Researchers have created a silicon-based optical communication link which combines two multiplexing technologies. This creates 40 optical data channels capable of simultaneously moving data. This new chip-scale optical interconnect can transmit 400GB per second, which is equivalent to about 100,000 streaming movies. This could make it easier to use data-intensive internet services such as video streaming and high-capacity stock market transactions.
Peter Delfyett was the head of the University of Central Florida College of Optics and Photonics’ (CREOL), research team. He stated, “As the demand to move more information over the internet continues to grow, we require new technologies to push data speeds further.” Our work could allow faster and better data processing in data centers that make up the backbone of internet. “Because optical interconnects are able to move more data than electronic counterparts,” said Peter Delfyett.
Optics Letters is describing the new optical communication link by a multi-institutional group. The 40-channel system combines a frequency comb lightsource based on a new photonic resonator (NIST), with a mode-division multiplexer optimized by Stanford University researchers. Each channel can carry information in the same way that different stereo channels transmit different music stations.
Chinmay Shirpurkar (co-first author) said, “We show that these frequency combs are possible to be used in fully integrated optic interconnects.” “All of the photonic components were made with silicon-based material which shows the potential to make optical information handling devices using low-cost and easy-to-manufacture optical connectors.
The new technology can be used to improve internet data transmission and could also be used for faster optical computers. This could allow for high computing power that is required to support large-scale emulation, artificial intelligence, machine learning, and other applications.
Using multiple light dimensions
This new work was carried out by research teams that included Firooz Alfouni of Penn, Scott B. Papp of NIST, JelenaVuckovic from Stanford University, and Delfyett of CREOL. It is part the DARPA Photonics Package for Extreme Scalability program. This program uses light to greatly improve digital connectivity in packaged integrated circuits by using microcomb-based light source.
Researchers created the optical link by using tantalum pentoxide waveguides (Ta2O5) on a silicon substrate. The silicon substrate was then fabricated into a ring that has a nanopatterned oscillation. The photonic crystal micro-ring resonance converts a laser input to ten wavelengths. The mode-division multiplexer, which transforms each wavelength into four different beams with different shapes, was also developed and optimized by the researchers. This spatial dimension allows for a fourfold increase of data capacity, resulting in 40 channels.
After the data has been encoded on each beam shape and beam color, the light beam is recombined and sent to its destination. The wavelengths and beam shapes of the final destination are separated so that each channel can receive and be detected separately, without interfering with other channels.
Jizhao Zang, co-first author at NIST, stated that “our link has an advantage because the photonic crystal resonance enables easier soliton generator and a flatter spectrum than those demonstrated using conventional ring resonators.” These features are advantageous for optical data links.
Inverse design delivers better performance
The researchers used photonic inverse design, a computational nanophotonics design approach to optimize mode division multiplexer. This approach allows for more efficient exploration of a wide range of designs, while also offering smaller footprints and better efficiency.
“The photonic-inverse-design approach to our link makes it highly customizable to meet specific applications,” stated Kiyoul Yang, co-first author at Stanford University.
The new device passed simulations with no problems. Crosstalk was less than 20 dB in tests. The link transmitted data without errors in 34 of the 40 channels. It used a PRBS31 pattern to transmit data, which is a standard for testing high-speed circuits under strain.
Researchers are currently working on improving the device by adding photonic crystal micro-ring resonances that produce more wavelengths and using complex beam shapes. These devices could be commercialized by fully integrating a transmitter chip and receiver chip. They would have high bandwidth, low power consumption, and a small footprint. This could allow for the next generation optical interconnects to be used in data-center networks.
Open-source code is available for the photonic optimization software in the paper on GitHub.
Source code: github.com/stanfordnqp/spins-b
