High-speed phosphorescent white LED visible light
communications without utilizing a blue filter
Honglei Li (李洪磊)
1
, Yini Zhang (张旖旎)
2
, Xiongbin Chen (陈雄斌)
1,
*,
Chunhui Wu (吴春晖)
1
, Junqing Guo (郭俊清)
1
, Zongyu Gao (高宗余)
1
,
and Hongda Chen (陈弘达)
1
1
State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors,
Chinese Academy of Sciences, Beijing 100083, China
2
School of Computer and Communication Engineering, University of Science and Technology Beijing,
Beijing 100083, China
*Corresponding author: chenxiongbin@semi.ac.cn
Received March 12, 2015; accepted May 27, 2015; posted online July 1, 2015
We experimentally demonstrate a high-speed phosphorescent white light emitting diode (LED) visible light
communication (VLC) system without utilizing an optical blue filter. Here, the white light response is equalized
by using the proposed analog equalizers. The 3 dB bandwidth of the VLC link could be extended from 3 to
132 MHz, which allows 330 Mbit/s non-return-to-zero on–off keying (NRZ-OOK) data transmission with a
bit error ratio (BER) of 7.2 × 10
−10
and 672 Mbit/s 64-quadrature amplitude modulation (64-QAM) data trans-
mission with a BER of 3.2 × 10
−3
. These resultant BERs are less than the forward error correction (FEC) limit of
3.8 × 10
−3
. The VLC link distance is 1 m using a single 1 W LED. The transmitter and receiver modules are
integrated to a compact size. Furthermore, the relationships between the signal performance and illumination
level or optical power are investigated and analyzed.
OCIS codes: 060.4510, 060.2605, 200.2605.
doi: 10.3788/COL201513.080605.
White light emitting diodes (LEDs) are replacing tradi-
tional incandescent lamps and becoming major candidates
for future illumination. Visible light communication
(VLC) technology based on white LEDs has many attrac-
tive advantages, such as high security, immunity to radio
frequency interference, worldwide availability and unli-
censed bandwidth
[1]
. VLC could be applied in many areas,
such as high-accuracy indoor positioning systems
[2–4]
, high
data rate downlink communication in homes and offices
[5]
,
and light fidelity (Li-Fi)
[6]
. VLC is a promising technology
for optical wireless communication networks
[7]
that has
been the subject of worldwide research and global stand-
ardization efforts
[8]
.
Despite the fact that the 3 dB modulation bandwidths
of phosphorescent white LEDs are only a few megahertzs,
there are a number of methods, such as blue filtering
[9]
,
pre-equalization
[10–14]
, post-equalization (POE)
[15,16]
, sweep-
ing out the remaining carriers
[17]
, spectrally efficient
modulation techniques
[18–26]
, and so on that have been
reported to enhance the bandwidths and data rates of
VLC systems. Since Minh et al. first reported pre-equali-
zation
[10]
in a VLC system, equalization technologies, in-
cluding analog and digital equalization
[19,26]
, have been
widely used in the area of VLC research.
Sung et al. first explicitly analyzed the function of blue
filters
[27]
. They showed that in the discrete multitones
(DMT) VLC system, the blue optical filter may be unnec-
essary. Yeh et al. demonstrated a 37 Mbit/s real-time
white-light phosphor-LED VLC system based on orthogo-
nal frequency division multiplexing (OFDM) modulation
without using a blue filter
[28]
. Yeh et al. demonstrated an
adaptive 84.44 to 190 Mbit/s white-light phosphor-LED
VLC system based on 16-quadrature amplitude modula-
tion (16-QAM) OFDM modulation scheme utilizing no
blue filter
[29]
. However, they only analyzed and showed
DMT or OFDM VLC systems, and introduced little about
high-speed on–off keying (OOK) or QAM VLC system
without using a blue filter.
In our previous work
[12]
, the proposed analog equalizers
are designed for a blue light response, not a white light re-
sponse. In addition, at the transmitter, the pre-emphasis
(PRE) circuit, the amplifier, and the bias tee are not
integrated together. In this Letter, we optimize analog
equalizers for a white light response with out utilizing a blue
filter. In order to further to reduce the cost and complexity
of the VLC link, we integrated PRE, the amplifier, and the
self-made bias tee circuits together into a transmitter
module. The experiments are further research based on pre-
vious work, but the work is not overlapped or repeated.
Here, we experimentally demonstrate a high-speed
phosphor-based white LED VLC system. At the receiver,
an optical blue filter is not used. The 3 dB bandwidth of the
white light response is enhanced to 132 MHz using analog
equalizers. Then, the 330 Mbit/s non-return-to-zero
(NRZ) OOK data transmission with a bit error ratio
(BER) of 7.2 × 10
−10
and 672 Mbit/s 64-quadrature-
amplitude-modulation (64-QAM) data transmission with
a BER of 3.2 × 10
−3
are achieved. These resultan t BERs
are less than the forward error correction (FEC) limit of
3.8 × 10
−3
[21,29]
. In addition, the relationships between
COL 13(8), 080605(2015) CHINESE OPTICS LETTERS August 10, 2015
1671-7694/2015/080605(5) 080605-1 © 2015 Chinese Optics Letters
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