Communication Optical Cable Line Failure Reason and Test

1 The main structure of common optical cables

The optical cable is mainly composed of optical fiber, PBT loose tube and PE sheath. There is no metal such as gold, silver, copper and aluminum in the optical cable and generally has no recycling value.

1.1 The core of the fiber optic cable

There are mainly two types of outdoor optical cable cores commonly used in integrated wiring: central tube type and layer twist type. The central tube core consists of a bundle of optical fiber units housed in a PBT loose tube. In order to distinguish easily, the coating of each fiber and each yarn are usually colored. In addition, the PBT loose tube is filled with special fiber paste, which can greatly reduce the microbending loss. The layer-stranded cable core is composed of one or at most PBT loose tubes installed in the PE sheath. The PBT loose tubes are filled with special fiber paste, and the SZ twisting method is adopted to make the optical fibers arranged in the optical cable according to a certain rule. .

1.2 Protective layer of optical cable

The raw material used for the protective layer of the optical cable is PE sheath material. The PE sheath material is continuous and complete. It is tested by electric spark without breakdown, and meets the tensile strength, elongation at break and thermal shrinkage rate in the mechanical and physical properties of the sheath. , Environmental stress cracking resistance, etc.

Communication optical cable line

2 The main reasons for the failure of communication optical cable lines

2.1 Faults at line connectors

Faults are most likely to occur at the line joints. This is because the optical fibers at the joints no longer have the protection power to the original optical cable structure or the protection power has been significantly weakened. Therefore, the daily operation and protection work can only be carried out by relying on the joint box. The probability of failure is greatly increased.

2.2 Influence of external forces

Line faults are often caused by external forces. Since many communication optical cable lines are laid in the field, the general burial standard is deep below the stratum, so the damage of many external factors to the optical cable line cannot be effectively avoided.

2.3 Poor insulation of optical cable lines

If the communication optical cable line is not well insulated, the operating strength of the optical cable will be greatly reduced due to stress corrosion and static fatigue after the splice box enters the water or is wet, and the optical cable will break in severe cases. .

2.4 The impact of lightning

The armored components of the optical cable are all metal conductors. If the power line is short-circuited or the lightning strikes the metal parts, a strong current will be generated to destroy the optical cable line equipment, and even serious casualties may occur.

3 Protective measures for communication optical cable line faults

3.1 Do a good job in daily inspection and maintenance

Routine inspection and maintenance are the most fundamental protective measures. During inspections, planned inspections should be carried out in strict accordance with relevant quality standards, and communication optical cable lines should be inspected and maintained regularly to fully ensure that the equipment is in good condition. Down.

3.2 Regular technical maintenance

In order to protect the normal operation of the optical cable system, it is necessary to carry out timely technical maintenance, regularly and irregularly detect the use characteristics of the optical cable line, pay attention to check the details of the insulation of the metal outer sheath of the optical cable to the ground, and solve the potential problems of the optical cable line in time. technical problems in order to achieve the purpose of preventing problems before they occur.

3.3 Do a good job in the treatment of metal reinforcements

When performing fault protection for the optical cable circuit that does not contain copper wires but only has a metal reinforcing core, it should be noted that the metal reinforcing members at both ends of the optical cable at the joint of the optical cable are not electrically connected, which can fully reduce the impact of strong electricity.

3.4 Adopt new protective materials

Due to the electrochemical action of the surrounding medium, the metal sheath is often corroded to varying degrees, which reduces the service life of the optical cable. Therefore, a corrosion-resistant coating with good waterproof performance should be used to fully ensure the normal operation of the communication optical cable line. .

4 Test methods for communication optical cable line faults

The biggest feature of the failure of the communication optical cable line is that the loss of the entire line increases significantly, so generally by measuring the attenuation of the optical fiber line, it is possible to roughly judge the point of the line failure and the basic nature of the failure.

4.1 Backscattering method

The backscattering method can accurately measure the loss degree of the optical fiber. The specific steps are to inject a narrow pulse with relatively large power into the fiber to be tested, and then detect the backscattered light power of the fiber at the same end. Because the main scattering of the fiber is Rayleigh scattering, generally after the measurement of the fiber, the Scattering the light power to Rayleigh can obtain the variation law of the attenuation degree of light along the fiber and other related information.

4.2 Optical Time Domain Reflectometer

In the process of using the optical time domain reflectometer, the analysis and sampling of the optical signal transmitted in the optical fiber is based on the principle of optical pulse excitation. The sampling integrator can effectively determine the connection point of the communication optical cable and the loss of the optical fiber.

5 Points for attention in fault test of communication optical cable

When testing the fault of the communication optical cable, the first thing to pay attention to is to accurately locate the distance. For non-reflective conditions and reflective joints, it is necessary to maximize the magnification of the curve when performing precise positioning, so as to make the detection results more accurate.