Radio-over-fiber systems employing remote antenna units (RAUs) based on coherent optical heterodyne detection of two phase uncorrelated lasers and envelope detection have been recently demonstrated. By using two uncorrelated lasers, this system concept allows simple implementation that can additionally be improved, if thermally uncooled lasers are used. Although such asynchronous receiver design is mildly affected by the laser phase noise, it suffers from the wavelength drift that occurs between the uncooled laser sources. Also, there are performance penalties due to high laser line-width when complex modulation formats are used for transmission. In this work, we analyze the performance of heterodyne based optical receivers, using OOK and multilevel modulation.
Effective situation awareness is a critical element for decision support in a wide range of military and para-military
operational surveillance scenarios. Effective situation awareness in a surveillance scenario can greatly increase
operational effectiveness, by improving the quality and timeliness of decisions. In this paper we outline a three level
integrated design approach to promote situation awareness. Our approach allows deployed wireless sensor nodes to
efficiently self-organise into dynamic clusters, based on a current common perceived threat situation (context). Firstly
our distributed predator aware situation assessment system (PORTENT) models, detects and presents, in terms of quality
of information (QoI), potential situations occurring within an uncertain environment. Secondly, we utilise a Bayesian
belief network to understand the significance associated with the potential situation. Finally in order to obtain a better
shared awareness we have developed a "context aware" service protocol that supports group formation and efficient
management of sensor network assets. By combining this three level approach, we present our VIGILANT "situation
aware" QoI interest group system. Extensive simulations have been undertaken to verify the VIGILANT concept, to
demonstrate the effectiveness of our approach, in improving performance for network management efficiency, through
utilisation of a shared "context" service provision time and QoI surveillance presentation.
In this paper, we propose a distributed predator aware situation assessment system (PORTENT) to model and detect
potential events occurring within an uncertain environment. PORTENT draws inspiration from how the mammalian
brain detects and makes rational decisions through assessing fragmented signals of threat, within uncertainty, at different
speeds. PORTENT represents the faster system using standard signal detection theory and the slower more accurate
system as the integration of sensory data over time, until a certain level of confidence is reached. We also consider
strategies to how both these systems could be combined optimally, to enhance PORTENT situation assessment
performance. Our experimental simulations to verify the PORTENT concept demonstrates the effectiveness of our approach.
Technologies for the transport of radio over optical fiber links have been developing rapidly in recent years and
bandwidth demands have spurred researchers to look into higher frequencies and smaller cell sizes. Although many of
the underlying techniques are developed, significant challenges still remain before these technologies can be integrated
in fully functioning networks. This talk will review the recent developments in Radio-Over-Technologies, highlight the
challenges that remain and outline the work being undertaken within the EU Network of Excellence BONE to meet these
Proc. SPIE. 6194, Millimeter-Wave and Terahertz Photonics
KEYWORDS: Signal to noise ratio, Optical filters, Radio optics, Modulation, Interference (communication), Wavelength division multiplexing, Data transmission, Modulators, Signal detection, Hybrid fiber radio
This paper investigates the use of optical spectrum slicing techniques for radio over fibre networks. We show that the transmission of complex-modulated data is possible by directly modulating a Super-luminescent Light Emitting Diode (SLED) with an Intermediate Frequency (IF) signal. This signal can then be up-converted to a higher frequency (18 GHz) using a Mach-Zehnder modulator. This has the advantage that a number of WDM channels can be up-converted using a single device. We demonstrate that due to dispersion the system performance over a given distance decreases as the width of the slice increases. This runs counter to the usual trend observed in spectrum slicing systems whereby, an increase in slice width is required to increase SNR. It is shown that although optical suppressed carrier modulation is used the length dependant nulls can be observed due to the width of the slices. It is seen that the intensity noise of the source and the required optical amplification stage degrades the signal by introducing intensity noise on the received signal. We detail the achievable performance of such a system with the potential to be used with multiple WDM channels.
Radio Over Fibre (RoF) techniques have received a great deal of interest in recent years with a number of manufacturers now offering production RoF systems. However, in many cases component cost is still a critical limiting factor to the wide spread adoption of the technology. In this paper we evaluate the performance of Wavelength Division Multiplexed (WDM) RoF links constructed using spectrum sliced broadband sources as the optical transmitter.
The main limitation in spectrum sliced system is the excess beat noise produced by the incoherent nature of the optical source. For digital transmission links this has a severe effect on the achievable transmission bit rate as the signal-to-noise ratio (SNR) of such limits is approximately the ratio of the optical slice bandwidth to electrical bandwidth. In radio over fibre systems, due to the relatively narrowband nature of most radio signals, it is common that although the radio signal may be at a high frequency, its electrical bandwidth is relatively narrow allow for an acceptable SNR to be achieved with relatively narrow optical slice widths.
This paper will define the performance limits of such systems, demonstrating that acceptable transmission of radio frequency (RF) signals is possible over fibre distances typical in access networks.