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In visible light communications (VLC) system, the linearity of the light emitting diode is an issue when being intensity modulated with an analogue signal. In optical orthogonal frequency division multiplexing (O-OFDM) based VLC systems, the source nonlinearity imposes a tight restriction on the achievable peak-to-average-power-ratio. To address this issue, we propose a hybrid OFDM-PTM (pulse time...
The properties and performance of CdSSe/ZnS colloidal quantum dot composite materials for use as InGaN LED color converters in visible light communications applications is reported. 500Mb/s optical wireless transmission is demonstrated.
In this paper, a review on radio-over-fiber (RoF) technology is conducted to support the exploding growth of mobile broadband. An RoF system will provide a platform for distributed antenna system (DAS) as a fronthaul of long term evolution (LTE) technology. A higher splitting ratio from a macrocell is required to support large DAS topology, hence higher optical launch power (OLP) is the right approach...
Conventional Brillouin based carrier generator may produce optical wavelengths at the spacing of 10 GHz (odd) or 20 GHz (even), which in turn will be heterodyned for microwave/millimeter wave (mm-wave) generation. Therefore, in the scenario where both odd and even order carriers are required, two laser units have to be utilized. In this paper, a new type of Brillouin fiber laser is proposed with bidirectional...
The optical gain of a simple new type of wide field of view optical concentrator is predicted and easy modifications that will significantly increase its gain without changing its field of view are identified.
We propose an artificial neural network (ANN) equalizer for transmission performance enhancement of coherent optical OFDM (C-OOFDM) signals. The ANN equalizer showed more efficiency in combating both chromatic dispersion (CD) and single-mode fibre (SMF)-induced non-linearities compared to the least mean square (LMS). The equalizer can offer a 1.5 dB improvement in optical signal-to-noise ratio (OSNR)...
This paper focuses on evaluating the performance of two aperture averaging methods used for compensating the effects of the air turbulence in free space optical (FSO) communications. These methods are based on using a concentration lens and spherical concave mirrors (SCM). The preliminary experimental results show that the quality of the received signal in terms of the Q-factor and the scintillation...
In this paper we experimentally demonstrate a 10 Mb/s error free visible light communications (VLC) system using polymer light-emitting diodes (PLEDs) for the first time. The PLED under test is a blue emitter with ∼600 kHz bandwidth. Having such a low bandwidth means the introduction of an intersymbol interference (ISI) induced penalty at higher transmission speeds and thus the requirement for an...
This paper presents experimental results demonstrating a > 100 Mb/s visible light communications (VLC) system using linear adaptive equalizers for the first time. In order to achieve high transmission speeds, generally the research community has adopted spectrally efficient modulation formats such as discrete multi-tone and equalizers are overlooked. The reason for this is unclear as equalizers...
In this paper, the attenuation of free space optical (FSO) communication systems operating at selected wavelengths of 0.83 μm, 1.31 μm and 1.55 μm in the controlled laboratory based fog and smoke environments are compared. The fog and smoke are generated and controlled homogeneously along the indoor atmospheric chamber of length 6 m. The experimental results from the selected wavelengths are compared...
This paper investigates the requirements for uniform illumination using white LEDs, showing the balance between lighting and visible light communications. The communications system performance of the is also investigated for mobility with a varying field of view at the receiver, showing that there is a limit that beyond which there are no longer gains to be made in mobility.
This paper studies the optimised Lambertian order (OLO) of light-emitting diodes (LEDs) for an indoor non-directed line of sight optical wireless communication (NLOS-OWC) systems. We firstly derive an expression of the OLO from a conventional Lambertian LED model, Then, we analyse the indoor multi-cell NLOS-OWC channel characteristics including optical power distribution and multipath time dispersion...
In this paper, the performance of binary polarisation shift keying (BPOLSK) with the direct detection (DD) scheme is experimentally investigated. BPOLSK scheme is used to mitigate the atmospheric turbulence induced fading in a free space optical (FSO) communication link. For comparison the experimental and analytical results for the non-return-to-zero on-off keying (NRZ-OOK) have also been presented...
The paper presents the concept, design and analysis for a visible light communications receiver which has a full 180° perception angle thus offering the guard against blocking and enhancing the system mobility. The proposed receiver includes seven sub-receivers with the proposed geometrical shape investigated and analyzed in MATLAB® for evaluating the received power, RMS delay spread and corresponding...
This paper presents the concept, design and analysis for a visible light communications receiver to guard against blocking and enhance mobility. Different geometrical shapes have been investigated, with two being chosen and analyzed in MATLAB for the received power and the root-mean-square (RMS) delay spread. The results show that the receiver is fully mobile within the test area and can handle data...
This paper proposes a method of generating 30 GHz optical millimeter wave (MMW) radio-over-fibre (RoF) by using one dual drive Mach-Zehnder modulator (DD-MZM) which is biased at maximum transmission biasing point to generate optical double sideband suppressed carrier (ODSB-SC) signal. The nonlinear effects of self phase modulation (SPM) in the standard single mode fibre (SSMF) are considered. We compare...
There is a increasing demand for high speed data services while travelling on trains and other means of public transportation. Hence, an alternative technology to radio frequency (RF) communications called free space optics (FSO) could be used to provide truly high-speed broadband services in trains. This paper presents a Lambertian source modelling of FSO ground-to-train communication link along...
In this paper, the effect of the equal gain combining (EGC) spatial diversity for the free space optical (FSO) link for the new hybrid pulse position modulation binary phase shift keying subcarrier intensity modulation (2-PPM-BPSK-SIM) scheme in a turbulence channel is investigated. The analytical unconditional bit error rate (BER) of 2-PPM-BPSK-SIM with the EGC diversity under lognormal and negative...
In this paper, we compare the fog attenuation of free space optical (FSO) communication systems operating at infrared wavelengths of 830 and 1550 nm in the controlled laboratory based fog environment. The fog is generated and controlled homogeneously along the atmospheric chamber of length 5.5 m. The visibility (V) is measured to characterize the fog within the chamber using Koschmieder relationship...
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