An optic-fiber evanescent wave sensor based on new type D-shaped fiber is designed. By letting the energy of the evanescent wave field and the analyte interact with each other directly and increasing the effective area of the sensing fiber
the sensitivity of the sensor is improved greatly. Compared with the sensors fabricated by B.Culshaw and G.Stewart
the new sensor is found to be three orders of magnitude more sensitive. Per equal length
the sensor’s sensitivity is about 1.2 times of the open-path cell sensing. Also we propose a new
low-cost and efficient method fabricating D-shaped fiber based on machine grinding.