We report a high-energy optical parametric oscillator (OPO) synchronously pumped by a $7.19\mathrm{MHz}$ , Yb:fiber- amplified, picosecond, gain-switched laser diode. The 42-m-long ring cavity maintains a compact design through the use of an intracavity optical fiber. The periodically poled MgO-doped ${\mathrm{LiNbO}}_3$ OPO provides output pulse energies as high as $0.49\mathrm{\mu J}$ at $1.5\mathrm{\mu m}$ (signal) and $0.19\mathrm{\mu J}$ at $3.6\mathrm{\mu m}$ (idler). Tunability from 1.5 to $1.7\mathrm{\mu m}$ and from 2.9 to $3.6\mathrm{\mu m}$ is demonstrated, and typical ${\mathit{M}}^2$ values of 1.5\times 1.3 and 2.8\times 1.9 are measured for the signal and idler, respectively, at high power.