Granite River Labs (GRL), a global leader in engineering services and test solutions for connectivity, today introduced a comprehensive methodology for characterizing PAM4-enabled 200 Gigabit Ethernet optical transceivers to support the growing need for reliable, high-speed connectivity in data center applications. The methodology, developed in collaboration with Anritsu, Tektronix, and iXblue, is documented in the application note, “Constructing a 50G PAM4 Optical Stressed Receiver Eye.” GRL offers independent test services from their world-wide labs following this methodology and others for high speed networking interfaces, as well as consultation for hardware engineers to implement or modify the methodology in their own lab.
The expansion in Ethernet data bandwidth to 200G and beyond is a direct result in the rapid growth of capacity in modern data centers, which demands higher capacity data center network infrastructure. Many networking standards have moved to Pulse Amplitude Modulation – 4 (PAM4) to successfully achieve ever-increasing data rates. These fast bi-directional signaling technologies necessitate careful and thorough characterization of the transmitter and receiver.
GRL’s application note explains the steps to calibrate the stressed input eye diagram for optical receiver testing in accordance with 802.3bs Clause 121 200GBASE-DR4, an optical interface that specifies four optical lanes operating at 26.5625 Gbaud/s (53 Gbits/s) with PAM4 modulation in parallel across single mode fiber. The 802.3bs 200G optical specifications are supported by a pair of electrical interfaces: four-lane 200GAUI-4 and eight-lane 200GAUI-8.
Testing a 50G PAM4 receiver requires calibrating a “cocktail” of stresses (jitter, noise, etc.) on the signal input to the product under test. Testing an optical receiver presents the added challenge of converting an electrical source into a 50G optical signal with PAM4 modulation that can be reliably and precisely controlled and impaired in both the horizontal (time) and vertical (optical power) directions, and verifying the stressed input eye pattern in accordance with the specification requirements. GRL’s application note explains how to achieve this calibration using the following primary instruments:
- Anritsu MP1900A Pattern Generator and Error Detector with dual Pulse Pattern Generators (PPGs).
- iXblue Photonics 28Gbaud PAM4 ModBox optical reference transmitter, which performs the electrical to optical conversion and allows for fine-tuning the stressed optical eye.
- Tektronix DPO75902SX 59GHz real-time oscilloscope, equipped with DP070E1 33GHz optical probe/reference receiver and PAM4 analysis software.
“GRL’s proactive development of optical test methodologies benefits the entire ecosystem,” said Ara Nazarian, Vice President of Engineering at Rockley Photonics. “We expect that GRL’s support will be instrumental in providing independent testing of our silicon photonics products for high volume optics applications.”
“We are excited that GRL used the Anritsu MP1900A as the critical signal source for their 50G PAM4 optical receiver test methodology, “said Hiroshi Goto, BERT Business Development Manager of Anritsu Corporation. “The MP1900A outputs high-quality, multi-channel NRZ and PAM4 signals to support characterization up to 400 Gigabit Ethernet, with expandable and high-performance PPG, a high-sensitivity input error detector (ED), and integrated stress sources.”
“For short reach at 850nm, or longer reach in the o-band, iXblue PAM4 Optical Reference Transmitters address the need for very high speed test solutions for next-generation data center applications,” said Hervé Gouraud, Sales and Marketing Manager, iXblue Photonics. “Operating at up to 56 Gbaud, featuring eye high quality diagrams with low jitter and very fast rise and fall times, the high linearity Optical Reference Transmitter PAM4 ModBox proved an excellent centerpiece for GRL’s methodology.”
“Keeping pace with the fast evolution of data center networks requires instruments with high bandwidth and high dynamic range because of the smaller amplitude sizes and tight margins of PAM4 modulated signaling,” said Karen Brownell, Segment Lead Optical Networking at Tektronix, Inc. “Characterizing optical signals with the precise analysis advantages afforded by a real-time oscilloscope requires a robust optical reference receiver and analysis software, and the DPO75902SX with DPO7OE1 calibrated optical probe and analysis software are a perfect fit for GRL’s methodology.”
“While most high speed networking standards specify physical layer requirements, they generally do not prescribe specific test methodologies, leaving it to the adopter and test equipment manufacturers to interpret and apply an approach on the bench,” said Miki Takahashi, Vice President of Engineering for Granite River Labs. “Even through this application note specifically addresses 200GBASE-DR4, GRL hopes that the guidance and insights will help engineers working on next generation data center designs produce repeatable physical layer test results efficiently and with confidence across a broad array of standards.”
To learn more about this methodology or to schedule a consultation, contact Quintin Anderson, GRL co-Founder and Chief Operating Officer.
About Anritsu Corporation
Anritsu Corporation is a global provider of innovative communications test and measurement solutions for 120 years. Anritsu’s “2020 VISION” philosophy engages customers as true partners to help develop wireless, optical, microwave/RF, and digital solutions for R&D, manufacturing, installation, and maintenance applications, as well as multidimensional service assurance solutions for network monitoring and optimization. With offices throughout the world, Anritsu has approximately 4,000 employees in over 90 countries. Learn more at https://www.anritsu.com/.
About iXBlue Photonics
iXBlue Photonics helps photonics engineers all around the world to get the most out of the light by providing high performance, innovative and reliable photonic solutions. We offer specialty fibers, Bragg gratings and optical modulation solutions based on the company integrated modulators for a variety of applications including optical communications, fiber lasers and amplifiers, fiber optics sensors, space and sciences. Learn more at https://photonics.ixblue.com/.
About Tektronix
Headquartered in Beaverton, Oregon, Tektronix delivers innovative, precise and easy-to-operate test, measurement and monitoring solutions that solve problems, unlock insights and drive discovery. Tektronix has been at the forefront of the digital age for over 70 years. Join us on the journey of innovation at https://www.tek.com/.
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