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Performance & Intermateability

Comparison between different ferrule technologies

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Optical Interface

There are three main possibilities to have a fiber optic connection: demountable connections (fiber optic connectors), partly demountable connections (i.e. mechanical

splices), fixed connections (i.e. thermal “fusion” splices).

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Optical InterfaceIntrinsic Losses

Differences in the fiber specifications (Not correctable fiber imperfections).

core area mismatch numerical aperture NA refractive index profile (profile parameter AN) (elliptical fiber core) (core eccentricity)

Different core diameter

Different numerical aperture

Different index profile

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Optical InterfaceExtrinsic Losses

Improper interface design or manufacture. End face losses:

reflection surface quality (smoothness) end angle (flatness,

perpendicularity) Losses due to:

lateral offset (coaxiality) angular misalignment longitudinal distance (end gaps)

Lateral offset

Angular misalignment

End distance

End angle

Reflection losses

Surface quality

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Fiber Optic ConnectorsTypical Requirements

There are many critical elements, technical and commercial, to be considered in an demountable fiber optic connection. The most important are :

Insertion Loss (IL) Return Loss (RL) mechanical reliability and long working life thermal stability packing density possibility of field termination sturdy, rugged and handy construction prices

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Fiber Optic ConnectorsPrinciple

High precision ferrules High precision split ceramic sleeve

Does not utilize phosphor bronze or metal to reduce possibility of endface contamination

Ferrule and split sleeve maintain precise tolerances

enabling precise alignment of fiber and ferrule frontfaces

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Fiber Optic Connectors Most important Parameters

The critical factor in a fiber optic junction is alignment. Loss is minimized when the two fibers - and especially the light carrying cores - are perfectly aligned.

Angular misalignment (Tilt Angle) Insertion Loss

The end face geometry strongly affect light transmission. Return Loss

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Fiber Optic Connectors Most important Parameters

Tilt angle distribution of centered plug according to DIAMOND factory specifications

Core eccentricity distribution according to DIAMOND factory specifications (measured values from production)

Tilt angle distribution

0

200

400

600

800

1000

1200

1400

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1

(°)

Qua

ntity

(-)

Eccentricity distribution

0

200

400

600

800

1000

1200

1400

1600

1800

0

0.0

5

0.1

0.1

5

0.2

0.2

5

0.3

0.3

5

0.4

0.4

5

0.5

(m)Q

uant

ity (

-)

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Fiber Optic ConnectorsFerrule technologies

DIAMOND’s Multi-component ferrule with Cu-Ni alloy insert

Active Core Alignment Geometrical parameters

under control.

Monobloc ceramic ferrule

Tuning Geometrical parameters are

process dependent.

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Fiber Optic ConnectorsStandards CECC 86275-802: 1998

Dimension Value UnitAB max. 32 degrees

Theoretical: 30degreesBB 0.0004 mm

With BB 0.4 mm, is the position of the minimum attenuation no more detectable

CB 0.0015 mmDB 0.0005 mm

AB AB

BBDB

CB

Active core aligned 0.5 m)

Tuned connector 0.4 m 1.5m

tuning within 30° area !

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Fiber Optic ConnectorsReference connectors A reference connector has to be characterized by clear, reproducible parameters, aiming to be perfect!

All the core characteristics of a reference connector have to be within the specified tolerances of each standard.

Taking the eccentricity into consideration, theoretically the only clearly reproducible value is 0 mm, being exactly the geometric center of the ferrule and also unequivocally defined. In practice today’s physics allow a value of 0.1 mm.

Concentricity range using active aligned connectors against reference

Concentricity range using tuned connectors against reference

Ferrule outer diameter (class 0) 2.499 -0/+0.0005 mm

Eccentricity of the fiber core centerto the ferrule center 0.0002 mm

Deviation of axis of fiber to axis of ferrule 0.2 degree

Eccentricity of spherically polishedferrule end-face 30 m

Visual examination of fiber end surfacewith 200x magnification No defects in core zone

Attenuation between two reference plugs 0.15 dB

Visual examination Every 50 matings

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Fiber Optic Connectors End-face geometry

POLISHING RADIUS(radius of curvature) 

FIBER HEIGHT(fiber position)

Fiber

Ferrule

10-30 mmradius

Fiber

Ferrule

Top of the ferrule

Top of the fiber

+h

-h

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Fiber Optic Connectors End-face geometry

APEX OFFSETPOLISH ANGLE

Polishingradius

8°(+/- .5°)

Fiber

Ferrule

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Epoxy glue

E-Modules:ZrO2: 22.000 N/mm2

Cu-Ni Alloy 17.000 N/mm2

Silica 6.000 N/mm2

Ferrule with Cu-Ni insert

ZrO2Cu-Ni Alloy Silica

Epoxy glue

ZrO2

Silica

ZrO2 ferrule

E-Modules:ZrO2: 22.000 N/mm2

Silica 6.000 N/mm2

Used materials and their specifications

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Ferrule with Cu-Ni insert ZrO2 ferrule

15

0

m

126m

125m

125 m is the ideal fiber diameter.Within mono-block technology, the inside diameter of the hole must be changed in relation to the diameter of the fiber in order to achieve proper fit.

128m

is calibrated without gluebefore curing

Geometry of the ferrules

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128m

is calibrated without glue

15

0

m

The role of the fiber position into the DIAMOND’s ferrule The pressure at the fiber front face is absorbed by the glue, which is also deformed

(see next figure). The larger the thickness, the higher possibility of deformation. The thickness of the glue surrounding the fiber inside the ferrule still remains pretty

large in relation to the fiber‘s outer dimensions, therefore, the fiber can easily adapt its position with respect to the pressure made by the opposite connector. The optical characteristics of the fiber are also controlled.

The lower E-modulus of silica and the higher adaptability of the fiber position permit larger tolerances for radius of curvature, fiber protrusion and apex offset.

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Geometry of mated the ferrules the contact area will show a diameter of

approx. 200-220 mm and the end-surface will be nearly perpendicular to the fiber axis.

The lower E-modulus of the Cu-Ni insert allows a slightly higher deformation than the ZrO2 ferrule, therefore the radius of curvature at the front face of ferrules with Cu-Ni insert might be larger than the front radius of ZrO2 ferrules.

Regardless of the mentioned material differences, ferrules with Cu-Ni insert and ZrO2 ferrules are intermated worldwide with excellent results.

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Test ResultsIL-Measurements

Reference Diamond / Test monobloc

Insertion loss @ 1550 nm Average 0.1 dB STD 0.06 dB Max 0.28 dB 80 measurements

Reference monobloc / Test Diamond

Insertion loss @ 1550 nm Average 0.08 dB STD 0.03 dB Max 0.18 dB 80 measurements

Max offset: = 0.6 m

Estimated mean offset: = 0.3-0.4 m

Area of reference plug

Area of measured plugsMax offset:

= 1.75 m

Estimated mean offset: = 0.7-0.8 m

Area of measured

plugs

Area of reference plug

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Test ResultsGeometry & Performance

Correlation between geometry & optical parameters

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Samples [-]

Ecc

en

tric

ity

[um

] In

sert

ion

Lo

ss [

dB

]

0

0.1

0.2

0.3

0.4

0.5

0.6

Eccentricity[um]

Tilt Angle [°]

IL @ 1310nm againstcentered Reference [dB]

IL @ 1550nm againstcentered Reference [dB]

The measured Insertion Loss values vary depending on geometry, which confirms that the mentioned parameters have to be rigorously controlled.

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Test ResultsIL comparison

Comparison IL against batch master & IL against reference

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

1 3 5 7 9 11 13 15 17 19 21 23

Sample [-]

IL [

dB

]

Measured IL @ 1550nm [dB]

IL @ 1550nm againstcentered Reference [dB]

Suplierspecs.

The measurement against reference plug according to the worldwide standards is the only repeatable condition which can be assumed as a universally valid requirement.

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Test ResultsConclusion

Attenuation as a function of w [°] & c [um]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

0 0.5 1 1.5 2 2.5 3

Concentricity c [um]

Til

t A

ng

le w

[°]

0.1 dB

0.2 dB

0.3 dB

0.4 dB

0.5 dB

0.6 dB

0.7 dB

0.8 dB 0.9 dB 1 dB

Area of Active Core Aligned 0.1 dB connectors

Area for Active Core Aligned 0.5 dB connectors

Area of Monobloc 0.1 dB connectors

Area of Monobloc 0.5 dB connectors

Measured monobloc sample plugs (various supplier)

There is a correlation between geometrical criteria and performance of fiber optic connectors.

The compatibility between connectors of different ferrule technologies is guarantied only using connectors that entirely fulfill the standard geometrical and surface quality requirements.

LOW TILT ANGLE

LOW ECCENTRICITY

LOW ATTENUATION