a system for determining gas compositions includes a probe , inserted into a source of gaseous material , the probe having a gas permeable sensor tip and being capable of sending and receiving light to and from the gaseous material , a sensor body , connected to the probe , situated outside of the source and a fiber bundle , connected to the sensor body and communicating light to and from the probe . the system also includes a laser source , connected to one portion of the fiber bundle and providing laser light to the fiber bundle and the probe a raman spectrograph , connected to another portion of the fiber bundle , receiving light from the probe and filtering the received light into specific channels and a data processing unit , receiving and analyzing the received light in the specific channels and outputting concentration of specific gas species in the gaseous material based on the analyzed received light .