White Paper

March 2012

T.W.A.L.
TRANSMISSION WITH
APPLIED TENSILE LOAD
Ky Ly - Senior Staff Engineer

America
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T.W.A.L.
TRANSMISSION WITH
APPLIED TENSILE LOAD

Contents

4Introduction

4Problem Statement

4Telcordia GR-326-Core T.W.A.L. why does it matter?

5

What about Pre-angled or other short boots?

5Solution

6

Summary7

Supplemental Comparisons

Problem Statement

Introduction

Fiber optic cables do not take too kindly to being bent andcrammed into tight spaces. In many cases it is not possible
to organize long lengths of cable tidily to prevent excessive
bending and strain. Long lengths of vertical cable used asinterconnects between racks not only bend, but also applies
tensile loading on the cable, causing macro bending, leading
to degradation or loss of signal. This is much more than just aninconvenience, leading to down time, loss of revenue, and evencritical data loss.

In the not so distant past, it was enough to be able toaccess the internet and desktop PCs or laptops, andwatch TV on, well, on your TV. Now we can stream TV,
movies and music to our TVs at our convenience, as
well as to the plethora of mobile devices we at ourdisposal. On-demand services such as Netflix, iPlayerand Lovefilm have sprung up in recent years to provide
us with all the media content we crave for, whenever
we want it.

For use in a confined space, fiber optic cables must utilize a low
macro bending sensitive fiber, supported by a well-designed
strain relief boot must be used. Bend insensitive fibers allow themathematical length of the boot to be shortened, but the bootdesign must be such that it can negate tensile loads on applied
onto or by the cable in such a way to maintain signal integrity.

With Google’s launch of Google TV and the unveiling ofSamsung’s, Sony’s and LG’s net enabled TVs powered by
Google TV at this year’s CES exhibition, not to mention
the emergence of IPTV, Cloud gaming and storage, weare seeing a convergence of all these technologies andservices into a single device in the home.

Random Telcordia GR-326-Core, section 4.4.3.5 T.W.A.L. is a live
Insertion Loss test where varying tensile loads are applied at aseries of angles, and the IL taken during the application of theloads. For example, with the connector held at 135° a 0.25kgf
tensile load is applied, Insertion Loss shall not exceed 0.5dB.

However, for such services and technologies to provide
the better, faster, more responsive on-demand services
that are required, an inevitable emphasis will be placedon not only greater bandwidth, but just as importantly,network stability. To provide this, evermore compact,high density enclosures are used in datacenters andstreet cabinets. This however, is easier said than done.
Using fiber optic cables in confined spaces provide
obstacles, critical to the system integrity of any serveror network architecture.

4

TRANSMISSION WITH APPLIED TENSILE LOAD

Telcordia GR-326-Core T.W.A.L.
why does it matter?

Unlike taking measurements before and after applying the loads
at different angles, this live testing more accurately replicates inservice use to ensure signal, and therefore, service integrity. This
underlines compliance with Telcordia GR-326-Core, section 4.4.3.5
is not an option, it is a must for fiber optic cable assemblies
targeted for use in confined spaces, and for them to do so the useof a well-designed, short strain relief boot is essential.

TWAL test setup

What about Pre-angled or othershort boots?

Fig 1
Load and Angle applied during test

These are of course alternatives boots, however, they cannot be
considered to be alternatives to the Mini Boots. They either are
simply not able to comply with the T.W.A.L. testing or are too longfor use in confined spaces.

0°

Load applied at 135°
0.25kgf
+135°

-135°

Jumper Cable

Load applied at 90°
2kgf

Test Arm

22-28 cm

Connector

Solution
SENKO has designed a Mini Boot series using a different material
than previous series of boots. Various designs and materials weretested during testing and selection processes. The final designs
and material were decided after samples passed T.W.A.L. Jumper
assemblies using Mini Boot and cables utilizing macro bending
insensitive fiber easily passes Telcordia GR-326-Core, section
4.4.3.5. Transmission With Applied Tensile Load (T.W.A.L) criteria.
This combination has enabled SENKO to produce a boot, thatwhen used with SENKO’s current connectors, reduces overall
connector length by up to 30%, ideally suited for use in confined
enclosures.

Guides

Weights

Fig 2
This paper describes the benefits of SENKO’s new Mini Boots in comparison tothat of standard boots in the key area of Telcordia GR-326-Core, section 4.4.3.5
T.W.A.L. compliance.
Load

0°

90°

135°
X

Media Type I (2mm or 3mm jacketed type)0.25 kgf (0.55 lbf)

XX

0.7 kgf (1.54 lbf)

XX

1.5 kgf (3.3 lbf)

XX

2.0 kgf (4.4lbf)

X

X

Media Type II (900µm buffer type)0.25 kgf (0.55 lbf)

XX

0.7 kgf (1.54 lbf)

X

X

0.25 kgf (0.55 lbf)

XX

0.5 kgf (1.1 lbf)

X

X

X

Media Type III (250µm bare fiber)

TRANSMISSION WITH APPLIED TENSILE LOAD5Summary
The SENKO Mini Boot, although much shorter, easily outperforms
the conventional boot at all four wavelengths with all appliedloads, especially with applied loads at 135°, where the attenuationis only a third of that of the conventional boot.
Although the weight of typical 2 meter LC 2mm and 3mm
patchcords are only approximately 10g and 15g respectively, cablemanagement systems will increase the tensile loading and bend
the cable beyond 90°, highlighting the importance of applied load
testing beyond 90°.

The importance of the of Mini Boot’s performance at 1625nm
cannot be overlooked. With the growing use of this wavelength,
having cable assemblies able to pass T.W.A.L. at 1625nm in place
will save countless hours of future down time and upgrade costs.

SENKO 2mm LC Mini Boot
Average IL loss with G657A1 (R10) fiber

Conventional 2mm LC bootAverage IL loss with G652.D fiber
1.01310

1310

0.45

1490

0.9

1490

0.40

1550

0.8

1550

0.35

1625

0.7

1625

0.30
0.25
0.20
0.15
0.10

Insertion Loss Increase (dB)

Insertion Loss Increase (dB)

0.50

For Mini Boot and conventional boot comparison, please
see the two graphs below.

0.05

0.6
0.5
0.4
0.3
0.2
0.1

0.00

0.0.55 lbs
135°.37 lbs
90°.37 lbs 1.54 lbs 1.0 lbs 3.3 lbs 2.2 lbs
135°
90°
90°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs90°

2.9 lbs
90°

With the use of G657A2 (R7.5) fiber, the performancegraph almost flat-lines for all wavelengths, for all applied loads
at 90 and 135, highlighting the performance benefits of acombination of bend insensitive fiber and high quality strain
relief boot. They also clearly illustrate bend insensitive fiber is not
the only determining factor for T.W.A.L. compliance, the strain
relief boot is also crucial. See graph to the right.

.55 lbs90°.55 lbs
135°.37 lbs90°.37 lbs 1.54 lbs 1.0 lbs 3.3 lbs 2.2 lbs
135°
90°
90°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs90°

2.9 lbs
90°

SENKO 2mm LC Mini Boot
Average IL loss with G657A2 (R7.5) fiber
0.50

Insertion Loss Increase (dB)

.55 lbs
90°

1310

0.45

1490

0.40

1550

0.35

1625

0.30
0.25
0.20
0.15
0.10
0.05
0.00.55 lbs
90°

6TRANSMISSION WITH APPLIED TENSILE LOAD.55 lbs
135°.37 lbs
90°.37 lbs 1.54 lbs 1.0 lbs 3.3 lbs 2.2 lbs
135°
90°
90°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs90°

2.9 lbs90°

Supplemental Comparisons

VSSENKO
Mini BootsSENKO 2mm LC Mini Boot
Average IL loss with G657A1 (R10) fiber

Competitor 2mm LC
Average IL loss with G657A1 (R10) fiber

0.50

0.61310

0.45

1490

0.40

1550

0.35

1625

0.30
0.25
0.20
0.15
0.10

1310
1490

0.5

Insertion Loss Increase (dB)

Insertion Loss Increase (dB)Competitor withconventional boots

1550
1625

0.4

0.3

0.2

0.1

0.05
0.0

0.00

.55 lbs
90°.55 lbs
135°.37 lbs
90°.37 lbs 1.54 lbs 1.0 lbs 3.3 lbs 2.2 lbs
135°
90°
90°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs90°

2.9 lbs
90°

SENKO 2mm SC APC
Average IL loss.55 lbs
135°.37 lbs
90°.37 lbs 1.54 lbs 1.0 lbs 3.3 lbs 2.2 lbs
135°
90°
90°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs90°

2.9 lbs
90°

Competitor 2mm SC APC
Average IL loss

0.50

0.6

1310

0.45

1490

0.40

1550

0.35

1625

0.30
0.25
0.20
0.15
0.10

1310
1490

0.5

Insertion Loss Increase (dB)

Insertion Loss Increase (dB)

.55 lbs
90°

1550
1625

0.4

0.3

0.2

0.1

0.05
0.0

0.00

.55 lbs
90°.55 lbs
1.54 lbs
3.3 lbs
135°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs
90°.55 lbs
90°.55 lbs
1.54 lbs
3.3 lbs
135°
90°
90°
Load (lbs) - Angle (degrees)

4.4 lbs
90°

TRANSMISSION WITH APPLIED TENSILE LOAD

78TRANSMISSION WITH APPLIED TENSILE LOAD