•Light is an electromagnetic wave that satisfies Maxwell’s Equations. •The electromagnetic spectrum is a range of frequencies classified into groups.
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2 Why go digital?
Analog (continuous) Time
Digital (discrete) 1 0 1 0 1 Time
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Chapter 1
By QianSheng, HDU
Page 23
Cause
Effect Attenuation
By QianSheng, HDU
Page 25
Digitizing Steps
1) Pick the highest frequency: fu = 4 kHz for voice 2) Sample at twice the highest frequency
yielding: :
Sampling Rate = 2fu = 8000 samples/second
2012年2月27日4时18分 Chapter 1 By QianSheng, HDU Page 13
The electron volt (eV) is another useful unit for analysis of fiber optic systems. The electron volt is defined as the energy acquired by an electron
Transmitter
Message Origin Modulator
Receiver
Destination Processor
Electric Domain Carrier Source Coupler
Detector
Optic Domain
Channel
Coupler
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where v is the velocity of the wave in the medium.
2012年2月27日4时18分
Chapter 1
பைடு நூலகம்
By QianSheng, HDU
Page 8
Example: If is 0.85 m, find the frequency. In this example the medium is not specified, so let us assume that the medium is free space.
The major operation regions (windows) are: Wavelength Window
0.8-0.9 m
~1.300 m
First Window
Second Window
~1.550 m
~1.600 m
Third Window
Fourth Window
2012年2月27日4时18分
accelerated across a 1 volt potential difference. The
conversion between electron volts and joules is:
1 eV = 1.6 x 10-19 J
The 0.8 m photon has an energy of: (2.48/1.6) = 1.55 eV
= 0.8 m? Answer
m 3 10 c s W p h 6.626 1034 J s 6 0.8 10 m J 19 W p 2.48 10 photon
8
W Pt 106 1 106 Joules W 106 J 4.03 1012 photons W p 2.48 1019 J photon
光纤通信 Fiber Optic Communications
联系方式
姓 名： 钱胜 Email： hiqian@ Handset: 13777455099 办公地点：第一教研楼北楼428光纤通信网实验室
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2
Reference
• 《光纤通信第五版（英文版）》, J C Palais, 电子工业出版社（教材）
photon has energy:
W p hf h
c

(1.4)
h = 6.626 x 10-34 J s (Planck’s constant) Shorter wavelength (higher frequency) waves have greater photon energy.
Information: voice, video data
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Chapter 1
By QianSheng, HDU
Page 15
A typical telephone system
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Chapter 1
By QianSheng, HDU
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Loss
Gain
Amplification & Noise
Dispersion
Distortion
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Chapter 1
By QianSheng, HDU
Page 24
Pulse-code modulation(PCM) technique
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Chapter 1
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From 29th ICCNC
1987年9月20日,在德国卡尔斯鲁厄大学教授维纳· 措恩的帮 助下,中国首次接入国际互联网.当天,维纳· 措恩教授和中国互联 网先驱王运丰教授联手起草了中国第一封跨国电子邮件,从北京 成功发往德国的卡尔斯鲁厄.这标志着中国跨出了走向互联网时 代的第一步.
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Chapter 1
By QianSheng, HDU
Page 14
◆ Telecommunications
★ What It is
Tele-over a distance; communicationsexchange of information; Telecommunications: exchange of information over a distance using some type of equipment
Information
Information Channel
Information
N
5
Link
Station
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Chapter 1
By QianSheng, HDU
Page 18
★Information- carrying capacity
1 Why produce more information?
Electric
phone
Radio TV
AM无线电 同轴电缆 双铰线
FM无线电
micro wave
卫星/微波
infra red
Visible light
光纤
107
106
105
104
103
102
101
100
10-1
10-2
10-3
10-4
10-5
10-6
Wave length（m）
2012年2月27日4时18分 Chapter 1 By QianSheng, HDU Page 7
Most of the frequencies in fiber optic systems are
In the Infrared.
Wavelength and frequency are related by:
v f
In free space, v = c = 3 x108 m/s
(1.3)
3 108 m / s 14 f 3.53 10 Hz 6 0.85 10 m c
The period of oscillation T is defined as the time it takes for the wave to complete one cycle. The period for the frequency in the preceding example is then
◆ Nature of Light
Sometimes light behaves as a wave and sometimes light behaves as a particle. We will look at both
behaviors.
1.3.1
Wave Nature of Light
• Fiber-Optic Communications Technology, Djafar K. Mynbaev, Lowell L. Scheiner eds., Pearson Education, Inc., 2001（教材） • 《光纤通信技术》, Djafar K. Mynbaev, 徐功 权等译, 机械工业出版社
1 1 14 T 0.28 10 s 14 f 3.53 10 Hz
2012年2月27日4时18分 Chapter 1 By QianSheng, HDU Page 9
Fiber optic systems must have low loss. For