Systems and methods for coupling a light beam into an optical receiver

Abstract

The present invention relates to a system (100) for coupling at least one light beam (120, 121) into an optical receiver (160), each light beam having an elliptical beam cross-section (330), the optical receiver (160) having a circular light receiving cross-section (340), the system (100) comprising: at least one beam inlet (180, 181), each beam inlet being configured to allow each of the at least one light beam (120, 121) to enter the system (100); a beam outlet (190), configured to allow the at least one light beam (120, 121) to leave the system (100) for coupling the at least one light beam into the optical receiver (160), the beam outlet (190) including a lens (170) for performing a Fourier transform; at least one beam deflector (110, 111, 112, 130) for deflecting the light beam in the at least one light beam; and an optical substrate element (300), at least one of the at least one beam deflectors (110, 111, 112, 130) being directly fixed to the substrate element (300).

Description

Technical Field

[0001] The inventive concept relates to a system and method for coupling a light beam into an optical receiver, in particular for coupling at least one light beam into an optical receiver having a substantially or completely circular light receiving cross-section, each light beam having a substantially or completely elliptical beam cross-section. Background Art

[0002] In many applications, light beams generated by lasers such as semiconductor lasers or laser diodes need to be coupled into optical receivers such as optical fibers. It is often necessary to couple more than just one light beam into such an optical receiver. For example, for many microscopy applications, such as laser scanning techniques, it is advantageous to transmit light including multiple laser lines to the microscope itself via a single-mode optical fiber. In this case, the stability of the laser power at the end of the optical fiber is very important. Due to the small fiber core diameter of only a few micrometers of a single-mode optical fiber, fiber coupling requires precise alignment of the optical elements that guide and deflect the light beam into the corresponding optical fiber. If several laser lines are involved, dichroic mirrors are typically used to combine the light beams onto the same beam path. Such a dichroic mirror allows a first light beam to pass through the dichroic mirror while deflecting a second light beam, such that the two light beams will then propagate in the same direction and preferably coaxially.

[0003] For these applications, systems including mirrors / dichroic mirrors (also referred to herein as "beam deflectors") are typically used to deflect one or more light beams onto the same propagation path leading to the optical receiver / fiber. Generally, the necessary precise alignment of the light beam is accomplished by using precise optomechanics that have mirrors fixed thereto by adhesives or by locking screws. Such a mirror mount includes a three-point support, where at least two support points can be moved back and forth, for example, by screws with fine threads. Thus, the vertical and horizontal tilts can be set independently. The mirror mounts of the prior art can move very precisely and are well-suited for fiber coupling. In addition, the mechanical devices can mostly be locked, resulting in fairly good long-term stability. However, there are some disadvantages in using such mirror mounts. First, they are very expensive. Second, the achieved beam alignment must be stable over a long period to ensure the stability of the laser power at the end of the optical fiber, which further increases the requirements for the optomechanics. Finally, typically the user has to align the mirror for the desired coupling purpose, which is a time-consuming process. This type of mirror mount or optomechanics is hereinafter referred to as an "adjustment device".

[0004] Today, laser diodes are commonly used as compact and most cost-effective laser sources. However, they have significant drawbacks in combination with fiber optic coupling. After collimation, the laser beam has an elliptical shape / beam cross-section, while a single-mode fiber presents a circular and symmetric core, which means that the TEM00 mode coupled into the fiber is also circular. As a result, the coupling efficiency from the laser diode to the fiber is not high because a large portion of the focus of the elliptical laser beam cannot be coupled into the circular fiber core.

[0005] The standard solution to this problem is beam shaping, i.e., transforming the elliptical laser beam into a circular beam by using, for example, anamorphic prism pairs or cylindrical lenses. This increases the complexity and cost of the optical system, which is again disadvantageous. Summary of the Invention

[0006] In view of the above problems, there is a need for an improved beam coupling system and corresponding method, particularly reducing the need for ultra-stable opto-mechanics.

[0007] Embodiments of the inventive concept provide a system for coupling at least one light beam (e.g., one or more light beams generated by corresponding semiconductor lasers or laser diodes) into an optical receiver (e.g., an optical fiber), each light beam having a substantially or fully elliptical beam cross-section and the optical receiver having a substantially or fully circular light receiving cross-section, wherein the system includes: at least one light beam inlet, each inlet being configured to allow each of the at least one light beam to enter the system; a light beam outlet, configured to allow the at least one light beam to leave the system for coupling the at least one light beam into the optical receiver; at least one light beam deflector, such as a mirror and / or a dichroic mirror, for deflecting the light beam in the at least one light beam; and an optical substrate element, such as an optical substrate extending in the (x-y) plane of the system. In this system, at least one of the at least one light beam deflectors is directly fixed to the substrate element, in other words, unintermediately, especially without using any adjustment means, such as the above-mentioned optomechanics or brackets. In particular, the light beam deflector fixed in this way cannot be adjusted after its fixation. Due to the fixation, especially during or even after the fixation, as will be explained in more detail below, the directly fixed light beam deflector may generally rotate within a small rotation angle range about a rotation axis, which rotation results in an additional deflection of the corresponding light beam. This "additional" deflection occurs outside the normal desired deflection. In this system, at least one light beam inlet and / or at least one light beam is further configured such that the semi-major axis of the elliptical cross-section of the corresponding light beam on the deflection surface of the light beam deflector is substantially or fully parallel to the rotation axis. Finally, in this system, at least one light beam deflector is oriented such that after or near the light beam has passed through the light beam outlet, the elliptical cross-section of the at least one light beam overlaps with the circular cross-section of the optical receiver.

[0008] So far, in commercial coupling systems, each deflector element / light beam deflector or at least one deflector element / light beam deflector immediately preceding the light beam outlet is equipped with its own optomechanics / adjustment means, increasing the cost of the system. Advantageously and more user-friendly, for example, special optomechanics are used to align the mirror in the factory and then, after the mirror has been fixed to the system, the mirror is released from the optomechanics, which can then be used to manufacture another system. The inventive concept precisely achieves this advantage. The single, some, or even all light beam deflectors used in the system can be directly fixed to the substrate element of the system without the need to deliver the corresponding optomechanics to the user of the system.

[0009] Furthermore, the inventive concept overcomes the problem of fixing a mirror to a base element / substrate of a system. One might think, for example, of using some screws or simply fixing the mirror by using an adhesive. Unfortunately, each of these processes slightly moves the mirror when fixing it. Screws usually cause a slight movement of the mirror when tightening it. On the other hand, adhesives often shrink when hardening, thus moving the mirror. Furthermore, with thermal changes in the environment, adhesives often shrink or expand, resulting in a thermally induced movement of the mirror after its fixation, which affects the coupling efficiency. Further, there are different ways of fixing a mirror to a base element / substrate. The back side of the mirror can be fixed to a bracket connected to the base element. Another way is to directly fix the mirror to the base element with a side surface on one side of the mirror. Fixation can be done using an adhesive. During the hardening of the adhesive and subsequently due to thermal fluctuations, the adhesive moves, moving the mirror and thus resulting in different angular orientations. This usually invalidates the time-consuming and complex alignment process.

[0010] However, the inventive concept solves this problem, as described below according to a preferred embodiment.

[0011] The idea of orienting the elliptical cross-section of the light beam in the above manner takes advantage of the supposed disadvantage of the elliptical light beam cross-section in order to compensate for the movement of the mirror associated with directly fixing the mirror to the base element. This is described below with reference to FIG. 3.

[0012] Figure 3a A beam deflector / mirror 310 directly fixed to a base element 300 by an adhesive 314 is schematically shown, where the base element 300 is a base plate extending in the x-y plane of the system. The mirror or beam deflector 310 has a deflection surface 311 and a back side 313 opposite to the deflection surface 311, and also has four side surfaces on four sides of the mirror 310. In this embodiment, the mirror is directly fixed to the base element 300 with one of its side surfaces 312 via the adhesive 314. It should be noted that in the context of fixing a beam deflector to a base element, "directly" or "non-indirectly" should be understood in particular as fixing the beam deflector without an adjustment device that allows free adjustment of the beam deflector after its fixation. However, such "direct" fixation does not exclude that the beam deflector can be, for example, irreversibly fitted into a bracket or into a frame, or that the beam deflector and the bracket / frame are a composite unit as an integral part, and the bracket / frame can be fixed to the base element. The fixation itself can be done via an adhesive and / or by means of at least one screw and / or welding or other fixing means. Similarly, it should be noted that the fixation is especially without using, as Figure 2done in the case of any type of adjustable bracket or optomechanics by means of which the beam deflector will be indirectly fixed to the base element.

[0013] Figure 3a The beam 320 is further shown, for example a laser beam travelling in the x-y plane and reflected by the deflection surface 311 of the mirror 310. The irradiation area on the deflection surface 311 is also shown. The arrow 320 indicates the propagation direction of the laser beam, not the beam shape.

[0014] The mirror 310 is fixed to the base element 300 by means of a layer of adhesive 314 which typically creates a layer between the side surface 312 and the substrate 300 that is never truly perfectly uniform but can be in the form of a slight wedge for example. When the wedge of adhesive shrinks or expands due to hardening or thermal changes, this wedge of adhesive will cause the mirror 310 to rotate about an axis parallel to the x-axis. This is explained in Figure 3b However, the rotation of the mirror 310 about an axis parallel to the x-axis does not affect the direction of the reflected beam 320, in other words it does not cause an "extra" deflection as defined above.

[0015] Additionally or alternatively, the wedge of adhesive can be formed as shown in Figure 3c Again, during shrinkage or expansion of the adhesive due to hardening of the adhesive or due to thermal changes, the thicker side of the wedge expands more than the thinner side of the wedge, causing the mirror 310 to tilt or rotate about the axis of rotation y' parallel to the y-axis. However, as shown in Figure 3c the movement of the mirror 310 about the y'-axis causes a deflection of the beam when it is reflected out of the x-y plane, thus causing an additional undesired deflection. However, as explained below, the inventive concept is to a large extent insensitive to such a deflection of the beam out of the x-y plane as long as the elliptical cross-section overlaps with the circular cross-section of the light receiver.

[0016] As mentioned above, another possibility of fixing the mirror 310 to the base element 300 is to use a bracket fixed to the base element to which the mirror 310 is at least partially fixed at its rear side 313. As can be seen from Figure 3, such a fixation may cause the mirror 310 to rotate slightly about an axis parallel to the z-axis when the adhesive shrinks or expands. In this case, it must be ensured that the semi-major axis of the elliptical cross-section of the beam on the deflection surface 311 is (substantially) oriented parallel to the axis of rotation / z-axis.

[0017] As will be further explained below in connection with an embodiment of the inventive concept, Figure 3c the case where the rotation of the mirror 310 about the y'-axis causes the elliptical cross-section to shift with its semi-major axis in the z-direction, as shown in Figure 3dAs indicated by the arrow adjacent to the elliptical beam cross-section 330 in [figure]. As long as the elliptical cross-section 330 overlaps with the circular cross-section 340 of the optical receiver, this shift hardly affects the coupling efficiency.

[0018] It should be noted that each focusing lens performs a Fourier transform on the beam cross-section of the beam passing through the lens. In the case of an elliptical shape, this Fourier transform basically causes the elliptical shape to rotate by 90°. Thus, for example, as Figure 1 shown, the lens 170 rotates the elliptical shape of the beams 120, 121, which include elliptical cross-sections oriented substantially parallel to the x-y plane between the dichroic beam deflector 130 and the lens 170, such that the semi-major axis of the beam near the beam exit 190 / at the optical receiver 160 is oriented along the z-direction, as Figure 3d indicated by the arrow adjacent to the elliptical beam cross-section 330 in [figure].

[0019] It should be noted that "substantially or completely elliptical" or "elliptical or at least substantially elliptical" is intended to describe an elliptical shape that can vary due to interaction with optical elements such as (dichroic) mirrors, optical lenses, etc. This also applies to the expressions "substantially or completely circular" and the definitions of "substantially or completely parallel" and "substantially or completely perpendicular". Further, deviations are allowed within the usual tolerances.

[0020] Referring again to Figure 3, the adhesive wedge between the side surface 312 of the beam deflector 310 and the substrate element 300 will have a relevant effect only if the movement of the wedge causes the beam deflector to rotate about the y'-axis (see Figure 3c ). As already discussed above, this causes the beam to deflect in the z-direction, resulting in the focus moving along the z-direction on the light receiving element (see Figure 3d ). If the adhesive shrinks or expands, the beam deflector will hardly rotate significantly about the z-axis. Keeping this in mind, if the beam is correctly oriented, the elliptical shape of the laser beam cross-section can even help the laser to be stably coupled into the optical receiver / fiber. By orienting the beam such that the semi-major axis of the elliptical cross-section lies in the x-y plane after the beam entrance of the system, the focus of the beam will present its semi-major axis oriented parallel to the z-axis after passing through the exit including the lens, as Figure 3d shown. Thus, if the beam moves in the z-direction, due to the elongation of the elliptical focus 330 in this direction, the circular light receiving cross-section 340 will still be significantly illuminated.

[0021] In an advantageous embodiment, at least one beam inlet or each beam inlet includes a collimating lens. According to the inventive concept, the beam outlet includes a lens for performing a Fourier transform, in particular a focusing lens. When the collimating lens generates a parallel beam of light, the focusing lens focuses a parallel beam of light into a focal point. The coupling end of the optical receiver / fiber should be located at this focal point.

[0022] In another advantageous embodiment, the beam outlet is also configured to receive an optical fiber serving as an optical receiver so that the optical fiber can be mounted to the beam outlet. Similarly, it is advantageous if a laser, in particular a laser diode, can be mounted to the beam inlet.

[0023] Generally, the side surface of the beam deflector is substantially or completely perpendicular to the deflection surface of the beam deflector for deflecting the beam.

[0024] The inventive concept is particularly advantageous for coupling two or more beams into an optical receiver such as an optical fiber. In this case, at least one of the beam deflectors is a dichroic beam deflector that allows a first beam to pass through the dichroic beam deflector and deflects a second beam, for example due to the wavelength characteristics of the dichroic beam deflector. Such a dichroic beam deflector is particularly suitable for superimposing two beams. In the case of more than two beams, more than one dichroic beam deflector can be used. Such a dichroic beam deflector is advantageously arranged for guiding the first beam and the second beam to the beam outlet.

[0025] In an advantageous embodiment, at least the beam deflector immediately preceding the beam outlet is directly fixed to the substrate element. Generally, the system is set up to start adjusting the beam deflector in the direction from the inlet to the outlet. Any deviation of the preceding mirror / beam deflector can be compensated to some extent by correspondingly adjusting the beam deflector / dichroic beam deflector immediately preceding the beam outlet. For this purpose, the beam deflector / dichroic beam deflector has hitherto usually been provided with opto-mechanics, i.e., adjusting means. However, with the inventive concept, even these opto-mechanics can become redundant. In this context, it is particularly advantageous if each of at least one beam deflector is directly fixed to the substrate element without using any opto-mechanics.

[0026] In a second aspect of the inventive concept, a method for coupling at least one light beam into a light receiver is provided. A method for coupling at least one light beam (each light beam having an elliptical or at least substantially elliptical beam cross-section) into a light receiver having a circular or at least substantially circular light receiving cross-section includes the steps of: providing at least one beam deflector for deflecting the light beam in at least one light beam, and providing an optical substrate element, in particular an optical substrate element extending in a plane, wherein at least one beam deflector in the at least one beam deflector is directly fixed to the substrate element directly after an orienting step for orienting the at least one beam deflector, in particular without an adjustment device, the adjustment device allowing adjustment of the directly fixed deflector element after its fixing, wherein due to the fixing, the corresponding directly fixed beam deflector is allowed to rotate about a rotation axis within a small range, the rotation causing an additional (undesired) deflection of the corresponding light beam, and the semi-major axis of the elliptical cross-section of the corresponding light beam on the deflection surface of the corresponding beam deflector is oriented parallel to or at least substantially parallel to the rotation axis, wherein the orienting step for orienting the at least one beam deflector includes orienting the at least one beam deflector such that the elliptical cross-section of the at least one light beam overlaps the circular cross-section of the light receiver.

[0027] In a preferred embodiment, the method includes the steps of: providing at least one beam deflector for deflecting the light beam in at least one light beam, and providing an optical substrate element extending in the x-y plane, wherein at least one beam deflector in the at least one beam deflector is directly fixed to the substrate element with a side surface of the beam deflector directly after an orienting step for orienting the at least one beam deflector such that the deflection surface of the beam deflector extends at least substantially perpendicular to the surface / x-y plane of the substrate element, and when the corresponding light beam collides / strikes the deflection surface of the corresponding beam deflector, the semi-major axis of the elliptical cross-section of the corresponding light beam is oriented parallel to or at least substantially parallel to the x-y plane.

[0028] It should be noted that the above features related to the system according to the first aspect of the inventive concept represent a similar description of the corresponding features of the method according to the second aspect of the inventive concept. Some or all of the method steps may be performed (or performed by using) a hardware device, for example, a processor, a microprocessor, a programmable computer, an electronic circuit. In some embodiments, one or more of the most important method steps may be performed by such a device.

[0029] The term “and / or” used herein includes any and all combinations of one or more of the related listed items and may be abbreviated as “ / ”.

[0030] It should be noted that the features of the above examples and the examples explained below can be combined in whole or in part with other examples not explicitly mentioned herein, yet still be part of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A top view of a system according to an embodiment of the inventive concept is schematically shown;

[0032] Figure 2 An example of an optical-mechanical mirror support of the prior art is shown;

[0033] FIG. 3 schematically shows a beam deflector directly fixed to a substrate element used in a system according to an embodiment of the inventive concept; and

[0034] Figure 4 is schematically shown in Figure 1 a perspective view of a part of the system shown therein and a light receiver according to an embodiment of the inventive concept. DETAILED DESCRIPTION

[0035] In Figure 1 , two light beams 120, 121 are coupled into a light receiver 160 having a circular light-receiving cross-section, each light beam having an elliptical beam cross-section. The system is labeled 100. The system 100 includes two light beam inlets 180, 181, each inlet being configured to allow each of the light beams 120 and 121 to enter the system 100. In the illustrated embodiment, the light beam inlet 180 includes a collimating lens 150 and is configured to mount a laser diode 140 for generating the light beam 120. The same applies to the light beam inlet 181, which includes a collimating lens 151 and is configured to receive a laser diode 141 for generating the light beam 121.

[0036] The system 100 further includes a light beam outlet 190, which is configured to allow the combined two light beams 120 and 121 to leave the system 100 for coupling the light beams into the light receiver 160, which is an optical fiber in the illustrated embodiment. The light beam outlet 190 also includes a condenser lens 170 and is further configured to receive the optical fiber 160. Generally, the system 100 includes not only the elements shown in Figure 1 and an optical substrate element preferably in the form of a substrate 300 (see, for example, FIG. 3 or Figure 4 ), but also at least one side wall (not shown in the figure), and in particular a top cover element (not shown in the figure), such that the system can be in a box shape. In this case, at least one of the light beam inlets 180, 181 and the light beam outlet 190 are formed in the side wall.

[0037] System 100 also includes a plurality of beam deflectors 110, 111, 112 and 130, for example, fitted into corresponding frames or onto corresponding brackets (not shown), for deflecting beams 120, 121 so as to direct them towards beam outlet 190. Beam deflectors 110, 111, 112 may be in the form of simple mirrors, while beam deflector 130 may be a dichroic beam deflector which allows beam 121 to pass through and deflects beam 120 so as to combine the two beams 120, 121 onto the same optical path and preferably propagate in a substantially coaxial manner in the direction towards beam outlet 190.

[0038] System 100 may also include optical elements and may include more than two beam inlets. A person skilled in the art can easily modify system 100 into a system for coupling more than two beams into optical receiving element 160.

[0039] System 100 also includes an optical substrate element extending in the x-y plane of the system, which plane corresponds to Figure 1 the drawing plane. At least one beam deflector, in particular dichroic beam deflector 130 and advantageously also mirrors 110, 111, 112, are directly fixed to the substrate element by their side surfaces. This will be further described with reference to FIG. 3. The deflection surfaces of the fixed beam deflectors extend substantially or completely perpendicular to the substrate element / Figure 1 the drawing plane. Such fixed beam deflectors are advantageously fixed by an adhesive. Alternatively or additionally, the fixing can be achieved by at least one screw and / or by welding.

[0040] System 100 can advantageously be set up in the factory by first aligning mirrors 110 and 111, secondly aligning mirror 112, and finally aligning dichroic mirror 130, and fixing each aligned mirror to the substrate element with an adhesive. Then, the pre-built system 100 can be delivered to the user without the user having to perform alignment with the aid of opto-mechanics.

[0041] Figure 2 A photograph of an opto-mechanical mount or opto-mechanics 200 for a beam deflector is shown. The opto-mechanical mount or opto-mechanics 200 has hitherto generally been used as an adjustment device for aligning and fixing beam deflectors. The mirror mounting surface of opto-mechanics 200 is designated as 210. Opto-mechanics 200 includes ball bearings 220, springs 240 and adjustment screws 230. At least two support points of mirror mounting surface 210 can be moved back and forth by corresponding screws 230 having fine-pitch threads. Thus, vertical and horizontal tilts can be set independently. This allows highly precise movement of the beam deflector. Such opto-mechanics 200 is costly and the alignment process is time-consuming.

[0042] FIG. 3 schematically shows a beam deflector 310 directly fixed to an optical substrate element 300 as Figure 1 part of an embodiment of the system 100 shown. The beam deflector 310 can be Figure 1 any one of the beam deflectors 110, 111, 112, 130 in Figure 3a . The beam deflector 310 is directly fixed to the substrate element 300 by its side surface 312 via an adhesive layer 314. As Figures 3a to 3d shown, the semi-major axis of the elliptical cross-section 330 of the beam 320 is oriented parallel to the x-y plane, the optical substrate element 300 extends in the x-y plane and the beam 320 travels in the x-y plane in a direction towards the deflection surface 311. Figure 3c More details of Figures 3a to 3d have been discussed above. As explained above, the fixing process and any possible subsequent thermal variations can cause the mirror to move. Although movement about the z-axis is unlikely, movement about the x-axis is irrelevant to the coupling efficiency. The only relevant movement is about the y'-axis, as Figure 3c shown. Such movement causes the deflected beam 320 to deflect out of the x-y plane, resulting in movement of the focus 330 in the z-direction, as Figure 3d shown. As long as the elliptical cross-section 330 of the beam 320 overlaps with the circular cross-section of the optical fiber 160, movement of the semi-major axis in the z-direction hardly affects the coupling efficiency.

[0043] Figure 4 is schematically shown in perspective as part of a system such as shown in Figure 1 and an optical receiver 160 according to an embodiment of the inventive concept. The beam deflector 310 can be a mirror, especially in the case where only one beam is coupled to the optical receiver, or a dichroic beam deflector (as Figure 1 shown for two beams) in the case where two or more beams are coupled to the optical receiver. In the latter case, Figure 4 the beam 320 in Figure 4 corresponds to the beam 120 in Figure 1 , and the beam deflector 310 corresponds to the dichroic beam deflector 130 in Figure 1 . Similarly, the arrow 320 indicates the laser beam propagation direction and the elliptical shape represents the corresponding beam cross-section. The beam 320, after being deflected by the beam deflector 310, is directed to a condenser lens 170, Figure 4 where an elliptical illumination area (on the surface of the beam deflector 310 and on the side of the condenser lens 170 facing the beam deflector 310) is shown. The condenser lens 170 focuses the beam onto the front side of the optical receiver, which is here the optical fiber 160, and the optical fiber 160 is arranged such that its front side is in the focal plane of the lens 170. This arrangement results in a beam having an elliptical beam shape 330 being coupled into an optical fiber 160 having a circular light receiving cross-section 340, asFigure 3d As shown. The elliptical shape of the light beam 320 between the beam deflector 310 and the condenser lens 170 is oriented such that its major axis is substantially parallel to the x-y plane. Through the Fourier transform function of the lens 170, the lens 170 rotates the elliptical shape of the light beam 320 by approximately 90 degrees, thereby generating an (focused) elliptical shape of the light beam 320 whose major axis is oriented substantially parallel to the z-axis (as Figure 3d shown).

[0044] For example, from Figure 3a and Figure 4 it can be seen that the mirror size in the y-direction, or more generally, the mirror width, should be ensured to fully cover the elliptical light beam shape. Since the major axis of the elliptical light beam shape is oriented parallel to the x-y plane, if the light beam impinges on the mirror non-vertically, the major axis is magnified on the mirror surface. (For illustrative purposes, for example, if the light beam impinges on the mirror non-vertically, a circular light beam profile will produce an elliptical illumination area on the mirror surface). Therefore, according to the inventive concept, an elliptical light beam profile with a major axis parallel to the x-y plane may require a mirror with a relatively large size in the y-direction (as Figure 3a and Figure 4 shown), and this fact generally prevents those skilled in the art from choosing such an orientation of the light beam profile, but rather leads to the selection of a preferred orientation with the major axis parallel to the z-direction. However, as explained above, the inventive concept provides significant advantages such as better optical coupling stability.

[0045] List of reference numerals

[0046] 100 System

[0047] 110 Beam deflector, mirror

[0048] 111 Beam deflector, mirror

[0049] 112 Beam deflector, mirror

[0050] 130 Beam deflector, dichroic beam deflector

[0051] 120 Light beam

[0052] 121 Light beam

[0053] 140 Laser diode

[0054] 141 Laser diode

[0055] 150 Collimating lens

[0056] 151 Collimating lens

[0057] 160 Optical receiver, optical fiber

[0058] 170 Condensing lens

[0059] 180 Beam inlet

[0060] 181 Beam inlet

[0061] 190 Beam outlet

[0062] 200 Optical machine support, optomechanics

[0063] 210 Mirror mounting surface

[0064] 220 Ball bearing

[0065] 230 Adjusting screw

[0066] 240 Spring

[0067] 300 Optical substrate element, substrate

[0068] 310 Beam deflector, mirror, dichroic beam deflector

[0069] 311 Deflection surface

[0070] 312 Side surface

[0071] 313 Back side

[0072] 314 Adhesive layer, adhesive

[0073] 320 Beam

[0074] 330 Oval cross-section

[0075] 340 Circular cross-section

Claims

1. A system for coupling at least one light beam into a light receiver having a substantially or completely circular light-receiving cross-section, each light beam having a substantially or completely elliptical beam cross-section, the system comprising: at least one beam inlet, each beam inlet being configured to allow each of the at least one light beams to enter the system, a beam outlet configured to allow the at least one light beam to leave the system for coupling the at least one light beam into the light receiver, the beam outlet including a lens for performing a Fourier transform, at least one beam deflector for deflecting the light beam in the at least one light beam, and an optical substrate element extending in the x-y plane of the system, at least one of the at least one beam deflectors being directly fixed to the substrate element, wherein, due to the fixing, the corresponding directly-fixed beam deflector is allowed to rotate about a rotation axis parallel to the y-axis in the x-y plane, the rotation causing an additional deflection of the corresponding light beam, wherein the corresponding light beam and / or its assigned beam inlet is further configured such that the semi-major axis of the elliptical cross-section of the light beam on the deflection surface of the corresponding beam deflector is substantially or completely oriented parallel to the rotation axis, and wherein the at least one beam deflector and the lens are oriented such that after passing through the beam outlet, the elliptical cross-section of the at least one light beam overlaps the circular cross-section of the light receiver, and the semi-major axis of the elliptical cross-section of the at least one light beam is oriented along the z-direction perpendicular to the x-y plane.

2. The system according to claim 1, wherein, at least one directly-fixed beam deflector is fixed to the substrate element by a side surface of the beam deflector, and the corresponding light beam and / or its assigned beam inlet is further configured such that the semi-major axis of the elliptical cross-section of the light beam on the deflection surface of the corresponding beam deflector is substantially or completely oriented parallel to the x-y plane.

3. The system according to claim 1 or 2, for allowing more than one light beam to enter the system, wherein, at least one of the at least one beam deflectors is a dichroic beam deflector for allowing a first light beam in the light beam to pass through the dichroic beam deflector system, having more than one beam inlet and for deflecting a second light beam in the light beam.

4. The system according to claim 3, wherein, the dichroic beam deflector is arranged to direct the first light beam and the second light beam to the beam outlet.

5. The system according to claim 1, wherein, at least the beam deflector immediately before the beam outlet is directly fixed to the substrate element.

6. The system according to claim 1, wherein, each of the at least one beam deflectors is directly fixed to the substrate element.

7. The system according to claim 1, wherein, at least one beam deflector is directly fixed to the substrate element by an adhesive and / or by means of at least one screw and / or by welding.

8. The system according to claim 2, wherein, the side surface is substantially or completely perpendicular to the deflection surface of the corresponding beam deflector for deflecting the light beam.

9. The system according to claim 1, wherein, At least one beam inlet is also configured to mount a respective laser for generating a respective beam to the system.

10. The system according to claim 1, wherein, at least one beam inlet includes a collimating lens.

11. The system according to claim 1, wherein, the beam outlet is also configured to receive an optical fiber as a light receiver.

12. The system according to claim 1, wherein, the lens performs a Fourier transform or includes a condenser lens.

13. The system according to claim 1, wherein, at least one beam deflector of the at least one beam deflector is directly fixed to a substrate element without an adjusting device, and the adjusting device allows the directly fixed beam deflector to be adjusted after its fixation.

14. A method for coupling at least one beam into a light receiver having a circular or at least substantially circular light receiving cross-section, each beam having an elliptical or at least substantially elliptical beam cross-section, the method comprising the steps of: providing at least one beam deflector for deflecting a beam in the at least one beam, providing a lens for focusing the deflected beam and for performing a Fourier transform, and providing an optical substrate element extending in the x-y plane of the system, wherein at least one beam deflector of the at least one beam deflector is directly fixed to the substrate element after an orienting step for orienting the at least one beam deflector, and wherein due to the fixation, the respective directly fixed beam deflector is allowed to rotate about an axis of rotation parallel to the y-axis of the x-y plane, and this rotation causes an additional deflection of the corresponding beam, and orienting the semi-major axis of the elliptical cross-section of the respective beam on the deflection surface of the respective beam deflector parallel to or at least substantially parallel to the axis of rotation, wherein the orienting step for orienting the at least one beam deflector includes orienting the at least one beam deflector and the lens such that after passing through the beam outlet, the elliptical cross-section of the at least one beam overlaps the circular cross-section of the light receiver, and the semi-major axis of the elliptical cross-section of the at least one beam is oriented along the z-direction perpendicular to the x-y plane.

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