All-Optical Signal Processing Technologies for Network Applications Prof. Paul Prucnal Department of Electrical Engineering PRINCETON UNIVERSITY Globecom Access 06 Business Forum Advanced Technologies for Optical and Wireless Access and Metro Networks Prof. Chunming Qiao and Dr. Ting Wang, Chairs November 29, 2006
Virtues of All-Optical Processing Uses light to directly control light in a host material without any intervening electronics. Bandwidth High carrier frequency provides large information bandwidth Simplicity Avoids the cost & complexity of optoelectronic conversion Parallelism Processing of multiple wavelengths occurs simultaneously Performance Switching times can be much faster than electronics
All-Optical Processing in Today s Long-Haul Networks is used primarily for transport. Wavelength Division Multiplexing Raman Amplification and Dispersion Compensation Erbium Doped Fiber Amplfiers Bandwidth X Distance [bits/sec X Km]
The Performance of Today s Switching Technology in Optical Networks 7 th Avenue, NY City, c. 1910, prior to introducing first traffic control devices in 1915.
Limitations of Electronic Switching Electronic switching speed is limited by the carrier transit times of electrons and holes across transistor gates (nanosecs or picosecs). Limit determined by minimum gate length and carrier mobility e.g., 25 nm base, 75 nm collector, 509 GHz. Univ. Illinois, 2004
Dynamic Wavelength Switch/Crossconnect 2D MEMs Technology IEEE Communications Magazine March 2002, page89 MEMs can be switched at glacial speeds!
The TOAD: Ultrafast All-Optical Switch x soa SOA Control 1 t cs Mach Zehnder Control Data SOA Output SOA F Data F Output Control 2 Terahertz optical asymmetric demultiplexer Employs differential fast onset of nonlinearity in an interferometer Ultrafast switching speed ~1Tb/s Low switching energy, < 100 fj Low crosstalk and polarization sensitivity Loop: Sokoloff et al, IEEE Photonics Technology Lett., 5, #7, pp 787-790, 1993 Mach Zehnder: K. Kang et al., Electronics Lett., Vol. 31, Issue 9, 27 April 1995, 749 750.
Multiple Functionalities of the TOAD (a) All-optical sampling Deng et al, IEEE PTL,10, pp397, 1998 (b) Optical switching and routing IN PS 2τ 1x2 Header TOAD 1 Clock Read Address Delay OI SOA Route Packet TOAD 2 Glesk et al, Electron Lett, 30, pp339, 1994 OUT 1 OUT 2 (c) Optical signal regeneration (d) Demultiplexing Wang et al, Opt Commun,199, pp83, 2001 Glesk et al, Electron Lett,30, pp339, 1994
100 GHz Optical Sampling Oscilloscope 80 ps 80 ps 20 GHz Photodetector -100-50 0 50 100 Calibrated Time (ps) Signal from a 20GHz photodetector followed by a 50GHz oscilloscope -100-50 0 50 100 Calibrated Time (ps) Terahertz-sampled & downconverted waveform on 100 MHz oscilloscope Deng, K. et al, IEEE Photonics Tech. Lett., Vol. 10, No. 3, March 1998.
00 Gbit/sec Optical Routing in ShuffleNet TOAD Packets Look-up ADD Routing control TOAD Crossbar Switch Node Receiver DROP 0 1 2 3 00 4 5 6 7 10 0 1 2 3 10 4 5 6 7 11 Rx Header at TOAD Outputs Digital Threshold Switch Optical Outputs TOAD 1 TOAD 1 Threshold Memory Memory Up Up TOAD 2 TOAD 2 Threshold Down Down Receive Receive 0 4 1 7 0 4 1 7 0 4 1 7 Toliver et al, IEEE/OSA J. Lightwave Technol., 16, # 12, 2169-2180, 1998
All-Optical Regeneration interplay of cross-gain and cross-phase modulation in the TOAD restores pulse sha Noisy Data Reshaped Data CW Light Probe light TOAD Tunable filter Kailight Photonics Input OSNR = 18dB/0.1nm Output OSNR = 35db/0.1nm Chayet, H. et al., Optical Fiber Communication Conf., Volume 5, 6-11 March 2005, Vol. 6.
All-Optical Wavelength Management Blocking occurs if two channels with the same color are routed to the same output port. Wavelength conversion resolves contention. C D TOAD Wavelength conversion demo With λ converters B E New request E D Input Data New Color TOAD Output Data Xu, L. et al., IEEE Photonics Tech. Lett., Vol. 15, No. 2, February 2004.
100Gb/s reconfigurable OTDM interconnect OTDM Tx1 CH 1 All-Optical Demultiplexer OTDM Tx1 CH 2 Σ TOAD OTDM Tx3 CH 3 10 ps Clock TDL Experimental results Chan 1 Chan 2 Chan 3 1 random 1 30 ps/div 10 ps 10 ps/div 1 30 ps/div 1 Chan1 random 1 random 1 Chan 2 Chan 3 1 Input channels MUX 100 Gb/s TDM frame Received channels Deng, K. et al., J. Lightwave Tech., Vol. 18, No. 12, December 2000.
Passive Optical Networks Access networks require flexibility, low cost, and support for diverse traffic & bandwidth. etro Core synchronous Passive Splitters Optical Network Units asynchronous 1550nm CATV 15xx DWDM Business & Residential Access Current access technologies don t provide flexibility: TDM based approaches require ranging for synchronization WDM PONs provide a path for upgradeability but lack flexibility, fine granularity and capability for QoS provisioning
Code Division Multiple Access (CDMA) Wireless CDMA Fastest growing wireless technology Allows: Asynchronous multiple access Frequency reuse Provides: Immunity to interference Fine granularity, variable QoS, variable data rates Soft blocking Leverages burstiness to increase capacity Cellular Systems Optical CDMA Why? WDM has hard limit on the number of users OTDM needs synchronization Apply concept of wireless CDMA to optical domain λ 1 λ 2 λ 3 λ 4 OCDMA encoder T bit T bit Incoherent OCDMA Example: time/wavelength encoding (also spectral amplitude, spatial coding etc ) Φ 1 Φ 2 Φ 3 Φ 4 OCDMA encoder T bit T bit Coherent OCDMA Example: temporal phase encoding (also spectral phase encoding etc )
Incoherent Optical CDMA OCDMA Tx Data OCDMA Rx OCDMA Encoder 1 OCDMA Decoder 1 Receiver Electronics Data OCDMA Domain OCDMA Decoder N Receiver Electronics OCDMA Encoder N N λ 1 2 N t Wavelength-hopping time-spreading OCDMA 2 1 Multi λ source D E M U X TDL TDL TDL M U X D E M U X TDL TDL TDL M U X TOAD Asynchronous multiple access Fast (GHz) code selection achieved with tunable delay-line coders & decoders Incoherent transmission is robust to fiber nonlinearities (>50 km simulated)
Probability of Error Some Advantages of OCDMA Soft Blocking Variable data rates and QoS 10-2 10-4 asynchronous (4,101) CH Prime Code High QoS, Low Data Rate 10-6 10-8 10-9 10-10 Low QoS, Low Data Rate 10-12 10-14 Number of simultaneous users High Data Rate, High QoS
TOAD-based OCDMA receiver Multiaccess interference Auto-correlation (desired data) Gated Auto-correlation Electronic Data Gated Output OCDMA Decoder TOAD TOAD control signal D Probability of Error Input with MAI 2ps TOAD gating window P.R. Prucnal, Optical Code-Division Multiple Access: Fundamentals & Applications, Taylor and Francis, 2006. 0 50 Number of simultaneous users 100
Advantages of OCDMA in Networks PON Proce ssor Mem Interconnects Proce ssor Mem... Proce ssor Mem LAN high data rates per user variable data rates & QoS soft blocking & scalability asynchronous multiple access scalability high data rates per user variable data rates & QoS soft blocking & scalability FSO Metro high data rates flexible network planning immunity to interference scalability flexibility security
Summary Optics already provides high B L providing the backbone for global networking Nonlinear optics offers the promise of all-optical signal processing Optical sampling & A/D conversion Signal shaping and regeneration Optical switching and logic Ultrafast demultiplexing for OTDM and OCDMA Application areas Scalable passive optical networks - soft blocking, multi-rate, multi-qos Metro networks scalability, steganography and physical security Ultrafast A/D for wireless performance enhancement