Laser temperature performance compensation
The invention presents a method that calibrates the laser optical power in a continuous manner without disrupting the flow of information in the optical communications link. The method utilizes knowledge of the measured value of the laser optical power and makes necessary adjustments to optimize the values of the Extinction Ratio, Bit Error Rate and to compensate for aging. The method utilizes knowledge of the temperature from a sensor and mathematical models, which contain parameters which are updated for a specific laser configuration.
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6 . A method for initial calibration of laser output power comprising:
finding an initial threshold bias current value by applying an increasing bias current signal to a laser, and sensing a laser output monitoring signal with a photodiode sensor while applying a mathematical threshold determination algorithm to the signal to determine when a first slope of the laser output monitoring signal changes;
storing the initial threshold bias current value in non-volatile memory;
determining at least two output monitoring data points created by continuing to sense the laser output monitoring signal with the photodiode sensor;
applying a mathematical photodiode responsiveness algorithm to the two output monitoring data points to determine the slope of the laser output monitoring signal;
determining at least two power output bias data points created by applying a bias current to the laser and sensing a laser output bias power signal with an optical power meter;
applying a mathematical bias slope determination algorithm to the two power output bias data points to determine a slope of the laser output bias power signal;
determining at least two power output modulation data points created by applying a modulation current to the laser and sensing a laser output modulation power signal with the optical power meter;
applying a mathematical modulation slope determination algorithm to the two power output modulation data points to determine a slope of the laser output modulation power signal;
determining a temperature coefficient of the laser output bias power signal slope;
determining a temperature coefficient of the laser output modulation power signal slope;
storing the bias power signal slope temperature coefficient in non-volatile memory; and,
storing the modulation power signal slope temperature coefficient in non-volatile memory.
7 . The method of claim 6 wherein the calibration is performed in a factory setting at an initial temperature T 1 .
8 . The method of claim 6 further comprising averaging the laser output monitoring signal to account for noise.
9 . The method of claim 6 wherein a mathematical algorithm comprises a signal processing algorithm using a digital filter.
10 . The method of claim 6 further comprising applying an operating bias current to the laser and storing an operating bias current value in non-volatile memory.
11 . The method of claim 6 further comprising applying an operating modulation current to the laser and storing an operating modulation current value in non-Volatile memory.
12 . A method for compensating laser characteristic changes with temperature comprising:
determining a temperature change from an original temperature to a new temperature;
determining a new initial threshold bias current computed from the temperature change and a stored initial threshold bias current;
determining a new operating bias current computed from the temperature change, a stored bias power signal slope temperature coefficient and a stored operating bias current value;
applying the new operating bias current to a laser;
determining a new operating modulation current computed from the temperature change, a stored modulation power signal slope temperature coefficient and a stored operating modulation current value; and,
applying the new operating modulation current to the laser.
13 . A method for compensating laser characteristic changes with temperature comprising:
determining a temperature change from an original temperature to a new temperature;
determining a new initial threshold bias current computed from the temperature change and a stored initial threshold bias current;
determining a new operating bias current computed from an average power value sensed by a photodiode sensor and a stored operating bias current value;
applying the new operating bias current to a laser;
determining a new operating modulation current computed from the temperature change, a stored modulation power signal slope temperature coefficient and a stored operating modulation current value; and,
applying the new operating modulation current to the laser.