Low-noise receivers for fiber-optic microwave signal transmission

The problem of low-noise reception of high-frequency narrowband modulated optical radiation is discussed. Relatively simple p-i-n diode/FET based optical receiver structures which achieve good narrowband optical sensitivity are proposed. These receivers achieve good gain and noise performance due to a lossless parallel resonance circuit which shunts the input to the detector and FET. Design characteristics are presented for S-band receivers constructed using low-capacitance photodetectors, and GaAs MESFETs. Experimental realizations of these receiver designs, which achieve conversion efficiencies on the order of 250 V/W and optical noise equivalent power of less than 10 pW/ square root Hz for 0.8- mu m radiation, are reported. Scaling rules which should be of use in optimizing the performance of more advanced designs are stated and other types of receiver structures which can be expected to yield high narrowband optical sensitivity are discussed.>