Fundamentals of Optical Communications

Transcription

1 University of Applied Science Departement of Electrical Eng. and Computer Science Fundamentals of Optical Communications Referent: Prof. Dr.-Eng. habilitas Steffen Lochmann Slide 1

2 Table of Contents 1. Basics of Optical Fibers 2. Dispersion 3. Optical Amplifiers / Pulse Reshaping 4. Optical Communication Systems 5. Outlook Folie 2

3 Why Optical Fibres... Low Signal Attenuation High Bandwidth Proof against Short-circuiting, Earthing and Fire No EMI Components with low Weight and Volume Data Security Multi-utilization results in high efficiency! Pinciple Folie 3

4 Fiber Structure and Light Guiding Mechanism r n cladding = 1.48 n core = 1.5 n 125µm Step Index (SI) Fiber

5 Fiber Structure and Light Guiding Mechanism n cladding = 1.48 n core = 1.5 Step Index (SI) Fiber high dispersion > 100 ns/km attenuation ca db/km

6 Fiber Structure and Light Guiding Mechanism r n cladding = 1.48 n core = 1.5 n Gradient Index (GI) Fiber

7 Fiber Structure and Light Guiding Mechanism n cladding = 1.48 n core = 1.5 V 2 =c/1.48 V 1 =c/1.5 Gradient Index (GI) Fiber low dispersion > 2 ns/km attenuation ca db/km

8 Fiber Structure and Light Guiding Mechanism n cladding = 1.48 n core = µm Single Mode (SM) Fiber almost no dispersion > 18ps/nm km attenuation ca. 0.2 db/km

9 Fiber attenuation and optical windows 1 db/km S C L µm GHz WDM 1.25 [µm] 1.65 DWDM [µm] Folie 9

10 Table of Contents 1. Basics of Optical Fibers 2. Dispersion 3. Optical Amplifiers / Pulse Reshaping 4. Optical Communication Systems 5. Outlook Folie 10

11 Dispersion: due to: path differences modal dispersion (intermodal dispersion) polarisation mode dispersion (PMD) spectrum of light source chromatic dispersion (intramodal dispersion) material dispersion waveguide dispersion Folie 11

12 Modal Dispersion: C modal, SI 2 4 NA NA Cmo dal, GI n c 80 3 n c 1 1 with NA 2 2 n 1 n2 Folie 12

13 Material Dispersion: Folie 13

14 Waveguide Dispersion: can be neglected in multimode fibers caused by the different extension of LP01 into the cladding b( ) leading to a wavelength dependent effective refractive index: 50 ps nm km D WG D Mat D Chrom Folie 14 [mm]

15 Fiber dispersion of DSF Chromatic dispersion : 50 ps nm km D WG D Mat D Chrom m Dispersion of a Dispersion Shifted Fiber (DSF) Folie 15

16 Fibers for dispersion compensation Chromatic dispersion : 50 ps nm km negative slope! D Chrom m Folie 16

17 Table of Contents 1. Basics of Optical Fibers 2. Dispersion 3. Optical Amplifiers / Pulse Reshaping 4. Optical Communication Systems 5. Outlook Folie 17

18 Erbium Doped Fiber Amplifier (EDFA) P opt = ca.17dbm 10-50m Erbium doped fiber 30db isolator coupler pump laser Folie 18

19 Optical pulse reshaping ca.120km SMF ca.120km SMF ca. 10km fiber with negative dispersion slope Folie 19

20 Table of Contents 1. Basics of Optical Fibers 2. Dispersion 3. Optical Amplifiers / Pulse Reshaping 4. Optical Communication Systems 5. Outlook Folie 20

21 How does it work? Point-to-point: OC1 OC3 STS1 OC1 OC3 STS1 M U X D M U X E / O E / O O / E O / E D M U X M U X OC1 OC3 STS1 OC1 OC3 STS1

22 How does it work? Point-to-point: ATM/Ethernet/SDH line board

23 How does it work? MUX, but still point-to-point: OC1 OC3 STS1 OC1 OC3 STS1 M U X D M U X E/O E/O OC12/1 OC12/2 OC12/3 OC12/4 OC12/1 OC12/2 OC12/3 OC12/4 (active) DWDM MUX 3 Tbps via 50km (2/1999) 10.9 Tbps via 117km (9/2001)

24 How does it work? MUX, but still point-to-point: Wave Line EL2: 32channels, 200GHz spacing

25 Table of Contents 1. Basics of Optical Fibers 2. Dispersion 3. Optical Amplifiers / Pulse Reshaping 4. Optical Communication Systems 5. Outlook Folie 25

26 MUX-Generations OTDM frequency OFDM => DWDM FDM TDM SDM OSDM OFDM => CWDM space Folie 26

27 University of Technology, Business and Design Departement of Electrical Eng. and Computer Science Thank you for listening to Fundamentals of Optical Communications Referent: Prof. Dr. Steffen Lochmann Folie 27