What is a Fiber-Optic Cable?

Optical fiber cable is manufactured to meet optical, mechanical or environmental performance specifications. It uses one or more optical fibers placed in a sheath as a transmission medium and can be used individually or in groups. Cable assembly. The optical cable is mainly composed of optical fiber (thin glass fiber as thin as hair) and plastic protective sleeve and plastic sheath. There is no metal such as gold, silver, copper and aluminum in the optical cable, and there is generally no recycling value. An optical cable is a type of communication line in which a certain number of optical fibers form a cable core in a certain way, which is sheathed with an outer sheath, and some are also covered with an outer sheath for optical signal transmission. That is: a cable formed by an optical fiber (light transmission carrier) through a certain process. The basic structure of an optical cable is generally composed of a cable core, a reinforced steel wire, a filler, and a sheath. In addition, there are components such as a waterproof layer, a buffer layer, and an insulated metal wire as required.

In 1976, the Bell Institute in the United States

Optical cable is made up of

The basic common sense is introduced through the laying, type, construction, precautions and the limits of the optical fiber. The specific content is as follows:

I. Laying

1.General requirements

1.1 The bending radius of the optical cable should not be less than 15 times the outer diameter of the optical cable, and it should not be less than 20 times during construction.

1.2 The traction force of laying the optical cable should not exceed 80% of the allowable tension of the optical cable. The maximum instantaneous traction force must not exceed 100% of the allowable tension of the optical cable. The main traction should be added to the reinforcement (core) of the optical cable.

1.3 Optical cable traction ends can be prefabricated or made on site. Buried or underwater armored optical cables can be used as net sleeves or traction ends.

1.4 In order to prevent twisting damage to the optical cable during traction, a swivel should be added between the traction end and the traction cable.

1.5 When laying the fiber optic cable, the fiber optic cable must be released from above the cable tray and maintained in a relaxed arc. There should be no twisting during the laying of the optical cable. It is strictly forbidden to make small loops or surges.

1.6 When the optical cable is laid by mechanical traction, centralized traction, intermediate auxiliary traction or scattered traction should be selected according to traction length, terrain conditions, traction tension and other factors.

1.7 The tractor used for mechanical traction should meet the following requirements:

1) The adjustment range of traction speed should be 0 20m / min, and the adjustment method should be stepless speed regulation;

2) Traction tension can be adjusted and has automatic stop performance, that is, when the traction force exceeds the specified value, it can automatically issue an alarm and stop traction.

1.8 For laying optical cables, they must be closely organized and under the direction of a special person. There should be good communication means during traction. Untrained personnel are not allowed to work or work without communication tools.

1.9 After laying the optical cable, check whether the optical fiber is good. The end of the optical cable should be sealed and protected against moisture.

2. Pipeline optical cable

2.1 The following preparations should be made before laying pipeline optical cables

1) Check the position of the tube hole occupied by the optical cable according to the design;

2) The hole positions selected on the same route should not be changed. For example, when changing or turning, it should meet the requirements of the bending radius of the optical cable;

3) The hole used must be cleaned.

2.2 When entering the optical cable manually, each entry hole should be guarded; when the optical cable is mechanically laid, the entry hole should be guarded.

2.3 When the optical cable enters the tube hole or the pipe is turned or there is a cross, a guiding device or a bell mouth protection tube shall be used, and the outer sheath of the optical cable shall not be damaged. If necessary, apply a neutral lubricant around the cable.

2.4 The length of one-time haul of optical fiber cable is generally not more than 1000 meters. When it is too long, it should adopt 8-character segmented traction or intermediate plus auxiliary traction.

2.5 After the optical cable is laid, it shall be under the unified command of a special person, and the optical cable shall be placed one by one into the prescribed supporting board, and an appropriate margin shall be left to prevent the optical cable from being too tight.

2.6 The reserved length of the optical cable in the hole where the connector is located shall meet the requirements in the table; the optical cable that is specially reserved for design requirements is too tight.

2.7 The protective measures for pipeline optical cables shall meet the following requirements:

1) The optical cable in the hole can be protected by a serpentine hose (or soft plastic tube) and tied to the cable tray or treated according to the design requirements;

2) Plugging measures shall be taken at the nozzle;

3) The optical cable in the hole should be identified;

4) Frost-proof measures should be taken according to design requirements in severe cold areas to prevent damage to optical cables.

2.8 The laying method of the plastic sub-pipe is basically the same as that of the optical cable, and it should also meet the following requirements:

1) When laying more than two colorless sub-tubes, they should be marked at the ends;

2) The ambient temperature for laying plastic sub-pipes should be between -5 ° C and + 35 ° C;

3) The length of continuous plastic sub-pipes should not exceed 300 meters;

4) The maximum tensile force of the traction tube should not exceed the tensile strength of the pipe, and the traction speed must be uniform;

5) The remaining length of the sub tube in the entry hole shall meet the design requirements;

6) A plastic pipe plug should be installed through the pipe hole of the plastic sub pipe (other methods can also be used) to fix the sub pipe;

7) There must be no joints in the middle of the pipeline;

8) After the laying of the sub-pipes, the pipe mouth should be temporarily blocked; the sub-pipes not used in the current project must be installed with a block (cap) at the pipe end.

3. Direct buried optical cable

3.1 The buried depth of the optical cable shall meet the requirements of Table 3.1.

Laying lot or soil

Buried depth (m)

Remarks:

Ordinary soil (hard soil) 1.2

Semi-lithic (sand gravel, weathered rock) 1.0

All stone quality

Count from the top of the trench with 10 cm of fine soil

Quicksand 0.8

Suburbs, villages and towns

Urban sidewalk 1.0

Crossing railways and highways

From ballast or pavement

Ditch, canal, pond 1.2

Farm drains (within a ditch width of 1 meter) 0.8

3.2 The distance between the buried optical cable and other buildings and underground pipelines shall meet the requirements.

3.3 The optical cables laid in the same trench shall not cross or overlap, and it is advisable to adopt the method of separate hauling and laying at the same time.

3.4 The laying of direct buried optical cables shall meet the following requirements:

1) The depth of the cable trench should meet the requirements, and the bottom of the trench should be level and free of gravel; the bottom of stone and semi-stone trenches should be paved with 10 cm thick fine soil or sand;

2) When mechanical traction, ground pulley should be used;

3) During manual lifting, the optical cable should not be bent less than the specified radius of curvature, drag the ground, and be too tight;

4) The optical cable must be laid flat on the bottom of the trench, and it must not be vacated or arched;

5) When laying the optical cable on a slope with a slope greater than 20 ° and a slope length greater than 30 meters, it is advisable to use "S" -shaped laying or the measures required by the design;

6) During or after deployment, the outer sheath of the optical cable should be inspected in a timely manner, and any damage should be repaired immediately; after the laying of the directly buried optical cable, the insulation resistance to the ground of the optical cable sheath should be checked.

7) The optical fiber and copper wires in the optical cable must be inspected to confirm that they meet the quality acceptance standards before they can be returned to the soil.

3.5 The backfill soil of optical cable trench shall meet the following requirements:

1) Backfill 15 cm thick crushed or fine soil first. It is strictly forbidden to push stones, bricks, frozen soil, etc. into the trench, and it shall be leveled manually.

2) The backfill should be 10 cm above the ground.

3.6 The protective measures for buried optical cables shall be in accordance with design requirements and meet the following requirements:

1) When the optical cable line crosses the railway and the road without excavation, the pipe jacking method is adopted. Pipe jacking should be kept straight, and the specifications and location of steel pipes should meet the design requirements. Where the soil is allowed to be broken, buried pipes can be used for protection. The pipe mouth should be blocked when jacking or buried protection pipes.

2) When the fiber-optic cable line crosses machine-cultivated roads, rural avenues, and urban, residential, or movable land sections, it shall be constructed in accordance with the protection methods required by the design. When laying red bricks above the optical cable, it should be covered with 20 cm thick crushed soil before laying red bricks vertically. If two optical cables are laid in the same trench, red bricks should be laid horizontally.

3) When the optical cable line passes through trenches, canals and ponds that have been dredged and dredged for fertilizer, the top of the optical cable should be covered with cement boards or sandbags for protection.

4) The optical cable should be used for slope protection when it passes through trenches and terraces with a length of more than 0.8 meters (including 0.8 meters), and the slope protection method is in accordance with the design requirements. When crossing trenches below 0.8 meters, except for special design requirements, slope protection is generally not performed, but it must be compacted and restored in layers.

5) The optical cable lines passing through termite active areas shall be treated as ant-proof in accordance with regulations.

6) Lightning protection measures for optical cable lines must be handled in accordance with design regulations. When using lightning protection drainage lines, single or double drainage lines should be laid 30 cm above the optical cable; when the optical cable is dug out for re-filling after some reason, it must be checked strictly whether the drainage line is above the optical cable. The upside-down phenomenon is strictly prohibited.

7) The laying of special zone marking tapes shall meet the design requirements.

3.7 The reserved optical cable at the joint point should be properly placed in the joint pit, and the end must be sealed and protected from moisture to prevent the optical cable from immersion in water or human damage.

3.8 The laying of markers for optical cable lines shall meet the following requirements:

1) Fiber optic cable connector, fiber optic cable turning point, drainage line starting and ending point, starting and stopping point of laying optical fiber cable in the same trench, special reserved point for optical cable, crossing point with other cables, crossing obstacles and every 200 meters in urban areas Ordinary markers should be set every 250 meters in suburbs and long distances.

2) Monitoring points shall be set at the joints of the metal sheath of the optical cable to the ground insulation and potential.

3) When there is a sign that can be used, a fixed sign can be used instead of a mark.

4) The marker stone is buried at a depth of 60 cm and 40 cm. The soil around the marker stone should be compacted.

5) Ordinary beacon should be buried directly above the optical cable. The marker stone at the joint should be buried in the route of the optical cable line, and the marked side of the marker stone should face the optical cable connector. The marker at the turn should be buried at the intersection of the turn of the optical cable line, and the marker should face the side with the smaller bend angle of the cable. When the cable is laid along the highway at a distance of no more than 100 meters, the marker stone can face the highway.

6) The standard stone is made of hard stone or reinforced concrete. There are two specifications: short standard stone is used in general areas and the size should be 100 × 14 × 14 cm; 14 cm.

7) The number of the standard stone is red (or black) lacquered letters on a white background, the font is straight, and the surface is clean. The number should be arranged according to the transmission direction, from the A end to the B end. Generally, one hop is used as an independent numbering unit.

4.Underwater optical cable

4.1 The laying method of the underwater optical cable should be based on the soil quality, river width, water depth, velocity and site conditions of the riverbed. Underwater excavators, manual excavation or flushing pumps can be used, as well as slow anchoring, fast tug, artificial laying The method, no matter which construction method is adopted, should meet the design requirements.

4.2 The buried depth of the underwater optical cable shall be based on the specific conditions of the river's water depth, navigability, and soil quality of the riverbed, as specified in the design documents, and shall meet the following requirements:

1) Sections with a water depth of less than 8 meters (referring to the dry season): when the river bed is unstable or the soil is soft, the burial depth should not be less than 1.5 meters; when the river bed is stable or the soil is hard, the burial depth should not be less than 1.2 meters; Semi-lithic riverbed, the burial depth should not be less than 0.5 meters;

2) Sections with a water depth of more than 8 meters: Generally, optical cables can be directly placed on the bottom of the river without being buried, and special sections should be handled according to the requirements of design documents.

4.3 The laying of underwater optical cables shall meet the following requirements:

1) The speed and position of fiber optic cables should be controlled;

2) During the laying process, the optical cable must not be emptied on the river bed, and small loops must not be made;

3) During and after the laying, the optical fiber should be monitored for good performance and problems should be handled in time to ensure the laying quality of the underwater optical cable;

4) The laying length should be the length of the optical cable determined when retesting the route. Generally, the underwater optical cable should extend 50 meters outside the bank or the bank;

5) When the design stipulates that the optical cable is laid in an arc at the bottom of the river, it should be laid upstream in accordance with the baseline at the time of measurement.

4.4 The burial depth and protection of the bank and beach shall meet the following requirements:

1) The burial depth at the bank should be no less than 1.5 meters. For stone and semi-stone areas, the bottom of the ditch is filled with 10-20 cm of fine soil or sandy soil. The top of the cable is filled with crushed or sandy soil. After compaction, it is filled up to the ground. Banks and beaches are subject to flooding, unstable areas, and areas where ships are near shore. After the ground cable is filled with crushed soil or sand, it should be covered with cement boards or sand bags.

2) The slope of the bank should be less than 30 degrees, and reinforcement measures should be taken according to the design requirements when exceeding.

4.5 For navigable rivers where underwater optical cables are laid, the area where anchoring is prohibited shall be delineated according to the design requirements, and waterline signs shall be set on the embankment or bank of the river section, and shall meet the following requirements:

1) The waterline signboard shall adopt single-pole or double-pole signboards according to design requirements or river size, and shall be installed in a position determined by the design before laying the waterline;

2) The waterline signboard should be set in a place with high terrain and without obstructions, and the front face of the card should be at an angle of 250-300 with the upstream or downstream direction, respectively;

3) When the waterline sign is installed in the soft soil area or the burial depth can not reach the stipulation, the cable should be added, and the cement rod root should be reinforced with the chassis and chuck.

5.Overhead optical cable

5.1 The sag of overhead optical cables should be determined very carefully. The elongation rate during the installation of optical cables and the maximum load after installation should be less than 0.2%. In the project, the sag of the overhead cable should be calculated according to the cable structure and the suspension method, and the elongation of the cable should be calculated so that the selected sag of the cable can ensure that the elongation of the cable does not exceed the specified value.

5.2 The laying of aerial optical cables should be hauled by pulleys, and excessive bending is not allowed during the laying process.

5.3 In the middle load area, heavy load area and super heavy load area, hanging overhead optical cables should be reserved on each pole, and the light load area should be reserved for every 3 to 5 poles. For reservation and protection, please refer to Figure 5.3-1. The optical cable should also be installed with a protective tube at the cross hanging wire or T-shaped hanging wire, as shown in Figure 5.2-3.

5.4 Hanging overhead optical cables should be adjusted uniformly after laying. The hook procedure can be selected according to the outer diameter of the optical cable with reference to Table 5.4. The hanging distance of the optical cable hook is 50 cm, and the allowable deviation should not be greater than ± 3 cm. The direction of the hooks on the hanging line should be the same, and the hook pallets are complete.

Selection table of hook program Table 5.4

Hook program optical cable outer diameter (mm)

65 or more

55 25 32

45 19 24

35 13 18

25 12 and below

5.5 The installation method and requirements of the lead-in optical cable of the suspended aerial optical cable can refer to Figure 5.5.

5.6 The anti-strength and lightning protection measures for aerial optical cables shall meet the design requirements. When the suspended overhead optical cable crosses the power line, the steel strand should be insulated with rubber hose or bamboo sheet. The area where the fiber optic cable is in contact with the tree should be protected by rubber hose or serpentine pipe.

6.Intra-office optical cable

6.1 Intra-office optical cables are generally led from the front entrance of the office to the optical transceiver through the underground entry room. Due to the complexity of the routing, manual deployment is recommended. Special personnel should be set up and down the stairway and each turn during deployment, and the traction should be carried out according to the unified command. During the traction, the fiber optic cable should be kept in a relaxed state. Small loops and dead bends are strictly prohibited.

6.2 The optical cables in the office shall be marked for identification.

6.3 The optical cable should choose a safe location in the incoming room. When it is in a location vulnerable to external damage, protective measures should be taken.

6.4 Optical cables should be bundled through cable trays and turning points (front and rear). Rubber bands should be placed on the binding parts of the upper and lower walkways or climbing walls to avoid side pressure on the optical cables.

6.5 The optical cables reserved on the terminal side according to regulations can be left in the optical terminal room or the cable entry room. Optical cables reserved for special requirements shall be adequately reserved according to design requirements.

7. Manufacturing of optical cables

The manufacturing process of optical cable is generally divided into the following processes:

1. Fibre screening: choose excellent transmission characteristics and

The main methods are permanent connection, emergency connection,

In addition to the selection of optical fiber cores and fiber types, the outer sheath of the optical cable should be selected according to the environment in which the optical cable is used.

1. When the outdoor optical cable is buried directly, it should be selected

example:

I. Sheath: Indoor optical cables are generally made of polyvinyl chloride or flame retardant polyvinyl chloride. The appearance should be smooth, bright, and

With the advent of the information age, the development of various industries in China today is closely related to communication technology. Therefore, both enterprises and people have high requirements on the communication level, and the development of the communication industry is also very rapid. However, there are still many problems that have not been resolved. The quality of communication technology is directly related to the current maintenance of communication optical cable lines. This article analyzes the meaning and specific methods of communication optical cable line maintenance for practical applications.

Common obstacle causes of fiber optic cable

Obstacle phenomenon	Possible cause of obstacle
Increased loss of original splice point of one or more optical fibers	Optical fiber splice point protection tube installation problem or water leak in the connector box
Steps in the attenuation curve of one or more fibers	Optical cable was sprained by mechanical force, part of the fiber was broken but not yet broken
One optical fiber has a step or a broken fiber, the others are intact	Optical cable is affected by mechanical force or caused by optical cable manufacturing
Horizontal extension of the original step attenuation step	Fiber breakage disorder near the original splicing point
All communication is blocked	1. The optical cable is cut, blasted or collapsed due to external force 2. Interruption of the power supply system

Finding obstacles

The method steps of judging the obstacle point of the optical cable line by using the OTDR test at the endpoint or the relay station are as follows:

1) Use OTDR to test the distance from the obstacle to the test end.

2) When the optical cable is blocked by external forces such as natural disasters or external construction, find the location of the obstacle according to the crew. If this is not the case, it will be difficult for inspectors to find obstacles from the road. At this time, you must check the distance between the obstacle point and the test end measured by the OTDR and check with the original test data to find out which standard stone (or which two joints) the obstacle point is. After necessary conversion, The exact position of the obstacle can be determined by measuring the length of the ground in between.

3) If the fiber break is due to the structural defect of the optical cable or the aging of the optical fiber, it is difficult to accurately detect the break point with OTDR, and only the obstacle section can be measured, then a section of optical cable should be used.

Method for improving accuracy of optical cable line fault location

First of all, it is necessary to understand how to use the meter and master the use of the meter to help accurate measurement.

1. Set the parameters of the OTDR. When using OTDR test, you must first set the instrument parameters, the most important of which is to set the refractive index and test wavelength of the test fiber. Only when the basic parameters of the test instrument are accurately set can conditions be created for accurate testing.

2. Use the instrument's zoom function. By applying the zoom function of OTDR, the cursor can be accurately set at the corresponding inflection point. Using the zoom function key, the graph can be enlarged to 25 meters / div, so that a more accurate test result with a resolution of less than 1 meter can be obtained.

3. Adjust the accurate test range file. For different test range files, the distance resolution of the OTDR test is different. When measuring the optical fiber obstacle point, you should choose the test range file that is greater than the measured distance and the closest, so that you can make full use of the instrument's own accuracy to perform the measurement.

Secondly, accurate and completed original documents should be established during the maintenance and management process. These accurately completed optical cable line files are the basic basis for fault measurement and location. Therefore, carelessness must not be neglected in the process of maintenance and management. Real, credible and complete line materials should be established.

When the fiber optic cable is continuously monitored, the cumulative length of the optical fiber and the total attenuation value of the optical fiber at the junction between the test end and each joint point are recorded. At the same time, the test instrument model and the set value of the refractive index during the test are also registered. Accurately record all kinds of optical cable remaining. Record the length of the optical cable reel in each joint pit, special lot, S-shaped laying, entering the room, etc., and the length of the optical fiber reel in the joint box, terminal box, ODF rack, etc., so that it can be deducted when converting the fault point route length.

In addition, consistency of test conditions should be maintained during the measurement. The obstacle test should try to ensure the consistency of the test instrument model, operation method and instrument parameter settings, so that the test results are comparable. Therefore, each type of test instrument and the setting of test parameters must be recorded in detail for future use.

Finally, comprehensive analysis. The test of obstacles requires operators to have clear ideas and flexible methods of handling problems. Clear logical thinking is useful no matter where they are. Under normal circumstances, the two ends of the fiber-optic cable line are tested in both directions, and then combined with the original data to analyze, and then prepare to determine the specific location of the fault. When the link around the fault point has no obvious characteristics and the specific site cannot be determined, then we can adopt the measurement method at the nearest joint, which can be excavated at the obstacle point of the preliminary test, and the end station test instrument is in a real-time measurement state.

Repair of optical cable obstacles

Obstacles in the optical cable line must be fought against every second. Temporarily tune the circuit or lay out the emergency optical cable to temporarily rush through the circuit, and force should be organized to repair it as soon as possible.

1. Emergency repair

1) All optical cable lines are blocked in one direction

According to a predetermined circuit scheduling plan, all or some of the main circuits are temporarily connected immediately.

2) Individual optical fibers of optical cable lines in a certain direction are blocked

If there is a spare fiber in the optical fiber, or if there is another detour circuit, immediately use the spare fiber or the detour circuit to temporarily tune the obstacle circuit; if there is a spare fiber in the optical cable without a detour circuit, handle it according to the prescribed scheduling principles to ensure the smooth flow of important circuits Pause the secondary circuit.

3) Part of the fiber optic cable line is blocked

If there is a spare fiber in the optical cable, in addition to using the spare fiber to temporarily tune the circuit, you can select an unblocked fiber to temporarily pair the circuit and temporarily tune the circuit according to the specified scheduling principles and scheduling order. If the temporarily paired fiber is not enough, Without a bypass circuit, the secondary circuit is suspended.

Note :

1. The temporary dispatching of the above optical fibers must be completed with the close cooperation of both parties after the dispatching plan is jointly discussed by both sides of the machine line and reported to the higher authority for approval.

2. The optical fibers paired in the original line order can be switched by the maintenance station at both ends according to the system, and the circuits can be switched. For the temporary pairing of optical fibers, the optical distribution rack (or terminal box) in the relay station on both sides of the obstacle point should be connected. On the device.

3. If the main optical fiber is connected with an optical attenuator, and the standby optical fiber is not pre-connected with an attenuator, when the standby optical fiber is called, the corresponding optical attenuator should also be connected. You should also pay attention to this problem when using temporary fiber pairing.

2. Lay out emergency cables

1) Conditions for laying emergency optical cables

When all the optical cable lines are blocked in a certain direction, after all the circuits or main transfer, you can consider repairing the optical cable at one time, without using an emergency snatch circuit. When there is no condition to temporarily tune the circuit, or if some circuits cannot temporarily meet the needs of large-capacity communications, emergency optical cables should be laid, and the circuits should be rushed in accordance with the scheduling principles and scheduling order specified in the "Circuit Scheduling System". Resume communication, and then re-route the new fiber optic cable for formal repair.

2) Determination of emergency fiber optic cable laying range

The optical cable is blocked by natural disasters or external forces. Generally, after determining the approximate location of the obstacle, it is easier to find the obstacle according to the peculiarity of the road surface, and the emergency cable deployment range can be determined. However, with OTDR, only the obstacle point is detected at the end station or the relay station, which two joints occur, and the specific location of the obstacle cannot be determined, so it is difficult to determine the emergency cable deployment range. At this time, if conditions permit, you can use OTDR for testing at the peer relay station and comprehensively analyze the test results on both sides. Generally, you can accurately determine the breakpoint of the optical cable. If there is no condition to use OTDR testing from two directions, you can send two Deal with this situation:

a) The obstacle point is relatively close to a certain connector. The emergency optical cable is to be routed from this connector. Open this connector and use OTDR to test at the connector in the direction of the obstacle. At this time, the test distance is short, and the obstacle can be detected more accurately. The specific location can determine where the emergency cable is routed.

b) The obstacle point is at the center of the two connectors. It is not appropriate to start the emergency cable from a certain connector. You must further determine the location of the obstacle point and route a section of emergency cable on both sides of the obstacle point. In this case, you can use the gradual extension test to find the exact location of the obstacle, that is, use OTDR to initially detect the obstacle point at the end station or relay station, dig out the optical cable in front of the obstacle point, and cut a certain fiber for re-testing. If you find that the obstacle is not in the cut range, you should determine how far it is, then dig the optical cable forward, cut another fiber, and repeat the test until the obstacle is included in the cut point, and the emergency can be determined. Fiber optic cable routing range. Generally, the exact location of the obstacle point can be determined by repeating the test twice.

c) Emergency repair of the same type of fiber optic cable acceleration connector

Another type of emergency repair method for optical cables is to use the same type of optical cable as the obstruction emergency cable as an emergency repair cable, use a connector (live joint) plus matching liquid for temporary connection, and grab the circuit.

3. Formal repair

When formally repairing optical cable line obstacles, communication must be maintained as much as possible, especially the communication of important circuits must not be interrupted. The construction quality must meet the requirements of the optical cable line building quality standards and maintenance quality standards.

When formally repairing the total resistance obstacles of optical cable lines, the following issues should be paid attention to:

1. The obstacles near the connector box or the connector should be repaired by using the reserved optical fiber in the connector box or the reserved optical cable in the connector pit without adding another connector. When there is a reserved optical cable near the obstacle point, the reserved optical cable should be used for connection, and only one connector is added.

2. When it is necessary to formally repair optical cable obstacles by intervening or replacing the optical cable, the same manufacturer and the same type of optical cable should be used.

3. The length of the cable involved or replaced can be considered by the following three factors:

(1) Consider that the OTDR monitoring must be used by the end station or the relay station to formally repair the spliced optical fiber, or to facilitate the identification of obstacles adjacent to the two splicing points during routine maintenance work; the minimum length of intervention or replacement of the optical cable must meet the response of the OTDR instrument Resolution (two-point resolution) requirements should generally be greater than 100 meters.

(2) Considering that it does not affect the single-mode fiber's working under single-mode steady-state conditions to ensure communication quality, the minimum length of intervention or replacement of the optical cable should be greater than 22 meters.

(3) For the length of the optical cable involved or replaced, you can refer to the principle requirements of (1) and (2), take into consideration the actual situation, and grasp it flexibly. For example, if there is a connector near the intervention or replacement of the optical cable, the optical cable should be extended to the connector as far as possible, and only one connector is added.

4. Involving or replacing optical cables, the general sequence of fiber cutover :

(1) First, both parties should agree on the fiber cutover plan in accordance with the scheduling principles and scheduling order stipulated in the "Circuit Scheduling System", and report to the superior authority for approval.

(2) Try not to interrupt the circuit (especially important circuits). The original and newly deployed optical fiber is cut by the emergency optical cable, and the backup optical cable should be connected first. Use the spare optical fiber as the replacement wire pair. According to the original cut order, cut and restore the circuit one by one. If the matching circuit is used, or there is no spare fiber cable in the original optical cable, the secondary circuit should be suspended. First, cut the fiber of the system as an alternative wire pair, and then cut and restore the circuit one by one according to the original cut sequence. . ^[1]