photonics systems - introduction

Photonics Systems -Introduction

Sergiusz Patela, Dr Sc

Room I/48, Th. 13:00-16:20, Fri. 9:20-10:50

[email protected]

eportal.pwr.wroc.pl

www.patela.netCopying and processing permitted for non-commercial purposes, on condition that proper reference to the source is given.

© Sergiusz Patela, 2001-6

© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 2/23

Fiber-optic-transmission milestones

1854 - Demonstration of optical waveguide principle in water jets (J. Tyndal)

1960 - Laser (ruby, T. Maiman)

1972 - 4 dB/km multimode fiber

1982 - Single mode fiber reported

1991 - SONET telecommunications standards created

1995 - DWDM deployment began

1998 - > 1 Tb/s in one fiber

2000 - L-band system introduced (1570-1610nm)40 Gb/s transmission in one channel.


Fiber optic link

Light source(transmitter)

Light detector(receiver)

Electrical output signal

Lightguide with splices connectors and couplers

Electrical input signal

„noise”


Light wave

Light wave: electromagnetic wave (signal carrier) characterized by intensity, phase (coherence level), wavelength (frequency), polarization and propagation direction.

Physical phenomena and effects that explain how waveguide works:

• Light wave frequencyLight = electromagnetic wave of frequency 3x1014Hz, (almost million GHz).

• Total internal reflection effect and extremely low glass attenuation Fibers can guide light at long distances without regeneration

• Wave nature of light and fiber modesMany waveguide parameters and construction details can be explained only if one takes into account that light is a wave guided by a structure of very low cross-section.


Construction of optical fiber

Core Cladding Cover


Total internal reflection at the border core-cladding

Fiber diameter: 10 to 50 µmat 1 m distance creates 10 000 reflections.

For the reflection coefficient of 99% after 1 m the signal will be attenuated by 0.9910 000 = 10-44

n1

n2

Total internal reflection


Waveguides’ classification

1. Mode structure (SM, MM)

2. Material (silica, plastic, …)

3. Geometry: planar and fiber waveguides

4. Refractive index distribution (step, gradient index)


Optical fibers

Multimode step index fiberCladding

Core

Multimode graded index fiberCladding

Core

Single mode (step index)Cladding

Core


Lightwave spectrumWavelength (µm)

106

4×104

6×103

1.5×103

770

622

587

577

492

455

390

300

250

200

10

Wavelength (nm)

Radio waves

Microwaves

Infrared

Ultraviolet

X-rays

Gamma rays

Cosmic rays

Far

Middle

Near

RedOrangeYellowGreen

Blue

Violet

Near

Far

UV

Visible

IR

1014

1013

1012

1011

1010

109

108

107

106

105

104

103

102

10110-1

10-2

10-3

10-4

10-5

10-6

10-7

10-8

10-9

10-10

10-11

10-12

10-13

10-14

Fiber optics windows

1: 15502: 13003: 850

L : 1570-1620C : 1525-1560 S : 1450-1510

Fiber optics telecomm bands

Note: 1625 - 1650 band is used to continuously monitor the integrity of the fiber without interfering with the signals at 1550 or 1310

1625 - 1650


0.6 0.8 1.0 1.2 1.4 1.6 1.8

0.30.5

1

0.1

35

10

3050

wavelength[µm]

Atte

nuat

ion

[dB/km]

Spectral attenuation of silica glass fiber

Attenuation of optical fibers

I win

dow

II w

indo

w

III tr

ansm

issi

on w

indo

w


10 advantages of optical fibers

1. High information capacity of a single fiber2. Low loss = repeaterless transmission at long distances3. Total immunity for EMI (electro magnetic interference)4. Low weight5. Small dimensions (diameter)6. High work safety (low risk of fire, explosion, ignition)7. Transmission safety (data taping almost impossible). 8. Relatively low cost (getting lower).9. High reliability10 Simplicity of installation.


Optical fiber networks -technology enablers and stimuli

1. Gigabit Ethernet,

2. vertical-cavity surface-emitting lasers (VCSELs),

3. 100Base-SX,

4. small-form-factor (SFF) connectors,

5. quick-cure adhesives,

6. mechanical connectors,

7. centralized cabling,

8. reduced cost of ferrules,

9. reduced cable costs,

10. preterminated cablesEric R. Pearson, Lightwave Magazine, Ten Reasons Fiber is Becoming More Cost-Effective in the Horizontal


Installations cost, comparison

C a te g o r y 5 U T P F ib e r

S o c k e t $ 5 .3 5 $ 5 .7 0

P a tc h p a n e l $ 5 .0 6 $ 5 .1 9

C o n n e c to r s N o t n e e d e d $ 1 8 .2 4

C a b e l ( 5 0 m ) $ 4 1 .5 8 $ 4 3 .5 6

I n s ta l l a t io n c o s t $ 7 1 .2 5 $ 6 6 .7 5

T o ta l $ 1 2 3 .2 4 $ 1 3 9 .4 4

Comparison of 50 m fiber waveguide and copper links (Cat. 5 UTP).


Light sources - definitions

Light Emitting Diode (LED)

A semiconductor junction device that emits incoherent optical radiation when biased in the forward direction

Laser

Acronym for Light Amplification by Stimulated Emission of Radiation.

A device that produces a coherent beam of optical radiation by stimulating electronic, ionic, or molecular transitions to higher energy levels so that when they return to lower energy levels they emit energy

Laser Diode (LD, Synonyms - injection laser diode, semiconductor laser ) A laser that uses a forward biased semiconductor junction as the active medium


Light sources - types

Light Emitting Diode (LED)

Surface Light Emitting Diode (SLED)

Edge Light Emitting Diode (ELED)

Resonance Cavity Enhanced (RCE) LED

Laser

FP (Fabry-Perot)

DFB (Distributed Feed-Back)

DBR (Distributed Bragg Reflectors)

VCSEL (Vertical Cavity Surface Emitting Lasers)


Light sources - LED parameters

LED parameters

8 - 9/1251550InGaAsPELED3506020 - 9/1251300InGaAsPELED

50nm

spectral width (FWHM)

5095 - 62.5/12560 - 50/1252.5 - 9/125

860AlGaAsSLEDMHzµWnm

bandwidth 3 dB

fiber coupled power - fiber type

wave-length

materialtype

Both LED’s and LD’s emitting wavelengths are set by material selection: AlGaAs: 780-860 nm, InGaAsP: 1300, 1550 nm.


Light sources - LD parameters

mWmWnm

9/125151550DFB

62.5/125251310FP1550

1310

wave-length

9/12515FP

9/12515FP

fiber typefiber coup-led power

laser power

LD type

Fiber optics LD are available in pigtailed versions and with standard fiber optic receptacles


Detectors - definition

Definition

A device that is responsive to the presence or absence of a stimulus

In an optical communications receiver is a device that converts the received optical signal to another form.

Note: Currently, this is conversion is from optical to electrical power, however optical-to-optical techniques are under development

DetectorStimulus Output


Detector - construction

For fiber optic applications detectors are available in standardized packages,

• pigtailed or

• combined with standard receptacles

ST SC FC


Detectors - parameters

3500.651300 (800-1500)Ge10.45850 (400-1100)Si

0.10.751300 (1000-1700)InGaAsnAA/Wnmmaterial

dark currentresponsivitywavelength (high respons. range)

Detector type

detectors are available as pin or APD structures


Splices and connectorsStandard and SFF connectors (~ 1dB)

Fiber splicing (~0.1dB)

Fusion splicing

Mechanical splice

electric arc

index matching gel

alignment sleeve

fiber fiber

fiber fiber


Literature

G. P. Agrawal, Fiber-optic communications systems, John Willey & Sons 1992


Summary

Creating fiber optic networks is an adventure not comparable to any

other technical task today . Designer have to select everything -

hardware type, „standards“, topology and protocols.

On the other hand, properly designed and build networks can be in

use even after 20 years - they can be used and evaluated by our

children.

photonics systems - introduction

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