Non-invasive monitoring of mode-division multiplexed channels on a silicon photonic chip

We demonstrate on-chip non-invasive monitoring of orthogonal modes transmitted in a silicon photonic waveguide. The proposed technique exploits a recently developed ContactLess Integrated Photonic Probe (CLIPP) realizing a fully transparent integrated light detector. The optical intensity of the modes propagating in the waveguide is tracked in time by the CLIPP, with no signal quality degradation induced by monitoring operations. We exploit this concept for the simultaneous monitoring of two intensity modulated 10 Gbit/s data channels transmitted at the same wavelength and multiplexed on the fundamental transverse electric and magnetic modes of the silicon waveguide. By labeling each signal with a weakly modulated pilot tone, the CLIPP can discriminate at the same time the two channels, the monitoring of one signal not affecting the readout of the other one. The scalability of the presented technique to several modes on arbitrary polarization states, along with the fabrication simplicity and CMOS compatibility of the CLIPP detector, makes this approach promising for the monitoring and control of integrated components for mode-division multiplexing systems.