  Optical amplification, crucial for modern communication, primarily relies on
erbium-doped fiber amplifiers (EDFAs) to enhance signals without distortion.
However, EDFAs only cover a portion of the low-loss spectrum of optical fibers.
Optical parametric amplification, utilizing material nonlinearities, offers
expanded capacity, but has faced limitations in gain and bandwidth. Addressing
this, we present a high-gain continuous-traveling-wave parametric amplifier,
surpassing the erbium gain window. Leveraging low-loss gallium
phosphide-on-insulator photonic integrated waveguides, we achieve up to 35 dB
of parametric gain, with a fiber-to-fiber net gain exceeding 10 dB across a
wide wavelength range of approximately 140 nm centered at 1550 nm. We
demonstrate the capability to amplify ultra-weak signals, extending over 6
orders of magnitude of input powers, optical frequency combs, and communication
signals, highlighting the practical potential of our photonic-chip-based
amplifier.
