Z. Ghassemlooy , H. Le Minh, and Wai Pang Ng Optical Communications Research Group

1. Investigation of Header Extraction Based on Symmetrical Mach-Zehnder Switch and Pulse Position Modulation for All-Optical Packet-Switched Nnetworks Z. Ghassemlooy, H. Le Minh, and Wai Pang Ng Optical Communications Research Group Northumbria University, UK http://soe.unn.ac.uk/ocr/ ICEE2006, Iran

2. Contents • Overview of header processing in optical networks • Header processing based on pulse-position modulation (PPM) and the proposed node architecture • Header extraction module (HEM) • Simulation results: HEM, Node and Network Performances • Summary

3. Demand traffic [bit/s] NEC-2001 1P 100T 10T 1T 100G 10G 1G 100M Total Data Voice 1995 2000 2005 2010 Year Optical Communication Network (OCN) • Future OCNs: faster signal processing and switching to cope with the increase of the demanding network traffic • Existing OCNs: depends on electronic devices for processing the packet address to obtain the routing path. However, the limitation ofelectronic responsewill cause thespeed bottleneck • Solution:All-optical processing & switching  Photonic network

4. Optical transparent path Future OCNs • Future OCN will have the processing and switching data packets entirely in optical domain, i.e. generateoptical transparent pathfor routing data packets •  Require:compactandscalableprocessing scheme

5. N-bit Port 1 ? Port 2 Port 3 Current All-optical Processing Scheme Routing table (RT) Example:N = 4, node with M = 3 • All-optical logic gates • All-optical correlators • Problems: • Large size routing tableincreased processing time • Optical device complexitypoor scalability • Solution: • Reduce the size of the routing table

6. H SW1 SW2 SWM PPRT Entry 1 Entry 2 ... Entry M Data Data H H C C lk lk & 1 & 2 & M Proposed Node with PPM Processing All-optical switch 1 • Clock extraction: synchronize the arrival of data packet and the node processing • S-P converter: convert the serial address bits to parallel bits • PPM-ACM: (PPM address conversion module): convert binary address to the PPM-converted address • PPRT: store M entries (M PPM frames) • Switch synchronisation: synchronise SW with data packet • All-optical switch: controlled by matching signals to open the correct SW 2 ... M S - P ... PPM - ACM Converter Clock extraction ... Switch Sync. ... Header processing unit

7. Data packet (a) (b) payload a0 a1a2a3 Clk Address extraction PPM Header (packet address) PPM-HEM No of slots = 2M PPM – Concept/Operation

8. PPRT Generation • Is self-initialised with the extracted clock pulse. The M entries are filled by: • Single optical pulse + Array of 2N optical delay lines; Or, • M pattern generators + M optical modulators.

9. PPM Based Routing Table Pulse-position routing table (N = 4, M = 3) • Grouping address patterns having the same output ports • Each new pulse-position routing table (PPRT) entry has optical pulses at the positions corresponding to the decimal values of group’s patterns

10. Processing-time gain: Header Correlation Matched • Single AND operation is required for matching PPM-address and multiple address patterns (PPRT entry)

11. A A×B SOA1 B SOA2 SMZ Based AND Gate Implementation: Using optical interferometer configuration + optical nonlinear devices Symmetric Mach-Zehnder Interferometer (SMZI)

12. Problems: 1-Residual power due to large TSW 2-Low extinction ratio ~ 10 to 15 dB SPC a3 a2 a1 a0 SMZ3 SMZ2 SMZ1 SMZ0 Clk TSW (Extracted) SOA1 SOA2 a0 a1 a2 a3 HEM: Serial-to-parallel Conversion (SPC) 1- SPC diagram 2- SMZ interferometer

13. Problem: Multiple pulseat the PCM-ACM output instead of onlyy(t) SPC due to low switching extinction ratio of SW HEM: PPM-ACM 1- N-bit address-codeword: A = [ai {0,1}], i = 0, …, N–1 2- PPM-format address: y(t) = x(t + iai2iTs)

14. SW HEM: PPM-ACM Solution: Combine 2 SMZs in their complement switching modes by single control pulse 1- SMZ1 in ON state  SMZ2 in OFF state 2- SMZ1 in OFF state  SMZ2 in ON state Achieved high switching extinction ratio for SW (>30 dB)

15. CP1 1 SMZ-1 1 M CP2 2 SMZ-2 … CPM M SMZ-M Hall-Optical Switch

16. Simulation Results – HEM Performance SOA parameters Packet parameters

17. SPC Simulation Results – HEM Performance The PPM-ACM extinction ratiobetween y(t) power andundesired multiple-pulseat PPM-ACM output against Tsw for the best and worst cases (among 2N) This ratio ~ 30 dB for TSW = 1ps

18. Simulation Results – Node Performance For an all-optical core network up to 25 = 32 nodes

19. Simulation Results – Node Performance Demonstrate the PPM processing and Tx modes PPRT with 3 entries:

20. Input Output 1 Port 1 Input Port 2 Output 2 Port 3 Output 3 Simulation Results – Node Performance

21. Simulation Results – Node Performance 0 1 1 1 0 Packet with address 01110 PPM-converted address PPRT entry 1 Synchronized matching pulse

22. Simulation Results – Network Performance 1- Multiple-hop OSNR 2- Predicted & simulated OSNRs

23. Conclusions • PPM processing scheme • Reduces the required processing time • Provides the scalability: adding/dropping network nodes and node outputs • Applications: • All-optical core/backbone networks (N > M ~ 3-6) • Optical bypass router (electrical router + optical bypass router) • Challenges: • Optical switch with long and variable switching window • Timing jitter and received pulse dispersion

24. Acknowledgements • Northumbria University for sponsoring the research work

25. Thank You!

26. H SW1 SW2 SWM PPRT Entry 1 Entry 2 ... Entry M Data Data Data H H H C C C lk lk lk & 1 & 2 & M Node with Multicast Tx Mode All-optical switch 1 2 ... M S - P ... PPM - ACM Converter Clock extraction ... Switch Sync. ... Header processing unit