Here is a quick overview of the OCT (Optical Coherence Tomograhphy) testers from OCTPRO.
The OFE-001 is a fiber pigtailed compact optical incremental frequency encoder that can measure the instantaneous optical frequency change of tunable lasers or other light sources.
OFE-DSP incorporates a DSP circuitry with OFE-001 to output absolute optical frequency in both analog and digital formats.