An Integrated Photonic Router Using Fifth-Coordinate Phase Steps

Photonic integrated circuits route light with phase shifters, and their performance is set by loss, crosstalk and switching energy. This paper designs an 8 by 8 routing fabric in which each switching element applies a discrete phase step associated with the fifth-coordinate phase ladder, and computes the fabric-level figures. The worst-case path loss is 1.92 dB, crosstalk from a phase error of 0.02 rad is -37.0 dB, and the switching energy is 10.9 pJ per element. Discrete phase steps, rather than continuously trimmed phases, are the design's central choice: they trade a small, calculable crosstalk for the elimination of per-element analogue calibration. The fabric is a simulated design; no chip has been fabricated.