Inspection And Cleaning Of Optical Connectors

Contents

1About This Document

2

Introduction

3

General Handling of Fiber for Inspection
3.1Fiber Bend Radius
3.2Insertion of Fiber to Bulkhead Adapter
3.3Dust Caps and Bulkhead Adapters

4

Inspection
4.1Inspection Equipment
4.2Ferrule Inspection
4.3Connector End-Face Inspection
4.4Bulkhead Adapter Inspection

5

Defect Definition and Criteria
5.1Criteria

6

Cleaning Optical Fiber Connectors
6.1Cleaning Fiber Tails
6.2Optical Cleaning Equipment
6.3Cleaning Process

Glossary

Reference List
Copyright

© Ericsson AB 2010. All rights reserved. No part of this document may be reproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due to continued progress in methodology, design and manufacturing. Ericsson shall have no liability for any error or damage of any kind resulting from the use of this document.

Trademark List
Ericsson and the Ericsson logo are trademarks of Telefonaktiebolaget LM Ericsson.
All trademarks and registered trademarks mentioned in a document of this collection are the property of their respective holders.

1   About This Document


 Warning! 
To reduce the risk of bodily injury and damage to equipment, observe all safety precautions, procedures, and details contained in Reference [1] and Reference [2].

2   Introduction

Any attempt at mating optical connectors without first cleaning them can lead to data transport failure. The presence of any dirt or particles on the connector will be transferred to the patch cord and to any connectors that are subsequently brought into contact with it. This can cause irreparable damage to both faces of the inter-connection

Optical connectors are vulnerable every time they are separated or when the dust cap is removed. Connectors should be separated and dust caps removed only when absolutely necessary and if so, they should be cleaned.

3   General Handling of Fiber for Inspection

When handling optical devices it is essential that all Electrostatic Discharge (ESD) precautions are observed at all times.

Unless previously agreed with Process Quality Assurance, the cleaning and inspecting as specified within this document must be carried out immediately prior to any optical connector mating.

3.1   Fiber Bend Radius

When handling any fiber optic cables for inspection, care should be taken not to stress the fiber. In particular a bend radius of less than 30mm should not be broken. This will prevent fractures from being introduced to the fiber due to mishandling.

Figure 1   Inspection Criteria for Fiber Optic Cables

3.2   Insertion of Fiber to Bulkhead Adapter

Care should be taken during insertion to avoid contact with any sharp edges such as the keyway. This is particularly relevant where the keyway has been subjected to multiple insertions such as on captive units.

3.2.1   SC, LC, and Mu

Offer the connector squarely up to the bulkhead adapter as shown in Figure 2. Push all the way in until a positive click is felt.

Figure 2   Insertion of Fiber to Bulkhead Adapter

3.2.2   FC-PC Type Connectors

The connector should be presented to the bulkhead adapter at an acute angle such that the connector face is just inside the bulkhead adapter; see Figure 3. At this point the connector should be rotated until the connector and bulkhead adapter are correctly aligned at which point the insertion can be completed.

Figure 3   FC-PC Type Connectors

3.2.3   HDMT Type Connectors

Prior to insertion ensure that the epoxy window is in the correct attitude; see Figure 4. Carefully align the connector and ensure that the attached ribbon is not kinked or put under stress.

Figure 4   HDMT Type connectors

3.3   Dust Caps and Bulkhead Adapters

Any dust caps or bulkhead adapters that are not in use should be contained within a sealed bag in order to stop any contamination while not in use. It is essential that this is followed in order to minimize cross contamination when a dust cap is fitted to a disconnected optical fiber. Dust caps and bulkhead adapters should not be left in a open-air environment at any time, as this will allow dust or contamination to settle in them over a period of time will cause cross contamination of these components.

Dust caps are to be fitted at all times when optical fibers or bulkhead adapters are disconnected. Immediately after the connector is disconnected, the free ends of the optical fiber and the bulkhead adapter must be protected with appropriate dust caps. The dust caps should be obtained from a sealed bag; not ones that are lying in and around the vicinity of the equipment. This is essential to the overall serviceability of the optical fiber as any dust or contamination ingress can cause upstream problems, such as scratching or pitting even during the cleaning process. It is therefore essential to limit any contamination to a minimum at all times.

Care must be exercised when removing or replacing dust caps to avoid stress being introduced to the optical fiber; see Section 3.1.

4   Inspection


 Warning! 
To inspect optical connectors on a fiber trail, the power should not be restored until the field engineer at the distant end has received instruction from the person carrying out the connector examination. To inspect the optical connectors on equipment, remove the optical unit from the shelf and place it on a convenient work surface.

 Warning! 
The use of laser components in Ericsson equipment has been classified in Reference [1] and Reference [2] according to the way the equipment design control-measures have been implemented to comply with the laser standards.

 Warning! 
The lasers used in this equipment have the potential to cause harm. Do not use the equipment in any way not specified by Ericsson, and do not adjust or tamper with any laser or its control circuitry as this may result in laser emissions in excess of safe limits.

4.1   Inspection Equipment

The two acceptable methods of inspection are optical and charge-coupled device (CCD) camera with monitor fiberscopes.


The following criteria should be met with the both optical and CCD.

4.1.1   Optical

Apparatus for the this method includes:

Figure 5   Optical

4.1.2   CCD Camera With Monitor

Apparatus for this method includes:

Figure 6   CCD Camera

4.2   Ferrule Inspection

All optical fiber connectors must be inspected immediately before a connection or reconnection is made and carefully cleaned. The inspection criteria is supported in the appendices of this document; see Section 5.1.1. Some of the defects shown in the Appendix (Appendix) may not be visible until the connector is cleaned.

The sides as well as the end of the ferrule should be inspected for serious scores or scratches (visible to the naked eye). The side can be cleaned with a specified wipe as per the cleaning equipment list. The ferrule end should then be inspected using a suitable microscope as mentioned in document.

4.3   Connector End-Face Inspection

Inspect the connector end-face using the methods outlined in Section 4.1 this document. Particular attention should be given to the core area of the fiber. If the fiber end is generally smooth and free from cracks, scratches, chips and dirt (see Appendix on Appendix) the ferrule is acceptable. Slight chipping in the ferrule region is permissible, but no obvious cracks or damage, that extends into the fiber area, are permitted.

There will always be some score marks present on the ferrule end-face since most of these connectors are polished epoxy. Some connectors employ a compressed metal alloy which when viewed through a microscope will appear to have small black inclusions. However, obvious deep score marks are usually evidence of damage by foreign bodies. If these marks are pronounced or extend near to or into the fiber then the connector should be rejected to enable the fiber to be reterminated.

4.4   Bulkhead Adapter Inspection

Inspect the bulkhead adapter to ensure that there is no evidence of dust, dirt, grease or metal particles. If any of the above are present then the bulkhead adapter must be cleaned reinspected and if necessary recleaned.

5   Defect Definition and Criteria

Contamination - Defect on the surface face of the ferrule, Cladding or core attributable to dust, grease or moisture. Removable by cleaning method.

Pits - Permanent features caused by polishing or mishandling of fiber. Non removable with cleaning method.

Scratches - Permanent lines caused by polishing or mishandling of fiber. Non removable with cleaning.

5.1   Criteria

5.1.1   Fiber Measurement Table

Figure 7   Fiber Measurement


Table 1    Fiber Measurement Table

Fiber Measurement Table

Description

Multimode

Single Mode FC-PC, SC

Single mode


LC, Mu

Comment

 

Unit of measure Y

&mgr;m

&mgr;m

&mgr;m

 

Core

50 /62.5

9

9

Signal Carrier. Not always visible

Cladding

250

125

125

Maintains the signal within the core.

Epoxy

2

2

2

Thin layer between Cladding & Ferrule

Contact Zone

200

200

200

Area that actually contacts when connectors are mated

Ferrule

2.5mm

2.5mm

1.5mm

 

5.1.2   Fiber Inspection Zones

Figure 8   Fiber Inspection Zones

Table 2    Fiber Inspection Zones Table

Fiber Inspection Zone Table

 

Description

Multimode

Single Mode FC-PC, SC

Single mode


LC, Mu

 
 

Unit of measure Y

&mgr;m

&mgr;m

&mgr;m

A

Core

70

25

25

B

Cladding

240

115

115

C

Epoxy

255

130

130

D

Contact Zone

300

250

250

E

Ferrule

400

400

400


5.1.3   Visual Criteria for Connectors Primary Incoming

Table 3    Visual Criteria for Connectors Primary Incoming Table

Zone

Requirement

Reference

Westover camera zone

Cracks

Scratches (No Length Limits)

Pits

Contamination

   

A

None

Individual None Width ³ 0.7mm


Occurrences < x 1


Discount any under Ø 0.7mm

Individual None ³ Ø 1mm


Occurrences < x 1


Sum < 1mm


Discount any under Ø 0.7mm

Individual None ³ Ø 1mm


Occurrences < x 1


Sum < 1mm


Discount any under Ø 0.7mm

Figure 15

A (0-25mm)

 
 
 

B

None

Individual None Width ³ 1mm


Occurrences < x 2


Discount any under Ø 0.7mm

Individual None ³ Ø 2mm


Occurrences < x 3


Sum < Ø 6mm


Discount any under Ø 0.7mm

Individual None ³ Ø 2mm


Occurrences < x 3


Sum < Ø 6mm


Discount any under Ø 0.7mm

Figure 15

B(15-115mm)

 
 
 

C

None

Individual None Width ³ 2mm


Occurrences < x 6


Epoxy ring width < 2mm


Discount any under Ø 0.7mm

Individual None ³ Ø 2mm


Occurrences < x 6


Sum < Ø 10mm


Epoxy ring width < 2mm


Discount any under Ø 1mm

Individual None ³ Ø 2mm


Occurrences < x 6


Sum < Ø 10mm


Epoxy ring width < 2mm


Discount any under Ø 1mm

Figure 15

C(115-130)

 
 
 
 

D

None

Individual None Width ³ 5mm


Occurrences < x 6


Discount any under Ø 0.7mm

Individual None ³ Ø 5mm


Occurrences < x 6


Sum < Ø 20mm


Discount any under Ø 2mm

Individual None ³ Ø 5mm


Occurrences < x 6


Sum < Ø 20mm


Discount any under Ø 2mm

Figure 15

D(130-250mm)

 
 
 

E

None

Individual None Width ³ Ø 5mm


Occurrences < x 6


Sum width < 20mm


Discount any under Ø 2mm

Individual None ³ Ø 10mm


Occurrences < x 10


Sum < Ø 50mm


Discount any under Ø 2mm

Individual None ³ Ø 10mm


Occurrences < x 10


Sum < Ø 50mm


Discount any under Ø 2mm

 

E(250-400mm)

 
 
 

5.1.4   Visual Criteria for Connectors Secondary Outgoing

Table 4    Visual Criteria for Connectors Secondary Outgoing

Zone

Requirement

Reference

Westover camera zone

Cracks

Scratches (No Length Limits)

Pits

Contamination

   

A

None

Individual None Width ³ 0.7mm


Occurrences < x 1


Discount any under Ø 0.7mm

Individual None ³ Ø 1mm


Occurrences < x 1


Sum < 1mm


Discount any under Ø 0.7mm

Individual None ³ Ø 1mm


Occurrences < x 1


Sum < 1mm


Discount any under Ø 0.7mm

Figure 15

A (0-25mm)

 
 
 

B

None

Individual None Width ³ 1mm


Occurrences < x 2


Discount any under Ø 0.7mm

Individual None ³ Ø 5mm


Occurrences < x 3


Sum < Ø 15mm


Discount any under Ø 0.7mm

Individual None ³ Ø 5mm


Occurrences < x 3


Sum < Ø 15mm


Discount any under Ø 0.7mm

Figure 15

B(15-115mm)

 
 
 

C

None

Individual None Width ³ 4mm


Occurrences < x 6


Epoxy ring width < 2mm


Discount any under Ø 0.7mm

Individual None ³ Ø 5mm


Occurrences < x 6


Sum < Ø 15mm


Epoxy ring width < 2mm


Discount any under Ø 11.8mm

Individual None ³ Ø 5mm


Occurrences < x 6


Sum < Ø 15mm


Epoxy ring width < 2mm


Discount any under Ø 11.8mm

Figure 15

C(115-130)

 
 
 
 

D

None

Individual None Width ³ 5mm


Occurrences < x 6


Discount any under Ø 0.7mm

Individual None ³ Ø 20mm


Occurrences < x 10


Sum < Ø 100mm


Discount any under Ø 2mm

Individual None ³ Ø 20mm


Occurrences < x 10


Sum < Ø 100mm


Discount any under Ø 2mm

Figure 15

D(130-250mm)

 
 
 

E

None

Individual None Width ³ Ø 5mm


Occurrences < x 6


Sum width < 20mm


Discount any under Ø 2mm

Individual None ³ Ø 25mm


Occurrences < x 15


Sum < Ø 100mm


Discount any under Ø 2mm

Individual None ³ Ø 25mm


Occurrences < x 15


Sum < Ø 100mm


Discount any under Ø 2mm

 

E(250-400mm)

 
 
 

5.1.5   Example of Defect Calculation for Above Primary Criteria

The above example fails on three points for section D contamination. (Sum <20&mgr;m or None 5&mgr;m or occurrences <6)

The sum of contamination in D is calculated by adding all the contamination.

For example 1: V+W+X+Y+Z+U=21.5&mgr;m sum contamination. (This should be less than 20&mgr;m)

For example 2: U=6&mgr;m (This should be Not greater or equal to 5&mgr;m)

For example 3: V+W+X+Y+Z+U = 6 Occurrences (This should be <6 Occurrences)

Figure 9   Example of Defect Calculation for Above Primary Criteria

6   Cleaning Optical Fiber Connectors

The following procedure combines the procedures intended for safety, cleaning and examination of optical connectors (pigtails) utilizing an optical microscope.

It is essential, for the correct operation of any optical system, that all of the optical interfaces and bulkhead adapters are clean and free from contamination and damage.

Note:  
It is equally important that all instruments, Optical Microscopes, Power meters, and Optical Time-Domain Reflectometer (OTDR) interfaces that is are maintained and cleaned to reduce the risk of cross contamination occurring from this source.

This procedure shall be applied immediately before pigtails are connected to any equipment (card or optical aid) and on each and every occasion an optical dis-connect is undertaken where this occurs as the result of a fault finding activity.

Disconnection of optical pigtails shall be kept to a minimum. Where necessary, such pigtails shall be protected from mechanical damage and contamination. Where a ‘dust cap’ is employed for such purpose the cap shall itself be clean and suitable for the purpose’ and shall at all times of storage be held in a clean plastic bag to protect from contamination.

Note:  
Pigtails shall not be left in rack bases or in any place that may result in contamination or damage to the ferrule of the pigtail.

6.1   Cleaning Fiber Tails

Note:  
All dust caps should be removed and discarded. They may in themselves be the most common source of contamination to the face of pigtails. If caps are left in the open, contamination may settle inside the cap and may be subsequently transferred to the pigtail when used. Spare dust caps, where held by the engineer for future use, shall be stored in a clean plastic bag at all times.


6.2   Optical Cleaning Equipment

To be used when cleaning connector ferrules of Physical Contact (PC) and Angled Physical Contact (APC) type and connector of Mechanical Transfer (MT) and Multiple-Fibre Push-On/Pull-off (MP-) type before termination.

Table 5    Optical Cleaning Equipment

Description

Part Number

Part Number for Refill

Notes

CLEANING CASSETTE FOR PC AND APC TYPE (Cletop-S)

LTT 179 001 (including 1 cleaning tape/refill)

1/LTT 179 001 (6 pcs/set)

Preferably for connectors with ferrule Ø 2.5mm

Anti-Static CLEANING CASSETTE FOR PC and APC Ø 1.25 and 2.5mm.

LTT 179 001/1 (including 1 cleaning tape/refill)

1/LTT 179 001/1 (6 pcs/set)

And MP and MT TYPE without pins (Optipop)

6.3   Cleaning Process

There are two approved methods of cleaning.

Both the methods listed below must be proceeded with a wipe around the side surfaces of the ferrule, using a lint free cloth. The first and main cleaning method is with the use of a Cletop cleaner. This is a dry method and will clean adequately for the vast majority of applications. If however upon inspection the fiber will not clean to the inspection criteria then the second wet method can be used followed by the Cletop method.


6.3.1   Initial Cletop Cleaning Process

Using a Cletop cartridge cleaner, the end face of the ferrule can be polished which results in uniform results.

Note:  
Care should be exercised when cleaning the angled end faces of the ferrules to follow the connector profiles as shown below.

Do not use the Cletop cartridge for mechanical transfer pull off (MTP) fibers as the end-face locating pins prevent contact of the tape with the fiber ferrules.


Figure 10   Cleaning Process

  1. Hold the cassette in the palm of the hand and depress/rotate the lever with the thumb. This action winds the cleaning cloth tape inside the cassette case and simultaneously opens the shutter as shown in Figure 11.

Figure 11   Cletop Cartridge Cleaning Cassette

Note:  
Each depression of the lever facilitates the exposure of a new cleaning cloth face. Exercise caution not to double click the lever as such an action will waste one of the available cleaning faces and reduce the life of the cassette.

Figure 12   Cartridge Cleaning Cassette

  1. Rotate the lever with the thumb. Ensure that the lever is kept depressed during the cleaning operation; see Figure 12.
  2. Press the optical ferrule end face of the connector to be cleaned against the cleaning cloth and drag the connector in the direction shown in Figure 13 below.

Figure 13   Cartridge Cleaning Cassette (optical ferrule)

Note:  
Ensure that the optical end face is pressed snug against the cleaning tape surface while dragging the connector (cleaning may not be complete if the connector end face is insufficiently pressed).

  1. When the cleaning procedure is complete, release the shutter lever allowing it to return to its initial position.
    Note:  
    When the cleaning cloth is completely used, The user shall return the cassette to the supervisor and request a replacement.

  2. Re-examine the connector using the microscope. (If the connector does not come clean after 3 attempts then carry out a clean with the wet process followed by the Cletop process.
  3. Fit the connector when fiber is clean.

6.3.2   Secondary Wet Cleaning Process

  1. Wipe the end face and surrounding area (The sides of the ferrule) at the front of the connector with an impregnated wipe to remove any greasy contamination.
  2. Fit the connector, using the appropriate adapter, into the hand held microscope.
  3. Examine the ferrule end, check that it is free from dust, grease or particles of grit:
    1. Dust will manifest itself as lumps, flakes and fibers.
    2. Grease, commonly introduced during handling, will appear as a blob or smear
    3. Particular attention must be paid to the core area of the ferrule area. It should be generally smooth and free from cracks. Slight chipping in the cladding area is permissible but not obvious cracks, scratches or other damage across the core area.
  4. As the connector is of epoxy/polish type, score marks will always be present on the surface of the ferrule end face. Obvious deep score marks, particularly where they appear circular in shape, are normally evidence of damage by foreign bodies. If such score marks are pronounced, or extend into the core region, the connector should be rejected and replaced.
  5. To remove any grease, soak a lint free wipe with a small amount of the approved solution (IPA/De-Ionised water). Carefully stroke it across the ferrule end face several times in the same direction before repeating the stroking with a clean and dry wipe. For safe disposal of the wipes, Section 3.2 refers.
  6. Follow with the Cletop procedure for FC-PC, SC, LC Din and Mu connectors.

6.3.3   Cleaning Process for the HDMT TYPE

After ensuring that the guide pins, where present, are below the surface, use a moistened, approved, cleaning tissue to lightly clean the surface to remove any large particles. This cleaning should be performed using a circular motion.

Figure 14   Cleaning for the High Density MT (HDMT) TYPE

6.3.3.1   Cleaning the Connector End Face

Inspect connector, as above. Remove dust from the connector end face by carefully wiping the connector surface using a circular motion. Do this with a Cletop purple stick as per cleaning equipment list moistened with approved solvent from the dispenser, or alternatively dip the tip of the connector (not HDMT Type) into the solvent. Either of the above should then be followed by cleaning using a clean dry Cletop stick using circular motions throughout.

Reinspect the connector and repeat the cleaning if necessary.

If the connector is still dirty after the recleaning then it should be considered unsatisfactory for use.


 Caution! 
Do not shake the aerosol can prior to use.

Blow any dust from the bulkhead adapter using an approved aerosol dust remover.

Reinspect the bulkhead adapter, as above. Any remaining dirt, dust or metallic particles should be removed with a portion of dry tissue rolled to create a cylinder, which should be pulled through the bulkhead adapter. Alternatively use an approved cleaning bud (not cotton).


Appendix

Figure 15   General View of End Face

Figure 16   Examples of pitting

Figure 17   Scratches

Table 6    Scratches Table

Scratch

Reject or OK

Comment

A

OK

Scratch is just outside of Fiber Core Zone. However if there were more than 1 through the fiber cladding this would amount to a fail. Also if this scratch was greater than 1 micron it would also fail.

B

OK

Scratch is through ferrule area and below 5 microns in width and hence is acceptable

C

Reject

Scratch is through core. Any scratch through the core is a failure.

D

Reject

Scratch is through ferrule area but is Above 5 microns in the Contact Zone D. This amounts to a failure.

Figure 18   Diamond Metallic Ferrule Connector

Figure 19   Cords and Pigtails

Reject if:

  1. Cracks which do not start and finish at the cladding edge.
  2. If adhesive forms a crescent on one side of fiber.

Glossary

APC
Angled Physical Contact
 
CCD
Charge-Coupled Device
 
DIN
Deutsches Institut für Normung
 
ESD
Electrostatic Discharge
 
FC/PC
Ferrule Connector/Physical Contact
 
HDMT
High Density MT
 
LC
Lucent Connector
 
LLSR
Local Laser Safety Representative
 
LSO
Laser Safety Officer
 
MP-
Multiple-Fibre Push-On/Pull-off
 
MT
Mechanical Transfer
 
MTP
Mechanical Transfer Pull Off
 
OTDR
Optical Time-Domain Reflectometer
 
PC
Physical Contact
 
SC
Subscriber Connector

Reference List

[1] Safety Guide, 1/124 46-CSA 113 62/5 Uen.
[2] SFP/XFP Optical Safety Rules, 3/124 46-CSA 113 62/5 Uen.
[3] System Safety Information, 124 46-2886 Uen.
[4] Personal Health and Safety Information, 124 46-2885 Uen.