Fig. 4: Sub-ns optical circuit switching (OCS) and data transmission using on-chip SOAs and on-chip AWG along with soliton microcomb.

a Schematic of the setup used to perform the OCS and data transmission. The multi-wavelength optical carriers, generated via the frequency comb generator (FCG), are coupled to an InP chip containing an AWG and SOAs via an optical circulator. The coupled optical carriers are aligned to the AWG by changing the temperature of InP chip. The aligned carriers are transmitted to integrated SOAs; if one of them is biased, then the AWG channel (waveguide) connected to that particular SOA is reflected from the high-reflection coated facet of the chip while non-biased SOAs block the light. The reflected-back channels are coupled back via an anti-reflection coated optical fiber for encoding the information using the data transmission unit (DTU). b Microscope image of PIC showing the SOAs (red arrows) and AWG. c Optical spectrum of comb channels with different spacing while switching after the InP chip indicating more than 20 dB isolation with adjacent AWG channels (cross talk). The red curve shows CH 36 and 42 with 4.8 nm wavelength spacing, the blue curve CH 35 and 42 (5.6 nm) and the purple curve CH 40 and 41 (0.8 nm). d The sub-ns wavelength switching between two different comb channels using on-chip SOAs. The overshoot in the switching signal is due to impedance mismatch between the high-speed radio-frequency (RF) probes and the on-chip electrodes. This effect can be minimized by optimizing the drive signal. e The left and right figures show the zoomed-in view of switching signals between two different comb channels (CH35 and CH 42). f The bit error ratio (BER) performance of the 25 GBd NRZ PIC-based switching system for different combinations of two comb channels.