Download the WDM Introduction Guide which covers WDM technical basics, WDM transceivers, MUX and DEMUX, CWDM and DWDM, laser and range.
Multi-Fiber Push On (MPO) solutions are known for their quick and simple plug and play installation. All MPO cassettes, cables and connectors are tested at the factory and ready to install, ensuring quality and eliminating the need for lengthy welding on-site.
MPO connectors with 8, 12 or 24 fibers are common in data center applications (connectors with up to 72 fibers are available), helping to reduce the amount of rack space and are ideal for migrating from 10G to 100G, for example.
To ensure you get the best from your MPO deployment, however, there are one or two factors that need to be taken into consideration to ensure you select the right MPO cables and connectors and install them successfully.
The term “polarity” refers to the direction of flow, for example, of an electrical current or, in fiber optics, the direction the light flows through fiber optical cable from one end to another. Ensuring the correct polarity is essential to ensure that a transmitted signal is correctly directed to the receiving equipment and that there is a continuous connection.
In fiber applications, such as 10G, the transmission of data is bi-directional over two fibers, with each fiber connecting to the transmitter on one end and the receiver at the other. With multi-fiber maintaining correct polarity is more complex, and the TIA-568 standard covers three polarity methods, each using different types of MPO cable, that ensure that each transmitter is correctly connected to the receiver at the other end of the MPO cable. We’ll cover the three methods later in this article.
MPO connectors also meet specific physical interconnectivity standards. For example, they have a key on one side, and how this key is oriented determines the cable’s polarity. In addition, a white dot on one side of the connector indicates fiber #1.
MPO connectors are also either male (two alignment pins) or female (two alignment holes). An MPO connection is made between a male and female connector to make sure that there is proper alignment.
Interfaces on active MPO equipment, such as transceivers are usually male, so any MPO trunk cable connecting will need to be female, for example.
3) MPO Connection Methods
As mentioned earlier, there are three methods/polarity schemes for connecting MPO trunk and patch cables defined by TIA-568 Polarity A, B and C.
Method 1: Polarity A
Polarity A uses a straight cable, with neutral polarity. This results in the fibers at each end of the connection having the same fiber position, with the fiber at one end (X) in the Pin 1 position arriving at the Pin 1 position at the other end (Y).
Method 2: Polarity B
The second method or Polarity B uses “flipped” or “reversed” polarity, which results in the fiber positions being reversed, with Pin1 at one end (X) mapping into Pin 12 at the receiving end (Y), Pin 2 at Pin 11, and so on, as shown in the diagram below.
Method 3: Polarity C
This is one of the more recent, but less common standards. It uses pairwise flip sending Pin 1 at one end (X) to Pin 2 at the other end (Y), and the reverse, with Pin 2 (Y) sent to Pin 1 at the opposite end (X). Connectors are used to maintain duplex integrity while still using standard cassettes. This connection method can only be built using micro-distribution cable (not ribbon cable).
With the variety of different MPO cables available, it is important to select the most suitable for your specific needs, but once selected, MPO provides flexible and rapid installation with plug-in cassettes, cables and connectors that are tested at the factory, eliminating the need to spend time verifying system performance. With low loss levels and high-performance and reliability, MPO solutions are ideal for data centers, looking to increase network capacity whilst reducing the amount of cabling with the flexibility to expand capacity easily as needed.
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