Characterization of time-resolved fluorescence response measurements for distributed optical-fiber sensing

Abstract

A distributed optical-fiber sensing system based on pulsed excitation and time-gated photon counting has been used to locate a fluorescent region along the fiber. The complex Alq3 and the infrared dye IR-125 were examined with 405 and 780 nm excitation, respectively. A model to characterize the response of the distributed fluorescence sensor to a Gaussian input pulse was developed and tested. Analysis of the Alq3 fluorescent response confirmed the validity of the model and enabled the fluorescence lifetime to be determined. The intrinsic lifetime obtained (18.2±0.9 ns) is in good agreement with published data. The decay rate was found to be proportional to concentration, which is indicative of collisional deactivation. The model allows the spatial resolution of a distributed sensing system to be improved for fluorophores with lifetimes that are longer than the resolution of the sensing system.

Fiber optic approach for detecting corrosion

“…This experiment, described in detail in Ref. 11, demonstrated the that distributed fluorescence detection of cations, and in particular Al 3+ , is possible. The power fraction (PF) of guided light propagating along the outside of the glass core was able to be used to excite the 8-HQ complex and the fraction of emitted florescence recaptured by the fiber core could be measured by time-gated electronics.…”

Optical Fibres for Distributed Corrosion Sensing - Architecture and Characterisation

“…Figure 4 This OTDR experiment, conducted at Swinburne University, and described in detail in Ref. [7], shows that distributed fluorescence detection of the Al cations is possible. The fraction of power from the guided light propagating along the outside of the core was able to be used to excite the 8-HQ complex and the fraction of emitted florescence recaptured by the fibre core could be measured by the time-gated electronics.…”

An Optical Fiber Sensor for Remote pH Sensing and Imaging

“…The GRIN lens used in this experiment had a diameter of 2.0 mm and a length of 5.5 mm. The end face of the GRIN lens was cleaned in a piranha solution (three parts of concentrated H 2 SO 4 added to 1 part 30 wt % H 2 O 2 solution in water; Warning: Piranah solution is highly reactive; handle with appropriate precautions ) to obtain clean hydroxylated surfaces, which facilitated adhesion of the eosin-CA film to the glass surface of the GRIN lens. The eosin-CA solution was spread uniformly across the surface of the GRIN lens by placing a drop of it on the hydroxylated end face of GRIN lens and spinning the GRIN lens.…”

“…Optical fiber sensors display desirable features such as electromagnetic immunity, capability of remote measurements, and miniature analytical detectors so that small volume samples such as single biological cells can be measured. 1,,–6 Optical fiber-based pH sensors and biosensors have been considered one of the most important analytical methods in diverse fields such as environmental sciences, medicine, agriculture, and biosensing. 7,,–11 A major advantage of this approach is that no exogenous indicator is added to the solution, providing for relatively unperturbed measurements.…”