDW)” as used herein is referred to as a wavelength at which the value of a dispersion coefficient is zero. In general, ZDW is the wavelength at which material dispersion and waveguide dispersion cancel one another.
The term “attenuation” as used herein is referred to as reduction in power of a light signal as it is transmitted. Specifically, the attenuation is caused by Rayleigh scattering, absorption of the light signal, and the like.
The term “cable cut-off wavelength” as used herein refers to a wavelength above which a single-mode fiber will support and propagate only one mode of light. The optical fiber transmits a single mode of optical signal above a pre-defined cut-off wavelength known as cable cut-off wavelength measured on 22 meters sample length of the optical fiber.
The term “core peak” as used herein is referred to as the maximum refractive index value of the core of the optical fiber.
DETAILED DESCRIPTION
The detailed description of the appended drawings is intended as a description of the currently preferred aspects of the present disclosure, and is not intended to represent the only form in which the present disclosure may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different aspects that are intended to be encompassed within the spirit and scope of the present disclosure.
FIG. 1 illustrates an optical fiber 100, according to an aspect of the present disclosure. The optical fiber 100 may have a mode field diameter in a range of 8.2 micrometer (µm) to 9.0 µm at a wavelength of 1310 nanometer (nm). The optical fiber 100 may further have a cut-off wavelength of the optical fiber 100 less than or equal to 1260 nm. In some aspects of the present disclosure, a glass diameter of the optical fiber 100 without coating (i.e., a bare optical fiber) may be in a range of 80 µm to 125 µm with a tolerance of + 0.7 µm. In some aspects of the present disclosure, the optical fiber 100 may have a bare fiber diameter of less than or equal to 125 µm with a deviation of 0.7 µm.
In some aspects of the present disclosure, the optical fiber 100 may have at least one of, a micro bend loss of less than 0.5 decibel per kilometer (dB/Km) at a wavelength of 1550 nm, an attenuation of less than or equal to 0.35 dB/Km at a wavelength of 1310 nm, an attenuation of less than or equal to 0.35 dB/Km at a wavelength of 1383 nm, an attenuation of less than or equal to 0.2 dB/Km at a wavelength of 1550 nm, and an attenuation of less than or equal to 0.23 dB/Km at a wavelength of 1625 nm.
In some other aspects of the present disclosure, the optical fiber 100 may have a macro bend loss of 0.2 dB/turn at a bend radius of 7.5 mm and a wavelength of 1550 nm. The optical fiber 100 may further have a macro bend loss of 0.5 dB/turn at a bend radius of 7.5 mm and a wavelength of 1625 nm.
In some aspects of the present disclosure, the optical fiber 100 may be coated with at least one of, a first set of coatings, a second set of coatings, and a third set of coatings. In some aspects of the present disclosure, the first set of coatings may have a primary coating (not shown) that may surround the cladding 104, a secondary coating (not shown) that may surround the primary coating, and a colored coating (not shown) that may surround the secondary coating. The second set of coatings may have a primary coating (not shown) that may surround the cladding 104, and a secondary-colored coating (not shown) that may surround the primary coating. The third set of coatings may have a primary-colored coating (not shown) that may surround the cladding 104.
In some other aspects of the present disclosure, the optical fiber 100 may be coated with the primary coating, the secondary coating, and the colored coating.
In some aspects of the present disclosure, a coating thickness of the primary coating may be in a range of 10 µm to 30 µm. In some aspects of the present disclosure, a coating thickness of the secondary coating may be in a range of 10 µm to 30 µm. In some aspects of the present disclosure, a coating thickness of the colored coating may be in a range of 4 µm to 8 µm.
In some aspects of the present disclosure, a young’s modulus of the primary coating may be less than 0.6 Megapascals (MPa). In some aspects of the present disclosure, a young’s modulus of the secondary coating may be less than 1500 MPa. In some other aspects of the present disclosure, the young’s modulus of the secondary coating may be in a range of 1200 MPa to 1500 MPa.
In some aspect of the present disclosure, the optical fiber 100 may be coated with at least one coating layer that may have a thickness of less than 60 µm. In some other aspects of the present disclosure, a diameter of the optical fiber 100 that may be coated by at least one coating layer may be in a range of 125 µm to 180 µm. In some other aspects of the present disclosure, the diameter of the optical fiber 100 that may be coated by at least one coating layer may be in a range of 160 µm to 200 µm. In some other aspects of the present disclosure, the diameter of the optical fiber 100 that may be coated by at least one coating layer may be less than 250 µm.
The optical fiber 100 may have a core 102, that may be up doped with one of Germanium (Ge) and/or Chlorine (Cl). The optical fiber 100 may further have a cladding 104 that may surround the core 102. In some aspects of the present disclosure, the refractive index profile of the core 102 may be an alpha profile such that a core refractive index ‘n1’ may be derived from a core alpha value ‘ac’ corresponding to a peak shaping parameter alpha ‘’. The peak shaping parameter ‘’ may be defined as how refractive index changes as a function of radius.
The cladding 104 may have a first cladding 104a that may be defined by a first relative refractive index difference ‘?1’. In some aspects of the present disclosure, the first cladding 104a may be down doped. The first cladding 104a (hereinafter interchangeably referred to and designated as “the down-doped region 104a”) may be a continuous region adjacent to the core 102 such that a relative refractive index profile of the first cladding 104a may be an alpha profile such that a first cladding refractive index ‘n2’ may be derived from a first alpha value ‘a1’ of the peak shaping parameter ‘’. The peak shaping parameter ‘’ may be defined as how refractive index changes as a function of radius.
In some aspects of the present disclosure, the core alpha value ‘ac’ of the core 102 may be in a range of 3 to 8, and the first alpha value ‘a1’ of the first cladding 104a may be in a range of 1.5 to 4.
In some aspects of the present disclosure, the optical fiber 100 may be independent of one or more pure silica regions that is generally formed between core region and a down doped region or trench region of an optical fiber. The pure silica region (i.e., buffer clad region) increases the manufacturing cost and makes fiber manufacturing process tedious and time taking. In some aspects of the present disclosure, the optical fiber 100 may not comprise any pure silica region or undoped region adjacent to the core 102 that makes the manufacturing of optical fiber 100 less complex and achieves the required waveguide properties. In some aspects of the present disclosure, the optical fiber 100 may not comprise any pure silica region or undoped region adjacent to the core 102 that may provide better control over required optical parameters of the optical fiber.
In some aspects of the present disclosure, the cladding 104 may further have a second cladding 104b that may surround the first cladding 104a. The second cladding 104b may be defined by a second relative refractive index difference ‘?2’. The first relative refractive index difference ‘?1’ may be less than the second relative refractive index difference ‘?2’. In some aspects of the present disclosure, the second cladding 104b may be undoped. The second cladding 104b may have a second cladding refractive index ‘n3’. In some aspects of the present disclosure, the second cladding refractive index ‘n3’ may be equal to a refractive index of pure silica ‘nsilica’ with a deviation of +0.0001
FIG. 2 illustrates a refractive index profile 200 of the optical fiber 100. The core 102 may have a core radius ‘Rcore’, the first cladding 104a may have a first cladding radius ‘R1’, and the second cladding 104b may have the second cladding radius ‘R2’. In some aspects of the present disclosure, the core 102 may be up doped. The core 102 may have the core relative refractive index difference ‘?core’. The core relative refractive index difference ‘?core’ may be derived from the core refractive index ‘n1’. In some aspects of the present disclosure, the core relative refractive index difference ‘?core’ of the core 102 may be in a range of 0.55 percent (%) to 0.65%. In an exemplary aspect of the present disclosure, the core relative refractive index difference ‘?core’ can be determined as: ?core= (n1 - nsilica) *100 (%),
where nsilica is the refractive index of pure silica.
The relative refractive index profile of the core 102 may be the alpha profile such that the core refractive index ‘n1’ may be derived from the core alpha value ‘ac’ of the peak shaping parameter ‘’. In some aspects of the present disclosure, the core alpha value ‘ac’ of the core 102 may be in a range of 3 to 8. The core refractive index ‘n1’ may further be dependent on a core peak with a maximum refractive index value ‘n1max’ (i.e., a maximum value of the core refractive index ‘n1’), the core radius ‘Rcore’, the core relative refractive index difference ‘?core’, and a radial position ‘r’ from a center of the optical fiber 100. In an exemplary aspect of the present disclosure, the core refractive index ‘n1’ at the radial distance ‘r’ can be determined as: n1r=n1max1-2?core(rRcore)ac1/2.
In some aspects of the present disclosure, the first cladding 104a may be down doped. The first cladding 104a may have the first relative refractive index difference ‘?1’. The first relative refractive index difference ‘?1’ may be derived from the first cladding refractive index ‘n2’. In some aspects of the present disclosure, the first relative refractive index difference ‘?1’ of the first cladding 104 may be in a range of -0.15% to -0.25%. In an exemplary aspect of the present disclosure, the first relative refractive index difference ‘?1’ can be determined as: ?1= (n2 - nsilica) *100 (%), where nsilica is the refractive index of pure silica.
In some aspects of the present disclosure, the first cladding 104a may have a suppressed region 202 (hereinafter interchangeably referred to and designated as a trench 202). In some aspects of the present disclosure, the first cladding radius ‘R1’ may be in a range of 16 µm to 18 µm. In some aspects of the present disclosure, a thickness of the first cladding 104a is in a range of 12 µm to 14 µm. The trench 202 may have the minimum value of the first relative refractive index difference ‘?1’ at a radius range of 13 µm to 15 µm of the optical fiber 100. The minimum value of the first relative refractive index difference ‘?1’ may be optimized at the specified radial distance such that the optical fiber 100 achieves very low micro bending loss and enhanced waveguide properties in compliance with G.657.A2 standard. In some aspects of the present disclosure, a trench volume (i.e., a volume of the trench 202) may be in a range of 14 to 20 percent micrometer square (% µm2). In some aspects of the present disclosure, a ratio of the trench volume to a core volume (i.e., a volume of the core 102) may be in a range of 2 to 3.5. The ratio of the trench volume to a core volume may be designed in above specified range to achieve the target optical parameters of the optical fiber 100 along with a reduction in cost of manufacturing of the optical fiber 100. The optical fiber 100 may exhibit higher bend loss when the thickness, first cladding radius ‘R1’, trench volume and other parameters of the first cladding 104a is less than the disclosed ranges in the present disclosure. The optical fiber 100 may exhibit an increase in cable cutoff wavelength when the thickness, first cladding radius ‘R1’, trench volume and other parameters of the first cladding 104a is greater than the disclosed ranges in the present disclosure.
The relative refractive index profile of the first cladding may be the alpha profile such that the first cladding refractive index ‘n2’ may be derived from the first alpha value ‘a1’ of the peak shaping parameter ‘’. In some aspects of the present disclosure, the first alpha value ‘a1’ of the first cladding 104a may be in a range of 1.5 to 4. The first cladding refractive index ‘n2’ may further be dependent on a minimum refractive index value ‘n2min’ (i.e., a minimum value of the first cladding refractive index ‘n2’), the core radius ‘Rcore’, the first cladding radius ‘R1’, the first relative refractive index difference ‘?1’, and the radial position ‘r’ from a center of the optical fiber 100. In an exemplary aspect of the present disclosure, the first cladding refractive index ‘n2’ at the radial distance ‘r’ can be determined as: n2r=n2min1-2?1{r-R1Rcore-R1}a11/2.
The second cladding 104b may be undoped. In some aspects of the present disclosure, the second cladding 104b may have a second relative refractive index difference ‘?2’. The second relative refractive index difference ‘?2’ may be derived from the second cladding refractive index ‘n3’. In an exemplary aspect of the present disclosure, the second relative refractive index difference ‘?2’ can be determined as: ?2= (n3-nsilica) *100 (%), where nsilica is the refractive index of pure silica. In some aspects of the present disclosure, the second relative refractive index difference ‘?2’ may be zero. In some aspects of the present disclosure, the second relative refractive index difference ‘?2’ may be in a range of -0.01% to +0.01%.
In an exemplary aspect of the present disclosure, the optical fiber 100 may have the core radius ‘Rcore’ equal to 5.5 µm, the core relative refractive index difference ‘?core’ equal to 0.62%, the first cladding radius ‘R1’ equal to 16.1 µm, the first relative refractive index difference (i.e., trench relative refractive index difference) ‘?1’ equal to -0.18%, the second cladding radius ‘R2’ equal to 62.5 µm, the second relative refractive index difference ‘?2’ equal to zero, the core volume equal to 5.8 % µm2, the trench volume equal to 14.01 % µm2, the mode field diameter equal to 8.39 µm, the cut-off wavelength equal to 1239 nm, a zero dispersion wavelength equal to 1308 nm, a macro bend loss equal to 0.081 dB/turn at the bend radius of 7.5 mm and the wavelength of 1550 nm, a macro bend loss equal to 0.285 dB/turn at the bend radius of 7.5 mm and the wavelength of 1625 nm, and an attenuation of 0.194 at the wavelength of 1550 nm.
In another exemplary aspect of the present disclosure, the optical fiber 100 may have the core radius ‘Rcore’ equal to 5.3 µm, the core relative refractive index difference ‘?core’ equal to 0.59%, the first cladding radius ‘R1’ equal to 16.2 µm, the first relative refractive index difference ‘?1’ equal to -0.25%, the second cladding radius ‘R2’ equal to 62.5 µm, the second relative refractive index difference ‘?2’ equal to zero, the core volume equal to 5.6 % µm2, the trench volume equal to 16.15 % µm2, the mode field diameter equal to 8.62 µm, the cut-off wavelength equal to 1217 nm, the zero dispersion wavelength equal to 1307 nm, the macro bend loss equal to 0.132 dB/turn at the bend radius of 7.5 mm and the wavelength of 1550 nm, the macro bend loss equal to 0.357 dB/turn at the bend radius of 7.5 mm and the wavelength of 1625 nm, and an attenuation of 0.190 at the wavelength of 1550 nm.
In another exemplary aspect of the present disclosure, the optical fiber 100 may have the core radius ‘Rcore’ equal to 4.8 µm, the core relative refractive index difference ‘?core’ equal to 0.62%, the first cladding radius ‘R1’ equal to 16.3 µm, the first relative refractive index difference ‘?1’ equal to -0.19%, the second cladding radius ‘R2’ equal to 40 µm, the second relative refractive index difference ‘?2’ equal to zero, the core volume equal to 4.8 % µm2, the trench volume equal to 17.3 % µm2, the mode field diameter equal to 8.43 µm, the cut-off wavelength equal to 1245 nm, the zero dispersion wavelength equal to 1308 nm, a macro bend loss equal to 0.091 dB/turn at the bend radius of 7.5 mm and the wavelength of 1550 nm, a macro bend loss equal to 0.184 dB/turn at the bend radius of 7.5 mm and the wavelength of 1625 nm, and an attenuation of 0.194 at the wavelength of 1550 nm.
In another exemplary aspect of the present disclosure, the optical fiber 100 may have the core radius ‘Rcore’ equal to 4.9 µm, the core relative refractive index difference ‘?core’ equal to 0.63%, the first cladding radius ‘R1’ equal to 15.9 µm, the first relative refractive index difference ‘?1’ equal to -0.2%, the second cladding radius ‘R2’ equal to 50 µm, the second relative refractive index difference ‘?2’ equal to zero, the core volume equal to 5.1 % µm2, the trench volume equal to 14.9 % µm2, the mode field diameter equal to 8.45 µm, the cut-off wavelength equal to 1202 nm, the zero dispersion wavelength equal to 1311 nm, a macro bend loss equal to 0.135 dB/turn at the wavelength of 1550 nm, a macro bend loss equal to 0.402 dB/turn at the wavelength of 1625 nm, and an attenuation of 0.196 at the wavelength of 1550 nm.
In another exemplary aspect of the present disclosure, the optical fiber 100 may have a maximum value of the core radius ‘Rcore’ equal to 5.5 µm, a maximum value of the core relative refractive index difference ‘?core’ equal to 0.65%, a maximum value of the first cladding radius ‘R1’ equal to 17 µm, a maximum value of the first relative refractive index difference ‘?1’ equal to -0.25%, a maximum value of the second cladding radius ‘R2’ equal to 62.5 µm, a maximum value of the second relative refractive index difference ‘?2’ equal to 0.01, a maximum value of the core volume equal to 5.8 % µm2, a maximum value of the trench volume equal to 20 % µm2, a maximum value of the mode field diameter equal to 9 µm, a maximum value of the cut-off wavelength less than 1260 nm, a maximum value of the zero dispersion wavelength equal to 1324 nm, a maximum value of a macro bend loss equal to 0.2 dB/turn at the wavelength of 1550 nm, a maximum value of a macro bend loss equal to 0.5 dB/turn at the wavelength of 1625 nm, and a maximum value of an attenuation of 0.20 at the wavelength of 1550 nm.
In another exemplary aspect of the present disclosure, the optical fiber 100 may have a minimum value of the core radius ‘Rcore’ equal to 4.5 µm, a minimum value of the core relative refractive index difference ‘?core’ equal to 0.55%, a minimum value of the first cladding radius ‘R1’ equal to 15 µm, a minimum value of the first relative refractive index difference ‘?1’ equal to -0.15%, a minimum value of the second cladding radius ‘R2’ equal to 40 µm, a minimum value of the second relative refractive index difference ‘?2’ equal to -0.01, a minimum value of the core volume equal to 4.8 % µm2, a minimum value of the trench volume equal to 14 % µm2, a minimum value of the mode field diameter equal to 8.2 µm, and a minimum value of the zero dispersion wavelength equal to 1300 nm.
FIG. 3 illustrates a graph 300 that represents a comparison of micro-bending loss with respect to wavelength of the optical fiber 100 with general G.657.A2 optical fiber (prior art). X-axis of the graph 300 represents values of wavelength (in nm) and a Y-axis of the graph 300 represents micro bending loss (in dB/Km). A variation in the value of the micro bending loss of general G.657.A2 optical fiber (prior art) with respect to change in the wavelength is represented as 302. A variation in the value of the micro bending loss of optical fiber 100 with respect to change in the wavelength is represented as 304. From the graph 300, it is evident that the micro bending loss of the optical fiber 100 is less than the micro bending loss of general G.657.A2 optical fiber (prior art).
FIG. 4 illustrates an optical fiber cable 400. Preferably, the optical fiber cable 400 may be a ribbon fiber cable. In some aspects of the present disclosure, the optical fiber cable 400 may have an attenuation of less than 0.25 dB/km at the wavelength of 1550 nm.
The optical fiber cable 400 may have a plurality of buffer tubes 402. Although FIG. 4 illustrates that the plurality of buffer tubes 402 has six buffer tubes (i.e., first through sixth buffer tube 402a-402f), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, the plurality of buffer tubes 402 may have any number of buffer tubes, without deviating from the scope of the present disclosure. In such a scenario, each buffer tube of the plurality of buffer tubes 402 may be structurally and functionally similar to the first through sixth buffer tubes 402a-402f as described herein.
The plurality of buffer tubes 402 may have a plurality of optical fiber ribbons 404 that may be a type of intermittently bonded ribbons (IBRs) (hereinafter interchangeably referred to and designated as “plurality of IBRs 404”). Although FIG. 4 illustrates that the plurality of buffer tubes 402 has twenty-four IBRs (i.e., first through twenty fourth IBRs 404a-404x), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, the plurality of buffer tubes 402 may have any number of IBRs, without deviating from the scope of the present disclosure. In such a scenario, each IBR of the plurality of IBRs 404 may be structurally and functionally similar to the first through twenty-four IBRs 404a-404x as described herein. FIG. 4 further illustrates that each buffer tube of the plurality of buffer tubes 402 has four IBRs (for example the first buffer tube 402a is shown to have the first through fourth IBRs 404a-402d), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, each buffer tube of the plurality of buffer tubes 402 may have any number of IBRs, without deviating from the scope of the present disclosure. In such a scenario, each IBR of the plurality of IBRs 404 may be structurally and functionally similar to the first through twenty fourth IBRs 404a-404x as described herein.
Each IBR of the plurality of IBRs 404 may have a plurality of optical fibers 100. In some aspects of the present disclosure, each optical fiber of the plurality of optical fibers 100 (hereinafter interchangeably referred to and designated as “the optical fiber 100”) may be coated with at least one coating (not shown) that may have the thickness of less than or equal to 65 µm. In some other aspects of the present disclosure, the diameter of the optical fiber 100 that may be coated by at least one coating may be in the range of 125 µm to 180 µm. In some other aspects of the present disclosure, the diameter of the optical fiber 100 that may be coated by at least one coating may be in the range of 160 µm to 200 µm. In some other aspects of the present disclosure, the diameter of the optical fiber 100 that may be coated by at least one coating may be less than 250 µm.
The optical fiber 100 may have the core 102, that may be up doped. The optical fiber 100 may further have the cladding 104 that may surround the core 102. In some aspects of the present disclosure, the refractive index profile of the core 102 may be an alpha profile such that the core refractive index ‘n1’ may be derived from the core alpha value ‘ac’ corresponding to the peak shaping parameter alpha ‘’.
The cladding 104 may have the first cladding 104a that may be defined by the first relative refractive index difference. In some aspects of the present disclosure, the first cladding 104a may be down doped. The first cladding 104a may be the continuous region adjacent to the core 102 such that the relative refractive index profile of the first cladding 104a may be the alpha profile such that the first cladding refractive index ‘n2’ may be dependent on the first alpha value ‘a1’ of the peak shaping parameter ‘’.
In some aspects of the present disclosure, the optical fiber 100 may be independent of the one or more pure silica regions that may be adjacent to the core 102. In other words, the optical fiber 100 may not have any un doped region with a predefined radial thickness between the core 102 and the first cladding 104a. The pure silica region (i.e., buffer clad region) increases the manufacturing cost and makes fiber manufacturing process tedious and time taking. In some aspects of the present disclosure, the optical fiber 100 may not comprise any pure silica region or un doped region adjacent to the core 102 to make the manufacturing of optical fiber 100 less complex and achieves the target optical parameters or properties of the optical fiber 100.
In some aspects of the present disclosure, the cladding 104b may further have the second cladding 104b that may surround the first cladding 104a. The second cladding 104b may be defined by the second relative refractive index difference ‘?2’. The first relative refractive index difference ‘?1’ may be less than the second relative refractive index difference ‘?2’. In some aspects of the present disclosure, the second cladding 104b may be un doped. The second cladding 104b may have the second cladding refractive index ‘n3’. In some aspects of the present disclosure, the second cladding refractive index ‘n3’ may be equal to the refractive index of pure silica ‘nsilica’.
The optical fiber cable 400 may further have a sheath 406 that surrounds the plurality of buffer tubes 402. Specifically, the sheath 406 may be adapted to act as an outermost covering for the optical fiber cable 400 such that the sheath 406 facilitates in reduction of abrasion and to provide the optical fiber cable 100 with extra protection against external mechanical effects such as crushing, and the like. In some aspects of the present disclosure, the sheath 406 may be made up of a material such as, but not limited to, a synthetic plastic material, a natural plastic material, and the like. Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for the sheath 406, known to a person of ordinary skill in the art, without deviating from the scope of the present disclosure.
The sheath 406 may have a plurality of strength members 408 that may be partially or completely embedded in the sheath 406. Specifically, the plurality of strength members 408 may be adapted to provide strength to the optical fiber cable 400 that may be required during an installation process of the optical fiber cable 400. Further, the strength members 408 may be adapted to provide majority of structural strength and support to the optical fiber cable 400. Furthermore, the strength members 408 may enhance a tensile strength of the optical fiber cable 400, which is highly desirable during the installation process. Although FIG. 4 illustrates that the plurality of strength members 408 has six strength members (i.e., first through sixth strength members 408a-408f), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, the plurality of strength members 408 may have any number of strength members, without deviating from the scope of the present disclosure. In such a scenario, each strength member of the plurality of strength members 408 may be structurally and functionally similar to the first through sixth strength members 408a-408f as described herein.
Furthermore, the optical fiber cable 400 may have one or more ripcords 410. The one or more ripcords 410 may facilitate ripping, tearing or opening up of the optical fiber cable 400. In some aspects of the present disclosure, the one or more ripcords 410 may facilitate the ripping, tearing or opening up of the optical fiber cable 400 to access the plurality of strength members 408 from the sheath 406. Although FIG. 4 illustrates that the one or more ripcords 410 has two ripcords (i.e., first and second ripcords shown as 410a and 410b, respectively), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, the one or more ripcords 410 may have any number of ripcords, without deviating from the scope of the present disclosure. In such a scenario, each ripcord of the one or more ripcords 410 may be structurally and functionally similar to the first and second ripcords 410a, 410b as described herein.
Furthermore, the optical fiber cable 400 may have a plurality of water swellable yarns 412. The plurality of water swellable yarns (WSYs) 412 may provide water resistance to the plurality of optical fibers 100 inside the optical fiber cable 400 by restricting penetration of water inside the optical fiber cable 400. Although FIG. 4 illustrates that the plurality WSYs 412 has five WSYs (i.e., first through fifth WSYs 412a-412e), it will be apparent to a person skilled in the art that the scope of the present disclosure is not limited to it. In various other aspects, the plurality WSYs 412 may have any number of WSYs, without deviating from the scope of the present disclosure. In such a scenario, each WSY of the plurality WSYs 412 may be structurally and functionally similar to the first through fifth WSY 412a-412e as described herein.
Thus, the optical fiber 100 and the optical fiber cable 400 of the present disclosure provides ultra-low bend losses as well as optimized mode field diameter (MFD) values which complies with the G.657.A2 recommendations and even improved optical properties as compared to the G.657.A2 recommendations. The refractive index profile of the optical fiber 100 has been modified in such a way that it becomes ultra-bend sensitive and shows highly improved micro-bending loss. The refractive index profile includes exactly one trench 202 that is adjacent and continuous to the core 102. The optical fiber 100 is independent of any buffer cladding (i.e., pure silica region) adjacent to the core 102. The optical fiber cable 400 has low micro-bending losses due to a single trench 202 with down doping, that is present in each optical fiber 100.
While various aspects of the present disclosure have been illustrated and described, it will be clear that the present disclosure is not limited to these aspects only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the present disclosure, as described in the claims. Further, unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements.
, Claims:I/WE CLAIMS:
1. An optical fiber (100) comprising:
a core (102), where the core (102) is up doped; and
a cladding (104) that surrounds the core (102), and comprising a first cladding (104a) that is defined by a first relative refractive index difference (?1), where the first cladding (104a) is a continuous region adjacent to the core (102) such that a relative refractive index profile of the first cladding (104a) is an alpha profile, where the continuous region is defined as a region not having one or more pure silica region between the core (102) and the first cladding (104a),
where a mode field diameter of the optical fiber (100) is in a range of 8.2 micrometer (µm) to 9.0 µm at a wavelength of 1310 nanometer (nm), and a cable cut-off wavelength of the optical fiber (100) is less than or equal to 1260 nm.

2. The optical fiber (100) as claimed in claim 1, where a first alpha value (a1) of the first cladding (100) is in a range of 1.5 to 4.

3. The optical fiber (100) as claimed in claim 1, where the first cladding (104a) comprises a suppressed region (202) having a minimum relative refractive index difference at a radius in a range of 13 µm to 15 µm.

4. The optical fiber (100) as claimed in claim 1, where the first cladding (104a) comprises a trench (202), where the trench (202) has a trench volume in a range of 14 to 20 percent micrometer square (% µm2).

5. The optical fiber (100) as claimed in claim 4, where a ratio of the trench volume to a core volume of the core (202) is in a range of 2 to 3.5.

6. The optical fiber (100) as claimed in claim 1, where a thickness of the first cladding (104a) is in a range of 12 µm to 14 µm.

7. The optical fiber (100) as claimed in claim 1, where the cladding (104) further comprising a second cladding (104b) that surrounds the first cladding (104a), and is defined by a second relative refractive index difference (?2), where the first relative refractive index difference (?1) is less than the second relative refractive index difference (?2).

8. The optical fiber (100) as claimed in claim 1, where a first relative refractive index difference (?1) of the first cladding (104a) is in a range of -0.15% to -0.25%.

9. The optical fiber (100) as claimed in claim 1, where the optical fiber (100) is coated with at least one of, (i) a primary coating that surrounds the cladding (104), a secondary coating that surrounds the primary coating, and a colored coating that surrounds the secondary coating, (ii) a primary coating that surrounds the cladding (104), and a secondary-colored coating that surrounds the primary coating, and (iii) a primary-colored coating that surrounds the cladding (104).

10. The optical fiber (100) as claimed in claim 1, where a glass diameter of the optical fiber (100) is in a range of 80 µm 125 µm.

11. The optical fiber (100) as claimed in claim 1, where the optical fiber (100) has at least one of, (i) a micro bend loss of less than 0.5 decibel per kilometer (dB/Km) at a wavelength of 1550 nm, (ii) an attenuation of less than or equal to 0.35 dB/Km at a wavelength of 1310 nm, (iii) an attenuation of less than or equal to 0.35 dB/Km at a wavelength of 1383 nm, (iv) an attenuation of less than or equal to 0.2 dB/Km at a wavelength of 1550 nm, and (v) an attenuation of less than or equal to 0.23 dB/Km at a wavelength of 1625 nm.

12. The optical fiber (100) as claimed in claim 1, where the macro bend loss of the optical fiber is (i) 0.2 dB/turn at a bend radius of 7.5 mm and a wavelength of 1550 nm, and (ii) 0.5 dB/turn at a bend radius of 7.5 mm and a wavelength of 1625 nm.

13. An optical fiber cable (400) comprising:
a plurality of optical fiber ribbons (404) twisted spirally, where each optical fiber ribbon of the plurality of optical fiber ribbons (404) comprising a plurality of optical fibers (100) such that each optical fiber of the plurality of optical fibers (100) comprising:
a core (102), where the core (102) is up-doped; and
a cladding (104) that surrounds the core (102), and comprising a first cladding (104a) that is defined by a first relative refractive index difference (?1), where the first cladding (104a) is a continuous region adjacent to the core (102) such that a relative refractive index profile of the first cladding (104a) is an alpha profile; and
where, a mode field diameter of the optical fiber (100) is in a range of 8.2 micrometer (µm) to 9.0 µm at a wavelength of 1310 nanometer (nm), and a cable cut-off wavelength of the optical fiber (100) is less than or equal to 1260 nm.

14. The optical fiber cable (400) as claimed in claim 14, where an attenuation of the optical fiber cable (400) is less than 0.25 dB/km at a wavelength of 1550 nm.