Space-Time Optical Systems for Encryption of Ultrafast Optical Data J.-H. Chung, D. E. Leaird, J.D. McKinney, N.A. Webster, and A. M. Weiner Purdue University Ultrafast Optics and Optical Fiber Communications Laboratory School of Electrical and Computer Engineering & Center for Education and Research in Information Assurance and Security Ultrahigh-Speed Optical Communications Capacity increased at over 2.5x per year. Experiments with 1 Tb/s and higher. Commercial systems with 400-Gb/s. Electronic encryption has difficulties above ~ 10Gbit/s. Our research aims toward using OPTICAL ENCRYPTION BOXES AT THE PHYSICAL LAYER to achieve these high speeds. 1
Progress in Network Capacity [A. R. Chraplyvy; Bell Labs Technical Journal, Vol. 4, No. 1, 1999] Optical Time-Division-Multiplexed (TDM) Transmission Resembles conventional electronic networks. Focus on packet processing including header recognition and encryption of TDM optical data at 100 Gb/s and beyond. Short Pulse Gen Signal Optical Mod ~20Gb/s Modified from [S. Kawanishi, NTT; IEEE Journal of Quantum Electronics, Vol. 34, No. 11, Nov. 1998] Opt Mux 100Gb/s ~ 1Tb/s 2
High-Speed Optical Encryption Box Adapted from [J. Ingle and S. McNown, DARPA/NSF Workshop on the Role of Optical Systems and Devices in Security and Anticounterfeiting (Washington, D.C., 1996)] Necessary Subsystems for Ultrahigh-Speed Optical Encryption Serial-to-parallel converterto allow header recognition and packet processing at rates compatible with electronics Key generator array Ultrahigh-speed optical XOR gate or array of high-speed optoelectronic XOR gates for stream cipher (for example) Parallel-to-serial converter to reform the ultrahigh-speed TDM data stream We are working on novel parallel optical/optoelectronic subsystems to implement the serial-to-parallel conversion, parallel XOR gating, and parallel-to-serial conversion. 3
Schematic of Generalized Space-Time Processing Systems Time-to- Space Converter Smart Pixel Array Space- To-Time Converter Detection Regeneration Permutation Switching Amplification Correlation Bit interleaving Logic operations Encipherment Time-domain Space-domain Time-domain Manipulates optical data in parallel to keep up with high speed stream. Pulse shaper: generate ultrafast test waveforms Time-to-space converter: Serial stream => Parallel data input Smart Pixel optoelectronic array: Digital logic operations like header recognition Space-to-time converter: Parallel data output => Serial stream Time-to-Space Converter gratings E s (ω c ) Nonlinear crystal S(2ω c ) Lens 1 Temperaturecontrolled Lens 2 mount E r (ω c ) 1) Using a reference pulse, we create a spatial replica of the input signal pulses. 2) We have previously demonstrated 500x sensitivity improvement, which is key for operation at realistic power budgets in high-speed systems. 3) In current work, we are moving to a new center frequency, 1560nm, applicable to optical communications. Previous References: [A.M. Weiner and A.M. Kan an; IEEE Journal of Selected Topics In Quantum Electronics, Vol. 4, No. 2, Mar/Apr.1998]] Modified from [P.C.Sun, Y.T. Mazurenko and Y. Fainman; Journal of the Optical Society of America A, Vol. 14, P. 1159, 1997] 4
Time-to-Space Converter Output Images (a) Stack of images produced by varying the delay (b) Mapping image generated by a pulse doublet introduced into the signal beam only (c) Correlation image for identical reference and signal pulse doublets (d) Red spots sorted by the corresponding delay values -80 Delay (ps) 80-1 0.8 Displacement (mm) Digital Logic Operation of Smart Pixel Array Processes the spatially-converted data in parallel, using an array of detectors. The data would be XORed electronically with a stored key to implement a stream cipher. The processed data then drives an optoelectronic modulator array, inserted in a suitable space-to-time converter, to return the data to a serial ultrafast optical signal. Works out to frame rates of a few Gb/s to be able to achieve overall data rates exceeding 100 Gb/s. 5
Optoelectric-VLSI Smart Pixel Array Hybrid CMOS/GaAs from Lucent foundry 200 Optical I/O s High-speed modulator array functionality for ultrafast optical packet generation AND gate array functionality for experiments on ultrafast optical header recognition XOR gate array functionality for experiments on ultrafast optical stream cipher Optoelectronic Array Fabrication at Purdue metallic back reflector back reflector wafer as grown (MBE) p- InAlAs spacer n- InAlAs spacer InP substrate Intrinsic InGaAs/InAlAs MQW x80 InGaAs/InAlAs MQW x80 n- InAlAs spacer p- InAlAs spacer Glass substrate active region n-layers are electrically isolated cavity tuning etch partial reflector n- InAlAs p- InAlAs ohmic contacts back reflector n- InAlAs n- InAlAs MQW p- InAlAs Glass substrate Glass substrate back reflector We have initiated a project to fabricate arrays of optoelectronic modulators operating in the 1.55 mm lightwave communications band. These modulators will be integrated with the direct space to time pulse shaper. 6
Optical Word Generation (Parallel to Serial Converter) Electrical Data IN 1 0 1 1 0 1 1 0 0 1 Optical Packet Generator Optical Data OUT 1 0 1 1 0 1 1 0 0 1 High-speed optoelectronic modulator array combined with ultrafast optical parallel to serial conversion Direct Space-to-Time Pulse Shaping (Optical Parallel-to-Serial Conversion ) at 1.5 mm For high-speed optical encryption and transmission, high-speed sources, operating at communications wavelengths, are necessary. To this end, we are incorporating a high repetitionrate optical source, operating in the lightwave communications band. Actively modelocked Erbium Fiber laser (~1 ps pulses @ 10 GHz, 1.5 µm) To achieve packets with equal intensity features: Use a Diffractive Optical Element (DOE) for beam pixelation Utilize an integrated version of the DST pulse shaper: modified Arrayed Waveguide Grating (AWG) 7
Femtosecond Data Packets Target application of DST. The state of each temporal pulse is determined by the transmission at a unique spatial location. 01 11 10 10 11 001 00 01 11 1 10 00 11 011 00 11 10 01 011 [D.E. Leaird and A.M. Weiner; Optics. Letters Vol. 24, P. 853-856, 1999] -30-20 -10 0 10 20 30 Time (ps) Rate Multiplication Using a DST Pulse Shaper Our method of optical parallel-to-serial conversion has the potential to enable extremely high-speed sources to be created for use in ultrahigh-speed lightwave systems. 10 GHz Fiber Laser (input) Diffractive Optical Element (DOE) DST Input - pulses @ 10 GHz 1 Intensity 0.5 0-150 -100-50 0 50 100 150 psec DST Output -1psec pulses @ 100 GHz 1 Intensity 0.5 0-150 -100-50 0 50 100 150 psec 100 GHz output DST Pulse Shaper (Work in Progress) 8
Integrated Implementation For optical word generation, the function of a bulk optics DST pulse shaper can be achieved in an integrated optic device! Bulk optics Integrated U.S. Quarter DST Arrayed Waveguide Grating (AWG) (Integrated Direct Space-To-Time Pulse Shaper) DST AWG 21 pulses at 500 GHz repetition rate! Input Output 0-25 -20-15 -10-5 0 5 10 15 20 25 Time ( psec) 9
Summary Using novel space-time processing techniques, we are developing exploratory technology that may allow us to encrypt optical data at the physical layer, with particular application to ultrahigh-speed optical TDM transmission. 10