After some minor adjustments for the laser done by Rodolfo, the laser is back 
at ESR and visible by the PD-SO.
We checked the timing between the cooling signal of the e-cooler and the 
signal produced of the PD-SO, which is suppose to be at the end of the 
cooling ramp - seems to work as expected. Picture is attached.

Note added (Carsten): The "cool" signal is generated by the microcontroller. It 
is only in sync if the laser signal is put on the input line to the microcontroller. 
Otherwise both have independent clocks.