Evaluation Engineeering - 14

COMMUNICATIONS TEST

Optical coherent transmission technology was originally used in long-haul
transmissions, but now encompasses
metropolitan networks and data center
interconnects. Keysight's application
note goes on to say the key challenges in
making measurements on coherent optical systems are in providing known, repeatable, clean, and distorted test signals
at data rates above 32 GBd and with the
flexibility to support diverse modulation
formats.
To dive deeper into the topic of optical
communications technology and the testing involved, we at Evaluation Engineering
gathered input from several vendors about
trends they're seeing, challenges, customer needs, and what newer solutions are
available. Here's what they told us.

What's trending?
What technology or market trends are
vendors seeing in the area of optical communications test?
Hiroshi Goto, business development
manager at Anritsu Company: "Data
center and network traffic volumes are
increasing exponentially as 5G networks
are rolled out and Big Data applications
expand. The result is that physical-layer
devices must accommodate ultra-highspeed data transmissions using technologies such as PAM4 to transport 100 Gbps
per lane or per wavelength."
Heike Tritschler, marketing segment
lead - optical & electrical networking,
and Pavel Zivny, domain expert - serial
data measurements at Tektronix: "The
optical test spans 26 GBd devices and 53
GBd devices, majority of them multiple
lanes-up to eight lanes. This is a large
number of devices/lanes to test."

Challenges
What key challenges are optical communications test vendors or their partners
facing today?
Goto, Anritsu Co.: "The integration of
100 Gbps PAM4 data with Forward
Error Correction (FEC) means that a
new test metrology must be established.
Test solutions need improved sensitivity

14

EVALUATION ENGINEERING SEPTEMBER 2019

to accurately analyze PAM4 signals because those signals automatically lose 10
dB optical signal-to-noise ratio (OSNR)
compared to NRZ signals. In addition to
ONSR, the signal integrity of PAM4 affects
the eye closure of the PAM4 signal."
Tritschler and Zivny, Tektronix: "The
methodology changes, in particular the
TDECQ test, came just at the same time
as the big change in architecture (PAM4).
This created a lot of uncertainty that has
been worked through."

What are customers asking for?
What features or innovations are customers asking for in optical communications
test?
Goto, Anritsu Co: "Engineers need a test
solution that is simple to operate and can
analyze and characterize PAM4 signals
and data quickly. They also need instruments that can conduct optical stressed
eye testing for 100 Gbps PAM4."

it does the traditional optics vendors. A
new focus for us is the backhaul for 5G."

Compliance/Regulatory
What recent or upcoming compliance,
regulatory, or compatibility issues-if
any-are impacting technology in optical communications test?
Goto, Anritsu Co.: "IEEE 802.3bs
(200GAUI-4 and 400GAUI-8), 802.3cd
(CR4, KR4), and OIF-CEI-56G-VSR/MR/
LR, OIF-CEI-112G-VSR address 100G
PAM4 optical signal characterization,
while InfiniBand Trade Association
(IBTA) HDR establishes standards to
verify 200G interconnects. Anritsu has
been involved in industry associations
and standards bodies, which has allowed
the MP1900A to support standards-based
specifications."

Tritschler and Zivny, Tektronix: "Users
need fast compliance testing on many
channels; and users are asking for help
interpreting the results."

Tritschler and Zivny, Tektroni x:
"Tektronix is participating in the work
at the IEEE 802.3. As with any new technology, there is a learning cycle and this
is impacts our direction. We see our work
with IEEE as a very productive involvement, which is enabling rather than burdening our work."

Areas of focus

Now on the market

Optical communications test spans applications from datacenters, to 5G-related
networks, to photonic integrated circuits,
and beyond. Here's what vendors told us
they're focusing on.

Here's what vendors shared as newer
solutions or accessories they've recently
introduced in the area of optical communications test, and their key features.

Goto, Anritsu Co.: "With our MP1900A,
Anritsu is focused on verifying
the design and manufacture of
high-speed data center interconnects and backplanes such
as active optical cable (AOC)
and QSFP-DD optical modules. The MP1900A BERT supports high-speed computer bus
interfaces, such as PCI Express
5.0 and USB 3.2, as well as nextgeneration 400G Ethernet communications interfaces."
Tritschler and Zivny, Tektronix: "We see a
lot of overlap in the key areas-datacenter
attracts the PIC suppliers just as much as

Anritsu Company's MP1900A BERT was recently
enhanced with four PAM4 BERT options.

Goto, Anritsu Co.: "Anritsu recently enhanced its MP1900A BERT with four
PAM4 BERT options that add multichannel synchronization, multilane FEC
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