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100G/lane linear drive optical solutions provide optimal power consumption

How many pit stops does a race car driver make? As few as necessary to win a race.
How many times does a signal need to be retimed in a link? Ideally, once. By the receiving end point which then processes the data. If the far end receiver has the horsepower to compensate for the entire channel, it should be given the opportunity to do so. If the receiver is not capable of meeting link level performance, retiming can be leveraged to improve bit-error performance by segmenting the link into more manageable portions. Retiming is akin to swapping the engine of a car at each pit stop. Yes, you get a brand-new engine, but it comes at a cost. In an optical link, each retiming point comes with associated power, latency, and performance. As the industry moved to PAM-4 and now 100Gb/s per lane, the cost vs. benefit for retiming has changed significantly based on the capability of the end point ASICs. This dynamic necessitates taking a fresh look at optimal link partitioning.

The power consumption associated with retiming in optical modules for 100G/lane is material. 800G multi-mode optical modules with DSP functionality can consume more than 13W. This is in stark contrast with 800G multi-mode optical modules leveraging MACOM PURE DRIVE technologies consuming less than 4W. That is a jaw-dropping 70 % reduction in power . Single-mode modules benefit similarly in absolute power savings by removing DSP/retiming from the module. Not only is that power saved from a consumption and system cooling perspective, but it is also a reduction of heat sitting next to optical components within the module.  Retiming/DSP ICs are also expensive. They are designed in the latest fine geometry CMOS nodes and require ancillary BOM components. Avoiding retiming therefore translates to material module cost savings. Lastly, DSP/Retiming functionality adds latency, both at power up based on multiple segments needing to adapt, as well as in mission mode based on serial-to-parallel conversions needed to digitally process the signal. This is in contrast with lightning quick (on the order of pico-seconds) time of flight through an optical module with MACOM PURE DRIVE technology since the signal is kept serial.

To unlock the benefits of Linear Drive within optical modules, it is necessary to allow endpoint ASICs to exercise their capabilities to the fullest and minimize channel impairments. To enable this, MACOM has developed its line of MACOM PURE DRIVE components to linearly compensate for channel losses as well as perform high bandwidth electro-optical conversion with appropriate optical components to achieve required link performance. Think of this as a quick tire change before the signal is sent over the optical fiber. To complete the link, within the latest 100G/lane ASICs, equalization and retiming capabilities leverage the latest process nodes, providing the margin necessary to achieve required performance.

With MACOM PURE DRIVE technologies, the optics industry has an opportunity to materially improve efficiency through optimization and specialization. Let’s shift gears and take the checkered flag.