Accurate core pitch measurement

Abstract

A method for determining core spacing values and / or errors of optical fibers positioned in a two-dimensional fiber array unit is provided herein. The optical fiber array unit comprises a first optical fiber layer and a second optical fiber layer. The method includes positioning one of the fiber array unit or the core spacing measurement device relative to each other to effect a measurement of at least one core spacing value. The method continues by measuring a first horizontal component and a first vertical component corresponding to a first optical fiber in the first layer and a second horizontal component and a second vertical component corresponding to the optical fiber in the second layer. The method continues by determining an adjusted second vertical component based on an angle of an end face of the fiber array unit, the first vertical component, and the second vertical component, and thereby determining a core pitch value and / or error.

Description

[0001] Priority Application

[0002] This application claims priority to U.S. Application No. 63 / 425,332, filed Nov. 15, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] Embodiments of the present disclosure generally relate to fiber optic array units, and more particularly, to precise measurement of the core pitch of optical fibers within a fiber optic array unit. Background Art

[0004] A fiber optic array unit includes one or more optical fibers configured to transmit data. The fiber optic array unit can be coupled to other components, such as transmitters, receivers, and / or other optical fibers. In this regard, due to the coupling of the optical fibers and other components, there may be yield losses at each coupling point. The higher the yield loss, the lower the efficiency of the fiber optic array unit, as data and the ability to transmit data are reduced with each coupling.

[0005] Inaccuracies in the spacing of light beams transmitted from the optical fibers within a fiber optic array unit can magnify coupling losses. In this regard, inaccurate spacing can result from positioning errors, polishing angle errors, defects on the end faces of the optical fibers, displacements (e.g., due to adhesives), and other errors.

[0006] To account for coupling losses, each fiber optic array unit can be manufactured with a certain tolerance. The tolerance can allow light beams from each optical fiber to be emitted within a certain parameter threshold corresponding to the expected position of the optical fiber within the fiber optic array unit. In this regard, at both ends of the tolerance (e.g., both ends of the parameter threshold), the yield of the optical fibers can still be within an acceptable range. However, since fiber optic array units are manufactured on a microscale, small errors in measurement (e.g., 0.2 micrometers) can result in significant yield losses. Summary of the Invention

[0007] A fiber optic array unit can include a single layer of optical fibers positioned on a first substrate, or multiple layers of optical fibers stacked on top of each other, with, for example, spacers therebetween. Each optical fiber is positioned and fastened (e.g., adhesively, welded, sintered with nanoparticles) to the corresponding substrate such that once the optical fibers are positioned, they cannot be repositioned to adjust for any errors.

[0008] After assembly, the core pitch values of each optical fiber within the fiber optic array can be obtained. The core pitch values can include horizontal and vertical components to indicate the position of the core of the optical fiber relative to other optical fibers within the fiber optic array unit, for example. The measured core pitch values can be compared to desired core pitch values to determine the core pitch error of each optical fiber within the fiber optic array unit.

[0009] To maintain the integrity of data transmission and minimize yield loss, the core pitch error of each optical fiber is determined. In this regard, a lower core pitch error results in lower yield loss during data transmission. Each data transmission component can define a tolerance indicating the maximum allowable core pitch error acceptable for data transmission. To accurately determine whether the optical fibers within the fiber optic array unit are within the tolerance, the core pitch value of each optical fiber should be accurately determined. Since the fiber optic array unit is manufactured on a micron scale, even a small inaccuracy in the core pitch value (e.g., due to the vertical and / or horizontal components) can cause the fiber optic array unit to fall outside the tolerance range, which may require, for example, discarding the entire fiber optic array unit.

[0010] However, it is noted that current measurement devices are limited in their ability to accurately determine the vertical component of the core pitch value of the optical fibers in a two-dimensional fiber optic array unit. Specifically, when the ends of the two fiber layers extend along an angled (e.g., not perpendicular to the bottom surface of the base of the fiber optic array unit) end face of the fiber optic array unit, the relative distance and angle to the measurement device result in inaccurate current vertical component measurements. This leads to a misunderstanding as to whether the optical fibers are actually within the acceptable tolerance.

[0011] Example embodiments of the present disclosure relate to methods for accurately determining the positioning of the cores of optical fibers in a fiber optic array unit, particularly for a fiber optic array unit having an angled end face. In this regard, embodiments of the present disclosure account for the angled end face and adjust the core pitch measurement values to accurately reflect the core pitch values. Subsequently, the adjusted core pitch values can be accurately used to determine the viability of the fiber optic array unit. Corresponding methods for manufacturing such fiber optic array units and verifying the core pitch error tolerance are also provided herein.

[0012] In an example embodiment, a method is provided for determining a core pitch value of an optical fiber positioned in a two-dimensional optical fiber array unit. The two-dimensional optical fiber array unit includes a first optical fiber array layer and a second optical fiber array layer. The first optical fiber array layer includes a first optical fiber that defines a first end face configured to emit a first light beam. The second optical fiber array layer includes the optical fiber that defines a second end face configured to emit a second light beam. The first optical fiber array layer and the second optical fiber array layer are vertically spaced apart. The first end face and the second end face are disposed on an angled end face of the optical fiber array unit. The angled end face extends from a base of the optical fiber array unit at an angle that is not perpendicular to a bottom surface of the base of the optical fiber array unit. The method includes positioning the optical fiber array unit or at least one core pitch measuring device relative to each other to enable measurement of at least one core pitch value. The method further includes measuring, using the at least one core pitch measuring device, a first horizontal component and a first vertical component of the first optical fiber corresponding to the first optical fiber array layer. The method further includes measuring, using the at least one core pitch measuring device, a second horizontal component and a second vertical component of the optical fiber corresponding to the second optical fiber array layer. The method further includes determining an adjusted second vertical component of the optical fiber based on the angle of the angled end face, the measured first vertical component, and the measured second vertical component. The method further includes determining the core pitch value of the optical fiber based on the measured second horizontal component and the adjusted second vertical component.

[0013] In some embodiments, the first optical fiber and the optical fiber are parallel. In some embodiments, the measurement direction of the at least one core pitch measuring device can be positioned to be parallel to the bottom surface of the base of the optical fiber array unit. In some embodiments, the angled face of the two-dimensional optical fiber array unit can have a glass cover.

[0014] In some embodiments, the adjusted second vertical component of the second light beam can be provided by the following equation: where Y' is the adjusted second vertical component of the second light beam, α is the angle of the angled end face, h' is the measured vertical component distance between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the optical fiber array unit.

[0015] In some embodiments, the two-dimensional fiber optic array unit may be positioned on a wedge, the wedge being positioned on a flat surface, wherein the wedge is configured such that the angled end face is perpendicular to the flat surface. In some embodiments, the adjusted second vertical component is provided by the equation: Y′ = hsin(α), where Y' is the adjusted second vertical component of the second exit pitch, α is the angle of the angled end face, and h is the distance between the measured first vertical component and the measured second vertical component.

[0016] In some embodiments, the method may further include determining a first core pitch value of the first optical fiber based on the measured first horizontal component and the measured first vertical component.

[0017] In some embodiments, the method may further include determining a core pitch error based on the adjusted second vertical component, the measured second horizontal component, the desired second horizontal component, and the desired second vertical component, wherein the desired second horizontal component and the desired second vertical component result in desired transmission characteristics. In some embodiments, the core pitch error is determined by the equation: where dR i is the core pitch error, dX i is the difference between the desired second horizontal component and the measured second horizontal component, and dY i is the difference between the desired second vertical component and the adjusted second vertical component.

[0018] In some embodiments, the first end face and the second end face may be coated with an anti-reflection coating. In some embodiments, the method may further include repositioning one of the two-dimensional fiber optic array unit or the at least one core pitch measuring device to effect a core pitch measurement of a second core pitch value.

[0019] In yet another example embodiment, a method for determining a core separation distance extending between a first optical fiber and a second optical fiber of a two-dimensional optical fiber array unit is provided. The two-dimensional optical fiber array unit includes a first optical fiber array layer and a second optical fiber array layer. The first optical fiber array layer includes a first optical fiber that defines a first end face configured to emit a first light beam. The second optical fiber array layer includes a second optical fiber that defines a second end face configured to emit a second light beam. The first optical fiber array layer and the second optical fiber array layer are vertically spaced apart. The first end face and the second end face are disposed on an angled end face of the optical fiber array unit. The angled end face extends from a base of the optical fiber array unit at an angle that is not perpendicular to a bottom surface of the base of the optical fiber array unit. The method includes measuring a first vertical component of the first light beam using at least one core pitch measuring device. The method further includes measuring a second vertical component of the second light beam using the at least one core pitch measuring device. The method further includes determining a vertical separation between the measured first vertical component of the first light beam and the measured second vertical component of the second light beam. The method further includes determining an adjusted second vertical component of the second light beam based on the angle of the angled end face and the determined vertical separation. The method further includes determining a core pitch error by comparing the adjusted second vertical component of the second light beam with a desired vertical component of the second light beam.

[0020] In some embodiments, the first optical fiber and the second optical fiber may be parallel. In some embodiments, the at least one core pitch measuring device may be configured to measure the first light beam and the second light beam in a manner parallel to the bottom surface of the base of the optical fiber array unit.

[0021] In some embodiments, the adjusted second vertical component of the second light beam is provided by the following equation: where Y' is the adjusted second vertical component of the second light beam, α is the angle of the angled end face, h' is the measured vertical component distance separation between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the optical fiber array unit. In some embodiments, the core separation value may be the difference between the adjusted second vertical component and the measured first vertical component.

[0022] In yet another example embodiment, a method is provided for determining a core pitch error of an optical fiber positioned within a two-dimensional optical fiber array unit. The two-dimensional optical fiber array unit includes a first optical fiber array layer and a second optical fiber array layer. The first optical fiber array layer includes a first optical fiber that defines a first end face configured to emit a first light beam. The second optical fiber array layer includes the optical fiber that defines a second end face configured to emit a second light beam. The first optical fiber array layer and the second optical fiber array layer are vertically spaced apart. The first end face and the second end face are disposed on an angled end face of the optical fiber array unit. The angled end face extends from a base of the optical fiber array unit at an angle that is not perpendicular to a bottom surface of the base of the optical fiber array unit. The method includes positioning at least one core pitch measurement device such that a measurement direction of the at least one core pitch measurement device is parallel to the bottom surface of the base of the optical fiber array unit, wherein the at least one core pitch measurement device is configured to be at least movable vertically perpendicular to the bottom surface of the base of the optical fiber array unit. The method further includes using the at least one core pitch measurement device to measure a first horizontal component and a first vertical component corresponding to the first optical fiber. The method further includes using the at least one core pitch measurement device to measure a second horizontal component and a second vertical component corresponding to the optical fiber. The method further includes calculating an adjusted second vertical component of the optical fiber based on the angle of the angled end face, the measured first vertical component, and the measured second vertical component. The method further includes determining the core pitch error based on the adjusted second vertical component, the measured second horizontal component, a desired second horizontal component, and a desired second vertical component, wherein the desired second horizontal component and the desired second vertical component result in a desired transmission characteristic.

[0023] In some embodiments, the adjusted second vertical component of the second light beam is provided by the following equation: where Y' is the adjusted second vertical component of the second light beam, α is the angle of the angled end face, h' is the measured vertical component distance between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the optical fiber array unit.

[0024] In some embodiments, the optical fiber array unit is positioned on a wedge, and the second adjusted vertical component is provided by the following equation: Y′ = hsin(α), where Y' is the adjusted second vertical component, α is the angle of the angled end face, and h is the distance between the measured first vertical component and the measured second vertical component.

[0025] In yet another example embodiment, a process-generated two-dimensional fiber optic array unit is provided. The process includes forming a two-dimensional fiber optic array unit. The two-dimensional fiber optic array unit includes a first fiber optic array layer and a second fiber optic array layer. The first fiber optic array layer includes first optical fibers that define first end faces configured to emit first light beams, and the second fiber optic array layer includes second optical fibers that define second end faces configured to emit second light beams. The first fiber optic array layer and the second fiber optic array layer are vertically spaced apart. The first end faces and the second end faces are disposed on angled end faces of the fiber optic array unit, and the angled end faces extend from a base of the fiber optic array unit at an angle that is not perpendicular to a bottom surface of the base of the fiber optic array unit. The process further includes confirming that a core pitch error is within tolerance by positioning one of the fiber optic array unit or at least one core pitch measuring device relative to the other to achieve measurement of at least one core pitch value. The confirmation further includes measuring, using the at least one core pitch measuring device, a first horizontal component and a first vertical component of the first optical fibers corresponding to the first fiber optic array layer, and measuring, using the at least one core pitch measuring device, a second horizontal component and a second vertical component of the second optical fibers corresponding to the second fiber optic array layer. The confirmation further includes determining an adjusted second vertical component of the second optical fibers based on the angle of the angled end face, the measured first vertical component, and the measured second vertical component. The confirmation further includes determining a core pitch error based on the adjusted second vertical component, the measured second horizontal component, a desired second horizontal component, and a desired second vertical component, where the desired second horizontal component and the desired second vertical component result in optimal transmission. The confirmation further includes comparing the determined core pitch error to the tolerance.

[0026] In some embodiments, the adjusted second vertical component of the second light beam is provided by the following equation: where Y' is the adjusted second vertical component, α is the angle of the angled end face, h' is the measured vertical component distance between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the fiber optic array unit.

[0027] In some embodiments, confirming that the core pitch error is within tolerance may further include positioning the two-dimensional fiber optic array unit on a wedge, and where the second adjusted vertical component is provided by the equation: Y′ = hsin(α), where Y' is the adjusted second vertical component, α is the angle of the angled end face, and h is the distance between the measured first vertical component and the measured second vertical component.

[0028] In yet another example embodiment, a process-generated two-dimensional fiber optic array unit is provided. The process includes forming a two-dimensional fiber optic array unit. The two-dimensional fiber optic array unit includes a first fiber optic array layer and a second fiber optic array layer. The first fiber optic array layer includes first optical fibers that define first end faces configured to emit first light beams. The second fiber optic array layer includes second optical fibers that define second end faces configured to emit second light beams. The first fiber optic array layer and the second fiber optic array layer are vertically spaced apart. The first end faces and the second end faces are disposed on angled end faces of the fiber optic array unit. The angled end faces extend from a base of the two-dimensional fiber optic array unit at an angle that is not perpendicular to a bottom surface of the base of the fiber optic array unit. The process further includes confirming that a core pitch error is within tolerance by measuring a first vertical component of the first light beam using at least one core pitch measurement device and measuring a second vertical component of the second light beam using the at least one core pitch measurement device. Confirming that the core pitch error is within tolerance also includes determining a vertical spacing between the measured first vertical component of the first light beam and the measured second vertical component of the second light beam and determining an adjusted second vertical component of the second light beam based on the angle of the angled end face and the determined vertical spacing. Confirming that the core pitch error is within tolerance also includes determining the core pitch error by comparing the adjusted second vertical component of the second light beam with a desired vertical component of the second light beam and comparing the determined core pitch with the tolerance.

[0029] In some embodiments, the core pitch error is determined by the following equation: where dR i is the core pitch error, dX i is the difference between the desired second horizontal component and the measured second horizontal component, and dY i is the difference between the desired second vertical component and the adjusted second vertical component. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Now, with reference to the drawings, which are not necessarily to scale, and in which:

[0031] Figure 1A A front view of an example two-dimensional fiber optic array unit in accordance with some embodiments discussed herein is shown;

[0032] Figure 1B Shown in accordance with some embodiments discussed herein Figure 1A A side view of the fiber optic array unit shown in

[0033] Figure 1C Shown in accordance with some embodiments discussed herein Figure 1A A top view of the fiber optic array unit shown in

[0034] Figure 2A Front view showing an example fiber optic array unit according to some embodiments discussed herein;

[0035] Figure 2B Showing according to some embodiments discussed herein Figure 2A Measurement of the core pitch and core pitch error of the optical fibers of the example fiber optic array unit shown in;

[0036] Figure 3 Showing according to some embodiments discussed herein Figure 1A Positioning of the core pitch and core pitch error of the optical fibers of the fiber optic array unit shown in;

[0037] Figure 4 Cross-sectional view showing an example fiber optic array unit and a core pitch measuring device according to some embodiments discussed herein;

[0038] Figure 5 Cross-sectional view showing another example fiber optic array unit with angled end faces and a core pitch measuring device according to some embodiments discussed herein;

[0039] Figure 6A Cross-sectional view showing an example fiber optic array unit according to some embodiments discussed herein, wherein the angled end face shown in Figure 5 is positioned on a wedge;

[0040] Figure 6B Showing according to some embodiments discussed herein having Figure 6A Cross-sectional view of an example fiber optic array unit with the angled face shown in, wherein the wedge is removed to show example measurements and various angles;

[0041] Figure 7 Flowchart showing an example method for determining the core pitch of a fiber optic array unit according to some embodiments discussed herein; and

[0042] Figure 8 Flowchart showing an example method for manufacturing a fiber optic array unit with a defined tolerance according to some embodiments discussed herein. DETAILED DESCRIPTION

[0043] Some example embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, example embodiments are shown. In fact, the examples described and depicted herein should not be construed as limiting the scope, applicability, or configuration of the present disclosure. Rather, these example embodiments are provided so that the present disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout.

[0044] An optical fiber array unit (FAU) includes one or more optical fibers configured to transmit optical data. The FAU can be one-dimensional, where the optical fibers are positioned in a single layer (e.g., along a horizontal axis or x-axis), or two-dimensional, where the optical fibers are positioned in one of two layers, with one layer vertically above the other. In some embodiments, a two-dimensional FAU can have two or more optical fiber layers separated by a spacer layer. The two-dimensional FAU can be used to create a high fiber density optical interconnect for high density applications in optical communication. To achieve high yield from a two-dimensional FAU, the measured core pitch values can be within tolerance values. Since the FAU is manufactured on a micron scale, the core pitch values may require measurement accuracy and precision.

[0045] Figure 1A -C shows a view of an example two-dimensional optical fiber array unit (2D FAU) 100. Figure 1A The front view of the 2D FAU 100 is shown. The 2D FAU 100 includes a first optical fiber layer 110 positioned on a first substrate 152. In some embodiments, the first substrate 152 can be a substrate with V-grooves to create a V-grooved optical fiber array unit, while in other embodiments, the first substrate 152 can be a planar substrate. In some embodiments, the first substrate 152 can be a glass substrate, and in other embodiments, the first substrate 152 can be formed of other materials, such as ceramic materials, silicon-based materials, or metallic materials.

[0046] In some embodiments, the first optical fiber layer 110 can be adhered to the first substrate 152, for example, using an adhesive. In some embodiments, the adhesive can be epoxy resin, nanoparticles, glue, welding, or other adhesives for fixing the position of the first optical fiber layer 110 on the first substrate 152.

[0047] The 2D FAU 100 can further include a second optical fiber layer 120. The second optical fiber layer 120 can be positioned on one or more spacers 130. In some embodiments, one or more spacers 130 can be positioned on the first optical fiber layer 110. In this regard, one or more spacers 130 can be configured to separate the first optical fiber layer 110 and the second optical fiber layer 120.

[0048] In some embodiments, the second substrate 151 is positioned around the second optical fiber layer 120. In this regard, in some embodiments, the second substrate 151 can be a V-groove substrate such that each of the grooves in the second substrate 151 is around one of the optical fibers in the second optical fiber layer 120. In some embodiments, the second substrate 151 can be a planar substrate. In this regard, a layer of epoxy resin or other adhesive can be positioned to surround each optical fiber within the second optical fiber layer 120 such that the second optical fiber layer 120 maintains a desired spacing on the spacer layer 130.

[0049] In some embodiments, each of the first substrate 152 and the second substrate 151 can be configured as a V-groove substrate. In this regard, one or more spacers 130 can be configured to abut the surfaces of each of the first substrate 152 and the second substrate 151. In some embodiments, the V-grooves can be sized such that the optical fibers of each of the first optical fiber layer 110 and the second optical fiber layer 120 can fit within the V-grooves and can abut the one or more spacers 130. In some embodiments, the second substrate 151 can be a glass substrate, and in other embodiments, the second substrate 151 can be formed of other materials such as ceramic materials, silicon-based materials, or metallic materials.

[0050] In some embodiments, each of the first substrate 152 and the second substrate 151 can be configured to receive alignment pins 140. In some embodiments, the alignment pins 140 can extend along the body of each of the first substrate 152 and the second substrate 151 (e.g., longitudinally and parallel to the optical fibers) to align the first substrate 152 and the second substrate 151. In this regard, in some embodiments, to form the 2D FAU 100, the first optical fiber layer 110 can be positioned on the first substrate 152, and the second optical fiber layer 120 can be positioned on the second substrate 151. The alignment pins 140 can be positioned on the first substrate 152, and one or more spacers 130 can be positioned to abut and adhere to both the first substrate 152 and the first optical fiber layer 110. Subsequently, in some embodiments, the second substrate 151 and the second optical fiber layer 120 can be positioned to abut and adhere to the one or more spacers 130 and the alignment pins 140. In this regard, aligning the second substrate 151 on the alignment pins 140 will correctly align each optical fiber in the second optical fiber layer 120 relative to the optical fibers in the first optical fiber layer 110. Although a one-to-one alignment of the first and second optical fiber layers is shown, some embodiments contemplate that one or more of the optical fibers are offset relative to each other. In this regard, in some embodiments, the alignment pins 140 can be designed to vertically grade the optical fibers within the first optical fiber layer 110 and the second optical fiber layer 120.

[0051] Figure 1BA side view of the 2D FAU 100 is shown. In some embodiments, one or more spacers 130 may be configured to be positioned between a first fiber layer 110 and a second fiber layer 120 in more than one dummy fiber (but any material or structure may be used for the one or more spacers). Using more than one spacer may maintain the spacing of the fibers along the length of the 2D FAU 100.

[0052] In some embodiments, an epoxy resin 153 is positioned around the fibers of the 2D FAU 100. In some embodiments, the epoxy resin 153 fixes the positioning of the fibers within the first fiber layer 110 and the second fiber layer 120 along the length of the fibers. Additionally, the epoxy resin may provide a protective layer to protect the body of the fibers.

[0053] In some embodiments, as shown, the 2D FAU 100 may define an angled end face (see, for example, 100b, Figure 5 ). In this regard, each of the first substrate 152, the second substrate 151, and each fiber within the first fiber layer 110 and the second fiber layer 120 may define an angled end face. The angled end face may change the way in which a light beam reflects at the end face and may affect losses when coupling the 2D FAU to other components.

[0054] In some embodiments, the second substrate 151 may not extend along the entire length of the fibers of the second fiber layer 120. In this regard, the second substrate 151 may be configured as a cover for the 2D FAU 100.

[0055] In some embodiments, the fibers of the first fiber layer 110 and the second fiber layer 120 may be coupled to a data source 105. In some embodiments, the data source may provide optical data to each fiber within the 2D FAU 100.

[0056] Figure 1C A top view of the 2D FAU 100 without the second substrate is shown. Thus, as shown, the second fiber layer 120 may be positioned above one or more spacers 130, while the first fiber layer (e.g., 110, Figure 1B ) may be positioned directly below the second fiber layer 120.

[0057] In some embodiments, the alignment pins 140 may extend the length of the second substrate (e.g., 151, Figure 1B ) and, in other embodiments, the alignment pins 140 may extend the length of the first substrate 152.

[0058] Simply return Figure 1A, each optical fiber within the first optical fiber layer 110 and the second optical fiber layer 120 defines a core pitch value. In this regard, the position of each optical fiber can include a horizontal component and a vertical component. The horizontal and vertical components of each optical fiber can be measured relative to a reference optical fiber.

[0059] For illustration, Figure 2A a one-dimensional FAU 101 is shown in []. The one-dimensional FAU 101 includes a first optical fiber layer 110 positioned on a first substrate 152 and aligned with a second substrate 151. Each optical fiber within the FAU 101 defines a core pitch value. Figure 2B is shown Figure 2A a schematic illustration of the one-dimensional FAU 101 shown in []. Each of the optical fibers 1-6 of the FAU includes a core pitch measurement value 103 measured by a core pitch measurement device (e.g., 160, Figure 5 ), which is indicated by a measured horizontal component X' i and a measured vertical component Y' i , where i is the optical fiber number. In addition to the measured core pitch value 103, each optical fiber further includes a desired core pitch value 103', which includes a desired horizontal component X i and a desired vertical component Y I , where i is the optical fiber number.

[0060] A deviation from the desired horizontal component X i or the desired vertical component Y i results in a core pitch error, which in turn leads to a yield loss. Therefore, it may be desirable for the optical fibers within the optical fiber array unit to have a minimum deviation in each of the measured horizontal component X' i and the measured vertical component Y' i , because large deviations may render the optical fiber array unit unusable. It should be noted that since the optical fibers are adhered to the first substrate and / or the second substrate, the optical fibers cannot be repositioned after manufacturing.

[0061] The desired core pitch value 103' of each optical fiber can be based on a reference optical fiber. In the illustrated embodiment, the reference optical fiber can be optical fiber 1. In this regard, the measured core pitch value (X'1 and Y'1) of optical fiber 1 can also be the desired core pitch value (X1 and Y1) of optical fiber 1. Thus, in some embodiments, the measured and desired core pitch values of the other optical fibers (2-6) can be based on the reference optical fiber.

[0062] The desired core pitch value 103' of each of the optical fibers 1-6 can define a desired vertical component Y i aligned, for example, along a reference line 135. i, and can be the vertical component Y1 of the optical fiber 1 (e.g., the reference optical fiber). Therefore, the deviation from the reference line 135 can be referred to as dY i . In this regard, in order to minimize the vertical component Y i of the core pitch value, the cores of the optical fibers (1-6) (e.g., 113, Figure 2B ) can be aligned on the reference line 135. Although the core position can be determined by the position where the optical fiber adheres to the first substrate (e.g., 152), the manufacturing, splitting method, and / or the angle of the end face of the individual optical fibers may also contribute to the light beam (e.g., 115, 125) leaving the core of the optical fiber at the FAU air interface.

[0063] The desired horizontal component X i can be the distance between two adjacent optical fibers along the x-axis. In an exemplary embodiment, each of the optical fibers (1-6) in the first optical fiber layer is desirably spaced apart by C P . Therefore, the desired position of each optical fiber along the x-axis can be C P away from the corresponding adjacent optical fiber.

[0064] In the illustrated embodiment, the horizontal component X1 defined by the optical fiber 1 as the reference optical fiber is 0. Therefore, the desired horizontal component X i of the optical fibers 2-5 can be defined as (i-1)C P , where i is the optical fiber position.

[0065] Figure 2B The core pitch error of the reference optical fiber 2 is further illustrated. The desired position 110' of the core 113' of the optical fiber 2 can define the horizontal component X 2＝ C P , and the vertical component Y2 = 0. However, as shown, the core 113 of the optical fiber 2 deviates from the desired core pitch in both the horizontal component X'2 and the vertical component Y'2. As shown, the core 113 of the optical fiber 2 is positioned below the reference line 135, and thus, deviates from the desired vertical component Y2 = 0 by dY2. Therefore, the measured vertical component is Y'2 = 0 + dY2. Similarly, the core 113 of the optical fiber 2 is shifted by dX2 in the horizontal direction from the desired horizontal component X2 = C P . Therefore, the measured horizontal component X'2 = C P + dX2. In some embodiments, the core pitch error can be individually defined as the horizontal component dX and the vertical component dY in each direction, while in other embodiments, the core pitch error dR i can be defined as a single core pitch error determined by Equation 1:

[0066]

[0067] where dRi is the core pitch error, i is the optical fiber number, dX is the difference between the measured horizontal component and the desired horizontal component, and dY is the difference between the measured vertical component and the desired vertical component. The core pitch error dR i should be as small as possible to minimize the yield loss in the fiber optic array unit.

[0068] Subsequently, the core pitch error can be compared with the tolerance of the fiber optic array unit to determine whether the core pitch value of each optical fiber falls within the acceptable tolerance, enabling the acceptable manufacture of the fiber optic array unit.

[0069] Figure 2A The measurement method of the one-dimensional fiber optic array 101 shown in Figure 1A can be applied to the 2D FAU100 shown in Figure 3 A schematic diagram of a two-dimensional fiber optic array unit 102 is shown in which each optical fiber has a corresponding desired core pitch value and a measured core pitch value.

[0070] In Figure 3 the schematic diagram shown, optical fibers 1 - 6 include one fiber layer and optical fibers 7 - 12 include another fiber layer. As shown, compared with Figure 2A , optical fibers 1 - 6 can correspond to the second fiber layer 120 and optical fibers 7 - 12 can correspond to the first fiber layer 110.

[0071] In the illustrated embodiment, optical fiber 1 is a reference optical fiber. In this regard, the desired horizontal component X i and the desired vertical component Y i of each optical fiber are based on optical fiber 1. As shown, the desired core pitch value and the measured core pitch value of optical fiber 1 are equal. Therefore, the desired core pitch values of the other optical fibers can be defined based on the core pitch value of optical fiber 1. In the illustrated example, optical fiber 1 includes a measured horizontal component X'1 = 0 and a measured vertical component Y'1 = 0.

[0072] As discussed with reference to Figure 2B , each of the optical fibers 2 - 6 can have a desired vertical component Y i = 0. However, each of the optical fibers 7 - 12 can define a desired vertical component Y i = -S, where S is the desired vertical spacing between each optical fiber. As discussed with reference to Figure 2B , the desired horizontal component X i of each optical fiber can be spaced apart by C P distance. In this regard, the second fiber layer (1 - 6) is vertically aligned with the first fiber layer (7 - 12), and thus, the desired horizontal component of each of the optical fibers (7 - 12) corresponds to the desired horizontal component of the corresponding optical fibers 1 - 6 in the second layer.

[0073] Thus, as discussed, each of the optical fibers 1-6 can define a desired horizontal spacing X i =(i - 1)C P , where i is the position of the optical fiber relative to a reference optical fiber (e.g., optical fiber 1). In this regard, the optical fibers in the first optical fiber layer (e.g., 7-12) can have i values corresponding to the vertically aligned optical fibers. For example, optical fiber 10 can have an i value of 4 because optical fiber 10 is vertically aligned with optical fiber 4.

[0074] Figure 3 Also shown are each of the desired core pitch values 103' and the measured core pitch values 103 of the second optical fiber layer and the desired core pitch values 104' and the measured core pitch values 104 of each of the first optical fiber layers. As discussed with reference to Figure 2B , the core pitch error in each optical fiber should be within the tolerance value to ensure the quality of the optical fiber array unit.

[0075] Figure 4 A cross-sectional view of an exemplary optical fiber array unit FAU 200' is shown. FAU 200' includes a first optical fiber 110a within a first optical fiber layer 110 and a second optical fiber 120a within a second optical fiber layer 120. The first optical fiber 110a includes a first end face 114 configured to emit a first light beam 111. The second optical fiber 120a includes a second end face 124 configured to emit a second light beam 121. The positions of the emitted light beams (e.g., first light beam 111 and second light beam 121) are measured by a core pitch measuring device 160. The core pitch measuring device 160 can be configured to move relative to FAU 200'. In this regard, the core pitch measuring device 160 is configured to move from a first position that measures a first core pitch value of the first optical fiber 120a including a first horizontal component (e.g., X1) and a first vertical component (e.g., Y1) to a second position 160' that measures a second core pitch value of the second optical fiber 120a including a second horizontal component (e.g., X7) and a second vertical component (e.g., Y7).

[0076] The core pitch measuring device 160 can be configured to move vertically relative to FAU 200'. In the illustrated embodiment, the core pitch measuring device 160 can move along a line perpendicular to the bottom surface 299 of FAU 200' between the measurements of the first light beam 111 and the second light beam 121. It is noted that the end face 199 of FAU 200 extends perpendicular to the bottom surface 299 of FAU 200'. In this regard, the distances between the first end face 114 and the core pitch measuring device 160 and between the second optical fiber end face 124 and the core pitch measuring device 160' are the same, resulting in an accurate measurement.

[0077] In some embodiments, the FAU can be repositioned relative to the core pitch measuring device 160 instead of moving the core pitch measuring device 160 from a first position to a second position.

[0078] In the illustrated embodiment, the first end face 114 and the second end face 124 and thus the FAU 200' define a polishing angle of 90 degrees (relative to the bottom surface 299). In this regard, the first beam 111 and the second beam 121 respectively exit the first core of the first optical fiber 110a and the second core of the second optical fiber 120a without any refraction at the air - glass interface. Accordingly, the vertical component Y' of the core pitch value between the first optical fiber 110a and the second optical fiber 120a is accurately measured.

[0079] In some embodiments, as Figure 5 shown, the 2D FAU 200 can have an angled end face 100b. The angle α between the bottom surface 299 of the base 100a of the FAU 200 and the angled end face 100b can be measured. In some embodiments, the angle α can be greater than 0 degrees and less than 90 degrees. In some embodiments, the angle α can be greater than 80 degrees. In some embodiments, the angle α can be specified for the application of the 2D FAU 200. As noted herein, according to the previously described measurement method, the angle with the angled end face 100b can introduce an error into the core pitch value measured by the core pitch measuring device 160.

[0080] For explanation, the angled end face 100b causes refraction at the air - glass interface. Accordingly, the second beam 121 exits the angled end face 100b as a refracted second beam 115 instead of extending away from the angled end face 100b as an unrefracted second beam 115' as in the example with a 90 - degree polishing angle. Similarly, the first beam 111 exits the angled end face 100b as a refracted first beam 125.

[0081] Referring Figure 5 , when the core pitch measuring device 160 measures the first vertical component and the first horizontal component of the first beam 125 at the first position 160 and the core pitch measuring device 160 measures the second horizontal component and the second vertical component at the second position 160' (e.g., vertically displaced by a desired vertical distance between arrays, for example), the core pitch measuring device 160 does not measure the position of the cores of the respective optical fibers, but rather measures the horizontal and vertical components of the refracted beams (it is noted that the measurement positions are shown as stars). Generally, the first refracted beam 125 and the second refracted beam 115 can define the same horizontal component (e.g., X i ) as the non - refracted beam. However, the vertical component (e.g., Y i ) can deviate due to refraction.

[0082] Thus, in the illustrated embodiment, the measured vertical component spacing distance between the first refracted beam 125 and the second refracted beam 115 is indicated as h'. In other words, the measured vertical component distance h' represents the difference between the second vertical component of the second refracted beam 115 and the first vertical component of the first refracted beam 125. Due to the refraction at the angled end face 100b, the measured vertical component distance h' between the first refracted beam 125 and the second refracted beam 115 may be different from the actual vertical component Y' (or the adjusted vertical component) between the first optical fiber 110a and the second optical fiber 120a.

[0083] As discussed above, a small inaccuracy in the measurement of the core pitch value may result in a large and unacceptable core pitch error calculation, which may hinder the use of the fabricated FAU. Therefore, it is necessary to determine a way to accurately calculate the vertical component of the core pitch in a 2D FAU with an angled end face.

[0084] The measured vertical component distance h' and the angle α of the 2D FAU 200 can be used to determine the vertical component Y' between the first optical fiber 110a and the second optical fiber 120a. To accurately determine the actual vertical component Y' using the second optical fiber 120a as a reference, the angle β between the second beam 121 and the normal angle of the angled end face 100b is given by Equation 2:

[0085] β = 90 - α (2)

[0086] Using Snell's law, the angle γ between the second refracted beam 125 and the normal angle of the angled end face 100b can be calculated by Equation 3:

[0087]

[0088] where n0 is the refractive index of air and n1 is the refractive index of glass (e.g., the first substrate 152 and the second substrate 151).

[0089] The end face distance h between the first beam 111 and the second beam 121 parallel to the angled end face 100b can be calculated by Equation 4:

[0090]

[0091] The perpendicular distance p between the first refracted beam 125 and the second refracted beam 115 can be determined by Equation 5:

[0092]

[0093] The measured distance h' between the first refracted beam 125 and the second refracted beam 115 can be derived from Equations 4 and 5, resulting in Equation 6:

[0094]

[0095] Using Equation 6, the relationship between the measured vertical component distance h' and the actual vertical component Y' is determined in Equation 7:

[0096]

[0097] In an example embodiment, the FAU defines an angle α of 84°, and the measured vertical component distance h' is 108 microns. Thus, without correction, the measured vertical component of the core pitch is determined to be 108 microns. However, after considering the described variables, the actual vertical component Y' is calculated using Equation 7, and the actual vertical component is 108.6 microns.

[0098] Without this correction, an error of 0.6 microns in the measured vertical component distance may carry over to an error in the vertical component and further to a core pitch error. In some embodiments, the core pitch error (e.g., vertical and horizontal components) may need to be less than 1.5 microns. In this regard, in an example embodiment where the actual vertical component is not calculated, the overall core pitch error may be artificially increased by 0.6 microns. In some embodiments, the calculated error of 0.6 microns may reduce the yield of the 2D FAU 200 by 10 - 30%.

[0099] Thus, various example embodiments adjust the measurements of the core pitch measurement device to achieve an accurate determination as to whether the manufactured fiber optic array unit falls within an acceptable tolerance range.

[0100] In some embodiments, a wedge may be employed during core pitch measurement. However, due to the relative vertical positioning of the core pitch measurement device, a similar error occurs in the vertical component measurement. It is noted, however, that this measurement method requires different adjustments. Thus, some embodiments provide a second computational adjustment, as shown in Figure 6A -B. The adjustment may allow the core pitch measurement device 160 to maintain the same distance d between the core pitch measurement device 160 and the angled end face of the FAU between the first fiber layer and the second fiber layer. In the measurement correction shown in Figure 5 the distance d between the end face 100b and the core pitch measurement device changes from the first refracted beam 125 to the second refracted beam 115. In this regard, although the core pitch measurement device 160 may be focused for measuring the first refracted beam 125, the core pitch measurement device 160' may become defocused when moved to a second position to measure the second refracted beam 115.

[0101] In another example embodiment, to reduce the focusing error, the 2D FAU 200 may be positioned on the wedge 170. The wedge 170 may define a wedge angle δ measured between a wedge base 171 and a wedge face 172.

[0102] The base of the 2D FAU 100 (e.g., 100a, Figure 5 ) may be positioned on the wedge base 171. The wedge angle δ may be selected such that the sum of the wedge angle δ and the angle α is equal to 90 degrees. In this regard, the distance (e.g., d, Figure 6B ) between the first optical fiber 110a and the second optical fiber 120a at the core pitch measurement device 160 and the end face 100b is the same at the first position and the second position 160'. Accordingly, the core pitch measurement device 160 measures the vertical components of the first refracted beam 125 and the second refracted beam parallel to the end face, and thus measures the end face distance h when the 2D FAU 200 is positioned on the wedge 170. In this regard, Equation 4 may be used to determine the actual vertical component Y' between the first optical fiber 110a and the second optical fiber 120b. Thus, in this case, the actual vertical component Y' may be determined as Y' = h sin α.

[0103] Returning to the example where the angle α of the angled end face 100b is 84°, using the above equation, the actual vertical component Y' would be Y' = 0.99452h. If the 2D FAU 200 is positioned on a wedge 170 having a wedge angle δ of 6°, the end face distance h would be measured as 109.198 microns, and the actual vertical component Y' would be 108.6 microns. Thus, the end face h measurement results in an increase in error of nearly 0.6 microns.

[0104] As discussed with reference to Figure 3 , the actual vertical component Y' can be used to determine the core pitch value of the optical fiber and the core pitch error of the optical fiber when compared to a reference optical fiber.

[0105] Accordingly, traditional measurement methods for two-dimensional fiber array units can introduce significant errors in core pitch determination and thus in the determination of the quality of the fiber array unit. As previously described, when the measurement of the vertical component is incorrect, errors can occur in core pitch determination and thus a core pitch error results. In fact, in the absence of the corrected methods provided by the various example embodiments, errors in the vertical component (e.g., Y i ) due to inaccuracies in measuring the vertical components of the refracted beams (e.g., 115, 125) can cause FAUs within the error tolerance to be discarded or alternatively can cause FAUs outside the error tolerance to be sent to the customer.

[0106] Example Flow Chart

[0107] Figure 7 It is a flowchart showing an example method 300 for determining the core pitch value of an optical fiber based on a measured second horizontal component and an adjusted vertical component according to some embodiments discussed herein. At operation 310, a first vertical component corresponding to a first optical fiber is measured. In some embodiments, the first vertical component may be a reference measurement value. At operation 320, a first horizontal component corresponding to the first optical fiber may be measured. In this regard, the first vertical component measurement value and the first horizontal component measurement value may be regarded as the core pitch of the first optical fiber and may be obtained by a core pitch measuring device (it should be noted that although provided separately, the measurement values may also be obtained simultaneously).

[0108] At operation 330, a second vertical component corresponding to the optical fiber may be measured. At operation 340, a second horizontal component corresponding to the optical fiber may be measured (it should be noted that although provided separately, the measurement values may also be obtained simultaneously).

[0109] At operation 350, the angle of the angled end face of the optical fiber array unit may be determined. The angle may be obtained between the base (e.g., bottom surface) of the first substrate of the FAU and the angled end face of the FAU. In this regard, each end of the first optical fiber and the optical fiber may fall along the angle.

[0110] At operation 360, an adjusted second vertical component of the optical fiber is determined based on the angle of the angled end face, the measured first vertical component, and the measured second vertical component. In some embodiments, the adjusted second vertical component may be the actual vertical component Y', as described herein.

[0111] At operation 370, the core pitch value of the optical fiber is determined based on the measured second horizontal component and the adjusted second vertical component.

[0112] At operation 380, a core pitch error is determined based on the core pitch value, the desired second vertical component, and the desired second horizontal component.

[0113] Although the various operations are shown and described herein in a certain order Figure 7 the order of the operations may be changed in other embodiments. Additionally, although the various operations are shown and described herein Figure 7 certain operations may be omitted in some embodiments, and additional operations may be performed in some embodiments.

[0114] Figure 8is a flowchart showing an example method 400 for fabricating FAU and verifying that the FAU is within a threshold tolerance error according to some embodiments discussed herein. At operation 410, a two-dimensional FAU is fabricated that includes a first fiber layer having a first optical fiber and a second fiber layer having a second optical fiber. Notably, the FAU defines an end face in an angular configuration. In this regard, the angled end face of the FAU is in an angular configuration that is not 90 degrees relative to the bottom surface of the FAU. At operation 420, a first vertical component corresponding to the first optical fiber is measured. In some embodiments, the first vertical component may be a reference measurement. At operation 430, a first horizontal component corresponding to the first optical fiber may be measured. In this regard, the first vertical component measurement and the first horizontal component measurement may be regarded as the core pitch of the first optical fiber and may be obtained by a core pitch measuring device (notably, although provided separately, the measurements may also be obtained simultaneously together).

[0115] At operation 440, a second vertical component of the second optical fiber is measured. At operation 450, a second horizontal component of the second optical fiber is measured (notably, although provided separately, the measurements may also be obtained simultaneously together).

[0116] At operation 460, an adjusted second vertical component is determined based on the angle of the end face, the measured first vertical component, and the measured second vertical component. In some embodiments, the adjusted second vertical component is further determined based on the refractive index of the FAU and the refractive index of air.

[0117] At operation 470, a core pitch value of the second optical fiber is determined based on the measured second horizontal component and the adjusted second vertical component.

[0118] At operation 480, a core pitch error is determined based on the core pitch value of the second optical fiber and the desired core pitch position. In some embodiments, the desired core pitch position is based on the desired second vertical position and the desired second horizontal position of the core of the second optical fiber.

[0119] At operation 490, the core pitch error is compared with a threshold tolerance value. In some embodiments, if the core pitch error is greater than the threshold tolerance value, the FAU is discarded.

[0120] Although the various operations are shown and described herein in a certain order Figure 8 in, the order of the operations may be changed in other embodiments. Additionally, although the various operations are shown and described herein Figure 8 in, certain operations may be omitted in some embodiments, and additional operations may be performed in some embodiments.

[0121] Conclusion

[0122] Therefore, those skilled in the art will readily appreciate that the inventions disclosed herein admit of a wide range of utility and application. Without departing from the essence or scope of the present invention, many embodiments and adaptations, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the foregoing description and disclosure, in addition to those described herein. Accordingly, while the present invention has been described in detail herein in terms of its preferred embodiments, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for the purpose of providing a complete and enabling disclosure thereof.

[0123] The foregoing disclosure is not intended or should not be construed to limit the present invention or otherwise exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements.

Claims

1. A method for determining the core pitch value of an optical fiber positioned in a two-dimensional optical fiber array unit, the optical fiber array unit including a first optical fiber array layer and a second optical fiber array layer, the first optical fiber array layer including a first optical fiber defining a first end face, wherein the first end face is configured to emit a first light beam, and the second optical fiber array layer including the optical fiber defining a second end face, wherein the second end face is configured to emit a second light beam, wherein the first optical fiber array layer and the second optical fiber array layer are vertically spaced apart, and wherein the first end face and the second end face are disposed on an angled end face of the optical fiber array unit, wherein the angled end face extends from a base of the optical fiber array unit at an angle not perpendicular to a bottom surface of the base of the optical fiber array unit, the method comprising: Positioning the optical fiber array unit or one of at least one core pitch measuring device relative to each other to enable measurement of at least one core pitch value; Measuring, using the at least one core pitch measuring device, a first horizontal component and a first vertical component corresponding to the first optical fiber of the first optical fiber array layer; Measuring, using the at least one core pitch measuring device, a second horizontal component and a second vertical component corresponding to the optical fiber of the second optical fiber array layer; Determining an adjusted second vertical component of the optical fiber based on the angle of the angled end face, the measured first vertical component, and the measured second vertical component; And Determining the core pitch value of the optical fiber based on the measured second horizontal component and the adjusted second vertical component.

2. The method according to claim 1, wherein the first optical fiber and the optical fiber are parallel.

3. The method according to any one of claims 1 to 2, wherein the measurement direction of the at least one core pitch measuring device is positioned to be parallel to the bottom surface of the base of the optical fiber array unit.

4. The method according to any one of claims 1 to 3, wherein the angled end face of the two-dimensional optical fiber array unit has a glass cover.

5. The method according to any one of claims 1 to 4, wherein the adjusted second vertical component of the second light beam is provided by the following equation: where Y' is the adjusted second vertical component of the second light beam, α is the angle of the angled end face, h' is the measured vertical component distance between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the fiber array unit.

6. The method according to any one of claims 1 to 2 and 4, wherein the two-dimensional optical fiber array unit is positioned on a wedge, the wedge is positioned on a flat surface, and the wedge is configured such that the angled end face is perpendicular to the flat surface.

7. The method according to claim 6, wherein the adjusted second vertical component is provided by the equation: Y′ = hsin(α), where Y' is the adjusted second vertical component of the second exit pitch, α is the angle of the angled end face, and h is the distance between the measured first vertical component and the measured second vertical component.

8. The method according to any one of claims 1 to 7, the method further comprising determining a first core pitch value of the first optical fiber based on the measured first horizontal component and the measured first vertical component.

9. The method according to any one of claims 1 to 8, the method further comprising: Determine a core pitch error based on the adjusted second vertical component, the measured second horizontal component, the desired second horizontal component, and the desired second vertical component, wherein the desired second horizontal component and the desired second vertical component result in desired transmission characteristics.

10. The method according to claim 9, wherein the core pitch error is determined by the following equation: where dR i is the core pitch error, dX i is the difference between the desired second horizontal component and the measured second horizontal component, and dY i is the difference between the desired second vertical component and the adjusted second vertical component.

11. The method according to any one of claims 1 to 10, wherein the first end face and the second end face are coated with an anti-reflection coating.

12. The method according to any one of claims 1 to 11, the method further comprising: Relocating one of the two-dimensional fiber array unit or the at least one core pitch measuring device to effect a core pitch measurement of a second core pitch value.

13. A method for determining a core separation distance extending between a first optical fiber and a second optical fiber in a two-dimensional optical fiber array unit, the fiber array unit comprising a first optical fiber array layer and a second optical fiber array layer, the first optical fiber array layer comprising the first optical fiber, wherein the first optical fiber defines a first end face and is configured to emit a first light beam, and the second optical fiber array layer comprising the second optical fiber, wherein the second optical fiber defines a second end face and is configured to emit a second light beam, wherein the first optical fiber array layer and the second optical fiber array layer are vertically spaced apart, and wherein the first end face and the second end face are disposed on angled end faces of the fiber array unit, wherein the angled end faces extend from a base of the fiber array unit at an angle not perpendicular to a bottom surface of the base of the fiber array unit, the method comprising: Measuring a first vertical component of the first light beam using at least one core pitch measuring device; Measuring a second vertical component of the second light beam using the at least one core pitch measuring device; Determining a vertical separation between the measured first vertical component of the first light beam and the measured second vertical component of the second light beam; Determining an adjusted second vertical component of the second light beam based on the angle of the angled end face and the determined vertical separation; and Determining a core pitch error by comparing the adjusted second vertical component of the second light beam with a desired vertical component of the second light beam.

14. The method according to claim 13, wherein the first optical fiber and the second optical fiber are parallel.

15. The method according to any one of claims 13 to 14, wherein the at least one core pitch measuring device is configured to measure the first light beam and the second light beam in a manner parallel to the bottom surface of the base of the fiber array unit.

16. The method according to any one of claims 13 to 15, wherein the adjusted second vertical component of the second light beam is provided by the following equation: where Y' is the adjusted second vertical component of the second light beam, α is the angle of the angled end face, h' is the measured vertical component distance interval between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the fiber array unit.

17. The method according to claim 16, wherein the core separation value is a difference between the adjusted second vertical component and the measured first vertical component.

18. A method for determining the core pitch error of an optical fiber positioned in a two-dimensional optical fiber array unit, the optical fiber array unit comprising a first optical fiber array layer and a second optical fiber array layer, the first optical fiber array layer comprising a first optical fiber defining a first end face, wherein the first end face is configured to emit a first light beam, and the second optical fiber array layer comprising the optical fiber defining a second end face, wherein the second end face is configured to emit a second light beam, wherein the first optical fiber array layer and the second optical fiber array layer are vertically spaced apart, and wherein the first end face and the second end face are disposed on an angled end face of the optical fiber array unit, wherein the angled end face extends from a base of the optical fiber array unit at an angle not perpendicular to a bottom surface of the base of the optical fiber array unit, the method comprising: Positioning at least one core pitch measuring device such that a measurement direction of the at least one core pitch measuring device is parallel to the bottom surface of the base of the optical fiber array unit, wherein the at least one core pitch measuring device is configured to be at least movable vertically perpendicular to the bottom surface of the base of the optical fiber array unit; Measuring, using the at least one core pitch measuring device, a first horizontal component and a first vertical component corresponding to the first optical fiber; Measuring, using the at least one core pitch measuring device, a second horizontal component and a second vertical component corresponding to the optical fiber; Calculating an adjusted second vertical component of the optical fiber based on the angle of the angled end face, the measured first vertical component, and the measured second vertical component; And Determining the core pitch error based on the adjusted second vertical component, the measured second horizontal component, a desired second horizontal component, and a desired second vertical component, wherein the desired second horizontal component and the desired second vertical component result in a desired transmission characteristic.

19. The method according to claim 18, wherein the adjusted second vertical component of the second light beam is provided by the following equation: where Y' is the adjusted second vertical component of the second light beam, α is the angle of the angled end face, h' is the measured vertical component distance between the measured first vertical component and the measured second vertical component, n0 is the refractive index of air, and n1 is the refractive index of the angled end face of the fiber array unit.

20. The method according to claim 18, wherein the optical fiber array unit is positioned on a wedge, and the second adjusted vertical component is provided by the equation: Y′ = hsin(α), where Y' is the adjusted second vertical component, α is the angle of the angled end face, and h is the distance between the measured first vertical component and the measured second vertical component.

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