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Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26980
Long-distance indoor optical camera
communication using side-emitting fibers as
distributed transmitters
KLÁRA EÖLL ˝
OS-JAROŠÍKOVÁ,1,* VOJT ˇ
ECH NEUMAN,1CRISTO
MANUEL JURADO-VERDÚ,2SHIVANI RAJENDRA TELI,1
STAN ISL AV ZVÁNOVEC,1AND MAT ˇ
EJ KOMANEC1
1Department of Electromagnetic Field, Faculty of Electrical Engineering, Czech Technical University in
Prague, Technická 2, 166 27 Prague, Czech Republic
2
Institute for Technological Development and Innovation in Communications, University of Las Palmas de
Gran Canaria, Calle Practicante Ignacio Rodríguez, 35017 Las Palmas de Gran Canaria, Spain
*eollokla@fel.cvut.cz
Abstract:
We present a design approach for a long-distance optical camera communication
(OCC) system using side-emitting fibers as distributed transmitters. We demonstrate our approach
feasibility by increasing the transmission distance by two orders up to 40m compared to previous
works. Furthermore, we explore the effect of the light-emitting diode (LED) modulation frequency
and rolling shutter camera exposure time on inter-symbol interference and its effective mitigation.
Our proposed OCC-fiber link meets the forward-error-correction (FEC) limit of 3.8
·
10
−3
of
bit error rate (BER) for up to 35 m (with BER
=
3.35
·
10
−3
) and 40 m (with BER
=
1.13
·
10
−3
)
using 2-mm and 3-mm diameter side-emitting fibers, respectively. Our results at on-off keying
modulation frequencies of 3.54 kHz and 5.28 kHz pave the way to moderate-distance outdoor
and long-distance indoor highly-reliable applications in the Internet of Things and OCC using
side-emitting fiber-based distributed transmitters.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Optical camera communication (OCC) has been evolving rapidly over the last few years, showing
achievements in terms of illumination, communication, and localization functionalities within a
range of applications such as indoor Internet of Things (IoT) based sensor networks and smart
environments (homes, offices, and cities) [1,2]. In conventional OCC, a signal from a modulated
light source, typically a light-emitting diode (LED), is captured in the form of a set of images or
a video by using a rolling shutter (RS) camera [3]. The transmitted data are contained in the
form of light and dark stripes depicting signal levels as a part of the captured image set.
Considering achieved link distances, [4] demonstrates several techniques to improve the
transmission range from 10 m to 60 m. The listed techniques were a combination of under-
sampled phase-shift on-off keying (UPSOOK), wavelength-division multiplexing (WDM), and
multiple-input–multiple-output (MIMO) implemented on a red, green, and blue LED-based
OCC channel. Outdoor long-distance OCC ranging from 60 m to 400 m transmission span for
vehicle-to-vehicle and vehicle-to-infrastructure communication was reported in [5,6] using stereo
camera-based distance measurement and convolutional neural network to optimize the source
detection and recognition and camera defocusing techniques. These breakthroughs were based on
the conventional OCC systems that utilize standard LEDs for data transmission and illumination
purposes.
One major limitation of the above-mentioned configurations is the LED radiation pattern
limiting the field-of-view (FOV) to 120
◦
, along with the fact that an LED can be considered
a point source. The point source limitation can be overcome using an LED strip or an LED
#495805 https://doi.org/10.1364/OE.495805
Journal © 2023 Received 26 May 2023; revised 19 Jul 2023; accepted 20 Jul 2023; published 28 Jul 2023
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26981
panel [7], which can be covered in a diffuser to create smoother light [8,9]. However, an LED
strip or LED panel still does not have a 360
◦
radiation pattern. As an alternative, side-emitting
fibers (often also denoted as illuminating optical fibers or light-diffusing fibers) provide a 360
◦
radiation pattern, and, moreover, they can transmit signal along the whole fiber length.
Side-emitting optical fibers are specially designed to gradually emit light along the fiber
length, which is opposed to conventional optical fibers, where the primary purpose is to guide as
much power as possible from one end fiber to the other. This side-emission effect, described
as glowstick-like, decreases exponentially alongside the fiber length and may be achieved using
multiple approaches, which vary according to the material composition of the side-emitting fiber
[10]. In silica-based side-emitting fibers, the presence of nanovoids in the fiber core served
to scatter light to the cladding and then emit along the fiber [11]. Similarly, particle-modified
cladding silica side-emitting fiber was reported in [12]. The main parameter of side-emitting
fibers is the diffusion length (DL) which defines the fiber length over which 90% of the optical
signal power is lost, e.g., for DL
=
1 m, we will get 10% of the coupled light at the output of
1-m-long side-emitting fiber [13]. The other parameters are the spectral transmission of the
side-emitting fiber, which generally covers the whole visible region; the fiber diameter which is
critical for OCC performance and fiber flexibility; and fiber material (glass or plastic).
The progress in side-emitting fibers has led to a number of possible applications of side-
emitting fibers, such as door frame illumination, advertisement purposes, escape exit indicators,
or transmitting location-specific information. Reports on the use of side-emitting fibers in fabrics
for design purposes and sensing [14] and for microalgae growth [15] were presented.
Furthermore, side-emitting optical fibers were used as a spatially multiplexed light source
within OCC in [16]. An extended use of side-emitting fibers as a distributed source has recently
been proposed for OCC by our group [17] with a maximum link distance of 75 cm [18], whereas
the distance of 35 cm was presented in [19] using a laser source, instead of an LED, coupled to
the side-emitting fiber. Recently a study on side-emitting fibers in OCC was published, claiming
a transmission distance of 23 m with bit error rate (BER) below the forward-error-correction
(FEC) limit [20]. A long-short-term-memory neural network (LSTM-NN) processing approach
and a telescope were employed in [20] to boost the transmission distance. Moreover, theoretical
studies were published focusing on modeling and validating of power coupling into side-emitting
fiber and its radiation [10,21].
In this paper, we present a new approach to OCC using side-emitting fibers as distributed
transmitters, which brings unprecedented distance increase by more than two orders compared
to previous results [17,19] (and almost double transmission distance published in [20], which
uses a more complex and less reliable data processing technique of LSTM-NN). We achieve this
significant transmission distance increase by employing a new method of exposure time and
LED modulation frequency optimization accompanied by a reworked data processing routine.
In comparison to [20], which employs the LSTM-NN processing, we use the matched filtering
method as matched filtering is a fast-processing method and needs only a limited amount of
information for perfect data processing, whereas LSTM-NN uses previous data samples to process
the current data sample, thus the LSTM-NN system is very sensitive to slight deviations in the
sampling clock. Therefore, the transmission distance presented in this paper is close to double of
[20] but has the significant advantage of more reliable data processing.
We show that by using only 3 mm diameter side-emitting fiber, we can reach a transmission
distance of up to 40 m with an LED modulation frequency above 5kHz once employing our
new approach using optimized data generation and processing. Results presented in this paper
demonstrate that OCC using side-emitting fibers as distributed transmitters can be used for both
long-distance indoor and mid-range outdoor communication, IoT, or sensory networks.
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26982
2. System design optimization
The following sections discuss the OCC link design using side-emitting fibers as distributed
transmitters. We start with the RS camera settings, which define the essential parameters of our
new side-emitting fiber-based OCC concept. Then we focus on the processing of captured data.
2.1. Exposure time and sampling period
In RS cameras, one row of pixels is exposed during an exposure time t
exp
. The time period
between the activation of two consecutive rows corresponds to the sampling period T
s
[22].
The sampling period T
s
is an intrinsic property of RS cameras and can also be presented as
row sampling time or sampling rate f
s
. The exposure time t
exp
generally spans over multiple
sampling periods T
s
. The exposure time is either set manually by the user or is set automatically
in dependence on the ambient light level. The impact of both parameters of T
s
and t
exp
on the
overall OCC link performance is significant and will be explained in the following paragraphs.
When a long t
exp
is used (Fig. 1(a)), the image sensor captures light for a period of time in
which the transmitted symbol changes (from logical 1 to logical 0, or vice versa). The pixel is
illuminated both with logical 0 and with logical 1 resulting in inter-symbol interference (ISI),
implying that a long t
exp
is unsuitable for OCC. The effect and the absence of the ISI in an image
are illustrated in Fig. 1(a) and Fig. 1(b), respectively, by gray-scale bars in the right part of the
image, where the result of each pixel illumination is integrated. When a short (proper) t
exp
is
used (Fig. 1(b)), each pixel is illuminated only for a short period of time, minimizing the ISI and
thus generating a much clearer image. This tells us that to avoid significant ISI, the exposure time
cannot be arbitrary, as with increased t
exp
pixels integrate light over more time and the irradiance
of several consecutive symbols might be captured on the same pixels during the exposition.
Therefore, texp acts as a low-pass filter [22,23].
Time
Row of pixels
logical 1 logical 0 logical 1
light integrated
in each pixel
pix 1
pix 2
pix 3
pix 4
pix 5
pix 6
pix 7
pix 8
pix 9
pix 10
symbol time tsymbol
Ts
sampling period
exposure
time texp
(a)
Time
Row of pixels
logical 1 logical 0 logical 1
light integrated
in each pixel
pix 1
pix 2
pix 3
pix 4
pix 5
pix 6
pix 7
pix 8
pix 9
pix 10
symbol time tsymbol
Ts
sampling period
exposure
time texp
(b)
Fig. 1.
Different exposure times in a rolling shutter camera can either (a) deepen the presence
of inter-symbol interference (long exposure time), or (b) minimize it (short exposure time).
To efficiently suppress the effect of ISI, the exposure time texp must comply
texp ≤tsymbol
2, (1)
where t
symbol
is the symbol duration, i.e., the time the RS camera needs to capture one logical bit.
The tsymbol is defined as
tsymbol =Npps ·Ts=
1
fTx , (2)
where N
pps
is the theoretically expected number of pixel rows (samples) per symbol, e.g., N
pps =
10, 15, or 20 px/symbol (pps). This means that we can choose what N
pps
we want by selecting
the t
symbol
according to the RS camera sampling period T
s
. Furthermore, the t
symbol
translates
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26983
into modulation frequency f
Tx
of the data signal to the LED transmitter as an inverse proportion.
Previous statements imply the trade-off between t
exp
and N
pps
, and thus between data throughput
and received signal magnitude. In the case of low-light conditions, the received signal quality
might be improved by increasing the analog gain of the RS camera [24,25]. This can also
significantly improve the signal-to-noise ratio (SNR).
2.2. Data processing
In our experiments, we capture all the data (image frames), and the processing is then carried out
in an offline mode. A schematic diagram of the data processing of the captured image frames
is shown in Fig. 2. To recover transmitted data, the received image is turned into a grayscale
image, and an approximate ROI is found. As the side-emitting fiber might not be perfectly
straight in real-case scenarios, the post-processing algorithm is based on peak detection (spots
of highest intensity representing logical 1), compensating for slight curvature deviations of the
side-emitting fiber. The captured image is cropped and adjusted according to this information.
Next, the adjusted image is converted to an intensity profile and preprocessed, which starts with
compensation of data trend followed by digital filtration and, finally, equalization, preparing
the signal for demodulation. The preprocessing itself is necessary to eliminate distortions from
data generation, transmission, and capturing. Compensation of the data trend is necessary due
to the exponential decrease of power illuminated from the side-emitting fiber (due to the fiber
loss). To counter these differences in illumination we use singular spectrum analysis (SSA) [26],
see Fig. 3(c). For digital filtering, we employ an infinite impulse response (IIR) filter as for the
limited number of data samples the use of a finite impulse response (FIR) filter would lead to a
massive data loss. Before the demodulation, we apply standard matched filtering and finally, we
carry out a symbol synchronization.
Gray
scale
Select
ROI
Side-emitting fiber
curvature correction
Crop
image
Preprocessing Normalization Binarization
Image
frame
Intensity
profile
Intensity
profile
Data
Fig. 2. Schematic diagram of the data processing of captured image frames.
We show, for better illustration, the whole image processing routine, including the signal
generation in Fig. 3on an example of I) a side-emitting fiber with a 2 mm diameter (Fig. 3(I))
at a distance d
=
21 m and f
Tx
of 3.54 kHz, and II) a side-emitting fiber with a 3 mm diameter
(Fig. 3(II)) at d
=
30 m and f
Tx
of 5.28 kHz. The LED is modulated using an on-off-keying
(OOK) modulation scheme. Figure 3(a) demonstrates the generated logical data in the form of
black and white rectangle-shaped sections along the fiber (the logical zeros and ones), which
represents a region of interest (ROI). We aim to showcase an undistorted capture of the ROI,
i.e., without distortions from system components or at the LED. Figure 3(a) thus serves as an
ideal reference for understanding the outcome in an optimal scenario. Next, Fig. 3(b) shows
the ideal logical data compared to the real measured voltage on the LED. We already see some
signal distortion given by the LED response. On the camera receiver side, Fig. 3(c) illustrates the
captured image already cropped to the selected ROI. Figure 3(d) provides the comparison of the
measured and normalized intensity profile and the intensity profile after the processing, when the
signal was equalized by the elimination of unwanted peaks. Figure 3(e) shows a reconstruction of
the original signal obtained from the image and signal processing of received data. Comparison
with the representation of the ideal ROI from Fig. 3(a) shows that the processed signal from
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26984
I) 2-mm fiber, distance 21 m, fTx =3.54 kHz
(a) Representation of the ideal ROI
0
1
Logical values [-]
2 4 6 8 10 12 14 16 18 20 22 24
2.6
2.8
3
3.2
3.4
Time [ms]
Voltage [V]
Logical data
LED voltage
(b) Ideal data and voltage on the LED
(c) Captured ROI
100 200 300 400 500 600 700 800 900 1,000
−2
−1
0
1
2
3
Pixel r ow number [- ]
Normalized intensity [-]
Normalized data
Processed data
(d) Intensity profiles
(e) Reconstruction of the ROI after data processing
Data transmission steps
II) 3-mm fiber, distance 30 m, fTx =5.28 kHz
(a) Representation of the ideal ROI
0
1
Logical values [-]
2 4 6 8 10 12 14 16 18 20 22 24
2.6
2.8
3
3.2
3.4
Time [ms]
Voltage [V]
Logical data
LED voltage
(b) Ideal data and voltage on the LED
(c) Captured ROI
100 200 300 400 500 600 700 800 900 1,000
−2
−1
0
1
2
3
Pixel r ow number [- ]
Normalized intensity [-]
Normalized data
Processed data
(d) Intensity profiles
(e) Reconstruction of the ROI after data processing
Fig. 3.
Example images I) and II) with parts: (a) Representation of the ideal ROI, (b) ideal
logical data and corresponding voltage on the LED, (c) captured ROI, (d) intensity profile
of measured and preprocessed data, (e) reconstruction of the ROI after data processing (to
show differences with the captured ROI).
Fig. 3(d) matches nicely with the initially generated signal in Fig. 3(b) thus demonstrating reliable
performance of the processing algorithm.
When capturing the data, the first captured bit might not be captured completely. That is
something that must be taken into consideration when processing the captured image frames.
The demodulation itself is then based on matched filtering.
3. Measurements setup
The block diagram of the measurement setup with a photo of the distributed transmitter and the
camera receiver side is shown in Fig. 4. An arbitrary waveform generator (Rohde & Schwarz,
HMF2550) produced an OOK signal. The data signal was fed to an LED driver (Thorlabs,
LEDD1B), which was connected to a white LED (Light Avenue, CW28WP6). Optimal coupling
from the LED into the side-emitting fiber was ensured by using a 5D stage consisting of a
3-Axis NanoMax and a pitch and yaw tilt platform (Thorlabs, MAX313D/M and PY003/M).
We used side-emitting fibers made of polymethyl methacrylate (PMMA) with outer diameters
of 2 mm and 3 mm. A light block was put behind the side-emitting fiber to create the optimal
environment for image capture. The side-emitting fiber image was captured by an RS camera
placed perpendicularly to the side-emitting fiber with a maximum distance of 40m. The RS
camera was a Raspberry Pi camera module 2 with a Sony IMX219 sensor with a Pentacon auto
50 mm f/1.8 lens.
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26985
AWG &
LED driver
LED
Side-emitting fiber
Camera
LED
5D stage
Side-emitting fiber
Camera
Side-emitting fiber
Data Coupling
Free space,
up to 40 m
OCC
data
b)
c)
a)
Fig. 4.
Measurement setup of the side-emitting fiber-based OCC system: (a) a block
diagram of the setup, (b) a close-up photo of the distributed transmitter, and (c) the camera
receiver with the side-emitting fiber transmitter in the background.
When preparing the measurement setup, it is important to keep in mind the orientation of the
camera’s RS with respect to the side-emitting fiber orientation. It is best to keep the side-emitting
fiber perpendicular to the RS. However, even when the side-emitting fiber is placed diagonally in
the image frame, the system performance should not be negatively affected. Only small deviations
of the camera angle by
±
10
◦
will have no effect on the OCC performance. In [27], we studied the
effect of 0
◦
to 90
◦
bending radius of the side-emitting fiber on the system performance. It was
possible to achieve a 100% success of reception (BER below the FEC limit) and we concluded
that the bending of the fiber up to 90◦does not negatively affect the system performance.
The RS camera resolution was set to a standard Full HD 1920
×
1080 px with the analog gain
G
v
of 4. This value was determined as a middle-ground solution for our setup after a series of
initial test measurements. The digital gain was equal to 1 to minimize noise increase.
The system was designed to test N
pps
of 10 pps and 15 pps. To achieve this, Eq. 2 was applied
and gave us symbol times t
symbol =
189
µ
s and 282
µ
s and modulation frequencies f
Tx =
5.28 kHz
and 3.54 kHz for N
pps =
10 pps and 15pps, respectively. The symbol times t
symbol
also determine
the optimal exposure time, as stated in Eq. 1. For N
pps =
10 pps, the used exposure time was
t
exp =
90
µ
s, and for N
pps =
15 pps it was t
exp =
140
µ
s. Data packets of six bits ([010011]) were
sent. Note, it is possible to use longer packets with the packet length limit at the half-size of the
ROI, otherwise, the packet may not be captured completely [28]. To ensure sufficient amount of
data for precise BER calculation, we process multiple packets in each of the 25 captured image
frames. This gives us enough processed data that the BER can get as low as 3.7
·
10
−4
. If we
capture even more image frames, we can lower the BER level and possibly reach even better
BER results which we considered not necessary as we were able to safely validate below FEC
limit data transmission using our current approach. The list of used equipment, its fundamental
parameters, and used variables are provided in Table 1.
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26986
Table 1. Equipment, its fundamental parameters, and used variables.
Parameter Value
Side-emitting fiber ZDEA, Super bright
Diameter 2 and 3 mm
Fiber to camera distance d[5, 40] m
LED LA CW28WP6, cold white
Modulation frequencies fTx 3.54 kHz & 5.28kHz
Data packet size 6 b/packet [010011]
LED driver LEDD1B, ThorLabs
Camera Receiver Raspberry Pi Camera Module 2
Lens Pentacon auto 50 mm f/1.8
Sensor Sony IMX219
Resolution 1920 ×1080 pixels Full HD
Exposure times texp 140 µs&90 µs
Number of pixels per symbol Npps 15 px/symbol &10 px/symbol
4. Results
The experiment was performed indoors and under ambient light conditions, which according
to previous findings [17], does not influence the measurement results. The measurements were
carried out for the modulation frequencies f
Tx
of 3.54 kHz and 5.28 kHz. The side-emitting
fiber-camera distance dranged from 5 m to 40 m with a 1m step for both side-emitting fibers.
A set of 25 image frames was captured at each distance dand frequency f
Tx
. The captured image
frames were processed individually, and the final success of reception (SoR) is their mean value.
Two metrics are used to evaluate the system performance: the SoR and the BER. The limit
of well functioning system evaluated by the BER corresponds with the FEC limit, which is
3.8
·
10
−3
[29]. The calculated BER values are displayed in Fig. 5(a) and Fig. 5(b). The frequency
f
Tx =
5.28 kHz for the 2-mm side-emitting fiber follows the FEC limit of 3.8
·
10
−3
up to 30 m
and for the 3-mm side-emitting fiber up to 38m. Moreover, the frequency f
Tx =
3.54 kHz
combined with the 2-mm side-emitting fiber follows the FEC limit up to 35 m and for the 3-mm
side-emitting fiber at least up to 40 m. The SoR results are depicted in Fig. 6(a) and Fig. 6(b).
Our experimental results at f
Tx =
5.28 kHz show that for both side-emitting fibers, the SoR was at
least 98% up to 40 m distance and at least 99% up to 38 m. For f
Tx =
3.54 kHz, the SoR was up
5 10152025303540
10−3
10−2
FEC limit=3.8·10−3
d[m]
BER [-]
fTx =3.54kHz
fTx =5.28kHz
fTx =3.54kHz fitted
fTx =5.28kHz fitted
(a)
5 10152025303540
10−3
10−2
FEC limit=3.8·10−3
d[m]
BER [-]
fTx =3.54kHz
fTx =5.28kHz
fTx =3.54kHz fitted
fTx =5.28kHz fitted
(b)
Fig. 5.
BER for (a) the 2-mm and (b) the 3-mm side-emitting fiber with marked FEC limit
of 3.8 ·10−3.
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26987
to 99% up to 40 m for both side-emitting fiber diameters. Comparing this to the best previously
published results in [17] where the SoR of up to 100% was adhered to only up to 0.75m. Such a
significant improvement was mainly due to the improved calculation of f
Tx
and t
exp
as we here
used the optimal values to minimize inter-symbol interference. More suitable camera settings
were also enabled by using a better camera in comparison to previous papers. Enhancement
in data processing was ensured by our new algorithm for compensation of the side-emitting
fiber curvature. All these modifications lead to an improvement in transmission distance by the
above-mentioned two orders.
5 10152025303540
98
98.5
99
99.5
100
d[m]
Success of Reception [%]
fTx =3.54kHz
fTx =5.28kHz
fTx =3.54kHz fitted
fTx =5.28kHz fitted
(a)
5 10152025303540
98
98.5
99
99.5
100
d[m]
Success of Reception [%]
fTx =3.54kHz
fTx =5.28kHz
fTx =3.54kHz fitted
fTx =5.28kHz fitted
(b)
Fig. 6. Success of reception (SoR) for (a) the 2-mm and (b) the 3-mm side-emitting.
From the results, it can be concluded that increasing the fiber diameter just by 1mm from 2 mm
to 3 mm allows us to increase the distance by more than 5 meters for the modulation frequency of
3.54 kHz, as seen in Fig. 6, considering the errors in the SoR. This shows that the redundancy
in the columns of region-of-interest, which comes with thicker fiber, helps the demodulation
process conducted by the matched filtering. As more image sensor columns are affected by the
same illumination, more redundancy is introduced in the system. Thus, the signal-to-noise ratio
can increase considerably, which is linked to reduced transmission errors and improved channel
performance.
5. Conclusion
This paper demonstrates a new link design approach to optical camera communication using
side-emitting fibers as distributed transmitters resulting in more than a two-order link distance
increase compared to previous works.
We demonstrated the importance of the LED modulation frequency dependence and the
corresponding RS camera exposure time on the minimization of the inter-symbol interference.
As a practical demonstration, we selected two modulation frequencies, 3.54 kHz and 5.28 kHz,
giving us exposure times of 140
µ
s and 90
µ
s resulting in 15 and 10 pixels per symbol at the
rolling shutter camera, respectively.
In terms of the success of reception, with the 2-mm side-emitting fiber, the measurement
results provide at least 98% success of reception for up to 40 m distance, whereas, with the
3-mm side-emitting fiber, the success of reception was at least 99% up to 40 m distance. When
discussing BER and the 3.8
·
10
−3
FEC limit for the 2-mm side-emitting fiber, the FEC limit
adhered up to 30 m for 5.28 kHz and up to 35m for 3.54kHz. For the 3-mm side-emitting fiber,
the FEC limit has been met up to 38 m for 5.28 kHz and up to 40m for 3.54kHz.
The proposed OCC system using side-emitting fiber as a distributed transmitter has shown
highly-reliable long-distance indoor coverage. The modulation frequency of 5.28 kHz offers
Research Article Vol. 31, No. 16 / 31 Jul 2023 / Optics Express 26988
various indoor sensory applications. With the cost of lower modulation frequency and, thus, the
data rate, the proposed side-emitting fiber-based OCC system might be stretched into even longer
transmission distances, possibly also promising for mid-/long-range outdoor OCC links. In future
experiments, we plan to improve the system by using real data clustered in longer packets with
the 6-bit packet headers that we used in this paper.
Funding.
Technology Agency of the Czech Republic (FW01010571); České Vysoké Učení Technické v Praze
(SGS23/168/OHK3/3T/13).
Disclosures. The authors declare no conflicts of interest.
Data availability.
Data underlying the results presented in this paper are not publicly available at this time but may
be obtained from the authors upon reasonable request.
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