NL2037871B1

NL2037871B1 - An optical wireless communication system comprising a transmitter and a receiver as well as a corresponding method of operating the optical wireless communication system and a corresponding transmitter and receiver for operating in the optical wireless communication system.

Info

Publication number: NL2037871B1
Application number: NL2037871A
Authority: NL
Inventors: Marcellus Jozef Koonen Antonius
Original assignee: Univ Eindhoven Tech
Priority date: 2024-06-06
Filing date: 2024-06-06
Publication date: 2026-01-08
Also published as: WO2025254529A1

Abstract

An optical wireless communication system comprising a transmitter and a receiver, the transmitter arranged for transmitting a wireless beam comprising multiple wavelengths, the transmitter comprising: an Arrayed Wavelength Grating Router, AWGR, comprising multiple input ports which each may feed multiple wavelengths into the AWGR, wherein the AWGR also comprises multiple output ports, which each emit a single wavelength of the multiple wavelengths from each input port, and wherein the same wavelength from each input port exits from a different output port in a cyclic sequence; a fiber array comprising a plurality of fibers, wherein each of the fibers is uniquely connected to one output of the AWGR such that a wireless beam comprising the multiple wavelengths is output from one of the fibers of the plurality of fibers.

Description

Title

An optical wireless communication system comprising a transmitter and a receiver as well as a corresponding method of operating the optical wireless communication system and a corresponding transmitter and receiver for operating in the optical wireless communication system.

Technical Field

The present disclosure relates to the field of optical wireless communication, specifically transmitting and receiving optical wireless communication beams able to transfer a higher data density.

Background

Optical wireless communication, also known as free-space optical communication, FSO, is a technology that enables the transmission of data through free space using optical signals, typically in the form of light beams. This method makes use of the properties of light to transmit data over distances without the need for physical cables. One of the primary advantages of FSO over traditional wired communication is the potential for reduced propagation time. Moreover, no physical cabled communication infrastructure is needed, which reduces system installation efforts.

In free space, the propagation time of data can be significantly smaller than through an optical fiber, which is commonly used in wired data transfer. This reduction in latency can be of importance for applications requiring real-time or near- real-time bidirectional data transmission for delay-sensitive applications.

FSO is particularly beneficial in scenarios where high-speed data transfer is of importance. It offers greater flexibility and mobility due to the absence of physical cables. Installation of these cables can be cumbersome, and they may limit the scalability and adaptability of communication networks. This may make FSO suitable for high data rate telecommunications, data centers, and high-performance computing environments, where the demand for rapid and reliable data exchange is continuously increasing.

The technology employs narrow optical beams, which are well-suited for creating high-capacity communication links. These beams can carry large amounts of data over long distances with minimal interference and signal degradation, and they are not susceptible for disturbances by electro-magnetic fields. These optical beams typically comprise a narrow spectrum (single wavelength) of light.

The absence of cables reduces infrastructure costs and installation times, and the technology's inherent high bandwidth supports the increasing data demands of modern applications. As the field continues to evolve, ongoing research and development are focused on further enhancing the performance of FSO systems.

This continued innovation holds the promise of making FSO an integral component of future communication networks, providing a complementary solution to existing fiber- optic technologies and radio-based wireless technologies.

Summary

It would be advantageous to achieve an optical wireless communication system which has better performance compared to traditional optical wireless communication systems.

It would further be advantageous to achieve a method for operating the optical wireless communication system.

In a first aspect of the present disclosure, there is provided an optical wireless communication system comprising a transmitter and a receiver.

Here, the transmitter is arranged for transmitting a wireless beam comprising multiple wavelengths. The transmitter comprises: - an Arrayed Wavelength Grating Router, AWGR, comprising multiple input ports which each feed multiple wavelengths into the AWGR, wherein the AWGR further comprises multiple output ports, each of which emit a single wavelength of the multiple wavelengths coming from each input port, and wherein the same wavelength from each input port exits from a different output port in a cyclic sequence;

- a fiber array comprising a plurality of fibers, wherein each of the fibers is uniquely connected to one output of the AWGR such that a wireless beam comprising the multiple wavelengths in that output is emitted from one of the fibers of the plurality of fibers.

The receiver is arranged for receiving a wireless beam comprising multiple wavelengths. The receiver comprises: - asensor arranged for capturing the wireless beam comprising the multiple wavelengths and for injecting the captured light beam into an interferometer configuration; - the interferometer configuration arranged for separating the multiple wavelengths of the captured wireless beam such that each output of the interferometer configuration comprises a single wavelength of the multiple wavelengths.

The inventor has found that it might be beneficial to utilize the wavelength-cyclic routing characteristics of an AWGR with multiple output ports, for use in an optical wireless communication transmitter. Using this cyclic routing characteristic, additional, i.e. more than one, input optical waveguides or fibers each carry one or more wavelengths which are cyclically multiplexed into an optical beam from the same output port of the AWGR.

Multiplexing refers to a technique where multiple signals or streams of data are combined into a single transmission medium, such as a fiber optic cable or a wireless channel, for efficient transmission and reception. Multiplexing is therefore performed in combination with the cyclical routing characteristic to obtain multiple output ports each comprising multiple wavelengths.

The characteristics of the AWGR are then used in combination with an array of fibers for transmitting the optical beam. The optical wireless communication system in accordance with the present disclosure allows an operator to provide multiple wavelengths to (different) input ports of the AWGR such that all these wavelengths couple into the same output port of the AWGR. The output port of the

AWGR is connected to one fiber of the array of fibers. This will result in an optical beam comprising all these multiple wavelengths.

As for the receiver side, the following is observed.

The inventor has found that it may be beneficial to apply an interferometer configuration, in particular a Mach-Zehnder Interferometer, MZI, configuration, comprising multiple stages, to separate the wavelengths comprised in a single optical beam and feed these wavelengths each to a separate receiver unit.

This interferometer configuration is incorporated into an optical wireless receiver. Each additional stage of the interferometer configuration divides an incoming optical signal into two output optical signals, wherein the wavelengths of the incoming optical signal are also separated into those two output optical signals.

The optical wireless communication system as described above allows for generating optical wireless beams with multiple wavelengths.

The interferometer configuration, for example the MZI, of the optical wireless communication receiver is made complementary to the AWGR of the optical transmitter.

The MZI is an optical device consisting of a beamsplitter, two parallel arms with optical paths having different optical path lengths, and recombining optics.

It splits light into two paths, which induce a phase shift in one path with respect to the other one due to the path length difference. When the two paths recombine, interference occurs. The phase shift induced in the one path is dependent on the wavelength of the light, and may cause destructive or constructive interference. The set of wavelengths that experience constructive interference will be fed into a first channel and the set of wavelengths that experience destructive interference will be fed into a second channel; thus separating the two sets of wavelengths. The MZI separation characteristics are periodic, which implies that a wavelength A which differs by a Free Spectral Range (FSR) from an other wavelength A+Aàrsr at the same input port will emerge at the same output channel.

By adjusting path length or utilizing materials with wavelength- dependent refractive indices, two separate sets of wavelength channels can be obtained. When placing an additional MZI in series to this MZI, an additional filtering of these sets of wavelengths into more refined sets of wavelengths may be achieved.

Cascading multiple MIZ stages thus eventually results in the recovery of the individual wavelengths of the beam. This method does not depend on the absolute value of the wavelengths. A conventional receiver might use a set of fixed spectral filters to separate the wavelengths wherein each filter is configured for a specific wavelength,

and hence is less flexible for the wavelength changes required for the beam steering by the AWGR-based transmitter. Therefore the proposed combination of the MZI- based receiver and AWGR-based transmitter allows for a unique advantage.

Furthermore, this allows for a higher data rate to be used in the 5 communication between the transmitter and the receiver, as multiple wavelengths in a single beam lead to a multiplication of the data transport capacity of that beam.

In an example, the AWGR comprises: - a plurality of input ports for receiving the multiple wavelengths to be transmitted.

As mentioned above, the optical wireless communication system may be used such that the operator may determine the specific input ports for the multiple (different) wavelengths such that all of these wavelengths couple into the same output port, i.e. such that these multiple wavelengths will be included in a single optical beam.

In a further example, the AWGR has a Free Spectral Range, FSR, and wherein each of the plurality of input ports is arranged for receiving wavelengths having a FSR difference from one another such that these wavelengths are coupled to the same output port of the AWGR.

The inventor has found that the cyclic property of the AWGR allows inputting wavelengths with a FSR difference to the same input port, such that these wavelengths will exit via the same output port. Reference is made to figure 2, wherein this cyclic property of the AWGR is depicted.

In a further example, the transmitter further comprises a 1D-2D interposer, wherein the output channels of the AWGR are 2D interposed by the 1D-2D interposer, thereby forming the 2D fiber array.

A 2D fiber array followed by a lens allows for a narrow beam to be generated.

In yet a further example, the transmitter further comprises a lens for directing the optical wireless beam having the multiple wavelengths, from each output channel of the AWGR, towards a specific receiver.

That is, the lens in combination with the fiber array allows for creating a specific direction for the beam. So, the direction of the optical beam corresponding to each of the optical fibers of the array is different and is determined by the relative position of that optical fiber with respect to the lens.

In yet another example, the receiver further comprises: an optical waveguide, wherein the sensor injects the captured wireless beam into the optical waveguide, and wherein the optical waveguide is connected to the interferometer configuration.

The sensor may comprise a surface grating coupler, SGC.

In a further example, the interferometer configuration comprises a Mach-

Zehnder Interferometer, MZI, configuration which has the same FSR as the AWGR in the transmitter.

In yet another example, the MZI configuration comprises at least one stage for demultiplexing the wavelengths.

In another example, the number of wavelengths demultiplexed by the

MZI configuration is equal to N=2*M, wherein M indicates the number of MZI stages and wherein N indicates the number of wavelengths.

The wavelength demultiplexing characteristics of the MZI are periodic with a wavelength period FSR. The MZI should be designed such that these characteristics are aligned with the periodic wavelength multiplexing characteristics of the AWGR.

In yet another example, the optical wireless communication system further comprises a photonic integrated circuit, PIC, wherein the PIC comprises the

SGC and the MZI and outputs to a plurality of photonic receivers, equal to the number of demultiplexed wavelengths.

In a second aspect of the present disclosure there is provided a receiver arranged for operating in an optical wireless communication system in accordance with any of the previous examples.

It is noted that the advantages as explained with reference to the first aspect of the present disclosure, being the optical wireless communication system, are also applicable to the second aspect of the present disclosure, being the receiver.

In a third aspect of the present disclosure, there is provided a transmitter arranged for operating in an optical wireless communication system in accordance with any of the previous examples.

It is noted that the advantages as explained with reference to the first aspect of the present disclosure, being the optical wireless communication system, are also applicable to the third aspect of the present disclosure, being the transmitter.

In a fourth aspect of the present disclosure, there is provided a method of operating the wireless communication system according to any of the previous examples, wherein the operating of the transmitter comprises the steps of: - receiving the multiple wavelengths at its multiple respective inputs; - coupling the multiple wavelengths of the multiple respective inputs into a same output beam; - outputting the multiple wavelengths from one of the fibers of the plurality of fibers; and wherein the operating of the receiver comprises the steps of: - capturing the wireless beam, comprising multiple wavelengths, by means of the sensor; - injecting the captured light beam into an interferometer configuration, and - separating the multiple wavelengths by the interferometer configuration.

In an example, the operating of the transmitter comprises the further step of: - determining, based on the multiple wavelengths, input ports for each of said multiple wavelengths such that said multiple wavelengths couple to the same output port.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

The above and other aspects of the disclosure will be apparent from and elucidated with reference to the examples described hereinafter.

Brief description of the figures

Fig.1A shows the AWGR comprising a single input and multiple outputs.

Fig. 1B shows the 2D fiber array in combination with a lens

Fig. 2 shows the cyclic wavelength routing properties of an AWGR.

Fig. 3 shows the AWGR, the 2D fiber array and the lens, wherein the

AWGR comprising multiple inputs and multiple outputs.

Fig. 4 shows the Mach-Zehnder Interferometer.

Fig. 5 shows the MZI wavelength filtering characteristics of the MZI.

Fig. 6 shows a receiver for demultiplexing two wavelengths per optical beam.

Fig. 7 shows an M-stage cascaded MZI for demultiplexing many wavelength channels (in this case M=2).

Fig. 8 shows the MZI wavelength filtering characteristics of a cascaded

MZI setup.

Fig. 9 shows the receiver for demultiplexing N=2*M wavelengths within an optical beam.

Detailed description

It is noted that in the description of the figures, same reference numerals refer to the same of similar components performing a same of essentially similar function.

A more detailed description is made with reference to particular examples, some of which are illustrated in the appended drawings, such that the features of the present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the claims. The drawings are incorporated for facilitating an understanding of the disclosure and are thus not necessarily drawn to scale. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings.

The ensuing description above provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiment(s} will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the disclosure, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of the disclosure.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof.

Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed

Description using the singular or plural number may also include the plural or singular number respectively. The word "or" in reference to a list of two or more items, covers all the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

These and other changes can be made to the technology considering the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein.

As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology 30 encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims.

Fig. 1 shows the 2D steering of optical beams using a high port count

AWGR. In Figure 1A, an input fiber 11 carrying one input wavelength to an arrayed wavelength grating router, AWGR 12. In this AWGR 12, wavelengths of the input wavelength signal are distributed among multiple ports 17. Each port 17 therefore carries a single wavelength. The total number of ports is equal to the number of wavelengths utilized in the system.

This may be equal to N'M. These ports 17 may be connected to corresponding output optical fibers 18 which exit the AWGR 12. Further, the optical fibers 18 are placed in a NxM fiber array 14, which is shown in figure 1B. The 2D fiber array ends before encountering a lens 15, the light exits the 2D fiber array and is directed towards the lens. The relative location of the fiber from which a light beam comprising a single wavelength interacts or enters the lens will determine the direction in which that light beam will travel.

Each beam 16 comprises a single wavelength which significantly hinders the total data rate of the communication.

Fig. 2 shows the cyclic wavelength routing properties of an AWGR. The

AWGR is capable of combining different wavelengths of different input fiber signals to each output fiber. The result of the cyclic wavelength routing of the AWGR is the shuffling of wavelengths into wavelength channels such that a single fiber comprises several wavelengths. This property of the AWGR is used in combination with the optical wireless communication receiver, as the receiver will be able to separate the “unique” wavelengths present in the beam comprising multiple wavelengths.

Fig. 3 shows the wavelength multiplexing of multiple wavelength signals 33 into the 2D steered beams 16. Multiple input fibers 35 are fed into the AWGR 12, wherein the cyclic routing characteristics as depicted in Figure 2 are employed to distribute the wavelengths over N fibers 18. In contrast to the configuration depicted in Figure 1, the output fibers 18 of the AWGR 12 comprise multiple wavelengths equal to the number of input ports.

It is noted that a wavelength could mean a narrow band of wavelengths or a wavelength peak with a certain FWHM or any similar definition. The output fibers 18 are fed into a 1D-t0-2D interposer 31 which transforms the 1xN fiber array 18 to a

VN x VN output fiber array 34, which is then directed towards a lens 15 which steers the 2D beam 16. As mentioned before, the location of the fiber with respect to the lens determines the direction of the emitted beam. Each emitted beam from each output fiber may then carry a wavelength channel 35 carrying multiple wavelengths.

Fig. 4 shows a Mach-Zehnder Interferometer 401, MZI, capable of separating two (sets of) wavelengths. It splits the beam into two paths, whereby each beamlet comprises the multiple wavelengths, using a beamsplitter or a 3 dB coupler.

One path remains unchanged during the operation of the MZI. The other path introduces a time delay At. This delay depends on an optical path length difference within the MZI stages. Thereafter, the two paths recombine in a 3 dB coupler, which results in constructive and deconstructive interference of the two channels, wherein the wavelength sets are split into two sets.

Fig. 5 shows the MZI wavelength filtering characteristics as two curves.

The outputs of an MZI are two separate wavelength channels each comprising of different wavelength bands or peaks per wavelength channel such that all original wavelengths are present but split into two channels. The wavelength spacing and number of wavelength channels is dependent on the MZI and the number of cascaded

MZI channels. Herein, the difference in the first and second peak of a wavelength channel is defined by the FSR of the MZI. In this case, two wavelength channels are output from the MZI shown in Figure 4. This MZI can be implemented in an optical wireless communication receiver in accordance with the present disclosure, in a cascaded configuration, meaning multiple MZIs are placed in series.

Fig. 6 shows the optical wireless communication receiver 601 in accordance with the present disclosure. In the optical wireless communication receiver 61, an optical beam containing multiple wavelengths 62 is directed onto the surface grating coupler 63, SGC, which captures the beam containing multiple wavelength channels or wavelengths 62 and couples it to an optical waveguide 64 using diffraction.

The optical waveguide 64 transports the multiple wavelengths 62 towards the MZI stage 401, as seen in Figure 4, which demultiplexes the signal into (in this case) two wavelength channels. Demultiplexing is the process of separating multiple wavelength channels or wavelengths of light that have been combined into a single optical signal back into their individual components or into a wavelength channel composed of wavelengths separated by a free spectral range. The separated wavelength channels or wavelengths then are fed to photonic receivers 65, which deliver the demultiplexed data streams 66.

Fig. 7 depicts an M-stage cascaded MZI 402 for demultiplexing many wavelength channels (in this case M=2). The number M defines how much the wavelength channels are demultiplexed. Here is depicted a two stage MZI, the number of demultiplexed wavelength channels is equal to N=2Y=22=4. This can also be seen in the figure, where there is depicted a single beam comprising the multiple wavelength channels, which is demultiplexed into four separate wavelength channels. Increasing the number of stages results in more wavelength channels as is clear from the difference of Figure 4 and Figure 7. As seen in Figure 3, the optical wireless communication transmitter in accordance with the present disclosure comprises N optical fibers comprising the N wavelength channels. This means that to retrieve the

N wavelength channels, the number of stages should be chosen such that N=2" In this case the variable N is the same as the variable N from Figure 4. The delay of the

MZI stage defines how the wavelengths are demultiplexed, therefore each stage has a different delay, as otherwise no demultiplexing might occur in subsequent stages.

The delay in the m'" stage Atm is given by Atm=2M" At, where Ar is the delay in the final stage, M is the total number of stages and m is the stage number. This allows the first stage to act as the most “rough” demultiplexing and each step thereafter comprises of a more fine demultiplexing.

Fig. 8 shows the MZI wavelength filtering characteristics as four curves.

The outputs of an MZI are four separate wavelength channels each comprising of different wavelength bands or peaks per wavelength channel such that all original wavelengths are present but split into four channels. The wavelength spacing and number of wavelength channels is dependent on the MZI and the number of cascaded

MZI channels, here, the number of filtered wavelengths is equal to four. Herein, the difference in the first and second peak of a wavelength channel is defined by the FSR of the MZI, which may be/is coupled to the FSR of the AWGR of the optical wavelength transmitter. In this case, four wavelength channels are output from the MZI shown in

Figure 7. This MZI can be implemented in an optical wireless communication receiver in accordance with the present disclosure, in a cascaded configuration, meaning multiple MZIs are utilized.

Fig. 9 depicts the integration of the M-stage cascaded MZI into the optical wireless communication receiver in accordance with the present disclosure, comprising N output data streams. In the optical wireless communication receiver 802, a beam containing multiple wavelength channels or wavelengths 62 is directed onto the surface grating coupler 63, SGC, which captures the beam containing multiple wavelength channels or wavelengths 62 and couples it to an optical waveguide 64 using diffraction. The optical waveguide 64 transports the multiple wavelength channels or wavelengths 62 towards the MZI stage 402, as seen in Figure 7 and as explained above, demultiplexes the signal into N wavelength channels. The separated

N wavelength channels or wavelengths then are fed to photonic receivers 65, which deliver the demultiplexed data streams 66.

Note that when mentioning wavelength channels, it might be possible that only one wavelength is present in a channel, meaning that that would be equal to wavelengths, meaning that if the latter is not mentioned explicitly, it is still included implicitly, though it must be mentioned that they are not equal.

As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims.

Claims

CONCLUSIONS

1. An optical wireless communications system comprising a transmitter and a receiver, the transmitter configured to transmit a wireless beam comprising a plurality of wavelengths, the transmitter comprising: - an Arrayed Wavelength Grating Router, AWGR, comprising a plurality of input ports each feeding a plurality of wavelengths into the AWGR, the AWGR further comprising a plurality of output ports, each of which emits a single wavelength of the plurality of wavelengths from each input port, and wherein the same wavelength from each input port emerges from a different output port in a cyclic sequence; - a fiber array comprising a plurality of fibers, each of the fibers uniquely transmitted with one output from the AWFR such that a wireless beam comprising the plurality of wavelengths is output from one of the fibers of the plurality of fibers; the receiver comprising: - a sensor configured to capture the wireless beam comprising the plurality of wavelengths and to inject the captured light beam into an interferometer device; - the interferometer device arranged to separate the plurality of wavelengths of the wireless beam such that each output of the interferometer device comprises a single wavelength of the plurality of wavelengths.

2. The optical wireless communication system of claim 1, wherein the AWGR comprises: - a plurality of input ports for receiving the plurality of wavelengths.

The optical wireless communication system of claim 2, wherein the AWGR has a Free Spectral Range, FSR, and wherein - each of the plurality of input ports is configured to receive wavelengths having an FSR difference from each other such that these wavelengths are coupled to the same output port of the AWGR.

4. The optical wireless communication system according to any preceding claim, wherein the transmitter further comprises a 1D-2D interposer, wherein the output channels of the AWGR are 2D interleaved by the 1D-2D interposer, thereby forming the fiber array.

5. The optical wireless communication system of any preceding claim, wherein the transmitter further comprises a lens for directing the optical wireless street having multiple wavelengths from multiple output channels of the AWGR toward a specific receiver.

6. The optical wireless communication system according to any of the preceding claims, wherein the receiver further comprises: - an optical waveguide, the sensor injecting the captured wireless beam into the optical waveguide, and the optical waveguide being connected to the interferometer device.

7. The optical wireless communications system of any preceding claim, wherein the sensor comprises a Surface Grating Coupler, SGC.

8. The optical wireless communication system of any preceding claim, wherein the interferometer device comprises a Mach-Zehnder Interferometer, MZI, device.

9. The optical wireless communication system of claim 8, wherein the MZI device comprises at least one platform for demultiplexing the wavelengths.

The optical wireless communication system of any preceding claim, wherein the MZI device has an FSR equal to the FSR of the AWGR.

The optical wireless communication system of any preceding claim, wherein the MZI device is designed such that the wavelength-dependent transmission characteristics from the input ports of the MZI to each of its output ports are aligned with those of the AWGR and have a wavelength periodicity FSR equal to the FSR of the AWGR.

12. The optical wireless communication system of claim 9, wherein the number of wavelengths demultiplexed by the MZI device is N=2, where M denotes a number of platforms and N denotes the number of wavelengths.

13. The optical wireless communication system of any preceding claim, further comprising a photonic integrated circuit, PIC, the PIC comprising and outputting the SGC and the MZI to a plurality of photonic receivers equal to the number of demultiplexed wavelengths.

14. A receiver adapted for use in an optical wireless communications system according to any one of the preceding claims.

15. A receiver adapted for use in an optical wireless communications system according to any of claims 1-13.

A method for operating the optical wireless communications system according to any of claims 1 to 13, wherein operating the transmitter comprises the steps of: - receiving the plurality of wavelengths at its plurality of respective inputs; - coupling the plurality of wavelengths from the plurality of respective inputs into a same output;

- outputting the plurality of wavelengths from one of the fibers of the plurality of fibers; and wherein operating the receiver comprises the steps of: - capturing the wireless beam comprising the plurality of wavelengths, by means of the sensor; - injecting the captured light beam into an interferometer arrangement, and - separating the plurality of wavelengths by the interferometer arrangement.

A method according to claim 16, wherein operating the transmitter comprises the further step of: - determining, based on the plurality of wavelengths, input ports for each of the plurality of wavelengths such that the plurality of wavelengths couple to the same output.