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Equalization Strategies for 10-Gb/s Transmission over Multimode Fibre

Equalization Strategies for 10-Gb/s Transmission over Multimode Fibre. Bertram Leesti Ph.D. Candidate Department of Electrical and Computer Engineering June 24, 2005. Motivation. Interest in using installed multimode fibre at 10 Gb/s

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Equalization Strategies for 10-Gb/s Transmission over Multimode Fibre

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  1. Equalization Strategies for 10-Gb/s Transmission over Multimode Fibre Bertram Leesti Ph.D. Candidate Department of Electrical and Computer Engineering June 24, 2005

  2. Motivation • Interest in using installed multimode fibre at 10 Gb/s • Problem: modal dispersion causes severe intersymbol interference (ISI)  Requires adaptive equalization!

  3. Feedforward Equalization • Can be implemented in continuous-time or discrete-time • At multi-Gb/s speeds, continuous-time implementation popular (less power) • Problem with FFE: noise enhancement

  4. Decision-Feedback Equalization • Less noise enhancement than FFE alone since decisions are noise-free • Error propagation can occur • Delay through feedback path limits speed, so look-ahead architecture often used

  5. Max. Likelihood Sequence Detection • Problem with DFE: by canceling ISI, some signal energy is lost • MLSD: • Uses ISI to determine the most likely sequence of bits • Computes metrics for different sequences, and chooses sequence with minimum metric • Complexity grows exponentially with length of channel impulse response • FFE followed by MLSD: • FFE equalizes to a simple response (e.g., 1+D) • MLSD complexity is minimized

  6. Performance Comparison • For this example: • DFE is 1 dB better than FFE • FFE + MLSD is 1.2 dB better than DFE • MLSD is 0.7 dB better than FFE + MLSD • Future work: • Timing recovery • Implementation Fibre impulse responses obtained at http://www.ieee802.org/3/aq/

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