What are the advantages of blowing or jetting fiber optic cable vs. traditional pulling?
Pulling and blowing are the two primary fiber installation methods. But each of these techniques can impact the longevity, performance, and return on investment (ROI) of a fiber optic network. If you take into account the fragility of glass or fused silica during installation, distance to be covered, efficiency, and costs, you may see that jetting (blowing) offers many advantages over traditional cable-pulling techniques.
An Overview of Fiber Optic Cable Installation Methods
• Pulling: It involves pulling the fiber optic cable through pre-installed underground or aerial ducts. You can pull the cable manually or using a reeling machine. You’ll also need a pulling tape to haul the cable while measuring the distance covered.
• Blowing: With this technique, high-speed air pressure pushes fiber optic cables through standard ductwork or microduct systems.
Here are the reasons why cable jetting is superior to traditional pulling methods:
Minimal Risk of Tension Damage
Each brand of optical fiber cable has a maximum tensile strength. But in pulling, there’s a risk of straining the cable beyond its limit, which can compromise the fiber’s performance and cut its service life. Unchecked resistance forces, such as friction, on the sidewalls of cables and ducts, can also cause damage during a “pulling” installation.
In contrast, jetting involves little or no pulling, which significantly minimizes strain on the fiber optic cable. You can not only configure the system’s hydraulic pack or air-compressing equipment to control airflow inside the duct but also monitor the conduit and fiber to minimize damage.
To minimize friction during cable jetting, consider applying lubricants meant for the method. Ducts with low-friction interior walls may also help.
Suitability for Long-Haul Fiber Optic Networks
Pulling isn’t the best option for placing outside plant (OSP) fiber optic cable. With the technique, there’s always a high possibility of pulling the cable into conduit bends. And as bend angles continue to accumulate, it becomes increasingly difficult to optimize pull length. The bad news is that ducts for cross-country fiber optic networks can have many bends.
As such, pulling is ideal for short-distance fiber optic cable deployment. Distance will vary from one manufacturer to another and cable jacket material plays a role too.
With high air speed blowing fiber optic installation, however, conduit bends and undulations aren’t as much of an issue as they are with traditional cable-pulling techniques. The blowing force doesn’t pull the cable into a duct bend. It instead pushes it smoothly around every turn or curve.
In other words, the duct route geometry doesn’t impact installation distance in this case. Consequently, air-assisted installation lets you place fiber optic cable thousands of feet between jetting sites. That’s why it’s suitable for OSP fiber deployments, for example, telecommunication, CATV, and internet networks.
Cable jetting equipment and ductwork may be initially expensive. But you can amortize these upfront costs depending on current needs, and your initial investment may pay off in future savings on upgrades. For example, you don’t have to invest in redundant higher fiber counts when you can cheaply upgrade capacity in tandem with changing requirements.
Likewise, “pulling” is more labor-intensive than the blowing method. The technique involves more equipment movement, and it may require the positioning of placing tools at intermediate points and both ends of long OSP runs. Additional workers and extra equipment translate to higher installation costs. Cable jetting requires fewer cabling technicians, however.
Keep in mind that air-assisted optical fiber installation minimizes the number of splices needed. Cables installed this way don’t usually require “figure-eight” looping to prevent twisting every time duct changes direction. Since the approach has fewer intermediate-assist placement operations, it limits the number of handholes and other access points required along the cabling route.
Suitability for Microduct Installation
Jetting is very effective in pushing fiber optic cable through microducts. With the blowing method, you can place microduct cable in continuous lengths. The technique is most suitable for modern optical fiber cables that tend to contain bare fibers, and sometimes reduced cladding diameters, both of which contribute to decreased outer cable diameters.
The thinner a fiber optic cable is, the larger the number of fibers you can place in specific innerduct. As such, jetting is the best installation technique when you wish to make the most of the available duct capacity. It also allows you to work with small but flexible fibers that go through multiple microduct twists and turns over long distances with near-zero bend losses.
Additionally, when setting up microducts for fiber optic cable jetting, you may include redundant ductwork to accommodate new fiber in the future as required. This way, you avoid the unnecessary costs of placing dark fiber, which may become obsolete sooner than anticipated.
Appropriate for Removal of Old Fiber
Pulled fiber optic cable may be difficult to remove when no longer needed. The presence of old and unwanted cables in mission-critical physical pathways may limit your ability to optimize your optical network capacity or even upgrade to higher-performance fibers.
But after installing optical fiber by cable jetting, you may easily remove it by the same approach when necessary. You may be able to reuse the removed fiber optic cable since the removal process is gentle enough to minimize or avoid damage.
Cable jetting is faster than the “pulling” method. The pushing device can move fiber optic cable at speeds of 350 feet per minute or higher. With the air-jetting technique, you can quickly push cables through pre-installed innerduct or underground ductwork. But in most cases, you can only pull fiber at a rate of 100-200 feet per minute, or even slower.
Choose cable jetting to upgrade your optical fiber with minimal interruption to ongoing workflows or operations. The cable-pulling approach is more disruptive.