IMPROVED DESIGN OF TUNED OPTICAL RECEIVERS

We present new design principles for improved heterodyne tuned optical receivers where several tuning inductances reduce the influence of thermal receiver noise over a broad frequency range. A theoretical example for a 600 MHz tuning bandwidth shows a reduction of thermal receiver noise (and thus in required local oscillator power) of up to 13 db. The example is tested experimentally for the so-called mixed tuning configuration. We obtain good agreement with theoretical predictions. The experimental rms noise current is less than 5 pa/ ROOT (Hz) over a 580 MHz bandwidth with the lowest value of 3. 5 pa ROOT (Hz) at 950 MHz.