Anti Rodent Fiber Optic Cable
Rodents pose a significant threat to fiber optic cable, as their gnawing can cause serious damage to the delicate optical fiber. This article aims to discuss the commonly used methods for preventing rodent bites
The methods of anti-rodent
- Chemical methods It is the addition of a spiciness to the sheath of the optical cable. When rodents bite on the sheath, the spiciness can strongly stimulate the oral mucosa and taste nerves of rodents, causing them to give up biting. The chemical properties of spiciness are relatively stable, but when the optical cable is used in long-term outdoor environments, the spiciness will gradually leak out of the sheath due to factors such as water solubility, making it difficult to ensure the long-term rodent prevention effect of the optical cable.
- Steel armor It is to apply a hard metal reinforcement layer or armor layer (hereinafter referred to as the armor layer) outside the core of the optical cable, making it difficult for rats to bite through the armor layer, thus achieving the purpose of protecting the cable core. Metal armor is a conventional manufacturing process for optical cables, and the manufacturing cost of optical cables using armor protection method is not much different from that of ordinary optical cables. Therefore, currently, anti-rodent optical cables mainly use armor protection method.
- Glass Yarn It is to add a layer of glass yarn or FRP (Fiber Reinforced Plastics) between the inner and outer protective layers of the optical cable, as shown in Figure 2. Due to the extremely fine and brittle nature of glass fibers, the shattered glass debris during rodent biting can damage the rodent’s oral cavity, causing fear of optical cables.
How to choose an anti-rodent fiber optic cable
The Mohs hardness of rodent incisors can reach 3.0-5.5, with the highest being close to stainless steel. According to the research results of Belden, a Dutch company, steel wires and strips have the highest effectiveness in rodent prevention, at around 95%. The schematic diagram of the effectiveness of optical cable armor in rodent prevention is as follows.
From the figure, it can be seen that the chemical method is not efficient，furthermore it is not environmentally friendly. Therefore, the main method currently used is steel wire and steel tape. In some overhead applications with weight limit and less severe rodent infestation, glass yarn can also be considered.
When use armored fiber optic cable, The key to preventing rodents is “penetration resistance”, which means the ability of armor to prevent penetration. The general penetration resistance is closely related to the thickness of the steel tape. According to research, steel tape with a thickness of 0.2, 0.18, 0.15, and 0.13 millimeters can respectively achieve penetration resistance of 120N, 95N, 76N, and 59N. When the thickness of the steel tape is the same, the corrugated steel has a much higher penetration resistance than the flat type steel, while the stainless steel is much better than the chrome plated material steel, and its corrosion resistance is several times higher than that of ordinary steel. According to relevant research, the biting force of mice can reach 26-50N, and the biting force of squirrels and bamboo rats can reach 80-120N. Therefore, it is generally required that the thickness of the steel tape should not be less than 0.2mm.
|Thickness of steel tape||Resistance|
Here are some suggestions:
- Direct Bury applications
Usually, GYTA53 is a good choice. while sandy soil areas where Frequent rodent activity happened，GYTS53 will work better.
- Duct Applications
Generally, GYTS has good rodent prevention ability;
But for the applications in the wild where rodents are very active,
GYTS53 is more suitable.
- Aerial Applications
Usually, glass yarn or FRP armor is a good choice for aerial applications. It is mostly non-metallic, light weight.
But still some people choose GYTS for its better anti-rodent ability. Even choose GYTS53 used in the wild where frequent rodent activity happened. It is heavy but it has excellent anti-rodent ability.
Some other ways of anti-rodent
- Make the diameter bigger than 45mm
Install plastic tube with larger diameters in the directly buried application. The experiment shows that the larger the cable diameter, the corresponding anti-rodent ability will increase. When the outer diameter of a tube is greater than 45mm, it can basically avoid mouse bites. Therefore, using silicon core tubes larger than 45mm in the directly buried application can effectively reduce rodenticide. At the same time, stainless steel wire sealing is needed to prevent small rodents from entering the pipe.
- Make the depth no less than 1.2 meter
Ensure direct burial depth no less than 1.2m. 80% to 90% of rodents living in underground caves dig at depths less than 0.5 meters; The depth of movement of hamsters is about 1m; The drilling depth of bamboo mice is about 2 meters. Ensuring that the depth of the cable trench is greater than 1.2 meters can avoid most rodent damage.