A system for in-situ gas analysis in a flue gas region, wherein said system comprises: • An enclosure; • A laser beam source housed in said enclosure, said laser beam source configured to generate laser beams; • A tubular probe insertable for probing in the flue gas region, said probe comprising: ∘ optical waveguides configured to receive and conduct laser beams generated by said laser beam source; ∘ a dead zone configured to support and isolate said optical waveguides contained therein from surrounding flue gases, said optical waveguides extending upto and projecting said generated laser beams from the farther end of said dead zone; ∘ a measurement zone configured to receive said projected laser beams by said optical waveguides, said measurement zone configured to allow said flue gas to pass therethrough and get exposed to said projected laser beams; and ∘ a reflection chamber located at the farther end of said measurement zone, said reflection chamber comprising a first focusing lens for focusing said projected laser beams that are exposed to said flue gases in said measurement zone, and at least two mirrors (54a,54b) for reflecting back said focused laser beams towards said optical waveguides and positioned one after the other along the longitudinal axis of said reflection chamber, wherein a first mirror is configured to reflect a first generated laser beam and a second mirror is configured to reflect a second generated laser beam; • at least one detector configured to detect said at least one reflected laser beam and generate at least one corresponding sensed signal; and • a processing unit configured to process said sensed signal from said detector for computing composition of said flue gas. • An enclosure; • A laser beam source housed in said enclosure, said laser beam source configured to generate laser beams; • A tubular probe insertable for probing in the flue gas region, said probe comprising: ∘ optical waveguides configured to receive and conduct laser beams generated by said laser beam source; ∘ a dead zone configured to support and isolate said optical waveguides contained therein from surrounding flue gases, said optical waveguides extending upto and projecting said generated laser beams from the farther end of said dead zone; ∘ a measurement zone configured to receive said projected laser beams by said optical waveguides, said measurement zone configured to allow said flue gas to pass therethrough and get exposed to said projected laser beams; and ∘ a reflection chamber located at the farther end of said measurement zone, said reflection chamber comprising a first focusing lens for focusing said projected laser beams that are exposed to said flue gases in said measurement zone, and at least two mirrors (54a,54b) for reflecting back said focused laser beams towards said optical waveguides and positioned one after the other along the longitudinal axis of said reflection chamber, wherein a first mirror is configured to reflect a first generated laser beam and a second mirror is configured to reflect a second generated laser beam; ∘ optical waveguides configured to receive and conduct laser beams generated by said laser beam source; ∘ a dead zone configured to support and isolate said optical waveguides contained therein from surrounding flue gases, said optical waveguides extending upto and projecting said generated laser beams from the farther end of said dead zone; ∘ a measurement zone configured to receive said projected laser beams by said optical waveguides, said measurement zone configured to allow said flue gas to pass therethrough and get exposed to said projected laser beams; and ∘ a reflection chamber located at the farther end of said measurement zone, said reflection chamber comprising a first focusing lens for focusing said projected laser beams that are exposed to said flue gases in said measurement zone, and at least two mirrors (54a,54b) for reflecting back said focused laser beams towards said optical waveguides and positioned one after the other along the longitudinal axis of said reflection chamber, wherein a first mirror is configured to reflect a first generated laser beam and a second mirror is configured to reflect a second generated laser beam; • at least one detector configured to detect said at least one reflected laser beam and generate at least one corresponding sensed signal; and • a processing unit configured to process said sensed signal from said detector for computing composition of said flue gas.