Absolute noise characterisation of avalanche photodiodes

Excess noise in four types of commercially obtained avalanche photodiodes (a.p.d.s) has been measured absolutely, by comparing avalanche noise from the a.p.d. with shot noise from an illuminated p-i-n diode. The method used yields directly the noise-current spectral density, simplifies the deduction of the quantum efficiency keff and hence the true value of the multiplication factor, and ultimately yields a measured value of the noise parameter x.