Lecture 1: Introduction

Transcription

1 Optical Fibre Communication Systems Lecture 1: Introduction Professor Z Ghassemlooy Electronics & It Division School of Engineering Sheffield Hallam University U.K. 1

2 Contents Reading List Lecture 1: Introduction Transmission Media History Communication Technologies Applications System Challenges Ahead Lecture 2: Nature of Light & Light Propagation Lecture 3: Light Sources and Transmitter Lecture 4: Light Detectors and Receivers Lecture 5: Optical Devices Lecture 6: Optical Networks Lecture 7: System Characterisation Laboratory Tutorials and Solutions: Visit 2

3 Reading List ij M Senior, Optical Fibre Communications, Prentice-Hall ig P Agrawal, Fiber-Optic Communication Systems, J Wiley ij N Sibley, Optical Communications, Macmillan ir J Ross, Fiber Optic Communications - Design Handbook, Prentice Hall. it E Stern, et al, Multiwavelength Optical Networks, Addison Wiley ir Ramaswami et al, Optical Networks - A practical perspective, Morgan Kaufmann 3

4 Transmission Media itransmission Medium, or channel, is the actual physical path that data follows from the transmitter to the receiver. icopper cable is the oldest, cheapest, and the most common form of transmission medium to date. ioptical Fiber is being used increasingly for high-speed applications. 4

5 Transmission by Light: why? iability to transmit huge amount of information using a single carrier frequency iincreased transmission length iimproved performance ietc. 5

6 Historical Developments 800 BC Use of fire signal by the Greeks 400 BC Fire relay technique to increase transmission distance 150 BC Encoded message 1880 Invention of the photophone by Alexander Graham Bell 6

7 Historical Developments - contd Experiments with silica fibres, by Lamb (Germany) The birth of clad optical fibre, Kapany et al (USA) 1962 The semiconductor laser, by Natan, Holynal et al (USA) 1960 Line of sight optical transmission using laser: - Beam diameter: 5 m - Temperature change will effect the laser beam Therefore, not a viable option A paper by C K Kao and Hockham (UL) was a break through - Loss < 20 db/km b - Glass fibre rather than crystal (because of high viscosity) - Strength: kg /m 2. Contd. 7

8 Historical Developments - contd Low attenuation fibre, by Apron and Keck (USA) from 1000 db/km - to - 20 db/km - Dopent added to the silica to in/decrease fibre refractive index. Late 1976 Japan, Graded index multi-mode fibre - Bandwidth: 20 GHz, but only 2 GHz/km Start of fibre deployment s 800 nm Graded multimode 2 Gbps/km nm Single mode 100 Gbps/km nm Single mode 1000 Gbps/km - Erbium Doped Fibre Amplifier 8

9 Historical Developments - contd s - Soliton transmission (exp.): 10 Gbps over 10 6 km with no error - Optical amplifiers - Wavelength division multiplexing, - Optical time division multiplexing (experimental) OTDM 2000 and beyond - Optical Networking - Dense 40 Gbps/channel, 10 channels - Hybrid DWDM/OTDM ~ 50 THz transmission window > 1000 Channels WDM > 100 Gbps OTDM Polarisation multiplexing - Intelligent networks 9

10 Existing Systems Tbps WDM DWDM Typical bit rate 40 Gbps / channel ~ 8 THz (or 60 nm) Amplifier bandwidth 32 channels (commercial) with 0.4 nm (50 GHz) spacing 2400 km, no regeneration (Alcatel) Total bandwidth = (Number of channels) x (bit-rate/channel) OTDM Typical bit rate 6.3 Gbps / channel ~ 400 Amplifier bandwidth 16 channels with 1 ps pulse width 10

11 Communications Technologies Year Service Bandwidth distance product 1900 Open wire telegraph 500 Hz-km 1940 Coaxial cable 60 khz-km 1950 Microwave 400 khz-km 1976 Optical fibre 700 MHz-km 1993 Erbium doped fibre amplifier 1 GHz-km 1998 EDFA + DWDM > 20 GHz-km EDFA + DWDM > 80 GHz-km OTDM > 100 GHz-km 11

12 Optical Technology - Advantages High data rate, low transmission loss and low bit error rates High immunity from electromagnetic interference Bi-directional signal transmission High temperature capability, and high reliability Avoidance of ground loop Electrical isolation Signal security Small size, light weight, and stronger 62 mm 21mm 648 optical fibres 363 kg/km 448 copper pairs 5500 kg/km 12

13 Applications Electronics and Computers Broad Optoelectronic Medical Application Instrumentation Optical Communication Systems High Speed Long Haul Networks (Challenges are transmission type) Metropolitan Area Network (MAN)? Access Network (AN)? Challenges are: - Protocol - Multi-service capability - Cost Optics is here to stay for a long time. 13

14 System Block Diagram Source Transmitter Drive circuit Optical source Connector Optical splice Optical Tx Optical-toelectronics Regenerator Optical Rx Optical coupler Fibre Optical amplifier Optical detector Receiver Sink 14

15 Source Source coding Modulation Analogue Digital Multiplexing Frequency Time Modulation External Internal Pulse shaping Channel coding Encryption etc. 15

16 Receiver 1 st -stage amplifier 2 nd -stage amplifier Pre-detection filtering Sampler & detector Demultiplexer Equalizer Demodulator Decoder Decryption Output signal 16

17 All Optical Network IP IP ATM ATM SDH ATM IP Other SDH SDH Open Optical Interface Challenges ahead: Network protection All Optical Networks Network routing True IP-over-optics 17

18 Challenges Ahead Modulation and detection and associated high speed electronics Multiplexer and demultiplexer Fibre impairments:. Loss. Chromatic dispersion. Polarization mode dispersion. Optical non-linearity. etc. Optical amplifier. Low noise. High power. Wide bandwidth. Longer wavelength band S 18

19 Challenges Ahead - contd. Dedicated active and passive components Optical switches All optical regenerators Network protection Instrumentation to monitor QoS Next Lecture: Nature of Light and Light Propagation 19