To meet the growing requirements of collaborative multimedia services and applications, to respond to the fast-changing traffic patterns, and to better accommodate users’ bandwidth demands, 100G connections have been positioned for significant growth in data centers with the introduction of the latest 100G optical modules. The upgrade to 100Gbps is not more than gaining capacity. It’s also about gracefully evolving your network at your own pace to achieve greater efficiency, streamline costs and support new services. Many systems now support four or more 100G ports on each line card, with some systems supporting many hundreds of 100G ports. 100G optical modules, as an integral part of the overall system design, support highly reliable operations, optimized for entire architecture. This article puts its focus on one predominant 100G form factor: QSFP28.

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Fiberstore (FS.COM) | 100G QSFP28 Optics Introduction
To meet the growing requirements of collaborative multimedia services and applications, to
respond to the fast-changing traffic patterns, and to better accommodate users’ bandwidth
demands, 100G connections have been positioned for significant growth in data centers with the
introduction of the latest 100G optical modules. The upgrade to 100Gbps is not more than gaining
capacity. It’s also about gracefully evolving your network at your own pace to achieve greater
efficiency, streamline costs and support new services. Many systems now support four or more
100G ports on each line card, with some systems supporting many hundreds of 100G ports. 100G
optical modules, as an integral part of the overall system design, support highly reliable operations,
optimized for entire architecture. This article puts its focus on one predominant 100G form factor:
QSFP28.
QSFP28 Optics Benefits
100G QSFP28 transceivers are commonly seen in two types: QSFP28 100GBASE-SR4 (QSFP28 SR4)
and QSFP28 100GBASE-LR4 (QSFP28 LR4), designed with four 25Gbps lanes for high port-count
100G data center applications, enabling the implementation of various reaches in the QSFP28 MSA
form factor in 100G systems. They allow for greater port density, lower power consumption and
significantly lower cost of ownership for 100G connectivity. With these optical transceivers,
state-of-the-art 100Gbps performance and new levels of infrastructure consolidation have been
made possible.
QSFP28 100GBASE-SR4 Overview
The QSFP28 100GBASE-SR4 transceiver is a parallel 100Gbps QSFP28 optical module designed with
form factor, optical/electrical connection and digital diagnostic interface according to the QSFP28
100G QSFP28 Optics
Introduction

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Fiberstore (FS.COM) | 100G QSFP28 Optics Introduction
Multi-Source Agreement (MSA). It offers 4 independent transmit and receive channels, each
capable of 25Gbps operation for an aggregated data rate of 100Gbps for 100 meters on 12-fiber
MPO/MTP OM4 multi-mode fiber (MMF). Often, an optical fiber ribbon cable with an MTP/MPO
connector can be plugged into the QSFP28 module receptacle for high functionality and feature
integration. Proper alignment is ensured by the guide pins inside the receptacle. The cable usually
cannot be twisted for proper channel to channel alignment.
The QSFP28 SR4 module is a vertically integrated solution that meets IEEE 802.3 standards and MSA
requirements with power dissipation well under 3.5W. It supports both 100GBASE-SR4 as well as
4x25G breakout applications, say 100G QSFP28 to QSFP28 DAC and 100G QSFP28 SR4 to 4x25G
SFP28 break-out cables, meeting the harshest external operating conditions including temperature,
humidity and EMI interference.
 Working Principle
QSFP28 SR4 transceiver converts parallel electrical input signals into parallel optical signals, by a
driven Vertical Cavity Surface Emitting Laser (VCSEL) array. The transmitter module accepts
electrical input signals compatible with Common Mode Logic (CML) levels. All input data signals are
differential and internally terminated. The receiver module then converts parallel optical input
signals via a photo detector array into parallel electrical output signals. The receiver module outputs
electrical signals are also voltage compatible with Common Mode Logic (CML) levels. All data signals
are differential and support a data rates up to 25Gbps per channel. The following figure shows the
functional block diagram of this module.
QSFP28 100GBASE-LR4 Overview
The QSFP28 100GBASE-LR4 transceiver is also a 100Gbps transceiver module designed for optical
communication applications, compliant to 100GBASE-LR4 of the IEEE P802.3ba standard. This
module converts 4 input channels of 25Gbps electrical data to 4 channels of LAN WDM optical
signals and then multiplexes them into a single channel for 100Gbps optical transmission. Reversely
on the receiver side, the module de-multiplexes a 100Gbps optical input into 4 channels of LAN
WDM optical signals and then converts them to 4 output channels of electrical data. The high
performance cooled LAN WDM EA-DFB transmitters and high sensitivity PIN receivers provide
superior performance for 100GbE applications up to 10km links over single-mode fibers (SMFs) and
compliant to optical interface with IEEE802.3ba Clause 88 100GBASE-LR4 requirements.

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Fiberstore (FS.COM) | 100G QSFP28 Optics Introduction
 Working Principle
The transceiver module receives 4 channels of 25Gbps electrical data, which are processed by a
4-channel Clock and Data Recovery (CDR) IC that reshapes and reduces the jitter of each electrical
signal. Subsequently, each of 4 EML laser driver IC's converts one of the 4 channels of electrical
signals to an optical signal that is transmitted from one of the 4 cooled EML lasers which are
packaged in the Transmitter Optical Sub-Assembly (TOSA). Each laser launches the optical signal in
specific wavelength specified in IEEE802.3ba 100GBASE-LR4 requirements. These 4 lane optical
signals will be optically multiplexed into a single fiber by a 4-to-1 optical WDM MUX. The optical
output power of each channel is maintained constant by an automatic power control (APC) circuit.
The transmitter output can be turned off by TX_DIS hardware signal and/or 2-wire serial interface.
Here goes the picture of QSFP28 100GBASE-LR4 module functional block diagram.
Ready for 100G Connections
100G connectivity is now ready for widespread deployment. With so many 100G modules (CFP,
CFP2, CFP4 and QSFP28) having been introduced in the market, the number of companies deploying
100GbE networks is sure to see a significant growth. Although the expense of 100G connectivity
maybe an issue for some companies, further developments which are under way are expected to
reduce the cost.
Conclusion
100G QSFP28 transceivers enable higher speeds, greater scalability, and higher levels of
performance and reliability, so as to better meet business demands. To optimize business
investment, Fiberstore supplies many 100G QSFP28 modules which experience rigorous

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Fiberstore (FS.COM) | 100G QSFP28 Optics Introduction
qualification and certification testing, sold at affordable prices. Besides QSFP28 transceivers, QSFP28
cable can also be found here. If you want to know more information about QSFP28 optics, you can
visit ww.fs.com.
Contact Us
Manufacturing R & D (China)
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Technology Park, No.6, Keyuan Road,
Nanshan District, Shenzhen 518057,
China
Tel: +86 (755) 8300 3611
Fax: +86 (755) 8326 9395
Email: sales@fs.com
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Hong Kong
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Email: sales@fs.com
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Third Floor 207 Regent Street, London,
W1B 3HH, United Kingdom
Tel: +44 2081441980
Notice: This document is for informational purposes only and does not set forth any warranty, expressed or
implied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.
Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes no
responsibility for its use. This information document describes features that may not be currently available.
Contact a Fiberstore sales team for information on feature and product availability.
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