Why are there 8 Fiber MPO Patch Cord and MPO 12 cable?

Generally speaking, if you need to buy MPO MPO patch cord, will face a choice between 8 fiber and 12 fibers. Because 8 core material is often the same as the 12 core, but the number of fibers is different. Then, what scheme will choose 8 fiber MPO fiber patch cords, and what scheme will choose 12 fiber MPO fiber patch cords?

Firstly, let’s take a look at mpo fiber connector types: 8-core, 12 core, and 24 core

The normal 8 core connector uses a 12 core MPO connector, but does not use the middle 4 fibers or the left and right 2 fibers to achieve 8-core optical communication, as shown in the following figure:

We can see the 8 Fiber Channel MPO Connector in below table.

Starting from 10 Gb Ethernet, plug and play 12 core MPO solutions have been widely used in multimode fiber backbone networks of data centers for many years. The 12 core MPO components are connected to MPO LC fiber cassettes or modules, converting the 12 core MPO connections into 6 sets of duplex LC connections.

The use of pre terminated plug and play MPO solutions has many benefits, including fast installation, reduced path filling, and factory terminated performance. Another reason for its wide application is that it is easy to transplant to higher speed 40Gb and 100Gb that require MPO connectors. Simply remove the MPO to LC fiber cassettes and replace it with an MPO adapter plate with MPO adapters only.

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In addition to the benefits of pre terminated cables, a 12 fibers MPO solution wastes 33% of fiber if used for 40 Gb and 100 Gb applications. Because 40GBASE-SR4 and 100GBASE-SR4 applications only use 8 out of 12 cores (4-core transmission and 4-core reception), with speeds of 10 Gb/s or 25 Gb/s. The other 4 cores are not used. When 40 Gb and 100 Gb deployments become a reality, active devices using MPO interfaces are introduced to the market. At the same time, 24 core MPO components with terminal boxes can be used to convert to 8 core MPO, thereby solving the problem of fiber waste, or fiber optic MPO patch cable can be used to divide a single 24 core MPO into three groups of 8-core MPO.

Meanwhile,we all know that 40G transmission is mainly achieved through the 8 transceiver channels of the optical module (each channel has a transmission rate of 10Gbps), and MPO fiber patch cords are usually used together with this type of optical module, but these solutions themselves have problems. The terminal box or called fiber MPO cassette that converts 24 core MPO to 8 core MPO introduces additional losses for each channel. The MPO fanout cable is difficult to manage, which means that if one of the 8 core MPO connections is damaged, all three ports must be disconnected in order to replace the MPO fanout cable.

Here are three commonly used MPO jumper usage schemes. Although common 40G optical modules use 8 core fiber optic cables, we can still use 12 core connection technology to connect to QSFP ports. In fact, many people who use 40G MPO cable now use 12 core MPO connection technology in backbone networks.

• Scheme 1: Insert the 12 core fiber optic MPO connector into an optical module that only requires 8 core fibers, as there are four fibers that are not in use.
• Scheme 2 and Scheme 3: Although the scheme achieves 100% utilization of the backbone fiber through conversion modules or branch patch cables from 12 core optical cables to 8 core optical cables, it will increase additional MPO connectors and insertion loss.

So far, 8-core connection is the best solution for 40G network cabling. However, from both a cost perspective and fiber optic cable performance perspective, these cannot be considered the best solution, therefore a more reasonable solution is needed.

Conclusion

Due to the early emergence of 12 core connections and their high advantage in fiber density, both 8 core and 12 core connections will have a place in the 40G network of data centers. The specific choice of connection method needs to be determined based on actual applications and requirements.