Dual mode fused optical fiber couplers suitable for mode division multiplexed transmission.

We experimentally demonstrate 2 × 2 and 3 × 3 fused fiber couplers made from dual mode fiber. A unique mode dependent power transfer characteristics as a function of pulling length is obtained that support various optical functionalities. Exploiting this we demonstrate several devices of interest for mode division multiplexed data transmission including LP11 mode filter, LP11 mode tap coupler, and 50:50 power splitter for both LP01 and LP11 modes.

The endothelium: an interface between autoimmunity and atherosclerosis in systemic lupus erythematosus?

Patients with systemic lupus erythematosus (SLE) have an increased risk of developing cardiovascular disease (CVD). Traditional risk factors fail to fully explain all of this increased risk. As atherosclerosis is recognized as a chronic inflammatory disease, it has been advocated that persistent inflammatory activity in patients with SLE is the principal mechanism that promotes accelerated atherogenesis. Autoantibodies in SLE might contribute to the pathogenesis of atherosclerosis by causing injury to the endothelium and altering the metabolism of lipoproteins involved in atherogenesis. Circulating immune complexes and anti-endothelial cell antibodies can induce expression of a proinflammatory and proadhesive endothelial cell phenotype. Similarly, antiphospholipid antibodies (aPL) may directly activate the endothelium or, via cross-reactivity with other antigens, interfere with lipoprotein metabolism. Antibodies to oxidized low-density lipoprotein (anti-oxLDL) rise with anti-double-stranded DNA antibody titres, complement activation and disease activity scores in patients with SLE. Both clinical and in vitro studies, however, have yielded conflicting results regarding the role of anti-oxLDL and aPL antibodies in CVD. Elevated levels of antibodies to high-density lipoprotein (HDL) and apolipoprotein A1 (the principal protein fraction of HDL) are found in patients with coronary ischaemia. Titres of these antibodies are significantly higher in SLE patients with persistent inflammatory disease and correlate inversely with activity of paraoxonase, a key enzyme that gives HDL its anti-oxidant properties. This review summarizes the evidence that autoantibodies in SLE might contribute to the pathogenesis of atherosclerosis by causing injury to the endothelium and altering the metabolism of lipoproteins involved in atherogenesis.

First demonstration and detailed characterization of a multimode amplifier for Space Division Multiplexed transmission systems.

We present the first demonstration of a multimode (two mode-group) erbium-doped fiber amplifier for Space Division Multiplexed (SDM) applications and demonstrate various design and performance features of such devices. In particular we experimentally demonstrate that differential modal gains can be controlled and reduced both by fiber design and control of the pump field distribution. Using a suitably designed fiber we demonstrate simultaneous modal gains of ~20 dB for different pair-wise combinations of spatial and polarization modes in an EDFA supporting amplification of 6 distinct modes.

Use of monoclonal antibodies to dissect specificity and pathogenesis of antiphospholipid antibodies.

Monoclonal antiphospholipid antibodies (aPL) have been utilized to dissect the relationship between their sequence, structure, binding and biological properties relevant to the pathogenesis of the antiphospholipid syndrome. In particular, sequence analysis of aPL has highlighted the clustering of certain amino acid residues in the antigen contact sites of their heavy and light chains. Therefore, these sequence motifs are likely to be important in determining aPL binding properties and their pathogenic effects. Experiments, however, using monoclonal aPL engineered to contain specific point mutations in their sequence which alter their ability to bind relevant antigens have shown that these alterations in binding are not directly mirrored by their pathogenic effects. In this review we focus on work carried out by others and ourselves using monoclonal antibodies with specific binding properties to extend our knowledge of the non-linear structure-binding-function relationship of aPL.

Review of presentations at the 6th European Lupus Meeting 3-5 March 2005.

The 6th European Lupus Meeting was held at the Royal College of Physicians of London and was attended by 450 delegates. The conference brought together leading speakers from Europe and North America who reviewed current knowledge and exciting new developments in both clinical and basic science aspects of systemic lupus erythematosus. This review summarizes the major points covered in each session.

Quasi-distributed pressure sensor using intensity-type optical coherence domain polarimetry.

We investigate a quasi-distributed optical fiber sensor that locates the positions of sensing units along a high-birefringence fiber by using white-light interferometry and measures the physical parameters by directly detecting the measured-induced cross coupling between two polarization modes. Important factors that affect the performance of the system, such as cross-term spurious signals and thermostability, are analyzed. Preliminary experimental results of such a system with 10 pressure sensors are presented.

All-fiber optic intensity modulators using liquid crystals.

A novel configuration for single-mode all-fiber optic, liquid crystal based intensity modulation is suggested. The electrodes have the form of two thin indium tin oxide films, one of which is directly deposited on top of the polished face of the optical fiber. Intensity modulation using nematic and ferroelectric liquid crystal is demonstrated showing that the device offers the potential for low loss (<0.5 dB), high modulation depth (>20 dB), and moderate drive voltages for frequencies up to several megahertz at 633-nm wavelength.

Performance of surface-plasma-wave fiber-optic polarizers.

Variations in the TM-like polarization transmission characteristics and polarization extinction ratio of surface-plasma-wave fiber-optic polarizers owing to variations in the depth of polishing and the metal film thickness are presented. The two effects have been isolated in carefully designed experiments and studied separately.

Effects of stimulated Brillouin scattering on the performance of polarization-maintaining all-fiber ring resonators.

Low-loss, polarization-maintaining, all-fiber ring resonators can exhibit nonlinear propagation effects occurring at relatively low input powers. Observations have been made of stimulated Brillouin scattering with input powers of 65 microW that lead to significant nonlinear variations in the measured value of finesse owing to depletion of the power through the stimulated-Brillouin-scattering process. Variations of measured finesse from 320 to 210 have been observed for a variation in input power of 155 microW. The nature of this variation in resonator finesse with input power has been studied and is shown to depend on the level of the input power when the resonator response is optimized.

Polarization mode coupling in highly birefringent optical-fiber ring resonators.

The transmission characteristics of a polarization-maintaining optical-fiber ring resonator are examined. The resonator's response is found to be strongly dependent on the differential phase delay between the fiber birefringence axes. Large cross talk of as much as 40% between the fiber modes and splitting of the resonance notch can occur, even for very good (better than -35-dB) isolation between the fiber polarization modes.

Evaluation of performance parameters of single-mode all-fiber Brillouin ring lasers.

An analytical theory of the operation of all-fiber Brillouin ring lasers that accounts for pump depletion is presented. Expressions for stimulated Brillouin scattering lasing threshold power, output Stokes power, and conversion efficiency are derived. It is shown that the fiber cavity detunes from its resonant value owing to the buildup of the counterpropagating Stokes wave, which can be a limitation in the performance of all-fiber resonator systems. The application of the theory is in the design and optimization of performance parameters of devices using all-fiber ring resonators, particularly Brillouin lasers and gyroscopes.

Optical-fiber phase modulator with enhanced modulation efficiency.

A novel piezoelectrically driven optical-fiber phase modulator is described. The modulator has low thermal drift and minimum polarization modulation and is immune to variations in the characteristics of the piezoelectric transducer. The theoretical model of the modulator accurately predicts the experimental performance, showing a phase-modulation enhancement over a wraparound fiber modulator at resonance.

Dynamic response of an all-fiber ring resonator.

An analysis of the dynamic response of a single-mode all-fiber ring resonator is presented in which a time-varying phase shift is induced in the ring by a phase modulator. In particular, the deviation of the response from that expected from the steady-state analysis is discussed.

Optical-fiber systems with nonreciprocal couplers.

The effectively nonreciprocal behavior of a single-mode to multimode optical-fiber coupler is discussed and results from polished couplers given. Two different applications in local-area networks and recirculating rings are investigated and the results presented.