Compensation for variations in temperature and aging of laser diode by use of small signal, square-law portion of transfer function of diode detection circuit

Claim 1

A method of controlling the operation of an energy emitter having a non-linear output versus input transfer function that varies with an ambient parameter comprising the steps of: (a) applying a modulation signal to said energy emitter, said modulation signal having a frequency component derived from an information signal and a magnitude component derived from a magnitude control signal, so as to cause said energy emitter to emit output energy having a frequency that varies in accordance with said information signal and an intensity that is defined in accordance with the response of said non-linear output versus input transfer function to said magnitude control signal; (b) detecting a portion of said output energy emitted by said energy emitter in step (a) and producing therefrom an output that is proportional to power of said output energy emitted by said energy emitter; and (c) generating said magnitude control signal in accordance with a prescribed relationship between said output and a reference quantity representative of a prescribed peak-to-peak excursion of said energy emitted by said energy emitter.

Claim 2

A method of controlling the operation of an energy emitter having a non-linear output versus input transfer function that varies with an ambient parameter comprising the steps of: (a) applying a modulation signal to said energy emitter, said modulation signal having a frequency component derived from an information signal and a magnitude component derived from a magnitude control signal, so as to cause said energy emitter to emit output energy having a frequency that varies in accordance with said information signal and an intensity that is defined in accordance with the response of said non-linear output versus input transfer function to said magnitude control signal; (b) detecting a portion of said output energy emitted by said energy emitter in step (a) and producing therefrom an output that is proportional to power of said output energy emitted by said energy emitter; and (c) generating said magnitude control signal in accordance with a prescribed relationship between said output and a reference quantity representative of a prescribed peak-to-peak excursion of said energy emitted by said energy emitter.

Claim 4

An apparatus for controlling the operation of an energy emitter having a non-linear output versus input transfer function that varies with an ambient parameter comprising: a stimulus modulator which is operative to apply a modulated stimulus to said energy emitter, said modulated stimulus having a frequency component derived from an information signal and a magnitude component derived from a stimulus magnitude control input, so as to cause said energy emitter to emit output energy having a frequency that varies in accordance with said information signal and a peak-to-peak excursion that is defined in accordance with the response of said non-linear output versus input transfer function to said stimulus magnitude control input; an output energy detector coupled to said energy emitter and operative to detect a portion of said output energy emitted by said energy emitter and to produce therefrom an output that is proportional to power of said output energy emitted by said energy emitter; and a stimulus magnitude control input generator coupled to said output energy detector and operative to generate said stimulus magnitude control input in accordance with a prescribed relationship between said output and a reference quantity representative of a prescribed peak-to-peak excursion of said energy emitted by said energy emitter.

Claim 5

An apparatus for controlling the operation of an energy emitter having a non-linear output versus input transfer function that varies with an ambient parameter comprising: a stimulus modulator which is operative to apply a modulated stimulus to said energy emitter, said modulated stimulus having a frequency component derived from an information signal and a magnitude component derived from a stimulus magnitude control input, so as to cause said energy emitter to emit output energy having a frequency that varies in accordance with said information signal and a peak-to-peak excursion that is defined in accordance with the response of said non-linear output versus input transfer function to said stimulus magnitude control input; an output energy detector coupled to said energy emitter and operative to detect a portion of said output energy emitted by said energy emitter and to produce therefrom an output that is proportional to power of said output energy emitted by said energy emitter; and a stimulus magnitude control input generator coupled to said output energy detector and operative to generate said stimulus magnitude control input in accordance with a prescribed relationship between said output and a reference quantity representative of a prescribed peak-to-peak excursion of said energy emitted by said energy emitter.

Claim 23

An apparatus for controlling the operation of a laser device having a non-linear optical output versus input current transfer function that varies with temperature, comprising: a laser current driver which is operative to convert a serial data input voltage supplied to a data input port thereof into a modulating, laser-extinction control current that drives said laser device, wherein the magnitude of the modulation drive current output by said laser current driver is defined in accordance with a peak-to-peak control voltage supplied to a magnitude control port thereof, said laser current driver producing a modulating laser drive current I MOD that is summed with a threshold DC bias current I TH from a threshold bias current control loop, so as to cause said laser device to emit a light beam, said light beam having a frequency component corresponding to the data signal component of said modulating laser drive current and a peak-to-peak optical power excursion defined in accordance with the response of the laser device's non-linear optical output power versus laser drive current transfer function to the magnitude of said modulating laser drive current; a monitoring optical energy detector producing an output current in proportion to the power in said light beam, said output current being coupled to a current-to-voltage converter, which produces a voltage signal that is coupled to an RF amplifier, which outputs an amplified output voltage; a square-law based rectifier circuit coupled to receive the amplified voltage output by said RF amplifier, and comprising a pair of small signal, non-switched, square-law detector diodes, one of which is coupled to the output of said RF amplifier and is operative to generate a first rectified output voltage in accordance with the square of the amplified voltage output by said RF amplifier, and a second detector diode which generates a second reference voltage in accordance with the square of a reference current I REF representative of a prescribed optical output power to be generated by said laser device for a predetermined value of operating temperature; and a differential integrator which is coupled to said one and the other of said pair of square law detector diodes and generates said peak-to-peak control voltage that is proportional to the integral of the difference between the rectified output voltage from said one detector diode, and a voltage derived from said other detector diode.

Claim 24

An apparatus for controlling the operation of a laser device having a non-linear optical output versus input current transfer function that varies with temperature, comprising: a laser current driver which is operative to convert a serial data input voltage supplied to a data input port thereof into a modulating, laser-extinction control current that drives said laser device, wherein the magnitude of the modulation drive current output by said laser current driver is defined in accordance with a peak-to-peak control voltage supplied to a magnitude control port thereof, said laser current driver producing a modulating laser drive current I MOD that is summed with a threshold DC bias current I TH from a threshold bias current control loop, so as to cause said laser device to emit a light beam, said light beam having a frequency component corresponding to the data signal component of said modulating laser drive current and a peak-to-peak optical power excursion defined in accordance with the response of the laser device's non-linear optical output power versus laser drive current transfer function to the magnitude of said modulating laser drive current; a monitoring optical energy detector producing an output current in proportion to the power in said light beam, said output current being coupled to a current-to-voltage converter, which produces a voltage signal that is coupled to an RF amplifier, which outputs an amplified output voltage; a square-law based rectifier circuit coupled to receive the amplified voltage output by said RF amplifier, and comprising a pair of small signal, non-switched, square-law detector diodes, one of which is coupled to the output of said RF amplifier and is operative to generate a first rectified output voltage in accordance with the square of the amplified voltage output by said RF amplifier, and a second detector diode which generates a second reference voltage in accordance with the square of a reference current I REF representative of a prescribed optical output power to be generated by said laser device for a predetermined value of operating temperature; and a differential integrator which is coupled to said one and the other of said pair of square law detector diodes and generates said peak-to-peak control voltage that is proportional to the integral of the difference between the rectified output voltage from said one detector diode, and a voltage derived from said other detector diode.