Noise and transport characteristics of CdTe gamma - and X-ray detectors have been carried out to
determine the 1/f noise sources and their correlation with charge carriers mobility. The noise spectral
density was measured by standard set-up. The no
ise of low ohmic samples has 1/f noise spectral
density which increases with the square of voltage. The high ohmic samples show 1/f type noise in low
frequency range. This flicker noise leads to degradation in the homogeneity of the contact. The excess
of noise changes as 1/fa , 1 a 2 at 10Hz, and it is due to the multitrapping of the CdTe. Thiscontributes to the loss in charge collection efficiency.
The effect of thermal noise and shot noise on the receiver sensitivity in a digital
optical communication system will be studied and analyzed. Also, the positive and
negative effects of Parameters on the receiver sensitivity will be highlighted. Th
e
programming tools (MATLAB) is used to study the relationship between the receiver
sensitivity and bit rate. It showed that the shot-noise-limited receiver sensitivity is much
better than the thermal -noise-limited receiver sensitivity with best 30dB. The study also
provided an explanation for the preference of optical detector (APD) compared to that in
(PIN) optical detector from sensitivity side due to its internal gain, this can be achieved
when the thermal noise is dominant. However, the preference of optical detector(PIN) will
be better in case of shot noise is dominant.
Analyzed results show that there is a significant improvement in the shot-noiselimited
receiver sensitivity for high quantum efficiency and high wavelength. However, the
sensitivity is deteriorated to get a lower error rate. The thermal -noise-limited receiver
sensitivity showed an improving by increasing the responsivity and the load resistance.
However, it decreases by increasing the number of noise and the error rate.
