This paper presents an optical waveguide with freestanding structure to detect theanastomosis leakage after colon surgery. Different parameters of the waveguide isinvestigated and two materials (SiC and TiO2) are chosen as the core. Simulationshave been performed to optimise the structure and compare the difference in errortolerance and sensitivity between two materials. Waveguide with TiO2 core wasfabricated and tested. The experimental results showed the sensitivity of the sensorS = 1 dB/%.