Visible light communications: 3.75 Mbits/s data rate with
a 160 kHz bandwidth organic photodetector and
artificial neural netwo rk equalization [Invited]
Zabih Ghassemlooy,
1,
* Paul Anthony Haigh,
1,
** Francesco Arca,
2
Sandro Francesco Tedde,
2,
***
Oliver Hayden,
2
Ioannis Papakonstantinou,
3
and Sujan Rajbhandari
4
1
Optical Communications Research Group, Northumbria University, NE1 8ST, UK
2
Siemens AG, Corporate Technology, Erlangen CT T DE HW3, Germany
3
Department of Electronic & Electrical Engineering, University College London, WC1E 7JE, UK
4
Department of Engineering Science, University of Oxford, OX1 3PJ, UK
*Corresponding author: z.ghassemlooy@northumbria.ac.uk
**Corresponding author: paul.haigh@northumbria.ac.uk
***Corresponding author: sandro.tedde@siemens.com
Received March 5, 2013; revised May 9, 2013; accepted May 10, 2013;
posted May 10, 2013 (Doc. ID 186399); published July 19, 2013
This paper presents an experimental demonstration of a visible light communications link with an light emitting
diode and a low-bandwidth organic photodetector as transmitter and receiver, respectively, that achieves sub
4 Mbits∕s speeds. An artificial neural network (ANN) equalizer is required in order to achieve such high data rates
because of the influence of intersymbol interference. The digital modulation formats tested in this paper are non-
return-to-zero on–off keying (OOK), and fourth-order pulse position modulation (4-PPM). Without equalization,
data rates of 200 and 300 kbits∕s can be achieved for 4-PPM and OOK, respectively. With ANN equalization, data
rates of 2.8 and 3.75 Mbits∕s can be achieved for the first time for OOK and 4-PPM, respectively. © 2013 Chinese
Laser Press
OCIS codes: (060.4510) Optical communications; (250.2080) Polymer active devices.
http://dx.doi.org/10.1364/PRJ.1.000065
1. INTRODUCTION
Visible light communications (VLC) is an area for research
that is picking up focus as an alternative to radio frequency
(RF) technologies because of its bifunctionality, offering data
communications and solid-state lighting, not to mention the
ability to transmit data rates of 3.4 Gbits∕s [1], which exceeds
current commercial Wi-Fi technologies. Organic photodetec-
tors (OPDs) are of interest for optical communications sys-
tems [2–5] due to advantages such as the possibility to
fabricate the devices on flexible substrates and to achieve
effortless large active area devices by using cost-effective
processing techniques such as spray coating [6]. So far a meg-
abit per second data rate has not been demonstrated in a wire-
less medium; however reports have emerged of organic
optical communications in the fiber domain [3]. Here we re-
port a data rate of 3.75 Mbits∕s using a white phosphor light
emitting diode (LED) as transmitter and an OPD as receiver.
OPDs are not expected to replace Si photodiodes in the
near future in optical communications because of the latter’s
strong market position and wide user base. On the other hand,
OPDs can be of interest for applications where Si photodiodes
are not suitable and therefore are a really exciting technology
for the future, also considering the significant cost reduction
offered by spray coating at room temperature. Due to the low
charge carrier mobility in organic semiconductors, which are
orders of magnitude lower than in Si, the bandwidths (BWs) of
OPDs are usually much lower than the BWs of Si devices,
which is a major challenge.
The OPDs under test (produced under collaboration by
Siemens AG Corporate Technology) are based on the bulk
heterojunction principle [7]. Four diodes with 1 cm
2
active
area each are fabricated on a single 5 cm × 5 cm transparent
glass substrate as illustrated in Fig. 1.
The thin-film (∼500 nm) organic semiconductor layer, a
blend of poly-3-hexyl-thiophene (P3HT) as the donor material
and [6,6]-phenyl C
61
butyric acid methyl ester (PCBM) as the
acceptor material, is deposited by spray coating from a xylene
solution as in [6], which leads to extremely low-material-cost
devices (∼€0.20 cm
−2
). This simple fabrication technique
is extremely attractive for VLC systems. The OPD BW is
dynamic and dependent on the incident light intensity
(W · cm
−2
), as reported in [8]. In high light densities, the num-
ber of charge carriers is greater than the number of interface
traps, and therefore the BW is proportional to the time con-
stant of the plate capacitance. Conversely, in low light den-
sities, the number of interface traps outnumbers the number
of charge carriers; so the BW is proportional to the traps’ time
constant.
Further, the OPD is also attractive for VLC systems due to
its superior responsivity compared to Si photodetectors in the
visible range under a much smaller reverse bias, as shown in
Fig. 2. It also has a sharp cutoff wavelength at ∼620 nm due to
the larger bandgap of P3HT (∼2 eV) in comparison to Si
(∼1.16 eV). It should be noted that a bandgap of 2 eV is rel-
atively high and has a cutoff wavelength around 620 nm (red
wavelengths), which could be a problem for VLC applications
Ghassemlooy et al. Vol. 1, No. 2 / August 2013 / Photon. Res. 65
2327-9125/13/020065-04 © 2013 Chinese Laser Press
下载后可阅读完整内容，剩余3页未读，立即下载
weixin_38736529
- 粉丝: 2
- 资源: 875
我的内容管理
展开
最新资源
- Ansys Comsol实现力磁耦合仿真及其在电磁无损检测中的应用
- 西门子数控系统调试与配置实战案例教程
- ELM多输出拟合预测模型：简易Matlab实现指南
- 一维光子晶体的Comsol能带拓扑分析研究
- Borland-5技术资料压缩包分享
- Borland 6 技术资料分享包
- UE5压缩包处理技巧与D文件介绍
- 机器学习笔记：深入探讨中心极限定理
- ProE使用技巧及文件管理方法分享
- 增量式百度图片爬虫程序修复版发布
- Emlog屏蔽用户IP黑名单插件：自定义跳转与评论限制
- 安装Prometheus 2.2.1所需镜像及配置指南
- WinRARChan主题包：个性化你的压缩软件
- Neo4j关系数据映射转换测试样例集
- 安装heapster-grafana-amd64-v5-0-4所需镜像介绍
- DVB-C语言深度解析TS流
资源上传下载、课程学习等过程中有任何疑问或建议，欢迎提出宝贵意见哦~我们会及时处理！
点击此处反馈
