Zero-Dispersion Wavelength Estimation and Optimization Method for Penalty-Free and Equalizer-Free 53-Gbps/ IM-DD Transmission Over 100 Km

We propose the method to estimate the zero-dispersion wavelength (ZDW) and to optimize the emission wavelength for high-speed intensity modulation and direct detection (IM-DD) transmission. The feature of this method can estimate the ZDW by using the unique notch frequency caused by chromatic dispersion from the frequency spectrum of the received signal, and reduce chromatic dispersion by tuning the emission wavelength to the estimation value of the ZDW in a configuration that using only general transmitters/receivers without additional dedicated equipment. With the proposed method, the limitation of transmission distance can be relaxed in high-speed IM-DD transmission without using a dispersion compensation device or an equalizer. We experimentally demonstrated that the notch frequency was observed at a condition of the pseudorandom binary sequence (PRBS) 2(15)-1 and 2(31)-1 non-return-to-zero (NRZ) signals at 53.125 Gbps for a total 80 and 100 km, and the ZDW was estimated with fast Fourier transformation sizes of 256, 512, and 1024. The results indicated that the proposed method can be estimated with an accuracy of about +/- 1 nm from the true value of the ZDW. In addition, to confirm the feasibility of the proposed method, we experimentally demonstrated that PRBS 2(15)-1 and 2(31)-1 NRZ signals at 53.125 Gbps were transmitted over 100 km by tuning the emission wavelength to the estimated ZDW value. For the ZDW with a true value of 1312.20 nm, the chromatic dispersion penalty was up to 1.5 dB under the conditions of a 53.125 Gbps NRZ signal with an emission wavelength of 1303.73 nm and a transmission distance of 100 km. Penalty-free and equalizer-free transmission was demonstrated by applying this method.