This paper proposes a trace hydrogen sensing system based on distributed feedback fiber laser (DFB-FL). The sensor head was fabricated by inserting the DFB-FL into a glass capillary coated with hydrogen sensitive material. The wavelength of the DFB-FL changed under the exothermic reaction of Pt-WO3 with hydrogen and was demodulated by a Michelson interferometer. The experimental results at hydrogen concentration of 50 to 3800 ppm show that the hydrogen sensitivity of the system is 0.0386 pm/ppm and the linearity index R2 is >0.99. The repeatability of the system is 99.4% and the accuracy is 97.43% at hydrogen concentration of 50 ppm. The figure of merit of the system is 0.0385. The proposed DFB-FL sensor with good repeatability and anti-electronic interference has application prospects in many fields such as the detection of trace hydrogen in transformer oil.
The concentration of iodide (I − ) ions was determined by a fluorescence quenching method; a polymer-tipped optical fiber (PTOF) was used as the sensing head. The polymer tip, made by a free-radical photopolymerization method, combined the advantages of high sensitivity of the tapered fiber with a flexible and simple fabrication process. A sol–gel encapsulated fluorescein, used as the fluorescence indicator, was dip coated on the surface of the PTOF. Experimental results indicate that the backscatter fluorescence intensity collected by PTOF is 9.60 times higher than that of the flat-cut fiber. When the I − ions concentration changed from 6 to 36 mM, the backscatter fluorescence intensity collected by PTOF decreased linearly with a response time of 2 s. We demonstrate a method that can detect remote ion concentration with high repeatability, with stability, and which is simple to carry out. This method can be used in applications such as chemical production and water quality monitoring.
A competitive homemade two-coordinate autocollimator is presented, which is able to measure the angle along the
horizontal and vertical axis by using a single linear CCD to detect the three image point positions of the N shape
reticle on the CCD, with total measurement error no greater than 5urad in the measurement range of ±2100urad
and the dynamic response frequency 2KHz.
An anti-noise subpixel algorithm of phase-shifting of fundamental frequency was presented based on the phase-shifting
of Fourier transform and the anti-noise characteristics of low-frequency part of the phase spectrum of the image. The
essence of the algorithm is that the displacement caculation of the image is replaced by the movement caculation of the
coordinate, which makes the phase of the fundamental frequency zero under different coordninates when image position
changes. Under the circumstances that the image of the CCD autocollimator is polluted by the noises caused by
tempreture, the measuring accuracies of the normally-used barycenter, edge detection, Gaussian fitting algorithm and the
algorithm presented in this paper were compared. Experiment results show, the subpixel algorithm demonstrated here has
the advantages of strong anti-noise ability and high precision. The reliability of the algorithm is also disproved by the
peak location of the reconstructed image after the removal of higher harmonics. When applied to the one-dimensional
CCD photoelectric autocaollimator used in field conditions, fine linearity and ±3// measurement accuracy were
simutaneously obtained in the whole ±3600// measurement range when the temperature varies between -400C-600C.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.