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

Abstract

This invention provides a small-diameter single-mode optical fiber with reduced coating thickness without significantly compromising puncture resistance. [Solution] The optical fiber comprises a core region, a cladding region surrounding the core region, which includes an inner cladding directly adjacent to the core region and an outer cladding surrounding the inner cladding, 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. The low modulus coating layer has a layer thickness in the range of 4 μm to 20 μm and an elastic modulus of about 0.35 MPa or less, and the high modulus coating layer has a layer thickness in the range of 4 μm to 20 μm and an elastic modulus of about 1.6 GPa or more. The optical fiber has puncture resistance of more than 20 g and a microbend attenuation penalty of less than 0.03 dB / km, and the outer diameter of the coated optical fiber is 175 μm or less.

Description

Cross-reference of related applications

[0001] This application claims priority under Section 119 of the United States Patent Act to U.S. Provisional Patent Application No. 63 / 054,563 filed on 21 July 2020, the contents of which the said Provisional Patent Application is relied upon and incorporated herein by reference in its entirety. [Technical Field]

[0002] This disclosure relates to a single-mode optical fiber. More specifically, this disclosure relates to a small-diameter single-mode optical fiber. More specifically, this disclosure relates to a small-diameter single-mode optical fiber in which the coating thickness is reduced without a significant reduction in puncture resistance. [Background technology]

[0003] Optical fiber technology is permeating data centers due to cloud computing and the Internet of Things, which require high bandwidth, low latency, low power consumption, and immunity to EMI / RFI. Future hyperscale data centers will require specific features such as 100,000 servers spread across 500,000 square feet, creating a demand for greater capacity, flexibility, and efficiency in the interconnection schemes within the data center. Consequently, a large number of interconnections will be needed within the data center. While ribbon cables can increase the number of fibers, such a high fiber count necessitates smaller diameter fibers to accommodate the ribbon cable. For example, using a bare fiber ribbon cable with an overall diameter of 125 μm instead of a 2-layer acrylate-coated fiber ribbon cable with an overall diameter of 250 μm reduces volume by at least 75%. However, processing bare fibers into ribbon cables can result in fiber breakage.

[0004] Furthermore, submarine fiber optic cables are designed to carry long-distance communication signals across land and sea. Over the past few decades, long-distance communication signals via submarine cables have increased dramatically, and currently, 90% of intercontinental communication signals are transmitted through these cables. Consequently, the demand for transmission capacity of such submarine cables is increasing due to the growth of internet traffic between different continents. Such capacity increases have traditionally been facilitated by increasing the bandwidth capacity of each fiber, for example, by simply increasing the bit rate while keeping the number of fibers low, typically 4 to 8 pairs of fibers, or by using high-density wavelength division multiplexing (DWDM).

[0005] However, the implementation of these advanced transmission technologies caused the power consumption of the optical repeaters in this system to exceed the level that could be supplied by the terminals. These power constraints forced the designers of the submarine system to use a larger number of fibers. As the number of fibers increases, it becomes necessary to use smaller diameter fibers to fit into the limited space inside the optical repeater. The cladding diameter of these fibers should preferably be maintained at 125 micrometers to facilitate fusion splicing to conventional single-mode fibers, which means achieving such a relatively small diameter by reducing the thickness of the protective coating. This relatively thin coating, along with a sufficiently large cross-sectional area, must have a high modulus of elasticity to ensure high resistance to puncture and abrasion. [Overview of the project] [Problems that the invention aims to solve]

[0006] Improvements in the above-mentioned areas are desired. Therefore, the inventors have developed an improved thin, coated single-mode optical fiber with sufficiently high mechanical reliability. [Means for solving the problem]

[0007] According to a first embodiment of the present disclosure, the present description relates to an optical fiber comprising: 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, the radius of the cladding region being less than approximately 62.5 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, the thickness of the low modulus inner coating layer being 4 micrometers. The optical fiber includes a polymer coating having a chromate of ~20 micrometers, an elastic modulus of the low modulus inner coating layer of approximately 0.35 MPa or less, a thickness of 4 to 20 micrometers for the high modulus coating layer, an elastic modulus of approximately 1.6 GPa or more, a puncture resistance of the optical fiber exceeding 20 g, a microbend attenuation penalty of the optical fiber less than 0.03 dB / km, an outer diameter of the coated optical fiber of 175 micrometers or less, and the puncture resistance of the optical fiber is given by formula P R =P0+C1E s A s It is calculated by, where A s This is the cross-sectional area of ​​the high modulus coating described above, and E s The above high modulus coating has a modulus of elasticity, P0 is a coefficient with a value of 11.3 g, and C1 is 2.1 g / MPa / mm 2 The coefficient has a value of , and the above microbend attenuation penalty of the optical fiber is given by the formula:

[0008]

number

[0009] It is calculated by, 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.

[0010]

Number

[0011] and is

[0012]

Number

[0013] and is

[0014]

Number

[0015] and is

[0016]

Number

[0017] and is, R g is the radius of the glass, R s is the outer radius of the high elastic modulus outer coating, t p is the thickness of the inner low elastic modulus coating, t s is the thickness of the high elastic modulus outer coating, E g is the elastic modulus of the glass, E p is the elastic modulus of the low elastic modulus inner coating, E s is the elastic modulus of the high elastic modulus coating.

[0018] According to the second embodiment of the present disclosure, in the optical fiber of the first embodiment, the microbend attenuation penalty of the optical fiber is 0.01 dB / km or less.

[0019] According to the third embodiment of the present disclosure, in the optical fiber of the first embodiment, the microbend attenuation penalty of the optical fiber is 0.007 dB / km or less.

[0020] According to the fourth embodiment of this disclosure, in the optical fiber of the first embodiment, the microbend attenuation penalty of the optical fiber is 0.003 dB / km or less.

[0021] According to the fifth embodiment of this disclosure, in the optical fiber of the first embodiment, the puncture resistance of the optical fiber is 25 g or more.

[0022] According to the sixth embodiment of this disclosure, in the optical fiber of the first embodiment, the puncture resistance of the optical fiber is 30 g or more.

[0023] According to the seventh embodiment of this disclosure, in the optical fiber of the first embodiment, the radius of the cladding region is less than 52.5 micrometers, and the puncture resistance of the optical fiber is greater than 40 g.

[0024] According to the eighth embodiment of this disclosure, in the optical fiber of the first embodiment, the thickness of the high modulus coating layer is 9 micrometers to 18 micrometers.

[0025] According to the ninth embodiment of this disclosure, in the optical fiber of the first embodiment, the attenuation of the optical fiber is less than 0.20 dB / km.

[0026] According to the tenth embodiment of this disclosure, in the optical fiber of the first embodiment, the mode field diameter of the optical fiber at 1310 nm is 8.6 or greater.

[0027] According to the eleventh embodiment of the present disclosure, the present description relates to an optical fiber comprising: 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, the radius of the cladding region being 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 inner coating layer is The present invention relates to an optical fiber having a polymer coating, wherein the thickness is 6 to 20 micrometers, the modulus of elasticity of the low modulus inner coating layer is approximately 0.35 MPa or less, the thickness of the high modulus coating layer is 12 to 18 micrometers, and the modulus of elasticity of the high modulus coating layer is approximately 1.6 GPa or more, the puncture resistance of the optical fiber is greater than 30 g, the microbend attenuation penalty of the optical fiber is less than 0.03 dB / km, the outer diameter of the coated optical fiber is 175 micrometers or less, and the puncture resistance of the optical fiber is given by formula P R =P0+C1E s A s It is calculated by, where A s This is the cross-sectional area of ​​the high modulus coating described above, and E s The above high modulus coating has a modulus of elasticity, P0 is a coefficient with a value of 11.3 g, and C1 is 2.1 g / MPa / mm 2 The coefficient has a value of , and the above microbend attenuation penalty of the optical fiber is given by the formula:

[0028]

number

[0029] It is calculated by, 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.

[0030]

number

[0031] And,

[0032]

number

[0033] And,

[0034]

number

[0035] And,

[0036]

number

[0037] And R g R is the radius of the glass. s is the outer radius of the above-mentioned high modulus outer coating, and t p is the thickness of the above-mentioned inner low modulus coating, t s This is the thickness of the above-mentioned high modulus outer coating, E g E is the elastic modulus of glass. p This is the modulus of elasticity of the low modulus inner coating described above, and E s This is the modulus of elasticity of the high modulus coating described above.

[0038] According to the twelfth embodiment of this disclosure, in the optical fiber of the eleventh embodiment, the microbend attenuation penalty of the optical fiber is 0.01 dB / km or less.

[0039] According to the 13th embodiment of this disclosure, in the optical fiber of the 11th embodiment, the microbend attenuation penalty of the optical fiber is 0.007 dB / km or less.

[0040] According to the 14th embodiment of this disclosure, in the optical fiber of the 11th embodiment, the microbend attenuation penalty of the optical fiber is 0.003 dB / km or less.

[0041] According to the 15th embodiment of this disclosure, in the optical fiber of the 11th embodiment, the puncture resistance of the optical fiber is 25g or more.

[0042] According to the sixteenth embodiment of the present disclosure, the present description includes an optical fiber having: a core region; a cladding region surrounding the core region, wherein the cladding region comprises an inner cladding directly adjacent to the core region and an outer cladding surrounding the inner cladding; and a polymer coating having a thickness of 25 μm or less, wherein the polymer coating comprises a high modulus coating layer surrounding the cladding region, and the Young's modulus of the high modulus coating layer is 1.5 GPa or more, and the outer diameter of the coated optical fiber is 175 micrometers or less.

[0043] According to the 17th embodiment of this disclosure, the optical fiber of the 16th embodiment further comprises 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.

[0044] According to the 18th embodiment of this disclosure, in the optical fiber of the 16th embodiment, the ratio of the thickness of the low modulus coating layer to the thickness of the high modulus coating layer is 0.8 to 1.2.

[0045] According to a 19th embodiment of the present disclosure, the description encompasses a method for coating an optical fiber, the method comprising: drawing the optical fiber from a drawing furnace along a first vertical path; routing the optical fiber so that it passes through a coating system to which a polymer coating is applied, the coating system comprising an inlet, a sizing die having a diameter of 129 μm to 203 μm facing the inlet, and a coating chamber positioned between the inlet and the sizing die, the coating chamber being filled with a coating material in liquid form; and curing the coated optical fiber to form an outer diameter of 175 micrometers or less of the coated optical fiber.

[0046] According to the 20th embodiment of this disclosure, in the optical fiber of the 19th embodiment, the concentricity of the polymer coating is greater than 70%.

[0047] Further features and advantages are described below in the "Modes for Carrying Out the Invention," some of which will be readily apparent to those skilled in the art from this description or will be recognized by carrying out the embodiments as described in this description and the claims, as well as the accompanying drawings.

[0048] Please understand that the above-mentioned "Outline of the Invention" and the following "Modes for Carrying Out the Invention" are merely examples and are intended to provide an overview or framework for understanding the nature and characteristics of the claims.

[0049] The accompanying drawings are included to provide further understanding and are incorporated herein and constitute part of this specification. These drawings are illustrative of selected embodiments of this disclosure and, together with this description, serve to illustrate the principles and operation of the methods, products, and compositions contained herein. [Brief explanation of the drawing]

[0050] [Figure 1]Schematic diagram of coated optical fiber according to some embodiments of the present disclosure [Figure 2] Schematic diagram of a typical optical fiber ribbon according to several embodiments of this disclosure. [Figure 3] Schematic diagram of a typical optical fiber cable according to several embodiments of this disclosure. [Figure 4] Cross-sectional view of a single-mode optical fiber according to several embodiments of the present disclosure [Figure 5] Relative refractive index profiles of single-mode optical fibers according to some embodiments of the present disclosure [Figure 6] Relative refractive index profile of optical fiber according to embodiments of this disclosure [Figure 7] Relative refractive index profile of optical fiber according to embodiments of this disclosure [Figure 8] The dependence of the puncture load on the strength of the high modulus coating according to this disclosure as a function of cross-sectional area. [Figure 9] Relative refractive index profiles of single-mode optical fibers according to some embodiments of the present disclosure [Figure 10] Schematic diagrams of core mode and cladding mode distributions in optical fibers with thick coatings according to some embodiments of the present disclosure. [Figure 11] Schematic diagrams of core mode and cladding mode distributions in optical fibers with thin coatings according to some embodiments of the present disclosure. [Figure 12] Influence of coating material viscosity and die size on coating thickness in some embodiments of the present disclosure [Figure 13] Exemplary parameter windows for forming the target final coated diameter according to some embodiments of the present disclosure [Figure 14] Regarding several systems with different die sizes according to some embodiments of this disclosure, the standard deviation of coating thickness obtained from the viscosity of various coating materials. [Figure 15]The effect of draw speed on coating thickness according to some embodiments of the present disclosure [Figure 16] A graph plotting the correlation between lubrication pressure and die size with respect to the viscosity of a series of coating materials, according to some embodiments of the present disclosure. [Figure 17] Correlation between lubrication pressure and draw speed according to some embodiments of the present disclosure [Figure 18] Relative refractive index profiles of single-mode optical fibers according to some embodiments of the present disclosure [Figure 19] Microbend attenuation penalty (MAP) with respect to the thickness of a low modulus coating for a fiber having a step-index fiber profile and a trench-type fiber profile and a cladding diameter of 100 micrometers, according to some embodiments of the present disclosure. [Figure 20] Microbend attenuation penalty (MAP) with respect to the thickness of a low modulus coating for a trench-type fiber profile and a fiber having a cladding diameter of 100 micrometers, relating to a plurality of high modulus coatings with different moduli according to some embodiments of the present disclosure. [Figure 21] Puncture resistance of a trench-type fiber profile and a fiber having a cladding diameter of 100 micrometers to a low modulus coating thickness, relating to a plurality of high modulus coatings with different moduli according to some embodiments of the present disclosure. [Figure 22] Microbend attenuation penalty (MAP) with respect to the thickness of a low modulus coating for a trench-type fiber profile and a fiber having a cladding diameter of 100 micrometers, relating to a plurality of low modulus coatings with different moduli according to some embodiments of the present disclosure. [Modes for carrying out the invention]

[0051] This disclosure is provided as teachings that enable the invention and can be more readily understood by referring to the following description, drawings, examples and claims. For this purpose, those skilled in the art will recognize and understand that many modifications can be made to various aspects of the embodiments described herein, and that the beneficial results can still be obtained. It will also be apparent that some of the desirable benefits of these embodiments can be obtained by selecting some of the features and not utilizing others. Thus, those skilled in the art will recognize that many modifications and adaptations are possible and may even be desirable in certain circumstances, and that these are part of this disclosure. Accordingly, unless otherwise stated, this disclosure should be understood as not being limited to the specific compositions, articles, devices and methods disclosed. It should also be understood that the terminology used herein is intended solely to describe specific aspects and is not intended to limit them.

[0052] Numerous terms will be referenced in this specification and the subsequent claims, and these terms shall be defined as having the following meanings:

[0053] An "optical fiber" refers to a waveguide having a glass portion surrounded by a coating. The glass portion includes a core and cladding and is referred to herein as a "glass fiber."

[0054] "Radial position," "radius," or radial coordinate "r" refers to the radial position relative to the fiber's centerline (r=0).

[0055] Unless otherwise specified, "refractive index" refers to the refractive index at a wavelength of 1550 nm.

[0056] A "refractive index profile" is the relationship between the refractive index, or relative refractive index, and the radius. With respect to relative refractive index profiles shown herein as having a stepped boundary between adjacent core and / or cladding regions, typical variations in process conditions can be made such that a steep stepped boundary is not obtained at the interface of adjacent regions. While the boundary of the refractive index profile may be shown herein as a stepped change in refractive index, it should be understood that the actual boundary may be smooth or otherwise deviate from a perfect step function characteristic. Furthermore, it should be understood that the value of the relative refractive index may vary with the radial position within the core region and / or any cladding region. When the relative refractive index varies with the radial position within a particular region of the fiber (e.g., the core region and / or any cladding region), the relative refractive index is expressed as an actual or approximate functional dependency, as a value at a particular location within that region, or as an average value applicable to the entire region. Unless otherwise specified, 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 single parameter (e.g., Δ or Δ%) applicable to the entire region: it is understood that the relative refractive index of the region is constant or approximately constant and corresponds to the single value; or that the single value or parameter represents the average value of the transient relative refractive index, which depends on the radial position within the region. For example, unless otherwise specified, if "i" is a region of glass fiber, then the parameter Δ i is the average value of the relative refractive index in the region, as defined by the following equation (1). The dependence of the relative refractive index with respect to radial position may be inclined, curved, or otherwise non-constant, whether due to design or normal manufacturing variations.

[0057] As used herein, “relative refractive index” means in the following equation (1):

[0058]

number

[0059] Defined as, where n i Unless otherwise specified, the radial position r of the glass fiber i The refractive index at n ref Unless otherwise specified, this refers to the refractive index of pure silica glass. Therefore, as used herein, the relative refractive index percentage is for pure silica glass having a value of 1.444 at a wavelength of 1550 nm. As used herein, the relative refractive index is expressed as Δ (or "delta") or Δ% (or "delta %)", and its value is given in units of "%" unless otherwise specified. The relative refractive index may also be expressed as Δ(r) or Δ(r)%.

[0060] The average relative refractive index (Δ) in a region of the fiber ave ) is equation (2):

[0061]

number

[0062] It was decided from here, inner is the inner radius of the region, and r outer Δ(r) is the outer radius of the region, and Δ(r) is the relative refractive index of the region.

[0063] The refractive index of an optical fiber profile can be measured using commercially available devices such as the IFA-100 Fiber Index Profiler (Interfiber Analysis LLC, Sharon, Massachusetts, USA) or the S14 Refractive Index Profiler (Photon Kinetics, Inc., Beaverton, Oregon, USA). These devices measure the refractive index n(r)-n relative to the reference refractive index. measMeasure the refractive index n, which is the reference of measurement. meas n(r) is typically a calibrated refractive index that matches oil or pure silica glass. The measurement wavelength may 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 refractive index in between. Then, the relative refractive index is calculated using the absolute refractive index n(r) as defined by equation (1).

[0064] The term "α-profile (α-profile or alpha profile)" is given by equation (3):

[0065]

number

[0066] This refers to a relative refractive index profile Δ(r) having the form of a function defined by r o Δ(r0) is the radial position where Δ(r) is maximum, and Δ(r0) > 0, r z >r0 is the radial position where Δ(r) decreases to its minimum value, and r is r i The range is ≤r ≤ rf, and r i is the initial radial position of the α profile, and r f is the final radial position of the α profile, where α is a real number. Δ(r0) with respect to the α profile is expressed herein as Δ max , or Δ if relating to a specific region i of the fiber i,max This can be called the relative refractive index profile of the fiber core region, where r0 occurs at the center line (r=0), and r z If we describe it by an α profile that corresponds to the outer radius r1 of the core region, then equation (3) becomes equation (4):

[0067]

number

[0068] It is simplified to this.

[0069] If the core region has a refractive index described by equation (4), the outer radius r1 can be determined from the measured relative refractive index profile by the following procedure: Maximum relative refractive index Δ 1max , α, and outer radius r 1est The estimated value of r is obtained by examining the measured relative refractive index profile, and using these, r = -r 1est and r=r 1est Test function Δ between trial This is generated. The relative refractive index profiles of typical glass fibers having a core described by an α profile according to embodiments of the present disclosure are shown in Figures 5 and 6.

[0070] "Trench volume" is:

[0071]

number

[0072] Defined as, where r Trench,inner is the inner radius of the trench region of the refractive index profile, and r Trench,outer Δ is the outer radius of the trench region of the refractive index profile. Trench (r) is the relative refractive index of the trench region of the refractive index profile, and r is the radial position of the fiber. The trench volume is an absolute and positive quantity, and as used herein, %Δ micrometers 2 %, %Δ-micrometer 2 , %Δ·μm 2 , or %Δμm 2 These units are expressed in units, and these units are interchangeable as used herein. The trench region is also referred to herein as the depressed-index cladding region, and the trench volume is also referred to herein as V3.

[0073] The mode field diameter (MFD) of an optical fiber is given in equation (6) as follows:

[0074]

number

[0075] It is defined as follows, where f(r) is the transverse component of the electric field distribution of the guided optical signal and r is the radial position within the fiber. The "mode field diameter" or "MFD" depends on the wavelength of the optical signal and is reported herein for wavelengths of 1310 nm, 1550 nm, and 1625 nm. When referring to the mode field diameter herein, the wavelength is specified. Unless otherwise specified, the mode field diameter is the LP at the specified wavelength. 01 This refers to the mode.

[0076] The "effective cross-sectional area" of an optical fiber is given by equation (7) as follows:

[0077]

number

[0078] Defined as, where f(r) is the transverse component of the electric field distribution of the guided optical signal and r is the radial position within the fiber. "Effective cross-section" or "A eff This depends on the wavelength of the optical signal, and in this specification, it is understood that a wavelength of 1550 nm is being referred to.

[0079] As used herein, the term "attenuation" refers to the loss of optical power as a signal travels along an optical fiber. Attenuation was measured as specified in the IEC-60793-1-40 standard, "Method for measuring attenuation."

[0080] The bending resistance of an optical fiber, expressed herein as "bend loss," can be measured by inductive attenuation under specified test conditions, such as those specified in IEC-60793-1-47 standard "Measurement method and test procedure - Macrobend loss." For example, the above test conditions may include the steps of unfolding, i.e., winding, the fiber around a mandrel of a specified diameter, for example, one turn around a mandrel with a diameter of 15 mm, 20 mm, or 30 mm (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 per turn.

[0081] As used herein, "cable cutoff wavelength" or "cable cutoff" refers to the 22m cable cutoff test as specified in IEC 60793-1-44 standard "Measurement methods and test procedures - Cutoff wavelength".

[0082] 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 made of glass. The cladding region includes a plurality of regions, which are preferably concentric regions. The cladding region includes an inner cladding region, a refractive index suppression cladding region, and an outer cladding region. The inner cladding region surrounds the core region and is directly adjacent to it. The refractive index suppression cladding region surrounds the inner cladding region and is directly adjacent to it, so that the refractive index suppression cladding region is located radially between the inner cladding and the outer cladding. The outer cladding region surrounds the refractive index suppression cladding region and is directly adjacent to it. The refractive index suppression cladding region has a lower relative refractive index than the inner cladding region and the outer cladding region. The refractive index suppression cladding region may also be referred to herein as a trench or trench region. The relative refractive index of the inner cladding region may be less than, equal to, or greater than the relative refractive index of the outer cladding region. The refractive index-suppressing cladding region may contribute to reducing bending loss and susceptibility to microbending. The core region, inner cladding region, refractive index-suppressing cladding region, and outer cladding region are also referred to as the core, cladding, inner cladding, refractive index-suppressing cladding, and outer cladding, respectively.

[0083] Where used herein, radial position r1 and relative refractive index Δ1 or Δ1(r) always represent the core region, radial position r2 and relative refractive index Δ2 or Δ2(r) represent the inner cladding region, radial position r3 and relative refractive index Δ3 or Δ3(r) represent the refractive index suppression cladding region, radial position r4 and relative refractive index Δ4 or Δ4(r) represent the outer cladding region, radial position r5 represents any low modulus inner coating, radial position r6 represents a high modulus coating, and radial position r7 represents any colored outer coating.

[0084] The relative refractive index Δ1(r) is the maximum value Δ 1max and minimum value Δ 1minIt has the relative refractive index Δ2(r), which is the maximum value Δ 2max and minimum value Δ 2min It has the relative refractive index Δ3(r), which is the maximum value Δ 3max and minimum value Δ 3min It has the relative refractive index Δ4(r), which is the maximum value Δ 4max and minimum value Δ 4min In embodiments where the relative refractive index is constant or substantially constant over a region, the maximum and minimum values ​​of the relative refractive index are equal or substantially equal. Unless otherwise specified, if a single value is reported with respect to the relative refractive index of a region, this single value corresponds to the average value over that region.

[0085] It is understood that the central core region is substantially cylindrical, and that the surrounding inner cladding region, refractive index suppressing cladding region, outer cladding region, low modulus coating, and high modulus coating are substantially annular. The annular region is characterized with respect to its inner and outer radii. In this specification, radial positions r1, r2, r3, r4, r5, r6, and r7 refer to the outermost radii of the core, inner cladding, refractive index suppressing cladding, outer cladding, any low modulus inner coating, high modulus coating, and any colored outer coating, respectively. In embodiments without a colored outer coating, radius r6 also corresponds to the outer radius of the optical fiber. The colored outer coating may have a high modulus. If a colored outer coating is present, radius r7 corresponds to the outer radius of the optical fiber.

[0086] When two regions are directly adjacent to each other, the outer radius of the inner region coincides with the inner radius of the outer region. For example, an optical fiber includes a refractive index suppression cladding region that is directly adjacent to the outer cladding region and surrounded by the outer cladding region. Radius r3 corresponds to the outer radius of the refractive index suppression cladding region and the inner radius of the outer cladding region. The relative refractive index profile also includes a refractive index suppression cladding region that 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 refractive index suppression cladding region. Similarly, radial position r1 corresponds to the outer radius of the core region and the inner radius of the inner cladding region.

[0087] The difference between radial position r2 and radial position r1 is referred to herein as the thickness of the inner cladding region. The difference between radial position r3 and radial position r2 is referred to herein as the thickness of the refractive index suppressing cladding region. The difference between radial position r4 and radial position r3 is referred to herein as the thickness of the outer cladding region. The difference between radial position r5 and radial position r4 is referred to herein as the thickness of the low modulus coating. The difference between radial position r6 and radial position r5 is referred to herein as the thickness of the high modulus coating.

[0088] As will be further explained later, the relative refractive indices of the core region, inner cladding region, refractive index suppression cladding region, and outer cladding region may differ. Each region may be formed from doped or undoped silica glass. The refractive index variation for undoped silica glass can be achieved by incorporating levels of up-dopant or down-dopant designed to provide a target refractive index or refractive index profile using techniques known to those skilled in the art. Up-dopant is a dopant that increases the refractive index of the glass compared to the undoped glass composition. Down-dopant is a dopant that decreases the refractive index of the glass compared to the undoped glass composition. In one embodiment, the undoped glass is silica glass. When the undoped glass is silica glass, examples of up-dopant are Cl, Br, Ge, Al, P, Ti, Zr, Nb, and Ta, and examples of down-dopant are fluorine and boron. Regions with a steady refractive index can be formed by not doping, or by doping with a uniform concentration throughout the entire thickness of the region. Regions with variable refractive index are formed by the non-uniform spatial dispersion of dopants throughout the entire thickness of the region, and / or by incorporating different dopants in different regions.

[0089] The values ​​for Young's modulus, % elongation, and tear strength refer to values ​​determined under the measurement conditions according to the procedure described herein.

[0090] The exemplary embodiments described herein will now be referenced in detail.

[0091] One embodiment relates to an optical fiber. The optical fiber includes a glass fiber surrounded by a coating. An example of an optical fiber is shown in a schematic cross-sectional view in Figure 1. The optical fiber 10 includes a 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 a pigment. Further descriptions of the glass fiber 11, the optional low modulus inner coating 16, and the high modulus coating 18 are provided below. Furthermore, one or more colored outer coating layers may surround the high modulus coating 18.

[0092] Figure 2 shows an optical fiber ribbon 30, which may include a plurality of optical fibers 20 and a matrix 32 that encapsulates the plurality of optical fibers. Each optical fiber 20 includes a core region, a cladding region, an optional low modulus inner coating, and a high modulus coating, as described above. The optical fiber 20 may also include a colored outer coating, as described above.

[0093] As shown in Figure 2, the optical fibers 20 are aligned substantially in a plane and parallel to one another. The optical fibers in the optical fiber ribbon 30 are encapsulated by the ribbon matrix 32 in any of several known configurations (e.g., edge-bonded ribbon, thin-film encapsulated ribbon, thick-film encapsulated ribbon, or multilayer ribbon) by conventional optical fiber ribbon manufacturing methods. The optical fiber ribbon 30 in the embodiment of Figure 2 contains 12 optical fibers 20. However, it is intended 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) may be used to form an optical fiber ribbon 30 for a particular application. The ribbon matrix 32 has tensile properties similar to those of a high modulus coating and can be formed from the same, similar, or different composition as those used in the preparation of the high modulus coating.

[0094] Figure 3 shows an optical fiber cable 40, which includes a plurality of optical fibers 20 surrounded by a jacket 42. In some embodiments, the optical fiber cable 40 is a submarine cable. In some embodiments, the optical fiber cable 40 is used for fiber ribbons in interconnection schemes within a data center. The optical fibers 20 may be tightly or loosely packed within a conduit surrounded by the inner surface 44 of the jacket 42. The number of fibers arranged within the jacket 42 is referred to as the “fiber count” of the optical fiber cable 40. As will be further described below, the optical fibers of this disclosure have reduced diameter and therefore provide a high “fiber count”.

[0095] The jacket 42 is formed from an extruded polymer material and may contain multiple concentric layers of polymer or other material. The optical fiber cable 40 may contain one or more reinforcing members (not shown) embedded within the jacket 42 or placed within a conduit defined by the inner surface 44. The reinforcing members may contain fibers or rods having greater rigidity than the jacket 42. The reinforcing members may be made from metal, braided steel, glass-reinforced plastic, fiberglass, or other suitable materials. The optical fiber cable 40 may contain other layers surrounded by the jacket 42, such as an armor layer, a moisture-proof layer, or a rip cord. Furthermore, the optical fiber cable 40 may have a core of stranded loose tubes or other optical fiber cable configurations.

[0096] glass fiber As shown in Figure 1, the glass fiber 11 includes a core region 12 and a cladding region 14, as is known to those skilled in the art. The core region 12 has a higher refractive index than the cladding region 14, and the glass fiber 11 functions as a waveguide. In many applications, the core region 12 and the cladding region 14 have an identifiable core-cladding boundary. Alternatively, there may be no clear boundary between the core region 12 and the cladding region 14.

[0097] In some embodiments, the refractive index of the core region 12 changes with distance from the center of the glass fiber. For example, the core region 12 may have a relative refractive index profile having an α profile (defined by equation (3) above) with an α value of 2 or more and 10 or less, or 2 or more and 6 or less, or 2 or more and 4 or less, or 4 or more and 20 or less, or 6 or more and 20 or less, or 8 or more and 20 or less, or 10 or more and 20 or less, or 10 or more and 40.

[0098] A schematic cross-sectional view of an exemplary optical fiber is shown in Figure 4. In some embodiments, the optical fiber of Figure 4 can be used in submarine cables or for optically connecting components of submarine repeaters. In some embodiments, the optical fiber of Figure 4 can be used for interconnecting data centers. In Figure 4, the optical fiber 46 includes a core region 48, a cladding region 50, an optional low modulus coating 56, and a high modulus coating 58. The cladding region 50 includes an inner cladding region 51, a refractive index suppression cladding region 53, and an outer cladding region 55. Optionally, a colored outer coating layer (e.g., an ink layer) surrounds the high modulus coating or is directly adjacent to the high modulus coating.

[0099] As described above, the diameter of the coating of the optical fiber 46 can be reduced. This reduction of one or more diameters can increase the fiber density (e.g., "number of fibers") of the optical fiber 46, for example, when used in submarine cables, repeaters, or data center interconnections. To use optical fibers 46 with relatively small diameters, the fiber characteristics are specifically adjusted, as further described below, to reduce attenuation, increase the effective cross-sectional area, reduce bending loss, and sufficiently enhance mechanical reliability.

[0100] A typical relative refractive index of a glass fiber according to an embodiment of the present disclosure is shown in Figure 5. The profile of the optical fiber 60 in Figure 5 is: outer radius r1 and relative refractive index Δ1 (maximum relative refractive index Δ 1maxThe profile of Figure 5 shows a core region (1) having a relative refractive index Δ2; an inner cladding region (2) extending from radial position r1 to radial position r2 and having a relative refractive index Δ2; a refractive index suppression cladding region (3) extending from radial position r2 to radial position r3 and having a relative refractive index Δ3; and an outer cladding region (4) extending from radial position r3 to radial position r4 and having a relative refractive index Δ4. Of the profiles in Figure 5, the refractive index suppression cladding region (3) may be referred to herein as a trench and has a steady or average relative refractive index lower 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 this profile. In some embodiments, the core region (1) may include a region of relatively low refractive index on or near the centerline (known in the art as a "centerline dip") (not shown). In some embodiments, the core region (1) may include a region with a relatively high refractive index at or near the centerline (referred to in the art as a "centerline spike") (not shown).

[0101] In the relative refractive index profile of Figure 5, the core region (1) of the glass fiber has an α profile with an α value of 2 or more and 20 or less. 1max The radial position r0 (corresponding to) corresponds to the fiber's centerline (r=0), and the radial position r of the α profile described above. z This corresponds to the core radius r1. In embodiments having a centerline dip, the radial position r0 may be offset from the fiber centerline. In some embodiments, the relative refractive index Δ1 decreases continuously in the radial direction away from the centerline. In other embodiments, the relative refractive index Δ1 varies over several radial positions between the centerline and r1, and also includes a constant or substantially constant value over other radial positions between the centerline and r1.

[0102] In Figure 5, the transition region 61 from the inner cladding region (2) to the refractive index suppression cladding region (3), and the transition region 62 from the refractive index suppression cladding region (3) to the outer cladding region (4) are shown as stepwise changes. It should be understood that the stepwise changes are idealized, and that the transition regions 61 and / or 62 may not actually be strictly vertical as shown in Figure 5. Rather, the transition regions 61 and / or 62 may have a slope or curvature. If the transition regions 61 and / or 62 are not vertical, the inner radius r2 and outer radius r3 of the refractive index suppression cladding region (3) correspond to the midpoints of the transition regions 61 and 62, respectively. These midpoints correspond to half the depth 63 of the refractive index suppression cladding region (3).

[0103] The relative order of relative refractive indices Δ1, Δ2, Δ3, and Δ4 in the relative refractive index profile shown in Figure 5 is given by condition Δ 1max >Δ4>Δ3 and Δ 1max The condition Δ2 > Δ3 is satisfied. The values ​​of Δ2 and Δ4 may be equal, or one may be greater than the other, but both Δ2 and Δ4 must satisfy Δ 1max It is between and Δ3.

[0104] The relative refractive indices Δ1, Δ2, Δ3, and Δ4 are based on the materials used in the core region, inner cladding region, refractive index suppression cladding region, and outer cladding region. A description of these materials with respect to relative refractive indices Δ1, Δ2, Δ3, and Δ4 is ​​provided below.

[0105] Figure 5 shows a schematic cross-sectional view of an exemplary optical fiber, but other suitable optical fibers may be used in the embodiments described herein. For example, Figure 9 is a schematic cross-sectional view of a typical profile design of a single-mode fiber that can be used in the embodiments described herein. The optical fiber profile in Figure 9 shows: 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 refractive index suppression 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 profile designs that can be used in the embodiments described herein, and Table 3 shows various optical properties of various exemplary optical fiber profile designs that can be used in the embodiments described herein.

[0106] [Table 1]

[0107] [Table 2-1]

[0108] [Table 2-2]

[0109] [Table 3]

[0110] Core area The core region includes silica glass. The silica glass in the core region may be undoped silica glass, updoped silica glass, and / or downdoped silica glass. Updoped silica glass includes silica glass doped with alkali metal oxides (e.g., Na2O, K2O, Li2O, Cs2O, or Rb2O). Downdoped silica glass includes silica glass doped with F. In one embodiment, the silica glass in the core region may be Ge-free and / or Cl-free, i.e., the core region includes silica glass that does not contain Ge and / or Cl.

[0111] Furthermore, the core region may include silica glass doped with at least one alkali metal, such as 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 alkali concentration of the silica glass may be 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. Alkali metal doping within the scope of this disclosure results in a reduction of Rayleigh scattering and thus provides optical fiber attenuation.

[0112] In some embodiments, the core region comprises silica glass doped with alkali metals and also doped with F as a down dopant. The concentration of F in the fiber core is about 0.1% to about 2.5% by weight, or about 0.25% to about 2.25% by weight, or about 0.3% to about 2.0% by weight.

[0113] In other embodiments, the core region comprises Ge and / or Cl-doped silica glass. The concentration of GeO2 in the fiber core may be 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 concentration of Cl in the fiber core may be 1.0 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 1.5 wt% or more (e.g., 2 wt% or more, 2.5 wt% or more, 3 wt% or more, 3.5 wt% or more, 4 wt% or more, 4.5 wt% or more, 5 wt% or more, etc.).

[0114] In embodiments in which the core substantially does not contain Ge or Cl, the relative refractive index of the core region is Δ1 or Δ 1max The minimum relative refractive index of the core is approximately -0.10% to approximately 0.20%, or approximately -0.05% to approximately 0.15%, or approximately 0.0% to approximately 0.10%. 1min This ranges from 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 and Δ 1min The difference is greater than 0.05%, greater than 0.10%, greater than 0.15%, greater than 0.20%, or between 0.05% and 0.40%, or between 0.10% and 0.35%.

[0115] In embodiments in which the core is doped with Ge and / or Cl, the relative refractive index of the core region is Δ1 or Δ 1max The minimum relative refractive index of the core is approximately 0.20% to 0.45%, or approximately 0.25% to 0.40%, or approximately 0.30% to 0.38%. 1min This is approximately -0.05% to approximately -0.05%, or approximately -0.03% to approximately 0.03%, or approximately -0.02% to approximately 0.02%. 1max and Δ 1min The difference is greater than 0.20%, greater than 0.25%, greater than 0.30%, or between 0.25% and 0.45%, or between 0.30% and 0.40%.

[0116] The radius r1 of the core region is approximately 3.0 micrometers to approximately 6.5 micrometers, or approximately 3.5 micrometers to approximately 6.0 micrometers, or approximately 4.0 micrometers to approximately 6.0 micrometers, or approximately 4.5 micrometers to approximately 5.5 micrometers. In some embodiments, the core region includes a portion with a constant or substantially constant relative refractive index, having a radial width of at least 1.0 micrometer, or at least 2.0 micrometers, or at least 3.0 micrometers, or 1.0 micrometer to 3.0 micrometers, or 2.0 micrometer to 3.0 micrometers. In some embodiments, the relative refractive index of the portion of the core region with a constant or substantially constant relative refractive index is Δ 1min That is the case.

[0117] Inner cladding region In embodiments in which the core is substantially free of Ge or Cl, the inner cladding region is composed of F-doped down-doped silica glass. The average concentration of down-dopant in the inner cladding region is higher than the average concentration of down-dopant in the core region.

[0118] The relative refractive index of the inner cladding region is Δ2 or Δ 2max The relative refractive index Δ2 is preferably constant or nearly constant. 1max -Δ2 (or difference Δ) 1max -Δ 2max The percentages are approximately over 0.25%, or over 0.30%, or over 0.35%, or between approximately 0.25% and 0.45%, or between approximately 0.30% and 0.40%.

[0119] The radius r2 of the inner cladding region is approximately 7.0 micrometers to 15.0 micrometers, or approximately 7.5 micrometers to 13.0 micrometers, or approximately 8.0 micrometers to 12.0 micrometers, or approximately 8.5 micrometers to 11.5 micrometers, or approximately 9.0 micrometers to 11.0 micrometers, or approximately 9.5 micrometers to 10.5 micrometers. The thickness r2-r1 of the inner cladding region is approximately 3.0 micrometers to 10.0 micrometers, or approximately 4.0 micrometers to 9.0 micrometers, or approximately 4.5 micrometers to 7.0 micrometers.

[0120] In embodiments in which the core is doped with Ge and / or Cl, the inner cladding region comprises silica that is substantially free of Ge and / or Cl. The relative refractive index of the inner cladding region is Δ2 or Δ 2max The relative refractive index Δ2 is preferably constant or nearly constant. 1max -Δ2 (or difference Δ) 1max -Δ 2max The percentages are approximately over 0.20%, or over 0.25%, or over 0.30%, or between approximately 0.25% and 0.40%, or between approximately 0.30% and 0.38%.

[0121] The radius r2 of the inner cladding region is approximately 8.0 micrometers to 16.0 micrometers, or approximately 9.0 micrometers to 15.0 micrometers, or approximately 10.0 micrometers to 14.0 micrometers, or approximately 10.5 micrometers to 13.5 micrometers, or approximately 11.0 micrometers to 13.0 micrometers. The thickness r2-r1 of the inner cladding region is approximately 3.0 micrometers to 10.0 micrometers, or approximately 4.0 micrometers to 9.0 micrometers, or approximately 5.0 micrometers to 8.0 micrometers.

[0122] Refractive index suppression cladding region The refractive index suppression clad region contains doped silica glass. As described above, a preferred dopant is fluorine. The concentration of fluorine in the refractive index suppression clad region is from about 0.30 wt% to about 2.50 wt%, or from about 0.60 wt% to about 2.25 wt%, or from about 0.90 wt% to about 2.00 wt%.

[0123] The relative refractive index Δ3 or Δ 3min is from about -0.30% to about -0.80%, or from about -0.40% to about -0.70%, or from about -0.50% to about -0.65%. The relative refractive index Δ3 is preferably constant or substantially constant. The difference Δ 1max -Δ3 (or the difference Δ 1max -Δ 3min , or the difference Δ1 - Δ3, or the difference Δ1 - Δ 3min ) is greater than about 0.50%, or greater than about 0.55%, or greater than about 0.6%, or from about 0.50% to about 0.80%, or from about 0.55% to about 0.75%. The difference Δ2 - Δ3 (or the difference Δ2 - Δ 3min , or the difference Δ 2max -Δ3, or the difference Δ 2max -Δ 3min ) is greater than about 0.10%, or greater than about 0.20%, or greater than about 0.30%, or from about 0.10% to about 0.70%, or from about 0.20% to about 0.65%.

[0124] The inner radius of the refractive index suppression clad region is r2 and has the values specified above. The outer radius r3 of the refractive index suppression clad region is from about 10.0 micrometers to 20.0 micrometers, or from about 12.0 micrometers to about 19.5 micrometers, or from about 13.0 micrometers to about 19.0 micrometers, or from about 13.5 micrometers to about 18.5 micrometers, or from about 14.0 micrometers to about 18.0 micrometers, or from about 14.5 micrometers to about 17.5 micrometers. The thickness r3 - r2 of the refractive index suppression clad region is from 1.0 micrometer to 12.0 micrometers, or from about 2.0 micrometers to about 10.0 micrometers, or from about 2.5 micrometers to about 9.0 micrometers, or from about 3.0 micrometers to about 8.0 micrometers.

[0125] The refractive index suppression cladding region has a trench volume of approximately 30%Δ-micrometers. 2 or more, or approximately 50% Δ-micrometers 2 or more, or approximately 75% Δ-micrometers 2 The following, or approximately 30% Δ-micrometers 2 More than 75% Δ-micrometers 2 The following, or approximately 50% Δ-micrometers 2 More than or equal to approximately 75% Δ-micrometers 2 The following offset trench designs are possible. If the trench volume is smaller than the scope of this disclosure, the bending performance will be reduced, and if the trench volume is larger than the scope of this disclosure, it will not function as a single-mode fiber.

[0126] The offset trench design disclosed herein includes an inner cladding region. Furthermore, the offset trench design disclosed herein offers advantages over conventional trench designs adjacent to the core region. More specifically, the offset trench design disclosed herein reduces the confinement of fundamental modes and provides improved bending loss at large bending radii (e.g., bending radii greater than 25 mm) for the target optical fiber mode field diameter and cable cutoff characteristics. In addition, the trench design disclosed herein has a refractive index suppression trench region that favorably confines the intensity profile of fundamental LP01 modes propagating through the optical fiber, thereby reducing the optical fiber mode field diameter.

[0127] Outer cladding region In embodiments where the core is substantially free of Ge or Cl, the outer cladding region comprises down-doped silica glass. A preferred down-dopan is fluorine. The concentration of fluorine in the outer cladding region is about 0.30% to about 2.20% by weight, or about 0.60% to about 2.00% by weight, or about 0.90% to about 1.80% by weight. The relative refractive index of the outer cladding region is Δ4 or Δ 4maxThis range is approximately -0.20% to -0.50%, or approximately -0.25% to -0.45%, or approximately -0.30% to -0.40%, or approximately -0.33% to 0.37%. The relative refractive index Δ4 is ​​preferably constant or nearly constant. As shown in Figure 5, the relative refractive index Δ4 may be approximately equal to the relative refractive index Δ2.

[0128] In some embodiments, the outer cladding is substantially pure silica. Alternatively, the outer cladding may be doped with Cl to a relative refractive index of about 0.01% to about 0.1%, or about 0.02% to about 0.08%, or about 0.03% to about 0.06%. The concentration of Cl in the outer cladding may be about 0.1% to about 1.0% by weight, about 0.2% to about 0.8% by weight, or about 0.3% to about 0.6% by weight. Alternatively, the cladding surface may be strengthened by doping the outer cladding with titania to prevent defects such as scratches from propagating through the fibers. In some embodiments, the outer cladding may be doped with titania at a concentration of about 5% to about 25% by weight.

[0129] The inner radius of the outer cladding is r3, which has the value specified above. In some embodiments, the outer radius r4 is approximately 62.5 micrometers to facilitate splicing to a conventional fiber with a cladding diameter of 125 micrometers using a cladding alignment splicer. The outer radius r4 of the outer cladding region is 60.0 to 65.0 micrometers, or 61.0 to 64.0 micrometers, or 62.0 to 63.0 micrometers, or 62.25 to 62.75 micrometers. Thus, for example, the diameter of the cladding region (i.e., twice the outer radius r4) is 120.0 to 130.0 micrometers, or 122.0 to 128.0 micrometers, or 124.0 to 126.0 micrometers, or 124.5 to 125.5 micrometers. The thickness r4-r3 of the outer cladding region is approximately 20.0 micrometers to approximately 60.0 micrometers, or approximately 30.0 micrometers to approximately 55.0 micrometers, or approximately 40.0 micrometers to approximately 50.0 micrometers. In some embodiments, the outer radius r4 is approximately 50 micrometers so that the thickness of the low modulus coating and the high modulus coating can be increased. The outer radius r4 of the outer cladding region is 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 cladding region (i.e., twice the outer radius r4) is 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 of the outer cladding region r4-r3 is approximately 20.0 micrometers to approximately 50.0 micrometers, or approximately 25.0 micrometers to approximately 45.0 micrometers, or approximately 30.0 micrometers to approximately 40.0 micrometers.

[0130] Characteristics of optical fiber The optical fibers according to embodiments of this disclosure may have mode field diameters of approximately 9.0 to 10.0 micrometers at 1310 nm and approximately 10.0 to 11.0 micrometers at 1550 nm, along with a cable cutoff of less than 1520 nm. In some embodiments, the 22-meter cable cutoff wavelength is less than 1500 nm, or less than 1450 nm, or less than 1400 nm, or less than 1300 nm, or less than 1260 nm. In some embodiments, the 2-meter fiber cutoff wavelength is less than 1520 nm, or less than 1500 nm, or less than 1450 nm, or less than 1400 nm, or less than 1300 nm, or less than 1260 nm.

[0131] Furthermore, the optical fiber according to the embodiments of this disclosure is approximately 75.0 micrometers at 1550 nm. 2 Ultra-high, approximately 80 micrometers 2 More than, or approximately 85 micrometers 2 More than, or approximately 75 micrometers 2 ~approximately 95 micrometers 2 , or approximately 80 micrometers 2 ~approximately 90 micrometers 2 , or approximately 85 micrometers 2 ~approximately 90 micrometers 2 It may have an effective cross-sectional area.

[0132] The attenuation of the optical fibers disclosed herein is 0.36 dB / km or less, or 0.30 dB / km or less, or 0.28 dB / km or less, or 0.26 dB / km or less at a wavelength of 1310 nm. The attenuation of the optical fibers disclosed herein is 0.24 dB / km or less, or 0.22 dB / km or less, or 0.20 dB / km or less at a wavelength of 1550 nm.

[0133] As shown in Figure 5, the optical fiber 60 provides an exemplary embodiment of an optical fiber having an alkali-doped core, a relative refractive index Δ1(1) in the core region of approximately -0.3% to approximately -0.42%, and a core radius (r1) of approximately 4 micrometers to approximately 6.5 micrometers. Furthermore, the thickness of the inner cladding region of the optical fiber 60 is approximately 2 micrometers to approximately 12 micrometers. The optical fiber 60 has a trench volume of 54.5%Δ-micrometers. 2 It has an offset trench design. The cladding of the optical fiber 60 is doped with fluorine, and the radius (r3) of the refractive index suppression cladding region is approximately 17.5 micrometers. The optical properties of the optical fiber 60 are shown in Table 4 below.

[0134] [Table 4]

[0135] Figure 6 shows an alkali-doped core with a trench volume of approximately 50%Δ-micrometers. 2 The second embodiment 64 and the third embodiment 65 of the optical fiber are shown, in which the cladding is doped with fluorine and the radius (r3) of the refractive index suppression cladding region is approximately 17.5 micrometers. As shown in Table 5 below, the mode field diameter at 1310 nm of optical fiber 64 is 9.07 micrometers and the mode field diameter at 1310 nm of optical fiber 65 is 9.39 micrometers. The optical properties of optical fibers 64 and 65 are shown in Table 5 below.

[0136] [Table 5]

[0137] Figure 7 shows a Ge-doped core with a trench volume of 50%Δ-micrometers. 2An embodiment of the optical fiber 66 is shown, in which the inner and cladding regions are substantially pure silica, and the radius (r3) of the refractive index-suppressing cladding region is approximately 16.8 micrometers. As shown in Table 6 below, the mode field diameter of the optical fiber 66 at 1550 nm is 10.6 micrometers. The refractive index profile parameters and optical properties of the optical fiber 66 are shown in Table 6 below.

[0138] [Table 6]

[0139] The offset trench designs of optical fibers 60, 64, 65, and 66 provide improved bending performance for the relatively small diameter fibers disclosed herein. More specifically, the offset trench designs disclosed herein provide low attenuation, a large effective cross-sectional area, and low bending loss in compact forms with a cladding diameter of about 125 micrometers and an outer coating diameter of less than 175 micrometers.

[0140] Coating characteristics The transmittance of light passing through the optical fiber depends on the properties of the coating applied to the glass fiber. As described above (and also referring to Figure 4), the coating may include an optional low modulus inner coating 56 and a high modulus coating 58, the high modulus coating surrounding the optional low modulus inner coating, and the optional low modulus inner coating in contact with the glass fiber (including a central core region surrounded by a cladding region). An optional colored outer coating layer (e.g., an ink layer) surrounds the high modulus coating and also in direct contact with the high modulus coating.

[0141] The high modulus coating 58 is a harder (higher Young's modulus) material than any low modulus coating 56 and is designed to protect the glass fiber from damage caused by friction or external forces during processing, handling, and deployment of the optical fiber. The low modulus inner coating 56 is a softer (lower Young's modulus) material 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. Any low modulus coating can help dissipate stress caused by microbending when the optical fiber is deployed in a cable, but is not essential for short-length applications such as optical interconnects. Microbending stress transmitted to the glass fiber needs to be minimized because it creates localized disturbances in the refractive index profile of the glass fiber. Localized disturbances in the refractive index lead to a loss of intensity of light transmitted through the glass fiber. By dissipating stress, any low modulus coating minimizes the intensity loss caused by microbending.

[0142] The thinner the coating on the optical fiber, the less protection it provides against external perturbations, which is thought to increase microbend losses. These perturbations cause power coupling from light guided within the core (core modes) to higher-order modes within the cladding (cladding modes). As shown in Figure 10, the cladding modes can overlap considerably with the coating layer, which has a high absorptivity. This coupling and absorption process by the coating material results in a loss of optical power.

[0143] An approach to quantifying the microbending loss of optical fibers in relation to the coating properties is published in the article "Relationship of Mechanical Characteristics of Dual Coated Single Mode Fibers and Microbending Loss" by J. Baldauf, N. Okada, and M. Miyamoto in IEICE Trans. Commun., Vol. E76-B, No. 4, pp. 352-357 (April 1993). The authors identified the parameter χ as the effective spring constant of the force bonding the secondary (high modulus) coating to the glass fiber. s This parameterization of the spring constant provides qualitative guidance that thick primary (low modulus) coatings with low modulus offer better microbend performance, but it does not fully capture the contributions of glass and high modulus.

[0144] The combination of the glass, the low modulus inner coating, and the high modulus coating results in the following macrobend damping penalty (MAP):

[0145]

number

[0146] This results in the following, where f0 and σ are the average lateral pressure and the standard deviation of roughness, respectively, of the outer surface in contact with the high modulus coating.

[0147]

number

[0148] f RIP This explains the role of the refractive index profile, and its order is 1. The attenuation data is f RIPHowever, this is approximately 1.0 for single-mode fibers with a step-index refractive index profile, and approximately 0.5 for bend-insensitive single-mode fibers with a refractive index profile that includes refractive index suppression trenches in the cladding. The other three terms in Equation 8 are the contributions to the microbend response of the glass, the low modulus inner coating, and the system including both the low modulus inner and high modulus coatings:

[0149]

number

[0150] Given by, where R g R is the radius of the glass (i.e., the outer radius of the outer cladding region), s is the outer radius of the high modulus outer coating, and t p This is the thickness of the inner low modulus coating, t s This is the thickness of the high modulus outer coating, E g , E p and E s These are the moduli of glass, low modulus inner coating, and high modulus coating, respectively. When the units of modulus and radius are GPa and micrometers, respectively, the unit of MAP is dB / km. Low modulus inner coating coefficient f p This is simply 1 / t, as predicted by the parameterization of the spring constant. p not (1 / t p ) 2 It depends on f cs The coating coefficient is such that the high modulus coating is relatively thick (t s This becomes very large when the thickness of the high modulus coating is over approximately 20 micrometers (which corresponds to a low MAP), and is therefore important for fibers with relatively thin coatings. However, this is due to the thickness of the high modulus coating t sWhen the microbend attenuation is less than approximately 10 micrometers, it becomes extremely small, resulting in a MAP value exceeding 0.01 dB / km. This is a result of reduced rigidity of the outer coating. Assuming that the fiber attenuation without the microbend attenuation penalty is approximately 0.19 dB / km, the net attenuation of the coated optical fiber system is 0.19 dB / km plus the microbend attenuation penalty.

[0151] The inventors have discovered that microbend loss can be reduced as described herein when the coating is below a certain thickness. As shown in Figure 11, when the thickness of the polymer coating is sufficiently reduced, an anti-resonance effect occurs within the coating layer, preventing light from being guided within the coating layer. This anti-resonance effect significantly reduces absorption by the coating layer, thus reducing microbend loss. Conventional coating thicknesses exceeding 37 micrometers are too large for this anti-resonance effect to occur. To generate 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 to about 25 micrometers, or about 2 to about 20 micrometers, or about 2 to about 15 micrometers, or about 2 to about 10 micrometers, or about 2 to about 5 micrometers.

[0152] As used herein, the term "puncture load" refers to the amount of force acting upon the fiber coating described herein. As used herein, the term "puncture resistance" refers to the force from the fiber coating against the puncture load. As will be further explained below, if the puncture load exceeds the maximum puncture resistance of the coating, the coating will tear. Regarding puncture resistance, an analysis by Glaesemann and Clark on fibers with one type of coating in the article "Quantifying the Puncture Resistance of Optical Fiber Coatings" (Proc. 52nd IWCS, pp. 237-245 (1993)) showed that puncture resistance of a high modulus coating is greater than the cross-sectional area A s It has been shown to have a linear dependence on . The analysis in this paper assumes that the puncture resistance is due to the hoop stress of the high modulus coating, and the authors model the high modulus coating as a thin cylinder subjected to internal pressure from the low modulus inner coating. However, in most optical fibers, the thickness t of the high modulus coating relative to the outer radius r6 of the high modulus coating s Since the ratio is on the order of 10%, the low modulus coating of the fiber is at pressure P o It can be approximated as a thick-walled cylinder, with a puncture load applied from the outside. At the limit point where the external pressure is much higher than the internal pressure from the low modulus inner coating, the maximum hoop stress is:

[0153]

number

[0154] And here A s This is the cross-sectional area of ​​the high modulus coating. The hoop stress is A s It was observed that there is an inverse dependence on P, and puncture resistance is P R =P0+C1E s A s And here Es The modulus of elasticity of the high modulus coating is as follows: coefficients P0 and C1 are approximately 11.3 g and 2.1 g / MPa / mm², respectively. 2 It has the value of .

[0155] Examples of coatings - preparation and measurement techniques The properties of any low modulus inner coating and high modulus coating disclosed herein were determined using the measurement techniques described below.

[0156] Tensile properties A curable high modulus coating composition was cured and formed into a cured rod sample for measuring Young's modulus, tensile strength at yield, yield strength, and elongation at yield. The cured rod was prepared by injecting the curable high modulus coating composition into a Teflon® tube with an inner diameter of approximately 0.025 inches (0.635 mm). The rod sample was subjected to a dose of approximately 2.4 J / cm². 2 The coating was cured using a Fusion D-type valve (measured over the wavelength range of 225–424 nm using an International Light Light Bug model IL390). After curing, the "Teflon" tube was removed to provide cured rod samples of the high modulus coating composition. Before testing, the cured rods were left at 23°C and 50% relative humidity for 18–24 hours. Young's modulus, tensile strength at fracture, 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 Tester at a test speed of 250 mm / min. Tensile properties were measured according to ASTM standard D882-97. These properties were determined as the average of at least five samples, and defective samples were excluded from the average.

[0157] In-situ glass transition temperature T gMeasurements were performed on fiber tube-off samples obtained from fibers having a low modulus inner coating surrounded by a high modulus coating. The coated fibers consisted of a glass fiber with a diameter of 125 micrometers, a low modulus inner coating with a thickness of 32.5 micrometers surrounding the glass fiber and in direct contact with it, and a high modulus coating with a thickness of 26.0 micrometers surrounding the glass fiber and in direct contact with it. The glass fiber and the low modulus inner coating were identical for all samples measured. The low modulus inner coating was formed from a reference low modulus inner coating composition described below. Samples with a high modulus coating of a comparative example and a high modulus coating according to this disclosure were measured.

[0158] A fiber tube-off sample was obtained using the following procedure: A 0.0055-inch (0.1397 mm) Miller stripper was clamped approximately 1 inch (2.54 cm) below the end of a coated fiber. A 1-inch (2.54 cm) area of ​​this fiber was dropped into a stream of liquid nitrogen and held in the liquid nitrogen for 3 seconds. The coated fiber was then removed from the liquid nitrogen stream, and the coating was removed by rapid stripping. The stripped end of the fiber was inspected for 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 a clean glass fiber and a hollow tube of stripped coating, including intact low modulus inner coating and high modulus coating. The above hollow tube is referred to as the "tube-off sample." The diameters of the glass, low modulus inner coating, and high modulus coating were measured from the end face of the unstripped fiber.

[0159] In-situ T of tube-off sample gThe values ​​were measured using a Rheometrics DMTA IV test instrument with a sample gauge length of 9-10 mm. The width, thickness, and length of the tube-off sample were entered into the test instrument's operating program. After setting the tube-off sample, it was cooled to approximately -85°C. After stabilization, a temperature gradient was performed using the following parameters: Frequency: 1Hz Distortion: 0.3% Heating rate: 2℃ / min Final temperature: 150℃ Initial static force=20.0g Static forces are only 10.0% greater than dynamic forces.

[0160] On-the-spot coating g is defined as the maximum value of tanδ in a plot of tanδ as a function of temperature, where tanδ is: tanδ = E'' / E' It is defined as follows: E'' is the loss modulus, which is proportional to the loss of energy as heat during the deformation cycle, and E' is the storage modulus or modulus, which is proportional to the energy stored during the deformation cycle.

[0161] The tube-off sample showed several clear maximum values ​​in the tanδ plots for the low modulus inner coating and the high modulus coating. The maximum value at low temperature (approximately -50°C) was the in-situ T for the low modulus inner coating. g In response to this, the maximum value at high temperatures (above 50°C) is the in-situ T for high modulus coatings. g It corresponds to.

[0162] Low modulus of elasticity in-situ modulus of elasticity of inner coating In embodiments including this optional coating layer, the in-situ modulus was measured using the following procedure: A 6-inch (15.24 cm) fiber sample was obtained, and a 1-inch (2.54 cm) section from the center of the fiber was stripped with a window stripper and wiped with isopropyl alcohol. The fiber processed with the window stripper was placed on a sample holder / alignment stage equipped with 10 mm × 5 mm rectangular aluminum tabs used to fix the fiber. The two tabs were oriented horizontally and positioned so that their 5 mm shorter sides faced each other, separated by a 5 mm gap. The fiber processed with the window stripper was placed horizontally on the sample holder, across both tabs and across the gap separating the tabs. One coated end of the window stripper-processed region of the fiber was positioned on one tab, extending about halfway into the 5 mm gap between the tabs. The 1-inch (2.54 cm) area processed with the window stripper extended across the remaining half of the gap, traversing the opposite tab. After alignment, the sample was removed, and a small dot of adhesive was applied to the half of each tab closest to the 5 mm gap. The fiber was then returned to its place, and the alignment stage was raised until the adhesive made contact with the fiber. The coated end was pulled out of the gap so that the majority of the 5 mm gap between the tabs was occupied by the area of ​​the fiber processed with the window stripper, allowing it to pass through the adhesive. The remaining portion of the area processed with the window stripper on the opposite tab was brought into contact with the adhesive. Only the very tip of the coated end was left to extend beyond the tab into the gap between the tabs. This portion of the coated end was not embedded in the adhesive and was subject to measurement of its in-situ modulus. The adhesive was dried with the fiber sample in this configuration to fix the fiber to the tabs. After drying, the length of the fiber fixed to each tab was trimmed to 5 mm. The length of the coated material embedded in the adhesive, the length of the unembedded coated material (the portion extending into the gap between the tabs), and the primary diameter were measured.

[0163] In-situ modulus measurements were performed on a Rheometrics DMTA IV dynamic mechanical testing apparatus at a constant strain of 9e-6 1 / s for 45 minutes at room temperature (21°C). The gauge length was 15 mm. Changes in force and length were recorded, and these were used to calculate the in-situ modulus of the low modulus coating. To ensure that the clamp and fiber did not come into contact and that the sample was fixed straight to the clamp, the fiber sample was prepared in a tab-mounted state by removing any epoxy from the tab that interfered with the 15 mm clamp length of the testing apparatus. The force of the instrument was set to zero. The tab with the uncoated end of the fiber fixed to it was placed in the lower clamp (measuring probe) of the testing apparatus, and the coated end of the fiber fixed to it was placed in the upper (fixed) clamp of the testing apparatus. The test was then performed, and the sample was removed after the analysis was complete.

[0164] In-situ modulus of elasticity of high modulus coating For high modulus coatings, the in-situ modulus was measured using fiber tube-off samples prepared from fiber samples. A 0.0055-inch (0.1397 mm) Miller stripper was clamped approximately 1 inch (2.54 cm) below the end of the fiber sample. This 1-inch (2.54 cm) area of ​​the fiber sample was immersed in a stream of liquid nitrogen and held for 3 seconds. The fiber sample was then removed and rapidly stripped. Next, the stripped end of the fiber sample was inspected. If any coating remained on the glass portion of the fiber sample, the tube-off sample was considered defective, and a new tube-off was prepared. A suitable tube-off sample consists of a hollow tube with a low modulus inner coating and a high modulus coating, cleanly stripped from the glass. The diameters of the glass, low modulus inner coating, and high modulus coating were measured from the end face of the unstripped fiber sample.

[0165] Measurements were performed on tube-off samples using the Rheometrics DMTA IV test instrument with a sample gauge length of 11 mm to obtain the in-situ modulus of the high modulus coating. The width, thickness, and length were determined and provided as input to the test instrument's operating software. The samples were then set up, and measurements were performed at ambient temperature (21°C) using a time-sweep program with the following parameters: Frequency: 1 Rad / second Distortion: 0.3% Total time = 120 seconds Time per measurement = 1 second Initial static force=15.0g Static forces are only 10.0% greater than dynamic forces. After completion, the last five E' (storage modulus) data points were averaged. Three measurements were performed on each sample (using a new sample for each measurement), yielding a total of 15 data points. The average value of these three measurements was reported.

[0166] Puncture resistance of high modulus coating Puncture resistance was measured on samples containing a glass fiber and a low modulus inner coating surrounded by a high modulus coating. The glass fiber cladding diameter 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 cross-sectional area of ​​the high modulus coating was varied as described below by adjusting the thickness of the low modulus inner coating and the high modulus coating. 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 for all samples.

[0167] Puncture resistance was measured using the technique described in the paper "Quantifying the Puncture Resistance of Optical Fiber Coatings" by G. Scott Glaesemann and Donald A. Clark (incorporated herein by reference), published on pages 237-245 of the proceedings of the 52nd International Wire & Cable Symposium (2003). An outline of this method is provided here. This method is an indentation method. A 4 cm long optical fiber was placed on a 3 mm thick glass slide. One end of the optical fiber was attached to a device that could rotate the optical fiber under control. The optical fiber was inspected for transmission at 100x magnification, and the optical fiber was rotated until the thickness of the high modulus coating was equal on both sides of the glass fiber in a direction parallel to the glass slide. At this position, the thickness of the high modulus coating was equal on both sides of the optical fiber in a direction parallel to the glass slide. The thickness of the high modulus coating above or below the glass fiber in the direction perpendicular to the glass slide differed from the thickness of the high modulus coating in the direction parallel to the glass slide. One of the thicknesses in the direction perpendicular to the glass slide was greater than the thickness in the direction parallel to the glass slide, while the other thickness in the direction perpendicular to the glass slide was smaller. The optical fiber was fixed in this position by taping both ends to the glass slide. This position is the optical fiber position used for indentation testing.

[0168] Indentation was performed using a standard test machine (Instron model 5500R or equivalent). An inverted microscope was positioned under the crosshead of the test machine. The microscope's objective lens was positioned directly below a Vickers diamond wedge indenter (75° angle) installed inside the test machine. A glass slide with the fiber taped to it was placed on the microscope stage and positioned directly below the indenter so that the width of the wedge was perpendicular to the direction of the fiber. With the fiber in place, the diamond wedge was lowered until it contacted the surface of the high modulus coating. The diamond wedge was then pushed into the high modulus coating at a speed of 0.1 mm / min, and the load on the high modulus coating was measured. The load on the high modulus coating increased as the diamond wedge was pushed deeper into the coating until puncture occurred, at which point a sharp decrease in load was observed. The indentation load at which puncture was observed was recorded. This is reported herein as weight in grams (g) and is also referred to herein as "puncture load." Experiments were repeated using optical fibers of the same orientation, and 10 measurement points were obtained and averaged to determine the puncture load for this orientation. A second set of 10 measurement points was obtained by rotating the orientation of the optical fiber by 180°.

[0169] Macrobend loss Macrobend loss was determined using the mandrel wrap test specified in standard IEC 60793-1-47. In the mandrel wrap test, a fiber is wrapped one or more times around a cylindrical mandrel of a specified diameter, and the increase in attenuation at a specified wavelength due to bending is determined. The attenuation in the mandrel wrap test is expressed in units of dB / turn, where one turn means one rotation of the fiber around the mandrel. Macrobend loss at wavelengths of 1310 nm, 1550 nm, and 1625 nm was determined for the selected examples described below using mandrel wrap tests with diameters of 10 mm, 15 mm, and 20 mm.

[0170] Exemplary embodiments of an optical fiber having a low elastic modulus inner coating surrounded by a high elastic modulus coating By adjusting the specific properties of any low elastic modulus inner coating 56 and high elastic modulus coating 58, sufficient robustness and good microbend performance can be provided to the relatively small diameter fibers disclosed herein. For example, the low elastic modulus inner coating 56 may have a low Young's modulus and / or a low in-situ elastic modulus. The Young's modulus of the low elastic modulus inner coating is about 0.7 MPa or less, or about 0.6 MPa or less, or about 0.5 MPa or less, or about 0.4 MPa or less, or about 0.1 MPa to about 0.7 MPa, or about 0.1 MPa to about 0.4 MPa. The in-situ elastic modulus of the low elastic modulus inner coating is about 0.50 MPa or less, or about 0.30 MPa or less, or about 0.25 MPa or less, or about 0.20 MPa or less, or about 0.15 MPa or less, or about 0.10 MPa or less, or about 0.05 MPa to about 0.25 MPa, or about 0.10 MPa to about 0.20 MPa.

[0171] The low elastic modulus inner coating 56 preferably has a refractive index higher than that of the cladding region 50 of the glass fiber, whereby the low elastic modulus inner coating 56 can remove irregular optical signals from the core region 48. The low elastic modulus inner coating 56 needs to maintain sufficient adhesion to the glass fiber during aging due to heat and hydrolysis, but also needs to be peelable from the glass fiber for splicing.

[0172] To facilitate making the diameter of the optical fiber smaller, the low elastic modulus inner coating may not be present or may have a thickness smaller than that of the low elastic modulus inner coating used in conventional optical fibers. The high elastic modulus coating 58 may have a smaller thickness and a smaller cross-sectional area compared to conventional optical fibers. However, the high elastic modulus coating 58 still needs to maintain the required robustness and puncture resistance necessary for the high reliability of submarine cables and repeaters. The thinner the high elastic modulus coating, the lower its protective function. Puncture resistance is a measure of the protective function of the outer coating, including the high elastic modulus coating and any colored outer coating. A high elastic modulus coating with high puncture resistance can withstand high abrasion pressure without damage and provide better protection to the glass fiber.

[0173] To provide the required robustness and puncture resistance, the in-situ elastic modulus of the high elastic modulus coating 58 may be 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 between about 1500 MPa and about 3000 MPa, or between about 1800 MPa and about 2800 MPa, or between about 2000 MPa and about 2800 MPa, or between about 2400 MPa and about 2800 MPa.

[0174] To further provide the required robustness and puncture resistance, the product of the cross-sectional area of the high elastic modulus coating 58 and its in-situ elastic modulus may 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 between about 10 N and 30 N, or between about 15 N and about 30 N, or between about 20 N and about 30 N, or between about 25 N and about 30 N.

[0175] To provide the required combination of low microbend performance 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 56 may be greater than approximately 4000, or greater than approximately 5000, or greater than approximately 6000, or greater than approximately 7000, or greater than approximately 8000, or greater than approximately 9000, or greater than approximately 10,000, or between approximately 4000 and approximately 10,000, or between approximately 4000 and approximately 10,000, or between approximately 5000 and approximately 10,000, or between approximately 6000 and approximately 10,000, or between approximately 7000 and approximately 10,000, or between approximately 8000 and approximately 10,000.

[0176] Low modulus and high modulus coatings are typically formed by applying a curable coating composition to a glass fiber as a viscous liquid and allowing it to cure. The optical fiber may include a colored outer coating surrounding the high modulus coating. The colored outer coating may contain a colorant for marking the optical fiber for identification purposes and typically has a Young's modulus equivalent to that of the high modulus coating.

[0177] The high modulus coating 58 may be composed of a trifunctional monomer. The glass transition temperature (Tg) of the high modulus coating 58 may be greater than approximately 50°C, or greater than approximately 60°C, or greater than approximately 70°C, or greater than approximately 80°C, or greater than approximately 90°C, or greater than approximately 100°C.

[0178] By using a suitable low modulus inner coating 56 and a high modulus coating 58, the cross-sectional area of ​​the high modulus coating is approximately 10,000 micrometers. 2 If the value is less than the specified value, the puncture resistance of the optical fiber 46 can be set to approximately 28g or more, or approximately 30g or more, or approximately 32g or more, or approximately 34g or more, or approximately 36g or more, or approximately 38g or more, or approximately 40g or more.

[0179] By using a suitable low modulus inner coating 56 and a high modulus coating 58, the cross-sectional area of ​​the high modulus coating is approximately 8,000 micrometers. 2If the value is less than the specified value, the puncture resistance of the optical fiber 46 can be set to approximately 22g or more, or approximately 24g or more, or approximately 26g or more, or approximately 28g or more, or approximately 30g or more.

[0180] Figure 19 shows the microbend attenuation penalty (MAP) with respect to the thickness of the low modulus inner coating for fibers having step-index and trench-type profiles, a cladding diameter of 100 micrometers, a high modulus coating with an elastic modulus of 1200 MPa and an outer radius of 82.5 micrometers, and a low modulus inner coating with an elastic modulus of 0.5 MPa. As shown in Figure 19 and Table 7a, a MAP of less than 0.1 dB / km can be achieved when the fiber has a trench-type profile, a cladding diameter of approximately 100 micrometers, and a low modulus inner coating thickness of approximately 10 to 26 micrometers. Calculations were also performed for fibers having step-index and trench-type profiles, a cladding diameter of 125 micrometers, a high modulus coating with an elastic modulus of 1200 MPa and an outer radius of 82.5 micrometers, and a low modulus inner coating with an elastic modulus of 0.5 MPa. As shown in Table 7b, a MAP of less than 0.1 dB / km can be achieved when the fiber has a trench-type profile, the cladding diameter is approximately 125 micrometers, and the thickness of the low modulus inner coating is approximately 8 to 17 micrometers.

[0181] [Table 7a]

[0182] [Table 7b]

[0183] Figure 20 shows the MAP against the thickness of the low modulus inner coating for fibers having a trench-type fiber profile (for example, as shown in Table 2 above), a cladding diameter of 100 micrometers, a low modulus inner coating with an elastic modulus of 0.5 MPa, and high modulus coatings with elastic moduli of 1.2, 1.6, and 2.0 GPa. As shown in Figure 20 and Table 8a, a MAP of less than 0.1 dB / km can be achieved when the elastic modulus of the high modulus coating is 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 elastic modulus of the high modulus coating is 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 elastic modulus of the high modulus coating is 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 modulus of elasticity of the high modulus coating is 2.0 GPa and the thickness of the low modulus inner coating is approximately 11 to 26 micrometers. Calculations were also performed for fibers with a trench-type profile, a cladding diameter of 125 micrometers, a low modulus inner coating with a modulus of elasticity of 0.5 MPa, and high modulus coatings with moduli of elasticity of 1.2, 1.6, and 2.0 GPa. As shown in Table 8b, a MAP of less than 0.1 dB / km can be achieved when the modulus of elasticity of the high modulus coating is 1.6 GPa and the thickness of the low modulus inner coating is approximately 6 to 18 micrometers. A MAP of less than 0.06 dB / km can be achieved when the modulus of elasticity of the high modulus coating is 1.6 GPa and the thickness of the low modulus inner coating is approximately 10 to 14 micrometers. A MAP of less than 0.1 dB / km can be achieved when the modulus of elasticity of the high-modulus coating is 2.0 GPa and the thickness of the low-modulus inner coating is approximately 6 to 18 micrometers. A MAP of less than 0.05 dB / km can be achieved when the modulus of elasticity of the high-modulus coating is 2.0 GPa and the thickness of the low-modulus inner coating is approximately 10 to 14 micrometers.

[0184] Table 8a

[0185] Table 8b

[0186] Figure 21 shows the puncture resistance of fibers with a trench-type profile (as shown in Table 2 above, for example), a cladding diameter of 100 micrometers, a low modulus inner coating with an elastic modulus of 0.5 MPa, and high modulus coatings with elastic moduli of 1.2, 1.6, and 2.0 GPa, relative to the thickness of the low modulus inner coating. As shown in Figure 21 and Table 9a, puncture resistance exceeding 30 g can be achieved when the elastic modulus of the high modulus coating is 1.6 GPa and the thickness of the low modulus inner coating is less than approximately 14 micrometers. Puncture resistance exceeding 35 g can be achieved when the elastic modulus of the high modulus coating is 1.6 GPa and the thickness of the low modulus inner coating is less than approximately 8 micrometers. Puncture resistance exceeding 30 g can be achieved when the elastic modulus of the high modulus coating is 2.0 GPa and the thickness of the low modulus inner coating is less than approximately 18 micrometers. Puncture resistance exceeding 35g can be achieved when the modulus of elasticity of the high modulus coating is 2.0 GPa and the thickness of the low modulus inner coating is less than approximately 14 micrometers. Puncture resistance exceeding 40g can be achieved when the modulus of elasticity of the high modulus coating is 2.0 GPa and the thickness of the low modulus inner coating is less than approximately 9 micrometers. Calculations were also performed for fibers with a trench-type profile, a cladding diameter of 125 micrometers, a low modulus inner coating with a modulus of elasticity of 0.5 MPa, and high modulus coatings with moduli of elasticity of 1.2, 1.6, and 2.0 GPa. As shown in Table 9b, puncture resistance exceeding 20g can be achieved when the modulus of elasticity of the high modulus coating is 1.6 GPa and the thickness of the low modulus inner coating is less than approximately 12 micrometers. Puncture resistance exceeding 25g can be achieved when the modulus of elasticity of the high modulus coating is 1.6 GPa and the thickness of the low modulus inner coating is less than approximately 7 micrometers. Puncture resistance exceeding 20g can be achieved when the modulus of elasticity of the high-modulus coating is 2.0 GPa and the thickness of the low-modulus inner coating is less than approximately 13 micrometers. Puncture resistance exceeding 25g can be achieved when the modulus of elasticity of the high-modulus coating is 2.0 GPa and the thickness of the low-modulus inner coating is less than approximately 9 micrometers.A puncture resistance of more than 30 g can be achieved when the elastic modulus of the high elastic modulus coating is 2.0 GPa and the thickness of the low elastic modulus inner coating is about 6 micrometers or less.

[0187]

Table 9a

[0188]

Table 9b

[0189] Figure 22 shows the MAP against the thickness of the low modulus coating for fibers having a trench-type fiber profile (for example, as shown in Table 2 above), a cladding diameter of 100 micrometers, a high modulus coating with an elastic modulus of 1.6 GPa, and low modulus inner coatings with elastic moduli of 0.5, 0.35, and 0.2 MPa. As shown in Figure 22 and Table 10a, a MAP of less than 0.05 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 8 to approximately 29 micrometers. A MAP of less than 0.02 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 16 to approximately 21 micrometers. A MAP of less than 0.05 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.2 MPa and the thickness of the low modulus inner coating is approximately 4 to approximately 31 micrometers. A MAP of less than 0.02 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 7 to 29 micrometers. A MAP of less than 0.01 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 11 to 25 micrometers. A MAP of less than 0.007 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 16 to 21 micrometers. Calculations were also performed for fibers with a trench-type fiber profile, a cladding diameter of 125 micrometers, a high-modulus coating with a modulus of elasticity of 1.6 GPa, and low-modulus inner coatings with moduli of elasticity of 0.5, 0.35, and 0.2 MPa. As shown in Table 10b, a MAP of less than 0.05 dB / km can be achieved when the modulus of elasticity of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 6 to 18 micrometers. A MAP of less than 0.03 dB / km can be achieved when the modulus of elasticity of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 10 to 14 micrometers.A MAP of less than 0.03 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 4 to 19 micrometers. A MAP of less than 0.02 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 6 to 17 micrometers. A MAP of less than 0.01 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 10 to 13 micrometers.

[0190] [Table 10a]

[0191] [Table 10b]

[0192] Table 11a shows the MAPs for fibers with trench-type fiber profiles (e.g., as shown in Table 2 above), a cladding diameter of 100 micrometers, a high modulus coating with an elastic modulus of 2.0 GPa, and low modulus inner coatings with elastic moduli of 0.35, 0.2, and 0.1 MPa, against the thickness of the low modulus inner coating. As shown in Table 11a, a MAP of less than 0.02 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 6 to approximately 30 micrometers. A MAP of less than 0.02 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 13 to approximately 23 micrometers. A MAP of less than 0.02 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.2 MPa and the thickness of the low modulus inner coating is approximately 6 to approximately 30 micrometers. A MAP of less than 0.01 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 9 to 27 micrometers. A MAP of less than 0.005 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 14 to 22 micrometers. A MAP of less than 0.005 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.1 MPa and the thickness of the low-modulus inner coating is approximately 6 to 29 micrometers. A MAP of less than 0.002 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.1 MPa and the thickness of the low-modulus inner coating is approximately 13 to 23 micrometers. Calculations were also performed for fibers with trench-type fiber profiles, a cladding diameter of 125 micrometers, a high modulus coating with an elastic modulus of 2.0 GPa, and low modulus inner coatings with elastic moduli of 0.35, 0.2, and 0.1 MPa. As shown in Table 11b, a MAP of less than 0.03 dB / km can be achieved when the elastic modulus of the low modulus inner coating is 0.35 MPa and the thickness of the low modulus inner coating is approximately 5 to approximately 12 micrometers.A MAP of less than 0.02 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 5 to 18 micrometers. A MAP of less than 0.01 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.2 MPa and the thickness of the low-modulus inner coating is approximately 8 to 14 micrometers. A MAP of less than 0.005 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.1 MPa and the thickness of the low-modulus inner coating is approximately 5 to 18 micrometers. A MAP of less than 0.01 dB / km can be achieved when the modulus of elasticity of the low-modulus inner coating is 0.1 MPa and the thickness of the low-modulus inner coating is approximately 8 to 14 micrometers.

[0193] [Table 11a]

[0194] [Table 11b]

[0195] By combining the calculated MAP and puncture resistance results given in Figures 19-23 and Tables 7-11, the maximum modulus of elasticity (Ep) of the low modulus primary coating, the minimum modulus of elasticity (Es) of the high modulus coating, the glass radius (Rg), and the radius (R) of the high modulus coating can be determined. S It is possible to provide a minimum thickness of low modulus inner coating and high modulus coating that yields the maximum MAP and minimum puncture resistance for the input value of ). Table 12a summarizes the coating characteristics of Examples 1 to 4, where the cladding diameter is 100 micrometers and Es = 1.6 GPa. Tables 12b and 12c summarize the coating characteristics of Examples 5 to 14, where the cladding diameter is 100 micrometers and Es = 2.0 GPa. Tables 12d and 12e summarize the coating characteristics of Examples 15 to 21, where the cladding diameter is 100 micrometers.

[0196] [Table 12a]

[0197] [Table 12b]

[0198] [Table 12c]

[0199] [Table 12d]

[0200] [Table 12e]

[0201] Exemplary embodiment with reduced diameter As described above, the glass diameter of the optical fiber in the embodiments disclosed herein may be about 125 micrometers, and the outer diameter of the reduced coating may be about 175 micrometers or less, or about 170 micrometers or less, or about 165 micrometers or less, or about 160 micrometers or less, or about 145 micrometers or less. Note 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 is the overall outer diameter of the optical fiber 46 (if a colored outer coating layer is not applied).

[0202] In some cases, the outer diameter of the clad region 50 is approximately 125 micrometers, or the outer diameter of the high modulus coating 58 is approximately 155 to 175 micrometers, or the outer diameter of the clad region 50 is approximately 125 micrometers and the outer diameter of the high modulus coating 58 is approximately 160 to 170 micrometers.

[0203] As described above, the glass diameter of the optical fiber in the embodiments disclosed herein may be about 100 micrometers, and the outer diameter of the reduced coating may be about 175 micrometers or less, or about 170 micrometers or less, or about 165 micrometers or less, or about 160 micrometers or less, or about 145 micrometers or less. Note 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 is the overall outer diameter of the optical fiber 46 (if a colored outer coating layer is not applied).

[0204] In some examples, the outer diameter of the clad region 50 is approximately 100 micrometers, the outer diameter of the high modulus coating 58 is approximately 155 to 175 micrometers, or the outer diameter of the clad region 50 is approximately 100 micrometers and the outer diameter of the high modulus coating 58 is approximately 160 to 170 micrometers.

[0205] As described above, the reduced-diameter optical fiber profile design of this disclosure offers certain advantages, such as an increase in the number of fibers in submarine cables and repeaters. However, reducing the cladding diameter of the optical fiber reduces the cladding profile, which can cause some light to leak out of the cladding. Therefore, the offset trench design of this disclosure is designed to favorably reduce tunneling or radiation losses caused by light leakage through the reduced-diameter cladding by approximately 30% Δ-micrometers. 2 It has the above trench volume.

[0206] To facilitate the reduction in the diameter of the optical fiber, it is preferable to minimize or completely remove the thickness r5-r4 of the low modulus inner coating. The thickness r5-r4 of the low modulus coating is approximately 8.0 micrometers or less, or approximately 7.0 micrometers or less, or approximately 6.0 micrometers or less, or approximately 5.0 micrometers or less, or approximately 4.0 micrometers to approximately 8.0 micrometers, or approximately 5.0 micrometers to approximately 7.0 micrometers. However, removing or reducing the thickness of the low modulus inner coating of the optical fiber increases its susceptibility to microbending. This increased susceptibility is approximately 30%Δ-micrometer in the designs of this disclosure. 2 This is mitigated by adding an offset trench with a larger volume.

[0207] The radius r6 of the high modulus coating is approximately 87.5 micrometers or less, or approximately 85.0 micrometers or less, or approximately 82.5 micrometers or less, or approximately 80.0 micrometers or less. Furthermore, it is preferable to optimize the thickness r6-r5 of the high modulus coating in order to balance the reduction of fiber diameter with having a sufficiently large cross-sectional area for high puncture resistance. The thickness r6-r5 of the high modulus coating is approximately 25.0 micrometers or less, or approximately 20.0 micrometers or less, or approximately 15.0 micrometers or less, or approximately 15.0 micrometers to approximately 25.0 micrometers, or approximately 17.5 micrometers to approximately 22.5 micrometers, or approximately 18.0 micrometers to approximately 22.0 micrometers. The total thickness of the low modulus coating and the high modulus coating is approximately 25 micrometers or less, preferably approximately 20 micrometers or less. In some embodiments, the total thickness of the low modulus coating and the high modulus coating is approximately 10 micrometers to approximately 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 is 0.8 to 1.2.

[0208] Accordingly, the optical fibers according to the embodiments of this disclosure have a reduced coating diameter compared to conventional optical fibers. Such a reduction in size helps to increase the number of fibers and fiber density, for example, in submarine repeaters or cables.

[0209] Table 10 below shows the average coating thickness for five high modulus coating samples. Examples 1 and 2, compared with Examples 3, 4, and 5, show that average high modulus coating thicknesses of 8.0 micrometers to 20.0 micrometers produced higher tensile strength than average thicknesses below this range. The relatively high tensile strength shown in Examples 1 and 2 allows for the use of thinner high modulus coatings on optical fibers, such as those used in submarine cables and repeaters.

[0210] [Table 13]

[0211] Exemplary low modulus and high modulus coatings Examples of low-modulus and high-modulus coatings are described below, along with the measured values ​​of their strength and puncture resistance.

[0212] Low modulus coatings - compositions The low modulus coating composition has the formulations listed in Table 11 below and is typical of commercially available low modulus coating compositions.

[0213] [Table 14]

[0214] Here: The oligomer material was prepared from H12MDI, HEA, and PPG4000 using a molar ratio n:m:p = 3.5:3.0:2.0 as described herein; SR504 was ethoxylated (4) nonylphenol acrylate (manufactured by Sartomer); NVC was N-vinylcaprolactam (manufactured by Aldrich); TPO (photoinitiator) was (2,4,6-trimethylbenzoyl)-diphenylphosphine oxide (manufactured by BASF); Irganox 1035 (antioxidant) is benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester (manufactured by BASF); 3-acryloxypropyltrimethoxysilane is an adhesion promoter (manufactured by Gelest); and pentaerythritol tetrakis (3-mercaptopropionate) (also known as tetrathiol, manufactured by Aldrich) is a chain transfer agent. The unit of concentration "pph" represents the amount relative to the base composition containing all monomers, oligomers, and photoinitiators. For example, a concentration of 1.0 pph for Irganox 1035 corresponds to 1 g of Irganox 1035 per 100 g of a combination of oligomer material, SR504, NVC, and TPO.

[0215] Oligomer materials were prepared by mixing H12MDI (4,4'-methylenebis(cyclohexyl isocyanate)), dibutyltin dilaurate, and 2,6-di-tert-butyl-4methylphenol in a 500 mL flask at room temperature. The 500 mL flask was equipped with a thermometer, a CaCl2 drying tube, and a stirrer. While continuously stirring the contents of the flask, PPG4000 was added over a period of 30-40 minutes using an additive funnel. During the addition of PPG4000, the internal temperature of the reaction mixture was monitored, and the introduction of PPG4000 was controlled to prevent excessive heat (due to the exothermic nature of this reaction). After the addition of PPG4000, the reaction mixture was heated in an oil bath at approximately 70°C-75°C for approximately 1-1.5 hours. Samples of the reaction mixture were taken at various intervals for infrared spectroscopy (FTIR) analysis to monitor the progress of the reaction by determining the concentration of unreacted isocyanate groups. The concentration of unreacted isocyanate groups was 2265 cm⁻¹. -1 The intensity of the characteristic isocyanate stretching mode in the vicinity was evaluated. The flask was removed from the oil bath and its contents were cooled to below 65°C. Supplementary HEA was added to ensure complete quenching of the isocyanate groups. The supplementary HEA was added dropwise over 2–5 minutes using an addition funnel. After the addition of the supplementary HEA, the flask was returned to the oil bath and its contents were heated again to approximately 70°C–75°C for approximately 1–1.5 hours. FTIR analysis was performed on the reaction mixture to assess the presence of isocyanate groups, and this process was repeated until sufficient supplementary HEA was added to completely react any unreacted isocyanate groups. The reaction was considered complete when no evaluable isocyanate stretching intensity was detected in the FTIR measurement.

[0216] High modulus coating composition Four high modulus coating compositions (A, SB, SC, and SD) are listed in Table 12.

[0217] [Table 15]

[0218] PE210 is bisphenol-A epoxy diacrylate (manufactured by Miwon Specialty Chemical, South Korea); M240 is ethoxylated (4) bisphenol-A diacrylate (manufactured by Miwon Specialty Chemical, South Korea); M2300 is ethoxylated (30) bisphenol-A diacrylate (manufactured by Miwon Specialty Chemical, South Korea); M3130 is ethoxylated (3) trimethylolpropane triacrylate (manufactured by Miwon Specialty Chemical, South Korea); TPO (photoinitiator) is (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (manufactured by BASF); Irgacure 184 (photoinitiator) is 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF); Irganox 1035 (antioxidant) is benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester (manufactured by BASF). DC190 (slip agent) is silicone-ethylene oxide / propylene oxide copolymer (manufactured by Dow Chemical). The unit of concentration "pph" represents the amount relative to the base composition, which includes all monomers, oligomers, and photoinitiators. For example, for high modulus coating composition A, a concentration of 1.0 pph for DC-190 corresponds to 1 g of DC-190 in 100 g of the combination of PE210, M240, M2300, TPO, and Irgacure 184.

[0219] High modulus coating - tensile properties The Young's modulus, tensile strength at yield, yield strength, and elongation at yield of high modulus coatings prepared from high modulus coating compositions A, SB, SC, and SD were measured using the technique described above. The results are summarized in Table 13.

[0220] [Table 16]

[0221] The results show that the high modulus coatings prepared from compositions SB, SC, and SD exhibited higher Young's modulus and yield strength compared to the high modulus coating prepared from the comparative example composition A. Furthermore, the high modulus coatings prepared from compositions SB, SC, and SD showed higher fracture toughness compared to the high modulus coating prepared from composition A. These high values ​​exhibited by compositions SB, SC, and SD allow for the use of thinner high modulus coatings on optical fibers without sacrificing performance. As mentioned above, thinner high modulus coatings reduce the overall diameter of the optical fiber and increase the number of fibers within a given cross-sectional area (such as in a submarine repeater).

[0222] Exemplary optical fiber embodiment The experimental examples and principles disclosed herein demonstrate that sufficiently low attenuation and sufficiently high puncture resistance can be achieved in optical fibers with reduced diameter by adjusting the refractive index profile and coating characteristics of the optical fiber. More specifically, high modulus coatings provide sufficient puncture resistance to fibers with reduced diameter despite their small cross-sectional area.

[0223] Figure 8 plots the dependence of puncture load (g) on ​​the cross-sectional area of ​​the high modulus coating. The dashed line represents 0.00263 g / micrometer. 2 The gradient corresponds to a comparative example fiber having a high modulus coating with an in-situ modulus of approximately 1500 GPa. The solid line is a linear fit to measurement data for five fibers having a high modulus coating with an in-situ modulus of approximately 1850 GPa. The gradient is 0.00328 g / micrometer 2This is approximately equal to multiplying the gradient of the reference fiber by the ratio of the in-situ modulus, 1850 / 1500. The dotted line represents the modeled dependence of the puncture load (g) on ​​the cross-sectional area of ​​the high modulus coating with an in-situ modulus of 2200 GPa. These results demonstrate that increasing the in-situ modulus of the high modulus coating allows for a reduction in cross-sectional area and thickness without significantly reducing the puncture resistance of relatively small diameter fibers.

[0224] Fiber Draw Process The optical fibers disclosed herein can be formed by a continuous optical fiber manufacturing process, during which glass fibers are drawn from a heated preform to a target diameter. For fibers with a low modulus inner coating, the glass fibers are subsequently cooled and directed to a coating system for applying a liquid low modulus coating composition to the glass fibers. After applying the liquid low modulus coating composition to the glass fibers, two process options are feasible. In the first process option (wet-on-dry 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 process option (wet-on-wet process), a liquid high modulus coating composition is applied to the liquid low modulus coating composition, and both liquid coating compositions are cured simultaneously to provide a solidified low modulus coating and a solidified high modulus coating. After the fibers leave the coating system, they are recovered and stored at room temperature. Fiber recovery typically involves winding the fibers onto a spool and storing this spool.

[0225] In some processes, the coating is further applied to a high modulus coating by coating a colored outer coating composition and curing the colored outer coating composition to form a solidified colored outer coating. Typically, the colored outer coating is an ink layer used to mark fibers for identification purposes and has a similar composition to the high modulus coating, but contains pigments. The colored outer coating is applied to the high modulus coating and cured. The high modulus coating is typically cured at the time of application of the colored outer coating. Low modulus, high modulus, and colored outer coating compositions can be applied and cured in a common continuous manufacturing process. Alternatively, the colored outer coating can be formed by applying and curing the low modulus and high modulus coating compositions in a common continuous manufacturing process, collecting the coated fibers, and applying and curing the colored outer coating composition in a separate offline process.

[0226] Coating application, viscosity of coating material, and size of coating die In some embodiments, an optical fiber drawn from a preform in a drawing furnace is passed through a coating system in which a polymer coating is applied to the optical fiber. The coating system may include an inlet and a sizing die. A coating chamber is positioned between the inlet and the sizing die. 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 die, where any excess coating material is removed as the optical fiber exits the coating system, thereby obtaining a coated optical fiber of a specified diameter, as described in some embodiments of this specification.

[0227] Figure 12 shows the effect of the viscosity of the coating material and the die size on the coating thickness at a given constant draw speed (60 m / min in this case). As shown in Figure 12, the coating thickness is mainly affected by the diameter of the sizing die, while the viscosity of the coating material has only a slight effect. For example, the diameter of the coated fiber varies from 127 μm to 169 μm when the sizing die changes from 5.1 mil (129.54 μm) to 8.0 mil (203.2 μm), but the coating thickness varies only slightly with a wide range of viscosity coating materials, assuming a particular die size. 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.

[0228] Figure 13 shows an exemplary parameter window for forming a target final coated diameter of 132 ± 1 μm on an optical fiber with a glass diameter of 125 micrometers. As shown in Figure 13, the sizing die is specified within the range of 5.35 mil (135.89 μm) to 5.51 mil (140 μm), but the viscosity of the coating material can span a wide range within this parameter window. Thus, although the viscosity of the coating material has only a slight effect on the final coating thickness, the effective magnitude differs for multiple systems with different die sizes. Figure 14 shows the standard deviation of coating thickness obtained from various coating material viscosities for multiple systems with different die sizes. Figure 14 shows that the above standard deviation increases slightly with increasing die size and dramatically increases when the die size is greater than 7 mil. Figure 15 shows the effect of draw speed on coating thickness in some embodiments of the present disclosure. As seen in Figure 15, the fiber draw speed has only a limited effect on the coating thickness.

[0229] Regarding the concentricity of the coating, the lubrication pressure within the coating die is assumed to act as a centering force to ensure that the optical fiber is centered within the coating applicator. Higher lubrication pressure results in a stronger centering force and thus better coating concentricity. Figure 16 shows a graph plotting the correlation between lubrication pressure and die size for the viscosity of a series of coating materials. Figure 16 shows that the lubrication pressure decreases with increasing die size and increases with increasing viscosity of the coating material. Furthermore, Figure 17 shows the correlation between lubrication pressure and draw speed. As shown in Figure 17, the lubrication pressure initially increases dramatically, and then increases at a slower pace with increasing draw speed. Therefore, combined with the effect of viscosity on coating thickness described above, the concentricity of the coating can be improved without degrading the quality of the coating thickness by increasing the draw speed and using a higher viscosity material at a given die size.

[0230] Performance data for optical fibers with thin coatings Key performance metrics for these optical fibers with thin coatings include their overall outer diameter, polymer coating thickness, number of fractures per unit length during a 50 kpsi strength screening, and the longest length retained after the 50 kpsi screening. A high modulus coating layer was applied to 125 μm single-mode fiber (SMF) with a total coating thickness of approximately 7 μm (see reel IDs 121-6599-3 and 122-6645-4 in Table 15). Lower screening forces resulted in longer, undamaged fiber segments. The high modulus coated fiber (reel ID 121-6599-3) exhibited fiber strength comparable to that of a new high modulus coated fiber (reel ID 122-6645-4). The inventors have found that thin acrylate rigid fiber coatings using novel high modulus coated fibers exhibit concentricity of over 70%, over 80% in some embodiments, over 85%, over 90%, or over 95%.

[0231] [Table 17]

[0232] Compared to thin acrylate coatings applied to aged 125 μm SMF fibers so that the total coating thickness was approximately 7 μm (see reels ID 121-6602-10 and 121-6602-12 in Table 16), the new high modulus coated fibers shown in reel ID 121-6599-3 showed significantly higher figures for both the longest length held (m) and the ratio of meters / (number of fractures + 1) of screened thin coated fibers when the thin coated fibers were screened at a force of 50 kpsi. The fractures of these three fibers were fairly uniformly distributed across the entire screened length of the fibers. This strongly suggests that the older high modulus coated fibers were likely partially degraded during storage. Nevertheless, all three of these thin acrylate coated fibers still exhibited good concentricity (i.e., over 70%).

[0233] [Table 18]

[0234] A new high modulus coating layer was applied to 125 μm SMF fibers with a total coating thickness of 15 μm (see reels ID 121-6599-4 and ID 122-6645-3 in Table 15). By using the new high modulus coating layer and increasing the coating thickness from 7 μm in reel ID 121-6599-3 to 15 μm in reel ID 121-6599-4, the thin-film coated fibers are significantly strengthened, as indicated by a substantial increase in both the maximum length held (m) and the ratio of meters / (number of fractures + 1) of screened thin-film coated fibers when the thin-film coated fibers were screened at 50 kpsi. By using a new high modulus coating layer and increasing the coating thickness from 7 μm for reel ID 122-6645-4 to 15 μm for reel ID 122-6645-3, the thin coated fibers are significantly strengthened, as indicated by a substantial increase in both the maximum length held (m) and the ratio of meters / (number of fractures + 1) of screened thin coated fibers when screened at a force of 50 kpsi. Furthermore, the thin acrylate rigid fiber coating exhibits good concentricity (i.e., over 70%). These thin acrylate coated fibers with a total coating thickness of 15 μm (reels ID 121-6599-4 and reel ID 122-6645-3 in Table 15) possess sufficient strength to withstand ribbon cable processing.

[0235] We also performed drawing of a thin, two-layer acrylate fiber coating with a new low modulus coating layer and a new high modulus coating layer (see reel ID 121-6599-5 in Table 16). The thickness of the low modulus coating layer is 9 μm, and the thickness of the high modulus coating layer is 8 μm. The total thickness, adding the thicknesses of the low modulus and high modulus coating layers, is 17 μm. The execution of the thin acrylate coating was smooth, and there were no defects in the coating on the fiber. This thin coated fiber was screened at 50 kpsi. The screening results were equivalent to the new high modulus coating layer on a 125 μm SMF fiber with a total coating thickness of 15 μm (see reel ID 121-6599-4 in Table 15). The thin acrylate hard fiber coating has good concentricity (i.e., over 70%). This thin acrylate coated fiber also has sufficient strength to withstand the ribbon cable process. The presence of a soft, thin, low-modulus coating layer gives this two-layer thin coated fiber improved micro-bend performance compared to single-layer thin rigid coated fibers.

[0236] [Table 19]

[0237] Drawings of thin, two-layer acrylate fiber coatings—a new low modulus coating layer and a new high modulus coating layer—were performed on standard single-mode fibers on a graded index core with a silica inner cladding and an undoped outer cladding, having relative refractive index profiles as shown in Figure 18. Fiber coating parameters and measured optical parameters are shown in Table 18 below. The table below shows three thin coating configurations with low modulus coating diameter / high modulus coating diameters of 145 μm / 175 μm, 140 μm / 160 μm, and 0 μm / 140 μm. A fiber with a low modulus coating diameter / high modulus coating diameter of 190 μm / 250 μm is a standard coating used as a control. For the thin-coated fibers described above, the measured cable cutoff wavelength and MFD were equivalent to those of the control fiber, indicating that these thin coatings did not affect these parameters. For fibers with a low modulus inner coating diameter / high modulus coating diameter of 145 μm / 175 μm and 140 μm / 160 μm, the attenuation at 1310 and 1550 nm was identical to that of the control fiber, indicating that these thin coating configurations did not result in any attenuation penalty. The attenuation of fibers with a low modulus coating diameter / high modulus coating diameter of 0 μm / 140 μm is slightly higher than the other fibers due to the single coating layer, but is acceptable for many applications using short fibers, such as data centers.

[0238] [Table 20]

[0239] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the present invention. Since modifications, combinations, partial combinations and variations of the embodiments of this disclosure that incorporate the spirit and substance of the present invention can be conceived to those skilled in the art, the present invention shall be construed as encompassing all of the appended claims and their equivalents.

[0240] Preferred embodiments of the present invention are described below in separate sections.

[0241] Embodiment 1 Core area; A cladding region surrounding the core region, wherein the cladding region comprises an inner cladding directly adjacent to the core region and an outer cladding surrounding the inner cladding, and the radius of the cladding region is less than approximately 62.5 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 inner coating layer is 4 micrometers to 20 micrometers, the modulus of the low modulus inner coating layer is approximately 0.35 MPa or less, the thickness of the high modulus coating layer is 4 micrometers to 20 micrometers, and the modulus of the high modulus coating layer is approximately 1.6 GPa or more. An optical fiber comprising, The above optical fiber has a puncture resistance of over 20g, a microbend attenuation penalty of less than 0.03dB / km, and a coated optical fiber with an outer diameter of 175 micrometers or less. The above puncture resistance of the optical fiber is given by formula P R =P0+C1E s A s It is calculated by, where A s This is the cross-sectional area of ​​the high modulus coating described above, and E sThe above high modulus coating has a modulus of elasticity, P0 is a coefficient with a value of 11.3 g, and C1 is 2.1 g / MPa / mm 2 It is a coefficient having a value, The above microbend attenuation penalty for the optical fiber is given by the formula:

[0242]

number

[0243] It is calculated by the following, 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.

[0244]

number

[0245] And,

[0246]

number

[0247] And,

[0248]

number

[0249] And,

[0250]

number

[0251] And R g R is the radius of the glass. s is the outer radius of the above-mentioned high modulus outer coating, and t p is the thickness of the above-mentioned inner low modulus coating, t sThis is the thickness of the above-mentioned high modulus outer coating, E g E is the elastic modulus of glass. p This is the modulus of elasticity of the low modulus inner coating described above, and E s The above modulus of elasticity is that of the above-mentioned high modulus coating, and is an optical fiber.

[0252] Embodiment 2 The optical fiber according to Embodiment 1, wherein the above microbend attenuation penalty of the optical fiber is 0.01 dB / km or less.

[0253] Embodiment 3 The optical fiber according to Embodiment 1, wherein the above microbend attenuation penalty of the optical fiber is 0.007 dB / km or less.

[0254] Embodiment 4 The optical fiber according to Embodiment 1, wherein the above microbend attenuation penalty of the optical fiber is 0.003 dB / km or less.

[0255] Embodiment 5 The optical fiber according to Embodiment 1, wherein the above-mentioned puncture resistance of the optical fiber is 25g or more.

[0256] Embodiment 6 The optical fiber according to Embodiment 1, wherein the above-mentioned puncture resistance of the optical fiber is 30g or more.

[0257] Embodiment 7 The optical fiber according to Embodiment 1, wherein the radius of the cladding region is less than 52.5 micrometers, and the puncture resistance of the optical fiber is greater than 40 g.

[0258] Embodiment 8 The optical fiber according to Embodiment 1, wherein the thickness of the high modulus coating layer is 9 micrometers to 18 micrometers.

[0259] Embodiment 9 The optical fiber according to Embodiment 1, wherein the attenuation of the optical fiber is less than 0.20 dB / km.

[0260] Embodiment 10 The optical fiber according to Embodiment 1, wherein the mode field diameter of the optical fiber at 1310 nm is 8.6 or greater.

[0261] Embodiment 11 Core area; A cladding region surrounding the above-mentioned core region, wherein the cladding region comprises an inner cladding directly adjacent to the core region and an outer cladding surrounding the inner cladding, and 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 inner coating layer is 6 micrometers to 20 micrometers, the modulus of the low modulus inner coating layer is approximately 0.35 MPa or less, the thickness of the high modulus coating layer is 12 micrometers to 18 micrometers, and the modulus of the high modulus coating layer is approximately 1.6 GPa or more. An optical fiber comprising, The above optical fiber has a puncture resistance of over 30g, a microbend attenuation penalty of less than 0.03dB / km, and a coated optical fiber with an outer diameter of 175 micrometers or less. The above puncture resistance of the optical fiber is given by formula P R =P0+C1E s A s It is calculated by, where A s This is the cross-sectional area of ​​the high modulus coating described above, and E s The above high modulus coating has a modulus of elasticity, P0 is a coefficient with a value of 11.3 g, and C1 is 2.1 g / MPa / mm 2 The coefficient has a value of , and the above microbend attenuation penalty of the optical fiber is given by the formula:

[0262]

number

[0263] It is calculated by the following, 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.

[0264]

number

[0265] And,

[0266]

number

[0267] And,

[0268]

number

[0269] And,

[0270]

number

[0271] And R g R is the radius of the glass. s is the outer radius of the above-mentioned high modulus outer coating, and t p is the thickness of the above-mentioned inner low modulus coating, t s This is the thickness of the above-mentioned high modulus outer coating, E g E is the elastic modulus of glass. p This is the modulus of elasticity of the low modulus inner coating described above, and E s The above modulus of elasticity is that of the above-mentioned high modulus coating, and is an optical fiber.

[0272] Embodiment 12 The optical fiber according to Embodiment 11, wherein the above microbend attenuation penalty of the optical fiber is 0.01 dB / km or less.

[0273] Embodiment 13 The optical fiber according to Embodiment 11, wherein the above microbend attenuation penalty of the optical fiber is 0.007 dB / km or less.

[0274] Embodiment 14 The optical fiber according to Embodiment 11, wherein the above microbend attenuation penalty of the optical fiber is 0.003 dB / km or less.

[0275] Embodiment 15 The optical fiber according to Embodiment 1, wherein the above-mentioned puncture resistance of the optical fiber is 25g or more.

[0276] Embodiment 16 Core area; A cladding region surrounding the core region, wherein the cladding region comprises an inner cladding directly adjacent to the core region and an outer cladding surrounding the inner cladding; and A polymer coating having a thickness of 25 μm or less, wherein the polymer coating comprises a high modulus coating layer surrounding the cladding region, and the Young's modulus of the high modulus coating layer is 1.5 GPa or more. An optical fiber comprising the above, wherein the outer diameter of the coated optical fiber is 175 micrometers or less.

[0277] Embodiment 17 The optical fiber according to embodiment 16, further comprising 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.

[0278] Embodiment 18 The optical fiber according to Embodiment 17, wherein the ratio of the thickness of the low modulus coating layer to the thickness of the high modulus coating layer is 0.8 to 1.2.

[0279] Embodiment 19 A method for coating optical fibers: Steps include drawing the material from the drawing furnace along a first vertical path; A step of routing an optical fiber so that a polymer coating is applied to the optical fiber, wherein the coating system comprises an inlet, a sizing die with a diameter of 129 μm to 203 μm facing the inlet, and a coating chamber positioned between the inlet and the sizing die, the coating chamber being filled with a coating material in liquid form; and The step of curing the coated optical fiber to form an outer diameter of 175 micrometers or less. Methods that include...

[0280] Embodiment 20 The method according to Embodiment 19, wherein the concentricity of the polymer coating is greater than 70%. [Explanation of symbols]

[0281] 10, 20, 46, 60 optical fibers 11. Glass fiber 12, 48 core areas 14, 50 Clad areas 16, 56 Low modulus inner coating, low modulus coating 18, 58 High modulus coating 30 Fiber Optic Ribbons 32 matrix, ribbon matrix 40 Fiber Optic Cables 42 Jacket 44 Inside of jacket 42 51 Inner cladding region 53 Refractive index suppression cladding region 55 Outer cladding region 61, 62 transition region 63 Depth of the refractive index suppression cladding region

Claims

1. It is an optical fiber, Core area; A cladding region surrounding the core region, wherein the cladding region comprises an inner cladding directly adjacent to the core region and an outer cladding surrounding the inner cladding; 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. It has, The low modulus coating layer has a layer thickness ranging from 4 μm to 20 μm and an elastic modulus of approximately 0.35 MPa or less. The aforementioned high modulus coating layer has a layer thickness in the range of 4 μm to 20 μm and an elastic modulus of approximately 1.6 GPa or higher. The optical fiber has puncture resistance exceeding 20 g and a microbend attenuation penalty of less than 0.03 dB / km, and the outer diameter of the coated optical fiber is 175 μm or less. The puncture resistance of the optical fiber is expressed by the formula P Ｒ = P ０ + C １ E ｓ A ｓ and is calculated by the formula, where A ｓ is the cross-sectional area of the high elastic modulus coating, E ｓ is the elastic modulus of the high elastic modulus coating, P ０ is a coefficient having a value of 11.3 g, and C １ is a coefficient having a value of 2.1 g / MPa / mm ２ ​ The microbend attenuation penalty of the optical fiber is given by the formula: [Math 1] It is calculated by, where f ０ σ 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. [Math 2] And, [Math 3] And, [Math 4] And, [Math 5] And R ｇ R is the radius of the glass. ｓ is the outer radius of the above-mentioned high modulus outer coating, and t ｐ is the thickness of the above-mentioned inner low modulus coating, t ｓ This is the thickness of the above-mentioned high modulus outer coating, E ｇ E is the elastic modulus of glass. ｐ This is the modulus of elasticity of the low modulus inner coating described above, E ｓ This is the modulus of elasticity of the above-mentioned high modulus coating. Optical fiber.

2. The aforementioned core region is GeO ２ doped silica glass, Maximum relative refractive index Δ in the range of 0.25% to 0.40% １ｍａｘ , Outer radius r in the range of 4.0 μm to 6.0 μm １ , The optical fiber according to claim 1, having at least one of the following.

3. The aforementioned inner cladding region is Relative refractive index Δ in the range of -0.05% to 0.05% ２ , Outer radius r in the range of 9.0 μm to 15.0 μm ２ , The optical fiber according to claim 1, having at least one of the following.

4. The cladding region further includes a refractive index suppression cladding region between the inner cladding region and the outer cladding region. The aforementioned refractive index suppression cladding region is The relative refractive index Δ of the inner cladding region ２ and the relative refractive index Δ of the outer cladding region ４ Lower relative refractive index Δ ３ , Relative refractive index Δ in the range of -0.30% to -0.80% ３ , Outer radius r in the range of 14.0 μm to 18.0 μm ３ , The optical fiber according to claim 1, having at least one of the following.

5. The outer cladding region has an outer radius r in the range of 60.0 μm to 65.0 μm, or 61.0 μm to 64.0 μm, or 62.0 μm to 63.0 μm. ４ An optical fiber according to claim 1, comprising the features of the optical fiber.

6. The optical fiber according to claim 1, wherein the thickness of the high modulus coating is in the range of 9 μm to 18 μm.

7. The optical fiber according to claim 1, wherein the thickness of the low modulus coating is 25 μm or less.

8. The optical fiber according to claim 1, wherein the outer diameter of the coated optical fiber is in the range of 155 μm to 175 μm, or in the range of 160 μm to 170 μm.

9. The optical fiber according to claim 1, wherein the microbend attenuation penalty of the optical fiber is 0.01 dB / km or less, 0.007 dB / km or less, or 0.003 dB / km or less.

10. The optical fiber according to claim 1, wherein the puncture resistance of the optical fiber is 26 g or more, or 34 g or more.

11. The attenuation of the optical fiber is 0.20 dB / km at a wavelength of 1550 nm, and / or The optical fiber according to claim 1, wherein the mode field diameter of the optical fiber is 8.6 μm or more at a wavelength of 1310 nm.

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