Preface:
10G optical modules have just become common, while 40G and 100G optical modules are already in mass production, completely unable to keep up with the pace of technology! Let's learn about optical modules under 40G network today!
 
Main text:
QSFP+is an optical module packaging type defined by IEEE for 40G networks, which greatly meets the market's demand for higher density high-speed pluggable solutions. Nowadays, 40G networks are very common in most data centers, and optical modules are one of the essential components for interconnecting data center equipment. So, how much do you know about 40G QSFP+optical modules?
 
1、 Basic knowledge of 40G QSFP+optical module
The 40G QSFP+optical module complies with various standards such as SCSI, 40G Ethernet, 20G/40G Infiniband, etc. It has four data transmission channels, each with a transmission rate of about 10Gbps. Simultaneous transmission of the four channels can achieve a transmission rate of 40Gbps. This type of optical module mainly has two interfaces: LC and MTP/MPO (as shown in the figure below), which are respectively used in single-mode applications and multi-mode applications.
 
2、 40G QSFP+Optical Module Interface Specification
QSFP+was born to meet the demand for high-density and high-speed plug-in solutions in the market. As one of the most common packaging forms, the 40GQSFP+optical module outperforms the 4-channel CX4 interface in both speed and density. The two basic interface specifications for QSFP+optical modules are 40GBASE-SR4 and 40GBASE-LR4. The former is used in multimode applications, while the latter is used in single-mode applications.
 
The 40GBASE-LR4 QSFP+optical module complies with the 802.3ba (40GBASE-LR4) standard and can be used with LC fiber connectors to achieve a transmission rate of up to 40Gbps. This optical module has 4 data transmission channels, each with a transmission rate of approximately 10.3125Gbps. Simultaneous transmission of data through 4 channels can achieve 40Gbps transmission. The 40GBASE-LR4 QSFP+optical module is typically used between data centers and internet exchange points, in conjunction with single-mode fiber, with a transmission distance of up to 10km.
 
The 40GBASE-SR4QSFP+optical module complies with the 802.3ba D3.2 (40GBASE-SR4) standard and can achieve 40Gbps optical connection when used with MPO/MTP fiber optic connectors. This type of optical module also transmits through four channels, with the same transmission rate as LR4. In data centers, 40GBASE-SR4 QSFP+optical modules can be used with multimode OM3/OM4 fiber to achieve 100m (OM3) and 150m (OM4) transmission, enabling interconnection between two Ethernet switches.
 
3、 Application of 40G QSFP+Optical Module
There are multiple types of 40G QSFP+optical modules, including 40GBASE-SR4, 40GBASE-LR4, 40GBASE-ER4, etc. This section will provide a detailed introduction to these three types of optical modules and their applications.
 
The 40GBASE-SR4 optical module adopts MTP/MPO interface, with a working wavelength of 850nm, and is generally used in multimode applications. When used together with OM3/OM4 multimode fiber, its transmission distance is 100m and 150m respectively, mainly used to connect network equipment in data centers. The 40GBASE-SR4 optical module can not only use MTP/MPO fiber jumpers to connect two 40G network devices, but also be used together with MTP/MPO to LC fiber jumpers to connect 40G network devices to 10G network devices.
 
The 40GBASE-LR4 and 40GBASE-ER4 optical modules use duplex LC interfaces and are generally used in single-mode applications. These two types of optical modules have 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 optical fibers. The transmission distance of 40GBASE-LR4 optical module can reach 10 km, while the transmission distance of 40GBASE-ER4 optical module is even longer.