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Extending the Lifecycle of Fiber Optic Cables. John Culbert President and Partner, Megladon Mfg. Group Austin, TX. Introduction. Fiber optic cables are considered a weakness in optical networks Fiber cables are very fragile and sensitive to damage when handling

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Extending the lifecycle of fiber optic cables

Extending the Lifecycle of Fiber Optic Cables

John Culbert

President and Partner, Megladon Mfg. Group

Austin, TX


Introduction

  • Fiber optic cables are considered a weakness in optical networks

  • Fiber cables are very fragile and sensitive to damage when handling

  • Making fiber optics meet performance expectations and withstand field/installation handling are important challenges

  • Industry Best Practices can help us achieve these goals, but robust connector technology can help us avoid the challenges


Outline

  • 1) Common Physical and Mechanical causes for Performance Decline in Fiber Optic Connectors

    • Inspection and evaluation criteria

    • Individual Factors

    • Case Study Discussions and Experimental Evidence

    • Industry Best Practices and Prevention Techniques

  • 2) Proposed Solution through Tempering Technology


  • Scratches and Pitting

    Scratches on the end face of a fiber optic surface drastically reduce its performance

    Scratches are created by:

    Improper Handling

    Improper Cleaning

    Insertions into Inspection Equipment

    Multiple Matings

    Any time the end face contacts something other than a cleaning tool or another properly oriented fiber end face, there is the potential for scratches to develop


    Scratches and Pitting

    Case Study –

    International Electronics Manufacturing Initiative (iNEMI)

    Zone Descriptions

    Scratches have a negative effect on Return Loss (RL), a key fiber performance indicator

    Connectors under regular test environment use for 18 months saw return loss increased from -55db to an average of -42db

    Conclusions: Scratches significantly degrade optical performance, especially return loss

    Zone 3

    Ferrule

    Zone 1B

    Cladding

    Zone 1C

    Epoxy Ring

    Zone 1A

    Core

    Zone 3

    Ferrule

    Zone 2

    Contact Area


    Inspection Criteria

    From IPC-8497-1

    Cleaning Methods and Contamination Assessment for Optical Assembly


    Scratches and Pitting

    Prevention

    • Inspection – Follow inspection criteria. Any scratch can degrade performance

    • Proper Handling – protect end face at all times. Cap un-used connectors

    • Proper Cleaning – Use only approved cleaning products to prevent scratching

    • Carefully insert connectors into inspection ports – even this can create scratches

    Solutions

    • Proper Technician Training

    • More robust connectors that withstand handling


    Contamination

    Contamination

    • Consists of dust, dirt and various other forms of debris

    • Difficult to avoid – Contamination happens anytime you remove the end cap and endface is exposed

    • Subject to the inspection guidelines mentioned earlier

    • Prevents even contact between cable end faces during mating

    • Blocks signal through core

    • 80% of contaminants are silica particles


    Contamination

    Case Study –

    International Electronics Manufacturing Initiative (iNEMI)

    Experimental Dust Applied

    During repetitive connector mating and de-mating cycles, dust particles can accumulate and redistribute at the connector end face.

    Electrostatic charge force was one of the mechanisms responsible for the particle accumulation, redistribution and their movement in the core area.


    Contamination

    Case Study – iNEMI

    5th Mating, 200x

    Particles had a tendency to migrate specifically towords the core over the course of multiple matings

    The core is EXTREMELY sensitive to contamination. The accumulation of dust particles seriously impaired fiber performance

    A dust particle 5um wide in the core of a SM fiber assembly can effect more than one half of the signal


    Contamination

    Best Practices – Per IPC-8497-1

    • Always inspect and clean fiber connectors before insertion

    • Clean with dry wipes and cleaning fluid

      • Absorbent wipes of woven or entangled nature

      • Use IPA or other solvent to clean end face

      • Always clean with dry wipe again after solvent use

    • Clean connectors again when re-inserting in another port

    • Careful – some contamination can lead to scratches during cleaning

    • See IPC-8497-1 for cleaning methodology

    Solutions

    • Reduction in ESD Generation during cleaning

    • Smoother end face is more resistant to contamination gathering


    Multiple Insertions

    • Multiple insertions can impact cable performance by:

    • Creating scratches

    • Increasing contamination

    • Migrating contamination towards core of fiber

    • Damaging epoxy ring

    • All connectorized fiber assemblies have a limited number of matings that they can withstand and still perform adequately


    Multiple Insertions

    Case Study - iNEMI

    Based on iNEMI research in 60 % of all examined LC connectors, a series of five repeated matings/demating operations resulted in an increase of IL of 0.5 to 1.1 dB due to particle movement from the ferrule and cladding areas towards the core


    Multiple Insertions

    Prevention

    Exercise Cleanliness Best practices between matings

    Verify both connectors are free of contaminants

    Solutions

    Develop connectors that are resistant to the effects of multiple matings

    Note that connectorized assemblies have a mating limit – replace cables that have exceeded their life cycle


    Inspection Best Practices

    Inspection Criteria - Revisited

    Zone Descriptions

    Zone 3

    Ferrule

    Zone 1B

    Cladding

    Zone 1C

    Epoxy Ring

    Zone 1A

    Core

    Zone 3

    Ferrule

    Zone 2

    Contact Area


    Inspection Best Practices

    Keys to Successful Inspection

    Use Proper Inspection Equipment

    Bench Top Scope

    Handheld Scope, Port Probe

    Scratches can be identified @ 200x or 400x magnification

    Scratches and contamination on the core or cladding is unacceptable

    If scratches, re-polish the connector

    Contamination should be cleaned, then connector re-inspected


    Cleaning Best Practices

    Keys to Successful Cleaning

    Use Proper Cleaning Equipment and Technique

    Dry Wipe on soft surface – Hard surfaces may damage ferrule

    Cleaning Cassettes

    IPA or other non-water based cleaning solvent

    Always use dry wipe after solvent use

    Contamination on the core or cladding is unacceptable

    Contamination should be cleaned, then connector re-inspected

    If contamination contains oils or residues, a solvent must be used


    Cleaning Best Practices

    From IPC-8497-1

    Comparison of Cleaning Fluid Properties


    Installation Guidelines

    Fiber Mechanical Limits

    • Maximum Cable lengths

    • Minimum Bend Radius

    • Pull Tension Restriction


    Installation Guidelines

    • Never Pull by the Connector

    • Use Pulling Eye or Grip for Trunks

    • Monitor Pulling Tension

    • Use “Straight Pull”

    • Do not twist cable


    Proposed Alternative

    Tempered Mating Surface

    Accomplished by heat treating mating surface similar to a tempered windshield

    Hardness of Mating Surface increases

    Smoothness of mating surface increases


    Tempered Mating Surface

    Features

    Scratch Resistant

    Promotes minimum insertion loss and return loss

    Heat anneals mating surface to prevent contaminant leaching

    Heat “heals” any imperfections near the end of the glass

    Smooth surface reduces ESD build up (less friction)

    Smooth surface reduces build up of contaminants

    Extended life span

    Easy Cleaning

    Durable enough to handle multiple matings

    Compatible with all existing connectors


    Tempered Mating Surface

    Benefits

    Easy to install

    Repeatable Network Performance and Reliability

    Reduced Network Downtime

    Increased Customer Satisfaction

    Saves Time and Money



    Tempered Mating Surface

    Number of Matings VS Insertion Loss


    Conclusions

    • Scratches and Contamination on Fiber Optic cables drastically reduce performance

    • By following industry best practices, we can prevent some scratches and make better efforts to keep connectors clean from contamination

    • Following these practices does not guarantee clean connectors and a scratch free surface

    • Tempering (heat treated) technology exists that creates a scratch resistant mating surface and extends the life cycle of the product


    References
    References

    (1) “Accumulation of Particles near the Core during repetetive Fiber Conenctor Matings and De-matings.” NFOEC 2007 Presentation. Berdinskikh, Tatiana, March 29, 2007

    (2) “Cleaning Methods and Contamination Assessment for Optical Assembly.” OFC 2006 Presentation. Berdinskikh, Tatiana, March 6, 2006

    (3) “Degradation of Optical Performance of Fiber Optic Connectors in a Manufacturing Environment.” iNEMI Presentation. Berdinskikh, Tatiana

    (4) “The Investigation of ESD effects on Mated Fiber Optic Connectors.” iNEMI Presentation. Culbert, John

    (5) IPC-8497-1 Cleaning Methods and Contamination Assessment for Optical Assembly


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