We demonstrate a subharmonically Fourier domain mode-locked wavelength-swept laser source with a substantially reduced cavity fiber length. In contrast to a standard Fourier domain mode-locked configuration, light is recirculated repetitively in the delay line with the optical bandpass filter used as switch. The laser has a fundamental optical round trip frequency of $285\mathrm{kHz}$ and can be operated at integer fractions thereof (subharmonics). Sweep ranges up to $95\mathrm{nm}$ full width centred at $1317\mathrm{nm}$ are achieved at the $1∕5\text{th}$ subharmonic. A maximum sensitivity of $116\mathrm{dB}$ and an axial resolution of $12\mu \mathrm{m}$ in air are measured at an average sweep power of $12\mathrm{mW}$ . A sensitivity roll-off of $11\mathrm{dB}$ over $4\mathrm{mm}$ and $25\mathrm{dB}$ over $10\mathrm{mm}$ is observed and optical coherence tomography imaging is demonstrated. Besides the advantage of a reduced fiber length, subharmonic Fourier domain mode locking (shFDML) enables simple scaling of the sweep speed by extracting light from the delay part of the resonator. A sweep rate of $570\mathrm{kHz}$ is achieved. Characteristic features of shFDML operation, such as power leakage during fly-back and cw breakthrough, are investigated.