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100G optical transceivers – The true harbingers of faster data communication

100G Optical Transceivers are the perfect communication solutions for the coming times. It is because the world is becoming increasingly dependent on services like faster content delivery, cloud services and IPTV facilities that need data centers to be more robust in architecture and functioning. 100G speed is said to be just the tip of the iceberg. The possibilities beyond 100G are endless and statistically speaking, the IP traffic would be handling the movement of around zillions of bytes of data, making it relevant for the network managers to shift to 100G networks. 

Types of 100G transceivers

Market of 100G transceivers is quite enriched. A number of 100G transceivers have been introduced to meet the compatibility demands of varying cabling specifications and data reach needs. Accordingly, 100G transceivers are classified as CXP optical module, CFP optical module, CFP2 optical module, CFP4 optical module and QSFP28 optical module. C stands for 100 in C-series optical modules. Currently, QSFP28 is in high demand as 4 25Gbps lanes of QSFP28 can be used to achieve 100G optical transceiver functionality. 


Standards followed by 100G transceivers

100G transceivers are designed in accordance with the specifications mentioned in QSFP MSA and IEEE. Here is an overview of cabling standards, connectors and data reach etc. mentioned in various quality standards:


A few of these optical transceivers cannot be used interchangeably, even if these are made inter-operable. For example, 100G CLR4 transceiver slot cannot be used for 100G CWDM4 directly. 

Why 100G QSFP28 transceivers are being used preferably

QSFP28 transceiver is the main component in any interconnect arrangement that delivers 100G connectivity functionality. It is because of these reasons:

1. Better port density: The first generation 100G transceiver is CFP, it is quite bulky in size. CFP2 and CFP4 form the next generation 100G module. The size is so small that the CFP4 is almost a quarter in the width of CFP. QSFP28, however, is even smaller than CFP4 with the same footprint and panel density as delivered by a typical QSFP +.Higher port density advantage is quite desirable for a  QSFP28, as 1 RU switch on the front panel can house up to 36 QSFP28s.


2. More power efficient: While other 100G transceivers are consuming power as high as 24W starting from 6W, the QSFP28 transceivers require only 3.5W or less of wattage to operate. 







82 x 14 x 145

42 x 13 x 104

22 x 10 x 92

18 x 8.5 x 52


< 25 W

< 12W

< 6W

< 3.5W

3. Very Versatile: A switch with CXP port is not usable across any single mode fiber application utilized in a modern day data center. This puts lots of restrictions on the use of CFP or CFP2 transceivers. The CFP or CFP2 modules can be used only for the transceiver, thereby forcing the designer to add CXP form factor for cables separately in the network. A QSFP28 port is made compatible with all networking equipment such as transceiver, direct-connect cable (DACs), or active cable (AOCs), thereby making the networking easy to manage and seamless to operate.

4. Cost-efficient: QSFP28, because of the high port density and low power requirement contributes significantly to cost saving. Since QSFP28 is the result of integration of four lanes of 25G each, the migration of each 10G line to 25G proves to be a cost-effective proposition and no significant expenditure or complete change of networking plan is to be managed. 

Interface and cabling solutions compatible with 100G transceivers

To switch to a 100G network, the designer would require following connecting interfaces and cabling solutions. 

Transceiver Types


Fiber type











LC Duplex




LC Duplex



The above table reveals that 100GBase-SR4, QSFP28 and 100GBASE-PSM4 modules are provided with MTP/MPO interface, whereas, 100GBASE-CWDM4 QSFP28 and 100GBASE-LR4 QSFP28 are configured with duplex LC interface. What cabling solutions are compatible with 100G transceivers? Let’s find out.

100GBASE-SR4 QSFP28 can create 100G optical links over eight fibers, which, in turn, can be connected with a 12-fiber MTP/MPO patch cable. This arrangement leaves four fibers unused effectively. Also, 100GBASE-PSM4 QSFP28 uses 12-fiber MTP/MPO patch cable. For data transmission covering a distance of 100m, the 100GBASE-SR4 QSFP28 can be used over a multimode cable and for the data links reaching 500m of distance, 100GBASE-PSM4 QSFP28 can be used over a single mode fiber.

In addition to these, 100GBASE-CWDM4 QSFP28 and 100GBASE-LR4 QSFP28 are designed which are actually the duplex modules and can support 2km and 10 km link length. Both these transceiver types are compatible with single mode duplex LC patch cable. Illustrated here are the two 100GBASE-CWDM4 QSFP28 transceivers that connect with a single-mode duplex LC patch cable:


Cable assemblies of 100G QSFP28 transceivers

DACs and AOCs are two single assembly options that would require minimum parts and also eliminate the scope of error which are quite possible due to numerous connections, some of which may be faulty too. The DACs (Direct Attached Cables) are designed for 0-15m long connections and AOCs (Active Optical Cables) for up to 70m. AOC cable assemblies can perform in similar fashion when connected with transceivers and fiber cables discretely.


100GbE QSFP28 AOC is basically an OM4 multimode cable that can house two QSFP28 connectors on either end. The form factor design facilitates easier plugging as well as de-plugging. The QSFP28 AOC is compliant with the QSFP MSA (multi-source agreement) and follows 100G QSFP28 standards. This AOC is available in lengths of 1 to 30 meters.

QSFP28 passive DAC products include QSFP28 to QSFP28 DACs and QSFP28 to 4x SFP28 DACs. These DACs are ideal for attaining the 100GbE connectivity within 5 m which are typical reach of intra-rack connections.

How QSFP, QSFP+ and QSFP28 are different

All QSFP, QSFP+ and QSFP28 have the same size, but their differences can be summed up as below:

QSFP is a compact, hot-pluggable transceiver used for data communications. The QSFP supports Ethernet, Fiber Channel, InfiniBand and SONET/SDH standards delivering data transmission at different data rates.  QSFP+ transceivers are designed to support 40G Ethernet which is evolved from 4x1G lanes (QSFP) to 4x10G lanes. In addition, QSFP+ also supports Serial Attached SCSI, QDR (40G) and FDR (56G) Infiniband and other communications standards. QSFP28 is a hot-pluggable transceiver module designed for 100G data rate. QSFP28 integrates 4 transmit and 4 receiver channels.

QSFP28 features 4 electrical lanes that can be used in configuration styles such as - 4x10GbE, 4x25GbE, 2x50G breakout, or 1x100G depending on the transceiver used. QSFP+ can break out into 4x10G or 1x40G connection. So, a 100G QSFP28 port can generally take either QSFP+ or QSFP28 transceiver. It is important to note that you must not put the QSFP + transceiver into the QSFP28 port; else it may cause damage to the optics.

Future of 100G transceivers

High speed optical modules are the present as well as the future of data communications market. The market reported $4.62 billion of sales in 2015 and it is expected to reach $7.1bn in 2020. The need for faster data transmission requires introduction of high speed and better capacity optical modules in the data center networks. As a result, 100G optical modules are growing the fastest, and these are going to capture more than 50% of the optical module market in coming times.



Cozlink is the leading manufacturer of fiber optical products like high quality 100G QSFP28 transceivers and 100G QSFP28 DAC and AOC cables. For more information, please visit 

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