Thermal compensation of injection laser diodes driven by shunt current modulations
AssigneeHarris Corporation
InventorEdward Tegge
Life of this patent
Estimating the term…
Abstract
A laser driver for an injection laser diode (ILD) protects the ILD during ILD temperature changes so that the ILD is not subjected to a potentially harmful operating current. The ILD may be operated near it maximum limit and modulated by decreasing the available current to the ILD. The temperature of the ILD may be sensed and the maximum ILD driving current changed proportionally to a change of the sensed temperature.
Claims22
A method of operating an injection laser diode (ILD) in the presence of ILD temperature changes so that the ILD is not subjected to a potentially harmful operating current, the method comprising the steps of:
- (a) providing an operating current for the ILD from a power source, the operating current
- (i) being provided through a circuit that renders the operating current insensitive to fluctuations in the power source output, and
- (ii) for operating the ILD at a level that does not harm the ILD;
- (b) modulating the operating current by decreasing the operating current so that the ILD is below its maximum level for any level of modulation;
- (c) sensing a temperature of the ILD;
- and
- (d) changing the operating current proportionally to a change of the sensed temperature.
The method of claim further comprising the step of shunting a portion of the operating current from the ILD with a transistor operated by an amplifier having as inputs a stable base voltage and a variable voltage.
A method of adjusting a maximum available drive current provided to an injection laser diode (ILD) responsive to ILD temperature changes, the method comprising the steps of:
- (a) providing a bridge network comprising plural resistors and a thermistor for providing a first signal related to ILD temperature, and a second signal not affected by ILD temperature changes;
- (b) providing an operating current to the ILD with a transistor having its base current provided by an amplifier having the first and second signals as inputs;
- whereby the base current adjusts the operating current provided by the transistor responsive to ILD temperature changes indicated by changes in the first signal.
A laser driver for an injection laser diode (ILD) comprising:
- first circuit means for providing an operating current to drive the ILD at slightly less than the ILD maximum level;
- a modulator for decreasing the operating current so that the ILD is below its maximum level for all levels of modulation;
- a thermistor for sensing a temperature of the ILD;
- second circuit means for (a) changing the operating current that operates the ILD near its maximum level proportionally to a change of the sensed temperature, and (b) compensating for changes in an output from a power source that provides the operating current.
A circuit for adjusting a maximum current provided to an injection laser diode (ILD) responsive to ILD temperature changes, the circuit comprising:
- a bridge network of resistors, one of said resistors having a resistance related to ILD temperature;
- a transistor for providing an operating current to the ILD;
- an amplifier for providing a base current to said transistor, said amplifier having as inputs a first signal from said bridge network and a second signal from a feedback resistor connected to an output of said amplifier;
- and
- a source of a fixed voltage for providing a fixed voltage to said bridge network and to a terminal of said transistor,
- whereby said base current adjusts the operating current provided by said transistor responsive to temperature changes sensed at said one of said resistors having a resistance related to ILD temperature.
A circuit for providing an operating current to an injection laser diode (ILD) comprising:
- a power source with a fixed voltage for providing an operating current for two parallel subcircuits,
- a first of said subcircuits comprising an ILD, and a second of said subcircuits comprising a resistor in series with a transistor for shunting a portion of the operating current from the ILD;
- and
- an amplifier for providing a base current for said transistor, said amplifier having as inputs a stable base voltage and a variable voltage for modulating the ILD by operating said transistor to decrease the operating current available to the ILD when the ILD is modulated.
A method of operating an injection laser diode (ILD) so that the ILD is not subjected to a potentially harmful operating current, the method comprising the steps of:
- (a) providing an operating current for the ILD from a power source, the operating current
- (i) being provided through a circuit that renders the operating current insensitive to fluctuations in the power source output, and
- (ii) for operating the ILD at a level that does not harm the ILD;
- and
- (b) modulating the operating current by decreasing the operating current so that the ILD is below its maximum level for any level of modulation.
A laser driver for an injection laser diode (ILD) comprising:
- first circuit means for providing an operating current to the ILD that operates the ILD near its maximum level;
- a modulator for decreasing the operating current so that the ILD is below its maximum level for all levels of modulation;
- and
- second circuit means for compensating for changes in an output from a power source that provides the operating current.
Dependencies are inferred from the claim text.