optical fibre communications · audio and tv broadcasting (1920s –1940s) digital communications...

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“Optical Fibre Communications”

Dr. G.C. Pagiatakis

Associate Professor

([email protected], [email protected])

School of Pedagogical & Technological Education (ASPETE)

Athens, Greece

March 2015

mailto:[email protected]

mailto:[email protected]

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Telecommunications overview


Dept. of Electronics Eng. Educators / G. Pagiatakis

Telecom subject overview

Signals & information

Transmission techniques

Telecom links

Networks & services

Market issues

Audio & TV

Computer networks (data com)

Telephony, ISDN, mobile telephony

Wireless links (satellite)Wireless links (terrestrial)

Fiber-optic links

Multiplexing

Modulation

A/D conversion

Cable links

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Telecommunications overview



Landmarks in the development of telecommunications

Telegraphy (Morse, 1844)

Telephony (Bell, 1876)

Wireless communications (Marconi, 1901)

Audio and TV broadcasting (1920s – 1940s)

Digital communications (1930s, 1960s and beyond)

Computer networks – Internet (1960s)

Fibre-optic communications (Kao & Hockham,1966)

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A fibre-optic link



Analog signal

Digital (PCM)

signal

Optical

amplifier

Optical

transmitter

Optical

receiver

A/D

Regeneration

& D/A

~ original analog signal

source + converter

(e.g. voice+μ-phone

converter

(e.g. loudspeaker)

voice

Fibre-optic link (schematic)

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A fibre-optic link: Transmitters and receivers



Optical Transmitter

Optical Receiver

Optical

ASK signal

photodiode

Decision and

signal

processing

circuit

D/A

Electrical

signal

Optical

ASK signal

Electrical

signal

Laser

or

LED

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Revision: Transmission techniques



g(t): digital (unipolar) signal

s(t): transmitted (ASK) signal

s(t) = (1/U).m(t).c(t)

s(t) = c(t) or = 0

c(t): carrier (not shown)

c(t) = Accos(2πfct)

Amplitude (On-Off) Shift Keying (ASK or OOK)

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63 x Ε1 signals

ADM-1 ADM-1

Main route

(2 optical fibers)

Alternative route

(2 optical fibers)

63 x Ε1 signals

Automatic

switching

Revision: Transmission techniques



Level Signal rate –

exact

(Μb/s)

Signal rate –

approximate

(Mb/s or Gb/s)

STM-1 Είτε 63 σήματα Ε1

Είτε 3 σήματα Ε3

Είτε 1 σήμα Ε4

155,520 155 Mb/s

STM-4 4 x STM-1 622,080 622 Mb/s

STM-16 4 x STM-4 2448,320 2,5 Gb/s

STM-64 4 x STM-16 9953,280 10 Gb/s

STM-256 4 x STM-64 39813,120 40 Gb/s

Synchronous Digital Hierarchy (SDH)

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Optical tranmsitter: A laser source



Optical Transmitters: A typical semiconductor laser (schematic)

[Keiser X., Fernando X]

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Optical transmitter: A LED source



Optical transmitters: A typical semiconductor LED (schematic)


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An optical receiver



Photodiode and optical receiver (schematic)


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Signal transmission through a fibre link



Signal travelling through a fibre link (schematic)


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The optical fibre



Fibre types: Single mode (1 ray) – multimode (more rays)

Single-mode fibres:

Small core (d < 10 μm)

Suitable for long-distance links

(due to low dispersion)

Multimode fibres:

“Large” core (d = 50 or 62.5 μm)

Suitable for short-distance links

(intra- and inter-building)

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The optical fibre



Core (glass)

(d = 9 μm)

cladding (glass)

(d = 120 μm)

Coating (plastic)

Core

(glass or plastic)

(d = 50 or 62,5 μm)

cladding

(glass or plastic)

(d = 120 μm)

Coating (plastic)

core

Fundamental

mode

(HE11)

HE and EH modesTE and TM modes

core

The optical fibre

Single-modemulti-mode

Fundamental

mode (HE11)

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Transmission properties of fibres: Attenuation



αf

(dB/km)

10

1,0

0,1

800 900 1000 1100 1200 1300 1400 1500 1600 λ (nm)

Rayleigh limit

1st

tran

sm

issio

n w

ind

ow

(aro

un

d 8

50 n

m)

3rd

tra

nsm

issio

n w

ind

ow

(aro

un

d 1

550 n

m)

2n

d t

ran

sm

issio

n w

ind

ow

(aro

un

d 1

310 n

m)

IR limit

Transmission properties of fibres: Attenuation coefficient

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Transmission properties of fibres: Chromatic dispersion


Dept. of Electronics Eng. Educators / G. pagiatakis

Dc (ps/nm.km)

1310 nm 1550 nm λo1200 nm

G.652

(standard fibre) G.653

(DS fibre)G.655

(NZ-DS fibre)

Transmission properties of fibres: Chromatic dispersion coefficient

τc = Dc.Δλ.L (Dc in ps/nm.km, Δλ in nm, L in km)

R 0.25/τc (R in b/s)

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Transmission properties of fibres: Chromatic dispersion



Transmission properties of fibres: The effect of dispersion

[G. Keiser, Optical Fibre Communications,

Mc Graw-Hill]

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Fibre-Optics: State of the art



-Digital signals, rates, usually, up to 10 Gbit/s

-2nd or 3rd window (1310 or 1550 nm)

-Single-mode fibres, type G.652 or G.655

(attenuation 0.4dB/km@1310nm - 0.2dB/km@1550nm)

-Use of lasers (rather than LEDs)

-Use of external OOK modulation

-Use of EDFAs for optical amplification

-Use of WDM technology (mainly in the trunk network)

-Fibres in the access networks (FTTH or VDSL solutions)

Long-haul fibre links

-Digital signals (Gbit Ethernet)

-2nd or 3rd window (1310 or 1550 nm)

-Multi-mode fibres (cheaper, easier to handle)

-Use of LEDs (cheaper)

-Use of direct OOK modulation

Short-haul fibre links (intra- or inter-building)

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Fibre cables



Fibre fabrication

1500o

Glass prototype (d~2cm, L~1m)

Wrapping of fibre (fibre length ~ 2km)

[Vassilopoulos, Pagiatakis] Advanced infrastructures and services

(vol 1), OTE 2001 (in greek)]

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Fibre cables



Fibre-optic cables

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Fibre cables



Αποσχιστήριο

νήμα

Στοιχείο Μηχανικής Ενίσχυσης

Οπλισμός (μεταλλικός ή

αραμίδης)

Μανδύας πολυαιθυλενίου

Σωλήνας χαλαρής δομής

Γέλη

Οπτική ίνα

coating

Fibers (12 per tube – specific colour code)

Jell (to fill the gaps)

Tube (contains 12 fibers)

Strengthening

element

Fiber

(inside

tube)

Colour Fiber

(inside

tube)

Colour

1 red 7 grey

2 green 8 turqoise

3 yellow 9 white

4 colourless 10 pink

5 brown 11 orange

6 purple 12 blue

[Vassilopoulos, Pagiatakis] Advanced infrastructures and

services (vol 1), OTE 2001 (in greek)]

Fibre-optic cables (loose-tube)

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Fibre cables



Fibre-optic cables

Terrestrial cables Submarine cables (usually < 12 fibres)



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Cable

deployment

Fibre submarine cables



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Fibre submarine cables



Cable

repair

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Fibre-cable measurements



Optical-Time-Domain Reflectometer (OTDR)

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Fibre-cable measurements



Optical-Time-Domain Reflectometer (OTDR): A typical display

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Fibre interconnection



Fibre connectors (temporar interconnection)



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Fibre connectors (temporar interconnection)



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Fibre splicing (permanent interconnection)

Microscope view of

fibre splicing

Fibre splicer

Splicing tubes



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Fibre cables



Dept. of Electronics Eng. Educators G. Pagiatakis

Fibres are one-to-one

spliced

Fibre organiser

Fibre organisers

Entrance / exit of optical cables

Interconnection set for underground

optical cables

Permanent interconnection of fibres through splicing

[G. Pagiatakis, Fibre-optic Comms, Tziolas 2003 (in greek)]

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Fibre organisers

[Vassilopoulos, Pagiatakis] Advanced

infrastructures and services (vol 1), OTE 2001

(in greek)]

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Fibre Interconnection




Fibre organisers inside

interconnection sets



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Interconnection set for

underground optical cables

cable input/output



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Optical Distribution Frame (ODF)



Πλαίσιο διασύνδεσης

Πλαίσιο διασύνδεσης

Ενεργός Εξοπλισμός

Σύνδεσμοι

Κορδόνι Διασύνδεσης

Καλωδιο-ουρά

Συνένωση

Οργανωτήρας

Ίνα τεματιζόμενου καλωδίου

Ενεργός Εξοπλισμός Σύνδεσμοι

Κορδόνι Διασύνδεσης

Ίνα τερματισμένη σε σύνδεσμο

Ίνα τεματιζόμενου . καλωδίου (σφικτής δομής)

Active

equipment

connectors

Interconnection frame

fiber cable

outer jumper

inner jumper

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Optical Distribution Frame (ODF)



Interconnection frames:

Fibers of the (outer) optical

cables are interconneted to

the inner fibres (jumpers) that

are, in turn, interconnected to

the active equipment

Storage space for

the inner fibers

(jumpers)

Entrance

of the incoming fiber cable:

Fibers are separated and routed

to the interconnection frames

above.

Active equipment

outer jumper

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TV signal

(from a camera)

Event site (e.g. a football stadium)

Optical termination

box

Core

optical cablesOptical

jumpers

Optical Tx

Access

optical cables

Optical distribution frame (ODF)

at the local exchange “A”

Optical termination

box

Receiving site (e.g. the TV station)

Optical distribution frame (ODF)

at the local exchange “B”

TV signal

(to master control)

Optical Rx

Example of a fibre-link (end-to-end)

[G. Pagiatakis, Fibre-optic Comms, Tziolas 2003 (in greek)]

optical fibre communications · audio and tv broadcasting (1920s –1940s) digital communications...

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