Extinction ratio
The extinction ratio (engl. Extinction Ratio ER, symbols r e ) is the quotient of two measured values of the attenuation ( extinction ) of a light radiation in two different states, z. B. different wavelengths.
telecommunications
In telecommunications , the extinction ratio is the ratio or the dynamic range of two optical levels p of a digital signal at the output of an optical fiber . Measurements are made with the light-emitting diode switched on and off (the term extinction "ratio" is therefore not exactly exact here, because when the light source is switched off, there is no signal fed in, nor is it attenuated). It is calculated as follows:
The smaller the extinction ratio , the greater the bit error rate . This results from the fact that it is more difficult for the recipient to differentiate between and evaluate the two states (e.g. “On” and “Off”). When transmitting data, the extinction ratio should be over 20 dB if possible.
The dark current of the receiver ( photodiode ) must be taken into account for a measurement . At high frequencies, the extinction ratio can also be reduced by reflections at the ends of the respective optical waveguides.
The polarization extinction ratio is the crosstalk ratio between signals of different polarization.
The definition of the extinction ratio is given in Federal Standard 1037C and MIL-STD-2196.
Molecular biology
In molecular biology , the purity of a DNA sample is measured using the extinction ratio. The extinction E is measured when the sample is irradiated with light wavelengths of 260 nm and 280 nm. A sample applies e.g. B. as pure with ratios E (260) / E (280) over 1.8. Values below this indicate phenol or protein contamination .
swell
Helge Schnerr: Diploma thesis (PDF 1.43 MB)