Rapid detection of vaccinia virus using biofunctionalized fiber-optic ball-tip biosensors.

In this work, we present the development and biofunctionalization of a fiber-optic ball-resonator biosensor for the real-time detection of vaccinia poxvirus. We fabricated several ball-tip resonators, functionalized through a silanization process to immobilize two bioreceptors: the monoclonal anti-L1R antibody targeting the L1R protein, and the polyclonal rabbit serum antibodies targeting the whole vaccinia virus (VV) pathogen. Experimental measurements were carried out to detect VV in concentrations from 103 to 108 plaque-forming units (PFU), with a limit of detection of around 1.7-4.3 × 103 PFU and a log-quadratic pattern, with a response up to 5 × 10-4 RIU (refractive index units). The specificity was assessed against herpes simplex virus, used as a non-specific control, with the best results obtained with anti-L1R monoclonal antibodies, and through the detection of vaccinia virus/herpes simplex-1 combination. The obtained results provide a real-time viral recognition with a label-free sensing platform, having rapid response and ease of manufacturing, and paving the road to the seamless detection of poxviruses affecting different human and animal species using optical fibers.

Optical Fiber Sensors for the Detection of Hydrochloric Acid and Sea Water in Epoxy and Glass Fiber-Reinforced Polymer Composites.

Optical fiber sensors (OFSs), which rely on evanescent wave sensing for the early detection of the diffusion of water and hydrochloric acid through glass fiber-reinforced polymers (GFRPs), have been developed and tested. Epoxy and GFRP specimens, in which these sensors were embedded, were subjected to tests in artificial sea water and hydrochloric acid. The sensors were able to detect the diffusion of chemicals through the epoxy and GFRP samples on the basis of a drop in the reflected signal from the tip of the optical sensor probe. Water and hydrochloric acid diffusion coefficients were calculated from gravimetric measurements and compared with the experimental response of the OFSs. Furthermore, mechanical tests were carried out to assess the influence of the sensors on the structural integrity of the GFRP specimens.

Multipath interference characterization of bend-insensitive optical fibers and short jumpers.

Multipath interference (MPI) in bend-insensitive optical fibers is investigated by analyzing different aspects, ranging from a review of the theoretical background, through the analysis of measurement issues, to the characterization of short patch cords. Two setups for the characterization of MPI are analyzed, highlighting their advantages and limitations. Then, a number of commercial bend-insensitive fibers are compared, showing that they generally exhibit a level below -30 dB in the range of 1250-1350 nm. The investigation also includes short offset-spliced fiber segments, with lengths to 1 cm, to simulate the behavior of field-installable connectors and isolate their contribution to the MPI. The results show a step-like increment of MPI when two or more cm-long fiber segments are cascaded.

Photonic bandgap confinement in an all-solid tellurite-glass photonic crystal fiber.

We report on the fabrication and optical assessment of an all-solid tellurite-glass photonic bandgap fiber. The manufacturing process via a preform drawing approach and the fiber characterization procedures are described and discussed. The fiber exhibits some minor morphological deformations that do not prevent the observation of optical confinement within the fiber by bandgap effects. The experimental fiber attenuation spectrum displays clear bandgap confinement regions whose positions are confirmed by modeling the guiding properties of the ideal geometry using a plane-wave expansion method. The model identifies the bound modes of the structure and provides confirmation of experimentally observed mode field profiles.

Analysis of Faraday effect in multimode tellurite glass optical fiber for magneto-optical sensing and monitoring applications.

The design and fabrication of a tellurite glass multimode optical fiber for magneto-optical applications are presented and discussed. The analysis of the polarization shows that an optical beam, linearly polarized at the fiber input, changes to elliptically polarized with an ellipticity of 1∶4.5 after propagating down the fiber. However, the elliptical distribution remains unchanged with or without an applied magnetic field, demonstrating that no circular dichroism occurs within the fiber. The Verdet constant of the tellurite glass in the fiber is measured to be 28±0.5 rad·(T·m)-1, diverging by less than 3% from the Verdet constant found on the same glass composition in bulk form. These results demonstrate the feasibility to develop reliable tellurite glass fibers by the preform drawing method for magneto-optical applications.

Low-cost fiber Bragg grating vibroacoustic sensor for voice and heartbeat detection.

A fiber Bragg grating (FBG) vibroacoustic sensor exploiting an intensity-based interrogation principle is presented. The optical system is complemented by signal processing techniques that allow disturbances to be mitigated and improve the spectral estimation. The sensor is capable of performing frequency analysis of sounds up to 3 kHz, with top sensitivity in the 100-500 Hz frequency range, and of dynamically tracking pulsed phenomena that induce a strain to the FBG. The sensor has been applied to the detection of voice, showing a great intelligibility of the speech despite the low-quality environment, and to the monitoring of the heartbeat rate from the wrist.

UV-written Integrated Optical 1xN Splitters.

The first demonstration of UV-written, silica-on-silicon integrated optical 1xN power splitters with up to 32 outputs ports is presented. The fabricated components exhibit 450 nm bandwidth, low excess loss and good channel uniformity.

Direct UV-written broadband directional planar waveguide couplers.

We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation.