Patent Description:
The push for higher data rates in digital communications has driven the integration of optics with electronics. In particular, the use of silicon photonics for electro-optical transceivers has resulted in very dense optical circuitry concentrating many separate optical signal lines into one photonic chip. For optical signal transmission over large distances, the optical signals need to be coupled into optical fibers. <CIT> discloses an optical fiber that is made of silica-based glass and includes a core and a cladding, having a mode field diameter of <NUM> micrometers or larger at a wavelength of <NUM>, transmitting at wavelength of <NUM> in a single mode, and having a bending loss of <NUM> dB/turn or smaller when the optical fiber is bent with a curvature radius of <NUM> millimeter. <CIT> discloses a bend-resistant single-mode optical waveguide fiber at <NUM> and at higher wavelengths. <CIT> discloses a high-density fiber ribbon with bend-resistant small diameter optical fibers.

The standard geometry for optical fibers is a glass diameter of <NUM> micrometers and a coating diameter of <NUM> micrometers. This standard geometry is well-suited for connections between optical fiber cables and between an optical fiber cable and relatively large telecommunication devices. On the other hand, the standard geometry is relatively large for chip-scale interconnections and severely restricts the maximum density of optical input and output connections for photonic chips. This problem is exacerbated by the fact that standard optical fibers cannot be bent into very tight radii without incurring high macrobend losses.

An embodiment of the invention is a high-density fiber ribbon, comprising: a) a plurality of small diameter optical fibers arranged in one or more rows, wherein each small diameter optical fiber comprises: i) a glass section with a diameter d4; ii) non-glass coating section that surrounds the glass section and having a diameter dC and that defines an outer surface; iii) a mode-field diameter at a wavelength of <NUM> of between <NUM> and <NUM> microns; iv) a fiber cutoff wavelength less than <NUM>; and v) a bend loss for a single turn of the small diameter fiber around a mandrel with a <NUM> diameter of less than <NUM> dB at a wavelength of <NUM>; b) a matrix layer that encapsulates the plurality of small diameter optical fibers; and c) an attenuation per each of the small diameter optical fibers as encapsulated in the matrix layer of less than <NUM> dB/km at a wavelength of <NUM> and less than about <NUM> dB/km at a wavelength of <NUM>, wherein the ratio dC/d4 is an integer value to within <NUM> percent, the diameter d4 is smaller than <NUM> microns, and the diameter dC is smaller than <NUM> microns.

Another embodiment of the invention is a high-density ribbon cable, comprising the high-density fiber ribbon.

Another aspect of the invention is a high-density ribbon cable interconnect, comprising the high-density fiber ribbon.

Another aspect of the invention is an optical data transmission system that comprises the high-density fiber ribbon.

Additional features and advantages are set forth in the Detailed Description that follows, and in part will be apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following Detailed Description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims.

The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the Detailed Description explain the principles and operation of the various embodiments. As such, the disclosure will become more fully understood from the following Detailed Description, taken in conjunction with the accompanying Figures, in which:.

Reference is now made in detail to various embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same or like reference numbers and symbols are used throughout the drawings to refer to the same or like parts. The drawings are not necessarily to scale, and one skilled in the art will recognize where the drawings have been simplified to illustrate the key aspects of the disclosure.

The claims as set forth below are incorporated into and constitute part of this Detailed Description.

Cartesian coordinates are shown in some of the Figures for the sake of reference and are not intended to be limiting as to direction or orientation.

Likewise, relative terms like top, bottom, side, horizontal, vertical, etc. are used for convenience and ease of explanation and are not intended to be limiting as to direction or orientation.

The abbreviation "nm" stands for nanometer.

The abbreviation "µm" stands for micron or micrometer.

The "relative refractive index" as used herein is defined as: <MAT> where n(r) is the refractive index of the fiber at the radial distance r from the fiber's centerline, unless otherwise specified, and ncl is the index of the outer cladding. When the outer cladding is essentially pure silica, ncl = <NUM> at a wavelength of <NUM>. As used herein, the relative refractive index percent (also referred herein as the relative refractive index) is represented by Δ (or "delta"), Δ% (or "delta %"), or %, all of which are used interchangeably herein, and its values are given in units of percent or %, unless otherwise specified. Relative refractive index may also be expressed as Δ(r) or Δ(r)%.

The expression "A/B microns" such as "<NUM>/<NUM> microns" or "<NUM>/<NUM> microns" is shorthand notation to describe the configuration of an optical fiber, where A is the diameter of the glass section (core and cladding) of the optical fiber in microns and B is the diameter of the coated optical fiber (i.e., core and cladding and protective coatings) in microns.

The acronym "ABR" stands for "aggregated bit rate.

The acronym "MPO" stands for "multifiber push on" and refers to a type of optical fiber connector.

The term "fiber density" means the number of optical fibers per unit length for optical fibers arranged in a single row or the number of fibers per unit area for optical fibers arranged in more than one row. Likewise, the term "waveguide density" means the number of optical waveguides per unit length for optical waveguides arranged in a single row or the number of optical waveguides per unit area for optical waveguides arranged in more than one row.

The term "high density" when applied to optical fibers or optical waveguides means a greater number of optical fibers or optical waveguides per unit length or unit area as compared to configurations of conventional <NUM>/<NUM> micron optical fibers or optical waveguides.

The macrobend performance of the small diameter fibers can be gauged by measuring the induced attenuation increase in a mandrel wrap test. In the mandrel wrap test, the small diameter fiber is wrapped one or more times around a cylindrical mandrel having a specified diameter (e.g., <NUM>, or <NUM>, etc.), and the increase in attenuation at a specified wavelength due to the bending is determined. Attenuation in the mandrel wrap test is expressed in units of dB/turn, where one turn refers to one revolution of the small diameter fiber about the mandrel.

The cutoff wavelength λC is the minimum wavelength where an optical fiber will support only one propagating mode. If the optical fiber is used at a wavelength that is below (i.e., smaller than) the cutoff wavelength, multimode operation may take place and the introduction of an additional source of dispersion may limit the fiber's information carrying capacity. The fiber and cabled fiber cutoff wavelengths can be measured according to the procedures defined in FOTP-<NUM> IEC-<NUM>-<NUM>-<NUM> Optical Fibres - Part <NUM>-<NUM>: Measurement Methods and Test Procedures - Cut-Off Wavelength. All methods require a reference measurement, which in the case of bend-insensitive SD fibers, should be the multimode-reference technique rather than the bend-reference technique.

The various values for fiber-related parameter discussed herein such as fiber pitch, waveguide pitch, etc., are provided as nominal values and it will be understood that deviations from the nominal values provided based on normal manufacturing tolerances and fabrication shortcomings can result in slight variations from the stated nominal values, e.g., to within <NUM>% or <NUM>%, depending on the particular application.

The high-density optical fiber cable interconnects disclosed herein employ small diameter optical fibers ("SD fibers") of the type disclosed in <CIT>.

The SD fibers employed herein have excellent microbending and macrobending performance and a mode field diameter that may permit splicing and connecting to G. <NUM> single-mode fibers (e.g. Corning® SMF-28e+® fibers and Corning® SMF-<NUM>® Ultra fibers) with minimal losses. The SD fibers can overcome trade-offs in the mode field diameter (MFD), attenuation and/or bending losses that have accompanied previous efforts to manufacture reduced diameter optical fibers. The SD fibers can be utilized in the high-density ribbon cables and ribbon cable interconnects as discussed below for internal installations and yet provide good matching and low losses when integrated with conventional <NUM>/<NUM> micron single-mode fibers. The SD fibers have refractive index profiles that result in good fiber microbend and macrobend performance even when the thicknesses of the coating layers are small.

The SD fibers employed herein have low fiber cutoff wavelengths, which is required for them to provide single-mode operation at <NUM>. The fiber cutoff wavelength is less than <NUM>, and in some embodiments, is less than or equal to <NUM>. The SD fibers also have low cabled-fiber cutoff wavelengths, which are less than or equal to the fiber cutoff wavelengths and also less than or equal to <NUM>, which ensures compliance with the G. A2 standards.

The example SD fibers employed herein include a core, a cladding, a primary coating, a secondary coating, and an optional tertiary coating, where the cladding may include two or more regions with differing refractive index profiles, wherein the overall size (diameter) of the fiber is reduced as compared to a conventional optical fiber, and wherein the bend loss is less than that of a conventional optical fiber.

In an example, the SD fibers meet the G. A2 international fiber specification, and also in an example meet the G. B2 international fiber specification.

<FIG> is a schematic elevated view of an example SD fiber <NUM> showing an exposed glass section <NUM> with a diameter d4 and a non-glass protective coating section <NUM> with a diameter dC surrounding the glass section. The SD fiber <NUM> has a centerline AC that runs in the z-direction. A radial polar coordinate r extends perpendicular to the z-axis. The SD fiber <NUM> is assumed to be circularly symmetric about the z-axis (and thus the centerline AC) so that the angular polar coordinate is not needed.

<FIG> are schematic x-y cross-sectional diagrams of example configurations of the glass section <NUM> of the SD fiber <NUM> of <FIG> as employed herein. The example SD fiber <NUM> of <FIG> includes a core <NUM>, a cladding <NUM>, a primary coating <NUM> of diameter dP and a radial thickness tP, a secondary coating <NUM> of diameter dS and a radial thickness tS and an optional tertiary coating <NUM> of thickness tT. The cladding <NUM> includes inner cladding region <NUM> and outer cladding region <NUM>. The core <NUM> and cladding <NUM> constitute the glass section <NUM> while the primary coating <NUM>, secondary coating <NUM> and optional tertiary coating <NUM> constitute the coating section <NUM>.

The example SD fiber <NUM> of <FIG> includes a core <NUM>, a cladding <NUM>, a primary coating <NUM> of radial thickness tP, a secondary coating <NUM> of thickness tS, and an optional tertiary coating <NUM> of thickness tT. The cladding <NUM> includes a first inner cladding region <NUM>, a second inner cladding region <NUM>, and an outer cladding region <NUM>. The cladding <NUM> constitute the glass section <NUM> while the primary, secondary and optional tertiary coatings <NUM>, <NUM> and <NUM> constitute the coating section <NUM>. The primary coating <NUM> has a diameter dP, the secondary coating <NUM> or <NUM> has a diameter dS, and the tertiary coating <NUM> or <NUM> has a diameter dT.

With reference again also to <FIG>, in one example, the diameter dC of the coating section <NUM> is defined by the diameter dS when the secondary coating <NUM> or <NUM> is the outermost coating, and in another example by the diameter dT when the tertiary coating <NUM> or <NUM> is the outermost coating.

<FIG> and <FIG> are plots of the relative refractive index Δ% (relative to pure silica glass) versus the radius r (µm or microns) for the example SD fiber <NUM> of <FIG>. <FIG> shows the core <NUM> with an outer radius r<NUM> and relative refractive index Δ<NUM>. The cladding <NUM> has the first inner cladding region <NUM> extending from the radial position r<NUM> to a radial position r<NUM> and having relative refractive index Δ<NUM>, the second inner cladding region <NUM> extending from the radial position r<NUM> to a radial position r<NUM> and having relative refractive index Δ<NUM>, and the outer cladding region <NUM> extending from the radial position r<NUM> to a radial position r<NUM> and having relative refractive index Δ<NUM>.

In the example profile of <FIG>, the second inner cladding region <NUM> may be referred to herein as a rectangular trench and may have a constant relative refractive index that is less than the relative refractive indices of the first inner cladding region <NUM> and the outer cladding region <NUM>. The rectangular trench <NUM> shown in <FIG>, for example, may be established by incorporating Fluorine as a downdopant, to provide a relative refractive index Δ<NUM>. The core <NUM> may have the highest relative refractive index (Δ<NUM>) in the profile. The core <NUM> may include a lower relative refractive index region at or near the centerline (known in the art as a "centerline dip"). The core relative refractive index profile may be or may approximate a Gaussian profile, may be an α profile, may be a step index profile, or may be a rounded step index profile. The SD fiber <NUM> of <FIG> includes the primary coating <NUM> and a secondary coating <NUM>, but only the glass section <NUM> of the SD fiber is shown in the profile.

<FIG> is similar to <FIG> and shows an example measured relative refractive index profile, also expressed in Δ% relative to pure silica glass. The small oscillations in the plot are due to measurement noise. With reference to <FIG> and <FIG>, the example SD fiber <NUM> has the following configuration: the core <NUM> has an outer radius r<NUM> and a relative refractive index Δ<NUM>, and the cladding <NUM> has a first inner cladding region <NUM> extending from the radial position r<NUM> to the radial position r<NUM> and having a relative refractive index Δ<NUM>, a second inner cladding region <NUM> extending from the radial position r<NUM> to the radial position r<NUM> and having a relative refractive index Δ<NUM>, and an outer cladding region <NUM> extending from the radial position r<NUM> to the radial position r<NUM> and having relative refractive index Δ<NUM>.

In the profile of <FIG>, the rectangular trench <NUM> may have a constant relative refractive index that is less than the relative refractive indices of the first inner cladding region <NUM> and the outer cladding region <NUM>. The example rectangular trench shown may be established by incorporating Fluorine as a downdopant, to provide a minimum relative refractive index Δ<NUM>. In the example of <FIG>, the rectangular trench has a bottom slope with the minimum relative refractive index Δ<NUM> occurring at radius r<NUM>. In the embodiment of <FIG>, the core <NUM> has have highest relative refractive index (Δ<NUM> = Δ1MAX) in the core-cladding profile, with a slight dip in the profile at r = <NUM>. The SD fiber <NUM> of <FIG> includes the primary coating <NUM> and a secondary coating <NUM>, but only the glass section <NUM> of the SD fiber is shown in the profile.

The relative refractive index profiles for the configuration of SD fiber <NUM> of <FIG> have a simpler form as those for <FIG>, with the cladding <NUM> of the <FIG> configuration having one fewer region than the cladding <NUM> of the <FIG> configuration.

The core <NUM> or <NUM> and the cladding <NUM> or <NUM> may comprise silica or silica-based glass and may optionally include an updopant or a downdopant. The silica-based glass may be silica glass modified by an alkali or alkaline earth element, one or more halogens, or other dopants. The radius r<NUM> of the core <NUM> or <NUM> may be in the range of <NUM> to <NUM> microns, for example <NUM> to <NUM> microns or <NUM> to <NUM> microns. The refractive index across the core <NUM> or <NUM> may be constant or variable. The refractive index of the core <NUM> or <NUM> may be at a maximum at or near the center of the core and may continuously decrease in the direction of the outer core boundary. The refractive index profile of the core <NUM> or <NUM> may be or may approximate a Gaussian profile, an α-profile, a step profile or a rounded step index profile with an alpha value in the range between <NUM> and <NUM>. The maximum or peak refractive index delta of the core Δ1MAX may be in the range from <NUM> % to <NUM>%, or from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

The core <NUM> or <NUM> may be characterized by a core profile volume, V<NUM>, in units of %-microns<NUM>, equal to: <MAT> The magnitude |V<NUM>| of the core volume may be at least <NUM> %-microns<NUM>, or at least <NUM> %-microns<NUM>, or at least <NUM> %-microns<NUM>. The magnitude |V<NUM>| of the core volume may also be less than <NUM> %-microns<NUM>, or less than <NUM> %-microns<NUM>, or between <NUM> %-microns<NUM> and <NUM> %-microns<NUM>, or between <NUM> %-microns<NUM> and <NUM> %-microns<NUM>.

The glass cladding <NUM> or <NUM> may include the aforementioned two or more regions, which differ in refractive index profile and that may extend to an outer radius r<NUM> of not greater than <NUM> microns, or not greater than <NUM> microns, or not greater than <NUM> microns, or not greater than <NUM> microns, or not greater than <NUM> microns, or not greater than <NUM> microns. According to some embodiments the outer radius r<NUM> of the glass cladding <NUM> or <NUM> is between <NUM> microns and <NUM> microns, or between <NUM> microns and <NUM> microns, or between <NUM> microns and <NUM> microns, or between <NUM> microns and <NUM> microns, or between <NUM> microns and <NUM> microns. According to some embodiments, at least one region of the glass cladding <NUM>, <NUM> is down-doped relative to silica (for example, by Fluorine or Boron).

The cladding <NUM> or <NUM> may include at least one inner cladding region surrounded by an outer cladding region, where the inner cladding region may have a lower refractive index than the outer cladding region. For example, the SD fiber <NUM> of <FIG> has an inner cladding region <NUM> and an outer cladding <NUM> while the SD fiber of <FIG> has two (first and second) inner cladding regions <NUM> and <NUM> and an outer cladding region <NUM>. The refractive index of the inner cladding region may be constant or continuously varying. The refractive index of the inner cladding region may form a trench in the refractive index profile of the coated fiber. The trench is a depressed index region and may be approximately rectangular or triangular. The outer cladding region may have a constant or continuously varying refractive index. The minimum refractive index of the inner core region may be less than the maximum refractive index of the outer cladding region.

The refractive index of the second inner cladding region <NUM> may be lower than the refractive index of the first inner cladding region <NUM>. The minimum refractive index of the second inner cladding region <NUM> may be lower than the maximum refractive index of the first inner cladding region <NUM>. The refractive index of the second inner cladding region <NUM> may be lower than the refractive index of the outer cladding region <NUM>. The minimum refractive index of the second inner cladding region <NUM> may be lower than the maximum refractive index of the outer cladding region <NUM>. The refractive index of the second inner cladding region <NUM> may be lower than the refractive indices of the first inner cladding region <NUM> and the outer cladding region <NUM>. The minimum refractive index of the second inner cladding region <NUM> may be lower than the maximum refractive indices of the first inner cladding region <NUM> and the outer cladding region <NUM>.

The refractive index of the second inner cladding region <NUM> may be constant or varying (e.g., continually varying). The refractive index of the second inner cladding region <NUM> may form the aforementioned rectangular trench ("trench") in the refractive index profile. The trench is a depressed index region and may be rectangular or triangular, and can include a bottom with a non-uniform relative refractive index such as shown in <FIG>. The minimum relative refractive index delta Δ<NUM> of the trench may be less than -<NUM>%, less than -<NUM>%, less than -<NUM>% or less than -<NUM>%. The minimum relative refractive index delta Δ<NUM> of the trench Δ<NUM> may be greater than -<NUM>%, greater than -<NUM>%, greater than - <NUM>%, greater than -<NUM>%, or between -<NUM>% and -<NUM>%, or between -<NUM>% and -<NUM>%, or between -<NUM>% and -<NUM>%. The inside radius r<NUM> of the trench may be greater than <NUM> microns, or greater than <NUM> microns, or greater than <NUM> microns. The inside radius r<NUM> of the trench may be less than <NUM> microns, or less than <NUM> microns, or less than <NUM> microns, or between <NUM> and <NUM> micron, or between <NUM> and <NUM> microns. The outside radius r<NUM> of the trench may be greater than <NUM> microns, or greater than <NUM> microns, or greater than <NUM> microns. The outside radius r<NUM> of the trench may be less than <NUM> microns, or less than <NUM> microns, or less than <NUM> microns, or between <NUM> and <NUM> micron, or between <NUM> and <NUM> microns.

The depressed index region may be characterized by a profile trench volume, V<NUM>, in units of %-microns<NUM>, equal to: <MAT> The magnitude |V<NUM>| of the trench volume may be at least <NUM> %-microns<NUM>, or at least <NUM> %-microns<NUM>, or at least <NUM> %-microns<NUM>. The magnitude |V<NUM>| of the trench volume may also be less than <NUM> %-microns<NUM>, or less than <NUM> %-microns<NUM>, or between <NUM> %-microns<NUM> and <NUM> %-microns<NUM>.

The primary coating <NUM> or <NUM> of the SD fiber <NUM> is structured to act as a spring (shown schematically as a spring S in <FIG>) that couples the glass section <NUM> (i.e., cladding <NUM> or <NUM>) of the SD fiber to the secondary coating <NUM> or <NUM>.

Commercially-available optical fibers with small outer cladding diameters and small coated fiber diameters suffer from microbending losses unless the mode field diameter is reduced or the cutoff wavelength is increased. Improving microbending losses for such fibers has been difficult if the total thickness of the primary and secondary coatings has a smaller value than the <NUM>-<NUM> micron value in standard telecommunication fibers.

Decreasing the elastic modulus EP and thickness tP of the primary coating <NUM> or <NUM> can help reduce the microbending sensitivity of the SD fiber <NUM>, but the thickness tP of the primary coating can only be increased if there is a concomitant decrease in the thickness ts of secondary coating <NUM> or <NUM> given that the total thickness tP + tS of the two coating layers is constrained. Decreasing the secondary coating thickness ts is undesirable because it reduces puncture resistance of the coated SD fiber <NUM>. However, the SD fibers <NUM> with their relatively small outer coating diameters dC ≤ <NUM> microns, and relatively small outer cladding diameter (d4 ≤ <NUM> microns) can have surprisingly good microbending and good resistance to puncture if the thicknesses tP and tS of the primary and secondary coatings are each at least about <NUM> microns. In some embodiments, the relative coating thickness, tP/tS, is in the range <NUM> ≤ tP/tS ≤ <NUM>.

More specifically, the primary coating <NUM> or <NUM> can have an in situ elastic modulus EP of <NUM> MPa or less and a minimum thickness of tP of <NUM> microns (e.g., a thickness of <NUM> microns, <NUM> microns, <NUM> microns, or <NUM> microns), and in these embodiments the primary coating <NUM> or <NUM> acts as the aforementioned spring S that couples the stiff glass cladding (e.g., cladding <NUM> or <NUM>) to the relatively stiff secondary coating <NUM> or <NUM> that has an in situ elastic modulus Es greater than <NUM> MPa, or greater than <NUM> MPa, or greater than <NUM> MPa, or even greater than1800 MPa. The spring constant χP of the primary coating <NUM>, <NUM> is defined as χP = EP·d<NUM>/tP, where d<NUM> is the diameter of the glass section of the fiber (i.e., it is the outer diameter of the glass cladding <NUM> or <NUM>, wherein d4 = 2r<NUM>), and tP and EP are the thickness and elastic modulus, respectively, of the primary coating <NUM> or <NUM>. In some embodiments, the spring constant χP of the primary coating <NUM> or <NUM> has a value χP ≤ <NUM> MPa (preferably χP ≤ <NUM>. 2MPa, more preferably χP ≤ <NUM> MPa, and even more preferably χP ≤ <NUM> MPa ), which is desirable for improved microbending resistance (lower microbending losses), since a small spring constant provides lower degree of coupling between the glass section <NUM> of the fiber and the secondary coating <NUM> or <NUM>.

Thus, embodiments of the SD fiber <NUM> can have an outer coating diameter dC ≤ <NUM> microns, and an outer glass cladding diameter d4 ≤ <NUM> microns, a secondary coating <NUM> or <NUM> with in situ elastic modulus ES greater than <NUM> MPa (and preferably >1500MPa) and a thickness tS greater or equal to <NUM> microns, and a primary coating <NUM> or <NUM> with an in situ elastic modulus EP ≤ <NUM> MPa, a spring constant χP ≤ <NUM> MPa and a thickness of at least <NUM> microns (e.g., <NUM> microns ≤ tP ≤ <NUM> microns). It is even more preferable that χP <<NUM> MPa or χP ≤<NUM> MPa, or χP ≤ <NUM> MPa, or χP ≤ <NUM> MPa. In at least some embodiments disclosed herein the primary coating <NUM> or <NUM> has a spring constant χP ≤ <NUM> MPa, χP ≤ <NUM> MPa χP ≤ <NUM> MPa, χP ≤ <NUM> MPa, χP ≤ <NUM> MPa, or χP ≤ <NUM> MPa. For example, in some embodiments, <NUM> MPa ≤ χP ≤<NUM> MPa; <NUM> MPa ≤ χP ≤<NUM> MPa; <NUM> MPa ≤ χP ≤<NUM> MPa. Alternatively, if the SD fiber <NUM> has an additional coating (tertiary coating <NUM> or <NUM>) situated on top of the secondary coating (e.g., an ink or a coating containing ink) of thickness tT, then the sum of the secondary and tertiary coating thicknesses (ts + tT) is preferably ≥ <NUM> microns, and more preferably ≥ <NUM> microns, for example <NUM> microns ≤ (ts + tT) ≤ <NUM> microns.

The combined cross-sectional areas of the secondary and optional tertiary coating layers <NUM> or <NUM> for the embodiments of SD fibers <NUM> employed herein is preferably <NUM>,<NUM> sq. microns or greater, more preferably <NUM>,<NUM> sq. microns or greater and even more preferably <NUM>,<NUM> sq. microns or greater, which advantageously ensures that the fiber has sufficient puncture resistance.

In some embodiments, the tertiary thickness tT of the tertiary coating <NUM> or <NUM> is between <NUM> and <NUM> microns, for example, tT = <NUM> microns, <NUM> microns, or <NUM> microns.

Table 1A below lists example parameters for four example SD fibers <NUM>, where as noted above, d4 is the diameter of the glass section <NUM> of the SD fiber (i.e., <NUM> or <NUM>), dC is the diameter of the non-glass coating section <NUM>, EP is the primary elastic modulus, tP is the primary thickness of the primary coating <NUM> or <NUM>, ts is the secondary thickness of the secondary coating <NUM> or <NUM>, TT is the tertiary thickness of the optional tertiary coating <NUM> or <NUM> that immediately surrounds the secondary coating <NUM> or <NUM>, and χP is the spring constant of the primary coating <NUM> or <NUM>. The ratio dC/d4 is an example value based on the values for d4 and the selected values within the range of values for the thicknesses tP and tS and tT that define the diameter dC.

An example SD fiber <NUM> can have a diameter d4 = 2r<NUM> of the outer cladding <NUM> (or glass section <NUM>) of about <NUM> microns (i.e., r<NUM> = <NUM> microns), a diameter dC of the secondary coating <NUM> or <NUM> less than <NUM> microns (e.g., dC = <NUM> microns so that <NUM> ≤ dC/d4 ≤ <NUM>).

An example SD fiber <NUM> can also have: a primary coating in situ modulus EP ≤ <NUM> MPa, a primary coating thickness tP such that <NUM> micron ≤ tP ≤ <NUM> microns; a primary coating spring constant χP ≤ <NUM> MPa (e.g., χP ≤ <NUM> <MPa, ≤ <NUM> MPa and even ≤ <NUM>. 8MPa), a secondary coating diameter dS in the range between about <NUM> and <NUM> microns, a secondary coating in situ modulus ES ≥ <NUM> MPa, and a secondary coating thickness ts such that <NUM> microns ≤ tS ≤ <NUM> microns.

The optional tertiary coating thickness tT can be in the range between <NUM> and <NUM> microns (i.e., in some embodiments there is no tertiary coating <NUM> or <NUM>, thus the tertiary coating thickness tT = <NUM>). Other embodiments of the SD fiber <NUM> can contain a tertiary coating <NUM> or <NUM> with a thickness tT between <NUM> and <NUM> microns. In these exemplary embodiments, the sum tS + tT can be between <NUM> and <NUM> microns, i.e., <NUM> microns ≤ (tS+tT) ≤ <NUM> microns.

In some embodiments, the puncture resistance load of the SD fiber <NUM> can be greater than <NUM> grams. In some embodiments, the puncture resistance load of the SD fiber <NUM> can be greater than <NUM> grams. In some embodiments, the puncture resistance load of the SD fiber <NUM> can be greater than <NUM> grams. The combined cross-sectional areas of the secondary coating <NUM> or <NUM> and optional tertiary coating layers <NUM> or <NUM> for the embodiments of SD fibers <NUM> can also be greater than <NUM>,<NUM> sq. microns, which further improves the puncture resistance.

The refractive index profile parameters and modeled attributes often exemplary embodiments of the SD fiber <NUM> (i.e., Fiber <NUM> through Fiber <NUM>) corresponding to <FIG> are set forth in Tables 1B and 1C, below, where MFD is the mode field diameter as determined by the Petermann II method.

Some of the optical properties of these exemplary embodiments of the SD fibers <NUM> are as follows: the mode field diameter MFD at <NUM> is between <NUM> and <NUM> microns; the mode field diameter MFD at <NUM> is between <NUM> and <NUM> microns, the zero dispersion wavelength is between <NUM> and <NUM>; the fiber cutoff wavelength is between <NUM> and <NUM>; and the macrobend loss at <NUM> is less than <NUM> dB/turn when the fiber is wrapped around a mandrel having a diameter of <NUM>. The SD fiber embodiments of Tables 1B and 1C (Fiber <NUM> through Fiber <NUM>) can be constructed, for example, with an outer cladding diameter 2r<NUM> of about <NUM> to <NUM> microns. In some exemplary embodiment of the example SD fibers (Fiber <NUM> through Fiber <NUM>), the relative refractive index Δ<NUM>(%)= <NUM>, and the outer cladding <NUM> or <NUM> is made of pure silica. In other exemplary embodiments, the diameter d4 = 2r<NUM> has a value of about <NUM> to <NUM> microns and the outer cladding can be updoped or down doped relative to pure silica, but with Δ<NUM> >Δ<NUM>.

<FIG> is an end-on view of a <NUM><NUM> stack <NUM> of standard fiber ribbons <NUM> made using standard <NUM>/<NUM> micron optical fibers ("standard fibers") <NUM>. <FIG> is an end-on view of a <NUM><NUM> stack <NUM> of fiber ribbons <NUM> using <NUM>/<NUM> micron SD fibers <NUM>. The stack <NUM> contains a total of <NUM> standard fibers 10C while the stack <NUM> contains a total of <NUM> SD fibers <NUM>. This corresponds to a <NUM>% increase in the fiber density. This increase in fiber density allows for either reducing the size of an optical fiber cable for the same fiber count, or deploying more optical fibers in the same size optical fiber cable.

<FIG> is an elevated view of an example high-density optical fiber ribbon cable interconnect ("ribbon cable interconnect") <NUM>. The ribbon cable interconnect <NUM> has a first end <NUM> and a second end <NUM> and comprises a ribbon cable <NUM> having a first end <NUM> adjacent the first end <NUM> and a second end <NUM> adjacent the second end <NUM>.

<FIG> is a cross-sectional views of an example configuration of the optical fiber ribbon <NUM>. The fiber ribbon <NUM> comprises a plurality of SD fibers <NUM>. The example configuration of <FIG> comprises the SD fibers <NUM> shown arranged in a single row and encapsulated by a matrix layer <NUM> to define the fiber ribbon <NUM>. In an example, the matrix layer <NUM> comprises a thin layer of clear acrylate (e.g., a few microns thick) that serves to bond together adjacent SD fibers <NUM>. The bond provided by the matrix layer <NUM> is strong enough to keep the SD fibers together in their ribbon configuration under general use but not so strong that the SD fibers <NUM> cannot be easily separated when needed. Various other configurations for the ribbon as known in the art can be employed. Note that the encapsulation may be such that portions of the SD fibers <NUM> are exposed, e.g., the end faces <NUM> or one or more of the end sections <NUM>, etc..

In one example, the fiber ribbon <NUM> comprises multiples of <NUM> SD fibers <NUM>, e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc. In an example, the SD fibers <NUM> in the fiber ribbon <NUM> have a pitch PR of about <NUM> microns, about <NUM> microns or about <NUM> microns. It is noted here that in a typical fiber ribbon <NUM> the end faces <NUM> of the SD fibers <NUM> are exposed so that in an example the matrix layer <NUM> surrounds the outer surfaces of each of the SD fibers <NUM> but not the end faces <NUM>. Furthermore, portions of the matrix layer <NUM> can be removed to expose one or more of the SD fibers <NUM> (e.g., end sections <NUM>), so that in an example, the matrix layer surrounds the SD fibers except for one or more select sections. In such an embodiment, the fiber ribbon <NUM> can comprise one or more bonded sections that include the matrix layer <NUM> and one or more unbonded sections that do not include the matrix layer <NUM> or that do not include the entire matrix layer.

In examples, one or more fiber ribbons <NUM> are used to form an optical fiber ribbon cable ("ribbon cable"). Example configurations of ribbon cables that can be formed using one or more fiber ribbons <NUM> are disclosed in <CIT>, entitled "fiber optic ribbon cable and ribbon". In some applications, it may be advantageous to use the one or more fiber ribbons to form a ribbon cable, such as when an optical connection needs to be made over a substantial distance that could put the one or more fiber ribbons at risk.

<FIG> are cross-sectional views of two different example configurations of optical fiber ribbon cables in which the fiber ribbon <NUM> is surrounded by one or more protective layers <NUM>, which in the example of <FIG> comprises a strength layer <NUM> (e.g., aramid yarn) that surrounds the fiber ribbon <NUM>, and an outer jacket <NUM> that surrounds the strength layer. The example configuration of <FIG> comprises the fiber ribbon and the one or more protective layers <NUM> comprise a binder layer <NUM> that surrounds the fiber ribbon, a strength layer <NUM> that surrounds the binder layer, and the outer jacket <NUM> that surrounds the strength layer. In an example, one or more fiber ribbons <NUM> may be loosely arranged within the one or more protective layers <NUM>.

<FIG> is similar to <FIG> and shows an example of the ribbon cable <NUM> having multiple (e.g., two) fiber ribbons <NUM> in a stacked configuration and surrounded by the one or more protective layers <NUM>. In an example, the multiple fiber ribbons <NUM> are loosely stacked within the one or more protective layers <NUM>. Each fiber ribbon <NUM> can include two or more SD fibers <NUM>, with four, eight, twelve and sixteen being convenience and useful numbers of SD fibers per fiber ribbon. A variety of other configurations of the ribbon cable <NUM> can be employed as known in the art using one or more fiber ribbons <NUM>.

With reference again to <FIG>, the first end <NUM> of the ribbon <NUM> or ribbon cable <NUM> is terminated by a first optical fiber connector ("first connector") <NUM>, which defines the first end <NUM> of the ribbon cable interconnect <NUM>. The first connector <NUM> has an end face ("connector end face") <NUM>. In an example, the first connector <NUM> comprises a standard optical fiber connector, such an MPO connector, as shown in the elevated views of <FIG> and <FIG>. The first connector <NUM> can include a ferrule <NUM> with a central axis A1. The ferrule <NUM> includes a front end <NUM>, a back end <NUM>, and an array <NUM> of axial holes <NUM> that run substantially parallel to the central axis A1, with each hole having a hole diameter DH, an edge-to-edge hole spacing SH, and a center-to-center spacing SF, as shown in the close-up inset of <FIG>. The holes <NUM> are sized to support the SD fibers <NUM>, and the center-to-center distance (spacing) SF between adjacent holes <NUM> defines a fiber pitch P1 at the end face <NUM> of the first connector.

The first connector <NUM> shown in <FIG> supports the SD fibers at a pitch P1, with a double pitch (2P1) between the eighth and ninth SD fibers <NUM>. The example first connector <NUM> of <FIG> supports the SD fibers <NUM> in an industry standard configuration, e.g., with a pitch P1 of <NUM> microns, but the diameters DH of the holes <NUM> at the connector end face <NUM> have been reduced from the standard value of <NUM> microns to <NUM> microns, as shown in the close-up inset (not to scale).

In examples, the hole diameter DH can be <NUM> microns or <NUM> microns or <NUM> microns while the edge-to-edge hole spacing SH can be approximately equal to or twice the hole diameter DH (e.g. DH and SH are both about <NUM> microns, or DH is about <NUM> microns and SH is about <NUM> microns). The hole spacing SH and the hole diameter DH defines the pitch P1, which can be defined as the center-to-center spacing SF between adjacent holes <NUM>. The array <NUM> of holes <NUM> can be arranged in a single row (<FIG>) or in multiple rows (<FIG>).

The first connector can include one or more alignment features <NUM>, such as alignment pins are alignment holes. The first end <NUM> of the ribbon cable can also include a flexible boot <NUM> that flexibly connects the standard connector to the ribbon <NUM> or ribbon cable <NUM>.

<FIG> is a front elevated view of an example configuration of the ribbon cable interconnect <NUM> wherein the ribbon <NUM> or ribbon cable <NUM> includes three branches 210B or 221B, each of which terminated by a first connector <NUM>. Or said differently, the first connector <NUM> can comprise multiple first connectors (which could be called sub-connectors), such as the multiple MPO connectors shown in <FIG>. In general, the first end <NUM> of the ribbon <NUM> or ribbon cable <NUM> can include any reasonable number of branches 210B and corresponding first connectors <NUM>.

<FIG> is a y-z cross-sectional view of an example ferrule <NUM> of the first connector <NUM> of <FIG> as taken along one of the holes <NUM>. The ferrule <NUM> has a front end <NUM> and a back end <NUM>. <FIG> also shows a first end section <NUM> of the SD fiber <NUM> adjacent the back end <NUM> of the ferrule and in position to be inserted into the hole <NUM>. The first end section <NUM> of the SD fiber <NUM> has an end face <NUM>.

<FIG> is similar to <FIG> and shows the SD fiber <NUM> supported by the ferrule <NUM> within the hole <NUM> so that the end face <NUM> of the SD fiber resides substantially at the front end <NUM> of the ferrule, which in an example defines the connector end face <NUM>. The example of <FIG> shows the hole <NUM> having a slightly larger hole diameter DH than diameter d4 of the glass section <NUM> of the SD fiber, which in an example can be nominally <NUM> or <NUM> microns.

The example of <FIG> is similar to <FIG> but shows an example where the hole <NUM> has a diameter DH much larger than the glass section <NUM> of the SD fiber <NUM> (e.g., <NUM> microns) so that the end section <NUM> of the SD fiber includes the coating section <NUM>, i.e., it is not stripped down to the glass section <NUM> as in <FIG>. The diameter dC of the coating section <NUM> of the example of <FIG> is slightly smaller than the hole diameter DH.

With reference again to <FIG>, the second end <NUM> of the ribbon <NUM> or ribbon cable <NUM> is terminated by a second optical fiber connector ("second connector") <NUM> having an end face <NUM>. In an example, the second connector <NUM> comprises a high-density connector, where the term "high density" means it has a fiber density greater than a conventional or standard connector such as an MPO connector.

<FIG> is an exploded front elevated view of an example method of forming a high-density connector assembly ("connector assembly") <NUM> that can be used directly as the second connector <NUM> or can be used to form the second connector (e.g., by adding further connector components). The connector assembly <NUM> includes a grooved substrate <NUM> having a front-end section <NUM> with a front end <NUM>, a back-end section <NUM> with a back end <NUM>, and a central axis A2 that runs in the z-direction. The front-end section <NUM> has a planar top surface <NUM> while the back-end section <NUM> has a planar top surface <NUM> that is lower than the top surface <NUM> of the front section. The front-end section <NUM> includes an array <NUM> of grooves <NUM> formed in the planar top surface <NUM> and that run parallel to the central axis A2. In an example, the grooves <NUM> are V-grooves as shown.

<FIG> shows the SD fibers <NUM> extracted from the fiber ribbon <NUM>. Each of the SD fibers <NUM> has an end section <NUM> with an end face <NUM>. The end section <NUM> is shown stripped of the protective coating section <NUM> to expose the glass section <NUM>. The grooves <NUM> of the front-end section <NUM> of the grooved support substrate <NUM> are sized to accommodate the bare glass end sections <NUM> of the SD fibers <NUM> while the back-end section <NUM> accommodates the coated sections <NUM> of the SD fibers. Once the end sections <NUM> of the SD fibers <NUM> are supported in the grooves <NUM>, then a bonding agent (e.g. epoxy) <NUM> can be applied to the SD fibers at the back-end section <NUM>. A cover glass <NUM> having a front end <NUM>, a back end <NUM>, a top surface <NUM> and a bottom surface <NUM> is then placed over the top of the array <NUM> of the grooves <NUM> to secure the end sections <NUM> of the SD fibers <NUM> in the front-end section <NUM> of the grooved support substrate <NUM>. The cover glass <NUM> is held in place by the bonding agent <NUM> contacting the back end <NUM> of the cover glass. The bonding agent <NUM> can also be added to the grooves <NUM>.

<FIG> show the resulting connector assembly <NUM>, with the end faces <NUM> of the SD fibers residing substantially at the front end <NUM> of the grooved substrate <NUM>. The connector assembly <NUM> supports the SD fibers <NUM> at a pitch P2 at the end face <NUM>.

<FIG> is y-z cross-sectional view of the second end <NUM> of the ribbon <NUM> or ribbon cable <NUM> showing the connector assembly <NUM> and one of the SD fibers <NUM> supported therein. In an example, the front end <NUM> of the grooved substrate <NUM>, the front end <NUM> of the cover glass and the end face <NUM> of the SD fiber are angled by up to about <NUM> degrees relative to the x-z plane (i.e., the vertical plane VP) to reduce reflection losses.

<FIG> is similar to <FIG> and illustrates an example high-density second connector <NUM> formed by at least partially enclosing the high-density connector assembly <NUM> within a connector housing <NUM> having a front end <NUM> and a back end <NUM>. In an example, the high-density second connector includes at least one alignment feature <NUM>, which is shown by way of example as alignment pins that extend from the front end <NUM> of the connector housing to define a plug connector configuration. The alignment features <NUM> could also be alignment holes for receiving alignment pins, thereby defining a receptacle connector configuration.

In an example, the front end <NUM> of the grooved substrate <NUM> resides at or proximate to the front end <NUM> of the connector housing <NUM> while the SD fibers <NUM> extend from the back end <NUM> of the connector housing. In another example, the front end <NUM> of the grooved substrate <NUM> can extend from the front end <NUM> of the connector housing <NUM>.

<FIG> is a top-down view that illustrates an example embodiment of how the SD fibers <NUM>-<NUM> and <NUM>-<NUM> of respective first and second ribbons <NUM>-<NUM> and <NUM>-<NUM> can be interleaved in the second connector <NUM>. As part of the interleaving process in this example and the examples below, when starting with two fiber ribbons <NUM>-<NUM> and <NUM>-<NUM>, the matrix layer <NUM> and coating sections <NUM> of the SD fibers <NUM> are removed from the end section <NUM> of each of the SD fibers <NUM>-<NUM> and <NUM>-<NUM> to expose the respective glass sections <NUM>. This process can be performed using commercially available mechanical or thermal strippers.

Continuing with the present example, the glass sections <NUM> of the SD fibers <NUM>-<NUM> and <NUM>-<NUM> are interleaved in the grooves <NUM> of the grooved support substrate <NUM> to define the high-density second connector <NUM>. <FIG> is a close-up end-on view of the second connector <NUM>. In the example shown, the glass sections <NUM> of the interleaved SD fibers <NUM>-<NUM> and <NUM>-<NUM> are supported by the grooved substrate <NUM> at "<NUM>/<NUM> pitch" P2, i.e., wherein the glass sections <NUM> have a center-to-center spacing SF that is approximately one-half of the pitch PR of ribbons <NUM>-<NUM> and <NUM>-<NUM> or ribbon cables <NUM>-<NUM> and <NUM>-<NUM>. The cover glass <NUM> is shown as having grooves <NUM> in the bottom surface <NUM> and sized to engage the end sections <NUM> of the SD fibers <NUM>. The interleaved (interdigitated) SD fibers <NUM>-<NUM> and <NUM>-<NUM> are denoted as "<NUM>" and "<NUM>" respectively in the end-on view for ease of illustration.

<FIG> and <FIG> are similar to <FIG> and <FIG> and illustrate the interleaving configuration for first, second and third ribbons <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> respectively having SD fibers <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>. The resulting SD fibers <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> can be supported by the grooved substrate <NUM> at <NUM>/<NUM> pitch P2, i.e., wherein the glass sections <NUM> have a center-to-center spacing SF that is approximately <NUM>/<NUM> of the pitch PR of the ribbons <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>.

<FIG> are similar to <FIG> and <FIG> and illustrate the interleaving configuration for first, second, third and fourth ribbons <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> respectively having SD fibers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>. The resulting SD fibers <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> can be supported by the grooved substrate <NUM> at a <NUM>/<NUM> pitch P2, i.e., wherein the glass sections <NUM> have a center-to-center spacing SF that is approximately <NUM>/<NUM> of the pitch PR of ribbons <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>. In the example of <FIG>, the cover glass <NUM> is shown as having a flat bottom surface <NUM> and the grooves <NUM> can be configured to provide a pitch P2 = <NUM>, i.e., an edge-to-edge spacing SH = d4.

The example ribbon interconnects <NUM> disclosed herein address the pitch-compatibility problem of connecting high-density fiber ribbons or ribbon cables to legacy (standard density) ribbon cables. In one example, a ribbon interconnect <NUM> with SD fibers <NUM> having a glass section with a diameter d4 = <NUM> microns can be coated and colored to a total outside diameter dC of a standard fiber, e.g., dC = <NUM> microns (see <FIG>). These SD fibers <NUM> can be incorporated into a fiber ribbon <NUM> or ribbon cable <NUM> with a pitch PR of about <NUM> microns, and the glass sections <NUM> fitting directly into the holes <NUM> of a ferrule <NUM> of a connector <NUM> with a standard pitch P1 of <NUM> microns but with hole diameters of <NUM> microns rather than <NUM> microns.

At the second end <NUM>, rather than putting only one fiber ribbon <NUM> into the second connector <NUM>, the glass sections <NUM> of the SD fibers <NUM> of two or more fiber ribbons <NUM> can be interleaved to have a relatively small pitch P2, e.g., on the order of the diameter d4, e.g., P2 = <NUM>/<NUM> = <NUM> microns for interleaving three ribbon <NUM>. The relatively small pitch P2 of the second connector <NUM> translates into a relatively high fiber density as compared to the fiber density of the first connector <NUM>.

Table <NUM> below summarizes other examples where the ratio between the outer coating diameter dC and glass diameters d4 (i.e., dC/d4) is substantially integral, i.e., is an integer value to within <NUM>%, and more preferably to within <NUM>%. This enables two or more fiber ribbons <NUM> (or a ribbon cable <NUM> with two or more fiber ribbons <NUM>) to be terminated with a standard (e.g., MPO) connector <NUM> at one (first) end and terminated with a high-density second connector <NUM> at the other (second) end or interfaced to another ribbon cable terminated with an MPO/MTP connector having the same geometry.

In Table <NUM> below, "NR" is the number of rows of SD fibers <NUM> in the first connector <NUM>, P1 is the fiber pitch at the end face <NUM> of first connector, DH is the hole diameter, IR is the interleave ratio, i.e., the number of ribbons being interleaved, and FP is the "fiber footprint," i.e., the length of the row of SD fibers <NUM> at the front end of the first connector from one end to the other. The number of SD fibers <NUM> in each row is sixteen for all of the examples in Table <NUM>, so that the fiber density (fibers/length) is given by <NUM>/FP for the various examples. In other embodiments, the number of SD fibers <NUM> is twelve, so that the fiber density (fibers/length) is <NUM>/FP. The ratio of the pitch P1 to the hole diameter DH are all approximately integral (e.g., to within <NUM>%), with example values of <NUM>, <NUM> or <NUM>.

<FIG> is a schematic diagram of an optical data transmission system <NUM>. The optical data transmission system <NUM> comprises a photonic device <NUM>, a telecommunications device <NUM> having a connector receptacle <NUM>, and the ribbon cable interconnect <NUM> as disclosed herein.

<FIG> is a top-down view of an example photonic device <NUM>. The example photonic device <NUM> includes a circuit board <NUM> having a top surface <NUM> and that operably supports a photonic chip <NUM>, e.g., silicon-photonic chip. The photonic chip operably supports an array of optical waveguides <NUM>. As used herein, the term "photonic chip" means any component having optical waveguides <NUM>. The photonic device <NUM> may further include additional drive circuitry (not shown) to control active optical components to effectuate the conversion of optical signals into electrical signals and vice-versa.

The photonic chip <NUM> may be fabricated from any material capable of having optical waveguides <NUM> disposed thereon or therein. As non-limiting examples, the photonic chip <NUM> may be fabricated from a glass-based material (e.g., glass, glass-ceramic, and fused silica) or a semiconductor material (e.g., silicon). The optical waveguides <NUM> may be configured as any known or yet-to-be-developed optical waveguides. Non-limiting example optical waveguides <NUM> include thin-film deposition, photolithographic masking and etching processes, laser written waveguides, ion-exchanged waveguides, channel waveguides, among others. It should be understood that the optical waveguides <NUM> may be suitably configured for the operations of the photonic chip <NUM> and are merely schematically depicted in a straight-line configuration.

<FIG> also shows the second connector <NUM> at the second end of the ribbon interconnect <NUM> in position to operably engage the photonic device <NUM>. The photonic chip <NUM> has a front end <NUM> at which the optical waveguides <NUM> can terminate. Eight optical waveguides <NUM> are shown by way of example. The optical waveguides <NUM> are shown by way of example as operably connected to respective active photonic elements <NUM>, which in an example can comprise optical transceivers, optical light sources (e.g., a vertical-cavity surface-emitting lasers or VCSELs) or optical detectors. In an example, the photonic chip <NUM> is configured to generate and/or receive optical data signals using the active photonic elements <NUM> and the optical waveguides <NUM>. In an example, the photonic chip <NUM> can comprise a first sub-chip that includes the optical waveguides <NUM> and a second sub-chip that includes the active photonic elements <NUM>.

The front-end <NUM> of the photonic chip <NUM> can include one or more alignment features <NUM>, which are shown by way of example as alignment holes. Also shown in <FIG> is the second connector <NUM> having one or more alignment features <NUM> that are complementary to the one or more alignment features <NUM> of the photonic device <NUM>. The example alignment features <NUM> are shown in the form of alignment pins sized and configured to closely engage the alignment features <NUM> when the second connector <NUM> is operably engaged with the photonic chip <NUM>, as shown in <FIG>. The photonic device <NUM> is shown as having additional alignment features <NUM> that help guide the second connector into position relative to the photonic chip <NUM>.

The front end <NUM> of the photonic chip <NUM> and the alignment features <NUM> can comprise an optical connector <NUM> configured to receive the second connector <NUM> and that allows mating and de-mating of the second connector with the photonic device <NUM> to establish optical communication between the photonic chip <NUM> and the ribbon interconnect <NUM>. The optical connector <NUM> can be configured as receptacle connector (as shown) or as a plug connector.

The optical waveguides <NUM> have a pitch that matches the pitch P2 of the SD fibers <NUM> of the second connector <NUM> so that when the second connector is operably engaged with the photonic device <NUM> (e.g., via the optical connector <NUM>), the SD fibers are in optical communication with respective optical waveguides <NUM>. The optical waveguides <NUM> have a high waveguide density, i.e., greater than that associated with standard connectors used in standard optical fiber cables.

With reference again to <FIG>, at the other end of the ribbon interconnect <NUM>, the first connector <NUM> is operably engaged with the connector receptacle <NUM> of the telecommunications device <NUM>. The telecommunications device <NUM> can be a wide variety of standard telecommunication devices known in the art, such as a server, a fiber optic cable, an electronics panel in a data center, etc. The first connector has the aforementioned standard fiber density associated with industry standard telecommunication systems.

Claim 1:
A high-density fiber ribbon, comprising:
a) a plurality of small diameter optical fibers (<NUM>) arranged in one or more rows, wherein each small diameter optical fiber (<NUM>) comprises:
i) a glass section (<NUM>) with a diameter d4;
ii) a non-glass coating section (<NUM>) that surrounds the glass section (<NUM>) and having a diameter dC and that defines an outer surface;
iii) a mode-field diameter at a wavelength of <NUM> of between <NUM> and <NUM> microns;
iv) a fiber cutoff wavelength less than <NUM>; and
v) a bend loss for a single turn of the small diameter fiber (<NUM>) around a mandrel with a <NUM> diameter of less than <NUM> dB at a wavelength of <NUM>;
wherein the ratio dC/d4 is an integer value to within <NUM> percent, the diameter d4 is smaller than <NUM> microns, and the diameter dC is smaller than <NUM> microns;
b) a matrix layer (<NUM>) encapsulating the plurality of small diameter optical fibers (<NUM>); and
c) an attenuation per each of the small diameter optical fibers (<NUM>) as encapsulated in the matrix layer (<NUM>) of less than <NUM> dB/km at a wavelength of <NUM> and less than about <NUM> dB/km at a wavelength of <NUM>.