Back to results
US 2003/0150978 A1Published application
Signal strength detection in high-speed optical electronics
AssigneeFinisar Corporation
InventorPhil Shapiro
Life of this patent
Estimating the term…
Abstract
A fiber optic transceiver or receiver having circuitry for detecting signal strength of a photo-diode therein is disclosed. In one embodiment, the photo-current generated by the photo-diode is provided to a pre-amplifier circuit. The pre-amplifier circuit generates differential signals including a first signal and a second signal whose difference is representative of the detected photo-current. The fiber optic receiver further includes a post-amplifier circuit that is coupled to the pre-amplifier circuit to receive the differential signals. In one embodiment, the post-amplifier circuit includes circuitry to accurately derive a signal strength of the photo-current from the differential signals.
Claims43
A voltage difference detector circuit, comprising:
- a first circuit element configured to receive a first voltage of a differential voltage pair;
- a second circuit element configured to receive a second voltage of the differential voltage pair;
- a third circuit element connecting the first circuit element to the second circuit element, said third circuit element configured such that a first current proportional to a difference between said first voltage and said second voltage passes through said third circuit element;
- a fourth circuit element coupled to the first circuit element and to a fifth circuit element, said fourth circuit element configured to be affected by the first current such that a second current substantially equal in amplitude to the first current passes through said fourth circuit element to the fifth circuit element when the second voltage is greater than the first voltage;
- and
- a sixth circuit element coupled to the second circuit element and to the fifth circuit element, said sixth circuit element configured to be affected by the first current such that a third current substantially equal in amplitude to the first current passes through said sixth circuit element to the fifth circuit element when the first voltage is greater than the second voltage;
- whereby
- the difference between said first voltage and said second voltage may be determined by reference to the second current and the third current that flow to the fifth circuit element.
5 more elements
A voltage difference detector circuit, comprising:
- a voltage-to-current converter, a first current regulator, a second current regulator, and a current-to-voltage converter;
- the voltage-to-current converter configured to
- receive a first voltage and a second voltage of a differential voltage pair,
- convert a difference between said first voltage and said second voltage to a first current,
- draw a second current from the first current regulator substantially equal to a current offset plus the first current,
- draw a third current from the second current regulator substantially equal to a current offset minus the first current;
- the first current regulator configured to
- produce at least a first amount of current,
- produce a fourth current that flows to the current-to-voltage converter when said first amount of current is greater than-the second current, said fourth current substantially equal to a difference between said second current and said first amount of current;
- the second current regulator configured to
- produce at least a second amount of current,
- produce a fifth current that flows to the current-to-voltage converter when said second amount of current is greater than the third current, said fifth current substantially equal to a difference between said third current and said second amount of current;
- the current-to-voltage converter configured to
- convert the fourth current to a third voltage,
- convert the fifth current to a fourth voltage;
- whereby
- the third voltage and the fourth voltage are proportional to a difference between said first voltage and said second voltage.
14 more elements
A signal detector circuit, comprising:
- a first portion coupled to receive a first signal;
- a second portion coupled to receive a second signal that is complementary to the first signal;
- a first resistor coupled to the first portion and the second portion;
- a second resistor coupled to the first portion and the second portion, wherein a current generated in response to a difference between the first signal and the second signal and flowing across the first resistor causes a corresponding current to flow across the second resistor to produce a potential difference that is representative of said difference between the first and second signals.
1 more element
A signal detector circuit comprising:
- a first left transistor having a first emitter terminal coupled to a first resistor and a first left constant current source, a first collector terminal coupled to a left current drain, a second left constant current source, and a third left current source, and a first base terminal that receives a first signal, the first signal fluctuating between a maximum voltage and a minimum voltage;
- a first right transistor having a second emitter terminal coupled to the first resistor and a first right constant current source, a second collector terminal coupled to a right current drain, a second right constant current source, and a third right current source, and a second base terminal that receives a second signal that is complementary to the first signal;
- and
- a second resistor coupled to the left current drain and the right current drain, wherein a current generated in response to a difference between the first signal and the second signal and flowing across the first resistor causes a corresponding current to flow across the second resistor to produce a potential difference that is representative of a difference between the first signal and the second signal.
1 more element
An optoelectronic device, comprising:
- a photo-diode that generates a photo-current in response to an optical signal;
- a pre-amplifier circuit coupled to the photo-diode to detect the photo-current, the pre-amplifier circuit generating a differential output having a first signal and a second signal based on the photo-current;
- and
- a post-amplifier circuit coupled to the pre-amplifier circuit to receive the first signal and the second signal, the post-amplifier circuit comprising:
- a first portion coupled to receive the first signal;
- a second portion coupled to receive second signal;
- a first resistor coupled to the first portion and the second portion;
- a second resistor coupled to the first portion and the second portion;
- and wherein
- a current generated in response to a difference between the first signal and the second signal and flowing across the first resistor causes a corresponding current to flow across the second resistor to produce a potential difference that is representative of a difference between a maximum voltage and a minimum voltage of at least one of the first signal and second signal.
7 more elements
An optoelectronic device, comprising:
- a photo-diode that generates a photo-current in response to an optical signal;
- a pre-amplifier circuit coupled to the photo-diode to detect the photo-current, the pre-amplifier circuit generating a differential output having a first voltage and a second voltage based on the photo-current, said first voltage and said second voltage each alternating between a maximum voltage and a minimum voltage;
- and
- a post-amplifier circuit coupled to the pre-amplifier circuit to receive the first voltage and the second voltage, the post-amplifier circuit comprising:
- a first circuit element configured to receive the first voltage;
- a second circuit element configured to receive the second voltage;
- a third circuit element connecting the first circuit element to the second circuit element, said third circuit element configured such that a first current proportional to a difference between said first voltage and said second voltage passes through said third circuit element;
- a fourth circuit element coupled to the first circuit element and to a fifth circuit element, said fourth circuit element configured to be affected by the first current such that a second current substantially equal in amplitude to the first current passes through said fourth circuit element to the fifth circuit element when the second voltage is greater than the first voltage;
- and
- a sixth circuit element coupled to the second circuit element and to the fifth circuit element, said sixth circuit element configured to be affected by the first current such that a third current substantially equal in amplitude to the first current passes through said sixth circuit element to the fifth circuit element when the first voltage is greater than the second voltage;
- whereby an amplitude of the optical signal can be determined by reference to the second current and the third current that flows to the fifth circuit element.
8 more elements
An optoelectronic device, comprising:
- a photo-diode that generates a photo-current in response to an optical signal;
- a pre-amplifier circuit coupled to the photo-diode to detect the photo-current, the pre-amplifier circuit generating a differential output having a first voltage and a second voltage based on the photo-current, said first voltage and said second voltage each alternating between a maximum voltage and a minimum voltage;
- and
- a post-amplifier circuit coupled to the pre-amplifier circuit to receive the first voltage and the second voltage, the post-amplifier circuit comprising:
- a voltage-to-current converter, a first current regulator, a second current regulator, and a current-to-voltage converter;
- the voltage-to-current converter configured to
- receive the first voltage and the second voltage,
- convert a difference between said first voltage and said second voltage to a first current,
- draw a second current from the first current regulator substantially equal to a current offset plus the first current,
- draw a third current from the second current regulator substantially equal to a current offset minus the first current;
- the first current regulator configured to
- produce at least a first amount of current,
- produce a fourth current that flows to the current-to-voltage converter when said first amount of current is greater than the second current, said fourth current substantially equal to a difference between said second current and said first amount of current;
- the second current regulator configured to
- produce at least a second amount of current,
- produce a fifth current that flows to the current-to-voltage converter when said second amount of current is greater than the third current, said fifth current substantially equal to a difference between said third current and said second amount of current;
- and
- the current-to-voltage converter configured to
- convert the fourth current to a third voltage,
- convert the fifth current to a fourth voltage;
- whereby the third voltage and the fourth voltage are proportional to a difference between said first voltage and said second voltage.
18 more elements
Dependencies are inferred from the claim text.