Ultrawide-bandwidth low-noise optical receiver

An optical receiver having a bandwidth that extends from near dc to the multi-gigahertz range for converting a received optical signal to an amplified electrical signal at the output of the receiver comprising:

• photodetector means for converting the received optical signal to a proportional low-level electrical signal,
• inductive/resistive frequency enhancement means connected to said photodetector means for extending the high frequency response of a first amplifying stage and for providing a high input impedance to said first amplifying stage,
• said first amplifying stage having said high input impedance and an intermediate output impedance for amplifying the enhanced low-level electrical signal, said first amplifying stage comprising a first transistor amplifier and a first output microwave matching circuit for providing said intermediate impedance, said first output microwave matching circuit comprising a modified T-network having a series-arm impedances inductive elements and as a shunt-leg impedance a microwave element in series with a resistor,
• a second amplifying stage cascaded with said first stage having an intermediate input impedance and an intermediate output impedance for further amplifying the enchanced low-level electrical signal amplified by said first amplifying stage, said second amplifying stage comprising a second transistor amplifier and a second output microwave matching circuit for providing said intermediate impedance, said second output microwave matching circuit comprising a modified T-network having as series-arm impedances inductive elements and as a shunt-leg impedance a microwave element in series with a resistor, and
• a third amplifying stage cascaded with said first and second stages having an intermediate input impedance and a low output impedance at the receiver output for providing an impedance transform to the amplified enchanced electrical signal, said third amplifying stage comprising a third transistor amplifier and a third output microwave matching circuit for providing said low output impedance, said third amplifying stage comprising a third transistor amplifier and a third output microwave matching circuit for providing said low impedance, said third output microwave matching circuit comprising a modified T-network having as series-arm impedances inductive elements and as a shunt-leg impedance a microwave element in series with a resistor,
• the resistor in each of said modified T-networks being chosen to extend the bandwidth of each stage to near the dc level and the inductive and microwave elements in each of said modified T-networks being chosen to preserve the high frequency response of each stage as extended by said frequency enhancement means.