  Integrated optical amplifiers and light sources are of great significance for
photonic integrated circuits (PICs) and have attracted many research interests.
Doping rare-earth ions in materials as a solution to realize efficient optical
amplifiers and lasing has been investigated a lot. We investigate the
erbium-doped lithium niobate on insulator (LNOI). Here, spiral waveguide
amplifiers were fabricated on a 1-mol\% erbium-doped LNOI by CMOS-compatible
technique. We demonstrated a maximum internal net gain of 8.3 dB at 1530 nm
indicating a net gain per unit length of 15.6 dB/cm with a compact spiral
waveguide of 5.3 mm length and $ \sim $0.06 mm$ ^{2} $ footprint. The
erbium-doped integrated lithium niobate spiral waveguide amplifiers would pave
the way in the PICs of the lithium niobate platform, especially in achieving
efficient integration of active and passive devices on a lithium niobate thin
film, which will make full use of its excellent physical properties such as
remarkable photoacoustic, electro-optic, and piezoelectric characteristics.
