An optical spectrometer may include: an adjustable sampling space having two opposing side-walls between which in use a sample for analysis is charged and in at least one of which is formed an optical interface translucent to optical energy emitted by an optical energy source; an actuator mechanically coupled to one or both of the opposing side-walls and configured to operate in response to a command signal applied thereto to effect relative movement of the opposing side-walls; and/or an optical position sensor configured to detect interference fringes generated by the optical energy traversing a distance between the side-walls a plurality of times, having passed through the at least one optical interface, and configured to generate the command signal in dependence thereof. The adjustable sampling space may be brought into an analysis position at which the side-walls are relatively inclined to form a wedge shape.