Understanding Polarity in MPO System

13/11/2017
About Us
Understanding Polarity in MPO System
Shop at fs.com
Search this site...
HOME
Home
Data Center
Cabling
Cabling
WDM & FTTX
Test Tool
Enterprise Network
How To
Industry Trends
Understanding Polarity in MPO System
Understanding Polarity in MPO System
Posted on October 29, 2015 by FS.COM
4
MPO/MTP technology, which is of high density, flexibility and reliability with scalable, upgradeable properties, is one of the
contributors that lead the migration to 40/100GbE. However, the network designers face another challenge which is how to assure the
proper polarity of these array connections using multi-fiber MPO/MTP components from end-to-end. Maintain the correct polarity
across a fiber network ensures that a transmit signal from any type of active equipment will be directed to receive port of a second
piece of active equipment – and vice versa. To ensure the MPO/MTP systems work with correct polarity, the TIA 568 standard
provided three methods, which will be introduced in this article.
MPO Connector
To understand the polarity in 40/100 GbE Transmission, the key of MPO technology—MPO connector should be first introduced. MPO
connector usually has 12 fibers. 24 fibers, 36 fibers and 72 fibers are also available. Each MTP connector has a key on one of the flat
side added by the body. When the key sits on the bottom, this is called key down. When the key sits on top, this is referred to as the
key up position. In this orientation, each of the fiber holes in the connector is numbered in sequence from left to right and is referred
as fiber position, or P1, P2, etc. A white dot is additionally marked on one side of the connector to denote where the position 1 is.
(shown in the following picture) The orientation of this key also determines the MPO cable’s polarity.
http://community.fs.com/blog/understanding-polarity-in-mpo-system.html
1/5
13/11/2017
Understanding Polarity in MPO System
Three Cables for Three Polarization Methods
The three methods for proper polarity defined by TIA 568 standard are named as Method A, Method B and Method C. To match these
standards, three type of MPO truck cables with different structures named Type A, Type B and Type C are being used for the three
different connectivity methods respectively. In this part, the three different cables will be introduced firstly and then the three
connectivity methods.
MPO Trunk Cable Type A: Type A cable also known as straight cable, is a straight through cable with a key up MPO connector on
one end and a key down MPO connector on the opposite end. This makes the fibers at each end of the cable have the same fiber
position. For example, the fiber located at position 1 (P1) of the connector on one side will arrive at P1 at the other connector. The
fiber sequence of a 12 fiber MPO Type A cable is showed as the following:
Recent Posts Tags
10G SFP+ 40G
QSFP+
Cable Management CWDM
MUX/DEMUX
Data Center
DWDM fiber enclosure fiber
converters fiber
media
optic
cable fiber optic communication fiber
MPO Trunk Cable Type B: Type B cable (reversed cable) uses key up connector on both ends of the cable. This type of array mating
results in an inversion, which means the fiber positions are reversed at each end. The fiber at P1 at one end is mated with fiber at
P12 at the opposing end. The following picture shows the fiber sequences of a 12 fiber Type B cable.
http://community.fs.com/blog/understanding-polarity-in-mpo-system.html
optic transceiver fiber optic
transceivers
FTTH fusion splicer ONT
OTDR PLC Splitter PON QSFP+
2/5
13/11/2017
Understanding Polarity in MPO System
transceiver RJ45 connector SFP+ SFP
transceiver WDM
MPO Trunk Cable Type C: Type C cable (pairs flipped cable) looks like Type A cable with one key up connector and one key down
connector on each side. However, in Type C each adjacent pair of fibers at one end are flipped at the other end. For example, the
fiber at position 1 on one end is shifted to position 2 at the other end of the cable. The fiber at position 2 at one end is shifted to
position 1 at the opposite end etc. The fiber sequence of Type C cable is demonstrated in the following picture.
Three Connectivity Methods
Different polarity methods use different types of MTP trunk cables. However, all the methods should use duplex patch cable to
achieve the fiber circuit. The TIA standard also defines two types of duplex fiber patch cables terminated with LC or SC connectors to
complete an end-to-end fiber duplex connection: A-to-A type patch cable—a cross version and A-to-B type patch cable—a straightthrough version.
http://community.fs.com/blog/understanding-polarity-in-mpo-system.html
3/5
13/11/2017
Understanding Polarity in MPO System
The following part illustrates how the components in MPO system are used together to maintain the proper polarization connectivity,
which are defined by TIA standards.
Method A: the connectivity Method A is shown in the following picture. A type-A trunk cable connects a MPO module on each side of
the link. In Method A, two types of patch cords are used to correct the polarity. The patch cable on the left is standard duplex A-to-B
type, while on the right a duplex A-to-A type patch cable is employed.
Method B: in Connectivity Method B, a Type B truck cable is used to connect the two modules on each side of the link. As mentioned,
the fiber positions of Type B cable are reversed at each end. Therefore standard A-to-B type duplex patch cables are used on both
sided.
Method C: the pair-reversed trunk cable is used in Method C connectivity to connect the MPO modules one each side of the link.
Patch cords at both ends are the standard duplex A-to-B type.
Conclusion
http://community.fs.com/blog/understanding-polarity-in-mpo-system.html
4/5
13/11/2017
Understanding Polarity in MPO System
Network designer using MPO/MTP components to satisfy the increasing requirement for higher transmission speed, during which one
of the big problems—polarity, can be solved by selecting the right types of MPO cables, MPO connectors, MPO cassette and patch
cables. The three different polarization methods can be applied according to the satisfy requirements in different situations. For more
information about polarity in MPO systems and 40/100GbE transmission polarity solutions, please visit Fiberstore tutorial at “Polarity
and MPO Technology in 40/100GbE Transmission“.
Tags: 40/100 GbE, MPO, MPO/MTP cassettes, MTP, MTP cable, MTP trunk cable, polarity
Comments are closed.
Recent Posts
Most Used Categories
QinQ vs VLAN vs VXLAN
Cabling (209)
Layer 2 Switch vs. Layer 3 Switch: Which One Do
You Need?
Data Center (202)
Calendar
November 2017
S
M
T
WDM & FTTX (136)
TCP/IP vs. OSI: What’s the Difference Between the
Two Models?
Comparison Between Store-and-Forward Switching
and Cut-Through Switching
Network Switch, Router & Firewall—Why Need All
Three?
Test Tool (59)
How To (43)
Enterprise Network (41)
W
T
F
S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
« Oct
Copyright © 2002-2017 FS.COM. All Rights Reserved.
http://community.fs.com/blog/understanding-polarity-in-mpo-system.html
5/5