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1. Optical Fiber Communication
- An Overview
Speaker : S. L. Maskara
[ Retired (2004 ) Professor of IIT Kharagpur ]
maskara.shankar@gmail.com
Lecture in STC at
NSIT, New Delhi
09 July 2018

2. Fiber Optics communication
• Introduced 1970
• Fiber installed for Telephony 1980’s early
• Long distance land based fiber installation completed 1988
• Submarine F.O. cables installation began 1988
• LAN applications using O.F. 1988
• Million (10) km of O.F. by 1994 worldover
• Point to point to distributed network.
• Fiber to home (FTTH)
• Optical Fibers
• Sources and Detectors
• Components like: connectors, splices
• Advances: Optical amplifier, circulator, attenuator, filters, WD multiplexer, external modulators

3. • Bit rate, Fiber attenuation (loss), Repeaterless Span, Transmitted
power, Receiver Sensitivity

5. OPTICAL COMMUNICATION

6. ELEMENTS OF FIBER TRANSMISSION SYSTEM

7. FIBER OPTICS
OPTICAL GLASS FIBERS
PROPOGATION, TECHNOLOGY, APPLICATIONS
ATTENUATION
DISPERSION MODAL, CHROMATIC
MATERIAL
WAVEGUIDE
MULTIMODE STEP GRADED INDEX
50ns/km 0.25ns/km
SINGLE MODE 90 <0.1 20 ps/km.nm
0.8-0.9 1.3 1.55
ZERO DISPERSION SHIFTED & FLATTENED FIBER

8. ZERO DISPERSION SHIFTED & FLATTENED FIBER
ADVANTAGES
SMALL SIZE
LESS WEIGHT
NONREACTIVE
LARGE BANDWIDTH
HIGH DATA RATE
LOW LOSS
LONG REPEATERLESS SPAN
NO EMI/RFI/CROSSTALK
NONINDICTIVE

9. Electrooptic Semiconductor Devices
SOURCES LED, LD 0.85 1.3 1.55 𝜇𝑚
DETECTORS APD , PIN ,, ,, ,, ,,
PIN-FETs
GaAs GaAlAs Quarter nary Compounds
INTEGRATED OPTICS
COHERENT TECHNIQUES: 10-20 dB improvement.
WDM - MULTICHANNEL OPTICLAL SYSTEMS
F.O. Components
CONNECTORS, COUPLERS, OPTICAL MULTIPLEXERS, TAPS, (SPLICES)
OTHER F.O. DEVELOPMENTS
SENSORS & INSTRUMENTATION, PHOTONIC SWITCHING, OPTICAL
COMPUTING & SIGNAL PROCESSING.OPTICAL AMPLIFIERS, TUNABLE
LASERS, SOLITONS

18. SOURCES:
SEMICONDUCTOR DIODES-GaAlAs
REQUIREMENTS-
(1) Longer Wavelengths
(2)Reduced Operating Currents
(3)Better mode stability
(4) Longer Life

19. INJECTION LASER
• PHOTONS EMITTED WITH ELECTRONS FALL FROM C.B. TO V.B.
• STIMULATED EMISSION
• MUCH BRIGHTER (10mW)
• FASTER RESPONSE
• NARROW LINE WIDTH
• LIFE 10000 - 20000 Hours – 105 Hours
• NON LINEAR CHARACTERSTICS
• B.W. SEVERAL MHz AT FULL POWER

20. LEDs
• PHOTONS EMITTED WITH ELECTRONS FALL FROM C.B. TO V.B.
• SPONTANEOUS EMISSION
• LESS BRIGHTER (OUTPUT 0.1mW To 2mW)
• SLOWER RESPONSE
• WIDER SPECTRAL WIDTH
• LIFE 107 Hours
• LINEAR CHARACTERSTICS
• B.W. 50 MHz

23. DETECTOR (SILICON PHOTODIODE)
REQUIREMENTS:
(1) SMALL SIZE
(2) COMPATIBLE WITH OPTICAL FIBER AND SOURCES
(3) GOOD SENSITIVITY
(4) ROBUST DEVICE
(5) FAST RESPONSE TIME
(6) LONG LIFE

24. AVALANCHE PHOTODIODE (APD)
• LOWER OPTICAL POWER REQUIRED
• GAIN CONTROL POSSIBLE
• HIGH B.W.
• LIMITED LINEARITY
• MULTIPLICATION NOISE
• 100-400V BIAS - CRITICAL

25. PIN DIODE
• LARGER OPTICAL POWER REQUIRED
• EASE OF USE
• LOWER B.W. (<50MHz)
• HIGH LINEARITY
• NO MULTIPLICATION NOISE
• 5 TO 80 VOLTS BIAS

26. SOURCE OF NOISE
• THERMAL NOISE
• SHOT NOISE
• EXCESS NOISE IN MUTIPLICATION
• SOURCE NOISE
• MODAL NOISE – DUE TO MISALIGNMENT

27. Quaternary crystals lattice matched to substrates and related optical materials for detectors

29. OVERVIEW OF FIBRE OPTIC COMMUNICATION
SUBSCIBER LOOPS
• FDDI
• ISDN
• BISDN
• PHOTONIC
SWITCHING
• HDTV
• ATV
• LARGE NO. OF
• WDM/FDM/TDM
• COHERENT
• EXTERNAL
MODULATION
• OPT. AMP.
PHOTONIC SWITCH
LIGHTWAVE TRANSMISSION
PHOTONIC ERA

32. 1. FIBRE OPTIC MEDIUM & LIGHTWAVE TECHNOLOGY ARE ADVANCING
FAST WITH CONTINUOUS ENHANCED PERFORMANCE.
2. TRADITIONAL LONG-HAUL/ TRUNK DEMAND IS BEING GREATLY MET
BY FIBRE OPTICS.
400 MBPS, 1.6 GBPS, 2.4 GBPS, 3.8 GBPS SYSTEMS HAVE BECOME
REALITY. MILLIONS OF KMS OF FIBRE INSTALLED.
3. SUBMARINES FIBRE OPTIC SYSTEMS OVER ATLANTIC, PACIFIC OCEANS
& OTHER SEAS ARE OPERATIONAL, BEING INSTALLED AND BEING
PLANNED CARRYING LARGE VOLUMES OF INTERNATIONAL TRAFFIC.
4. NEW SERVICES AND APPLICATIONS EMERGING WITH IMPROVED
FIBRE OPTIC TECHNOLOGY AND PERFORMANCE LANS, FIBRE
DISTRIBUTED DATA INTERFACE (FDDI), MULTIPLEXED BACKBONES,
ISDN, B-ISDN, MULTIMEDIA.
5. POWER COMPANIES, RAILWAYS, PIPELINES – MAJOR USER OF
DEDICATED SYSTEMS- LARGE BANDWIDTH, FLEXIBILITY, RELIABILITY.
RECENT TRENDS IN FIBRE OPTIC COMMUNICATION

33. 6. LOCAL LOOPS/ SUBSCRIBER LOOPS:
• PROMOTION OF SERVICES BRINGING FIBRE TO THE HOME (FTTH) &
FIBRE IN THE LOOP (FITL)
• NOT ONLY FOR LARGE BANDWIDTH BUT EVEN FOR PLAIN OLD
TELEPHONE SERVICE (POTS).
• FIBRE TO SOLVE PROBLEM OF THE LAST MILE.
• FOR ISDN- FIBRES RECOMMENDED FOR EVEN BASIC RATE ACCESS.
SUITABILITY FOR PRIMARY RATE ACCESS ALREADY ESTABLISHED.
• LET THERE BE EXPRESSWAY IN THE LOOP – THEN WALK, CYCLE OR RUN
A BULLET TRAIN…
Cont..

34. 7. FUTURE – FITL, OPTICAL NETWORKS- OPTICAL ETHER WITH WDM,
COHERENT TECHNOLOGY AND PHOTONICS SWITCHING
DEVELOPMENTS. FUTURE OF FIBRE OPTICS IS AS BRIGHT AS LIGHT.
DISTRIBUTION, MULTI-ACCESS , RE-CONFIGURABILITY
8. PLASTIC/POLYMER FIBRE HOLD BETTER PROMISE AT LEAST FOR
LAN APPLICATIONS.
9. OPTICAL AMPLIFIERS – ERBIUM DOPED FIBRE AMPLIFIER, MULTI
QUANTUM WELL MATERIALS/DEVICES.
10. SOLITONS – 10 GBPS X 2000 KM FEASIBLE
11. PHOTONIC – OPTOELECTRONIC IC’S.
Cont..

36. CONCEPTUAL DEVELOPMENT OF OPTICAL NETWORKING
(ACHIEVED/ TO BE ACHIEVED)
1. POINT TO POINT :
MULTIWAVELENGTH TRANSMISSION (WDM)
IMPROVED FURTHER WITH EDFA COMING.
CAPACITY INCREASE ON EXISTING SYSTEMS.
2. BROADCAST AND SELECT NETWORKS:
CONCURRENCY
STAR NETWORK
SIMPLE
3. BROADCAST-STAR SWITCHING FABRICS:
SWITCHING IN WAVELENGTH
DOMAIN-AVOID COMPLEXITY
OF TIME & SPACE SWITCHES

37. Cont..
4. WAVELENGTH ROUTING:
SELECTIVE ROUTING OF OPTICAL SIGNALS ACCORDING
TO THEIR WAVELENGTHS AS THEY TRAVEL THROUGH
THE NETWORK.
WAVELENGTH REUSE, WDM CROSSCONNECT,
REARRANGEABILITY THROUGH SPACE SWITCHES
WAVELENGTH SELECTIVE ELEMENTS
ADD-DROP CAPABILITY
5. SCALABILITY:
ADD MORE NODES WAVELENGTH REUSE IN MULTIHOP NETWORKS,
WAVELENGTH CONVERSION
6. WAVELENGTH TRANSLATION:
CHANGE WAVELENGTH BEYOND BOUNDARIES OF
ADMINISTRATIVE DOMAINS- LARGE SCALE NETWORKS

38. Cont..
7. TRANSPARENCY:
DATA FORMAT etc.
8. NETWORK LAYERING:
OPTICAL CONNECTIVITY LAYER. FIBRE-SONET-ATM.
NOW FIBRE-OPT CONN-TRANSPORT-SWITCHING
9. NETWORK MANAGEMENT, CONTROL AND OPERATIONS IN
TRANSPARENT SYSTEMS:
MONITORING & CONTROL

43. SYNCHRONOUS TRANSFER MODULE (STM)
C4 + PON ≡ V04 +SOH ≡ STM PON CAPABLE OF INDICATING ERRORS
OCCURING DURING ITS JOURNEY FROM
POINTS LOADING TO UNLOADING
RESPONSIBLE NETWORK ELEMENT CANNOT
BE IDENTIFIED BY Vo4PON
SOH → TO IDENTIFY NET ELEMENTS WHERE
ERROR CAME IN.
STM-1 → VC4
9 ROWS X 270 COLUMNS ≡ 2430 BYTES ≡ 2430 X 8 b/s X 8000 Fr/sec
= 155.52 Mbps
9 COLUMNS→ SOH
1 COLUMN → POH
260 COLUMN→ VC4 PAYLOAD VC4= 261 X 4 = 2349 BYTES

59. TWO WAY OPTICAL TRANSMISSION

64. Thank you
Any Questions please ?