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Microsemi Pushes OTN to Terabits

April 3, 2018

Author: Bob Wheeler

Microsemi’s Digi-G5 is the industry’s first OTN framer/mapper chip to handle 400G Ethernet as well as Flex Ethernet (FlexE). Due to sample this quarter, it combines up to 1.2Tbps of bandwidth and unprecedented flexibility. It follows by three years the 400Gbps Digi-G4, which handled OTN rates as high as 100Gbps. These products come from the company’s 2016 acquisition of PMC-Sierra.

The Digi-G5 starts with obvious improvements such as a move from 28nm to 16nm technology and support for 400GbE-over-OTN. It also adopts 56Gbps PAM4 long-reach serdes, which serve both client- and line-side interfaces. For standard Ethernet rates, it handles 2x400GbE, 12x100GbE, and 24x25GbE. The new chip also, however, adds flexible port rates enabled by new standards. Specifically, it implements FlexE on the client side, aggregating as many as six 100GbE ports into a single flow of up to 600Gbps. On the line side, the chip handles the ITU’s new OTUCn scheme and flexible OTN short-reach interface (FlexO), which likewise aggregate Nx100Gbps channels.

Like its predecessor, the Digi-G5 offers subwavelength AES-256 encryption, allowing each customer’s traffic to be encrypted end to end as it’s transported over shared wavelengths. It supports up to 600Gbps of wire-speed encryption, which increases latency by only 180ns. The new chip adds an ARM CPU (of undisclosed type) to offload statistics collection, protection switching, and other real-time tasks from the external host CPU. Its SDK implements a hardware abstraction layer that exposes a high-level API to the OEM software stack.

Historically, five major vendors developed optical-transport framer/mapper chips, but now only Microsemi remains active. At the same time, Microchip is acquiring Microsemi, with the deal expected to close this quarter. Lacking merchant competition, the Digi-G5 positions the company to continue its share gains as OEMs roll out next-generation OTN systems.

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