WO2019089221A1

WO2019089221A1 - Tuned high-density collimator and method for tuning

Info

Publication number: WO2019089221A1
Application number: PCT/US2018/056058
Authority: WO
Inventors: Dong GUI; Yao Li; Chen Xia; Shudong Xiao; Shiping Zhang; Andy Fenglei Zhou
Original assignee: Alliance Fiber Optic Products, Inc.
Priority date: 2017-10-31
Filing date: 2018-10-16
Publication date: 2019-05-09

Abstract

A tuned high-density collimator is disclosed herein. A collimating lens is secured to a mount and includes a first interface and defines a first central axis. A pigtail includes a ferrule secured to the mount and an optical fiber having a portion positioned within the ferrule. The ferrule defines a second central axis aligned with the first central axis of the collimating lens along a z-axis perpendicular to a y-axis. The optical fiber includes an end face at least partially defining a second interface. The first interface of the collimating lens and/or the second interface of the pigtail is planar and non-perpendicular to the z-axis. The collimating lens and the pigtail are rotationally oriented around the z-axis relative to each other such that a light pointing angle of an optical light path within the collimating lens is perpendicular to the y-axis.

Description

TUNED HIGH-DENSITY COLLIMATOR AND METHOD FOR TUNING

PRIORITY APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 62/579,396, filed on October 31, 2017, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

[0002] The present disclosure relates generally to micro-optical systems, and particularly relates to tuned high-density collimators and methods for tuning.

[0003] Micro-optical systems employ optical elements that typically range in size from a few microns to a few millimeters and are used in a variety of optical and optical- electrical technologies and applications that require a small foot print or small form factor. With the increasing miniaturization of many types of optical and optical-electrical devices and systems, increasing demands are being placed on the size, performance, and integration requirements of micro-optical systems.

[0004] An example application where micro-optical systems are seeing increased use and increasing demands on size, performance, and integration is optical telecommunications. As high-speed optical telecommunications and data communications evolve, multiple wavelength channels are becoming widely adopted even in short-distance data center applications. As a result, multiplexer/de-multiplexer (Mux/DeMux) devices that employ micro-collimators and optical wavelength filters are becoming an important component in optical modules, such as C-form factor pluggable (CFP) optical modules, to functionally combine/split multiple optical signals, each operating at a designated wavelength into/from a common input/output (I/O) optical fiber.

[0005] The ever-increasing demands for greater bandwidth are driving the telecommunications industry toward greater number of wavelength channels. Adding to this trend, the dimensions of the optical transceivers are decreasing dramatically, requiring increasingly smaller micro-optical beam collimators and pitches between adjacent channels to keep the size of wave-division multiplexing (WDM) devices as small as possible. Further, increasing demands for greater device reliability calls for the use of fabrication techniques that keep the optical components in the WDM device in relative alignment. In addition, the micro-optical beam collimators occupy significant space in WDM and largely define the device form factor while also playing a key role in device reliability and optical performance.

[0006] In this regard, FIG. 1 is a perspective view of a collimator assembly array 100. In particular, the collimator assembly array 100 includes a plurality of collimator assemblies 102(1)-102(3) (referred to generally as collimator assembly 102). Each collimator assembly 102 includes a collimator 104 and a wedge mount 106. The wedge mount 106 includes a left wedge 108A and a right wedge 108B. Alignment and tuning of the collimator 104 is accomplished by translating and/or rotating the left wedge 108A and right wedge 108B relative to one another. For example, the left wedge 108A and right wedge 108B may be rotated in opposite directions to alter the vertical alignment of the collimator 104. The wedge mount 106 provides flexibility in assembly of passive optical sub-assembly (POSA) and other optical assemblies, but limits the minimum width (PI) between adjacent collimators 104 in the collimator assembly array 100 and the minimum height (HI) of the array. For example, the wedge mount 106 creates a gap (H2) between a substrate 110 and a bottom of the collimator 102. Accordingly, the wedge mounts 106 and other similar mounts limit collimator density.

[0007] No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.

SUMMARY

[0008] The disclosure relates generally to micro-optical systems, and particularly relates to tuned high-density collimators and methods for tuning. One embodiment of the disclosure relates to a tuned collimator comprising a mount, a collimating lens, and a pigtail. The mount defines a vertical y-axis. The collimating lens is secured to the mount. The collimating lens includes a first interface and defines a first central axis. The pigtail includes a ferrule secured to the mount and an optical fiber having a portion positioned within the ferrule. The ferrule defines a second central axis aligned with the first central axis of the collimating lens along a z-axis perpendicular to the y-axis. The optical fiber includes an end face at least partially defining a second interface. The collimating lens and the pigtail form an optical light path from the end face of the optical fiber through the collimating lens. The first interface of the collimating lens and/or the second interface of the pigtail is planar and non-perpendicular to the z-axis. The collimating lens and the pigtail are rotationally oriented around the z-axis relative to each other such that a light pointing angle of the optical light path within the collimating lens is perpendicular to the y-axis. In other words, axial rotation of the ferrule relative to the collimating lens vertically aligns the optical light path within the collimating lens. Vertical alignment of the optical light path by rotation of the ferrule allows for collimator tuning without wedge mounts or other similar mounts, thereby allowing for a higher- density and lower profile configuration.

[0009] One embodiment of the disclosure relates to a tuned collimator comprising a mount, a collimating lens, and a pigtail. The mount has a top and a bottom and defines a vertical y-axis extending therebetween. The bottom of the mount is configured to be secured to a substrate. The collimating lens is secured to the mount. The collimating lens has a first front surface and a first back surface and defines a first central axis extending therebetween. The first back surface at least partially defines a first interface. The pigtail includes a ferrule secured to the mount and an optical fiber having a portion positioned within the ferrule. The ferrule has a second front surface and a second back surface and defines a second central axis extending therebetween. The second central axis of the ferrule is aligned with the first central axis of the collimating lens along a z- axis perpendicular to the y-axis. The optical fiber includes an end face at least partially defining a second interface. The collimating lens and the pigtail form an optical light path from the end face of the optical fiber through the first back surface and the first front surface of the collimating lens. At least one of the first interface of the collimating lens or the second interface of the pigtail is planar and non-perpendicular to the z-axis. The collimating lens and the pigtail are rotationally oriented around the z-axis relative to each other such that a light pointing angle of the optical light path within the collimating lens is perpendicular to the y-axis. [0010] A further embodiment includes a method for tuning a collimator. The method includes positioning a collimating lens to a mount of a collimator. The collimating lens has a first front surface and a second back surface and defines a first central axis extending therebetween. The mount has a top and a bottom and defines a vertical y-axis extending therebetween. The method further includes aligning a second central axis of a ferrule of a pigtail with the first central axis of the collimating lens along a z-axis perpendicular to the vertical y-axis. The ferrule has a second front surface and a second back surface and a second central axis extending therebetween. The method further includes rotating at least one of the pigtail or the collimating lens about the z-axis relative to each other to change a light pointing angle of an optical light path within the collimating lens from being non-perpendicular to the y-axis to being perpendicular to the y-axis. The optical light path extends from an end face of an optical fiber of the pigtail through the first back surface and the first front surface of the collimating lens. The optical fiber having a portion is positioned within the ferrule.

[0011] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0012] 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 understanding 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 embodiments, and together with the description serve to explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a perspective view of a collimator assembly array including wedge mounts.

[0014] FIG. 2 A is a perspective view of a square tube collimator.

[0015] FIG. 2B is a top view of the square tube collimator of FIG. 2A. [0016] FIG. 3A is a front view of a square tube collimator array of a plurality of the square tube collimators of FIGS. 2A-2B.

[0017] FIG. 3B is a top view of a micro-optical assembly including the square tube collimator arrays of FIG. 3A.

[0018] FIG. 4A is a top view of an aligned pigtail and a collimating lens with ideal cuts and alignment.

[0019] FIG. 4B is a top view of the aligned pigtail and collimating lens of FIG. 4A illustrating an optical light path therethrough.

[0020] FIG. 4C is a side view of the pigtail and collimating lens of FIG. 4B.

[0021] FIG. 4D is a diagram illustrating orientation of the pigtail of FIG. 4A.

[0022] FIG. 4E is a diagram illustrating orientation of the collimating lens of FIG. 4A.

[0023] FIG. 5A is a top view of a pigtail and collimating lens with a vertically imperfect cut and/or alignment before tuning.

[0024] FIG. 5B is a top view of the aligned pigtail and collimating lens of FIG. 5A illustrating an optical light path therethrough.

[0025] FIG. 5C is a side view of the pigtail and collimating lens of FIG. 5B.

[0026] FIG. 5D is a diagram illustrating orientation of the pigtail of FIG. 5A.

[0027] FIG. 5E is a diagram illustrating orientation of the collimating lens of FIG. 5A.

[0028] FIG. 6A is a top view of a pigtail and collimating lens with a vertically imperfect cut and/or alignment after tuning.

[0029] FIG. 6B is a top view of the aligned pigtail and collimating lens of FIG. 6A illustrating an optical light path therethrough.

[0030] FIG. 6C is a side view of the pigtail and collimating lens of FIG. 6B.

[0031] FIG. 6D is a diagram illustrating orientation of the pigtail of FIG. 6A.

[0032] FIG. 6E is a diagram illustrating orientation of the collimating lens of FIG. 6A.

[0033] FIG. 7A is a top view of a pigtail and collimating lens with a laterally imperfect cut and/or alignment before tuning. [0034] FIG. 7B is a top view of the aligned pigtail and collimating lens of FIG. 7A illustrating an optical light path therethrough.

[0035] FIG. 7C is a side view of the pigtail and collimating lens of FIG. 7B.

[0036] FIG. 7D is a diagram illustrating orientation of the pigtail of FIG. 7A.

[0037] FIG. 7E is a diagram illustrating orientation of the collimating lens of FIG. 7A.

[0038] FIG. 8A is a top view of a pigtail and collimating lens with a laterally imperfect cut and/or alignment after tuning.

[0039] FIG. 8B is a top view of the aligned pigtail and collimating lens of FIG. 8A illustrating an optical light path therethrough.

[0040] FIG. 8C is a side view of the pigtail and collimating lens of FIG. 8B.

[0041] FIG. 8D is a diagram illustrating orientation of the pigtail of FIG. 8A.

[0042] FIG. 8E is a diagram illustrating orientation of the collimating lens of FIG. 8A.

[0043] FIG. 9 is a front view of a triangular tube collimator array.

[0044] FIG. 10 is a front view of a hexagonal tube collimator array.

[0045] FIG. 11A is a side view of a v-groove collimator.

[0046] FIG. 11B is a front view of the v-groove collimator of FIG. 11A.

[0047] FIG. 12 is a flowchart illustrating processing steps for tuning a collimator.

DETAILED DESCRIPTION

[0048] Reference will now be made in detail to the present preferred embodiments, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. Cartesian coordinates are provided in some of the drawings for the sake of reference and for ease of discussion and are not intended to be limiting as to direction and orientation.

[0049] The terms "left," "right," "top," "bottom," "front," "back," "horizontal," "parallel," "perpendicular," "vertical," "lateral," "coplanar," and similar terms are used for convenience of describing the attached figures and are not intended to limit this description. For example, the terms "left side" and "right side" are used with specific reference to the drawings as illustrated and the embodiments may be in other orientations in use. Further, as used herein, the terms "horizontal," "parallel," "perpendicular," "vertical," "lateral," etc., include slight variations that may be present in working examples.

[0050] The disclosure relates generally to micro-optical systems, and particularly relates to tuned high-density collimators and methods for tuning. One embodiment of the disclosure relates to a tuned collimator comprising a mount, a collimating lens, and a pigtail. The mount defines a vertical y-axis. The collimating lens is secured to the mount. The collimating lens includes a first interface and defines a first central axis. The pigtail includes a ferrule secured to the mount and an optical fiber having a portion positioned within the ferrule. The ferrule defines a second central axis aligned with the first central axis of the collimating lens along a z-axis perpendicular to the y-axis. The optical fiber includes an end face at least partially defining a second interface. The collimating lens and the pigtail form an optical light path from the end face of the optical fiber through the collimating lens. The first interface of the collimating lens and/or the second interface of the pigtail is planar and non-perpendicular to the z-axis. The collimating lens and the pigtail are rotationally oriented around the z-axis relative to each other such that a light pointing angle of the optical light path within the collimating lens is perpendicular to the y-axis. In other words, axial rotation of the ferrule relative to the collimating lens vertically aligns the optical light path within the collimating lens. Vertical alignment of the optical light path by rotation of the ferrule allows for collimator tuning without wedge mounts or other similar mounts, thereby allowing for a higher- density and lower profile configuration.

[0051] FIGS. 2A-2B are views of a square tube collimator 200 (also referred to as a micro-optical system). In particular, FIG. 2A is a perspective view of a square tube collimator 200, and FIG. 2B is a top view of the square tube collimator 200 of FIG. 2 A. The tuned collimator (embodied as a square tube collimator 200) includes a mount (embodied as glass tube 202), a collimating lens 204, and a pigtail 206. The mount 202 defines a vertical y-axis. The collimating lens 204 is secured to the mount 202. The collimating lens 204 includes a first interface 208 (FIG. 2B) and defines a first central axis Al (not shown but coaxial with the z-axis). The pigtail 206 includes a ferrule 210 secured to the mount 202 and an optical fiber 212 having a portion positioned within the ferrule 210. The ferrule 210 defines a second central axis A2 (not shown but coaxial with the z-axis) aligned with the first central axis Al of the collimating lens 204 along a z-axis perpendicular to the y-axis. The optical fiber 212 includes an end face 214 at least partially defining a second interface 216. The collimating lens 204 and the pigtail 206 form an optical light path from the end face 214 of the optical fiber 212 through the collimating lens 204. The first interface 208 (FIG. 2B) of the collimating lens 204 and/or the second interface 216 (FIG. 2B) of the pigtail 206 is planar and non-perpendicular to the z-axis. The collimating lens 204 and the pigtail 206 are rotationally oriented around the z-axis relative to each other such that a light pointing angle of the optical light path within the collimating lens 204 (and exiting the collimating lens 204) is perpendicular to the y-axis. In other words, axial rotation of the pigtail 206 relative to the collimating lens vertically aligns the optical light path within the collimating lens 204. Vertical alignment of the optical light path by rotation of the pigtail 206 allows for collimator tuning without wedge mounts 106 (see FIG. 1) or other similar mounts, thereby allowing for a higher- density and lower profile configurations.

[0052] It is noted that the light pointing angle within the collimating lens 204 is in the range of 0 to 0.2 degrees, and in particular, between 0.01 and 0.1 degrees. The light pointing angle achieved by the high-density tuned collimator 200 of the present disclosure is far more accurate than other collimators which could only achieve a light pointing angle greater than 0.2 degrees, and in particular, about 0.5 degrees.

[0053] The high-density tuned collimator 200 (such as a square tube collimator and/or v-groove collimator) increase channel density (also referred to as port density). See U.S. Provisional Patent Application No. 62/423,364 and U.S. Patent Application No. 15/422,705, entitled "Micro-Optical Systems and Assemblies using Glass Tubes and Methods of Forming Same," which are incorporated herein by reference in their entireties. Accordingly, the increased port density and more compact form factor increases the signal transport channels within a given space, which in turn provides higher signal transport speed and broad bandwidth. Such collimators may be used in constructing a Receiver Optical Sub-Assembly (ROSA) and/or a Transmitter Optical Sub-Assembly (TOSA), such as in a passive optical sub-assembly (POSA) within a transceiver. The utilization of square glass tube 202 and/or V-groove in the assembly of collimators reduces the packing density of collimators in the device, thereby reducing the POSA form factor.

[0054] The glass tube 202 (e.g., cylindrical) has a front end 218A, a back end 218B (opposite the front end 218A), a left side 220A, and a right side 220B (opposite the left side 220A) a top side 222A, and a bottom side 222B (opposite the top side 222A). In particular, the glass tube 202 defines an x-axis that extends between and through the left side 220A and the right side 220B, a y-axis that extends between and through the top side 222A and the bottom side 222B, and a z-axis that extends between and through the front end 218A and the back end 218B. It is noted that the bottom side 222B may be mounted to a substrate. As used herein, the term "cylindrical" is used in its most general sense and can be defined as a three-dimensional object formed by taking a two-dimensional object and projecting it in a direction perpendicular to its surface. Thus, a cylinder, as the term is used herein, is not limited to having a circular cross-section shape but can have any cross-sectional shape, such as the square cross-sectional shape, triangular cross-sectional shape, hexagonal cross-sectional shape, etc.

[0055] The glass tube 202 includes a body 224 defining a central bore 226. In particular, the body 224 includes an inner surface 227 defining the central bore 226 with a round cross-sectional shape (although other cross-sectional shapes may be used) and an outer surface 228 defining a square cross-sectional shape (although other cross-sectional shapes may be used). In particular, the outer surface 228, including the left side 220A, right side 220B, top side 222A, and bottom side 222B, are each flat, perpendicularly oriented to form a square shape. The square cross-sectional shape provides for high- density, ease of manufacturability, and ease of assembly to a substrate, among other advantages. In certain embodiments, the bore 226 is centered within the body 224 of the glass tube 202 so that the central bore 226 is co-axial with the body 224 along central tube axis AT (not shown but coaxial with the z-axis). In other embodiments, it may be desirable to have the bore 226 off-center relative to a central axis of the body 224.

[0056] The glass tube 202 has an axial length L in the z-direction and widths WX and WY in the x-direction and y-direction, respectively. In certain embodiments, the length L is from 1 mm to 20 mm, or between 5 mm and 20 mm, or between 5 mm and 10 mm. In certain embodiments, WX and WY have a maximum dimension, or width, measured in a plane that is perpendicular to the tube central axis AT, that is in the range from about 0.1 mm to about 20 mm, or in the range from about 0.1 mm to about 10 mm, or in the range from about 0.125 mm to about 5 mm, or in the range from about 0.125 mm to about 2 mm. The central bore 226 has a diameter DB in the range from 50 microns to 1 cm, or more preferably 125 microns to 1.8 mm. In an example where the widths WX = WY = W, the diameter DB can be in the range (0.3)W < DB < (0.8) W.

[0057] The square tube collimator 200 further includes optical elements, such as the collimating lens 204 (also referred to as a c-lens), ferrule 210, etc., which can be secured to the glass tube 202 using a securing mechanism (e.g., an adhesive). The collimating lens 204 has a front surface 230A and a back surface 230B opposite thereto, and defines an optical axis OA (not shown but coaxial with the z-axis). In the example shown, the front surface 230A is convex while the back surface 230B is planar and angled (also referred to as tilted), such as in the x-z plane. However, in other embodiments the front surface 230A is planar. It is noted that the back surface 230B of the collimator 200 at least partially defines the first interface 208. In certain embodiments, the front surface 230A of collimating lens 204 can reside or protrude outside of the central bore 226. In other words, a front-end portion of the collimating lens 204 can extend slightly past the front end 218A of the glass tube 202. In certain embodiments, the collimating lens 204 can be formed as a gradient- index (GRIN) element that has a planar front surface 230A. The collimating lens 204 can consist of a single lens element while in another example it can consist of multiple lens elements. In the discussion below, the collimating lens 204 is shown as a single lens element for ease of illustration and discussion.

[0058] The ferrule 210 provides optical fiber support. The ferrule 210 includes a central bore 232 that runs between a front end and a back end along a ferrule central axis AF (not shown but coaxial with the z-axis), which in an example is co-axial with the tube central axis AT of the glass tube 202 and the optical axis OA of the collimating lens 204. The central bore 226 can include a flared portion 234 at the back end of the ferrule 210. The ferrule 210 includes a front surface 236A and a back surface 236B (opposite the front surface 236 A). [0059] An optical fiber 212 has a coated portion 238 and an end portion 240. The end portion 240 is bare glass (e.g., is stripped of the coated portion 238) and is thus referred to as the "bare glass portion." The bare glass portion 240 includes the polished end face 214 that defines a proximal end of the optical fiber 212. The bare glass portion 240 of the optical fiber 212 extends into the central bore 232 of the ferrule 210 at the back end of the ferrule 210.

[0060] The fiber optic pigtail 206 includes the ferrule 210, optical fiber 212, and securing element 244. In this way, the fiber optic pigtail 206 resides at least partially within the bore 226 adjacent the back end 218B of the glass tube 202. The securing element 244 (e.g., adhesive, a mechanical fastener, etc.) can be disposed around the optical fiber 212 at the back end of the ferrule 210 to secure the optical fiber 212 to the ferrule 210. The front surface 236A of the ferrule 210 and/or the end face 214 of the optical fiber 212 are planar and angled in the x-z plane (around the y-axis). In particular, the front surface 236A of the ferrule 210 and the end face 214 of the optical fiber 212 may be coplanar, and in certain embodiments, may be coplanar within 200 nm of each other, and in particular within 100 nm of each other. Further, the front surface 236A and/or end face 214 are axially spaced apart from the angled back surface 230B of the collimating lens 204 to define a gap 246 that has a corresponding axial gap distance DG.

[0061] The square tube collimator 200 includes the glass tube 202, the collimating lens 204, and the fiber optic pigtail 206. The glass tube 202 serves in one capacity as a small lens barrel that supports and protects the collimating lens 204 and the fiber optic pigtail 206, particularly the bare glass portion 240 and its polished end face 214. The glass tube 202 also serves in another capacity as a mount or mounting member that allows for the square tube collimator 200 to be mounted to a support substrate. In this capacity, at least one flat surface (e.g., bottom side 222B) serves as a precision mounting surface. In an example, the glass tube 202, the collimating lens 204, and the ferrule 210 are all made of a glass material, and further in an example, are all made of the same glass material. Making the glass tube 202, the collimating lens 204 and the ferrule 210 out of a glass material has the benefit that these components will have very close if not identical coefficients of thermal expansion (CTE). This feature is particular advantageous in environments that can experience large swings in temperature. [0062] In an example, the optical elements used in micro-optical systems are sized to be slightly smaller than the diameter of the bore 226 (e.g., by a few microns or tens of microns) so that the optical elements can be inserted into the bore 226 and be movable within the bore 226 to a select location. In an example, the select location is an axial position where optical element resides for the micro-optical system to have optimum or substantially optimum optical performance. Here, substantially optimum performance means performance that may not be optimum but that is within a performance or specification for the micro-optical system. In another example, the optical elements have a clearance with respect to the bore 226 in the range of a few microns (e.g., 2 microns or 3 microns) to tens of microns (e.g., 20 microns up to 50 microns). A relatively small value for the clearance allows for the optical elements 110 to be well-aligned with a central bore axis AB (not shown but coaxial with the z-axis), e.g., to within a few microns (e.g., from 2 microns to 5 microns).

[0063] The optical elements and the support/positioning elements can be inserted into and moved within bore 226 to their select locations using micro-positioning devices. The optical elements and the support/positioning elements can be secured within the bore 226 using a number of securing techniques. One example securing technique uses a securing feature that is an adhesive (e.g., a curable epoxy). Another securing technique uses a securing feature that involves a glass soldering to create one or more glass solder points. Another securing technique uses glass welding to create a securing feature in the form of one or more glass welding points. A combination of these securing features can also be employed. Thus, one or more optical elements can be secured within the bore 226 using a securing feature and can also be supported and/or positioned using one or more support/positioning elements. The non-adhesive securing techniques allow for the micro- optical systems disclosed herein to remain free of adhesives so that, for example, micro- optical systems can consist of glass only.

[0064] FIG. 3A is a front view of a square tube collimator array 300 of a plurality of the square tube collimators 200(l)-200(3) of FIGS. 2A-2B. The square tube collimators 200(l)-200(3) (referred to generally as square tube collimator 200) provide high density, and in particular, a higher density than the collimator array 100 using the wedge mounts 106 of FIG. 1. In other words, the tuned collimators (or micro-optical systems) disclosed form square tube collimator arrays 300 (or micro-optical assemblies) that require a small form factor.

[0065] The array 300 has a pitch P2 in the x-direction (e.g., of approximately p = WX). In certain embodiments, the pitch P2 is about 2 mm or between 0.1 mm to 10 mm, which is less than the PI of the collimator array 100 of FIG. 1. The ability to form compact arrays 300 of micro-collimators 200 is advantageous considering that some complex wave division multiplexing (WDM) micro-optical assemblies can have tens or even hundreds of channels. Further, the array 300 has a minimized height compared to the collimator array 100 of FIG. 1.

[0066] The one or more flat sides 214A-216B of glass tubes 202 also provide an advantage in configuring the array 300 by being able to place sides of adjacent collimators 200 in close proximity to one another and secure them to each other as well as to an upper surface of a support substrate 302. Once a first collimator 200 is properly aligned on the support substrate 302 (e.g., relative to a reference or alignment feature thereon), then the other collimators 200 can be added immediately adjacent the first aligned collimator 200. As explained in more detail below, each collimator 200 may be individually tuned.

[0067] After alignment, the array 300 of collimators 200 can be held together by an adhesive (e.g., a UV curable adhesive) that wicks into gaps 303 between adjacent glass tubes 202. In an example, the adhesive can then be activated by UV light. The collimators 200 can also be formed as a stand-alone array 300 and then attached to an upper surface of a support substrate 302. The collimators 200 that make up the array 300 can also be secured to one another using at least one of the laser welding process and the glass soldering process as described above to form an adhesive-free array 300. A gap is shown between adjacent collimators 200 in FIG. 3A for ease of illustration and, in practice, the adjacent collimators 200 may be much closer to each other with space provided for, for example, an adhesive, or may be in contact with each other.

[0068] FIG. 3B is a top view of a micro-optical assembly 304 including the square tube collimator arrays 300 of FIG. 3A. Once again, a gap is shown between adjacent collimators 200(1), 200(3), and collimators 200(2), 200(4) for ease of illustration and, in practice, the adjacent collimators 200(1), 200(3), and 200(2), 200(4) may be much closer to each other with space provided for, for example, an adhesive, or may be in contact with each other. In general, the micro-optical assembly 304 comprises at least one collimator 200 supported on an upper surface 306 of the support substrate 302. In an example, the micro-optical assembly 304 can include a housing 308 that defines a WDM module. In an example, the WDM module can have a small form factor as defined by length (e.g., in the range of 30mm to 41 mm), width (e.g., in the range of 14 mm to 28 mm), and height (within the range of 5 mm to 6 mm).

[0069] The particular example of micro-optical assembly 304 is in the form of a four- channel WDM device that employs five of the micro-collimators 200 disclosed herein and so is referred to hereinafter as the WDM micro-optical assembly 304. It is noted that a more basic WDM micro-optical assembly 304 can employ only three micro-collimators 200 and is used to separate or combine two wavelengths. Likewise, more complicated WDM micro-optical assemblies 304 can employ many more micro-collimators 200 to separate or combine many more wavelengths besides two wavelengths or even four wavelengths (e.g., tens or even hundreds of different wavelengths). In examples, the WDM channels can be dense WDM (DWDM) channels or coarse WDM (CWDM) channels. Other types of micro-optical assemblies 304 besides the WDM micro-optical assembly described herein can also be formed using the basic techniques described herein. For example, the micro-optical assembly 304 can be used to form many types of free-space optical fiber devices, as well as compact variable optical attenuators, switches, optical amplifiers, taps, optical couplers/splitters, optical circulators, optical isolators, optical time-domain reflectometer (OTDRs), etc.

[0070] In an example, the support substrate 302 is made of glass (e.g., quartz) or sapphire. In another example, the support substrate 302 is made of a glass that is receptive to the formation of glass bumps. In other examples, the support substrate 302 can be made of stainless steel or silicon, a low-CTE metal alloy (e.g., having a CTE of < 10 ppm/°C, or more preferably CTE < 5 ppm/°C, or even more preferably CTE < 1 ppm/°C). Examples of metal alloys having such a low CTE include the nickel-iron alloy 64FeNi also known in the art under the registered trademarked INVAR® alloy or the nickel-cobalt ferrous alloy known in the art under the registered trademark KOVAR® alloy. In an example, the upper surface 306 is precision polished to be flat to within a tolerance of 0.005 mm so that the collimators 200 can be precision mounted to the upper surface using the bottom side 216B. As discussed above, the bottom side 216B can be processed (e.g., polished, including laser performing laser polishing) to a tolerance similar to that of the upper surface 306 of the support substrate 302. In an example, the support substrate 302 includes one or more reference features, such as alignment fiducials, for positioning and/or aligning the micro-collimators 200 and other optical components (e.g., optical filters, other micro-collimators, etc.).

[0071] The micro-collimators 200 are individually denoted 200P and 200(1), 200(2), 200(3), and 200(4) and are arranged as shown in FIG. 3B. The micro-collimator 200P serves as an input/output (I/O) port for a multi-wavelength light 310 having wavelengths λι to λ4 while the micro-collimators 200(l)-200(4) (referred to generally as micro- collimators 200) serve as the four individual channel ports. The I/O micro-collimator 200P and the first micro-collimator 200(1) are disposed facing each other along a first axis. The micro-optical assembly 304 also includes four optical filters 312(1)-312(4) (referred to generally as optical filters 312) operably arranged relative to the collimators 200 and respectively configured to transmit wavelengths

, and %\ and reflect the other wavelengths. The first optical filter 312(1) is disposed between the I/O micro- collimator 200P and the first micro-collimator 200(1) and defines a second axis along which is disposed the second optical filter 312(2) and the second micro-collimator 200(2). The second optical filter 312(2) defines a third axis along which is disposed the third optical filter 312(3) and the third micro-collimator 200(3). The third optical filter 312(3) defines a fourth axis along which is disposed the fourth optical filter 312(4) and the fourth micro-collimator 200(4).

[0072] In the DeMux operation, the multi-wavelength light 310 exits the I/O micro- collimator 200P that defines the I/O port and travels towards the first optical filter 312(1). The first optical filter 312(1) transmits the wavelength λι to the first micro-collimator 200(1) along the first axis and reflects the remaining wavelengths

and

of multi- wavelength light 310 along the second axis. This reflected multi-wavelength light 310 is then incident upon the second optical filter 312(2), which transmits the wavelength λι to the second micro-collimator 200(2) and reflects the remaining wavelengths λ₃ and %\ of multi-wavelength light 310 along the third axis. This process is repeated for the remaining two optical filters 312(3) and 312(4) and micro-collimators 200(3) and 200(4) along the third and fourth axes so that the wavelength components λι, λ₂, λ₃, and %\ of the multi-wavelength light 310 are distributed to their respective collimators 200(l)-200(4). In the DeMux operation, the direction of the light 310 is reversed and the individual wavelengths λι, λ₂, λ₃, and %\ from the individual micro-collimators 200(l)-200(4) are recombined by the optical filters 312(1)-312(4) into I/O micro-collimator 200P.

[0073] The dimensions WX, WY and DB of the glass tubes 202 of the micro- collimators 200 may facilitate determination of the position of each wavelength channel on the support substrate 302. The precision fabrication of the glass tubes 202 for the collimators 200 provides several advantages when fabricating optical assemblies such as the WDM micro-optical assembly described herein. For example, the distance between the bottom side 216B and axis of the bore 226 can be selected to define a precise height and in-plane positioning of the optical axis and of the Gaussian optical beam associated with the given micro-collimator 200.

[0074] The transparent nature of the glass tube 202 facilitates machine-vision-based assembly of the micro-optical assembly 304, such as by being able to view one or more reference features (e.g., alignment fiducials) on the substrate 302 through the glass tube 202. The transparent nature of the glass tube 202 also allows for visual inspection of the optical elements and support/positioning elements supported within the bore 226 of the glass tube 202 for reliability (e.g., inspecting the adhesive or securing features) or to control the gap distance between adjacent optical elements or the support/positioning elements by direct observation of the gap during assembly. In an example, the micro- collimators 200 and optical filters 312 can be secured to the upper surface 306 of the glass support substrate 302 using an adhesive, glass soldering or glass welding using a laser. A combination of these different securing techniques can also be employed. In an example, no adhesive is used in securing the collimators 200 and optical filters 312 to the upper surface 306 of the support substrate 302. A no-adhesive embodiment of the micro- optical assembly 304 may be preferred in cases where uncertainty in the reliability of the adhesive is a concern.

[0075] FIGS. 4A-4E are views illustrating alignment of a pigtail 206(1) and collimating lens 204(1). In particular, FIG. 4 A is a top view of an aligned pigtail 206(1) and a collimating lens 204(1) with ideal cuts and alignment. In this ideal situation, the first interface 208(1) of the collimating lens 204(1) and the second interface 216(1) of the pigtail 206(1) are parallel to each other with the same tilted angles a. Both of the pigtail 206(1) and collimating lens 204(1) may be manufactured to have a tilted angle (e.g., eight degree) to reduce induced return signals. In particular, when emitting a light signal from the pigtail 206(1) to the collimating lens 204(1), the pigtail 206(1) includes an incident angle ΘΙΝ I and a refraction angle θουτ ι and the collimating lens 204(1) includes an incident angle ΘΙΝ 2 and a refraction angel θουτ i .

[0076] As illustrated, k₀ is the unit vector representing the transfer direction of light within the pigtail, k₁ is the unit vector representing the transfer direction of light within the air gap between the pigtail and the collimating lens, and k₂ is the unit vector representing the transfer direction of light within the collimating lens 204(1). The unit vector k₂ includes a light pointing angle (also referred to as a beam pointing angle) relative to the z-axis within the collimating lens 204(1). The indices of refraction of both glass components of pigtail 242(1) and collimating lens 204(1) are written as n. The normal direction of the first interface of the first glass component of the pigtail 206(1) is s_l5 and the normal direction of the second interface of the collimating lens 204(1) is s₂. As explained in more detail below, the collimator 200 is tuned to ensure the light pointing angle of is within the x-z plane (also referred to as the substrate plane) or without y component For simplicity, the axis direction of the pigtail (or the direction of

the incoming light) is along the z-axis such that

[0077] It is noted that the travel of optical light across different media interface obeys Snell's law as in Equation 1 below in which

and are the media index of

refraction on the sides of the interface, are the incident angle and the

reflected angle respectively.

[0078] The vector form of light refraction across an interface could be written as in Equation 2 below, in which n_in and n_out are the media index of refraction on sides of the interface, 9_in and 9_0Ut are the incident angle and the reflected angle respectively. v_in and v_out are light direction vector before and after refraction with interface normal vector

[0079] Applying Equation 2 on the first and second interface of the collimator system with surface normal direction and produces:

[0080] The combination of Equations 3 and 4 produces Equation 5 below:

[0081] With constant and

being positive, this equation indicates how the outgoing light pointing angle

changes with the pointing angle of the incoming light , and the normal direction of

the tilted surfaces and in the x-z plane.

[0082] The incident angle ΘΙΝ I from air gap 246 into the collimating lens 204(1) is the same as the refraction angle from pigtail 206(1) into the air gap 246. The

pointing angle or pointing direction of the light within the collimating lens k₂ is the same as the original light direction k₀. As long as the direction of light inside the pigtail k₀ is in plane of substrate (X-Z plane), the outgoing light k₂ is in the plane of substrate without any pointing angle issue.

[0083] FIGS. 4B-4C illustrate an optical light path 400(1) through the pigtail 206(1) and collimating lens 204(1). The optical light path 400(1) is perfectly aligned with no deviation in the x, y, or z direction. FIG. 4D is a diagram illustrating orientation of the pigtail of FIG. 4A, and FIG. 4E is a diagram illustrating orientation of the collimating lens of FIG. 4A. As shown, there is no misalignment of the pigtail 206(1) or the collimating lens 204(1).

[0084] In certain embodiments, assembling the collimator 200(1) includes sliding the collimating lens 204(1) into the glass tube 202 (shown in FIGS. 2A-2B). Once secured within the glass tube 202, the pigtail 206(1) is slid into the glass tube 202 from the other side of the glass tube 202. The angled back surface 230B (shown in FIGS. 2A-2B) of the collimating lens 204(1) is used as a reference to align the pigtail 206(1) to ensure both the first interfaces 208(1) of the collimating lens 204(1) and the second interface 216(1) of the pigtail 206(1) are parallel with the air gap 246 in between. However, due to tolerance variations or other inaccuracies, the pigtail 206(1) and/or collimating lens 204(1) may not be perfectly cut and/or aligned. Such deviations require further tuning to compensate for these inaccuracies, as discussed in more detail below.

[0085] FIGS. 5A-5E are views of a pigtail 206(2) and collimating lens 204(2) with a vertically imperfect cut and/or alignment before tuning. In particular, FIG. 5A is a top view of a pigtail and collimating lens with a vertically imperfect cut and/or alignment before tuning. Oftentimes it is difficult to manufacture or/and position both collimating lens 204(2) and pigtails 206(2) inside the glass tube 202 accurately, which may lead to some imperfections either in sizes or tilted angles (e.g., due variation within tolerance range). This may lead to deviation of the beam direction, also referred to as pointing angle offset.

[0086] One such type of pointing angle offset, as shown in FIG. 5A, is rotational misalignment out of the x-z plane (around the y-axis) or vertical misalignment. For example, the collimating lens 204(2) may be rotationally misaligned or have an imperfect cut. As a result, the collimating lens 204(2) may be rotationally misaligned within the glass tube 202 (shown in FIGS. 2A-2B) out of the x-z plane by an angle of Δφ_α around the z-axis. Due to this rotational misalignment, the normal direction of the second air- glass interface s is changed by Δ around the z-axis, and has a non-zero vertical

component out of the x-z plane. In this situation, since originally there is no y component of light vector in the air gap the light vector pointing out of x-z plane per

Equation 5 above.

[0087] FIGS. 5B-5C illustrate an optical light path 400(2) through the pigtail 206(2) and collimating lens 204(2). The optical light path 400(2) is misaligned with deviation in the y direction. FIG. 5D is a diagram illustrating orientation of the pigtail 206(2) of FIG. 5A, and FIG. 5E is a diagram illustrating orientation of the collimating lens 204(2) of FIG. 5A. As shown, there is no misalignment of the pigtail 206(2), but there is misalignment of the collimating lens 204(2). In particular, the collimating lens 204(2) is rotationally misaligned about the z-axis.

[0088] FIGS. 6A-6E are views of a pigtail 206(2) and collimating lens 204(2) with a vertically imperfect cut and/or alignment after tuning. FIG. 6A is a top view of a pigtail 206(2) and collimating lens 204(2) with a vertically imperfect cut and/or alignment after tuning. As noted above, the square tube collimators 200 (shown in FIGS. 2A-2B) are devoid of the wedge mount 106 illustrated in FIG. 1, and thus require a different mechanism for controlling the beam pointing angle.

[0089] To tune the pointing direction of the outgoing light back into the x-z plane (to cancel its y component), the direction of the light vector in the air gap 246 should be

rotated (around the z-axis) in the reverse direction (similar to Equation 4 above) as in Equation 6 below.

[0090] Rotational adjustment of light vector

requires a rotational change of surface normal on the reverse direction as the (see Equation 3 above) as in

Equation 7 below.

[0091] To compensate the rotational misalignment of the collimating lens 204(2) around the z-axis, the pigtail 206(2) may be rotated around the z-axis in the same direction. Alternatively, when a beam profiler is used to monitor the pointing angle offset in the practice, a positive offset of the pointing angle in the y direction could be corrected by counter-clockwise rotating the collimating lens 204(2) and/or clockwise rotating the pigtail 206(2) about the z-axis, such as when facing the front (with the collimating lens 204(2) in front of the pigtail 206(2)). In the same manner, the negative offset of the pointing angle in the y direction could be corrected by clockwise rotating the collimating lens 204(2) and/or counter-clockwise rotating the pigtail 206(2) (as per Equation 5 above).

[0092] Rotating only the collimating lens 204(2) or the pigtail 206(2) may provide an upward limit on altering the y component of above) as in

Equation 8 below.

[0093] For example, at standard tilted angle of and with glass material index

of refraction n Any observed pointing angle offset values in

Y component beyond this boundary would require tuning of the light propagation direction k₀ within the pigtail 206(2) simultaneously with the collimating lens 204(2).

[0094] FIGS. 6B-6C illustrate an optical light path 400(2)' through the pigtail 206(1) and collimating lens 204(2). The optical light path 400(2)' is aligned without any deviation in the y direction. FIG. 6D is a diagram illustrating orientation of the pigtail 206(2) of FIG. 6A, and FIG. 6E is a diagram illustrating orientation of the collimating lens 204(2) of FIG. 6A. As shown, the pigtail 206(2) has been rotated to adjust alignment relative to the collimating lens 204(2). Accordingly, there is no misalignment of the pigtail 206(2) in the x, y, or z direction. In other words, the light pointing angle

is within the x-z plane or without y component

[0095] This methodology applies to cases of inaccurate pointing of the collimating lens 204(2) and/or the pigtail 206(2) in the orientation around the z-axis due to assembly or size inaccuracies, inaccurate cut of the angled surface of the collimating lens 204(2) and/or pigtail 206(2) out of the x-z plane, fiber off center of the collimator 200 out of the x-z plane, or any combination thereof.

[0096] FIGS. 7A-7E are views of a pigtail and collimator lens with a laterally imperfect cut and/or alignment before tuning. In particular, FIG. 7A is a top view of a pigtail and collimating lens with a laterally imperfect cut and/or alignment before tuning. Oftentimes it is difficult to manufacture or/and position both collimating lens 204(2) and pigtails 206(2) inside the glass tube 202 accurately, which may lead to some imperfections either in sizes or tilted angles (e.g., due variation within tolerance range). This may lead to deviation of the beam direction, also referred to as pointing angle offset.

[0097] Another type of pointing angle offset, as shown in FIG. 7A, is rotational misalignment within the x-z plane or horizontal misalignment. For example, the collimating lens 204(3) may be rotationally misaligned in the x-z plane by an angle of ΔΘ around the y-axis. As a result, the normal direction of the second air-glass interface is changed by ΔΘ (around the y-axis), but still in the x-z plane. As long as both the surface normal vectors and in the x-z plane without y components, the light

vectors remain in the x-z plane without y component as (see Equation 4 above).

[0098] FIGS. 7B-7C illustrate an optical light path 400(3) through the pigtail 206(3) and collimating lens 204(3). The optical light path 400(3) is misaligned with deviation around the y-axis (within the x-z plane). FIG. 7D is a diagram illustrating orientation of the pigtail of FIG. 7A, and FIG. 7E is a diagram illustrating orientation of the collimating lens of FIG. 7A. As shown, there is no misalignment of the pigtail 206(3), but there is misalignment of the collimating lens 204(3). In particular, the collimating lens 204(3) is rotationally misaligned about the y-axis.

[0099] FIGS. 8A-8E are views of a pigtail 206(3) and collimating lens 204(3) with a laterally imperfect cut and/or alignment after tuning. In particular, FIG. 8A is a top view of a pigtail 206(3) and collimating lens 204(3) with a laterally imperfect cut and/or alignment after tuning. In such a circumstance, the collimator 200 is rotated about the y- axis to rotationally adjust the collimator 200 in the substrate plane x-z to compensate for the pointing angle offset. In this way, the collimator 200 is usually vertically aligned before the collimator is horizontally aligned, because rotating the pigtail 206(3) and/or collimating lens 204(3) about the z-axis may alter horizontal alignment (in the x- direction) of the light pointing angle as well as vertical alignment (in the y-direction) of the light pointing angle.

[00100] FIG. 8B-8C illustrate an optical light path 400(3)' through the pigtail 206(3) and collimating lens 204(3). The optical light path 400(3)' is aligned without any deviation in the y direction. FIG. 8D is a diagram illustrating orientation of the pigtail of FIG. 8A, and FIG. 8E is a diagram illustrating orientation of the collimating lens of FIG. 8A. As shown, the pigtail 206(2) and collimating lens 204(3) have been rotated to adjust alignment relative to the collimating lens 204(3). Accordingly, there is no misalignment of the optical path within the collimating lens in the x, y, or z direction.

[00101] This methodology applies to cases of inaccurate pointing of the collimating lens 204(3) and/or the pigtail 206(3) in the orientation around the y-axis due to assembly or size inaccuracies, inaccurate cut of the angled surface of the collimating lens 204(3) and/or pigtail 206(3) in of the x-z plane, fiber off center of the collimator 200 out of the x-z plane, or any combination thereof.

[00102] It is noted that the collimator 200 discussed in FIGS. 4A-8E above may also be tuned by altering the gap distance DG. In other words, translating the pigtail 206 and/or collimating lens 204 toward or away from each other may alter the light pointing angle within the collimating lens 204.

[00103] FIG. 9 is a front view of a triangular tube collimator array 900. The triangular tube collimator array 900 includes five collimators 902(l)-902(5) (referred to generally as collimators 902), although fewer or more collimators 902 may be used. The collimators 902 are the same as those discussed above with respect to FIGS. 2A-3B except where otherwise noted. Each collimator 902 includes a glass tube 202' with a triangular cross-section. In this way, the first collimator 902(1), third collimator 902(3), and fifth collimator 902(5) are oriented in the same direction around the z-axis. The second collimator 902(2) and fourth collimator 902(4) are oriented in the same direction as each other, but rotated about the z-axis. This minimizes the pitch between adjacent collimators 902. Epoxy 904 secures the collimators 902 to the substrate 302 and to each other. It is anticipated that the collimators 902 are each individually tuned and aligned, and then the epoxy 904 is applied. In particular, the collimators 902 are tuned as described above with respect to FIGS. 4A-8E.

[00104] FIG. 10 is a front view of a hexagonal tube collimator array 1000. The hexagonal tube collimator array 1000 includes five collimators 1002(1)-1002(5) (referred to generally as collimators 1002), although fewer or more collimators 1002 may be used. The collimators 1002 are the same as those discussed above with respect to FIGS. 2A-3B except where otherwise noted. Each collimator 1002 includes a glass tube 202" with a hexagonal cross-section. In this way, collimators 1002 may be stacked on top of one another. In other words, the first collimator 1002(1) is stacked on top of and between the third collimator 1002(3) and the fourth collimator 1002(4). Further, the substrate 302' is grooved to receive the hexagonal collimators 1002 for ease of manufacture. Epoxy 1004 secures the collimators 1002 to the substrate 302' and to each other. It is anticipated that the collimators 1002 are each individually tuned and aligned, and then the epoxy 1004 is applied. In particular, the collimators 1002 are tuned as described above with respect to FIGS. 4A-8E.

[00105] FIG. 11A is a side view of a v-groove collimator 1100, and FIG. 11B is a front view of the v-groove collimator of FIG. 11A. The collimator 1100 is the same as those discussed above with respect to FIGS. 2A-3B except where otherwise noted. The collimators 1100 are tuned as described above with respect to FIGS. 4A-8E.

[00106] The collimator 1100 includes a collimating lens 204 (e.g., a glass or silica collimating lens), a fiber optic pigtail 206 and a groove 1104 (e.g., a generally V-shaped groove) formed in a mount 1102. The collimating lens 204 and the fiber optic pigtail 206 are disposed in the groove 1104. The collimating lens 204 is configured to receive a light signal provided to the WDM multiplexer/demultiplexer from an external optical transmission system or provide a light signal multiplexed or demultiplexed by the WDM to an external optical transmission system. The collimating lens 204, for example, may be configured to receive a light signal from a fiber optic element for multiplexing or demultiplexing and/or to provide a multiplexed or demultiplexed light signal to an external fiber optic element. The fiber optic pigtail 206 is optically coupled to the collimating lens 204 and is configured to provide a light signal to the collimating lens 204 from the external fiber optic element and/or to receive the light signal from the collimating lens 204 for transmission to the external fiber optic element.

[00107] In various embodiments, the collimating lens 204 and the fiber optic pigtail 206 may or may not contact each other. The collimating lens 204 and the fiber optic pigtail 206 may be securable to the groove 1104 independent of each other to allow for precise adjustment of a pointing angle between an optical beam from the collimator 1100 and a side and/or bottom surface of the groove. In addition, the collimating lens 204 and fiber optic pigtail 206 may have the same or different outer diameter.

[00108] The mount 1102 of the collimator 1100 has a top side 1106A and a bottom side 1106B (opposite the top side 1106A). The bottom side 1106B is generally flat for mounting on a substrate of a WDM multiplexer/demultiplexer or other optical system. The mount 1102 further includes a width that is less than a width of the collimating lens 204 and a width of the fiber optic pigtail 206. The groove 1104 is in the top side 1106A to hold the collimating lens 204 and fiber optic pigtail 206.

[00109] The collimator 1100 can be tuned and altered according to the methodology discussed above with respect to FIGS. 4A-8E. Also, an additional adjustment freedom could be achieved by using a pigtail 206 and a collimating lens 204 with slightly different diameters. When the axis of the pigtail 206 is closer to the groove 1104 than the axis of the collimating lens 204, the out-going beam tends to tilt away from the substrate x-z plane. When the axis of the pigtail 206 is farther away from the groove 1104 than the axis of the collimating lens 204, the out-going beam tends to tilt closer toward the substrate plane. In this way, the v-groove collimator 1100 could be tuned in the direction normal to the substrate. The difference in distance for the collimating lens 204 and pigtail 206 to the groove 1104 could be controlled with different thickness of epoxy used to secure the collimating lens 204 and the pigtail 206 on the groove 1104.

[00110] FIG. 12 is a flowchart illustrating processing steps 1200 for tuning a collimator. As embodied herein and depicted in FIG. 12, step 1202 includes positioning a collimating lens 204 to a mount 202 of a collimator 200. In particular, the collimating lens 204 may be positioned within a glass tube 202 or on top of a v-groove mount 1102 (or other similar mount). Step 1204 includes aligning a second central axis of a ferrule 210 of a pigtail 206 with the first central axis of the collimating lens 204 along a z-axis perpendicular to the vertical y-axis. Step 1206 includes rotating at least one of the pigtail 206 or the collimating lens 204 about the z-axis relative to each other to cause a light pointing angle of an optical light path within the collimating lens 204 to be perpendicular to the y-axis. The collimating lens 204 and pigtail 206 may be rotated in opposite directions. For example, the collimating lens 204 may be rotated clockwise, and the pigtail 206 may be rotated counterclockwise. Step 1208 includes rotating the collimator 200 about the y-axis relative to a substrate 302 to align the light pointing angle within the collimator 200 with an optical component mounted to the substrate 302. This process may be repeated for multiple collimators independently of one another.

[00111] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention.

[00112] Further, as used herein, it is intended that terms "fiber optic cables" and/or "optical fibers" include all types of single mode and multi-mode light waveguides, including one or more optical fibers that may be upcoated, colored, buffered, ribbonized and/or have other organizing or protective structure in a cable such as one or more tubes, strength members, jackets or the like. Likewise, other types of suitable optical fibers include bend- insensitive optical fibers, or any other expedient of a medium for transmitting light signals. An example of a bend- insensitive, or bend resistant, optical fiber is ClearCurve^® Multimode fiber commercially available from Corning Incorporated. Suitable fibers of this type are disclosed, for example, in U.S. Patent Application Publication Nos. 2008/0166094 and 2009/0169163, which are incorporated herein by reference in their entireties.

[00113] Many modifications and other embodiments of the embodiments set forth herein will come to mind to one skilled in the art to which the embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the description and claims are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. It is intended that the embodiments cover the modifications and variations of the embodiments provided they come within the scope of the appended claims and their equivalents. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

What is claimed is:

1. A collimator, comprising:

a mount having a top and a bottom and defining a vertical y-axis extending therebetween, the bottom of the mount configured to be secured to a substrate;

a collimating lens secured to the mount, the collimating lens having a first front surface and a first back surface and defining a first central axis extending therebetween, the first back surface at least partially defining a first interface; and

a pigtail comprising a ferrule secured to the mount and an optical fiber having a portion positioned within the ferrule, the ferrule having a second front surface and a second back surface and defining a second central axis extending therebetween, the second central axis of the ferrule aligned with the first central axis of the collimating lens along a z-axis perpendicular to the y-axis, the optical fiber comprising an end face at least partially defining a second interface;

wherein the collimating lens and the pigtail form an optical light path from the end face of the optical fiber through the first back surface and the first front surface of the collimating lens;

wherein at least one of the first interface of the collimating lens or the second interface of the pigtail is planar and non-perpendicular to the z-axis; and wherein the collimating lens and the pigtail are rotationally oriented around the z- axis relative to each other such that a light pointing angle of the optical light path within the collimating lens is perpendicular to the y-axis.

2. The collimator of claim 1, wherein the first interface is planar and non- perpendicular to the z-axis.

3. The collimator of either of claims 1 or 2, wherein the second interface is planar and non-perpendicular to the z-axis.

4. The collimator of any of claims 1-3, wherein the first interface and the second interface are planar and non-perpendicular to the z-axis.

5. The collimator of any of claims 1-4, wherein the mount comprises a glass tube having an outer surface defining a square cross-sectional shape.

6. The collimator of any of claims 1-5, wherein the mount comprises a v-groove mount.

7. The collimator of any of claims 1-6, wherein the end face of the optical fiber is coplanar with the second front surface of the ferrule.

8. A micro-optical assembly, comprising:

a substrate comprising a top surface;

a first optical component mounted to a top surface of the substrate; and a first collimator according to claim 1 mounted to the top surface of the substrate; wherein the light pointing angle of the optical light path within the collimating lens of the first collimator is non-parallel to the z-axis; and wherein the first collimator is rotationally oriented around the y-axis relative to the substrate so that the light pointing angle within the first collimator is aligned with the first optical component.

9. The micro-optical assembly of claim 8,

further comprising an array comprising the first collimator and a second collimator according to claim 1 mounted to the substrate; wherein the collimating lens and the pigtail of the second collimator are rotationally oriented around the z-axis relative to each other independent of the first collimator.

10. The micro-optical assembly of either of claims 8 or 9, further comprising a second optical component mounted to the top surface of the substrate;

wherein the second collimator is rotationally oriented around the y-axis relative to the substrate so that the light pointing angle within the second collimator is aligned with the second optical component, the second collimator rotationally oriented around the y-axis independent of the first collimator.

11. A method for tuning a collimator, comprising:

positioning a collimating lens to a mount of a collimator, the collimating lens having a first front surface and a second back surface and defining a first central axis extending therebetween, the mount having a top and a bottom and defining a vertical y-axis extending therebetween;

aligning a second central axis of a ferrule of a pigtail with the first central axis of the collimating lens along a z-axis perpendicular to the vertical y-axis, the ferrule having a second front surface and a second back surface and the second central axis extending therebetween; and

rotating at least one of the pigtail or the collimating lens about the z-axis relative to each other to cause a light pointing angle of an optical light path within the collimating lens to be perpendicular to the y-axis, the optical light path extending from an end face of an optical fiber of the pigtail through the first back surface and the first front surface of the collimating lens, the optical fiber having a portion positioned within the ferrule.

12. The method of claim 11, wherein the step of rotating at least one of the pigtail or the collimating lens about the z-axis relative to each other comprises rotating the pigtail about the z-axis relative to the collimating lens.

13. The method of either of claims 11 or 12, wherein the step of rotating at least one of the pigtail or the collimating lens about the z-axis relative to each other comprises rotating the collimating lens about the z-axis relative to the pigtail.

14. The method of any of claims 11-13, wherein the step of rotating at least one of the pigtail or the collimating lens about the z-axis relative to each other comprises:

rotating the pigtail in a first direction about the z-axis relative to the collimating lens; and

rotating the collimating lens in a second direction about the z-axis relative to the collimating lens, the second direction opposite the first direction.

15. The method of any of claims 11-14, wherein the step of positioning a collimating lens to a mount of a collimator comprises positioning a collimating lens within a bore of a glass tube having an outer surface with a square cross-sectional shape.

16. The method of any of claims 11-15, wherein the step of positioning a collimating lens to a mount of a collimator comprises positioning a collimating lens on a v-groove mount.

17. The method of any of claims 11-16, further comprising rotating the collimator about the y-axis relative to a substrate to align the light pointing angle within the first collimator with a first optical component mounted to the substrate.

18. A method of assembling a micro-optical assembly, comprising positioning an array of collimators on the substrate, the array comprising a first collimator tuned according to the method of claim 11, and a second collimator tuned according to the method of any of claims 11-17.

19. The method of claim 18, further comprising tuning the second collimator along the y-axis independently of the first collimator.

20. The method of claim 19, further comprising tuning the second collimator around the y-axis independently of the first collimator.