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

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

Towards faster, secure and more energy efficient optical networks

A rapid penetration of multimedia into our lives has triggered unparallel demand for high speed Internet access and secure reliable and very efficient data transport. To satisfy these demands will require new and innovative approaches. It is becoming more clear that electronics alone will not be able to offer the needed solution. Today we already benefit from advances which revolutionized data and voice communications. The implementation of optical transport layer became the backbone of today’s high performance networks. Optical fiber offers enormous transport capacity and is capable to accommodate the growing volume of voice and data traffic. Further more, the capacity of each fiber can be further augmented. Today commercially deployed Dense Wavelength Division Multiple Access (DWDMA) networks are capable of transporting tens of Gigabits of data per second over a single DWDM wavelength channel, offering tremendous aggregate data throughputs exceeding ten Terrabits/sec. This creates new communications bottleneck at the fiber endpoints where the routing and switching takes place. Today’s routers use electronics to process and route incoming optical data packets. These electronic crossbars, however, do not provide sufficient capacity to timely, efficiently, and without any delays route terabits of incoming data traffic. The switching speed of these devices is limited by the frequency response of used materials and can not any more support desired bandwidth. Given all the above, it seems unlikely that electronics will deliver the needed bandwidth to support existing fiber capacity. We need to look for alternative solutions. There is growing believe, that all-optical switching/signal processing may offer the needed solution. We will review some of the promising approaches which if successfully implemented could result in manufacturable ultra-fast optical devices. We will attempt to predict the applicability of such devices for different applications within existing and newly emerging markets

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

Wireless sensor network for cattle monitoring system

This paper describes a cost effective Wireless Sensor Network (WSN) technology for monitoring the health of dairy cows. By monitoring and understanding the cow individual and herd behaviour, farmers can potentially identify the onset of illness, lameness or other undesirable health conditions. However, the WSN implementation needs to cope with various technical challenges before it can be suitably and routinely applied in cow management. This paper discusses results concerning data transportation (i.e. mobility) from the cow mounted sensory devices

Empirical modelling and simulation of transmission loss between wireless sensor nodes in gas turbine engines

Transmission loss measurements between a grid of hypothetical WSN node locations on the surface of a gas turbine engine are reported for eight frequencies at 1 GHz intervals in the frequency range 3.0 to 11.0 GHz. An empirical transmission loss model is derived from the measurements. The model is incorporated into an existing system channel model implemented using Simulink as part of a wider project concerning the development of WSNs for the testing and condition monitoring of gas turbine engines

Statistical interaction modeling of bovine herd behaviors

While there has been interest in modeling the group behavior of herds or flocks, much of this work has focused on simulating their collective spatial motion patterns which have not accounted for individuality in the herd and instead assume a homogenized role for all members or sub-groups of the herd. Animal behavior experts have noted that domestic animals exhibit behaviors that are indicative of social hierarchy: leader/follower type behaviors are present as well as dominance and subordination, aggression and rank order, and specific social affiliations may also exist. Both wild and domestic cattle are social species, and group behaviors are likely to be influenced by the expression of specific social interactions. In this paper, Global Positioning System coordinate fixes gathered from a herd of beef cows tracked in open fields over several days at a time are utilized to learn a model that focuses on the interactions within the herd as well as its overall movement. Using these data in this way explores the validity of existing group behavior models against actual herding behaviors. Domain knowledge, location geography and human observations, are utilized to explain the causes of these deviations from this idealized behavior

Positioning system for wireless sensor networks with location fingerprinting

Wireless sensor networks (WSN) are networks that deploy hundreds or thousands of wireless sensors in a pre-defined area that can communicate with each other to detect, for example the ambient environment. Each sensor is composed of the four basic elements: transmitting unit, processing unit, power unit and sensing unit. The main task of each sensor is to detect events, perform a restricted set of local data processing tasks and then transmit the data. This technology still in its early stage new researches are being conducted intensively in MAC protocols, network and routing layer, and adaptation into various domains applications. In this proposal, the focus is placed to investigate algorithms in mapping the location of sensor nodes. Knowing the location of the sensor node is critically important; the knowledge of the location of the sensor node that reported a detected event can reduce the time for assistants reaching to the outbreak point. This can potentially save life or can bring the outbreak event under control in shortest time. As the sensor node's physical hardware is mainly comprises of low specification and low cost componentry to facilitate mass production hence affordable to be applied intensively in monitoring zone. This has created a tough challenge in mapping the locations of sensor nodes as the hard-ware can not provide precise timing in calculating time of flight of a packet which is an important parameter in estimating distance between transmitting node and receiving node. In general the sensor node is only equipped with a single antenna which has also rule out the possibility of using techniques rely on angle of arrival packet. Therefore, the research is limited to use the received signal strength as the main source in estimating the travelling distance for the received packet. This paper investigates positioning algorithms that based on received signal strength i.e., location fingerprinting. In positioning systems, location fingerprinting is also referred as pattern matching of radio signature. The advantages of using RF fingerprinting are it does not require any hardware modifications to the sensor node and in comparison to other algorithms it is immune environmental influences that caused signal attenuation such as multipath, fading, reflection, non line of sight, and etc. This paper focuses on challenges that relate specifically to the location mapping of wireless sensor node including radio propagation of low specification WSN hardware, accuracy, operational range and impact of environmental factors. The optimized positioning system for WSN is documented, and results gained from experiment based on IEEE 802.15.4 WSN platform is provided