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22 Jan 2010

Update on optical fiber and cable

standards

Daniel Daems

Tyco ElectronicsBelgium


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Slide 2Daniel Daems March 2010

Most relevant standardization bodies

Leading standardization bodies for:

Fibers: ITU-T SG15:

G650 test method series G651 multimode 50/125 m G652 dispersion unshifted singlemode optical fiber G653 dispersion shifted singlemode optical fiber G654 cut-off shifted singlemode optical fiber G655 non-zero dispersion-shifted singlemode optical fiber

G656 non-zero dispersion-shifted singlemode fiber for wideband optical transport G657 bending loss insensitive singlemode optical fiber

Recent changes seen in G657 for low bend loss fibers

FO Cables: IEC SC86A

60793 series for fibers 60794 series for cablesRecent changes seen in patchcord cables IEC 60794-2-50

TELCORDIA GR 20


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Low Optical Bend Loss Fibers

Why needed?

Cable attachments with staples!?

Corners

Staples

According to Verizon the radius around corners and under staples can go down to 5 mm!

Smaller boxes and wall

outlets with fiber bend

radius 20 mm

Sharp bends


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Bending loss performance of standard singlemode fiber (ITU-T G. 652D)


Radius Loss increaseG.652 matched

30 mm < 0.05 dB

25 mm < 0.05 dB20 mm < 0.05 dB15 mm 0.49 dB

10 mm 17.3 dB

1625 nm results

Radius 10 mm

Radius 15 mm

Radii 20 mm

Spectral macrobending loss of SMF 28 fiber for 10 loops

0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

4

1250 1300 1350 1400 1450 1500 1550 1600 1650

Loss(indB)

Wavelength (in nm)

MFD (1310 nm) : 8.9m ...9.5m

R

Observations: Loss becomes important once bending radius becomes smaller than 20 mm Splicing trays with 25 mm and 30 mm bending radius will not affect transmission at 1625 nm

in G. 652D fibers In some limited cases (max 2 meter) a 20 mm radius is allowed (see ITU-T L13 and IEC

61756)


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R

nRefractive index profile:

Characteristics:

General:

Optimized bandwidth for 1310 nm transmission(= Minimum chromatic dispersion at 1310 nm)

Lowest attenuation at 1550 nm

Mode field diameter at 1310 nm: 9.2 m 0.4 m


Cladding diameter: 125 m 0.7 m

Mode field concentricity error: 0.5 m @ 1310 nm

1550 nm loss performance: < 0.05 dB for 100 turns

on 50 mm mandrel diameter

Chromatic dispersion:

3.5 ps/(nm.km) @ 1310 nm 18 ps/(nm.km) @ 1550 nm

Proofstress strain test: 1%Attenuation:


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R

n

Refractive index profile:

Characteristics (not up-to-date!):Mode Field Diameter at 1310 nm: 8.8 m 0.5 m


Cladding diameter: 125 m 1.0 m

Mode field concentricity error: 0.8 m @ 1310 nm

PMD (fiber): 0.5 ps/km at 1310 nm

Chromatic dispersion: 18 ps/(nm.km)at 1550 nm1550 nm loss performance: < 0.1 dB for 100 turns

on 75 mm mandrel diameterProofstress strain test: 1%Attenuation:


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How can you improve the bending loss performance?

Light in a waveguide is better contained when the difference of

refractive index between the core and cladding is increased.

This results in a better bend loss performance, but it will result in a

lower bandwidth or transmission capacity (modal dispersion, higher

chromatic dispersion)



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Radius

Refractive index

Radius

Refractive index

Radius

Refractive index

Radius

Refractive index

Matched claddingsinglemode fiber (standard)

Depressedcladding singlemode fiber

Trench assisted

Ring assistedsinglemode fiber

A lower refractive index can beachieved by fluor doped solid glass orby air-holes in glass

Examples Hole Assisted Fiber (HAF):

Betterbendlos

sperformance

Different low microbend loss fiber types


!

The mechanical reliability remainsthe same for all these 125/250 mfibers since the cladding andcoating has not changed!

Radius

Refractive index

Hole assisted


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ITU has published in Dec 2006 a recommendation for such fibers:

ITU-T G.657A fiber: These are G. 652D fibers with tighter dimensional tolerances

that will result in a better optical performance during bending. These fibers are also

known as Low Macrobend Loss fibers. The specifiedminimum bending radius for

optical attenuation is 10 mm. Roughly 10 times better bending performance than

traditional single-mode fiber

ITU-T G.657B fiber: Fibers designed to have a very low loss during bending, but

they are not always compatible with the G. 652 fibers anymore and thereforerestricted to shorter distances (associated with indoor cabling). These fibers can

have connection and splicing problems for some types. These fibers are typically

called Bend Tolerant Fibers. The specifiedminimum bending radius for optical

attenuation is 7.5 mm. Roughly 100 times better bending performance than

traditional single-mode fiber

ITU-T G. 657 recommendation


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Installation inside houses:

Assume cable is routed though 3 rooms on the 1st floor:

This results in about 15x 90turns around a corner When nails or staples are used every 30 cm, about 70 staples will be used in this example.

Assume that each staple or nail creates a bend with radius 5 mm over 15 In total 2 meter of fiber is stored in the floor distribution box and wall terminal with radius 15 mm

7 m

1 m

5 m

5 m4 m

Total

probability:

2 meter

0,1 meter

0.125 meter

Length fiber

under stress

20 x 360(15 mm)

70 x 15(5 mm)

15 x 90(5mm)

Number of turns

Boxes

Staples

Corners

Item

10-5

3. 10-5

8.10-6

10-5

Probability

failure over 25

years


Mechanical reliability concerns

Important: In this casethe estimated contribution ofbending loss will be 1 dB at1550 nm and 3 dB at 1625 nmfor a G 657 B3 fiber!


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Issues seen with bend insensitive fibers

Some fusion splicing machines do not recognize the

core of the new fibers and will not perform a core

alignment (switch to cladding alignment to solve this)

Hole assisted fiber types give problems during fusion

splicing (unexpected and unpredictable deformations).

Fluids may enter the holes when cleaning the fiber

ends with alcohol

Higher losses seen when different fiber types arespliced or connected together (mode field diameter

mismatch with most G. 657B type fibers). Losses

above 1 dB can be seen!

Insertion Loss = - 10 Log10 [ 4 ( + ) ]Rt

Rt

RR

- 2RR

Rt and RR = Mode Field Radii of connected fibers


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Issues seen with bend insensitive fibers

OTDR traces will show strange effects (gainers or higher losses) when mixing fiber

types in connections or splices! Non-trained installers might make wrong

conclusions about the splice loss or connector loss quality!

OTDR652 652652652 652

Distance

Loss

Distance

Loss

OTDR

652 657652657 652

Loss seems high

Loss seems high


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IEC fiber standards

IEC SC86A Working group 1 (fibers)

Mainly copy of ITU-T G6xx fiber documents for the singlemode fibers, but IEC

86A is the leader for the multimode fiber specifications.

Fiber standards Title60793-1-1 Optical fibres - Part 1-1: Measurement methods and test procedures - General and guidance

60793-2-10Optical fibres - Part 2-10: Product specifications - Sectional specification for category A1 multimodefibres

60793-2-20Optical fibres - Part 2-20: Product specifications - Sectional specification for category A2 multimodefibres

60793-2-30Optical fibres - Part 2-30: Product specifications - Sectional specification for category A3 multimode

fibres60793-2-40

Optical fibres - Part 2-40: Product specifications - Sectional specification for category A4 multimodefibres

60793-2-50 Optical fibres - Part 2-50: Product specifications - Sectional specification for class B single-mode fibres

60793-2-60Optical fibres - Part 2-60: Product specifications - Sectional specification for category C single-modeintraconnection fibres


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Cable standards Title

60794-1-1 Optical fibre cables - Part 1-1: Generic specification - General60794-1-2 Optical fibre cables - Part 1-2: Generic specification - Basic optical cable test procedures60794-2 Optical fibre cables - Part 2: Indoor cables - Sectional specification

60794-2-10 Optical fibre cables - Part 2-10: Indoor cables - Family specification for simplex and duplex cables60794-2-11

Optical fibre cables - Part 2-11: Indoor cables - Detailed specification for simplex and duplex cablesfor use in premises cabling

60794-2-20Optical fibre cables - Part 2-20: Indoor cables - Family specification for multi-fibre optical distributioncables

60794-2-21Optical fibre cables - Part 2-21: Indoor cables - Detailed specification for multi-fibre opticaldistribution cables for use in premises cabling

60794-2-30 Optical fibre cables - Part 2-30: Indoor cables - Family specification for ribbon cables

60794-2-31 Optical fibre cables - Part 2-31: Indoor cables - Detailed specification for optical fibre ribbon cablesfor use in premises cabling

60794-2-40 Optical fibre cables - Part 2-40: Indoor optical fibre cables - Family specification for A4 fibre cables

60794-2-50Optical fibre cables - Part 2-50: Indoor cables - Family specification for simplex and duplex cablesfor use in terminated cable assemblies

IEC SC86A Working group 3

Leading group for cable "family specifications". In fact a set of test is

standardized, but the severities can be freely chosen between the

manufacturer or customer in the detail specifications. As a result, there are noreal worldwide "cable standards" existing for pigtail cables or other cables!

IEC cable standards


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Conclusions

ITU-T G.657 A1 and A2 fibers are gaining market share in the distribution

part of the network (till the wall outlet). For indoor cabling the G 657 B types

might be considered as well. Watch out! Cable manufacturers can misuse the advantages of bend

improved fibers for making lower quality cables! Specifications should be

carefully updated to avoid more cable end interface issues.

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