Optical cable line troubleshooting. Optical cable blocking does not necessarily lead to service interruption. If a fault causes service interruption, it will be handled according to the fault repair procedure, and if it does not affect the business but does not cause a fault, it will be handled according to the cutover procedure.
Optical cable line failure
1. Classification of cable line faults
According to the interruption of the optical fiber of the faulty cable, the fault types can be divided into three types: total interruption of the optical cable, interruption of part of the bundle tube, and interruption of part of the fiber in a single bundle tube.
1. The optical cable is completely broken
If there are reservations on both sides of the site, take centralized reservations and add a joint to deal with them;
There are joints near the fault point and there are enough reservations on site, use the method of pulling reservations and using the original joints;
There is neither reservation nor joint near the fault point, so it should be solved by cable extension.
2. Part of the bundle tube in the cable is interrupted or part of the fiber in the single bundle tube is interrupted
The repair is based on the premise that it does not affect other optical fibers in use. It is recommended to use the skylight connection method to repair the faulty optical fiber.
2. Analysis of the cause of the failure of the optical cable line
The causes of cable line failure can be roughly divided into four categories: external force factors, natural disasters, defects of the cable itself and human factors.
1. Line failure caused by external force factors
(1) Excavation by external force: To deal with the fault of excavator construction, the pipeline fiber optic cable is opened by manpower well near the fault point to check whether the fiber optic cable is damaged in the manpower well, and the two-way test interrupts the fiber optic cable
(2) Vehicle hang-up: When dealing with vehicle hang-up faults, first conduct a two-way test on the fiber optic cable at the fault point to confirm the number of places where the cable is blocked, and then deal with it in a targeted manner.
2. Line faults caused by natural disasters
Rat bites and bird pecks, fires, floods, high winds, icicles, lightning strikes, electric shocks
3. Line failure caused by the fiber itself
(1) Natural fiber breakage: Since the optical fiber is drawn from glass and plastic fibers, it is relatively fragile, and static fatigue will occur over time, and the gradual aging of the optical fiber will lead to natural fiber breakage. Or the splice box is flooded, resulting in increased fiber loss or even fiber breakage.
(2) Effect of ambient temperature: If the temperature is too low, the water in the splice box will freeze, the cable sheath will shrink longitudinally, and the pressure on the optical fiber will cause micro-bending to increase the attenuation or interrupt the optical fiber. If the temperature is too high, it is easy to damage the cable sheath and other protective materials and affect the characteristics of the optical fiber.
4. Line faults caused by human factors
(1) Work failure: Human failure caused by technicians in maintenance, installation and other activities. For example, when the optical fiber is spliced, the optical fiber is scratched, the bending radius of the optical fiber is too small; the running optical cable is cut off by mistake when the optical fiber is spliced; Broken fiber.
(2) Stealing: criminals steal and cut the optical cable, causing the optical cable to be blocked.
(3) Destruction: Man-made sabotage, causing the cable to be blocked.
3. Troubleshooting principles
With the purpose of prioritizing the transmission of the active system, and based on the compression of the fault duration, regardless of day or night, regardless of whether the weather is good or bad, and regardless of maintenance boundaries, the fastest method is used to temporarily clear the active transmission system.
The general principle of fault handling is: get through first, then repair; first the core, then the edge; first the local end, then the opposite end; When two or more failures occur at the same time, the major failures shall be dealt with first. Before the line obstacle is removed, the inspection and repair shall not be suspended.
4. Optical cable line fault repair process
1. The processing after the fault occurs, different types of line faults, the focus of processing is different.
(1) The same route has a total resistance fault that can be replaced by an optical cable. The personnel on duty in the computer room should use other good fiber cores to block the services on the fiber according to the emergency plan at the first time, and then repair the faulty fiber as soon as possible.
(2) For a total resistance fault where there is no optical fiber to replace it, follow the emergency plan to implement emergency communication or direct repair of the obstacle point.
(3) There is non-total resistance in the optical cable, and there are remaining optical fibers available. Use spare fiber cores or other optical cables on the same route to pass through services on faulty fiber cores. If there are many faulty fiber cores, not enough free fiber cores, and no other optical cables with the same route, the secondary circuit can be sacrificed to pass through the important circuit, and then the faulty fiber core can be repaired without interrupting the circuit.
(4) There is non-total resistance in the optical cable, and there is no remaining optical fiber or optical cable with the same route. If the blocked fiber is an important circuit, use other non-important circuit fibers to pass through the blocked fiber, and use the method of continuous cutover to repair the faulty fiber core urgently.
(5) The transmission quality is unstable, and the system is up and down. If there is a spare fiber core or other fiber optic cable with the same route, the service on this fiber can be transferred to other fibers. Find out the reason for the decline in transmission quality and deal with it in a targeted manner.
2. Fault location
If it is determined that the optical cable line is faulty, you should quickly determine which relay section the fault occurred in and the specific situation of the fault, and ask the network management room in detail, for example, the AB system from Huanggang to Xishui is interrupted, and the Huanggang to Bahe If the loop is interrupted, it can be judged that the fault point is located in the connection section from Huanggang computer room to Bahe. According to the judgment result, immediately notify the relevant line maintenance unit to judge the fault point.
1. Distance judgment
When the computer room determines that the fault is an optical cable line fault, the line maintenance department should test the faulty optical cable line in the computer room as soon as possible, and use the OTDR test to determine the location of the line fault point.
2. Possible cause estimation
According to the curves displayed by the OTDR test, the cause of the fault is preliminarily judged, and the fault is handled in a targeted manner.
According to the fault analysis, there are many problems in the splice box for optical cable faults caused by non-external forces, and the reasons for fiber breakage or increased attenuation in the splice box are divided into the following situations:
(1) The optical fiber in the fiber tray is loose, causing the optical fiber to bounce up and be squeezed at the edge of the fiber tray or the screw on the tray. In severe cases, the optical fiber will be crushed or broken.
(2) The local bending radius of the remaining fibers in the splice box is too small or the fibers are seriously twisted when they are stored in the reel, resulting in large bending loss and static fatigue. The test at 1310nm wavelength does not change significantly, but the test at 1550nm wavelength shows significant splice loss. increase.
(3) When making the end face of the optical fiber, the bare optical fiber is too long or the optical fiber protection position is improper when the heat-shrinkable protective tube is heated, causing a part of the bare optical fiber to be outside the protective tube, and the bare optical fiber is broken when the splice box is subjected to external force.
(4) The bare optical fiber is injured when the coating is stripped, and the damage expands after a long time, and the loss of the joint increases, and in severe cases, the fiber will be broken.
(5) Water enters the splice box and freezes in winter, resulting in increased fiber loss and even fiber breakage.
3. Find the specific location of the fault point of the optical cable line
When the fiber optic cable line is blocked by obvious external forces such as natural disasters or external construction, the inspection and repair personnel will carefully inspect along the fiber optic cable line route according to the fault phenomenon and approximate fault location provided by the tester, and it is generally easier to find the fault location. If it is not the above situation, it is not easy for inspectors to find the fault location from the abnormal phenomenon on the route. At this time, according to the distance from the fault point to the test end measured by OTDR, it must be checked with the original test data to find out which two markers (or which two joints) the fault point is between, and after necessary conversion, Find the specific location of the fault point. If conditions permit, a two-way test can be carried out, which is more conducive to accurately judging the specific location of the fault point.
4. The main reasons that affect the accurate judgment of the obstacle point of the optical cable line
(1) OTDR has inherent bias
The inherent deviation of OTDR is mainly reflected in the distance resolution. Different test distance deviations are different. When the test range is 150 km, the test error reaches ±40m.
(2) Errors caused by improper operation of test instruments
When testing optical cable fault location, the correctness of OTDR use is directly related to the accuracy of obstacle testing. For example, factors such as improper instrument parameter setting or inaccurate cursor setting will lead to errors in test results.
5. A method to improve the accuracy of cable line fault location
(1) Correctly and proficiently master the use method of the instrument
Accurately set the parameters of the OTDR, select the appropriate test range file, and use the amplification function of the instrument to accurately place the cursor on the corresponding inflection point, such as the inflection point of the fault point, the beginning and end points of the optical fiber, and the inflection point at the end of the optical fiber, so that more accurate results can be obtained. Test Results.
