We present a new configuration based on multimode interference with a microring resonator feedback waveguide. The proposed configuration can create a deep Fano shape and provide a high sensitive sensor structure. In this paper, we is applied to seawater salinity sensor with a high sensitivity. We also propose an approach for these optical sensors integated with wireless sensor networks for online and real-time applications. The sensor structure can provide a sensitivity of 581nm/RIU based on wavelength shift based mechanism. We use silicon waveguides for the whole sensor designs and working at operating wavelength of 1550nm.
