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Introduction Siemens
TT2530EU02AL_011
Contents
1 Definition of Fiber 3
2 History of Optical Transmission 7
3 Loss of a Few Optical Media 11
4 Advantages and Disadvantages of Optical Fibers 13
5 Principle of Transmission with Light 15
6 Regenerator Spacing 19
7 Exercise 21
8 Solution 25
Introduction
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Introduction Siemens
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1 Definition of Fiber
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In optical transmission an effect of total internal reflection is desired. This effectoccurs if two transparent media are arranged one above the other. The externalmedium must be "better" than the internal one.
The combination of glass and air would also fulfil this condition. However, oneachieves more favorable characteristics with two almost equally "good" types ofglass.
A technically functional optical fiber (OF) consists of the following components:
The information-carrying glass (the core) is covered
with a slightly "better" glass (the cladding).
A protective layer of plastic (the coating) is applied over the cladding.
This combination of core - cladding - coating is the fiber.
The fiber-glass factory delivers the fibers with a naturally colored coating.
If fibers are processed into cables, they are colored for identification in the cablefactory according to the specifications of the customer.
Introduction Siemens
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125
250
Potical fibres use din transmission applications have the following dimensions:
Diameter of the core approx.:8�m, 50 �m, 62,5 �m
Diameter with cladding:125 �m
Diameter with the coating:250 �m
Fibre cross section
and
refraction index.
Fig. 1
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Introduction Siemens
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2 History of Optical Transmission
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Use of light signals in the early epoch (such as signal fluch)
1626 Snell's law
1794 First telegraph line in France
1870 John Tydall demonstrated the light conductivity of a water jet
1880 Graham Bell developed the Opthophon (voice signals were sent via light butwere effected by the whether)
1888 Demonstration of electromagnetic waves by Hertz
1897 Analysis of the waveguide
1934 Norman R. French patented an optical telephone system using glass rodsor something similar in order to transport voice signals.
1958 Arthur Schawlow and Charles H. Townes developed the laser.
1960 Theodor H. Maiman operated the laser the first time.
1962 First semiconductor laser by GE, IBM, MIT
1966 Charles H. Kao and George A. Hockham proposed the glass fiber asconductor.
1968 Optical wave guides with an attenuation of 1000 dB/km.
1970 Corning Glassworks produces an OWG with less than 20 dB/km at 633 nm.
1972 Attenuation of 4 dB/km at 850 nm and a bandwidth of 20 - 50 MHz/km isachieved.
1973 The first FO cables for telephone purposes are employed on militaryvessels.
1974 The concept for graded index fiber is introduced 500-1000 MHz/km.
1976 First system trials in the USA by Western Electric in Atlanta. Siemens startsa 2.1 km long test line in Munich.
1977 Field trial in Chicago over 2.5 km by Bell Systems.
Simultaneously in Long Beach over 9.5 km by General Telephone.
Siemens installs the first FO link for DBP in Berlin.
1981 Dispersion 4 ps/nm x km Beales GB
1983 Siecor delivers the first single mode fiber cable.
1984 In the laboratory, over 200 km spans are achieved at 1.55 µm.
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1985 Dispersion-shifted fiber
1987 Foundation of the Siecor company in Neustadt with 80,000 km processedglass fiber. LA 140 LWL
1992 Siemens, together with Siecor, installs more than 3,000,000 km of cabledfiber in over 25 countries. SLA 4/SLA 16
1995 The cable factory Neustadt processes 500,000 km fiber into cables for thefirst time.
1996 Foundation of PT Trafindo Perkasa in Indonesia. The production startstemporarily with 70,000 km of fiber.
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Introduction Siemens
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3 Loss of a Few Optical Media
Medium
Pure Water
Window glass
Optical glass
Thick fog
City air in Dusseldorf
Glass fibre 1970
Good fibre 1978
Good fibre 1986
Optical Attenuation
100,000
50,000
3,000
500
10
20
3
0,2
Penetration depth at 50% light gloss
33 mm
66 mm
1,000 mm
6,6 m
330 m
165 m
1,000 m
18,000 m
Fig. 2
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Introduction Siemens
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4 Advantages and Disadvantages of OpticalFibers
Advantages:
� High transmission capacity
� Low susceptibility to electromagnetic interference important for use in industrialplants control lines in power plants in principle, no spacing requirements when runin parallel.
� Potential separation between transmitter and receiver (no ground loop)
� Long distances between repeaters over 300 km is possible for sea cables largeproduction lengths therefore greater distances between couplings therefore fewercouplings therefore fewer installation errors.
� No line interference, no signal dispersion
� Highly resistant to eavesdropping
� Short-circuit-free (no spark formation) important in areas where there is a risk ofexplosions.
� Light weight, highly flexible lighter equipment easier handling less volume forshipping smaller cable reels lighter trailers smaller winches.
� Smaller dimensions smaller cable diameter more effective utilization of cableducts.
� No corrosion of fibers.
� Unlimited material availability (SiO2 is available in nearly limitless supply) 1 gram
of silicon corresponds to 10 kg of copper.#
Disadvantages:
� Installation technology
� high level of precision required
� sophisticated devices necessary
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Introduction Siemens
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5 Principle of Transmission with Light
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Message transmission with light can be easily explained:
In the transmitter, the electrical signal is converted into a light signal in an electro-optical converter (e.g. a light emitting diode (LED) or a laser diode (LD)). To be moreprecise: The light intensity of the transmitting diode is modulated by the binary pulse-modulated diode current i1, and light with the power P (0) is coupled with the opticalfiber. After traversing the optical fiber, the light is converted back into an electricalsignal in an opto-electric converter (e.g. photodiode) at the end of the transmissionroute. The optical transmission route therefore begins and ends with an electricalinterface whose data is normed independently of the transmission medium. There-fore, digital systems with fiber optics use, in principle, the same interfaces (CCITTrecommendations G. 703) they use for radio relay and multiplex units.
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i1
CCITT Interface
Light-emitting
or laser code
optical
transmitter
i2+
-
Photodiode optical
receiver
Optical fibre
P (0)
P (L)
L Length of optical transmission routei1, i2 Laser diode or photodiode currentP(0), P(L) Optical transmit or receive power
Fig. 3
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Introduction Siemens
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6 Regenerator Spacing
The diagram shows regenerator spacing independently of transmission capacity andthe various transmission media.
An analog system (for example with 10,800 channels over a 2.6/9.5 coaxial cable)requires a repeater every 1.55 km.
A glass fiber can transmit more than three times as many channels across approx.100 km without a regenerator.
Maximum regenerator spacing
100
50
20
10
5
2
1100 200 500 1000 2000 5000 10000 20000 50000
m
MM fibre
1500 nm
V300
V960
V2700
V3600coaxial pair 2.6/9.5 mm
V10800
LA 34 KX
LA 140 KX
LA 565 KX
8 Mbit/s 34 Mbit/s 140 Mbit/s
565 Mbit/s
622 2.5 Gbit/s
bit rate
SM fibre
Fig. 4
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Introduction Siemens
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7 Exercise
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Introduction Siemens
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Exercise
1. Name at least 5 decisive advantages of fiber-optic technology over standardcopper cable technology.
a)
b)
c)
d)
e)
2. In what year did the Corning Glassworks company succeed in manufacturing anoptical fiber with an attenuation of less than 20 dB/km (the beginning of fiber-optic technology)?
3. Describe the basic design of a fiber-optic transmission route!
4. Name the three elements of an optical fiber.
a)
b)
c)
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Introduction Siemens
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8 Solution
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Introduction Siemens
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Solution
1. a) high transmission capacity
b) low weight
c) large production lengths
d) not susceptible to electromagnetic influence
f) resistant to eavesdropping
2. 1970
3. telephone - electro-optical converter - fiber - electro-optical converter - telephone
4. a) core
b) cladding
c) coating
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