What is uncut cable?

In the article “Methods to reduce project costs in broadband access network 2”, Yingda introduced the uncut cable splicing method. This technology refers to a construction technique that the number of optical cable cores in the main route remains unchanged, only the branch connection fiber core is spliced, while the rest fiber optic cables will pass through directly to the next point(without disconnection), as shown in Figure 1.

Due to only a portion of the fiber core needs to be spliced  if use uncut splicing, the cost of fiber optic splicing can be significantly reduced. Moreover, the significant reduction in the number of fiber optic joints in the fiber optic link also improves the attenuation index of the link. However, commonly used fiber optic cables such as GYTA and GYTS (hereinafter referred to as common cables) have very high requirements for fiber optic cable stripping and other processes during fiber optic cable splicing, making implementation difficult. Therefore, fiber optic uncut splicing has not been widely promoted in the current network. In view of this, an easy to splice uncut cable that facilitates the splicing of fiber core has emerged.  

What is uncut cable?

Uncut cable Features

Easy to splice uncut cable is actually a type of optical cable that is easy to peel off, with an inner elliptical structure, see Figure 2. When the number of cores in the optical cable is 24 or less, separate tight buffer fibers are usually used; When the number of cores exceeds 24, multiple micro bundle tubes are usually installed, and each micro bundle tube can accommodate 4-24 bare optical fibers.

Micro bundle tubes are similar to loose tubes, but have a smaller outer diameter, thinner sheath, and are very soft. When peeling, no tools are needed and can be directly torn open by hand, as shown in Figure 3.    

There are peeling point marks on the cable sheath. When peeling, fix the optical cable and use a cable stripper to easily make a cut on the sheath, exposing the optical fiber or micro bundle tube inside the cable, as shown in Figure 4. This opening is usually called a skylight, with a length of about 10cm.

Compared with common cables, uncut cables have a smaller outer diameter but lower tensile forces. For example, the comparison between the outer diameter, allowable tensile force, and allowable flattening force of a manufacturer’s uncut cable and GYTS cable is shown in Table 1.

Compared with common cables, uncut cables have better flexibility, but lower tensile strength and no moisture barrier layer. Therefore, it is more suitable for indoor and outdoor overhead applications. If underground pipeline laying, recommend to use it in sections with better access layer conditions.

Uncut cable splicing methods 

There are two ways to splice for uncut cable.

Method 1:

Draw a skylight 1 on the sheath of the cable at the fiber cutting point as shown in Figure 4, with a distance of about 1 meter from the fiber cutting point towards the far end of the optical intersection (the distance can be adjusted as needed). Draw another skylight 2 on the sheath of the cable, cut off the fiber core at skylight 2, and pull out the corresponding fiber core at skylight 1, as shown in Figure 5. The spliced fiber core can be terminated in the splitter box or connected to a branch optical cable, and then the skylight 2 can be protected with PVC tape.    

Method 2:

At the peeling point, peel off the protective sheath of the optical cable by about 1 meter (the stripping length can be adjusted as needed), and pay attention to protecting the optical fibers inside the cable during stripping. Then fix the stripped optical fibers or micro bundle tube both ends cables in the fiber optic splice closure or optical splitter box, cut off the fiber cores that need to be spliced, them terminate with connectors or fusion splicing. Afterwards, leave the straight through optical fibers or fiber bundles on the reel, as shown in Figure 6.

Method 1 is usually used for the splicing of indoor cables inside the fiber distribution box, as shown in Figure 7. Method 2 can be used for the splicing of indoor or outdoor optical cables at distribution boxes, splice boxes, junction boxes, and other locations.     

Unuct cable application

Uncut cables are suitable for scenarios where there are dense fiber joints in the cable line, such as the entrance and introduction sections of fiber access network, as well as the backbone and distribution sections for users.

Introduction section

The use of uncut cables in the introduction section (distribution cabinet to fiber distribution box section) can reduce the number of fiber joints by several times, as shown in Figure 1a. If use common cable, the splicing joints will be 10 cores, but if use uncut cable it is only 2 cores.

In the vertical wiring in buildings, fiber optic cable terminations are often required on each floor or every few floors. When using common cable solutions, it is often necessary to set up fiber optic cable joints or lay multiple vertically routed cables; When using uncut cable scheme, only one optical cable needs to be laid, and the uncut cable is relatively soft, which is more conducive to the construction of optical cables inside the building. This also makes uncut cables more suitable for vertical wiring inside buildings. Vertically laying cables inside the building is shown in Figure 8.    

Entrance section (Drop section)

The entrance section (fiber distribution box to user section) usually distributes figure 8 drop cables to users. Often, multiple drop cables need to be repeatedly laid in the same optical cable route, as shown in Figure 9. Thus, it increases the workload of laying drop cables, and the safety of drop cables decreases with the increase of laying length.

When multiple household fiber optic cables need to be laid on the same optical cable route, uncut cable can also be used. At the location where the fiber optic cable needs to branch, an introduction box (like ftth outlet)should be set up for every 1-4 users. When the user installs it, simply connect a fiber core to the introduction box and attach a drop cable or pigtail to the user, as shown in Figure 10.

Backbone and distribution section

When the backbone or distribution cable adopts a ring network structure, as shown in Figure 11, the uncut cable splicing method can also be used at the optical intersection. The dedicated fiber core and shared fiber core are branched and spliced into termination in the intersection, but the straight through fibers can be directly coiled and left in the fusion fiber tray.

Because the uncut cable is easy to connect, it is very suitable for use in multiple branch connections. In fact, the easy to peel and small outer diameter characteristics are the demands of end users for all types of optical cables. At present, the uncut cables in China is still very limited, and related products are mainly suitable for deploying and overhead laying in buildings. Highly recommend that manufacturers optimize the structure of uncut cable, enhance their tensile and moisture resistance, and make them suitable for more scenarios.