A device for measuring the absolute value of the refractive index of a liquid by immersion uses the optical properties of a cylindrical waveguide with a solid core and normal angle of incidence of the light source. The device consists of a transparent tube forming the enclosure of the waveguide, impervious to the surrounding liquid and partially filled with a transparent solid or liquid material of appropriate index of refraction, a fiber optic means of inputting light via a LED or laser and fiber optic means of coupling emerging light to a photodetector. The emerging light intensity is a function of the index of refraction of the surrounding liquid.

Embodiments as disclosed herein may provide a sensor system including a container, such as a bag, having a port assembly integrated therewith. The port assembly includes an optically transparent window and be configured such that a sensor may be mechanically attached to the port assembly to interface with the optical window. The sensor may include an index of refraction (IoR) sensor that measures the chemical concentration of a liquid inside the container based on a refractive index.

A thermo-optic coefficient measurement system can include a housing structure configured to retain at least a first plate sample, a second plate sample, and a third plate sample in a stacked, alternating stagger arrangement such that a gap exists between the first plate sample and the third plate sample that is the thickness of the second plate sample. The system can also include a first optical device connected to the housing to output a first laser configured to be coincident with the first plate sample and the third plate sample. The first optical device can be configured to receive a first return signal. The system can also include a second optical device connected to the housing to output a second laser configured to be coincident with the second plate sample, the second optical device can be configured to receive a second return signal. The system can include an optical interrogator module configured to be connected to the first optical device to output the first laser thereto and to receive the first return signal therefrom. The optical interrogator module can be configured to be connected to the second optical device to output the second laser thereto and to receive the second return signal therefrom. The optical interrogator module can be configured to determine a thermo-optical coefficient as a function of the first return signal and the second return signal at a plurality of temperatures.

The present invention discloses a system, apparatus and method for analysing the contents of a phase change material. More specifically, the present invention discloses an apparatus for analysing the compositions of PCMs, as well as blends of anhydrous salts and blends of organic PCMs by their refractive indices.