Tunable laser based light source

Abstract

A tunable laser based light source for Li-Fi communication comprising a laser (1), a first optical element (3) and a second optical element (4). The first optical element (3) is configured to reflect and / or refract a scanning beam (2) emitted from the laser (1). The second optical element (4) is configured to widen the scanning beam (2) reflected / refracted by the first optical element (3). The scanning beam (2) is configured to scan a scan area extending with a first scan length in a widening direction (S1) and with a second scan length in a scanning direction (S2). The second optical element (4) is configured to widen the scanning beam (2) in the widening direction (S1) to a width greater than the first scan length, and the laser (1) and the first optical element (3) are configured to cooperate to enable the scanning beam (2) to sweep along the scanning direction (S2).

Description

Technical Field

[0001] This invention relates to a tunable laser-based light source for Li-Fi communication. Background Technology

[0002] Li-Fi (Li-Fi) has emerged as an emerging technology in wireless communication. Li-Fi systems offer high data transmission speeds and large bandwidth, reducing the risk of interference from other sources. However, the risk of interference still exists in Li-Fi systems (especially if several devices are operating on the same Li-Fi system).

[0003] For example, an office environment might have several access points, each illuminating a few square meters to achieve sufficient coverage. Devices capable of communicating with these access points can also illuminate an area of ​​several square meters to ensure a connection is established with at least one access point. Devices connected to the same access point will share that access point's bandwidth, although in some cases these devices will connect to more than one access point, which can lead to unwanted interference. Interference with access points results in lower bandwidth, which is particularly undesirable as the demand for higher data rates is anticipated to increase.

[0004] To avoid interference issues, point-to-point communication has been proposed for use in Li-Fi systems. Point-to-point communication relies on a narrow beam to illuminate only a small area, specifically targeting the point of interest. Beam aiming can be achieved using mirrors or gratings that adjust the narrow beam. In Ton Koonen's… Indoor Optical Wireless Systems: Technology, Trends, and Applications The article in the Journal of Lightwave Technology, Vol. 36, No. 8, pp. 1459-1467, April 15, 2018, explains a passive two-dimensional setup for manipulating narrow beams, in which two gratings are used in combination with a wavelength-tunable laser to achieve manipulation of the narrow beam.

[0005] However, these systems that rely on point-to-point communication still have several drawbacks: using two gratings to manipulate a narrow beam is a complex setup that may require extensive scanning before locking can be achieved to enable point-to-point communication. Summary of the Invention

[0006] One object of the present invention is to overcome these problems and to provide a light source based on a tunable laser that overcomes or at least mitigates the problems of the prior art, and thus reduces scanning time and is easy to set up.

[0007] According to a first aspect of the invention, this and other objectives are achieved by a tunable laser-based light source for Li-Fi communication, the light source comprising a laser for emitting a scanning beam in operation, a first optical element configured to reflect and / or refract the scanning beam emitted from the laser, and a second optical element configured to broaden the scanning beam reflected / refracted by the first optical element, wherein the scanning beam is configured to scan a scanning region extending in a broadening direction by a first scan length and in the scanning direction by a second scan length, wherein the broadening direction and the scanning direction are perpendicular to each other, wherein the second optical element is configured to broaden the scanning beam in the broadening direction to a width greater than the first scan length, and wherein the laser and the first optical element are configured to cooperate such that the scanning beam can sweep along the scanning direction.

[0008] Providing a widened scanning beam for tunable laser-based light sources used in Li-Fi communications enables more continuous scanning behavior. When the scanning beam is widened to a width greater than the first scan length, it allows for one-dimensional scanning using only the beam. This reduces the degrees of freedom involved in scanning with the beam, thereby reducing the complexity associated with scanning. Furthermore, since the beam only needs to scan in one dimension, higher scanning speeds can be achieved, which is particularly significant for high-speed Li-Fi systems.

[0009] In the context of this invention, the term "scanning beam" refers to any beam that can be used for scanning. A scanning beam can have a fixed wavelength or an adjustable wavelength.

[0010] In the context of this invention, the term "scanning area" refers to the area scanned by the scanned beam. In one embodiment, the laser is a wavelength-tunable laser and the first optical element is a diffraction grating, thereby allowing the reflected / refracted scanned beam to sweep along the scanning direction as the wavelength changes.

[0011] By altering the laser wavelength to sweep the scanning beam, the need for moving parts is eliminated, thereby reducing the risk of mechanical failure and minimizing noise during operation. Furthermore, the laser wavelength can be changed almost continuously, resulting in high scanning resolution along the scanning direction. The diffraction grating can be either a reflective diffraction grating or a transmission grating.

[0012] In one embodiment, the first optical element is a blazed grating.

[0013] Using a blazed grating ensures maximum grating efficiency for a specific diffraction order. This is advantageous for a broadened scanning beam, ensuring that the scanning beam does not diffuse as it sweeps along the scanning direction.

[0014] In one embodiment, the first optical element is a rotatable and / or deformable grating configured to reflect the scanning beam and broaden the scanning beam in the broadening direction.

[0015] Therefore, by moving the grating, the broadening of the beam in the first direction is variable. This can be used to both broaden and focus the scanning beam. Furthermore, narrowing the scanning beam can be used to zoom in on the receiver to establish an improved data connection. When searching for a data connection, a wide beam is desired to reduce scan time, but once the connection is established, a narrow beam may be desired because it concentrates more power on the receiver (which improves the signal-to-noise ratio).

[0016] In one embodiment, the first optical component and the second optical component are the same optical component.

[0017] Providing the characteristics of broadening and sweeping the scanning beam in the same optical components can facilitate a compact system.

[0018] In one embodiment, the laser is a fixed-spectrum laser, and the first optical element is a rotatable mirror configured to reflect the scanning beam and sweep the scanning beam by rotating along the scanning direction.

[0019] The use of fixed-spectrum lasers and pivotable mirrors is an inexpensive and easy-to-manufacture setup. The pivotable mirror can be a microelectromechanical system (MEMS) device or a current mirror.

[0020] In one embodiment, the second optical element is a widening lens that extends in the widening direction and longitudinally in the scanning direction, wherein the curvature of the widening lens in the scanning direction is substantially zero.

[0021] The provision of lenses for widening provides a system that is easy to manufacture. Lenses can take on a wide variety of geometries, such as biconvex, plano-convex, plano-concave, or biconcave.

[0022] In one embodiment, the light source based on the tunable laser includes a third optical element arranged such that a scanning beam emitted from the laser passes through the third optical element before being reflected / refracted by a first optical element, the third optical element including collimator optics for collimating the scanning beam.

[0023] Collimating the scan beam before reflecting and widening it ensures that the beam is focused, thus allowing for a longer signal range for the scan beam.

[0024] In one embodiment, a third optical element is configured to collimate the scanning beam in the scanning direction.

[0025] Collimating the scanning beam in the scanning direction minimizes the loss of scanning resolution in that direction.

[0026] In one embodiment, the light source based on the tunable laser further includes a housing, and the laser, the first optical element, and the second optical element are integrated with the housing.

[0027] Integrating the optical components with the housing ensures that the tunable laser-based light source is easy to transport and compact. Furthermore, the housing protects the optical components, preventing contamination of the system by dust and other particles. Integrating the components with the housing also helps reduce calibration time when moving the tunable laser-based light source, adjusting it to a new receiver, or implementing the light source in a system, because all optical components can be moved together, rather than individually.

[0028] In one embodiment, the housing includes a light exit window for transmitting light, wherein a portion of the light exit window is formed to define a widening lens.

[0029] Furthermore, integrating a widened lens into the light exit window of the housing allows for a compact tunable laser-based light source.

[0030] In one embodiment, the widening lens is arranged to extend such that the widening direction extends parallel to or perpendicular to the direction of the laser emitting the scanning beam.

[0031] In particular, it may be advantageous to extend the widening lens in a widening direction (perpendicular to the direction in which the laser emits the scanning beam). This is because it allows for a narrow housing, as it allows the widening lens to extend longitudinally parallel to the direction in which the laser emits the scanning beam.

[0032] According to a second aspect of the present invention, the present invention relates to a Li-Fi system comprising a tunable laser-based light source according to a first aspect of the present invention.

[0033] Note that this invention relates to all possible combinations of the features described in the claims. Other objects, features, and advantages of the inventive concept will become apparent from the following detailed disclosure, the appended claims, and the accompanying drawings. A feature described with respect to one aspect may also be incorporated into another aspect, and the advantages of that feature apply to all aspects incorporating that feature. Attached Figure Description

[0034] This and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which illustrate multiple embodiments of the invention.

[0035] Figure 1 A schematic diagram illustrating the principle of the present invention is shown.

[0036] Figure 2 A schematic cross-sectional view of a first embodiment of the invention is shown, in which the optical components have been integrated with the housing.

[0037] Figure 3 A schematic perspective view of a second embodiment of the invention is shown, in which the optical components have been integrated with the housing.

[0038] Figure 4 A schematic perspective view of a third embodiment of the invention is shown, in which the optical components have been integrated with the housing.

[0039] As illustrated in the figures, the dimensions of layers and regions have been enlarged for illustrative purposes, and thus these dimensions are provided to illustrate the general structure of embodiments of the invention. Similar reference numerals always refer to similar elements. Detailed Implementation

[0040] The invention will now be described more fully below with reference to the accompanying drawings, which illustrate presently preferred embodiments of the invention. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness and to fully convey the scope of the invention to those skilled in the art.

[0041] First refer to Figure 1 The diagram illustrates the principle of the invention. Laser 1 emits a scanning beam 2, which is reflected away from the first optical element 3. Laser 1 can be a fixed-wavelength laser or a tunable-wavelength laser. The first optical element 3 can be a diffraction grating, a mirror, or a deformable grating. The cooperation between laser 1 and the first optical element 3 allows the scanning beam 2 to sweep along the scanning direction S2. Figure 1 Not shown above is a second optical element configured to broaden the scanning beam 2. The second optical element is configured to broaden the scanning beam 2 reflected away from the first optical element 3. Specifically, the second optical element is configured to broaden the scanning beam 2 along the broadening direction S1. The sweeping of the broadened scanning beam 2 along the scanning direction S2 allows the scanning beam 2 to scan a scanning area extending along both the broadening direction S1 and the scanning direction S2. Specifically, the second optical element is configured to broaden the scanning beam to a width greater than the width of the scanning area along the broadening direction S1.

[0042] In another embodiment, sweeping and broadening of the scanning beam 2 can be achieved using the same optical element. This can be accomplished, for example, by providing a deformable grating that can be tilted and / or shaped (e.g., from planar to cylindrical, concave, or convex). The tilting and / or deformation of the grating can then be used to broaden or narrow the scanning beam 2, and sweeping of the broadened scanning beam can be accomplished by adjusting the wavelength of the scanning beam 2. The first optical element 3 and the second optical element 4 can then be integrated into a single optical assembly.

[0043] refer to Figure 2 The illustration depicts a schematic cross-sectional view of a first embodiment of the invention, with optical components integrated into a housing 6. The laser 1, the first optical element 3, and the second optical element 4 are all integrated into the housing 6. Furthermore, a third optical element 5 is also integrated into the housing 6. In the illustrated embodiment, the third optical element 5 is a collimator. The third optical element 5 is arranged between the laser 1 and the first optical element 3. The laser 1 emits a scanning beam 2 that passes through the third optical element 5, thereby aligning the scanning beam 2 parallel to the first optical element 3 before reflection. The first optical element 3 is an echelle grating. After reflection from the first optical element 3, the scanning beam 2 passes through a light exit window 7 in the housing 6. The light exit window 7 is preferably made of an optically transparent material to limit the loss of the scanning beam 2 passing through it. In the illustrated embodiment, a portion of the light exit window has been formed to define a second optical element 4. The second optical element 4 is a broadened lens with a plano-convex geometry. The scanning beam 2 passing through the second optical element 4 is broadened. In the illustrated embodiment, the laser 1 is a wavelength-tunable laser. By changing the wavelength of laser 1, the scanning beam reflected from the second optical element 3 is reflected in different directions. Thus, a scanning mechanism is achieved through the cooperation between laser 1 and the first optical element 3. Although the scanning beam 2 is shown as being reflected from the echelle grating, in other embodiments, other types of refractive gratings or diffraction gratings can be used to refract or reflect the scanning beam 2 through the grating.

[0044] refer to Figure 3 This shows a schematic perspective view of a second embodiment of the invention, in which optical components 3 and 4 are integrated with the housing 6. In contrast to the first embodiment of the invention, see [reference needed]. Figure 2The scanning mechanism is not achieved through the cooperation of a wavelength-tunable laser and a diffraction grating. Instead, laser 1 is a fixed-wavelength laser and the first optical element 3 is a rotatable mirror. The scanning mechanism is achieved by reflecting the scanning beam 2 emitted from laser 1 away from the first optical element 3 while simultaneously rotating the first optical element 3, thereby allowing the scanning beam 2 to be scanned along the scanning direction S2. The first optical element 3 is capable of rotating about a rotation axis parallel to the broadening direction S1. The second optical element 4 is a lens configured to broaden the scanning beam 2 along the broadening direction S1. This lens is formed as part of the light exit window 7 of the housing 6. The lens extends longitudinally parallel to the scanning direction S2 and perpendicular to the direction in which the laser 1 emits the scanning beam 2. Furthermore, the curvature of this lens in the scanning direction S2 is essentially zero. This essentially zero curvature ensures that the scanning beam 2 is not broadened in the scanning direction S2, thereby ensuring no loss of resolution along the scanning direction S2.

[0045] refer to Figure 4 The diagram shows a schematic perspective view of a third embodiment of the invention, in which the first optical element 3 and the second optical element 4 are integrated with the housing 6. The third embodiment is similar to the second embodiment, except that the second optical element 4 (which is a broadening lens) has been rotated by 90 degrees. The rotation of the broadening lens 4 causes the broadening lens to extend longitudinally parallel to the scanning direction S2 and parallel to the direction in which the laser 1 emits the scanning beam 2.

[0046] Those skilled in the art will recognize that the invention is by no means limited to the preferred embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims. For example, even though only a lens has been mentioned as a second optical component, a reflector or other optical components may also be used to broaden the scanning beam in the broadening direction. The invention is also not limited to the optical components mentioned herein, but may incorporate several other optical components, such as beam splitters or phase modulators. These other optical components may be placed between the laser and the first optical component, between the first and second optical components, and / or after the second optical component.

[0047] Additionally, by studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The mere fact that certain measures are referenced in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously.

Claims

1. A tunable laser-based light source for Li-Fi communication, comprising: A laser (1) is used to emit a scanning beam (2) during operation. The first optical element (3) is configured to reflect and / or refract the scanning beam emitted from the laser, and The second optical element (4) is configured to broaden the scanning beam reflected / refracted by the first optical element. The scanning beam (2) is configured to scan the scanning area. The scanning region extends with a first scan length in the widening direction (S1) and with a second scan length in the scanning direction (S2). The widening direction (S1) and the scanning direction (S2) are perpendicular to each other. The second optical element (4) is configured to broaden the scanning beam to a width greater than the first scanning length in the broadening direction (S1), and The laser (1) and the first optical element (3) are configured to cooperate so that the scanning beam can sweep along the scanning direction (S2).

2. The light source based on a tunable laser according to claim 1, wherein the laser (1) is a wavelength-tunable laser and the first optical element is a diffraction grating, thereby allowing the reflected scanning beam to sweep along the scanning direction when the wavelength changes.

3. The light source based on a tunable laser according to claim 2, wherein the first optical element (3) is a blazed grating.

4. The light source based on a tunable laser according to claim 2 or 3, wherein the first optical element is a rotatable and / or deformable grating, the rotatable and / or deformable grating being configured to reflect the scanning beam and broaden the scanning beam in the broadening direction.

5. The light source based on a tunable laser according to any one of claims 1-3, wherein the first optical element and the second optical element are the same optical element.

6. The light source based on a tunable laser according to claim 1, wherein the laser (1) is a fixed-spectrum laser and the first optical element (3) is a rotatable mirror configured to reflect a scanning beam and to sweep the scanning beam by rotation along the scanning direction.

7. The light source based on a tunable laser according to any one of claims 1-3, wherein the second optical element (4) is a widening lens extending in the widening direction and longitudinally extending in the scanning direction, wherein the curvature of the widening lens in the scanning direction is substantially zero.

8. A light source based on a tunable laser according to any one of claims 1-3, comprising a third optical element (5) arranged such that a scanning beam emitted from the laser passes through the third optical element before being reflected / refracted by the first optical element, the third optical element comprising collimator optics for collimating the scanning beam.

9. The light source based on a tunable laser according to claim 8, wherein the third optical element (5) is configured to collimate the scanning beam in the scanning direction.

10. The tunable laser-based light source according to any one of claims 1-3, wherein the tunable laser-based light source further comprises a housing (6), and wherein the laser, the first optical element and the second optical element are integrated with the housing.

11. The tunable laser-based light source according to claim 7, wherein the tunable laser-based light source further includes a housing (6), and wherein the laser, the first optical element and the second optical element are integrated with the housing.

12. The tunable laser-based light source of claim 11, wherein the housing includes a light exit window (7) for transmitting light, wherein a portion of the light exit window is formed to define the widening lens.

13. The light source based on a tunable laser according to claim 7, wherein the widening lens is arranged to extend such that the widening direction (S1): Extending parallel to the direction of the scanning beam emitted by the laser, or It extends perpendicular to the direction in which the laser emits the scanning beam.

14. A Li-Fi system comprising a tunable laser-based light source according to any one of the preceding claims.

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