Highly functional microfluidic systems need to be supported by subsystem making possible to efficiently analyse properties of liquids flowing in the microchannel. In this work we have shown both numerical and experimental analysis of Microcavity in-line Mach-Zehnder Interferometer (µIMZI) induced in the side surface of a single-mode optical fiber and a microfluidic system. First, it must be noted that after the integration µIMZI maintains its high sensitivity to refractive index changes in the cavity. Secon d, amount of liquid flowing in the microchannel and the flow rate need to be adjusted to effectively exchange the liquid in the microcavity, but orientation of the cavity versus the flow direction has a minor impact on the exchange. Finally, we additionall y integrated electrodes with the system making possible to initiate reduction and oxidation reactions directly in the microchannel. It has been shown that even when the oxidized or reduced form is created in part of the channel, the products of the reactions can be identified both electrochemically and optically. The finding indicates that capability to modify the properties of the liquids outside the microcavity and thanks to microfluidic system analyse them in the flow. The results allow for considering the developed system as a promising and universal solution for highly sensitive biochemical analysis in the microscale.