Abstract: The invention provides an adaptive frequency hopping spread-spectrum (FHSS) transmission system and method, which efficiently utilizes available transmission bandwidth, whilst providing robustness to jamming techniques in wireless communication systems. The proposed technique operates by transmitting a wide-band signal over multiple, single-carrier, parallel transmission subbands, which may occupy non-contiguous frequency regions. The proposed scheme exhibits significant gain in error rate performance, as compared to a data rate equivalent single-subband system in the presence of signal jamming and/or interference without a reduction in the transmission data rate nor an increase in transmitter power. In addition, the proposed system and method are adaptive and enable more efficient use of the available bandwidth for communicating, thus increasing the overall bandwidth utilization of the system.

Abstract: An optical sensor for sensing information relating to an analyte liquid or gas, has a a planar substrate having a refractive index nc. The planar substrate supports a ridge waveguide having an unclad top portion having a refractive index nr. The substrate serves as cladding layer for the ridge waveguide at a location where the ridge waveguide contacts the substrate. A Bragg grating inscribed in the ridge waveguide has two modes for providing information relating to both temperature and refractive index of the surrounding analyte liquid or gas. A cladding mode has a different response to the analyte when compared to a Bragg resonance response. Both modes have a same reaction to temperature, wherein said Bragg grating is formed within the unclad region of ridge waveguide, wherein nc.<nr. Advantageously multiple parameters can be sensed using only a single Bragg grating.

Abstract: A method for lost speech samples recovery in speech transmission systems is disclosed. The method employs a waveform coder operating on digital speech samples. It exploits the composite model of speech, wherein each speech segment contains both periodic and colored noise components, and separately estimates these two components of the unreliable samples. First, adaptive FIR filters computed from received signal statistics are used to interpolate estimates of the periodic component for the unreliable samples. These FIR filters are inherently stable and typically short, since only strongly correlated elements of the signal corresponding to pitch offset samples are used to compute the estimate. These periodic estimates are also computed for sample times corresponding to reliable samples adjacent to the unreliable sample interval. The differences between these reliable samples and the corresponding periodic estimates are considered as samples of the noise component.

Abstract: A method of increasing the refractive index in a photosensitive glass is disclosed so as to induce an refractive index change of at least 10?5 within a region of the glass. The method includes the step of providing a hydrogen or deuterium loaded doped glass material wherein a dopant within the glass is photosensitive to infrared radiation in the presence of hydrogen or deuterium. The hydrogen or deuterium loaded doped glass is subsequently irradiated with femtosecond pulses of infrared light having an intensity of at least 109 W/cm2 and less than 5×1013 W/cm2.

Abstract: The invention relates to a method and an apparatus for reducing blocking artifacts in block-wise coding of still and video images. A learning filter generator is provided at the image encoder for generating a set of filters and associated filtering rules for filtering cross-boundary image patterns based on representative original and decoded training images using a supervised machine learning algorithm. An adaptive filter at the image decoder receives the generated filters and associated filtering rules and performs locally adaptive filtering in accordance with the received filtering rules.

Abstract: Fiber Bragg gratings were written in pure silica photonic crystal fibers and photonic crystal fiber tapers with 125 fs, 800 nm IR radiation. High reflectivites were achieved with short exposure times in the tapers. Both multimode and single mode grating reflections were achieved in the fiber tapers. By tapering the photonic crystal fibers scattering that would otherwise have occurred was lessened and light external to the fiber could reach the core effectively to write a grating.

Abstract: The invention provides a method for fabricating planar waveguiding structures with embedded microchannels. The method includes the step of depositing, over a planar template having at least one indented feature comprising a ridge of a first optical material and a narrow trench adjacent thereto, a second optical material, and the step of subsequent annealing thereof, so that an embedded hollow microchannel forms within the trench. The method provides planar structures wherein the ridge and the embedded microchannel cooperate to form an optical waveguiding structure having a waveguiding direction collinear with the embedded microchannel. Embodiments of the method for forming microfluidic devices integrating ridge waveguides with hollow microchannels having surface access points for fluid delivery, and for forming photonic crystals, are disclosed together with corresponding device embodiments.

Abstract: An iterative channel estimation and inter-carrier interference (ICI) cancellation process is provided for OFDM receivers, and more particularly for mobile OFDM receivers. The iterative process uses decision feedback to estimate both the channel gain and the ICI gains, the latter being the multiplicative gain applied to the adjacent sub-carriers. Thus the receiver performs equalization and ICI cancellation in an iterative fashion and is advantageous for estimating fast fading channels.

Abstract: A biologically-inspired process for universal audio coding based on neural spikes is presented. The process is based on the generation of sparse two-dimensional time-frequency representations of audio signals, called spikegrams. The spikegrams are generated by projecting the audio signal onto a set of over-complete adaptive gamma-chirp kernels. A masking model is applied to the spikegrams to remove inaudible spikes and to increase the coding efficiency. In respect of one aspect of the invention, the masked spikegram is then quantized using a genetic-algorithm-based quantizer (or its simplified linear version). The values are then differentially coded using graph based optimization and entropy coded afterwards.

Abstract: A curved wavelet transform and a related image/video compression system are disclosed. The curved wavelet transform (CWT) is carried out by applying one-dimensional (1-D) wavelet filters along curves, rather than along only horizontal and vertical directions. The image/video compression system includes a curve determination unit, a curved wavelet transform unit, a wavelet coefficient quantization unit, a wavelet coefficient coding unit, and a curve coding unit. The quantization and coding of the wavelet coefficients are related to the curves. In one embodiment, recursive wavelet filters are used for inverse wavelet decomposition. The system provides higher compression capability than conventional wavelet-based image compression systems.

Abstract: The invention relates to an optical fiber polarizer comprising an optical fiber with at least a core, a cladding and surrounding medium (or outer cladding) where one or more sections of the optical fiber include periodic/aperiodic (chirped, quasi-periodic) modulation of the dielectric properties of the fiber in the direction of propagation of the light (the longitudinal axis of the fiber). The modulation of the dielectric properties of the fiber is such that it introduces periodic/aperiodic birefringence along the direction of propagation of the light, such a modulation usually but not necessarily being confined to the vicinity of the core region of the fiber. Means are included to attenuate preferentially some of the modes of propagation of the fiber, specifically modes of one principal state of polarization and not the orthogonal state of polarization.

Abstract: A retro-reflective sensor for sensing mechanical, chemical or temperature related information, is disclosed. The sensor is formed of an optical waveguide suitable for use in-situ in a high temperature environment having a Bragg grating written into a core region thereof with short-pulsed electromagnetic radiation, said optical waveguide having a glass transition temperature substantially higher than that of silica. Preferably the sensor is written into a length of sapphire fiber or within a zirconium waveguide. Preferably the pulse duration of the short pulsed electromagnetic radiation is less than 500 picoseconds.

Abstract: The invention relates to a transmitter identification system, which utilizes an identification signal embedded into a digital television signal, enabling the transmitter of origin to be identified at a receiving station. Ideally the identification signal is an orthogonal pseudo-random sequence time synchronized to the signal frame structure of the digital television signal. Particularly designed for single frequency networks, identification of the various transmitted signals enables the network to be tuned to eliminate or minimize multi-path effects at certain locations, which receive transmissions from various transmitters.

Abstract: The invention relates to an optical waveguide device for monitoring a characteristics of light, e.g. a wavelength. The device incorporates a waveguide, such as an optical fiber, with an embedded tilted Bragg grating operating in a regime of wavelength detuning. The grating is designed to disperse light azimuthally in two or more different directions about the fiber axis, said directions changing with wavelength. A photodetector array is provided for detecting the azimuthal distribution of light. A processor coupled to the photodetector array determines wavelength information from the detected azimuthal distribution of the out-coupled light.

Abstract: The invention relates to a transmitter identification system, which utilizes an identification signal embedded into a digital television signal, enabling the transmitter of origin to be identified at a receiving station. Ideally the identification signal is an orthogonal pseudo-random sequence time synchronized to the signal frame structure of the digital television signal. Particularly designed for single frequency networks, identification of the various transmitted signals enables the network to be tuned to eliminate or minimize multi-path effects at certain locations, which receive transmissions from various transmitters.

Abstract: A method of decoding soft input information related to a transmitted word of a linear block code (n, k) and providing hard or soft output information is disclosed. The method comprises the steps of forming a reliability vector from the input information, identifying (n?k) linearly independent least reliable symbols and k most reliable symbols, converting a parity check matrix of the linear block code to a pseudo-systematic form with respect to the least reliable symbols, calculating extrinsic information and composite information for the most reliable symbols using the soft input information and the pseudo-systematic parity check matrix, and calculating extrinsic information for the least reliable systems using composite information for the most reliable symbols.

Abstract: A capacitively loaded multilevel transmission line network for operation at a microwave frequency f is disclosed wherein microstrip conductors are disposed over or under a uniplanar transmission line (UTL), electrically connected thereto at or near opposing ends of the UTL and coupled to portions of the UTL separated therefrom by a thin dielectric film. The microstrip conductors and the portions of the UTL coupled thereto form thin-film microstrip (TFMS) shunt stubs capacitively loading the ends of the UTL for increasing its electrical length. The present invention enables considerable size reduction of microwave circuits having uniplanar transmission lines.

Abstract: A planar lightwave circuit device includes one or more planar lightwave circuits (PLCs) each having an optical layer deposited on a substrate, and a package base including one or more support structures for suspending the planar lightwave circuit above a portion of the package base. Each substrate has a first coefficient of thermal expansion, whereas the package base has a second coefficient of thermal expansion. The first and second coefficients of thermal expansion differ such that a change in temperature causes the support to apply one of a compressive and a tensile force to the planar lightwave circuit in a plane within or parallel to the plane of the planar lightwave circuit. The induced stress can modify the optical performance of the PLC device, e.g. to reduce the temperature sensitivity of the device and thus maintain device performance, or for providing efficient passive or dynamic tuning of the device.

Abstract: A novel Bragg grating filter in optical waveguiding fiber with suppressed cladding mode coupling and method of producing same is disclosed. The novel grating structure is induced in both the core and the cladding of the optical fiber irrespective of the photosensitivity of the core or cladding to actinic radiation. Such core and cladding of the optical fiber need not be chemically doped to support the grating. The method incorporates an ultra short duration pulse laser source. Electromagnetic radiation provided from the laser propagates to a diffractive element positioned a specific distance to the target material such that the diffracted electromagnetic radiation forms a 2-beam interference pattern, the peaks of which are sufficiently intense to cause a change in index of refraction.

Abstract: A volume hologram for modifying a characteristic of an input microwave beam and a method for manufacturing thereof are disclosed. The hologram is fabricated from a multi-layer artificial dielectric wherein each layer is made of a dielectric material and includes a lattice of inclusions, for example metal disks disposed on one side thereof, and wherein a pre-determined three-dimensional grating pattern of dielectric perturbations is induced by spatial modulating the lattice of the inclusions. The hologram can be designed for efficiently steering, reshaping, combining or splitting microwave beams.