Abstract: A semiconductor laser light emitting circuit includes a semiconductor laser diode emitting a laser light by modulating a current supplied thereto, a light intensity detection circuit that detects the laser light and generates a voltage, and a voltage-current conversion circuit converting a voltage into a current supplied to the laser diode. A S/H capacitance is provided to store electric charge and output a voltage to the voltage/current conversion circuit. A first operational amplifier is provided to output a first current charging the S/H capacitance. A rapidly charging circuit is provided to charge the S/H capacitance with a second current. The rapidly charging circuit terminates charging when the voltage is equal to or more than a second reference voltage.

Abstract: An automatic closed loop power control system is described for simultaneously adjusting an output power and an extinction ratio P1/P0 of a laser diode in order to maintain a desired average output power and a desired extinction ratio. The bias current component of a laser diode drive current is adjusted to compensate for changes in the average output power caused by ambient characteristics such as temperature and aging. Simultaneously, a modulation current component of the laser diode drive current is adjusted to maintain an extinction ratio of the laser diode output signal. The bias current and modulation current adjustments are based on the second order statistics of an average output power of the laser diode and a variance in the power output of the laser diode.

Abstract: A tunable optical local oscillator is used for optical heterodyne signal detection using an electrooptic Mach-Zehnder modulator to produce a rapidly tunable optical signal from a tunable RF frequency generator. A combination of the Mach-Zehnder modulator and optical fibers for providing stimulated Brillouin scattering are used to suppress unwanted signals for providing a spectrally pure optical local oscillator waveform. Suppression of unwanted optical signals, up to 50 dB, generated by the Mach-Zehnder modulator is obtained, resulting in high spectral purity of the optical local oscillator waveform with an extended tuning range of the tunable optical oscillator equal to the operating bandwidth of up to 60 GHz of the Mach-Zehnder modulators.

Abstract: A multi-tone photonic oscillator comprises a laser; an optical modulator coupled to the laser; and a delay line and a photodetector coupled to the optical modulator for generating a delayed electrical signal representation of the output of the optical modulator; wherein the optical modulator being responsible for the delayed electrical signal for generating multiple tones where the frequency intervals of the tones is a function of the amount of delay imposed by the delay line.

Abstract: A method and apparatus for feedback control of a laser, which includes outputting a laser beam from the laser to an optical bundle. The intensity of the laser beam is measured at a point between the laser and the optical bundle and a raw feedback signal is output in response thereto. The raw feedback signal is multiplied by a laser calibration factor and an optical bundle calibration factor and output as an adjusted feedback signal. A controller is then used to control the intensity of the laser in response to the adjusted feedback signal.

Abstract: A laser oscillator capable of executing a high-speed feedback control by reducing the control load of a main processor in the feedback control of the laser output. The laser is excited by an excitation source activated by one or more power supplies. The laser radiation is detected by a power sensor or a photodiode. A detected signal is A/D converted and fed to a sub processor or a high-speed DSP. The sub processor compares the current laser output value to a desired control value and calculates a deviation value in a predetermined period. The sub processor outputs a feedback signal to each of the power supplies according to a command from the main processor. Each power supply adjusts the supplied current to control the laser output. The main processor monitors conditions of the power supplies and controls a coolant circulation device. A factor regarding a load on a sequential control process, which may delay the feedback control, is eliminated and an analog circuit is unnecessary.

Abstract: An apparatus for and a method of controlling an output of a laser diode in an optical recording/reproducing apparatus. The apparatus includes a sampling circuit sampling a present power value output from the laser diode with a predetermined frequency, an arithmetic unit connected to the sampling circuit, outputting a control power value applied to the laser diode in response to the present power value output from the sampling circuit and a reference power value, and a controller connected to the sampling circuit and the arithmetic unit, generating control signals, which control the operations of the sampling circuit and the arithmetic unit.

Abstract: An apparatus comprising a first reference element having an output power that varies monotonically with input frequency over an operating frequency range and receiving at least a portion of an output beam of light from an optical source. A second reference element having an output power that is frequency dependent receives at least a portion of the output beam of light. A first optical detector measures the power of a first reference beam of light from the first reference element. A second optical detector measures the power of a second reference beam of light from the second reference element. Electronic circuitry is coupled to the first and second optical detectors for receiving first and second reference signals therefrom and producing a coarse error signal for permitting coarse adjustment and a fine error signal for permitting fine adjustment of the frequency of the output beam of light.

Abstract: A control apparatus for stabilizing optical wavelength output by a laser module in which a laser element, temperature sensor and cooling/heating element are installed, comprises a temperature deviation detecting circuit comprising a temperature monitor for detecting a laser temperature, and a first comparator for outputting a first control signal indicating a difference between the laser temperature and a control target value, a wavelength deviation detecting circuit comprising a wavelength monitor for detecting light output from the laser element, and a second comparator for outputting a second control signal indicating a difference between the wavelength of the detected output light and a control target value, a selector circuit for selecting either of the detecting circuits according to the external conditions of the laser element, and a current controller for controlling the current supplied to the cooling/heating element based on the output signal from the selected detecting circuit.

Abstract: A method for determining a condition of the laser system includes determining a change in a laser current from an initial value. A method for measuring a laser current includes determining a difference between the values of a power supply current, which is the value of the laser current. A method for measuring a transmitted power includes generating a first control signal that sets a magnitude of a bias current supplied to a laser, generating a second control signal that sets a of a modulation current supplied to the laser, and determining a difference between values of a high and a low transmitted powers. A method for measuring a received optical power includes determining a received OMA corresponding to the power signal, which is the transmitted OMA minus a known loss through a calibration fiber that couples the laser transmitter to the laser receiver.

Abstract: A method of determining the time for executing optimal power calibration in an optical drive. First, relationships between values of a driving signal and ambient temperatures of the optical drive are recorded in look up table in a memory. According to the look up table, mappings from the values of a driving signal output by a compensator to the ambient temperature of the optical drive can be obtained. When the ambient temperature of the optical drive is higher than a predetermined temperature, an optimal power calibration is executed.

Abstract: A laser control circuit comprises a temperature control circuit and a data processing circuit. The temperature control circuit adjusts the temperature of a laser diode by controlling a temperature regulator. The data processing circuit receives the output of a wavelength monitor. The data processing circuit first adjusts the, temperature of the laser diode to a temperature value previously associated with the target wavelength. Then the data processing circuit finely adjusts the temperature of the laser diode according to the output of the wavelength monitor. Because rough adjustment has been carried out, it is not necessary to change the wavelength significantly according to the output of the wavelength monitor. Therefore, the periodic wavelength dependence of the output of the wavelength monitor does not decrease the accuracy of the control.

Abstract: A method for controlling a laser beam power balance in a laser scanning unit is disclosed. The method of present invention comprises the steps of obtaining a first voltage value and a second voltage value corresponding to detection time points of a first laser beam and a second laser beam, respectively, emitted from the laser scanning unit. The first voltage value and the second voltage value are recorded in the laser scanning unit. After the laser scanning unit is mounted on a image forming apparatus, a third voltage value and a fourth voltage value are obtained corresponding to the detection time points of the first laser beam and the second laser beam, respectively, emitted from the laser scanning unit by driving the laser scanning unit mounted on the image forming apparatus. The third voltage value and the fourth voltage value are compared with the first voltage value and the second voltage value, respectively, thereby correcting the control voltage controlling the laser scanning unit by that variation.

Abstract: The object of the present invention is to provide an optical module for the WDM communication system, in which the oscillation wavelength is on the grid of the WDM regulation, moreover the optical output power and the oscillation wavelength can be controlled independently. The present module comprises a semiconductor light-emitting device, a wedge shaped etalon device and two light-receiving devices. The etalon device contains a first portion, on which the anti-reflection films are coated, and a second portion. One of the receiving devices detects light transmitted through the first portion of the etalon device, while the other device detects light through the second portion. Signal from the former device controls the output power of the light-emitting device, while the signal from the latter receiving device controls the oscillation wavelength of the laser.

Abstract: One embodiment of the present invention includes an optical cavity, a source to provide light to the optical cavity, a sensor to detect the light and generate a corresponding sensor signal, and a servo device including a feedforward input and a feedback input. Feedback from the sensor signal is provided to the servo device to regulate operation of the source at a frequency selected to generate an optical field resonating in the first mode in the cavity. An input device provides a control signal to a control input of the servo device that selectively alters operation of the light source to corresponding halt resonance in the first mode. An evaluation device is also included to evaluate decay of the optical field after resonance in the first mode is halted.

Abstract: A method for stabilizing a laser frequency using sub-Doppler spectral spectrum of atoms, and a laser frequency stabilization device used in the method which is comprised of a gas charged cell, a laser, a laser frequency adjusting means, a laser beam dividing means for dividing the laser beam into a pump beam and a probe beam, a photo detector for measuring intensity of the probe beam after passed through the cell, an ON/OFF means for cutting off the pumping beam at a constant time interval, a computing means for obtaining the intensity of the probe beam, a demodulated signal of the probe beam, the difference in intensity between the probe and pumping beam, and a difference in demodulated signal, and a feedback means which feeds back the information to the laser frequency adjusting means, thereby stabilizing the frequency of the laser.

Abstract: A laser system for controlling output of a laser oscillator based on a monitor light obtained by splitting a laser beam, comprising a light emitting means for emitting the laser beam, a luminous flux splitting means disposed on an optical path of the laser beam and reflecting a part of the laser beam as a monitor light, and a photodetecting means for receiving the monitor light, wherein the luminous flux splitting means has a reflection surface of an incident angle so that reflectivity is kept at approximately constant level with respect to the laser beam regardless of condition of polarization of the incident laser beam.

Abstract: An optical transmitter is equipped with a laser diode and a light detector provided on a packaging base, in which the light detector has a semiconductor substrate side arranged on a packaging base side, a semiconductor junction plane, a side surface which is roughly orthogonal to the semiconductor junction plane, and a facing surface which faces the side surface, wherein the facing surface is partially or completely inclined to reflect the output light from the laser diode incident from the side surface to the semiconductor junction plane of the light detector.

Abstract: A laser system includes a pump source that produces a first output. The pump source has a feedback loop with a first summing junction and a first command that has step quantization or digitized set point. An output device is coupled to the pump source to receive the first output and produce a second output. A feedback loop is coupled to the first summing junction. The feedback loop includes a second summing junction coupled to at least a portion of the second output. The second summing junction receives a second command and provides an input to the first summing junction. The feedback loop reduces the step quantization from the first output to provide finer control step of a property of the second output.

Abstract: Multiple operational parameters for a laser device are simultaneously controlled, optimized and/or stabilized by a software-based system with nested and interactive feedback control loops. Start-up mode, channel lock mode and channel change mode operations are described. The invention may be applied to a laser device with monolithic DBR tuning and gain sections, and also to systems with separate amplifiers. An optical filter system for normalizing-out changes in output power in relation to wavelength control is also disclosed.

Abstract: Embodiments of the present invention include a thermistor and resistor network coupled to change the effective responsivity of a monitor photodiode positioned to monitor laser power output to compensate for changes in optical fiber tracking caused by changes in temperature and maintain constant or proportional the ratio of light coupled into the optical fiber to the light coupled to the monitor photodiode.

Abstract: 1. A pulse oscillating type solid laser unit that has a laser unit body whose exciting source is a laser diode that emits light in a principal energy absorbing spectrum of a solid laser activated media, and characterized by that prior to radiating laser light outside the laser unit body as a calibrating operation of a pulse laser output value, specified several varieties of rectangle pulse current values are conducted to a laser diode inside the pulse oscillating type solid laser unit so as to pulse-oscillate the laser unit body, a mean laser output value in each rectangle pulse current value is measured by the use of a laser output measuring instrument arranged inside the laser unit body so as to obtain a mean laser output value data, and in case that the laser output light is radiated outside the laser unit body, a pulse current value linear-predicted based on an obtained mean output value data is conducted to the laser diode so as to obtain a desired pulse laser output value.

Abstract: Tunable laser systems use servo control loops to control and monitor laser parameters such as channel, temperature, and power. The many control loops operate asynchronously, which means that noise generated by input sampling and/or output updating from one or more loops could interfere with the sampled inputs of one or more of the other loops. Embodiments of the present invention synchronize setting and sampling of tunable laser parameters to reduce noise. Noise that is related to synchronized setting and sampling of tunable laser parameters allows the noise to be reduced to constant offsets to be compensated for in the laser parameters of interest.

Abstract: An arrangement for tuning a micro-electro-mechanical (MEM) laser center wavelength to exactly match the passband of its associated filter. A dither wavelength locked feedback loop dynamically adjusts the position of the MEM element, and hence the laser, wavelength, to keep it nominally centered at the filter passband peak. The dither wavelength locked feedback loop compensates for many internal variables of the laser, filter, and the MEM with a single mechanism that stabilizes the laser and locks the wavelength to any desired value.

Abstract: A fiber optic phased array, as well as associated methods and apparatus for controllably adjusting the frequency of the optical signals emitted by a fiber optic phased array, are provided that permit wide band phase control and may be implemented utilizing conventional analog electronics. In this regard, the method and apparatus can independently control the phase of the optical signals propagating through each fiber optic amplifier of the fiber optic phased array, even as large optical phase disturbances occur. As such, the control method and apparatus permit a fiber optic phased array to generate a flat phase front that, in turn, can provide a diffraction limited output laser beam. Alternatively, the control method and apparatus may be designed such that the output signals emitted by an array of fiber optic amplifiers has any other desired phase front, such as to compensate for atmospheric perturbations or the like.

Abstract: An apparatus and method for controlling the phase of a tunable laser is provided. Stabilization of the mode of a laser beam is provided as the laser is tuned to a target frequency. For one embodiment, a laser generates a reference beam and an output beam. The power of each of beam is measured by optical detectors, and a ratio thereof is utilized to detect when a mode hop occurs as the laser is coarsely tuned. The average of the pre and post mode hop ratios is utilized as a control setpoint while finely tuning the laser to the target frequency. Wavelength lockers, optical power dividers and optical detectors are utilized to determine power levels of the reference and output beams while also monitoring frequency characteristics thereof. A control unit utilizes the outputs from the wavelength locker to control the operation of the extended cavity laser during and after tuning.

Abstract: In order to tune an oscillation wavelength of a semiconductor laser diode to a target wavelength, the amount of change of a wavelength to the amount of change of a wavelength varying item is determined by actual measurement and a basic wavelength coefficient is renewed by using the ratio of both amounts of change as a corrective wavelength coefficient, and thus the characteristic when the wavelength of an actual device is made closer to a target wavelength is utilized.

Abstract: A controller for use with an optical device having an optical source and a frequency reference element. The controller includes a frequency processing module coupled to the optical device. The frequency processing module generates an error signal indicative of a deviation between the output frequency of the optical source and a reference frequency corresponding to a reference point. A driver module communicates with the optical device and the frequency processing module. The driver module adjusts a parameter of the optical source in response to the error signal. An offset processing module is coupled to the frequency processing module. The offset processing module derives an offset signal based on an estimate of a temperature of the frequency reference element. The offset processing module provides the offset signal to the frequency processing module which updates the reference point in response to the offset.

Abstract: A light frequency locker (10) able to accept a light beam (14) generated by a controllable light source (12) into a light diverter (16) and impart to it a transverse displacement characteristic which can be detected in a light detection unit (20) connected to a processor (22). The processor (22) then controls the light source (12). Optionally, a light diverger (18) may be provided to enhance angular resolution. The light diverter (16) and the light diverger (18) may either transmit or reflect the light. The light diverter (16) may particularly include a diffraction grating (116, 156), Fabry-Perot interferometer (216), multiple slit plate (316), or an acousto-optical unit (416).

Abstract: A laser transmitter capable of transmitting large numbers of WDM channels but requiring locking of only a single channel. Each of the channels can be individually modulated using an external modulator.

Abstract: A wavelength stabilized laser module is provided which is so configured as to be simplified and smaller in size and is capable of emitting semiconductor laser light whose wavelength is stablized with high accuracy. The wavelength stablized laser module includes a semiconductor laser, a substrate, a lens to convert emitted semiconductor laser light to parallel luminous flux, a first photoelectric converter to receive a part of the parallel luminous flux and to convert it to electric signals, a filter to receive a part of the parallel luminous flux, a second photoelectric converter to receive light transmitted through the filter and to convert it to electric signals, wherein a control signal to be used for stabilization obtained by computations of electric signals fed from the converters is fed back to the semiconductor laser device and/or the substrate so that said semiconductor laser is able to stably emit laser light having a reference wavelength to be used as a target for stabilization.

Abstract: An object of the invention is to provide a wavelength locker which has a wider locking range than that of the wavelength locker in the prior art and which can cope with a plurality of wavelengths. The aforementioned objects are achieved by a wavelength locker, which comprises a periodic filter, a detecting part for detecting the intensity of a laser beam through the periodic filter, and a controlling part for controlling the wavelength of the laser beam to a desired wavelength in accordance with the output of the detecting part. In this wavelength locker, the FSR of the periodical filter is controlled according to space between the wavelengths, and refers to the number of wavelength to be locked, so that the characteristics corresponding to output wavelengths that vary in every period twice the space of wavelengths and are complementary to each other, can be obtained, and the locking range will become wider.

Abstract: A method and device for the nonlinear combination of laser light which produces a beam of uniform intensity, high spatial purity, and high conversion efficiency. The method includes emitting a laser light from a tunable distributed feedback fiber laser having both thermal and piezoelectric control elements which produces a laser light at a given frequency, wavelength, and intensity; converting the laser light in a nonlinear resonator which uses a nonlinear optical crystal for frequency conversion or mixing; and measuring the resonant frequency of the nonlinear resonator and adjusting the laser light frequency using both the thermal and piezoelectric elements of the fiber laser light source to match the resonant frequency conditions within the nonlinear resonator.

Abstract: Apparatus and method for stabilizing the wavelength of a tunable laser to a target wavelength, by correspondingly adjusting the electrooptical performance of the laser's gain medium, whereby to eliminate the frequency shift due to vibrational factors. The electrooptical performance of the laser's gain medium is adjusted, in the case of an electrically pumped laser, by changing the injection current used to pump the laser; and the electrical performance of the laser's gain medium is adjusted, in the case of an optically pumped laser, by changing the intensity of the pump laser used to energize the laser. The system is implemented with a feedback mechanism.

Abstract: A die having a semiconductor laser driven by a differential drive circuit is provided. The die provides a matched load to the drive circuit by also having a balancing load with an impedance, including both resistive and reactive components substantially identical to the load impedance of the semiconductor laser fabricated on the die. With the balancing load and semiconductor laser pair, the die prevents impedance-mismatch-induced drive problems that occur in high frequency operation, e.g., above about 1 GHz. The semiconductor laser may be a vertical cavity surface emitting laser (VCSEL), for example, as are used in high bandwidth applications like Gigabit Ethernet and Fibre Channel Applications. Furthermore, the die can form an array of balancing and semiconductor laser pairs.

Abstract: A laser diode drive circuit for an optical disc recording and/or reproducing apparatus includes a plurality of laser diodes to output laser beams having different wavelengths, a switch circuit for selectively connecting a required laser diode from a plurality of laser diodes, a laser diode drive power supply circuit for driving the laser diode selectively connected by the switch circuit, a photodiode for detecting at least part of laser beams emitted from the laser diode to convert a detected part of laser beams into an electrical signal, a plurality of current-to-voltage conversion amplifiers connected to an output of the photodiode and whose conversion resistance values can be adjusted and having differently designed center conversion resistance values and an automatic power control circuit connected to outputs of the current-to-voltage conversion amplifiers to output a feedback signal to the laser diode drive power supply circuit.

Abstract: A digital laser driver circuit is provided in which a digital synthesizer synthesizes a modulation index signal for precisely setting the modulation level of the laser, and a pair of feedback loops control the average power level and modulation index of the laser diode. The laser diode includes a back-facet photodiode that is used to monitor the laser's average and peak optical power levels. The average power level is measured by an analog feedback loop and compared to an externally supplied reference voltage in order to maintain the laser at a particular average optical power level. The peak power is measured by a digital feedback loop and compared to a pair of threshold levels based on a ratio of the average power level using digital comparators. The comparators provide signals to the digital synthesizer in order to indicate that the modulation level is too low or too high.

Abstract: In the initial state, any wavelength variation of the output signal light with a change of the current injected into the laser is monitored with a wavelength meter, the quantity of wavelength variation is fed back to the wavelength compensation circuit, a compensation voltage for maintaining the wavelength in the initial stage is figured out, and that voltage is recorded into a memory element or the like. A configuration to add this compensation voltage to a comparator makes it possible to compensate for fluctuations of the characteristics of the optical splitter, wavelength filter and light receiving elements and thereby to obtain a stable optical wavelength. By constantly monitoring the injected current applied to the laser when the optical transmitter is in operation and giving a compensation voltage matching the current variation to the comparator, stabilization of the optical wavelength can be realized.

Abstract: In a method and apparatus for synchronizing the output of two passively modelocked pulsed lasers, the output of each laser is sampled and delivered to two photodiodes, one for each laser. The output of the each photodiode is converted to a train of digital pulses having the pulse repetition frequency of each laser. The digital pulses are processed in a digital phase detector that generates from the digital pulses a first analog voltage representative of the phase difference at the photodiodes between corresponding pulses in each train. This analog voltage is summed with a second analog voltage representative of a desired phase relationship of the laser pulses at a target location remote from the photodiodes. The sum of the analog voltages provides an error signal that commands a device to adjust the length of the resonator of one of the lasers. When the error signal is minimized, pulses from each laser have the same repetition frequency and have the desired phase relationship at the target.

Abstract: A servo technique for concurrently providing wavelength locking and stimulated Brillouin scattering (SBS) suppression in an external cavity laser. Respective wavelength locking and SBS suppression signals are generated by a controller and combined into a composite drive signal. The composite drive signal is used to drive an optical path length adjustment element to modulate the optical path length of the laser cavity. The wavelength locking and SBS suppression portions of the drive signals produce concurrent modulations of the laser optical path length having different modulation frequencies and causing different frequency (wavelength) excursions. These modulations produce corresponding wavelength and intensity amplitude modulations in the laser's output. A feedback signal indicative of the intensity amplitude modulations is filtered to attenuate the portion of the signal due to the SBS suppression modulation, and is received as a tuning feedback signal by the controller.

Abstract: A device for adjusting laser diodes includes a pilot signal adjustment device for adjusting the signal current using a pilot signal frequency that is modulated onto the signal current. The device includes a bias direct current source supplying the laser diode with a bias direct current. A switching device switches the adjustment device between a state where the pilot signal adjustment device is connected to the modulator and the bias direct current source such that the signal current can be adjusted using the pilot signal adjustment device, and another state where the modulator is connected to the temperature compensation device such that the signal flow can be adjusted and/or controlled by the temperature compensation device.

Abstract: A wavelength locked tunable laser source comprising a tunable laser source, an optical reference source characterized by a frequency spectrum with two combs of discrete components of different spacing, an optical mixing device and feedback control circuitry. An optical output of the laser source is heterodyned with an output of the optical reference source at the optical mixing device to produce an electrical signal in dependence on a difference beat frequency of the two optical outputs, the feedback control circuitry being operative to process the electrical signal to provide a feedback signal which is used to tune the wavelength of the laser source so as to minimize the beat frequency and thereby substantially lock the wavelength of the laser source to a wavelength in the spectrum of the optical reference source. The use of an optical reference source with a spectrum comprising two frequency combs provides a mechanism for determining the absolute frequency to which the laser has been locked.

Abstract: A system and method for reducing or eliminating the speckle intensity distribution of a laser imaging system. In one embodiment of the invention, a radio frequency signal is injected into a semiconductor laser light source (12) for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, optical feedback is used to induce a laser light source for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, the laser light source wavelength is Doppler shifted to produce different speckle patterns. In another embodiment of the invention, a means of deflection is used to directionally move the beam to reduce noticeable speckle.

Abstract: A tunable laser source changes the resonator length of an external resonator, which is constituted including a laser diode and a diffraction grating, by a driver controlled by a drive control section, to continuously or intermittently vary the wavelength of an emitted light from a start wavelength to a stop wavelength that are desired. A point wavelength information setting section sets the point wavelength information representing the positional information of the driver that corresponds to each resonator length of the external resonator regarding the start wavelength, the stop wavelength and a plurality of the wavelengths obtained by dividing a period between the start wavelength and the stop wavelength into arbitrary steps. An emitted wavelength information detecting section detects emitted wavelength information corresponding to the wavelength of the emitted light from the tunable laser source.

Abstract: A laser system includes a pump source that produces a first output. The pump source has a feedback loop with a first summing junction and a first command that has step quantization or digitized set point. An output device is coupled to the pump source to receive the first output and produce a second output. A feedback loop is coupled to the first summing junction. The feedback loop includes a second summing junction coupled to at least a portion of the second output. The second summing junction receives a second command and provides an input to the first summing junction. The feedback loop reduces the step quantization from the first output to provide finer control step of a property of the second output.

Abstract: An optical transmitter circuit including a light receiving element, such as a photodiode, which monitors the optical output of a light emitting element such as a semiconductor laser. A current-voltage converting circuit supplies a drive current from a drive circuit to the light emitting element and converts the output voltage of the light receiving element into voltage. An APC amplifier compares the converted output signals and a reference signal, and a hold circuit holds the output signal of the APC amplifier and uses the output signal as a current control signal of the drive circuit. A “1” continuous signal detecting circuit detects the continuation of “1” in a specified number of bits in the input data (DATA) and updates the hold value in the hold circuit.

Abstract: A compact, low-cost semiconductor laser driving apparatus which can assuredly prevent the influence of mode-hopping noise, a semiconductor laser driving method and an image forming apparatus are provided. Automatic Temperature Control and Automatic Power Control are performed and then the temperature of a laser diode (LD) is raised in small increments (0.1° C.). At each temperature level, the LD is driven in accordance with predetermined image data and an LD light amount is detected for each of a predetermined number of image lines. When the proportion of these line light amounts that are outside a range of tolerance is less than a predetermined proportion (5%) for a predetermined number of consecutive temperature levels, the temperature is stored to serve as a control temperature of the LD during actual optical scanning. This process is performed for all LDs.

Abstract: A light emitting module packaging two light sources emitting two light beams of different wavelengths, and a compatible optical pickup device adopting the module are provided. The light emitting module includes a base, first and second light sources installed on the base, for emitting laser beams in different wavelength regions, a beam splitter and a monitoring photodetector for monitoring the optical outputs of the first and second light sources by receiving the beams emitted from the first and second light sources and split from the beam splitter in one direction.

Abstract: Systems and techniques for suppressing the carrier signal using an optical delay element and an electrical interferometer in an opto-electronic noise suppression module.

Abstract: Apparatus for stabilizing an output wavelength of a laser assembly (80), including a plurality of optical elements (88, 92, 97, 96) coupled together so as to form a laser cavity resonating in a single mode dependent upon an optical length of the cavity, and an optical length changer (86) which varies an optical length of at least one of the optical elements so as to vary accordingly the optical length of the cavity. The apparatus further includes a detector (91) which monitors the output of the laser assembly responsive to the variation in the optical length of the at least one of the optical elements. There is also included a stabilizer (93) which responsive to the measured output from the detector supplies a control signal to the optical length changer to control an optical length of at least one of the optical elements, so that the cavity resonates stably at the output wavelength in the single mode.