ApcCal bit in oemcal0 is used to turn the APC function,
At the factory, the APC is off default.
When the APC is closed, the value back of the APCSetx register is directly transmitted to the VBIAS DAC, which does not consider Lookup Table, which can directly control the Laser Diode Bias when Setup and Calibration.
When the APC is turned on, the value in the APCSETX register is added to the value corresponding to each temperature in the Lookup Table, and transferred to the VBIAS DAC.
ApcCal bit 0 Normal Mode on
Apcal Bit 1 Calibration Mode OFF
