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' Centre d'Electronique et de Micro-optoélectronique de Montpellier,

Code Division Multiple Access with MMI mineral organic circuits. Y. Moreau 1 , K.Kribich 1 , P. Coudray 1 P. Etienne 2 , J.Galy 3. ' Centre d'Electronique et de Micro-optoélectronique de Montpellier, Université Montpellier II, France

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' Centre d'Electronique et de Micro-optoélectronique de Montpellier,

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  1. Code Division Multiple Access with MMI mineral organic circuits • Y. Moreau1, K.Kribich1 , P. Coudray1 • P. Etienne2, J.Galy3 . ' Centre d'Electronique et de Micro-optoélectronique de Montpellier, Université Montpellier II, France 2Laboratoire des Verres, Université Montpellier II, France 3 Laboratoire d’Informatique, de Robotique et de Microélectronique, Université Montpellier II, France

  2. Integrated optics • Data Exchange: + 85 % /year • Voice traffic : + 10% /year • Integrated optics was a next day technology for thirty years ! • 55 % of Europeans have not yet emails. • IDC (consultant) predicts 28 millions of connected objects to the Web sold in 2002 in the US => Now optical technologies have their « niche »: channel multiplication and broad band transmission.. => high demand for high rate. • Available rates reaches now 5 Terabits/sec « DWDM has proven to be one of the hottest niches in the telecommunications market. » • Highways for telecoms :rather underwater (optical fibres) than in the sky (satellites). DWDM market: US $ 8 billions in 2003

  3. Materials for Integrated Optics Electronics Compatibility Active Circuits Passive Circuits Optical fiber Compatibility Cost      Semi-conductors     Glasses      Dielectric layers      Polymers       Lithium Niobate

  4. Mineral Organic UV Mask   Cost Substrate   Temperature   Transparency   Thermal stability   Mechanical stability   Layer deposition Our choice : organic-inorganic material mineral network (sol-gel)=> • Reticulation organic network • Polymerization (UV) => Index change to write optical circuits

  5. Output beams: equal intensities, different phases Input beam The set of output phases depends on the selected input Simulation of a MMI device available onInternet : http://w3.cem2.univ-montp2.fr/~moreau/ Multimode interference devices Multimode interference appears when exciting a large guide, where each mode has its propagation speed Photograph of the outputs of a 1 x 32 power divider:

  6. l =1.548µm l =1.550µm =1.552µm l l =1.554µm Wavelength Division Multiple access : WDM made with our organic-mineral technology: • Two Multimode interference devices: • a splitter in input, • a combiner in ouput An array of single mode guides to build a set of phases depending on the wavelength

  7. New approach to share the optical bandwidth : Code division multiple access (C.D.M.A.) Radio frequency CDMA is used in third generation mobile telephony (UMTS) Optical CDMA : • Optical make coders and decoders • Difficult interception : appears as noise when code is unknown • « soft » division versus WDMA • Can maximize the number of users • Can use non coherent sources (super LED, EDFA). Several variants : Various implementations : • time CDMA with unipolar codes (Salehi) • time CDMA with bipolar (phase) codes (Salehi-Wiener) • spectral encoding (Nguyen, Zacarrin, Kavehrad) • spectral with synchronizing pulse (Lam) • fast frequency hopping (Rusch) • array of fibers, • array of MachZehnders, • free space gratings

  8. Code CA = [1,-1,1,1,-1,1,-1,-1] Code CB = [-1,-1,1,-1,1,1,-1,1] coded [C ;-C ;C ] A A A Basics of CDMA Each symbol « 1 » or « 0 » is coded as a sequence of « chips » (time CDMA) or as a spectrum (wavelength CDMA) Message A :[1,0,1]=> MessageB: [1,1,0]=> coded [ CB;CB;-CB] Transmitted = Sum of coded signals: A + B + C = (Transmitted * CA) A -decoding : correlation with + Low pass filtering (time CDMA) C A

  9. star Coupler=> spectrum "0" coupler WDM Transmitter implementation : Message A M M broad Coupler=> spectrum "1" M M band I I Source Other messages • The WDM makes the spectral encoding. Input switching = code switching. • Non coherent source (such as E-TEK BLS 1300: bandwidth=50 nm). • Gap between spectrum wavelength components, depending on symbol rate.

  10. Coupler=> spectrum "0" WDM Decoder receiver M M Coupler=> Balanced photo-diodes M M spectrum "1" I I The sum of other codes yield balanced detection Orthogonal codes : • Unipolar codes (Salehi) for time CDMA = time distribution of a few short pulses => few users • Hadamard Walsh codes : generated with Hadamard matrix, null cross correlation, can ’t be used in time CDMA for synchronisation (autocorrelation too high). • m-sequences: generated as random sequence, quasi orthogonality, allows theoretically a great number of users • Gold codes : combination of codes from m-sequences.

  11. Conclusion: • Organic-mineral technology has many qualities : low cost, simple process, versatility... • Index change (to write optical circuits) is directly and simply created by UV polymerisation, adjustable up to 0.03 => Multiple access to the optical link: • Wavelength division multiplexing (WDMs), • Code division multiplexing (CDM • Visit our web site : http://www.cem2.univ-montp2.fr/~moreau/

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