〉〉New Products

Bend-Insensitive Single-Mode Optical Fiberfor In-Building Applications
INTRODUCTION
1.1. INTRODUCTION
Fiber-to-the-home (FTTH) is now being deployed aroundthe world. In order to generate revenue, it is essential tocost-effectively connect customers to the network.
Unfortunately, one challenge is that the number of theskilled operator is limited and connecting end users canbe time-consuming. This has spurred considerable innovation in ultra-bend-insensitive single-mode optical fibers.
These fibers are described in the International
Te l e c o m m u n i c a t i o n U n i o n Te l e c o m m u n i c a t i o nStandardization Sector (ITU-T) Recommendation G.657,and FTTH construction can be streamlined by this innovative fiber product.
AllWave FLEX Max Fiber and EZ-Bend Fiber, which are
the optical fiber products of Furukawa Electric Group, arenewly developed products which have superior properties that outperform the most stringent requirements ofthe G.657 recommendation, and can be easily and aesthetically friendly installed in buildings.

MINIMIZATIONOF
OF THETHE ALLOWABLE
ALLOWABLE
2.2. MINIMIZATION
BENDINGRADIUS
RADIUS
BENDING
30 mm is adopted in the communication network for over
30 years as the allowable minimum bending radius of thesingle-mode optical fiber cable. With the rapid development of FTTH, the introduction of optical fiber cable topersonal and home subscribers has been accelerated,but the effort to connect each subscriber by optical fiber
remains a handicap for the following reasons.
・A variety of wiring techniques are adopted and thenumber of connections becomes substantial.
・The number of skilled installation contractor is small.
The wiring system achieved with the ultra bend-insensitive optical fiber, eliminated the problem of tight opticalfiber cable bending in the building wiring, and therefore
subscribers and the access network can be connectedwith a simpler technique.
ITU-T G.657 recommendation standardized several
types of the bend-insensitive optical fibers. They differ inthe minimum design bending radius. The minimum bending radius can be used while satisfying the guaranteed
bending loss performance.
Table 1 shows subcategories of the standardized bendinsensitive single-mode optical fibers and FurukawaElectric Group products, which comply with thoserequirements.
Table 1ITU-T standardized bend-insensitive single-mode fibers
and the compliant Furukawa Group fibers.

Maximum bending loss
at 1550 nm
Designedfor 1 full turn
Furukawa
minimum
ITU-T
at the minimum
Electricbending subcategory bending radiusGroup products
radiusStandard(Furukawa ElectricGroup products)
Conventional single-mode optical fiber
16 mm

G.652.D

N/A（0.5 dB）

AllWave Fiber

Bend-insensitive single-mode fiber
10 mm

G.657.A1

0.75 dB（0.20 dB）

AllWave FLEX
Fiber

7.5 mm

G.657.A2 orG.657.B2

0.5 dB（0.5 dB）

AllWave
FLEX ＋ Fiber

5.0 mm

G.657.B3

0.1 dB（0.10 dB）

AllWave FLEXMax Fiber

2.5 mmExceed
G.657.B3N/A（0.2 dB）

EZ-Bend Fiber

The excellent bending loss performances of theseproducts are obtained by optimizing the wave-guidedesign to control the bending loss performance, thefusion splicing performance and the optical properties.
Figure 1 shows examples of the various designs of singlemode optical fiber products of Furukawa Electric Group.
From the simplest design used for the standard singlemode fiber at the left end, to the construction used in
EZ-Bend Fiber at the right end are listed.
It has been demonstrated that the best bending loss
performance can be obtained by the hole-assisted fibers,
though Furukawa Electric Group actively made efforts inthe development of solid-type bend-insensitive opticalfibers to improve the interconnect properties. As a result,
all of our bend-insensitive optical fibers can be spliced in
low attenuation with the fusion splicing and the connector
splicing which are applied to the standard single-mode
optical fibers. Fusion splicing losses of the combination ofthe various optical fibers shown in Figure 1, using aV-groove system fusion splicer, are less than 0.2 dB.
Therefore, these products can be applied to the network
without deteriorating interconnection performance.

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Bend-Insensitive Single-Mode Optical Fiber for In-Building Applications

The optical fiber is housed in 2 kinds of cables to compare the optical fiber cable products for wiring in buildings and is tested; the test result is shown in Table 2.
Table 2

Step index

DepressedCladTrenchassisted

Cable test results for Verizon TPR 9424 MDU
simulation.
4.8 mm
3.0 mmdiameter cable diameter cable(Fiber minimum (Fiber minimum
bending radius bending radius: 5 mm): 2.5 mm)Resonance
assisted

Figure 1 Wave-guide designs for bend-insensitive single-mode
optical fibers.

Furthermore, the bending loss at 1550 nm of EZ-Bend
Fiber at one full turn wound to a mandrel with 2.5 mm ofradius is less than 0.2 dB. This unique performance has
not been achieved by other solid-type single-mode optical fibers available on the market today.

DEPLOYMENTEXAMPLES
EXAMPLES OF3.3. DEPLOYMENTOF THETHEULTRABEND-INSENSITIVE
BEND-INSENSITIVE OPTICALULTRAOPTICALFIBER
FIBER
Frequently, severe conditions are imposed in optical fiberwirings in buildings. In order to simulate the condition, anexample was developed by Verizon Communications ofthe United States and was used to simulate multi-dwelling
units (MDU). The simulation method is as follows. Usingan optical fiber cable, 30 U-shaped staples fastening and10 right angle bends are applied, and the optical cable isgiven 2-turns on a mandrel with 10 mm of radius. 2 kg ofweight at one right angled part and 14 kg of weight at
another right angled part are loaded. Thus, the wiring in
the building is simulated. The setting situation of the test
is shown in Figure 2. The required specification for thistest is less than 0.4 dB of net attenuation increase at 1550
nm of wavelength.

Competitive fiber sample
Designed minimum bending
radius : 7.5 mm
Compliant with ITU-T G.657.A2

0.6 dBNot tested

AllWave FLEX Max Fiber
Designed minimum bending
radius : 5.0 mm
Compliant with ITU-T G.657.B3
and G.652.D

0.4 dBNot tested

EZ-Bend Fiber
Designed minimum bending
radius : 2.5 mm
Compliant with ITU-T G.657.B3

0.2 dB

0.3 dBThe result shows that the optical fiber bending loss oftwo ultra bend-insensitive optical fibers, AllWave FLEXMax Fiber and EZ-Bend Fiber, have better performancefor this severe test than the ITU-T G.657.A2 compliant
optical fiber.
Based on these early installation evaluation tests, thefurther thin optical cable InvisiLight was commercialized
and its aesthetically friendly installations became possible. This is an optical fiber of 0.9 mm diameter that canbe adhered directly to the wall, and already installed invarious buildings. The installation examples of the opticalcable of 4.8 mm diameter and InvisiLight are shown inFigure 3.

Stapled 4.8 mm

Installed InvisiLight
cable

Actual Installation
Figure 3 Examples of the deployed ultra-bend-insensitive
single-mode optical fiber in the existing buildings.

CONCLUSION
4.4. CONCLUSION

Figure 2 Image of the MDU simulation apparatus for the Verizon
TPR 9424 testing.

The ultra bend-insensitive optical fiber has started to be
widely deployed in FTTH networks. Quick and cost-effective installations in existing buildings are possible with thenew cables such as drop cable having a diameter of 4.8mm and InvisiLight products that are friendly to aestheticity. These innovative optical fibers were realized byAllWave FLEX Max Fiber.
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Bend-Insensitive Single-Mode Optical Fiber for In-Building Applications

For more information please contact:
Engineering Department
Optical Fiber and Cable Products Division
TEL +81-3-3286-3428 FAX +81-3-3286-3190
e-mail: opticalfiber2@furukawa.co.jp

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201452