Discontinuous Losses Caused in Optical Fiber Applications and Solutions


Discontinuous wear and tear and solutions

The key to discontinuous loss in optical fiber applications is bending loss and loss caused by other engineering construction elements and application scenarios.


(1) Loss of radiation source caused by bending When the optical fiber is subjected to a large bending, and the core diameter between the two bending half diameters is comparable, its transmission characteristics will vary greatly. Many transmission modes are converted into radiation source modes, which are not transmitted again, but enter the insulating layer and are digested and absorbed by the coating layer or insulating layer, thereby causing additional loss of the fiber. There are two types of bending losses in optical fibers: macrobending losses and microbending losses.


① Macro-bending loss The radius of curvature of the optical fiber is much larger than the diameter of the optical fiber. The additional loss caused by bending (macro-bending), the key reasons are: router bending and bending during laying; various pre-embedding of optical fibers Bending (pre-embedded ring, various bending, natural bending); coiling of optical fibers in products, surrounding of pigtails in host rooms and machinery and equipment, etc.


②Micro-bending loss The optical fiber shaft causes additional losses caused by μm-level bending (micro-bending). The key reasons are: when the optical fiber is cabling, the slight arc on the surface of the support plate causes the uneven ground stress of each part. Occasional micro-bending ;

ftth cable

Microbending caused by unevenness of the split page between the fiber core and the insulating layer; microbending caused by asymmetrical support force of each part when the optical cable is laid; microbending caused by asymmetrical lateral pressure on the optical fiber; Microbending caused by thermal expansion and contraction.


Fiber Repair

(2) Loss caused by other engineering construction elements and application scenarios

①The loss caused by the release of non-standard optical cables. Layer-twisted looper flange structure optical cable is very easy to cause this kind of loss, the reason depends on, the first is that multiple loose waterproof casings are twisted with each other at the release point of the optical cable; the second is to use cable ties to bundle the loose waterproof casing to the product When the optical fiber reel interface is connected, the loose waterproof casing will turn sharply; the third is that the metal material lifting prefabricated member and the optical fiber loose waterproof casing will shift up and down, left and right when the optical cable is released. This element will lead to increased wear and tear.


②The wear and tear caused by the thermal melting maintenance with poor thermal shrinkage. The key reasons are: the first is the product quality problem of the hot-melt cable sleeve itself, which is distorted after hot-melting, causing bubbles; the second is that when the electric heater of the welding machine is heated, the basic heating parameters are not good, resulting in hot-melting The cable casing is deformed or causes bubbles; the third is that the heat shrinkable tube is untidy, dusty or gritty, which will damage the continuation point during heat melting, resulting in increased wear and tear.


③ Loss caused by non-standard engineering construction of direct buried optical cable. The reason depends on, the first is that the optical cable is not buried deep enough, and is damaged after being rolled by the load block; the second is that the optical cable router is not properly selected, and the optical cable is subjected to external forces that exceed its allowable load range due to changes in the natural environment and landforms; third The bottom of the optical cable trench is uneven, the optical cable is in the state of supplying and offline, and there is internal stress after backfilling the soil; fourth, the outer sheath of the optical cable is damaged and leaks due to other reasons, resulting in hydrogen loss.


④The loss caused by the non-standard engineering construction of the empty optical cable. The key reasons are as follows: first, at the construction site of optical cable laying, the optical cable is looped, bent, distorted and buckled on the back. When the traction belt is pulled violently, a surge occurs, and the driving force is too large in an instant; the second is the hanging of the optical cable. The hook is wrongly operated, the orientation of the hook is not the same, there is a meandering bend, the spacing is too scarce, and the optical cable is supported due to the excessive vertical crossing; third, the optical cable stored on the rod is not fixed and firm, and the optical cable is subjected to long-term external force and short-term effects. The fourth is that the fortification of the optical cable is too tight, and the natural elongation rate of the optical cable is not considered; the fifth is that the outer sheath of the optical cable is damaged and leaks due to other reasons, resulting in hydrogen loss.


 ⑤The loss caused by non-standard engineering construction of pipeline optical cable. The reason depends on the first, when the optical cable is fortified by the net sleeve method, the speed control of the traction belt is not very good, and the optical cable is buckled and surged. ; The third is that the outer sheath of the optical cable is damaged and leaks due to other reasons, resulting in hydrogen loss.


⑥ The pigtails and optical fiber jumpers in the host room and equipment are bundled and surrounded by non-standard, cross-coiled and other conditions, resulting in loss.


⑦The quality of the optical cable joint box is not good, the product packaging and installation are not standard, the product is damaged due to external effects, etc., resulting in water leakage and hydrogen loss.


⑧Drawing deformation of the optical cable in the whole process of construction, high pressure for clamping the optical cable in the splice box, too tight pressure on the hot-melt tube in the fiber accommodating tray, and loss caused by the non-standard surrounding of the optical fiber in the optical fiber accommodating tray.


Plans for dealing with discontinuous wear and tear

(1) The design concept and construction site of the engineering project should be surveyed, and the best router and route laying method should be selected.

(2) It is particularly important to establish and select a high-quality construction worker to ensure the quality of the project construction. Carelessness at the construction site will often lead to the expansion of optical fiber loss.

(3) In the design concept, engineering construction, and maintenance, effective and effective "four defenses" countermeasures (lightning protection, electricity protection, corrosion protection, and mechanical equipment damage prevention) should be actively adopted to improve safety protection work.

(4) Use the support frame to support the cable reel to distribute the optical cable. It is not necessary to lay the cable reel flat and use a similar method to distribute the optical cable from the spool, and it is not necessary to subject the optical cable to torque. When the optical cable is issued, it should be commanded together to improve the connection, and a scientific and standardized leash method should be used. The fortification rate should not be too fast; the length of continuous fortification should not be too long. If necessary, the inverted "8" should be used and issued from the center to both sides. Care must be taken in areas where the cable will be damaged, such as on bends, and the necessary maintenance practices must be used. When it is necessary to temporarily lay out the optical cable, such as the distribution of optical cable in the bustling area, the figure 8 should be used to prevent the optical cable from being subjected to torque.


(5) When issuing the optical cable, be sure to pay attention to the allowable rated tensile force and the limit of bending half warp. At the construction site of the optical cable laying, it is forbidden to make small circles, bending and distorting the optical cable, so as to avoid back buckles and surge conditions. The driving force does not exceed 80% of the allowable optical cable, and the maximum driving force does not exceed 100% in an instant. The driving force should be added to the lifting piece of the optical cable, and care should be taken not to jerk and kink. When the optical cable is bent, the bending semi-diameter should not be less than 15 to 20 times the diameter of the optical cable.


(6) It is not necessary to use fake and inferior ones, especially for heat shrinkable sleeves that have already been bent and deformed. Such waterproof sleeves will cause internal stress during heat shrinkage, which will be released on the optical fiber to increase the loss. When bringing and storing the waterproof casing, pay attention to cleaning it, and do not let the dirt enter the waterproof casing.


(7) When continuing the actual operation, the length of the stripping should be decided according to the specifications of the storage tray, and the stripping length should be as long as possible, so that the optical fiber can be coiled in the closing market (the length of coiling is 60-100cm). High attention should be paid to the storage of the optical fiber after fusion (the fiber is coiled and fixed). When coiling the fiber, the larger the semi-longitude of the coil, the larger the inclination, and the smaller the loss of the entire route. Therefore, it is necessary to maintain the necessary semi-longitude. (R ≥ 40mm), to prevent excess loss, the main point of the connection of large-core fiber optic cables is storage. When continuing the actual operation, it is necessary to master the depth 1 of the cable opening knife to select the optical cable, and it is not necessary to squeeze the loose waterproof casing to support the optical fiber. Select qualified connector raw materials and properly package and install products in accordance with standards and actual operating regulations.


(8) The main room is as clean and tidy as possible. The pigtail should be maintained with a looped tape, or a separate line should be applied to the pigtail to avoid the middle of the pigtail or the intersection with other connecting lines. Fibers (even for temporary applications) are placed in areas where the feet can reach. When installing the optical cable terminal, pay attention to prevent the leakage line from being inclined in the wiring. It is very important not to use plastic tape to tie the leakage line into a bevel, otherwise the optical fiber will be damaged due to the long-term influence of ground stress. The leakage line should follow the curve diagram when turning, and the bending semi-longitude should not be less than 40mm. When releasing, make sure that the leakage line is not supported or stressed, so as to prevent the long-term ground stress fatigue of the leakage line. The pigtails do not have to be tied too tightly when the optical fiber ends in actual operation (ODF).


(9)The usual maintenance and technical overhaul of the optical cable route is in progress. Fiber to the home (FTTH) is an inevitable trend in the information age, and optical Internet interconnection is the future of the digital earth. With many basic constructions and operations of various optical fiber communication Internets, recognizing and dealing with the transmission loss problems caused by optical fiber applications will ultimately greatly improve and enhance optical fiber communication data transmission in the design, construction, and maintenance of optical fiber communication buildings. characteristic.


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