A novel UV sensor was manufactured and characterized using the evanescenffield coupling between fiber-planar waveguide (PWG) coupler and prism. A spiroxazine dye was chosen as planar waveguide because its photochromic isomerization induced by UV irradiation. A novel UV sensor was proposed to measure the variation of refractive index and absorption coefficient simultaneously. The wavelength responses of these sensors by UV exposure times were measured 0.48 nm/sec, 0.757 nm/sec, and ATR output power variations were measured -0.424 μW/sec and -0.62 μW/sec when UV exposure power were 3 mW and 5 mW, respectively.