Duplex Connectivity And Parallel Connectivity in Data Center

As the size of data center becomes larger and larger, the network deployment in data center is more and more complicated. In data center, duplex connectivity and parallel connectivity are two of the most commonly deployed cabling system. However, to satisfy different requirements for cabling system, these two connectivity solutions are often utilized together. This article is going to introduce duplex connectivity and parallel connectivity in data center as well as their cross-connectivity solutions.

Duplex Connectivity

It is not difficult to understand that duplex connectivity is completed by two fibers. When it comes to duplex connectivity, what first appears in the mind is the LC duplex cable. According to TIA standard, there are two types of LC duplex patch cables: A-to-A patch cable and A-to-B patch cable. From the figure below we can see that the former one is a cross version while the latter one is a straight one. As is often the case, A-to-B patch cable is used in the cabling system.

A-to-A patch cable and A-to-B patch cable

As shown in the following figure, the duplex direct connectivity can be achieved by using A-to-B patch cable to connect two SFP+ transceivers with LC interface.

Duplex Direct Connectivity

Parallel Connectivity

Parallel connectivity is accomplished by two or more channels. It is usually used for high speed data transmission, such as MTP link for 40G and 100G network applications. For 40G network application, 12 fibers MTP trunk cable can be used, 4 fibers for Tx and 4 fibers for Rx; for 100G network application, 24 fibers MTP trunk cable can be used, 12 fibers for Tx and 12 fibers for Rx. As shown in the following figure, the parallel direct connectivity can be achieved by using 12 fibers MTP trunk cable to connect two QSFP+/QSFP28 transceivers with MTP interface.

Parallel Direct Connectivity

Duplex and Parallel Cross-connectivity

This type of connectivity solution is commonly used for conversion between 10G and 40G network. The following figure shows the simplest connectivity solution from parallel to duplex connectivity. To realize the conversion between 40G QSFP+ transceiver and SFP+ transceiver, MPO LC fanout cable is needed. The MPO LC fanout cable has four LC duplex connectors and the fibers will be paired in a specific way, assuring the proper polarity is maintained.

parallel to duplex connectivity

The following connectivity solution uses MTP adapter panel (Item 2) and MPO cassette (Item 4). It allows for patching on both ends of the fiber optic link.

Parallel to Duplex Interconnect

The following figure shows two duplex and parallel cross-connectivity solutions. The main difference for one above and one below is on the QSFP+ side. The below cross-connectivity solution is better for a greater distance between distribution areas where the trunk cables need to be protected from damage in a tray.

Duplex and Parallel Cross-connectivity

Conclusion

The connectivity solutions mentioned above are simple explanations to duplex connectivity and parallel connectivity in data center. It seems that different cabling environments require different connectivity solutions, and different fiber optic components will be utilized.

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