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9 December 1999 Gas sensors based on fiber laser intracavity spectroscopy (FLICS)
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Intra-cavity spectroscopic measurements may be obtained with any material that has an absorption signature under the gain bandwidth of a fiber laser. The high sensitivity of the intra- cavity technique combined with the compact size of a fiber laser makes this approach very attractive for a wide range of applications. Experiments have been carried out with acetylene and a tunable erbium-doped fiber laser. Compared to regular absorption measurements, an enhancement in sensitivity limited mainly by laser noise is observed. Since intra-cavity spectroscopy is essentially a single beam technique, dual beam noise reduction is not possible with this arrangement. However, if we consider the fact that a single mode fiber can support two modes of polarization, we can create two lasers using the fiber as a common element for both optical cavities. The proposed fiber laser configuration uses a polarization beam splitter to create two independent cavities (x and y polarization) with the same noise, of which one cavity contains the absorber. This permits the convenient use of Balanced Ratiometric Detection in conjunction with sensitive intra-cavity absorption. Although tested using bulk devices, this fiber laser sensor can easily be implemented in an all- fiber version using off the shelf fiber optic components, which makes it a good candidate for compact field spectroscopic measurements.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Juan Hernandez-Cordero and Theodore F. Morse "Gas sensors based on fiber laser intracavity spectroscopy (FLICS)", Proc. SPIE 3860, Fiber Optic Sensor Technology and Applications, (9 December 1999);

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