Abstract: A reservoir fiber optic chemical sensor (FOCS) is formed of a modular cell body. A fiber optic is attached using a quick connect standard fiber optic connector. A semipermeable membrane is attached at the opposite end of the cell body using a quick attach membrane retainer. Multiple sensors can be made uniformly. Specific sensors for TCE vapor, O.sub.2 and CO.sub.2 are produced by utilizing a suitable reaction chemistry in the cell. A non-imaging optical focusing element can be included in the cell to increase sensitivity. A reaction cell can be placed adjacent to the reservoir cell with the semi-permeable membrane separating the two cells to produce a photolysis FOCS. TOC and TOCl can be detected with the photolysis FOCS.

Abstract: A fiber optic element is used to detect the presence of chemical or biological species by measuring changes in the total internal reflection characteristics of the element produced by changes in the index of refraction of a clad or layer of a material which reacts with the chemical or biological species.

Abstract: A modular fiber optic chemical sensor (FOCS) is formed using a capillary tube clad. A fiber optic core with reactive surface is exposed to a sample environment and then the capillary tube is fitted over the core. The capillary could also be porous so that in-situ measurements can be made. The capillary can be spaced from the core so that a flow channel for gas and liquid sensing is formed, or an index matching fluid may fill the channel. Measurements can be made in a compact portable modular detector unit in which the FOCS is placed between an excitation source and a detector or single ended where the excitation source and detector are at the same end of the core and a reflector is placed at the end of the core.