QSFP Optical Module Classification

QSFP+is a 40G optical module packaging form defined by the IEEE organization, which greatly meets the market's demand for high-end products
The demand for density and high speed. 40GQSFP+optical module is a compact hot swappable optical module with four components
The transmission channel has a data rate of 10Gbps for each channel, and this optical module complies with SCSI and 40G Ethernet
Various standards such as internet, 20G/40GB Infiniband, etc.
40G LR4 QSFP+optical module:
 
The 40G LR4QSFP+optical module complies with the 802.3ba standard, with a maximum transmission distance of up to 10km. It has the advantages of high density, low cost, high speed, large capacity, and low power consumption.
The 40G LR4 QSFP+optical module complies with the 802.3ba (40GBASE-LR4) standard and has advantages such as high density, low cost, high speed, large capacity, and low power consumption. Usually used between data centers and internet exchange points, typically connected to LC connectors. It has four independent optical signal receiving and transmitting channels, which require the use of WDM technology to multiplex and demultiplexing optical signals, thereby achieving the transmission of optical signals over long-distance single-mode fibers.
When the serial data stream is transmitted to the laser driver, the laser driver will directly modulate the laser modulated optical signal, which will then pass through the optical signal and multiplexer, and be combined together for transmission on a single-mode fiber. When approaching the receiving end, these transmitted signals are further decomposed by the demultiplexer into four channels with a transmission rate of 10.3125Gbps. The simultaneous transmission of data by the four channels can achieve 40Gbps transmission. Then, PIN detectors or mutual negative amplifiers recover each data stream, and finally transmit the optical signal, with a maximum transmission distance of 10km.
 

40G SR4 QSFP+optical module:

 
The working wavelength of the 40G SR4 QSFP+optical module is 850nm, and it transmits data through four independent full duplex channels at the same transmission rate as the 40GLR4QSFP+optical module.
The working wavelength of the 40G SR4 QSFP+optical module is 850nm, which complies with the 802.3ba D3.2 (40GBASE-SR4) standard. It is commonly used with MPO/MTP connectors in 40G data transmission and has four independent full duplex channels for transmission, with the same transmission rate as LR4. Differently, 40G SR4 QSFP+optical modules are often used with multimode fiber, and in data centers, they can be used with multimode OM3/OM4 fiber to achieve 100m (OM3) and 150m (OM4) transmission. When transmitting signals at the sending end, the laser array first converts the electrical signal into an optical signal. When the signal is received at the parallel sending and receiving end through a ribbon multimode fiber, the photodetector array then converts the parallel optical signal into a parallel electrical signal, achieving interconnection between two Ethernet switches.
 

40G LR4 PSM QSFP+optical module:

 
The transmission distance of the 40GLR4PSMQSFP+optical module is 10km, and its advantages are high port density and low cost. The optical port of this optical module adopts parallel single-mode technology - PSM.
 
40G QSFP+PSM is a high-performance, low-power, and long-term interconnect solution that supports 40G Ethernet, fiber channel, and PCIe. It is primarily designed based on the QSFP+multi-source protocol for appearance, optical/electrical connectivity, and digital diagnostic interfaces. As a highly integrated 4-channel optical module, it has the advantage of higher port density and also saves a lot of costs for the operation of the entire system. The optical port adopts PSM (Parallel Single Mode) parallel single-mode technology with 8 single-mode fibers, and utilizes 4 parallel designed MPO/MTP interfaces to achieve effective transmission of 10km. It is a combination of 4 full duplex channels, each capable of transmitting up to 10Gb/s of data and providing an aggregation rate of 40Gb/s.
 
 The working principle of the 40G LR4 PSM optical module is the same as that of the 40G SR4 QSFP+optical module, both of which convert electrical signals into optical signals through a laser array, and then convert the optical signals into electrical signals through a photodetector array. Differently, 40G LR4 PSM optical modules are commonly used to connect with single-mode ribbon fibers, meaning that parallel optical signals are transmitted in parallel through 8 single-mode fibers.
 

Summary:

The 40G SR4 QSFP+optical module is suitable for short distance transmission and is commonly used in data centers to connect Ethernet switches with OM3/OM4 ribbon cables. The 40G LR4 QSFP+optical module and the 40G LR4 PSM optical module are suitable for long-distance transmission. Compared to these two optical modules alone, the 40GLR4 QSFP+optical module is more cost-effective. Because in long-distance transmission, the 40G LR4 QSFP+optical module only requires two single-mode fibers, while the 40G LR4 PSM optical module requires eight single-mode fibers.
 
Packaging of optical module QSFP+:
QSFP+(Quad Small Form factor Pluggable) is an optical module packaging standard that supports 40G interface transmission (SFF-8436 Specification for QSFP+4X 10 Gb/s Pluggable Transceiver). In order to increase port bandwidth without increasing the interface baud rate, the IEEE association proposed the 40G Ethernet standard for transmitting 40G signals with 4 10G signals in the subsequent interface standard of 10G Ethernet. The SFF association also launched the QSFP+(Quad Small Form factor Pluggable) optical module packaging standard (SFF-8436 Specification for QSFP+4X 10 Gb/s Pluggable Transceiver) that supports parallel transmission of 4 10Gbps signals.
 
Due to the addition of more high-speed electrical interface signals (4 pairs of differential transmission and 4 pairs of differential reception), the QSFP+module adopts a wider 38 pin connector for the electrical interface, and the corresponding module size has also increased to 72.4mm (D) x 18.35mm (W) x 8.5mm (H), which is wider and longer than the SFP+module. The electrical ports of QSFP+optical modules still follow the SFI interface specification, and the optical ports refer to IEEE optical port related specifications such as multi-mode 40G-SR and single-mode 40G-LR/ER. The following figure shows the definition of electrical interface pins and typical internal structure of QSFP+optical module.