Single fiber QSFP28 modules (commonly called BiDi transceivers) enable full-duplex 100G communication over a single optical strand. They do this by using Wavelength Division Multiplexing (WDM) to carry upstream and downstream signals at different wavelengths on the same fiber. We all know that there are many types of 100G optical modules, including the most well-known 100G-SR4, 100G-CWDM4 using CWDM technology, and 100G-LR4 suitable for long-distance transmission. However, in this article, we will introduce a type of module that improves transmission efficiency through a. What is QSFP 100G LR4 Optical Module As one of the most popular transceiver types in 100G Ethernet applications, the QSFP 100G LR4 offers a powerful combination of long reach, compact form factor, and compatibility with single-mode fiber networks. To better understand why it has become an industry. The common 100G optical standards, such as 100G SR4, 100G LR4, 100G CWDM4, 100G PSM4, and 100G ER4 optical modules, utilize four 25G optical channels for either parallel transmission or WDM transmission. It features low power consumption, high port density, compact size, and cost efficiency. This article reviews QSFP28 module types and key WDM technologies like CWDM and DWDM.