1,833 research outputs found
Transmission of natural scene images through a multimode fibre
The optical transport of images through a multimode fibre remains an
outstanding challenge with applications ranging from optical communications to
neuro-imaging. State of the art approaches either involve measurement and
control of the full complex field transmitted through the fibre or, more
recently, training of artificial neural networks that however, are typically
limited to image classes belong to the same class as the training data set.
Here we implement a method that statistically reconstructs the inverse
transformation matrix for the fibre. We demonstrate imaging at high frame
rates, high resolutions and in full colour of natural scenes, thus
demonstrating general-purpose imaging capability. Real-time imaging over long
fibre lengths opens alternative routes to exploitation for example for secure
communication systems, novel remote imaging devices, quantum state control
processing and endoscopy
In situ method for power re-equalization of wavelength pulses inside of OCDMA codes
A simple in-situ method to equalize power among individual wavelengths pulses representing two-dimensional wavelength-hopping time-spreading OCDMA code originally generated by a fibre Bragg grating-based OCDMA encoder is presented. Experimental data obtained in a field-based multiuser OCDMA testbed shows that applying this method results in system performance enhancements which was demonstrated by observing improved bit error rate (BER) during the field trials
Rate-Distortion-Based Physical Layer Secrecy with Applications to Multimode Fiber
Optical networks are vulnerable to physical layer attacks; wiretappers can
improperly receive messages intended for legitimate recipients. Our work
considers an aspect of this security problem within the domain of multimode
fiber (MMF) transmission. MMF transmission can be modeled via a broadcast
channel in which both the legitimate receiver's and wiretapper's channels are
multiple-input-multiple-output complex Gaussian channels. Source-channel coding
analyses based on the use of distortion as the metric for secrecy are
developed. Alice has a source sequence to be encoded and transmitted over this
broadcast channel so that the legitimate user Bob can reliably decode while
forcing the distortion of wiretapper, or eavesdropper, Eve's estimate as high
as possible. Tradeoffs between transmission rate and distortion under two
extreme scenarios are examined: the best case where Eve has only her channel
output and the worst case where she also knows the past realization of the
source. It is shown that under the best case, an operationally separate
source-channel coding scheme guarantees maximum distortion at the same rate as
needed for reliable transmission. Theoretical bounds are given, and
particularized for MMF. Numerical results showing the rate distortion tradeoff
are presented and compared with corresponding results for the perfect secrecy
case.Comment: 30 pages, 5 figures, accepted to IEEE Transactions on Communication
Programming multi-level quantum gates in disordered computing reservoirs via machine learning and TensorFlow
Novel machine learning computational tools open new perspectives for quantum
information systems. Here we adopt the open-source programming library
TensorFlow to design multi-level quantum gates including a computing reservoir
represented by a random unitary matrix. In optics, the reservoir is a
disordered medium or a multi-modal fiber. We show that trainable operators at
the input and the readout enable one to realize multi-level gates. We study
various qudit gates, including the scaling properties of the algorithms with
the size of the reservoir. Despite an initial low slop learning stage,
TensorFlow turns out to be an extremely versatile resource for designing gates
with complex media, including different models that use spatial light
modulators with quantized modulation levels.Comment: Added a new section and a new figure about implementation of the
gates by a single spatial light modulator. 9 pages and 4 figure
Definition, analysis and development of an optical data distribution network for integrated avionics and control systems. Part 2: Component development and system integration
Fiber optic transmission is emerging as an attractive concept in data distribution onboard civil aircraft. Development of an Optical Data Distribution Network for Integrated Avionics and Control Systems for commercial aircraft will provide a data distribution network that gives freedom from EMI-RFI and ground loop problems, eliminates crosstalk and short circuits, provides protection and immunity from lightning induced transients and give a large bandwidth data transmission capability. In addition there is a potential for significantly reducing the weight and increasing the reliability over conventional data distribution networks. Wavelength Division Multiplexing (WDM) is a candidate method for data communication between the various avionic subsystems. With WDM all systems could conceptually communicate with each other without time sharing and requiring complicated coding schemes for each computer and subsystem to recognize a message. However, the state of the art of optical technology limits the application of fiber optics in advanced integrated avionics and control systems. Therefore, it is necessary to address the architecture for a fiber optics data distribution system for integrated avionics and control systems as well as develop prototype components and systems
A Model for Estimating Network Infrastructure Costs: A Case for All-Fibre Networks
The 21st century is an era that has been characterised by phenomenal growth in data rates at the local area network (intranet), extranet and the Internet, a trend pushed by deployment of âbandwidth hungryâ applications such VoIP, security surveillance systems, video conferencing and streaming of online multimedia content. Due to demand placed on network resources by these applications physical layer cabling solutions have had to evolve to support faster, improved LAN technologies such as Gigabit Ethernet. Although new network architectures (such as Centralised Fibre networks) address current and long term demands of the modern networking environment, concerns have been raised about its cost viability. The key problem identified in this study was an inadequacy of suitable tools that aid decision making when estimating the cost of a network infrastructure project. Factors of importance in this regard were collected in a survey and used in development of a cost model. A network was designed based on two architectures â centralised fibre (all-fibre network) and hierarchical star (UTP for horizontal cabling and optical fibre for backbone cabling). Thereafter, cost of implementing these two architectures was calculated using the model. Based on the results computed from the cost model, the all-fibre network (centralised fibre architecture) was found to be more cost effective than the hierarchical star network. Keywords: centralised fibre architecture, hierarchical star architecture, structured cabling, multimode optical fibre, singlemode optical fibre, backbon
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