A compact conical diffraction Littrow spectrometer is disclosed. The distortion of the conically diffracted spectral component beams is compensated and as a result, the diffracted spectral beams can still be focused into a substantially straight line to shine onto a detector array. A spectral domain optical coherence tomography (SD-OCT) system incorporating a Littrow spectrometer or a spectrometer having one or more shared focusing element(s) and an SD-OCT system incorporating a spectrometer that is substantially polarization independent are also disclosed.