TDLAS architecture for widely spaced wavelength

A system for measuring a concentration of at least one target species, comprising:

• a first tunable diode laser configured to generate laser light at a first wavelength, a second tunable diode laser configured to generate laser light at a second wavelength, and a third tunable diode laser configured to generate laser light at a third wavelength, wherein the first wavelength, the second wavelength, and the third wavelength are different from one another;
• a first optical fiber having a proximal end and a distal end, the first optical fiber optically coupled to the first tunable diode laser at the proximal end and being configured to carry light at the first wavelength;
• a second optical fiber having a proximal end and a distal end, the second optical fiber optically coupled to the second tunable diode laser at the proximal end and being configured to carry light at the second wavelength;
• a third optical fiber having a proximal end and a distal end, the third optical fiber optically coupled to the third tunable diode laser at the proximal end and being configured to carry light at the third wavelength;
• a pitch head comprising a transmitting optic optically coupled to the first, second, and third tunable diode lasers via the distal ends of the first, second, and third optical fibers, and being oriented to project respective beams from each of first, second, and third distal ends through a measurement zone, the pitch head being configured to project the respective beams in accordance with a time-division multiplexing (TDM) scheme;
• a photodetector configured to detect an optical power of light in the first, second, and third wavelengths;
• a catch head located across the measurement zone from the pitch head in optical communication with the pitch head to receive the respective beams from the first, second, and third distal ends and direct the respective beams thereof to the photodetector;
• a fiber bundle assembly comprising the first, second, and third distal ends of the first, second, and third optical fibers, respectively;
• wherein the first, second, and third wavelengths each correspond to respective absorption lines of the at least one target species;
• wherein, in the fiber bundle assembly:
• the distal ends of the first and second optical fibers are stripped of their respective coatings;
• and
• a first fiber optic core of the first optical fiber, a second fiber optic core of the second optical fiber, and a third fiber optic core of the third optical fiber are arranged with their claddings adjacent to each other forming a triangular configuration.