QSFP (quad small form-factor pluggable), quad means 4 channel. It integrates 4 channel lanes 10G transmit and receiver signals together to support 40G bandwidth . It is compliant with SFF-8436 and QSFP Multi-source Agreement (MSA). The QSFP+ module is a compact, hot-pluggable transceiver module which used for both telecommunication and data communication applications. As the requirement of higher speed network, and considering price, 40G is a good choice for system integrator and operators. It provides increased port density and total system cost savings. Do you know how many types of 40G modules? See below chart shows:

QSFP+SR4: this one is most popular customer order product for short distance transmission on multimode fiber. Transmission distance reach 100m over OM3 and 150m over OM4. Wavelength is 850nm, with MPO/MTP interface. Normally connect with SR4 patch cable is MPO Female to MPO Female patch cord, type B version.

QSFP+eSR4: also 850nm, with MPO/MPT interface, but with longer distance. Transmission distance up to 300m over OM3 and 400m over OM4.

QSFP+ IR4 2km: it is 4 channel, parallel transmission module. With MPO/MTP interface, transmission distance up to 2km on Single mode fiber (SMF).

QSFP+PSM LR4: PSM is stand for Parallel Single Mode fiber 4-lane, it also uses MPO/MTP connector on the optical interface, but transmission distance is 10km on Single mode fiber (SMF).

QSFP-40G-SR-BD: This is a special one, transmit two 20G signal over one pair of duplex MMF (Multi Mode Fiber) with LC connector. Transmission distance is 100m over OM3 and 150m over OM4. QSFP+Bidi is high cost-performance transceiver module. Compare with SR4 module, which need MPO/MTP patch cords， QSFP-40G-SR-BD enable to use existing 10 gigabit cabling system for migration to 40 Gigabit Ethernet connectivity.

QSFP+LR4: It converts 4 inputs channels of 10Gb/s electrical data to 4 CWDM optical signals ( 1270, 1290, 1310 and 1330nm), and multiplexes them into a single channel for 40Gb/s optical transmission. Reversely, on the receiver side, the module optically de-multiplexes a 40Gb/s input into 4 CWDM channels signals, and converts them to 4 channel output electrical data. Link length up to 0km on single mode fiber cable with duplex LC connector.

QSFP+ER4 Lite: same working way as QSFP+LR4, just transmission distance is 30km

QSFP+ER4: suitable for long distance transmission, link length up to 40km over G.652 single-mode fiber with duplex LC connectors. 40GE or OTU3 signal is carried over four wavelengths (1270-1330nm).