photonics systems - introduction
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Photonics Systems -Introduction
Sergiusz Patela, Dr Sc
Room I/48, Th. 13:00-16:20, Fri. 9:20-10:50
sergiusz.patela@pwr.wroc.pl
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.
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 3/23
Fiber optic link
Light source(transmitter)
Light detector(receiver)
Electrical output signal
Lightguide with splices connectors and couplers
Electrical input signal
„noise”
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 4/23
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.
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 5/23
Construction of optical fiber
Core Cladding Cover
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 6/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 7/23
Waveguides’ classification
1. Mode structure (SM, MM)
2. Material (silica, plastic, …)
3. Geometry: planar and fiber waveguides
4. Refractive index distribution (step, gradient index)
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 8/23
Optical fibers
Multimode step index fiberCladding
Core
Multimode graded index fiberCladding
Core
Single mode (step index)Cladding
Core
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 9/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 10/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 11/23
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.
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 12/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 13/23
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).
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 14/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 15/23
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)
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 16/23
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.
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 17/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 18/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 19/23
Detector - construction
For fiber optic applications detectors are available in standardized packages,
• pigtailed or
• combined with standard receptacles
ST SC FC
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 20/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 21/23
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
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 22/23
Literature
G. P. Agrawal, Fiber-optic communications systems, John Willey & Sons 1992
© Sergiusz Patela, 2001-6 Photonics Systems - Introduction 23/23
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.
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