Fiber Optics

Three Kinds of QSFP28 Optical Transceiver Differences

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.

Summary:

QSFP28 SR4 optical transceiver is suitable for use in 12-way MTP fiber cabling systems and also for short-distance transmission of OM3, OM4 multimode fiber. QSFP28 PSM4 optical transceiver is also suitable for transmission with 12 MTP interfaces, but it is suitable for use with single-mode fibers and can transmit distances up to 500m. QSFP28 LR4 optical transceiver is for data transmission up to 2km.

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