Optical cable installation solution,Laying of optical cables
The laying of optical cables is divided into three types: Duct fiber optic cable, Aerial Fiber Optic Cable and Direct Buried Fiber Optic Cable.
Duct fiber optic cable
The method often used in cities is usually laid on urban streets. Since streets often have turns and undulations, a manhole is usually set up at the turn to facilitate the traction of optical cables. Each section of optical cable is 1km~2km long. Between two sections of optical cable The connection is completed through the manhole in between. In the connected manhole, 8-10m of optical cable needs to be reserved and hung on the wall of the manhole.
Aerial Fiber Optic Cable
In provincial secondary trunk lines (local networks in cities and regions), overhead laying is often used because the wilderness is open. The hanging wire hanging method is the most commonly used in China, which involves laying steel wire hanging wires on poles and hanging optical cables with hooks. Aerial optical cables generally use a black outer sheath, which has been exposed to sunlight.
Generally, 2 electric poles are erected at a distance of 100m, and 5-10 hooks are installed between the electric poles. In order to prevent climate changes, telescopic bends are generally set under the poles, and certain reserves are reserved at the joints.
Direct Buried Fiber Optic Cable
Direct burial is used for national first-level trunk lines (ministerial-level trunk lines) and second-level trunk lines (provincial-level trunk lines). When directly buried, the relay section is often larger than 70km, and currently even reaches 140km. The length of the optical cable section is often 4 meters. Cable Purchase It is required to be 1.2m deep. After the fiber optic cable is connected, use a connector box to ensure ground insulation, waterproofing, and ant release. After inspection, it is directly buried underground and backfilled with soil. Generally, marking stones are set every 50m on the optical cable route. There are insulation monitoring points at the connection.
Optical fiber connection
The optical cable enters the office from the pole or manhole outside the transmission machine room, passes through the wiring room to the optical cable terminal box or distribution box (ODP) in the machine room, and is hot-connected and cold-connected with a jumper. The reserved length of the optical cable is generally 15~20m. There is also 80cm reserved for the optical fiber in the storage tray. The FC/PC connector of the optical jumper is connected to the enamel tray on the ODF rack.
Optical fibers outside the computer room are connected by fusion splicing. The process is: prepare the connector box, open the cable, each section is 80cm, install it in the connector box, fix the strengthening core, remove the loose tube, waterproof grease, prepare the optical fiber and heat shrink tube, and perform fusion splicing. Heat shrink, fix to the storage tray, seal the joint box, and install the joint box.
Measurements for construction
Optical fiber connecting devices and fusion joints will increase the attenuation of the optical fiber. The design document will have strict requirements for the attenuation of the entire optical cable. Generally, the average attenuation of mechanical joints is around 0.5dB, and the current fusion splice point can also reach Below 0.1dB, or even below 0.05dB. Generally, the light emitted by the optical terminal is around -5dB, while the light received by the optical receiver must be greater than -30 dB. In order to meet the requirements of the project, it is usually measured after welding with an optical time domain reflectometer (OTDR). For the attenuation of the welding point, the joint box must be sealed after meeting the attenuation requirements of a single welding point. The light source and optical power meter can also be used to test the entire optical attenuation. A single OTDR can monitor each event point.
Maintenance and repair
The maintenance work of optical cables is carried out on a certain date. After the optical cable fails, rapid repairs must be carried out. Maintenance is generally monitored within a fixed time using OTDR, etc. to detect faults, aging and other problems as much as possible to prevent communication interruption. Currently, network alarm monitoring systems can also be used.
Emergency repair tools ensure that the system can be quickly and temporarily restored after a failure.
Optical cable laying specifications
a、Length and integrity
The length of each optical cable should be controlled within 800M, and there should be no relays in the middle.
b、Minimum installation bending radius of optical cable
Under static loads, the minimum bending radius of a fiber optic cable is 10 times the diameter of the cable; under load conditions during cabling operations, such as pulling the cable out of a pipe, the minimum bending radius is 20 times the diameter of the cable.
For 4-core optical cable, the minimum installation bend radius must be greater than 2 inches (5.08CM).
c、Installation stress
The maximum installation stress exerted on the 4-core/6-core fiber optic cable shall not exceed 100 pounds (45 kg).
When installing multiple 4-core/6-core optical cables at the same time, the maximum installation stress of each optical cable should be reduced by 20%. For example, for a 4*4-core optical cable, the maximum installation stress is 320 pounds (144 kg).
d、Installation tension of optical fiber jumper
Fiber optic patch cords are designed with a single optical fiber. Double-span fiber optic patch cords contain 2 single optical fibers encapsulated in a common fire-resistant composite jacket. These fiber optic patch cords are used to interconnect equipment within a distance of up to 100 feet (30M).
Optical fiber jumpers can be divided into single-core fiber cords and dual-core fiber cords. The maximum pulling force of single-core fiber cords is 27 pounds (12.15 kg), and the maximum pulling force of dual-core fiber cords is 50 pounds (22.5 kg).
How to lay outdoor optical cables
There are three ways to lay outdoor optical cables: underground pipe laying, that is, laying optical cables in underground pipes; direct underground laying; and overhead laying, that is, laying in the air from telegraph poles to telegraph poles.
a、Underground pipeline laying
This method is widely used. When laying optical cables in this way, you will encounter three situations: small hole-small hole, that is, the optical cable enters the underground pipe from the ground through a small hole in a building, and then comes out from a small hole in another building; manhole-manhole hole, that is, the optical cable enters the pipe through the manhole, and is led to another manhole, in which the optical cable runs in a straight line; the optical cable is pulled in a pipe with one or more turns.
In the above situations, manpower or machines can be used for traction. When choosing a method, you might as well try whether manual traction is feasible. Otherwise, use a machine for traction. However, no matter what method, you need to pay attention to the bending radius and installation of the optical cable. Stress specifications.
When selecting the pipelines that can be used, please note that the selected pipelines can ensure that the length of each optical cable is within 800M, and must be separated from the power pipelines by at least 8CM of concrete or 30CM of compacted soil.
b、Direct underground burial laying
This method is suitable for use when the distance is long and there is no convenient condition for overhead. The burial depth should be at least 0.5M below the ground, or should comply with the depth stipulated by the relevant regulations of the local urban management department.
c、Overhead laying
When there are telegraph poles between buildings, a steel wire rope can be erected between the building and the telegraph pole, and the optical cable can be tied to the wire rope; if there are no telegraph poles between the buildings, but the distance between the two buildings is about 50 meters , or optical cables can be installed directly between buildings through steel cables.
Aerial optical cables are usually 3M above the ground. When entering a building, they must pass through the U-shaped steel protective sheath on the exterior wall of the building, and then extend downward or upward. The aperture of the cable entrance is generally 5CM.
If overhead line clearance is an issue, a mast-type entrance can be used. The bracket of this antenna pole should generally not be 1.2M higher than the roof. This height is just right so that people can touch the optical cable, making it easy to operate.
Laying of optical cables in the building
a、High-rise residential buildings
If there is a weak current shaft (shaft) in this building and the building network center is located in the weak current shaft (shaft), the optical cable shall be laid to the building network center along the vertical metal trunking laid in the weak current shaft (shaft); otherwise (including this building) If there are no weak points or shafts), the optical cables are laid to the building network center along the vertical metal trunking laid in the corridor.
b、Multi-story residential building
After the optical cable is laid to the unit where the building network center is located, it is laid upward (or downward) along the outer wall of the building to the third floor and then enters the building. It is laid along the corners and top edges of the corridor to the location of the building network center.
c、Fixation of optical cables
There is no need for steel wire ropes when laying optical cables in the building. If they are laid along vertical metal trunking, they only need to be hung with cable clamps every 2 floors or every 35 feet (10.5M) along the optical cable path.
Margin of optical cable
Since optical cables have high quality requirements, and the two ends of each optical cable are most vulnerable to damage, after the optical cable reaches its destination, there needs to be a 10M margin at both ends to ensure that the damaged optical cable is cut off when the optical fiber is melted. Does not affect required length.
Optical fiber splicing and patching
Melt the optical fiber and the ST head, and then fix them together with the coupler on the optical fiber termination box. Plug one end of the optical fiber jumper into the coupler and the other end into the optical fiber port on the switch.
Technical requirements for optical cable laying
1、Aerial Fiber Optic Cable Laying requirements
1) When laying aerial optical cables on flat ground, use hooks for hanging. When laying optical cables on mountains or steep slopes, use binding methods to lay optical cables. Optical cable joints should be positioned on straight poles that are easy to maintain, and the reserved optical cables should be fixed on the poles with reserved brackets.
2) Optical cables on overhead pole paths are required to make U-shaped telescopic bends every 3-5 poles, and approximately 15 meters are reserved every 1 km.
3) The overhead (wall) optical cables should be protected with galvanized steel pipes, and the pipe openings should be blocked with fireproof mud.
4) Optical cable warning signs should be hung around every 4th gear pole for overhead optical cables and in special areas such as across roads, rivers, and bridges.
5) The intersection of the hanging wire and the power line should be protected by a three-prong protective tube, and the extension of each end should not be less than 1 meter.
6) The electric pole cables near the highway should be wrapped with light rods, with a length of 2 meters.
7) In order to prevent the electric current induced by the hanging wire from injuring people, each pole wire is required to be electrically connected to the hanging wire. Each wire position should be installed with a pull-type ground wire. The hanging wire is required to be directly connected with a bushing ring and directly grounded at the terminal.
2、Duct fiber optic cable Laying requirements
1) Before laying the optical cable, put the sub-hole in the tube hole. Select 1 hole of the same color sub-tube for the optical cable and always put it through. All the remaining sub-tube openings should be protected by plugs.
2) Considering the manual laying method, in order to reduce the loss of optical cable joints, the pipeline optical cable should be laid in the entire tray.
3) In order to reduce the traction force during laying, the entire optical cable should be laid from the middle to both sides, and personnel should be arranged in each manhole for auxiliary pulling in the middle.
4) The hole positions for optical cables should meet the requirements of the design drawings. The pipe holes must be cleaned before laying the optical cables in the pipeline. The remaining length of the sub-hole in the hand hole should be about 15cm exposed from the tube hole.
5) The interface between the sub-tube in the hand hole and the plastic textile network tube is wrapped with PVC tape to prevent sediment from infiltrating.
6) The optical cable is installed in the man (hand) hole. If there is a supporting plate in the hand hole, the optical cable is fixed on the supporting plate. If there is no supporting plate, the optical cable is fixed on the expansion bolt. The expansion bolt requires the hook mouth to be downward.
7) The optical cable outlet hole should not be bent within 15cm.
8) Plastic signs are used in each hand hole and on the optical cables and ODF racks in the computer room to indicate the difference.
3、Wall optical cable laying requirements
1) Except for the upper part of the underground optical cable, it is strictly prohibited to lay armored or linoleum optical cable on the wall.
2) When crossing neighborhoods or courtyard passages, the lowest point of the cable should be no less than 4.5 meters from the ground.
3) The hanging thread type adopts 7/2.2, 7/2.6, the support spacing is 8 to 10 meters, and the distance between the terminal fixation and the first middle support should be no more than 5 meters.
4) When the hanging wire is laid horizontally or vertically on the wall, its terminal fixation and the middle support of the hanging wire should comply with the “Acceptance Specifications for Local Network Communication Line Engineering”.
5) The fastening screws must be on the same side of the optical cable. Optical cables should not be laid along the wall with hooks. When it is inevitable,
6) A sleeve tube should be added to the optical cable for protection. When the optical cable is laid along the hanging wire protruding from the wall on the indoor floor, the hook distance is 1 meter.
4、Requirements for laying optical cables within the office
1) Intra-office optical cables should be tied when passing through the wiring rack and turning points (front and back). The vertical ascending section should be tied in sections (the section length is no more than 1 meter). The upper and lower walkways or walls should be tied with 2 to 3 circles every 50cm. When binding, the binding parts should be padded with rubber tubes to avoid lateral pressure.
2) When the program of the intra-office optical cable does not change, it should be wrapped with PVC flame-retardant tape for fire prevention treatment, and the cable entry holes must be blocked with fire-proof mud.
3) The office direction and serial number of each terminal should be clearly marked on the terminal board of the ODF rack.
4) The reserved coils for the intra-office optical cables are tied and fixed on the wiring rack or wall, and the base station optical cables can be reserved on the terminal poles outside the base station.
5) Intra-office optical cables are generally led from the hand shaft in front of the office through the underground cable entry room to the optical transmission equipment. Intra-office optical cables should be hung with identification plates made in accordance with relevant regulations for easy identification.
6) The optical cable should be placed in a safe location in the cable entry room. When it is in a position vulnerable to external damage, protective measures should be taken.
7) The optical cables in the office should be laid out neatly and beautifully, and the optical cables laid along the upper line shaft should be tied to the upper line reinforcement horizontal iron.
8) Optical cables reserved on the equipment side according to regulations can be left in the transmission equipment room or incoming line room. If there are special requirements for reserved optical cables, enough should be reserved according to the design requirements.
9) After the optical cable is introduced into the central station, the inlet pipe hole should be blocked to prevent water seepage or leakage.
5、fiber optic cable ends
1) Sufficient reserved optical cables should be reserved according to regulations or design requirements.
2) The installation location of the optical cable terminal connector in the equipment room should be stable and safe, away from heat sources.
3) Ended optical cables and single-core soft optical fibers derived from optical cable terminal connectors should be processed in accordance with ODF instructions.
4) Route the cables and protect and bind them according to the design requirements.
5) The connectors of the single-core soft optical fiber should be inserted into the optical distribution frame (distribution panel) in the order required by the design.
6) The interface end of the optical distribution frame (distribution panel) that is not connected to the soft optical fiber should be covered with a plastic dust cap.
7) The coiling of soft optical fiber in the rack should be greater than the specified radius of curvature.
8) At the end of the optical fiber distribution frame (ODF), lead out the metal components with copper core PVC sheathed cables and connect them to the protective ground wire.
9) The direction and serial number of the soft optical fiber should be marked in a conspicuous place.
