Thanks to all who stopped by the Cisco booth at OFC 2019 in San Diego! It was a bustling show and our booth was constantly packed.
One of them was Cisco’s silicon photonics platform that our talented team of engineers have been developing for years. We demonstrated it live, showing 100Gb PAM-4 modulation on a single wavelength. That’s 100G per lambda (wavelength), which will be key for the next generation of 400G transceivers and future 100G transceivers in smaller form factors.
The modulation quality was a highlight of the booth. The eye diagram was so clean that we ran it through 10km of single-mode fiber, and it still looked the same as if it didn’t go through any fiber at all. No signal degradation!
The demo set up is shown in the figure below. We plugged two of our 100G single-wavelength PAM4 modules into a Cisco Nexus 9k ethernet switch. We also plugged in a traffic generator using standardized IEEE 100GBASE-LR4 modules. The PAM4 modules (green in the diagram) had two different spools of single-mode fiber inserted, one for each direction of traffic. One was 2km long and the other was 10km. Optical couplers tapped off a portion of the light at three different points:
1. Before entering the 2km spool.
2. After exiting the 2km spool.
3. After exiting the 10km spool.
An optical switch allowed us to select which tap to direct toward an optical amplifier and high speed oscilloscope (Tektronix scope with 80C10C head and 80A04B phase reference). A bench top CDR (Clock and Data Recovery) unit was also used for triggering.
The results on the Tek scope were that no matter which optical tap we selected, the eye looked mostly the same, even after 10km of fiber. This indicates a clean chirp-free signal from the transmitter.
OFC will be in San Diego again next year. See you there!