The Cisco® 40GBASE QSFP+ (Quad Small Form-Factor Pluggable Plus) modules offer customers a wide variety of high-density 40 Gigabit Ethernet connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, and service provider transport applications.

Main features of Cisco 40GBASE QSFP+ modules include:

- Support for 40GBASE Ethernet
- Hot-swappable input/output device that plugs into a 40-Gigabit Ethernet QSFP+ Cisco switch port
- Flexibility of interface choice
- Interoperable with other IEEE-compliant 40GBASE interfaces available in various form factors
- Support for "pay-as-you-populate" model
- Support for the Cisco quality identification (ID) feature which enables a Cisco switch to identify whether the module is certified and tested by Cisco

Cisco QSFP-40G-SR4
The Cisco 40GBASE-SR4 QSFP+ Module supports link lengths of 100m and 150m respectively on laser-optimized OM3 and OM4 multimode fiber cables. It primarily enables high-bandwidth 40G optical links over 12-fiber ribbon r cables terminated with MPO/MTP multi-fiber connectors. It can also be used in 4x10G mode along with ribbon to duplex fiber breakout cables for connectivity to four 10GBASE-SR optical interfaces. Maximum channel insertion loss allowed is respectively 1.9dB over 100m of OM3 cable or 1.5dB over 150m of OM4 cable.

Cisco QSFP-40G-CSR4
The Cisco 40GBASE-CSR4 QSFP+ Module is similar to the 40GBASE-SR4 interface extends supported link lengths to 300m and 400m respectively on laser-optimized OM3 and OM4 multimode fiber cables. Each 10-gigabit lane of this module is compliant to IEEE 10GBASE-SR specifications. This module can be used for native 40G optical links over 12-fiber ribbon cables with MPO/MTP connectors, or in 4x10G mode with ribbon to duplex fiber breakout cables for connectivity to four 10GBASE-SR interfaces. Maximum channel insertion loss allowed is respectively 2.6dB over 300m of OM3 cable or 2.9dB over 400m of OM4 cable.

Cisco QSFP-40GE-LR4
The Cisco 40GBASE-LR4 QSFP+ Module (Figure 2) supports link lengths of up to 10km over a standard pair of G.652 single-mode fiber with duplex LC connectors. The 40 Gigabit Ethernet signal is carried over four wavelengths. Multiplexing and demultiplexing of the four wavelengths are managed within the device.