Improved Two-Fiber Probe for in Situ Spectroscopic Measurement

Abstract

A simple two-fiber probe has been modified and improved for in situ spectroscopic measurements that utilize frontsurface geometry. The efficiency of the probe for fluorescence measurement across a window is improved by maximizing the overlap of the light cones of the two fibers at the outside surface of the window where the sample is in contact with the window. This is achieved by polishing the ends of the fibers at predetermined angles and using different probe geometries. Improvement factors up to 14 have been obtained for fluorescence of phenol in distilled water, anthracene in 75% methanol, and the solutions mixed with sands and clay. The improved twofiber probe can be used for fluorescence as well as phosphorescence, Raman, and infrared (reflectance) spectroscopic measurements.

Fiber‐Optic Chemical Sensors: A General Review

“…More com plex sys tems have been designed, such as us ing long fi bers or dou ble fi ber re mote systems. 106,107 Lin et al 108 im proved two-fiber probe for in-situ spec tro scopic mea sure ment. They pol ished the ends of fi bers at pre de ter mined an gles and dif fer ent probe ge om e tries.…”

Direct-push, fluorescence-based sensor systems forin situ measurement of petroleum hydrocarbons in soils

“…The multichannel LIF system (Figure 4) developed by Kenny's group [17][18][19][20] at Tufts University uses a hydrogenmethane Raman shifter, pumped by the fourth harmonic of a 20-Hz pulsed Nd:YAG laser to produce a large number of output beams at different wavelengths (over the range of ) and intensities. As many as 10 of the resulting 250 -400 nm beams are coupled into separate fibers and transmitted down the penetrometer probe to separate sapphire windows.…”

Field demonstration of a multichannel fiber-optic laser-induced fluorescence system in a cone penetrometer vehicle

“…10 Contaminant fluorescence is collected by a separate fiber (collection fiber) in each channel that is approximately tangent to the excitation fiber and mounted at an angle determined to optimize collection efficiency. 11 Total fiber length was 25 m in two sections, 5 and 20 m, joined by a standard ST connector (Augat, Kent, WA). Appropriate cutoff filters for each collection channel were inserted in the ST connectors.…”

“…Appropriate cutoff filters for each collection channel were inserted in the ST connectors. 11 The collection fibers for all 10 channels are arranged in a vertical array in a plug that interfaces with an imaging spectrograph (Acton Spectrapro 150, Acton Research Corp., Acton, MA). The dispersed fluorescence is detected by a thermoelectrically cooled charge-coupled device (CCD) camera (TE/ CCD-576EMUV, Princeton Instruments, Trenton, NJ).…”