SIJ recently caught up with Timothy Vang, vice president of marketing and applications for Semtech’s Signal Integrity Products Group about the company’s latest product for 50Gbps PAM4 5G front haul deployments, how signal integrity and RF/wireless design overlap, and what is next for the team at Semtech. Below is part of our conversation (edited for brevity).
Prior to joining Semtech, Timothy was the executive vice president of Archcom Technology. He founded VSK Photonics in 2000 and has held roles at companies such as TRW, Jet Propulsion Laboratory (NASA), and AT&T Bell Laboratories. Timothy received his Ph.D. in Electrical Engineering from the University of Bradford.
SIJ: Talk to us about your customers’ needs for low latency in their applications. How has this changed? What is driving it? And what are the technical challenges?
Timothy Vang (TV): In supercomputing data centers with compute and data intensive applications, data availability and timing is critical. As the complexity of mathematical modeling increases, the need for additional compute power grows. In environments that strive to maximize compute throughput and reduce server idle time, low latency interconnects are critical, as every nanosecond of interconnect delay reduces a supercomputer’s overall performance. In these parallel computing environments, interconnect latency has a large effect on overall performance and the lowest latency is required.
Another need for reduced latency comes with the implementation of artificial intelligence (AI) in data centers, which can offer highly desirable services to consumers. The use of AI requires additional interconnects within a single data center due to the parallel compute algorithms used and the latency, or time delay, of a data center’s interconnects, which affects the overall performance. Implementing analog CDR PAM4 optical interconnects alleviates some of the common problems data centers face. The reduced latency of analog PAM4 solutions is a key benefit for AI and for high-performance compute data centers where reducing CPU wait times greatly enhances the overall compute efficiency and the low power of analog CDRs provides more power budget for the servers.
SIJ: Tell us a bit about your company’s product portfolio for signal integrity.
TV: Our optical networking product platforms provide high-performance signal integrity for optical module solutions used by leading companies in hyper scale data center applications, enterprise networking, wireless infrastructure, and passive optical network/fiber-to-the-X markets. We offer optical, analog, and mixed-signal transceiver IC portfolios, which support all main optical communications applications.
Semtech’s Tri-Edge™ PAM4 clock and data recovery (CDR) technology is the first analog PAM4 retiming product platform available on the market for optical communication links. The technology addresses the data center and high-performance computing (HPC) market, as well as the 5G wireless fronthaul, midhaul and backhaul markets, enabling optical links from 100m to 40km.
SIJ: Your company recently rolled out the GN2255, a Tri-Edge clock data recovery (CDR) IC to enable emerging 50Gbps PAM4 5G front haul deployments. Tell us a bit about the development of this product and how it evolved from your data-center version of this product?
TV: The Tri-Edge GN2255 is a bidirectional PAM4 CDR with integrated driver for directly modulated lasers (DMLs) enabling 50G PAM4 optical links in 5G networks. It is the first product in our Tri-Edge wireless platform that will enable multiple optical modules for 5G front haul. The GN2255 is based on the data center Tri-Edge IP, but adds in capability to work with low cost transmit optical assemblies (TOSAs) and receive optical assemblies (ROSAs) needed in wireless deployments. The GN2255 combines Semtech’s proprietary analog Tri-Edge technology with enhanced laser driver compensation, to enable IEEE-compliant optical modules over industrial temperature ranges.
SIJ: What were the technical challenges in developing GN2255, and how did you overcome them?
TV: As the 5G ecosystem transitions to 50G PAM4 links, the deployment will be in the form of SFP56 optical modules. The small size and limited power budget of these modules is strongly supported by the Tri-Edge Technology, as the alternative DSP technology adds size, power, and latency that are not acceptable in the 5G deployments. Semtech worked closely with 5G system vendors to ensure our platform met their system performance, power, and latency requirements, and we met with the optical module vendors to ensure we designed our solution to deliver the electrical and optical performance needed based on the TOSAs and ROSAs used.
SIJ: What applications is the GN2255 serving?
The GN2255 is targeting the optical links in 5G front haul. Today, 5G requires 25Gbps links, but as 5G moves to higher radio frequencies and wider channel bandwidths, front haul links will require up to 50Gbps per channel capacity.
As 5G delivers more bandwidth, the GN2255 then supports a number of emerging 5G applications, including edge computing, enhanced mobile broadband and device streaming, and fixed wireless access (i.e., home Internet).
SIJ: How do you see the challenges of signal integrity and RF/wireless design overlapping? What does each discipline need to realize about the other?
TV: The challenges of signal integrity and RF design really merge at higher speeds. As optical links move to higher and higher speeds, they are borrowing from RF designs by implementing PAM4 and other modulation schemes. These modulation schemes increase the spectral efficiency of the signaling, but degrade the signal to noise level – or the signal integrity of the system. So, the value of optimizing signal integrity becomes even more important. In this way, both disciplines benefit each other.
SIJ: What is the next big technical challenge facing your designers? How are current data-consumption trends effecting IC development?
TV: The next challenge is to deliver optimized power, cost and latency performance for next-gen optical interconnects across data center, wireless and other markets. This includes enabling higher speeds, longer reaches and new lower cost optics. Current data consumption trends suggest an ever-increasing demand for data and compute, and we are seeing a convergence of infrastructure for data centers and wireless as data centers move toward edge compute models that are tied directly into 5G networks. We are investing heavily to deliver Tri-edge solutions to help meet that increasing demand.