Keysight N4891A 400GBASE
FEC-Aware Rx Test Solution
User Guide
Notices
CAUTION
WARNING
© Keysight Technologies 2021
No part of this manual may be reproduced in
any form or by any means (including electronic storage and retrieval or translation
into a foreign language) without prior agreement and written consent from
Keysight Technologies as governed by
United States and international copyright
laws.
Manual Part Number
N4891-90119
Edition
Second edition, January 2021
Keysight Technologies Deutschland GmbH
Herrenberger Strasse 130,
71034 Böblingen, Germany
Technology Licenses
The hardware and/or software described in
this document are furnished under a license
and may be used or copied only in accordance with the terms of such license.
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The Software is “commercial computer software,” as defined by Federal Acquisition
Regulation (“FAR”) 2.101. Pursuant to FAR
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Defense FAR Supplement
(“DFARS”) 227.7202, the U.S. government
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Accordingly, Keysight provides the Software
to U.S. government customers under its
standard commercial license, which is
embodied in its End User License Agreement
(EULA), a copy of which can be found at
http://www.keysight.com/find/sweula. The
license set forth in the EULA represents the
exclusive authority by which the U.S. government may use, modify, distribute, or disclose the Software. The EULA and the
license set forth therein, does not require or
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Warranty
THE MATERIAL CONTAINED IN THIS
DOCUMENT IS PROVIDED "AS IS," AND IS
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Safety Notices
A CAUTION notice denotes a hazard. It
calls attention to an operating procedure, practice, or the like that, if not
correctly performed or adhered to,
could result in damage to the product
or loss of important data. Do not proceed beyond a CAUTION notice until the
indicated conditions are fully understood and met.
A WARNING notice denotes a hazard. It
calls attention to an operating procedure, practice, or the like that, if not
correctly performed or adhered to,
could result in personal injury or death.
Do not proceed beyond a WARNING
notice until the indicated conditions are
fully understood and met.
Contents
1 Introduction
2 Getting Started with the N4891A Solution
Contents
Safety Issues 8
Safety and damage messages 8
Safety Warnings 8
Introduction to the N4891A Solution 9
N4891A 400G Multi-Port Tester 9
N4891A 400GBASE FEC-aware Receiver Test Solution 9
Specifications 10
Chassis Setup 12
Installing the N4891A equipment 12
Front Panel Overview 14
Controlling the Equipment 15
Connecting to the N4891A chassis 15
Configuring the Hostname 16
Setting up the N4891A solution 16
Installing License 18
3 Using the KiOS Interface for the N4891A Solution
Accessing the KiOS interface 22
Landing Page 22
Line Speed Control 25
Port Settings 26
Mode 27
BERT 28
Host QSFP-DD 29
Statistics page 31
BERT statistics page 31
FEC Statistics Page 34
eBERT Statistics 38
CMIS 40
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 3
Contents
Menu Options 43
New tab 43
Test A u tomation 43
System Admin 44
System Logs 46
Software Update 47
License Manager 49
Help 51
4 Testing Optical Transceivers
About Optical Transceivers 54
Basic Functional Testing 55
Workflow 55
5 FEC-aware Receiver Testing
Hardware & Software Requirements 58
N4891A options 58
M8070B requirements 59
M8045A options 59
Accessories 59
Recommended Port setup 59
Setup Configuration 61
Connection Setup 61
Procedure 62
Setting PRBS Mode 65
Loopback Configuration—BERT mode 65
Checking BER on STATS View 66
Setting FEC-aware Mode 67
Loopback Configuration—KP4 FEC-aware mode 67
Synchronizing with M8040A 68
Receiver Compliance Testing 70
Jitter Injection 71
Using the M8070B DUT Control Interface 72
Testing 100G/l Optical Interfaces 72
4 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Troubleshooting 74
Scenario 1: Link is not up in BERT mode 74
Scenario 2: Link is not up in KP4 mode, BERT mode works as
intended
76
Contents
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 5
Contents
6 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution
User Guide
1 Introduction
Safety Issues / 8
Introduction to the N4891A Solution / 9
Specifications / 10
1 Introduction
Safety Issues
Safety and damage messages
The safety alert symbol is used to indicate a hazard. Specific keywords and additional
graphical representations are used to explain the specific nature of each hazard. Table 1describes
the safety warning and equipment damage icons and textual conventions used in this document.
Table 1 Types of hazard
Type of Hazard Icon Description
CAUTION Indicates a hazardous situation that, if not avoided, could result in minor or moderate injury.
Indicates a hazardous situation that, if not avoided, could result in death or serious injury.
Additional icons are used to indicate specific types of warnings.
Laser radiation hazard warning.
Safety Warnings
Reliable Earthing
Touch Current from Coaxial Cables
Fan Instruction
Electrostatic discharge hazard warning.
WARNING
High voltage hazard warning.
Hot surface hazard warning.
Moving fan blades hazard warning.
NOTICE Indicates a condition or occurrence that could result in property damage.
Protective earthing connection of the socket-outlet should be verified by a SKILLED PERSON.
Connect the shield coaxial cables to building earth in accordance with applicable local, national, and
international electrical codes.
Moving fan blade. Keep body parts away from fan blades.
8 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Introduction to the N4891A Solution
N4891A 400G Multi-Port Tester
The N4891A is a compact Bit Error Rate (BER) and Forward Error Correction (FEC) test system. You
can use it to characterize and quantify, at line rate, the actual BER and FEC performance of silicon
communication devices, ASICs, fiber and copper interconnects, optical transceivers, and the port
electronics of switches, routers, and other networking equipment with 26.5625 GBaud PAM4
interfaces. You can also use it to test the interconnection interoperability for all types of networking
devices and equipment.
It is available in two models: 2-port or 4-port. The 2-port model is field-upgradeable to 4 ports.
For both models, an optional RS-544 (KP4) FEC test capability is available that simplifies FEC lane
testing.
The N4891A is powered by IXIA's KiOS operating system, and includes Layer 1 BERT 400GE test
software. A browser-based user interface makes it easy to run tests and manage the N4891A
equipment. Keysight N4891A and Ixia A400GE-QDD offer the same capabilities and are
interchangeable.
The N4891A chassis can be mounted on a bench-top or in a rack. See “Installing the N4891A
equipment” on page 12 for more information.
Introduction 1
N4891A 400GBASE FEC-aware Receiver Test Solution
When used in combination with the Keysight M8040A, the N4891A offers a unique 400GBASE
FEC-aware Receiver Test Solution. This solution enables measurement of frame loss ratio in 400G
Ethernet links using FEC by supplying one stressed lane, while maintaining the proper FEC striped
test pattern data. The test method is prescribed in the IEEE 802.3 standard clauses 121,122, 124 and
136, 137 and 138 (802.3bs and 802.3cd respectively). This solution provides unique insights to
understand how component and system design trade-offs are affected by Forward Error Correction
(FEC) requirements and to predict the system margin under realistic conditions.
For more information regarding the M8040A J-BERT system, refer to
https://www.keysight.com/find/M8040A.
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 9
1 Introduction
Specifications
Tabl e 2 lists out the specifications for various characteristics of the N4891A chassis. For the more
detailed set of specifications, refer to the N4891A 400GBASE FEC-aware Receiver Test Solution Data
Sheet.
Table 2 N4891A Specifications
Device Characteristics Specification values
Physical Interfaces Native QSFP-DD MSA form factor compatible physical ports
Chassis Configurations 2- or 4-port base chassis system, desktop or rack mount, 2 RU
Chassis Connector Systems Power ON/OFF button
Chassis Clock IN – Electrical Specifications Frequency: 166.015625 MHz +/- 100 PPM
Chassis Clock OUT – Electrical Specifications Frequency: 166.015625 MHz +/- 100 PPM
Hardware Trigger IN / OUT – Electrical
Specifications
Chassis System Electrical Power Operates on 100-240VAC, 50/60Hz,
Chassis System Dimensions 11.14” (L) x 17.4” (W) x 3.65” (H)
Chassis System Weights Hardware only: 21.75 lbs. (9.87 kg)
Temperature (Ambient Air) Operating: 41°F to 95°F (5°C to 35°C)
1 LED per port
Clock IN / OUT: 2 SMA female connectors
Trigger IN / OUT: 2 SMA female connectors
4 USB: (2) USB 2.0 (2) USB 3.0 compatible ports
1 RJ45: 1000/100/10Mbps Ethernet management port
1 Display Port, supports a maximum resolution of 4096 x 2304 @60Hz
50 ohm termination
Minimum = 0.5 Vpk-pk = 0.18 Vrms (sine)
Maximum = 3.0 Vpk-pk = 1.06 Vrms (sine)
HCSL, 50 Ohm
VOH > 0.55V, VOL < 0.15V, Swing > 0.55V
Trigger In: 50 ohm termination; Minimum = -1.0V, Maximum = +4.0V, Swing > 0.2V
Trigger Out: HCSL, 50 ohm; VOH > 0.55V, VOL < 0.15V, Swing > 0.55V
• 8 Amps on 100-125VAC
• 4 Amps on single phase, 200-240VAC
283mm (L) x 442mm (W) x 92.65mm (H)
Shipping: 30.49 lbs. (13.83 kg)
Includes rack mount ears, cable support bracket, power cord, accessories and packaging.
Storage: 41°F to 122°F (5°C to 50°C)
Humidity (Ambient Air) Operating: 0% to 80%, non-condensing
Regulatory Compliance Specifications IEC 60950-1, UL 60950-1, CSA C22.2 No.60950-1, IEC 62368-1, UL 62368-1,
10 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Storage: 0% to 80%, non-condensing
CSA 62368-1, CE (LVD, EMC, RoHS), EN/IEC 55032, EN/IEC 55024, CFR 47, FCC Part 15B, ICES-003, AS/NZ CISPR
32/24, KN32/35
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution
User Guide
2 Getting Started with the
N4891A Solution
Chassis Setup / 12
Front Panel Overview / 14
Controlling the Equipment / 15
Installing License / 18
2 Getting Started with the N4891A Solution
Chassis Setup
The workflow to install and use a new N4891A chassis is as follows:
1 Unpack the N4891A.
2 Attach the accessories depending on how you will mount the equipment (see “Installing the
N4891A equipment” on page 12):
• On a bench: Attach the rubber feet.
• In a rack: Attach the mounting ears and then insert the N4891A chassis into the rack.
3 Connect the N4891A's management port to a network, and obtain an IP address.
4 Activate the license for the N4891A.
5 Connect the N4891A to the DUT.
6 Access the KiOS software and begin testing.
Installing the N4891A equipment
The N4891A chassis can be mounted on a bench or in a rack.
Bench mounting
To mount the N4891A chassis on a bench, install the four rubber feet to the bottom of the unit, one
at each corner, using the supplied screws. Refer to Figure 1.
Figure 1 Illustration for bench mounting the N4891A chassis
12 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Getting Started with the N4891A Solution 2
Bench mounting
To mount the N4891A chassis in a rack (refer to Figure 2):
1 Install the mounting ears (one at each corner).
2 Insert the N4891A chassis into the rack and fasten the ears to the rack.
Figure 2 Illustration for bench mounting the N4891A chassis
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 13
2 Getting Started with the N4891A Solution
Front Panel Overview
The N4891A front panel includes the following components:
• Power ON/OFF button
• 1 link/activity LED per port
• Clock in/out: 2 SMA female connectors
• Trigger in/out: 2 SMA female connectors
• 4 USB: 2 USB 2.0 + 2 USB 3.0 ports
• 1 RJ45: 1000/100/10Mbps Ethernet management port
• 1 Display Port supporting a maximum resolution of 4096 x 2304 @60Hz
14 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Controlling the Equipment
Connecting to the N4891A chassis
The N4891A is pre-configured to obtain an IP address over DHCP. To set up N4891A and to use it for
testing, you must find the IP address assigned to it.
There are two methods you can use to find the IP address assigned to the N4891A:
• DisplayPort: You can plug a monitor into the DisplayPort on the front panel.
• USB flash drive: After booting and obtaining an IP address, the N4891A chassis automatically
copies its address to a USB flash drive inserted into any of the USB ports.
DisplayPort method
1 With the N4891A chassis powered off, connect one end of an Ethernet cable to the management
port of the chassis, and connect the other end to a switch port that has access to a network that
includes a DHCP server.
2 Connect a monitor to the DisplayPort on the front panel of the N4891A chassis, and a keyboard
and mouse to the USB ports.
3 Power on the N4891A chassis.
4 Use either a web browser or a console window to fetch the IP address.
•Web Browser:
i Launch a browser window.
ii In the URL field, type localhost.
iii When the Landing page appears, select System Admin from the main menu (in the upper right
corner).
iv Note the IP address from the Linux OS attributes.
Getting Started with the N4891A Solution 2
Figure 3 Finding IP address using the web browser
•Console window:
i Launch a console window on the N4891A chassis.
ii Use the ifconfig command to display the IP address.
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 15
2 Getting Started with the N4891A Solution
Flash Drive method
1 With the N4891A chassis powered off, connect one end of an Ethernet cable to the management
port of the chassis, and connect the other end to a switch port that has access to a network that
includes a DHCP server.
2 Insert a thumb drive into and of the USB ports.
3 Power on the N4891A chassis.
4 Remove the flash drive and use a file explorer to find a file named hostname.txt in the root
directory of the file system on the flash drive.
5Open the hostname.txt file and make a note of the IP address in it.
Configuring the Hostname
1 With the N4891A chassis powered off, connect one end of an Ethernet cable to the management
port of the chassis, and connect the other end to a switch port that has access to a network that
includes a DHCP server.
2 Power on the N4891A chassis.
3 Launch a terminal window to the N4891A chassis.
4 Use the following command to set the host name:
hostnamectl set-hostname <host name>
Setting up the N4891A solution
The setting up of the N4891A 400GBASE FEC-aware Receiver Test Solution requires following
additional steps:
1 Connect the ‘Clock Out’ of the N4891A chassis to the ‘Ref CLK In’ of the M8045A pattern
generator.
2 Connect the ‘Trigger Out’ of the N4891A chassis to the ‘Ctrl In A’ of the M8045A pattern
generator.
3 Connect the device under test (DUT).
i Plug a QSFP-DD HCB Tx breakout adapter in an N4891A port.
ii Connect lanes #2-8 of the QSFP-DD HCB Tx breakout adapter to a module compliance board
(MCB).
iii Terminate lane #1 of the QSFP-DD HCB Tx breakout adapter with a 50Ohm terminations.
4 Connect the M8045A pattern generator data out signal (from M8057A/B remote head) to the
remaining MCB lane loopback the DUT to a different N4891A port.
i Using a compatible QSFP-DD module or cable.
ii Using a QSFP-DD HCB Rx breakout adapter.
16 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Getting Started with the N4891A Solution 2
Figure 4 Connection diagram sample for the N4891 solution
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 17
2 Getting Started with the N4891A Solution
NOTE
Installing License
You must install and activate the license for the KiOS software before you can use it.
Before you begin, ensure that you:
• know the MAC address of the N4891A chassis (you can find the MAC address on the System
Admin page)
• have a valid license
To activate a license:
1 Ensure that you know the IP address assigned to the N4891A chassis.
2 On a PC that can access the same network as the N4891A chassis is on, open a browser window
and enter the IP address into the URL field.
The KiOS software landing page is displayed.
3 Select License Manager from the main menu in the upper-right corner.
The License Manager page is displayed.
Figure 5 The License Manager page in KiOS software
4 On the License Manager page, click the MyKeysight.com link at the top of the page.
5 Login to the Keysight website, and download your license file.
6 On the License Manager page, select Add New License.
7 Select Choose File, then select the license file.
8 Select OK to add the license file to the KiOS.
After license options are installed, the Options field in the Status table of
the SYSTEM ADMIN displays ‘4 Ports’ as 4P, ‘-KP4 option’ as FEC, ‘-SYC
option’ as SYNC, and ‘-BRT option’ as EBERT.
18 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Getting Started with the N4891A Solution 2
Tabl e 3 shows the fields that appear in the License Manager page along with their description.
Table 3 License Manager fields and description
License Manager field Description
Feature Feature enabled after installing the license.
Description Description of the licensed feature.
Version Version of the licensed feature.
Expiration Date and time that the license shall expire.
Type Type of license.
Count Number of licenses installed.
Filename Name of the license file.
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 19
2 Getting Started with the N4891A Solution
20 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution
User Guide
3 Using the KiOS Interface for
the N4891A Solution
Accessing the KiOS interface / 22
Line Speed Control / 25
Port Settings / 26
Statistics page / 31
CMIS / 40
Menu Options / 43
3 Using the KiOS Interface for the N4891A Solution
NOTE
Accessing the KiOS interface
Landing Page
The landing page of the KiOS web interface is displayed in Figure 6. The “Landing” page is the
top-level page in the software. Figure 7, Figure 8 and Figure 9 describe the various components on
the page.
The latest features and changes in the application are reflected in the
A400GE User Guide, which can be found under the Help entry in the
Options menu. For more information, see
“Menu Options" on page 43.
Figure 6 Main components of the landing page
22 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
Figure 7 Landing page components (top-right corner)
Using the KiOS Interface for the N4891A Solution 3
Figure 8 Landing page components (bottom)
Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide 23
3 Using the KiOS Interface for the N4891A Solution
Figure 9 Landing page components (left)
24 Keysight N4891A 400GBASE FEC-Aware Rx Test Solution User Guide
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