Micro-device for coupling, multiplexing and demultiplexing using elliptical-core two-mode fiber

We propose and demonstrate experimentally a fiber optic micro-device that is capable of tunably splitting, multiplexing, and demultiplexing optical signals using elliptical-core two-mode optical fiber. A crosstalk of 15 dB with an insertion loss of 1.2 dB was obtained

Elliptical-core two mode fiber sensors and devices incorporating photoinduced refractive index gratings

Results of experiments performed using germanium-doped, elliptical core, two-mode optical fibers whose sensitivity to strain was spatially varied through the use of chirped, refractive-index gratings permanently induced into the core using Argon-ion laser light are presented. This type of distributed sensor falls into the class of eighted-fiber sensors which, through a variety of means, weight the strain sensitivity of a fiber according to a specified spatial profile. We describe results of a weighted-fiber vibration mode filter which successfully enhances the particular vibration mode whose spatial profile corresponds to the profile of the grating chirp. We report on the high temperature survivability of such grating-based sensors and discuss the possibility of multiplexing more than one sensor within a single fiber

Design and fabrication of an intrinsically gain flattened Erbium doped fiber amplifier

We report design and subsequent fabrication of an intrinsically gain flattened Erbium doped fiber amplifier (EDFA) based on a highly asymmetrical and concentric dual-core fiber, inner core of which was only partially doped. Phase-resonant optical coupling between the two cores was so tailored through optimization of its refractive index profile parameters that the longer wavelengths within the C-band experience relatively higher amplification compared to the shorter wavelengths thereby reducing the difference in the well-known tilt in the gains between the shorter and longer wavelength regions. The fabricated EDFA exhibited a median gain ?28 dB (gain excursion below $\pm$2.2 dB within the C-band) when 16 simultaneous standard signal channels were launched by keeping the I/P level for each at ?20 dBm/ channel. Such EDFAs should be attractive for deployment in metro networks, where economics is a premium, because it would cut down the cost on gain flattening filter head

Advances and new applications using the acousto-optic effect in optical fibers

This work presents a short review of the current research on the acousto-optic mechanism applied to optical fibers. The role of the piezoelectric element and the acousto-optic modulator in the excitation of flexural and longitudinal acoustic modes in the frequency range up to 1.2 MHz is highlighted. A combination of the finite elements and the transfer matrix methods is used to simulate the interaction of the waves with Bragg and long period gratings. Results show a very good agreement with experimental data. Recent applications such as the writing of gratings under the acoustic excitation and a novel viscometer sensor based on the acousto-optic mechanism are discussed

Research activities arising from the University of Kent

In this paper I describe research activities in the field of optical fiber sensing undertaken by me after leaving the Applied Optics Group at the University of Kent. The main topics covered are long period gratings, neural network based signal processing, plasmonic sensors, and polymer fiber gratings. I also give a summary of my two periods of research at the University of Kent, covering 1985–1988 and 1991–2001

Diffuse calvarial meningioma: a case report.

A rare case of a diffuse calvarial meningioma in a sixty-three year-old female is reported. The patient presented with headache, painful proptosis and chemosis of the left eye. Imaging showed that the frontoparietal calvarium on both sides and the left orbital roof were thickened. The thickened bone showed patchy rarefaction. In relationship to the thickened bone, there was an enhancing en-plaque meningioma. The tumour extended on to the superolateral aspect of the left orbit and resulted in proptosis. Excision of the left frontoparietal calvarium and the orbital tumour was performed. The management of diffuse calvarial meningioma is discussed and the relevant literature is briefly reviewed

High Temperature Fabry-Perot Based Strain Sensor for Ceramic Cross Flow Filters

The objectives of this research program were to develop instrumentation methods to allow in-situ analysis of ceramic cross flow (CXF) filters. Information from such instrumentation is needed to determine how the filters perform during operation, how subsequent filter and combustor designs may be improved based on the knowledge of such performance, and how and where damage and degradation occur. CXF filters are used for hot gas clean-up of coal-fired power generation systems, such as pressurized fluidized-bed combustors and integrated gasifier-combined cycles. The ceramic cross flow filter is analogous to cross-flow heat exchangers, except gas is passed between channels instead of thermal energy (heat). The CXF filters are made from multiple layers of thin, flat, porous ceramic (alumina or silicon nitride) with grooves which form channels in each layer. The layers are stacked to form a filter element that is approximately 30 cm high by 30 cm long by 10 cm wide. Consecutive layers of ceramic are oriented such that the channels formed are perpendicular to each other. One of the sides of the filter element is sealed. Gas enters the filter through the openings of the channel on the two sides that are perpendicular to the sealed end, permeates the porous ceramic, and exits through the openings on the side that is parallel to the sealed end.</p