December 2019  18  LDC-3706 Series Laser Controller 
 
Photodiode Connections:  Many laser diode modules contain an internal photodiode that monitors 
the back-facet emission of the laser.  Usually, this photodiode is internally connected to either the 
laser anode or cathode.  The photodiode and laser connections of the LDC-3706 Laser Controller are 
electrically isolated from ground and each other.  So, if a 4-pin connection is made (no common 
connections) no additional jumpers are required.  Figure 2.1 shows the recommended connections 
and shielding for 3-pin lasers (where the common connection is internal to the device).  A 4-pin laser 
should be connected with the same shielding as shown in Figure 2.1. It is recommended that the 
laser and photodiode remain isolated when possible.