[32] In the present document, the word "exemplary" is used herein to mean "serving as an
15 example, instance, or illustration." Any embodiment or implementation of the present subject
matter described herein as "exemplary" is not necessarily to be construed as preferred or
advantageous over other embodiments.
[33] While the disclosure is susceptible to various modifications and alternative forms,
20 specific embodiment thereof has been shown by way of example in the drawings and will be
described in detail below. It should be understood, however that it is not intended to limit the
disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all
modifications, equivalents, and alternatives falling within the scope of the disclosure.
25 [34] The terms “comprises”, “comprising”, or any other variations thereof, are intended to
cover a non-exclusive inclusion, such that a setup, device or method that comprises a list of
components or steps does not include only those components or steps but may include other
components or steps not expressly listed or inherent to such setup or device or method. In
other words, one or more elements in a system or apparatus proceeded by “comprises… a”
30 does not, without more constraints, preclude the existence of other elements or additional
elements in the system or method.
[35] In the following detailed description of embodiments of the disclosure, reference is
made to the accompanying drawings which illustrates specific embodiments in which the
10
disclosure may be practiced. These embodiments are described in sufficient detail to enable
those skilled in the art to practice the disclosure, and it is to be understood that other
embodiments may be utilized and that changes may be made without departing from the
scope of the present disclosure. The following description is, therefore, not to be taken in a
5 limiting sense.
[36] Embodiments of the present disclosure provides an optical reconfigurable system and
a method for a multi-user optical wireless communication. The optical reconfigurable system
comprises a multi-segmented Spatial Light Modulator (SLM), a machine-vision camera and a
10 SLM programming unit communicatively coupled to the machine-vision camera and the
multi-segmented SLM. The multi-segmented SLM comprises of a segmented SLM with each
segment used to steer at least one modulated communication signal to at least one wireless
receiver based on a dynamic reconfiguration. The steering mechanism is implemented using
the machine-vision camera to precisely locate receiver position and thereafter, using this
15 information to steer the at least one modulated communication signal towards the at least one
wireless receiver. Dynamic reconfigurability of the multi-segmented SLM is implemented by
suitably steering the at least one modulated communication signal using a beam-steering
phase profile for each of the at least one wireless receiver compensated for light aberration
correction. The beam-steering phase profile is one of a blazed grating phase profile and a
20 decentred Fresnel lens phase profile. Light aberration correction to compensate for defocus
and astigmatism is implemented by adding Zernike polynomial-based phase functions to the
beam-steering phase profile for each of the at least one wireless receiver. The optical
reconfigurable system of the present disclosure implemented by integrating the machine vision camera with the multi-segmented SLM and the SLM programming unit allows
25 accurate identification of receiver position, which is used for generating suitable beamsteering phase profiles for steering at least one modulated communication signal to at least
one wireless receiver. The use of light aberration compensation function to correct for
defocus and astigmatism in beam-steering phase profiles performed in the optical
reconfigurable system of the present disclosure enables high throughput light collection at the
30 receiver for directed line-of-sight and/or non-line-of-sight communication between different
transmitter-receiver pairs. Further, the optical reconfigurable system of the present disclosure
enables multi-gigabit-per-second high throughput data communication combined with high
light throughput and precise beam steering. The optical reconfigurable system of the present
disclosure provides a low-cost and high data-rate solution for either short-haul indoor optical
11
communication (also called as Li-Fi) as an access solution or medium-haul free-space optical
communication (for e.g., between two tall buildings) as a distribution solution.
[37] FIG. 1 illustrates a schematic block diagram of a multi-user optical wireless
5 communication system in accordance with some embodiments of the present disclosure.
[38] In the FIG. 1, the multi-user optical wireless communication system 100 comprises at
least one transmitter (Tx) 101, a multi-segmented SLM 103, at least one wireless receiver (Rx)
105, a machine-vision camera 107 and a SLM programming unit 109. Each wireless receiver
10 (Rx) 105 of the at least one wireless receiver (Rx) 105 has a corresponding transmitter (Tx)
101 from the at least one transmitter (Tx) 101 forming a transmitter (Tx) and receiver (Rx)
pair. The multi-user optical wireless communication system 100 includes one or more
transmitter (Tx) and receiver (Rx) pairs. The wireless receiver 105 is, but not limited to, one
of a user terminal (also, referred as mobile terminal or user equipment), a cell phone, a
15 laptop, a desktop computer, and a tablet. The transmitter 101 is, but not limited to, one of a
light source, and an access point transmitting optical signal. In one embodiment, the light
source includes a laser source. The multi-segmented SLM 103, the machine-vision camera
107 and the SLM programming unit 109 together form an optical reconfigurable system of
the present disclosure for the multi-user optical wireless communication. The SLM
20 programming unit 109 may be a part of the multi-segmented SLM 103 or a separate
unit/entity. The SLM programming unit 109 is communicatively coupled to the machine vision camera 107 and the multi-segmented SLM 103. In one embodiment, the multisegmented SLM 103 is a phase-only Liquid-Crystal on Silicon (Locos) SLM (i.e., SLM,
Pluto-2-NIR-011), which is used as a micro-display with independent control of pixels. The
25 multi-segmented SLM 103 is segmented into multiple parts. Each part/segment of the multisegmented SLM 103 is programmed independently to coordinate with a transmitter (Tx) and
receiver (Rx) pair. The machine-vision camera 107 is used to track a position of each of the at
least one wireless receiver 105. In one embodiment, the machine-vision camera 107 is an
Allied Vision U-507C, pixel resolution-2464x2056. An image processing unit (not shown in
30 FIG. 1) comprises an algorithm to process acquired or captured real-time images of the at
least one wireless receiver 105 by the machine-vision camera 107. The image processing unit
may be implemented as a part of the machine-vision camera 107 or as a separate unit/entity
that is communicatively coupled to the machine-vision camera 107.
12
[39] The operation of the optical reconfigurable system for a multi-user optical wireless
communication is explained below.
[40] The multi-segmented SLM 103 receives at least one modulated communication signal
5 from a corresponding transmitter 101. The at least one modulated communication signal is an
optical signal spanning the optical frequency range of the electromagnetic spectrum. At the
same time, the machine-vision camera 107 tracks a position of each of the at least one
wireless receiver 105. Using the captured one or more images, the machine-vision camera
107 identifies at least one of coordinates and dimensions of each of the at least one wireless
10 receiver 105. In detail, the machine-vision camera 107 captures one or more real-time images
of the at least one wireless receiver 105. The one or more real-time images may be colour
images. The machine-vision camera 107 uses a machine vision technique to (recognize and)
track the position of each of the at least one wireless receiver 105. The machine-vision
camera 107 continuously captures one or more real-time images using a standard image
15 acquisition toolbox. Thereafter, the machine-vision camera 107 converts the captured one or
more real-time images into respective grayscale images and segments the respective
grayscale images. The image processing unit, which may be a part of the machine-vision
camera 107 or a separate unit/entity that is communicatively coupled to the machine-vision
camera 107, processes the segmented images to find dimensions or shapes (for example, of
20 circular object) in the segmented images and their coordinates or positions (of the circular
object) and reject other objects from the segmented images. Based on the identified at least
one of coordinates and dimensions, (the image processing unit of) the machine-vision camera
107 estimates at least one of link length and receiver offset for each of the at least one
wireless receiver 105. The link length is the distance between the transmitter (Tx) and
25 receiver (Rx) pair. The receiver offset refers to offset in the position of the receiver from an
optical axis of the system 100. The estimated link length is used to control the signal (i.e., at
least one modulated communication signal) divergence with steering angle according to the
receiver’s position such that power losses can be minimized. Subsequently, the machine vision camera 107 transmits the at least one of link length and receiver offset of each of the at
30 least one wireless receiver 105 to the SLM programming unit 109. Using the at least one of
link length and receiver offset of each of the at least one wireless receiver 105 received from
the machine-vision camera 107, the SLM programming unit 109 determines a beam-steering
phase profile for each of the at least one wireless receiver 105. The beam-steering phase
profile is one of a blazed grating phase profile or a decentered Fresnel lens phase profile.
13
Using the beam-steering phase profile, the SLM programming unit 109 compensates the
beam-steering phase profile for each of the at least one wireless receiver 105 for light
aberration correction. The light aberration comprises defocus and astigmatism aberrations.
The beam-steering phase profile for each of the at least one wireless receiver 105 is
5 compensated for correcting light aberration using Zernike polynomial-based phase functions.
Based on the corrected or compensated beam-steering phase profile associated with each of
the at least one wireless receiver 105, the SLM programming unit 109 reconfigures
dynamically each segment of the multi-segmented SLM 103 associated with each of the at
least one wireless receiver 105. Based on the dynamic reconfiguration, the multi-segmented
10 SLM 103 steers the at least one modulated communication signal to at least one wireless
receiver 105.
[41] FIGS. 2a and 2b illustrate flowcharts showing a method for a multi-user optical
wireless communication in accordance with some embodiments of the present disclosure.
15
[42] As illustrated in FIGS. 2a and 2b, the method 200 and the method 203, respectively,
include one or more blocks for a multi-user optical wireless communication. The method 200
and the method 203 may be described in the general context of computer executable
instructions. Generally, computer executable instructions can include routines, programs,
20 objects, components, data structures, procedures, modules, and functions, which perform
particular functions or implement particular abstract data types.
[43] The order in which the method 200 and the method 203 are described is not intended
to be construed as a limitation, and any number of the described method blocks can be
25 combined in any order to implement the method. Additionally, individual blocks may be
deleted from the methods without departing from the scope of the subject matter described
herein. Furthermore, the method can be implemented in any suitable hardware, software,
firmware, or combination thereof.
30 [44] At block 201, the multi-segmented SLM 103 of the optical reconfigurable system
receives at least one modulated communication signal from a corresponding transmitter 101.
The at least one modulated communication signal is an optical signal spanning the optical
frequency range of the electromagnetic spectrum.
14
[45] At block 203, the machine-vision camera 107 of the optical reconfigurable system
tracks a position of each of at least one wireless receiver 105. A wireless receiver is one of
user terminal, a laptop, a desktop computer, and a tablet.
5 [46] At block 205, the SLM programming unit 109 of the optical reconfigurable system
determines a beam-steering phase profile for each of the at least one wireless receiver 105
using at least one of link length and receiver offset of each of the at least one wireless
receiver 105. The at least one of link length and receiver offset are identified from the
position of each of at least one wireless receiver 105 utilizing images acquired by the
10 machine vision camera 107. The beam-steering phase profile is one of a blazed grating phase
profile or a decentred Fresnel lens phase profile.
[47] At block 207, the SLM programming unit 109 of the optical reconfigurable system
compensates the beam-steering phase profile for each of the at least one wireless receiver 105
15 for light aberration correction. The beam-steering phase profile for each of the at least one
wireless receiver 105 is combined with Zernike polynomial-based phase functions for light
aberration correction. The light aberrations comprising of defocus and astigmatism are
compensated using Zernike polynomial-based phase functions.
20 [48] At block 209, the SLM programming unit 109 of the optical reconfigurable system
reconfigures dynamically each segment of the multi-segmented SLM associated with each of
the at least one wireless receiver 105 based on the corrected (or compensated) beam-steering
phase profile associated with each of the at least one wireless receiver 105.
25 [49] At block 211, the multi-segmented SLM 103 of the optical reconfigurable system
steers the at least one modulated communication signal to at least one wireless receiver 105
based on the dynamic reconfiguration.
[50] The operation/method of tracking the position of each of at least one wireless receiver
30 105 performed by the machine-vision camera 107 of the optical reconfigurable system at
block 203 comprises following operational steps.
[51] At block 221, the machine-vision camera 107 of the optical reconfigurable system
captures one or more real-time images of the at least one wireless receiver 105.
15
[52] At block 223, the machine-vision camera 107 of the optical reconfigurable system
identifies at least one of coordinates and dimensions of each of the at least one wireless
receiver 105 using the captured one or more images.
5
[53] At block 225, the machine-vision camera 107 of the optical reconfigurable system
estimates at least one of link length and receiver offset for each of the at least one wireless
receiver 105 based on the identified at least one of coordinates and dimensions.
10 [54] At block 227, the machine-vision camera 107 of the optical reconfigurable system
transmits the at least one of link length and receiver offset of each of the at least one wireless
receiver 105 to the SLM programming unit 109 of the optical reconfigurable system.
[55] The block 201 to 211 including the blocks 221 to 227 are performed continuously by
15 the optical reconfigurable system of the present disclosure for multi-user optical wireless
communication.
[56] FIG. 3a illustrates a working example of the optical reconfigurable system for a multiuser optical wireless communication in accordance with some embodiments of the present
20 disclosure.
[57] The working example of the optical reconfigurable system is experimentally
demonstrated for an indoor optical wireless communication. The multi-segmented SLM 103
is a phase-only Liquid-Crystal on Silicon (LCoS) SLM (i.e., SLM, Pluto-2-NIR-011), which
25 is used as a micro-display with independent control of pixels. The multi-segmented SLM 103
is segmented into multiple parts. For working example, the multi-segmented SLM 103 is
segmented into two parts/segments. Each part/segment of the multi-segmented SLM 103 is
programmed independently to coordinate with a transmitter (Tx) and receiver (Rx) pair. In this
case, each part/segment of the multi-segmented SLM 103 is programmed independently for
30 the two incident laser beams at 785 nm wavelength (i.e., laser source Thorlabs L785H1). The
laser beams are polarized parallel to the horizontal axis of the multi-segmented SLM 103
using wire-grid polarizers 305. A 4f lens pair 309 (also, referred as 4f system) consisting of
100 mm (i.e., optical lens AL50100M-A) and 16 mm focal length lenses is used to magnify
the steering angle range by a factor of 6.6-times. Subsequently, a diffuser 313 consisting of
16
roughened glass surface is used to diffuse the laser beams with a resultant beam spread of
full-width-half-maxima of 10o
. A white LED ring array 311 of 12 LEDs is also used in
combination with the laser beams for illumination with illuminate close to D65, with colour
co-ordinates of (0.3128, 0.3290). The light from the LED ring 313 and the laser sources are
5 combined at the diffuser surface and directed using a transmitter lens 315 of focal length 75
mm (i.e., optical lens AC508-075-A). In one embodiment, the 4f system 309, the LED ring
313, the diffuser 313, and the transmitter lens 315 are part of the optical reconfigurable
system. The machine-vision camera 107 is used to track a position of each of the at least one
wireless receiver 105. In one embodiment, the machine-vision camera 107 is an Allied Vision
10 U-507C, pixel resolution-2464x2056. An image processing unit (not shown in FIG. 1)
comprises an algorithm to process acquired or captured real-time images of the at least one
wireless receiver 105 by the machine-vision camera 107. The image processing unit may be
implemented as a part of the machine-vision camera 107 or as a separate unit/entity that is
communicatively coupled to the machine-vision camera 107. Two receivers 321, 323 are
15 used with separate shape-based labels for the machine-vision camera 107 to recognize the
receivers 321, 323. Each receiver consists of a receiver lens 317, 319 of focal length 32 mm
(i.e., optical lens Thora's ACL50832U-A) to collect the light onto a small area pre-amplified
silicon photoreceiver (i.e., photodetectors Menlo systems FPD310-FS-VIS). The location of
the transmitter 315 and receiver 317, 319 lens are optimized from the diffuser surface and
20 photodetector respectively to maximize the collection efficiency for an on-axis, line-of-sight
link. The image processing unit continuously processes acquired or captured real-time images
of the receivers 321, 323 by the machine-vision camera 107 and feedback the position
information to the SLM programming unit 109 to determine beam-steering phase profiles.
The decentred Fresnel lens phase profile is programmed on both the segmented part of the
25 multi-segmented SLM 103 for independent 2D beam steering with an angular range of +/-
11.3o
. The defocus and astigmatism aberrations in the received signal/beam are
corrected/compensated by the SLM programming unit 109 using the Zernike polynomial based phase functions. The communication capacity of the OWC link is characterized by
uploading offline generated MATLAB 16-QAM-OFDM waveforms onto an arbitrary/any
30 waveform generator 327 (i.e., waveform generator Tektronix AWG5204) to generate the
modulated communication signal (also, referred as data-modulated optical signal). The
generated waveforms are amplified using low noise power amplifiers 329, 331 (i.e.,
amplifiers Mini-Circuits ZX60-43-S+) and superimposed on to a DC-biasing current to
directly modulate the laser diode/source 301, 303. The oscilloscope 325 (i.e., oscilloscope
17
Rhode-Schwartz RTO-2044) is used to store the photo-received signal to process the
data/signal offline using programming tool such as MATLAB for Bit-Error-Rate (BER) and
Signal-to-Noise (SNR) analysis of the communication links between the transmitter 315 and
the receiver 317, 319.
5
[58] With reference to FIG. 3b, blazed grating-based beam steering is explained. The
computer-generated blazed grating holograms are programmed independently on each
segmented part of the multi-segmented SLM 103. The horizontally polarized left and right
beams are incident on the multi-segmented SLM 103 left and right segmented part
10 respectively. The beam-steering angle is found to be a non-linear function of the grating
pitch, as shown in FIG. 3b(a). From FIG. 3b(a), it is observed that this technique is prone to
the blind zones, which refers to the angular range across which the beam/signal cannot be
steered using blazed gratings. The blind zone is found to increase with increasing beam steering angle. The pitch of 3, 4, and 5-pixels for the blazed grating steers the beam/signal at
15 an angle of 2.9°, 2.1°, and 1.7°, respectively. The blind zone is found to vary from 0.8° to
0.4° as pitch size is changed from 3 to 5 pixel. Similarly, the steering angle per unit pixel also
varies non-linearly with decrease in pitch size. The maximum beam steering angular range is
+/-2.9°. The diffraction efficiency of the +1st and -1
sty order decreases and increases,
respectively with decrease in pitch size as shown FIG. 3b(a) while 0th order remains
approximately constant. For the left (right) segmented part, the +1st and -1
sty 20 diffraction
efficiency decreases from ~50% (45%) to 17.7% (25%) and increases from ~1.4% (0.65%) to
10.8% (10%) respectively, with decrease in pitch size as shown in FIG. 3b. FIG. 3b(b) and
FIG. 3b(c) shows the 0th and 1st order diffraction efficiency performance of the left and right
segmented part, respectively, as steering angle varies.
25
[59] With reference to FIG. 3c, decentred Fresnel lens phase profile beam steering is
explained. For the two-incident laser beams/signals of size ~2.5 mm each, the multisegmented SLM 103 is segmented into two parts and each segment is programmed with the
decentred Fresnel lens phase profile to steer the beam/signal. The beams/signals are
30 horizontally polarized and incident on the multi-segmented SLM 103 after passing through
the polarizer 305. The estimated focal length of the programmed Fresnel lens phase profile is
50.8 cm. The lens profile of fixed focal length of 50.8 cm is used to steer the beam by
changing the de-cantering only. The centre of the lens profile coincides with the centre point
of the polarized collimated incident laser beam spot for 0o
steering angle. The decentring of
18
the beam spot and the lens profile leads to a change in the steering angle. The Laser Diode
(LD) beams can be steered independently in any arbitrary direction depending on the
decentring direction between the centre of the beam spot and the programmed Fresnel lens
phase profile. The entire optical path including the steered beams/signals through the multi5 segmented SLM 103 with uniform power and plane wave front, the 4f system 309, the
diffuser 313, the LEDs array ring 311 and the achromatic/transmitter lens 315 are modelled
in ZEMAX non-sequential mode. The decentred Fresnel lens phase profile holograms and
corresponding raytracing diagrams of the setup are shown in FIG. 3c. The steering angle is 0o
for both the beams/signals cantered with respect to the Fresnel lens, as shown in FIG. 3c(a)
10 with corresponding ray-tracing diagrams shown in FIG. 3c(b). As decentering changes from 0
to 500 pixel towards the right (left) side for the right (left) beam/signal as shown in FIG.
3c(c), the beam/signal steers +/-1.5o
. After the 4f system 309, the right and left amplified
beam/signal angles are +/-9
o
. After the diffuser 311 and transmitter lens 315, the steering
range reduces to +/-6
o
, which is also shown in the raytracing diagram in FIG. 3c(d).
15 Similarly, as decentring changes from 0 to 500 pixel towards the left (right) side for the left
(right) beam/signal as shown in FIG. 3c(d), the beam/signal steers -/+1.5o
. After the 4f
system 309, the right and left amplified beam/signal angles are -/+9o
. After the diffuser 311
and transmitter lens 315, the steering range reduces to -/+6o
, which is also shown in the
raytracing diagram in FIG. 3c(e).
20
[60] The experimental steering angle after the multi-segmented SLM 103 varies as a linear
function of the Fresnel lens decentring as shown in FIG. 3d(a) for the left and right
segmented part of the multi-segmented SLM 103. From the experimental data, it is observed
that beam/signal can steer at any arbitrary angle after the multi-segmented SLM 103 within
the angular range of +/-4.26o
25 with a resolution of 32.6 μradian per pixel decentring. The
experimental steering angle after the 4f system 309 and the transmitter lens 315 as a function
of the multi-segmented SLM 103 steered angle is shown in FIG. 3d(b) and FIG. 3d(c) for the
left and right segmented part respectively (data points), including the ZEMAX ray-tracing
simulated data (solid lines) for comparison. The resolution magnifies to ~210 μradian/pixel
30 after the 4f system 309 and de-magnifies to ~130 μradian/pixel after the transmitter lens 315.
[61] The LD beams/signals are parallel with each other and incident on either side of
optical axis at the 4f system 309 which causes a slight asymmetry between the positive and
negative steering angle of both left and right segmented part of the multi-segmented SLM
19
103. The diffraction efficiency for the steered angle reduces and 0th order diffraction
efficiency increases with increase in Fresnel lens decentring on either side as shown in FIG.
3e(a) and FIG. 3e(b). The 1st order diffraction efficiencies reduce from ~14.17 to 44.09% and
~11.5 to 40%, while the zeroth order diffraction efficiencies increase from 42% to 73% and
5 46% and 75% for left and right segments of the multi-segmented SLM 103 respectively.
[62] With reference to FIG. 3f, light aberrations correction using the Zernike polynomialbased phase functions is explained. The aberrations experienced by the optical beam/signal
can result in distorted beam profile, especially at larger steering angles resulting in reduced
10 light collection at the receiver 321, 323. The aberrations can be pre-compensated by
programming the aberration correction phase pattern on the multi-segmented SLM 103 in
addition to the phase profiles (i.e., the blazed grating phase profile and/or the decentred
Fresnel lens phase profile) used for beam steering. Defocus and astigmatism aberrations can
be corrected on the transmitter side using a second order Zernike polynomial. The
15 expressions given in equations (1) to (3) are used to generate the Zernike polynomial of the
defocus, and astigmatism at 0o
and 45o
, respectively. The generated profiles are multiplied
with suitable scaling factor to generate the aberration compensation phase profiles.
alignment optimization. FIG. 3f illustrates multi-segmented SLM programmed phase profile
for decentered Fresnel lens phase profile beam steering combined with aberration correction
profile. The diffraction efficiency decreases with an increase in steering angle as shown in
FIG. 3f(e). To optimize the path-loss, the defocus Zernike polynomial-based phase function
5 is used with suitable scaling factor to generate the defocus lens phase profile that increases
the overall light collection at the receiver 321, 323. Astigmatism also increases with increase
in steering angle and is corrected using the astigmatism at 0° as shown in FIG. 3f(g). The
multi-segmented SLM 103 is programmed with the sum of all the generated phase profile as
shown in FIG. 3f(d) to FIG. 3f(h) for a beam steering angle of ~1.5° after the multi10 segmented SLM 103, which is subsequently magnified to ~6° after transmitter lens 315. The
on-axis diffraction efficiency can be as high as 100% which often requires reducing the
power intensity below Maximum Permissible Exposure (MPE) limit. The beam/signal
divergence using defocused lens profile can be intentionally used to reduce the optical
intensity below the MPE level.
15
[68] FIG. 3g illustrates link length and receiver offset calibration using image data in
accordance with some embodiments of the present disclosure. In FIG. 3g(a), filled area of the
object decreases with increase in link length with standard deviation of ~1.5 pixel. The
estimated link length is used to control the signal (i.e., at least one modulated communication
20 signal) divergence with steering angle according to the receiver’s position such that power
losses can be minimized. FIG. 3g(b) shows that there is linear relationship between the
receiver’s horizontal offset from the optical axis and pixel offset from the center of the image
at a link length of 100 cm and 160 cm, respectively, with standard deviation of ~0.04 pixel.
The horizontal calibration with slope (cm/pixel) at any link length can be used in combination
25 with link length calibration to calculate the angle to be steered and corresponding hologram
for receiver’s location. The calculated slope of this curve of 23.68 cm/pixel at 100 cm
decreases with increase in link length. On average, the time required for image processing to
identify and track the receiver's object is approximately 112 milliseconds, as depicted in FIG.
3g as circles. After determining the Cartesian coordinates of the receiver, the time taken to
30 generate the hologram and program the SLM is approximately 3 milliseconds and 110
milliseconds, respectively, as shown in FIG. 3g as squares. The dashed line represents the
mean, while the data points represent the experimental results.
1. A method for a multi-user optical wireless communication, the method comprising:
receiving (201), by an optical reconfigurable system, at least one modulated
5 communication signal from a corresponding transmitter (101);
tracking (203), by the optical reconfigurable system, a position of each of at least one
wireless receiver (105);
determining (205), by the optical reconfigurable system, a beam-steering phase profile
for each of the at least one wireless receiver (105) using at least one of link length and
10 receiver offset of each of the at least one wireless receiver (105), wherein the at least one of
link length and receiver offset are identified from the position of each of at least one wireless
receiver (105) utilizing images acquired by a machine vision camera of the optical
reconfigurable system;
compensating (207), by the optical reconfigurable system, the beam-steering phase
15 profile for each of the at least one wireless receiver (105) for light aberration correction;
reconfiguring dynamically (209), by the optical reconfigurable system, each segment
of a multi-segmented Spatial Light Modulator (SLM) associated with each of the at least one
wireless receiver (105) based on the corrected beam-steering phase profile associated with
each of the at least one wireless receiver (105); and
20 steering (211), by the optical reconfigurable system, the at least one modulated
communication signal to the at least one wireless receiver (105) based on the dynamic
reconfiguration.
2. The method as claimed in claim 1, wherein the tracking the position of the at least one
25 wireless receiver (105) comprising:
capturing (221), by the optical reconfigurable system, one or more real-time images of
the at least one wireless receiver (105);
identifying (223), by the optical reconfigurable system, at least one of coordinates and
dimensions of each of the at least one wireless receiver (105) using the captured one or more
30 images;
estimating (225), by the optical reconfigurable system, at least one of link length and
receiver offset for each of the at least one wireless receiver (105) based on the identified at
least one of coordinates and dimensions; and
28
transmitting (227), by the optical reconfigurable system, the at least one of link length
and receiver offset of each of the at least one wireless receiver (105) to a SLM programming
unit (109) of the optical reconfigurable system.
5 3. The method as claimed in claim 1, wherein the beam-steering phase profile is one of a
blazed grating phase profile or a decentered Fresnel lens phase profile.
4. The method as claimed in claim 1, wherein the beam-steering phase profile for each
of the at least one wireless receiver (105) is combined with Zernike polynomial-based phase
10 functions for light aberration correction.
5. The method as claimed in claim 1, wherein the light aberrations comprising of
defocus and astigmatism are compensated using Zernike polynomial-based phase functions.
15 6. The method as claimed in claim 1, wherein a wireless receiver is one of user terminal,
a laptop, a desktop computer, a cell phone, and a tablet.
7. The method as claimed in claim 1, wherein the at least one modulated communication
signal is an optical signal spanning the optical frequency range of the electromagnetic
20 spectrum.
8. An optical reconfigurable system for a multi-user optical wireless communication, the
optical reconfigurable system comprising:
a multi-segmented Spatial Light Modulator (SLM) (103) configured to:
25 receive at least one modulated communication signal from a corresponding
transmitter (101); and
steer the at least one modulated communication signal to at least one wireless
receiver (105) based on a dynamic reconfiguration;
a machine-vision camera (107) configured to:
30 track a position of each of the at least one wireless receiver (105);
a SLM programming unit (109) communicatively coupled to the machine-vision
camera (107) and the multi-segmented SLM (103) and configured to:
determine a beam-steering phase profile for each of the at least one wireless
receiver (105) using at least one of link length and receiver offset of each of the at
29
least one wireless receiver (105), wherein the at least one of link length and receiver
offset are identified from the position of each of at least one wireless receiver (105)
utilizing images acquired by the machine vision camera (107);
compensate the beam-steering phase profile for each of the at least one
5 wireless receiver (105) for light aberration correction; and
reconfigure dynamically each segment of the multi-segmented SLM (103)
associated with each of the at least one wireless receiver (105) based on the corrected
beam-steering phase profile associated with each of the at least one wireless receiver
(105).
10
9. The optical reconfigurable system as claimed in claim 8, wherein the machine-vision
camera (107) is configured to:
capture one or more real-time images of the at least one wireless receiver (105);
identify at least one of coordinates and dimensions of each of the at least one wireless
15 receiver (105) using the captured one or more images;
estimate at least one of link length and receiver offset for each of the at least one
wireless receiver (105) based on the identified at least one of coordinates and dimensions;
and
transmit the at least one of link length and receiver offset of each of the at least one
20 wireless receiver (105) to the SLM programming unit (109).
10. The optical reconfigurable system as claimed in claim 8, wherein the beam-steering
phase profile is one of a blazed grating phase profile or a decentred Fresnel lens phase
profile.
25
11. The optical reconfigurable system as claimed in claim 8, wherein the beam-steering
phase profile for each of the at least one wireless receiver (105) is compensated for correcting
light aberration using Zernike polynomial-based phase functions.
30 12. The optical reconfigurable system as claimed in claim 8, wherein the light aberration
comprising of defocus and astigmatism aberrations are compensated using Zernike
polynomial-based phase functions.
30
13. The optical reconfigurable system as claimed in claim 8, wherein a wireless receiver
is one of user terminal, a laptop, a desktop computer, a cell phone, and a tablet.
14. The optical reconfigurable system as claimed in claim 8, wherein the at least one
5 modulated communication signal is an optical signal spanning the optical frequency range of
the electromagnetic spectrum.