Coherent Subcarrier Processing Node Based on Optical Frequency Conversion and Free-Running Lasers

We demonstrate the use of frequency conversion in optical fiber to implement a coherent add/drop architecture. Its application is experimentally investigated in an optical frequency-division multiplexing scenario with up to three subcarriers which are modulated by quadrature phase-shift keying. We show subcarrier drop and replacement in a bus topology. Furthermore, we quantify tolerances with respect to delay and amplitude mismatch by experiments and simulations. Finally, we discuss on the scalability of the scheme.