Centralized, Pilot-Tone-Based Wavelength-Locking for WDMPON with 1 GbE Data Rate

In this article an optical network unit (ONU) has been demonstrated with real-time data traffic based on a tunable laser operating without a thermo-electric cooler (TEC) and without an integrated wavelength reference (etalon). Instead a centralized wavelength control system has been deployed, which uses only one shared etalon at the optical line terminal (OLT) to transmit wavelength locking information to all attached ONUs. Different wavelengths can be distinguished in this scheme by different pilot-tones. The control information on wavelength accuracy is provided back to the ONU through an embedded communication channel (ECC). The data rate of the upstream traffic has been set to 1.25 Gb/s (1 GbE). We have shown in a laboratory experiment that the ONU can tune automatically to the desired wavelength and can keep this wavelength within a small tolerance region even when the temperature is changing.