mobile | classic
Dataweek Electronics & Communications Technology Magazine

Follow us on:
Follow us on Facebook Share via Twitter Share via LinkedIn


Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


100G network testing challenges
20 July 2011, Test & Measurement

The combination of digital media, personal computing and global networking is creating a radical shift in the telecom industry. The key trend is towards IP-fixed/mobile network convergence for the delivery of voice, video and data applications with IP (and Ethernet) as a common universal platform fuelled by the exponential growth of video, gaming, collaboration and cloud computing applications. This trend significantly stresses the transport backbones, which have been built on 10G wavelengths, and is driving the need for upgrades to 40G and 100G.

The IEEE 802.3ba standard defines a single architecture capable of supporting both 40G and 100G Ethernet, while producing physical layer specifications across backplanes, copper cabling, multimode fibre and single-mode fibre. The new 40G/100G Ethernet architecture is based on the concept of virtual lanes or physical coding sublayer (PCS) lanes, which would get multiplexed and transported over the four or 10 parallel wavelengths on a single fibre. For example, 100GBASE-LR4 has four optical wavelengths of 25G on the fibre coming from 10 electrical CAUI signals of the Gbps on the host side.

In the process of transmitting a 40G/100G Ethernet signal (as illustrated in the figure), the Ethernet packet is broken into blocks, which are then mapped into PCS lanes using a round robin distribution. To ensure a clean realignment of the entire block and to manage the skew between blocks at the receive side, a marker block is added on each logical lane. This marker is sent at a fixed cycle of 210 μs.

The 20 PCS logical lanes will then be multiplexed down to 10 lanes at 10 Gbps, also called CAUI lanes, using the physical medium attachment (PMA) located in the CFP optical interface. The unique property of the PCS lanes is that no matter how they are multiplexed together, all bits from the same PCS lane follow the same physical path; this enables the receiver to correctly reassemble the aggregate channel. At the same time, the unique lane marker enables the deskew operation in the receiver.

The 40G/100G Ethernet implementation introduces new challenges at the electrical and optical layers. These challenges are due to the data distribution over multiple channels, combined with the skew effect. This triggers the need to test individual concepts, such as PCS lanes, PCS skew and the alignment markers, to ensure that the 40G/100G Ethernet device under test (DUT) supports the proper realignment capabilities, thus compensating for physical characteristics of the link. By inserting multiple UI of skew on different lanes, engineers can identify receiver buffer issues, which is crucial when validating the skew tolerance of the 100G system.

Since many of the initial deployments of 100G Ethernet address bandwidth needs at the core, optical transport networks (OTNs) for transport applications become prevalent. The newly defined OTU4 (112 Gbps) rate in ITU-T G.709 addresses the need for carrying 100G Ethernet services over OTN. This is in addition to the fundamental benefits of OTN in general, such as supporting operations, administration and maintenance (OA&M) procedures, as well as providing a standardised forward error correction (FEC) mechanism for enhanced network performance and better deployment economics.

Similar to those defined by IEEE P802.3ba, ITU T SG 15 had defined a new layer on top of the optical channel transport unit (OTU), which is known as the ‘optical channel transport lane’ (OTL) protocol. The OTL layer is defined as OTL x.y, where x is the data rate and y is the number of optical lanes. For example, OTL 4.4 represents an OTU4 signal running on four wavelengths at 28G.

OTL introduces elements such as OTL lanes, OTL skew and OTL alignment markers, which are conceptually similar to the PCS lanes, PCS skew and the PCS alignment marker described in IEEE P802.3ba. As with Ethernet, the OTL layer uses the logical lane markers to realign all the sent blocks. The main differences in this case are that the marker is embedded in the frame alignment signal (FAS) and the multiframe alignment signal (MFAS) Bytes of the OTN frame. Therefore, when validating 100G devices supporting OTN capabilities, it is crucial to test the skew at the OTL layer, in addition to testing all other OTN layers, including OTU4, ODU4, OPU4 and FEC to ensure the proper mapping and de-mapping of 100G Ethernet client signal and reporting of fault management.

Qualifying the performance of the OTN physical layer by testing the line rate of the signal with a pseudo random bit sequence (PRBS) pattern is a key step. This test is critical for designers and system engineers during the development of the 100G line cards. One of the main tests is to inject a complex PRBS pattern onto each of the physical lanes and analyse the bit error rate (BER) at the receiver end. The power to inject different patterns per lane provides a complete overview of the crosstalk between the channels as well as a maximum density pattern, which can be configured to verify the receiver PLL response to unbalanced bit density.

EXFO’s FTB-851100G Packet Blazer 100G/40G Ethernet test module offers a wide range of 40G/100G testing capabilities for the physical layer with its signal conditioning interface designed to qualify CFPs to IP testing at 40G/100G line rates and Ethernet mapping into OTN. These tests are critical from network equipment manufacturers’ perspective during the development, design and validation stages.

For more information contact Chris Nel, Lambda Test Equipment, +27 (0)12 349 1341,,

Supplied By: Lambda Test
Tel: +27 12 349 1341
Fax: +27 12 349 1493
  Share on Facebook Share via Twitter Share via LinkedIn    

Further reading:

  • 4-channel PC-based oscilloscope
    28 August 2019, Vepac Electronics, Test & Measurement
    The newly developed Model 1330 from Peaktech is a 4-channel PC oscilloscope with 100 MHz bandwidth and 1 GSps sample rate, which is suitable for mobile use on a laptop, and permanent installation in control ...
  • Handheld PoE tester
    26 June 2019, Coral-i Solutions , Test & Measurement
    Ideal Networks has launched a new handheld tester that eliminates guesswork when installing, maintaining and troubleshooting PoE devices and data cabling. PoE Pro measures and reports PoE class, voltage/voltage ...
  • Debugging probe for STM32 MCUs
    31 July 2019, Altron Arrow, Test & Measurement
    The STLINK-V3MINI probe, new from STMicroelectronics, combines the features of the STLINK-V3SET with standalone simplicity for faster programming and ease of use. The compact, portable probe can be ...
  • Digitiser for advanced applications
    31 July 2019, Comtest, Test & Measurement
    Tektronix, Inc. has unveiled the 6 Series low-profile digitiser, a 4-channel instrument offering up to 8 GHz bandwidth, 25 GSps sampling rate and a 12-bit ADC (analog-to-digital converter) on every channel, ...
  • Cost-effective tools for makers and small businesses to innovate
    31 July 2019, TRX Electronics, Test & Measurement
    In addition to professional engineers, makers and hobbyists are now able to contribute significantly to innovation in our modern world – as they can develop ideas with passion and without the financial and logistical constraints that often stifle ideas in large corporations.
  • Sniffer software gets J-Link RTT terminal plugin
    31 July 2019, RF Design, Test & Measurement
    Despite being fans of the Real-Time Trace (RTT) feature in Segger’s J-Link debug probes, engineers at Tibbo found that Segger’s own RTT Viewer software was a bit too simple for their needs, and so created ...
  • EXFO launches new category of fibre testing solutions
    26 June 2019, Lambda Test, Test & Measurement
    EXFO has launched what it describes as the first optical fibre multimeter (OFM). Called Optical Xplorer, it aims to make fibre testing simple for all frontline technicians, whether beginner or expert, ...
  • Handheld industrial Ethernet tester
    26 June 2019, Coral-i Solutions , Test & Measurement
    Ideal Networks has launched NaviTEK IE, a handheld network tester designed for commissioning, preventative maintenance and troubleshooting of PROFINET industrial Ethernet networks, plus standard Ethernet ...
  • PCB cleaning diagnostic system
    26 June 2019, Electronic Industry Supplies, Test & Measurement
    The Verinas system from PBT Works is a dedicated piece of AOI (automatic optical inspection) equipment for evaluating remaining flux residues on PBT glass test boards. The system can be used by electronics ...
  • 2-channel digital storage oscilloscope
    26 June 2019, Vepac Electronics, Test & Measurement
    The Model 1335 is PeakTech’s latest-generation 2-channel digital storage oscilloscope (DSO) for the education and professional sector. With its attractive price-performance ratio, modern technology and ...
  • New MDO and MSO from Tektronix
    26 June 2019, Comtest, Test & Measurement
    Tektronix has grown its portfolio with the launch of the 3-Series mixed domain oscilloscope (MDO) and 4-Series mixed-signal oscilloscope (MSO) delivering the most powerful, versatile and easy-to-use oscilloscopes ...
  • Body-worn EMF monitor
    29 May 2019, Accutronics, Test & Measurement
    For those working with high-intensity electromagnetic fields (EMF), such as in the near field region of radar antennas, broadcast transmitters or cellular base stations, it is vital to wear personal safety ...

Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronics Buyers’ Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Terms & conditions of use, including privacy policy
PAIA Manual


    Classic | Mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.