| 摘要 |
A method and apparatus for detecting the presence of hydrocarbon analyte in at least one of a liquid and vapor state. The apparatus (21) includes an optical fiber (22), an absorber-expander (31) mechanically coupled (32) to the optical fiber (22) to produce a change in transmission of light along the fiber (22) upon absorption of the hydrocarbon (33). The absorber-expander (31) is selected to absorb hydrocarbons, but not water, and to be capable of multiple reversible expansion and contraction cycles without significant structural degradation. Methyl terminated, silica and iron oxide filled, dimethyl polysiloxane provides a material which will experience substantial swelling in the presence of a hydrocarbon and yet is substantially reversible on desorption of the hydrocarbon from the absorber-expander (31). The method includes positioning an optical fiber (22) having such an absorber-expander (31) for absorption of hydrocarbons and detecting the decrease in light transmission produced by expansion of the absorber-expander (31), for example, by one of microbending and axial misalignment. The location of the absorber-expander (31) along strand (22) can be determined by optical time domain reflectometry or by digital sensing nodes (122), and multiple couplings (57) and biasing couplings (153) for mounting the absorber-expanders (152) to the optical fiber (151) can be used to enhance sensitivity.
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