Download Photonics Systems - Introduction Sergiusz Patela, Dr Sc

Photonics Systems Introduction
Sergiusz Patela, Dr Sc
Room I/48, Th. 13:00-16:20, Fri. 9:20-10:50
[email protected]
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Copying and processing permitted for noncommercial purposes, on condition that
proper reference to the source is given.
© Sergiusz Patela, 2001-6
www.patela.net
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.
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Photonics Systems - Introduction
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Fiber optic link
Light source
(transmitter)
„noise”
Light detector
(receiver)
Electrical output signal
Electrical input signal
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Lightguide with splices
connectors and couplers
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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 frequency
Light = 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 modes
Many 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.
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Construction of optical fiber
Core
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Cladding
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Cover
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Total internal reflection
n2
n1
Total internal reflection at the
border core-cladding
Fiber diameter: 10 to 50 µm
at 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
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Waveguides’ classification
1. Mode structure (SM, MM)
2. Material (silica, plastic, …)
3. Geometry: planar and fiber waveguides
4. Refractive index distribution (step, gradient index)
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Optical fibers
Multimode step index fiber
Cladding
Core
Multimode graded index fiber
Cladding
Core
Single mode (step index)
Cladding
Core
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Lightwave spectrum
Wavelength (µm)
Wavelength (nm)
1625 - 1650
106
L : 1570-1620
C : 1525-1560
S : 1450-1510
4×104
Far
6×103
Middle
1: 1550
2: 1300
3: 850
1.5×103
770
622
Fiber optics
telecomm bands
587
Fiber optics
windows
577
492
455
390
Note: 1625 - 1650 band
is used to continuously
monitor the integrity of
the fiber without
interfering with the
signals at 1550 or 1310
© Sergiusz Patela, 2001-6
Near
IR
Red
Orange
Yellow
Green
200
Microwaves
Infrared
Visible
Ultraviolet
Blue
X-rays
Violet
UV
300
250
Radio waves
Gamma rays
Near
Far
10
Photonics Systems - Introduction
Cosmic rays
1014
1013
1012
1011
1010
109
108
107
106
105
104
103
102
10
1
10-1
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
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Attenuation of optical fibers
III transmission window
[dB/km]
50
I window
10
Attenuation
II window
30
5
3
1
0.5
0.3
0.1
0.6
0.8
1.0
1.2
1.4
1.6
1.8
[µm]
wavelength
Spectral attenuation of silica glass fiber
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10 advantages of optical fibers
1. High information capacity of a single fiber
2. Low loss = repeaterless transmission at long distances
3. Total immunity for EMI (electro magnetic interference)
4. Low weight
5. 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 reliability
10 Simplicity of installation.
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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 cables
Eric R. Pearson, Lightwave Magazine, Ten Reasons
Fiber is Becoming More Cost-Effective in the
Horizontal
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Installations cost, comparison
Comparison of 50 m fiber waveguide and copper links (Cat. 5 UTP).
C a te g o ry 5 U T P
F ib e r
Socket
$ 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 rs
N ot needed
$ 1 8 .2 4
C ab el (5 0 m )
$ 4 1 .5 8
$ 4 3 .5 6
In s ta lla tio n c o s t
$ 7 1 .2 5
$ 6 6 .7 5
$ 1 2 3 .2 4
$ 1 3 9 .4 4
T o ta l
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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
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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)
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Light sources - LED parameters
Both LED’s and LD’s emitting wavelengths are set by material
selection: AlGaAs: 780-860 nm, InGaAsP: 1300, 1550 nm.
LED parameters
type
material
wave- fiber coupled power
length - fiber type
spectral width bandwidth
3 dB
(FWHM)
nm
µW
nm
MHz
860
95 - 62.5/125
60 - 50/125
2.5 - 9/125
50
50
ELED InGaAsP 1300
20 - 9/125
60
350
ELED InGaAsP 1550
8 - 9/125
SLED AlGaAs
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Light sources - LD parameters
Fiber optics LD are available in pigtailed
versions and with standard fiber optic
receptacles
LD type
wavelength
laser
power
fiber coupled power
nm
mW
mW
FP
1310
5
1
9/125
FP
1310
5
2
62.5/125
FP
1550
5
1
9/125
DFB
1550
5
1
9/125
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Photonics Systems - Introduction
fiber type
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Detectors - definition
Definition
A device that is responsive to the presence or absence of a stimulus
Stimulus
Detector
Output
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
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Detector - construction
For fiber optic applications
detectors are available in
standardized packages,
• pigtailed or
• combined with standard
receptacles
ST SC FC
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Detectors - parameters
Detector
type
wavelength
(high respons. range)
responsivity
dark current
material
nm
A/W
nA
InGaAs
1300 (1000-1700)
0.75
0.1
Si
850 (400-1100)
0.45
1
Ge
1300 (800-1500)
0.65
350
detectors are available as pin or APD structures
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Photonics Systems - Introduction
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Splices and connectors
Standard
and
SFF connectors (~ 1dB)
Fiber splicing (~0.1dB)
electric arc
Fusion splicing
fiber
fiber
index matching gel
Mechanical splice
fiber
fiber
alignment sleeve
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Literature
G. P. Agrawal, Fiber-optic communications systems, John
Willey & Sons 1992
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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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