Design of a coherent optical receiver on a silicon nitride platform for mode multiplexed systems

Current coherent optical systems carry information at high bit rates over long distances in single-mode optical fibers. However, expanding data traffic is increasingly demanding higher transmission rates which could be employed by spatial mode multiplexing. In this work, an optical hybrid for C-band on a silicon nitride platform is proposed. The hybrid is composed by a 2×2 and 1×2 multimode interferometers, and a mode converter. Losses less than 0.5 dB and 0.75 dB for TE0 and TE1 modes are achieved and common mode rejection ratio near 50 dB, and phase error below 0.5°.