The cathode of the Avalanche Photodiode should be connected to APD pin of MAX15059 instead of the output. The output of MAX15059 should be connected to pin BIAS directly or through a low-pass filter. The BIAS pin is connected to APD pin through a current limit circuit internally. The APD pin could provide voltage to Avalanche Photodiode and limit its current. But if connect the Avalanche Photodiode to output, then there will be no current-limit function.