Optical sensing based on functionalized evanescent fiber sensor for process fluid flow analysis

An optical fiber sensor for detecting a chemical analyte, comprising:

• a first optical fiber segment including a first core and a first cladding surrounding the first core configured to cause light to be confined to the first core;
• and
• a second optical fiber segment including:
• a second core connected to the first core;
• a second cladding surrounding the second core to cause an evanescent field to be generated at a boundary between the second core and the second cladding;
• and
• a sensing material layer disposed on the second cladding to cause the evanescent field to interact with the chemical analyte through the sensing material layer,
• wherein the second cladding is thinner than the first cladding.

A flow cell for process fluid flow analysis, comprising:

• a liquid flow path through which an analyte flows;
• an optical path through which a waveguide is arranged to direct a light beam toward the analyte;
• and
• an evanescent fiber segment arranged at a cross point between the liquid flow path and the optical path to optically detect properties of the analyte, wherein the evanescent fiber segment includes a fiber having a partially removed cladding on a core and a sensing material layer disposed on the partially removed cladding.