3. July 2007 David Britz AT&T Labs Slide To deliver greater bandwidth, every new 802.11 standard has historically demanded new spectrum allocation! As an example 802.11n, to deliver 100Mbs requires spectrum at 40 MHz channels. So what spectrum will be needed for Gigabit WLAN’s? How many bits per Hz? (cheap or expensive systems) Does the FCC even have the available spectrum needed to support Gigabit WLAN’s? To follow Moore's Law in bandwidth scaling, perhaps it’s time to consider going above the FCC’s spectrum purview!

4. July 2007 David Britz AT&T Labs Slide How many 1 gigabit channels are available (assuming 2.5 Gigahertz channel spacing)? 2 (channels) 3 (channels) 1 (channel) 6 (channels) 8 (channels) 10 (channels) 5 (channels) 4 (channels) 2 (channels) 6 (channels) 10 (channels) 10 (channels) 4 (channels) 5 (channels)

5. July 2007 David Britz AT&T Labs Slide Terahertz Frequencies ter·a·hertz (tĕr ' ə-hûrts') n. ( Abbr. THz) One trillion (10 ) hertz. So what’s it good for? Truly enormous bandwidth per channel (10-100+ Gbps)! But nature gives you nothing for free Think short distances 10 -100 meters 12

6. July 2007 David Britz AT&T Labs Slide X Ray Energies Radio Energies Ultra Violet Energies Far Infra Red Energies 0.001 µm 0.4 µm 0.75 µm 3.0 µm 30.0 µm 1.0 mm Radio Spectrum Spectra of Optical, Terahertz and Radio Frequencies Visible Light Current Commercial Radio Spectrum “ Optical” Spectrum Mid Infra Red Energies Near Infra Red Energies 0.91 µ 1.5-1.6 µ ITU 1.3 µ 10 µ 0.85 µ 1.0 µm 1000.0 µ 1.0 µm= 1 Millionth of a Meter 25.4 µ = 1/1000 of an inch 75 µ (3/1000”) thickness of human hair Scale: “ Terahertz” Spectrum 1nm channel @1550nm = 124.8 GHz 1.0 nm = 1 Billionth of a Meter Wavelength 300.0 µm 1THz 1.0 THz = 1000 GHz (300 µm) Thickness of 4 human hairs 0.4 -0.75 µm= Visible light 10 THz 300 GHz FCC Cutoff 100 THz 100 GHz spacing Current Commercial Optical Fiber & FSO Spectrum There is plenty of unused spectrum out there We Just haven't figured out how to use it 100 GHz Advanced Laser designs provide optical channels at Visible Light Energies

7. July 2007 David Britz AT&T Labs Slide Optical Photon Emission Tightly bound electrons can only move when provided discreet (quantized ) excitation energy matching a particular shell radius. Electrons closer to the binding nucleous require more excitation energy. The higher the energy the shorter the wavelength (higher frequency) photon released. - Conservation of Energy Excitation energy gained by an accelerated electron (momentum) is released by the electron as an electromagnetic disturbance called a photon λ Terahertz Photon Emission Unbound electrons oscillating within a magnetic field (Free Electron Laser) Intermediate excitation levels, intermediate wavelengths released λ - e‾ + Radio Photon Emission Loosely bound electrons jumping between the outer electron shells of conductor atoms. Lower energy excitation needed, lower energy (longer wavelength) Released. - + - - λ e‾ + +

8. July 2007 David Britz AT&T Labs Slide The Absorption Chasm Between The Optical And Radio Electromagnetic Spectrum Terahertz

9. July 2007 David Britz AT&T Labs Slide 100 THz 3 µm 10 THz 30 µm 1 THz 0.30 mm 100 GHz 3 mm 10 GHz 30 mm 0.1 100.0 1000 1.0 10.0 ATTENUATION dB/Km DRIZZL 0.25mm/Hr Heavy Rain 25mm/Hr Deluge 150mm/Hr FOG (0.1gm 3 Visibility 50m 20” 1Atm H 2 O H 2 O H 2 O H 2 O CO 2 CO 2 CO 2 O 2 O 2 H 2 O 1000 THz 0.3 µm Visible Millimeter Sub-Millimeter Infrared 0.01 O 3 Avoiding Deep Molecular Absorption Bands Broadening IR spectrum into longer wave Broadening Radio spectrum into Sub Millimeter wave 1000 dB/Km wall FCC 300GHz Radio Boundary Existing Optical Fiber & FSOC Commercial RF Spectrum

11. July 2007 David Britz AT&T Labs Slide FSOC P to P & Mesh P to MP 10 feet 100 feet 1 mile 10 miles 1 Peak Data Rate Range Wider Area, More Mobility 10 100 4G Wireless NAN 2.4 & 5 GHz 4G H/S Wireless LAN 2.4 & 5 GHz Unlicensed 3G/802.16 Wireless Various Bands 3G/MAN Fixed or Pedestrian Higher Rate, Less Mobility Megabits per Second/User 2.5G Mobile/Pedestrian 3G/MAN Mobile .1 Bluetooth PANs 2.4GHz and UWB ZigBee (Europe) 2/2,5G Wireless 800 MHz, 2 GHz ZigBee ZigBee (US) UWB Slide provided by Robert R. Miller, Director AT&T Labs Research THz Shrinking Radio Cell Size

12. July 2007 David Britz AT&T Labs Slide Electronic Entertainment, Gaming, Shopping, Smart Home And Medical Monitoring PAN’s Education, Business Information And Telepresence Services In Home Terahertz Network Entertainment Productivity 2005+ Vision GATEWAY Utility IP Home QoS Networks Metallic Narrowband Optical Fiber Legacy Eqpt. Wireless 4G Radio FSOC Audio Video Telematics Vehicle Monitoring Etc… Wireless Terahertz TV VCR Audio System Remote Control Camcorder... PC Printer Scanner... Phone Fax Environmental Security Medical & PAN’s Domestic apps… Wireless Terahertz Electronic Entertainment, Gaming, Shopping, Smart Home And Medical Monitoring PAN’s Education, Business Information And Telepresence Services In Home Terahertz Network Entertainment Productivity 2005+ Vision GATEWAY Utility IP Home QoS Networks Metallic Narrowband Optical Fiber Legacy Eqpt. Wireless 4G Radio FSOC Audio Video Telematics Vehicle Monitoring Etc… Wireless Terahertz TV VCR Audio System Remote Control Camcorder... PC Printer Scanner... Phone Fax Environmental Security Medical & PAN’s Domestic apps… Wireless Terahertz FoodMart FoodMart

13. July 2007 David Britz AT&T Labs Slide Terahertz (GigE) up/down link From terminal to airplane Terminal Link (fiber back to building ) Airplane Link Short distance Terahertz links use low power safe wavelengths and are capable of transmitting GigE capacity Autonomous reading (imaging scanning) of freight destination tags In-Plane broadband connectivity

14. July 2007 David Britz AT&T Labs Slide 3 Tiered Overlay / Underlay Optical Fiber, FSOC, Terahertz Access Network Layers are transparent and non-interfering with each other

15. July 2007 David Britz AT&T Labs Slide Nano Wire Terahertz detector chip level device University at Buffalo; Andrea Markelz and Jonathan Bird MIIM Terahertz detector announced May 16 th 2006 EE Times 2 µm SiO2 encapsulated Nb microbolometer Array Free electron laser producing terahertz radiation from localized surface charges moving across a grating Vermont Photonics An electromagnetic wave is produced by this broadband short-pulse terahertz source when a dc bias is placed across the antenna and an ultra short pump-laser pulse is focused in the gap. Terahertz wireless links will connect the customer or device to the surrounding network or to other devices via short distance , intelligent, cooperative and widely distributed In-building and terrestrial wireless access points. (Micro - Municipality model) Examples Of Terahertz Sources and Receivers

16. July 2007 David Britz AT&T Labs Slide Creating Imaging systems at Terahertz frequencies is conceptually and practically easy. Building a robust communications infrastructure is not! P-to-P P-to-MP Free Space Terahertz Transmission LOS O to T Optical Signal Electromagnetically Driven Modulators 10¹ ² Hertz Optical Signal Source T to E Tx Module Rx Module Optical Modulation RF Signal Processing AD AD Demodulator Decoder Data Baseband Q I Direct Optical Signal Processing T-to-O? Phase Based on maturing transceiver devices, Bandwidth beyond 100+Gbps are possible

20. July 2007 David Britz AT&T Labs Slide Thank You David Britz AT&T Shannon Labs dbritz@research.att.com

21. July 2007 David Britz AT&T Labs Slide Empirical relationship based on measured liquid water content and using analytic expression based on Mie scattering calculations. Ground effect microclimate Ground Effect On Fog Courtesy of Christos Kontogeorgakis Virginia Polytechnic Institute and State University

22. July 2007 David Britz AT&T Labs Slide At Low temperatures the peak of the blackbody power curve lies in the THz range. The dashed line is the wave number at 1THz, wave numbers from 3.3 to 333.3cm­¹ corresponds to 0.1 to 10THz.