Multimode optical fiber with increased bandwidth

Abstract

A multimode optical fiber having a core region. The core region includes silica, has an outer radius r1, and has a maximum relative refractive index of about 1.5% or less. Further, the multimode optical fiber is configured to have an effective bandwidth of about 4.7 GHz-Km or more for an excited portion of the core region having a diameter greater than 50 microns, the effective bandwidth being at a wavelength in a range of about 800 to about 1370 nm.

Description

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 010,271, filed April 15, 2020, and U.S. Provisional Patent Application Serial No. 63 / 023,487, filed May 12, 2020, the contents of which are relied upon and incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present disclosure relates to optical fibers, and more particularly to high bandwidth multimode optical fibers. BACKGROUND

[0003] Optical fibers, including multimode optical fibers, are used in applications such as data center and fiber to the home networks. In particular, multimode optical fibers are used for optical communications in local area networks (LANs) and for data centers due to their large data carrying capacity (bandwidth) and their ability to carry optical signals at different optical wavelengths via wavelength division multiplexing (WDM). Different types of multimode optical fibers used for optical communications include OM1, OM2, OM3, and OM4 types, with the OM4 type being widely used for 10 gigabit (G), 40G, and 100G Ethernet networks, for data centers, financial centers, and enterprise campuses. In recent years, TIA has introduced and standardized a new standard for multimode optical fibers, which is referred to as OM5 and documented in TIA-492AAAE. SUMMARY

[0004] To meet the OM4 standard for modal bandwidth as stated by TIA, a multimode optical fiber must have an effective modal bandwidth (EMB) of 4700 MHz-km at 850 nm. To enable a multimode optical fiber to meet the OM5 standard, the fiber must provide an effective modal bandwidth of 2470 MHz-km at 953 nm while meeting the OM4 effective modal bandwidth requirement at 850 nm.

[0005] The multimode optical fibers disclosed herein have an effective modal bandwidth that meets both the OM4 and OM5 standards. In addition, the multimode optical fibers disclosed herein provide such high effective modal bandwidth while advantageously maintaining low attenuation loss. The multimode optical fibers disclosed herein also have high connector offset tolerance and low insertion loss, thus providing a very advantageous fiber for optical fibers used for server applications (FTTS), for example. In addition, the multimode optical fibers disclosed herein have a wide operating wavelength range, which can be optimized for a target peak bandwidth wavelength for a given refractive index profile.

[0006] As discussed further below, the multimode optical fiber disclosed herein includes a larger core diameter than conventional multimode optical fibers. The large core diameter advantageously provides an effective relative refractive index depression of the excited core region when used with a ring-flux launch condition or directly launched from a commercial VCSEL-based transceiver. Due to the effective relative refractive index depression over the excited portion of the core, the multimode optical fiber has a greatly increased effective modal bandwidth compared to conventional multimode optical fibers.

[0007] According to a first aspect, a multimode optical fiber is provided having a core region. The core region includes silica having an outer radius r1 and having a maximum relative refractive index of about 1.5% or less. Further, the multimode optical fiber is configured to have an effective bandwidth of about 4.7 GHz-Km or more for an excited portion of the core region having a diameter greater than 50 microns, the effective bandwidth being at a wavelength in a range of about 800 to about 1370 nm.

[0008] According to another aspect, a multimode optical fiber is provided having a core region. The core region includes silica and has an outer radius r1 of about 30 microns or more. Further, the core region is configured to have an effective relative refractive index in a range of about 0.3% to about 0.80% for an excited portion of the core region having a diameter greater than 50 microns.

[0009] According to another aspect, a multimode optical fiber is provided having a core region. The core region includes silica and has an outer radius r1. Further, the core region has a maximum relative refractive index of about 1.5% or less. The multimode optical fiber is configured to have an effective relative refractive index of about 0.95% or less for an excited portion of the core region having a diameter greater than 50 microns.

[0010] According to another aspect, a multimode optical fiber is provided having a core region. The core region includes silica and has a maximum relative refractive index of less than 1.0% and an alpha value of about 0.9 to about 2.3 at a wavelength of 850 nm. The core region has an etendue in a range of about 110 microns 2 to about 150 microns 2 when excited with a ring-flux launch condition. Further, the multimode optical fiber is configured to have a modal bandwidth of about 4.7 GHz-Km or more, the modal bandwidth being at a wavelength in a range of about 800 to about 1370 nm.

[0011] As discussed below, the effective relative refractive index and the effective bandwidth refer to the relative refractive index and the bandwidth, respectively, of the excited portion of the core region.

[0012] Additional features and advantages are set forth in the detailed description which follows, and in part will become apparent to those skilled in the art on examination of the following or can be learned by practice of the application. The advantages of the application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

[0013] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the nature and character of the application. BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment and together with the description serve to explain principles and operation of the various embodiments. Thus, the disclosure will be better understood with reference to the following detailed description when considered in connection with the accompanying drawings, in which:

[0015] Figure 1 is a front isometric view of an exemplary multi-mode optical fiber according to embodiments disclosed herein;

[0016] Figure 2 is a front isometric view of an exemplary multi-mode optical fiber according to embodiments disclosed herein; Figure 1 is a cross-sectional view of an exemplary multi-mode optical fiber of

[0017] Figure 3 is a cross-sectional view of an exemplary multi-mode optical fiber of Figure 1 and 2 is a cross-sectional magnified view of a glass segment of an exemplary multi-mode optical fiber of

[0018] Figure 4 is an exemplary relative refractive index profile of a multi-mode optical fiber according to embodiments disclosed herein, a plot of relative refractive index Δ versus radial coordinate r;

[0019] Figure 5 is another exemplary relative refractive index profile of a multi-mode optical fiber according to embodiments disclosed herein, a plot of relative refractive index Δ versus radial coordinate r;

[0020] Figures 6A-6D is a plot of effective bandwidth versus wavelength for a multi-mode optical fiber according to embodiments disclosed herein;

[0021] Figure 7A is another exemplary relative refractive index profile of a multi-mode optical fiber according to embodiments disclosed herein, a plot of relative refractive index Δ versus radial coordinate r;

[0022] Figure 7B is a plot of effective bandwidth versus wavelength for a multi-mode optical fiber of Figure 7A according to embodiments disclosed herein;

[0023] Figure 8is a graph of effective bandwidth versus wavelength for a multimode optical fiber according to embodiments disclosed herein;

[0024] Figure 9A is a graph of effective bandwidth versus wavelength for a multimode optical fiber according to embodiments disclosed herein;

[0025] Figure 9B shows Figure 7A is a graph of relative refractive index profile for a multimode optical fiber according to embodiments disclosed herein;

[0026] Figure 9C shows a graph of the functional relationship of tension versus peak bandwidth wavelength range and core diameter according to embodiments disclosed herein;

[0027] Figure 10 is a graph of attenuation versus wavelength for a multimode optical fiber according to embodiments disclosed herein;

[0028] Figure 11A is a schematic diagram of components for measuring relative insertion loss versus offset for a multimode optical fiber;

[0029] Figure 11B is a graph of relative insertion loss versus offset for a multimode optical fiber according to embodiments disclosed herein and for comparative example multimode optical fibers;

[0030] Figure 11C is a graph of modal bandwidth versus offset for a multimode optical fiber according to embodiments disclosed herein;

[0031] Figure 12A is a schematic diagram of components for measuring bit error rate;

[0032] Figure 12B is a graph of bit error rate versus received optical power for a multimode optical fiber according to embodiments disclosed herein;

[0033] Figure 13A is a schematic diagram of an exemplary fiber optic data communication system employing the optical fibers disclosed herein to form a fiber optic link between a VCSEL-based transmitter and receiver; and

[0034] Figure 13B is similar to Figure 13A and shows an exemplary fiber optic data communication system having two VCSEL-based transceivers. DETAILED DESCRIPTION

[0035] Various embodiments of the present disclosure are described in detail below. Examples of these embodiments are shown in the drawings. Whenever possible, the same or like reference numerals and symbols are used in all drawings and illustrations to refer to the same or like parts. The drawings are not necessarily to scale and the skilled person will appreciate that simplifications have been made in order to illustrate the key aspects of the invention.

[0036] The use of any relative terms such as top, bottom, side, horizontal, vertical, and the like are for convenience and ease of explanation and are not intended to limit the orientation or direction.

[0037] Unless otherwise stated, the limits of any range as stated herein are considered to be inclusive, thus falling within the range.

[0038] “Optical fiber” refers to a waveguide having a glass portion surrounded by a cladding. The glass portion includes a core and a cladding, and is referred to herein as a “glass fiber”.

[0039] “Radial position”, “radius”, or radial coordinate “r” refers to a radial position relative to the centerline of the optical fiber (r = 0).

[0040] As used herein, the term “refractive index profile” or “relative refractive index profile” is the relationship between the refractive index or relative refractive index and the fiber radius.

[0041] As used herein, the term “relative refractive index” is defined as follows:

[0042]

[0043] where n(r) is the refractive index at fiber radius r, and r = 0 corresponds to the centerline of the optical fiber, unless otherwise stated. The relative refractive index is defined at 850 nm, unless otherwise stated. In embodiments described herein, the reference refractive index n REF is the refractive index of the outer cladding. In embodiments that do not include an outer cladding, the reference refractive index n REF is the refractive index of pure silica. Unless otherwise stated, the relative refractive index as used herein is expressed in Δ or called “Delta” or ‘D’, and its numerical value is in “%”. Unless otherwise stated, the relative refractive index percentage is negative in the case where the refractive index of a region is less than the reference refractive index n REF , and the region can be called a depressed region or depressed refractive index, and the minimum relative refractive index is calculated at the point where the relative refractive index is most negative. The relative refractive index percentage is positive in the case where the refractive index of a region is greater than the reference refractive index n REF , and the region can be called a raised region or positive refractive index.

[0044] As used herein, the term "positive dopant" refers to a dopant that increases the refractive index of the glass relative to pure, undoped Si02. As used herein, the term "negative dopant" refers to a dopant that tends to decrease the refractive index of the glass relative to pure, undoped Si02. A positive dopant can be present in a region of the optical fiber having a negative relative refractive index, along with one or more other dopants that are not positive dopants. Similarly, one or more other dopants that are not positive dopants can be present in a region of the optical fiber having a positive relative refractive index. A negative dopant can be present in a region of the optical fiber having a positive relative refractive index, along with one or more other dopants that are not negative dopants. Similarly, one or more other dopants that are not negative dopants can be present in a region of the optical fiber having a negative relative refractive index.

[0045] As used herein, the term "alpha-profile" or "alpha profile" refers to a relative refractive index profile, denoted by Δ, in units of "%", where r is the radius, and satisfies the equation,

[0046]

[0047] where Δ(r) is the relative refractive index, r is the radial position in the fiber, and r 1最大值 is the maximum relative refractive index, r1is the core radius, r ranges from r i ≤ r ≤ r f , Δ is defined above, r i is the start of the alpha profile, r f is the end of the alpha profile, and α is the exponent, which is a real number. For a graded index profile, the value of α is less than 10. As used herein, the term "parabolic" includes: a refractive index profile that is substantially parabolic, which can deviate slightly from the case where α has a value of 2.0 at one or more points in the core; and profiles that have a small amount of variation and / or a central line sink.

[0048] "Groove volume" is defined as follows:

[0049]

[0050] where r 凹槽，内 is the inner radius of the groove region of the refractive index profile, r 凹槽，外 is the outer radius of the groove region of the refractive index profile, Δ 凹槽 (r) is the relative refractive index of the groove region of the refractive index profile, and r is the radial position in the fiber. Groove volume is an absolute value and is positive, and the units are expressed herein as follows: %Δ microns 2 , %Δ-microns 2 , %Δ-μm 2 , or %Δ μm 2These units are used interchangeably herein. The trench region is also referred to herein as a depressed-index cladding region, and the trench volume is also referred to herein as V3.

[0051] Macrobend performance is determined in accordance with FOTP-62 (JEC-60793-1-47) by wrapping the optical fiber around a 15 mm and / or 30 mm diameter mandrel for 2 turns, and measuring the increase in attenuation due to the bend using the Encircled Flux (EF) launch condition (also referred to as the "restricted launch condition"). The encircled flux is measured by launching an overfilled pulse into the input end of a 2 m length of 50 micron core optical fiber arranged to be wrapped around a 25 mm diameter mandrel near the midpoint. The output end of the 50 micron core optical fiber is spliced to a measurement fiber, and the measured bend loss is the difference in attenuation under the prescribed bend condition and the attenuation without the bend. 50 micron core optical fiber is spliced to a measurement fiber, and the measured bend loss is the difference in attenuation under the prescribed bend condition and the attenuation without the bend.

[0052] The term "bandwidth" is denoted as BW, and as used herein the term is modal bandwidth. For the multimode optical fibers in the present application, the modal bandwidth is also referred to as effective bandwidth and is obtained / defined using the Encircled Flux launch condition (which represents a standard compliant launch condition, as further described below) for measuring the bandwidth capability of the optical fiber under study.

[0053] In the discussion that follows, the core of the multimode optical fibers disclosed herein can be referred to as the "core region," and the cladding of the optical fiber and the inner region, intermediate region, and outer region thereof can be referred to as the cladding region, inner cladding region, intermediate cladding region, and outer cladding region, respectively, to distinguish from the corresponding regions or segments of the preform used to form the co-doped wideband multimode optical fiber.

[0054] Reference will now be made in detail to the exemplary embodiments of the present specification.

[0055] Figure 1 is a front isometric view of an exemplary wideband multimode optical fiber 10 disclosed herein, while Figure 2 is a cross-sectional view of the optical fiber 10. As Figure 1 and 2 shown, the optical fiber 10 has a centerline AC, a core region 20, and a cladding region 30 immediately surrounding the core region 20. Both the core region 20 and the cladding region 30 are made of glass and define a glass segment 40 having an outer surface 42 (as shown in Figure 2 ).

[0056] The optical fiber 10 also includes a protective coating 50 immediately surrounding the outer surface 42 of the glass segment 40. The protective coating 50 can include two or more layers of different polymeric materials (e.g., acrylate). In some embodiments, the protective coating 50 includes a low modulus primary coating and a high modulus secondary coating. As​Figure 2 As shown, the protective coating 50 has a thickness TH, and the outer diameter of the protective coating 50 defines the fiber diameter DF of the optical fiber 10. In one exemplary embodiment, the core region 20 has a diameter of approximately 100 micrometers, the glass segment 40 has a diameter of approximately 125 micrometers, the light diameter DF is approximately 250 micrometers, and the thickness TH of the protective coating 50 is approximately 62.5 micrometers.

[0057] Figure 3 This is a cross-sectional view of the glass segment 40 of optical fiber 10 (i.e., optical fiber 10 has no protective coating 50). Figure 3 As shown, the core region 20 has an outer radius r1. The cladding region 30 surrounds and is arranged directly adjacent to the core region 20, and includes an inner cladding region 32 with an outer radius r2, an intermediate cladding region 34 with an outer radius r3, and an outer cladding region 36 with an outer radius r4. It should also be noted that the outer radius r4 is also the outer radius of the cladding region 30 and the glass segment 40. The diameter of the cladding region 30 and the glass segment 40 is D4 = 2·r4. In some embodiments, the diameter of the glass segment 40 is: about 100 micrometers or greater, or about 125 micrometers or greater, or about 150 micrometers or greater, or about 175 micrometers or greater, or about 200 micrometers or greater, or about 225 micrometers or greater, or about 250 micrometers or greater, or about 275 micrometers or greater, or about 300 micrometers or greater, or about 325 micrometers or greater, or about 350 micrometers or greater, or about 375 micrometers or greater, or about 400 micrometers or greater.

[0058] As discussed further below, it is also considered that the cladding region 30 may not include one or more of the inner cladding region 32, the intermediate cladding region 34, and the outer cladding region 36. For example, in some embodiments, the cladding region 30 may include only the inner cladding region 32 and the intermediate cladding region 34 and may not include the outer cladding region 36. In this embodiment, the intermediate cladding region 34 may extend from the outer radius (r2) of the inner cladding region 32 to the outer radius (r4) of the cladding region 30 (therefore the outer radius of the intermediate cladding region 34 forms the outer surface 42 of the glass segment 40). In another embodiment, the cladding region 30 may include only the intermediate cladding region 34. In this embodiment, the intermediate cladding region 34 surrounds and is directly adjacent to the core region 20, and the intermediate cladding region 34 extends from the outer radius (r1) of the core region 20 to the outer radius (r4) of the cladding region (therefore the outer radius of the intermediate cladding region 34 forms the outer surface 42 of the glass segment 40).

[0059] In some embodiments, the cladding region 30 does not contain positive dopants. Therefore, in these embodiments, the cladding region 30 is entirely free of positive dopants. However, in these embodiments, the cladding region 30 may still contain one or more negative dopants.

[0060] In some other embodiments, the optical fiber 10 does not include the cladding region 30. Therefore, in these embodiments, the glass segment 40 is formed only by the core region 20, and the outer radius of the core region 20 forms the outer surface 42 of the glass segment 40.

[0061] Figure 4 An idealized relative refractive index distribution of optical fiber 10 was plotted, showing the relationship between the relative refractive index Δ and the radial coordinate r. The core region 20 has a relative refractive index Δ1(r) and a maximum refractive index Δ0 = Δ1. 最大值 Located at r = 0 and with a gradient α distribution, as described in more detail below. The inner cladding region 32 has a relative refractive index Δ2 and a width W2. The intermediate cladding region 34 can be in the form of a recessed region or a groove, and has a width W3 and a relative refractive index Δ3 < Δ2, with a minimum value Δ 3最小值 The outer cladding region 36 has a width W4 and a relative refractive index Δ4, which is shown, for example, as Δ2 = Δ4. Other configurations of the relative refractive index distribution are discussed further below.

[0062] Core area

[0063] The core region 20 comprises silica glass, which is either undoped or positively doped silica glass. Positively doped silica glass includes silica glass doped with, for example, germanium (e.g., GeO2), phosphorus (e.g., P2O5), aluminum (e.g., Al2O3), or chlorine. In some embodiments, the concentration of the germanium positive dopant in the core region 20 may range from about 10 wt% to about 40 wt%, or from about 15 wt% to about 35 wt%, or from about 20 wt% to about 30 wt%.

[0064] As discussed above, the relative refractive index of the core region 20 of the glass fiber is described by an α distribution with α values ​​ranging from about 0.9 to about 2.6, about 0.9 to about 2.3, about 1.5 to about 2.6, about 1.6 to about 2.5, about 1.7 to about 2.4, about 1.8 to about 2.3, about 1.9 to about 2.3, about 1.9 to about 2.2, or about 2.0 to about 2.1, measured at 850 nm.

[0065] The outer radius r1 of the core region 20 is in a range of about 20 microns or more, about 25 microns or more, about 30 microns or more, about 35 microns or more, about 40 microns or more, about 45 microns or more, about 50 microns or more, about 55 microns or more, or about 60 microns or more. Additionally or alternatively, the radius r1 of the core region 20 is in a range of about 70 microns or less, about 65 microns or less, about 60 microns or less, or about 50 microns or less. In some embodiments, the outer radius r1 is in a range of about 25 microns to about 50 microns, or about 30 microns to about 65 microns, or about 30 microns to about 62.5 microns, or about 45 microns to about 55 microns, or about 50 microns, or about 62.5 microns. As discussed above, the outer radius r1 of the core region 20 is larger than that of a conventional multi-mode optical fiber.

[0066] The maximum relative refractive index Δ0 or Δ 1最大值 of the core region 20 is about 3.0% or less, or about 2.5% or less, or about 2.0% or less, or about 1.5% or less, or about 1.0% or less, or about 0.5% or less. Additionally or alternatively, the maximum relative refractive index of the core region 20 is about 0.2% or more, or about 0.5% or more, or about 0.7% or more, or about 0.9% or more. In some embodiments, the maximum relative refractive index of the core region 20 is in a range of about 0.3% to about 0.95%, or about 0.5% to about 2.0%, or about 0.5% to about 0.8%, or about 0.6% to about 1.7%, or about 0.7% to about 1.5%, or about 0.8% to about 1.2%, or about 0.3% to about 0.95%. For example, the maximum relative refractive index can be about 1.0%, or about 0.80%, or about 0.75%, or less than 1.0%.

[0067] Although Figure 4 not shown in FIG. 1, in some embodiments, the refractive index of the core region 20 can have a central line sink, such that the location of the maximum relative refractive index of the core region 20, as well as the maximum relative refractive index of the entire optical fiber 10, is a small distance away from the central line of the core region 20, rather than being located at the central line of the core region 20 as shown in FIG. 1. Figure 4

[0068] The inner cladding region

[0069] ​The inner cladding region 32 can comprise undoped silica glass. The inner radius of the inner cladding region 32 is r1, as discussed above. The outer radius r2 of the inner cladding region 32 is in a range from about 30 microns or more, or about 40 microns or more, or about 45 microns or more, or about 50 microns or more, or about 55 microns or more, or about 60 microns or more. Additionally or alternatively, the outer radius r2 of the inner cladding region 32 is in a range from about 70 microns or less, or about 65 microns or less, or about 60 microns or less, or about 55 microns or less, or about 50 microns or less.

[0070] The relative refractive index Δ2 of the inner cladding region 32 is in a range from about -0.20% to about 0.20%, or about -0.15% to about 0.15%, or about -0.10% to about 0.10%, or about -0.05% to about 0.05%. In some embodiments, the relative refractive index Δ2 is about 0.0%. The relative refractive index Δ2 is preferably constant or approximately constant.

[0071] As discussed above, in some embodiments, it is also contemplated that the cladding region 30 does not include the inner cladding region 32.

[0072] Intermediate cladding region

[0073] The intermediate cladding region 34 comprises a negatively-doped silica glass. In some embodiments, the intermediate cladding region 34 is negatively-doped with fluorine. However, the negative doping of the intermediate cladding region 34 can also be accomplished by incorporating holes in the silica glass. The holes correspond to local regions filled with air or other gases (e.g., N2, Ar, SO2, CO2, Kr, O2) and / or vacuum spaces having a length less than the full length of the glass fiber. Preferably, the holes are randomly distributed or non-periodically distributed along the length of the glass fiber.

[0074] The inner radius of the intermediate cladding region 34 is r2, as discussed above. The outer radius r3 of the intermediate cladding region 34 is in a range from about 35 microns or more, or about 45 microns or more, or about 55 microns or more, or about 60 microns or more, or about 62.5 microns or more, or about 65 microns or more. Additionally or alternatively, the outer radius r3 is in a range from about 70 microns or less, or about 65 microns or less, or about 60 microns or less. In some embodiments, the outer radius r3 is about 62.5 microns. The width W3 of the intermediate cladding region 34 can be in a range from about 1 micron to about 15 microns, or about 2 microns to about 10 microns, or about 3 microns to about 8 microns, or about 4.5 microns to about 5.5 microns.

[0075] In some embodiments, the intermediate cladding region 34 is a depressed-index cladding region forming a trench design. The trench design can be an offset trench. The relative index Δ3 of the intermediate cladding region 34 is in the range from about -0.70% to about -0.10%, or from about -0.60% to about -0.20%, or from about -0.55% to about -0.25%, or from about -0.50% to about -0.30%, or from about -0.45 to about -0.35%. In some embodiments, the relative index Δ3 is about -0.40%.

[0076] The transition regions from the inner cladding region 32 to the intermediate cladding region 34 and from the intermediate cladding region 34 to the outer cladding region 36 are shown in Figure 4 as step-wise changes. However, it is to be understood that the step-wise changes are idealized, and in practice, the transition regions can not be strictly vertical. Rather, the transition regions can have a slope or a curvature.

[0077] The trench volume of the intermediate cladding region 34 can be from about 100% Δ- microns 2 to about 500% Δ-microns 2 , or from about 150% Δ-microns 2 to about 450% Δ-microns 2 , or from about 200% Δ-microns 2 to about 400% Δ-microns 2 .

[0078] The trench design of the intermediate cladding region 34 as disclosed herein provides advantages over conventional designs. For example, the trench design disclosed herein advantageously limits the intensity profile of higher order modes propagating through the outer core portion of the optical fiber, thereby reducing the loss of these modes due to bending and other perturbations. Further, by placing the location of the trench at an optimal offset relative to the core region, the trench can help reduce the differential mode delay of the outer mode group, resulting in higher bandwidth. The offset of the trench relative to the core region 20 (r2-r1) is from about 0.0 microns to about 6.0 microns, or from about 0.5 microns to about 5.0 microns, or from about 1.0 microns to about 4.0 microns, or from about 1.5 microns to about 2.5 microns.

[0079] As discussed above, in some embodiments, it is also contemplated that the cladding region 30 does not include an intermediate cladding region 34.

[0080] The outer cladding region

[0081] Similar to the inner cladding region 32, the outer cladding region 36 may also comprise undoped silica glass. The inner radius of the outer cladding region 36 is r3, as discussed above. The outer radius r4 of the outer cladding region 36 is in the range of approximately 55 micrometers or greater, or approximately 60 micrometers or greater, or approximately 65 micrometers or greater. Alternatively, the outer radius r4 of the outer cladding region 36 may be in the range of approximately 90 micrometers or less, or approximately 80 micrometers or less, or approximately 75 micrometers or less, or approximately 70 micrometers or less, or approximately 65 micrometers or less. In some embodiments, the outer radius r4 is approximately 62.5 micrometers.

[0082] The relative refractive index Δ4 of the cladding region 36 is in the following range: about -0.20% to about 0.20%, or about -0.15% to about 0.15%, or about -0.10% to about 0.10%, or about -0.05% to about 0.05%. In some embodiments, the relative refractive index Δ4 is ​​about 0.0%. The relative refractive index Δ4 is ​​preferably constant or approximately constant. Furthermore, in some embodiments, the relative refractive index Δ4 is ​​equal to or substantially equal to the relative refractive index Δ2.

[0083] As discussed above, in some embodiments, it is also considered that the cladding region 30 does not include the outer cladding region 36.

[0084] Exemplary optical fiber

[0085] Figure 5 The relative refractive index distribution of an exemplary optical fiber 60 according to an embodiment disclosed herein is plotted as a graph relating the relative refractive index Δ% to the radial coordinate r. Figure 5 As shown, the core region 20 of the exemplary optical fiber 60 has a maximum relative refractive index Δ0 or Δ1.0%. 1最大值 The outer radius r1 is 50 micrometers, and the Alpha (α) value is 2.1. The cladding region 30 of the exemplary optical fiber 60 includes only the intermediate cladding region 34 and excludes either the inner cladding region 32 or the outer cladding region 36. For example... Figure 5 As shown, the intermediate cladding region 34 has a relative refractive index Δ3 of approximately -0.38% and an outer radius r3 of 62.5 micrometers. Figure 5 In this embodiment, the outer radius of the intermediate cladding region 34 is the outer radius of the exemplary optical fiber 60 (without a protective coating). Figure 5 In this embodiment, the intermediate cladding region 34 is a recessed groove region that is negatively doped with fluorine and has a 460% Δ-micron thickness. 2 The volume of the groove.

[0086] exist Figure 5 In this embodiment, the cladding region 30 of the exemplary optical fiber 60 does not contain any positive dopants.

[0087] Relative refractive index of the core region

[0088] The optical fiber 10 disclosed herein can be used in traditional ring-flux launch conditions, e.g., VCSEL launch conditions, providing a 50-micron radial Gaussian laser light. The TIA-526-14-B and IEC 61280-4-1 Ed. 2.0 Ring-Flux standards define parameters for multimode launch conditions of an optical test source. Manufacturers produce equipment, such as the MC-FC-50-N from Arden Photonics, that produces a 50-micron radial Gaussian laser light. It converts the output from any launch source into a ring-flux launch that meets the above-mentioned standards. In the embodiments disclosed herein, the ring-flux launch conditions are set so that the conditions excite a traditional 50-micron core diameter multimode fiber with 86% of the power at a 19-micron radius from the center of the fiber.

[0089] Thus, in the embodiments disclosed herein, less than the entire diameter of the optical fiber 10 is excited when excited in ring-flux launch conditions as described above. As discussed above, the core region 20 includes a larger outer radius than a traditional multimode fiber. In some embodiments, the outer radius r1 of the core region 20 is about 1.15 times, about 1.25 times, about 1.40 times, about 1.5 times, about 1.65 times, about 1.75 times, about 1.9 times, about 2.0 times, about 2.15 times, about 2.25 times, about 2.40 times, or about 2.50 times as large as the outer radius of a traditional 50-micron core diameter multimode fiber. In some embodiments, less than the entire core region 20 is excited by the ring-flux launch conditions due to its increased size. Thus, the excited portion of the core region 20 has a reduced effective relative refractive index Δ eff that is less than the maximum relative refractive index Δ0 of the core region 20. Thus, and as discussed further below, the reduced effective relative refractive index Δ ef results in a significant increase in the effective bandwidth of the excited portion of the core region 20.

[0090] As used herein, the effective relative refractive index Δ eff refers to the maximum relative refractive index Δ0 and the relative refractive index Δ ro of the portion of the core region 20 that is excited by the laser light under ring-flux launch conditions. Thus, the effective relative refractive index Δ eff is bounded by the maximum relative refractive index Δ0 and the relative refractive index Δ ro . Furthermore, the relative refractive index Δ ro is bounded by the radius of the optical etendue from the ring-flux launch conditions. As Figure 5 shown, this radius is the effective radius r0, which corresponds to the radius of the excited portion of the core region 20.

[0091] In contrast to the multi-mode optical fiber disclosed herein, the core region of conventional multi-mode optical fibers has a reduced diameter. Thus, when a conventional multi-mode optical fiber is excited, for example, by the annular flux launch condition described above, the core body (as a whole) is excited. Thus, in these conventional multi-mode optical fibers, the effective relative refractive index Δ eff substantially equal to the maximum relative refractive index Δ0(thereby Δ eff equal to Δ0, Δ ro equal to zero, and r0equal to r1).

[0092] However, in embodiments of the present disclosure, the diameter of the core region 20 is relatively larger than conventional multi-mode optical fibers. Thus, when the annular flux launch condition described above is employed, only a portion of the core region 20 is excited (less than the entire diameter of the core region 20). Thus, a portion of the core region 20 is not excited. For example, a radially central portion of the core region 20 can be excited, while a radially outer perimeter portion of the core region 20 can not be excited. As Figure 4 and 5 shown, by the annular flux launch condition described above, a portion A of the core region 20 is excited and a portion B of the core region 20 is not excited. Thus, in embodiments of the present disclosure, the maximum relative refractive index Δ0of the core region 20 is greater than the effective relative refractive index Δ eff of the excited portion of the core region 20, and the radius r1of the core region 20 is greater than the effective radius r0of the excited portion of the core region 20.

[0093] Also as Figure 4 and 5 shown, r1refers to the outer radius of the core region 20, and r0refers to the effective radius of the excited portion of the core region 20, as discussed above. During the annular flux launch condition, r0is greater than the radius of the laser light of the annular flux launch condition after the launched light enters the large core multi-mode optical fiber of the present disclosure. Due to the conservation of etendue, the portion of the core region 20 illuminated by the laser light of the annular flux launch condition is greater than the diameter of the laser light itself. Thus, when the annular flux launch condition is employed, the effective radius r0of the excited portion (portion A) of the core region 20 can be greater than the radius of the laser light. For example, when the radius of the laser light is 25 microns, the effective radius r0is greater than 25 microns. The effective radius r0of the excited portion of the core region 20 can be selected such that the etendue of the excited portion of the core region from the annular flux launch condition is substantially equal to the etendue of a standard multi-mode optical fiber having a 50 micron core diameter and a 1% core Δ. In some embodiments, the etendue of the excited portion of the core region is about 80 microns 2 to about 180 microns.2 Thus, as discussed above, the optical spread from the annular flux launch condition excites less than the entire core area of the multimode fiber. The optical spread is calculated according to Equation (1) as follows:

[0094]

[0095] where E is the optical spread of the fiber, n0is the refractive index in the center of the core, Δ0is the maximum relative refractive index of the core area, a is a refractive index profile shape parameter of the core area, and D is the core diameter. Equation 1 shows that Δ(Δ0) can be reduced and the core diameter (D) increased to maintain the same spread. For a 50 micron core multimode fiber with a 1% Δ, the optical spread is approximately 130 microns 2 For multimode fibers with core diameters greater than 50 microns, the effective radius r0of the excited portion of the core area is less than the outer radius r1of the core area, thereby providing an optical spread substantially equal to approximately 130 microns 2 or approximately 80 microns 2 to approximately 180 microns 2 .

[0096] However, it is also contemplated that in some embodiments, the outer radius r1of the core area 20 is substantially equal to the effective radius r0of the excited portion of the core area 20 when illuminated with the laser light of the annular flux launch condition. Thus, in these embodiments, the optical spread from the annular flux launch condition excites the entire core area, and the portion B is substantially equal to 0.0 microns.

[0097] The relationship between the effective radius (r0) of the excited portion of the core area 20 having an outer radius (r1) of the core area 20 and the laser light radius of the annular flux launch condition can be shown according to Equations (2) and (3) derived from the transformation of the optical spread as follows. For a transceiver designed for a conventional 50 micron core diameter multimode fiber, the core Δ and the core radius of the conventional 50 micron core diameter multimode fiber can be employed to estimate its optical spread of the laser light.

[0098] More specifically, Equation (2) calculates the relative refractive index Δr0of the excited portion of the core area 20:

[0099] Δ r0 = Δ0[1 - (r0 / r1) α ] (2)

[0100] and Equation (3) calculates the radius r0of the excited portion of the core area 20:

[0101]

[0102] In the formula, r0 is the radius of the excitation portion of the fiber core region, r1 is the outer radius of the fiber core region, and r 1c It is the radius of a conventional 50-micron core diameter multimode fiber (i.e., r). 1c =25 micrometers), α is the shape parameter of the refractive index distribution in the core region, Δ0 is the maximum relative refractive index in the core region, and Δ 0c It is the maximum relative refractive index of a conventional 50-micron core diameter multimode fiber (approximately 1.0%).

[0103] Then, the effective refractive index Δ can be calculated according to the following equation (4). eff :

[0104] Δ eff =Δ0-Δr0

[0105] In the formula, Δ0 is the maximum refractive index of the fiber core region, and Δ r0 It is the refractive index at r0 in the excitation region of the fiber core.

[0106] For example, such as Figure 5 As shown, when emitted under the annular flux emission conditions described above, the exemplary optical fiber 60 has a radius r0 of the excited portion (part A) of the core region 20 of approximately 35 micrometers, and a relative refractive index Δ of approximately 0.53% of the excited portion of the core region 20. r0 and an effective relative refractive index difference of approximately 0.47% Δ. eff Therefore, the relative refractive index Δ r0 and effective relative refractive index Δ eff The maximum relative refractive index Δ0 is less than 1.0%.

[0107] In some embodiments, the relative refractive index Δ of the excited portion of the core region 20 r0 Determined by the threshold of the integrated power from the annular flux emission condition, reaching approximately 100% or less, or approximately 95% or less, or approximately 90% or less, or approximately 85% or less, or approximately 80% or less, or approximately 75% or less, or approximately 70% or less, or approximately 65% ​​or less, or approximately 60% or less. Relative refractive index Δ r0 It can be in the following ranges: about 1.45% or less, or about 1.30%, or about 1.15% or less, or about 1.00% or less, or about 0.95% or less, or about 0.75% or less, or about 0.60% or less, or about 0.45% or less, or about 0.30% or less. In some embodiments, the relative refractive index Δ r0is: about 0.35%, or about 0.38%, or about 0.45%, or about 0.48%, or about 0.55%, or about 0.58%, or about 0.65%, or about 0.68%. As discussed above, the effective relative refractive index Δ eff is the difference between the maximum relative refractive index Δ0 and the relative refractive index Δ r0 of the excited portion of the core region. In some embodiments, Δ eff is in the range of about 0.30% to about 0.80%, or about 0.35% to about 0.75%, or about 0.40% to about 0.70%, or about 0.45% to about 0.65%, or about 0.60% to about 0.62%, or about 0.50%, or about 0.55%, or about 0.60%.

[0108] The excited portion (e.g., portion A) of the core region 20 can have a diameter that is equal to or less than the diameter of the outer surface 42 of the glass segment 40. In some embodiments, the excited portion of the core region 20 can have a radius r0in the range of about 10 microns to about 55 microns, about 15 microns to about 50 microns, about 20 microns to about 45 microns, or about 25 microns to about 35 microns. In some embodiments, the radius r0is: about 25 microns or greater, or greater than about 25 microns, or greater than about 26 microns, or greater than about 27 microns, or greater than about 28 microns, or greater than about 29 microns, or greater than about 30 microns, or about 35 microns or greater, or about 35.5 microns or greater, or about 36.5 microns or greater, or about 37.5 microns or greater, or about 38.5 microns or greater, or about 39.5 microns or greater, or about 40 microns or greater. As discussed above, the radius r0of the excited portion of the core region 20 can be less than the radius of the outer surface 42 of the glass segment 40. Figure 5 As shown in the example embodiment of FIG. 1, the radius r0of the excited portion of the core region 20 is 35 microns. Accordingly, in the example embodiment of FIG. 1, the diameter of the excited portion of the core region 20 is 70 microns. Figure 5 As shown in the example embodiment of FIG. 1, the radius r0of the excited portion of the core region 20 is 35 microns. Accordingly, in the example embodiment of FIG. 1, the diameter of the excited portion of the core region 20 is 70 microns.

[0109] The effective bandwidth of the core region

[0110] As discussed above, the reduced effective refractive index Δ eff of the embodiments disclosed herein advantageously provides an increased effective bandwidth for the optical fiber 10. The effective bandwidth is proportionally related to the effective refractive index Δ eff , such that as Δ eff is reduced, the effective bandwidth increases. As shown in Table 1 below, as the core diameter of the optical fiber of the present disclosure is increased, the effective refractive index Δ eff is reduced (while other parameters, including launch conditions and core Δ, remain constant), which results in an increase in the effective bandwidth of the optical fiber. The increase factor in effective bandwidth is 1 / Δ eff2 .

[0111] Table 1 below includes fiber parameters and their effective bandwidths for 20 exemplary optical fibers according to embodiments of this disclosure. However, it should be noted that each optical fiber may be associated with more than one effective bandwidth. During the manufacturing process of the optical fiber, variations may exist in the resulting fiber due to the specific manufacturing process employed. Therefore, even optical fibers with the same design may still exhibit minor variations in the resulting fiber. These minor variations may lead to different effective bandwidths for the optical fiber. See below. Figure 9A This concept was discussed further.

[0112] Table 1

[0113]

[0114]

[0115] As shown in Table 1 above, the effective bandwidth of the optical fiber increases with the increase of the fiber core diameter. Figure 5 In the example, the effective bandwidth increased by 4.3 times compared to traditional 50-micron core diameter multimode fiber.

[0116] For example, the excited portion of the fiber core region 20 has the following effective bandwidths: approximately 3.0 GHz-Km or greater, approximately 3.5 GHz-Km or greater, approximately 3.7 GHz-Km or greater, approximately 4.0 GHz-Km or greater, approximately 4.5 GHz-Km or greater, approximately 4.7 GHz-Km or greater, approximately 5.0 GHz-Km or greater, approximately 5.5 GHz-Km or greater, approximately 5.7 GHz-Km or greater, approximately 6.0 GHz-Km or greater, approximately 6.5 GHz-Km or greater, approximately 6.7 GHz-Km or greater, approximately 7.0 GHz-Km or greater, approximately 7.5 GHz-Km or greater, approximately 7.7 GHz-Km or greater, approximately 8.0 GHz-Km or greater, approximately 8.5 GHz-Km or greater, approximately 8.7 GHz-Km or greater, approximately 9.0 GHz-Km or greater, approximately 9.5 GHz-Km or greater, approximately 9.7 GHz-Km or greater, approximately 10.0 GHz-Km or greater, approximately 15 GHz-Km or greater, approximately 20 GHz-Km or greater, approximately 20 GHz-Km or greater, or approximately 25 GHz-Km or greater, or approximately 30 GHz-Km or greater, or approximately 35 GHz-Km or greater, or approximately 40 GHz-Km or greater.

[0117] It is noted that the effective bandwidth disclosed above is at any wavelength in the range of about 800 to about 1370, or about 800 nm to about 1100 nm, or about 840 nm to about 950 nm, or about 850 nm to about 940 nm, or about 840 nm to about 1060 nm, or about 850 nm to about 1060 nm, or about 940 nm to about 1060 nm, or about 1250 nm to about 1370 nm, or about 1270 nm to about 1320 nm, or about 980 nm, or about 1060 nm, or about 1310 nm.

[0118] It is further noted that the disclosed effective bandwidth is provided for the excited portion of the core region (e.g., portion A) having a diameter greater than about 50 microns, such that r0is greater than 25 microns. In other embodiments, the disclosed effective bandwidth is provided for the excited portion of the core region having a diameter greater than about 55 microns, greater than about 60 microns, greater than about 65 microns, greater than about 70 microns, greater than about 75 microns, or greater than about 80 microns. Additionally or alternatively, the disclosed effective bandwidth is provided for the excited portion of the core region having a diameter less than about 90 microns, less than about 85 microns, less than about 80 microns, or less than about 75 microns. In some embodiments, the disclosed effective bandwidth is provided for the excited portion of the core region having a diameter greater than about 50 microns and less than or equal to about 80 microns, or about 70 microns, or about 75 microns.

[0119] Additional example optical fibers

[0120] In other embodiments, the optical spread from the annular flux launch condition excites the entire core region of the multi-mode optical fiber, as discussed above. Accordingly, portion B is substantially equal to 0.0 microns, r0is substantially equal to r1, and Δ eff In these embodiments, the high bandwidth disclosed above is achieved by providing a core region 20 having a lower maximum relative refractive index Δ0. For example, the maximum relative refractive index Δ0may be: about 1.0% or less, or less than about 1.0%, or less than about 0.90%, or less than about 0.80%. In some embodiments, the maximum relative refractive index Δ0is in the range of about 0.3% to about 0.95%, or about 0.40% to about 0.85%, or about 0.60% to about 0.80%. For example, the maximum relative refractive index Δ0may be: about 0.80%, or about 0.75%, or about 0.65%, or about 0.50%.

[0121] By providing a lower maximum relative refractive index Δ0, these embodiments have a truncated core region, which reduces the consumption of positive dopants (e.g., germanium) required to produce the core region. Accordingly, the lower maximum relative refractive index Δ0of these embodiments advantageously reduces manufacturing costs.

[0122] In these embodiments, the core radius is selected so that the optical etendue from the annular flux launch condition has an area in the range of about 110 microns 2 to about 150 microns 2 , or about 120 microns 2 to about 140 microns 2 , or about 125 microns 2 , or about 130 microns 2 , or about 135 microns 2 .

[0123] Further, in these embodiments, the alpha value of the core region 20 is in the range of about 1.5 to about 2.5, or about 1.9 to about 2.3, or about 2.0 to 2.2. In some embodiments, the alpha value is about 2.0 or about 2.1 or about 2.3.

[0124] Table 2 below provides exemplary optical fibers according to these additional embodiments of the present disclosure. Exemplary optical fibers 61-64 each have a truncated core region (lower Δ0) relative to exemplary optical fiber 60 above.

[0125] Table 2

[0126]

[0127] As shown in Table 2, exemplary optical fibers 61-64 all have a middle cladding region with a recessed groove design. As discussed above, the optical offset of the groove relative to the core (r2-r1) is optimized to manage the high order modes (which are affected by the edges or ends of the alpha profile) so that the mode delays of the high order modes align with those of the low order modes. In exemplary optical fibers 61 and 62, the optical offset of the groove relative to the core is about 1.8 microns. In exemplary optical fibers 63 and 64, the optical offset of the groove relative to the core is about 2.4 microns.

[0128] Figures 6A-6D The modal bandwidth of exemplary optical fibers 61-64 is shown. Again, it is noted that the modal bandwidth is shown when the annular flux launch condition excites the entire core region (or at least a substantial portion of the entire core region) of the multimode optical fiber Figures 6A-6BThe modal bandwidth of exemplary fiber 65 is shown. Again, it is noted that the modal bandwidth is shown when the annular flux launch condition excites the entire core region (or at least a substantial portion of the entire core region) of exemplary fiber 65. The modal bandwidth of exemplary fiber 65 is shown in FIG. 18. Exemplary fiber 65 achieves a peak modal bandwidth of about 53 GHz.km at 850 nm (0.85 microns).

[0129] Figure 7A A relative refractive index profile of exemplary fiber 65 according to these additional embodiments disclosed herein is provided as a plot of relative refractive index Δ% versus radial coordinate r. Like exemplary fibers 61-64, exemplary fiber 65 also has a truncated core region (lower Δ0). As shown in FIG. 17, the core region 20 of exemplary fiber 65 has a maximum relative refractive index Δ0of 0.5%, an outer radius r1of 30.0 microns, and an alpha value of about 1.9 to about 2.3. The cladding region 30 of exemplary fiber 60 includes only the inner cladding region 32 and does not include either of the intermediate cladding region 34 or the outer cladding region 36. As shown in FIG. 17, the inner cladding region 32 has a relative refractive index Δ2of about 0.15% and an outer radius r2of 32.1 microns. The inner cladding region 32 in exemplary fiber 65 advantageously manages the higher order modal (which would be affected by the edge or end of the alpha profile) such that the modal delay of the higher order modes aligns with those of the lower order modes. Figure 7A Figure 7A

[0130] Figure 7B The modal bandwidth of exemplary fiber 65 is shown. Again, it is noted that the modal bandwidth is shown when the annular flux launch condition excites the entire core region (or at least a substantial portion of the entire core region) of exemplary fiber 65. The modal bandwidth of exemplary fiber 65 is shown in FIG. 18. Exemplary fiber 65 achieves a peak modal bandwidth of about 53 GHz.km at 850 nm (0.85 microns). Figure 7B

[0131] Fiber Manufacturing

[0132] The optical fiber 10 can be manufactured using standard fiber manufacturing draw techniques using a suitably manufactured glass preform 10P. Figure 8 is a schematic diagram of an exemplary fiber draw system ("draw system") 100 for manufacturing the optical fiber 10. As shown in FIG. 1, the draw system 100 includes a preform 10P, a furnace 102, a draw tower 104, and a fiber spool 106. Figure 8 As shown in FIG. 1, the preform 10P includes a preform core region 20P and a preform cladding region 30P, which includes: a preform inner cladding region 32P, a preform intermediate cladding region 34P, and a preform outer cladding region 36P. ​​​

[0133] The drawing system 100 may include: a drawing furnace 102 for heating the end of the preform 10P to its glass melting temperature (e.g., to about 2000°C); non-contact measuring sensors 104A and 104B (e.g., diameter control) for measuring the dimensions of the drawn optical fiber 10 as it leaves the drawing furnace; a cooling workstation 106 for cooling the drawn optical fiber 10; a coating workstation 110 for coating the drawn optical fiber 10 with a non-glass coating material 50M to form a protective coating 50; a tensioner 120 for pulling (drawing) the optical fiber 10; a guide wheel 130 for guiding the drawn optical fiber 10; and an optical fiber take-up roll (“roll”) 150 for storing the drawn optical fiber 10. The tensioner 120 has a surface 122, and the guide wheel 130 has a surface 132 on which the drawn optical fiber 10 passes. The drawing system 10 also includes a preform loader 160, which is located adjacent to the top side of the drawing furnace 102 and houses the co-doped preform 10P for forming the co-doped optical fiber 10.

[0134] Tensioner 122 can pull (draw) optical fiber 10 with different tensions, such as approximately 30g, approximately 35g, approximately 40g, approximately 45g, approximately 50g, approximately 55g, approximately 60g, approximately 65g, approximately 70g, approximately 75g, approximately 80g, approximately 85g, approximately 90g, approximately 95g, approximately 100g, approximately 105g, approximately 110g, approximately 115g, or approximately 120g. The tension of tensioner 122 can be changed and / or adjusted to provide optimized effective bandwidth at specific wavelengths for the drawn optical fiber 10.

[0135] Exemplary properties

[0136] For example, Figure 9A Diagrams for four types of optical fibers (70, 72, 74, and 76) are provided, each with the following characteristics: Figure 9B The distribution is shown, and each is stretched with different tensile tensions. It should be noted that, as... Figure 9B The distribution of curve 72 shown is similar to that of... Figure 5 Same as shown. In Figure 9A Multimode fiber 70 was drawn with a tension of 30g, multimode fiber 72 with a tension of 50g, multimode fiber 74 with a tension of 70g, and multimode fiber 76 with a tension of 100g. Although fibers 70-76 were drawn with different tensions, they all contained the same composition. Figure 9A As shown, fibers 70, 72, 74, and 76 provide optimized effective bandwidth at different wavelengths. Therefore, wavelength optimization can be performed based on the fiber tension. For example, fiber 74 has an optimized effective bandwidth of approximately 825 nm, while fiber 76 has an optimized effective bandwidth of approximately 872 nm. Figure 9AFiber 72 also shows the highest effective bandwidth compared to fibers 70, 72, 76. In particular, fiber 72 has a peak effective bandwidth of 24 GHz-Km. Further, fiber 72 has the largest wavelength window, corresponding to a bandwidth of 4.7 GHz-Km or more. In particular, fiber 72 has a bandwidth of 4.7 GHz-Km or more for wavelengths between about 810 nm and 930 nm over a 100 nm window. This is much greater than the required about 60 nm window for OM4 fiber. Note that the effective bandwidth of fibers 70-76 (as discussed above) is provided in the manner that the ring flux launch conditions are employed such that less than their entire core area is excited as Figure 9A shown in FIG. 8.

[0137] Figure 9A It is also shown that the fibers of the present disclosure have a bandwidth greater than 2470 MHz-km (2.47 GHz-km) at a 953 nm wavelength, thus meeting the OM5 standard. More specifically, fibers 70, 72, and 74 have a bandwidth greater than 2470 MHz-km at a 953 nm wavelength, as shown in FIG. 9. Figure 9A However, again note that the optimized bandwidth of the fibers disclosed herein is based on the draw tension and wavelength of the fiber.

[0138] In addition to this, the fibers of the present disclosure (e.g., multimode fiber 10) have a wide operating wavelength range, which can be optimized for a target peak bandwidth wavelength for a given index profile. In other words, the fibers of the present disclosure have a wide peak wavelength range, where the peak wavelength range is the wavelength window over which the fiber has the maximum bandwidth over a specified tension range. Figure 9C A plot of core diameter versus peak bandwidth wavelength range is shown, where the peak bandwidth range over a 45 g to 225 g tension range was estimated based on measurements of three multimode fibers according to embodiments of the present disclosure. As shown in FIG. 10, as the core diameter of the fiber increases, the wavelength window of the peak bandwidth also increases. More specifically, a 50 micron core diameter has a peak bandwidth over a 250 nm wavelength window. However, a 100 micron core diameter has a much larger wavelength window of 1050 nm. Thus, a 100 micron core diameter fiber advantageously has more tunability than a 50 micron core diameter fiber. Figure 9C

[0139] In various embodiments, the peak wavelength can be in the range of about 335 nm to about 1365 nm, or 840 nm to 1070 nm, or about 680 to about 1050, or about 980 nm to about 1050 nm, or about 1260 nm to about 1360 nm, or about 1300 nm to about 1320 nm, or any wavelength value therebetween. However, it is understood that the fibers disclosed herein can have any peak wavelength.​

[0140] The multimode optical fiber 10 disclosed herein has an increase in effective bandwidth without sacrificing attenuation. For example, the optical fiber of the present disclosure can have an attenuation at 850 nm of about 2.7 dB / Km or less, or about 2.6 dB / Km or less, or about 2.5 dB / Km or less, or about 2.4 dB / Km or less, or about 2.3 dB / Km or less. In addition, the optical fiber of the present disclosure has an attenuation at 1300 nm of about 0.9 dB / Km or less, or about 0.87 dB / Km or less, or about 0.84 dB / Km or less, or about 0.80 dB / Km or less, or about 0.77 dB / Km or less, or about 0.74 dB / Km or less, or about 0.70 dB / Km or less, or about 0.67 dB / Km or less, or about 0.64 dB / Km or less, or about 0.60 dB / Km or less, or about 0.57 dB / Km or less.

[0141] Figure 10 A graph showing an optical fiber having a profile as shown in Figure 5 and drawn at a draw tension of 50 g. As shown in Figure 10 the attenuation at 850 nm is 2.32 dB / km and the attenuation at 1300 nm is 0.60 dB / km, which is similar to a conventional multimode optical fiber. Thus, the multimode optical fiber of the present disclosure does not have a decreased attenuation, but rather has an increased effective bandwidth.

[0142] The multimode optical fiber of the present disclosure also has a decreased insertion loss when the optical fiber is connected to another optical fiber. Insertion loss is a measure of the amount of light lost when passing from one optical fiber to another via an optical fiber connector. The amount of light lost is primarily due to lateral core offset. If the matching optical fiber has approximately the same core size but is slightly offset, some light is directed into the cladding and is lost. It is also possible to have insertion loss due to different core sizes. For example, when the core diameter of an optical fiber is smaller than the optical fiber it is being matched to, some light can be lost in the cladding.

[0143] The multimode optical fiber disclosed herein has a larger core than a conventional multimode optical fiber, as discussed above. Due to the relatively larger core, the multimode optical fiber has a higher tolerance when the optical fiber is connected to another optical fiber. More specifically, due to the relatively larger core, the multimode optical fiber disclosed herein is able to capture more light from the optical fiber it is connected to, which advantageously results in a decrease in insertion loss.

[0144] Figure 11A A graph showing the optical fiber R1 in a conventional OM2, OM3, or OM4 multimode optical fiber (Fiber R1) being tested against a 1 km optical fiber (Fiber R2) being tested Figure 11A Figure 11A ​when connected to a fiber S) for measuring insertion loss. Conventional OM2, OM3 or OM4 multimode fibers have a core diameter of 50 microns. In a first example, the fiber under test is an exemplary multimode fiber of the present disclosure having a core diameter of 100 microns Figure 11B In a second example, the fiber under test is a conventional multimode fiber having a core diameter of 50 microns Figure 5 In a second example, the fiber under test is a conventional multimode fiber having a core diameter of 50 microns Figure 11B In a second example, the fiber under test is a conventional multimode fiber having a core diameter of 50 microns

[0145] In the setup of Figure 11A to provide a ring-flux launch of light into fiber Rl Figure 11A The fiber Rl and the test fiber S are placed on an alignment stage with the centers of the two fibers placed concentrically, and then the fiber cores are varied in offset by a controlled amount. The output of the test fiber S is connected directly to another conventional OM2, OM3 or OM4 multimode fiber Figure 11A In a second example, the fiber under test is a conventional multimode fiber having a core diameter of 50 microns Figure 11B The relative insertion loss of the two fibers tested is shown (as described above) in

[0146] In Figure 11B The horizontal axis represents the deviation of the fiber core from the aligned position of the core. The vertical axis represents the relative insertion loss when the fiber is excited by the ring-flux launch condition. As shown in Figure 11B Curve 82 has a generally lower relative insertion loss than curve 80. For example, for a 10 micron offset, curve 80 has a relative insertion loss of less than 0.3 dB, while curve 80 has a relative insertion loss of 1.8.

[0147] Figure 11C The modal bandwidth of a multimode fiber having a profile as shown in Figure 5 and drawn at a draw tension of 50 g and at a wavelength of 850 nm is shown. As shown in Figure 11C The modal bandwidth is consistently high (above 11.5 GHz-km) over a large offset range up to 45 microns.

[0148] ​The transmission performance of the multimode optical fiber disclosed herein was measured using various different constructions. Two fiber segments with lengths of 500m and 1000m were fabricated. Bit error rate (BER) measurements were performed at back-to-back (bb) lengths of approximately 200m, 300m, and 500m. Figure 12A As shown, a variable optical attenuator is used to change the optical attenuation level to obtain... Figure 12B The graph shows the different curves relating BER to the received optical power P (dBm).

[0149] BER was measured using a 25Gb / s SR transceiver (Hisense LTF8505-BC+) based on a multimode VCSEL transmitter. The system test setup is as follows: Figure 12A As shown. The controller (Keysight N4960A-CJ1) controls the pattern generator (Keysight N4951B) and the error detector (N4952A-E32), and also provides a clock signal to the pattern generator, which provides 2 31 -1PRBS pattern. Exemplary multimode optical fibers of this disclosure are fabricated with lengths of 200m, 300m, and 500m.

[0150] from Figure 12B The BER curve shows that in a back-to-back (bb) configuration, the transmission system can achieve error-free performance at approximately -11 dBm. With an exemplary 200m fiber segment, the system exhibits almost no power penalty. For a 300m fiber segment, some power penalty is observed, but essentially error-free performance is still achieved. At a length of 500m, system performance degrades, but still reaches 10 dBm. -11 The BER is below the forward error correction threshold used for short-range optical communication. Systems with 200m, 300m, and 500m test fibers can perform error-free tests for several minutes without a VOA in the setup.

[0151] The multimode fiber disclosed herein can be connected to data centers and can transmit data over distances of 100m to 2000m within or between data centers using VCSEL-based transceivers, achieving feasible data rates of 10Gb / s or higher (e.g., 25Gb / s or higher, depending on system capacity limited by power budget and fiber bandwidth). Higher data rates include 50Gb / s or 56Gb / s NRZ or 50Gb / s using PAM4 modulation with 25Gbd or 28Gbd, or 100Gb / s using PAM4 modulation with 50Gbd or 56Gbd. Furthermore, VCSEL-based transceivers allow light to propagate into the multimode fiber.

[0152] Figure 13Ais a schematic illustration of an exemplary fiber optic data communication system ("system") 300 that includes a transmitter 310 and a receiver 410 optically connected by a fiber optic connector 500. The fiber optic connector 500 includes at least a length of single-core multi-mode optical fiber 6S as disclosed herein. In an example, the fiber optic connector 500 has an input end 502, an output end 504, and a connection length LL measured along the connected optical fiber between the input and output ends (see enlarged inset IN1, which shows the "unwound" fiber optic connector 500 to show the connection length LL of the exemplary system disclosed herein). In an example, the connection length is up to 1000 meters. In an example, the fiber optic connector 500 can be constructed from a mid-section that is comprised of a length of optical fiber 6S and input and output end sections that are comprised of shorter jumper cables (e.g., up to several meters long). In an example, the jumper cables can also be made of optical fiber 6S.

[0153] The exemplary transmitter 310 includes a VCSEL 320 and a transmitter electronics unit 330 configured to operably support the operation of the VCSEL. In an example, the transmitter electronics unit 330 includes a transmitter electronics integrated circuit 340 that is operably supported by a transmitter circuit board (e.g., a printed circuit board or PCB) 350. In an example, the transmitter electronics 340 is configured with a VCSEL driver and associated electronics components (not shown) as known in the art.

[0154] The receiver 410 includes a photodetector 420 that is optically connected to the output end 504 of the fiber optic connector 500. The photodetector 420 is operably supported by a receiver electronics unit 430 that is configured to operably support the photodetector. In an example, the receiver electronics unit 430 includes a receiver that is operably supported by a receiver circuit board (e.g., a printed circuit board or PCB) 450. In an example, the photodetector 420 is configured to convert the optical signal OS encoded on the light 324 into an electrical signal ES (see enlarged inset IN2 in Figure 13A ), and the receiver is configured to receive and process the electrical signal.

[0155] The system 300 optimizes the bandwidth of multi-mode transmission at wavelengths l between 800 nm and 1100 nm with a multi-mode VCSEL 320.

[0156] Figure 13B Similar to Figure 13A , an exemplary system 300 is shown that includes two transceivers 610 that are in optical communication via two fiber optic connectors 500. Each transceiver 610 includes a transmitter 310 and a receiver 410. The system 300 provides two-way data communication between the optically connected transceivers 610 via the two fiber optic connectors 500.

[0157] It will be apparent to those skilled in the art that various modifications can be made to the preferred embodiments of the disclosure described herein without departing from the spirit or scope of the disclosure as defined in the appended claims. Thus, the disclosure covers the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

1. A multimode optical fiber comprising: a core region comprising silica and having an outer radius r1, wherein, the core region has a maximum relative refractive index of 1.5% or less, the multimode optical fiber is configured to have an effective bandwidth of 4.7 GHz-Km or more for an excited portion of the core region having a radius r0 and a diameter greater than 50 microns, the effective bandwidth being at a wavelength in a range of 800 nm to 1370 nm, and the excited portion of the core region has a radius r0 that is less than the outer radius r1 of the core region.

2. The multimode optical fiber of claim 1, wherein, the excited portion of the core region has a diameter greater than 60 microns.

3. The multimode optical fiber of claim 2, wherein, the excited portion of the core region has a diameter of 70 microns.

4. The multimode optical fiber of claim 1, wherein, the excited portion of the core region has an effective relative refractive index in a range of 0.3% to 0.80%.

5. The multimode optical fiber of claim 1, wherein, the outer radius r1 of the core region is 45 microns or more.

6. The multimode optical fiber of claim 5, wherein, the outer radius r1 of the core region is 50 microns or more.

7. The multimode optical fiber according to any one of claims 1-6, wherein, the excited portion of the core region has a radius r0 such that r0 is less than the outer radius r1 of the core region.

8. The multimode optical fiber of any of claims 1-6, wherein, the maximum relative refractive index is in a range of 0.7% to 1.5%.

9. The multimode optical fiber of any of claims 1-6, wherein, the effective bandwidth is 6 GHz-Km or more for the excited portion of the core region.

10. An optical fiber data transmission system comprising: an optical fiber connector comprising the multimode optical fiber of any one of claims 1-6, wherein the optical fiber connector has an input end, an output end, and a connector length LL between the input and output ends, wherein LL < 1000 meters; a transmitter comprising a VCSEL that emits light having a wavelength in a range of wavelengths and carries an optical signal at a data rate of at least 10 Gb / s, wherein the VCSEL is optically connected to the input end of the optical fiber connector; and a receiver comprising a photodetector that is optically connected to the output end of the optical fiber connector and is configured to receive the optical signal and convert the optical signal to an electrical signal.

11. A multimode optical fiber comprising: a core region comprising silica and having an outer radius r1 of 30 microns or more, wherein the core region is configured to have an effective relative refractive index in a range of 0.30% to 0.80% for an excited portion of the core region having a radius r0 and a diameter greater than 50 microns, and the excited portion of the core region has a radius r0 that is less than the outer radius r1 of the core region.

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