Alignment arrangement for aligning a first and a second optical component

Abstract

The present invention relates to an alignment arrangement for rotational alignment of a first to a second optical component. The first optical component comprises at least one optical fiber. The alignment arrangement comprises at least one cantilever and an actuator. Each cantilever is fixed at one end to the alignment arrangement, and has an opposite free end. Each cantilever is arranged for the free end thereof to abut, during use, the at least one optical fiber. The alignment arrangement further comprises at least one abutting element. The abutting element is arranged for a free end thereof to abut, during use, the at least one optical fiber. The free end of each cantilever is arranged for moving in a direction to rotate at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element. The invention further relates to an alignment system comprising the alignment arrangement according the first aspect and an inspection element for determining the rotational position of the at least one optical fiber. The invention further relates to a process of rotationally aligning a first to a second optical component using the alignment arrangement or the alignment system according the present invention.

Description

[0001] Title: Alignment arrangement for aligning a first and a second optical component

[0002] Field of the invention

[0003] The present invention relates to photonic assembly / testing and, more specifically, to an alignment arrangement for aligning a first and a second optical component.

[0004] Background of the invention

[0005] Light has two polarization directions, which can be utilized to increase the performance in a fiber optic communication system. Each polarization direction may independently transfer information, doubling the bandwidth of a system. However, polarization may also decrease the performance or reliability of the system. For example, some fiber optic devices exhibit a polarization sensitivity, which means that they will only perform well when a well-defined polarization direction is used. A photonic integrated circuit (PIC) may only accept light in a specific polarization direction, or a quantum photonic device may experience signal degradation when the propagation velocity is different for the two polarization directions due to polarization mode dispersion (PMD).

[0006] In such applications, traditional single-mode optical fibers cannot be used as this would leave the polarization direction undefined. Instead, polarization maintaining (PM) optical fibers are used. Like conventional fibers, PM fibers generally have a core region and a surrounding cladding, the cladding having generally a circular-cylindrical outer surface. However, unlike the conventional case, the distribution of the refractive index over a cross-section perpendicular to the longitudinal axis of PM fibers is not circular-symmetric with respect to the fiber axis.

[0007] For mounting PM fibers to a PIC, or in a connector of a fiber ribbon, or to another PM fiber, an important issue is therefore to achieve a good angular alignment or azimuthal alignment.

[0008] By using PM optical fibers, and by providing an accurate rotational alignment of the ends of such fiber, light of a well-defined polarization direction can be presented to a photonic device. The more accurate the rotational alignment, the more defined the polarization direction, i.e. the more power in the desirable polarization direction and the less power in the undesirable polarization direction.

[0009] It is often desirable to align not just one optical fiber, but numerous optical fibers with e.g. one or more photonic integrated circuits. For example, a plurality of optical fibers must commonly be aligned with respective ones of a plurality of optical waveguides of an electro-optic device. In other cases, it is desirable to mount numerous optical fibers of a fiber ribbon in a single connector. In these instances, the alignment of the optical fibers is typically further complicated by the relatively small lateral spacing between the optical fibers. Due to the relatively small lateral spacing between the optical fibers, the process of aligning of a first optical fiber can affect the positioning or rotation of adjacent optical fibers, thereby potentially misaligning the adjacent optical fibers.

[0010] EP1478958A1 relates to alignment of the polarization axes of the ends of two PM fibers in an automatic fiber splicer. The fiber ends are rotated by rotatable fixtures to capture images by a camera and therefrom light contrast profiles are determined as functions of the angular position. From the light contrast profiles the polarization axes are determined and then they are aligned with each other.

[0011] There is a need for an improved arrangement for aligning fibers that are not rotationally symmetric, such as polarization maintaining optical fibers or multicore fibers, specifically for a more automated and / or more accurate rotational alignment. There is a further need for an alignment arrangement that enables using PM optical fiber arrays in applications where multiple channels (fibers) are used in parallel.

[0012] Object of the invention

[0013] It is an object of the invention to provide for an arrangement for rotational alignment of optical components, such as optical fibers.

[0014] It is a further object of the invention to provide an arrangement for more accurate rotational alignment of optical components.

[0015] It is a further object of the invention to provide an arrangement for accurate and efficient rotational alignment of optical fibers in an optical fiber array.

[0016] Summary of the invention The foregoing object is achieved according to a first aspect of the present invention that relates to an alignment arrangement for rotational alignment of a first to a second optical component. The first optical component comprises at least one optical fiber. The alignment arrangement comprises at least one cantilever and an actuator. Each cantilever is attached or fixed at one end to the alignment arrangement, and has an opposite free end. Each cantilever is arranged for the free end thereof to abut, during use, the at least one optical fiber. The alignment arrangement further comprises at least one abutting element. The abutting element is arranged for a free end thereof to abut, during use, the at least one optical fiber. The free end of each cantilever is arranged for moving in a direction to rotate at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

[0017] In a second aspect, the invention relates to an alignment system comprising the alignment arrangement according the first aspect and an inspection element for determining the rotational position of the at least one optical fiber.

[0018] In a third aspect, the invention relates to a process of rotationally aligning a first to a second optical component using the alignment arrangement according to the first aspect of the invention or the alignment system according to the second aspect of the invention, comprising: the free end of at least one cantilever abutting the at least one optical fiber; the free end of at least one abutting element abutting the at least one optical fiber; the free end of the at least one cantilever moving in a direction and thereby rotating at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

[0019] Embodiments corresponding to one aspect of the invention are applicable correspondingly to any other aspect of the present invention.

[0020] Without wishing to be bound by theory, the inventors believe that an accurate alignment is achieved with the present invention. It is further believed that the alignment will be fast because the alignment can take place across multiple fibers simultaneously. This enables alignment of optical components in a high-density linear array or in a 2D array configuration, and allow for such rotational alignment independently of each other.

[0021] An array may for instance comprise 8-12 optical fibers. The small pitch between fibers in an array poses a challenge for currently available alignment tools. The present invention allows rotational alignment of fibers in an array with an accuracy of 3 or even 1 degree.

[0022] The present invention allows to automate this alignment process, for instance for PM fibers in an array of fibers. It enables a higher accuracy and the use of PM fiber arrays in demanding applications where multiple channels (fibers) are used in parallel. It allows doing so at a lower cost due to the elimination of the manual alignment. It also enables a smaller difference in power or signal loss between the channels due to the higher alignment accuracy. It also allows aligning multiple fibers simultaneously, which again allows for faster alignment and which allows for compensating for any cross-coupling alignment errors between adjacent fibers.

[0023] List of definitions

[0024] The following definitions are used in the present description and claims to define the stated subject matter. Other terms not cited below are meant to have the generally accepted meaning in the field.

[0025] “Optical fiber” as used in the present description means: a flexible fiber, made of glass or a polymer, that guides light

[0026] “Cantilever” as used in the present description means: a structural element that extends horizontally and is supported at only one end. The cantilever may either be rigid, in which case it translates or rotates in order to move its free end, or may be flexible, in which case it deforms to move its free end. In the alignment arrangement according to the present invention, multiple cantilevers can be attached to the arrangement for instance in a comb-like fashion.

[0027] “Actuator” as used in the present description means: a means for displacing and / or deforming the cantilever, which may be implemented across different technical implementations. The actuator may be embodied to employ technologies such as a piezo bimorph, an electromagnetic actuator, or mechanical systems like a rack and pinion or similar or different technologies. “Piezoelectric element” as used in the present description means: a material that generates an electric charge in response to applied mechanical stress. The reverse effect can also be achieved: by applying an electrical field to the material, the material expands or contracts and can be used as actuator to move objects with extreme accuracy. Examples of materials that exhibit piezoelectricity are crystalline materials such as quartz, ceramics, group lll-V and ll-VI semiconductors, and polymers.

[0028] “Electrode” as used in the present description means: an electrically conductive layer, often a metal, or semiconductor, on top, underneath, or in between one or more layers of piezoelectric material.

[0029] “Polarization direction” as used in the present description means: one of the two polarization directions that light has. In a fiber optic communication system, light is used to transfer information. Each polarization direction may independently transfer information, doubling the bandwidth of a system. The terms polarization axis, polarization state, and polarization direction may be used interchangeably.

[0030] Embodiments

[0031] As stated above, the invention relates in a first aspect to an alignment arrangement for rotational alignment of a first to a second optical component, wherein the first optical component comprises at least one optical fiber, wherein the alignment arrangement comprises at least one cantilever and an actuator, wherein each cantilever is fixed at one end to the alignment arrangement, and has an opposite free end, wherein each cantilever is arranged for the free end thereof to abut, during use, the at least one optical fiber, wherein the alignment arrangement further comprises at least one abutting element, wherein the abutting element is arranged for a free end thereof to abut, during use, the at least one optical fiber, wherein the free end of each cantilever is arranged for moving in a direction to rotate at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

[0032] The second optical component may for instance be a photonic integrated circuit, a sensor, a lens or another optical fiber. It can also be envisioned that the second optical component is a connector wherein the first optical component is comprised. The connector may be a housing or a casing, having a non-rotational symmetric cross-section or having alignment features, and that may be used to mount the optical component with a defined rotational alignment. The connector may accommodate multiple optical components. Rotational alignment of the fiber can then be seen as alignment to the connector, or to the other optical fibers in said connector. Alignment of two optical fibers to each other may be achieved by rotation of one of the fibers, while the other fiber is stationary, but also by rotation of both optical fibers.

[0033] In an embodiment, the actuator comprises at least one piezoelectric element, preferably with at least two electrodes.

[0034] It can be imagined that the cantilever is driven by the actuator. For this, the actuator can be connected to the cantilever, but is not necessarily a part of the cantilever. In an embodiment, the at least one cantilever comprises the actuator.

[0035] In an embodiment, said moving in a direction is a tangential displacement of the free end of each cantilever. Tangential refers to a direction tangential to the circular contour of the fiber’s cross-section. One way to achieve tangential displacement of the free end of each cantilever is by deforming the cantilever, e.g. by bending the cantilever. This bending can be achieved by a piezoelectric element, but also by use of a thermal bimorph or an electromagnetic actuator. Tangential displacement can also be achieved by rotation or translation of the cantilever, by using an elastic mechanism or bearing at the supported end of the cantilever. Such an elastic mechanism or bearing may introduce a single degree-of- freedom (DOF) at the supported end, allowing a rotation around a single axis or translation in a single direction. Examples of elastic mechanisms are elastic hinges or leaf springs. Examples of bearings are ball bearings or sliding bearings. Another envisioned possibility is by rotating a frame on which the cantilever or cantilevers are mounted. As stated above, the alignment arrangement is for rotating at least a section of the at least one optical fiber around its longitudinal axis. In an embodiment, this section of the at least one optical fiber is located at or near a free end of the optical fiber. It is possible that the entire fiber is rotated, but it may also be envisioned that one section is rotated while another section does not rotate - i.e. the fiber is twisted.

[0036] In an embodiment, said abutting element is at least one cantilever. This means that the fiber may, during use, be rotated between two or more cantilevers. The use of one cantilever and one abutting element that is fixed allows rotation of the fiber caused by movement of the cantilever, but will also lead to lateral displacement of (a section of) the fiber. When the fiber is clamped between a first and a second cantilever, movement of the free end of the second cantilever may cancel out the lateral displacement of the optical fiber caused by movement of the first cantilever.

[0037] In an embodiment, the number of cantilevers corresponds to the number of optical fibers.

[0038] In an embodiment, the number of cantilevers is two times the number of optical fibers. In another embodiment, the number of cantilevers is three times the number of optical fibers. In another embodiment, the number of cantilevers is four times the number of optical fibers. As stated above, the use of multiple cantilevers one optical fiber is beneficial because lateral displacement of the optical fiber can minimized or avoided.

[0039] In an embodiment, said at least one cantilever is arranged for sequential alignment of at least two optical fibers. This means that one cantilever, or one set of cantilevers, is used to align more than one optical fiber sequentially. The (set of) cantilever(s) may then rotate one optical fiber, be moved towards another, possibly adjacent optical fiber (or the fiber is moved towards the (set of) cantilever(s)), and then rotate this fiber. This process can be repeated until all fibers are rotated. It can also be imaged that there is more than one (set of) cantilever(s) that are used to each rotate a part of the optical fibers present in an array. For example, one (set of) cantilever(s) may be for aligning the first, third, fifth, etc. fiber in an array, and another (set of) cantilevers may be for aligning the second, fourth, sixth, etc. fiber an in array.

[0040] In an embodiment, the dedicated cantilever or cantilevers for each of the at least one optical fibers form a set of dedicated cantilevers per optical fiber, and wherein multiple sets of dedicated cantilevers are arranged in a staggered manner along the length direction in view of the optical fiber.

[0041] In an embodiment, the arrangement comprises at least one dedicated cantilever for each of the at least one optical fibers. It this embodiment, there is one cantilever, or one set of cantilevers, responsible for the rotation of one optical fiber. It can be envisioned that when adjacent optical fibers are located in close proximity of each other (i.e. when the pitch between fibers is small), the adjacent (sets of) cantilevers may be staggered along the length of the fibers, i.e. the (sets of) cantilevers do not need to be located at the same longitudinal position along the fibers.

[0042] In an embodiment, the free end of each cantilever is tapered. This allows an actuator to be wider than the pitch of the fiber array, or allows for a larger lateral displacement of an actuator, without the actuator touching a neighbouring fiber.

[0043] In an embodiment, the free end of each cantilever comprises a compliant tip. This has the benefit that the clamping force from the cantilever on the fiber is controlled by radial compliance. Radial is defined as any direction pointing towards or away from the center of the fiber. Alternatively, the clamping force could be monitored by a sensor, for instance based on a force sensor, a strain gauge, or a visual inspection of a deformation e.g. by a camera. Another alternative is to use a compliant cantilever, to use a compliant mechanism between the actuator and the cantilever, or to use an actuator or feedback control loop having a low stiffness. A compliant tip has the benefit that no additional space is required within the alignment arrangement. When aligning a fiber array with, for instance, one cantilever per optical fiber, the presence of a compliant tip on each of the cantilevers allows for an appropriate clamping force for each cantilever when the cantilevers abut the optical fibers. The use of a compliant tip has advantages. When employing a compliant tip, any minor radial movement of the cantilever towards the fiber would result in a gradual and controlled increase in contact force upon abutment with the fiber. Simultaneously, a slight radial movement of the cantilever away from the fiber would not lead to a loss of contact, as the compliant tip allows for a more forgiving interaction. In cases where multiple cantilevers are utilized for aligning multiple fibers concurrently, the use of compliant tips ensures a more consistent alignment. These tips accommodate variations in the radial distance between the cantilevers and their respective fibers, preventing disparities in contact forces and ensuring that all cantilevers maintain proper contact with their designated fibers. Employing a compliant tip, among other methods discussed earlier to control clamping force, serves as an effective measure to address these challenges and enhance the overall performance of the system.

[0044] Examples of a compliant tip include a spring and a tip comprising a compliant material. In an embodiment, said compliant tip comprises a compliant material. An example of a compliant material is a rubber-like epoxy or any otherwise compliant epoxy. It is beneficial when the material is elastic in the radial direction, and stiff in the other directions such that sufficient tangential force can be applied to the surface of the fiber by the tip. If the tangential force is low, then also the rotation of the section of the fiber to be rotated may be low in case a part of the fiber or the end of the fiber is clamped. In such case the twisting torque induced by the tangential force is low compared to the torsional stiffness of the fiber. The compliant tip may also consist of different materials or different layers, having different mechanical properties; for example, a first layer may be compliant to overcome alignment inaccuracies and to provide a well-defined contact force, whereas a second layer may be stiff and hard to reduce wear or to prevent the fiber from sinking too deeply into a compliant tip.

[0045] The tip comprising a compliant material may be moulded on top of the cantilever, such as with an accurate moulding process. It is possible for the compliant tip to span the full depth of the cantilever, but it may also cover only a fraction of the free end of the cantilever.

[0046] In an embodiment, the pitch between optical fibers is at most 250 micrometers. In a specific embodiment of this, the pitch is at most 127 micrometers.

[0047] As stated above, the invention relates in a second aspect to an alignment system comprising an alignment arrangement according to any of the preceding claims and an inspection element for determining the rotational position of the at least one optical fiber.

[0048] Any known method to assess the rotational angle of an optical component may be used. In an embodiment, the inspection element comprises a visual inspection element. This visual inspection element may be a digital imaging technique, for instance comprising a camera.

[0049] In an embodiment, the inspection element comprises a polarization filter and a photodetector.

[0050] Depending on the type of optical component that is (to be) aligned, different inspection tools can be used. For instance, for alignment of a multi-core optical fiber, a visual inspection element may be used. When the fiber to be aligned comprises stress rods, the location of these stress rods may also be assessed to obtain information on the rotation angle. For a PM fiber, a polarization filter and a photodetector may be used. It is also possible to add a marker in a cross section, allowing the determination of for instance luminance of a side image of the optical fiber.

[0051] Process for rotationally alianina a first to a second optical component

[0052] As stated above, the invention relates in a third aspect to a process of rotationally aligning a first to a second optical component using the alignment arrangement according to the second aspect or the alignment system according to the third aspect, comprising: the free end of at least one cantilever abutting the at least one optical fiber; the free end of at least one abutting element abutting the at least one optical fiber; the free end of the at least one cantilever moving in a direction and thereby rotating at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

[0053] In an embodiment, the process further comprises: determining the rotational position of the at least one optical fiber by an inspection element.

[0054] Optionally, the process comprises further alignment of the at least one optical fiber by the free end of the at least one cantilever moving in a direction and thereby rotating at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element. By repeating the steps of determining the rotational position of the fiber or fibers, and, if the determined rotation is not in agreement with a desired rotation needed for alignment to a second optical component, further rotation of the fiber or fibers, the rotational alignment can be monitored and established in an incremental process.

[0055] In an embodiment, the process further comprises: fixating of the at least one optical fiber after rotational aligning said optical fiber. For instance, the fibers can be clamped together or glued together once aligned such that they cannot rotate back or further and the achieved alignment is fixated.

[0056] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid- state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope thereof.

[0057] The above-mentioned and other features and advantages of the invention are illustrated in the following description with reference to the enclosed drawings which are provided by way of illustration only and which are not limitative to the present invention. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims.

[0058] Brief description of the drawings The present invention is described hereinafter with reference to the accompanying drawings in which embodiments of the present invention are shown and in which like reference numbers indicate the same or similar elements.

[0059] Fig. 1a shows an embodiment of the alignment arrangement according to the present invention, wherein there is one optical fiber and one cantilever.

[0060] Fig. 1b shows another embodiment of the alignment arrangement according to the present invention, wherein there is one optical fiber and one cantilever.

[0061] Fig. 2a shows another embodiment of the alignment arrangement according to the present invention, wherein there is one optical fiber and two cantilevers.

[0062] Fig. 2b shows another embodiment of the alignment arrangement according to the present invention, wherein there is one optical fiber and three cantilevers.

[0063] Fig. 3 shows an embodiment wherein there is incremental rotational alignment of an optical fiber.

[0064] Fig. 4 shows another embodiment wherein there is incremental rotational alignment of an optical fiber, using two sets of two cantilevers.

[0065] Fig. 5 shows an embodiment wherein there is sequential alignment of a plurality of optical fibers.

[0066] Fig. 6 shown an embodiment wherein there is a dedicated cantilever for each of the optical fibers.

[0067] Fig. 7 shows different views (A, B, C) of an embodiment wherein (sets of) dedicated cantilevers are arranged in a staggered manner along the length direction of the optical fibers.

[0068] Fig. 8A-E show different embodiments wherein the contact (force) between the cantilever and the fiber is controlled using some compliant feature

[0069] Fig. 9A-B show embodiments wherein the compliant tip is tapered.

[0070] Fig. 10A-B also show embodiments wherein the compliant tip is tapered.

[0071] Fig. 11A-B show embodiments of an alignment arrangement having an optical measurement system to determine the rotation angle of the fiber. Detailed description

[0072] Fig. 1a shows an embodiment of the alignment arrangement 1 according to the present invention. The alignment arrangement 1 is for rotational alignment of a first to a second optical component, wherein the first optical component comprises at least one optical fiber 3. The shown fiber is a type of PM fiber, having a core 4 and stress rods 6. Of course, any type of optical fiber may be aligned by the alignment arrangement, specifically any type of fiber not having a rotationally symmetric cross-section or circumference wherein rotational angle influences the function of the fiber after being connected to a second optical component. The alignment arrangement 1 comprises at least one cantilever 5 and an actuator. Each cantilever 5 is fixed at one end to the alignment arrangement 1 , and has an opposite free end 7. Each cantilever 5 is arranged for the free end 7 thereof to abut, during use, the at least one optical fiber 3. The alignment arrangement 1 further comprises at least one abutting element 9. The abutting element 9 is arranged for a free end thereof 11 to abut, during use, the at least one optical fiber 3. The free end 7 of each cantilever 5 is arranged for moving in a direction to rotate at least a section of the at least one optical fiber 3 around its longitudinal axis between the cantilever 5 and the abutting element 11. The vertical arrow depicted in the cantilever 5 indicates a movement of the cantilever 5 towards the fiber 3 such that the cantilever 5 abuts the fiber 3. The horizontal double-headed arrow indicates a subsequent movement of the free end 7 of cantilever 5 that causes at least a section of the optical fiber 3 to rotate. This rotation is indicated with the curved double-headed arrow depicted in the optical fiber 3. This section of the at least one optical fiber 3 is, for example, located at or near a free end of the optical fiber. The described movement of the cantilever 5 may be a tangential displacement of the free end 7 of each cantilever 5.

[0073] The actuator comprises at least one piezoelectric element, preferably with at least two electrodes. The actuator may be comprised on the cantilever.

[0074] Fig. 1 b shows another embodiment of the alignment arrangement 1 according to the present invention. This embodiment is similar to the embodiment shown in Fig. 1a, and further comprises additional pre-alignment surfaces 13. These pre-alignment surfaces are used to keep the fiber within range of the corresponding cantilever. These pre-alignment surfaces may be provided by a groove, having for example a rectangular or V-shaped cross-section. This groove may be located at a different position along the length of the fiber than the position of the cantilevers or abutting elements. The fibers may be inserted into their corresponding grooves before the cantilevers move towards the fibers.

[0075] The process of rotationally aligning a first to a second optical component using the alignment arrangement 1 can comprise the steps of: the free end 7 of at least one cantilever 5 abutting the at least one optical fiber 3; the free end 11 of at least one abutting element 9 abutting the at least one optical fiber 3; the free end 7 of the at least one cantilever 5 moving in a direction and thereby rotating at least a section of the at least one optical fiber 3 around its longitudinal axis between the cantilever 5 and the abutting element 9.

[0076] In Fig. 1a and b the number of cantilevers 3 corresponds to the number of optical fibers 3. The number of cantilevers 5 may also be a plurality of the number of optical fibers 3.

[0077] Fig. 2a and 2b show embodiments wherein there are more than one cantilevers 5 used for the rotation of an optical fiber 3. In these embodiments, the abutting element 9 is a cantilever 5. Fig. 2a has two cantilevers 5 and further comprises pre-alignment surfaces 13. The use of two (or more) cantilevers 5 that are, in use, abutting opposite sides of the optical fiber 3 has the benefit that lateral movement of the fiber 3 is minimized. Fig. 2b shows an embodiment having three cantilevers 5 involved in the rotation of optical fiber 3.

[0078] Figs. 3 and 4 shows different embodiments wherein there is incremental rotational alignment of an optical fiber. Fig. 3 shows an embodiment wherein there are two cantilevers 5 acting upon the optical fiber 3, and there are two clamping elements 15 that can fixate the rotational position of the optical fiber 3. The steps of the incremental rotation are indicated in Figs. 3A-3I. Fig. 3B shows the movement of the cantilevers 5 towards the optical fiber 3, such that the cantilevers 5 abut the fiber 3 on opposite sides of the fiber 3. Fig. 3C shows the tangential displacement of the free ends 7 of the cantilevers 5, wherein the two cantilevers 5 move in opposite directions. This movement causes a rotation of the optical fiber 3. Due to the opposite placement of the cantilevers 5, lateral displacement of the fiber 3 is avoided. In the step shown in Fig 3D the clamping elements 15 are moved towards the fiber 3, such that they abut the fiber 3 and therewith fixate the rotational position of the fiber 3, even when cantilevers 5 are moved away from the fiber 3 - which is shown in Fig. 3E. Next, as shown in Fig. 3F, the free ends 7 of cantilevers 5 are moved laterally in the opposite direction of their earlier displacement. The cantilevers 5 are then moved again towards the fiber 3 such that they abut the fiber 3, as shown in Fig. 3G. The clamping elements 15 can then release the fiber 3 (by moving away from the fiber), as shown in Fig. 3H. The next increment of rotation of fiber 3 can then be achieved by tangential displacement of the cantilevers 5, shown in Fig. 3I. The steps shown in Fig. 3D-3I can then be repeated as many times as necessary to achieve the desired rotation for alignment of the optical fiber 3.

[0079] Fig. 4 shows another embodiment wherein there is incremental rotational alignment of an optical fiber 3. Whereas Fig. 3 has one cantilever 5 and one clamping element 15 on each of two opposite sides of the optical fiber 3, Fig. 4 shows an embodiment wherein there are two parallel cantilevers 5a and 5b on each of two opposite sides of the optical fiber 3. Rotational alignment is achieved by steps similar to the steps discussed above for Fig. 3, but instead of clamping elements 15 cantilevers 5b are used. This has the benefit that these cantilevers 5b also achieve an increment of rotation of the optical fiber 3, in the same manner as cantilevers 5a, instead of only fixating the rotational position of the fiber 3 during time wherein the cantilevers 5a are not abutting the fiber 3.

[0080] Fig. 5 and Fig. 6 shows two different operating mechanisms for the rotational alignment of a plurality of optical fibers 3 with an alignment arrangement 1.

[0081] Fig. 5 shows an embodiment wherein there is sequential alignment of a plurality of optical fibers. One cantilever 5 sequentially aligns the optical fibers 3 present in an array of optical fibers 3. Starting from the left, the cantilever 5 aligns a first optical fiber 3, is then moved such that it can align a second, neighbouring, optical fiber 3, and this process is repeated until all fibers 3 of the array are rotationally aligned.

[0082] Of course, the shown embodiment may be combined with embodiments such as shown in Fig. 2a and 2b, wherein there are multiple cantilevers 5 applied for the rotation of one optical fiber 3. In that case, there is a set of cantilevers 5 that, together, sequentially align each of the optical fibers 3 in the array. Fig. 6 shown an embodiment wherein there is a dedicated cantilever for each of the optical fibers. Each cantilever 5 is assigned to a different optical fiber 3. Of course, the shown embodiment may be combined with embodiments such as shown in Fig. 2a and 2b, wherein there are multiple cantilevers 5 dedicated to one optical fiber 3. In that case, there is a set of dedicated cantilevers 5 for each optical fiber 3.

[0083] A combination of sequential and dedicated alignment is also possible. For example, there may be one (set of) cantilever(s) 5 dedicated for the sequential alignment of a selection of optical fibers 3, and another (set of) cantilever(s) 5 dedicated for the sequential alignment of another selection of optical fibers 3. An example of this would be two (sets of) cantilever(s) 5 each responsible for every other fiber 3, wherein the (sets of) cantilevers 5 are at an offset equal to the pitch of the fiber array compared to each other. In other words, one (set of) cantilever(s) 5 is dedicated for the sequential alignment of the first, third, fifth, etc. fiber 3 in an array, and the other (set of) cantilever(s) 5 is dedicated for the sequential alignment of the second, fourth, sixth, etc. fiber 3 of the array. There are many variations of this imaginable; and this is, of course, not limited to two (sets of) cantilevers 5.

[0084] Fig. 7 shows different views (A, B, C) of an embodiment wherein (sets of) dedicated cantilevers are arranged in a staggered manner along the length direction of the optical fibers. The dedicated cantilever 5 or cantilevers 5 for each of the at least one optical fibers 3 form a set of dedicated cantilevers 5 per optical fiber 3, and each set of dedicated cantilevers 5 is arranged in a staggered manner along the length direction in view of the set of dedicated cantilevers 5 corresponding to a neighbouring optical fiber 3. Fig. 7A shows a perspective view, Fig. 7B a top view and Fig. 7C a front view. Fig. 7 shows an array of optical fibers 3, each optical fiber having a dedicated set of two cantilevers 5 for the rotation of that fiber 3, the two cantilevers being located on opposite sides of the fiber (as shown earlier in Fig. 2A). Fig. 7 also shows a bar 2 that provides pre-alignment surfaces 13, in the shape of V-grooves. The set of cantilevers 5 from one fiber 3 is arranged in a staggered manner with respect to the set of cantilevers 5 from a neighbouring fiber 3. As can be seen in Fig. 7A and 7B, the sets of cantilevers 5 are divided into two groups, the two groups being arranged in a staggered manner such that the two groups are on different positions on along the length direction of the fibers 3. In the shown embodiment, the two groups do not overlap. In other embodiments, the groups may overlap. Of course, any arrangement of groups can be imaged, for instance three, four or five groups. The benefit of this alternation of the placement of the cantilevers 5 along the length direction is that this allows neighbouring cantilevers 5 to be placed in close proximity, i.e. the pitch between the fibers in the array can be small. For instance, the pitch between optical fibers can be at most 250 micrometers, or even at most 127 micrometers. Additionally, the pitch of the cantilevers within a set of cantilevers may be larger than the pitch of the fibers.

[0085] Fig. 8A-E show different embodiments wherein the contact (force) between the free end 7 of each cantilever 5 and the fiber is controlled by a compliant feature or structure. This has the benefit that the clamping force from the cantilever 5 on the fiber 3 is controlled by radial compliance. When aligning a fiber array with, for instance, one cantilever 5 per optical fiber 3, the presence of a compliance on or in each of the cantilevers 5 allows for an appropriate clamping force for each cantilever 5 when the cantilevers 5 abut the optical fibers 3.

[0086] Fig. 8A shows the use of a spring as compliant tip 17. When the cantilever 5 is moved towards the fiber 3, as indicated by the thick, vertical arrows, the spring can compress when the applied downwards force on the cantilever 5 is more than required for the cantilever 5 to abut the fiber 3. Fig. 8B shows a similar embodiment, in this case the spring not being located at the free end of the compliant tip.

[0087] Fig. 8B shows an example wherein the cantilever itself is compliant. In this example, cantilever, or a part of the cantilever 5 located at the free end 7 of the cantilever 5 is made of a material that can bend under the pressure, i.e. when the applied downwards force (indicated by the thick, vertical arrows) on the cantilever 5 is more than required for the cantilever 5 to abut the fiber 3.

[0088] Fig. 8C shows an example wherein the compliant tip 17 comprises a compliant material. In this example, the compliant material is located at the free end 7 of the cantilever 5. The compliant material may comprise for example a rubber-like epoxy. The elasticity of the material allows the material to compress when the applied downwards force (indicated by the thick, vertical arrows) on the cantilever 5 is more than required for the cantilever 5 to abut the fiber 3.

[0089] Fig. 8D shows another example of a compliant tip 17 In this example, the compliance is achieved by the specific shape of the free end 7 of the cantilever 5. This shape allows the compliant tip to act similar to a spring or to an elastic material when the applied downwards force (indicated by the thick, vertical arrows) on the cantilever 5 is more than required for the cantilever 5 to abut the fiber 3.

[0090] Fig. 8E shows a cantilever that rotates around a rotation point 8. This rotation point can be for example an elastic hinge or a rotational ball bearing. This rotation point supports one end of the cantilever. The other end is free and is brought into contact with the fiber by an actuation force 12, in which the actuation force is applied to the cantilever. This actuation force 12 is applied through a compliant actuator, a compliant mechanism, or a compliant control loop that controls the actuator. The spring 17 represents this compliance.

[0091] Fig. 9A-B show embodiments wherein the compliant tip 17 is tapered. Fig. 9A shows an embodiment wherein the compliant tip 17 is made from a single compliant material composition. Fig. 9B shows an embodiment wherein the compliant tip comprises two layers 17a and 17b, each made of a different compliant material composition. These layers 17a and 17b can have different mechanical properties; for example, a first layer 17a may be compliant to overcome alignment inaccuracies and to provide a well-defined contact force, whereas a second layer 17b may be stiff and hard to reduce wear or to prevent the fiber from sinking too deeply into a compliant tip.

[0092] Fig. 10A-B also show embodiments wherein the compliant tip is tapered. These figures show different examples of how the compliant tip 17 can be located in / on the cantilever 5. It is possible for the compliant tip to span the full depth of the cantilever, as shown in Fig. 10A, but it may also cover only a fraction of the free end of the cantilever, as shown in Fig. 10B.

[0093] Fig. 11A shows an alignment arrangement having an inspection element for determining the rotational position of an optical fiber, consisting of a lens 21 and a camera 20.

[0094] Fig. 11 B shows an alternative inspection method, in which a light beam 22 is injected into one end of the fiber 3. This light emanates again from the other end of the fiber 3, passes through a polarization filter 24, and is collected again by a photodetector 23. Modifications and additions to the method and arrangement disclosed above are obvious to those skilled in the art and covered by the scope of the appended claims.

Claims

CLAIMS1. Alignment arrangement for rotational alignment of a first to a second optical component, wherein the first optical component comprises at least one optical fiber, wherein the alignment arrangement comprises at least one cantilever and an actuator, wherein each cantilever is attached at one end to the alignment arrangement, and has an opposite free end, wherein each cantilever is arranged for the free end thereof to abut, during use, the at least one optical fiber, wherein the alignment arrangement further comprises at least one abutting element, wherein the abutting element is arranged for a free end thereof to abut, during use, the at least one optical fiber, wherein the free end of each cantilever is arranged for moving in a direction to rotate at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

2. Alignment arrangement according to claim 1 , wherein the actuator comprises at least one piezoelectric element, preferably with at least two electrodes.

3. Alignment arrangement according to claim 1 or 2, wherein the at least one cantilever comprises the actuator.

4. Alignment arrangement according to any of the preceding claims, wherein said moving in a direction is a tangential displacement of the free end of each cantilever.

5. Alignment arrangement according to any of the preceding claims, wherein the section of the at least one optical fiber is located at or near a free end of the optical fiber.

6. Alignment arrangement according to any of the preceding claims, wherein said abutting element is at least one cantilever.

7. Alignment arrangement according to any of the preceding claims, wherein the number of cantilevers corresponds to the number of optical fibers.

8. Alignment arrangement according to any of the preceding claims, wherein the number of cantilevers is two times, preferably three times, more preferably four times, the number of optical fibers.

9. Alignment arrangement according to any of the preceding claims, wherein said at least one cantilever is arranged for sequential alignment of at least two optical fibers.

10. Alignment arrangement according to any of the preceding claims, wherein the arrangement comprises at least one dedicated cantilever for each of the at least one optical fibers.

11. Alignment arrangement according to any of the preceding claims, wherein the dedicated cantilever or cantilevers for each of the at least one optical fibers form a set of dedicated cantilevers per optical fiber, and wherein each set of dedicated cantilevers is arranged in a staggered manner along the length direction in view of the set of dedicated cantilevers corresponding to a neighbouring optical fiber.

12. Alignment arrangement according to any of the preceding claims, wherein the free end of each cantilever is tapered.

13. Alignment arrangement according to any of the preceding claims, wherein the free end of each cantilever comprises a compliant tip, preferably wherein said compliant tip comprises a compliant material, more preferably wherein said compliant tip comprises an epoxy.

14. Alignment arrangement according to any of the preceding claims, wherein the cantilever is compliant, or wherein a compliant mechanism is used between the actuator and the cantilever, or wherein the actuator is compliant, or wherein a compliant feedback control loop is used that controls the actuator.

15. Alignment arrangement according to any of the preceding claims, wherein the pitch between optical fibers is at most 250 micrometers, preferably at most 127 micrometers.

16. Alignment system comprising an alignment arrangement according to any of the preceding claims and an inspection element for determining the rotational position of the at least one optical fiber.

17. Alignment system according to claim 16, wherein said inspection element comprises a visual inspection element, or wherein said inspection element comprises a polarization filter and a photodetector.

18. Process of rotationally aligning a first to a second optical component using the alignment arrangement according to any of claims 1-16 or the alignment system according to any of claims 15-16, comprising: the free end of at least one cantilever abutting the at least one optical fiber; the free end of at least one abutting element abutting the at least one optical fiber; the free end of the at least one cantilever moving in a direction and thereby rotating at least a section of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

19. Process according to claim 17, further comprising: determining the rotational position of the at least one optical fiber by an inspection element; optionally further alignment of the at least one optical fiber by the free end of the at least one cantilever moving in a direction and thereby rotating at least asection of the at least one optical fiber around its longitudinal axis between the cantilever and the abutting element.

20. Process according to claim 18 or 19, further comprising: - fixating of the at least one optical fiber after rotational aligning said optical fiber.

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