We put forward a new theory on Brillouin optical correlation-domain reflectometry (BOCDR) based on arbitrary waveform modulation. We derive a universal representation for the spatial resolution using the foot convexity of the beat spectrum. This result well explains the previous results based on sinusoidal modulation, and thus our theory is the consistent extension of the conventional theory on BOCDR. This representation is also applicable to the spatial resolution evaluation of more complicated modulation schemes, such as the combined use of intensity and frequency modulations even with some phase delay. We also discuss what kinds of modulation waveforms should not be employed for distributed measurement to ensure high spatial resolution.
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