Optical wireless communications omnidirectional receivers for vehicular communications

doi:10.1016/j.aeue.2017.05.042

AEU - International Journal of Electronics and Communications

Volume 79, September 2017, Pages 102-109

https://doi.org/10.1016/j.aeue.2017.05.042 Get rights and content

Abstract

Wide aperture omnidirectional free-space optical (FSO) receivers using wavelength shifting (WLS) fibers that enable the use of small active area high-speed photodetectors in optical wireless communications, are presented. In particular, the influence of WLS fiber decay time in the bit rate is evaluated when receiving intensity modulated light generated with commercial off-the-shelf light-emitting diodes. The option of increasing the photon collecting area of a $7 {mm}^{2}$ active area avalanche photodiode using WLS fiber, gave a 300% improvement in the bit rate, when compared with the option of using a bare $31 {mm}^{2}$ active area avalanche photodiode. It was also experimentally verified, that a WLS spiral receiver mounted over a reflective base gave more gain than simulated Lambert‘s cosine law, proving that reflective optics can be used to increase the WLS-FSO receiver aperture.

Introduction

The tetherless teleoperation of vehicles [1] using high-definition video, dense LIDAR data [2] and haptic virtual telepresence needs the existence of a broadband omnidirectional wireless system, whose implementation in tunnels, requires the use of optical wireless communications (OWC) to mitigate the intense attenuation that non-optical wavelengths have in those environments [3]. Tunnels are a common traffic infrastructure, with many not designed for high traffic volumes, forcing the implementation of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) visible light communications (VLC) integrated [4] in cooperative intelligent transportation systems (ITS). Vehicular communications using VLC-ITS, obligate the development of omnidirectional free-space optical (OFSO) receivers to mitigate the effects of turbulence [5] and pointing errors [6] in the propagation channel [7]. Targeting that objective, this work presents high aperture and field-of-view (FOV) FSO receivers using wavelength shifting (WLS) fibers with fluorescence and lifetime [8] characteristics compatible with high speed photodetectors. After verifying the suitability of WLS fiber for OWC, the sensitivities of spiral and toroidal WLS-OFSO receivers are evaluated with light generated by blue light-emitting diodes (LED), modulated with continuous sine waves or pulsed Direct-Current biased Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM) signals.

Section snippets

OFSO photodetection theoretical considerations

The two most important characteristics of an OFSO receiver are the receiving area (aperture) and FOV that are inversely related in geometrical optics because of the conservation of the etendue of light [9]. Standard flat photodetectors have a maximum FOV equal to half a sphere ( $2 π$ sr), with that value being reduced when the semiconductor die is mounted inside a deep cavity in a windowed case. The photon radiant flux received in the area of flat photodetectors falls with the cosine of the angle

Experimental setups

Experiments implementing type-1 receivers were undertaken using three different avalanche photodiodes (APD) described in Table 1, bare or coupled to Saint-Gobain BCF-91A and BCF-92 WLS fibers, with 12 and 2.7 ns decay time, respectively. After an initial WSL fiber evaluation, four types of single cladding WLS fiber with 0.8 mm diameters were ordered, BCF-92 WLS fiber doped with different levels of fluorescent dye concentrations (standard, half, double), and the photodetectors were selected for an

Results and discussion

An evaluation procedure was executed to identify a WLS fiber suitable for use in the implementation of OFSO receivers. Frequency response characterizations were made with two different decay time fluorescent materials used in the BCF-91A and BCF-92 fibers, and after confirming that BCF-91A is not suited for broadband OWC, the influence of BCF-92 fiber fluorescent dye concentration in the OWC receiver optical gain, was measured. Together with this WLS fiber OWC characterization, a procedure to

Conclusions

Our subject has been the development of OFSO receivers for vehicular OWC where the field of vision is normally limited with implementation restrictions. The 0 to 360 degrees flat gain of the toroidal receiver demonstrates its potential for use in V2I-OWC, to complement the more sensitive spiral arrangement that was developed with the intention to be integrated in vehicles where a 360-degree line-of-sight does not exist. V2V communication for tunnel traffic control is an application example,

Acknowledgement

This work was funded by Penguin Automated Systems Inc.

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Regular paperOptical wireless communications omnidirectional receivers for vehicular communications

Abstract

Introduction

Section snippets

OFSO photodetection theoretical considerations

Experimental setups

Results and discussion

Conclusions

Acknowledgement

AEU-Int J Electron Commun

AEU-Int J Electron Commun

AEU-Int J Electron Commun

AEU-Int J Electron Commun

Nucl Instrum Methods Phys Res Sect A

AEU-Int J Electron Commun

Renewable Sustainable Energy Rev

AEU-Int J Electron Commun

Nucl Phys B-Proc Suppl

Teleoperation of mining equipment using optical wireless communications

A survey of wireless communications and propagation modeling in underground mines

Commun Surveys Tutorials, IEEE

Visible light communication for cooperative ITS

Prototyping multi-transceiver free-space optical communication structures

Free-space-optical mobile ad hoc networks: auto-configurable building blocks

Wireless Networks

Proposal for a new cylindrical geometry for transverse infrared photodetectors

IEEE Trans Electron Devices

Regular paper
Optical wireless communications omnidirectional receivers for vehicular communications