TOKYO, Japan, March 25 — NEC Corporation has developed groundbreaking silicon integrated optical switch technology whose port count can be extended flexibly according to network size. This has been achieved by reducing optical insertion loss in compact, low-power optical switch modules that utilize silicon photonics-based optical integration technologies.
In this latest advancement, NEC has developed a spot size converter that optically couples silicon optical circuits and optical fibers with different light beam radiuses (spot sizes), dramatically reducing optical coupling loss to approximately one-tenth of previous levels. This improvement means that high capacity optical signals can be split into a larger number of branches owing to reducing optical coupling loss at optical switches. As a result, by adding switch modules, the number of optical switch input or output ports can be expanded by approximately ten times when compared with previous offerings, which allows the development of optical networks that are highly resilient to demand fluctuations and failures.
“As optical networks need to be reconfigured in the event of increased demand or failures, optical switches are being installed, which efficiently reconfigure high capacity optical signal paths without optical-electrical signal conversion. However, with conventional optical switching technologies, growing optical switch sizes and increased power consumption have stood in the way of efforts to expand network size. This newly developed technology utilizes silicon photonics to produce compact and low-power optical switches, allowing the development of optical networks that are highly resilient to demand variation and failures,” said Yuichi Nakamura, general manager, Green Platform Research Laboratories, NEC Corporation.
The main features of the technology are as follows.
- Development of a groundbreaking low-loss optical switch module that can be applied to optical networks
Using narrow silicon optical waveguides, compact and low-power optical switch functions have been integrated on silicon optical circuit chips with a high density. NEC developed a new proprietary spot size converter that optically couples silicon optical circuits and optical fibers with different light beam radiuses (spot sizes), drastically reducing optical coupling loss between silicon optical circuit chips and optical fibers down to approximately one-tenth of previous levels. Through this advancement, NEC has achieved low loss on top of previously proved polarization insensitivity and a high extinction ratio in developed silicon optical switch modules.
- Establishment of a simple scheme for extending optical switch systems
The arrangement of the many small thermo-optical elements that perform optical signal path switching on the silicon optical circuit have been optimized using NEC’s proprietary expertise to minimize thermal interference between elements and dependence on chip temperature fluctuations. As a result, in contrast to the previous version where control current values differed by individual thermo-optical elements, single control current settings have been used for all elements across the entire switch system. As well as reducing control circuit area by around half, adjustment work has been dramatically reduced, allowing the optical switch port count to be easily expanded with the addition of optical switch modules without increasing control circuit size.
Part of the technologies developed on this occasion have been pursued as a part of Research and Development on Photonic Transparent Transmission Technologies (λ-Reach Project), a project commissioned by the National Institute of Information and Communications Technology (NICT) that NEC has been involved with since 2011.