1、 Definition of optical cable

Fiber optic cables are mainly composed of optical fibers (fibers), plastic protective sleeves, and plastic sheaths. They are a type of communication line used to achieve optical signal transmission, with a certain number of fibers forming the cable core in a certain way, wrapped with a sheath, and some even wrapped with an outer protective layer.(Source: Dongguan HX Fiber Technology Co., Ltd)

That is, a cable formed by a certain process of optical fiber (optical transmission carrier).

2、 Types of optical cables

There are many types of optical cables, and there are more ways to classify them. According to different standards, there are different classifications:

① Classified by transmission performance, distance, and purpose

It is divided into local fiber optic cables, long-distance fiber optic cables, submarine fiber optic cables, and user fiber optic cables.

② Classified by type of optical fiber

It is divided into single-mode optical cables and multi-mode optical cables.

③ According to the method of fiber optic coating

Tight sleeve optical cable, loose sleeve optical cable, bundle tube optical cable, and ribbon optical cable.

④ Divided by the number of fiber optic cores

It is divided into single core, dual core, four core, six core, etc.

⑤ According to the method of configuring reinforcement components

It is divided into central reinforced component optical cables (such as layer twisted optical cables and skeleton optical cables), dispersed reinforced component optical cables (such as reinforced optical cables on both sides of the bundle tube and flat optical cables), protective layer reinforced component optical cables (such as bundle tube steel wire armored optical cables), and PE fine steel wire composite outer protective layer optical cables with a certain number of fine steel wires added to the PE outer protective layer.(Source: Dongguan HX Fiber Technology Co., Ltd)

⑥ Divided by laying method

It is divided into pipeline optical cables, buried optical cables, overhead optical cables, and underwater optical cables.

⑦ Classified by the properties of the protective layer material

It is divided into polyethylene sheathed ordinary optical cables, polyvinyl chloride sheathed flame-retardant optical cables, and nylon ant and rodent resistant optical cables.

⑧ Classified by transmission conductor and medium condition

It is divided into non-metallic optical cables, ordinary optical cables, and optoelectronic composite cables.

⑨ Divided by structural method

It is divided into flat structure optical cables, layer twisted structure optical cables, skeleton structure optical cables, armored structure optical cables (including single and double layer armor), etc.

⑩ At present, communication optical cables can be divided into

(1) Outdoor optical cable, used for outdoor direct burial, pipelines, channels, tunnels, overhead and underwater laying of optical cables.
(2) Flexible optical cable, a movable optical cable with excellent flexibility performance.
(3) Indoor optical cable, suitable for indoor distribution.
(4) Optical cable inside the equipment, used for laying optical cables inside the equipment.
(5) Submarine optical cable, used for laying optical cables across oceans.
(6) Special optical cables, in addition to the above-mentioned categories, are used for special purposes.

3、 Identification method for optical cable models

The model naming of communication optical cables is based on the Chinese communication industry standard YD/T 908-2000. Composition of optical cable models: The model consists of two main parts: type and specification, with a space between them.

① Classification code

Note: Between Part 1 and Part 2: Code for reinforcing elements (reinforcing cores)
Strengthening components refer to components inside or embedded in the sheath used to enhance the tensile strength of optical cables:
Unsigned - Metal reinforced components; G-Heavy metal reinforcement components F-Non metal reinforcement components; H-Non metallic heavy reinforcement components
(For example: GYTA: Metal reinforced core; GYFTA: Non metal reinforced core)

② Code for the filling structural characteristics of cable cores and optical cables

The structural characteristics of optical cables should indicate the main type of cable core and the derived structure of the cable. When there are several structural characteristics of the cable type that need to be indicated, a combination code can be used to represent it.

③ Code for protective sheath

Note: Between Part 3 and Part 4
Its code is represented by two sets of numbers, with the first set representing the armor layer, which can be one or two digits; The second group represents the coating layer, which is a single digit number (Source: Dongguan HX Fiber Technology Co., Ltd)

④ Armor layer code

⑤ Coating layer code

⑥ Fiber optic cable specifications and models

4、 Other characteristics of optical cables

① Defects in optical fibers:

Quartz optical fibers have high strength without surface defects. Unfortunately, although a protective layer is immediately applied during the drawing process to avoid cracking, large length quartz optical fibers still inevitably have some random surface defects. The size of these defects determines the strength of the optical fiber, and under stress, these cracks will gradually expand. High humidity will accelerate this expansion. When the crack extends to a certain extent, the optical fiber will fracture. In order to ensure that the initial crack of the optical fiber used is below a certain value, tension screening should be carried out on the optical fiber during the production process. According to statistical rules, the selected optical fibers have a certain guaranteed strength. (Source: Dongguan HX Fiber Technology Co., Ltd)

In order for optical fibers to be laid and used in various environments, it is necessary to combine them with other protective components to make optical cables.

② Other performance of optical cables

The requirements for the performance of optical cables are determined based on their transmission performance, environmental conditions, and laying methods.

(1) The transmission performance of optical cables mainly depends on the characteristics of the optical fibers selected.
(2) The mechanical properties of optical cables include stretching, flattening, impact, repeated bending, twisting, and shooting.
(3) The environmental performance of optical cables includes attenuation temperature characteristics, dripping performance, sheath integrity, water permeability, and flame retardancy.

The lifespan of optical fibers depends on the stress they are subjected to and the humidity in the environment they are located in. Simply put, optical fibers are afraid of moisture and stress. In addition, the attenuation of quartz optical fibers will increase under a certain hydrogen pressure. Therefore, optical fibers are also afraid of hydrogen gas. (Source: Dongguan HX Fiber Technology Co., Ltd)

③ Design principles of optical cables

In response to the weaknesses of optical fibers, the design of optical cables should follow the following principles:

(1) Provide mechanical protection for optical fibers to prevent stress in various environments;
(2) Fiber optic cables must prevent moisture and moisture from entering;
(3) It is necessary to avoid the generation of hydrogen gas in the optical cable, especially to avoid hydrogen loss.

5、 Two commonly used optical cables

At present, the commonly used optical cables produced by various manufacturers are divided into two types: loose sleeve layer twisted type and central bundle tube type. The cross-sectional structure diagrams of two types of optical cables are as follows:

Layer twisted optical cable

At present, our company mainly produces layer twisted optical cables. In a layer twisted optical cable, the sleeve is spirally twisted on the reinforcing core, and the smaller the twist pitch, the greater the degree of freedom of the optical fiber. If the pitch is too small, it will reduce the curvature radius of the optical fiber, thereby increasing bending stress. Therefore, the twist pitch of optical cables is also an important process parameter for layer twisted optical cables and must be optimized. In an ideal situation, the position of the optical fiber in the lower layer twisted optical cable should be in the center of the sleeve. When the optical cable elongates or contracts, the fiber will move inward or outward.

Differences and standards of A (S) sheath

(1) A (S) sheath standard

A (S) sheathed optical cable should be coated with a longitudinal overlapping aluminum (steel) plastic composite tape moisture barrier layer outside the cable core, and extruded at the same time the black polyethylene sheath layer is used to bond the polyethylene sheath and the composite tape, as well as the tape at the overlapping edges of the composite tape, to each other Integrated, if necessary, adhesive can be applied at the overlap to improve bonding strength. The overlapping width of the composite tape overlap should not be less than 6mm, or when the cable core diameter is less than 9.5mm, it should not be less than 20% of the cable core circumference. The nominal value of the polyethylene sleeve thickness is 1.8mm, and the minimum value should not be less than 1.5mm. The average value on any cross-section should not be less than 1.6mm.

The nominal thickness of the aluminum (steel) strip is 0.15 mm, and the nominal thickness of the composite film is 0.05 mm. In the manufacturing of optical cables a small number of composite tape joints are allowed on the degree, and the distance between the joints should not be less than 350m. The joint should have electrical conductivity and restore the plastic composite layer. The strength of composite strips with joints should not be less than 80% of the strength of adjacent sections without joints.

(2) A (S) sheath difference

The sheath of the optical cable provides further protection for the cable. It enables optical cables to have good mechanical properties such as resistance to lateral pressure, impact, and bending. The sheath varies depending on the purpose of the optical cable. (A) Aluminum strip longitudinal sheath is mainly used for moisture-proof and waterproof purposes, while corrugated steel strip is mainly used to improve lateral pressure and impact resistance. 5.1.2 Water resistance issue of optical cables: Due to the fear of moisture and water, it is required that the optical cable must have good waterproof performance. Waterproofing is divided into horizontal and vertical waterproofing.

The water blocking problem of optical cables

Due to the fear of moisture and water, optical fibers are required to have good waterproof performance. Waterproofing is divided into horizontal and vertical waterproofing. (Source: Dongguan HX Fiber Technology Co., Ltd)

(1) Lateral water blocking

Due to the vapor pressure gradient inside and outside the optical cable, moisture or moisture outside the cable can seep and migrate into the cable in a humid environment. Strictly speaking, the plastic sheath of optical cables cannot prevent the intrusion of moisture for a long time. Once moisture invades the optical fiber, it can cause corrosion of metal accessories, leading to electrochemical hydrogen evolution. This not only corrodes metal components but also increases fiber loss, affecting the stability of the long-term transmission performance of the optical fiber. To prevent lateral water seepage of optical fibers, longitudinal aluminum tape (steel tape) is usually used to complete the process.

(2) Longitudinal water blocking

During the laying process of optical cables, due to local damage to the protective layer of the cable or unexpected water seepage at the cable connection, water can penetrate the cable longitudinally, affecting its performance. The accumulated water can also enter the junction box and terminal equipment, disrupting the operation of the entire communication line. The traditional method for longitudinal water blocking of optical cables is to block the gaps in the cable structure with cable grease to prevent water from flowing through the cable. In addition, filling fiber paste, wrapping water blocking tape or wrapping water blocking yarn, and applying hot melt adhesive at the overlap of steel strips can also play a certain vertical water blocking role.

6、 Other:

(1) The main anti tensile component of optical cables is the reinforcing core. Generally, steel wire is used as the center reinforcement core, and commonly used is phosphatized steel wire. In order to prevent lightning strikes or electromagnetic induction, optical cables need to use non-metallic reinforced cores (FRP) instead of steel wires. In this case, aramid fibers can be added to the outer layer to compensate for the insufficient strength of FRP.

(2) The optical performance of optical fibers in optical cables is the most important indicator, as it directly affects the transmission of optical signals. In terms of optical performance indicators, the attenuation of optical fibers is the most easily affected factor during the production process of optical cables.

(3) After laying the optical cable, it should work continuously throughout the year. In the high temperature of summer and the severe cold of winter, the optical performance of optical cables must remain unchanged or within the allowable range. This requires optical cables to have good temperature performance. (Source: Dongguan HX Fiber Technology Co., Ltd)