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Updated: Jun 13, 2026

Transmission of Multiple Signals through an Optical Fiber Using Wavefront Shaping
Published on: March 20, 2017
Equalization of nonlinear transmission impairments by maximum-likelihood-sequence estimation in digital coherent
Md Khairuzzaman1, Chao Zhang, Koji Igarashi
1Department of Electrical Engineering and Information Systems, University of Tokyo, Tokyo, Japan. zaman@ginjo.t.u-tokyo.ac.jp
Abstract:
We describe a successful introduction of maximum-likelihood-sequence estimation (MLSE) into digital coherent receivers together with finite-impulse response (FIR) filters in order to equalize both linear and nonlinear fiber impairments. The MLSE equalizer based on the Viterbi algorithm is implemented in the offline digital signal processing (DSP) core. We transmit 20-Gbit/s quadrature phase-shift keying (QPSK) signals through a 200-km-long standard single-mode fiber. The bit-error rate performance shows that the MLSE equalizer outperforms the conventional adaptive FIR filter, especially when nonlinear impairments are predominant.
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