The early 400G optical modules used 16-channel 25G bps NRZ implementation (such as 400G-SR16), and were packaged in CDFP or CFP8 . The advantage is that it can borrow the mature 25G NRZ technology on the 100G optical module , but the disadvantage is that it requires 16 signals for parallel transmission, the power consumption and volume are relatively large, and it is not suitable for data center applications.
The current 400G optical module, the optical port side primarily to use 8 way 53Gbps PAM4 (400G-SR8 , FR8 , LR8) or 4 -way 106Gbps PAM4 (400G-of DR4 , FR4 , LR4) to achieve 400G signal transmission, in the electrical port side 8- channel 53Gbps PAM4 electrical signal, using OSFP or QSFP-DD package.
Both OSFP and QSFP-DD packages can provide 8 electrical signal interfaces . In comparison, the package size of QSFP-DD is smaller (similar to the QSFP28 package of traditional 100G optical modules), which is more suitable for data center applications; OSFP package size is slightly larger, because it can provide more power consumption, so it is more suitable for telecommunications applications.
Distinguish from the optical wavelength, the 400G optical module can be divided into multi-mode (MM) and single-mode (SM);
from the signal modulation method, it is divided into NRZ and PAM4 modulation (currently mainly PAM4);
distinguish from the transmission distance, 400G optical modules can be divided into SR , DR , FR , LR ; from the form of packaging, 400G optical modules can be divided into CDFP , CFP8 , OSFP , QSFP-DD, etc.
