The characteristics and classification of good and bad optical cables

Optical cable is a communication cable assembly that utilizes one or more optical fibers placed in a sheathing as a transmission medium and can be used individually or in groups. It can have different manifestations according to different environments, such as the need for waterproofing, buffering, etc.

Optical cable basics

Optical cable structure

The basic structure of optical cable is generally composed of cable core, reinforcing steel wire, filler and sheath, etc. In addition, there are waterproof layer, buffer layer, insulated metal wire and other components as needed.

Typical fiber optic cable structure

Layer-stranded optical cable: The strength member is located in the center of the cable, and multiple optical fibers or optical fiber ribbon sub-units are helically twisted around the central strength member (S twist or SZ twist). The color separation of the stranded loose tube is usually separated by the red and green color spectrum, which is used to distinguish different loose tubes and different optical fibers. The number of cores of the stranded fiber optic cable is relatively large.

Bundle type optical cable: The center of the optical cable is a loose tube, and the optical fiber or optical fiber ribbon is directly placed in the center of the optical cable without twisting, and the strengthening member is located around the loose tube. The number of cores of the optical cable is usually less than 12 cores.

Skeleton optical cable: The reinforcing member is located in the center of the optical cable, and the optical fiber or optical fiber ribbon is placed in the plastic skeleton groove by helical twisting.

Ribbon fiber optic cable: Arrange multiple primary-coated fibers in a row to make a ribbon fiber unit, and then put the ribbon fiber unit into a plastic sleeve to form a central bundled tube structure. You can also put the ribbon fiber unit. into the groove or into the loose tube to form a skeleton or layered structure.

cable name

According to the Communications Industry Standard of the People's Republic of China "Regulations on the Nomenclature of Optical Cable Models", the optical cable model consists of two parts: type and specification.

Main performance indicators of optical cable

tensile strength

The maximum tensile force that the optical cable can withstand depends on the material and cross-sectional area of ​​the reinforcing member, and generally requires a weight greater than 1KM optical cable (most optical cables are in the range of 100 to 400KG).

Compression resistance

The maximum lateral pressure that the optical cable can withstand depends on the material and structure of the sheath, and the maximum lateral pressure that most optical cables can withstand is 100 to 400KG/10cm.

bendability

The bending characteristics mainly depend on the relative refractive index Δ of the core and cladding and the material and structure of the cable.

Construction of fiber optic cables

The most important thing for long-distance cable laying is to choose a suitable path. When choosing a path, not only the distance, but also the land use rights must be paid attention to. There must be complete design and construction drawings, so that the construction and future inspections are convenient and reliable. During construction, be careful not to put the optical cable under heavy pressure or be punctured by hard objects. When the optical cable turns, its turning radius is 20 times larger than the diameter of the optical cable itself.

Overhead construction

Hanging wire bracket overhead method: This method is simple and cheap, and is the most widely used in my country, but it is time-consuming to add hooks and organize.

Hanging wire winding overhead method: This method is more stable and requires less maintenance, but requires a special winding machine.

Note: When overhead, a guiding device must be installed where the optical cable leads to the trunk, and the optical cable should not be dragged to the ground. A length of fiber optic cable should be left on each trunk for expansion and contraction.

Metal objects in the optical cable need to be grounded reliably, especially in mountainous areas and high-voltage power grid areas, there are generally 3 grounding points per kilometer, and even non-metallic optical cables are used.

Pipeline construction

1. Before construction, check the occupancy of the pipeline, clean and place the plastic sub-pipes, and put in the traction line at the same time.

2. Calculate the wiring length and have enough reserved length.

3. The length of one laying should not be too long (usually 2KM). When wiring, it should be pulled from the middle to both sides.

4. The traction force of the cable is generally not more than 120KG, and the reinforcing core part of the optical cable should be pulled, and the waterproof and strengthening treatment of the head of the optical cable should be done.

5. The lead-in and lead-out of the optical cable must be equipped with a follow-up device, and the floor cannot be directly mopped.

Direct Buried Construction

1. The depth of the direct buried optical cable trench should be excavated according to the standard.

2. The place where trenches cannot be dug can be laid overhead or by drilling pre-buried pipes.

3. The bottom of the ditch should be flat and firm, and a part of sand, cement or supports can be pre-filled when necessary.

4. After the laying is completed, the soil should be covered and compacted as soon as possible.

In-office construction

When the optical cable enters the office through the pipe, it first enters the underground cable entry room in the office from the front hole of the office, and then from the underground cable entry room through the ladder along the optical cable aisle in the equipment room until the ODF frame or terminal box ends.