Patent ID: 12209923

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth to provide a more thorough description of the specific examples described herein. It should be apparent, however, to one skilled in the art, that one or more other examples and/or variations of these examples may be practiced without all the specific details given below. In other instances, well known features have not been described in detail so as not to obscure the description of the examples herein. For ease of illustration, the same number labels are used in different diagrams to refer to the same items, however, in alternative examples the items may be different.

Exemplary apparatus(es) and/or method(s) are described herein. It should be understood that the word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any example or feature described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other examples or features.

Before describing the examples illustratively depicted in the several figures, a general introduction is provided to further understanding.

Fiber Bragg Gratings (“FBGs”) may be used in a sensing system. A Fiber Bragg Grating (“FBG”) sensor array may be interrogated by a broadband light source-based sensing system for temperature and strain sensing and/or a laser-based detection system for acoustic emission sensing. Additional information regarding FBG sensors and interrogation of data therefrom may be found in U.S. Pat. Pub. No. 20210118654, which is incorporated by reference herein for all purposes consistent herewith.

FIG.1-1is a planar diagram of a top-down inclined view depicting an example of a test wafer100. Even though a test wafer100is depicted for purposes of clarity by way of example and not limitation, other types of platforms, whether circular or other shape, may be used. For example, such a platform may have a planar or nonplanar surface. Even though test wafer100is a depicted as a wafer used in the manufacture of semiconductor devices, other materials may be used for formation of a test wafer or platform as described herein. For example, materials such as silicon, quartz, ceramic, metal, or other material suitable for attachment or coupling of an optical fiber as described herein may be used. In some aspects, a platform, which may be of a structure, is machinable, etchable, or otherwise capable of having a trench formed therein.

As described herein, trench101is a wavy trench. However, trench101may have one or more wavy or curved portions or sections, such as for example curved section101C, and/or one or more straight portions or sections, such as for example straight section101S. In this example, a distal or inner end104of trench101is formed as a straight section101S

At a high-level, trench101generally has a spiral or spiral-like overall pattern or shape102. However, other overall patterns or shapes, or combinations thereof, may be used such as for example a serpentine pattern, a yin and yang divider pattern, and/or another pattern. Furthermore, a spiral may be circular, oval, rectangular-like (e.g., with rounded corners), square-like (e.g., with rounded corners), or other shape or pattern or combination of shapes or patterns.

However, within an overall shape of trench101may be other forms, such as for example a serpentine or serpentine-like section103and an optional strain-relief section104. Optional strain-relief section104may have a serpentine pattern or shape. Optional strain-relief section104may be generally proximate to a test wafer100or platform signal ingress/egress end106with respect to providing an optical fiber for attachment or coupling to such wafer or platform. Furthermore, at least one retention curve105may be formed proximate to such ingress/egress end106of an optical fiber to such wafer or platform.

Further at such end106may optionally be a feed tube107. Feed tube107may be attached to test wafer100via a friction fit into trench101or by an adhesive or epoxy108as in this example. Feed tube107may be a peek tube for high-heat applications. However, a glass, PTFE, PEEK, ceramic, or other type of tubing may be used. In another example, a mechanical device may be used to attach feed tube107to test wafer100.

FIG.1-2is a planar diagram of a top-down view depicting an example of an enlarged portion110of test wafer100ofFIG.1-1with enlarged cross-sectional views of a portion of test wafer100for different types of trench profiles. With simultaneous reference toFIGS.1-1and1-2, test wafer100is further described.

Trench101may have a bottom surface111and sidewall surfaces113. Sidewall surfaces113may intersect an upper (or lower) surface112of test wafer100. Trench101may have a curvilinear profile114or a rectilinear profile115, such as for example in respective cross-sectional views inFIG.1-2, with respect to sidewall surfaces113and bottom surface111thereof.

As generally indicated with ellipsis109, there may be multiple trenches101formed with same of different patterns for having multiple optical fibers on a test wafer100. However, for purposes of clarity and not limitation, a single trench100for a single optical fiber is described. Furthermore, even though a one-to-one correspondence between trench and optical fiber is described, in another example more than one optical fiber may co-located fully and/or partially in a trench.

FIG.1-3is a planar diagram of a top-down inclined view depicting an example of a test wafer100. As test wafer100ofFIG.1-3is same or similar to that ofFIG.1-2, generally only differences are described for purposes of clarity and not limitation.FIG.1-4is a top-down view depicting an example of an enlarged portion110of test wafer100ofFIG.1-3with an enlarged cross-sectional view of a portion of test wafer100. With simultaneous reference toFIGS.1-1through1-4, test wafer100is further described.

An optical fiber120(a white-gray line on a black line for trench101inFIG.1-3and a black line inFIG.1-4) includes a plurality of FBG sensors121, generally depicted as white-gray segments on a black line inFIG.1-4). Even though FBG sensors are described for purposes of clarity by way of example, other types of inline optical fiber sensors may be used.

In this example, a free end portion118of optical fiber120may be attached or coupled to test wafer100with spin-on-glass117. In this example, trench101is not to a perimeter edge119of test wafer100, but rather starts inward therefrom after an optional trench offset or setback. An end portion118may be along upper surface112or cantilevered or free-standing away from such upper surface. In an application where strain is excessive, such as for example greater than 40,000 microstrains, a convention stress reducer (not shown) may be used.

FGB sensors121may be aligned in corresponding alignment regions101A to respectively be in curved sections101C. Because curved sections are used, each FBG sensor121is more isolated with respect to strain from one or more neighboring FBG sensors121. In other words, strain with respect to or on an FBG sensor121may be more localized to a curved section101C. Using curved sections101C for corresponding FGB sensors121reduces opportunity for strain to transfer from one sensor to another along an optical fiber120. While using a wavy trench101can provide localized strain, strain may buildup over the length of an optical fiber120in some applications exceeding 40,000 microstrains, and in such applications a strain reducer package may be used prior to processing information obtained from FBG sensors121.

In this example, a curvilinear profile114of trench101is used; however, in another example a rectilinear profile115, which may include rounded or straight corners, may be used. A bottom center of an FBG sensor120may be in direct contact with a bottom center of profile114, or bottom surface111, for a line contact125in a bottom-to-bottom surface-to-surface direct line contact region126. For example, a bottom center line of an FBG sensor121may be in direct contact along a length thereof with a bottom center line of bottom surface111for a line contact125in region126. Depending on geometries used in an application, such a contact region125may be from 0 to 90 degrees along an arc length of profile114.

In an example where an FBG sensor121diameter is less than a host optical fiber120diameter and is centered thereto, FBG sensor121may be pressed in place for such a bottom-to-bottom surface-to-surface direct line contact region125and held in place with a thermal adhesive or epoxy122after curing. Thermal epoxy122may be even with upper surface112. Along those lines, an uppermost surface of a core of optical fiber120may be below or even with124a top or upper surface112of test wafer100for use of thermal adhesive or epoxy122. While thermal adhesive or epoxy122may fill gaps between profile114and an outer surface of FBG sensor121, a gap123between such surfaces may be present. In another example, trench101may be lined with thermal adhesive or epoxy122and FBG sensors121may be pressed into position, namely a bottom-up attachment, rather than a top-down attachment as in this example. While an entire length of an optical fiber120may be attached with thermal adhesive or epoxy122, generally only FGB sensors121may be attached with thermal adhesive or epoxy122for obtaining thermal and/or strain readings. In an embodiment, an array of an FBG sensor121may not be subjected to epoxy122, but may be pinned down and ends of such sensor or near ends of such sensor. This may allow an array to expand to reduce strain.

FIGS.2-1through2-6are respective planar diagrams of cross-sectional views depicting examples of trenches101of corresponding portions of test wafers100. As test wafers100ofFIGS.2-1through2-6are same or similar to test wafers100ofFIGS.1-1through1-4, generally only differences are described for purposes of clarity and not limitation. Wafers100ofFIGS.2-1through2-6are further described with simultaneous reference toFIGS.1-1through2-6.

InFIG.2-1, FBG sensor121has a line contact125with a side portion of profile114to a side (left of bottom center) portion of FBG sensor121of a trench101having a profile114. InFIG.2-2, FBG sensor121has a line contact125with a bottom surface of trench101having a profile115. In this example profile115has rounded interior or bottom corners. Furthermore, in this example, other than optical fiber120, trench101may be filled with an epoxy122. However, in another example, a V-shaped groove profile116may optionally be used. Furthermore, in another example a combination of profiles115and116may optionally be used, such as a V-shaped groove on sidewalls though with a flat bottom. A V-shaped groove or a sloped sidewall or trapezoidal profile may be used to have one or more line contacts125.

InFIG.2-3, FBG sensor121has a line contact125with a bottom surface and another line contact125with a side surface of trench101having a profile115. InFIG.2-4, FBG sensor121has a line contact125B with a bottom surface, another line contact125L with a left-side surface of trench101having a profile115, and another line contact125R with a right-side surface opposite a left side surface line contact125L of trench101having a profile115.

InFIG.2-5, bottom-up thermal epoxy or adhesive122is applied to a bottom and/or lower surface of trench101having a profile114. In this example, an upper air gap or space123in trench101is left after epoxying. In this example, a portion127of FBG sensor121extends above or higher than a top surface of wafer100.

InFIG.2-6, thermal epoxy or adhesive122is applied to a bottom and/or lower surface of trench101having a profile114for surrounding FBG sensor121other than line contact125and other than an optional expansion gap128. In this example, an optional upper air gap or expansion gap128may be located between a top of FBG sensor121and a bottom of an optional upper layer or structure130. Expansion space in trench101may be left after epoxying with epoxy or adhesive122and after attachment or coupling of upper structure130.

In this example, an upper structure130may be another wafer of same of different material as wafer100. In another example, upper structure130may be a glass frit. In this example, upper structure130is another wafer of a same material as test wafer130in order to have same coefficients of thermal expansion. A bonding interface or interface layer129between an upper surface of test wafer100and a lower surface of upper structure130may be formed using conventional wafer-to-wafer bonding or hybrid bonding or other thin interface bonding. In another example, an optional upper layer or structure130may be deposited, which may include in part into trench101.

FBG sensors121can be used for determining or measuring temperature, acoustic emission (AE), and/or strain in a same fiber. Along those lines, one or more of FBG sensors121of an optical fiber120may be designated for temperature or AE, and one or more others of such FGB sensors121of such optical fiber120may be designated for strain. Temperature and AE information may be obtained from a same FBG sensor120, with multiplexing or bifurcating for information processing in different domains, as AE and temperature used different forms of information processing of sensor data. Transfer of strain information from an FBG sensor121is different than temperature or AE with respect to a Bragg wavelength.

Because of wavy contours of a trench101, temperature/AE and strain, including without limitation strain rosettes, FBG sensors121may all be on a same optical fiber120with multiplexing of information for each to parse out temperature data processing, AE data processing, and/or strain data processing. In other words, wavy contours allow for localization of information which facilitates an ability to parse such information for different contexts, namely temperature, strain, and AE. Furthermore, such FBG sensors121with respect to such different contexts may be in interleaved with respect to one another, have dedicated sections for each such context, or other form of arrangement. For example, a single channel may be used with different gratings of FBG sensors121with information multiplexing of output of an optical fiber120from such FBG sensors121.

Curves of a wavy trench in addition to localizing strain, namely do not readily transfer strain as compared with straight sections of an optical fiber, do not overly stress FBG sensors121, even in the presence of a large wavelength shift. This allows for strain compensation for AE to be avoided or substantially reduced.

Every strain rosette uses a temperature sensor. Many strain rosettes and corresponding temperature sensors may be on same structure by adding a strain reducer. For example, temperature sensors and strain rosette sensors may be on a same structure and may be on a same optical fiber with multiplexing of outputs due to positioning or conforming optical fiber120to wavy contours of a trench101with positioning of such FBG sensors in corresponding curved sections.

FIGS.3-1and3-2are planar diagrams of respective cross-sectional views depicting examples of surface mounting of optical fiber120to corresponding portions of test wafers100. As test wafers100ofFIGS.3-1and3-2are same or similar to test wafers100ofFIGS.1-1through1-4, generally only differences are described for purposes of clarity and not limitation. Wafers100ofFIGS.3-1through3-2are further described with simultaneous reference toFIGS.1-1through3-2.

InFIG.3-1, line contact125is formed by contacting an FBG sensor121of an optical fiber120to an upper surface112of a test wafer100. An epoxy or adhesive122may be disposed on opposing sides of optical fiber120, which may include on opposing sides of an FBG sensor121, an exterior coating or core of optical fiber120, and/or bare optical fiber120. Epoxy or adhesive122may be used for holding FBG sensor121in direct contact with upper surface122. Epoxy or adhesive122may be used for holding optical fiber120in direct contact with upper surface122.

InFIG.3-2, line contact125is formed by contacting an FBG sensor121of an optical fiber120to an upper surface112of a test wafer100. An epoxy or adhesive122may be disposed on opposing sides and over the top of optical fiber120, which may include on opposing sides and over the top of an FBG sensor121, an exterior coating or core of optical fiber120, and/or bare optical fiber120. Epoxy or adhesive122may be used for holding FBG sensor121in direct contact with upper surface122. Epoxy or adhesive122may be used for holding optical fiber120in direct contact with upper surface122.

Optical fiber120may have a jacket or coating137. For jacket tubing, such as stainless steel or PTFE tubing for example, An FBG sensor chain inside optical fiber120may be able to more freely expand, namely with little or without any strain, in a straight or slight curved shape. Along those lines, a jacket or coating137may be used for optical fiber120surface mounted, partially in a trench101, or wholly in a trench101, as described herein. Even though tubing is described, in another example a coating137may be used, such as for example a diamond or PTFE coating.

In a surface mounting, there may be no curves to mount sensors in such as in a wavy trench101example. Curve-to-FBG sensor alignment, uses curvature to localize an FBG sensor to a corresponding local curve from other neighboring sensors, which may or may not be in alignment with other curved sections. Localizing a sensor to a curved section or a flat section or a bumped section may include application of some force using elasticity of an optical fiber120. Along those lines, force may be localized to normal force to a line contact surface. By having curves, tangential forces with respect to each FBG sensor in a curved section may be substantially reduced or not present. Reduction of tangential forces may improve FBG sensor accuracy and/or repeatability.

FIGS.4-1through4-3are block diagrams of respective side views depicting examples of optical fiber normal force attachment. Even though top-down examples are provided, normal force to a sidewall may likewise be used. Moreover, even though examples of straight sections, curved sections may be used.

A line contact surface131may be of a top surface of a test wafer, a bottom surface of a trench of a test wafer, a sidewall surface of a trench of a test wafer, or other structure. An optical fiber120having an FBG sensor121may be positioned to line contact surface131, and a normal force within plus or minus 15 degrees may be applied to cause FBG sensor121to be in line contact125with line contact surface131. Force132against line contact surface131may be thought of as an elasticity force.

For line contact surface131including a step133or a bump134corresponding to approximately half of a difference between a diameter d1of FBG sensor121and a diameter d2of optical fiber120. To reduce tension, diameter d1may be about 75 to 95 percent of diameter d2. However, by using a curved surface for line contact, though a curved line contact, tangential force135with respect to such line contact may be reduced or avoided. Additionally, selecting an optical fiber120having a coefficient of thermal expansion same or similar to test wafer100may reduce tension. Furthermore, an optical fiber may have a coating, and such coating may have a coefficient of thermal expansion to consider.

FIG.5-1is a perspective diagram of a cross-sectional cutaway view depicting an example of a portion of a test wafer100having an FBG sensor121positioned in a curved section141of a trench101. In this example, a bottom of trench101has an undulating surface or a surface with bumps, such as for example bumps134. However, in another example, a flat-bottomed surface for trench101may be used as previously described with respect to a line contact surface.

However, in this example, depth D2from upper surface112to a bottom surface of trench101in regions of non-sensor optical fiber120is greater than depth D1from upper surface112to a bottom surface of trench101in regions of sensor optical fiber120.

In this example, a low thermal expansion epoxy122is located on either end and respectively spaced away from FBG sensor121. Epoxy122may be used to bridge non-sensor sections of optical fiber120. While in this example FBG sensor121is not covered with epoxy122, in another example FBG sensor121may be covered with epoxy122. However, in this example, a grating area or volume of FBG sensor121is in free space other than a line contact portion thereof.

Retention using alternating arcs or curves (e.g., concave, convex, concave, convex, etc.) may be useful for a length of fiber, which may be used at atmospheric pressure without epoxy using elasticity of optical fiber120and friction to create a contact retention region to hold or position to curved surfaces. However, for vacuum or near vacuum pressures, use of epoxy for retention may improve consistency of results. Optical fiber120may be have bending regions thereof to corresponding inside and outside curves of corresponding curved sections of a trench101, such as along a sidewall and/or bottom thereof.

Contacts can be uniform in amount, such as circumferential sections of FBG sensors to corresponding sidewall and/or bottom sections of a trench. In an example, a trench can have a general depth D2for non-sensor sections, and a depth D1for sensor sections, where D1is less than D2by an amount of approximately ½ (d2−d1) where d2is diameter of an outer fiber core in non-sensor sections of optical fiber120and d1is diameter of outer sensor core in sensor sections of optical fiber120.

FIG.5-2is a perspective diagram of a cross-sectional view depicting an example of a portion of a test wafer100having an optical fiber120positioned in a section of a trench101. Optionally, trench may be formed by an isotropic wet etch to form undercut regions142.

FIG.6-1is a planar diagram of a top-down view depicting an example of a flexible strip150having a trench101. Flexible strip150may be used to conform to a surface to be measured. Even though a rectangular strip is depicted for purposes of example, strip150may be any of a variety of shapes and sizes. Even though a flexible strip150is described, a test wafer, as described herein, may likewise have a trench101with an optical fiber120.

Optical fiber120includes FBG sensors121. Each of FBG sensors121may be in whole or in part in line contact with a corresponding outer radius of curvature of curve section, namely a curved section of a sidewall113-1of trench101. A corresponding inner radius of curvature of a curved section sidewall113-2with respect to sidewall113-1may have no FBG sensors121in line contact therewith. In this example, all FBG sensors121are on a same side, or more particularly an outer radius of curvature sidewall113-1.

FIG.6-2is a planar diagram of a top-down view depicting an example of a flexible strip150having a trench101. Flexible strip150may be used to conform to a surface to be measured. Even though a rectangular strip is depicted for purposes of example, strip150may be any of a variety of shapes and sizes. Even though a flexible strip150is described, a test wafer, as described herein, may likewise have a trench101with an optical fiber120.

Optical fiber120includes FBG sensors121. One or more of FBG sensors121of optical fiber120may be in whole or in part in line contact with a corresponding curve section of a sidewall113-1of trench101. A corresponding sidewall113-2with respect to sidewall113-1may have one or more other FBG sensors121of a same optical fiber120may be in line contact with corresponding curved section of sidewall113-2. In this example, FBG sensors121respectively alternate between sidewalls113-1and113-2for line contacts respectively therewith. Alternating line contacts from one sidewall to another of a trench101may be useful for reducing tangential force. Furthermore, alternating line contacts from one sidewall to another of a trench may be useful in an application where temperature can exceed 300 Celsius.

For temperature sensing in vacuum or near vacuum, an example implementation may include: a combination of epoxy bonding on both sides of an FBG sensor121; a curved FBG sensor121orientated for shape retention using fiber elastic axial (normal) force, namely contouring an FBG sensor121to a curved sidewall using a normal force and fiber elasticity; and line contact at a grating area between an FBG sensor121and a surface of a wafer100, fiber jacket137, or structure (if bare fiber is used).

An FBG sensor121can be coated or uncoated as part of an optical fiber120. For high temperature up to 350 C, a polyimide coated FBG sensor121can be used for example or other suitable temperature resistant coating. For a temperature above 350 C, a bare optical fiber120, namely with coating removed or no coating, or an optical fiber120with a high temperature coating, such as diamond coating, gold coating, or spin-on-glass coating for example, can be used.

For both strain and temperature sensing, a strain FBG sensor121can be separately packaged from a temperature package. For example, a strain package optical fiber120may have FBG sensors121calibrated for strain and for direct coupling or direct contact to a structure. This may allow an entire strain sensor package to be directly bonded to a surface structure for monitoring strain. Monitoring strain without some form of direct contact with a structure or direct coupling, such as through bonding, to a structure being monitored may be more problematic than using a direct contact or a direct coupling. In contrast, a temperature monitoring package, such as for example including an optical fiber120with FBG sensors121calibrated for monitoring temperature, which may or may not have a direct coupling or direct contact with a structure monitored, or an environment monitored. Along those lines, temperature sensors121on directly on a wafer or coupled with an intervening jacket can be in contact with a surface using tape, point contact using epoxy, or other mechanical means such as clamp, magnetic, or vacuum suction, to reduce or minimize strain transfer and enhance or maximize thermal conduction.

FIG.7is a planar diagram of a top-down view depicting another example of a fiber optic (FO) test wafer100. To affix a sensor chain in or to a wafer, a PTFE lift off mold, such as for example with 300 micron (um) deep, 3 mm wide trench/microchannel101formed in a spiral/straight curve pattern155with interspersed through hole vias154. Hole vias154may be located in corresponding curved sections151.

A portion of an optical fiber120is shown for purposes of clarity by way of example. Such an optical fiber120may include a sensor chain of FBG sensors and can be inserted in a mold along a microchannel trench101. Such mold may be covered with a thin cover glass or silicon wafer substrate, followed by injection of high temperature glass-based epoxy from a mold backside where via154openings are located.

Once such epoxy is cured, such mold may be lifted off leaving a surface mounted sensor chain of optical fiber120in place. To protect sensors, another cover glass/silicon wafer can be used over such sensor chain of optical fiber120, such as where lift off mold was previously located. Optionally, an edge of a base, as well as of a protective wafer or layer, can be sealed with a high temperature epoxy if hermetic seal is to be used for sensor protection.

In another example, a PTFE mold can be replaced with a glass/si wafer. In this example, there may be no gap between a substrate and cover wafers since optical fiber120is recessed inside such substrate wafer.

A mold may be formed with a CNC machine. Glass/silicon microchannels can be formed using lithographic-semiconductor fabrication processing. A high-temperature epoxy can be glass-based epoxy or high temperature glass solder, such as a high temp silica beads mixed in organic paste.

A short glass capillary can be used to protect a fragile fiber lead in (ingress) where a round via may be replaced with a rectangle through hole via at the edge153of test wafer100. In this example, FBG sensors reside in curved sections151. However, in another example, FBG sensors may reside in straight sections152. A tight bending optical fiber120may be used to limit or reduce optical loss.

With reference toFIG.8-1, there is shown a perspective diagram of a cross-sectional view depicting an example of a portion of a test wafer100having an optical fiber120positioned in a section of a trench101with a cover layer180. Optionally, trench may be formed by an isotropic wet etch to form undercut regions142, such as previously described with reference toFIG.5-2.

Cover layer180may be a wafer, such as for example a glass, silicon or ceramic wafer for example, a deposited layer, such as for example a diamond coating layer, or other layer. In this example, cover layer180is a glass frit. Along those lines, though a glass frit is generally bendable, a glass frit may bridge a trench101, where an upper surface portion of optical fiber120may or may not make contact with a lower surface portion of cover layer180.

A distinction between a structural layer and a deposited layer for a cover layer180may be observed where a portion of such deposited layer dips below an upper surface portion of optical fiber120in trench101. In this example, an FBG sensor121and optical fiber120may have a same diameter, as a bare fiber may be used. Such a bare fiber for optical fiber120may be original or may result from removal of a jacket from optical fiber120.

In this example, a solid cover layer180may be used. However, in another example, a perforated cover layer180may be used, where such cover layer defines one or more through holes181. Holes181may extend from an upper surface of cover layer180to a lower surface thereof. In this example, a through hole181is positioned to be directly above a trench101. In this example, a through hole181is further positioned to be directly above an FBG sensor121.

With reference toFIG.8-2, there is shown a perspective diagram of a cross-sectional view depicting an example of a portion of a test wafer100having an optical fiber120positioned in a section of a trench101with a deposited cover layer180. Optionally, trench may be formed by an isotropic wet etch to form undercut regions142, such as previously described with reference toFIG.5-2.

FIGS.8-1and8-2are similar, except that inFIG.8-2a deposited cover layer180is illustratively depicted. Along those lines, a deposited cover layer180may extend into trench101along each side of such trench, as well as along right and left sides of optical fiber120. In this example, gaps, such as air gaps, are illustratively depicted as between a bottom surface portion of trench101and a lower surface of cover layer180. Again, optional holes181may be formed in cover layer180. In this example, such holes181may be formed by first depositing a sacrificial masking layer patterned to define locations of holes181followed by deposition of cover layer180and then removal of such sacrificial or masking layer.

FIG.9is a flow diagram depicting an example of an assembly flow200. Assembly flow200is further described with simultaneous reference toFIGS.1-1through9.

At operation201, a platform is obtained. Such a platform may be a test wafer100as previously described. At operation202, an optical fiber120with FBG sensors121is placed in a trench101formed in such a platform. Trench101has curved sections101C, as previously described herein. Additionally, trench101may have an overall pattern, as previously described herein.

At operation203, FBG sensors121are respectively positioned in curved sections101C of trench101for line contacts along portions of such curved sections of such trench along a sidewall surface113thereof. Optical fiber101, away from FBG sensors121, may be bonded or otherwise coupled at operation204to such a platform, such as a test wafer100for example, for maintaining such line contacts. In an example, such curved sections may each be outer radii of curvature of such a sidewall surface113of trench101.

While the foregoing describes exemplary apparatus(es) and/or method(s), other and further examples in accordance with the one or more aspects described herein may be devised without departing from the scope hereof, which is determined by the claims that follow and equivalents thereof. Claims listing steps do not imply any order of the steps. Trademarks are the property of their respective owners.