suria3
Full Member level 5
Dear People,
I have some queries here about Rx Optical Sensitivity Measurement.
The measurement for the sensitivity of a receiver is given by the formula according to Maxim datasheet :-
Sensitivity = 10 Log { in * SNR * (re + 1) } dBm
------------------------- * 1000
ρ (re - 1) * 2
where in = input referred noise
SNR = Signal Noise Ratio
re = extinction ratio
ρ = responsivity of the photodetector
There are also some direct calculation which we can do by referring to the datasheet in order to get the receiver sensitivity. For example when we can know the responsivity of the diode which is in the unit of A/W, we can calculate the power by knowing the minimum current that the Transimpedance Amplifier can detect. Let say the responsivity is 0.8A/W and the miminum current going in to the TIA is 15uA. So, the power can be calculated as below:-
Power = Current/Responsisvity = 15uA / 0.8 = 18.75uW
So, power in dBm is = 10 Log 18.75uA / 1mA = -17.26dBm.
Then we say that the sensitivity of the TIA is -17.26dBm. So, is this calculation sensitivity is the same as the Maxim sensitivity calculation as above? Need some clarification on this?
2) When referred to some ROSA (Receiver Optical Sub Assembly ) datasheet, they put the Min , Typ & Max sensitivity as -18dBb,-16dBm,-14dBm. But according to my calculation based on responsivity, somehow I get the Min to Max as -14dBm to -18dBm. So, it is in the opposite power trend. Where is the problem for this calculation? If we go by theory, the negative the value is, the more accurate the receiver is, that is it can detect the minimum current. So, which trend am I suppose to follow?
Thanks in advance,
Suria3
I have some queries here about Rx Optical Sensitivity Measurement.
The measurement for the sensitivity of a receiver is given by the formula according to Maxim datasheet :-
Sensitivity = 10 Log { in * SNR * (re + 1) } dBm
------------------------- * 1000
ρ (re - 1) * 2
where in = input referred noise
SNR = Signal Noise Ratio
re = extinction ratio
ρ = responsivity of the photodetector
There are also some direct calculation which we can do by referring to the datasheet in order to get the receiver sensitivity. For example when we can know the responsivity of the diode which is in the unit of A/W, we can calculate the power by knowing the minimum current that the Transimpedance Amplifier can detect. Let say the responsivity is 0.8A/W and the miminum current going in to the TIA is 15uA. So, the power can be calculated as below:-
Power = Current/Responsisvity = 15uA / 0.8 = 18.75uW
So, power in dBm is = 10 Log 18.75uA / 1mA = -17.26dBm.
Then we say that the sensitivity of the TIA is -17.26dBm. So, is this calculation sensitivity is the same as the Maxim sensitivity calculation as above? Need some clarification on this?
2) When referred to some ROSA (Receiver Optical Sub Assembly ) datasheet, they put the Min , Typ & Max sensitivity as -18dBb,-16dBm,-14dBm. But according to my calculation based on responsivity, somehow I get the Min to Max as -14dBm to -18dBm. So, it is in the opposite power trend. Where is the problem for this calculation? If we go by theory, the negative the value is, the more accurate the receiver is, that is it can detect the minimum current. So, which trend am I suppose to follow?
Thanks in advance,
Suria3