23 May 2013

IQE and Chalmers report first 40Gb/s VCSELs operating at up to 85°C for data-centers

Epiwafer foundry and substrate maker IQE plc says that vertical-cavity surface-emitting laser (VCSEL) devices using wafers produced at its Cardiff, UK facility have broken the 40Gb/s barrier at high temperatures, which is reckoned to be a key milestone in the adoption of photonic technologies for a wide range of data communications applications.

Optical communications provide the only reliable means of transferring the large volumes of data at the ultra-high speeds needed in data-centers, says IQE. The computing environments in which the data is transferred generally operate at elevated temperatures, making reliable operation at high temperature an essential element for the deployment of optical components.

A joint paper ‘High-Speed Oxide Confined 850-nm VCSELs Operating Error-Free at 40Gb/s up to 85°C’ by Chalmers University of Technology and IQE published on 15 April in IEEE Photonics Technology Letters (vol. 25, no. 8, p768, 2013) reports the development of VCSEL devices operating at data rates of up to 47Gb/s at 25°C and 40Gb/s at 85°C.

VCSELs provide the primary light source for short-reach optical communication and currently provide the enabling technology for high-capacity optical interconnect cables in storage area networks such as data-centers and server farms. VCSEL-enabled multimode fibre-optic interconnects optimized for transmission speed at a wavelength of 850nm are also used in high-performance computing systems such as computer clusters and supercomputers.

Current high-speed optical interconnects use VCSEL technology to operate at serial data rates of 10-14Gb/s, with devices expected to perform at 25–28Gb/s under development. Next-generation optical interconnect standards are expected to require data rates in excess of 40Gb/s. Such devices will be required to operate at the high ambient temperatures expected inside datacoms equipment.

The results were achieved at a modulation bandwidth of 27GHz at 25°C and 21GHz at 85°C, which is the highest for any VCSEL, and the data rate is the highest of any VCSEL-based optical link without equalization, it is reckoned. This is also the first 40Gb/s VCSEL operating at elevated temperatures, which is of key importance for practical applications, says IQE.

The firm says that the results also generated commercial interest when they were presented at the Optical Fiber Communication Conference (OFC) in Anaheim, CA, USA in late March.

“Photonics applications are emerging as a key enabling technology and the deployment of devices such as VCSELs is expected to rapidly increase over the coming years as global data usage grows exponentially,” says IQE’s CEO Dr Drew Nelson. “IQE is pleased to work with notable experts in the field such as Chalmers University of Technology in the development of next-generation products.”

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