Signal strength detection in high-speed optical electronics

A signal detector, comprising:

• a multiplier having a signal input terminal configured to receive a first signal of a differential signal and a second signal of said differential signal, a control input terminal configured to receive a control signal, and a modified differential signal output terminal configured to output a modified differential signal, said modified differential signal being a function of said control signal and said differential signal;
• detector circuitry having a modified differential signal input terminal configured to receive the modified differential signal, a first transistor, a second transistor, a first resistor, and a second resistor configured to generate an active signal, and an active signal output terminal configured to output said active signal;
• the detector circuitry having a set of known factors that define said detector circuitry, said active signal being a function of said modified differential signal and said set of known factors;
• a first terminal of the first resistor being coupled to an emitter terminal of the first transistor and to an emitter terminal of the second transistor, a second terminal of the first resistor being coupled to a fixed potential circuit node;
• a first terminal of the second resistor being coupled to a collector terminal of the first transistor, to a collector terminal of the second transistor, and to the active signal output terminal to form a junction, the active signal emanating from said junction;
• a second terminal of the second resistor being coupled to a power supply;
• a base terminal of first transistor and a base terminal of the second transistor configured to receive a first signal of the modified differential signal and a second signal of said modified differential signal, respectively;
• and
• a comparator having an active signal input terminal configured to receive the active signal, a reference signal input terminal configured to receive a reference signal, and a control signal output terminal configured to output the control signal, said control signal a function of a difference between said reference signal and said active signal, wherein the multiplier, the detector circuitry, and the comparator form a feed-back loop that forces the active signal to approximate the reference signal and, in so doing, forces said modified differential signal to have a minimum peak-to-peak amplitude that corresponds to said differential signal;
• whereby a peak-to-peak amplitude of the differential signal may be accurately computed by reference to the control signal and the set of known factors.

A signal detector, comprising:

• a multiplier having a signal input terminal configured to receive a signal, a control input terminal configured to receive a control signal, and a modified signal output terminal configured to output a modified signal, said modified signal being a function of said control signal and said signal;
• detector circuitry have a modified signal input terminal configured to receive the modified signal, a capacitor, a diode, a resistor, and a voltage source configured to generate an active signal, and an active signal output terminal configured to output said active signal;
• the detector circuitry having a set of known factors that define said detector circuitry, said active signal being a function of said modified signal and said set of known factors;
• a first terminal of the capacitor configured to receive the modified signal;
• a second terminal of the capacitor coupled to an anode of the diode, to a first terminal of the resistor, and to a negative terminal of the voltage source;
• a cathode of the diode coupled to a fixed potential circuit node;
• a second terminal of the resistor coupled to a power supply;
• a positive terminal of the voltage source coupled to the active signal output terminal, the active signal emanating from said positive terminal of the voltage source;
• and
• a comparator having an active signal input terminal configured to receive the active signal, a reference signal input terminal configured to receive a reference signal, and a control signal output terminal configured to output the control signal, said control signal a function of a difference between said reference signal and said active signal, wherein the multiplier, the detector circuitry, and the comparator form a feed-back loop that forces the active signal to approximate the reference signal and, in so doing, forces said modified signal to have a minimum peak-to-peak amplitude that corresponds to said signal;
• whereby a peak-to-peak amplitude of the signal may be accurately computed by reference to the control signal and the set of known factors.

A signal detector, comprising:

• a multiplier having a signal input terminal configured to receive a signal, a control input terminal configured to receive a control signal, and a modified signal output terminal configured to output a modified signal, said modified signal being a function of said control signal and said signal;
• detector circuitry have a modified signal input terminal configured to receive the modified signal, a capacitor, a diode, and a resistor configured to generate an active signal, and an active signal output terminal configured to output said active signal;
• the detector circuitry having a set of known factors that define said detector circuitry, said active signal being a function of said modified signal and said set of known factors;
• an anode of the diode configured to receive the modified signal;
• a cathode of the diode coupled to a first terminal of the capacitor, to a first terminal of the resistor, and to the active signal output terminal to form a junction, the active signal emanating from said junction;
• a second terminal of the capacitor coupled to a fixed potential circuit node;
• a second terminal of the resistor coupled to the fixed potential circuit node;
• and
• a comparator having an active signal input terminal configured to receive the active signal, a reference signal input terminal configured to receive a reference signal, and a control signal output terminal configured to output the control signal, said control signal a function of a difference between said reference signal and said active signal, wherein the multiplier, the detector circuitry, and the comparator form a feed-back loop that forces the active signal to approximate the reference signal and, in so doing, forces said modified signal to have a minimum peak-to-peak amplitude that corresponds to said signal;
• whereby a peak-to-peak amplitude of the signal may be accurately computed by reference to the control signal and the set of known factors.

A communication system, comprising:

• an optoelectronic transmitter that transmits a light signal;
• a photo diode coupled to the optoelectronic transmitter that converts the light signal to an electrical signal;
• a first stage circuit coupled to the photo diode that produces differential signals from the electrical signal;
• and
• a second stage circuit coupled to the first stage circuit, including:
• a multiplier having a differential signal input terminal configured to receive a differential signal with a voltage differential from a first stage circuit, a control signal input terminal configured to receive a control signal with voltage Vc, an output terminal configured to output modified differential signals that are proportional to the differential signals and the control signal;
• detection circuitry means for receiving the modified differential signals and producing an active signal, with voltage Vactive, that corresponds to the voltage differential of the differential signal;
• a comparator having a first comparator input terminal configured to receive the active signal from the detection circuitry means, a second comparator input terminal configured to receive a reference voltage Vref, and a comparator output terminal configured to couple the control signal to the multiplier, such that in operation, Vactive is driven to Vref and, when Vactive is approximately equal to Vref, Vc is indicative of the voltage differential of the differential signal.

A method for calculating a voltage differential for differential signals, comprising:

• modifying a differential signal having a voltage differential with a control signal and a DC voltage offset;
• deriving an active signal with a voltage proportional to the voltage differential and a pre-determined value;
• producing the control signal from said active signal and a reference signal;
• measuring the control signal;
• and
• calculating the voltage differential from the measured control signal.