To cater for people’s demands on higher bandwidth, lower cost, longer transmission distance, QSFP28 optics appears. Under common circumstances, optical transceivers can be divided in the form of singlemode and multimode. Of course, QSFP28 optics are without exception. However, what are the differences between singlemode and multimode QSFP28 optics and which one is better? This article will have an introduction to them.

What Is Singlemode 100G QSFP28 Optical Transceiver?

It’s known that singlemode fiber is small in size of core and narrow in laser wavelength. It is due to it that singlemode fiber is available for signal transmission with higher bandwidth to realize data transmission at a longer distance. Singlemode QSFP28 usually adopts singlemode fiber, mainly works at a 1310nm wavelength and for long distance transmission. Different types of singlemode QSFP28 can achieve different data transmission distances, such as 100GBASE-PSM4 QSFP28 available for 500 meters, 100GBASE-CWDM4 QSFP28 available for 2 kilometers and 100GBASE-LR4 QSFP28 available for 10 kilometers. Simultaneously, there still exits some other differences among them, shown as the below table:

What Is Multimode 100G QSFP28 Optical Module?

Multimode fiber is bigger in the size of core and wider in the wavelength of light. It is available for connection with inexpensive LED light sources and alignment of the connectors with a coupler less critical than that of singlemode fiber. After that, optics transmitting over multimode fiber have a higher capability to gather light from the laser at a lower cost. Multimode QSFP28 usually utilizes the multimode fiber, mostly works at the 850mn wavelength. At the same time, it is available for short optical links, such as 70ms over OM3, and 100ms over OM4. Among QSFP28 optics, one belonging to multimode optics is only QSFP28 100GBASE-SR4 with 12-fiber MTP connector interface, connected with MTP cable(shown as the pic).

Singlemode QSFP28 vs. Multimode QSFP28 Optical Transceiver: What Are the Differences?

With respect to the differences between singlemode QSFP28 and multimode QSFP28 optics are mainly shown in these aspects:

• Transmission distance: the transmission distances that singlemode QSFP28 optical modules can reach include 500 meters, 2 kilometers and 10 kilometers; while transmission distance that multimode QSFP28 optic can achieve is 100 meters.
• Power consumption: multimode QSFP28 consumes less power than singlemode QSFP28, which is an important consideration especially when assessing the cost of powering and cooling in the data center.
• Cost: on account that singlemode fiber optics require more expensive laser sources, the cost of singlemode QSFP28 is nearly two or three times higher than that of multimode QSFP28 optic.
• Transmission media: singlemode QSFP28 is usually connected with singlemode fiber; while multimode QSFP28 is connected with multimode fiber. It is known that 100GBASE-PSM4 QSFP28 is used with single-mode MTP cable and 100GBASE-SR4 QSFP28 is used with multimode MTP cable; while 100GBASE-CWDM4 QSFP28 and 100GBASE-LR4 QSFP28 are used with a singlemode duplex LC patch cable.

Summary

By the comparison of the differences between single-mode and multimode QSFP28 optic fiber transceiver, the conclusion can be drawn that singlemode QSFP28 optics have more advantages than multimode QSFP28 optics in transmission distance, while multimode transceivers have more merits in cost and power consumption. Therefore, as for the question: which one is better, the answer is that the most suitable is the best.

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