Four commonly used optical module types and selection points

There are many kinds of optical modules on the market now, which are often dazzling. So, how to choose an optical module that is most suitable for your application among the many optical modules with different rates, different packages and different functions? This article will introduce several common optical modules. The types of optical modules and several important factors that should be paid attention to when purchasing optical modules, I hope to help everyone.

Common Optical Module Types

Before starting to discuss how to choose an optical module, it is necessary for us to have a basic understanding of the common packaged optical modules. This section will introduce the optical modules packaged in SFP, SFP+, QSFP+ and QSFP28 respectively. As for the optical modules packaged in GBIC, XFP, and CFP, we will not describe them in detail here.

SFP optical module

SFP optical module is a mini version of GBIC optical module. The functions of the two are roughly the same, but the volume of the SFP optical module is much smaller than that of the GBIC optical module. It is generally used in SONET/SDH networks, 100M/Gigabit Ethernet and other High-speed transmission applications.

10G SFP+ Optical Module

The 10G SFP+ optical module is an upgraded version of the SFP optical module. The physical package of the two is the same, but the SFP+ optical module can support the transmission rate of 10Gbps. Compared with other 10G optical modules (such as Xenpak and XFP optical modules), SFP+ optical modules have the smallest volume and are most suitable for high-density port applications, and have now become the most popular 10G optical modules.

40G QSFP/QSFP+ Optical Module

The 40G QSFP/QSFP+ optical module conforms to Ethernet, Fibre Channel, InfiniBand and SONET/SDH standards. The 40G QSFP optical module uses four 4Gbit/s transmission channels to transmit data, and the 40G QSFP+ optical module uses four 10Gbit/s transmission channels to transmit data. data.

QSFP28 optical module

The QSFP28 optical module is mainly used in 100G Ethernet and EDR InfiniBand applications. It uses four 25Gbit/s transmission channels to transmit data. Sometimes this optical module is also called QSFP100 or 100G QSFP optical module.

Factors to Consider When Buying Optical Modules

When purchasing optical modules, the following five points are the key factors to consider:

Transmission distance

The transmission distances supported by different optical modules are different. Generally speaking, the transmission distance of a multi-mode optical module is much shorter than that of a single-mode optical module, and the price is also cheaper. For example, the transmission distance of a 10GBASE-SR SFP+ optical module is The maximum transmission distance can only reach 400m, while the transmission distance of a 10GBASE-LR SFP+ optical module can reach 10km, so it is very important to figure out the transmission distance you want to achieve. In addition, considering the attenuation and dispersion of optical signals during transmission, it is recommended that you use an optical module that supports a transmission distance slightly larger than the actual requirement. For short-distance connections between devices in a rack, it is recommended that you use high-speed cables that are cheaper than optical modules.

transfer mode

There are three main data transmission methods for optical modules: simplex, half-duplex and full-duplex. Simplex transmission only supports data transmission in one direction; half-duplex transmission allows data transmission in two directions, but at a certain time Only data transmission in one direction is allowed; full-duplex transmission allows simultaneous data transmission in both directions. It is best to choose an optical module that supports full-duplex transmission.

Transmission medium

Copper cable and optical cable are the two most widely used transmission media at present. Therefore, some optical modules are designed with electrical ports, and some optical modules are designed with optical ports. Generally speaking, optical port optical modules are commonly used in 10G and 40G Ethernet transmission applications, while electrical port optical modules are used in 100M and Gigabit Ethernet applications, and the transmission distance of optical port optical modules is generally longer than that of electrical port optical modules. Far.

heat resistance

The working environment temperature of the optical module should not be too high. If the temperature exceeds the temperature that the optical module can withstand, a link failure is likely to occur. Therefore, an optical module with good heat resistance should be selected.

The above points are just the factors that are often considered when purchasing optical modules. In addition, the operating wavelength, operating speed, manufacturer brand, etc. need to be considered.