Optical fiber based gas sensors are currently started employed in many industrial environments for the accurate detection of harmful gases. Occupational Safety and Health Administration (OSHA) has specified certain threshold limit on the exposure of toxic gas like ammonia (25 ppm), chloroform (50 ppm) etc. based on risk evaluations. Electrical resistive type gas sensors employed in the nuclear environment are not suitable for the prolonged usage due to the impact of ionizing radiation on the seminconducting materials which leads to the variation in its electrical conduction. Hence, it is proposed to fabricate an optical fiber based gas sensor which can be operated under different physico chemical environment. Radiation dosimetry materials are exploited as a sensor element in the sensors. The common thread runs between the luminescence based dosimeter and the proposed optical fiber based gas sensor are the presents of defects in the material. Although defects play a major role in gas sensing, certain other factors like temperature and nature of the sensor materials will be studied extensively for the enhanced sensitivity with lower detection level. Along with this discussion, my previous research work on the nonlinear optical behavior of borate materials and preparation of porous silicon matrix will be explained.