Common Causes of Underground Fibre Cable Damage
Common Causes of Underground Fibre Cable Damage include excavation strikes, rodents, water entry, excessive pulling force, poor pathway design and unsuitable cable selection. Although underground installation protects fibre from many surface hazards, it does not remove every risk. Therefore, installers must consider the cable construction, pathway conditions and installation method together.
The RapidConnect® G-Series GRP Armoured Rodent Proof Fibre Optic Cable provides layered mechanical and biological protection for demanding underground environments. However, even an armoured cable still requires appropriate handling, pathway preparation and installation planning.
Why Underground Fibre Cable Becomes Damaged
Underground fibre cable can provide decades of reliable service when the cable and pathway suit the application. Nevertheless, failures occur when one or more risks remain uncontrolled.
Sometimes, an external event damages the cable after installation. For example, an excavator may strike a conduit during later construction work. In other cases, the original installation creates the weakness. Excessive pulling tension, tight bends or inadequate water management may cause immediate damage or reduce long-term reliability.
Furthermore, the wrong cable construction can leave the optical core exposed to conditions it was never designed to withstand. Consequently, cable selection should begin with the route rather than with a general indoor or outdoor classification.
1. Excavation and Accidental Digging
Excavation remains one of the most serious causes of underground communications cable damage. An excavator, trencher, directional drill, fence post or hand tool can cut through a conduit and cable within seconds.
In some cases, asset plans may be missing, outdated or incorrectly interpreted. Moreover, private fibre routes inside industrial sites do not always appear on external service plans. Therefore, project documentation and accurate route records remain essential.
Before excavation begins, contractors should obtain available service information and physically confirm asset locations where required. Safe Work Australia’s excavation guidance also directs those planning excavation work to check for underground services, including through Before You Dig Australia.
Additionally, installers can reduce future risk by:
- Recording accurate cable routes and depths
- Installing detectable marker tape above the route
- Using warning posts or route markers where appropriate
- Providing updated drawings to the asset owner
- Protecting conduit entries and exposed transition points
- Maintaining clearance from other underground services
- Using suitable conduit or mechanical protection in high-risk areas
Although these measures cannot prevent every incident, they make accidental strikes less likely.
2. Rodent Attack
Rodents may gnaw cable jackets, conduits and other polymer components. Once the outer jacket becomes damaged, the internal cable layers can become exposed to moisture, contamination and further mechanical attack.
Importantly, rodents do not need to consume the cable. Instead, their natural gnawing behaviour can puncture or strip the jacket. Therefore, ordinary polyethylene protection may not provide a sufficient barrier in locations with an established rodent population.
The article Why Rodents Damage Fibre Optic Cable explains the behaviour behind this type of damage. Meanwhile, Understanding Rodent Resistance in Fibre Cable Design examines how cable layers work together to protect the optical core.
Flat GRP armour elements create a hard, non-metallic barrier beneath the outer jacket. As a result, they make it substantially more difficult for rodents to reach the inner cable construction.
However, armour coverage matters. Large gaps, exposed transitions or unprotected entry points can weaken the overall system. For this reason, installers should assess the complete route rather than focusing only on the cable itself.
3. Termite Attack
Termites create a different risk from rodents. While rodents attack with their teeth, termites may travel through soil, pits and conduits before encountering a cable jacket.
A cable that offers rodent resistance does not automatically provide the same level of termite protection. Therefore, each biological threat requires an appropriate protective layer.
The RapidConnect® G-Series uses a Blue Nylon jacket beneath the flat GRP armour. The GRP elements provide the rodent barrier, while the Blue Nylon layer adds dedicated termite protection. Consequently, the two layers perform separate but complementary roles.
Furthermore, installers should consider cable ends and jointing locations. If the protective layers stop before the cable enters an enclosure, termites may gain access at the transition. Therefore, pits, closures, conduits and building entries should form one coordinated protection system.
4. Water Entry and Persistent Moisture
Underground pathways often contain moisture. For instance, rainwater can enter pits, groundwater can move through conduits, and condensation can form when temperatures change.
Although the glass fibre itself does not conduct electricity, water can still damage cable materials, closures and termination hardware. Furthermore, repeated water exposure can accelerate deterioration if the cable or pathway was designed only for dry conditions.
Loose-tube underground cables commonly include water-blocking materials that restrict longitudinal water movement. However, water blocking does not make poor pathway design acceptable. Installers should still manage drainage, seal conduit entries and avoid leaving vulnerable cable ends exposed.
Persistent immersion presents a more demanding condition than occasional moisture. Therefore, designers should identify whether the cable will pass through telecommunications pits, flooded conduits or low points where water can collect.
The RapidConnect® W-Series Indoor Outdoor Fibre Optic Cable uses a tight-buffered construction with water-blocking yarn. However, it is intended for indoor and protected external commercial pathways. It should not pass through telecommunications pits, persistently wet routes or direct-burial environments.
For a closer comparison, see GRP Armoured vs Indoor Outdoor Fibre Optic Cable.
5. Excessive Pulling Tension
Fibre optic cable can tolerate controlled pulling forces. Nevertheless, excessive tension may stretch or damage cable components.
Problems often arise when installers pull a cable through a pathway with too many bends, long conduit runs or inadequate access points. Similarly, sudden loading can occur when a cable snags and the pulling force continues.
Consequently, installers should follow the specified maximum pulling tension. They should also use suitable hauling equipment, approved pulling attachments and controlled lubrication where appropriate.
In addition, the pulling method should transfer force through the cable strength members rather than through exposed fibres or buffer tubes. A swivel can also reduce twisting during installation.
If the route requires unusually high pulling force, the pathway may need redesign. Adding pits, changing bend geometry or dividing the pull into shorter sections can reduce cable stress.
6. Tight Bends and Cable Kinking
Every fibre optic cable has a minimum bend radius. If installers bend the cable too tightly, they can create optical loss, fibre stress or physical damage.
A kink causes an even more concentrated deformation. Therefore, installers should never attempt to straighten and reuse a severely kinked section without assessing the damage.
Bend-radius problems commonly occur:
- At conduit entries
- Inside telecommunications pits
- Around enclosure mounting points
- During cable payout
- Where surplus cable has been stored incorrectly
- At building entry points
- Near joints and closures
Moreover, bend radius usually changes according to whether the cable is under tension or resting after installation. Installers should therefore consult the relevant cable specification rather than relying on a general rule.
7. Crushing and Point Loading
Underground cable can suffer crushing damage when heavy loads act directly on the cable or conduit. For example, rocks, poorly compacted backfill or vehicle loading may create concentrated pressure.
Likewise, cable ties, clamps and gland systems can produce point loading when overtightened. Although the outer jacket may appear intact, excessive pressure can deform buffer tubes and increase fibre attenuation.
Proper bedding material helps distribute load around the conduit or cable. In addition, installers should remove sharp rocks and debris before backfilling.
Where the route passes beneath roads, loading areas or heavy industrial equipment, the pathway may require stronger conduit, greater burial depth or additional mechanical protection.
8. Poor Conduit and Pit Design
A well-selected cable can still fail inside a poorly designed pathway. Therefore, conduit and pit design form an important part of cable protection.
Potential pathway problems include:
- Conduits with excessive bends
- Inadequate pit drainage
- Sharp conduit edges
- Blocked or collapsed ducts
- Open conduit ends
- Water-filled low points
- Insufficient space for bend-radius control
- Shared pathways with incompatible services
- Abrasive debris inside the conduit
Furthermore, small conduits increase pulling friction and make future cable replacement more difficult. Consequently, designers should allow enough space for installation, maintenance and reasonable expansion.
Pits also need enough room to support safe cable handling. If the cable must be forced around a small pit, the resulting bends may exceed the permitted radius.
9. Unsuitable Cable Selection
Cable selection should reflect the harshest credible condition along the route. However, specifications sometimes focus on only one part of the installation.
For example, a route may begin inside a building, travel through an external conduit and then pass through several pits. Describing that route simply as “indoor outdoor” does not identify the moisture, rodent or mechanical risks.
Therefore, designers should review:
- Indoor and external sections
- Telecommunications pits
- Moisture exposure
- Rodent and termite activity
- Electrical infrastructure
- Pulling distances
- Conduit condition
- Burial method
- Future excavation activity
- Termination requirements
For demanding underground routes, the RapidConnect® G-Series cable construction combines a Black PE outer jacket, flat GRP armour elements, a Blue Nylon termite-protection layer and a loose-tube optical core with dry water blocking.
By contrast, the W-Series uses a Black UV-resistant LSZH jacket, water-blocking yarn and tight-buffered fibres. Therefore, it suits indoor and protected external commercial pathways where easier handling and termination matter more than dedicated underground armour.
10. Inadequate Protection at Cable Transitions
Cable transitions often create weak points. For instance, an underground cable may leave a conduit, enter a cabinet and then pass through a gland or opening.
If the outer jacket or armour ends too early, the exposed section may become vulnerable to rodents, abrasion or impact. Likewise, an incorrectly sized gland may fail to grip or seal the cable properly.
Therefore, the protective pathway should continue as close as practical to the enclosure entry. Installers should also use suitable glands, bushes, seals and strain-relief components.
In addition, they should prevent water from following the cable into a cabinet or building. Drip loops, sealed entries and appropriate route geometry can help manage this risk.
11. Poor Jointing and Closure Installation
Underground joints require carefully selected closures and disciplined installation. Otherwise, water, dirt and insects may enter the splice environment.
Closure problems can result from:
- Incorrect cable preparation
- Damaged or contaminated seals
- Inadequate cable clamping
- Poor closure assembly
- Reused sealing components
- Incorrect port selection
- Excessive fibre bending
- Incomplete closure locking
Furthermore, cable armour and strength members must terminate correctly. If installers remove too much protective material, they may expose the cable core before it enters the sealed area.
Therefore, technicians should follow the closure manufacturer’s preparation dimensions and sealing procedure.
12. Electrical and Corrosion Risks from Metallic Armour
Metallic cable armour provides strong mechanical protection. However, it can introduce electrical continuity, earthing requirements and corrosion considerations.
For example, corrugated steel tape armour may need bonding or earthing under the relevant project design. In addition, damaged metallic armour can corrode when exposed to moisture or aggressive soil conditions.
By contrast, GRP armour is all-dielectric. Consequently, it does not create a conductive armour path and does not require armour earthing.
The article Why Non-Metallic Fibre Cable Armour Matters explains this distinction in more detail. Meanwhile, GRP Armoured vs CST Armoured Fibre Cable compares the two armour systems.
Nevertheless, all-dielectric construction does not remove the need for correct installation. It addresses electrical and corrosion risks while the remaining cable and pathway requirements still apply.
13. UV Exposure at Above-Ground Sections
An underground route often includes short above-ground sections near poles, cabinets, buildings or equipment.
If the exposed jacket lacks suitable UV resistance, sunlight can gradually weaken the material. Therefore, designers should review the complete cable route, including transition points.
Furthermore, exposed sections may face impact, vandalism, animals and garden equipment. Protective conduit or guard systems may therefore be necessary even when the main route runs underground.
14. Damage During Storage and Handling
Cable damage can occur before installation begins. For example, incorrect drum handling may crush the cable, loosen the wind or damage the flange.
Similarly, rolling a drum in the wrong direction can disturb the cable layers. Dropping the drum can also create hidden damage.
Therefore, installers should:
- Store drums on stable ground
- Keep protective battens and packaging intact until required
- Lift drums using approved methods
- Roll drums only in the marked direction
- Inspect the cable and drum before installation
- Protect exposed cable ends from moisture
- Use suitable payout equipment
- Avoid pulling cable from a stationary drum flange
Careful handling protects the cable and supports a controlled installation.
Diagnosing Underground Fibre Cable Damage
When a link fails, the visible fault location may not reveal the original cause. Therefore, technicians should combine optical testing with physical inspection.
An optical time-domain reflectometer can estimate the distance to a high-loss event or fibre break. However, the measured distance still needs to be compared with route drawings, pit locations and known pathway features.
A structured investigation should include:
- Confirming the affected fibres and services
- Reviewing recent excavation or construction work
- Testing from one or both ends
- Comparing test distances with the cable route
- Inspecting nearby pits, closures and transitions
- Looking for water, rodent activity or crushed conduit
- Recording the failure cause before repair
- Correcting the pathway problem as well as the cable fault
Otherwise, a repaired cable may fail again at the same location.
Preventing the Common Causes of Underground Fibre Cable Damage
A successful repair should address the root cause rather than only restoring optical continuity.
For example, if rodents damaged the cable, replacing it with the same unprotected construction leaves the original risk in place. Similarly, if a flooded pit caused deterioration, replacing the splice without improving the closure or pathway may provide only a temporary solution.
Therefore, the corrective action may involve:
- Upgrading to rodent-resistant armoured cable
- Improving pit drainage
- Replacing damaged conduit
- Adding mechanical guards
- Sealing conduit entries
- Increasing bend space
- Improving route documentation
- Relocating the cable
- Installing warning tape
- Changing the cable construction
- Improving closure selection
The article Rodent-Resistant Fibre Optic Cable for Underground Networks provides further guidance for routes with biological threats. Additionally, GRP Armoured Fibre for Industrial Facilities examines layered protection in demanding industrial environments.
When GRP Armoured Fibre Cable Is Appropriate
GRP armoured fibre cable is particularly useful where an underground pathway faces several risks at once.
These locations may include:
- Industrial facilities
- Utility infrastructure
- Renewable-energy sites
- Water and wastewater facilities
- Transport networks
- Resource and processing sites
- Remote communications routes
- Sites with known rodent or termite activity
- Pathways near electrical infrastructure
- Conduits and pits exposed to moisture
Because GRP is non-metallic, it provides mechanical protection without introducing conductive steel armour. Moreover, the Blue Nylon layer adds termite protection beneath the armour.
However, the project team should still confirm the proposed installation method, pathway design, soil conditions and project requirements. In particular, direct-burial suitability should form part of the project-specific cable selection process.
Frequently Asked Questions – Common Causes of Underground Fibre Cable Damage
What are the most common causes of underground fibre cable damage?
Excavation and accidental digging represent a major risk because machinery can cut through conduits and cables quickly. However, rodents, water, excessive tension and poor pathway design also cause significant damage.
Can rodents damage fibre optic cable?
Yes. Rodents can gnaw through ordinary cable jackets and expose the internal construction. Therefore, routes with rodent activity may require a dedicated protective barrier such as flat GRP armour.
Does underground fibre cable need to be waterproof?
The cable construction should suit the expected moisture conditions. However, water-blocking materials do not replace drainage, conduit sealing and suitable closures.
Can indoor outdoor fibre cable pass through telecommunications pits?
Not automatically. The RapidConnect® W-Series should not pass through telecommunications pits, persistently wet pathways or direct-burial environments. Instead, select a cable specifically designed for the route conditions.
Does GRP armour require earthing?
No. GRP is non-metallic and all-dielectric. Therefore, the armour itself does not create a conductive path or require armour earthing.
Is GRP armour the same as steel armour?
No. GRP uses glass-reinforced polymer elements, whereas CST armour uses corrugated steel tape. Consequently, the two systems differ in electrical behaviour, corrosion risk and mechanical construction.
Can fibre damage occur without breaking the outer jacket?
Yes. Excessive pulling tension, crushing or tight bends can damage internal fibres while leaving the outer jacket apparently intact. Therefore, optical testing remains important when a fault has no obvious external sign.
Protecting Underground Fibre Infrastructure
Ultimately, the common causes of underground fibre cable damage rarely operate in isolation. Excavation, rodents, termites, moisture, pulling stress and poor pathway design can combine to create a larger risk.
Therefore, reliable underground fibre infrastructure depends on three connected decisions: selecting the correct cable, designing the pathway properly and installing the system carefully.
The RapidConnect® G-Series GRP Armoured Rodent Proof Fibre Optic Cable provides a layered, all-dielectric construction for demanding underground environments. Its Black PE outer jacket, flat GRP armour elements, Blue Nylon termite-protection layer and loose-tube optical core work together to protect the fibres.
For additional product and installation information, visit the Anderson Corporation Fibre Optic Products YouTube channel.
To discuss a project pathway, fibre count or environmental risk, request a Rapid Quote.