A laser diode control circuit includes: a LD driver circuit for driving a laser diode; a direct current component remover circuit for generating a feedback signal based on a detected signal; a first conversion and filter circuit for generating a first filtered signal based on the feedback signal; a first rectifier for rectifying the first filtered signal to generate a first rectified signal; a reference signal generator for generating a reference signal; a second conversion and filter circuit for generating a second filtered signal based on the reference signal; a second rectifier for rectifying the second filtered signal to generate a second rectified signal; a rectified signals processing circuit for generating a processed signal based on the first and second rectified signals; and a comparator for generating a comparison signal based on the processed signal.

A system comprising drive circuitry configured to apply in a start-up phase a first drive current and then a second different drive current to a laser diode, the first drive current and second drive current being such that the laser diode is configured to provide a first optical output and a second optical output respectively. The system further comprising an optical sensor configured to provide a first sensor output corresponding to the first optical output of the laser diode and a second sensor output corresponding to the second optical output. The system further comprises a controller configured to use a value of the first drive current, a value of the second drive current, the first sensor output, the second sensor output and at least one supplied input value to provide control values for the drive circuitry to control an operating current of the laser diode, wherein the system is arranged to be used in a communication system wherein information is transmitted in at least one burst.

Systems and methods of laser bias calibration are presented. A preamplifier circuit may include a laser voltage monitor circuit and a laser bias control circuit configured to automatically adjust an output laser bias threshold voltage based on a monitored laser voltage. The laser bias control circuit may include a first differentiator circuit, a second differentiator circuit, and a threshold detection circuit. The preamplifier circuit may be utilized in a heat assisted magnetic recording device.

A system for dynamically adjusting a bias voltage for a laser diode or a light emitting diode is provided. An output voltage of the laser diode is measured and a level of a supply voltage applied to the laser diode is adjusted to change the bias voltage to the laser diode to manage power usage and avoid saturation of the laser diode. Also, a junction temperature of a laser diode may be estimated by mapping a measured output voltage and known current to device characteristic data based on temperature and the supply voltage adjusted in order to bias the laser diode to compensate for a temperature change. Further, data indicating an intensity level of data to be rendered by the laser diode is used to adjust the second supply voltage to bias the laser diode in advance of rendering the data.

A laser device includes a laser diode configured to emit radiation, an output power of the radiation being dependent on a laser diode driving current, and a photodiode configured to receive the radiation emitted by the laser diode. A photodiode current induced in the photodiode by the received radiation is dependent on a power of the received radiation. The laser device further includes circuitry configured to measure the photodiode current for a laser diode driving current and calculate a laser threshold current of the laser diode from the measured photodiode current as a measure of an actual laser threshold current of the laser diode. The circuitry is further configured to detect a malfunction or degradation of the laser diode.

A system for dynamically adjusting a bias voltage for a laser diode or a light emitting diode is provided. An output voltage of the laser diode is measured and a level of a supply voltage applied to the laser diode is adjusted to change the bias voltage to the laser diode to manage power usage and avoid saturation of the laser diode. Also, a junction temperature of a laser diode may be estimated by mapping a measured output voltage and known current to device characteristic data based on temperature and the supply voltage adjusted in order to bias the laser diode to compensate for a temperature change. Further, data indicating an intensity level of data to be rendered by the laser diode is used to adjust the second supply voltage to bias the laser diode in advance of rendering the data.

A laser diode control circuit includes, a control signal supply circuit that supplies a control signal including a direct current component and an alternating current component to a laser diode, an optical output signal acquisition circuit that acquires an optical output signal indicating an optical output of the laser diode according to the control signal, a phase determination circuit that determines whether a phase of the alternating current component included in the optical output signal is the same as the phase of the alternating current component included in the control signal, and a control signal determination circuit that determines to decrease the direct current component of the control signal when it is determined that the phase of the alternating current component included in the optical output signal is not the same as the phase of the alternating current component included in the control signal.

The present invention comprises: a light-emitting element group configured from columns of serially connected light-emitting elements, one of the ends from each of the columns of the light-emitting elements being collectively connected to a power source; current control elements, provided to correspond to the columns, and being connected to each of the columns of the light-emitting elements at the other end thereof, for controlling the current flowing through the light-emitting elements; a forward voltage monitoring circuit for monitoring, for each of the columns, the total forward voltage across the light-emitting elements; and a control circuit for controlling the current control elements, on the basis of the total forward voltage across the light-emitting elements from each of the columns detected by the forward voltage monitoring circuit, in such a manner that the variations in the total forward voltage across the columns of the light-emitting elements reach a threshold value or lower.

A drive apparatus includes a light emitting device, a light receiving device configured to receive light emitted by the light emitting device, a comparison circuit configured to compare a light quantity of light detected by the light receiving device with a target value indicating a light quantity of light to be emitted by the light emitting device and generate a control signal corresponding to a comparison result, and a drive circuit configured to supply a drive signal corresponding to the control signal to the light emitting device. The drive circuit includes a gain changing switch configured to change, in accordance with the target value, a gain of the drive circuit.

A laser power controller employs: selection circuitry configured to select one of a data input value, a logical high value or a logical low value such that the selection circuitry selects the data input value during a data transmission period during a defined burst period and selects one of the logical high value and the logical low value during an extension time period during the defined burst period and immediately following the data transmission period; drive circuitry configured to apply, to a laser diode, a current corresponding to the value selected by the selection circuitry during the defined burst period or a zero value otherwise, the current being such that the laser diode is configured to provide an optical output; an optical sensor module configured to provide a sensor module output corresponding to the optical output of the laser diode, and configured to provide an electrical output proportional to the laser diode's optical output corresponding to the logical high value or the logical low value; and a controller configured to receive desired values regarding minimum and maximum optical output power levels of the laser diode and to receive the electrical output from the optical sensor module proportional to the optical output power level corresponding to the logical high and the logical low values; the controller being configured to use the received information to provide control values for the drive circuitry.