Principles and Applications of Fiber Optic Cables (History)
In 1976, the U.S. Bell Research Institute built the first fiber optic communications experimental system in Atlanta, using fiber optic cables containing 144 fibers manufactured by Western Electric.In 1980, commercial fiber optic cables made of multimode fibers were begun to be used on intra-city interoffice trunks and a few long-distance lines. commercial fiber optic cables made of multimode fibers were introduced in 1980 for intrastate trunks and a few long-distance lines. Commercial fiber optic cables made of single-mode fibers began to be used on long-distance lines in 1983, and in 1988 the first trans-Atlantic submarine cable connecting the United States to Britain and France was successfully laid, followed soon after by the first submarine cable across the Pacific Ocean. China developed its own communications cable in 1978, the use of multi-mode optical fiber, cable core structure for the stranded type. Field tests have been carried out in Shanghai, Beijing, Wuhan and other places. Soon after the municipal telephone network as inter-bureau trunking trial, after 1984, gradually used for long-distance lines, and began to use single-mode optical fiber. Communication fiber optic cable has a greater transmission capacity than copper cable, relay section of the long distance, small size, light weight, no electromagnetic interference, since 1976 has been developed into a long-distance trunk lines, intra-city trunking, offshore and inter-oceanic submarine communications, as well as local area networks (LANs), private networks, such as the backbone of the wired transmission lines, and began to the city of the field of the user loop wiring network to the field of development, for the fiber-to-the-home, wide generation of integrated business digital network transmission lines. line.
Principle and application of fiber optic cable fiber optic cable is the cornerstone of the information superhighway)
Fiber optic cable is today's information society, a variety of information networks, the main transmission tool. If the Internet is called the information highway, then, fiber optic cable network is the cornerstone of the information highway --- fiber optic cable network is the physical routing of the Internet. Once a cable is damaged and blocked, the direction of the "information superhighway" that is destroyed. Through the fiber optic cable transmission of information, in addition to the usual telephone, telegraph, fax, and now a large number of transmission of television signals, bank remittances, stock market quotes and other information can not be interrupted for a moment. At present, long-distance communication cable transmission method has been developed from PDH to SDH, the transmission rate has been developed from the original 140MB/S to 2.5GB/S, 4 × 2.5GB/S, 16 × 2.5GB/S or even higher, that is to say, a pair of cores can be opened to 30,000, 120,000, 480,000 or even more to the development of the word road. Such a large transmission capacity, once the fiber optic cable blocked not only to the telecommunications sector causing huge losses, but also due to poor communications, will cause a lot of inconvenience to the general public, such as computer users can not access the Internet, stock quotes can not know, the bank can not be carried out remittances, off-site access to become a bubble, a variety of information can not be transmitted. In remote mountainous areas, once the fiber optic cable is interrupted, it will make the county and even several counties along the fiber optic cable in communication isolation, become an island. To the party, government and military organs and the people caused by the loss is incalculable.
Part I fiber optic cable principles and applications (theory and structure )
Light and its properties 1, light is an electromagnetic wave
Visible light part of the wavelength range is: 390 ~ 760nm (millimeters). Greater than 760nm part is infrared light, less than 390nm part is ultraviolet light. Currently more applications in the optical fiber: 850, 1310, 1550 three.
2, light refraction, reflection and total reflection.
Because the propagation speed of light in different substances is different, so the light from one substance to another substance, in the two substances at the interface will produce refraction and reflection. Moreover, the angle of the refracted light changes with the angle of the incident light. When the angle of incident light reaches or exceeds a certain angle, the refracted light will disappear and all the incident light will be reflected back, which is the total reflection of light. Different substances have different refraction angles for the same wavelength of light (i.e., different substances have different light refractive indexes), and the same substances have different refraction angles for different wavelengths of light. Fiber optic communication is based on the above principles and formed. Optical fiber structure and types 1, optical fiber structure:
Optical fiber bare fiber is generally divided into three layers: the center of the high refractive index glass core (core diameter is generally 50 or 62.5 μm), the middle of the low refractive index silica glass cladding (diameter of 125 μm), and the most outwardly reinforced with a resin coating.
2, numerical aperture:
The light incident on the end face of the optical fiber can not all be transmitted by the optical fiber, but only in a certain angle range of incident light can be. This angle is called the numerical aperture of the fiber. The numerical aperture of the optical fiber is larger for the optical fiber butt is advantageous. Different manufacturers of optical fibers have different numerical apertures (AT&TCORNING).
3, the types of optical fibers:
A, according to the mode of transmission of light in the optical fiber can be divided into: single-mode fiber and multi-mode fiber.
Multimode fiber: the center glass core is thicker (50 or 62.5μm), can transmit a variety of modes of light. However, its intermode dispersion is large, which limits the frequency of transmitted digital signals, and with the increase in distance will be more serious. For example: 600MB/KM of fiber in 2KM when only 300MB of bandwidth. Therefore, multi-mode fiber transmission distance is relatively close, usually only a few kilometers. Single-mode fiber: the center glass core is thin (core diameter is generally 9 or 10μm), can only transmit a mode of light. Therefore, its intermode dispersion is very small, suitable for long-distance communication, but its chromatic dispersion plays a major role, so that the single-mode fiber on the spectral width of the light source and the stability of the high requirements, that is, the spectral width should be narrow, the stability should be good.
B, according to the best transmission frequency window: conventional single-mode fiber and dispersion-shifted single-mode fiber.
Conventional type: fiber manufacturers will fiber optimal transmission frequency in a single wavelength of light, such as 1310nm.
Dispersion-shifted type: fiber optic manufacturers will fiber optimal transmission frequency in two wavelengths of light, such as: 1310nm and 1550nm.
C, according to the distribution of the refractive index: mutant and gradual change of the type of fiber.
Mutant type: the refractive index of the fiber center core to the glass cladding is mutated. Its low cost, high intermodal dispersion. Suitable for short-distance low-speed communication,
such as: industrial control. But single-mode fiber due to the small intermodal dispersion, so single-mode fiber are used mutant.
Fading type fiber: fiber center core to the glass cladding of the refractive index is gradually becoming smaller, so that the high-mode light propagation in the form of sinusoidal, which reduces the intermodal dispersion, improve the bandwidth of the optical fiber, increase the transmission distance, but the cost is higher, and now the multi-mode fiber is mostly a fading type fiber.
4, commonly used fiber specifications:
Single mode: 8/125μm, 9/125μm, 10/125μm
Multimode: 50/125μm, European standard
62.5/125μm, U.S. standards
Industrial, medical and low-speed network: 100/140μm, 200/230 μm
Plastic: 98/1000 μm, for automotive control Fiber Optic Manufacturing and Attenuation 1, Fiber Optic Manufacturing:
Now the main methods of fiber optic manufacturing: CVD (Chemical Vapor Deposition) method in the tube, CVD method in the rod, PCVD (Plasma Chemical Vapor Deposition) method and VAD (Axial Vapor Deposition) method.
2, the attenuation of optical fiber:
The main factors that cause optical fiber attenuation are: intrinsic, bending, extrusion, impurities, inhomogeneity and docking.
Intrinsic: the intrinsic loss of the fiber, including: Rayleigh scattering, intrinsic absorption.
Bending: when the fiber is bent part of the light inside the fiber will be lost due to scattering, resulting in loss.
Squeeze: the loss caused by the tiny bend of the fiber when it is squeezed.
Impurities: impurities in the fiber absorb and scatter the light propagating in the fiber, resulting in loss.
Uniformity: loss caused by uneven refractive index of the fiber material.
Docking: the loss generated when the fiber is docked, such as: different axes (single-mode fiber coaxiality requirements of less than 0.8 μm), the end face and the axis is not perpendicular to the end of the surface is not flat, docking diameter mismatch and poor fusion bonding quality, and so on. Advantages of optical fiber 1, optical fiber pass band is very wide. Theory up to 3 billion megahertz.
2, no relay section is long. Dozens to more than 100 kilometers, copper wire only a few hundred meters.
3, not affected by electromagnetic fields and electromagnetic radiation.
4, light weight, small size. For example: through 21,000 calls to the 900 pairs of twisted-pair cable, its diameter is 3 inches, weighing 8 tons / KM. And the amount of communication for its ten times the fiber-optic cable, 0.5 inches in diameter, weighing 450P / KM.
5, fiber-optic communication is not electrically charged, the use of safe for use in flammable, violent places.
6, the use of a wide range of ambient temperature.
7, chemical corrosion, long service life. The second part of the fiber optic cable principle and application (fiber optic cable knowledge) cable manufacturing The manufacturing process of fiber optic cable is generally divided into the following processes:
1, fiber optic screening: selecting the transmission characteristics of excellent and tension-qualified optical fiber.
2, the dyeing of optical fibers: the application of standard full chromatography to identify the requirements of high temperature does not fade and does not migrate.
3, the second extrusion: the choice of high modulus of elasticity, low coefficient of linear expansion of plastic extrusion into a certain size of the tube, the optical fiber will be incorporated and filled with moisture-proof and waterproof gel, and finally stored for a few days (not less than two days).
4, fiber optic cable stranding: several extruded optical fiber and strengthening unit stranded together.
5, extruded fiber optic cable sheath: in the stranded fiber optic cable plus a layer of sheath. Types of fiber optic cable 1, according to the laying method: self-supporting aerial cable, pipe cable, armored buried cable and submarine cable.
2, according to the structure of fiber optic cable: bundled fiber optic cable, stranded fiber optic cable, tightly embraced fiber optic cable, banded fiber optic cable, non-metallic fiber optic cable and can be branched fiber optic cable.
3, according to the use of: long-distance communication with optical fiber cables, short-distance outdoor optical fiber cables, hybrid optical fiber cables and buildings with optical fiber cables. Part III fiber optic cable principles and applications (cable construction)
Outdoor construction of fiber optic cable:
Longer distance cable laying is the most important thing is to choose a suitable path. Here it is not necessary that the shortest path is the best, but also pay attention to the right to use the land, the possibility of erected or buried in the ground, and so on.
There must be a very complete design and construction drawings, so that construction and future inspection is convenient and reliable. Construction should always be careful not to make the fiber optic cable by the heavy pressure or hard objects stabbed.
When the fiber optic cable turns, its turning radius should be more than 20 times the diameter of the cable itself.
1, outdoor aerial cable construction:
A, hanging line bracket hanging overhead way, this way is simple and cheap, China's most widely used, but hooks plus hanging, finishing more time-consuming.
B, hanging wire winding aerial way, this way is more solid, less maintenance. But the need for specialized winding machine.
C, self-supporting overhead mode, the trunk of the high requirements, construction, maintenance difficulties, high cost, the country is rarely used.
D, overhead, fiber optic cable lead to the trunk of the line must be added to guide the device, and to avoid dragging the cable on the ground. Attention to reduce friction when towing fiber optic cable. Each trunk to leave a section of fiber optic cable for expansion and contraction.
E, pay attention to the cable in the metal objects of reliable grounding. Especially in mountainous areas, high-voltage grid area and more areas generally have 3 grounding points per kilometer, and even choose non-metallic fiber optic cable.
2, outdoor pipeline cable construction:
A, before construction should check the pipeline occupancy, cleaning, placing the plastic sub-tube, and at the same time put into the traction wire.
B. Calculate the length of deployment, there must be enough reserved length.
C, the length of a deployment should not be too long (generally 2KM), the wiring should start from the center to both sides of the traction.
D, cable towing force is generally not greater than 120kg, and should be towed to strengthen the heart of the fiber optic cable part, and make a good head of fiber optic cable waterproof strengthening treatment.
E, the introduction of fiber optic cables and lead to the introduction of the device must be added to smooth the lead, can not be directly dragged to the ground.
F, pipe cable should also pay attention to reliable grounding.
3, direct buried cable laying:
A, direct buried cable trench depth should be excavated according to the standard, the standard is shown in the following table:
B, can not dig a trench can be overhead or drilled pre-buried pipe laying.
C, the bottom of the trench should be kept positive and gentle and strong, when needed, can be pre-filled with a portion of sand, cement or support.
D, laying can be manual or mechanical traction, but pay attention to guidance and lubrication.
E, laying is completed, should be back to the soil cover and tamping as soon as possible.
4, the laying of fiber optic cable in the building:
A, vertical laying, special attention should be paid to the weight of the fiber optic cable, generally every two floors to fix the cable.
B, fiber optic cable through the wall or through the floor, to add a protective plastic tube with mouth guard, and to fill the tube with flame-retardant filler.
C, in the building can also be pre-laying a certain amount of plastic pipe, to be laid later to shoot the fiber optic cable and then use traction or vacuum method of fiber optic cable. Part IV fiber optic cable principle and application (selection) The selection of fiber optic cable in addition to the number of cores and types of optical fiber, but also according to the use of fiber optic cable environment to choose the outer sheath of the cable.
1, outdoor fiber optic cable buried directly, it is appropriate to use armored fiber optic cable. Overhead, you can choose to use two or more black plastic sheath with two or more reinforcement of the fiber optic cable.
2, buildings with fiber optic cables in the selection should pay attention to its flame retardant, toxic and smoke characteristics. Generally in the pipeline or forced ventilation can be selected flame retardant but smoke type, the exposed environment should be selected flame retardant, non-toxic and non-smoke type.
3, vertical cable in the building, you can choose the layer stranded fiber optic cable; horizontal wiring, you can choose the branching fiber optic cable.
4, the transmission distance of 2km or less, you can choose multimode fiber optic cable, more than 2km can be used to relay or single-mode fiber optic cable.
Directly buried fiber optic cable burial depth standard
Laying lot or soil depth (m) Remarks
Ordinary soil (hard soil) ≥ 1.2
Semi-stony (gravelly soil, weathered stone) ≥ 1.0
All-stony ≥ 0.8 from the bottom of the trench with 10cm of fine soil or sand
Runny sand ≥ 0.8
Suburbs, towns and villages ≥1.2
Municipal sidewalks ≥1.0
Crossing railroads, highways ≥1.2 from the bottom of the road slag or from the road surface
Ditches, canals, ponds ≥1.2
Agricultural drainage ditches ≥0.8
Part V. Fiber Optic Cable Principles and Applications (Connection and Detection)
Connections of Optical Fiber Cables
Methods mainly include Permanent connection, emergency connection, active connection.
1, permanent fiber optic connection (also known as hot melt):
This connection is the method of discharge will be connected to the root of the fiber optic connection point melting and connected together. Generally used in long-distance splicing, permanent or semi-permanent fixed connections. Its main feature is that the connection attenuation is the lowest among all connection methods, with a typical value of 0.01~0.03dB/point. However, the connection requires special equipment (fusion splicer) and specialized personnel to operate, and the connection point also requires a special container to protect it.
2, emergency connection (also called) cold fusion:
Emergency connection is mainly mechanical and chemical methods, the two optical fibers are fixed and bonded together. The main feature of this method is to connect quickly and reliably, connecting the typical attenuation of 0.1 ~ 0.3dB / point. However, the connection point will be unstable for a long time and the attenuation will increase dramatically, so it can only be used for emergency purposes for a short period of time.
3, activity connection:
Activity connection is the use of various fiber optic connection devices (plugs and sockets), the site and site or site and fiber optic cable connected to a method. This method is flexible, simple, convenient, reliable, mostly used in computer network cabling in buildings. Its typical attenuation is 1dB/connector. Fiber optic testing The main purpose of fiber optic testing is to ensure the quality of the system connection, to reduce the failure factors as well as faults to find out the failure point of the fiber. Detection methods are many, mainly divided into manual simple measurement and precision instrumentation.
1, artificial simple measurement:
This method is generally used for rapid detection of fiber optic on and off and construction is used to distinguish the fiber made. It is a simple light source from one end of the fiber into the visible light, from the other end to observe which one glows to achieve. This method is easy, but it can not quantitatively measure the attenuation of the fiber and fiber breaks.
2, precision instrumentation:
The use of optical power meter or optical time domain reflectance mapping instrument (OTDR) for quantitative measurement of optical fiber, fiber attenuation and connector attenuation can be measured, and even the location of the fiber's breakpoints can be measured. Such measurements can be used to quantitatively analyze the causes of failures in fiber optic networks and to evaluate fiber optic network products. Part VI Principles and Applications of Fiber Optic Cable (Application and System Design) Applications of Fiber Optics Human society has now developed into an information society, with a very large amount of information exchanged, such as sound, images and data. The previous means of communication can not meet the current requirements, and fiber optic communication with its information capacity, good confidentiality, light weight and small size, no relay section of the long distance and other advantages have been widely used. Its application areas throughout the communication, transportation, industry, medical, education, aerospace and computer industries, and is to a wider and deeper level of development. The application of light and optical fiber is bringing profound influence and change to human life. Fiber optic network system design The design of fiber optic systems generally follow the following steps:
1, first of all, to figure out what kind of network to be designed, how its current situation, why use fiber optics.
2, according to the actual situation is to choose the right fiber optic network equipment, fiber optic cables, patch cords and other items used to connect. Selection should be based on the basis of available, and then based on performance, price, service, origin and brand to determine.
3, according to the customer's requirements and network type to determine the routing of the line, and draw wiring diagrams.
4, longer routes need to account for the attenuation margin of the system, accounting for the following formula:
Attenuation margin = transmitting optical power - acceptance of sensitivity - line attenuation - connectivity attenuation (dB) where the line attenuation = length of the fiber optic cable × unit attenuation;
Unit attenuation;
The line attenuation = length of the cable × unit attenuation. p>
Unit attenuation and fiber quality has a lot to do with the general single-mode 0.4 ~ 0.5dB/km; multi-mode 2 ~ 4dB/km.
Connection attenuation including fusion attenuation joint attenuation, fusion attenuation and fusion means and the quality of personnel related to the general hot fusion of 0.01 ~ 0.3dB / point; cold fusion 0.1 ~ 0.3dB / point; joint attenuation and joints Quality of the joint has a great relationship, generally 1dB/point. System attenuation margin is generally not less than 4dB.
5, accounting failed, should modify the design as appropriate, and then accounting. This situation may sometimes be repeated several times. Part VII Principles and Applications of Fiber Optic Cable (Model Identification Method)
Code of Classification
GY Communication with outdoor (field) cable GS Communication with equipment within the cable
GH Communication with submarine cable GT Communication with special cable
GJ Communication with indoor (bureau) cable GW Communication with metal-free optical cable
GR Communication with soft Fiber optic cables GM Communication mobile fiber optic cables
Note: Between the first part and the second part: the code name of the reinforcing member (reinforcing core)
Reinforcing member refers to the member within the sheath or embedded in the sheath used to enhance the tensile strength of fiber optic cables:
No symbols - metal reinforcing member; G-metal heavy-duty reinforcing member
F-nonmetallic reinforcing member; H-nonmetallic heavy-duty reinforcing member
F-nonmetallic reinforcing member; H-nonmetallic heavy-duty reinforcing member Heavy-duty reinforcing members
(For example: GYTA: metal reinforcing core; GYFTA: non-metallic reinforcing core) The code for the structural features of the cable core and fiber optic cable filling
The structural features of the fiber optic cable should indicate the main type of the core and the derived structure of the cable, and when there are several structural features of the fiber optic cable type that need to be indicated, a combination of the code may be used to indicate. B Flat shape C Self-supporting structure
D Fiber optic ribbon structure E Ellipsoidal
G Skeleton groove structure J Fiber optic ferrule coated structure
T Ointment-filled structure R Inflatable structure
X Cable bundled tubular (coated) structure Z Flame retardant
Designation of the jacket
A Aluminum-PE bonded jacket G Steel jacket
L Aluminum jacket Q Aluminum jacket Q Aluminum jacket Q Steel jacket
A Aluminum jacket Q Aluminum jacket Q Aluminum jacket Q Aluminum jacket Q Aluminum jacket Q
L Aluminum sheath Q Lead sheath
S Steel-polyethylene bonded sheath U Polyurethane sheath
V Polyvinyl chloride sheath Y Polyethylene sheath
W Steel-polyethylene bonded sheath entrapped with parallel steel wires
Note: Between the fourth part and the fifth part:
The designation is indicated by two groups of numbers, the first group indicates the armored layer, which may be one or two digits; the second group indicates the coating layer, which is one digit
Armor layer designation
Designation Armor layer
5 Crumpled steel strip
44 Double thick round steel wire
4 Single thick round steel wire
33 Double thin round steel wire
3 Single thin round steel wire
2 Wrap around the double steel tape
0 No armor layer p>0 No Armor Layer
Coating Layer Designator Designator Coating or Jacket Designator
1 Fiber Cover
2 Polyethylene Protection Tube
3 Polyethylene Sleeve
4 Polyethylene Sleeve Covered Nylon Sleeve
5 Polyvinyl Chloride Sleeve
Fiber Optic Cable Specification Model
A Multimode Fiber Optics
B Single-mode fiber
B1.1 (B1) Non-dispersion-shifted fiber G652
B1.2 Cut-off wavelength-shifted fiber G654
B2 Dispersion-shifted fiber optic cable G653
B4 Non-zero dispersion-shifted fiber G655
Note: Multi-mode fibers can not be used for long-distance optical transmission due to the reason of intermodal dispersion, and are almost eliminated.
Part VIII Principles and Applications of Optical Fiber and Cable (Judgment and Repair of Obstruction Points)
Common Obstruction Phenomena and Causes of Obstruction Points of Fiber Optic Lines Finding Obstruction Points of Fiber Optic Lines Using OTDR Tests at Endpoints or Relay Stations The method of judging obstruction points of fiber optic lines is roughly as follows:
1) Use the OTDR test to find out the obstruction point to the distance from the test end.
2) When the fiber optic cable is blocked due to external influences such as natural disasters or outside construction, the finder will find the obstacle location according to the obstacle provided by the engine personnel. If it is not the above situation, it is not easy for the inspection personnel to find the obstacle location from the road surface dissimilarity. At this time, it is necessary to follow the OTDR measured distance from the obstacle to the test end, with the original test data to check, find out the obstacle point is probably in which the marker (or which two joints) between the necessary conversion, and then accurately measure the length of the ground between them, you can determine the specific location of the obstacle.
3) If the broken fiber is due to structural defects in the cable or fiber aging caused by the OTDR is difficult to accurately measure the break point, can only measure the obstacles to the paragraph, it should be replaced with a section of fiber optic cable. Repair of the obstacles to the cable line obstacles, must be a minute and a second, temporary transfer of circuits or deployment of emergency cables to temporarily open the circuit, and should be organized as soon as possible to repair the force.
1, emergency repair
(1) a certain direction of fiber optic cable line all blocked
According to the predetermined circuit scheduling program, immediately and temporarily transfer all the circuits or part of the main circuit.
(2) a direction of fiber optic cable line individual fiber blocked
Fiber optic fiber if there is a spare fiber, or another circuit detour, immediately use the spare fiber or circuit detour to temporarily open the obstruction of the circuit; fiber optic cable, if there is a spare fiber, there is no circuit detour, according to the prescribed scheduling principles, to ensure that the important circuits are open and suspend the secondary circuits.
(3) a certain direction of fiber optic cable line part of the fiber optic blocking
fiber optic cable, such as spare fiber, in addition to spare fiber to temporarily open the circuit, can be selected without blocking the temporary pair of optical fiber, in accordance with the provisions of the scheduling principles and scheduling order, the temporary opening of the circuit, if the temporary pair of optical fiber is still not enough, and there is no circuit circuit, the suspension of secondary circuits.
2, Note:
(1) the temporary scheduling of the above fiber, must be by both sides of the line **** with the scheduling plan to report to the higher authorities for approval, the two sides in close cooperation with the completion.
(2) according to the original line order of the pair of optical fibers, as long as the two ends of the machine station according to the system scheduling, inverted circuit can be; optical fiber temporarily paired for use, it should be in the obstacle point on both sides of the relay station in the optical distribution frame (or terminal box) connector for transfer.
(3) If the main optical fiber is connected to the optical attenuator, and the spare fiber is not pre-wired attenuator, then in the call of the spare fiber, should also be connected to the corresponding optical attenuator. This problem should also be noted when the fiber is temporarily paired.
3, the deployment of emergency cable
(1) the conditions of the deployment of emergency cable
When a certain direction of the cable line all blocked, in all the circuits or after the main transfer, you can consider a one-time repair of fiber optic cables, do not have to use the emergency circuit. In the absence of conditions for the temporary transfer of circuits, or the temporary transfer of part of the circuit can not meet the needs of large-capacity communications, emergency cable should be deployed, in accordance with the "circuit scheduling system," the scheduling principles and scheduling order to rescue the circuit, the temporary restoration of communications, and then re-route the deployment of new fiber optic cables to carry out the official restoration.
(2) Emergency cable deployment range determination
Optical cable suffered natural disasters or external influence of blocking obstacles, generally in the determination of the approximate location of the obstacle point, according to the road surface is relatively easy to find the obstacle point, you can determine the scope of the emergency cable deployment. However, with OTDR in the end station or relay station only measured the obstacle point, which occurred between the two joints, but can not determine the specific location of the obstacle, it is difficult to determine the scope of emergency cable deployment. At this time, if the conditions, you can use OTDR in the opposite end of the relay station into the test, the two sides of the test results of a comprehensive analysis, generally can accurately determine the cable break point, if there are no conditions from both directions with OTDR test, can be sent to deal with the following two situations:
A, the obstacle is closer to a certain connector, the emergency cable to be deployed by the beginning of this connector, open the connector, and then use OTDR in the joints to the joints to the emergency cable deployment. OTDR in the joints to the direction of the obstacle test, the test distance is short, can be more accurately measured the specific location of the obstacle, it can be determined where the emergency cable deployment.
B, the obstacle is in the center of the two joints position, it is not suitable for a joint from the beginning of the deployment of emergency cables, you must further determine the location of the obstacle, in the obstacle on both sides of a section of the deployment of emergency fiber optic cable. Encountered this situation, can be used to gradually extend the test method to find the specific location of the obstacle, that is: in the end station or relay station with OTDR preliminary measurement of the obstacle point, the obstacle point in front of the digging out of the fiber optic cable, cut off an optical fiber for retesting, such as the obstacle point is not yet in the cut off range and so on, it should be judged to be roughly how far the difference between the cable, and then to the front of the cable, cut off another optical fiber and then retesting until the point of the obstacle is included in the cut off points Within the point, you can determine the scope of the emergency cable deployment. General retesting of two can determine the specific location of the obstacle.
C, the same type of cable accelerated connector emergency repair
Another cable emergency repair method, that is, the use of the same type of fiber optic cable with the obstacle cable as an emergency repair cable, the use of connectors (live joints) plus matching fluid for temporary connection, to open the circuit.
4, formal repair
Formal repair of fiber optic cable line obstacles, must try to maintain communications, in particular, can not interrupt the communication of important circuits, the quality of construction must be in line with the requirements of the quality standards of fiber optic cable line building quality standards and maintenance quality standards.
Formal repair of fiber optic cable line full obstruction obstacles, should pay attention to the following issues:
(1) connector box or connector near the obstacles, should be used in the connector box reserved optical fiber or connector pit reserved fiber optic cable repair, do not have to add another connector. When there is a reserved fiber optic cable near the obstacle point, the reserved fiber optic cable should be utilized to make the splice, and only one additional connector should be added.
(2) When it is necessary to formally repair the fiber optic cable obstacle by intervening or replacing the fiber optic cable, the same manufacturer and the same model of fiber optic cable should be used.
(3) The length of the intervention or replacement cable can be considered by the following three factors:
A, taking into account the formal repair of fiber optic cable splicing must be used by the end station or relay station OTDR monitoring, or in the day-to-day maintenance work to facilitate the differentiation of obstacles adjacent to the two splicing points; intervention or replacement of fiber optic cable length must meet the minimum length of the response resolution of the OTDR instrument (two-point resolution) requirements, it is generally appropriate to be greater than 100 meters. ) requirements, generally preferred to be greater than 100 meters.
B, taking into account the single mode fiber does not affect the single mode steady state conditions to ensure the quality of communication, intervention or replacement of the minimum length of the cable should be greater than 22 meters.
C. Intervention or replacement of the length of the fiber optic cable, can refer to (1), (2) the principle of the two requirements, combined with the actual situation of comprehensive consideration, flexibility. Such as: in the intervention or replacement of fiber optic cable in the vicinity of the existing joints, should try to extend the fiber optic cable put to the joints, only increase a joint.
5, intervention or replacement of fiber optic cable, fiber optic cut in general order:
(1) First of all, in accordance with the "circuit scheduling system," the principle of scheduling and scheduling order of the two sides of the line **** with the agreement on the fiber optic cut program, reported to the higher authorities for approval.
(2) fiber optic cut process should try not to interrupt the circuit (especially not interrupt the important circuit). From the emergency cable cut to the original new fiber optic deployment, should first be connected to the spare fiber optic cable, with a spare fiber as a replacement pair, according to the original order of cut, pair by pair cut to restore the circuit to the original obstacle in the fiber optic cable in a temporary pair to adjust the circuit, or the original cable in the original cable without a spare fiber optic cable, should be suspended for the secondary circuits, the first cut to the fiber optic system as a replacement pair, and then cut according to the original order of cut, pair by pair cut to restore the circuit. , restore the circuit.