“Unlike traditional systems that exploit only light intensity, this chip also uses the phase,” according to the university.
“We go from a speed of 56Gbit/s to 1,000Gbit/s,” said researcher Alireza Geravand (pictured), who studies in the university’s Center for optics, photonics and lasers.
Power consumption is low, said the university, with a test data set equivalent to 100 million books transferred for under 4J.
Key to the project has been understanding some of the vagaries of micro ring modulators that have left them confined to amplitude modulation, such as frequency chirp and dynamic non-linearity – particularly when asked to operate coherently.
The design uses a push-pull pair of ring modulators inside a Mach–Zehnder interferometer “enabling a bistable phase response and un-chirped amplitude modulation” according to a paper on the research in Nature Photonics. “Harnessing the ultra-fast coherent dynamics, we demonstrated an ultra-wide-bandwidth in-phase/quadrature modulator on a silicon chip fabricated using a CMOS-compatible photonic process.”
Chip edge bandwidth was 5Tbit/s/mm, coherent transmission was at 180Gbaud symbol rate, and net bit rate was above 1Tbit/s over 80km. Modulation energy was as low as 10.4fJ/bit.
The work is published as ‘Ultrafast coherent dynamics of microring modulators‘ in Nature Photonics.
Almost 10 years ago, University College London demonstrated 1Tbit/s optically by using fifteen wavelength channels and, unusually, 256QAM modulation on each , but only with the transmitter directly coupled to the receiver.
Photo credit: Dany Vachon
