An optical instrument including at least a first and second wavelength swept vertical cavity laser (VCL) sources. The wavelength sweeping ranges spanned by the first and second VCL sources may differ with a region of spectral overlap. The first and second VCL sources may be operable under different modes of operation, wherein the modes of operation differ in at least one of: sweep repetition rate, sweep wavelength range, sweep center wavelength, and sweep trajectory. A VCL source may also exhibit sweep-to-sweep variation. Apparatus and methods are described for aligning sample signal data from the first VCL and sample signal data from the second VCL to generate output digital data. The output digital data is aligned with respect to at least one of: wavelength, wavenumber, and interferometric phase. The apparatus and methods can also be used to phase stabilize successive sweeps from the same VCL source or wavelength swept source.
