Optic fiber cable (optic fiber cable) is manufactured to meet the optic, mechanical or environmental performance specifications. It uses one or more optic fibers placed in a coated jacket as a transmission medium and can be used individually or in groups. Cable assembly. The optic cable is mainly composed of optic fiber (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 optic cable, and generally there is no recycling value. An optic cable is a certain number of optic fibers composed of a cable core in a certain way, which is covered with a jacket, and some is also covered with an outer sheath, which is a communication line used to realize optic signal transmission. That is: a cable formed by an optic fiber (optic transmission carrier) after a certain process. The basic structure of an optic cable is generally composed of a cable core, reinforced steel wire, filler, and sheath. In addition, there are other components such as a waterproof layer, a buffer layer, and insulated metal wires as needed.
In 1976, the Bell Institute of the United States built the first optic fiber communication experiment system in Atlanta, using a 144 optic fiber cable manufactured by Western Electric Company. In 1980, commercial optic cables made of multimode optic fibers began to be used on inter-office trunk lines and a few long-distance lines in the city. Commercial optic cables made of single-mode optic fibers began to be used on long-distance lines in 1983. In 1988, the first trans-Atlantic submarine cable connecting the United States and Britain and France was successfully laid, and soon the first trans-Pacific submarine cable was built. China developed the communication optic cable by itself in 1978, using multimode optic fiber, and the core structure of the cable is layered. He has carried out field trials in Shanghai, Beijing, Wuhan and other places. Soon after, it was tried as an inter-office trunk line in the city's telephone network. After 1984, it was gradually used for long-distance lines and began to use single-mode fiber. Communication optic cable has a larger transmission capacity than copper wire cable. The distance of the relay section is long, the volume is small, the weight is light, and there is no electromagnetic interference. , And the backbone of wired transmission lines such as local area networks and private networks, and began to develop in the field of urban user loop distribution networks to provide transmission lines for fiber-to-the-home and broadband integrated service digital networks.
2. Cable Structure
The optic cable is composed of a cable core, a reinforced steel wire, a filler, and a sheath. In addition, there are other components such as a waterproof layer, a buffer layer, and insulated metal wires as needed.
The optic cable is composed of a reinforced core and a cable core, a sheath and an outer sheath. There are two types of cable core structure: single-core type and multi-core type: single-core type has two types: full type and tube bundle type; multi-core type has two types: ribbon and unit type. The outer sheath has two types of metal armor and non-armor.
3. Basic Knowledge of fiber optic cable
Basic common sense is introduced by laying, type, construction, precautions and the limit of optic fiber. The specific contents are as follows:
1.1 The bending radius of the optic cable should not be less than 15 times the outer diameter of the optic cable, and should not be less than 20 times during construction.
1.2 The traction force of laying the optic cable should not exceed 80% of the allowable tension of the optic cable. The instantaneous maximum traction force shall not exceed 100% of the allowable tension of the optic cable. The main traction should be added to the reinforcement (core) of the optic cable.
1.3 The traction end of the optic cable can be prefabricated or made on site. Directly buried or underwater armored fiber optic cable can be used as mesh sleeve or traction end.
1.4 In order to prevent twisting damage to the optic cable during traction, a swivel should be added between the traction end and the traction cable.
1.5 When laying the optic cable, the optic cable must be released from the top of the cable reel and maintain a slack arc. There should be no twisting during the laying of the optic cable, and it is strictly forbidden to hit small circles and surges.
1.6 When the optic cable is laid by mechanical traction, centralized traction, intermediate auxiliary traction or decentralized traction should be selected according to factors such as traction length, terrain conditions and traction tension.
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) The traction tension can be adjusted and has an automatic shutdown performance, that is, when the traction force exceeds the specified value, an alarm can be automatically issued and the traction can be stopped.
1.8 When laying optic cables, they must be closely organized and have someone to direct them. There should be good means of contact during traction. It is forbidden for untrained personnel to work and work without contact tools.
1.9 After the fiber optic cable is deployed, check whether the optic fiber is good. The end of the optic cable shall be sealed and protected from moisture, and shall not be immersed in water.
2. Pipeline optic cable
2.1 The following preparations should be made before laying pipeline optic cables
1) Check the position of the tube hole occupied by the optic cable according to the design;
2) The hole positions selected on the same route should not be changed, such as changing or turning, it should meet the requirements of the bending radius of the optic cable;
3) The tube holes used must be cleaned.
2.2 When the optic cable is manually laid, each entrance should be on duty; when the optic cable is mechanically laid, the entrance hole should be on duty.
2.3 When the optic cable penetrates into the pipe hole or the pipe turns or crosses, the guiding device or the bell mouth protection tube should be used, and the outer sheath of the optic cable should not be damaged. Neutral lubricant can be applied around the cable as needed.
2.4 The traction length of the optic cable is generally not more than 1000 meters. When it is too long, 8-character segment traction or intermediate traction should be adopted.
2.5 After the optic cable is laid, it should be under the unified command of a special person, and the optic cable should be placed on the specified pallet one by one through the hole, and an appropriate margin should be left to avoid the optic cable from being too tight.
2.6 The reserved length of the optic cable at the entrance where the connector is located should meet the requirements in the table; the optic cable with special reserved design requirements is too tight.
2.7 The protective measures of pipeline optic cable shall meet the following requirements:
1) The optic cable entering the hole can be protected by a serpentine hose (or soft plastic tube) and tied to the cable support plate or processed according to the measures required by the design;
2) The mouth of the pipe should be blocked;
3) The optic cable entering the hole should have an identification mark;
4) Anti-freezing measures should be taken according to design requirements in severely cold areas to prevent damage to optic cables.
2.8 The laying method of plastic sub-pipes is basically the same as the laying of optic cables, and it should also meet the following requirements:
1) When laying more than two colorless sub-tubes, the end should be marked;
2) The ambient temperature of the plastic pipes should be between -5 ℃ and + 35 ℃;
3) The length of continuous laying of plastic sub-pipes should not exceed 300 meters;
4) The maximum pulling force of the traction sub-tube should not exceed the tensile strength of the pipe, and the traction speed should be uniform;
5) The remaining length of the sub-tube in the entry hole should meet the design requirements;
6) Plastic pipe plugs should be installed in the hole of the plastic sub-pipe (other methods can also be used) to fix the sub-pipe;
7) The sub-tube must not have a joint in the middle of the pipeline;
8) After the sub-pipes are deployed, the nozzles should be temporarily blocked; the sub-pipes not used in this phase of the project must be plugged (caps) at the end of the pipes.
3. Direct buried optic cable
3.1 The buried depth of the optic cable should meet the requirements of Table 3.1.
Laying lot or soil quality
Buried depth (m)
Ordinary soil (hard soil) ≥1.2
Semi-stony (sand gravel, weathered stone) ≥ 1.0
All stone ≥0.8
Counting from the top of the trench with 10 cm of fine soil
Suburbs and villages≥1.2
Urban sidewalk ≥1.0
Crossing railway, highway ≥1.2
Ballast bottom or pavement
Ditch, canal, pond ≥1.2
Farmland drainage ditch (ditch width within 1 meter) ≥0.8
3.2 The distance between directly buried optic cable and other buildings and underground pipelines should meet the requirements.
3.3 The optic cables laid in the same ditch shall not cross or overlap, and should be separately towed and laid simultaneously.
3.4 The laying of directly buried optic cables shall meet the following requirements:
1) The depth of the optic cable trench should meet the regulations, and the bottom of the trench should be flat and free of gravel; the bottom of the stone or semi-stone trench should be paved with 10 cm thick fine soil or sand;
2) When mechanical traction, the ground pulley should be used;
3) When manually lifting, the optic cable should not be bent less than the specified radius of curvature, and the phenomenon of dragging and over-tightening;
4) The optic cable must be laid flat on the bottom of the ditch, and should not be emptied or arched;
5) When the optic cable is laid on a slope with a slope greater than 20 ° and a slope length greater than 30 meters, the "S" shape should be laid or treated according to the design requirements;
6) During or after deployment, the outer layer of the optic cable should be checked in time, and any damage should be repaired immediately; the insulation resistance of the cable sheath to the ground should be checked after the direct buried optic cable is laid.
7) The optic fiber and copper wire in the optic cable must be checked and confirmed to meet the quality acceptance standards before the whole trench can be returned to the soil.
3.5 The backfill of the optic 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 ditch, and should be leveled manually;
2) The backfill soil should be 10 cm above the ground.
3.6 The protective measures for buried optic cables shall be in accordance with the design requirements and meet the following requirements:
1) When the optic cable line crosses the railway and the road without excavation, the pipe jacking method is adopted. The jacking pipe should be kept straight, the specifications and location of the steel pipe should meet the design requirements, and the location of the broken soil can be protected by the buried pipe. When the pipe is jacked or buried, the nozzle should be blocked.
2) When the optic cable line crosses the machined road, rural avenue, urban area, residential area or easily movable land section, it should be constructed according to the protection method required by the design. When laying red bricks above the optic cable, it should first be covered with 20 cm thick crushed soil and then red bricks should be erected vertically. When laying two optic cables in the same ditch, the red bricks should be laid horizontally.
3) When the optic cable line passes through trenches, ditches and ponds with loosening and dredging for fertilizer, it should be covered with cement board or cement sandbag protection above the optic cable.
4) The optic cable should be used as a slope protection when it passes through the ridges and terraces of 0.8 meters or more (including 0.8 meters), and the slope protection method is according to the design requirements. Except for special design requirements when crossing ditches below 0.8 meters, generally no slope protection, but must be layered and compacted to restore the original state.
5) The optic cable line passing through the termite activity area shall be treated for ant prevention according to regulations.
6) Lightning protection measures for optic cable lines must be handled in accordance with design regulations. When using lightning protection drain wires, single or double drain wires should be laid 30 cm above the optic cable; when backfilling the soil and digging out the optic cable for re-laying, it must be strictly checked whether the drain wire is located above the optic cable. Upside-down phenomenon is strictly prohibited.
7) The laying of marking tapes in special locations should meet the design requirements.
3.7 The reserved optic cable at the joint point should be properly placed in the joint pit, and the end must be sealed and moisture-proof to prevent the optic cable from being immersed in water or man-made damage.
3.8 The laying of optic fiber line markers shall meet the following requirements:
1) Optic cable joints, optic cable turning points, starting and ending points of drain lines, starting and ending points of laying optic cables in the same ditch, special reserved points of optic cables, crossing points with other cables, crossing obstacles, and straight line sections every 200 meters in urban areas , Suburban and long-distance should be set at every 250 meters common stone.
2) The joints that need to monitor the insulation and potential of the metal sheath in the optic cable should be set with monitoring markers.
3) When there are signs that can be used, fixed signs can be used instead of markers.
4) The burial depth is 60 cm and the excavation is 40 cm. The soil around the plaque should be tamped.
5) Ordinary standard stones should be buried directly above the optic cable. The marker at the joint should be buried in the route of the optic cable line, and the side with the word on the marker should face the connector of the optic cable. The marking stone at the turn should be buried at the intersection of the optic cable line turning, and the marking stone should face the side where the optic cable bend angle is smaller. When the laying distance of the optic cable along the highway is not more than 100 meters, the marker can face the highway.
6) The standard stone is made of hard stone or reinforced concrete, and there are two specifications: short standard stones are used in general areas, and the size should be 100 × 14 × 14 cm; long standard stones are used in soft soil and slope areas, and the size is 150 × 14 × 14 cm.
7) The standard number is red (or black) lacquered letters on white background, the font is correct, and the surface is clean. The numbers should be arranged from the A end to the B end according to the transmission direction. Generally, one hop is taken as an independent numbering unit.
4. Underwater optic cable
4.1 The laying method of the underwater optic cable should be based on the riverbed soil quality, river width, water depth, flow velocity and site conditions. Underwater digging machines, manual digging or flushing with pumps, anchoring slow release, tug fast release, manual deployment, etc. can be used. The method, regardless of the construction method used, should meet the design requirements.
4.2 The buried depth of the underwater optic cable shall be in accordance with the specific conditions of the river's water depth, navigation, soil quality of the riverbed, etc., in accordance with 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; For semi-stony riverbeds, the burial depth should not be less than 0.5 meters;
2) Sections with a water depth of more than 8 meters: Generally, the optic cable can be directly placed on the bottom of the river without burial, and special sections are handled according to the design documents.
4.3 The laying of underwater optic cables shall meet the following requirements:
1) The speed and specified position of the fiber optic cable should be controlled;
2) During the laying process, the optic cable must not be vacated in the river bed, and no small circles should be played;
3) During the laying process and after laying, the optic fiber should be monitored for good quality, and problems should be dealt with in time to ensure the quality of the laying of the underwater optic cable;
4) The laying length should be according to the length of the optic cable determined during the re-testing route. Generally, the underwater optic cable should extend beyond the embankment or the shore 50 meters;
5) When the design stipulates that the optic cable is laid in an arc on the bottom of the river, the arc shall be laid upstream based on the baseline at the time of measurement.
4.4 Partial burial depth and protection of shore and beach shall meet the following requirements:
1) The burial depth of the shore beach should not be less than 1.5 meters. In the stone and semi-stone areas, the bottom of the trench is filled with 10-20 cm of fine soil or sand first, and the top of the optic cable is backfilled with crushed soil or sand, and then rammed to fill the ground. The beaches and beaches are washed by the flood, unstable sections and boats are docked sections. After filling the crushed soil or sand above the optic cable, it should be covered with cement boards or cement sand bags for protection.
2) The bank slope should be less than 30 degrees. If it exceeds, the reinforcement measures should be taken according to the design requirements.
4.5 For navigable rivers where underwater optic cables are laid, areas where anchorage is prohibited shall be delineated according to design requirements, and waterline signs shall be provided on embankments or banks crossing the river section, and shall meet the following requirements:
1) Waterline signs should be single pole or double pole signs according to design requirements or river size, and should be installed at the position determined by the design before laying the waterline;
2) The waterline sign should be placed in a place with high terrain and blocked by obstacles, and the front of the sign should be at an angle of 250-300 with the upstream or downstream direction;
3) When the waterline sign is installed in a soft soil area or the burial depth does not reach the specified value, the cable should be added, and the root of the cement rod should be reinforced with chassis, chuck and other reinforcement measures.
5. Overhead optic cable
5.1 The sag of the overhead optic cable should be determined with great care, and the elongation generated during and after the maximum load during the installation of the optic cable should be less than 0.2%. In the project, the overhead cable sag should be calculated according to the optic cable structure and the hanging method, and the cable elongation should be calculated so that the determined cable sag can ensure that the cable elongation does not exceed the specified value.
5.2 The laying of overhead optic cables should be towed by pulleys, and excessive bending is not allowed during the laying process.
5.3 Hanging overhead optic cables should be reserved on each pole in the mid-load area, heavy-load area and over-heavy-load area, and a light-load area should be reserved for every 3 to 5 poles. Refer to Figure 5.3-1 for reservation and protection methods. A protective tube should also be installed at the crossover cable or T-shaped suspension cable of the optic cable, as shown in Figure 5.3-2.
5.4 The hanging overhead optic cable should be adjusted uniformly after being deployed. The hook program can be selected according to the outer diameter of the optic cable with reference to Table 5.4. The distance between the hooks of the optic cable hooks is 50 cm, and the allowable deviation should not exceed ± 3 cm. The direction of the buckle of the hook on the suspension line should be the same, and the hook bracket is complete.
Hook program selection table Table 5.4
Hook program Optic cable outer diameter (mm)
65 32 or more
55 25 ～ 32
45 19 ～ 24
35 13 ～ 18
25 12 and below
5.5 The installation method and requirements of the overhead optic cable of the suspended overhead optic cable can refer to Figure 5.5.
5.6 The anti-strong electricity and lightning protection measures of overhead optic cable shall comply with the design requirements. When the overhead overhead optic cable crosses the power line, the steel strand should be insulated with rubber hose or bamboo. The parts where the optic cable contacts the tree should be protected by rubber tubes or serpentine tubes.
6. In-office optic cable
6.1 The intra-office optic cable is generally led from the front entrance of the office to the optic transceiver through the underground cable entry room. Due to the complicated routing, manual deployment should be used. Special personnel should be set up and down the corridor and each corner when laying, and the traction should be carried out according to the unified command. The optic cable should be kept slack during the traction.
6.2 The optic cable in the office shall be marked for identification.
6.3 The optic cable should choose a safe location in the incoming room. When it is in a location susceptible to external damage, protective measures should be taken.
6.4 The optic cable should be bound through the cable management frame and the turning points (front and rear). Rubber bands should be used for the lashings of up and down walkways or climbing walls to avoid side pressure on the optic cable.
6.5 The optic cable reserved on the side of the terminal according to the regulations may be left in the optic terminal room or the cable entry room. The optic cables reserved with special requirements should be kept according to the design requirements.
7. Manufacture of optic cable
The manufacturing process of optic cable is generally divided into the following processes:
1. Screening of optic fiber: select optic fiber with excellent transmission characteristics and qualified tension.
2. Dyeing of optic fiber: Use standard full chromatogram to mark, requiring no fading and migration at high temperature.
3. Secondary extrusion: use plastic with high elastic modulus and low linear expansion coefficient to extruded into a tube of a certain size, put the optic fiber into it and fill it with moisture-proof and waterproof gel, and store it for a few days (not less than two days) .
4. Twisted optic cable: Twisted several extruded optic fibers and reinforced unit together.
5. Squeeze the outer sheath of the optic cable: add a layer of sheath to the twisted optic cable.
3.2 Cable Types
According to different transmission performance, distance and use, optic cables can be divided into user optic cables, local telephone optic cables, long-distance optic cables and submarine optic cables.
2. According to different types of optic fibers used in optic cables, optic cables can be divided into single-mode optic cables and multi-mode optic cables.
3. According to the number of optic fiber cores in the optic cable, the optic cable can be divided into single-core optic cable and dual-core optic cable.
4. According to different configuration methods of reinforcements, optic cables can be divided into central reinforcing member optic cables, dispersed reinforcing member optic cables, sheath reinforcing member optic cables and integrated outer sheath optic cables.
5. According to different transmission conductors and medium conditions, optic cables can be divided into metal-free optic cables, ordinary optic cables, and integrated optic cables (mainly used for railway dedicated network communication lines).
6. According to different laying methods, optic cables can be divided into pipeline optic cables, direct buried optic cables, overhead optic cables and underwater optic cables.
7. According to different structural methods, optic cables can be divided into flat-structure optic cables, stranded optic cables, skeleton optic cables, armored optic cables and high-density user optic cables.
Over the years, we have established a set of mature methods and experience in fiber optic cable construction.
Optic cable tool use:
1 Double-port fiber stripping pliers 1 strip fiber coating / tight cladding
2 Combination socket wrench 1 set Install optic fiber connection box / terminal box
3 2m tape measure 1 measure the length of the stripping cable
4 Utility knife 1 auxiliary tool for stripping optic cable
5 Snake-head pliers
6 Horizontal cable cutter 1 longitudinal horizontal stripping cable
7 tweezers 1 set of fiber optic cable
8 scissors 1 pair cut fiber optic fiber
9 vise 1 piece cut the wire in the optic cable
10 Needle-nose pliers 1 connection auxiliary tool
11 Miniature screwdriver 2 for fastening screws
12 Allen wrench 1 set Install six screws
13 Adjustable wrench 1 connection auxiliary tool
14 Combined screwdriver 2 sets of optic fiber connection box
15 Alcohol pump bottle 1 clean fiber
16 marker pen 1 mark fiber number
17 flashlight 1 for night construction lighting
18 diagonal pliers 1 auxiliary construction tool
(1) Outdoor construction of optic cable
The most important thing for laying longer distance optic cables is to choose a suitable path. The shortest path here is not necessarily the best, but also pay attention to the right to use the land, the possibility of erection or burial, etc.
When the optic cable turns, its turning radius is greater than 20 times the diameter of the optic cable itself.
1. Outdoor overhead optic cable construction:
A. The overhead wire hanging method is simple and cheap. It is the most widely used in China, but it takes more time to add and hang the hook.
B. Hanging wire winding overhead method, this method is more stable, less maintenance work. But a special tying machine is required.
C. The self-supporting overhead method has high requirements on the wire rod, the construction and maintenance are difficult, and the cost is high, which is rarely used in China.
D. When the cable is overhead, a guide device must be added at the position where the optic cable is led to the pole, and the optic cable should not be dragged to the ground. Pay attention to reduce friction when pulling the optic cable. There must be a section of fiber optic cable remaining on each pole.
E. Pay attention to the reliable grounding of metal objects in the optic cable. Especially in mountainous areas, high-voltage power grid areas and areas with heavy thunderstorms, there are generally three ground points per kilometer, and even non-metallic optic cables are used.
2. Outdoor pipeline optic cable construction
A. Before construction, check the occupancy of the pipeline, clean and place the plastic sub-tube, and put it into the traction line at the same time.
B. Calculate the laying length, there must be enough reserved length. See the table below for details:
Natural bending increases
Length (m / km)
Increase the length (m / hole)
Joint overlap length (m / side)
0.5 ~ 1
8 ~ 10
15 ~ 20
Other reserves are reserved according to design
C. The length of one laying should not be too long (generally 2KM), and the wiring should be pulled from the middle to both sides.
D. The traction force of the cable is generally not more than 120kg, and the reinforcement core part of the optic cable should be pulled, and the waterproof reinforcement treatment of the optic cable head should be done.
E. Introducing and leading-out devices must be added at the entrance and exit of the optic cable.
D. Pay attention to reliable grounding of pipeline optic cable.
3. Laying the optic cable directly
A. The depth of the directly buried optic cable trench should be excavated according to the standard. The standard is shown in the table below:
Buried depth standard of direct buried optic cable
Laying lot and soil quality
Buried depth (m)
Ordinary soil, hard soil
Gravel soil, semi-stone soil, weathered stone
Full stone, quicksand
Suburbs and villages
Highway ditch: stone (hard stone, soft stone)
Side ditch design depth below 0.4
The design depth of the side ditch is below 0.8
Crossing the railway (from the road base) and highway (from the pavement base)
Ditches and ponds
According to the requirements of underwater optic cable
B. Overhead or bored pipelines can be laid where trenches cannot be dug.
C. The bottom of the ditch should be smooth and firm, and a part of sand, cement or support can be pre-filled if necessary.
D. You can use manual or mechanical traction when laying, but pay attention to guidance and lubrication.
E. After laying, the soil should be covered and tamped as soon as possible.
4. Laying of optic cables in buildings
A. When laying vertically, special attention should be paid to the load bearing of the optic cable. Generally, the optic cable should be fixed once every two layers.
B. When the optic cable passes through the wall or floor, a protective plastic tube with a protective mouth should be added, and the tube should be filled with flame retardant filler.
C. A certain amount of plastic pipes can also be laid in the building in advance, and the optic cable should be laid by traction or vacuum method later when the optic cable is to be laid.
3.4 Matters needing attention
1. After receiving the optic cable, the user should check the optic cable certificate and the optic data with the disk, check the cable number, model, number of cores and length, etc., and check the outer package for damage.
2. When laying the optic cable, a piece of traction rope must be connected with the optic cable reinforcement, and fixed with a mesh sleeve or tape to the sheath. If it is a pipeline optic cable, a special rotating traction head must be added between the traction rope and the cable reinforcement, and it is not allowed to directly pull the outer jacket of the optic cable for traction.
3. For the arming of the optic cable with a length of more than 2KM, it is not allowed to put it from the beginning to the end at one time. It is necessary to put the optic cable in the middle of the lot and put it in a figure-eight shape to both ends. 
4. When unloading the optic cable from the car, it is best to use a forklift or crane hoist to gently place the optic cable from the car on the ground
5. In the field of construction, when unloading the optic cable from the car, it is better to use a straight plate to be placed between the car platform and the ground to form a slope at 45 degrees. Use a rope to pass through the middle hole of the optic cable. It was the fiber optic cable that was sliding down the board slope. When unloading the optic cable, stack it strictly and lay it flat. It is strictly forbidden to directly drop the optic cable from a high place, and it will be damaged due to strong impact on the optic cable.
6. When you need to roll the optic cable, you should roll in the direction of the rotating arrow marked on the cable reel, but you cannot roll it for a long distance.
7. Single-disk inspection of optic cable is required before construction, such as outer sheath quality and attenuation index. 
8. The maximum pulling force when laying pipelines or overhead optic cables does not exceed 1500N, and the maximum pulling force when laying directly buried optic cables does not exceed 3000N.
9. When constructing and laying the optic cable, it is not allowed to bend or form a 90-degree right angle bend; for dynamic bending (such as during construction), the bending radius should be greater than 20 times the outer diameter of the optic cable for pipes and overhead optic cables; for straight buried optic cables, bending The radius should be greater than 25 times the outer diameter of the optic cable; when laying, the bending radius should be greater than 10 times the radius of the cable for pipelines and overhead optic cables; for direct buried optic cables, the bending radius should be greater than 12.5 times the outer diameter of the cable. Never bend the optic cable severely and cause a "dead buckle". 
10. During the construction of the optic cable, the tensile force shall not exceed the allowable transient force (pipeline, overhead optic cable: 1500N; directly buried optic cable: 3000N; ADSS optic cable: 20% RTS), and the operation shall not exceed the allowable long-term force Regulations (pipeline, overhead optic cable 600N; direct buried optic cable 1000N; ADSS optic cable: MAT). The construction of optic cables should be carried out under the guidance of corresponding qualified technical personnel.
It is very important that the optic cable is routed in the correct way. Improper construction can easily cause increased attenuation, shortened service life, fiber breakage, broken skin, and armor breakage. The optic cable, especially the feeder optic cable, has a larger diameter and heavier quality. When you pay off the cable, you must use a bracket to put up the optic cable reel. Pull the cable while rolling the optic cable reel. After wiring, the cable personnel and defense personnel should be equipped with walkie-talkies to keep in touch. Do not use force to pull when they are not able to pull. You must smooth them out before continuing, so as to ensure that our "fragile" optic cable is Safe deployment.
3.5 Optic cable limit
Allow tensile and flattening forces
The allowable tensile force and flattening force of the optic cable are shown in Table 1. 
Table 1-Mechanical properties of optic cable allowing tensile force and flattening force
Optic cable type
Allowable tensile force (N)
Allow flattening force (N / 100mm)
Pipeline and non-self-supporting overhead
Special direct buried
4. Connection method
Methods mainly include permanent connection, emergency connection, and active connection.
1. Permanent fiber connection (also called hot melt)
In this connection, the connection point of the two optic fibers is melted and connected together by a discharge method. Generally used in long-distance connection, permanent or semi-permanent fixed connection. Its main feature is that the connection attenuation is the lowest among all connection methods, and the typical value is 0.01 ~ 0.03dB / point. However, when connecting, special equipment (welding machine) and professionals are required to operate, and the connection point also needs to be protected by a special container.
2. Emergency connection (also called) cold melting
Emergency connection mainly uses mechanical and chemical methods to fix and bond two optic fibers together. The main feature of this method is that the connection is fast and reliable, and the typical attenuation of the connection is 0.1 ~ 0.3dB / point. However, the connection point will be unstable for a long time, and the attenuation will also increase greatly, so it can only be used for emergency in a short time.
3. Active connection
Active connection is a method that uses various optic fiber connection devices (plugs and sockets) to connect sites to sites or sites to optic cables. This method is flexible, simple, convenient, and reliable, and is mostly used in computer network wiring in buildings. Its typical attenuation is 1dB / connector.
5. How to select fiber optic cable
In addition to the selection of optic fiber cables, in addition to the number of optic fiber cores and optic fiber types, the outer sheath of the optic cable should be selected according to the use environment of the optic cable.
1. When outdoor optic cable is directly buried, armored optic cable should be used. When aerial, the optic cable with two or more black plastic outer sheaths can be selected.
2. When selecting optic cables used in buildings, attention should be paid to their flame retardant, poisonous and smoke characteristics. Generally, flame retardant can be used in pipes or forced ventilation
China-US Direct Submarine Optic Cable
China-US Direct Submarine Optic Cable
But for the smoke type (Plenum), flame-retardant, non-toxic and smoke-free type (Riser) should be selected in the exposed environment.
3. For vertical cabling in the building, you can use distribution cables (Distribution Cables); for horizontal wiring, you can use breakout cables.
4. If the transmission distance is within 2km, multi-mode optic cable can be selected, and if it exceeds 2km, relay or single-mode optic cable can be used. 
Buried depth standard of direct buried optic cable
Laying section or soil quality Buried depth (m) Remarks
Ordinary soil (hard soil) ≥1.2
Semi-stony (sand gravel, weathered stone) ≥1.0
Full stone ≥0.8 Add 10cm fine soil or sand from the bottom of the ditch
Suburbs, villages and towns ≥1.2
Sidewalks in the city ≥1.0
Crossing railways and highways ≥1.2 from road slag bottom or from road surface
Ditch, canal and pond ≥1.2
Farmland drainage ditch ≥0.8
6. Fiber inspection
The main purpose of optic fiber inspection is to ensure the quality of the system connection, reduce the fault factors and find the fault point of the fiber when the fault occurs. There are many detection methods, mainly divided into manual simple measurement and precision instrument measurement.
1. Manual simple measurement
This method is generally used to quickly detect the on and off of the optic fiber and to distinguish the optic fiber made during construction. It uses a simple light source to enter visible light from one end of the fiber and observe which one emits light from the other end. Although this method is simple, it cannot quantitatively measure fiber attenuation and fiber breakpoints.
2. Precision instrument measurement
Using an optic power meter or an optic time domain reflectometer (OTDR) to quantitatively measure the fiber, you can measure the attenuation of the fiber and the attenuation of the connector, and even the position of the fiber breakpoint. This measurement can be used to quantitatively analyze the causes of fiber network failures and evaluate fiber network products.
7. Identify the advantages and disadvantages
Skin: Indoor optic cables generally use polyvinyl chloride or flame-retardant polyvinyl chloride. The exterior should be smooth, bright, flexible, and easy to peel. The outer layer of optic cable with poor quality is not smooth enough to stick to the tight sleeve and aramid inside.
The PE sheath of the outdoor optic cable should be made of high-quality black polyethylene. After the cable is formed, the outer skin is flat, bright, uniform in thickness and free of small bubbles. Inferior fiber optic cable jackets are generally made of recycled materials, which can save a lot of costs. Such optic cable jackets are not smooth. Because there are many impurities in the raw materials, the outer jacket of the optic cable is made with many very small holes. water.
2. Optic fiber: Formal optic cable manufacturers generally use A-class cores from large manufacturers. Some low-cost and inferior optic cables usually use C-level and D-level optic fibers and smuggled optic fibers with unknown origin. These optic fibers have long delivery times due to complex sources. Often, it has become moist and discolored, and single-mode fibers are often mixed in multimode optic fibers. Generally, small factories lack the necessary testing equipment and cannot judge the quality of optic fibers. Because of the inability to distinguish such an optic fiber with the naked eye, common problems encountered during construction are: narrow bandwidth and short transmission distance; uneven thickness and inability to interface with pigtails; the lack of flexibility of the optic fiber, which breaks when it is bent.
3. Strengthen the steel wire: The steel wire of the outdoor optic cable of the regular manufacturer is phosphatized and the surface is gray. After such a steel wire is formed into a cable, it does not increase hydrogen loss, rust, and has high strength. Inferior fiber optic cable is generally replaced with thin iron wire or aluminum wire, and the identification method is easy-the appearance is white, and it can be bent freely when pinched in the hand. The optic cable produced with such a steel wire has a large hydrogen loss, and after a long time, the two ends of the fiber optic box will rust and break.
4. Steel armor: The regular production enterprise adopts the longitudinal banding steel belt with double-sided brush anti-rust paint. The inferior optic cable uses ordinary iron sheet, usually only one side has been treated with anti-rust.
5. Loose tube: PBT material should be used for loose tube in fiber optic cable. Such tube has high strength, no deformation and anti-aging. Inferior fiber optic cable generally uses PVC as a sleeve. The outer diameter of such a sleeve is very thin and flattened with a pinch. It is a bit like a straw for drinking drinks.
Sixth, ointment: ointment mainly includes fiber paste and cable paste. Normally, fiber paste should fill the entire loose tube, and cable paste should fill every gap of the optic fiber cable core under pressure. Fiber paste has the method of filling half full or less, some of the cable paste is only a layer outside the cable core, and some is not filled between the two ends of the optic cable. In this way, the optic fiber will not get good protection, affect the transmission performance such as optic fiber attenuation, and the waterproof performance will not reach the national standard. Once the optic cable accidentally seeps, it will cause the entire link to seep and be scrapped. Under normal circumstances, even accidental seepage only needs to be repaired, and there is no need to revisit. (The water blocking performance required by the national standard is: three meters of optic cable, one meter of water column pressure, and no water seepage for 24 hours.) The same problem will also occur if poor ointment is used, and it may be due to poor thixotropy of the ointment It will cause microbending loss of the optic fiber, and the transmission characteristics of the entire link are unqualified; if the paste is acidic, it will also react with the metal material in the optic cable to precipitate hydrogen molecules, and the attenuation of the optic fiber will rapidly increase when it encounters H, causing the entire The link is interrupted.
7. Aramid: Also known as Kevlar, it is a high-strength chemical fiber that is used most in the military industry. Military helmets and bulletproof vests are produced from this material. As of 2013, only DuPont and Aksu in the Netherlands were able to produce the product at a price of about 300,000 tons. Both indoor optic cables and power overhead optic cables (ADSS) use aramid yarn as reinforcement. Due to the high cost of aramid, inferior indoor optic cables generally have a very thin outer diameter, which can save costs by using few strands of aramid. Such an optic cable is easily pulled off when passing through the tube. Because the ADSS optic cable determines the amount of aramid used in the optic cable based on the span and wind speed per second, it generally does not dare to cut corners.
8. Water-blocking tape: The water-blocking tape or water-blocking yarn for optic cable has a strong water absorption performance through the highly absorbent resin that is evenly distributed inside the product. Under the combined action of penetration pressure, affinity and rubber elasticity, The super absorbent resin can quickly inhale water several times its own weight. In addition, the water blocking powder swells the gel as soon as it encounters water, and no matter how much pressure is applied to it, the water will not be squeezed out. Therefore, covering the cable core with a water-blocking tape containing a water-absorbent resin, in case the outer wall of the optic cable is damaged, the superabsorbent resin of the wound part expands to exert a sealing effect, which can prevent the entry of water to a minimum. Inferior fiber optic cable usually uses non-woven fabric or paper tape. Once the cable sheath is damaged, the consequences will be very serious.
7. Discuss the importance and specific countermeasures of communication optic cable line maintenance
With the advent of the information age, the development of various industries in China today is closely related to communication technology. Therefore, regardless of whether enterprises or people have high requirements for communication, the development speed of the communication industry is also very rapid, but there are still many problems that have not been solved. The quality of the communication technology is directly related to the current maintenance of the communication optic cable line. This article analyzes the significance and specific methods of the communication optic cable line maintenance for practical application.
Common causes of obstacles
Possible causes of obstacles
The loss of the original splicing point of one or several optic fibers increases
Installation problem of optic fiber splice protection tube or water leakage of splice box
There is a step in the attenuation curve of one or several fibers
The optic cable was sprained by mechanical force, and some optic fibers were broken but not broken yet
One optic fiber has decay steps or broken fiber, others are intact
Optic cable is affected by mechanical force or due to optic cable manufacturing
The original connection point attenuation step is horizontally elongated
Fiber breakage barrier near the original connection point
All communication is blocked
1. The optic cable is dug, blown or collapsed by external force
2. Power supply system interrupted
The method steps of using OTDR test at the end point or relay station to judge the fault point of the optic cable line are as follows:
1) Use OTDR to test the distance from the obstacle to the test end.
2) When the optic cable is blocked due to natural disasters or external forces such as external construction, find the obstacle location provided by the crew. If this is not the case, it is not easy for inspectors to find obstacles from the road surface. At this time, you must check the distance from the obstacle point measured by the OTDR to the test end, and check with the original test data to find out which obstacle (or which two joints) the obstacle point is between. After necessary conversion, The exact location of the obstacle can be determined by measuring the length of the ground in between.
3) If the fiber breakage is due to defects in the optic cable structure or the aging of the optic fiber, it is difficult to accurately measure the breakpoint with OTDR, and only the obstacle section can be detected, then a section of optic cable should be used.
7. Method for improving fault location accuracy of optic cable line
First of all, it is necessary to understand how to use the meter, and master the method of using the meter, which is helpful for accurate measurement.
1. Set the parameters of 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 by accurately setting the basic parameters of the test instrument can conditions be created for accurate testing.
2. Use the zoom function of the instrument. Using the zoom function of OTDR can accurately position the cursor on the corresponding inflection point, and use the zoom function key to zoom the graph to 25 meters / div, so that you can get more accurate test results with a resolution of less than 1 meter.
3. Adjust the accurate test range file. For different test range files, the distance resolution of the OTDR test is different. When measuring fiber obstacles, the closest test range file that is greater than the measured distance should be selected, so that the instrument's own accuracy can be used to make the measurement.
Secondly, accurate and completed original documents should be established during the maintenance management process. These accurately completed optic cable line files are the basic basis for fault measurement and location. Therefore, carelessness should not be neglected in the maintenance management process, and real, credible and complete line information should be established.
During the continuous monitoring of the optic cable, record the cumulative length of the fiber from the test end to the position of each splice point and the total attenuation value of the optic fiber of the relay section, and also register the test instrument model and the set value of the refractive index during the test. Accurately record the remaining of various optic cables. Record in detail the length of the fiber cable tray at each joint pit, special section, S-shaped laying, entry room, etc. and the length of the fiber tray at the joint box, terminal box, ODF rack, etc., so as to be deducted when converting the fault point routing length.
In addition, the test conditions should be kept consistent during the measurement. Obstacle testing should try to ensure the consistency of the test instrument model, operation method and instrument parameter settings, etc., so that the test results are comparable. Therefore, each test instrument model and test parameter settings must be recorded in detail for future use.
Finally, a comprehensive analysis. Obstacle testing requires operators to have clear ideas and flexible ways to deal with problems. Clear logical thinking is very useful everywhere. Under normal circumstances, the two ends of the fiber optic cable line are tested for bidirectional faults, and then combined with the original data for analysis, and then ready 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 take the measurement method of the nearest joint, which can be excavated at the obstacle point of the preliminary test, and the end station test instrument is in real-time measurement.
Obstacles to the optic cable lines must be contested every second. Temporarily adjust the circuit or deploy emergency optic cables to temporarily rush through the circuit, and organize forces to repair it as soon as possible.
1. Emergency repair
1) All optic cable lines are blocked in one direction
According to a predetermined circuit scheduling scheme, all or part of the main circuits are temporarily tuned up immediately.
2) Individual fiber blocking of the optic cable line in a certain direction
If there is a spare fiber in the optic fiber, or there is another detour circuit, immediately use the spare fiber or detour circuit to temporarily tune the obstacle circuit; if there is a spare fiber in the optic cable, and there is no detour circuit, it will be processed according to the prescribed scheduling principle to ensure that the important circuits are smooth Suspend the secondary circuit.
3) Part of the optic fiber of the optic cable line is blocked in a certain direction
If there is a spare fiber in the optic cable, in addition to using the spare fiber to temporarily tune the circuit, you can select an unblocked fiber to temporarily pair. According to the prescribed scheduling principle and scheduling sequence, temporarily tune the circuit. If the temporarily paired fiber is still not enough, If there is no circuitous circuit, the secondary circuit is suspended.
1. Temporary dispatch of the above optic fibers must be completed by the two sides of the machine line after discussing the dispatch plan and reporting to the superior competent department for approval, with the close cooperation of both parties.
2. The optic fiber paired according to the original line sequence, as long as the mechanical stations at both ends are scheduled according to the system and the circuit is switched; if the optic fiber is temporarily used, the connection of the optic distribution rack (or terminal box) in the relay station on both sides of the obstacle point should be On the device.
3. If the main optic fiber is connected with an optic attenuator and the backup optic fiber is not pre-attenuated, the corresponding optic attenuator should also be connected when calling the backup optic fiber. Attention should also be paid to this problem when optic fibers are temporarily paired.
2. Lay emergency optic cable
1) Conditions for laying emergency optic cables
When the optic cable lines in a certain direction are completely blocked, after all the circuits or main adjustments are made, it is possible to consider repairing the optic cables at one time without using emergency emergency circuit. When there is no condition to temporarily tune the circuit, or if some of the circuits temporarily cannot meet the needs of large-capacity communication, the emergency optic cable should be laid, and the circuit should be rushed according to the scheduling principles and scheduling order stipulated in the "circuit scheduling system". Restore communication, and then re-route the new fiber optic cable for formal repair.
2) Determination of the deployment range of emergency optic cables
The optic cable is blocked by natural disasters or external forces. Generally, after determining the approximate location of the obstacle point, it is easier to find the obstacle point according to the road surface abnormality, and the deployment range of the emergency optic cable can be determined. However, it is difficult to determine the deployment range of the emergency optic cable when using the OTDR to detect only the obstacle point at the end station or the relay station, and between which two connectors occur, and the exact location of the obstacle cannot be determined. If there are conditions at this time, you can use OTDR to test at the opposite relay station, and comprehensively analyze the test results on both sides. Generally, you can accurately determine the break point of the optic cable. If there is no condition to use OTDR to test from both directions, you can send two To deal with:
a) The obstacle point is closer to a certain connector. The emergency optic cable is planned to be laid from this connector. Open this connector and use the OTDR to test the direction of the obstacle at the connector. At this time, the test distance is short and the obstacle can be measured more accurately The specific location can determine where the emergency optic cable is placed.
b) The obstacle point is in the middle of the two connectors. It is not appropriate to start laying emergency optic cable from a certain joint. It is necessary to further determine the location of the obstacle point and lay a section of emergency optic cable on both sides of the obstacle point. In this case, you can use the gradual extension test method to find the specific location of the obstacle, that is: use the OTDR to initially detect the obstacle point at the end station or relay station, dig out the optic cable in front of the obstacle point, cut off a certain fiber and repeat the test If it is found that the obstacle point is not within the cut-off range, you should determine how far apart it is, then dig out the optic cable forward, cut another fiber and repeat the test again, until the obstacle point is included in the cut-off point, you can determine the emergency The deployment range of the optic cable. Generally, re-testing twice can determine the specific location of the obstacle.
c) Emergency repair of the same type of optic cable acceleration connector
Another emergency repair method for optic cable is to use the same type of optic cable as the emergency repair optic cable, and use the connector (live joint) and matching liquid for temporary connection to rush through the circuit.
3. Official repair
When officially repairing optic cable line obstacles, communication must be maintained as much as possible, especially the communication of important circuits cannot be interrupted, and the construction quality must meet the requirements of optic cable line construction quality standards and maintenance quality standards.
When officially repairing the full obstruction of the optic cable line, the following issues should be noted:
1. Obstacles in or near the connector box should be repaired by using the optic fiber reserved in the connector box or the optic cable reserved in the connector pit, without adding additional connectors. When there is a reserved optic cable near the obstacle point, the reserved optic cable should be used for connection, and only one connector is added.
2. When it is necessary to formally repair the optic cable obstacles by intervention or replacement of the optic cable, the same manufacturer and the same type of optic cable should be used.
3. The length of intervening or replacing the optic cable can be considered by the following three factors:
(1) Taking into account that the OTDR monitoring must be used by the end station or the relay station when the optic fiber connection is officially repaired, or in the daily maintenance work, it is easy to distinguish the two adjacent connection points; the minimum length of the intervention or replacement of the optic cable must meet the response of the OTDR instrument The resolution (two-point resolution) is generally greater than 100 meters.
(2) Considering that it does not affect the single-mode optic fiber to work under the single-mode steady-state conditions to ensure the communication quality, the minimum length of intervention or replacement of the optic cable should be greater than 22 meters.
(3) Refer to (1) and (2) the principle requirements of two points for intervening or replacing the length of the optic cable, and consider the actual situation in a comprehensive way, and master it flexibly. For example, if there is a connector in the vicinity of the intervention or replacement of the optic cable, the optic cable should be extended to the connector as far as possible, and only one connector is added.
4. Intervention or replacement of optic cable, the general sequence of optic fiber cutover:
(1) First, the optic fiber cutover plan should be agreed between the two parties in accordance with the scheduling principles and scheduling sequence specified in the "Circuit Dispatching System", and reported to the superior authority for approval.
(2) The optic fiber cutover process should try not to interrupt the circuit (especially important circuits). To cut the original newly-laid optic fiber by emergency optic cable, first connect the spare optic cable, use the spare optic fiber as a replacement pair, and restore the circuit one by one according to the original cutover sequence, and use the intact optic fiber in the original obstacle cable to temporarily If the matching circuit is matched, or if there is no spare optic cable in the original optic cable, the secondary circuit should be suspended. First cut the optic fiber of the system as an alternative pair, and then cut each pair in the original cut sequence to restore the circuit.