Basics and Selection Guide for Fiber Optic Connectors

Introduction:

Fiber optic connectors, commonly referred to as fiber optic splicing closures, play a crucial role in securing and maintaining the integrity of spliced fiber optic cables. As the backbone of modern communication networks, fiber optic cables need specialized enclosures to protect the sensitive glass fibers and cable splices from environmental hazards. This article will explore the fundamentals of fiber optic closures, highlighting the different types available and providing a comprehensive guide for selecting the most suitable closure for your network needs.

What is a Fiber Optic Closure?

A fiber optic closure is a rugged, sealed enclosure designed to organize, store, protect and provide access to fiber optic splices and cables. It houses the buffer tubes and individual fibers, providing a controlled environment that shields them from outside elements like moisture, dirt, chemicals, extreme temperatures, and mechanical damage.

Fiber optic closures allow cable network operators to securely connect fiber cables without exposing the delicate glass fibers. They are a key element for cable management, organizing individual fibers in an orderly manner and providing adequate space for future network expansion.

Types of Fiber Optic Closures

There are two major categories of fiber optic closures:

1. Horizontal Type Fiber Optic Closures

2. Vertical Type Fiber Optic Closures

Horizontal Type Fiber Optic Closures

Horizontal fiber optic closures feature a low-profile, elongated design suitable for aerial, direct buried and underground conduit applications. With a rugged, thermoplastic shell wrapped around the splice compartment, these offer reliable protection in harsh conditions involving moisture, insects, chemicals, vibrations and occasional impacts.

Key Features:

1. Cylindrical or rectangular shape for mounting flexibility

2. Craft-friendly and easy to install

3. Multiple sealed cable entry ports

4. Stackable splice trays providing termination, storage and organization

5. Space for heat shrink protective sleeves over splices

6. Removable waterproof splice compartment

Benefits:

1. All-weather performance for aerial, buried and underground settings

2. Modular and scalable to support network growth

3. Accommodates a wide range of cable sizes and fiber counts

4. Allows quick access to splices for moves, adds and changes

Example Configurations:

1. 144-fiber aerial closure with dual end caps

2. 288-fiber underground closure with four standard ports

3. 576-fiber underground closure with large cable entry ports

Vertical Type Fiber Optic Closures

As the name suggests, vertical fiber optic closures have a tall, dome-shaped enclosure ideally suited for pole attachments and aerial deployment. The vertical orientation saves space while safely securing a high density of splices and cable interfaces.

Key Features:

1. Dome-shaped housing with pressure seal lid

2. Multiple cable entry ports on sides

3. Hanging brackets for pole mounting

4. Stackable splice trays

5. Adjustable cable clamps and strength member attachments

Benefits:

1. Space-efficient vertical storage

2. Suitable for congested aerial routes

3. Allows direct overhead ladder access

4. Easy pole or strand mounting options

5. Craft-friendly pressurized re-entry

Example Configurations:

1. 144-fiber aerial closure with pass-through ports

2. 288-fiber aerial closure with dual-end bracket mounting

3. 576-fiber aerial closure withCablelok port seals

Underground Vs Aerial Deployment

While both horizontal and vertical enclosures can be used in aerial and underground settings, certain designs are better suited for specific installation environments:

Underground Applications

1. Horizontal closures in vaults and handholes

2. Protection against moisture, flood and chemicals

3. Larger ports for thick cables and armor sleeves

Aerial Applications

1. Vertical closures on aerial strands

2. Space and ladder access efficiencies

3. Mounting brackets for messenger wires

4. Protection against vibration/wind/ice

Factors to Consider When Selecting Fiber Optic Closures

Choosing the optimal fiber optic closure depends on several key factors:

1. Network Size

Consider the required termination capacity both currently and for future expansion. High fiber count networks will need appropriately sized closures.

Key Questions

1. How many fibers need to be terminated now?

2. What is the projected network growth over 5-10 years?

3. Will you add backbone, spur routes or FTTx drops later?

This determines the ideal fiber count, splice capacity and cable port density.

2. Installation Environment

Fiber route conditions dictate closure type selection. Carefully evaluate the deployment terrain.

Key Questions

1. Will it be aerial, underground or a hybrid plant?

2. What are the climate, temperature and seismic patterns?

3. Does the site see extreme weather like flooding or ice?

4. Are rodents/termite damage or vehicular impact likely?

This assesses the needed protection level, seal rating and structural reinforcement.

3. Ease of Installation

Closures should be craft-friendly and quickly installable to minimize fiber handling and accelerator network deployment.

Key Questions

1. Does the closure allow rapid, tool-free installation?

2. Can it be mounted on poles, strands or placed in vaults easily?

3. Are cable ports and splice trays easily accessible for technicians?

This ensures optimal field serviceability and faster fiber splicing & activation.

4. Scalability

Select enclosures designed for seamless expansion as network segments are added.

Key Questions

1. Can unused panel space accommodate future splice trays?

2. Are there empty cable ports to add drop cables later?

3. Can closure capacity be readily increased onsite if needed later?

This guarantees network growth support for tomorrow’s needs.

5. Physical Space Constraints

Evaluate any right-of-way restrictions, congestions or space limitations affecting closure selection.

Key Questions

For aerial plants:

1. How much clearance space is available from other utilities?

2. Are there any line-of-sight restrictions near the site?

For underground deployments:

1. What are the vault/manhole dimensions and entry points?

2. Will closure shape and footprint fit within available areas?

This ensures optimal hardware sizing tailored to physical site conditions.

Closure Selection Criteria Comparison

Criteria

Horizontal ClosuresVertical ClosuresTerrain SuitabilityUnderground (Handholes/Manholes)Aerial (Messenger/Strand Mounting)Weather ResistanceExcellent (Fully-Sealed)Excellent (Pressurized Dome)Space EfficiencyModerate (Elongated Shape)High (Compact Vertical Orientation)Access ConvenienceModerate (Removed From Access Points)High (Mounted Near Ladder Access)Initial Cost per FiberLow (Economies of Scale)Moderate (Specialized Brackets)Lifetime ValueHigh (Durable and Expandable)High (Craft-Friendly and Maintainable)

Key Closure Components

Modern fiber optic closures comprise intelligent subsystems and components engineered for simplicity, scalability and reliability:

1. Outer Enclosure

This provides the main protective shell manufactured from tough, corrosion-resistant thermoplastic. Resilient closures feature premium resins and additives to increase environmental durability.

2. Cable Entry Ports & Seals

Re-usable modular cable ports with integrated seals accommodate multiple cables securely. Rapid compression ports allow simple field installations.

3. Hanging Brackets

Corrosion-resistant mounting attachments are available for strand vises, messenger wires or pole cleats in aerial deployments.

4. Splice Trays

These organize individual fiber splices and store excess lengths, keeping buffer tubes neat and accessible via efficient routing. Trays are stackable as capacity grows.

5. Strength Member Attachment

Internal component secures the central strength member of cables to provide additional tensile reinforcement and prevent fiber damage from cable tugging/swaying.

6. Grounding Provisions

Integrated lugs, straps or meshes enable proper bonding for safety. They protect networks through bleed-off of dangerous electrical charges from lightning or power contact.

7. Cable Managers

Also called fiber organizers or radial brackets, these allow routing of multiple buffer tubes entering closure from all directions while maintaining optimal bend radius.

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Selecting Suitable Hardware & Accessories

Proper installation components ensure seamless closure deployment into existing cable networks:

1. Stainless steel closure mounting brackets

2. Strand vises for aerial messenger wires

3. Pole attachment bands for vertical stability

4. Support hangers to manage cable slack loops

5. Craft-friendly pressurized re-entry plugs

6. Aerial-to-underground transition fittings

7. Underground conduit termination caps

Closure Design & Material Considerations

1. Withstand Harsh Environments

Fiber closures situated outdoors endure temperature swings, moisture, chemicals, weathering and potential physical impacts. Resistant thermoplastic housings coupled with compression seals protect splices.

2. Absorb Cable Flexing Motion

Relative movement between closure and cables due to winds/vibrations is minimized using flexible ports, shield bonds and strain relief. This reduces mechanical damage risks.

3. Support Efficient Cable Routing

Well-designed cable managers and splice trays neatly organize individual fibers. This eases tracing/splicing specific fibers later and enables faster maintenance.

4. Accommodate Wide Service Loops

Adequate space is required for spare cable slack to enable rearrangements. Low friction routing guides prevent tight bend radiuses during looping/coiling.

5. Allow Quick Re-Entry

Simple field re-entry systems save technicians time and effort. Tool-free pressurized domes utilize quick release lid bolts. This facilitates moves, adds and changes.

6. Offer Adjustable Mounting

Versatile aerial mounting options like pendant eyes or strand vises adjust to accommodate different pole sizes and cable geometries onsite.

7. Enable Effortless Expansion

Scalable enclosures feature stackable splice trays and empty ports to readily increase capacity. On-site upgrades avoid network disruptions and re-engineering.

8. Provide Safety and Security

Robust seals keep dust and moisture from sensitive fibers, while sturdy covers prevent tampering. Integrated ground lugs discharge electrical surges safely.

Installation Best Practices

Correct installation technique ensures peak performance from fiber optic closures:

1. Select suitable closure capacity allowing for future network growth

2. Match chosen grounding method to site conditions

3. Arrange cables to minimize length and bends when entering closure

4. Bond metallic cable strength elements to interior ground straps

5. Loop slack service fiber generously before splicing

6. Insert flexible boots into cable ports for bend radius control

7. Stack splice trays neatly to organize connectivity

8. Clean fibers completely before applying splice protectors

9. Double check waterproof seals and properly torque closures

10. Attach informative labels for all cable IDs and fiber counts

Testing & Maintenance

After closure installations are complete, proper testing validates performance while ongoing maintenance guarantees longevity:

1. Link Loss Testing

Certify acceptable optical loss budgets across entire links to identify any defects before activation. Perform OTDR signature analysis if anomalies occur.

2. Visual Inspection

Periodically check for correctly installed seals, secure cable anchoring, sufficient slack loops and absence of external damage.

3. Re-sealing & Reconditioning

Replace worn entry seals and grommets periodically to prevent moisture ingress. Firms offer economical reconditioning services to extend closure lifespans.

4. Tracking & Documentation

Maintain site datasheets listing closure locations/contents and date of installations, tests, repairs or modifications. Keep digital photographic records.

Innovations in Fiber Optic Closure Technology

Companies are making enclosures smarter, smaller and simpler to install:

1. All-in-One Terminals

Converged fiber-electric boxes terminate optical and power lines using consolidated spaces. They eliminate errant stand-alone enclosures.

2. Low Profile Underground Designs

Shallow domes provide aerial density underground. Lower profiles suit congested ducts/handholes with limited height.

3. Pre-terminated “Plug-and-Play” Systems Factory-installed connectorized cable assemblies plug into modular termination panels. This enables tool-less scaling via prefab cable cassettes.

4. Robotic Assisted Precision Splicing

Automated, full-spectrum fusion splicers yield consistent low-loss alignments. Some feature camera systems and built-in test routines to save technicians time.

5. Real-Time Remote Monitoring

Network nodes with connected closure analytics offer temperature, humidity and entry alarms to dispatch teams rapidly.

Conclusion

The proper specification and installation of fiber optic closures shields sensitive network links from risks posed by hazardous outdoor terrain and jam-packed cable ducts alike. Developing a clear picture of current and future bandwidth demands across endpoints aids appropriate selection.

Seeking closures balancing craft-friendly access, ample room for cable maneuvering, density to minimize footprints, consistent protection against weather and other conditions, as well as smart future-proof elements is key for long lifespan.

By following best practice guidance around design areas like cable sealing, securing, splicing, grounding, troubleshooting, and documentation – operators reap the rewards through years of unimpaired signal integrity.