Abstract
A spatial optical filter based on splice misalignment between optical fibers with different cladding dimensions is proposed for gas refractometry. The sensing head is formed by a 2 mm-long optical fiber with 50 mu m diameter spliced with a strong misalignment between two single mode fibers (SMF28) and interrogated in transmission. This fiber structure causes a Fabry-Perot-behavior along the reduced-size fiber giving at its output end a well defined spatial filtering selectivity. Depending on the misalignment position of the lead-out SMF28, it is possible to obtain two different spectral responses, namely, bandpass or band-rejection filters. It is shown that this filter device is highly sensitive to refractive index changes on a nitrogen (N-2) environment by means of the gas pressure variation. A maximum sensitivity of -1390 nm/RIU for the bandpass filter was achieved.

Abstract
Tapering single mode-multimode-single mode structures to enhance sensitivity is proposed and experimentally demonstrated. 50 mm-long coreless MMF sections are spliced between SMFs and tapered. They are characterized in strain and an increase in strain sensitivity is obtained with taper diameter reduction. Sensitivities as high as -23.69 pm/mu epsilon for the 15 mu m taper are attained. A combination of an untapered and tapered SMS is proposed as a sensing system for the simultaneous measurement of strain and temperature.

Abstract
In this research programme methodologies to improve the accuracy in the results measured with embedded fibre Bragg gratings (FBG) sensors were studied and implemented in order to produce a composite overwrapped pressure vessel (COPV) prototype that incorporate a non-destructive sensing technologies. Using a carbon/epoxy prepreg system, test specimens were manufactured with longitudinally embedded FBG sensors. The combined behaviour of the sensors and the host material was characterized and a calibration rule (correction factor) was determined for the chosen material. The consistency of the results with both theoretical and empirical assumptions suggests that the proposed method is applicable to a wide range of FBG sensors and host materials. In this paper, the experimental setup and procedure used to assess to the calibration rule is addressed and further detailed.

Abstract
Real-time monitoring of the fabrication process of tapering down a multimode-interference-based fiber structure is presented. The device is composed of a pure silica multimode fiber ( MMF) with an initial 125 mu m diameter spliced between two single-mode fibers. The process allows a thin MMF with adjustable parameters to obtain a high signal transmittance, arising from constructive interference among the guided modes at the output end of the MMF. Tapered structures with waist diameters as low as 55 mu m were easily fabricated without the limitation of fragile splices or difficulty in controlling lateral fiber alignments. The sensing device is shown to be sensitive to the external environment, and a maximum sensitivity of 2946 nm/refractive index unit in the refractive index range of 1.42-1.43 was attained. (c) 2012 Optical Society of America

Abstract
A high-birefringent (Hi-Bi) Sagnac loop interferometer for torsion measurement is demonstrated. The sensing head is formed by a section of standard single mode fiber spliced between the output ports of a Hi-Bi coupler at 3 dB. The sensing configuration is characterized in torsion, temperature and strain. The results obtained indicate the viability of a torsion sensor independent of the temperature and strain cross-sensitivity effects. Additionally, in the proposed configuration all measurements are performed without the need of a polarization controller, a device most often required in standard Sagnac loops applied for sensing.

Abstract
This paper reflects on review of smart sensor activities for biomedical applications. The rise of biotechnology has provided innovative development of new therapies and detection methods for life threatening diseases. As a worldwide research focus, there is especially a strong interest in the use of microsystems in health care, particularly as smart implantable devices. Recent years have seen an increasing activity of hip and knee replacement and other type of implants, which are some of the most frequently performed surgical procedures in the world. Loosening of hip prosthesis is the dominant issue for many patients who undergo a hip arthroplasty. Artificial joints are subject to chronic infections associated with bacterial biofilms, which only can be eradicated by the traumatic removal of the implant followed by sustained intravenous antibiotic therapy. This review focuses on the clinical experience using all kinds of smart implants like orthopedic implants instrumented with strain gauges, retina implant system using image sensors. Technical design improvements will enhance function, quality of life, and longevity of total knee arthroplasty and all other kind of implants. Application of biocompatible nanomaterials in implantable biosensors for continuous monitoring of metabolites is an area of sustained scientific and technological interests. Crown Copyright