At present, most 100G optical modules in the market are transmitted using 4 -channels 25Gb/s parallel or WDM,such as 100G SR4, 100G PSM4, 100G LR4, 100G CWDM4 optical modules, etc. In order to reduce costs and improve transmission efficiency, the industry has proposed the 100G single-lambda specification, which refers to the use of PAM4 optical signaling and coding for single-lambda 100G transmission. This reduces the number of lasers and detectors used, and also reduces the optical complexity, so that a single-lambda 100G optical module costs less than a 4-channel 25Gb/s optical module.

At present, 100G single-lambda optical modules are respectively 100G-DR and 100G-FR. Both of them belong to single-mode optical modules with working wavelength of 1310nm, Duplex LC connector, PSM4 modulation technology and FEC function. The 100G-DR optical module can be transmitted up to 500 meters using single-mode OS2 fiber, while the 100G-FR optical module can be transmitted up to 2 kilometers using single-mode OS2 fiber.

With the continuous growth of service volume, cost-effective optical modules will be more favored by users, especially in the 200G/400G service. The use of 100G single-lambda optical modules can make the upgrade of 400G network more convenient. At the same time, the appearance of 100G single-lambda transmission technology laid the foundation for the development of 400G (4*100G) Ethernet.

400G optical module has two modulation modes: 8x50G PAM4 and 4x100G PAM4. Compared with 8x50G PAM4, 4x100G PAM4 reduces the number of optical materials used and the complexity of optical structure. Therefore, the emergence of 100G single-lambda technology provides a lower cost implementation way for 400G applications.

Since the 400GBASE-DR4 optical module adopts the 100GBASE-DR specification, the 400G DR4 optical module can be connected to 4x 100G DR Optical modules through branch patch cord, which helps to upgrade to the 400G Ethernet in the future.