Demonstration of Reconfigurable and Tunable Optical Format Aggregation of Two Independent Channels Using Nonlinear Wave Mixing

Optical communication networks employ various modulation formats depending on the performance capabilities and desired functionalities of their different zones. Different modulation formats may be used in different parts of a network, such that an edge node may aggregate multiple channels of lower-order formats into a single channel of higher-order format. In this work, we experimentally demonstrate the optical data aggregation of two independent channels into a single higher-order format channel using nonlinear wave mixing. By transmitting each data channel with two coherent pilot tones, we apply complex weights to the input data channels and shift the output constellation by a bias vector. These functions are achieved in a periodically poled lithium niobate (PPLN) waveguide. We show that our system is format reconfigurable, allowing for both amplitude- and phase-encoded inputs and that the two inputs can be in different formats. Moreover, we demonstrate the tunability of our approach by performing aggregation at two separate baud rates, 3 and 5 Gbaud. Bit error rate (BER) measurements for our cases show a power penalty is < = 1 dB for the aggregated quadrature phase shift keying (QPSK) output. Overall, we have shown the following format aggregations: (i) two on-off keying (OOK) inputs to one QPSK, (ii) two binary phase shift keying (BPSK) inputs to one QPSK, (iii) one OOK and one BPSK inputs to one QPSK, (iv) two 4-level pulse amplitude modulations (PAM4) inputs to one 16-ary quadrature amplitude modulation (16QAM), (v) two QPSK inputs to one 16QAM, and (vi) one QPSK and one 16QAM inputs to one 64QAM.