Things to Know About 40 Gigabit Ethernet

40G Standard Terms

HSSG has developed the 40G standard to support high-performance computing clusters, blade servers, storage area networks, and network storage. The 40G server has been commercialized. Optical transceivers for 40G networks will be QSFP optical modules with 12-core MPO. Using MPO technology to use “4 transmit and 4 receive” in 12-core fiber to realize the deployment of multimode fiber in 40G network. Each of the 4 “channels” is used to transmit 10G rates, and the parallel lines are 40G. The transmission of single-mode fiber is still realized by the CWDM technology of the two-core connector.

The 40G network transmission media defined by the HSSG include:

(1) 40GBase-SR4-100m OM3; 125m OM4-10Gx4 cores per direction.

(2) 40GBase-LR4 sparse wavelength division multiplexing -10km single mode – 4x10G works at 1300nm wavelength.

(3) 40GBase-CR4 7m/ copper cable 4x10G.

 Note that the first approach above defines two types of multimode fibers:

(1) The transmission distance of OM3 multimode fiber with EMB of 2000MHz·km can reach 100m.

(2) The transmission distance of OM4 multimode fiber with EMB of 4700MHz·km can reach 125m.

40G Evolution Road

For an installed 12-fiber MPO fiber optic module system to evolve to 40G, simply remove the existing modules from equipment cabinets and cross-connect fiber optic panels and replace them with MPO fiber optic adapter panels. Secondly, the cross-connection in the backbone distribution area and the interconnection of the QSFP are done with a suitable 12-core MPO fiber patch cord. Although the current 24-pin MPO connector has not achieved commercial scale in the pre-connection system, in the future, this 24-pin MPO connector will inevitably be used in trunk cables or fiber optic modules. Based on this, the 40G network necessarily requires the deployment of branch jumpers for connection between QSFP transceivers and trunk cables, and two 12-pin MPO connectors and one 24-pin MPO connector are pre-terminated at both ends. In this way, the necessary interface is provided for the 24-fiber MPO trunk cable and 40G QSFP. At the same time, a 24-core MPO fiber patch cord for system cross-connection provides the necessary guarantee for polarity maintenance and jitter requirements.

40G Polarity Management

Not only does the physical layer infrastructure need to be properly configured, but also to ensure polarity management of the optical components within it. The so-called polarity of pre-connection can be simply understood that the optical transmission component can ensure that the receiving end of the optical signal can receive the signal sent by the transmitting end from the correct port, and the transceiver link is bidirectional. In the international standard TIA 568C.0, there are descriptions of many ways to support the polarity management of dual-core connectors. However, when evolving to a 40G network based on parallel optical technology, its polarity management becomes somewhat complicated. The QSFP port transceiver point of the 40G network bit. Polarity must be considered when designing and building system links using pre-connected backbone cables and interconnects components.

More and more physical layer vendors are actively preparing, planning, and promoting their own 40/100G Ethernet solutions. Ultimately, the responsibility for ensuring the compatibility, scalability, and availability of the network infrastructure rests with the network designer. The 40/100G standard introduces new physical layer device interfaces, new requirements for link performance and transmission distance metrics, and an emphasis on fiber port density for active devices. Because of this, with a general understanding of these factors and requirements, network designers will ensure their data centers are ready for the upcoming 40/100G lanes.

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