A miniature fiber-optic chemical sensor system allowing for simultaneous detection of gas concentrations and physical parameters is described, fabricated and tested. The design is focused on minimizing influence of the sensor onto the system under test, therefore employing very thin and pliable fiber probes. Microfabrication of the sensor structure is described and a suitable interrogation setup is introduced. Measurements of O-2 and CO2 concentrations are presented and discussed. Applications in continuous medical monitoring and necessary design and operating parameters are described.