Optical receiver decision threshold tuning apparatus and method
First Claim
1. A method of adjusting a decision threshold in an optical receiver having a photodetector converting an optical signal received from an optical network to an electrical input data signal and a comparator comparing the electrical input data signal to a decision threshold to provide a binary output data signal, the method comprising:
- detecting a peak value of an optical signal received from an optical network with a peak detector operatively connected to a photodetector;
outputting a decision threshold to a comparator that is a commanded percentage of the peak value, wherein the outputting step is performed by an EEPOT operatively connected to said peak detector, a controller, and said comparator;
commanding said EEPOT with a percentage value to tune the decision threshold and switch the decision threshold to a predetermined reference value, wherein said commanding step is performed by said controller;
maintaining the decision threshold to be a fraction of the power of the optical signal, wherein the maintaining step is performed by said controller, and said controller is operatively connected to said comparator; and
switching the decision threshold from a current value to the predetermined reference value when the optical signal experiences an alarm condition; and
tuning the decision threshold with the controller according to an optimization control loop when the optical signal is in a substantially steady state condition.
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Abstract
A method of controlling an optical signal receiver utilizes three control loops: a first control loop tunes the decision threshold of the receiver when the optical network is in a substantially steady state and a second control loop rapidly switches to a reference decision threshold upon the occurrence of an alarm condition. The invention rapidly switches to a predetermined reference decision threshold to compensate for optical signal changes in eye Q and received power after a protection switch or traffic reroute. After a protection switch, a slower tuning algorithm is used to adjust the decision threshold to a more optimum value. In the third control loop, the optical signal receiver may utilize a peak detector that detects the optical signal peak and a potentiometer that is commanded by a controller to output a commanded percentage of this peak value to adjust the threshold and thereby respond to transients.
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Citations
30 Claims
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1. A method of adjusting a decision threshold in an optical receiver having a photodetector converting an optical signal received from an optical network to an electrical input data signal and a comparator comparing the electrical input data signal to a decision threshold to provide a binary output data signal, the method comprising:
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detecting a peak value of an optical signal received from an optical network with a peak detector operatively connected to a photodetector; outputting a decision threshold to a comparator that is a commanded percentage of the peak value, wherein the outputting step is performed by an EEPOT operatively connected to said peak detector, a controller, and said comparator; commanding said EEPOT with a percentage value to tune the decision threshold and switch the decision threshold to a predetermined reference value, wherein said commanding step is performed by said controller; maintaining the decision threshold to be a fraction of the power of the optical signal, wherein the maintaining step is performed by said controller, and said controller is operatively connected to said comparator; and switching the decision threshold from a current value to the predetermined reference value when the optical signal experiences an alarm condition; and tuning the decision threshold with the controller according to an optimization control loop when the optical signal is in a substantially steady state condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A control method for controlling the decision threshold of an optical receiver connected to an optical network, comprising:
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a first control loop for tuning a decision threshold when a condition of an optical network is in a substantially steady-state, wherein the first control loop is performed by a performance monitor, a microprocessor, an EEPOT, a peak detector, and a comparator, and wherein the first control loop utilizes data from the performance monitor to calculate a percentage amount value utilized by the EEPOT to adjust the decision threshold; a second control loop for switching the decision threshold to a predetermined reference value in response to the condition of the optical network experiencing a transient condition, wherein the second control loop is performed by the performance monitor, the microprocessor, the EEPOT, the peak detector, and the comparator, and wherein the second control loop utilizes the transient condition to switch the percentage amount value utilized by the EEPOT to suddenly adjust the decision threshold to the predetermined reference value responsive to the transient condition; and a third control loop for maintaining the decision threshold to be a fraction of the input optical signal power, wherein the third control loop is performed by the peak detector, the EEPOT, and the comparator, and wherein the third control loop utilizes a fixed percentage amount in the EEPOT to keep the decision threshold at the fraction of the input optical signal power in order to respond to large transients, wherein the first control loop is performed utilizing a software-based control algorithm and wherein the second and third control loops are performed utilizing hardware-based control algorithms. - View Dependent Claims (16, 17)
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18. An optical signal receiver, comprising:
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a photodetector optically coupled to a fiber optic network; said photodetector converting an optical signal received from the fiber optic network to an electrical input data signal; a comparator operatively coupled to said photodetector and to a decision threshold input port; said comparator comparing the electrical input data signal to a decision threshold to provide a binary output data signal; and a controller operatively connected to said comparator, a peak detector operatively connected to said photodetector, said peak detector detecting a peak value of the optical signal received from the optical network, an EEPOT operatively connected to said peak detector, said controller, and said comparator, said EEPOT outputting the decision threshold to the comparator that is a commanded percentage of the peak value; said controller commanding said EEPOT with a percentage value to tune the decision threshold and switch the decision threshold to a predetermined reference value, said controller maintaining the decision threshold to be a fraction of the power of the optical signal, said controller switching the decision threshold from a current value to the predetermined reference value when the optical signal experiences an alarm condition, and said controller tuning the decision threshold according to an optimization control loop when the optical signal is in a substantially steady state condition. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification