Overview of 100G Optical Module
With the development of science and technology, people's demand for fiber optic communication rate is also increasing, and now 100G optical modules are also used in various scenarios. 100G optical modules have a variety of encapsulation forms, including CFP, CFP2, CFP4, CXP and QSFP28, among these different encapsulation forms, the QSFP28 module has become the main encapsulation form of 100G optical modules due to its small size, high port density and low cost advantages. Among these different packages, QSFP28 optical module has become the main package form of 100G optical module, which is favored by enterprises, carriers and data centers due to its advantages of small size, high port density and low cost.

QSFP28 Optical Module Classification and Application
1. QSFP28 SR4 Optical Module
QSFP28 SR4 optical module is based on 100G Ethernet IEEE 802.3bm standard, which provides 4 independent transmit and receive channels, each supporting 25G, with a total bandwidth of 100G. the central wavelength is 850nm and adopts the MPO interface, which can transmit 70m on OM3 multimode fiber and 100m on OM4 multimodule fiber, which is suitable for short-distance transmission. short distance transmission. Because of its characteristics, QSFP28 SR4 optical module is mostly used in data centers, with multi-mode fiber in 100m distance for inter-switch cabling.

2. QSFP28 LR4 Optical Module
QSFP28 LR4 optical module is based on the 100G Ethernet IEEE 802.3ba standard. Unlike QSFP28 SR4, QSFP28 LR4 optical module adopts WDM technology, which multiplexes different wavelengths of four fiber channels into a single optical fiber for transmission, and the central wavelengths of four LAN WDM channels are 1295.56, 1300.05, 1304.58, 1309.58 and 1309.56 respectively. 1304.58 and 1309.14nm, the module adopts dual LC interfaces, with single-mode fiber transmission distance of up to 10km, suitable for medium and long-distance transmission applications, mostly used in large-scale data centers and enterprise parks.

Figure 1 QSFP28-SR4 and QSFP28-LR4 Optical Module
3. QSFP28 PSM4 Optical Module
QSFP28 PSM4 optical module is similar to QSFP28 SR4, providing 4 independent transmit and receive channels and using MPO interface, but the difference is that the center wavelength of QSFP28 PSM4 optical module is 1310nm, and with single-mode optical fiber, the maximum transmission distance can be up to 2km. it is important to note that Motech Optronics' QSFP28 PSM4 optical module. In order to minimize the reflection caused by MPO connection, this product adopts MPO socket with 8-degree angled end face. This product should use a female MPO connector with an 8-degree endface.

4. QSFP28 CWDM4 Optical Module

QSFP28 CWDM4 Optical Module is similar to QSFP28 LR4. It adopts WDM technology to convert four 25Gb/s electrical data input channels into four CWDM optical signals and multiplexes them into a single channel to realize 100Gb/s optical transmission. Similarly, at the receiving end, the module multiplexes 100Gb/s input optical signals into 4 CWDM channels and converts them into 4 channels of output electrical data. 4 channels with central wavelengths of 1271, 1291, 1311, and 1331nm are used as LC interfaces, which can be transmitted over 2km with single-mode fiber.

5. QSFP28 ER4 Lite Optical Module

QSFP28 ER4 Lite optical module is based on 100G Ethernet IEEE 802.3bm standard, similar to the principle of QSFP28 LR4 optical module, which converts four 25Gb/s electrical signals into four LAN-WDM wavelengths of optical signals, which are coupled into a single optical fiber through the internal multiplexer (MUX) to complete the 100Gb/s optical signal transmission. However, the difference is that the QSFP28 ER4 Lite optical module adopts APD receiver, which is suitable for long-distance transmission. If the host used has the FEC function, the QSFP28 ER4 Lite can transmit a maximum of 40km on the single-mode fiber of the optical module, and if the host used does not have the FEC function, the transmission distance is a maximum of 30km.

6. Difference between five types of 100G QSFP28 optical modules