Single-mode optical fiber with thin coating for high-density fiber optic cables and interconnects

Abstract

An optical fiber is provided that includes: a core region, a cladding region having a radius less than about 62.5 microns; a polymeric coating including a high modulus layer and a low modulus layer, wherein the low modulus inner coating has a thickness ranging from 4 microns to 20 microns, the low modulus inner coating has a modulus less than or equal to about 0.35 MPa, the high modulus coating has a thickness ranging from 4 microns to 20 microns, the high modulus inner coating has a modulus greater than or equal to about 1.6 GPa, and wherein the optical fiber has a puncture resistance greater than 20 g, and wherein the optical fiber has a microbend attenuation penalty less than 0.03 dB / km, and wherein the coated optical fiber has an outer diameter less than or equal to 175 microns.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 054,563, filed July 21, 2020, pursuant to 35 USC §119, the contents of which are based and incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure pertains to single-mode optical fiber. More specifically, it pertains to small-diameter single-mode optical fiber. Most specifically, it pertains to small-diameter single-mode optical fiber with reduced coating thickness without significantly reducing puncture resistance. Background Technology

[0004] Fiber optic technology is penetrating data centers due to the high bandwidth, low latency, low power consumption, and EMI / RFI immunity required by cloud computing and the Internet of Things (IoT). Future hyperscale data centers require specialized capabilities, such as 100K servers distributed across 500,000 square feet, creating a need for increased capacity, flexibility, and efficiency in interconnect solutions within the data center. Consequently, a large number of interconnect components are required within data centers. Ribbon cables allow for higher fiber counts; however, these higher fiber counts necessitate smaller diameter fibers to be installed in ribbon cables. For example, replacing a 250μm diameter double-layer acrylate-coated ribbon cable with a 125μm overall diameter bare fiber ribbon cable results in a volume reduction of at least 75%. Furthermore, processing bare fiber into ribbon cables can lead to fiber breakage.

[0005] Furthermore, submarine fiber optic cables are designed to carry telecommunication signals across land, ocean, and sea. In recent years, the number of telecommunication signals on submarine cables has increased dramatically, and they now carry over 90% of intercontinental communication signals. Therefore, the demand for the transmission capacity of these submarine cables has increased, driven by the growth of internet communication between different continents. Traditionally, this capacity growth has been driven by methods such as increasing the bandwidth capacity per fiber while increasing the bit rate or using dense wavelength division multiplexing (DWDM) while maintaining a small fiber count (typically between 4 and 8 fiber pairs).

[0006] However, implementing these advanced transmission technologies has led to optical repeaters in such systems consuming more power than the terminals can supply. This power limitation forces submarine system designers to use higher fiber counts, which in turn necessitates smaller diameter fibers to fit within the limited space inside the optical repeaters. Preferably, the cladding diameter of these fibers needs to be maintained at 125 micrometers to facilitate fusion splicing with conventional single-mode fibers, meaning a smaller diameter is achieved by reducing the thickness of the protective coating. This thinner coating needs to have a high modulus combined with a sufficiently large cross-sectional area to ensure high resistance to puncture and abrasion.

[0007] The inventors sought to improve upon the aforementioned situation. Therefore, they developed a thin-coated single-mode optical fiber with sufficiently high mechanical reliability. Summary of the Invention

[0008] According to a first embodiment of this disclosure, this specification extends to optical fibers having: a core region; a cladding region surrounding the core region, the cladding region comprising: an inner cladding directly adjacent to the core region, and an outer cladding surrounding the inner cladding, wherein the radius of the cladding region is less than about 62.6 micrometers; and a polymer coating comprising a high-modulus coating layer surrounding the cladding region and a low-modulus coating layer disposed between the cladding region and the high-modulus coating layer, wherein the thickness of the low-modulus coating inner layer ranges from 4 micrometers to 20 micrometers, and the modulus of the low-modulus coating inner layer is less than or equal to about 0.35 MPa; the thickness of the high-modulus coating layer ranges from 4 micrometers to 20 micrometers, and the modulus of the high-modulus coating inner layer is greater than or equal to about 1.6 GPa; wherein the puncture resistance of the optical fiber is greater than 20 g; wherein the microbending attenuation penalty of the optical fiber is less than 0.03 dB / km; and wherein the outer diameter of the coated optical fiber is less than or equal to 175 micrometers, wherein the puncture resistance of the optical fiber is calculated by the following equation: P R =P0+C1E s A s , where A S It is the cross-sectional area of ​​the high-modulus coating, where E S This refers to the elastic modulus of the high-modulus coating, where P0 is a coefficient with a value of 11.3g, and C1 is a coefficient with a value of 2.1g / MPa / mm. 2 The coefficient of is calculated using the following equation for the micro-bending attenuation penalty of the optical fiber: Where f0 is the average lateral pressure of the outer surface in contact with the high-modulus coating, and σ is the standard deviation of the roughness of the outer surface in contact with the high-modulus coating. And among them, And among them, And among them, Among them, R g R is the radius of the glass.s It is the outer radius of the high modulus outer coating, t p It is the thickness of the low-modulus inner coating, t s It is the thickness of the high modulus outer coating, E g It is the elastic modulus of glass, E p It is the elastic modulus of the low-modulus inner coating, and E S It is the elastic modulus of the high modulus coating.

[0009] According to the second embodiment of this disclosure, the optical fiber of the first embodiment has a microbending attenuation penalty of ≤0.01dB / km.

[0010] According to the third embodiment of this disclosure, the optical fiber of the first embodiment has a microbending attenuation penalty of ≤0.007dB / km.

[0011] According to the fourth embodiment of this disclosure, the optical fiber of the first embodiment has a microbending attenuation penalty of ≤0.003dB / km.

[0012] According to the fifth embodiment of this disclosure, the optical fiber of the first embodiment has a puncture resistance of ≥25g.

[0013] According to the sixth embodiment of this disclosure, the optical fiber of the first embodiment has a puncture resistance of ≥30g.

[0014] According to the seventh embodiment of this disclosure, the optical fiber of the first embodiment has a cladding region radius of less than 52.5 micrometers and an optical fiber puncture resistance greater than 40g.

[0015] According to the eighth embodiment of this disclosure, the optical fiber of the first embodiment has a thickness of 9 micrometers to 18 micrometers for the high-modulus coating layer.

[0016] According to the ninth embodiment of this disclosure, the optical fiber of the first embodiment has an attenuation of less than 0.20 dB / km.

[0017] According to the tenth embodiment of this disclosure, the optical fiber of the first embodiment has a mode field diameter ≥ 8.6 at 1310 nm.

[0018] According to the 11th embodiment of this disclosure, this specification extends to optical fibers having: a core region; a cladding region surrounding the core region, the cladding region comprising: an inner cladding directly adjacent to the core region, and an outer cladding surrounding the inner cladding, wherein the radius of the cladding region is approximately 45 micrometers to 55 micrometers; and a polymer coating comprising a high-modulus coating layer surrounding the cladding region and a low-modulus coating layer disposed between the cladding region and the high-modulus coating layer, wherein the thickness of the low-modulus coating inner layer ranges from 6 micrometers to 20 micrometers, and the modulus of the low-modulus coating inner layer is less than or equal to about 0.35 MPa; the thickness of the high-modulus coating layer ranges from 12 micrometers to 18 micrometers, and the modulus of the high-modulus coating inner layer is greater than or equal to about 1.6 GPa; and wherein the puncture resistance of the optical fiber is greater than 30 g; and wherein the microbending attenuation penalty of the optical fiber is less than 0.03 dB / km; and wherein the outer diameter of the coated optical fiber is less than or equal to 175 micrometers, wherein the puncture resistance of the optical fiber is calculated by the following equation: P R =P0+C1E s A s , where A S It is the cross-sectional area of ​​the high-modulus coating, where E S This refers to the elastic modulus of the high-modulus coating, where P0 is a coefficient with a value of 11.3g, and C1 is a coefficient with a value of 2.1g / MPa / mm. 2 The coefficient of is calculated using the following equation for the micro-bending attenuation penalty of the optical fiber: Where f0 is the average lateral pressure of the outer surface in contact with the high-modulus coating, and σ is the standard deviation of the roughness of the outer surface in contact with the high-modulus coating. And among them, And among them, And among them, Among them, R g R is the radius of the glass. s It is the outer radius of the high modulus outer coating, t p It is the thickness of the low-modulus inner coating, t s It is the thickness of the high modulus outer coating, E g It is the elastic modulus of glass, E p It is the elastic modulus of the low-modulus inner coating, and E S It is the elastic modulus of the high modulus coating.

[0019] According to the 12th embodiment of this disclosure, the optical fiber of the 11th embodiment has a microbending attenuation penalty of ≤0.01dB / km.

[0020] According to the 13th embodiment of this disclosure, the optical fiber of the 11th embodiment has a microbending attenuation penalty of ≤0.007dB / km.

[0021] According to the 14th embodiment of this disclosure, the optical fiber of the 11th embodiment has a microbending attenuation penalty of ≤0.003dB / km.

[0022] According to the 15th embodiment of this disclosure, the optical fiber of the 11th embodiment has a puncture resistance of ≥25g.

[0023] According to the 16th embodiment of this disclosure, this specification extends to optical fibers having: a core region; a cladding region surrounding the core region, the cladding region comprising: an inner cladding directly adjacent to the core region, and an outer cladding surrounding the inner cladding; a polymer coating with a thickness of 25 μm or less, wherein the polymer coating comprises a high-modulus coating layer surrounding the cladding region, wherein the Young's modulus of the high-modulus coating layer is 1.5 GPa or greater, and wherein the outer diameter of the coated optical fiber is less than or equal to 175 μm.

[0024] According to the 17th embodiment of this disclosure, the optical fiber of the 16th embodiment further includes a low-modulus coating layer surrounding the cladding region, wherein the low-modulus coating layer has a Young's modulus of 0.5 MPa or less and is disposed between the cladding region and the high-modulus coating layer.

[0025] According to the 18th embodiment of this disclosure, the optical fiber of the 16th embodiment has a ratio of the thickness of the low-modulus coating layer to the thickness of the high-modulus coating layer ranging from 0.8 to 1.2.

[0026] According to the 19th embodiment of this disclosure, this specification extends to a coating method for optical fibers, comprising: drawing an optical fiber from a drawing furnace along a first vertical path; guiding the optical fiber through a coating system, wherein a polymer coating is applied to the optical fiber, wherein the coating system includes: an inlet, a sizing mandrel with a diameter of 129 μm to 203 μm opposite the inlet, and a coating chamber disposed between the inlet and the sizing mandrel, wherein the coating chamber is filled with a coating material in liquid form; and curing the coated optical fiber to form an outer diameter of the coated optical fiber less than or equal to 175 μm.

[0027] According to the 20th and 19th embodiments of this disclosure, the optical fiber has a polymer coating having a concentricity of greater than 70%.

[0028] Other features and advantages are set forth in the following detailed description, some of which will be readily understood by those skilled in the art, or will be recognized by practicing the embodiments described in the text description and its claims and drawings.

[0029] It should be understood that the general description above and the detailed description below are merely exemplary, intended to provide an overall assessment or framework for understanding the nature and characteristics of the claims.

[0030] The accompanying drawings, which are incorporated in and form part of this specification, provide further understanding. The drawings are schematic representations of selected aspects of this disclosure and, together with the specification, serve to explain the principles and operation of the methods, products, and compositions belonging to this disclosure. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a coated optical fiber according to some embodiments of the present disclosure.

[0032] Figure 2 This is a schematic diagram of a representative optical fiber strip according to some embodiments of the present disclosure.

[0033] Figure 3 This is a schematic diagram of a representative optical fiber cable according to some embodiments of the present disclosure.

[0034] Figure 4 The cross-section of a single-mode optical fiber according to some embodiments of this disclosure is shown.

[0035] Figure 5 This shows the relative refractive index distribution of a single-mode optical fiber according to some embodiments of the present disclosure.

[0036] Figure 6 This shows the relative refractive index distribution of an optical fiber according to an embodiment of this disclosure.

[0037] Figure 7 This shows the relative refractive index distribution of an optical fiber according to an embodiment of this disclosure.

[0038] Figure 8 This shows the puncture load strength as a function of the cross-sectional area of ​​the high modulus coating, according to the present disclosure.

[0039] Figure 9 This shows the relative refractive index distribution of a single-mode optical fiber according to some embodiments of this disclosure.

[0040] Figure 10 This is a schematic diagram of the core and cladding mode distribution of an optical fiber with a thick coating according to some embodiments of this disclosure.

[0041] Figure 11 This is a schematic diagram of the core and cladding mode distribution of an optical fiber with a thin coating according to some embodiments of the present disclosure.

[0042] Figure 12This disclosure illustrates the effect of coating material viscosity and die size on coating thickness in some embodiments of the present disclosure.

[0043] Figure 13 This displays an exemplary parameter window for forming the final coating diameter of a target according to some embodiments of this disclosure.

[0044] Figure 14 This disclosure shows the standard deviation of coating thickness derived from the viscosity of various coating materials for different die head size systems according to some embodiments of the present disclosure.

[0045] Figure 15 This disclosure shows the effect of drawing speed on coating thickness in some embodiments of the present disclosure.

[0046] Figure 16 The diagram shows the correlation between lubrication pressure and die size for a range of coating material viscosities according to some embodiments of this disclosure.

[0047] Figure 17 This disclosure illustrates the correlation between lubrication pressure and drawing speed in some embodiments of the present disclosure.

[0048] Figure 18 This shows the relative refractive index distribution of a single-mode optical fiber according to some embodiments of this disclosure.

[0049] Figure 19 This disclosure shows the relationship between the microbending attenuation penalty (MAP) and the low-modulus coating thickness of an optical fiber having a stepped refractive index, a recessed auxiliary fiber distribution, and a cladding diameter of 100 micrometers, according to some embodiments of the present disclosure.

[0050] Figure 20 This disclosure illustrates the relationship between the microbending attenuation penalty (MAP) and the low-modulus coating thickness for different moduli of the high-modulus coating, the recessed auxiliary fiber distribution, and the fiber with a cladding diameter of 100 micrometers.

[0051] Figure 21 This disclosure illustrates the relationship between the puncture resistance of optical fibers with different moduli of high-modulus coatings, recessed auxiliary fiber distribution, and 100-micron cladding diameter, and the thickness of low-modulus coatings, according to some embodiments of the present disclosure.

[0052] Figure 22 This disclosure illustrates the relationship between the microbending attenuation penalty (MAP) and the low-modulus coating thickness for different moduli of the low-modulus coating, the recessed auxiliary fiber distribution, and the fiber with a cladding diameter of 100 micrometers. Detailed Implementation

[0053] This disclosure is provided as an implementation guide and can be more readily understood by referring to the following description, drawings, embodiments, and claims. Therefore, those skilled in the art will recognize and appreciate that various changes can be made to various aspects of the embodiments described herein while still obtaining beneficial results. It will also be apparent that some of the beneficial results desired by this embodiment can be obtained by selecting some features without utilizing others. Therefore, those skilled in the art will recognize that many changes and modifications are possible, and in some cases even desired, and are part of this disclosure. Therefore, it is to be understood that, unless otherwise stated, this disclosure is not limited to the specific compositions, articles, apparatus, and methods disclosed. It is also to be understood that the terminology used herein is for descriptive purposes only and not for limitation.

[0054] Many terms are used in this specification and the following claims, and these terms should be defined to have the following meanings:

[0055] "Optical fiber" refers to a waveguide with a glass portion surrounding a coated structure. The glass portion includes a core and a cladding, and is referred to herein as "glass fiber".

[0056] "Radial position", "radius", or radial coordinate "r" refers to the radial position relative to the centerline of the optical fiber (r=0).

[0057] Unless otherwise stated, “refractive index” refers to the refractive index at a wavelength of 1550 nm.

[0058] "Refractive index distribution" refers to the relationship between refractive index or relative refractive index and radius. For the relative refractive index distribution with stepped boundaries between adjacent core and / or cladding regions shown in this paper, normal variations in processing conditions can preclude obtaining sharp stepped boundaries at the interface of adjacent regions. It should be understood that while this paper may depict the boundaries of the refractive index distribution as a stepped change in refractive index, in practice, the boundaries may be circular or deviate from the perfect stepped functional characteristics in any other way. It should also be understood that the relative refractive index value may vary with radial position within the core region and / or any cladding region. When the relative refractive index varies with radial position within a specific region of the fiber (e.g., the core region and / or any cladding region), it can be represented by its actual or approximate functional dependence, or by its value at a specific location within the region, or by an average value applicable to the entire region. Unless otherwise stated, when the relative refractive index of a region (e.g., the core region and / or any cladding region) is expressed as a single value or as a parameter applicable to the region as a whole (e.g., Δ or Δ%), it should be understood that the relative refractive index in that region is constant or approximately constant, and the single value, or the single value or parameter, represents the average of non-constant relative refractive indices depending on the radial position within that region. For example, if “i” is a region of the glass fiber, unless otherwise stated, the parameter Δ i This refers to the average relative refractive index in the region as defined by the following equation (1). Whether as a result of design or normal manufacturing variations, the relative refractive index may be tilted, curved, or otherwise non-constant in its dependence on radial position.

[0059] As used in this paper, “relative refractive index” is defined as in equation (1):

[0060]

[0061] Unless otherwise stated, n in the formula i It is the radial position r in the glass fiber i The refractive index at that point; and unless otherwise specified, n ref This is the refractive index of pure silica glass. Therefore, as used herein, the relative refractive index percentage is relative to pure silica glass (a value of 1.444 at a wavelength of 1500 nm). Unless otherwise stated, the relative refractive index as used herein is expressed in Δ (or “Δ”) or Δ% (or “Δ%”), and its value is in “%”. The relative refractive index can also be expressed as Δ(r) or Δ(r)%.

[0062] The average relative refractive index (Δ) of a region of an optical fiber 平均 The following is determined by equation (2):

[0063]

[0064] In the formula, r 内 r is the inner radius of the region. 外 Δ is the outer radius of the region, and Δ(r) is the relative refractive index of the region.

[0065] Commercially available devices, such as the IFA-100 fiber refractive index analyzer (Interfiber Analysis LLC, Sharon, MA USA) or the S14 refractive index analyzer (Photon Kinetics, Inc., Beaverton, Oregon USA), can be used to measure the refractive index distribution of optical fibers. These devices measure the refractive index (n(r) - n) relative to a reference refractive index. meas In the formula, the reference refractive index n is used for measurement. meas This is the calibrated refractive index, typically matched to oil or pure silica glass. The measurement wavelength can be: 632.5 nm, 654 nm, 677.2 nm, 654 nm, 702.3 nm, 729.6 nm, 759.2 nm, 791.3 nm, 826.3 nm, 864.1 nm, 905.2 nm, 949.6 nm, 997.7 nm, 1050 nm, or any wavelength in between. The absolute refractive index n(r) is then used to calculate the relative refractive index as defined in equation (1).

[0066] The term "α-distribution" or "α-distribution" refers to the relative refractive index distribution Δ(r), which has the functional form defined by equation (3):

[0067]

[0068] In the formula, r o It is the radial position when Δ(r) is at its maximum value, Δ(r0)>0, r z >r0 is the radial position when Δ(r) decreases to its minimum value, and the range of r is r i ≤r≤r f In the formula, r i It is the initial radial position of the α-distribution, r f Let Δ be the final radial position of the α-distribution, and α be a real number. In this paper, Δ(r0) of the α-distribution can be referred to as Δ... max Or, when referring to a specific region i of the optical fiber, it is called Δ. imax When the relative refractive index distribution in the fiber core region is described by the α-distribution, and r0 is located at the centerline (r = 0) and rz Given the outer radius r1 of the corresponding fiber core region and Δ1(r1)=0, equation (3) simplifies to equation (4):

[0069]

[0070] When the core region has the refractive index described by equation (4), the outer radius r1 can be determined from the measured relative refractive index distribution as follows: Maximum relative refractive index Δ 1max α and outer radius r 1est The estimated value was obtained by examining the measured relative refractive index distribution and was used to generate r = -r. 1est with r = r 1est The trial function Δ between 试探 .like Figure 5 and 6 The diagram shows the relative refractive index distribution of a representative glass fiber having a core described by the α-distribution, according to an embodiment of this disclosure.

[0071] The definition of "depression volume" is as follows:

[0072]

[0073] In the formula, r 凹陷,内 It is the inner radius of the concave region of the refractive index distribution, r 凹陷,外 It is the outer radius of the concave region of the refractive index distribution, Δ 凹陷 (r) is the relative refractive index of the recessed region of the refractive index distribution, and r is the radial position in the optical fiber. The recess volume is an absolute value and a positive number, and is expressed in this paper in the following units: %Δmicrometer. 2 %Δ-micron 2 %Δ-μm 2 or %Δμm 2 These units are used interchangeably in this paper. The recessed region is also referred to as the recessed refractive index cladding region in this paper, and the recessed volume is also referred to as V3 in this paper.

[0074] The “mode field diameter” or “MFD” of an optical fiber is defined by equation (6):

[0075] MFD = 2w

[0076]

[0077] In the formula, f(r) is the transverse component of the electric field distribution of the optical signal, and r is the radial position in the fiber. The term "mode field diameter" or "MFD" depends on the wavelength of the optical signal, and is described herein for wavelengths of 1310 nm, 1550 nm, and 1625 nm. When referring to mode field diameter, the wavelength will be specified. Unless otherwise stated, mode field diameter refers to the LP at a specific wavelength. 01 model.

[0078] The "effective area" of an optical fiber is defined as shown in equation (7):

[0079]

[0080] In the formula, f(r) is the transverse component of the electric field of the optical signal, and r is the radial position in the optical fiber. "Effective area" or "A" eff "It depends on the wavelength of the optical signal, and it should be understood that in this article, we are referring to the case of a wavelength of 1550nm."

[0081] As used in this article, the term "attenuation" refers to the loss of optical power as a signal travels along an optical fiber. Attenuation is measured using the IEC-60793-1-40 standard ("Attenuation measurement methods").

[0082] In this document, the bending resistance of optical fibers can be measured by induced attenuation under specified test conditions as defined in IEC-60793-1-47 (“Measurement methods and test procedures—Macrobending loss”), referred to as “bending loss”. For example, test conditions may include deploying or winding the optical fiber around a mandrel of a specified diameter one or more times, such as one turn around a mandrel of 15 mm, 20 mm, or 30 mm or a similar diameter (e.g., “1×15 mm diameter bending loss”, “1×20 mm diameter bending loss”, or “1×30 mm diameter bending loss”) and measuring the increase in attenuation with each turn.

[0083] As used in this article, "optical cable cutoff wavelength" or "optical cable cutoff" refers to the 22m optical cable cutoff test specified in the IEC 60793-1-44 standard ("Measurement methods and test procedures – Cut-off wavelength").

[0084] The optical fiber disclosed herein includes: a core region, a cladding region surrounding the core region, and a coating surrounding the cladding region. The core region and the cladding region are glass. The cladding region comprises multiple regions. These multiple cladding regions are preferably concentric regions. The cladding region includes an inner cladding region, a depressed refractive index cladding region, and an outer cladding region. The inner cladding region surrounds and is directly adjacent to the core region. The depressed refractive index cladding region surrounds and is directly adjacent to the inner cladding region, such that the depressed refractive index cladding region is arranged radially between the inner and outer cladding. The outer cladding region surrounds and is directly adjacent to the depressed refractive index region. The relative refractive index of the depressed refractive index region is lower than that of the inner and outer cladding regions. The depressed refractive index cladding region may also be referred to herein as a depression or a concave region. The relative refractive index of the inner cladding region may be less than, equal to, or greater than that of the outer cladding region. The depressed refractive index cladding region can reduce bending loss and micro-bending sensitivity. The core region, inner cladding region, depressed refractive index cladding region, and outer cladding region are also referred to as the core, cladding, inner cladding, depressed refractive index cladding, and outer cladding, respectively.

[0085] As used anywhere in this document, radial position r1 and relative refractive index Δ1 or Δ1(r) relate to the core region, radial position r2 and relative refractive index Δ2 or Δ2(r) relate to the inner cladding region, radial position r3 and relative refractive index Δ3 or Δ3(r) relate to the sunken refractive index cladding region, radial position r4 and relative refractive index Δ4 or Δ4(r) relate to the outer cladding region, radial position r5 relates to an optional low-modulus inner coating, radial position r6 relates to a high-modulus coating, and radial position r7 relates to an optional pigment outer coating.

[0086] The relative refractive index Δ1(r) has a maximum value Δ 1max and minimum value Δ 1min The relative refractive index Δ2(r) has a maximum value Δ 2max and minimum value Δ 2min The relative refractive index Δ3(r) has a maximum value Δ 3max and minimum value Δ 3min The relative refractive index Δ₄(r) has a maximum value Δ. 4max and minimum value Δ 4min In embodiments where the relative refractive index is constant or approximately constant over a region, the maximum and minimum values ​​of the relative refractive index are equal or approximately equal. Unless otherwise stated, if a single value is recorded for the relative refractive index of a region, that single value corresponds to the average value of that region.

[0087] It is important to understand that the central core region is essentially cylindrical, while the surrounding inner cladding region, depressed refractive index cladding region, outer cladding region, low-modulus coating, and high-modulus coating are essentially annular. The annular regions can be characterized by their inner and outer radii. In this document, the radial positions r1, r2, r3, r4, r5, r6, and r7 relate to the outermost radii of the core, inner cladding, depressed refractive index cladding, outer cladding, low-modulus inner coating, high-modulus coating, and optionally pigment outer coating, respectively. In embodiments without a pigment outer coating, radius r6 also corresponds to the outer radius of the optical fiber. The pigment outer coating can have a high modulus. When a pigment outer coating is present, radius r7 corresponds to the outer radius of the optical fiber.

[0088] When two regions are directly adjacent to each other, the outer radius of the innermost region is the same as the inner radius of the outermost region. For example, an optical fiber includes a depressed refractive index cladding region, which is surrounded and directly adjacent to an outer cladding region. Radius r3 corresponds to the outer radius of the depressed refractive index cladding region and the inner radius of the outer cladding region. A relative refractive index distribution also includes a depressed refractive index cladding region, which surrounds and is directly adjacent to the inner cladding region. Radial position r2 corresponds to the outer radius of the inner cladding region and the inner radius of the depressed refractive index cladding region. Similarly, radial position r1 corresponds to the outer radius of the core region and the inner radius of the inner cladding region.

[0089] The difference between radial positions r2 and r1 is referred to in this paper as the thickness of the inner cladding region. The difference between radial positions r3 and r2 is referred to in this paper as the thickness of the depressed refractive index cladding region. The difference between radial positions r4 and r3 is referred to in this paper as the thickness of the outer cladding region. The difference between radial positions r5 and r4 is referred to in this paper as the thickness of the low-modulus coating. The difference between radial positions r6 and r5 is referred to in this paper as the thickness of the high-modulus coating.

[0090] As further detailed below, the relative refractive indices of the core region, inner cladding region, depressed refractive index cladding region, and outer cladding region can be different. Each of the regions can be formed from doped or undoped silica glass. The change in refractive index relative to undoped silica glass can be achieved using techniques known to those skilled in the art, by incorporating positive or negative dopants, with the incorporation level designed to provide a target refractive index or refractive index distribution. A positive dopant is a dopant that increases the refractive index of the glass relative to the undoped glass composition. A negative dopant is a dopant that decreases the refractive index of the glass relative to the undoped glass composition. In one embodiment, the undoped glass is silica glass. When the undoped glass is silica glass, positive dopants include Cl, Br, Ge, Al, P, Ti, Zr, Nb, and Ta, and negative dopants include fluorine and boron. Regions with constant refractive indices can be formed by leaving the region undoped or by doping at a uniform concentration across the thickness of the region. Regions with varying refractive indices are formed by non-uniform spatial distribution of dopants across the thickness of the region and / or by combining different dopants in different regions.

[0091] The values ​​for Young's modulus, % tensile strength, and tear strength refer to the values ​​determined under the measurement conditions described herein.

[0092] The illustrative embodiments described in this specification will be described in detail below.

[0093] One implementation involves optical fibers. The optical fiber comprises glass fibers surrounded by a coating. Figure 1 An example of an optical fiber is shown in cross-sectional view. Optical fiber 10 includes glass fiber 11 surrounded by an optional low-modulus inner coating 16 and a high-modulus coating 18. In some embodiments, the high-modulus coating 18 may contain pigment. Further description of the glass fiber 11, the optional low-modulus inner coating 16, and the high-modulus coating 18 is provided below. Additionally, one or more pigment outer coating layers may surround the high-modulus coating 18.

[0094] Figure 2 The fiber optic ribbon 30 is shown, which may include a plurality of optical fibers 20 and a matrix 32 encapsulating the plurality of optical fibers. Each of the optical fibers 20 includes a core region, a cladding region, an optional low-modulus inner coating, and a high-modulus coating, as described above. As described above, the optical fiber 20 may also include a pigment outer coating.

[0095] like Figure 2 As shown, optical fibers 20 are aligned with each other in a basic plane and parallel relationship. The optical fibers are encapsulated in the optical fiber ribbon 30 by the ribbon matrix 32 using any of the known construction methods (e.g., edge-bonded ribbon, thin-encapsulated ribbon, thick-encapsulated ribbon, or multilayer ribbon) through conventional methods of manufacturing optical fiber ribbons. Figure 2In the embodiment, the fiber optic ribbon 30 contains twelve (12) optical fibers 20. However, it is conceivable that any number of optical fibers 20 (e.g., 2 or more, 4 or more, 6 or more, 8 or more, 12 or more, or 16 or more) can be used to form an optical fiber ribbon 30 for a particular purpose. The tensile properties of the ribbon matrix 32 are similar to those of a high-modulus coating, and it can be formed using the same, similar, or different compositions used to prepare the high-modulus coating.

[0096] Figure 3 The fiber optic cable 40 is shown, comprising a plurality of optical fibers 20 surrounded by a jacket 42. In some embodiments, the fiber optic cable 40 is a submarine cable. In some embodiments, the fiber optic cable 40 is a fiber optic ribbon used in interconnect schemes in data centers. The optical fibers 20 may be densely or loosely encapsulated in a conduit encased in the inner surface 44 of the jacket 42. The number of optical fibers housed in the jacket 42 is referred to as the “fiber count” of the fiber optic cable 40. As discussed further below, the optical fibers of this disclosure have a reduced diameter, thereby providing a high “fiber count”.

[0097] The jacket 42 is formed from an extruded polymer material and may comprise multiple concentric layers of polymer or other materials. The fiber optic cable 40 may include one or more reinforcing elements (not shown) embedded in the jacket 42 or placed in a conduit defined by the inner surface 44. The reinforcing elements comprise fibers or rods that are more rigid than the jacket 42. The reinforcing elements may be made of metal, braided steel, glass-reinforced plastic, fiberglass, or other suitable materials. The fiber optic cable 40 may include other layers surrounding the jacket 42 (e.g., protective layers, moisture-proof layers, tear lines, etc.). Furthermore, the fiber optic cable 40 may have stranded loose tube cores or other fiber optic cable constructions.

[0098] Fiberglass

[0099] like Figure 1 As shown, the glass fiber 11 includes a core region 12 and a cladding region 14, as is known in the art. The refractive index of the core region 12 is higher than that of the cladding region 14, and the glass fiber 11 acts as a waveguide. In many applications, the core region 12 and the cladding region 14 have a identifiable core-cladding boundary. Alternatively, the core region 12 and the cladding region 14 may lack a distinguishable boundary.

[0100] In some embodiments, the core region 12 has a refractive index that varies with distance from the center of the glass fiber. For example, the core region 12 may have an α-distributed relative refractive index distribution (as defined by equation (3) above), where the α value is greater than or equal to 2 and less than or equal to 100, or for example, the α value is: greater than or equal to 2 and less than or equal to 10, or greater than or equal to 2 and less than or equal to 6, or greater than or equal to 2 and less than or equal to 4, or greater than or equal to 4 and less than or equal to 20, or greater than or equal to 6 and less than or equal to 20, or greater than or equal to 8 and less than or equal to 20, or greater than or equal to 10 and less than or equal to 20, or greater than or equal to 10 and less than or equal to 40.

[0101] like Figure 4 The diagram shown is a schematic cross-sectional view of an exemplary optical fiber. In some embodiments, Figure 4 The optical fiber can be used for submarine optical cables or optical connections to components in submarine repeaters. In some implementations, Figure 4 Fiber optic cables can be used for data center interconnects. Figure 4 In the fiber 46, the fiber includes a core region 48, a cladding region 50, an optional low-modulus inner coating 56, and a high-modulus coating 58. The cladding region 50 includes an inner cladding region 51, a recessed refractive index cladding region 53, and an outer cladding region 55. An outer pigment coating (e.g., an ink layer) optionally surrounds or is directly adjacent to the high-modulus coating.

[0102] As discussed above, fiber 46 can have a reduced coating diameter. Such a reduced diameter can increase the fiber density (e.g., "fiber count") of fiber 46, for example, when used in submarine cables or repeaters or data center interconnects. To provide low attenuation, large effective area, low bending loss, and sufficiently high mechanical reliability for fiber 46 with a smaller diameter, the properties of the fiber are specifically tuned, as discussed further below.

[0103] like Figure 5 The diagram shows a representative relative refractive index distribution of glass fiber according to an embodiment of the present disclosure. Figure 5 The distribution of the optical fiber 60 shows: core region (1), which has an outer radius r1 and a relative refractive index Δ1, wherein the refractive index Δ1 has a maximum relative refractive index Δ 1max The inner cladding region (2) extends from radial position r1 to radial position r2 and has a relative refractive index Δ2; the sunken refractive index cladding region (3) extends from radial position r2 to radial position r3 and has a relative refractive index Δ3; and the outer cladding region (4) extends from radial position r3 to radial position r4 and has a relative refractive index Δ4. Figure 5In the distribution, the sunken refractive index cladding region (3) may be referred to herein as a depression and has a constant or average relative refractive index that is less than the relative refractive index of the inner cladding region (2) and the outer cladding region (4). The core region (1) has the highest average and maximum relative refractive index in the distribution. In some embodiments, the core region (1) may have a lower refractive index region (known in the art as "centerline sinking") at or near the centerline (not shown). In some embodiments, the core region (1) may have a higher refractive index region (referred to as "centerline spike") at or near the centerline (not shown).

[0104] exist Figure 5 In the relative refractive index distribution, the core region (1) of the glass fiber has an α-distribution, with an α value greater than or equal to 2 and less than or equal to 20. The radial position r0 of the α-distribution (corresponding to Δ) 1max The α-distribution corresponds to the centerline of the optical fiber (r = 0), while the radial position r of the α-distribution... z This corresponds to the fiber core radius r1. In embodiments with centerline sinking, the radial position r0 may deviate from the fiber's centerline. In some embodiments, the relative refractive index Δ1 continuously decreases in the radial direction away from the centerline. In other embodiments, the relative refractive index Δ1 varies at some radial positions between the centerline and r1, and also includes constant or approximately constant values ​​at other radial positions between the centerline and r1.

[0105] exist Figure 5 In the diagram, the transition region 61 from the inner cladding region (2) to the depressed refractive index cladding region (3) and the transition region 62 from the depressed refractive index cladding region (3) to the outer cladding region (4) exhibit a step-like change. It should be understood that the step-like change is idealized; in practice, the transition regions 61 and / or 62 may not be as described. Figure 5 The case shown is strictly vertical. Alternatively, transition regions 61 and / or 62 may have a slope or curvature. When transition regions 61 and / or 62 are not vertical, the inner radius r2 and outer radius r3 of the depressed refractive index cladding region (3) correspond to the midpoints of transition regions 61 and 62, respectively. The midpoint corresponds to half the depth 63 of the depressed refractive index cladding region (3).

[0106] In such Figure 5 The relative order of the relative refractive indices Δ1, Δ2, Δ3, and Δ4 in the relative refractive index distribution shown satisfies the following condition: Δ 1max >Δ4>Δ3 and Δ 1max Δ2 > Δ3. The values ​​of Δ2 and Δ4 can be equal or one can be larger than the other, but both Δ2 and Δ4 are within the range of Δ3. 1max Between Δ3 and Δ3.

[0107] The relative refractive indices Δ1, Δ2, Δ3, and Δ4 are based on the materials used in the core region, inner cladding region, depressed refractive index cladding region, and outer cladding region. Descriptions of these materials for relative refractive indices Δ1, Δ2, Δ3, and Δ4 are provided below.

[0108] Although Figure 5 A schematic cross-sectional view of an exemplary optical fiber is shown, but other suitable optical fibers can be used in the embodiments described herein. For example, Figure 9 This is a schematic cross-sectional view of a general distribution design for single-mode optical fibers that can be used in the embodiments described herein. Figure 9 The fiber distribution is shown as follows: a core region having an outer radius r1 and a relative refractive index Δ1; an inner cladding region extending from radial position r1 to radial position r2 and having a relative refractive index Δ2; a recessed refractive index cladding region extending from radial position r2 to radial position r3 and having a relative refractive index Δ3; and an outer cladding region extending from radial position r3 to radial position r4 and having a relative refractive index Δ4. Tables 1 and 2 below show various exemplary fiber distribution designs that can be used in the embodiments described herein, and Table 3 shows various optical properties of the various exemplary fiber distribution designs that can be used in the embodiments described herein.

[0109] Table 1: Exemplary Fiber Distribution Design

[0110]

[0111]

[0112] Table 2: Exemplary Fiber Distribution Design

[0113]

[0114] Table 2 (continued)

[0115]

[0116] Table 3: Optical properties of exemplary fiber distributions

[0117]

[0118]

[0119] Core area

[0120] The core region comprises silica glass. The silica glass in the core region can be undoped silica glass, positively doped silica glass, and / or negatively doped silica glass. Positively doped silica glass includes silica glass doped with alkali metal oxides (e.g., Na₂O, K₂O, Li₂O, Cs₂O, or Rb₂O). Negatively doped silica glass includes silica glass doped with F. In one embodiment, the silica glass in the core region may be free of Ge and / or Cl; that is, the core region comprises silica glass that does not contain Ge and / or Cl.

[0121] As a supplement or alternative, the core region may comprise silica glass doped with at least one alkali metal (e.g., lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and / or francium (Fr)). In some embodiments, the silica glass is doped with a combination of sodium, potassium, and rubidium. The peak alkalinity concentration of the silica glass may be in the following ranges: about 10 ppm to about 500 ppm, or about 20 ppm to about 450 ppm, or about 50 ppm to about 300 ppm, or about 10 ppm to about 200 ppm, or about 10 ppm to about 150 ppm. Doping with alkali metals within the disclosed range results in a decrease in Rayleigh scattering, thereby providing lower fiber attenuation.

[0122] In some embodiments, the core region comprises silica glass doped with an alkali metal and doped with F as a negative dopant. The F concentration in the fiber core is in the range of about 0.1 wt% to about 2.5 wt%, or about 0.25 wt% to about 2.25 wt%, or about 0.3 wt% to about 2.0 wt%.

[0123] In other embodiments, the core region comprises silica glass doped with Ge and / or Cl. The GeO2 concentration in the fiber core can be in the range of about 2.0 to about 8.0 wt%, or about 3.0 to about 7.0 wt%, or about 4.0 to about 6.5 wt%. The Cl concentration in the fiber core can be in the range of 1.5 wt% to 6.0 wt%, or 1.2 wt% to 5.5 wt%, or 1.5 wt% to 5.0 wt%, or 2.0 wt% to 4.5 wt%, or greater than or equal to 1.5 wt% (e.g., ≥2 wt%, ≥2.5 wt%, ≥3 wt%, ≥3.5 wt%, ≥4 wt%, ≥4.5 wt%, ≥5 wt%, etc.).

[0124] In embodiments where the fiber core is essentially free of Ge or Cl, the relative refractive index Δ1 or Δ in the fiber core region is... 1maxThe range is as follows: approximately -0.10% to approximately 0.20%, or approximately -0.05% to approximately 0.15%, or approximately 0.0% to approximately 0.10%. The minimum relative refractive index Δ of the fiber core. 1min The range is as follows: approximately -0.20% to approximately -0.50%, or approximately -0.30% to approximately -0.40%, or approximately -0.32% to approximately -0.37%. Δ 1max With Δ 1min The difference is: greater than 0.05%, or greater than 0.10%, or greater than 0.15%, or greater than 0.20%, or in the range of 0.05% to 0.40%, or in the range of 0.10% to 0.35%.

[0125] In embodiments where the fiber core is doped with Ge and / or Cl, the relative refractive index Δ1 or Δ in the fiber core region is... 1max The range is as follows: approximately 0.20% to approximately 0.45%, or approximately 0.25% to approximately 0.40%, or approximately 0.30% to approximately 0.38%. The minimum relative refractive index Δ of the fiber core. 1min The range is as follows: approximately -0.05% to approximately -0.05%, or approximately -0.03% to approximately 0.03%, or approximately -0.02% to approximately 0.02%. Δ 1max With Δ 1min The difference is: greater than 0.20%, or greater than 0.25%, or greater than 0.30%, or in the range of 0.25% to 0.45%, or in the range of 0.30% to 0.40%.

[0126] The radius r1 of the core region is in the following range: about 3.0 micrometers to about 6.0 micrometers, or about 3.5 micrometers to about 6.0 micrometers, or about 4.0 micrometers to about 6.0 micrometers, or about 4.5 micrometers to about 5.5 micrometers. In some embodiments, the core region includes a portion having a constant or nearly constant relative refractive index, the width of which in the radial direction is: at least 1.0 micrometer, or at least 2.0 micrometers, or at least 3.0 micrometers, or in the range of 1.0 micrometers to 3.0 micrometers, or in the range of 2.0 micrometers to 3.0 micrometers. In some embodiments, the portion of the core region having a constant or nearly constant relative refractive index has a relative refractive index Δ. 1min .

[0127] Inner cladding region

[0128] In embodiments where the fiber core is substantially free of Ge and Cl, the inner cladding region comprises negatively doped F-doped silicon dioxide glass. The average concentration of the negative dopant in the inner cladding region is greater than the average concentration of the negative dopant in the fiber core region.

[0129] The relative refractive index Δ2 or Δ in the inner cladding region 2maxThe range is as follows: about -0.20% to about -0.50%, or about -0.25% to about -0.45%, or about -0.30% to about -0.40%, or about -0.33% to about -0.37%. The relative refractive index Δ2 is preferably constant or approximately constant. 1max -Δ2 difference (or Δ 1max -Δ 2max The difference is: greater than about 0.25%, or greater than about 0.30%, or greater than about 0.35%, or the range of about 0.25% to about 0.45%, or the range of about 0.30% to about 0.40%.

[0130] The radius r2 of the inner cladding region is in the following range: about 7.0 micrometers to about 15.0 micrometers, or about 7.5 micrometers to about 13.0 micrometers, or about 8.0 micrometers to about 12.0 micrometers, or about 8.5 micrometers to about 11.5 micrometers, or about 9.0 micrometers to about 11.0 micrometers, or about 9.5 micrometers to about 10.5 micrometers. The thickness r2-r1 of the inner cladding region is in the following range: about 3.0 micrometers to about 10.0 micrometers, or about 4.0 micrometers to about 9.0 micrometers, or about 4.5 micrometers to about 7.0 micrometers.

[0131] In embodiments where the fiber core is doped with Ge and / or Cl, the inner cladding region comprises silicon dioxide that is substantially free of Ge and / or Cl. The relative refractive index of the inner cladding region is Δ2 or Δ... 2max The range is as follows: about -0.05% to about -0.05%, or about -0.03% to about 0.03%, or about -0.02% to about 0.02%. The relative refractive index Δ2 is preferably constant or approximately constant. 1max -Δ2 difference (or Δ 1max -Δ 2max The difference is: greater than about 0.20%, or greater than about 0.25%, or greater than about 0.30%, or the range of about 0.25% to about 0.40%, or the range of about 0.30% to about 0.38%.

[0132] The radius r2 of the inner cladding region is in the following range: about 8.0 micrometers to about 16.0 micrometers, or about 9.0 micrometers to about 15.0 micrometers, or about 10.0 micrometers to about 14.0 micrometers, or about 10.5 micrometers to about 13.5 micrometers, or about 11.0 micrometers to about 13.0 micrometers. The thickness r2-r1 of the inner cladding region is in the following range: about 3.0 micrometers to about 10.0 micrometers, or about 4.0 micrometers to about 9.0 micrometers, or about 5.0 micrometers to about 8.0 micrometers.

[0133] Depressed refractive index cladding region

[0134] The depressed refractive index cladding region comprises negatively doped silicon dioxide glass. As discussed above, the preferred negative dopant is fluorine. The fluorine concentration in the depressed refractive index cladding region ranges from about 0.30 wt% to about 2.50 wt%, or about 0.60 wt% to about 2.25 wt%, or about 0.90 wt% to about 2.00 wt%.

[0135] Relative refractive index Δ3 or Δ 3min The range is as follows: about -0.30% to about -0.80%, or about -0.40% to about -0.70%, or about -0.50% to about -0.65%. The relative refractive index Δ3 is preferably constant or approximately constant. 1max -Δ3 difference (or Δ 1max -Δ 3min The difference, or the difference between Δ1 and Δ3, or Δ1 and Δ 3min The difference (Δ2 - Δ3) is: greater than about 0.50%, or greater than about 0.55%, or greater than about 0.6%, or in the range of about 0.50% to about 0.80%, or in the range of about 0.55% to about 0.75%. 3min The difference, or Δ 2max -Δ3 difference, or Δ 2max -Δ 3min The difference is: greater than about 0.10%, or greater than about 0.20%, or greater than about 0.30%, or between about 0.10% and about 0.70%, or between about 0.20% and about 0.65%.

[0136] The inner radius of the depressed refractive index cladding region is r2, and has the value specified above. The outer radius r3 of the depressed refractive index cladding region is in the following range: about 10.0 μm to 20.0 μm, or about 12.0 μm to about 19.5 μm, or about 13.0 μm to about 19.0 μm, or about 13.5 μm to about 18.5 μm, or about 14.0 μm to about 18.0 μm, or about 14.5 μm to about 17.5 μm. The thickness r3-r2 of the depressed refractive index cladding region is in the following range: 1.0 μm to 12.0 μm, or about 2.0 μm to about 10.0 μm, or about 2.5 μm to about 9.0 μm, or about 3.0 μm to about 8.0 μm.

[0137] The depressed refractive index cladding region can be an offset recess design with the following recess volume: approximately 30% Δ-micron. 2 Or larger, or about 50% Δ-micrometer 2 Or larger, or about 75% Δ-micrometer 2 Or smaller, or about 30% Δ-micrometer 2 Or larger and approximately 75% Δ-micrometer2 Or smaller, or about 50% Δ-micrometer 2 Or larger and approximately 75% Δ-micrometer 2 Or smaller. Recess volumes below the disclosed range have reduced bending performance, while recess volumes above the disclosed range no longer operate in single-mode fiber.

[0138] The offset recess design disclosed herein includes an inner cladding region. Furthermore, the offset recess design disclosed herein offers advantages over conventional recess designs adjacent to the core region. More specifically, the offset recess design disclosed herein reduces the limitation of the fundamental mode and provides improved bending loss at large bending diameters (e.g., bending diameter > 25 mm) for the target fiber mode field diameter and cable cutoff characteristics. In addition, the recess design disclosed herein features a depressed refractive index recess region, which advantageously restricts the intensity distribution of the fundamental LP01 mode propagating through the fiber, thereby reducing the fiber mode field diameter.

[0139] Outer layer area

[0140] In embodiments where the core is substantially free of Ge and Cl, the cladding region comprises negatively doped silica glass. A preferred negative dopant is fluorine. The fluorine concentration in the cladding region ranges from about 0.30 wt% to about 2.20 wt%, or about 0.60 wt% to about 2.00 wt%, or about 0.90 wt% to about 1.80 wt%. The relative refractive index of the cladding region is Δ4 or Δ... 4max The range is as follows: about -0.20% to about -0.50%, or about -0.25% to about -0.45%, or about -0.30% to about -0.40%, or about -0.33% to about 0.37%. The relative refractive index Δ4 is ​​preferably constant or approximately constant. Figure 5 As shown, the relative refractive index Δ4 can be approximately equal to the relative refractive index Δ2.

[0141] In one embodiment, the cladding is substantially pure silicon dioxide. Alternatively, the cladding may be doped with Cl to a relative refractive index ranging from about 0.01 to about 0.1%, or from about 0.02% to about 0.08%, or from about 0.03% to about 0.06%. The Cl concentration in the cladding may range from about 0.1 wt% to about 1.0 wt%, from about 0.2 wt% to about 0.8 wt%, or from about 0.3 wt% to about 0.6 wt%. Alternatively, the cladding may be doped with titanium oxide to strengthen the cladding surface and thus prevent defects such as scratches from propagating through the optical fiber. In some embodiments, the cladding may be doped with a titanium oxide concentration of about 5 wt% to about 25 wt%.

[0142] The inner radius of the cladding region is r3, and has the value specified above. In some embodiments, the outer radius r4 is approximately 62.5 micrometers, which facilitates splicing with conventional 125-micrometer cladding diameter fibers using cladding alignment splices. The outer radius r4 of the cladding region is in the following ranges: 60.0 micrometers to 65.0 micrometers, or 61.0 micrometers to 64.0 micrometers, or 62.0 micrometers to 63.0 micrometers, or 62.25 micrometers to 62.75 micrometers. Therefore, for example, the diameter of the cladding region (i.e., outer radius r4 multiplied by 2) is in the following ranges: 120.0 micrometers to 130.0 micrometers, or 122.0 micrometers to 128.0 micrometers, or 124.0 micrometers to 126.0 micrometers, or 124.5 micrometers to 125.5 micrometers. The thickness r4-r3 of the outer coating region ranges from about 20.0 micrometers to about 60.0 micrometers, or about 30.0 micrometers to about 55.0 micrometers, or about 40.0 micrometers to about 50.0 micrometers. In some embodiments, the outer radius r4 is about 50 micrometers to achieve increased thickness for both low-modulus and high-modulus coatings. The outer radius r4 of the outer coating region ranges from 45.0 micrometers to 55.0 micrometers, or 49.0 micrometers to 51.0 micrometers, or 49.5 micrometers to 50.5 micrometers, or 49.65 micrometers to 50.35 micrometers. Therefore, for example, the diameter of the coating region (i.e., outer radius r4 multiplied by 2) ranges from 90.0 micrometers to 110.0 micrometers, or 98.0 micrometers to 102.0 micrometers, or 99.0 micrometers to 101.0 micrometers, or 99.3 micrometers to 100.7 micrometers. The thickness r4-r3 of the outer cladding region is in the following range: about 20.0 micrometers to about 50.0 micrometers, or about 25.0 micrometers to about 45.0 micrometers, or about 30.0 micrometers to about 40.0 micrometers.

[0143] Fiber characteristics

[0144] The optical fiber according to embodiments of this disclosure may have a mode field diameter ranging from about 9.0 micrometers to about 10.0 micrometers at 1310 nm and from about 10.0 micrometers to about 11.0 micrometers at 1550 nm, with a cutoff wavelength of less than about 1520 nm. In some embodiments, the cutoff wavelength of a 22-meter optical fiber is less than about 1550 nm, or less than about 1450 nm, or less than about 1400 nm, or less than about 1300 nm, or less than about 1260 nm. In some embodiments, the cutoff wavelength of a 2-meter optical fiber is less than about 1520 nm, or less than about 1500 nm, or less than about 1450 nm, or less than about 1400 nm, or less than about 1300 nm, or less than about 1260 nm.

[0145] Furthermore, the optical fiber according to embodiments of this disclosure can have an effective area at 1550 nm that is greater than approximately 75.0 micrometers. 2 Larger than approximately 80 micrometers 2 or larger than approximately 85 micrometers 2 or about 75 micrometers 2 Approximately 95 micrometers 2 The range, or about 80 micrometers 2 Approximately 90 micrometers 2 The range, or about 85 micrometers 2 Approximately 90 micrometers 2 The range.

[0146] The fiber attenuation disclosed in this paper is less than or equal to 0.36 dB / km, or less than or equal to 0.30 dB / km, or less than or equal to 0.28 dB / km, or less than or equal to 0.26 dB / km at a wavelength of 1310 nm. At a wavelength of 1550 nm, the fiber attenuation disclosed in this paper is less than or equal to 0.24 dB / km, or less than or equal to 0.22 dB / km, or less than or equal to 0.20 dB / km.

[0147] like Figure 5 As shown, optical fiber 60 provides an exemplary embodiment of an optical fiber with a core doped with an alkaline substance, wherein the relative refractive index Δ1 of the core region (1) is about -0.3% to about -0.42%, and the core radius (r1) is about 4 micrometers to about 6.5 micrometers. Furthermore, the thickness of the inner cladding region of optical fiber 60 is about 2 micrometers to about 12 micrometers. Optical fiber 60 has a recess volume of 54.5%Δ-micrometers. 2 The fiber 60 features an offset recess design. The cladding of fiber 60 is fluorine-doped, and the lower refractive index cladding region has a radius (r3) of approximately 17.5 micrometers. Table 4 below shows the optical properties of fiber 60.

[0148] Table 4: Optical properties of fiber 60

[0149]

[0150]

[0151] Figure 6 The second and third exemplary embodiments of the optical fibers (64 and 65) are shown, having a core doped with an alkaline substance and a core density greater than about 50% Δ-micrometer. 2The recessed volume, and the cladding region therein, is fluorine-doped and has a radius (r3) of approximately 17.5 μm. As shown in Table 5 below, fiber 64 results in a mode field diameter of 9.07 μm at 1310 nm, while fiber 65 results in a mode field diameter of 9.39 μm at 1310 nm. Table 2 below shows the optical properties of fibers 64 and 65.

[0152] Table 5: Optical properties of optical fibers 64 and 65

[0153] Fiber 64 Fiber 65 Mode field diameter (at 1310 nm) 9.07 micrometers 9.39 micrometers Mode field diameter (at 1550 nm) 10.08 micrometers 10.48 micrometers Mode field diameter (at 1625 nm) 10.41 micrometers 10.83 micrometers Zero-dispersion wavelength 1319nm 1320nm Optical cable cut-off 1419nm 1339nm concave volume <![CDATA[55% Δ - micron 2 > <![CDATA[55% Δ - micron 2 > 15mm diameter bending loss 0.0137dB / cycle 0.042dB / cycle 20mm diameter bending loss 0.0003dB / cycle 0.009dB / cycle 30mm diameter bending loss 0.0002dB / cycle 0.001dB / cycle

[0154] Figure 7 The embodiment shown is optical fiber 66, with a Ge-doped core greater than 50% Δ-micron. 2 The recessed volume, and the inner and cladding regions therein, are essentially pure silica, and the recessed refractive index cladding region has a radius (r3) of approximately 16.8 micrometers. As shown in Table 6 below, fiber 64 results in a mode field diameter of 10.6 micrometers at a wavelength of 1550 nm. Table 6 below shows the refractive index distribution parameters and optical properties of fiber 66.

[0155] Table 6: Optical properties of fiber 66

[0156]

[0157]

[0158] The offset recess design of fibers 60, 64, 65, and 66 provides improved bending performance for the smaller diameter fibers disclosed herein. More specifically, the offset recess design disclosed herein provides low attenuation, large effective area, and low bending loss in a compact form, with a cladding diameter of approximately 125 micrometers and an outer coating diameter of less than 175 micrometers.

[0159] Coating properties

[0160] The light transmission coefficient through an optical fiber is highly dependent on the properties of the coating applied to the glass fiber. As discussed above (and refer to...), Figure 4 The coating may include an optional low-modulus inner coating 56 and a high-modulus coating 58, wherein the high-modulus coating surrounds the optional low-modulus inner coating and contacts the glass fiber (which includes a central core region surrounded by the cladding region). An optional pigment outer coating layer (e.g., an ink layer) surrounds and directly contacts the high-modulus coating.

[0161] The high-modulus coating 58 is a harder material (higher Young's modulus) than the optional low-modulus coating 56 and is designed to protect the glass fiber from abrasion or damage caused by external forces during optical fiber processing, handling, and deployment. The optional low-modulus inner coating 56 is a softer material (lower Young's modulus) than the high-modulus coating 58 and is designed to buffer or dissipate stress caused by forces applied to the outer surface of the high-modulus coating. The optional low-modulus coating can help dissipate stress caused by microbending encountered by the optical fiber when it is laid in an optical cable, but it is not necessary for short-length applications (e.g., optical interconnects). It is necessary to minimize the microbending stress transmitted to the glass fiber because microbending stress creates local perturbations in the refractive index distribution of the glass fiber. Local refractive index perturbations lead to intensity loss of light transmitted through the glass fiber. By dissipating stress, the optional low-modulus coating minimizes the intensity loss due to microbending.

[0162] It is believed that the thinner coating on the optical fiber increases microbending loss because it provides less protection against external disturbances. These disturbances cause the power of the light guided in the core (core mode) to couple into higher-order modes in the cladding (cladding mode). Figure 10 As shown, the cladding mode and the coating layer with high absorption exhibit significant overlap. This coupling, along with the absorption process of the coating material, leads to optical power loss.

[0163] The following article discloses a scheme for quantifying the relationship between coating properties and the microbending loss of optical fibers: J. Baldauf, N. Okada, and M. Miyamoto's article entitled "Relationship of Mechanical Characteristics of DualCoated Single Mode Fibers and Microbending Loss," IEICE Communications Affairs, Vol. E76-B, No. 4, pp. 352-357 (April 1993). The authors introduced the parameter χ. s This is the effective spring constant for the force that couples the secondary (high modulus) coating with the glass fiber. This spring constant parameterization provides reinforcement guidance that a thicker primary (low modulus) coating with a low modulus provides better micro-bending properties, but it does not fully capture the contributions of both the glass and the high modulus coating.

[0164] The combined roles of glass, low-modulus internal coating, and high-modulus coating result in the following micro-bending attenuation penalty (MAP):

[0165]

[0166] In the formula, f0 and σ are the average lateral pressure and the standard deviation of the roughness of the outer surface in contact with the high modulus coating, respectively.

[0167] f RIP The role of refractive index distribution is considered, and it is of uniform order. Attenuation data show that for single-mode fibers with a step-order refractive index distribution, f RIP The value is approximately 1.0; and for bending-insensitive single-mode fibers with a refractive index distribution including a depressed refractive index depression in the cladding, it is approximately 0.5. The other three terms in Equation 8 are the contributions of the glass, the low-modulus inner coating, and the system comprising both a low-modulus inner coating and a high-modulus coating to the corresponding microbending, and are as follows:

[0168]

[0169]

[0170] as well as

[0171] In the formula, R g R is the radius of the glass (i.e., the outer radius of the cladding region). s It is the outer radius of the high modulus outer coating, t p It is the thickness of the low-modulus inner coating, t s It is the thickness of the high modulus outer coating, and E g E p and E s These are the elastic moduli of the glass, the low-modulus internal coating, and the high-modulus coating, respectively. When the units for modulus and radius are GPa and micrometers, respectively, the unit for MAP is dB / km. The coefficient f for the low-modulus internal coating... p Depends on (1 / t) p ) 2 Not just 1 / t p (This is the case where the spring constant is parametrically predicted.) f cs The coating system coefficient is of interest for optical fibers with thinner coatings because when the high-modulus coating is thicker (t... s (Greater than approximately 20 micrometers) This is very large, corresponding to a low MAP. However, when the high modulus coating thickness t s At a size smaller than approximately 10 micrometers, it becomes quite small and yields a MAP value greater than 0.01 dB / km, a result of the reduced stiffness of the outer coating. Assuming no microbending attenuation penalty, the fiber attenuation is approximately 0.19 dB·km, thus the net attenuation of the coated fiber system is 0.19 dB / km plus the microbending attenuation penalty.

[0172] The inventors discovered that if the coating thickness is below a certain level (as described herein), micro-bending losses can be reduced. Figure 11 As shown, when the thickness of the polymer coating decreases sufficiently, an anti-resonance effect exists in the coating layer, which prevents light from being guided within the coating layer. This anti-resonance effect significantly reduces the absorption of the coating layer, thereby reducing microbending losses. Conventional coating thicknesses greater than 37 micrometers are too large for the anti-resonance effect. To produce this anti-resonance effect, the total thickness of the polymer coating is less than 25 micrometers, more preferably less than 20 micrometers, and even more preferably less than 10 micrometers. In some embodiments, the total thickness of the polymer coating is: about 2 micrometers to about 25 micrometers, or about 2 micrometers to about 20 micrometers, or about 2 micrometers to about 15 micrometers, or about 2 micrometers to about 10 micrometers, or about 2 micrometers to about 5 micrometers.

[0173] As used herein, the term "puncture load" refers to the force exerted upon the coating of an optical fiber as described herein. As used herein, the term "puncture resistance" refers to the force exerted upon the fiber coating in relation to the puncture load. As further described below, when the puncture load exceeds the coating's maximum puncture resistance, the coating will break. Regarding puncture resistance, Glaesemann and Clark's analysis of an optical fiber with one type of coating in their article "Quantifying the Puncture Resistance of Optical Fiber Coatings" (Proc. 52nd IWCS, pp. 237-245 (1993)) shows that puncture resistance is related to the cross-sectional area A of the high-modulus coating. s It exhibits a linear dependence. The analyses in this paper assume that the puncture resistance is due to circumferential stress on the high-modulus coating, modeling it as a thin cylinder subjected to internal pressure from the low-modulus inner coating. However, for most optical fibers, the thickness t of the high-modulus coating... s The ratio to the outer radius r6 is approximately on the order of 10%, so the low-modulus coating of the optical fiber can be approximated as a thick-walled cylinder, with pressure P... o The puncture load originates from the outside and is transmitted. Under the limiting condition where the external pressure is much greater than the internal pressure from the low-modulus inner coating, the maximum circumferential stress is... In the formula, A S This is the cross-sectional area of ​​the high-modulus coating. This circumferential stress is observed for A. s If there is an inverse correlation, then the puncture resistance is P. R =P0+C1E s A s In the formula, E S The modulus of the high-modulus coating, and the values ​​of the coefficients P0 and C1, are approximately 11.3 g and 2.1 g / MPa / mm, respectively.2 .

[0174] Coating Examples: Preparation and Measurement Techniques

[0175] The properties of the optional low-modulus internal coating and high-modulus coating disclosed herein were determined using the measurement techniques described below:

[0176] Tensile properties. A curable high-modulus coating composition was cured and constructed into cured rod samples for measuring Young's modulus, yield tensile strength, yield strength, and yield elongation. The curable high-modulus coating composition was injected into a rod with an inner diameter of approximately 0.025”. In the tube, a cured rod was prepared. A Fusion D bulb was used at approximately 2.4 J / cm². 2 The dose-cured rod sample was measured (using a Light Bug model IL390 purchased from International Light in the wavelength range of 225-424 nm). After curing, the sample was peeled off. Tubes were used to provide cured rod samples of high-modulus coating compositions. Before testing, the cured rods were placed at 23°C and 50% relative humidity for 18–24 hours. Young's modulus, tensile strength at break, yield strength, and elongation at yield were measured on defect-free rod samples with a gauge length of 51 mm using a Sintech MTS tensile testing machine at a test speed of 250 mm / min. Tensile properties were measured according to ASTM standard D882-97. Properties were determined by averaging at least five samples, excluding defective samples when averaging.

[0177] In-situ glass transition temperature. In-situ Tg measurements were performed on stripped fiber tube samples obtained from optical fibers having a low-modulus inner coating surrounded by a high-modulus coating. The coated optical fiber comprised: a glass fiber with a diameter of 125 micrometers, a low-modulus inner coating with a thickness of 32.5 micrometers surrounding and in direct contact with the glass fiber, and a high-modulus coating with a thickness of 26.0 micrometers surrounding and in direct contact with the glass fiber. For all measured samples, the glass fiber and the low-modulus inner coating were identical. The low-modulus inner coating was formed from a reference low-modulus inner coating composition described below. Measurements were performed on samples having a comparative high-modulus coating and a high-modulus coating according to this disclosure.

[0178] The following procedure was used to obtain samples of stripped fiber optic tubes: A 0.0055” Miller stripper was clamped approximately 1 inch from the end of the coated fiber. This 1-inch section of the fiber was immersed in a stream of liquid nitrogen and held for 3 seconds. The coated fiber was then removed from the liquid nitrogen stream and rapidly stripped to remove the coating. The stripped end of the fiber was inspected for any residual coating. If residual coating remained on the glass fiber, the sample was discarded and a new sample was prepared. The result of the stripping process was clean glass fiber and a hollow tube with the stripped coating (containing both the intact low-modulus inner coating and the high-modulus coating). The hollow tube was referred to as the “tube stripped sample.” The diameters of the glass, low-modulus inner coating, and high-modulus coating were measured from the end face of the unstripped fiber.

[0179] Using a sample gauge length of 9 to 10 mm, the in-situ Tg of the tube-stripped sample was measured using a Rheometrics DMTA IV instrument. The width, thickness, and length of the tube-stripped sample were entered into the instrument's operating program. The tube-stripped sample was then installed and cooled to approximately -85°C. Once stabilized, the temperature was increased using the following parameters:

[0180] Frequency: 1Hz

[0181] Strain: 0.3%

[0182] Heating rate: 2℃ / minute

[0183] Final temperature: 150℃

[0184] Initial static force = 20.0g

[0185] The static force is 10.0% greater than the dynamic force.

[0186] The in-situ Tg of the coating is defined as the maximum value of tanδ in the graph of tanδ versus temperature, where tanδ is defined as:

[0187] tanδ=E” / E'

[0188] And E” is the loss modulus, which is proportional to the energy loss as heating occurs during the deformation cycle, and E' is the storage modulus or elastic modulus, which is proportional to the energy stored during the deformation cycle.

[0189] For the low-modulus inner coating and the high-modulus coating, the tube-stripped samples exhibit different maximum values ​​in the tanδ plot. The maximum value at a lower temperature (approximately -50°C) corresponds to the in-situ Tg of the low-modulus inner coating, while the maximum value at a higher temperature (greater than 50°C) corresponds to the in-situ Tg of the high-modulus coating.

[0190] In-situ modulus of low-modulus inner coating. In embodiments including this optional coating layer, the in-situ modulus is measured as follows: A 6-inch sample of optical fiber is obtained, and a one-inch section is stripped from the center window of the fiber and wiped with isopropyl alcohol. The window-stripped fiber is mounted to a sample holder / alignment station fitted with 10mm x 5mm rectangular aluminum sheets for securing the fiber. Two sheets are horizontally aligned and positioned such that the shorter 5mm sides face each other and are spaced 5mm apart. The window-stripped fiber is placed horizontally on the sample holder across the sheets and the gap separating the sheets. The coated end of one side of the window-stripped area of ​​the fiber is placed on one sheet and extends halfway into the 5mm gap between the sheets. The one-inch window-stripped area extends over the remaining half of the gap and across the opposing sheet. After alignment, the sample is removed, and small dots of adhesive are applied to the half of each sheet closest to the 5mm gap. The fiber is then returned to position, and the alignment stage is raised until the adhesive just touches the fiber. Then, the coated end is pulled away from the gap by the adhesive, so that most of the 5mm gap between the sheets is occupied by the window stripping area of ​​the optical fiber. The portion of the window stripping area remaining on the opposite sheet is in contact with the adhesive. The very tip of the coated end is extended beyond the sheet and into the gap between the sheets. This portion of the coated end is not embedded in the adhesive and is the object for in-situ modulus measurement. The adhesive is allowed to dry, and the optical fiber sample in this configuration fixes the optical fiber to the sheet. After drying, the length of the optical fiber fixed to each sheet is trimmed to 5mm. The coated length embedded in the adhesive, the unembedded coated length (the portion extending into the gap between the sheets), and the primary diameter are measured.

[0191] In-situ modulus measurements were performed at room temperature (21°C) for 45 minutes at a constant strain of 9e⁻⁶ 1 / s on a Rheometrics DMTA IV dynamic mechanical testing apparatus. The gauge length was 15 mm. Force and length changes were recorded and used to calculate the in-situ modulus of the low-modulus coating. Optical fiber samples with the sheet mounted were prepared by removing any 15 mm clamping length of epoxy from the sheet that would interfere with the testing apparatus, ensuring no contact between the clamp and the fiber and that the sample was squarely fixed to the clamp. The instrument force was zeroed. The sheet fixed to the uncoated end of the fiber was then mounted to the lower clamp (measuring probe) of the testing apparatus, and the sheet fixed to the coated end of the fiber was mounted to the upper (fixed) clamp. Testing was then performed, and the sample was removed once analysis was complete.

[0192] In-situ modulus of high-modulus coatings. For high-modulus coatings, in-situ modulus is measured using fiber tube-off samples prepared from fiber samples. A 0.0055-inch Miller stripper is clamped approximately 1 inch below the end of the fiber sample. This 1-inch area of ​​the fiber sample is immersed in a stream of liquid nitrogen and held for 3 seconds. The fiber sample is then removed and quickly stripped. The stripped end of the fiber sample is then examined. If the coating remains on the glass portion of the fiber sample, the stripped sample is considered defective, and a new stripped sample is prepared. A suitable stripped sample is one where the glass has been clearly stripped and it consists of a hollow tube with both a low-modulus inner coating and a high-modulus coating. The diameters of the glass, low-modulus inner coating, and high-modulus coating are measured from the end face of the unstripped fiber sample.

[0193] The in-situ modulus of the high-modulus coating was obtained by running the fiber-removed sample with a sample gauge length of 11 mm using a Rheometrics DMTA IV instrument. The width, thickness, and length were determined and provided as input to the instrument's operating software. The sample was mounted, and a time-based scan program was run at ambient temperature (21°C) with the following parameters:

[0194] Frequency: 1 revolution / second

[0195] Strain: 0.3%

[0196] Total time = 120 seconds

[0197] The time for each measurement is 1 second.

[0198] Initial static force = 15.0g

[0199] The static force is 10.0% greater than the dynamic force.

[0200] Once complete, average the last 5 E' (storage modulus) data points. Run each sample 3 times (each run with fresh samples), for a total of 15 data points. Record the average of the 3 runs.

[0201] Puncture resistance of the high-modulus coating. Puncture resistance was measured on samples containing glass fibers and a low-modulus inner coating surrounded by the high-modulus coating. The cladding diameter of the glass fibers was 125 micrometers. The low-modulus inner coating was formed from the reference low-modulus inner coating compositions listed in Table 1 below. Samples with various high-modulus coatings were prepared as described below. The thicknesses of the low-modulus inner coating and the high-modulus coating were adjusted to vary the cross-sectional area of ​​the high-modulus coating, as described below. For all samples, the ratio of the thickness of the high-modulus coating to the thickness of the low-modulus inner coating was maintained at approximately 0.8.

[0202] Puncture resistance was measured using the technique described by G. Scott Glaesemann and Donald A. Clark in their paper entitled "Quantifying the Puncture Resistance of Optical Fiber Coatings" (2003), published in the proceedings of the 52nd International Symposium on Wires and Cables, pp. 237-245, which is incorporated herein by reference. A brief description of the method is provided below. The method is an indentation method. A 4 cm long optical fiber is placed on a 3 mm thick glass slide. One end of the fiber is attached to a device that allows for controlled rotation of the fiber. The transmittance of the fiber is examined at 100x magnification and the fiber is rotated until the thickness of the high-modulus coating on both sides of the fiber in the direction parallel to the glass slide is equal. At this position, the thickness of the high-modulus coating on both sides of the fiber in the direction parallel to the glass slide is the same. The thickness of the high-modulus coating perpendicular to the glass slide and above or below the fiber differs from the thickness of the high-modulus coating in the direction parallel to the glass slide. The thickness in the direction perpendicular to the glass slide is greater than the thickness in the direction parallel to the glass slide, while the thickness in the other direction perpendicular to the glass slide is smaller than the thickness in the direction parallel to the glass slide. This position of the optical fiber is fixed by attaching it to both ends of the glass slide, and this position is the optical fiber location used for indentation testing.

[0203] Indentation was performed using a general-purpose testing machine (Instron Model 5500R or equivalent). An inverted microscope was placed below the crosshead of the testing machine. The microscope objective was positioned directly below a diamond wedge indenter mounted at a 75° angle within the testing machine. A slide with the optical fiber attached was placed on the microscope stage, directly below the indenter, with the width of the indenter wedge perpendicular to the direction of the optical fiber. After the optical fiber was positioned, the diamond wedge was lowered until it contacted the surface of the high-modulus coating. The diamond wedge was then driven into the high-modulus coating at a rate of 0.1 mm / min, and the load on the high-modulus coating was measured. As the diamond wedge was driven deeper into the high-modulus coating, the load on the high-modulus coating increased until puncture occurred, at which point a sharp decrease in load was observed. The indentation load observed at puncture was recorded and denoted as the gravitational force (g) in this paper, referred to as the "puncture load". The experiment was repeated with the optical fiber in the same orientation to obtain 10 measurement points, and the average value was taken to determine the puncture load for that orientation. The second set of 10 measurement points was obtained by rotating the fiber orientation by 180°.

[0204] Macrobending loss. Macrobending loss is determined using the mandrel winding test specified in standard IEC 60793-1-47. In the mandrel winding test, the optical fiber is wound once or multiple times around a cylindrical mandrel of a specified diameter to determine the increase in attenuation at a specified wavelength due to bending. The attenuation in the mandrel winding test is measured in dB / turn, where one turn refers to one rotation of the fiber around the mandrel. For the selected examples described below, mandrels with diameters of 10 mm, 15 mm, and 20 mm are used to determine the macrobending loss at wavelengths of 1310 nm, 1550 nm, and 1625 nm.

[0205] Exemplary embodiments of optical fibers having a low-modulus inner coating surrounded by a high-modulus coating.

[0206] The specific properties of the optional low-modulus inner coating 56 and high-modulus coating 58 can be adjusted to provide sufficient robustness and good microbending properties for the small-diameter optical fibers disclosed herein. For example, the low-modulus inner coating 56 may have a low Young's modulus and / or a low in-situ modulus. The Young's modulus of the low-modulus inner coating is: less than or equal to about 0.7 MPa, or less than or equal to about 0.6 MPa, or less than or equal to about 0.5 MPa, or less than or equal to about 0.4 MPa, or in the range of about 0.1 MPa to about 0.7 MPa, or in the range of about 0.1 MPa to about 0.4 MPa. The in-situ modulus of the low modulus internal coating is: less than or equal to about 0.50 MPa, or less than or equal to about 0.30 MPa, or less than or equal to about 0.25 MPa, or less than or equal to about 0.20 MPa, or less than or equal to about 0.15 MPa, or less than or equal to about 0.10 MPa, or in the range of about 0.05 MPa to about 0.25 MPa, or in the range of about 0.10 MPa to about 0.20 MPa.

[0207] Preferably, the low-modulus inner coating 56 has a higher refractive index than the cladding region 50 of the glass fiber, thereby allowing it to strip erroneous optical signals from the core region 48. The low-modulus inner coating 56 should maintain sufficient adhesion to the glass fiber during thermal and hydrolytic aging processes, but should also be peelable from the glass fiber for splicing purposes.

[0208] To facilitate smaller diameter optical fibers, the low-modulus inner coating may be absent or have a thickness smaller than that used in conventional optical fibers. The high-modulus coating 58 can have a smaller thickness and smaller cross-sectional area compared to conventional optical fibers. However, the high-modulus coating 58 must still maintain the robustness and puncture resistance required for high reliability in submarine cables and repeaters. As the thickness of the high-modulus coating decreases, its protective function declines. Puncture resistance is a measure of the protective function of the cross-sectional area of ​​the outer coating (which includes the high-modulus coating and optional pigment outer coating). A high-modulus coating with higher puncture resistance withstands higher abrasive stress without failure and provides better protection for the glass fiber.

[0209] To provide the required strength and puncture resistance, the high modulus coating 58 may have the following in-situ modulus: greater than about 1500 MPa, or greater than about 1600 MPa, or greater than about 1800 MPa, or greater than about 2200 MPa, or greater than about 2500 MPa, or greater than about 2600 MPa, or greater than about 2700 MPa, or in the range of about 1500 MPa to about 3000 MPa, or in the range of about 1800 MPa to about 2800 MPa, or in the range of about 2000 MPa to about 2800 MPa, or in the range of about 2400 MPa to about 2800 MPa.

[0210] To further provide the required strength and puncture resistance, the product of the cross-sectional area of ​​the high modulus coating 58 and the in-situ modulus can be: greater than about 10 N, greater than about 12.5 N, greater than about 15 N, greater than about 20 N, greater than about 25 N, greater than about 30 N, or in the range of about 10 N to 30 N, or in the range of about 15 N to about 30 N, or in the range of about 20 N to about 30 N, or in the range of about 25 N to about 30 N.

[0211] To provide the desired combination of low (good) microbending properties and puncture resistance, the ratio of the in-situ modulus of the high modulus coating 58 to the in-situ modulus of the low modulus coating 58 may be: greater than about 4,000, or greater than about 5,000, or greater than about 6,000, or greater than about 7,000, or greater than about 8,000, or greater than about 9,000, or greater than about 10,000, or in the range of about 4,000 to about 10,000, or in the range of about 4,000 to about 10,000, or in the range of about 5,000 to about 10,000, or in the range of about 6,000 to about 10,000, or in the range of about 7,000 to about 10,000, or in the range of about 8,000 to about 10,000.

[0212] Low-modulus and high-modulus coatings are typically formed by applying a curable coating composition as a viscous liquid to glass fibers and curing it. The optical fiber may also include a pigment outer coating surrounding the high-modulus coating. The pigment outer coating may include colorants to mark the optical fiber for identification purposes and typically has a Young's modulus similar to that of the high-modulus coating.

[0213] The high modulus coating 58 may contain a trifunctional monomer. The glass transition temperature (Tg) of the high modulus coating 58 may be greater than about 50°C, or greater than about 60°C, or greater than about 70°C, or greater than about 80°C, or greater than about 90°C, or greater than about 100°C.

[0214] A suitable low-modulus inner coating 56 and a high-modulus coating 58 can be used such that the cross-sectional area of ​​the high-modulus coating is less than about 10,000 micrometers. 2 At that time, the fiber 46 has the following puncture resistance: greater than or equal to about 28g, or greater than or equal to about 30g, or greater than or equal to about 32g, or greater than or equal to about 34g, or greater than or equal to about 36g, or greater than or equal to about 38g, or greater than or equal to about 40g.

[0215] A suitable low-modulus inner coating 56 and a high-modulus coating 58 can be used such that the cross-sectional area of ​​the high-modulus coating is less than about 8,000 micrometers. 2 At that time, the fiber 46 has the following puncture resistance: greater than or equal to about 22g, or greater than or equal to about 24g, or greater than or equal to about 26g, or greater than or equal to about 28g, or greater than or equal to about 30g.

[0216] Figure 19 This illustrates the relationship between the microbending attenuation penalty (MAP) and the thickness of the low-modulus inner coating of an optical fiber having: a stepped refractive index and recessed auxiliary distribution (e.g., as shown in Table 2 above), a cladding diameter of 100 micrometers, a high-modulus coating with a modulus of 1200 MPa and an outer radius of 82.5 micrometers, and a low-modulus inner coating with a modulus of 0.5 MPa. Figure 19 As shown in Table 7a, a MAP of less than 0.1 dB / km can be achieved when the optical fiber has a recessed auxiliary distribution, a cladding diameter of approximately 100 μm, and a low-modulus inner coating thickness of approximately 10 μm to approximately 26 μm. Calculations were also performed on optical fibers with a stepped and recessed auxiliary distribution, a cladding diameter of 125 μm, a modulus of 1200 MPa, and an outer radius of 82.5 μm, as well as a low-modulus inner coating with a modulus of 0.5 MPa. As shown in Table 7b, a MAP of less than 0.1 dB / km can be achieved when the optical fiber has a recessed auxiliary distribution, a cladding diameter of approximately 125 μm, and a low-modulus inner coating thickness of approximately 8 μm to approximately 17 μm.

[0217] Table 7a: MAP of optical fibers with stepped and recessed auxiliary distributions, cladding diameter of 100 μm, Ep = 0.5 MPa, and Es = 1200 MPa

[0218]

[0219]

[0220] Table 7b: MAP of optical fibers with stepped and recessed auxiliary distributions, cladding diameter of 125 μm, Ep = 0.5 MPa, and Es = 1200 MPa

[0221]

[0222]

[0223] Figure 20 This shows the relationship between the MAP (Modal Apex) of the optical fiber and the thickness of the low-modulus inner coating. The optical fiber has: a recessed auxiliary fiber distribution (e.g., as shown in Table 2 above), a cladding diameter of 100 micrometers, a low-modulus inner coating with a modulus of 0.5 MPa, and high-modulus coatings with moduli of 1.2, 1.6, and 2.0 GPa. For example... Figure 20As shown in Table 8a, a maximum modulus (MAP) of less than 0.1 dB / km can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is approximately 8 to approximately 29 micrometers. A MAP of less than 0.05 dB / km can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is approximately 13 to approximately 24 micrometers. A MAP of less than 0.1 dB / km can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is approximately 7 to approximately 30 micrometers. A MAP of less than 0.05 dB / km can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is approximately 11 to approximately 26 micrometers. Calculations were also performed on optical fibers with recess-assisted distribution, a cladding diameter of 125 micrometers, a low-modulus inner coating with a modulus of 0.5 MPa, and high-modulus coatings with moduli of 1.2, 1.6, and 2.0 GPa. As shown in Table 8b, a maximum modulus (MAP) of less than 0.1 dB / km can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is approximately 6 to approximately 18 micrometers. A MAP of less than 0.06 dB / km can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is approximately 6 to approximately 18 micrometers. A MAP of less than 0.05 dB / km can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is approximately 10 to approximately 14 micrometers.

[0224] Table 8a: MAP of optical fibers with recess-assisted distribution, cladding diameter of 100 μm and Ep = 0.5 MPa

[0225]

[0226]

[0227] Table 8b: MAP of optical fibers with recess-assisted distribution, cladding diameter of 125 μm, and Ep = 0.5 MPa

[0228]

[0229] Figure 21 This illustrates the relationship between the puncture resistance of an optical fiber and the thickness of its low-modulus inner coating. The optical fiber has: a recessed, assisted distribution (e.g., as shown in Table 2 above), a cladding diameter of 100 micrometers, a low-modulus coating with a modulus of 0.5 MPa, and high-modulus coatings with moduli of 1.2, 1.6, and 2.0 GPa. For example... Figure 21As shown in Table 9a, a puncture resistance greater than 30g can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is less than about 14 micrometers. A puncture resistance greater than 35g can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is less than about 8 micrometers. A puncture resistance greater than 30g can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is less than about 18 micrometers. A puncture resistance greater than 35g can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is less than about 14 micrometers. A puncture resistance greater than 40g can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is less than about 9 micrometers. Calculations were also performed on optical fibers with recess-assisted distribution, a cladding diameter of 125 μm, a low-modulus inner coating with a modulus of 0.5 MPa, and high-modulus coatings with moduli of 1.2, 1.6, and 2.0 GPa. As shown in Table 9b, a puncture resistance greater than 20 g can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is less than approximately 12 μm. A puncture resistance greater than 25 g can be achieved when the high-modulus coating has a modulus of 1.6 GPa and the thickness of the low-modulus inner coating is less than approximately 7 μm. A puncture resistance greater than 20 g can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is less than approximately 13 μm. A puncture resistance greater than 25 g can be achieved when the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is less than approximately 9 μm. When the high-modulus coating has a modulus of 2.0 GPa and the thickness of the low-modulus inner coating is less than or equal to about 6 micrometers, puncture resistance greater than 30g can be achieved.

[0230] Table 9a: Puncture resistance of optical fibers with recessed auxiliary distribution, cladding diameter of 100 μm and Ep = 0.5 MPa

[0231]

[0232]

[0233] Table 9b: Puncture resistance of optical fibers with recessed auxiliary distribution and a cladding diameter of 100 μm and Ep = 0.5 MPa

[0234]

[0235]

[0236] Figure 22This illustrates the relationship between the MAP (Modal Apex) of an optical fiber and the thickness of its low-modulus inner coating. The optical fiber has: a recessed assisted fiber distribution (e.g., as shown in Table 2 above), a cladding diameter of 100 micrometers, a high-modulus coating with a modulus of 1.6 GPa, and low-modulus inner coatings with moduli of 0.5, 0.35, and 0.2 MPa. Figure 22 As shown in Table 10a, a modulus of less than 0.05 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.35 MPa and a thickness of about 8 to about 29 micrometers. A modulus of less than 0.02 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 4 to about 31 micrometers. A modulus of less than 0.02 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 7 to about 29 micrometers. A modulus of less than 0.01 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 11 to about 25 micrometers. When the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of approximately 16 to approximately 21 micrometers, a MAP of less than 0.007 dB / km can be achieved. Calculations were also performed on fibers with recess-assisted fiber distribution, a cladding diameter of 125 micrometers, a high-modulus coating with a modulus of 1.6 GPa, and low-modulus inner coatings with moduli of 0.5, 0.35, and 0.2 MPa. As shown in Table 10b, when the low-modulus inner coating has a modulus of 0.35 MPa and a thickness of approximately 6 to approximately 18 micrometers, a MAP of less than 0.05 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.35 MPa and a thickness of approximately 10 to approximately 14 micrometers, a MAP of less than 0.03 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 4 to about 19 micrometers, a maximum mean arterial pressure (MAP) of less than 0.03 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 6 to about 17 micrometers, a MAP of less than 0.02 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 10 to about 13 micrometers, a MAP of less than 0.01 dB / km can be achieved.

[0237] Table 10a: MAP of optical fibers with recess-assisted distribution, cladding diameter of 100 μm, and Es = 1.6 GPa

[0238]

[0239]

[0240] Table 10b: MAP of optical fibers with recess-assisted distribution, cladding diameter of 125 μm, and Es = 1.6 GPa

[0241]

[0242] Table 11a shows the relationship between the MAP (Modulus Amount) and the thickness of the low-modulus inner coating of the optical fiber having: a recessed auxiliary fiber distribution (e.g., as shown in Table 2 above), a cladding diameter of 100 micrometers, a high-modulus coating with a modulus of 2.0 GPa, and low-modulus inner coatings with moduli of 0.35, 0.2, and 0.1 MPa. As shown in Table 11a, a MAP of less than 0.02 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.35 MPa and a thickness of approximately 6 to approximately 30 micrometers. A MAP of less than 0.02 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.35 MPa and a thickness of approximately 13 to approximately 23 micrometers. A MAP of less than 0.02 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of approximately 6 to approximately 30 micrometers. When the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 9 to about 27 micrometers, a maximum mean arterial pressure (MAP) of less than 0.01 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of about 14 to about 22 micrometers, a MAP of less than 0.005 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.1 MPa and a thickness of about 6 to about 29 micrometers, a MAP of less than 0.005 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.1 MPa and a thickness of about 13 to about 23 micrometers, a MAP of less than 0.002 dB / km can be achieved. Calculations were also performed on fibers with recess-assisted fiber distribution, a cladding diameter of 125 μm, a high-modulus coating with a modulus of 2.0 GPa, and low-modulus inner coatings with moduli of 0.35, 0.2, and 0.1 MPa. As shown in Table 10b, a MAP of less than 0.03 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.35 MPa and a thickness of approximately 5 to approximately 12 μm. A MAP of less than 0.02 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of approximately 5 to approximately 18 μm. A MAP of less than 0.01 dB / km can be achieved when the low-modulus inner coating has a modulus of 0.2 MPa and a thickness of approximately 8 to approximately 14 μm. When the low-modulus inner coating has a modulus of 0.1 MPa and a thickness of approximately 5 to approximately 18 micrometers, a MAP of less than 0.005 dB / km can be achieved. When the low-modulus inner coating has a modulus of 0.1 MPa and a thickness of approximately 8 to approximately 14 micrometers, a MAP of less than 0.01 dB / km can be achieved. Table 11a: MAP of optical fibers with recess-assisted distribution, a cladding diameter of 100 micrometers, and Es = 2.0 GPa.

[0243]

[0244]

[0245] Table 11b: MAP of optical fibers with recess-assisted distribution, cladding diameter of 125 μm, and Es = 2.0 GPa

[0246]

[0247] Can be merged Figure 19-2 3. The calculated MAP and puncture resistance results given in Tables 7-11 provide the minimum thicknesses for obtaining the maximum MAP and minimum puncture resistance of the low-modulus inner coating and the high-modulus coating, to input the values ​​of the maximum modulus (Ep) of the low-modulus primary coating, the minimum modulus (Es) of the high-modulus coating, the glass radius (Rg), and the radius (Rs) of the high-modulus coating. Table 12a summarizes the coating properties of Examples 1-4 with a cladding diameter of 100 μm and Es = 1.6 GPa. Tables 12b and 12c summarize the coating properties of Examples 5-14 with a cladding diameter of 100 μm and Es = 2.0 GPa. Tables 12d and 12e summarize the coating properties of Examples 15-21 with a cladding diameter of 100 μm.

[0248] Table 12a: Minimum thickness of low-modulus inner coatings and high-modulus coatings providing maximum MAP and minimum puncture resistance for given values.

[0249]

[0250] Table 12b: Minimum thickness of low-modulus inner coatings and high-modulus coatings providing maximum MAP and minimum puncture resistance for given values.

[0251]

[0252]

[0253] Table 12c: Minimum thickness of low-modulus inner coatings and high-modulus coatings providing maximum MAP and minimum puncture resistance for given values.

[0254]

[0255] Table 12d: Minimum thickness of low-modulus inner coatings and high-modulus coatings providing maximum MAP and minimum puncture resistance for given values.

[0256]

[0257]

[0258] Table 12e: Minimum thickness of low-modulus inner coatings and high-modulus coatings providing maximum MAP and minimum puncture resistance for given values.

[0259]

[0260] Exemplary implementation of diameter reduction

[0261] As discussed above, the optical fiber of the disclosed embodiments may have a glass diameter of approximately 125 micrometers, and the reduced coating diameter may have an outer diameter of approximately 175 micrometers or less, or approximately 170 micrometers or less, or approximately 165 micrometers or less, or approximately 160 micrometers or less, or approximately 145 micrometers or less. It should be noted that the outer diameter of the cladding region 50 is the glass diameter of the optical fiber 46, and the outer diameter of the high-modulus coating 58 may be the overall outer diameter of the optical fiber 46 (when no pigment outer coating layer is applied).

[0262] In some exemplary embodiments, the cladding region 50 has an outer diameter of about 125 micrometers and the high modulus coating 58 has an outer diameter of about 155 to 175 micrometers, or the cladding region 50 has an outer diameter of about 125 micrometers and the high modulus coating 58 has an outer diameter of about 160 to 170 micrometers.

[0263] As discussed above, the optical fiber of the disclosed embodiments may also have a glass diameter of approximately 100 micrometers, and the reduced coating diameter may have an outer diameter of approximately 175 micrometers or less, or approximately 170 micrometers or less, or approximately 165 micrometers or less, or approximately 160 micrometers or less, or approximately 145 micrometers or less. It should be noted that the outer diameter of the cladding region 50 is the glass diameter of the optical fiber 46, and the outer diameter of the high-modulus coating 58 may be the overall outer diameter of the optical fiber 46 (when no pigment outer coating layer is applied).

[0264] In some exemplary embodiments, the cladding region 50 has an outer diameter of about 100 micrometers and the high modulus coating 58 has an outer diameter of about 155 to 175 micrometers, or the cladding region 50 has an outer diameter of about 100 micrometers and the high modulus coating 58 has an outer diameter of about 160 to 170 micrometers.

[0265] As discussed above, the reduced-diameter fiber distribution design of this disclosure offers specific advantages, such as higher fiber counts in submarine cables and repeaters. However, the reduced cladding diameter may allow some light to leak through the cladding due to the reduced cladding profile. Therefore, the offset recess design of this disclosure has approximately 30% Δ-micrometer. 2 The large recessed volume thus advantageously reduces “tunneling” or “radiation” losses caused by light leakage through the cladding with a reduced diameter.

[0266] To facilitate a reduction in fiber diameter, it is preferable to minimize or completely eliminate the thickness r5-r4 of the low-modulus inner coating. The thickness r5-r4 of the low-modulus inner coating is: less than or equal to about 8.0 micrometers, or less than or equal to about 7.0 micrometers, or less than or equal to about 6.0 micrometers, or less than or equal to about 5.0 micrometers, or in the range of about 4.0 micrometers to about 8.0 micrometers, or in the range of about 5.0 micrometers to about 7.0 micrometers. However, eliminating or reducing the thickness of the low-modulus inner coating of the fiber increases microbending sensitivity. In the design disclosed herein, by adding a volume greater than about 30% Δ-micrometer... 2 The offset depression is used to alleviate this increased sensitivity.

[0267] The radius r6 of the high-modulus coating is less than or equal to about 87.5 micrometers, or less than or equal to about 85.0 micrometers, or less than or equal to about 82.5 micrometers, or less than or equal to about 80.0 micrometers. It is also preferable to optimize the thickness r6-r5 of the high-modulus coating to balance the decrease in fiber diameter and to have a sufficiently high cross-sectional area for high puncture resistance. The thickness r6-r5 of the high-modulus coating is less than or equal to about 25.0 micrometers, or less than or equal to about 20.0 micrometers, or less than or equal to about 15.0 micrometers, or in the range of about 15.0 micrometers to about 25.0 micrometers, or in the range of about 17.5 micrometers to 22.5 micrometers, or in the range of about 18.0 micrometers to 22.0 micrometers. The total thickness of the low-modulus coating and the high-modulus coating is about 25 micrometers or less, preferably about 20 micrometers or less. In some embodiments, the total thickness of the low-modulus coating and the high-modulus coating is about 10 micrometers to about 25 micrometers. In some embodiments, the ratio of the thickness of the low-modulus coating layer to the thickness of the high-modulus coating layer ranges from 0.8 to 1.2.

[0268] Therefore, the optical fiber according to the embodiments of this disclosure has a reduced coating diameter compared to conventional optical fibers. This size reduction helps increase the "fiber count" and fiber density in, for example, submarine repeaters or optical cables.

[0269] Table 10 below provides the average coating thicknesses of five high-modulus coating samples. Examples 1 and 2, compared to Examples 3, 4, and 5, show that average high-modulus coating thicknesses in the range of 8.0 micrometers to 20.0 micrometers resulted in higher tensile strengths compared to average thicknesses below this range. The higher tensile strength exhibited by Examples 1 and 2 enables the use of thinner high-modulus coatings in optical fibers (e.g., those used in submarine cables and repeaters).

[0270] Table 10: Thickness of High Modulus Coating

[0271]

[0272] Exemplary low-modulus and high-modulus coatings

[0273] The following section discusses exemplary low-modulus and high-modulus coatings, as well as measurements of the coating's strength and puncture resistance.

[0274] Low modulus coating: Composition. The low modulus coating composition comprises the formulations given in Table 11 below and is a typical commercially available low modulus coating composition.

[0275] Table 11: Reference Low Modulus Coating Compositions

[0276] Components quantity oligomer materials 50.0% by weight SR504 46.5% by weight NVC 2.0% by weight TPO 1.5% by weight Irganox 1035 1.0pph 3-Acryloyloxypropyltrimethoxysilane 0.8pph Pentaerythritol tetra-(3-mercaptopropionate) 0.032pph

[0277] As described in this paper, oligomer materials were prepared from H12MDI, HEA, and PPG4000 using a molar ratio of n:m:p = 3.5:3.0:2.0; SR504 was ethoxylated (4) nonylphenol acrylate (purchased from Sartomer); NVC was N-vinylcaprolactam (purchased from Aldrich); TPO (photoinitiator) was (2,4,6-trimethylbenzoyl)-diphenylphosphine oxide (purchased from BASF); Irganox 1035 (antioxidant) is phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester (purchased from BASF); 3-acryloyloxypropyltrimethoxysilane is an adhesion promoter (purchased from Gelest); and pentaerythritol tetra-(3-mercaptopropionate) (also known as tetrathiol, purchased from Aldrich) is a chain transfer agent. The concentration unit "pph" refers to the amount relative to the base composition containing all monomers, oligomers, and photoinitiators. For example, a 1.0 pph concentration of Irganox 1035 corresponds to 1 g of Irganox 1035 per 100 g of oligomer material, SR504, NVC, and TPO.

[0278] Oligomeric materials were prepared by mixing H12MDI (4,4'-methylenebis(cyclohexyl isocyanate)), dilauryl dibutyltin, and 2,6-di-tert-butyl-4-methylphenol in a 500 mL flask at room temperature. The flask was equipped with a thermocouple, a CaCl2 drying tube, and a stirrer. PPG4000 was added over 30–40 minutes using a feeding funnel while the contents of the flask were continuously stirred. The internal temperature of the reaction mixture was monitored during the addition of PPG4000, and the introduction of PPG4000 was controlled to prevent overheating (due to the exothermic nature of the reaction). After the addition of PPG4000, the reaction mixture was heated in an oil bath at approximately 70–75 °C for approximately 1–1.5 hours. Samples of the reaction mixture were taken at various time intervals, and the reaction progress was monitored by Fourier transform infrared spectroscopy (FTIR) analysis to determine the concentration of unreacted isocyanate groups. The reaction time was based on a temperature of approximately 2265 cm⁻¹. -1 The intensity of the characteristic isocyanate stretching pattern is used to assess the concentration of unreacted isocyanate groups. The flask is removed from the oil bath and the contents are allowed to cool naturally to below 65°C. Supplemental HEA is added to ensure complete quenching of the isocyanate groups. Using a feeding funnel, supplemental HEA is added dropwise over 2–5 minutes. After adding supplemental HEA, the flask is returned to the oil bath, and the contents are reheated to approximately 70–75°C for approximately 1–1.5 hours. The reaction mixture is analyzed by FTIR to assess the presence of isocyanate groups, and this process is repeated until sufficient supplemental HEA has been added to completely react with any unreacted isocyanate groups. Complete reaction is considered achieved when no perceptible isocyanate stretching strength is detected in the FTIR measurement.

[0279] High modulus coatings: Composition. Table 12 lists four curable high modulus coating compositions (A, SB, SC, and SD).

[0280] Table 12: High Modulus Coating Compositions

[0281]

[0282] PE210 is bisphenol A epoxy diacrylate (purchased from Miwon Specialty Chemicals, Korea); M240 is ethoxylated (4) bisphenol A diacrylate (purchased from Miwon Specialty Chemicals, Korea); M2300 is ethoxylated (30) bisphenol A diacrylate (purchased from Miwon Specialty Chemicals, Korea); M3130 is ethoxylated (3) trimethylolpropane triacrylate (purchased from Miwon Specialty Chemicals, Korea); TPO (photoinitiator) is (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (purchased from BASF); Irgacure 184 (photoinitiator) is 1-hydroxycyclohexylphenyl ketone (purchased from BASF); Irganox 1035 (antioxidant) is phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester (purchased from BASF). DC190 (slip agent) is a silicone-ethylene oxide / propylene oxide copolymer (purchased from Dow Chemical Company). The concentration unit "pph" refers to the amount relative to the base composition containing all monomers and photoinitiators. For example, for high modulus coating composition A, a 1.0 pph concentration of DC-190 corresponds to 1 g of DC-190 per 100 g of the total amount of PE210, M240, M2300, TPO, and Irgacure 184.

[0283] High modulus coatings: tensile properties. The Young's modulus, yield tensile strength, yield strength, and yield elongation of high modulus coatings prepared from high modulus compositions A, SB, SC, and SD were measured using the techniques described above. The results are summarized in Table 13.

[0284] Table 13: Tensile properties of high modulus coatings

[0285]

[0286] The results showed that the high-modulus coatings prepared from compositions SB, SC, and SD exhibited higher Young's modulus and higher yield strength than the high-modulus coating prepared from comparative composition A. Furthermore, the high-modulus coatings prepared from compositions SB, SC, and SD exhibited higher fracture toughness compared to the high-modulus coating prepared from composition A. The higher values ​​exhibited by compositions SB, SC, and SD enabled the use of thinner high-modulus coatings in optical fibers without sacrificing performance. As discussed above, thinner high-modulus coatings reduce the overall diameter of the optical fiber and allow for a higher fiber count in a given cross-sectional area of ​​cable (e.g., in a submarine repeater).

[0287] Exemplary fiber optic implementation

[0288] The experimental examples and principles disclosed in this paper demonstrate that sufficiently low attenuation and puncture resistance can be achieved in optical fibers with reduced diameters by adjusting the refractive index distribution and coating properties. More specifically, despite a smaller cross-sectional area, the high-modulus coating provides sufficient puncture resistance for optical fibers with reduced diameters.

[0289] Figure 8 This is a graph showing the dependence of puncture load (in grams) on the cross-sectional area of ​​the high-modulus coating. The dashed line represents 0.00263 g / micron. 2 The slope corresponds to that of a comparative fiber with a high-modulus coating having an in-situ modulus of approximately 1500 GPa. The solid line is a linear fit of the measurement data for five fibers with a high-modulus coating having an in-situ modulus of approximately 1850 GPa. The slope is 0.00328 g / μm. 2 This is approximately equal to the ratio of the slope of the reference fiber to its in-situ modulus (1850 / 1500). The dashed line represents the modeling dependency of the puncture load (in grams) on the cross-sectional area of ​​the high-modulus coating with an in-situ modulus of 2200 GPa. The results show that increasing the in-situ modulus of the high-modulus coating achieves a reduction in cross-sectional area and thickness without significantly degrading the puncture resistance of smaller diameter fibers.

[0290] Fiber drawing process

[0291] The optical fibers disclosed herein can be formed using a continuous optical fiber manufacturing process, in which glass fibers are drawn from a heated preform and sized to a target diameter. In the optical fiber containing a low-modulus inner coating, the glass fibers are then cooled and guided to a coating system to apply a liquid low-modulus coating composition to the glass fibers. After the liquid low-modulus coating composition is applied to the glass fibers, two feasible processing options exist. In one processing option (dry-to-wet process), the liquid low-modulus coating composition is cured to form a solidified low-modulus coating, a liquid high-modulus coating composition is applied to the cured low-modulus coating, and the liquid high-modulus coating composition is cured to form a solidified high-modulus coating. In the second processing option (wet-to-wet process), a liquid high-modulus coating composition is applied to a liquid low-modulus coating composition, and both liquid coating compositions are cured simultaneously to provide solidified low-modulus and high-modulus coatings. After the optical fiber leaves the coating system, it is collected and stored at room temperature. Collection of the optical fiber typically requires winding the fiber onto a spool and storing the spool.

[0292] In some processes, the coating system also applies a pigment outer coating composition to the high-modulus coating and cures the pigment outer coating composition to form a solidified pigment outer coating. Typically, the pigment outer coating is an ink layer used to mark optical fibers for identification purposes and has a composition similar to the high-modulus coating in terms of pigments and other aspects. The pigment outer coating is applied to the high-modulus coating and cured. Typically, the high-modulus coating has already cured when the pigment outer coating is applied. The low-modulus, high-modulus, and pigment outer coating compositions can be applied and cured in a common continuous manufacturing process. Alternatively, the low-modulus and high-modulus coating compositions can be applied and cured in a common continuous manufacturing process for collecting the coated optical fibers, and the pigment outer coating composition can be applied and cured in separate offline processes to form the pigment outer coating.

[0293] Coating application, coating material viscosity and coating die size

[0294] In some embodiments, optical fibers are drawn from a preform in a drawing furnace and then passed through a coating system, where a polymer coating is applied to the optical fiber. The coating system may include an inlet and a sizing mandrel. A coating chamber is arranged between the inlet and the sizing mandrel. The coating chamber is filled with a polymer coating material in liquid form. The optical fiber enters the coating system through the inlet and passes through the coating chamber, where the polymer coating material is applied to the surface of the optical fiber. The optical fiber then passes through the sizing mandrel, where any excess coating material is removed as the optical fiber exits the coating system, thereby achieving a coated optical fiber with a specified diameter according to some embodiments described herein.

[0295] Figure 12 This shows the effect of coating viscosity and die size on coating thickness at a given constant drawing speed (60 m / min in this case). Figure 12 As shown, the coating thickness is primarily affected by the diameter of the size adjustment die, while the viscosity of the coating material has only a marginal effect. For example, when the size adjustment die changes from 5.1 mils (129.54 μm) to 8.0 mils (203.2 μm), the diameter of the coated optical fiber changes from 127 μm to 169 μm, while for a given die size, the coating thickness changes only slightly with a wide range of coating material viscosities. In some embodiments, the viscosity of the coating material is greater than 20 poise at 50 rpm and 25°C, or greater than 40 poise at 50 rpm and 25°C.

[0296] Figure 13 An exemplary parameter window shows the final target coating diameter of 132 ± 1 μm formed on a 125 μm glass fiber. (Example parameter window follows.) Figure 13As shown, the size adjustment die was identified as having a viscosity range of 5.35 mils (135.89 μm) to 5.51 mils (140 μm), while the coating material viscosity can have a wide range within the parameter window. Therefore, although the coating material viscosity has only a marginal effect on the final coating thickness, the effective size differs for different die size systems. Figure 14 This displays the standard deviation of coating thickness for different die head size systems, derived from the viscosity of various coating materials. Figure 14 The standard deviation shows that it increases slightly with the increase of the die size, and rises sharply when the die size is greater than 7 mils. Figure 15 This illustrates the effect of drawing speed on coating thickness according to some embodiments of this disclosure. For example... Figure 15 As can be seen, the fiber drawing speed has a limited impact on the coating thickness.

[0297] For coating concentricity, it is assumed that the lubrication pressure in the coating die acts as a centering force to ensure the fiber is centered in the coating applicator. Higher lubrication pressure represents a greater centering force, which results in better coating concentricity. Figure 16 The graph shown plots the correlation between viscosity of a series of coating materials, lubrication pressure, and die size. Figure 16 The results show that lubrication pressure decreases with increasing die size and increases with increasing coating material viscosity. Furthermore, Figure 17 This shows the correlation between lubrication pressure and drawing speed. For example... Figure 17 As shown, with the increase of drawing speed, the lubrication pressure first increases sharply and then increases at a slow pace. Therefore, considering the effect of viscosity on coating thickness discussed above, given the die size, increasing the drawing speed and using a material with higher viscosity can improve coating concentricity without degrading the coating thickness quality.

[0298] Performance data of optical fibers with thin coating

[0299] Key performance parameters for these thinly coated optical fibers include their total outer diameter, polymer coating thickness, number of breaks per unit length under a 50 kpsi strength screening, and longest surviving length after a 50 kpsi screening. A high-modulus coating layer was applied to 125 μm single-mode fiber (SMF) with an overall coating thickness of approximately 7 μm (see Reel ID 121-6599-3 and Reel ID 122-6645-4 in Table 15). Lower screening strength resulted in longer unbroken fiber segments. The high-modulus coated fiber (Reel ID 121-6599-3) exhibited similar fiber strength to the freshly high-modulus coated fiber (Reel ID 122-6645-4). The inventors found that the thin acrylate hard fiber coating using the freshly high-modulus coated fiber had a concentricity greater than approximately 70%, and in some embodiments, greater than approximately 80%, or greater than approximately 85%, or greater than approximately 90%, or greater than approximately 95%.

[0300] Table 15: Performance data of optical fibers with high-modulus coatings

[0301]

[0302] Compared to aged high-modulus thin acrylate-coated fibers with a total coating thickness of approximately 7 μm applied to 125 μm SMF fibers (see Reel ID 121-6602-10 and Reel ID 121-6602-12 in Table 16), the fresh high-modulus coated fiber shown in Reel ID 121-6599-3 exhibits significantly higher longest stored length (m) and a thin-coated fiber screening meter / (break count + 1) ratio when screened at 50 kpsi. The breakage of all three fibers is fairly uniformly distributed across the entire fiber screening length. This suggests that older high-modulus coated fibers are most likely to degrade, particularly during storage. Furthermore, all three thin acrylate-coated fibers exhibit good concentricity (i.e., >70%).

[0303] Table 16: Performance data of optical fibers with high-modulus coatings

[0304]

[0305] A thin layer of fresh high-modulus acrylate coating was applied to 125 μm SMF fiber, resulting in an overall coating thickness of 15 μm (see Reel ID 121-6599-4 and Reel ID 122-6645-3 in Table 15). By using a fresh high-modulus coating layer, the coating thickness was increased from 7 μm in Reel ID 121-6599-3 to 15 μm in Reel ID 121-6599-4. The thinly coated fiber was significantly stronger, as evidenced by a marked increase in both the longest preserved length (m) and the ratio of thin-coated fiber screening meters / (break count + 1) when the thin-coated fiber was screened at 50 kpsi. By employing a fresh high-modulus coating layer, increasing the coating thickness from 7 μm in Reel ID 122-6645-4 to 15 μm in Reel ID 122-6645-3, the thinly coated fibers are significantly stronger, as evidenced by a marked increase in both the longest surviving length (m) and the ratio of screening meters / (break count + 1) when screened at a force of 50 kpsi. Furthermore, the thin acrylate fiber hard coating exhibits good concentricity (i.e., >70%). These thin acrylate-coated fibers with a total coating thickness of 15 μm (Reel ID 121-6599-4 and Reel ID 122-6645-3 in Table 15) are strong enough to survive cable handling.

[0306] Thin bilayer acrylic fiber coatings were also applied, consisting of a fresh low-modulus coating layer and a fresh high-modulus coating layer (see Reel ID 121-6599-5 in Table 16). The low-modulus coating layer was 9 μm thick, and the high-modulus coating layer was 8 μm thick. The total thickness of the low-modulus coating layer plus the high-modulus coating layer was 17 μm. The thin acrylic coating ran smoothly, and there were no defects in the coating on the fiber. This thin-coated fiber was screened at 50 kpsi, and the screening results were similar to those of a fresh high-modulus coating layer with a total coating thickness of 15 μm on a 125 μm SMF fiber (see Reel ID 121-6599-4 in Table 15). The thin acrylic fiber hard coating exhibited good concentricity (i.e., >70%). This thin acrylic-coated fiber was also strong enough to survive cable-bearing operations. In the presence of a soft, thin low-modulus coating layer, this bilayer thin-coated fiber improved microbending performance compared to a single thin hard-coated fiber.

[0307] Table 17: Performance data of optical fibers with low-modulus and high-modulus coatings

[0308]

[0309]

[0310] For a standard single-mode fiber (graded refractive index core, with a silica inner cladding and a positively doped outer cladding, the relative refractive index distribution is as follows:) Figure 18 As shown in the figure, thin bilayer acrylate fiber coatings with fresh low-modulus and high-modulus coatings were drawn. The fiber coating parameters and measured optical parameters are shown in Table 18 below. The table shows three thin coating configurations with low-modulus coating diameter / high-modulus coating diameter ratios of 145μm / 175μm, 140μm / 160μm, and 0μm / 140μm. A standard coating with a low-modulus coating diameter / high-modulus coating diameter ratio of 190μm / 250μm was used as a control. For the thin-coated fibers, the measured cutoff wavelength and MFD were similar to the control fiber, indicating that the thin coating did not affect these parameters. For fibers with low-modulus inner coating diameters / high-modulus coating diameter ratios of 145μm / 175μm and 140μm / 160μm, the attenuation at 1310 and 1550nm was the same as the control fiber, showing that these thin coating configurations did not cause any attenuation penalty. Fibers with a low-modulus inner coating diameter of 0 μm / 140 μm and a high-modulus coating diameter have slightly higher attenuation than other fibers, which is due to the single coating layer, but is acceptable for many applications that use short fibers (e.g., data centers).

[0311] Table 18: Performance data of optical fibers with low-modulus and high-modulus coating diameters of 145μm / 175μm, 140μm / 160μm, and 0μm / 140μm.

[0312]

[0313] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope or spirit of the invention. Because those skilled in the art can conceive of various improved combinations, sub-combinations, and variations of the described embodiments that incorporate the spirit and essence of the invention, the invention should be considered to include all the contents within the scope of the appended claims and their equivalents.

Claims

1. An optical fiber, comprising: Core area; A cladding region surrounding a core region, the cladding region comprising: an inner cladding directly adjacent to the core region, and an outer cladding surrounding the inner cladding, the cladding region having a diameter range of 90.0 micrometers to 130.0 micrometers; as well as A polymer coating with a thickness of 2 micrometers to 20 micrometers, wherein the polymer coating comprises one of the following: (i) a high-modulus coating layer surrounding the cladding region, wherein the high-modulus coating layer has a Young's modulus of 1.5 GPa or greater, or (ii) a low-modulus coating layer surrounding the cladding region, wherein the low-modulus coating layer has a Young's modulus of 0.5 MPa or less and is disposed between the cladding region and the high-modulus coating layer, wherein the outer diameter of the coated optical fiber is less than or equal to 175 micrometers.

2. The optical fiber as described in claim 1, wherein, The diameter of the cladding region ranges from 120.0 micrometers to 130.0 micrometers.

3. The optical fiber as described in claim 1, wherein, The thickness of the polymer coating ranges from 2 micrometers to 15 micrometers.

4. The optical fiber as described in claim 1, wherein, Low-modulus coatings have a thickness of less than 8 micrometers.

5. The optical fiber as described in claim 1, wherein, The ratio of the thickness of the low-modulus coating layer to the thickness of the high-modulus coating layer ranges from 0.8 to 1.

2.

6. The optical fiber as described in claim 1, wherein, The cladding of the optical fiber consists of a titanium oxide doped layer with a titanium oxide doping concentration of 5% to 25% by weight.

7. The optical fiber as described in claim 1, wherein, The polymer coating has a concentricity of more than 70% relative to the fiber core.

8. The optical fiber as claimed in claim 1, wherein, The high-modulus coating layer has a Young's modulus of 1.6 GPa or greater, and the low-modulus coating layer has a Young's modulus of 0.35 MPa or less.

9. The optical fiber as claimed in claim 1, wherein, The fiber attenuation is 0.36 dB / km or less at 1310 nm and 0.24 dB / km or less at 1550 nm.

10. A method for coating an optical fiber, comprising: Fiber optic cable is drawn from a drawing furnace along a first vertical path; The optical fiber is guided through a coating system in which a polymer coating is applied to the optical fiber. The coating system includes: an inlet; a sizing mandrel with a diameter of 129 μm to 203 μm opposite the inlet; and a coating chamber disposed between the inlet and the sizing mandrel, wherein the coating chamber is filled with a coating material in liquid form. This process solidifies the coated optical fiber, resulting in an outer diameter of the coated optical fiber of 175 micrometers or less. The thickness of the polymer coating ranges from 2 micrometers to 20 micrometers. The optical fiber includes a cladding region with a diameter ranging from 90.0 micrometers to 130.0 micrometers.

11. The method of claim 10, wherein, The diameter of the cladding region ranges from 120.0 micrometers to 130.0 micrometers.

12. The method of claim 10, wherein, The coating thickness of the mold head can be adjusted to 25 μm or less by size adjustment.

13. The method of claim 10, wherein, The thickness of the polymer coating ranges from 2 micrometers to 15 micrometers.

14. The method of claim 10, wherein, The polymer coating has a concentricity of more than 70%.

15. The method of claim 10, wherein, At 50 rpm and 25°C, the viscosity of the coating material is greater than 20 poise.

16. An optical fiber comprising: Core area; The cladding region surrounding the fiber core region includes: The inner cladding layer directly adjacent to the fiber core region. The outer cladding surrounding the inner cladding, and A recessed region is arranged radially between the inner and outer cladding layers, the recessed region having a depth of 30% Δ-micrometer. 2 Or larger volume; A high-modulus coating surrounding the cladding region, wherein the high-modulus coating has an in-situ modulus E of 1500 MPa or greater. S ; A low-modulus coating surrounds the cladding region, wherein the low-modulus coating is disposed between the cladding region and the high-modulus coating. The outer diameter of the optical fiber is less than or equal to 175 micrometers. The cladding region includes a diameter range of 90.0 micrometers to 130.0 micrometers, and The total thickness of the low-modulus coating and the high-modulus coating is between 2 micrometers and 20 micrometers.

17. The optical fiber as claimed in claim 16, wherein, The diameter of the cladding region ranges from 120.0 micrometers to 130.0 micrometers.

18. The optical fiber as claimed in claim 16, wherein, The Young's modulus of the low-modulus coating ranges from 0.1 MPa to 0.7 MPa.

19. The optical fiber as claimed in claim 16, wherein, The low-modulus coating has a thickness of 8 micrometers or less.

20. The optical fiber as described in any one of claims 16-19, wherein, The total thickness of the low-modulus coating and the high-modulus coating is 2 micrometers to 15 micrometers.

21. The optical fiber as claimed in claim 16, wherein, The in-situ modulus range of high modulus coatings is 1600 MPa to 3000 MPa.

22. The optical fiber as claimed in claim 16, wherein, The glass transition temperature of the high modulus coating is greater than 50 degrees Celsius.

23. The optical fiber as claimed in claim 16, wherein, The radius r1 of the core region is 3.0 μm to 6.5 μm, the radius r2 of the inner cladding region is 7.0 μm to 15.0 μm, and the outer radius r3 of the recessed region is 10.0 μm to 20.0 μm.

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