The QSFP28 optical module has a smaller package size than the CFP4 optical module, which means the QSFP28 optical module has a higher port density on the switch. The following are several 100G QSFP28 series optical modules:

1. 100G QSFP28 Optical Transceivers: A Cost-effective Solution
The continuous and rapid development of the Internet as well as the desire of people for higher
speed optical networks facilitated the vigorous development of the entire optical
communications industry and strongly promoted the independent R & D and innovation in many
core technologies including optoelectronic devices technologies. 100g optical transceiver is
regarded as the product of this big data era.
The first generation of 100G optical modules is CFP optical module with very large volume, then
CFP2 and CFP4 optical modules appears. CFP4 optical module is the latest generation of 100G
optical module, the width is only 1/4 of CFP optical module. Its package size is not same as the
QSFP + optical module. The QSFP28 optical module has a smaller package size than the CFP4
optical module, which means the QSFP28 optical module has a higher port density on the switch.
The following are several 100G QSFP28 series optical modules:
Main Types of QSFP28 Optical Transceivers
100G QSFP28 LR4 is a 100Gb/s transceiver module designed for optical communication
applications compliant to 100GBASE-LR4 of the IEEE P802.3ba standard.
100G QSFP28 SR4 is a four-channel, pluggable, parallel, fiber-optic QSFP+ SR4 optical transceiver
module for 100/40 Gigabit Ethernet, Infiniband DDR/EDR and 32GFC applications.
100G QSFP28 PSM4 is a four-channel, pluggable, parallel, fiber-optic QSFP28 PSM4 optical
transceiver module for 100/40 Gigabit Ethernet and Infiniband DDR/EDR Applications.
100G QSFP28 CWDM4 is a 100Gb/s transceiver module which is designed for optical
communication applications compliant with the QSFP MSA, CWDM4 MSA and portions of IEEE
P802.3bm standard.
Of course, QSFP28 series also includes 100G QSFP28 active optical cables; these products have
played an important role in the development of 100G.

2. Advantages of 100G QSFP28 Optical Transceivers
1. Power Consumption
The power consumption of QSFP28 typically is no more than 3.5W, while the power consumption
of other 100G optical modules typically is between 6W and 24W. From this, the power
consumption of QSFP28 optical modules is much lower power than other 100G optical modules.
2. Cost
Now the data center is mainly 10G network architecture, in which the interconnection solutions
are mainly 10GBASE-SR optical module and duplex LC multimode fiber jumper. If the existing 10G
network architecture based on the direct is upgraded to 40 / 100G network, it will save a lot of
time and cost. Therefore, one of the major interconnection trends in data centers is to upgrade
from 10G networks to 40 / 100G networks without changing existing duplex multimode
infrastructure. In this case, the MPO / MTP branchable cable is undoubtedly the ideal solution for
a 10G upgrade to 40 / 100G.
3. Bandwidth
The QSFP28 uses the advanced 100G transport technology to provide the data center with a
connection between the chassis switch and the core network, providing up to 150% greater panel
bandwidth density than the 40G QSFP solution
Optical Module Test

3. When using optical modules, test performance is an essential step. Optical module is composed
of transmitter and receiver, so when we test, it is generally divided into four steps, which mainly
includes the transmitter and receiver test.
First, the transmitter part:
When testing, pay attention to the wavelength and shape of the transmitter output waveform, as
well as the receiver's jitter tolerance and bandwidth. When testing the transmitter, note the
following:
1. The quality of the input signal used to test the transmitter must be good enough. In addition,
the quality of the electrical measurements must also be confirmed by jitter and eye
measurements. Eye diagram measurements are a common way to check the transmitter's output
waveform because the eye diagram contains a wealth of information that reflects the overall
performance of the transmitter.
2. The output optical signal of the transmitter must be measured by the optical quality index such
as eye pattern test, optical modulation amplitude and extinction ratio.
Second, the receiver part
Unlike test transmitters, the quality of the optical signal must be sufficiently poor when testing
the receiver that a light pressure eye pattern representing the worst signal must be created. This
worst case optical signal must pass through jitter measurements and light Power test to calibrate.
1. Eye pattern test, this will ensure that the eye "eye" is open. Eye diagram testing is usually done
at the depth of the bit error rate;
2. Jitter test to test different types of jitter;
3. Jitter Tracking and Tolerance, testing the internal clock recovery circuit to track the jitter.
All in all, testing light modules is a complex undertaking, but it is also an indispensable step in
ensuring good performance. Eye diagram measurement is a widely used measurement method
that can effectively test the transmitter of an optical module. The optical module receiver test is
more complex, but also requires more testing methods.