Differences between QSFP28 PSM4, QSFP28 SR4 and QSFP28 LR4

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. 

An Introduction to 100G QSFP28 Optical Module and Its Advantages

After the optical module data rate, the development of optical module form factor, the market there are a variety of optical modules and a variety of packages, then QSFP28 optical module now appears, it has some advantages that can help become the mainstream of 100G optical networks. Below, we will introduce to everyone what is QSFP28 optical module and what are the advantages of QSFP28 optical module.

What Is QSFP28 Optical Module?

First, let's look first: What is QSFP28 optical module. Generally speaking, the optical module form factor refers to the optical module shape, with the progress of science and technology, optical module form factor is a step by step evolution, the volume is gradually smaller, of course, not only the appearance of the change in the rate, power consumption, distance , costs, etc. are also constantly moving forward.

Currently 100G optical modules have several main form factors, including: QSFP28 optical module, CFP optical module, CFP2 optical module, CFP4 optical module, these kinds of encapsulated optical modules all belong to 100G, of which the QSFP28 optical module is a mainstream 100G optical module on the current market.

The post will compare 100G QSFP28 optical module and other 100G optical modules in terms of port density, power consumption, and cost respectively.

What Are the Advantages of QSFP28 Optical Module?

1. Port Density

The first generation of 100G optical modules was a very large CFP optical module, and then CFP2 and CFP4 optical modules were launched, among which CFP4 optical module was the latest generation of 100G optical modules and had a width of only 1/4 of the CFP optical modules. However, the form factor of 100G QSFP28 optical module is smaller than the CFP4 optical module, which means the 100G QSFP28 optical module has a higher port density on the switch.

2. Power Consumption

The power consumption of 100G QSFP28 optical module is usually lower than 3.5W while that of other 100G optical modules is usually between 6W and 24W. From this, 100G QSFP28 optical modules have much lower power consumption than other 100G optical modules.

3. Cost

Now the data center is mainly 10G network architecture, in which the interconnection solution is mainly 10GBASE-SR optical module and duplex LC multimode fiber jumper. If the existing 10G network architecture can be directly upgraded to 40 / 100G networks, it will save a lot of time and cost.

Although 100G QSFP28 optical modules have many advantages, it is only one of many solutions for 100G network. For data centers and server rooms, suit is best. Therefore, other 100G optical modules also have a place in the 100G network. Gigalight thinks that 100G QSFP28 optical module series, like 100G QSFP28 SR4, 100G QSFP28 LR4, 100G QSFP28 CWDM4 and 100G QSFP28 PSM4, have brought a new solution for 100G applications that will promote the faster development of 100G.