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Otd mro
Otd mro
Otd mro
Otd mro
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Otd mro
Otd mro
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Otd mro

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  • 1. Sheffield Hallam University Simulation of an All Optical T ime Division M ultiplexing Router E mploying T OADs Razali Ngah and Z Ghassemlooy Optical Communications Research Group School of Engineering
  • 2. Contents 1. 2. 3. 4. 5. 6. 7. 8. Introduction OTDM Communication System OTDM Packet Format All optical switching OTDM Router Using TOADs Simulation Results and Discussions Conclusions Further works Sheffield Hallam University 2
  • 3. Introduction Why Optical domain? Sheffield Hallam University Cont. 3
  • 4. Introduction Multiplexing Techniques - to extend a transmission capacity - OTDM vs. WDM OTDM WDM Single wavelength Multiple wavelength High bit rate (up to 640Gb/s) Lower bit rate (2.5 – 100Gb/s) Immature technology Reaching an advanced stage of development Chromatic dispersion & timing jitter FWM, SRS & XPM OTDM can provide users with better throughput delay performance, faster single-channel access times for high-datarate end users
  • 5. OTDM Communication System - 10 Gbps is commercially available - There are two types: -Bit Interleaved TDM -Slotted (packet) TDM
  • 6. OTDM Packet Format Clock (Frame Sync.) Address Payload Format of OTDM packet Multiplexing of Clock Pulse - Space Division Multiplexing - Wavelength Division Multiplexing - Orthogonal Polarization - Intensity Division Multiplexing - Time Division Multiplexing Sheffield Hallam University Cont.
  • 7. OTDM Packet Format - Space division multiplexing -The clock is carried on by a separate transmission fibre from the data packets -Problems: (i) time varying differential delay between the clock and data, and (ii) the cost of installing a separate clock fibre for each network node in new installation is not practical for wide area networks Sheffield Hallam University Cont.
  • 8. OTDM Packet Format - Wavelength division multiplexing -Different wavelengths are allocated to clock and payload -Problems: Only practical for predetermined path lengths between nodes in single hop networks. The relative delay between the clock and data will be random in asynchronous packet-switched since the optical path length through which a packet travels is non-deterministic Orthogonal Polarization -An orthogonally polarized clock pulse is used -Problem: Difficult to maintain the correct polarization throughout the system Sheffield Hallam University Cont.
  • 9. OTDM Packet Format - Intensity Division Multiplexing -Higher intensity for the optical clock pulse is used to differentiate it from the data -Problem: The clock pulse amplitude and its position become difficult to maintain in long distance transmission - Time Division Multiplexing -Self-synchronization approach, the clock is located at the start of the packet Sheffield Hallam University Cont.
  • 10. All Optical Switching a). Asymmetric Terahertz Optical Demultiplexer (TOAD) b). Mach-Zehnders interferometer (MZI) c). Ultrafast nonlinear interferometer (UNI) - Optical control pulse is used to change SOA’s gain and refractive index Sheffield Hallam University
  • 11. Asymmetric Terahertz Optical Demultiplexer (TOAD) Sheffield Hallam University
  • 12. All Optical Router Using TOADs Clock Data packet Data Packet TOAD1 (Clock extra.) Data Packet TOAD2 (read address) Clock Port 1 TOAD3 (route payload) Address Payload Port 2 Block Diagram of 1x2 OTDM Router Sheffield Hallam University Cont. 5
  • 13. All Optical Router Using TOADs SOA Fibre loop PBS1 SOA PBS2 PC Reflected clock pulse Clock + data packet in 50:50 Data packet out Reflected Port (Port 1) Transmitted Port (Port 2) Clock recover module Sheffield Hallam University Clock out
  • 14. Simulation Results and Discussion - The model was simulated using Virtual Photonics (VPI) simulation package - Simulation parameters: Parameters Data bit rate (per channel) Clock pulse FWHM width Address bit FWHM width Injection current of SOA SOA length SOA active areas SOA confinement factor SOA Differential gain SOA carrier density transparency SOA Linewidth enhancement factor SOA recombination coefficient A SOA recombination coefficient B SOA recombination coefficient C SOA Initial carrier density Values 2.5 Gbps 1 ns 0.5ns 0.15A 0.5 mm 3x10-13 m2 0.15 2.78x10-20 m2 1.4x1024 m-3 5 1.43x108 1/s 1.0x10-16 m3/s 3.0x10-41 m6/s 3.0x1024 m-3 Cont.
  • 15. Simulation Results and Discussion - OTDM packet Cont.
  • 16. Simulation Results and Discussion Extracted Clock Signal Transmitted Output of TOAD1 Cont.
  • 17. Simulation Results and Discussion Reflected Output TOAD2 (Address bit) Transmitted output of TOAD2 (Payload) Cont.
  • 18. Simulation Results and Discussion Payload at Port 2 of TOAD3
  • 19. Conclusions -A node model for an OTDM router (1X2) for asynchronous packet routing is presented -The switching devices employed for clock recovery and payload routing are carried out in optical domain using TOADs -Simulation results demonstrate that clock recovery, address recognition and payload routing has been achieved successfully Sheffield Hallam University 30
  • 20. Further works - To simulate multiple input and output networks - Crosstalk and noise analysis for multiple input and output networks Sheffield Hallam University 31
  • 21. Thank you

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