4,080 research outputs found
Silicon optical modulators
Optical technology is poised to revolutionise short reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such interconnect is the optical modulator. Modulators have been improved dramatically in recent years. Most notably the bandwidth has increased from the MHz to the multi GHz regime in little more than half a decade. However, the demands of optical interconnect are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimising metrics such as the energy per bit, and device footprint, whilst maximising bandwidth and modulation depth are non trivial demands. All of this must be achieved with acceptable thermal tolerance and optical spectral width, using CMOS compatible fabrication processes. Here we discuss the techniques that have, and will, be used to implement silicon optical modulators, as well as the outlook for these devices, and the candidate solutions of the future
Development of a broadband and squint-free Ku-band phased array antenna system for airborne satellite communications
Novel avionic communication systems are required for various purposes, for example to increase the flight safety and operational integrity as well as to enhance the quality of service to passengers on board. To serve these purposes, a key technology that is essential to be developed is an antenna system that can provide broadband connectivity within aircraft cabins at an affordable price. Currently, in the European Commission (EC) 7th Framework Programme SANDRA project (SANDRA, 2011), a development of such an antenna system is being carried out. The system is an electronically-steered phased-array antenna (PAA) with a low aerodynamic profile. The reception of digital video broadcasting by satellite (DVB-S) signal which is in the frequency range of 10.7-12.75 GHz (Ku-band) is being considered. In order to ensure the quality of service provided to the passengers, the developed antenna should be able to receive the entire DVB-S band at once while complying with the requirements of the DVB-S system (Morello & Mignone, 2006). These requirements, as will be explained later, dictate a broadband antenna system where the beam is squint-free, i.e. no variation of beam pointing direction for all the frequencies in the desired band. Additionally, to track the satellite, the seamless tunability of the beam pointing direction of this antenna is also required. In this work, a concept of optical beamforming (Riza & Thompson, 1997) is implemented to provide a squint-free beam over the entire Ku-band for all the desired pointing directions. The optical beamformer itself consists of continuously tunable optical delay lines that enable seamless tunability of the beam pointing direction
Quantum Modelling of Electro-Optic Modulators
Many components that are employed in quantum information and communication
systems are well known photonic devices encountered in standard optical fiber
communication systems, such as optical beamsplitters, waveguide couplers and
junctions, electro-optic modulators and optical fiber links. The use of these
photonic devices is becoming increasingly important especially in the context
of their possible integration either in a specifically designed system or in an
already deployed end-to-end fiber link. Whereas the behavior of these devices
is well known under the classical regime, in some cases their operation under
quantum conditions is less well understood. This paper reviews the salient
features of the quantum scattering theory describing both the operation of the
electro-optic phase and amplitude modulators in discrete and continuous-mode
formalisms. This subject is timely and of importance in light of the increasing
utilization of these devices in a variety of systems, including quantum key
distribution and single-photon wavepacket measurement and conformation. In
addition, the paper includes a tutorial development of the use of these models
in selected but yet important applications, such as single and multi-tone
modulation of photons, two-photon interference with phase-modulated light or
the description of amplitude modulation as a quantum operation.Comment: 29 pages, 10 figures, Laser and Photonics Reviews (in press
Phased array receive antenna steering system using a ring resonator-based optical beam forming network and filter-based optical SSB-SC modulation
A novel phased array receive antenna steering system is introduced. The core of this system is an optical ring resonator-based broadband, continuously tunable optical beam forming network (OBFN). In the proposed system architecture, filter-based optical single-sideband suppressed-carrier modulation and balanced coherent optical detection are used. \ud
Such architecture has significant advantages over a straightforward architecture using optical double-sideband modulation and direct optical detection, namely relaxed bandwidth requirements on the optical modulators and detectors, reduced complexity of the OBFN chip, and enhanced dynamic range. Initial measurements on an actual 1Ă—8 OBFN chip and an optical sideband filter chip are presented. Both are realized in CMOS-compatible planar optical waveguide technology.\u
Output Filter Aware Optimization of the Noise Shaping Properties of {\Delta}{\Sigma} Modulators via Semi-Definite Programming
The Noise Transfer Function (NTF) of {\Delta}{\Sigma} modulators is typically
designed after the features of the input signal. We suggest that in many
applications, and notably those involving D/D and D/A conversion or actuation,
the NTF should instead be shaped after the properties of the
output/reconstruction filter. To this aim, we propose a framework for optimal
design based on the Kalman-Yakubovich-Popov (KYP) lemma and semi-definite
programming. Some examples illustrate how in practical cases the proposed
strategy can outperform more standard approaches.Comment: 14 pages, 18 figures, journal. Code accompanying the paper is
available at http://pydsm.googlecode.co
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