Generalizing prior results of Henry1 and Jacobs,2 we have shown that the sensitivity of a lightwave system using optical amplifiers both as linear intermediate repeaters and as a receiver preamplifier is given by where Np is the number of photons per bit to achieve 10−9 error probability, nsp(≥1) is the spontaneous emission factor, G is the gain and B is the bandwidth of the amplifier, T is the bit period, M is the number of amplifiers (M − 1 is the number of intermediate repeaters), and N1 is the number of photons per bit required without amplifiers. (N1 is a measure of the thermal noise performance of the electrical portion of the receiver. For transimpedance receivers N1 = 3000. Note that Np = N1 for M = 1, G = 1.) The above expression assumes that the gain of each amplifier is the same and compensates for the loss between amplifiers.
© 1991 Optical Society of AmericaPDF Article