QuickTreX MTP Assembly Builder

QuickTrex MTP Assembly Builder Tool

N/A = Not Supported/Not Applicable

Working with MTP®/MPO cable assemblies can be confusing, especially regarding polarity. But, for high density applications MTP is the best choice due to reduced labor costs, less congestion in cable pathways and spaces, and overall optical performance and reliability. Let’s break down some common questions regarding MTP polarity methods.

Let’s break down some common questions regarding MTP polarity methods.

MTP/MPO Polarity

Optical fiber networks require two fibers to make a complete circuit. The matching of the transmit Tx signal to the receive Rx equipment is referred to as polarity, and a transmit and receive side on optical transceivers usually use a duplex fiber connector to maintain the polarity. On most cabling systems, maintaining polarity just requires that the A side of one connector pair matches the B side of the other connector pair, with fiber connectors such as ST, LC, SC, and MTRJ.

MTP/MPO high density network design requires its own set of rules regarding maintaining polarity throughout the link. These three polarity methods are commonly referred to as Method A, Method B, and Method C, and we will discuss the difference further here.

MTP/MPO Connector Types

Although most people in the industry refer to this connector as MTP, it is actually correct to also call it MPO. The term MTP is a registered trademark of USConec and identifies their specific brand of the MPO-style connector. The name MPO stands for Multifiber Push On, and typically consists of a 12 strand Ribbon Fiber that is terminated to a single compact push on connector.

MTP Strand Counts

There are three popular MTP strand counts available on the market today.

Connecting MTP Connectors

When connecting, or mating, two MTP connectors together, you will need an MTP adapter to accomplish this. The male connector should be in the key up position, and the female in the key down position.

MTP Cassettes

Maintaining proper polarity across your network is also applicable when choosing a cassette. Cassettes come in a few different forms: 12 Fiber (1 x 12), 24 Fiber (2 x 12), and 24 Fiber (1 x 24). It is especially important to make sure the MTP configuration on your MTP Trunk Assembly or MTP Fanout Assembly is compatible with the MTP Cassette you choose.

Cassettes will be labeled as Method A/C or Method B. The main difference here is orientation of the way the MTP cables are mated together. Alignment pins are pre-installed in the MTP/MPO connector located inside the cassette. These pins precisely align the mating fibers in the MTP/MPO connectors at either end of the cables that plug into the cassettes.

For Method A or Method C Polarity:

Method-A cassettes make a key up to key down connection between the internal MTP connector and the MTP cable connector.

The cassettes will already be in a key up position, and when plugging in your MTP connector it needs to be in the key down position.

For Method B Polarity:
Method-B cassettes make a key up to key up, key down to key down connection. For these cables to perform properly, one of the cassettes would need to be inverted internally for Fiber 12 is mated with Fiber 1 at the end of the link. This method requires two different cassettes with special labeling to identify which one is flipped.

One cassette will be in the key up position, with the MTP cable also being key up.
One cassette will be in the key down position, with the MTP cable also being key down.

Method B cassettes are not recommended for Singlemode APC fiber applications, because the angles of the mating connectors do not line up properly with this configuration and are not sufficient for low loss applications.

*QuickTreX cassettes support a method A/C configuration, and are not compatible with Method B.

Method B in Parallel Optics

Method B polarity is particularly useful in regard to 40G parallel optic applications, and direct switch to switch connectivity. Method B MTP cables are also referred to as a QSFP/QSFP+ cable or direct attach 40GBASE-SR4, 40GBASE-PLR4 or 40GBASE-PLRL4. This orientation is useful because instead of an alternating Tx to Rx duplex pattern, 40G parallel optics utilizes the flipped Pin 1 to Pin 12, Pin 12 to Pin 1 pinout.

Female to Female type B trunk cables can also be used for a direct switch to switch connectivity going directly into 40G transceivers, or with an MTP adapter, used to connect a patch panel to a QSFP+ transceiver.

Method B in Parallel Optics

We have talked about the different types of MTP polarities, and how to properly mate two MTP connectors. The last step in a standard MTP application is breaking out the high-density fiber strands into standard fiber connectors.

If you are using a cassette, then you will need standard fiber jumper cables to complete the polarity methodology. If you are using an adapter, then you will be connecting the MTP trunk cable to an MTP Fanout Assembly which will have standard fiber connector fanouts. The MTP Fanout Builder will go into more depth on configuration there, so let’s focus on a MTP cassette method with patch cables.

There are two types of duplex fiber patch cables as defined in the TIA standard: A to A, and A to B. Maintaining proper polarity requires the B Tx signal to connect to the A Rx signal.

A to B patch cables are also known as “straight-through”
A to A patch cables are also known as “flipped”

Patch cords made with individual single fiber connectors at each end allow the flexibility for connections to be “swapped” when a polarity reversal is required. Our QuickTreX Custom USA fiber optic patch cables will provide the ability to be swapped.

The below diagrams are a macro overview of the entire MTP trunk cable to cassette connectivity flow. We have highlighted with a box, where the pairwise flipping (A to B swap) occurs in the MTP network.

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Our Offerings

At LANshack we have been manufacturing custom fiber optic cabling with premium Corning Glass in the USA for over 20 years. Our QuickTreX custom line of MTP Trunk Cables, MTP Fanout Cables, MTP cassettes and enclosures are a complete robust solution for all your MTP needs

MTP Accessories

There are a variety of hardware accessories that go along with most MTP/MTO installations. It's important to match what you need with what you have for maximum performance and full compatibility.

MTP Cabling and Fanouts

Matching your MTP trunk assembly to the appropriate fanout cabling situation isn't always simple. Here are some of the choices for what you might need to match with what you have for maximum performance and full compatibility.