Abstract

We propose a configuration for a wideband optical parametric amplifier (OPA) using cascaded periodically poled LiNbO₃ (PPLN) waveguides. These PPLN waveguides have different phase-matching characteristics by controlling the temperature of each waveguide, and thus, the input wideband signal is amplified complementarily. Pump light is shared across the PPLN waveguides. As a result, pump-power-efficient gain bandwidth extension can be achieved. We numerically calculate the gain spectrum of the proposed configuration and show that the optimization of the temperature state of the 2^nd PPLN modules can suppress the generation of excessive gain, resulting in a flat gain spectrum. We experimentally demonstrate an 8.7-THz amplification bandwidth (1545.32–1618.86 nm) with a >15-dB gain in the lower frequency band of the proposed OPA. We also conduct simultaneous amplification experiments with a 67-channel 125-GHz-spaced 120-Gbaud WDM signal over 8.375 THz using the proposed configuration.