Fiber Parameter-Independent Zero-Dispersion Wavelength Estimation Method and Its Feasibility With Reduced Quantization Bits and Sampling Rates

We propose a method for estimating the zero-dispersion wavelength (ZDW) of an optical fiber independently of fiber parameters and for tuning the emission wavelength for the ZDW to suppress waveform distortion in high-speed intensity modulation and direct detection (IM-DD) systems. By using two emission wavelengths and unique notch frequencies caused by chromatic dispersion (CD) calculated from the frequency spectra (FSs) of each received signal, the proposed method can estimate the ZDW independent of fiber parameters such as fiber length and dispersion slope. The ZDW can be estimated by using the emission wavelength on either the shorter-wavelength side or the longer-wavelength side of the ZDW. To evaluate the feasibility of the method, we estimate the ZDW of 60-km fiber using 50-Gbps pseudorandom binary sequence 2¹¹−1 PAM4 signals at 1300-nm and 1305-nm emission wavelengths. The obtained estimation accuracy of −0.78 nm is sufficiently good when using an 8-bit analogue-to-digital converter operating at a sampling rate of 200 GS/s. We also demonstrate that results similar to the estimated ZDW are obtained even when the number of quantization bits is reduced from 8 to 4 and the sampling rate is reduced from 200 to 50 GS/s. These results show that the functions of the proposed method can be implemented in optical transceivers. On the basis of this configuration, we also achieve penalty-free and equalizer-free transmission by using an emission wavelength tuned to the estimated ZDW. Furthermore, we discuss the challenges associated with implementing the method in practical applications. We show that the BtB FSs required for estimating the ZDW can be replaced with simulated data instead of experimental data, that the method can be applied even at the minimum receiver sensitivity, and that there is no CD penalty when the notch frequency does not appear below the baud rate. Finally, we modify the procedure of the method to be applicable when the notch frequency does not appear within the value of the baud rate. Since this method can suppress waveform distortion due to CD independently of baud rate, it is applicable to higher speed transmission systems with a larger capacity of 100 Gbps or more.