Analysis and design of micro-ring based switching elements in a silicon photonic integrated transponder aggregator

In this paper, we present and investigate a new architecture of a silicon photonic transponder aggregator as a new interconnect subsystem enabling the implementation of colorless, directionless, and contentionless ROADMs. Such subsystem is based on a microring resonator switching fabric integrated in a silicon photonics platform to achieve high functional integration together with reduction of cost, footprint, and power consumption. In the proposed device, microring resonators perform simultaneous add and drop of wavelength channels which suffer from two detrimental effects: residual dropped signal crosstalk and residual added signal crosstalk, respectively. Considering three microring-based switching elements, the transfer matrix method has been used to compute the add/drop transfer functions of the switches as a function of their geometrical parameters. The two crosstalk effects have been evaluated jointly with other important transmission parameters, such as bandwidth, insertion losses, side lobe suppression, adjacent channel rejection, extinction ratio, and group dispersion. In addition, device sensitivity with respect to the ring-waveguide coupling coefficients has been calculated. Finally, the performance of the different switches has been assessed to demonstrate that, by a proper design, the proposed transponder aggregator can support 100 Gb/s DP-QPSK modulated signal transmission.