Performance analysis of a 2-D time-wavelength OCDMA wavelength-aware receiver with beat noise

The effect of beat noise on two-dimensional time-wavelength optical code-division multiple-access systems utilising wavelength-aware receivers is examined. A derivation of a general formula for the bit error probability taking into consideration multiple access interference (MAI) and other noise sources is given. In addition, a comparison between the system performance of such a receiver and the traditional configuration is presented. Studies to date that have focused only on the MAI limited case showed that the wavelength-aware configuration yields a better performance when compared to the traditional receiver. When beat noise is considered, the numerical results reveal that the performance of wavelength-aware receiver is very sensitive to beat noise and is not superior over the traditional receiver

Semiconductor optical amplifiers: performance and applications in optical packet switching [Invited]

Semiconductor optical amplifiers (SOAs) are a versatile core technology and the basis for the implementation of a number of key functionalities central to the evolution of highly wavelength-agile all-optical networks. We present an overview of the state of the art of SOAs and summarize a range of applications such as power boosters, preamplifiers, optical linear (gain-clamped) amplifiers, optical gates, and modules based on the hybrid integration of SOAs to yield high-level functionalities such as all-optical wavelength converters/regenerators and small space switching matrices. Their use in a number of proposed optical packet switching situations is also highlighted

Increasing transmission efficiency with advanced signal processing

Optical CDMA is an advanced and flexible communication technology with a potential to offer very energy efficient and highly scalable networking. In addition it can also deliver increased physical layer privacy and on-demand bandwidth sharing management. We have developed, extensively investigated, and experimentally demonstrated highly scalable approach to incoherent OCDMA which can very efficiently increase the number of simultaneous users. In addition, the introduction of an advanced photonic signal processing results in an overall system power budget improvement by nearly 3dB. Error-free operation with the BER less than 10-12 was achieved. We have also shown that with demonstrated approach we can dramatically improve number of simultaneous network users (up to ten times) while keeping the related hardware count unchanged. By comparing this results to DWDM concept, this substantial increase in number of simultaneous users did not require to add any additional wavelength laser sources and was achieved by employing just three communication wavelengths

Mathematical Analysis in Characterization of Carbon Nanotubes (CNTs) as possible Mosquito Repellents

Mosquitoes are a great threat to human health to date and are a subject of interdisciplinary research involving scientists from many areas. Recently much attention has been put to novel approaches to mosquito repellent products that involve the use of novel materials, such as carbon nanomaterials, where it is essential to determine their properties. This research discusses the full molecular characterization of carbon nanotubes (CNTs) produced by electrolysis in molten salts. Each CNT has its mathematical representation due to its hexagonal lattice structure. Multi-wall carbon nanotubes (MWCNTs) are considered. The focus is on determining their structural parameters: innermost and outermost diameters, chiral indices m and n, number of walls, and unit cell parameters. Corresponding frequency parts of Raman spectra of four experimentally produced CNTs are elaborated, and Python programming and Mathematica are employed for the most accurate (m,n) assignment. Determining the chirality of these samples enables the calculation of other structural properties, which are performed now, including their graph representation. The latter enables the evaluation of different distance-based topological indices (Wiener, Balaban, Sum-Balaban, Harary index, etc.) to predict some index-related properties of the molecules

GMPLS energy efficiency scheme for green photonic networks

Since its emergence the internet has been a significant part of today's modern living. Defined by its interconnections and routing policies, it has fuelled increased demands for provisioning of new more advanced services that are able to dynamically react to changes within the network. These services however, lead to enormous energy consumption in contrast to a global drive for a greener environment. Hence the existence of an optical infrastructure that complies with the principles of zero-carbon emission is imperative. Subsequently, in this paper, we present an energy model of Generalized Multi-Protocol Label Switching (GMPLS) network for more power efficient Green Photonic Networks. We are proposing a greener network design based on a novel routing algorithm to deliver power reduction through implementation of so called "Hibernation" approach. The scheme includes network topology such as group the nodes configuration, segmentation of the link/ports, and wavelength provisioning via partitioning. The performance evaluations of these energy saving schemes are investigated by including various challenging issue on "greening the internet" and reduces carbon footprint. In addition, to study the impact of wavelength request, blocking probability and power consumption in relation to network load is taken into account. A trade-off is observed between energy per bit, wavelengths offered (Erlang) and blocking probability as a result of the idling nodes

Performance analysis of modified asymmetrically-clipped optical orthogonal frequency-division multiplexing systems

A modification to the Asymmetrically-Clipped Optical Orthogonal Frequency-Division Multiplexing (ACO-OFDM) technique is proposed through unipolar encoding. A performance analysis of the Bit Error Rate (BER) is developed and Monte Carlo simulations are carried out to verify the analysis. Results are compared to that of the corresponding ACO-OFDM system under the same bit energy and transmission rate; an improvement of 1 dB is obtained at a BER of 10-4. In addition, the performance of the proposed system in the presence of atmospheric turbulence is investigated using single-input multiple-output (SIMO) configuration and its performance under that environment is compared to that of ACO-OFDM. Energy improvements of 4 dB and 2.2 dB are obtained at a BER of 10-4 for SIMO systems of 1 and 2 photodetectors at the receiver for the case of strong turbulence, respectively

Measurements and physical-layer modelling of transmission loss for gas turbine engine sensor networks

The aim of this study is to extract a physical-layer wireless channel model from a set of channel measurements, in support of the wider, collaborative, WIDAGATE project to assess the potential of wireless sensor networks for the condition monitoring of gas turbine engines. The collaborative partners in WIDAGATE are Rolls-Royce, Selex and University College London. The resulting model is being incorporated into a complete system protocol stack as part of the wider project. The physical layer channel model incorporates interference [1] and noise in addition to signal transmission characteristics

Optimal Selection of Parameters for Production of Multiwall Carbon Nanotubes (MWCNTs) by Electrolysis in Molten Salts using Machine Learning

The production and use of carbon nanotubes (CNTs) have become extremely wide within the last decade. Hence, the high interest in producing non-expensive and quality CNTs has motivated many research projects. This research considers the design and development of new technology for producing MWCNTs by electrolysis in molten salts using non-stationary and stationary current regimes. The electrolysis is simple, ecological, economical, and flexible, and it offers possibilities for accurate control of various parameters, such as applied voltage, current density, or temperature. We infer the underlying relationship between the parameters and the quality of the experimentally produced MWCNTs by using explainable tree-based Machine Learning (ML) models. We train several models in a supervised manner, whereas in model covariates, we use the parameters of the MCWNTs, and as a target variable, the quality of the produced MWCNT. Domain experts label all the experimental examples in our data set. Controlling these parameters enables high-yield production and, particularly important, obtaining MWCNTs, which are up to ten times cheaper than other existing technologies

A priority based routing protocol for wireless sensor networks

Recently, the demands on wireless sensor networks have switched from low traffic rate and static topology to more challenging requirements in order to meet the rapid expansion of WSN into various domain applications. This paper proposes a seamless cross layer solution that integrates network layer and medium access control to accommodate some of the new challenges. This new solution allows routing paths being generated dynamically to meet the requirement of potential mobile nodes. Higher data throughput and flow control are part of the new demands required to be addressed urgently. The proposed solution integrates a priority based MAC to handle congestion and packet loss problems which commonly happened in WSN when an occurrence of event spread into wide are

Packet equalisation in PONs using adjustable gain-clamped semiconductor optical amplifiers (AGC-SOA)

The past ten years have witnessed a dramatic growth in the delivery of high bandwidth services through Passive Optical Networks (PONs), directly to the home or to the kerb. The bursty nature of upstream traffic in a PON (from the user to Optical Network Unit, ONU) combined with a wide dynamic range of signal strength (-15dB to -28dB the difference between a very close Optical Network Terminal (ONT) with a small split ratio and a distant ONT with a high split ratio), places severe demands on the burst mode receiver at the ONU. We report here on an adjustable gain-clamped semiconductor optical amplifier (AGC-SOA) designed to maximize the output saturated power while adjusting gain to regulate the power differences between packets without loss of linearity. This device is shown to be able to modulate gain at rates that are compatible with packet to packet equalisation. Through theoretical analysis coupled with experimental verification, this paper demonstrates for the first time that this is entirely feasible