DESC:TECHNICAL FIELD
The present disclosure relates to the field of optical fibers and, in particular, relates to an optical fiber cable with a reduced diameter. The present application is based on, and claims priority from an Indian Application Number 202311025821 filed on 5th April 2023, the disclosure of which is hereby incorporated by reference herein.

BACKGROUND
Optical fibers are widely used in optical cables, which are typically housed within an optical fiber enclosure to simplify handling and disposal. There are several patents that describe different types of optical fiber cables. For instance, CN212989723U discusses a multitube cable with buffer tubes, while references like WO2022251017A1 and EP3955041A1 delve into multitube cables with buffer tubes and their cable fill factors.
Due to increasing data transmission requirements, optical fiber cables have grown in size. However, as the demand for efficient space utilization is on the rise, there is a need to reduce the size of multitube cables while delivering performance.

SUMMARY
In an aspect of the present disclosure, an optical fiber cable is disclosed. The optical fiber cable has a central strength member (CSM), a plurality of buffer tubes, and a sheath. The plurality of buffer tubes are stranded around the CSM such that each buffer tube of the plurality of buffer tubes encloses one or more optical fibers such that each optical fiber of the one or more optical fibers has one or more protective coating layers that has a combined thickness of less than 30 micrometers (µm). The plurality of buffer tubes are stranded in at-least two concentric layers around the CSM and the optical fiber cable has a fill factor of greater than 7 fibers/millimeter square de(f/mm2). The sheath surrounds the CSM and the plurality of buffer tubes.

BRIEF DESCRIPTION OF DRAWINGS
Having thus described the disclosure in general terms, reference will now be made to the accompanying figures, where:
FIG. 1 illustrates a cross-sectional view of an optical fiber cable.
FIG. 2 illustrates a cross-sectional view of another optical fiber cable.
FIG. 3 illustrates a cross-sectional view of an optical fiber.
FIG. 4 illustrates a cross-sectional view of another optical fiber.
It should be noted that the accompanying figures are intended to present illustrations of exemplary embodiments of the present disclosure. These figures are not intended to limit the scope of the present disclosure. It should also be noted that accompanying figures are not necessarily drawn to scale.

DEFINITIONS
The term “optical fiber” as used herein refers to a light guide that provides high-speed data transmission. The optical fiber has one or more glass core regions and a glass cladding region. The light moving through the glass core regions of the optical fiber relies upon the principle of total internal reflection, where the glass core regions have a higher refractive index (n1) than the refractive index (n2) of the glass cladding region of the optical fiber.
The term “optical fiber cable” as used herein refers to a cable that encloses a plurality of optical fibers.
The term “fill factor” as used herein refers to a ratio of (i) number of optical fibers to (ii) a cross-sectional area of the optical fiber cable with respect to an outer diameter of a sheath.
The term “zero-dispersion slope” as used herein context of the optical fiber refers to rate of change of dispersion at zero-dispersion wavelength.
The term “macro bending loss” as used herein refers to losses induced in bends around mandrels (or corners in installations), generally more at a cable level or for an optical fiber. 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 “SHORE D” as used herein refers to a hardness scale.
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.
Moreover, although the following description contains many specifics for the purposes of illustration, anyone skilled in the art will appreciate that many variations and/or alterations to said details are within the scope of the present technology. Similarly, although many of the features of the present technology are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the present technology is set forth without any loss of generality to, and without imposing limitations upon, the present technology.
FIG. 1 illustrates a cross-sectional view of an optical fiber cable 100. The optical fiber cable 100 may adapted to be laid inside various ducts that may be used in different applications. The optical fiber cable 100 may have a central strength member (CSM) 104, a plurality of buffer tubes 106 of which first through twenty-two buffer tubes 106a-106v are shown, a plurality of Water Swellable Yarns (WSY) 108 of which first through third WSYs 108a-108c are shown, a binder yarn 110, a plurality of ripcords 112 of which first and second ripcords 112a-112b are shown, and a sheath 114. Although FIG. 1 illustrates that the optical fiber cable 100 has twenty-two buffer tubes (i.e., the twenty-two buffer tubes 106a-106v), three WSYs (i.e., the first through third WSYs 108a-108c), and two ripcords (i.e., the first and second ripcords 112a-112b), 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 optical fiber cable 100 may have any number of buffer tubes, WSYs, and ripcords, without deviating from the scope of the present disclosure. In such a scenario, each buffer tube, each WSY, and each ripcord is adapted to serve one or more functionalities in a manner similar to the first through twenty-two buffer tubes 106a-106v, the first through third WSYs 108a-108c, and the first and second ripcords 112a-112b, respectively, as described herein.
As illustrated, the plurality of buffer tubes 106 may be stranded around the CSM 104. Further, each buffer tube of the plurality of buffer tubes 106 may be adapted to enclose one or more optical fibers 116 (hereinafter interchangeably referred to and designated as “the optical fibers 116”) and a gel 118. For example, as illustrated, the first buffer tube 106a may be adapted to enclose the one or more optical fibers 116. Similarly, each buffer tube of the plurality of buffer tubes 106 may be adapted to enclose the one or more optical fibers 116. It will be apparent to a person skilled in the art that the one or more optical fibers 116 signifies that any number of optical fibers can be enclosed within each buffer tube of the plurality of buffer tubes 106, without deviating from the scope of the present disclosure.
In some aspects of the present disclosure, the one or more optical fibers 116 may be disposed within the gel 118 inside each buffer tube of the plurality of buffer tubes 106. Alternatively, in some aspects of the present disclosure, each buffer tube of the plurality of buffer tubes 106 may be a dry-type buffer tube that may enclose the one or more optical fibers 116 without any gel. Alternatively, in some aspects of the present disclosure, each buffer tube of the plurality of buffer tubes 106 may enclose the one or more optical fibers 116 with a WSYs of the plurality of WSYs 108.
In some aspects of the present disclosure, the optical fiber cable 100 may have a higher fill factor. Specifically, the optical fiber cable 100 may have the fill factor that may be greater than 7 fibers/millimeter square (f/mm2). For example, the optical fiber cable 100 may have the fill factor that may be 7 f/mm2, 8 f/mm2, 9 f/mm2, 10 f/mm2, and so on. The fill factor greater than 7 f/mm2 may advantageously facilitate the optical fiber cable 100 to accommodate greater number of optical fibers (such as the one or more optical fibers 116) while keeping an outer diameter of the optical fiber cable 100 substantially low. For example, by virtue of the fill factor being greater than 7 f/mm2, the optical fiber cable 100 with the outer diameter of less than or equal to 7 millimeter (mm) may accommodate 288 optical fibers (such as the optical fibers 116).
In some aspects of the present disclosure, the optical fiber cable 100 may have a lower weight per unit length. Therefore, the optical fiber cable 100 may be lighter in weight. The optical fiber cable 100 being lighter in weight may allow better blowing performance for installation. Further, the optical fiber cable 100 may be easier to handle, owing to the light weight of the optical fiber cable 100. Specifically, the weight per unit length of the optical fiber cable 100 may be 65 Kilograms/Kilometers (Kg/Km) with a tolerance value of + 10 Kg/Km with 288 optical fibers (such as the optical fibers 116).
In some aspects of the present disclosure, a cable weight per unit length per unit fiber count of the optical fiber cable 100 may have a lower range. Specifically, the cable weight per unit length per unit fiber count of the optical fiber cable 100 may be in a range of 0.19 Kg/Km/fiber to 0.26 Kg/Km/fiber. The lower range of the cable weight per unit length per unit fiber count may signify enhanced signal capacity of the optical fiber cable 100 with minimal weight of other components of the optical fiber cable 100. In some aspects of the present disclosure, the optical fiber 116 of the cable 100 may have a zero-dispersion slope that may be less than or equal to 0.092 temporal spread (ps) per unit propagation distance (in kilometers, Km), per square unit pulse spectral width (in nanometers square, nm2) (ps/nm2-Km). The lower zero-dispersion slope of the optical fibers enables the optical fiber cable 100 to maintain signal integrity over long distance and spectral width.
In some aspects of the present disclosure, the optical fiber cable 100 may have an outer diameter that may be less than 40 times of an outer diameter of each optical fiber of the optical fibers 116. The outer diameter of the optical fiber cable 100 greater than 40 times of the outer diameter of each optical fiber of the optical fibers 116 may increase weight of the optical fiber cable 100. Further, the outer diameter of the optical fiber cable 100 greater than 40 times of the outer diameter of each optical fiber of the optical fibers 116 may reduce the fill factor.
In some aspects of the present disclosure, each optical fiber of the optical fibers 116 may have a lower diameter. The lower diameter of each optical fiber of the optical fibers 116 may advantageously help to increase the fill factor of the optical fiber cable 100. Specifically, each optical fiber of the optical fibers 116 may have a diameter that may be in a range between 150 micrometers (µm) and 190 µm. Preferably, each optical fiber of the optical fibers 116 may have the diameter that may be one of 160 µm and 180 µm. Specifically, each optical fiber of the optical fibers 116 may have the diameter that may be less than 190 µm. The use of small diameter optical fibers 116 potentially enable higher packing density, reduced weight and flexibility inside the cable 100. In some aspects of the present disclosure, each optical fiber of the one or more optical fibers 116 may have a glass diameter of utmost 126 µm. In some aspects of the present disclosure, each optical fiber of the one or more optical fibers 116 may have a glass diameter between 60-126 µm. Specifically, the glass diameter of each optical fiber of the one or more optical fibers 116 has a core of the optical fiber and a cladding of the optical fiber (as discussed later in FIG. 3). In some aspects of the present disclosure, each optical fiber of the optical fibers 116 may have a mode field diameter that may be 8.6 µm with a tolerance value of + 0.4 µm at a wavelength of 1310 nanometers.
In some aspects of the present disclosure, each optical fiber of the optical fibers 116 may have lower macro bending loss. For example, each optical fiber 300 (as shown in FIG. 3) of the optical fibers 116 may have a macro bending loss that may be less than 0.03 Decibel (dB) at a wavelength of 1550 nanometers (nm) when deployed with 10 turns at a mandrel of 15 mm radius. In another example each optical fiber 300 of the optical fibers 116 may have a macro bending loss that may be less than or equal to 0.5 dB per turn at a wavelength of 1625 nm and the bend radius of 7.5 mm. The optical fibers 116 with greater macro bending loss may have high attenuations during bending or handling of the optical fibers 116. The optical fibers 116 with lower macro bending loss may facilitate in manufacturing of the optical fiber cable 100 with a reduced diameter and enables to maintain signal quality under bending conditions. The lower macro bending loss may further facilitate to manufacture the optical fiber cable 100 that may have a weight per unit length value of 65 Kg/Km with a tolerance value of + 10Kg/Km with 288 optical fibers (such as the optical fibers 116). In some aspect of the present disclosure, each optical fiber of the optical fibers 116 may have an attenuation of less than or equal to 0.35 dB/km at 1310 nm wavelength and an attenuation of less than or equal to 0.21 dB/km at 1550 nm wavelength.
The CSM 104 may be disposed at a center of the optical fiber cable 100. The CSM 104 may be adapted to provide physical strength to the optical fiber cable 100. Specifically, the CSM 104 may be adapted to provide rigidity to prevent the optical fiber cable 100 from buckling. In other words, the CSM 104 may be adapted to preserve an integrity of the optical fiber cable 100. In some aspects of the present disclosure, the CSM 104 may be made up of a material, including but not limited to, steel, fiberglass, fiber-reinforced plastic (FRP), aramid-reinforced plastic (ARP), and the like. Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for the CSM 104, without deviating from the scope of the present disclosure.
In some aspects of the present disclosure, the CSM 104 may be coated with a material, including but not limited to, polyethylene. Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for the coating that may be coated on the CSM 104, without deviating from the scope of the present disclosure.
The buffer tubes 106 may be stranded around the CSM 104. Specifically, the buffer tubes 106 may be stranded in at-least two concentric layers around the CSM 104. For example, the buffer tubes 106 may be stranded in at-least two concentric layers around the CSM 104 i.e., dual layers of the buffer tubes 106. In other words, the optical fiber cable 100 may have a dual layer design i.e., the buffer tubes 106 are stranded in dual layers. The at-least two concentric layers of buffer tubes 106 may advantageously reduce an overall diameter of the optical fiber 300. The plurality of buffer tubes 106 in each of the concentric layers are SZ stranded at a lay-length of at least 80 mm. The plurality of buffer tubes 106 SZ stranded below 80 mm may face high macrobending losses in the optical fibers 116 present inside the plurality of buffer tubes. In an aspect, the first layer of plurality of buffer tubes 106 is SZ stranded at a lay-length of 85 mm, second layer of plurality of buffer tubes 106 is SZ stranded at a lay-length of 100 mm. In an aspect, the first layer of plurality of buffer tubes 106 is SZ stranded at a lay-length of 85 mm, second layer of plurality of buffer tubes 106 is SZ stranded at a lay-length of 100 mm and a third layer of plurality of buffer tubes 106 is SZ stranded at a lay-length of 120 mm. The plurality of buffer tubes 106 in adjacent concentric layers have a lay-length difference of at least 15 mm. The difference in the stranding lay-length enable to maintain desired extra fiber length in each of the concentric layer, thereby helping minimum stress generation on optical fibers 116 of the cable 100 during handling and temperature variations conditions. Further, the plurality of buffer tubes 106 in each of the concentric layers are bound by two or more binders wound at a lay-length of 25±10 mm. The binding lay-length of binders is optimized to maintain the stranded integrity of the plurality of buffer tubes 106 while not generating any physical stresses on the buffer tubes 106 in each of the concentric layers.
In some aspects of the present disclosure, the outer diameter of the optical fiber cable 100 may be less than square root of number of optical fibers of the optical fibers 116 multiplied by an outer diameter of each optical fiber of the optical fibers 116. In some examples, the outer diameter of the optical fiber cable 100 may be 6.8 mm with a tolerance value of + 0.2 mm and number of optical fibers of the optical fibers 116 may be 288. Each optical fiber of 288 fibers of the optical fibers 116 may have the outer diameter of 190 µm. The square root of 288 fibers of the optical fibers 116 with each fiber of the optical fibers 116 having the outer diameter of 190 µm is v (288*190) = 7.4, which is less than the outer diameter of the optical fiber cable 100. The dual layer design of the optical fiber cable 100 may facilitate to keep the outer diameter of the optical fiber cable 100 less than the square root of number of fibers of the optical fibers 116 multiplied by the outer diameter of each optical fiber of the optical fibers 116. This relationship between the outer diameter of the optical fiber cable 100, the number of fibers of the optical fibers 116, and the outer diameter of each fiber of the optical fibers 116 may determine an overall size, functionality, and performance of the optical fiber cable 100. Therefore, the outer diameter of the optical fiber cable 100, the number of fibers of the optical fibers 116, and the outer diameter of each fiber of the optical fibers 116 may be carefully selected to meet required specifications of the optical fiber cable 100 that increases the performance of the optical fiber cable 100. The relationship between the outer diameter of the optical fiber cable 100, the number of fibers of the optical fibers 116, and the outer diameter of each fiber of the optical fibers 116 may increase compactness of the optical fiber cable 100 that may be easily installed and deployed in variety of applications. For example, in a telecommunication network. The optical fiber cable 100 being compact may be easily deployed in existing conduits of the telecommunication network. The relationship between the outer diameter of the optical fiber cable 100, the number of fibers of the optical fibers 116, and the outer diameter of each fiber of the optical fibers 116 may be carefully selected that may improve flexibility, bend resistance, and signal capacity and may reduce attenuation. The relationship between the outer diameter of the optical fiber cable 100, the number of fibers of the optical fibers 116, and the outer diameter of each fiber of the optical fibers 116 may be carefully selected that may facilitate easier splicing and terminating of the optical fiber cable 100 that may reduce installation time and cost involved in installation of the optical fiber cable 100.
In some aspects of the present disclosure, each buffer tube of the plurality of buffer tubes 106 may have a thickness that may be less than 120 µm. In some preferred examples, each buffer tube of the plurality of buffer tubes 106 may have the thickness that may be 100 µm with a tolerance value of + 10 µm. In some other preferred examples, each buffer tube of the plurality of buffer tubes 106 may have the thickness that may be 80 µm with a tolerance value of + 10 µm. The thickness of each buffer tube of the plurality of buffer tubes 106 may be kept less than 120 µm to reduce the diameter and weight of the optical fiber cable 100, which may make the optical fiber cable 100 more compact and easier to install. The optical fiber cable 100 being compact in size may be easily deployed in underground and aerial installations. Further, the thickness of each buffer tube of the plurality of buffer tubes 106 may be kept less than 120 µm to improve fill factor of the optical fiber cable 100. The thickness of each buffer tube of the plurality of buffer tubes 106 may be kept less than 120 µm to provide a hardness grade that may be greater than 70 in a hardness scale SHORE D. The hardness grade greater than 70 in the hardness scale SHORE D may prevent deformation of the optical fiber cable 100. Further, the hardness grade greater than 70 in the hardness scale SHORE D may provide requisite mechanical strength that may facilitate the optical fiber cable 100 to withstand mechanical stresses and bending. Furthermore, the SHORE D hardness of the optical fiber cable 100 being greater than 70 may prevent damage to the optical fiber cable while bending.
In some aspects of the present disclosure, each buffer tube of the plurality of buffer tubes 106 may be made up of a material, such as but not limited to, polybutylene terephthalate (PBT). Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for each buffer tube of the buffer tubes 106, without deviating from the scope of the present disclosure.
In some aspects of the present disclosure, the material of each buffer tube of the plurality of buffer tubes 106 may have a lower viscosity. Specifically, the material of each buffer tube of the plurality of buffer tubes 106 may have a viscosity that may be less than 150 cubic centimeter per gram (cm3/g) at 23°C. Preferably, the material of each buffer tube of the plurality of buffer tubes 106 may have the viscosity that may be 145 cm3/g at 23°C. The viscosity of the material of each buffer tube of the buffer tubes 106 being less than 150 cm3/g may advantageously ease processing of the material. The viscosity of the material of each buffer tube of the buffer tubes 106 being less than 150 cm3/g may advantageously allow to achieve low thickness of 100 µm. The lower viscosity of the material of each buffer tube of the buffer tubes 106 may advantageously allow manufacturing of the optical fiber cable 100 with a reduced diameter and helps to keep high fill factor for the optical fiber cable 100. In some aspects of the present disclosure, the optical fibers 116 may be arranged as one of, (i) loose fibers, (ii) ribbon fibers, and (iii) intermittently bonded ribbons. Aspects of the present disclosure are intended to include and/or otherwise cover any type of arrangement of the optical fibers 116, without deviating from the scope of the present disclosure.
The plurality of swellable yarns 108 may be disposed around the CSM 104. Specifically, the plurality of swellable yarns 108 may be disposed on a periphery of the CSM 104. Each swellable yarn of the plurality of swellable yarns 108 may be a super absorbent polymer impregnated high tenacity polyester fiber base swellable yarn. The plurality of swellable yarns 108 may be adapted to block water. Specifically, the swellable yarns 108 may provide water resistance to the optical fibers 116 over longer period of time. The plurality of swellable yarns 108 may facilitate complete insulation and may protect the optical fiber cable 100 against water ingression.
The binder yarn 110 may enclose the CSM 104, the buffer tubes 106, and the swellable yarns 108. The binder yarn 110 may be adapted to bind the buffer tubes 106 around CSM 104. The binder yarn 110 may therefore advantageously ensure that the CSM 104, the buffer tubes 106, and the swellable yarns 108 may remain intact at their respective locations or positions within the optical fiber cable 100.
The plurality of ripcords 112 may be disposed on the binder yarn 110. Specifically, the plurality of ripcords 112 may be disposed on outer periphery of the binder yarn 110 and beneath the sheath 114. The plurality of ripcords 112 may be utilized to tear apart sheath 114 to access the buffer tubes 106 and the optical fibers 116 inside the optical fiber cable 100.
In some aspects of the present disclosure, each ripcord of the plurality of ripcords 112 may be made up of a material such as, but not limited to, aramid yarn, fiberglass epoxy, and steel. Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for each ripcord of the ripcords 112, without deviating from the scope of the present disclosure.
The sheath 114 may enclose the binder yarn 110. Specifically, the sheath 114 may be arranged and/or disposed on a periphery of the binder yarn 110. In some aspects of the present disclosure, the sheath 114 may be made up of a material such as, but not limited to, polyethylene, thermoplastic polyurethane, low smoke zero halogen (LSZH), and the like. Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for the sheath 114, without deviating from the scope of the present disclosure.
FIG. 2 illustrates a cross-sectional view of another optical fiber cable 200. The optical fiber cable 200 may be substantially similar to the optical fiber cable 100, with like elements referenced with like reference numerals. However, the optical fiber cable 200 shows three concentric layers of the plurality of buffer tubes 106. Specifically, the plurality of buffer tubes 106 may be stranded around the CSM 104 of the optical fiber cable 200 in three concentric layers. Further, various constructional features of the optical fiber cable 200 may be similar to the various constructional features of the optical fiber cable 100 as described hereinabove, apart from the difference in number of concentric layers in which the plurality of buffer tubes 106 are stranded.
FIG. 3 illustrates a cross-sectional view of an optical fiber 300. The optical fiber 300 is one of the one or more optical fibers 116 of the optical fiber cable 100. The optical fiber 300 may have a core 302, a clad layer 304, one or more protective coating layer 306 of which a primary coating layer 306a and a secondary coating layer 306b is shown.
The core 302 may form a central region or portion of the optical fiber 300. The clad layer 304 may be deposited on the core 302. The clad layer 304 along with core 302 may be referred to as a glass layer. The one or more protective coating layers 306 may be deposited on the clad layer 304. Specifically, the primary coating layer 306a may be deposited on the clad layer 304 and the secondary coating layer 306b may be deposited on the primary coating layer 306a.
In some aspects of the present disclosure, the core 302 may be made up of a material such as, but not limited to, glass. Aspects of the present disclosure are intended to include and/or otherwise cover any type of material for the core 302, without deviating from the scope of the present disclosure.
In some aspects of the present disclosure, each optical fiber of the one or more optical fibers 116 may have a glass diameter of utmost126 µm. Specifically, the glass diameter may correspond to a diameter of the glass layer that has the clad layer 304 along with core 302. In some aspects of the present disclosure, the thickness of each buffer tube of the buffer tubes 106 may be less than the diameter of the glass layer. Specifically, the thickness of each buffer tube of the buffer tubes 106 may be 100 µm, which is less than the diameter of the glass layer i.e., 125 µm. The thickness of each buffer tube of the buffer tubes 106 being less than the diameter of the glass layer may facilitate easy removal of the optical fibers 116 from each buffer tube of the buffer tubes 106, which may advantageously allow easy maintenance and repair of the optical fiber cable 100. In other words, easy removal of the optical fibers 116 may allow a technician to access the optical fibers 116 without damaging.
In some aspects of the present disclosure, the one or more protective layers 306 may have a lower combined thickness. For example, the one or more protective layers 306 may have a combined thickness that may be less than 30 µm. The combined thickness of the one or more protective layer 306 being less than 30 µm may advantageously reduce an overall diameter of the optical fiber 300. Further, the combined thickness of the one or more protective layers 306 being less than 30 µm may advantageously provide high fill factor for the optical fiber cable 100. The one or more protective coating layers 306 may have a combined thickness of less than 30 micrometers (µm). In some aspects of the present disclosure, the primary coating layer 306a may have a thickness in a range of 2.5 µm to 10 µm. Specifically, the thickness of the primary coating layer 306a of less than 2.5 µm may not protect the optical fiber 300 and the thickness of the primary coating layer 306a greater than 10 µm may increase the overall diameter and bulkiness of the optical fiber 300.
In some aspects of the present disclosure, the primary coating layer 306a may have a young’s modulus that may be in a range between 0.1 megapascal (MPa) and 0.4 MPa. Further, the primary coating layer 306a may have a diameter that may be in a range between 130 µm and 145 µm that may ensure adequate protection of the optical fibers 116 from external factors. The diameter of the primary coating layer 306a being in the range between 130 µm and 145 µm may strike a balance between protection and efficiency of the optical fiber cable 100 and thereby allowing high quality signal transmission without compromising performance of the optical fiber 300. The young’s modulus of the primary coating layer 306a being in the range between 0.1 MPa and 0.4 MPa may provide sufficient rigidity to the primary coating layer 306a and may simultaneously provide flexibility to the primary coating layer 306a. The young’s modulus in the range between 0.1 MPa and 0.4 MPa may allow the primary coating layer 306a to serve as a cushion between the glass layer and the secondary coating layer 306b to maintain shape of the optical fiber 300. The young’s modulus in the range between 0.1 MPa and 0.4 MPa and the diameter of the primary coating layer 306a in the range 130 µm and 145 µm may advantageously facilitate the optical fiber cable 100 to have an optimal balance between protection, flexibility, and strength. This may ensure adequate protection of the optical fiber cable 100 from external factors and simultaneously maintaining flexibility that may facilitate the optical fiber cable 100 to withstand bending and mechanical stresses without causing any damage to the optical fiber cable 100, especially when the outer diameter of the optical fiber cable 100 is less than 190 µm. The young’s modulus in the range between 0.1 MPa and 0.4 MPa and the diameter of the primary coating layer 306a in the range 130 µm and 145 µm may further advantageously facilitate high quality signal transmission and reliable performance of the optical fiber 300 in a variety of applications.
In some preferred aspects of the present disclosure, the secondary coating layer 306b may have a thickness that may be in a range between 2.5 µm and 17.5 µm. The thickness of the secondary coating layer 306b less than 2.5 µm may not protect the optical fiber 300. The thickness of the secondary coating layer 306b greater than 17.5 µm may increase the overall diameter of the optical fiber 300.
In some aspects of the present disclosure, the secondary coating layer 306b may have a modulus that may be greater than 1.2 Gigapascal (GPa). In other words, the secondary coating layer (306b) has an in-situ modulus of greater than 1.2 Giga Pascal (GPa). The secondary coating layer 306b having the modulus less than 1.2 GPa may not be strong and therefore may not protect the optical fiber 300 during handling. In some aspects of the present disclosure, the secondary coating 306b may be a colored coating layer which helps in further reducing the overall diameter of the optical fiber 300.
In some aspects of the present disclosure, combination of (i) the combined thickness of the one or more protective layers 306 may be less than 30 µm, (ii) the modulus of the secondary coating layer 306b may be greater than 1.2 GPa, and (iii) the macro bending loss of each optical fiber of the optical fibers 116 may be less than 0.03 dB at the wavelength of 1550 nm, may increase the fill factor of the optical fiber cable 100. The modulus of secondary coating ensures optimized level of stiffness over the optical fiber 300 to protect it from abrasion, which further contribute to the cable’s mechanical integrity, especially when manufactured with small diameter optical fibers 300. The combination of the primary coating and secondary coating layers 306 within the specified thickness ranges provides unique protection for the optical fibers, which can be crucial in ensuring their performance and durability inside the optical fiber cable 100.
In some aspects of the present disclosure, combination of (i) properties of the optical fibers 116 (e.g., the optical fiber 300), and (ii) optimized thickness of each buffer tube of the buffer tubes 106 may increase the fill factor of the optical fiber cable 100.
FIG. 4 illustrates a cross-sectional view of another optical fiber 400. The optical fiber 400 is one of the one or more optical fibers 116 of the optical fiber cable 100. The optical fiber 400 may be substantially similar to the optical fiber 300, with like elements referenced with like reference numerals. However, the optical fiber 400 has an additional layer 402. Further, various constructional features of the optical fiber 400 may be similar to the various constructional features of the optical fiber cable 300 as described hereinabove, apart from the difference in incorporation of the additional layer 402 in the optical fiber 400. The additional layer 402 may be coated around the one or more protective layers 306. Specifically, the additional layer 402 may be coated around the secondary coating layer 306b. The additional layer 402 may be a color layer.
In some aspects of the present disclosure, the outer diameter of the optical fiber cable 100 may be less than 40 times of an outer diameter of the additional layer 402. In some other aspects of the present disclosure, the outer diameter of the optical fiber cable 100 may be around 37 times of the outer diameter of the additional layer 402. This may allow to increase a packing density of the optical fibers 116 that may be desired in applications having compact constructions or spaces.
Thus, the optical fiber cable 100 may have a reduced diameter, reduced weight, and better blowing performance. By virtue of high fill factor of the optical fiber 100, the optical fiber cable 100 may enclose a greater number of optical fibers of the optical fibers 116. The dual layer design of the optical fiber cable 100 may enable overall reduction in size of the optical fiber cable 100. Further, by virtue of low thickness of the protective layer 306, a greater number of optical fibers may be packed or embedded in less space in each buffer tube of the buffer tubes 106.
The foregoing descriptions of specific embodiments of the present technology have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present technology to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present technology and its practical application, to thereby enable others skilled in the art to best utilize the present technology and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present technology.
While several possible embodiments of the invention have been described above and illustrated in some cases, it should be interpreted and understood as to have been presented only by way of illustration and example, but not by limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments.
,CLAIMS:I/We Claim(s):
1. An optical fiber cable (100) comprising:
a central strength member (CSM) (104);
a plurality of buffer tubes (106) stranded around the CSM (104) such that each buffer tube of the plurality of buffer tubes (106) encloses one or more optical fibers (116) such that each optical fiber of the one or more optical fibers (116) has one or more protective coating layers (306) that has a combined thickness of less than 30 micrometers (µm), where each optical fiber of the one or more optical fibers (116) has a glass diameter of utmost 126 µm, where the glass diameter includes a core (302) and a cladding (304), where the plurality of buffer tubes (106) are stranded in at-least two concentric layers around the CSM (104) and the optical fiber cable (100) has a fill factor of greater than 7 fibers/millimeter square (f/mm2); and
a sheath (114) that surrounds the CSM (104) and the plurality of buffer tubes (106).

2. The optical fiber cable (100) of claim 1, where the one or more protective coating layers (306) comprising a primary coating layer (306a) and a secondary coating layer (306b), where (i) the primary coating layer (306a) has a thickness in a range of 2.5 µm to 10 µm and the secondary coating layer (306b) has a thickness in a range of 2.5 µm to 17.5 µm.

3. The optical fiber cable (100) of claim 1, where a diameter of each optical fiber (116) of the one or more optical fiber is less than 190 µm.

4. The optical fiber cable (100) of claim 3, where the secondary coating layer (306b) has an in-situ modulus of greater than 1.2 Giga Pascal (GPa).

5. The optical fiber cable (100) of claim 1, where each buffer tube of the plurality of buffer tubes (106) is made up of a material having a viscosity of less than 150 cubic centimeter per gram (cm3/g) at 23°C.

6. The optical fiber cable (100) of claim 1, where each buffer tube of the plurality of buffer tubes (106) has a thickness of less than 120 µm.

7. The optical fiber cable (100) of claim 1, where each optical fiber of the one or more optical fibers (116) has a macro-bending loss of less than 0.03 Decibel (dB) at 1550 nanometers (nm) when deployed with 10 turns around a mandrel of 15 mm radius.

8. The optical fiber cable (100) of claim 1, where a zero-dispersion slope of the optical fiber cable (100) is less than or equal to 0.092 temporal spread per unit propagation distance per square unit pulse spectral width nanometers square (ps/nm2-Km).

9. The optical fiber cable (100) of claim 1, where each optical fiber of the one or more optical fibers (116) has a mode field diameter (MFD) of 8.6±0.4 µm at a wavelength of 1310 nm.

10. The optical fiber cable (100) of claim 1, where the plurality of buffer tubes (106) in each of the concentric layers are stranded at a lay-length of at least 80 mm.

11. The optical fiber cable (100) of claim 1, where the plurality of buffer tubes (106) in two adjacent concentric layers are stranded at a lay-length difference of at least 15 mm.

12. The optical fiber cable (100) of claim 1, where the plurality of buffer tubes (106) in each of the concentric layers are bound by two or more binders wound at a lay-length of 25±10 mm.