Zabih Ghassemlooy
Northumbria University, Mpee, Faculty Member
- I am an academic with research interests in optical wireless communications, visible light communications, free space optics.edit
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... more
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. However, high OLP generates undesired nonlinearities, namely the stimulated Brillouin scattering (SBS). Three different aspects of solving the SBS process are covered in this paper, where the solutions ultimately provided an additional 4 dB link budget.
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This paper provides experimental results for a multi-user visible light communications system using multi-band carrier-less amplitude and phase (m-CAP) modulation scheme. We optimize the system performance by adapting pulse shaping filter... more
This paper provides experimental results for a multi-user visible light communications system using multi-band carrier-less amplitude and phase (m-CAP) modulation scheme. We optimize the system performance by adapting pulse shaping filter parameters, subcarrier spacing and allocating different baud rates to individual sub-bands called allocated m-CAP (Am-CAP). We show that a maximal system data rate of ∼468 Mb/s for four users can be supported while gaining higher flexibility for optimization and the same or lower computational complexity compared with the conventional m-CAP scheme.
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Research Interests: Electronic Engineering, Computer Science, Medical Imaging, Fiber Optics, Digital Signal Processing, and 15 moreMatlab, Artificial Neural Networks, Optical, Light, LED, Light Emitting Diodes, Fuzzy Adaptive Equalizer, Equalizers, Bandwidth, Electrical And Electronic Engineering, Amplitude shift keying, Blue Filter, Light Emitting Diode, Neural nets, and Adaptive Equalizer
This paper experimentally investigates, for the first time, a new wavelength-division multiplexing-based visible light communications link based on a defocused non-imaging multiple-input multiple-output (MIMO), which removes the need for... more
This paper experimentally investigates, for the first time, a new wavelength-division multiplexing-based visible light communications link based on a defocused non-imaging multiple-input multiple-output (MIMO), which removes the need for tuned optical bandpass filters paired with each receiver. The proposed system is based on using the natural diversity of the individual light emitting diodes (LEDs) within a single light source to generate an H-matrix, which is independent of spatial diversity. We show that, by transmitting K-independent sets of non-return to zero on-and-off keying signals on separate wavelengths, the received superposed symbols can be demultiplexed. The non-imaging MIMO diversity is achieved by considering the power-current characteristics of the light emitting diode, the responsivity of the photodetector array, and the defocused beam spot. The system is empirically verified for K = 3 using red, green, and blue LEDs with Q-factors of 7.66, 7.69, and 4.75 dB, respec...
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Abstract There is a huge demand for seamless high-speed communications in fast moving trains. People want broadband services while on board as in their home or in the workplace. This demand drives the motivation for a high speed... more
Abstract There is a huge demand for seamless high-speed communications in fast moving trains. People want broadband services while on board as in their home or in the workplace. This demand drives the motivation for a high speed dedicated optical wireless link. Here ...
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This paper present simulation-based results on the impact of transmitter (Tx) position and orientation uncertainty on the accuracy of the visible light positioning (VLP) system based on the received signal strength (RSS). There are... more
This paper present simulation-based results on the impact of transmitter (Tx) position and orientation uncertainty on the accuracy of the visible light positioning (VLP) system based on the received signal strength (RSS). There are several constraining factors for RSS-based algorithms, particularly due to multipath channel characteristics and set-up uncertainties. The impact of Tx uncertainties on positioning error performance is studied, assuming a statistical modelling of the uncertainties. Simulation results show that the Tx uncertainties have a severe impact on the positioning error, which can be leveraged through the usage of more transmitters. Concerning a smaller Tx’s position uncertainty of 5 cm, the average positioning errors are 23.3, 15.1, and 13.2 cm with the standard deviation values of 6.4, 4.1, and 2.7 cm for 4-, 9-, and 16-Tx cases, respectively. While for a smaller Tx’ orientation uncertainty of 5°, the average positioning errors are 31.9, 20.6, and 17 cm with stand...
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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... more
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 for two cases of one-cell and four-cell configurations. Furthermore, we estimate the transmission bandwidth by simulating the ...
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In this paper, we propose using an input packet with multiple wavelengths to achieve semiconductor optical amplifier (SOA) gain uniformity for high speed optical applications. Rapid SOA gain recovery is a key factor to minimise the output... more
In this paper, we propose using an input packet with multiple wavelengths to achieve semiconductor optical amplifier (SOA) gain uniformity for high speed optical applications. Rapid SOA gain recovery is a key factor to minimise the output gain standard deviation which results in reducing the system penalties. The SOA is modelled using a segmentation scheme and its theoretical analysis is
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Comparing with the existing incandescent, light-emitting diodes (LEDs) offer higher power efficiency, higher brightness, longer lifetime, and have a fast dynamic response in the order of a few megahertz. LEDs are recently expected to be... more
Comparing with the existing incandescent, light-emitting diodes (LEDs) offer higher power efficiency, higher brightness, longer lifetime, and have a fast dynamic response in the order of a few megahertz. LEDs are recently expected to be utilised for the next generation indoor optical wireless communication (OWC) system. In this paper, we present a mathematical design model as well as a practical measurement for an indoor diffuse cellular visible light communication (VLC) system. It operates at a date rate of 5 Mb/s using the on- ...
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This paper experimentally investigates, for the first time, a new wavelength-division multiplexing-based visible light communications link based on a defocused non-imaging multiple-input multiple-output (MIMO), which removes the need for... more
This paper experimentally investigates, for the first time, a new wavelength-division multiplexing-based visible light communications link based on a defocused non-imaging multiple-input multiple-output (MIMO), which removes the need for tuned optical bandpass filters paired with each receiver. The proposed system is based on using the natural diversity of the individual light emitting diodes (LEDs) within a single light source to generate an H-matrix, which is independent of spatial diversity. We show that, by transmitting K-independent sets of non-return to zero on-and-off keying signals on separate wavelengths, the received superposed symbols can be demultiplexed. The non-imaging MIMO diversity is achieved by considering the power-current characteristics of the light emitting diode, the responsivity of the photodetector array, and the defocused beam spot. The system is empirically verified for K = 3 using red, green, and blue LEDs with Q-factors of 7.66, 7.69, and 4.75 dB, respec...
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Abstract: In future high-speed self-routing photonic networks based on all-optical time division multiplexing (OTDM) it is highly desirable to carry out packet switching, clock recovery and demultplexing in the optical domain in order to... more
Abstract: In future high-speed self-routing photonic networks based on all-optical time division multiplexing (OTDM) it is highly desirable to carry out packet switching, clock recovery and demultplexing in the optical domain in order to avoid the bottleneck due to the optoelectronics ...
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ABSTRACT In this study, the authors propose an optical microwave (MW) radio-over-fibre system in which an integrated dualparallel Mach–Zehnder modulator (DP-MZM) is biased at the maximum transmission biasing point. A single drive Mach–... more
ABSTRACT In this study, the authors propose an optical microwave (MW) radio-over-fibre system in which an integrated dualparallel Mach–Zehnder modulator (DP-MZM) is biased at the maximum transmission biasing point. A single drive Mach– Zehnder modulator, in series with the DP-MZM, is used to modulate the 1 GHz radio frequency data onto the optical carrier. They characterise the efficiency of the practical system in terms of power penalty and error vector magnitude. Two modulation schemes are investigated, namely binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) over fibre spans of 10 and 25 km of standard single mode fibre. The results show that the second-order sideband of MW has the potential to provide error free transmission for BPSK and QPSK. The error free communication system is achieved for BPSK at 10 and 25 km fibre spans at optical launch power (OLP) of 7 dBm, whereas for QPSK, the OLP is ∼11 and ∼12 dBm for 10 and 25 km fibre spans, respectively.
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ABSTRACT A multi-band CAP system is experimentally demonstrated for the first time in VLC. We show that with an 8-CAP testbed spectral efficiencies (~4.75 b/s/Hz) at a realistic distance of 1 m can be reached.
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ABSTRACT This paper investigates the performance of free-space optical (FSO) communication systems under the influence of atmospheric loss, turbulence and pointing error. Considering the limiting Rytov-based scintillation theory... more
ABSTRACT This paper investigates the performance of free-space optical (FSO) communication systems under the influence of atmospheric loss, turbulence and pointing error. Considering the limiting Rytov-based scintillation theory associated with the simplified field models, the Gaussian-beam wave model is introduced to characterize the propagation properties of the optical signal through random turbulent medium. The bit-error rate (BER) and average channel capacity are evaluated, taking into account the effects of aperture averaging and beam width. In general, larger receiving apertures enable lower BER attainment with smaller signal-to-noise ratio (SNR), while beam width optimization is a feasible approach in promoting capacity enhancement.
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In this paper, we propose an all-optical packet switched router using new packet header address correlation scheme based on with pulse position modulation (PPM) signaling format. Both packet header address and all the routing table... more
In this paper, we propose an all-optical packet switched router using new packet header address correlation scheme based on with pulse position modulation (PPM) signaling format. Both packet header address and all the routing table entries are represented in PPM-format address ...
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In this paper, we propose a new receiver and demodulation method for use in wavelength division multiplexed visible light communications systems, utilising the natural diversity offered by photodiodes. This is based on the wavelength... more
In this paper, we propose a new receiver and demodulation method for use in wavelength division multiplexed visible light communications systems, utilising the natural diversity offered by photodiodes. This is based on the wavelength dependent photodiode responsivities, which lead to different signal-to-noise ratios at the receiver. Using this method, it is possible to transmit independent information using on different wavelengths but where signals occupy the same electrical frequency range and where they would, otherwise, interfere. We illustrate and experimentally demonstrate that through simple subtractions the signals can be extracted with the constellations showing Q-factors corresponding to sufficiently low bit error rates.
Visible Light Communication (VLC) is a short-range optical wireless communication technology that has been gaining attention due to its potential to offload heavy data traffic from the congested radio wireless spectrum. At the same time,... more
Visible Light Communication (VLC) is a short-range optical wireless communication technology that has been gaining attention due to its potential to offload heavy data traffic from the congested radio wireless spectrum. At the same time, wireless communications are becoming crucial to smart manufacturing within the scope of Industry 4.0. Industry 4.0 is a developing trend of high-speed data exchange in automation for manufacturing technologies and is referred to as the fourth industrial revolution. This trend requires fast, reliable, low-latency, and cost-effective data transmissions with fast synchronizations to ensure smooth operations for various processes. VLC is capable of providing reliable, low-latency, and secure connections that do not penetrate walls and is immune to electromagnetic interference. As such, this paper aims to show the potential of VLC for industrial wireless applications by examining the latest research work in VLC systems. This work also highlights and clas...
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All optical switches based on the cross-phase modulation (XPM) in conjunction with interferometric configurations such as Mach-Zehnder interferometers (MZIs), terahertz optical asymmetric demultiplexers (TOADs) and ultrafast nonlinear... more
All optical switches based on the cross-phase modulation (XPM) in conjunction with interferometric configurations such as Mach-Zehnder interferometers (MZIs), terahertz optical asymmetric demultiplexers (TOADs) and ultrafast nonlinear interferometers (UNIs) are widely studied [1]. Among ...
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ABSTRACT Radio over Fibre (RoF) has been proposedasan alternative medium to extend the coverage of radio frequency (RF) millimetre wave (MMW). The main challenges are the fibre attenuation and chromatic dispersion which degrade the signal... more
ABSTRACT Radio over Fibre (RoF) has been proposedasan alternative medium to extend the coverage of radio frequency (RF) millimetre wave (MMW). The main challenges are the fibre attenuation and chromatic dispersion which degrade the signal power and induces inter-symbol interference (ISI), respectively. Two electrical modulation schemes are employed in this paper, namely binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) at electrical bandwidth of 30 GHz. The proposed technique using optical continuous wave (CW) laser as the optical carrierto transmit BPSK and QPSK signals at 30GHz. The performance of the proposed method than compared to optical MMW carrier at 60 GHz inorder to carry 30 GHz BPSK and QPSK electrical signals. The results indicate the improvement in transmission distance of up to 20 km for both BPSK and QPSK modulation schemesat signaltonoise ratio (SNR) of 11 dB and 16 dB respectively for bit error rate (BER) of 10-5 in the proposed method. These results compared to 15 kmand 10 km in case of optical MMW using BPSK and MMW QPSK systemsat SNR of 18 dB and 26 dB to achieve the same BER value.
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... 165-169. [7] M. Hoa Le, Z. Ghassemlooy, D. O'Brien, and G. Faulkner, "Indoor Gigabit optical wireless communications: Challenges and possibilities," in Transparent Optical Networks (ICTON), 2010 12th... more
... 165-169. [7] M. Hoa Le, Z. Ghassemlooy, D. O'Brien, and G. Faulkner, "Indoor Gigabit optical wireless communications: Challenges and possibilities," in Transparent Optical Networks (ICTON), 2010 12th International Conference on, pp. ...
In this document, we investigate the outage performance of a serial FSO relaying system employing DF or AF scheme at the relays over an aggregate channel model that takes into account both path loss and turbulence-induced fading. For the... more
In this document, we investigate the outage performance of a serial FSO relaying system employing DF or AF scheme at the relays over an aggregate channel model that takes into account both path loss and turbulence-induced fading. For the case of DF signaling, an exact analytical expression of the end-to-end outage probability can be easily derived. However, for the case of AF signaling, we could obtain a closed-form expression using the known MGF method by assuming perfect available channel state information (CSI) at each relay.
In vast majority of the semiconductor laser applications such as communication systems employing a high pump source and optical fibre, the edge emitting lasers are the dominant source and are widely used. However, edge emitting lasers are... more
In vast majority of the semiconductor laser applications such as communication systems employing a high pump source and optical fibre, the edge emitting lasers are the dominant source and are widely used. However, edge emitting lasers are too costly requiring optical fibre coupling. Therefore attention has been focused on vertical-cavity surface-emitting lasers (VCSELs) with potentially low manufacturing cost for optical communication systems. In this paper the influence of current modulation on the polarization properties of VCSEL is subjected to different modulation schemes, which has been investigated experimentally. The results for three modulation techniques are compared in terms of reduction of the threshold current Ithof 850 nm single-mode VCSEL device. We demonstrated that both the modulation frequency and modulation amplitude of the input signal play an important role in reducing the current threshold of VCSEL.
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This paper presents a real-time 106 Mbit/s visible light communication (VLC) system using only non-return-to-zero on-off keying (OOK-NRZ) modulation and general lighting LED. With a pre-emphasis module based LED driver, the 3-dB... more
This paper presents a real-time 106 Mbit/s visible light communication (VLC) system using only non-return-to-zero on-off keying (OOK-NRZ) modulation and general lighting LED. With a pre-emphasis module based LED driver, the 3-dB modulation bandwidth of VLC link is extended from 4 to 106 MHz. Given the BER upper Limit was 1.3 × 10−3, the highest bit rates achieved through the designed system were 106 and 98 Mbit/s at the distances of 60 and 70 cm, respectively.
The large signal frequency response of a 1.53pm laser was assessed using a 5 Gbit/s, zz3 - 1 PRBS NRZ pattern from a word generator. The resulting eye pattern for a 5 : 1 extinction ratio is shown in Fig. 4. Rise and fall times were 60... more
The large signal frequency response of a 1.53pm laser was assessed using a 5 Gbit/s, zz3 - 1 PRBS NRZ pattern from a word generator. The resulting eye pattern for a 5 : 1 extinction ratio is shown in Fig. 4. Rise and fall times were 60 and 92 ps, respectively. A clear, open eye ...
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ABSTRACT 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... more
ABSTRACT 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 offer a substantial capacity for removing inter-symbol interference. As a result, in this paper we implement a line-of-sight VLC link with an ~8 MHz bandwidth and a linear feedforward equalizer; the number of taps is varied in order to gain insight into the system performance using varying complexity. The 120 Mb/s transmission speed ultimately achieved offers a bit-rate to bandwidth gain of ~15 times.
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Proc. Of 2 nd Inter. Sympo. On Communication Systems, Networks and DSP, 18-20 July 2000, Bournemouth University, UK., pp. 59-63 ... Crosstalk and Noise Characteristics of Non-linear Optical Loop Mirror Demultiplexer and Terahertz Optical... more
Proc. Of 2 nd Inter. Sympo. On Communication Systems, Networks and DSP, 18-20 July 2000, Bournemouth University, UK., pp. 59-63 ... Crosstalk and Noise Characteristics of Non-linear Optical Loop Mirror Demultiplexer and Terahertz Optical Asymmetric ...
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A 1×2 high contrast ratio (CR) all-optical switch based on the symmetric Mach-Zehnder (SMZ) interferometers is presented. Simulation results show a remarkable improvement of the inter-output CR (~25 dB) between the two outputs compared... more
A 1×2 high contrast ratio (CR) all-optical switch based on the symmetric Mach-Zehnder (SMZ) interferometers is presented. Simulation results show a remarkable improvement of the inter-output CR (~25 dB) between the two outputs compared with an existing SMZ switch. We have shown that the proposed optical switch offers over 35 dB of inter-output CR over a wide range of input powers using appropriate power of the control pulses. The proposed switch can also support broadcast and drop switching modes when using together with an additional XOR gate.