Ultimate Guide of Short-distance 40G Optical Transceiver Modules

Advantages of 40G Network

– The transmission band can be used more effectively and the spectral efficiency is relatively high.

– The cost of equipment is reduced. If the cost of 40G can be reduced to less than 3 times of the actual cost of 10G, it will reach the degree of reasonable application; If it can be reduced to this point, large-scale applications may be realized; If this is not reduced, it is difficult to apply.

– Reduce the cost, complexity and number of spare parts of OAM. This is obvious because it uses only one network element  instead of four network elements, so it becomes simple.

– The cost per bit is more economical than other man schemes.

– Usually, a single wavelength can handle multiple data connections, and the function of the core network will be greatly enhanced. Therefore, as the router has the port of log, the core transmission network should turn to 40G. In other words, the transmission network should be four times higher than the router interface speed, so the networking efficiency is high.

Short-distance 40G QSFP Optical Transceivers


QSFP-40G-SR4 is also called 40G QSFP+ SR4. It has four independent transmitting and receiving optical signal channels. Each channel can support 10Gbps data transmission, so the transmission rate of this optical module can reach 40Gbps. QSFP-40G-SR4 adopts the QSFP+ (Quad small form factor pluggable plus) package, that is, four channel small pluggable optical module. This package type is born to meet the market demand for higher density high-speed pluggable solutions. This optical module mainly realizes the connection of high bandwidth 40G optical fiber link through 8-core or 12 core optical fiber cable with MPO/MTP optical fiber connector; The connection of 4x10G duplex mode can also be realized by connecting four optical fiber branch cables and 10gbase-sr optical interfaces. VCSEL laser is adopted. The full name of VCSEL is vertical cavity surface emitting laser, which is referred to as surface emitting laser for short. Because it can arrange multiple lasers in parallel in the direction perpendicular to the substrate, it is very suitable for application in the fields of parallel optical transmission and parallel optical interconnection, and has high cost performance.

The maximum transmission distance of QSFP+ SR4 is 150m. It is used for multimode optical fiber transmission. It can support 100m signal transmission of OM3 jumper and 150m signal transmission of OM4 jumper. It is an optical module suitable for short-distance transmission. It is mainly used in switches, routers, host adapters, buses, enterprise storage, high-density and high-speed I/O, multi-channel interconnection, etc.



QSFP-40G-SR-BD is also called 40G QSFP+ BiDi transceiver. The common wavelengths of the 40G QSFP+ BiDi optical module are 850nm and 900nm, which can be stably transmitted in a multimode optical fiber system. In addition, the transmission distance using OM3 jumper is 100m, and that using OM4 jumper is 150m.

Different from other 40G QSFP+ optical modules, other 40G QSFP+ optical modules (such as QSFP+ SR4/QSFP+ LR4) use 8 channels to realize 40G transmission, but 40G QSFP+ BiDi only needs two 20G channels to realize this function. Each channel can transmit and receive signals from a multimode cable, but it should also be noted that 40G QSFP+ BiDi must be used in pairs. How does the 40G QSFP+ BiDi work? To realize 40G QSFP+ BiDi signal transmission, three steps are required. First, four electrical signals are combined with two 20G electrical signals. Then two 20G electrical signals are exchanged into two 20G optical signals with different wavelengths. Finally, 20G optical signals with different wavelengths are transmitted to an optical cable, and then 40G equipment receives the optical signal and works.


QSFP-40G-CSR4, also known as 40G QSFP+ CSR4, is based on IEEE 802.3ba 40GBASE-SR4 standard. It is an extended version of 40GBASE-SR4 and its working principle is the same as SR4. In addition, each 10G channel of 40G QSFP+ CSR4 module complies with IEEE 10GBASE-SR specification and adopts MTP/MPO interface. The maximum distance with OM3 optical fiber can reach 300m and 400m with OM4 optical fiber.


The above mentioned has introduced the advantages of 40G networks and the most common three types of short-distance 40G QSFP+ MMF fiber optic transceiver modules, including 40G QSFP+ SR4, 40G QSFP+ BiDi and 40G QSFP+ CSR4. Whether you are looking for short-distance transmission 40G optics or long-haul transmission 40G optics, you will find them at QSFPTEK. QSFPTEK is looking forward to receiving your orders and inquiries at sales@qsfptek.com.

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