Can the laser in the oxygen transmitter be tuned to measure gases other than oxygen?

Yes in theory, but not in practice. TDL (Tunable Diode Laser) as a technology is generic and can be used to measure practically any gas. However, the tuning range of the semiconductor laser used in the OMT355 is so small that it is not possible to tune an individual laser to measure more than one gas species. Therefore, separate instruments with different lasers would be required to measure other gases.