Receiver with dynamically adjustable decision threshold voltage based on input power
View Patent ↗According to embodiments of the present invention, an optical transponder and/or optical transceiver includes a decision circuit, which scales a decision threshold voltage based on power in a received optical signal. In one embodiment, the decision set point may be established based on an expected amplitude or power of an incoming optical signal and the transponder and/or transceiver uses the actual power of the incoming optical signal to adjust the decision threshold voltage.
1. A method, comprising:
receiving a value representing a threshold voltage set point for a circuit, the circuit to determine whether a data bit on a first optical signal is a logical one or a logical zero, the threshold voltage set point being based on a first average power of the first optical signal;
receiving second optical signal having a second average power different from the first average power;
adjusting the threshold voltage set point based on the second average power; and
multiplying a voltage that is proportional to the second average power of the second optical signal times the threshold voltage set point to generate a unipolar voltage representing the adjusted threshold voltage set point.
2. The method of claim 1 , further comprising generating a photocurrent proportional to the second average power.
3. The method of claim 2 , further comprising converting the photocurrent to the voltage proportional to the second average power of the second optical signal.
4. The method of claim 3 , further comprising converting the unipolar voltage to a bipolar voltage representing the adjusted threshold voltage set point.
5. The method of claim 4 , further comprising:
shifting the direct current level of the bipolar voltage; and
summing in a direct current voltage with the direct current shifted bipolar voltage.
6. An apparatus, comprising:
circuitry to generate a voltage proportional to an average power in an optical signal;
a digital-to-analog converter to multiply the voltage times a set point to obtain a scaled set point, the set point to determine whether a data bit on the optical signal is a logical one or a logical zero;
a first amplifier to decide whether a data bit on the optical signal is a logical one or a logical zero using the scaled set point; and
a second amplifier to convert the scaled set point from a unipolar voltage to a bipolar voltage.
7. The apparatus of claim 6 , further comprising a photodetector to receive the optical signal and to convert the optical signal to a photocurrent.
8. The apparatus of claim 7 , wherein the photodetector comprises an avalanche photodiode or a positive-intrinsic-negative diode.
9. The apparatus of claim 6 , further comprising:
an analog-to-digital converter to convert the set point from an analog value to a digital value; and
a microcontroller to provide the digital set point to the digital-to-analog converter.
10. The apparatus of claim 6 , further comprising a transimpedance amplifier to receive a photocurrent from a photodetector and to convert the photocurrent to a voltage proportional to the average power in the optical signal.
11. A method, comprising:
receiving a threshold voltage value to determine whether a data bit on an optical signal is a logical one or a logical zero;
receiving an optical signal;
convening the optical signal to a proportional voltage;
scaling the threshold voltage value in proportion to proportional voltage;
converting the optical signal to proportional current;
summing the proportional current with the scaled threshold voltage value; and
determining whether a data bit on the received optical signal is a logical one or a logical zero using the proportional current summed with the scaled threshold voltage value.
12. The method of claim 11 , further comprising shifting a direct current level of the scaled threshold voltage value.
13. The method of claim 11 , further comprising receiving a digital threshold voltage value to determine whether a data bit on an optical signal is a logical one or a logical zero.
14. The method of claim 11 , further comprising receiving an analog threshold voltage value to determine whether a data bit on an optical signal is a logical one or a logical zero.