We proposed a compact design of an optical biochemical sensor based on the Mach-Zehnder interferometer (MZI), which was coupled by a ring resonator (RR) as a sensing tool. The sensor sensitivity has been determined by power difference at the output ports. The sensor enhancement has been optimized by numerically evaluating the geometrical parameters of the MZI and RR. A great sensor sensitivity depicted by Fano resonance characteristic has been demonstrated as a function of the round trip phase in the range of 4×10–4 – 4×10–4, which was changed by the presence of the sample solution in the sensing area. This optimum sensitivity has been obtained for the values of two coupling coefficients of the MZI 120.5/mmκκ==and the coupling coefficient between the MZI arm and RR 0.5/mm.Rκ= Furthermore, a good profile of sensitivity exchange has been exhibited by inducing the direct current voltage to the coupling region of Rκ. Finally, the output power transmission of the ring-coupled arm was depicted as a function of tunable κR.