I made a script called SlowVoltageToHertzCalibration.py in the ctn_labdata/scripts/ Git repo.  It takes in a cavity scan like those found in ctn_labdata/data/20170817_LaserSlowFreqScan_RefCavResonances, with Laser Slow Control Voltage in the first column and Cavity Transmission DCPD Voltage in the second column.  The cavity scan changes the slow voltage between -10 V and 10 V.  Transmission light peaks with each FSR, and for the higher order modes... The script sorts out which peaks are the carrier peaks, finds the average slow voltage difference between peaks, and compares it to the FSR to generate a calibration.

The North Path laser slow control calibration is 3480.89915798  3480 MHz / SlowVolt

The South Path laser slow control calibration is 3644.56423675  3640 MHz / SlowVolt

The FSR for both cavities is 4069.94919902 4070 MHz for a cavity of length 3.683 cm.  The laser frequency is 281 THz.  (1 THz = 1000 GHz)

Cavity scans are shown below for convenience (except that I used a linear y-scale, so its not actually very convenient).