The appearance of the QSFP28 optical
transceiver is the same as that of the 40G QSFP + optical transceiver. The
difference is that QSFP28 optical transceiver can transmit optical signals up
to 100G. Therefore, QSFP28 optical transceiver has become the mainstream 100G optical
transceiver and the preferred solution for network upgrade of 100G. This
article describes the differences between the QSFP28 PSM4 optical transceiver,
the QSFP28 SR4 optical transceiver, and the QSFP28 LR4 optical transceiver.
The Definition of Different Types of QSFP28
Optical Transceiver:
QSFP28 PSM4 optical
transceiver is a high-speed, low-power product with a hot-swappable QSFP
form factor with built-in digital diagnostics and eight optical fibers, each
with a data rate of 25Gbps.
QSFP28 SR4 optical transceiver is a
parallel 100G optical transceiver with the advantages of high port density and
low cost. If you need a short distance transmission of optical transceivers for
100G network upgrade, you can choose QSFP28 SR4 optical transceiver.
QSFP28 LR4 optical transceiver, an optical
transceiver with transmission distances up to 2km, provide an ideal solution
for the ever-increasing transmission distance requirements of very large data
centers and will lead the use of single-mode optical fibers in the data center.
QSFP28 Optical transceiver Differences:
1. Transmission Methods
As we all know, QSFP28 optical transceiver
usually has four transmission channels, and each channel data rate is 25Gbp. This
transmission is very similar with 40G QSFP + optical transceiver transmission. 100G QSFP28 SR4 and 100G
QSFP28 PSM4 optical transceivers are 12-way MTP interface, while the
realization of the 8-way fiber 100G transmission is bidirectional. But the 100G
QSFP28 LR4 optical transceivers cannot do this, QSFP28 LR4 optical transceiver
is transmitted at the same time in two uses of LC duplex fiber in one direction
for 100G transmission.
2. Transmission Media and Transmission Distance
QSFP28 PSM4 optical transceiver, QSFP28 SR4
optical transceiver and QSFP28 LR4 optical transceiver transmission distance
are also different. QSFP28 SR4 optical transceiver operates at 850nm and is
used with OM3 or OM4 multimode fibers for transmission distances of up to 70m
with OM3 fibers and up to 100m with OM4 fibers. QSFP28 LR4 optical transceiver
is usually used with single-mode fiber, which operates at 1310 nm and has a
maximum transmission distance of up to 2km. QSFP28 PSM4 optical transceiver, is
generally used with a 12-way MTP interface and single-mode optical fiber with a
transmission distance of up to 500m.
3. The Wiring Structure Is Different
Optical transceiver transmission in the
optical fiber routing has a very important role. Because the QSFP28 SR4 optical
transceiver and the QSFP28 LR4 optical transceiver are used for short-distance
transmission and long-distance transmission respectively, their wiring
structures are different. The former requires multi-fiber cabling based on a
12-way MMF MTP interface, while the latter requires only a traditional
two-fiber SMF cabling. In this case, the conversion between multimode fiber and
single-mode fiber is very complicated because they use a completely different
wiring structure.
Although QSFP28 PSM4 optical transceiver
operates in single-mode fiber, its wiring structure is the same as that of the
QSFP28 SR4 optical transceiver. Using the QSFP28 PSM4 optical transceiver saves
conversion costs between multimode and single-mode without changing existing
cabling structures.
4. Different Working Principle
(1) How QSFP28 PSM4 optical transceiver
works:
The working principle of the QSFP28 PSM4 optical
transceiver is almost the same as that of the QSFP28 SR4 optical transceiver.
The difference is that the QSFP28 PSM4 optical transceiver operates on single-mode
fiber while the QSFP28 SR4 optical transceiver operates on OM4 multimode fiber.
(2) How QSFP28 SR4 optical transceiver
works:
QSFP28 SR4 optical transceiver transmits
signals at the transmitting end; the electrical signals are converted into
optical signals by the laser array and then transmitted in parallel on the
ribbon multimode fiber. Upon reaching the receiving termination, the photo
detector array converts the parallel optical signals into parallel electrical
signals.
(3)How QSFP28 LR4 optical
transceiver works:
QSFP28 LR4 optical transceivers are
typically used with LC single-mode fiber optic cables to convert 4×25Gbps electrical signals into 4 LAN WDM optical signals and then
multiplexed into a single channel for 100G optical transmission. At the
receiving end, the module demultiplexes the 100G optical inputs into 4 LAN WDM
optical signals, and then converts them into 4 channels of electrical signal
output.