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

Tuning the wavelength of a colorless laser transmitter, used to build an upstream channel in the WDM-PON transport domain of a 5G mobile radio access network, to the wavelength of the maximum transmission of its multiplexer channel is implemented by a number of regulated and proactive procedures. The first include the procedures associated with the construction of the AMCC control and management channel, regulated by the ITU-T G.989.3 recommendation. The second is the construction of systems with probing of the complete structure of the ascending channel of the pass and reflective types. The main attention in the article will be paid to the consideration of reflective type systems. Broadband and single-frequency reflective methods for tuning direct modulation lasers: VSCEL, DFB, DBR, and external modulation lasers: integral module on InP-substrate, with direct detection and heterodyne reception are analyzed, their advantages and disadvantages are determined. The transition to modulation reflectometric methods of tuning is substantiated, for which one-, two- and three-frequency technologies for multiplexer probing based on EML lasers with scanning are proposed. The use of both latter methods makes it possible to increase the signal-to-noise ratio, sensitivity and accuracy of multiplexer spectral characteristics measurements, and, consequently, the accuracy of tuning the wavelength of a colorless laser transmitter to the central wavelength of one of multiplexer channels.