Combined raman and IR fiber-based sensor for gas detection

摘要

A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through the waveguide where the light is detected at the same end as the light source. This double pass retro reflector design increases the interaction path length of the light and the gas sample, and also reduces the form factor of the hollow structure.

主权项

1. An apparatus, comprising:
a hollow gas sampling structure having a first end, a second end, a diameter ranging from at least 200 micrometers to no more than 3 millimeters, a reflector located at said second end, an opening configured wherein a gas can freely but not forcibly migrate into and out of said structure and a reflective inner wall comprising a reflective material selected from the group consisting of a metal and a dielectric, wherein said reflective material is reflective and not absorbing of (i) Raman excitation light and Raman light having a wavelength within a range from UV to visible and (ii) infrared (IR) radiation having a wavelength within a range from 3 μm to 20 μm; a fiber optic bundle comprising a first distal end operatively and proximately connected to said first end, wherein said fiber optic bundle further comprises: a multimode first fiber optic configured for transmitting said Raman excitation light into said gas to produce Raman light generated in said gas, wherein said first fiber optic comprises a first fiber optic proximal end and a first fiber optic distal end, wherein said first fiber optic distal end terminates at said first distal end; a multimode second fiber optic configured for transmitting said IR radiation into said gas to produce attenuated IR radiation, wherein said second fiber optic comprises a second fiber optic proximal end and a second fiber optic distal end, wherein said second fiber optic distal end terminates at said first distal end, wherein said second fiber optic is further configured for collecting said attenuated IR radiation; a multimode first collection fiber configured for collecting said Raman light, wherein said first collection fiber optic comprises a first collection fiber optic proximal end and a first collection fiber optic distal end, wherein said first collection fiber optic distal end terminates at said first distal end; a first source of said Raman excitation light, wherein said first source is configured to direct said Raman excitation light into said first fiber optic proximal end; a second source of said IR radiation, wherein said second source is configured to direct said IR radiation into said second fiber optic proximal end; a Raman light detector configured to receive said Raman light from said first collection fiber optic proximal end; and an IR radiation detector configured to receive said attenuated IR radiation.