How to reduce the loss of optical fiber in applications
Subordinate Classification：News CenterRelease Time：2017-08-30
transmission loss characteristics are one of the most important factors
in determining the optical network transmission distance, transmission
stability and reliability. There
are many reasons for the loss of fiber transmission. Among the
construction and maintenance of optical fiber communication networks,
the most noteworthy is the causes of transmission loss caused by fiber
use and how to reduce these losses. The transmission losses caused by the use of optical fiber are mainly
connected loss (loss of fiber, loss of welding loss and movable joint
loss) and loss of non-connection loss (bending loss and other
construction factors and application environment).
1, continuous loss and its solution
1.1 Continued loss
The splice loss of the optical fiber mainly includes three kinds of
welding loss and movable joint loss caused by the intrinsic loss caused
by the intrinsic factor of the optical fiber and the non-intrinsic
(1) The inherent loss of the fiber is mainly due to the inconsistency
of the fiber field field; the core diameter mismatch; the core section
is not round; the core and the cladding concentricity are four points;
the most influential is the mode field diameter is inconsistent.
welding loss non-intrinsic factors of the welding loss mainly by the
axial dislocation; axis (angle) tilt; end separation (gap); fiber end is
not complete; refractive index difference; fiber end face is not clean
and the level of personnel operation, Operating procedures, welding machine electrode cleaning degree,
welding parameters set, the working environment cleanliness and other
active joint loss of non-intrinsic factors of the activities of the
joint loss of the main components by the poor quality of the connector,
poor contact, not clean and welding losses with the same number of
factors (such as axial dislocation, end gap, angle, refractive index
difference ) Caused.
1.2 to solve the loss of the program
engineering design, construction and maintenance work should be used in
the same characteristics of high-quality fiber on a line as much as
possible with the same batch of high-quality brand-name bare fiber, in
order to match the characteristics of optical fiber, mold field diameter
on the impact of fiber splice loss To a minimum.
(2) cable construction should be strictly in accordance with procedures and requirements
the disk as much as possible to do the whole disk configuration (single
disk ≥ 500 meters), in order to minimize the number of joints. Laying in strict accordance with the cable number and the end of the order of cloth, so that the loss value to a minimum.
(3) the selection of experienced and well-trained staff to continue and test
level of the connection personnel directly affects the size of the
connection loss. The connection personnel should follow the process of
the fiber splicing process strictly and strictly control the loss of the
joint. During the welding process, the light field reflectometer (OTDR)
is used to monitor the connection loss (≤0.08dB / ), Do not meet the requirements should be re-fused. When using an optical time domain reflectometer (OTDR), the loss of
the joint should be measured in both directions and the average of the
two results should be obtained to eliminate the human factor error of
the one-way OTDR measurement.
(4) to ensure that the environment to meet the requirements
is strictly forbidden to open operation in dusty and humid environment.
The parts and tools and materials of the cable should be kept clean. Do
not let the fiber connector be damp. The fiber to be cut must be clean
and free from dirt. After cutting the fiber must not be exposed in the air for too long, especially in dusty and humid environments. When the ambient temperature is too low, take the necessary temperature measures.
(5) to prepare a perfect fiber end face
The preparation of fiber end face is the most critical process of fiber connection. The improvement of fiber end face is one of the important reasons to determine the loss of optical fiber connection. High-quality
end face should be flat, no burr, no defect, and perpendicular to the
axis, the fiber end of the axis of inclination should be less than 0.3
degrees, showing a smooth and smooth mirror, and keep clean, to avoid
dust pollution. Should use high-quality cutting knife, and the correct use of cutting knife cutting fiber. Bare fiber cleaning, cutting and welding should be tightly connected, not too long interval. Move the fiber to gently, to prevent wiping with other objects and damage the end of the fiber.
(6) the correct use of welding machine
Proper use of welding machine is to reduce fiber loss is an important guarantee and key links.
① should be in strict accordance with the welding machine operating
instructions and operating procedures, the correct operation of welding
② reasonable placement of fiber, the fiber placed in the V-groove welding machine, the action should be light. This is because the core diameter of 10 nm single-mode fiber, if the
welding loss is less than 0.1dB, the fiber axis of the radial offset is
less than 0.8nm.
③ According to the type of fiber correctly and properly set the
welding parameters (pre-discharge current, time and the main discharge
current, the main discharge time, etc.).
④ in use and after use should be promptly removed in the welding
machine in the dust (especially the fixture, the mirror and v-groove
within the dust and fiber crushing).
welding machine electrode life is generally about 2000 times, the use
of a long time after the electrode will be oxidized, resulting in large
discharge current leaving the welding loss value increases. At
this point you can remove the electrode, with alcohol dipped in medical
cotton cotton gently wipe and then installed on the welding machine,
and discharge cleaning time. If the discharge current is still large after several cleaning, the electrode must be replaced again.
(7) try to use high-quality qualified activities of the connector to
ensure that the connector performance in line with the relevant
provisions of the activities of the connector insertion loss should be
controlled at 0.3 dB / below (or even lower), additional loss of not
more than 0.2 dB /
(8) the activities of the connector should be plugged well, close tight, to prevent leakage phenomenon
(9) to ensure that the active connector is clean
Construction and maintenance should pay attention to cleaning the plug
and adapter (flange) and to ensure clean room and equipment
environment, to prevent plugs and adapters (flanges) have dirt and dust,
to minimize the scattering loss.
2, non-connected loss and its solution
2.1 Non-connected loss
The use of fiber in the non-loss caused by the main loss of wear and
other construction factors and application of the environment caused by
Radiation loss caused by bending When the fiber is greatly bent, the
bending radius is comparable to its core diameter, its transmission
characteristics will change. A
large number of conduction modes are converted into radiation patterns,
no longer continue to transmit, but into the cladding layer or cladding
absorption, resulting in additional loss of fiber. The bending loss of the fiber has two types: macro bending loss and micro bending loss.
The additional losses caused by the bending (radius) of the fiber with a
radius of curvature greater than that of the fiber are mainly due to
the bending of the routing and laying; the bending of the fiber optic
cable Circle, a variety of take the bend, natural bending); joint box in the
fiber of the disk, the engine room and equipment, such as the coiled
Micro-bend loss Fiber-optic axis to produce μm-level bending
(micro-bend) caused by additional losses, the main reasons are: fiber
into a cable, the surface of the small irregular surface caused by
uneven stress and the formation of random microbend; Core
and cladding interface is not smooth formation of the micro-bend; cable
laying, uneven tension throughout the formation of the micro-bend;
fiber by the side of the uneven pressure and the formation of
micro-bend; fiber encountered temperature changes, due to heat Expansion and contraction formed by the micro-bend.
(2) other construction factors and application environment caused by the loss
① non-standard cable caused by the loss of the shelves. Layer-type
loose-type structure of the cable is easy to produce such losses,
because one is the cable on the shelves of multiple loose tube twist
each other; the second is the use of cable ties loose tube to the joint
box of the fiber tray Mouth,
so that the loose tube appears sharp bend; the third is the cable when
the metal reinforcement components and fiber loose tube appear
dislocation. These factors can cause increased wear and tear.
② heat loss caused by heat shrinkage. The
main reason is that one is the quality of the hot melt protection tube
itself, after the hot melt distorted, resulting in bubbles; the other is
the welding machine heater heating, heating parameters set improperly,
resulting in hot melt protection tube deformation or bubble ; The third is the heat shrink tube is not clean, there are dust or
gravel, hot melt when the point of damage, causing increased wear and
③ direct buried cable is not standardized construction caused by the loss. The
reason is that one is the depth of the cable is not enough, by the load
after rolling damage; the other is the cable routing improper choice,
due to environmental and terrain changes to the cable beyond its
allowable load range of external forces; the third is the cable trench Uneven, the cable appears arched, hang the phenomenon, after the
backfill residual stress; the other four other causes of damage to the
outer sheath of the cable and water, resulting in hydrogen damage.
④ overhead cable is not standardized construction caused by the loss. The
main reason is that one is in the cable laying construction, the cable
to play a small circle, bending, twisting and playing back, pulling when
pulling, there is a surge, the moment the maximum traction is too
large; the second is the cable hook used improperly, The
cable is not consistent with the direction of the snake bend, the
interval is too sparse, the cable is too large due to the vertical
force; the third is to stay in the rod on the cable is not fixed firmly,
the cable by long-term external force and short-term impact and damage; Fourth, the cable is too tightly armed, did not consider the natural
elongation of the cable; the other five causes the outer sheath of the
cable damage and water, resulting in hydrogen damage.
⑤ pipe cable is not standardized construction caused by the loss. The
reason is that one is the cable with net sets of law when the
deployment, the traction speed control is not good, the cable appears
playing back button, surge; the second is put on the cable, no
deployment of plastic pipe, cable was scratched; Is caused by other causes of damage to the outer sheath of the cable and water, resulting in hydrogen damage.
⑥ room, equipment, pigtail fiber and fiber jumper banding, coiling is
not standardized, there are cross-winding phenomenon caused by loss.
⑦ fiber connector box quality is poor, the connector box package, the
installation is not standardized, due to external effects caused by
damage to the joint box, resulting in water and hydrogen loss.
⑧ cable in the erection process of the tensile deformation, then the
box clamping the cable pressure is too large, the capacity of the disk
in the hot melt pipe pressure too tight, the fiber tray in the fiber
coil is not standardized and other losses caused.
2.2 to solve the problem of non-connected loss
(1) engineering survey design, construction, should choose the best route and line laying.
(2) formation, choose a high-quality construction team to ensure the
quality of construction, which is essential, any construction of the
negligence are likely to cause fiber loss increases.
(3) design, construction, maintenance, and actively take effective
cable line "four anti" measures (lightning, anti-power, anti-corrosion,
anti-mechanical damage), strengthen the protection work.
use the bracket to hold the cable laying cable, do not put the cable
down after the use of a similar way from the spool on the layout of the
cable, do not let the cable by the torque. When laying the cable, should be unified command, strengthen contact, to adopt a scientific and reasonable traction method. Arming
speed should not be too fast; continuous arming length should not be
too long, if necessary, should be used down "8" word, from the middle to
the two cloth. In the corner, etc. may damage the cable where the place must be careful and take the necessary means of protection. Encountered in the downtown area, such as cable laying cable, such as
the need for temporary placement of the cable, the use of 8-shaped disk
to stay, do not let the cable by the torque.
When laying the cable, it is necessary to pay attention to the limit of
the rated tension and bending radius. In the cable laying construction,
it is strictly forbidden to make small circle and bend, twist and
prevent the buckle and surge phenomenon. Traction
does not exceed 80% of the allowable cable, instantaneous maximum
traction does not exceed 100%, traction should be added to the
reinforcement of the cable, with particular attention can not pull and
kink phenomenon. When the cable bending corner radius should not be less than 15 to 20 times the outer diameter of the cable.
Do not use poor, especially heat-shrink tubing that has been bent, so
that the casing will generate stress internally during heat shrinkage
and exert an increase in wear on the fiber. Carry, storage casing, pay attention to clean, do not let foreign body into the casing.
in the follow-up operation, according to the size of the tray to
determine the length of stripping, as far as possible to peel some of
the longer fiber so that coiled in the closing (disk length of 60 ~
pay attention to the fiber after the welding (fiber optic disc and
fixed), disk, the larger the radius of the circle, the greater the
curvature of the whole line, the smaller the loss, so be sure to
maintain a certain radius (R ≥ 40mm) , To avoid unnecessary losses, the number of large number of fiber optic cable connection in the shelter. Continued
operation, the cable cutter into the depth of the cable to grasp, do
not crush the loose tube to make the fiber force. The use of qualified joint materials and in accordance with the norms
and operational requirements, the correct package, install the connector
the machine room as clean as possible, the pigtail should be surrounded
by band protection, or alone to the pigtail using a line, not between
the pigtail or between the other lines of cross-winding, but also try
not to pigtail (even Temporary use) placed on the foot where you can step on. Fiber
optic cable terminal to avoid jumper in the alignment of the right
angle, in particular, should not use the plastic belt jumper into a
right angle, or fiber due to long-term stress caused by increased wear
and tear. Jumper in the corner should take the curve, bending radius should not be less than 40mm. Laying to ensure that the jumper is not force, not pressure, in order to avoid long-term stress fatigue jumper. When the fiber is operated (ODF), do not tighten the tail fiber.
(9) to strengthen the daily maintenance of fiber optic cable lines and technical maintenance work.
Optic Home (FTTH) is the inevitable development of the information age,
optical network interconnection is the digital earth tomorrow. With
the large number of various types of optical fiber communication
network construction and operation, face and solve the use of optical
fiber caused by the transmission loss problem in the optical fiber
communication engineering design, construction, maintenance greatly
improve and optimize the optical fiber communication network