Study on concentration measurement of small sample with optical fibers

It is valuable to detect concentration of a small quantity of liquid with suspended particles, especially for MEMS. In this paper, a structure is designed with two beams of optical fibers. Light scattering in different direction is simulated and analyzed based on Mie theory in order to find the optimal type of detection. The size character and refractive index have an affect on the extinction coefficient, and more detail simulations are presented in this paper. For different refractive indexes of suspending liquid, real number or complex number, the condition of scattering and absorption to light is analyzed. Based on the study of scattering theory, the comparison structure for concentration detection is presented, which receives light in range from 0 to 180 degree, and variable optical length from 2 to 5 mm, the value of angle and length change is straightly shown, respectively. The structure is characteristic of two sessions: rotational part and moving part, which receive the scattering light in any given angle and optical length. In the system design optical fiber is used, which emit light beam to a small sample accurately and receive scattering light. Concentration will be gained according to the detection of emitting and receiving light intensity.