Wikis Share

Fiber optic termination is a critical process in establishing reliable and efficient optical communication networks. Whether you're installing a new fiber network or performing maintenance on an existing one, proper termination techniques ensure optimal signal transmission with minimal loss. This comprehensive guide covers everything you need to know about terminating fiber optic cable, from understanding the basics to implementing best practices according to industry standards.

Understanding Fiber Optic Termination

Fiber optic termination refers to the process of connecting the end of a fiber optic cable to create a functional connection between similar or dissimilar devices. There are primarily two methods of terminating fiber optic cables: using connectors or splicing. Connector termination creates temporary connections that can be easily disconnected and reconnected, while splicing creates permanent connections between fibers.

Improper termination can lead to significant issues including signal loss, return loss, and even complete system failure. To minimize such losses, fibers must be aligned and connected with high precision.

Picture Source: How to Terminate Fiber Optic Cable

Types of Fiber Optic Termination Methods

1. Connector Termination

Connector termination involves attaching a connector to the end of a fiber cable. The most common connector types include:

• ST (Straight Tip) Connector: Features a bayonet-style socket with a long cylindrical ferrule to hold the fiber. Popular in multimode networks and easily inserted or removed due to its spring-loaded design.
• SC (Subscriber Connector): A snap-in connector that latches with a simple push-pull motion. Usually comes with a square plastic housing and is widely used in single-mode and duplex networks.
• LC (Lucent Connector): A standard ceramic ferrule connector that's half the size of the SC connector with a smaller ferrule (1.25mm). Primarily used for single-mode systems and high-density applications like data centers.
• MU Connector: A miniature SC connector with a square shape and push-pull mating mechanism, ideal for high-density applications.

Connector termination can be further categorized into:

• Field Termination: Connectors are added on-site using specialized tools. This approach offers customizable cable lengths but may require professional expertise.
• Factory/Pre-Termination: Cables are terminated in a controlled factory environment before shipment, offering plug-and-play deployment with higher precision and reliability.

2. Splicing

Splicing involves directly connecting two fiber strands without connectors. This method creates a permanent connection and is typically used when cable runs are too long for a single pull or for restoring broken cables. There are two main splicing techniques:

• Fusion Splicing: Uses an electric arc to melt and fuse two fiber ends together. This method provides the lowest loss connection but requires expensive equipment.
• Mechanical Splicing: Aligns two fiber ends to a common centerline using a mechanical device. Though simpler than fusion splicing, it typically results in higher insertion loss.

Essential Tools and Materials for Fiber Termination

Before beginning the termination process, gather these essential tools and materials:

Basic Tools:

• Fiber optic stripper
• Fiber cleaver
• Cable jacket stripper
• Kevlar scissors
• Crimping tool
• Polishing puck and glass plate (for epoxy connectors)
• Fiber microscope or inspection scope

Consumables:

• Appropriate connectors
• Cleaning supplies (isopropyl alcohol, lint-free wipes)
• Epoxy or adhesive (for epoxy-style connectors)
• Polishing films/papers (for epoxy connectors)
• Heat-shrink sleeves (for splices)

Safety Equipment:

• Safety glasses with side shields
• Fiber optic scrap container
• Proper work surface (dark, non-reflective)
• Protective gloves

Step-by-Step Connector Termination Process

The exact process varies depending on the connector type, but here's a general guide for epoxy-style connector termination:

1. Prepare the Cable

• Measure and mark the cable at the appropriate stripping length.
• Use a jacket stripper to remove the outer jacket of the cable.
• Separate and trim the strength members (Kevlar/aramid yarn) to the appropriate length.
• Strip the buffer coating from the fiber using the fiber stripper.

2. Prepare the Connector

• If using epoxy connectors, inject epoxy into the connector.
• Slide the strain relief boot and crimp sleeve onto the cable before proceeding.

3. Insert and Secure the Fiber

• Carefully insert the stripped fiber through the connector until it extends slightly beyond the ferrule tip.
• Ensure the fiber is fully seated and the buffer reaches the back of the connector.
• Crimp the connector onto the strength members and outer jacket for strain relief.

4. Cure the Epoxy (if applicable)

• Place the connector in a curing oven at the temperature and duration specified by the epoxy manufacturer.
• Ensure the connector is positioned appropriately during curing to prevent epoxy from wicking.

5. Cleave and Polish the Fiber

• After curing, cleave the excess fiber protruding from the ferrule tip.
• For epoxy connectors, polish the fiber end using successive grits of polishing paper to achieve a smooth, flat endface.
• Begin with coarser polishing film and work toward finer grits.

6. Clean and Inspect

• Clean the connector end face with isopropyl alcohol and lint-free wipes.
• Use a fiber microscope to inspect the connector end face for scratches, cracks, or contamination.

7. Test the Connection

• Test the terminated connector for insertion loss and return loss using appropriate test equipment.

Pre-Polished Connector Termination

Pre-polished connectors (also called "no-epoxy/no-polish" or quick-termination connectors) offer a faster alternative to traditional epoxy connectors:

1. Prepare the cable as described above.
2. Cleave the fiber to create a precise end face.
3. Insert the cleaved fiber into the pre-polished connector until it contacts the factory-polished fiber stub inside.
4. Secure the fiber using the connector's built-in mechanical mechanism.
5. Test the connection for proper performance.

Fusion Splicing Process

For permanent connections or when working with pigtails (pre-terminated short fiber segments):

1. Strip and prepare both fiber ends.
2. Cleave both fibers to create clean, perpendicular end faces.
3. Place the fibers in the fusion splicer, which will automatically align them.
4. Initiate the fusion process, which creates an electric arc to melt and join the fibers.
5. Place a protective sleeve over the splice and heat it to provide mechanical strength.
6. Test the splice for optical loss.

Safety Precautions for Fiber Termination

Working with fiber optics requires attention to several safety considerations:

• Eye Protection: Always wear safety glasses with side shields to protect against fiber shards and chemicals.
• Fiber Disposal: Never dispose of fiber scraps in regular trash. Use designated containers for all fiber scraps to prevent injuries.
• Clean Workspace: Maintain a clean, well-organized work area with a dark surface to make fiber scraps more visible.
• No Food or Drinks: Keep food and beverages away from the work area to prevent accidental ingestion of fiber particles.
• Chemical Safety: Be familiar with the Material Safety Data Sheets (MSDS) for all chemicals used in the termination process.
• Laser Safety: Never look directly into fiber ends without ensuring there's no light source connected.

Testing Terminated Fiber Connections

After termination, proper testing ensures the connection meets required performance standards:

Insertion Loss Testing

Using a light source and power meter (OLTS - Optical Loss Test Set) to measure the total light loss through the connection. This is the most accurate method for determining end-to-end loss and is required by industry standards.

OTDR Testing

An Optical Time Domain Reflectometer (OTDR) sends light pulses down the fiber and measures the backscattered and reflected light to locate and characterize events along the fiber, including:

• Connector and splice locations
• Loss at each event
• Breaks or bends
• Overall fiber length

While an OTDR provides valuable data about individual components along the fiber path, insertion loss testing remains the primary method for certifying total link loss.

Industry Standards for Fiber Termination

Several organizations develop and maintain standards for fiber optic termination:

• TIA/EIA (Telecommunications Industry Association/Electronic Industries Alliance): The TIA-568 series, particularly TIA-568.3-E, defines specifications for fiber optic cabling components including connectors, adapters, and cable types.
• ISO/IEC (International Organization for Standardization/International Electrotechnical Commission): Provides international standards for cabling infrastructure.
• NECA/FOA 301: A standard developed jointly by the National Electrical Contractors Association and the Fiber Optic Association for installing and testing fiber optic systems.
• ANSI (American National Standards Institute): Governs standards development in the United States.
• National Electrical Safety Code (NESC): Published by IEEE, specifies safe practices for installing and maintaining communications lines.

Best Practices for Successful Fiber Termination

To ensure optimal performance of terminated fiber connections:

• Cleanliness is Critical: Always clean fiber ends and connectors before mating. Even microscopic particles can cause significant loss.
• Use Proper Tools: Invest in quality tools designed specifically for fiber optic work.
• Practice Good Technique: Develop consistent, methodical procedures for termination.
• Control Your Environment: Work in a clean, well-lit area away from dust and contaminants.
• Verify Your Work: Always test terminated connections to confirm they meet performance requirements.
• Follow Standards: Adhere to relevant industry standards and manufacturer guidelines.
• Document Everything: Keep detailed records of all terminations, including test results.

Conclusion

Fiber optic termination requires precision, attention to detail, and adherence to proper procedures. By understanding the different termination methods, following safety protocols, and implementing best practices, you can create reliable connections that ensure optimal performance in your fiber optic network. Whether you choose connector termination or splicing will depend on your specific requirements, but in either case, proper technique and testing are essential for success.

Remember that while this guide provides a comprehensive overview, manufacturer-specific instructions should always be followed for the particular components you're using. Additionally, for critical installations, consider seeking certification or training from organizations like the Fiber Optic Association (FOA) to ensure you have the necessary skills and knowledge.

Recommended

• What Is A Primary Function of Fiber Optic Cables