The Cisco ® QSFP-DD Open Line System (QSFP-DD OLS) is a pluggable optical amplifier module that, together with the channel breakout options (described later), provides a simple yet powerful open line system solution in a QSFP-DD pluggable form factor (also compatible with QSFP28). The Cisco ® QSFP-DD Open Line System (QSFP-DD OLS) is a pluggable optical amplifier module that, together with the channel breakout options (described later), provides a simple yet powerful open line system solution in a QSFP-DD pluggable form factor (also compatible with QSFP28). The QSFP-DD OLS is a pluggable open line system solution that can be directly hosted on a Cisco router. It is being developed by the QSFP-DD MSA as a key part of the industry's effort to enable high-speed solutions. QSFP-DD extends the use. 400G QSFP-DD to 400G QSFP-DD Active Optical Cable enables low-power, high-reliability and high-speed interconnections over very thin copper cables without using any optical components. It is designed for relatively short connection, offering high-density solution alternative for system providers. QSFP-DD Interconnect System enables faceplate density equal to the current 2x1 QSFP form factor, but with 8-lane ports. Customers can upgrade their box in advance of new cables. This article provides a comprehensive comparison of mainstream optical transceivers, including SFP, SFP+, QSFP+, QSFP28, and QSFP-DD. QSFP-DD (Quad Small Form-Factor Pluggable Double Density) transceivers double the number of high-speed electrical interfaces in QSFP to achieve 400G Ethernet speeds – and double them again to reach 800G.