Sensitivity of optically preamplified receivers with optical filtering

The noise spectral densities resulting from detection of preamplified signals using an optical filter are discussed. The authors also carried out a simplified analysis of preamplified receiver sensitivities with ASK and FSK signals. The analysis shows that total optical bandwidths of less than 50 times the data rate result in (10/sup -9/ BER) sensitivities close to the limit set by the amplifier noise figure. The development of low-noise high-gain amplifiers in conjunction with narrowband tunable optical filters enable high-sensitivity FDM systems to be constructed, without the complication of a local oscillator or polarization control/diversity networks which are required for heterodyne coherent detection systems. >