As we all know, there are three kinds of product structures for main stream outdoor cables: loose tube stranded cable, central loose tube cable and grooved cable. Loose tube stranded cable is the most common outdoor cable, especially for airial application cable. Compared with central loose tube cable and grooved cable, loose tube stranded cable has stranded excess length which help it keeps low fiber strain at high tension stress. Therefore, loose tube stranded cable is more suitable to be airial application cable.
However, in order to keep its stranded structure, loose tube stranded cable usually has at least five basic units around central strength. If the basic units are less than five units, it will cause two problems:

1. It is hard to keep circle shape for cable.
2. It gives less space for central strength member.

Therefore, filler is always used in loose tube stranded cable to keep its stranded structure. It is common that each loose tube has 6-12 fibers for normal loose tube stranded cable. Therefore, for small cores optical fiber cable, such as 6 cores or 12 cores, it will have four or five fillers which is even much higher than the number of loose tubes. In order to keep stranded structure, loose tube stranded cable needs to use more material and this does not only raise the cost of cable, but also increase the weight of cable, especially for small cores cable.

Due to the rapid development of FTTH construction, demand of small cores cable is growing and growing. How to decrease the cost of small cores loose tube stranded cable becomes a challenge which we have to face. Three units stranded unitube cable is one kind of smart design to solve this problem. Follow figure is the cross-section of three units stranded unitube cable:

Figure. Cable Cross-Section

As we can see from the figure, the structure of three units stranded unitube cable is much more simple than normal loose tube stranded cable. Compared with loose tube stranded cable, three units stranded unitube cable only has three units to form the stranded structure, which makes it does not have space from central strength member. Therefore, two strength members are designed as stranded units to strengthen the cable. Usually, normal loose tube stranded cable will use aramid yarn as additional strength member to strengthen it, especially in airial application. Three units strand structure makes the cable has less stranded excess length than normal loose tube stranded cable, but contribute to two strength members, the cable can also have excellent transmission performance in air application without aramid yarn.

Compared with normal loose tube stranded cable, the diameter of three units stranded cable can be 30% less and the weight of three units stranded cable can be 40% less. Because of the reduced of diameter and weight, the cost of three units stranded cable can be much lower than normal loose tube stranded cable. In addition, it is also construction friendly than loose tube stranded cable because of its low weight.

However, three units stranded cable also has its disadvantage. As we can see from the cross-section of it, only one loose tube can be utilized. Limited by the number of loose tube, three units stranded cable always consists less than 24 fibers. If the fiber counts are over 24, on the one hand, large size of loose tube is needed to accommodate high count of fiber which will increase the size of whole cable. Finally, the cost of cable will increase dramatically. On the other hand, too much fiber in one loose tube increase the difficulty of identifying fibers. Therefore, for high cores cable, normal loose tube stranded cable is still a better choice.

Nowadays, FiberHome’s three units stranded cable has been exported to all over the world, especially in Latin America. It helps our clients reduce the cost and improve construction efficiency for FTTH project. Strict production and raw material control makes it possesses reliable performance and enable to have long lifespan. Reliable performance and long lifespan helps our clients provide stable and high quality of broadband service to their customers. Three units stranded cable help us get a double win between FiberHome and customers, even get a triple win among FiberHome, operator and individual customers.

It is reasonable to believe that three unit stranded cable will be more and more popular in the future and play more and more significant role for FTTH project in the future.