What is the Best Method of Fiber Optic Cables placement?

What is the best method of Fiber Optic Cables placement? OSP engineers work on fiber optic cable, but often they make some mistakes during the laying of fiber optic cables. Today I will explain what is the best method of fiber optic cable placement. Fiber Optic Cables (FOC) can be placed using the two basic methods of installation: Pulling and Blowing. The cable installation method is selected based on site conditions and availability of machinery & resources.

Fiber Optic Cable (FOC) construction is different whether the intended placement method is Pulling or Blowing.Fiber optic cable placement also depends on the network domain,access network,junction network or long-distance network. Fiber optic cable placement also depend upon the location of MH/HH and distance between MH/HH.

Method Of Fiber Optic Cables Placement

Pulling Method
A system to place Fiber Optic Cables (FOCs) for shorter length runs of underground plant and in previously installed underground, buried, and aerial ducts. The Fiber Optic Cables (FOC) is pulled through an existing conduit with the help of a pre-installed rope, manually or using a winch. Empty conduit would require a pull rope to be installed first. Blowing a pull line directly or blowing a lightweight line through the conduit using compressed air accomplishes this.

FOC Pulling Process

Fiber Optic Cables Pulling Method

A winch mechanism with a take-up reel is usually used to pull the rope with the Fiber Optic Cable (FOC) attached. The winch should have a tension meter to monitor the amount of tension being placed on the Fiber Optic Cable (FOC) during the pull. This monitor will reduce the risk of damaging the Fiber Optic Cable (FOC).

Lubricants should be applied to reduce friction during a pull and therefore allow longer

cable pulls.

When the cable is attached to the pull rope, it is recommended that a swivel be used between the two. This swivel will allow the Fiber Optic Cable (FOC) and the pull rope to move independently in the conduit during the pull and prevent unnecessary twisting of the Fiber Optic Cable (FOC).

Pulling method tends to be more popular for standard Fiber Optic Cables (FOCs) and in large-size ducts and subducts. It is possible to place Fiber Optic Cables (FOCs) using this approach in lengths up to 500 meter, depending upon the geometry of the conduit plant encountered. But longer pulls can be achieved if mid-assist points are available.

FOC pulling 

Fiber Optic Cable Pulling process

On very long pulls the use of mid-assists is very common. Mid-assist equipment can be as simple as a person pulling on the cable midway or it can be a capstan type device that provides a controlled amount of pulling tension to the Fiber Optic Cable (FOC) to reduce the tension and increase the possible length of the pull.

Jetting/blowing Method

Cable blowing requires specialized equipment that utilizes high volume air compressors. There are two categories of air-assisted cable placement: Low Volume/High Pressure, and High Volume/Low Pressure.

In the first case (Jetting) a dart seal is attached to the end of the Fiber Optic Cable (FOC) and compressed air is introduced into the duct building pressure behind the seal, thus forcing the dart forward and creating a tensile pull on the end of the Fiber Optic Cable (FOC). At the same time, the Fiber Optic Cable (FOC) is pushed into the conduit through a manifold seal using a tractor pusher. The Fiber Optic Cable (FOC) then experiences simultaneous push and pull forces.

FOC Jetting Process

Fiber Optic Cable Jetting Method

In the second case (Blowing), the Fiber Optic Cable (FOC) is tractor fed into the conduit, again through a manifold seal, but this time has no dart seal. Instead, cable progress is based on the viscous drag of high volume air alone.

Jetting/Blowing facilitates much longer lengths of  Fiber Optic Cable (FOC) than traditional cable pulling methods, and the tension applied to the cable is significantly reduced. They are most effective in smaller conduits, up to 40 mm diameter. Using blowing techniques it is possible to place  Fiber Optic Cables (FOCs) in microducts in PPS lengths up to 2,000 m, depending upon the geometry of the path.

MECHANICAL & THERMAL CONSIDERATIONS DURING FIBER OPTIC CABLES PLACEMENT

 Fiber Optic Cable (FOC) installation in underground conduit routes requires some special considerations. Failing to follow such a procedure can result in fiber/ Fiber Optic Cable (FOC) damages or high optical power losses after installation. All  Fiber Optic Cable (FOC) are sensitive to damage during shipping, handling, and installation.

Some important parameters that need special attention during Fiber Optic Cable installation:

➦Fiber Optic Cable (FOC) bending radius. 

Fiber Optic Cable (FOC) are designed with a minimum bending radius. The Fiber Optic Cable (FOC) should never be bent below its minimum bending radius. Doing so can result in bending losses and/or fiber breaks in the Fiber Optic Cable (FOC). Generally the minimum bending radius under load during Fiber Optic Cable (FOC) installation is 20×D, where D is the outer diameter of the Fiber Optic Cable (FOC). Permanent bending radius may be lower, generally 10xD.

➦Fiber Optic Cable (FOC) pulling Tension

Fiber Optic Cable (FOC) are designed with a maximum tensile strength and the Fiber Optic Cable (FOC) should never be pulled beyond its value. Exceeding the cable’s pulling tension can shorten its in-service lifetime.

Using traditional pulling techniques, a tension is developed in the Fiber Optic Cable (FOC) when pulled, due to the friction between the outer surface of the Fiber Optic Cable (FOC) and the surface over which it is pulled.Excessive Physical Path Sections (PPS) lengths can lead to high tensions during pulling, creating the risk of Fiber Optic Cable (FOC) damage, particularly at bends.

The following effects contribute to the pulling force build-up in the FOC:

➧Fiber Optic Cable (FOC) weight. Pulling force is proportional to the installed weight of the Fiber Optic Cable (FOC), which is directly related to its size, design, and the Fiber Optic Cable Section (FOCS) length installed.

➧Coefficient of friction. That coefficient relates the normal force to frictional force between Fiber Optic Cable (FOC) and the conduit. The coefficient of friction affects the cable tension linearly in straight runs. In bends, the tensile pulling force increases exponentially with respect to the curvature and the coefficient of friction. This effect is known as the capstan effect and it can dominate most cable pulls.

Solutions:Use of cable lubricants to reduce the coefficient of friction between the Fiber Optic Cable (FOC) outer surface and conduit inner surface is strongly recommended. The lubricant material should not react with cable outer sheath and be applied in the quantity suggested by the supplier.

➧Cable compressible force. The Fiber Optic Cable (FOC) can buckle under the compressible forces of a cable pusher and become crushed from additional forces that build up on the inside of a bend. This can also lead to a pulling force built-up that limits the distance it can be pushed.

➦Fiber Optic Cable (FOC) Twist

Cable twist can develop stress on the fiber-strands and therefore need to be avoided. Tension on the Fiber Optic Cable (FOC) and pull ropes can cause cable twisting. However, using appropriate methodologies and tools, the pulling tension causing twisting forces on the cable can be prevented.

➦Temperature

FOCs and conduits are subjected to the temperature cycles of their installation environment and thus they must be fully operational and material resistant at the peak temperatures of those cycles. FOCs are particularly susceptible to freezing temperatures because fiber optic strands may be bent by the tremendous forces that occur when water crystallizes into ice. Water can get into ducts by infiltration and condensation. At high temperatures, FOC and duct materials can soften and compromise their mechanical properties.

Last Word

I have explained best possible about the Fiber Optic Cables Placement and I hope this information guide you in practical life.If Fiber Optic Cables (FOCs) Installation is not done in a proper way then there are many problems occurred.How did you get this information?You can comment and suggest me.