100G is available in a variety of packaging forms, including CFP/CXP and QSFP28. Among these different 100G packaging forms, QSFP28 optical transceiver has become the main packaging method for 100G networks because of their advantages, such as high port density, low power consumption and low cost. We will focus on four types of 100G QSFP28 optical transceivers in this article.

1)       100G-QSFP28-SR4

100G-QSFP28-SR4 optical transceivers are parallel 100G optical transceivers. QSFP28 full duplex optical transceivers provide four independent transmit and receive channels, with each function capable of 25Gbps operation at 100 meters of OM4 MMF, for an overall data rate of 100Gbps.
When the 100G-QSFP28-SR4 optical transceiver transmits signals at the transmit end, the electrical signals are converted to optical signals by the laser array and then transmitted in parallel over the ribbon multimode fiber, and when it reaches the receive end, the photo detector array converts the parallel optical signals to parallel electrical signals

2)       100G- QSFP28-LR4

The 100G- QSFP28-LR4 optical transceiver is generally used with LC single-mode fiber optic patch cords, and the maximum transmission distance can reach 10km.
The 100G- QSFP28-LR4 optical transceiver converts four 25Gbps electrical signals into four LAN WDM optical signals, which are then multiplexed into a single channel for 100G optical transmission. At the receiving end, the module de-multiplexes the 100G optical input into 4-way LAN WDM optical signals, and then converts them into 4-way electrical output channels.

3)       100G- QSFP28-CWDM4

With a transmission rate of 103.1 Gbp, the QSFP28 CWDM4 optical transceiver is mainly used in computing and high-frequency trading applications, and it costs significantly more than the QSFP28 PSM4 optical transceiver.
Through coarse wavelength division multiplexing (CWDM) technology, the QSFP28 CWDM4 optical transceiver multiplexes four wavelengths - 1270nm, 1290nm, 1310nm and 1330nm - onto a single-mode fiber for transmission.

4)       100G- QSFP28-PSM4

The QSFP28 PSM4 optical transceiver is a high speed and low power product designed for optical interconnects in data communications applications. It complies with the PSM4 MSA optical interface specification, has a hot-swappable QSFP form factor, built-in digital diagnostics, and a total of four independent full-duplex channels with data rates of up to 25.78 Gbps per channel.
The QSFP28 PSM4 optical transceiver is mainly used in 40G and 100G Ethernet applications. The high-bandwidth module supports 100GbE optical links over single-mode fiber.