We present an optical fiber sensor for the corrosion process in metal (Aluminum) using the optical time domain
reflectometry (OTDR) technique. Our proposed sensor system consists of several sensor heads connected to a
commercial OTDR by a single-mode optical fiber and fiber couplers. Each sensor head consists of an optical fiber
having the cleaved end coated with an aluminum film. For laboratory measurements the corrosion action was simulated
by controlled etching of the Al film on the sensor head. The OTDR detects the light reflected by each sensor head. As the
aluminum is etched the reflection decreases and the etch rate can be obtained from the OTDR traces. We present
experimental results for the measurement of the corrosion rate of aluminum films in controlled laboratory conditions and
also for the evaluation of the maximum number of sensor heads the system supports. Our proposed sensor system is
multipoint, self-referenced, has no moving parts and can detect the corrosion rate for each head several kilometers away
from the OTDR. This system may have applications in harsh environments such as in deepwater oil wells, for the
evaluation of the corrosion process in the inner wall of the casing pipes.
The Surface Plasmon Resonance (SPR) technique is considered by many researchers as a very attractive approach for immunosensor development. By proper chemical modification of the gold surface, this technique avoids the use of a tracer material, such as a radioisotope, fluorophore, or enzyme, to identify the specific analyte, thus allowing kinetic analysis of biointeracting systems. However, the technique has found limited applications for the direct assay of complex biological samples due to the variable degree of non-specific binding that may occur along with the primary antigen-antibody reaction. This work describes a possible approach for the development of a new class of SPR based assays where non-specific binding effects could be minimized. The principle relies on selective UV inactivation of a gold surface coated with either antibody or antigen molecules. It is shown that under proper conditions it is possible to synthesize a surface with a pre-defined 2D variation of immunoactivity. Following exposure to a positive sample, image contrast under SPR illumination of the immunoactivated surface would be indicative of a positive reaction. The degree of SPR image contrast can be quantified and is a measure of the analyte concentration in solution. The approach minimizes non-specific binding effects, and the principle can be extended for the development of immunoassays for large scale testing of complex biological samples.
A novel optical fiber sensor is prosed for use in chemical analysis. The sensor probe is made of a gold coated multimode optical fiber, configured to exhibit surface plasmon resonance (SPR) when immersed on a set environment. The proposed detection strategy comprises measurement of the image pattern irradiated by the fiber under monochromatic illumination. A theoretical model is prosed to determine device performance. From computer simulations it is shown that the proposed configuration and detection strategy allows reaching a 30-fold enhancement in sensitivity relative to that obtained in previous SPR-based versions of the device.