Abstract: Measuring a concentration of at least one target species is described. A first and second tunable diode laser are configured to generate laser light at a respective wavelength different from one another. A pitch head comprising a transmitting optic is optically coupled to the first and second tunable diode lasers via distal ends of the first and second optical fibers, and is oriented to project respective beams from each of the first and second distal ends through a measurement zone. A photodetector is configured to detect an optical power of light in the first and second wavelengths. A catch head located across the measurement zone from the pitch head is in optical communication with the pitch head to receive the respective beams from the first and second distal ends and direct the respective beams to the photodetector.

Abstract: A combustion-zone chemical sensing system (100) is disclosed that includes pitch reflective optics (110) that collimate MIR electromagnetic energy from an input fiber (150), a reflector (120), catch reflective optics (112) that focus reflected MIR electromagnetic energy into an output fiber (152), and a detector (140) to detect MIR electromagnetic energy from the output fiber. An optical head (102) for sensing a combustion zone (104) is disclosed that includes pitch reflective optics (110) that collimate MIR electromagnetic energy from an input fiber (150) towards a reflector (120), catch reflective optics (112) that focus MIR electromagnetic energy, reflected from the reflector, into an output fiber (152), and an alignment housing that interfaces with structure adjacent the combustion zone.

Abstract: A demultiplexed filtering method includes propagating an optical beam from an input optical fiber to a diffraction grating to produce a first and a second diffracted beam having a respective first center wavelength ?1 and a second center-wavelength ?2>?1 of the optical beam. The first diffracted beam propagates back toward the input optical fiber at a first diffracted angle determined in part by ?1 and a diffraction order m1 of the first diffracted beam. The second diffracted beam propagates back toward the input optical fiber at a second diffracted angle determined in part by ?2 and a diffraction order m2<m1. The method also includes (i) coupling the first diffracted beam into a first optical fiber of a one-dimensional optical-fiber array that includes the input optical fiber, and (ii) coupling the second diffracted beam into a second optical fiber of the one-dimensional optical-fiber array.