A TDLAS sensing apparatus for sensing gas species characteristics within a process chamber, the sensing apparatus comprising: a pitch side optical fiber and at least one diode laser (12A, 12B, 12C) for producing an output beam of a select lasing frequency optically coupled to an input of the pitch side optical fiber; a pitch side beam controller comprising at least one of a beam splitter or an optical switch, the pitch side beam controller having at least one input optically coupled to an output of the pitch side optical fiber and at least two outputs; a pitch optic (20A-D) configured to be operatively associated with the process chamber and oriented to project the output beam of the at least one diode laser (12A, 12B, 12C) through the process chamber, wherein at least one of the at least two outputs of the pitch side beam controller is optically coupled to the pitch optic; a catch optic (24A-D) configured to be operatively associated with the process chamber in optical communication with the pitch optic to receive the output beam of the at least one diode laser (12A, 12B, 12C) projected through the process chamber; a catch side optical fiber having an input side optically coupled to the catch optic and an output side; a catch side beam controller comprising an optical switch having at least two inputs and one output, wherein the output side of the catch side optical fiber is optically coupled to an input of the catch side beam controller; a detector (30A-C) optically coupled to the catch side beam controller output, the detector being sensitive to the select lasing frequency; characterized by an FBG optical fiber having an input and an output, the FBG optical fiber comprising at least one fiber Bragg grating formed in a core of the FBG optical fiber, the at least one fiber Bragg grating being configured to partially reflect a laser beam of the select lasing frequency while passing the remainder of the laser beam to the FBG optical fiber output, the FBG optical fiber input being optically coupled to another one of the at least two outputs of the pitch side beam controller and the FBG optical fiber output being optically coupled to another one of the at least two inputs of the catch side beam controller. a pitch side optical fiber and at least one diode laser (12A, 12B, 12C) for producing an output beam of a select lasing frequency optically coupled to an input of the pitch side optical fiber; a pitch side beam controller comprising at least one of a beam splitter or an optical switch, the pitch side beam controller having at least one input optically coupled to an output of the pitch side optical fiber and at least two outputs; a pitch optic (20A-D) configured to be operatively associated with the process chamber and oriented to project the output beam of the at least one diode laser (12A, 12B, 12C) through the process chamber, wherein at least one of the at least two outputs of the pitch side beam controller is optically coupled to the pitch optic; a catch optic (24A-D) configured to be operatively associated with the process chamber in optical communication with the pitch optic to receive the output beam of the at least one diode laser (12A, 12B, 12C) projected through the process chamber; a catch side optical fiber having an input side optically coupled to the catch optic and an output side; a catch side beam controller comprising an optical switch having at least two inputs and one output, wherein the output side of the catch side optical fiber is optically coupled to an input of the catch side beam controller; a detector (30A-C) optically coupled to the catch side beam controller output, the detector being sensitive to the select lasing frequency; characterized by an FBG optical fiber having an input and an output, the FBG optical fiber comprising at least one fiber Bragg grating formed in a core of the FBG optical fiber, the at least one fiber Bragg grating being configured to partially reflect a laser beam of the select lasing frequency while passing the remainder of the laser beam to the FBG optical fiber output, the FBG optical fiber input being optically coupled to another one of the at least two outputs of the pitch side beam controller and the FBG optical fiber output being optically coupled to another one of the at least two inputs of the catch side beam controller.