Two-Frequency Initialization of the Upstream Central Wavelength in Transport WDM-PON Domain for 5G Mobile Radio Access Networks

To achieve a dense and efficient deployment of RRH microcells and easy initialization of their central wavelengths, tunable colorless laser transmitters are included in the ONU of the transport domain of 5G mobile radio access networks, making it easy to tune and control the radiation wavelength using various mechanisms. In the ONU, upstream wavelength control is necessary due to possible errors in setting the center wavelength during initial connection with OLT (BBU), as well as due to wavelength drift due to aging of the laser transmitter. The paper presents a new method of dual-frequency wavelength initialization in one of the WDM-PON channels, built on AWG, using the process of determining the maximum amplitude modulation coefficient of the probe radiation components beating envelope as a parameter that indicates tuning to its central wavelength. Using the method makes it possible to increase the signal-to-noise ratio of the initialization channel, its sensitivity, and the accuracy of tuning to the center of the AWG channel in comparison with the known methods using the processes of direct detection of single-frequency probe radiation.