Reducing cable congestion in constrained spaces is an important factor in designing fiber systems for data centers and large enterprise equipment rooms and data centers. Network designers turn to multi-fiber MTP/MPO cabling to overcome this challenge. Ensuring correct polarity across the system becomes more complex with higher data rates.
TIA-568 standard has approved 3 methods for configuring system polarity in multi-fiber arrays - Methods A, B and C.
Before getting into the methods in detail, let us take a look at the basic components of an MPO system.
MPO System Components
MPO Connector: MPO/MTP connectors utilize a pin and socket feature to ensure proper alignment of the connectors when mating two connectors. MPO connectors have an extrusion, called a key , on one side of the MPO/MTP connector to ensure proper polarity when connectors are mated. When discussing polarity, you will hear the terms key up and key down ; these terms describe the orientation of the connector. Key up means that the extrusion on the connector is facing up. Key down means that the extrusion on the connector is facing down. 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 marked on one side of the connector to denote where the position 1 is.
MPO Adapter: MPO (male) connectors are mated to MPO(female) connectors using a MPO adapter., There are 2 types of MPO adapters:Type A-key-up to key-down Type B-key-up to key-up
MPO Cables: MPO trunk cables which are available in 12, 24, 32, 48 etc. fibers with MPO connectors (male/female) on both ends serve as permanent links connecting the MPO modules to each other. There are 3 types of trunk cables, Type A, B and C.
MPO Cassette: Modular MPO cassette is enclosed unit that usually contains 12 or 24-fiber factory terminated fan-outs inside. It enables the user to take the fibers brought by a trunk cable and distribute them to a duplex cable with a MPO connector to the more common LC or SC interface.
Different polarity methods use different types of MTP trunk cables. However, all the methods employ duplex patch cables 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 straight-through version.
METHOD A: Polarity flip in A to A patch cord
For method A, the transmit receive flip must happen in the patch cords, and the trunk cable is a straight through transmission, with the key up on one end, and the key down on the opposite end. This means that the fiber in Position 1 of the connector on the left will arrive at Position 1 at the other connector.
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 one end is standard duplex A-to-B type, while on the other end a duplex A-to-A type patch cable is employed. Type A MPO adapters all have a key up on one side and the mating connector key down on the other side.
METHOD B: Polarity flip in adapter/cassette
Type B trunk cable uses key up connector on both ends. This type of array mating results in an inversion, which means the fiber positions are reversed at each end. The fiber that is at position 1 in one connector end is in position twelve at the opposite end and the fiber that is in position 12 at the originating end is in position 1 at the opposing end.
Connectivity method B employs standard A-to-B type duplex patch cables and type B key up to key up adapters on both ends.
METHOD C: Flip by pairs
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.
In this method, patch cords at both ends are the standard duplex A-to-B type. Note that for Method C polarity, Type A adapters should be used with Type C array cords.
Summary
A simple way to look at these polarity methods is that Method A is the most straight forward but requires a different patch cord at one end. Method B uses the same patch cord at both ends, but the cassettes must be flipped over at one end so that the fiber that originated in position 1 is mapped to position 12. Method C is a variant of Method A, but with the cross-over implemented in the trunk cable instead of the patch cord. Both Method B and Method C have the advantage of using the same patch cords at both ends.
Here is a table with components used in each method:
Vitex provides all 3 types of MTP and MPO trunk cables as well as fiber patch cords for datacomm and telecom applications. If you have any questions, please contact us at info@vitextech.com
Most recent headlines
06/10/2025
France T l visions, France's leading broadcaster, has received the 2025 EBU ...
04/09/2025
Monumental Sports & Entertainment (MSE), in collaboration with Dalet, has been a...
31/08/2025
Legrand | AV, a global specialist and industry leader in audiovisual solutions, returns to CEDIA Expo 2025, taking place Sept. 4-6 in Denver, with a powerful li...
31/08/2025
Global media technology company Backlight will unveil new capabilities in its Iconik, Wildmoka, and Zype product lines at IBC2025 (booth #1.D09), September 12 1...
30/08/2025
WASHINGTON The Federal Communications Commission has adopted its FY 2025 Regulatory Fees Order that establishes the regulatory fee rates for the broadcast stati...
29/08/2025
Australian Red Cross and SBS launch training to help workplaces in the fight aga...
29/08/2025
The National Film and Video Foundation (NFVF), an agency of the Department of Sp...
29/08/2025
L3Harris Technologies has concentrated decades of expertise across the entire enterprise to develop affordable and reliable best-of-breed solutions to rapidly c...
29/08/2025
BURBANK, Calif. The CW Network and the Pac-12 Conference have announced a new media rights deal that will extend their broadcast partnership beginning with the ...
29/08/2025
NEW YORK Gracenote has released a new analysis of its global video dataset showing that the number of FAST channels grew nearly 14% from Q1 2025 and 76% since 2...
29/08/2025
SAN JOSE, Calif. Harmonic has announced a series of improvements to its live sports streaming solution that the company said will improve fan engagement, protec...
29/08/2025
NEW YORK and LOS ANGELES Fox Corp. and YouTube TV last night announced a renewal of the full portfolio of Fox networks, including Fox News Channel, Fox Business...
29/08/2025
Budapest, Hungary, August 2025 - The integration of Microsoft Teams Rooms (MTR) with Lightware's Taurus universal matrix switchers delivers a new level of f...
29/08/2025
Frequency, the engine behind many of the world's best-known streaming television channels, today announced it will launch Studio Live, a next-generation uni...
29/08/2025
In an era when AI and cyber resilience are essential, Scality will mark the 10th anniversary of Scality Day on October 16, 2025 in Paris. This flagship global e...
29/08/2025
Disguise's In-House Creative and Technical Teams Pre-Visualised, Programmed and Delivered Content for the Experience, All Powered by EX 3+
Technology solu...
29/08/2025
Disguise will be demonstrating the latest workflows for TV, film and live events on a number of partner booths at the show
Disguise, the industry-leading tech...
29/08/2025
STOCKHOLM, Sweden Accedo will showcase Accedo Compose, its AI agent-powered modular orchestration layer that assists streaming providers in transitioning client...
29/08/2025
LOS ANGELES Cineverse has announced that it is working with Xperi to bring four of its streaming channels to automobiles for the first time as part of the DTS A...
29/08/2025
DALLAS & ATLANTA Gray Media has announced an agreement with the sports streaming service Victory+ to simulcast 17 Dallas Stars NHL games in 15 television market...
29/08/2025
NEW YORK AND CULVER CITY Comcast NBCUniversal and Amazon have announced new and extended distribution agreements that will expand the content available on their...
29/08/2025
FOOTHILL RANCH, Calif. RED Digital Cinema will feature its Cine-Broadcast Module supporting live broadcast workflows during IBC2025, Sept. 12-15, at the RAI Ams...
29/08/2025
29 Aug 2025
Kyivstar Rings Opening Bell at Nasdaq Marking Landmark Listing and ...
29/08/2025
More than half of all NFL games live on Sky for the first timeFriday 29 August 2025
Sky Sports has announced a new three-year deal with the NFL, extending its ...
29/08/2025
Back to All News
RIV4LRIES: The Trailer of the New Series With Samuele Carrino ...
29/08/2025
Get ready for an inspiring and emotional insight into the world of competitive Irish dancing with My Story: Tomi Champion of the World airing on RT 2 this monda...
29/08/2025
RT has today announced that David McCullagh is to be the new presenter of RT Radio 1's flagship Today programme, which airs every weekday at 10am, replaci...
28/08/2025
By Kristin Feeley, Director, Documentary Film & Artist Programs
If you want to tell untold stories, if you want to give voice to the voiceless, you've got ...
28/08/2025
Directed by Steven Bognar and Julia Reichert, Sundance Institute-supported Amer...
28/08/2025
Corridos have been a cornerstone of M sica Mexicana for generations, telling stories rooted in everyday life. Now, a new chapter is taking shape: motivational c...
28/08/2025
Los corridos han sido un pilar de la M sica Mexicana durante generaciones, contando historias enraizadas en la vida cotidiana. Ahora, un nuevo cap tulo est tom...
28/08/2025
Earlier this month, we promised our Verano Forever party would bring the heat, a...
28/08/2025
L3Harris will provide the Polish F-16V fleet with the Viper Shield electronic warfare system as part of an upgrade program....
28/08/2025
Bilbao, August 26, 2025 - AgileTV, an international television and video technol...
28/08/2025
Ken Wilkinson is an Emmy Awards nominated New York audio engineer who specialises in production sound mixing for film, commercial, episodic and documentary work...
28/08/2025
NEW YORK FuboTV today announced that it will launch Fubo Sports, a skinny bundle that focuses on sports with a subscription price of $56 monthly....
28/08/2025
NEVADA City, Calif. At IBC2025, Sept. 12-15 at the RAI Amsterdam, Telestream will debut its new Global Ingest strategy, introducing a next-generation ingest arc...
28/08/2025
Dr. Rhoda Bernard Releases Groundbreaking Debut Book on Accessible Arts Educatio...
28/08/2025
TAG Video Systems, the leader in software-based IP end-to-end workflow monitoring, deep probing, and real-time visualization, has named Oliver Gappa as Sales Di...
28/08/2025
AI-based voice enhancement will be among a series of innovations making their IBC 2025 debut on the DHD stand B46 in Hall 8 at the RAI Amsterdam Convention Cent...
28/08/2025
Telef nica Servicios Audiovisuales (TSA), the leading system integrator and service provider in the media sector in Spain, with the support of Appear, the globa...
28/08/2025
To fully immerse sailing fans in the world's biggest offshore yacht race, production company, Optical Media turned to LiveU's On-site Production solutio...
28/08/2025
Working with Calrec on its most recent overhaul, radio and television broadcaster, WNED has migrated to a fully IP infrastructure with multiple Type R consoles,...
28/08/2025
Cleeng, the Subscriber Retention Management (SRM ) inventor, has unveiled Cleeng Pro, the first-ever direct-to-consumer (D2C) subscription management platform t...
28/08/2025
Zixi, the industry leader in live broadcast-quality video over IP, today announced that French media distribution platform OKAST has selected Zixi to enable rel...
28/08/2025
Solution offers a streamlined, speaker-free architecture to optimize integration with premium external loudspeakers and advanced loudness metering
Nixer Pro Au...
28/08/2025
Cinegy, the premier provider of software-defined television technology, has announced a strategic partnership with Vision One Touch Film Production Services L.L...
28/08/2025
Telestream, a global leader in media workflow technologies, will debut its new Global Ingest strategy at IBC2025, introducing a next-generation ingest architect...
28/08/2025
Tier 1 operator selects Broadpeak to power high-performance, unified CDN solution across Norway, Sweden and Finland
Broadpeak, a leader in streaming and moneti...
Reducing cable congestion in constrained spaces is an important factor in designing fiber systems for data centers and large enterprise equipment rooms and data centers. Network designers turn to multi-fiber MTP/MPO cabling to overcome this challenge. Ensuring correct polarity across the system becomes more complex with higher data rates.
