1%White Paper

APRIL 2013

GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Revision 2
GR-326:
STRENGTHENING
THE WEAKEST LINKIN MODERN DAYULTRAFAST OPTICALNETWORKSAUTHORS:
Sean Grenon
Zach Forman
Joe Wong
Ky Ly
Tom Mamiya
Bernard Lee

2

GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

America
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3GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

GR-326:
STRENGTHENING
THE WEAKEST LINKIN MODERN DAYULTRAFAST OPTICALNETWORKS

Contents

4

Executive Summary

5

Introduction to GR-326: How it all began?

6

How is a jumper assembly made?
-Preparation of fiber cable,Termination,-Polishing7

Why is GR-326 CORE important and what
does the testing involve?
-Service Life Test
-Extended Service Life Test

11 Connector Defects: Case Studies
12 Summary
13 References
13 Biography

4GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Executive Summary
In 2012, leading market and technology analysts announced theirfinding which concluded that in 2016, the worldwide consumption
volume of connectors and mechanical splices will increase by a factorof 2, reaching over 1.57billion units as compared to the number of
703 million in 2011. The American region led in global market sharewith 54% in 2011. American consumption is forecast to expand to at
an average annual growth rate of 10.8% during the forecast period.
The Asia Pacific (APAC) region is forecasted to show the fastest
growth with an average annual growth rate of 25 percent (20112016). EMEA (Europe, Middle East and Africa) fiber optic connector
volume consumption, with 19.5 percent relative market share, trailed
the second-place APAC (Asia Pacific) region in 2011. The forecasted
trend is shown in Figure 1.

Figure 1

As demand for optical connectors increases globally, so does
the supply. When one visits trade shows, one will find numerous
suppliers offering from basic components to finished cable assembly
products. One key fact that end users have discovered in recent
years is ‘not all connectors are equal’. The quality, reliability, andperformance of optical components and cable assembly products
such as patch cords are assured by selecting the best components
and by terminating and polishing with the best equipment andprocedures. These components and procedures must assure that thejumper assemblies meet or exceed the requirements of all pertinentindustry specifications such as the internationally recognized GR-326
standards. This paper describes the relevance of the criteria in theapplicable industry specifications, as well as the importance of thephysical parameters and how they relate to the performance of thejumper assembly.

Source: Ligthwave Magazine, July 2012

Increase in Global Demand for Fiber Optic Connectors

Millions$

Growing

1600

17%
annually

1400
1200
1000
800
600
400
200
0

2011

2012

2013

2014

2015

2016

Growing annually

Americas

380

421

468

519

576

640

Apac

186

233

291

364

455

569

Emea

137

93

125

169

231

365

26% Americas
25% APAC
11% EMEA

5

GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Introduction to GR-326: How it all
began?
GR-326-CORE (Generic Requirements for Singlemode Optical
Connectors and Jumper assemblies) was initially created by Bellcore
and continues to evolve as one of the more popular standards inthe telecommunications industry. Bell Communications Research,
Inc. or Bellcore was established in the early 1980’s by the Regional
Bell Operating Companies (RBOC’S) upon their separation from
AT&T. Bellcore served as the research and development, training
and standard setting arm for the RBOC’s. Following a divestitureof the company in 1996, Bellcore was officially renamed Telcordia
Technologies in 1999. In 2012 Telcordia was acquired by Ericsson.
GR-326-CORE was written as part of Telcordia’s General Requirement
series to be consistent with the Telecommunications Act of 1996
and it is intended to be the industrial specifications for long
haul high-speed applications such as telecommunications andcable TV. There has been a total of four issues of GR-326, initial
release, Issue 2 December 1996, Issue 3 September 1999 andthe current Issue 4 February 2010. The Telcordia views in any
particular release are developed from the expressed needs of

the Telcordia Technical Forum (TTF), the TTF is made up from thecompanies who participated in the development of each new issue.
As networks evolve and new products are offered the standards
are typically reviewed to see if there are changes that need to bemade or criteria added. A good example of this was the additionof four wavelength testing (1310nm, 1490nm, 1550nm, 1625nm)
in GR-326 issue 4, this was added because of the heavy use ofconnectors and cable assemblies in FTTH networks. Field data is alsoa very important part of the process when determining the needfor reissues of the standard. As some of the current networks havebeen in service for many years, review of FIT (failure in time) rates
along with post mortem investigations provide invaluable data
about the components long term reliability. When the standards
are developed, there are many other industry standards that arereferenced. Standards from IEC, TIA/EIA, ASTM, ISO, ITU, UL as well asother Telcordia General Requirement standards are referenced fortest procedures, test criteria, intermatebility criteria etc. When thesestandards are updated, they need to be reviewed to determine if a GR326 reissue is needed to bring them in line. The purpose for GR-326 is
to determine a connector or connector assembly’s ability to perform
in various operating conditions, and to determine long term reliability.
The standard is broken down into 4 main categories (Table 1)

Table 1: List of Main Test Categories

General Requirements

These General requirements cover documentation, packaging, design features, intermateability, product markingsand safety

Service Life Testing

A sequence of environmental and mechanical tests thatsimulate possible conditions the connectors or connector
assemblies may be under while in service

Extended Service Life
Testing

Various tests intended to determine long term reliabilityof the connector or connector assemblies. Usuava simulated 25 year lifetime.

Reliability Assurance
Program

The program focuses on requirements for the manufacturing process that relate to long term reliability and performance of the finish product. Also includes additional testing to ensure the stability of the manufacturing process

6GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Preparationof fibre cable

Terminationof fibre cable

Polishingof connector endface

1. Stripping of outer cable jacket

1. Inject epoxy and insert fiber

1. Cleave fiber

2. Trimming of Kevlar fibers to length

2. Crimp Kevlar to back post

2. Remove excess epoxy by hand or machine

3. Stripping of 900um buffer

3. Crimp outer jacket

3. Polish endface

4. Clean bare fiber

4. Cure connector in oven

5. Check fiber for damage
6. Mix two part epoxy
7. Degas Epoxy
Wrong procedures by line operator (e.g.
trimmed kevlar length)

Wrong procedures by line operator (e.g.
curing stage)

Wrong procedures by line operator (e.g.
removal of epoxy)

Poorly maintain or wrong use of tools

Poorly mainteined or wrong use of tools

Poorly maintain or wrong use of tools (e.g.
cleaver)Low quality or inappropriate material (e.g:epoxy)

Low quality or inappropriate material (e.g:epoxy)

Low quality or inappropriate material (e.g:polishing films)

Preparation of fiber cable
1

Strip outer jacket - Using a suitable jacket stripper, theouter jacket is removed without damaging the 900um buffered fiber
inside. The stripper blade must be sharp and the appropriate inner diameter must be used so that it does not damage the 900um bufferedfiber inside. Even though the fiber is protected by a 900um buffer, if
this buffer is pinched or kinked, then there’s a high possibility of damage to the fiber inside.

2

Trimming of Kevlar fibers to length - This may

not seem serious, but long, protruding Kevlar fibers are at best unsightly, but at worst will hinder the correct fitting of the strain relief boot.
The result is insufficient mechanical support when a jumper assemblyof any significant length is left to dangle. Insufficient mechanical support in these circumstances will result in fiber stress and/or breakage.

3
Stripping of 900um buffer - At this stage, damage to the fiber may not be visible to the naked eye or even

Potential
Mistakes

8. Check ferule ID

Figure 2: Connector termination process and their potential mistakes

So what should be taken into consideration when choosing a ‘good’
product? What are the features that one should look for that defines
the quality of any connector or jumper assembly? In order to appreciate the significance of a standard compliant product, one must firstunderstand the process of actually making an optical connector assembly and the potential problems that could occur at each of thestages.

There are three main processes in the termination of a jumper, Preparation, Termination and Polishing (Figure 2) and a total of 15 steps
where negligence at any one of the steps will result in an inferior
jumper assembly. Each process consists of small steps, and each steprequires strict Quality Control of not only the equipment used, butalso how each step is carried out. So let us break these processes down
into their fundamental steps and see the potential quality issues. For
illustration purposes the process described here is the termination ofa connector on to a 3mm jacket cable with Kevlar reinforcement.

Procedures

How is a jumper assembly made?

seem superficial, but will cause performance degradation or in
the worst case scenario cause complete loss of transmission. Nevertheless, through the Extended Humidity Test, any defects to the fiber
during stripping will be detected. The stripper used must be sharp
and its internal diameter (ID) tight enough to remove not only the
900um buffer, but also the acrylate coating around the fiber. However,the ID cannot be so tight as to score or scratch the fiber. Close attention must also be paid to the length of buffer to be removed, especially in the case of tight buffered fiber. When using unheated strippers,
no more than 10mm of buffer should be removed at any one time.
Attempting to remove more will result in over bending, causing micro
and macro bending induced stress on the fiber. Such damage at thisstage will result in poor performance, but in the worst case will cause
fiber breakage during the epoxy curing process later on.

4
Clean bare fiber to ensure acrylate coating has been
removed. When this thin coating of acrylate isn’t completely removed
it is impossible to insert the fiber into the ferrule. Trying to do so willinvariably result in fiber breakage and a wasted connector.

7GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

5

Check for fiber damage - A four direction fiber bend

check should be performed to check for fiber damage or breakage
during the buffer removal process. If the fiber was scored or cracked
it will break. It’s important to check fiber damage at this stage before
insertion into the ferrule to minimize fiber breakage during the curing
process.

6
Mix the two part epoxy - Two-part epoxies suchas Epo-Tek 353ND are commonly used to bind the fiber inside theferrule. Some manufacturers have taken steps to lower their cost by
the use of glue or standard epoxy from hardware stores instead of
the proper epoxy compound which will result in premature failure of
the connectors (usually within months). Hence why one must always
avoid such inferior products. Poorly mixed epoxy will result in poor
adhesion and or lower glass transition operating temperatures and, asa result, the fiber will piston, varying the fiber height in relation to theferrule surface. Excessive fiber protrusion will lead to fiber damage.
7

Degas to ensure epoxy is free of air bubbles -Once mixed, the epoxy will have tiny air bubbles trapped inside it, andremoval of these air bubbles is essential. Air bubbles inside the epoxy
will expand under the temperatures it’s exposed to during curing; thiswill result in stress on the fiber, or in the worst case fiber breakage. In
either case, IL performance will suffer.

8

Check ferrule ID is clear of any obstruction- An obvious but sometimes overlooked step. Anything inside theferrule that obstructs the insertion of a fiber will result in wasted
preparation time as mentioned is the steps above. Although not a
critical step, it will possibly highlight an issue with a vendor’s ferruleor connector and help maintain productivity.

Termination1
Inject epoxy & Insert Fiber - Whether this isperformed manually or automatically, care must be taken to not inject
too much epoxy. Failure to control the amount of epoxy injected
will cause an over flow of epoxy, which can result in blockage of thecuring oven connector receptacles, polishing fixture receptacles and,of course, the seizing of connector mechanics. All of which are time
consuming and expensive to rectify. Care must always be taken to
avoid stubbing the fiber or to attempt to insert the fiber too quickly.
Doing may result in fiber breakage.
2

Crimp Kevlar to back post - Crimping must be

performed with a crimp tool set to the correct torque. The crimp die

must also be of the correct size and shape, usually round or hexagonal,
and must be in good condition. If the die size is too large or worn andthe torque set too low, the resulting crimp will not hold the Kevlar andconnector back post together securely enough to provide sufficienttensile load protection. If however, the die is too small or torque set
too high, it’s possible the back post can be crushed, damaging thefiber inside. Also, the Kevlar must be evenly place around the backpost. If the Kevlar is not placed around evenly, it will significantly
reduce the retention strength.

3
Crimp outer jacket - Same die size and shape concerns
as mention for Kevlar crimping, as well as the same concern regarding
the appropriate torque setting. Over crimping here will cause damage
to the fiber.
4
Cure connector in oven - Care must be taken whenplacing the connector into the curing oven. Stubbing the fiber
protruding from the ferrule may cause the fiber to break. Even if thefiber only partially breaks, it may potentially be cracked further down
the fiber. This essentially renders the termination useless and would
require re-termination with a fresh connector, wasting time andresources.

Polishing1
Cleave fiber - When cleaving, the cleave point should be
as close to the epoxy as possible, and performed with one clean cut.
Excessive force and any pushing action should be avoided to prevent
fiber cracking. Also the blade of the cleaver must be properly maintainand sharp enough. Fibers should be periodically checked under amicroscope to ensure the cleaver blade is working properly.
2

Remove epoxy by hand or by machine - Thisshould be performed at low speed with low pressure to prevent
cracking the fiber.

3
Polish using a suitable machine and procedure - Polishing isn’t just to make the ferrule end face nice and clean.
Polishing is the final and crucial part of jumper assembly termination.
Polishing defines the geometric parameters of the ferrule end face,parameters that affect connectivity and performance. Critical parameters such as apex offset, fiber protrusion, end face radius and end
face quality are created and controlled through polishing.

8GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Cost benefit of using
GR-326 CORE connectors?
Many have asked “what is the cost benefit of using a GR-326CORE
certified connector”. In comparison a GR-326CORE connector may be
double the price of a similar looking non GR-326-Core product. Thus
one must consider the network in totality and not just the cost of one
component itself. Also, one has to move away from the concept of
reducing the initial Capital Expenditure cost (CAPEX) to the conceptof reducing Total Cost of Ownership which takes into account thepotential maintenance costs in the near future. Hence, the authors
have made a model based on standard FTTH networks and cost
analysis provided by the FTTH Council Europe.
Based on a typical 1:32 PON network with 10 connectors from the OLT
to the ONT and assuming the cost per homes connect is US$1,000/
home, the difference in cost per Homes Connect is less than 1% of
the total homes connect cost when using a GR-326CORE certified
versus a non-GR-326CORE connector. 1% of US$1000 equals US$10/
home connect. Nevertheless, from a CAPEX point of view, the use of
the non-GR-326 connectors is still a saving although it is only US$10/
home (approximately the price of a large pizza).

Nonetheless, GR-326CORE does provides an assurance in reliability
unmatched by the other non-compliant connectors. An average costof replacing a faulty connector is approximately US$50/connector. If
a network operator takes into account that within the 20 years the
FTTH network’s lifetime, if a mere 2%, or 1 in 50 connectors fail, it will
already render the use of GR-326CORE connectors to be more costeffective than using a non-compliant product. This saving does notinclude losses in terms of:• Revenue due to down time (e.g. Video on Demand, voice calls, etc)
• Penalty due to service disruption (Service Level Agreement penalty)• Customer confidence
In Figure 3, we have compared a 20-year Total Cost of Ownership
between the uses of GR-326CORE versus non-GR-326CORE connectors.
The analysis clearly shows that although initial CAPEX is less for nonGR326CORE case but in the span of 20 years, the average cost (repairof faulty connectors and loss of revenue) will be 2x the cost of usinga GR-326CORE certified connector. The additional 1% per home passfor using a GR-326CORE certified connector is definitely a worthwhile
assurance by any experienced network operator.

Figure 3

Figure 4

Cost analysis of
GR-326CORE vs non-GR-326CORE connectors

Total Cost of Ownership Comparison between
GR-326CORE vs non-GR-326CORE Connectors
2
1,8
1,6

5%
78%

17%

1,4

15%

16%

1,2
1
0,8
0,6

2%

1%

GR
Certified

non GR
Certified

0,4
0,2
0

Civil+Labour

Connector cost

Active material cost

Repair cost

Passive material cost (excluding connector)

Potential loss of revenue

Connector cost (GR Certified)
Connector cost (non-GR Certified)9GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

What does GR-326
CORE testing involveand what does it
guarantee?
The GR-326-CORE test is one of the mostcomprehensive testing methodologies
which will not only test the product’s
material and manufacturing precision
but also the quality of workmanship. A
full test will take a minimum of 2000hrs
with multiple tests running in parallel. As
mentioned earlier, the GR-326-CORE test
is divided into two main tests (i.e. Service
Life Tests & Extended Service Life Tests).
In the majority of cases, when a sample
is requested, a ‘golden sample’ will be
provided which will most definitely pass
all tests with flying colors. Hence, one
should always ask for a GR-326-CORE
compliance certificate which is issued
to manufacturers whom has passed the
GR-326 compliance test at any accredited 3rd party test laboratory in theworld.

TABLE 2 – Environmental Tests

Thermal Aging

The Thermal Age Test is considered the least extreme of theenvironmental tests in terms of stress applied, and is intended tosimulate and accelerate the processes that may occur during shippingand storage of the product. Connectors are subjected to a temperateof 85 degrees Celsius with uncontrolled humidity for duration of 7days, with measurements taken before and after testing.

Thermal Cycle

During thermal cycling, the temperature fluctuates over an expansive
range, subjecting the product to extreme heat and cold. Thermal
cycling involves changing the ambient temperature of the connector
by 115 degrees Celsius (75° to -40°) over the course of three hours.
Heavy stresses and strains will be applied to each of the materials in the
product. This test will also expose any weaknesses in the termination.
If the design and procedures are not optimal, this can lead fiber cracks
or breakage.

Humidity Aging

Humidity aging is designed to introduce moisture into the connector
and to determine the effect that the moisture has on the samples. This
test is performed at the elevated temperature of 75 degrees Celsius for
7 days, while the connectors are exposed to 95% RH (relative humidity)

Humidity/
Condensation
Cycle

Humidity/Condensation cycling is performed in order to determine
the effect that water has on the connector when a rapid transitionin moisture occurs. This can cause water molecules to freeze or
evaporate within the connector assemblies, potentially exposing“gaps” in the physical contact between connectors within an adapter.
This phenomenon may have previously been masked by the water
acting as an optical intermediary. The purpose is to achieve heavy
condensation, so as to simulate a worse-case condition that may occur
in outside plant applications.

Dry-out Step

The product is exposed to a drying step at 75 degrees Celsius for 24hours before the Post-Condensation Thermal Cycle is performed.
The purpose is to remove any moisture that may remain from thepreviously performed Humidity/Condensation Cycling.

Post Condensation
Thermal Cycle

This is identical to the Thermal Cycle that was previously performed.
The changes that may occur in the connector during Humidity/
Condensation cycling are often revealed once the condensation isremoved (as is the purpose of the ‘Dry-Out’ step), and these changes
can potentially affect the loss and/or reflectance of the connector.

Service Life Test
The function of the Service Life test is tosimulate the stresses a connector may
experience during its lifetime. The test
is divided into two sections namely theEnvironmental Test & Mechanical Tests.
The Environmental Tests are NOT ONLY
performed to ensure the jumper assemblies
will be able to withstand prolonged exposure
to 85°C or temperature fluctuations of up to
125°C but also to accelerate the effects ofaging on jumper assemblies. Details of eachof the test are explained in Table 2.

10GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

There are several mechanical tests (Figure 6)
required to be performed once the aging iscomplete. These include: Flex Testing, Twist
Testing, Proof Testing, Impact Testing, Vibration Testing, Durability, and Transmission with
an Applied Load. Again, details of each of thetest are explained in Table 3.

TABLE 3 – Mechanical Tests

Vibration Test

Flex Test

Figure 6: Sub-standard material causesA) discoloration of components
B) structural defectIn a vibration test, the products being tested are mounted to a“shaker.” By stressing the connectors in this fashion, the test will reveal
whether high frequencies of vibration induce performance change inthe connectors being tested. The test is conducted on three axis fortwo hours per axis at an amplitude of 1.52mm with the frequency
sweeping continuously from 10 and 55 Hz at a rate of 45Hz per minute.

The purpose of performing the flex test is to simulate stresses on theterminated cable and mated connector that could be incurred overthe life of the connector. The boot, in particular, is important in thistest, as it serves as one of the main points of strain relief. Thus, if thematerials in the boot are inadequate, the boot may not function as
intended.
In addition, this will confirm that the fiber will not become uncoupledfrom the connector under such circumstances.

Twist TestAProof Test
Different colors

The twist test puts a rotational strain on the fiber, which tests thestrength by which it is coupled with the connector. In addition, theadequacy of the crimp will also be tested. This, like the flex test, will
help to identify weaknesses in the termination process.

Proof Testing ensures the strength of the latching mechanism of theconnector, as well as the crimp during the termination process. Should
the jumper assembly receive a sudden tug after installation, this test
ensures that the jumper assembly will neither break nor pull out of
the adapter.

TWAL testing will stress the samples by applying different weights at
multiple angles. The series of weights used depends on the media type
(Transmission With Applied of the cordage, as well as the form factor. Small Form Factor connectors
Load)
are subject to a more extensive range of measurements.

TWAL

B

*Note: Live measurements are made while the samples are under stress; this isdone to reflect any degradation in transmission that might have incurred while
the product is stressed in the field.

Impact Test

Durability Test

Impact Testing is performed to verify that the connectors are notdamaged when they are dropped. A cinderblock is mounted to thebottom of the fixture, approximately 1.5m from the horizontal planethat the connector will be dropped from. The connector contacts thecinderblock, and the process is repeated 8 times.

Durability testing is designed to simulate the repeated use of aconnector. This test involves repetitively inserting (200 times) theconnector into an adapter; this is done at different heights (3 ft., 4.5
ft., and 6ft) so as to simulate what a user in the field might encounter
when standing in front of a telecom rack. The test can potentiallyreveal any problems with the design and/or material flaws in theconnector, such as any part of the latching mechanism that may beheavily strained or flawed by frequent use

11GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Extended Service Life Test
The criteria for connector and jumper assembly extended
service life testing are exclusive to GR-326-CORE. The testing
includes exposure to a variety of environments, including
additional Environmental Testing and Exposure Testing. The
additional Environmental Tests include extended versions of the
Thermal Life, Humidity, and Thermal Cycle. These tests, which run
for at least 2000 hours each (83 days), are further studies in the lifeof the connector across a range of service environments. Testing
is non-sequential, so there is no cumulative effect. The Exposure
Tests include Dust, Salt Fog, Airborne Contaminants, Ground
Water Immersion, and Immersion/Corrosion.
During the extended Environmental Testing, many of the
extruded compounds used in jacketing and buffering will shrink
after exposure to elevated temperatures, which can cause micro
bending in the glass fibers and induce excessive loss.

Dust can seriously impair optical performance.
Particles that contaminate endface can block
optical signals and induce loss. Whether or not the
dust particles find an exposed path to a ferrule
endface is largely a matter of probability. Over time, dust particles
will find their way to the optical connection if it is possible. Whilethe dust particles are not difficult to remove, the cleaning process
involves disconnecting the connector, which not only stops thetransmission, but also exposes the endface to additional risk ofcontamination. This test involves intense exposure to a dust of
specified size particles in order to determine if there is a risk ofany particle finding its way to the ferrule endfaces.

Salt Fog (referred to as Salt Spray) is performed
to guarantee the performance of the jumper
assembly in free breathing enclosures near theocean.This test involves exposing the connector toa high concentration of Sodium Chloride (NaCl) over an extended
period. After the test, optical testing is performed, followed by avisual inspection to confirm that there is no evidence of corrosion
on the materials.
The Airborne

Contaminants test isdesigned to guarantee the performance andmaterial stability of connectors in outdoor
applications with high concentrations of pollution.

The test repeatedly exposes mated and unmated connectors tovarious gases and inspects the connector not only optically, but also
performing the same visual examination as in the Salt Fog test. An
assortment of volatile gases is used in a small chamber for 20 days tosimulate prolonged exposure to these elements.
Thematerials

are

also

Immersion/Corrosion

verifiedintest. This

the

test
has no optical requirements, but instead involves a
prolonged submersion in uncontaminated water. This
test, like Dust, Salt Fog, and Airborne Contaminants, involves bothmated and unmated connectors. Mated connectors are checked for
ferrule deformation by measuring the Radius of Curvature before
and after the test, and comparing the values. If the ferrule is notgeometrically stable during this test, it could be an indication of aflaw in the zirconia material used in the ferrule. Unmated connectors
are checked for Fiber Dissolution, which involves checking to see
if the fiber core has not recessed too far into the fiber cladding.
The final exposure test is

Groundwater

Immersion. This test verifies the ability of the
product to withstand underground applications.
The Immersion/Corrosion test is strictly to verify thematerials involved, and uses de-ionized or distilled water. Connectors
deployed in underground environments are much more likely
to be exposed to contaminated mediums if their enclosures fail.
During this test, the connector is exposed to a variety of chemicals
found in sewage treatment and agricultural fertilization, among
other applications, as well as biological mediums. These chemicals
include ammonia, detergent, chlorine, and fuel. Presence of thesechemicals can have a detrimental effect on the materials comprising
the connector and adapter, reducing optical performance.
In summary, the Key Product Features that we look at when
determining short and long term reliability are:1

Materials: Plastics (Flammability rating of V1 or better inaccordance with UL94, Fungus rating of 0 per ASTM G2196), Metals, Metallic Plated Surfaces (Corrosion, Salt Spray),Zirconia Grade (Extended Humidity Aging).

2

Termination Process: Cleanliness, Epoxy Type, Proper
Preparation and Application of Epoxy, Curing Time, Curing
Temperature, Correct Crimp Sizes and Pressure, Cable
Component Strip Lengths, Kevlar Placement, Polishing.

3Intermatebility: Critical Dimensions in accordance withapplicable TIA/EIA FOCIS Standards.

12GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Connector Defects: Case Studies
The adoption of GR-326-CORE standard is an assurance of not only
the performance but also the reliability of the product. Nevertheless,there are manufacturers all over the world whom are still not GR-326
compliant and have been selling their products in the market posing
as similar quality as those who have taken the effort to comply to thestandards. This section of the whitepaper would like to share some of
the case studies where non-compliant products have failed and has
affected the service providers’ network.

Figure 5: Non-compliant to standard dimension could cause
A) Fitting mismatch or even B) Damage during operations

A

B

Wrong dimension

Broken off ferrule

Dimension DefectConnector dimensional non-compliance can result in engagementand disengagement force issues, but just as seriously, they may not fit
into industry standard test equipment. Figure 5A shows an SC APC
connector unable to fit into a Data-Pixel interferometer chuck, due
to an inner housing that is wider than that specified by international
standards. Figure 5B shows a ferrule lodge into the adapter andunable to be removed as the dimension of the adapter was too small.
Eventually, the ferrule broke off from the connector body.

Figure 7: Sub-standard Material unable to withstand environmental test

NON GR-326 Compliant

GR-326 Compliant

Material DefectUse of substandard materials can result in discoloration, distortionand mechanical malfunction when put through environmental
testing. Discoloration as shown in Figure 6A is not of great concern,but distortion and mechanical failure is as seen in Figure 6B. Figure

Figure 8: Improper crimp ring placement during crimping

Crimp ring too low

Crimp ring right position

7 shows the worst case scenario of SC adapters melting during damp
heat testing. Note that in the same photograph, the GR-326 compliant
connectors attached to the adapter were not affected by the testing
and retained its integrity.

Workmanship DefectDue to improper crimp ring placement during crimping, the upper
most FC connector in Figure 8 exhibited cable retention pull force
well below the requirements specified GR-326. More seriously shownin Figure 9A & 9B, where there is a gap between the ferrule and theflange during the termination process. If the gap is too big, thatplace becomes an air pocket which will, during expansion at higher
temperature, exert pressure on the fiber thus causing the fiber tobreak (Figure 9C). A sample of a good connector can be seen in Figure
9D.

Figure 9: Samples of connector terminations quality

not fully inserted to back of
bubble due to poor production
A Buffer
B Air
ferruleprocess

Epoxy used in the
C Insufficient
processconnector that passed
D Acceptable
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GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

Summary
Jumper assembly reliability is guaranteed not only by using quality
components and manufacturing processes and equipment, butalso by adherence to a successful Quality Assurance program.
While jumper assemblies themselves are typically tested 100% for
insertion loss and return loss, there are many other factors that need
to be monitored to ensure the quality of the jumper assembly. Oneof the most important factors is the epoxy. Epoxies typically have alimited shelf life and working life, or “pot life.” Most epoxies used infiber optic terminations are two-part epoxies and, while they cureat elevated temperatures, preliminary cross-linking will begin upon
mixing. Once this has started, the viscosity of the epoxy can begin tochange, making application more difficult over time. Mixing two-partepoxies introduces trapped air, or “bubbles”, which is injected into
the connector. This trapped air introduces inconsistency in the cured
epoxy, leading to a high risk of mechanical failure. The trapped air, or
bubble count, must be minimized.
Many of the tools used in jumper assembly production also has
periodic maintenance and a limited tool life. This includes all
stripping, cleaving and crimping tools. Most stripping tools, whether
they are hand tools or automated machines, can be damaged by thecomponents of the cable, most notably the aramid yarn strength
members. When a cleaving tool wears out and a clean score is notmade, it is almost impossible to detect during manufacturing.
However, the result could be non-uniform fiber breakage during
cleaving, which can result in either breaking or cracking the fiber
below the ferrule endface.
In conclusion, the integrity of the incoming materials andmanufacturing processes, once specified, needs to adhere by all theappropriate guidelines and procedures. The importance of thesematerials not only has a strong influence on product reliability, butalso on product performance. GR-326 CORE is that assurance ofperformance and reliability.

GR
326
COMPLIANT

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GR-326: STRENGTHENING THE WEAKEST LINK IN MODERN DAY ULTRAFAST OPTICAL NETWORKS

References
1.

TIA/EIA-578-B.3, “Commercial Building Telecommunications Cabling Standard”, Telecommunications Industry
Association, April 2000

2.

Telcordia GR-326-CORE, “Generic Requirements for Singlemode Optical Connectors and Jumper Assemblies”, Issue 4,
Telcordia Technologies, February 2010

3.

“Patch Cord Quality, Reliability and Performance - The Impact of Industry Specifications and Physical Parameters on
Patch Cord Performance”, Panduit Corporation White Paper, December 2003

4.

“The Cost of Meeting Europe’s Network Needs”, FTTH Council Europe, July 2012

Biography
Zack Forman joined Resolute Technologies in June of 2012. Since then, he has been performing environmental andmechanical testing in accordance with GR-326, and has assisted in a number of projects since then. Currently, heserves as a fiber optic lab technician under Sean Grenon.

Ky is currently the Senior Staff Engineer at SENKO Shenzhen where he joined since 2007. Prior to joining SENKO, Ky
spent 3 years working as an engineer at Hamamatsu Photonics KK, as part of their Intelligent Vision Systems researchteam. Then, he was responsible for tests/experimentation and camera control software development. Prior to Hamamatsu Photonics Ky worked as an engineer at Panasonic for 7 ½ years in their European mobile phone division basedin the UK. Responsible for programming of automated SMT laser inspection machines and quality data feedback.

Sean Grenon joined Resolute Technologies in November 2008 as the Regional Lab Manager. Resolute Technologies is
an independent test facility with a focus on passive optical components and specializing in GR-326 testing for fiber optic
connectors and cable assemblies. Sean has been involved in many Telcordia Technical Forums (TTF) for various standards and is a member of the Verizon FOC program. Prior to joining Resolute Sean was the Verizon FOC Program andLab Manager for Curtis Strauss from 2007 to 2008. Before joining Curtis Straus, from 2000 to 2007 Sean held various
positions at Fiber Optic Network Solutions. Sean worked in Manufacturing Engineering, Research and Development
before starting the Reliability and FTTH Design Verification programs for FONS.

Tomoyuki (Tom) Mamiya joined SENKO Japan in July 1999, and then joined SENKO Advanced Components in the UnitedStates from Japan to manage all global engineering efforts as an Engineering Manager in February 2000. Tom worked
in various engineering and product development positions before being promoted to Global Vice President of Engineering in 2006. Tom went back to SENKO Japan in 2010 to be responsible for all engineering activities in Japan.
Prior to joining SENKO, Tom had worked for fiber optic component and equipment manufacturing company in Japanfor more than 5 years as R&D engineer. Tom held over 10 patents in fiber optic component field in world-widely, in the
US, Europe, Japan, and Taiwan.
Dr. Bernard Lee joined SENKO Advanced Components (Australia) Pty Ltd in 2011 as the R&D Director. Prior to joining
SENKO, Bernard was working at Telekom Malaysia (TM) R&D from 2003 till 2009. In 2010, Bernard was transferredto Telekom Malaysia’s (TM) Head Office as the Assistant General Manager for the Group Business Strategy where heoversees the company’s business direction on fixed and wireless broadband and applications. Bernard has publishedvarious technical papers, including international journals, conference papers and also white papers on high-speed
communications systems and networks especially on IP based communications and high speed communications
semiconductor devices. Currently, Bernard holds the Vice President position of the Asia Pacific FTTH Council.

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