Currently, under the call for 100G, 200G, and 400G high-speed optical modules, 40G QSFP+ optical modules have been widely used in access links. 40G/100G Ethernet is an Ethernet standard developed by the IEEE 802.3ba Group, supporting the transmission of 40/100Gb Ethernet frames per second, and establishing physical layer specifications for communication through backbone networks, copper cabling, multimode fiber optic cables, and single-mode fiber optic cables. 40G Ethernet has four times the capacity and can be economically migrated to 100G Ethernet.

Figure:40G QSFP+

What is a QSFP+ optical module?

QSFP+ is a form of 40G optical module packaging defined by the IEEE organization, which greatly satisfies the market's demand for high density and high speed. The 40G QSFP+ optical module is a compact hot-pluggable optical module with four transmission channels, each channel operating at a data rate of 10Gbps, and this type of optical module complies with various standards such as SCSI, 40G Ethernet, and 20G/40G Infiniband.

>>> Read More Cisco 400G QSFP-DD Optical Transceivers Overview 

What are the common QSFP+ optical modules?

40G-SR4 QSFP+ Optical Module

The 40G SR4 QSFP+ optical module is commonly used with MPO/MTP connectors in 40G data transmission. Unlike the 40G LR4 QSFP+ optical module, this type of optical module is often used for multimode fiber transmission, supporting signal transmissions of around 100 meters with OM3 jumpers and around 150 meters with OM4 jumpers. When transmitting signals at the transmitting end, the laser array first converts electrical signals into optical signals, which are then sent in parallel through ribbon multimode fiber. At the receiving end, when the signals are received, the optoelectronic detector array converts parallel optical signals into parallel electrical signals.

40G-LR4 QSFP+ Optical Transceiver Module

The 40G LR4 QSFP+ optical module is generally used with LC single-mode fiber jumpers, with a maximum transmission distance of up to 10km, and it has 4 data channels that transmit data simultaneously. Working principle: the laser driver controls the wavelength that arrives, the optical signals are then multiplexed and combined for transmission. When reaching the receiving end, these transmitted signals are demultiplexed into four channels with a transmission rate of 10Gbps each, then PIN detectors or transimpedance amplifiers recover the data stream, and the optical signals are transmitted again.

40G-LR4 PSM4 QSFP+ Optical Transceiver Module

The 40G-LR4 PSM4 QSFP+ optical transceiver module uses single-mode PSM (Parallel Single Mode) technology at the optical port and utilizes an MPO/MTP interface with four-channel full-duplex parallel design, enabling effective transmission of 10km. The laser array converts electrical signals into optical signals, which are then converted into electrical signals by the optoelectronic detector array. In short, parallel optical signals are sent in parallel through 8 optical fibers.

In addition to supporting conventional SDR/DDR/QDR bandwidth connections, 10/40G Ethernet, and data center applications, 40G PSM LR4 introduced by companies like Yifeiyang meets the application requirements of SONET OC-192, OTU1e, OTU2, OTU2e, and OTU3 rates, expanding or complementing the application areas of 40G LR.

40G-IR4 PSM QSFP+ Optical Module

The 40G-IR4 PSM QSFP+ optical module is a high-performance, low-power, long-distance interconnection solution that supports 40G Ethernet, fiber channel, and PCIe. It complies with PSM4 MSA and 40GbE QSFP. The 40G-IR4 PSM QSFP+ optical module is assembled on 4 full-duplex channels, each channel capable of transmitting data at a rate of 10Gb/s, providing an aggregate rate of 40Gb/s.

With the maturity of 40G optical modules and related product series, functional design is no longer the main selling point of the industry; cost-effectiveness takes its place, optimizing cost, performance, and reliability.

Additional Learning Hub Resources

What is the difference between 40G QSFP+ singlemode and QSFP+ multimode? 

QSFP Optical Module Wiki