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How Does LC Uniboot Patch Cord Reverse Polarity?

How Does LC Uniboot Patch Cord Reverse Polarity?

uniboot-HD-LCDLC Uniboot patch cords are now used as the preferred option of fiber patch cords for data center high density connectivity. They feature a reverse polarity uniboot designed LC connector, eliminating the need for the dual zip cord and reducing overall cabling bulk by 50%. But do you know how does the LC uniboot patch cord achieve polarity reversal? You may find the answer in this post.

Brief Introduction to LC Uniboot Patch Cord

LC uniboot patch cords are designed for high density applications in data center environment. Generally, the LC uniboot patch cord is designed with a polarization method that can help users easily reverse the fiber polarity. In addition, the LC uniboot fiber patch cord can reduce cable management space comparing to standard patchcords as it places both simplex fibers into one jacket while still terminating into a duplex LC connector. Similar to the standard patch cord, single-mode and multimode versions are available in LC uniboot patch cord.

Basic Types of Design Principle

As we know, for traditional cabling systems using single fiber connectors, maintaining polarity requires that the “B” transmit signal connects to the “A” receive signal. But duplex patch cords used to complete serial duplex pair connections are available in two types, depending on which polarity technique is used—”A-to-B” patch cord for “straight-through” wiring and “A-to-A” patch cord for “crossover” wiring. Thus, polarity reversal is usually required during fiber optic cabling.

However, for traditional LC patch cord, polarity reversal is very inconvenient. Therefore, vendors developed the LC uniboot that is easier for polarity reversal, without having to re-terminate the connectors. Nowadays, throughout the market, two basic types of design principle are mainly used in LC uniboot patch cord for polarity reversal.

  • Type One: Switching the A and B positions of the patch cord
    LC Uniboot switchable
  • Type Two: Rotating connector 180 degree to exchange the position
    LC Uniboot 180 degrees
Products in the Market

Based on the above two design principles, there are various of LC uniboot patch cord products in the market now. In type one, the early LC uniboot patch cord requires stop-ring and kevlar crimp sleeve for the best cable retention support. But now, switchable LC uniboot patch cords with more convenient design are launched to the market. Users can open the clip and switch the polarity easily without any tools during the whole process. Products based on type two design principles apply some separation and rotation on the connectors to achieve the polarity reversal, instead of A and B position exchange. According to different vendors, the rotating part may be in a different design, e.g. Flip the released section of the housing or separately turn the A and B connector 180 degrees in the corresponding direction.


At present, a variety of LC uniboot patch cords are on sale in the market. Though they are designed based on the above two principles, they have different features according to different vendors. Famous vendors such as Levtion, Panduit, FS.COM, SENKO, etc., can offer LC uniboot patch cords. Users can choose a reliable vendor and choose the type you preferred according to the actual requirement.

Understanding Fiber Polarity Method: Which to Choose?

Understanding Fiber Polarity Method: Which to Choose?

40G and 100G are now universally deployed in data centers. As the preferred array-based fiber connector option, the MPO/MTP connector and its cable assemblies are widely used for 40/100G connectivity in high-density data center environments. However, in complex high density cabling, the advantages of MPO/MTP cabling will be lost if you don’t have a proper polarity method. Thus, the TIA 568 standard provides three methods—Method A, B and C, for configuring systems to ensure that proper connections are made. In this blog, these three methods would be described in details which may guide you to select the best method for ensuring polarity across your array-based fiber installation.

Understanding MPO/MTP Basic Structure

Before looking at each method in detail, it is necessary to understand the basic structure of an MPO/MTP connector. As the following picture shows, an MPO/MTP connector contains several parts such as boot, coupling/housing assembly, ferrule, guide pins, and so on. When the MPO/MTP connector is designed with pins, it is called male connector. On the contrary, it is called female connector.

MPO MTP structure

In addition, there is a “key” on one side of the connector body. When the key sits on top, we call that it is the key-up position. In this orientation, each of the fiber holes in the connector is numbered in sequence from left to right. We will refer to these connector holes as positions, or P1, P2, etc. Generally, there is a marker called “white dot” on the side of the connector body that is used to designate the position 1 side of the connector when it is plugged in.

Polarity Method Introduction

The TIA-568-C.0 standard illustrated three array system connectivity methods—Method A, Method B and Method C. This section will introduce them respectively.

Method A
As shown in the picture below, two Method A cassettes with key-up to key-down adapters, a straight-through key-up to key-down MPO trunk cable as well as two patch cables are required in Method A connectivity. The straight-through key-up to key-down MPO trunk cable means that the fiber 1 located in P1 of the connector on the left will arrive at P1 at the other connector. What’s more, it should be noted that the transmit‐receive flip must happen in the patch cables for Method A. In other words, an “A-to-A” patch cable at one end of the connection while an “A-to-B” patch cable at the other end.

Method A

Method B
In Method B, as shown in the following picture, Method B cassettes which employs key-up to key-up adapters are required to link straight-through key-up to key-up MPO trunk cable. With the key up on both ends, the key-up to key-up trunk cable has a different fiber array with Method A type cable. In this type of trunk cable, fiber 1 (Tx) is mated with fiber 12 (Rx), fiber 2 (Rx) is mated with fiber 11 (Tx), and so on. Two straight “A-to-B” patch cables are required at the beginning and end of the link, namely patch cables do not need to be flipped in Method B.

Method B

Method C
Method C uses the same cassettes as Method A, but to link a special key-up to key-down trunk cable. For Method C, each adjacent pair of fibers at one end are flipped at the other end. Notice the swapping of the color positions in the picture below. Fiber channel is completed by utilizing straight “A-to-B” patch cables at the beginning and end of the link. Method C is similar with Method A. The only difference between this method and Method A is that the pair-wise flip occurs in the array cable itself rather than at the patch cables, so that odd-numbered Tx fibers leaving the near-end cassette are in even-numbered Rx positions when they arrive at the remote cassette, e.g. fiber 1 (Tx) is mated with fiber 2 (Rx).

Method C

Which to Choose?

The above section shows us the details of these three methods. The following table summarizes the advantages and disadvantages of them which may guide you to choose a proper one for your network. But, it is very important to know that the method choice should be maintained consistently throughout the installation. Do not mix them throughout the installations.

Method Pros Cons
A One cassette type, easy to produce and purchase Requires pre-configured “A-to-A” patch cables, or field configuration of same
Compatible with many legacy systems
Multiple sources for components
Industry standard
Single-mode and multimode
Standard provides migration path to parallel optics
Ribbon cables can be linked (need male/female connector)
B Single source for components Remote cassette must be flipped and re-labeled
“A-to-B” patch cable only Identification and maintenance of cassettes are different on each end
Industry standard Multimode only
Standard provides migration path to parallel optics Not compatible with legacy systems
Ribbon cables can only be liked using less available (Key Up to Key Up) adapters (need male/female cable)
Fewest vendors
C One cassette type, easy to produce and purchase Less reliable than Method A
Singlemode and multimode Specialized ribbon cable assembly
Industry standard Does not support parallel optics
“A-to-B” patch cable only Not compatible with legacy systems
Less vendor support than Method A
Difficult to extend link

This post introduced three array system connectivity methods and listed their pros and cons that may guide you for polarity selection. In a word, the Method A is polarity flip in A‐to‐A patch cord. The Method B is polarity flip in cassette. And the Method C is flip by pairs. When choosing one of them for your network, the most critical consideration is to select one method and stick with it.

Polarity and MPO Technology in 40/100GbE Transmission (FS.COM)
ANSI/TIA-568-C.0 Standard
Best Practices for Ensuring Polarity of Array-Based Fiber Optic Channels (PANDUIT)

Understanding Fiber Polarity Method: Which to Choose?

Learning Fiber Optic Connectors & Adapters in Animated Manner

Learning Fiber Optic Connectors & Adapters in Animated Manner

Fiber optic connectors and adapters are the most commonly used passive components for fiber optic connectivity. They are simple and easy-to-use components but some of their parameters and characteristics may be easy to confuse, especially to newbies. Today, I am going to use several animated pictures instead of the tedious words to show the basic of fiber optic connectors and adapters.

Fiber Optic Connector

Fiber optic connector is used to achieve temporary fiber termination. As the following picture shows, a fiber optic connector usually consists of several parts, including boot, connector sub-assembly, connector housing, ferrule and dust cap.

connector consist
connector consist 2

According to different applications, various connector types are optional, such as LC or SC for transceiver connection, FC for ODF (Optical Distribution Frame) application, MPO/MTP for parallel fiber transmission, and so on.


There are three ferrule polish types of fiber optic connectors: PC (Physical Contact), UPC (Ultra Physical Contact) and APC (Angled Physical Contact). The different polish types result in different performance, especially in back reflection (return loss). In general, PC type is required at least 35dB return loss or higher; UPC is 50 dB or higher; APC is 60 dB or higher. See the picture below:

polish type

Fiber Optic Adapter

Fiber optic adapters are designed to connect two fiber optic patch cables together. When used to connect two same types of connectors, it also called coupler. The working principle is shown as below:


Similar to fiber optic connectors, they are divided into various types, including LC, SC, ST, FC, and so on. In addition, they can also be divided into single-mode and multimode, female and male versions according to the corresponding connectors.


Thanks for reading! See you next week.

Difference Between Fiber trunk, Harness, and Patch Cables

Difference Between Fiber trunk, Harness, and Patch Cables

Pre-terminated fiber cables are considered as a convenient and cost effective solution for today’s fiber optic network, which help save up to 65% installation time. Pre-terminated fiber cables are generally divided into trunk cable, harness cable and patch cable. To many newbies, these classifications often make them confused. Don’t worry, this post will take you easy to understand the difference between them.

Fiber Trunk Cable

Fiber trunk cables are available with today’s required fiber types with MPO/MTP, LC and SC connectors. Trunk cable is generally used for data center infrastructures and backbone applications where cable distances are reasonably predictable and can be easily determined. In a word, it is used as backbone cabling.

trunk cable

Fiber Harness Cable

A fiber harness cable, also called fan-out or breakout cable, is a cable assembly used to break out an MPO/MTP trunk to discrete connectors (such as LC, SC, etc.), in order to feed in to active equipment. The most common configurations of fiber harness cables are 8-fiber MPO/MTP (QSFP+ standard) to 4 duplex LC, 12-fiber MPO/MTP to 6 duplex LC, and 24-fiber MPO/MTP to 12 duplex LC.

harness cable

Fiber Patch Cable

Fiber patch cable, also called fiber patch cord or fiber jumper, is a shorter length fiber cable that is usually used to make connections between a patch panel and active equipment or between two switch ports. According to the connection requirement, there is a variety of connector options for fiber patch cable, such as LC, SC, ST, FC, MPO/MTP, and so on.

patch cable

Do you have a better understanding of these three types of pre-terminated cables after reading the above contents? If not, write down your question in comment for further discussion.

24-fiber MPO/MTP Solution – the Right Migration Path to 40/100 GbE

24-fiber MPO/MTP Solution – the Right Migration Path to 40/100 GbE

MPO-MTP-CableNowadays, many data center are migrated to 40/100 GbE (Gigabit Ethernet) from 10 GbE in order to meet the increasing demands on high speed and bandwidth. 12-fiber and 24-fiber MPO/MTP cable, as the necessary assemblies for 40/100G migration are now applied in many solutions. 12-fiber multimode trunk cables are more often recommended to use between core switched and the equipment distribution area in the data center. But is the 12-fiber the best migration path? This article will give the opposite answer—24-fiber trunk cables may be better.

A 12-fiber MPO/MTP connector is used for 40 GbE (data rate up to 40Gbps, 4 x 10 Gbps). But among the 12 fibers, only 8 optical fibers are required—4 for Tx and 4 for Rx, and each channel has a transmission rate of 10 Gbps (usually use the 4 left and 4 right optical fibers, and the inner 4 optical fibers are left unused). And for 100 GbE (data rate up to 100 Gbps, 10 x 10 Gbps or 4 x 25 Gbps), there are two solutions. One is to use two 12-fiber MPO/MTP connectors, one transmitting 10 Gbps on 10 fibers and the other receiving 10 Gbps on 10 fibers. The other one is to use a 24-fiber MPO/MTP connector. Among the 24 fibers, only 20 fibers in the middle of the connector are used to transmit and receive at 10 Gbps and the 2 top and bottom fibers on the left and right are unused.


Is there anything wrong with the above solution? Why said the 24-fiber is better than 12-fiber? Actually, it all comes down to a better return on investment and reduced future operating and capital expense. Just see the following four advantages, you will believe it.

Advantage 1: Maximum Fiber Utilization

Using 24-fiber trunk cables with 24-fiber MPO/MTP connectors on both ends to connect from the back of the switch panel to the equipment distribution area can maximum the fiber utilization. For 10G applications, each of the 24 fibers can be used to transmit 10 Gbps, for a total of 12 links. For 40G applications, which requires 8 fibers (4 Tx and 4 Rx), a 24-fiber trunk cable provides a total of three 40G links. For 100 GbE, which requires 20 fibers (10 Tx and 10 Rx), a 24-fiber trunk cable provides a single 100G link (24-fiber solution is the more recommended configuration to used for 100 GbE than 12-fiber solution). This recoups 33% of the fibers that would be lost with 12-fiber trunk cables, providing a much better return on investment.

Advantage 2: Reduced Cable Congestion

24-fiber trunk cables provide more amount of fiber in less space. For instance, it takes three 12-fiber trunk cables to provide the same number of links as a single 24-fiber trunk cable—or about 1-1/2 times more pathway space for a 40G application.

Advantage 3: Increase Fiber Density

Density in fiber switch panels is critical as today’s large core switches occupying upwards of 1/3 of an entire rack. 24-fiber MPO connectors offer a small footprint which can ultimately provide increased density in fiber panels at the switch location. In addition, with fanout technology, a 24-fiber MPO patch cable can be designed with a 24-fiber MPO on one end and 12 duplex LCs on the other end which is an ideal solution for high density 40/100 GbE migration.

Advantage 4: Simple and Cost-effective

24-fiber MPO/MTP solution is a simple and cost effective migration path from 10G to 40/100G Ethernet. It effectively supports all three applications—10, 40 and 100 GbE. Data center managers can easily migrate to higher speeds, with less time and complexity, as 24-fiber solution offers guaranteed performance for 10, 40 and 100G applications, upgrading the cabling infrastructure is as simple as upgrading the fan-out cables or cassettes and patch cords to the equipment.

This year, 40/100G will become more universal. Choose the right migration path can help reach maximum benefit and save more budgets. Meanwhile, choose a good vendor for your 40/100G optics is also necessary. The same as usual, Fiberstore may be your good choice.