Sources	Monochromatic	Collimated	In Phase	Power Output	Inexpensive	Reliable	Stable
LED	OK – poor	poor	poor	low	very good	very good	poor
Laser diode	good	good	good	medium	good	good	good
Gas laser	very good	very good	very good	high	poor	poor	very good

Detectors	Sensitivity	Gain	Bandwidth	Low Noise	Inexpensive	Reliable	Stable
Photoconductors	fair	fair	fair	fair	very good	very good	very good
PIN diodes	good	good	good	good	good	good	very good
Avalanche photodiodes (APDs)	very good	very good	very good (100 GHz)	very good	poor	poor	good
Photo-multiplier tubes (PMTs)	extremely good	extremely good	extremely good	extremely good	very poor	fair	good