A compact, lab-sized dissemination chamber is designed to characterize the fluorescence of aerosols. The chamber,
designed according to short-range lidar principles, uses light-induced fluorescence (LIF) with a 355 nm pulsed source.
Aerosols concentration inside the chamber can reach hundreds of thousands of ppl. Background noise and irradiance are
very low and will allow accurate measurements of spectral signatures. The chamber will serve to study the correlation
with spectroscopic data obtained using a long-range lidar system owned by Defence Research and Development Canada
(DRDC). Pollens, bacteria, spores, dusts and other atmospheric aerosols will be studied under various environmental
conditions. The chamber will be used to create trustworthy libraries for the remote sensing of bio-aerosols.
This paper presents two different devices for tuning fiber Bragg gratings. The first one is called the beam bending technique while the other is based on purely axial compression. We demonstrate that with a proper choice of the embedding material, the composite beam bending method constitutes an effective and reliable approach for tuning fiber Braggs gratings. We present a long-term stable device with a dynamic range of 80 nm which exhibits insertion losses smaller than 0.28 dB and small variations of the full width at half maximum. In order to reduce the amount of insertion losses, we also demonstrate a new tuning device for fiber Bragg gratings with a wavelength tuning range in excess of 65 nm. A purely axial tuning technique using a highly deformable polymer molded in cylinder shape is used to embed a fiber Bragg grating and to achieve a wavelength tuning range from 1551.7 to 1485.5 nm without insertion losses.
An efficient standoff biological warfare detection capability could become an important asset for both defence and security communities based on the increasing biological threat and the limits of the presently existing protection systems. Defence R&D Canada (DRDC) has developed, by the end of the 90s, a standoff bioaerosol sensor prototype based on intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF). This LIDAR system named SINBAHD monitors the spectrally resolved LIF originating from inelastic interactions with bioaerosols present in atmospheric cells customizable in size and in range. SINBAHD has demonstrated the capability of near real-time detection and classification of bioaerosolized threats at multi-kilometre ranges. In spring 2005, DRDC has initiated the BioSense demonstration project, which combines the SINBAHD technology with a geo-referenced Near InfraRed (NIR) LIDAR cloud mapper. SINBAHD is now being used to acquire more signatures to add in the spectral library and also to optimize and test the new BioSense algorithm strategy. In September 2006, SINBAHD has participated in a two-week trial held at DRDC-Suffield where different open-air wet releases of live and killed bioagent simulants, growth media and obscurants were performed. An autoclave killing procedure was performed on two biological materials (Bacillus subtilis var globigii or BG, and Bacillus thuringiensis or Bt) before being aerosolized, disseminated and spectrally characterized with SINBAHD. The obtained results showed no significant impact of this killing process on their normalised spectral signature in comparison with their live counterparts. Correlation between the detection signals from SINBAHD, an array of slit samplers and a FLuorescent Aerosol Particle Sensor (C-FLAPS) was obtained and SINBAHD's sensitivity could then be estimated. At the 2006 trial, a detection limit of a few tens of Agent Containing Particles per Liter of Air (ACPLA) was obtained for a 15-m thick cloud of live BG located at a range of 400 m.
A compact chamber was developed for the dissemination of biological aerosols. The chamber, measuring 110 cm in length, was designed according to short-range LIDAR principles, and will be used to simulate open-air releases of aerosols. Measurements, carried out by light-induced fluorescence (LIF) techniques, will be correlated with spectroscopic data obtained with a long-range lidar system owned by Defence Research and Development Canada (DRDC). The chamber allows complete control over environmental factors, such as humidity, pressure and temperature, thus facilitating the creation of a trustworthy signature database for the standoff detection of bio-aerosols. Studies will also include the influence of growth stage, stress and growth media on the fluorescence spectra of various biological aerosols.
One of today's primary security challenges is the emerging biological threat due to the increased accessibility to
biological warfare technology and the limited efficiency of detection against such menace. At the end of the 90s, Defence
R&D Canada developed a standoff bioaerosol sensor, SINBAHD, based on intensified range-gated spectrometric
detection of Laser Induced Fluorescence (LIF) with an excitation at 351 nm. This LIDAR system generates specific
spectrally wide fluorescence signals originating from inelastic interactions with complex molecules forming the building
blocks of most bioaerosols. This LIF signal is spectrally collected by a combination of a dispersive element and a range-gated
ICCD that limits the spectral information within a selected atmospheric cell. The system can detect and classify
bioaerosols in real-time, with the help of a data exploitation process based on a least-square fit of the acquired
fluorescence signal by a linear combination of normalized spectral signatures. The detection and classification processes
are hence directly dependant on the accuracy of these signatures to represent the intrinsic fluorescence of bioaerosols and
their discrepancy. Comparisons of spectral signatures acquired at Suffield in 2001 and at Dugway in 2005 of bioaerosol
simulants, Bacillius subtilis var globiggi (BG) and Erwinia herbicola (EH), having different origin, preparation protocol
and/or dissemination modes, has been made and demonstrates the robustness of the obtained spectral signatures in these
particular cases. Specific spectral signatures and their minimum detectable concentrations for different
simulants/interferents obtained at the Joint Biological Standoff Detection System (JBSDS) increment II field
demonstration trial, Dugway Proving Ground (DPG) in June 2005, are also presented.
A highly efficient and high power Raman fiber laser was developed based on the use of broadband Fiber Bragg gratings
as optical couplers. The broadening of the Stokes signal is analyzed in both cases where the laser emission is restricted
or not by the FBGs bandwidth. Since broadband fiber Bragg gratings are involved, the effects of cladding mode losses
have to be considered. In order to reduce overall losses in the cavity, an optimal cavity configuration has been
determined based on the physical orientation of the fiber Bragg gratings.