Fine wavelength stabilization of the DFB laser at the flexible grid by photo-mixing with reference wavelengths

The lasers for the flexible grid need to have highly accurate wavelength tuning which corresponds to the optical frequency stability within ±0.1 GHz. Instead of the use of the conventional wavelength locker which detects the optical frequency with optical filters, we propose the microwave photonics approach in which the beat signals are generated by photo-mixing with reference lights and filtered by the microwave filter. In this method the frequency accuracy depends on the accuracy of the microwave filter. Experimental results show that the optical frequency is stabilized at the grid with the accuracy of ±0.1 GHz by using the band elimination filter which has the 3-dB bandwidth of 0.1 GHz.