The present thesis describes optical spectroscopic measurement technologies.The applications of optical monitoring in this work are directed towards some main areas:optical monitoring of fruit ripening, gas exchange, insects, food packaging and infectious diseases.All areas in the thesis belong to biophotonics, and has practical significance and implications for China as well as for the rest of the world.　　In this thesis, absorption spectroscopy is focused on gas constituents and volume assessment, by employing tunable diode laser absorption spectroscopy (TDLAS).According to the Beer-Lambert law, concentration of certain gas in media can be calculated with incident light intensity, transmitted light intensity and especially path length, all known.However, in porous materials, when the gas absorption path length cannot be obtained due to highly scattering in the turbid medium, the concentration of the gas cannot be calculated.The technique, referred to as GAs in Scattering Media Absorption Spectroscopy (GASMAS), based on the principle that the absorption spectrum of gases is much narrower than that for the condensed materials, is used to assess gas concentration in scattering media.The GASMAS technique was used in all studies on fruit ripening, fruit skin, food packages, and ear phantom to obtain gas content indirectly or recording gas exchange processes.In a study of the frontal sinuses, GASMAS was used to assess gas space volume under the condition of constant gas concentration, pertinent to water vapor.　　In addition, reflectance and fluorescence spectroscopy are two essential methods in extracting spectroscopic information.The comprehensive utilization of reflectance and fluorescence was involved in fruit and insect studies.