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.
Here are some key facts about MPO that will help guide you
through the selection and installation process:
1) Polarity
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.
2) MPO Connectors
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).
Conclusion
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.
Download the Fiber Optical Transceivers Introduction Guide for key technical facts and features to help you select the right transceiver for your application.
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