Abstract: In a laser array device, each laser of a transmitting unit 30 and each optical detector of a receiving unit 20 are arranged to be adjacent to each other. A plurality of unit modules 40 are formed so that each unit module 40 contains adjoining laser 30-1 and optical detector 20-1, and a laser control circuit 10-1. In each unit module, a part of laser beam outputted from the laser is reflected and outputted to the optical detector, an intensity of the laser beam outputted from the laser is detected based on a detection signal outputted from the optical detector, and when the detected laser-beam intensity exceeds a predetermined reference level, the output of the laser beam of the laser is stopped.

Abstract: High-speed measurements of the output power level of a laser are obtained by using a high-speed laser output power monitoring device that is capable of producing an electrical feedback signal having an amplitude that varies as the output power level of the laser varies. A high-speed amplitude detector receives the electrical feedback signal and detects the amplitude of the feedback signal and produces an optical modulation amplitude (OMA) detection signal. The OMA detection signal is received in a high-speed amplitude measurement device that measures the OMA and produces an OMA measurement value. The OMA measurement value is then processed by the laser controller to obtain a modulation current control signal, which is then output to the laser driver to cause the laser driver to adjust the laser modulation current to obtain a desired or optimum laser output power level.

Abstract: The aim of the invention is to adjust the operating point of a laser that can be modulated by a data signal. The operating point of the laser is adjusted by regulating a direct current flowing through the laser; whereby said direct current correlates with the optical characteristics of the laser. In order to carry out said adjustment, the direct current is controlled above an alterable threshold current. A differential current defined from the difference between the direct current and the threshold current or a variable correlating with the differential current is adjusted to a constant value or one that is solely dependent on temperature for the adjustment of said operating point.

Abstract: Threshold current may be determined and one or more bias sources may be programmed in a laser drive circuit. For example, a laser diode emits light along first and second optical paths. A polarizer is positioned in the first optical path between the laser diode and a first detector, which outputs a first detector signal corresponding to the measured optical power of polarized light. A second detector monitors light along the second optical path and provides a second detector signal. A bias compensation circuit receives the first and second detector signals and provides a bias current control signal, which is utilized to program a bias current source supplied to the laser diode. Additionally, multiple polarizer devices may be utilized e.g., a first polarizer in a first optical path aligned with the laser beam and a second polarizer in a second optical path aligned substantially orthogonal to the polarization of the laser beam.

Abstract: A laser beam temporally modulated in amplitude by a modulator and shaped into a long and narrow shape by a beam shaper is rotated around the optical axis of an image rotator inserted between the beam shaper and a substrate. Thus, the longitudinal direction of the laser beam having the long and narrow shape is rotated around the optical axis on the substrate. In order to perform annealing in a plurality of directions on the substrate, the laser beam shaped into the long and narrow shape is rotated on the substrate while a stage mounted with the substrate is moved only in two directions, that is, X- and Y-directions. In such a manner, the substrate can be scanned at a high speed with a continuous wave laser beam modulated temporally in amplitude and shaped into a long and narrow shape, without rotating the substrate. Thus, a semiconductor film can be annealed.

Abstract: This disclosure concerns systems, methods and devices for temperature-based control of laser performance. One example of a method is performed in connection with a laser of an optoelectronic transceiver. In particular, the laser is operated over a range of temperatures and the optical output of the laser is monitored. During operation of the laser, the bias current and current swing supplied to the laser are adjusted to the extent necessary to maintain a substantially constant optical output from the laser over the range of temperatures.

Abstract: A semiconductor laser wavelength control device capable of controlling the optical wavelength constant even if the optical output intensity of the semiconductor laser varies and permitting a reduction in overall size is to be provided. It is provided with control means which controls the optical wavelength of a laser diode 1 to a prescribed wavelength by driving a temperature control unit to control the temperature of the laser diode 1.

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 infrared transmitter circuit causes an output current to flow to a light emission diode via a current mirror circuit constituted of three transistors by using a current supplied from a power source circuit, so that the light emission diode emits light. When a voltage V1 varied by charging a capacitor with a current flowing from the power source circuit exceeds a reference voltage (voltage V2), an output of a comparator resets a D flip-flop, so that an output of the D flip-flop varies to “0”. Thus, an output of a NAND gate to which that output and a transmission signal are inputted causes a transistor (N-channel FET) to turn ON so as to stop operation of the current mirror circuit, and causes a transistor (P-channel FET) to turn OFF so as to cut a connection between the power source circuit and a power source line. Thus, it is possible to reduce power consumption in operation of a protection circuit which stops supplying the output current to the light emission diode.

Abstract: An adaptive laser diode driver capable of driving various laser diode types as well different laser diodes from the same type, while ensuring optimal optical performance over the lifetime and temperature change of the diode. The driver adaptively changes the voltage level of input data signals to achieve full current switching as well as short rise time (tr) and fall time (tf) in extreme modulation conditions. This is preformed by constantly monitoring the output signal of a laser diode. Based on the monitored signal a modulation current is adjusted and in response the low level and high level of the input data signals are set. In accordance with one embodiment, the adaptive laser diode driver can be integrated in an optical line terminal (OLT) or an optical network unit (ONU) of a passive optical network (PON).

Abstract: In case of driving each of light emitting parts of a surface emitting laser, each of light emitting parts is made to be in forward-bias state and switches appropriately change bias voltage, which is lower than laser oscillation threshold voltage, and drive voltages, which are not less than the laser oscillation threshold voltage to directly apply the changed voltage to each of drive ends of the light emitting parts. Whereby, each of light emitting parts is driven.

Abstract: A method of controlling a laser diode measures an average light output power of the laser diode and compares the average light output power to a desired average light output power within a target range. If the average light output power is not within the target range, the slope efficiency is determined by measuring two light output powers at two different bias conditions. Each of the two light output powers is greater than a selected minimum light output power, which insures that each measurement occurs within the slope efficiency portion of the laser diode curve. A new bias current for the laser diode is calculated based on the measured slope efficiency so as to produce a new average light output power within the target range.

Abstract: A voltage dividing apparatus for preventing sudden increases in power to a laser diode includes a laser diode module, a laser-driving unit and a Zener diode. The laser diode module includes a laser diode for receiving a driving current to emit light, and a photo diode for receiving the light emitted from the laser diode and transferring the light signal into a voltage signal. The voltage signal is fed back to the laser diode module for automatically balancing the power of the laser diode. The laser-driving unit is used for driving the laser diode to output power. When the circuit shorts, two voltage-dividing resistors and the Zener diode disable the laser-driving unit to protect the laser diode. It blocks the laser diode's outputting power to prevent the outputting power from suddenly increasing and prevent the laser with strong power from hurting a user's eyes.

Abstract: A multi-section laser diode control system comprising a multi-section laser diode (10), microprocessor controller (24), digital-to-analogue converter (28), driver circuit (30) and wavelength locker (14) is modified by inclusion of a locking circuit (40) which generates an analogue correction signal . . . 1 V ph responsive to measurements of the laser output made by the wavelength locker. The analogue correction signal is added to the preset phase voltage V ph asserted by the microprocessor controller to provide fast feedback that bypasses the microprocessor controller. This novel feedback is made possible by avoiding the use of the standard prior art control algorithm which requires a division calculation to be performed. Instead, novel control algorithms based purely on additions, subtractions and multiplications are used. The laser can thus be locked to its target output frequency without having to place slow analogue-to-digital and digital-to-analogue converters in the feedback control path.

Abstract: A method includes a scheme for trimming and compensation for a laser emitter in a fiber optic link. Data models of laser performance are provided and used to determine a base power level. It is then confirmed that the base power level is satisfactory. If necessary, adjustments are made to a set of user specified performance parameters until a satisfactory base power level is obtained. Then a table or relation of temperatures and associated current and target average optical power values is generated such that they can be used to regulate laser emitter performance over a range of temperature. Additionally, fiber optic links capable of trimming and compensation are also disclosed.

Abstract: A laser scanning device and an image forming device including the laser scanning device are provided. The laser scanning device includes: a laser diode (LD) driver arranged to control a driving signal supplied to a laser diode (LD); and a power source unit arranged to delay a current supplied from a bias power source for a predetermined period of time to remove a surge current transmitting to the LD driver. In this case, the laser scanning device further includes: a bead arranged to filter the surge current of the driving signal supplied from the LD driver to the laser diode (LD); and a diode connected to the laser diode (LD) in parallel to induce an inverse surge current flowing from a ground port toward the LD driver. As a result, the laser diode (LD) can be prevented from being deteriorated by the surge current.

Abstract: A light emitting device is disclosed that emits light from the surface in a broad spectral range and in a broad range of angles tilted with respect to the direction normal to the exit surface. An apparatus for generating wavelength-stabilized light is formed of a light-emitting device, an external cavity and at least one external mirror. Light emitted by the light-emitting device at a certain preselected angle, propagates through the external cavity, impinges on the external mirror and is reflected back. Light emitted at other angles does not impinge on the external mirror. Thus, a feedback occurs only for the light emitted at a preselected angle. Light impinged on the external mirror and reflected back undergoes interference with the emitted light. The interference can be constructive or destructive. Constructive interference results in a positive feedback. The positive feedback occurs, if light emitted by the light-emitting device is reflected back and reaches the active region in phase, i.e.

Abstract: An inexpensive laser drive device which is capable of driving a laser for emission of an appropriate amount of light. Electric currents supplied from a supply current control device formed in an integrated circuit to a plurality of predetermined ports of the integrated circuit are turned on and off by switching devices in response to a signal from a signal output device of the supply current control device, and the on currents are supplied, as a driving current, from the supply current control device to a laser beam-emitting device through corresponding ones of the predetermined ports and resistors externally attached to these ports. A generator device formed in the integrated circuit generates a pulse signal for turning on and off a laser beam based on image data.

Abstract: An integrated circuit is provided for driving a light source. The light source outputs light. A light receiver receives part of the light output from the light source. In response to a detection current from the light receiver, an automatic power controller adjusts an operating current of the light source. A power converter efficiently supplies power from a power supply to the light source. A modulation signal input unit inputs a modulation signal for modulation of light output power. This circuit structure performs a control operation for constantly maintaining the intensity of light even in a variation in an ambient temperature or deterioration in the light source and also reduces power consumption in the integrated circuit for driving the light source.

Abstract: An automatic power control (APC) circuit applicable to controlling a laser generation module including a laser generator for generating laser and a photosensor for outputting a detection result corresponding to the power of the laser, includes: a comparator, coupled to the photosensor and biased by a first voltage level, for comparing the detection result and a reference signal to generate a comparison result; a level shifter, coupled the comparator, for shifting an intermediate voltage level controlled by the comparison result to generate a control voltage; and a driver, coupled to the level shifter and the laser generator, for driving the laser generator according to the control voltage and a second voltage level.

Abstract: A semiconductor laser driving circuit includes a light amount detector, a frequency determiner, and an initialization circuit. The light amount detector detects an amount of light emitted by a laser diode, and outputs a first voltage corresponding to the amount of light. The frequency determiner determines a frequency for determining a time period of a detecting operation to detect differential quantum efficiency of the laser diode. The initialization circuit performs an initialization operation to detect differential quantum efficiency of the laser diode with a variation of the time period of the initialization operation according to the frequency determined by the frequency determiner.

Abstract: A temperature stabilizer for accurately stabilizing the temperature of an object is provided. The temperature stabilizer stabilizes the temperature of an object to a reference temperature. The temperature stabilizer includes an oscillator provided in proximity to the object, for generating an oscillation signal having a frequency corresponding to an inputted frequency control signal, a phase detector for detecting the phase difference between a feedback signal based on the oscillation signal and a reference clock signal having a predetermined frequency, a loop filter for generating the frequency control signal to synchronize the feedback signal with the reference clock signal based on the output from the phase detector, a comparator for comparing the value of the frequency control signal with a reference value determined corresponding to the reference temperature and an electric heating converter for heating or cooling the object based on the comparison result from the comparator.

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: A power control apparatus and method for an optical drive is disclosed. The power control apparatus estimates the temperature rising effect of a laser diode and performs a partial open-loop power control, achieving accurate write power control. Therefore, regarding to a high-speed, high-density optical disk recording medium combined with multi-pulse write waveforms, the invention can also achieve accurate write power control even though the response speed of a front photodiode is much slower than the modulation speed of recording pulses of the laser diode.

Abstract: Optical transmission components, systems, and packages where the package includes a common housing containing a laser for transmission of an optical signal, a photodetector optically coupled to the laser for monitoring the laser transmission, and a laser driver electrically coupled to the laser for providing a drive current to the laser. The optical package may be a TO-Can package, the laser may be a vertical cavity surface emitting laser (“VCSEL”), and the laser driver may be an AC modulation laser driver, where a bias current is supplied to the laser from external to the optical transmission component package. An external bias source may be used for providing a bias current to the laser. A temperature sensor located in the laser driver may be used to control operational parameters of the laser.

Abstract: A method and apparatus for driving lasers. An example laser driving system includes a laser current controller for providing a modulation signal and a bias signal. The modulation signal and bias signal is used by a plurality of high-speed current drivers that accept the modulation signal and the bias signal and produce a plurality of laser drive signals. The example system also has a disable input that disconnects power from a high-speed current driver when the high-speed current driver is not in use. The exemplary system develops the modulation and bias signals by feeding back a signal developed from detection of laser light from one of the lasers driven by the system. The laser may be a data laser or a control laser that is modulated by a signal having a lower frequency than the data lasers. If a control laser is used then the photodetector circuit used for feedback can have a lower frequency response because of the lower frequency of the control laser signal.

Abstract: An electric discharge, narrow band gas laser with improvements in wavelength stability. Improvements result from reduced laser beam directional fluctuations or fast correction of those fluctuations. Applicant has discovered, using an extremely sensitive knife edge optical technique, that gas discharge laser windows in a trapezoidal configuration were causing slight wavelength perturbations when laser gas density varied during laser operation. The optical technique involves using test laser beam directed through the discharge region of the gas discharge laser, blocking a portion of the beam with a knife edge and measuring the non-blocked portion of the beam to monitor beam deflection. With this technique, Applicant can measure beams deflection with an accuracy of about 0.3 microradians and with a time response of about 1 microsecond.

Abstract: Systems and methods for biasing an externally modulated laser. An inductorless bias T network is provided that includes a terminating resistor in series with a capacitor. The capacitor is an open circuit for a bias signal and a virtual ground for an RF signal. Thus, the RF signal is terminated by the terminating resistor without dissipating the bias signal through a ground return path of the RF signal. Using a charge pump inverter, a positive supply can be used to positively bias a laser and negatively bias the external modulator through the terminating resistor. A negative power supply is not required. A swing voltage provided by the RF signal causes the external modulator to modulate the light emitted by the laser.

Abstract: A method and apparatus for driving a laser diode source, such as a laser diode or a laser diode array. The driver controlling current in response to a signal indicative of excessive current or current density. The signal may be derived from the drive current, the voltage across the laser diode source or the impedance of the laser diode source. The circuit may be pulsed using a switch, such as a GCT. The current to generate drive the laser diode source provided by a capacitive or inductive charging circuit.

Abstract: A high power driver system has a predetermined number of driver modules for driving a high power device such as a laser-emitting device. Each driver module has a driver circuit and a corresponding feedback circuit. The driver circuits respectively generate driving currents, and then the driving currents are collected to drive the high power laser-emitting device or other high power devices. In addition, these feedback circuits of the driver modules receive the same detection signal that represents the output power of the high power laser-emitting device. Then, each feedback circuit responds to the same detection signal to generate a feedback signal, respectively, which makes the corresponding driver circuit carry out a feedback action for adjusting the driving currents.

Abstract: Systems and methods for regulating optical power are described. A system for regulating optical power includes a laser driver circuit that receives an enable/disable signal and a data modulator input. The enable/disable signal regulates asynchronous mode operation. The system also includes a laser module including a laser diode emitter and a photodiode detector. The laser module is coupled to the laser driver circuit and receives a laser bias current from the laser driver circuit. The system also includes a switch coupled to the photodiode to receive a signal from the photodiode detector. The system also includes an automatic power control (APC) feedback circuit that receives a signal from the switch and provides a laser bias current feedback signal to the laser driver circuit to compensate for power output changes in the laser diode emitter over time.

Abstract: An optical transmission controller includes a semiconductor-laser, a semiconductor laser driver, a monitor photoreceptor, a waveform detector and a phase relation adjuster. The semiconductor laser driver allows the semiconductor laser to output an optical signal. The monitor photoreceptor monitors the optical signal output. The waveform detector detects a fall state of the optical signal output. The phase relation adjuster adjusts a phase relation between a fall timing of an input current and a variation timing of a relaxation oscillation of the optical signal output in accordance with a detection result of the waveform detector.

Abstract: A laser system based on a common platform capable of being tailored to meet specific application requirements through simple and flexible means is disclosed. The output beam characteristics of the laser source are fully determined by a plug-in module that can be easily replaced on demand to modify one or more of those output beam characteristics. A connection module provides a robust, flexible and detachable connection between the common laser platform and the plug-in module, thus ensuring stable and well defined laser output beam without precluding on demand adjustment of its characteristics. Several embodiments are disclosed for a laser system with single or multiple output beams both with similar or dissimilar characteristics.

Abstract: At least one of a feedback path and a feed path is divided into two paths, and the divided feedback path and the feed path for feeding a signal form a twisted pattern to suppress radiation noise of a high frequency by a twisted pair effect. The other divided feedback path decreases a resistance value of a direct current component and decreases a whole direct current resistance to feed a sufficient current to the path.

Abstract: An automatic power control system provides a control signal that regulates the output power of at least one laser diode. Coarse adjustment of the control signal is provided by a first means, preferably a digital variable resistor, while fine adjustment and compensation is provided by a second means, preferably by a digital-to-analog converter that receives an input signal proportional to a sensed control system parameter. The control system includes an operational amplifier having a first input coupled to sense output power, and a second input coupled to a DAC to provide finer resolution control. Memory can store system parameter or system parameter variations that can be coupled to the DAC and/or variable resistor to enhance system stability over ambient variations.

Abstract: Disclosed herein is a laser noise cancel circuit for reducing laser noises in a reproduction system for an optical disk device including, a gain-variable amplifying noise cancel circuit for amplifying a monitor output signal for laser light, a first low-pass filter for extracting low frequency signal components of a monitor output signal for noise canceling, a second low-pass filter for extracting low frequency signal components, a negative return loop circuit for controlling a gain in the amplifying noise cancel circuit based on the low frequency signal components of the monitor output signal for noise canceling extracted as well as on the low frequency signal components of the reproduced high frequency signal extracted, to determine the low frequency signal component rate of the monitor output signal for noise canceling as identical to the low frequency signal component rate of the reproduced high frequency signal, and an arithmetic circuit for generating the reproduced high frequency signal with the laser

Abstract: A system and method of sensing temperature at an optical fiber tip, including the steps of positioning a slug of fluorescent material adjacent the optical fiber tip, providing an optical stimulus having a wavelength within a first predetermined range through at least one fiber optically linked to the optical fiber tip, wherein a desired optical fluorescent response having a wavelength within a second predetermined range from the fluorescent slug is generated, detecting a signal representative of the optical stimulus, detecting a signal representative of the optical fluorescent response, digitally processing the optical stimulus signal and the optical fluorescent response signal to determine a phase difference therebetween, and calculating a temperature for the optical fiber tip as a function of the phase difference.

Abstract: High frequency laser diode (LD) and electro-absorption modulator (EAM) integrated circuit drivers using a cascaded output switch architecture that increases the output current and voltage edge speed and reduces the peaking and ringing of the output waveform, thus improving the deterministic jitter performance. Also disclosed is a method and apparatus that provides a modulation current dependence of both turn-on and turn-off driving currents that lead to an optimal compromise between the edge speed and output overshoot for a wide range of modulation currents. A PTAT temperature dependence of both voltage swing and current level in the predriver assures a low variation of the overshoot and rise/fall time over a wide temperature range. Using the cascaded output switch architecture provides an easy way of on-chip summation of the modulation and bias currents. Biasing the cascode device with a supply and modulation current dependent base voltage provides an optimum headroom output switch.

Abstract: A laser scanning apparatus is provided with a laser diode that is driven to emit a laser beam, a scanning optical system that scans the laser beam emitted by the laser diode on a surface to be scanned, and a controller that drives the laser diode by supplying electrical current to the laser diode. The controller supplies an extra electrical current to the laser diode only at an initial stage of driving of the laser diode so as to cancel an effect of a rising delay of its output intensity.

Abstract: A laser beam irradiation device is equipped with a very strict safety arrangement, thereby assuring that a user can use it safely. A hand-held applicator has a face formed on its top, and a push button switch on its side. The face has a spherical lens press-fitted in its center hole, and the face has a hollow cylinder integrally connected to its circumference, encircling the spherical lens. The hand-held applicator is applied to one's skin by the hollow cylinder at its edge. The hollow cylinder has a cylindrical electrode embedded in and somewhat projecting forward. A heat sink is placed behind the spherical lens, and a semiconductor laser diode is press-fitted in the through hole, which is made in the center of the heat sink. A cooling fan is placed behind the heat sink.

Abstract: Even for a driving impedance of 25 ?, high transmission waveform quality of an optical transmission module is maintained using an optical modulator element designed for a driving impedance of 50 ?. The above can be achieved by adopting an optical module 100 that includes an input electrode for electrical signals, an optical modulator element for modulating laser light using the electrical signals, a termination resistance element, a first bonding wire for connecting the input electrode and the optical modulator element, a second bonding wire for connecting the optical modulator element and the termination resistance element, and a third bonding wire for connecting the input electrode and the termination resistance element.

Abstract: This disclosure is concerned with digital optical circuits, including an optical astable multivibrator. In one example, an optical astable multivibrator is provided that includes a lasing semiconductor optical amplifier (LSOA), such as a VLSOA for example. The LSOA is optically coupled to a time delay component and includes a pump input, amplifier input, amplifier output, and a ballast laser output. The time delay component includes an input that is optically coupled with the ballast laser output of the LSOA. The time delay component further includes an output that is optically coupled with the amplifier input of the LSOA. The output of the LSOA is a clock signal having a periodic square waveform whose frequency is determined by the time delay component.

Abstract: The slope efficiency of a laser diode is determined by temporarily adjusting a current applied to the laser and measuring a corresponding change in the average output power. Such prior art techniques require the laser modulation current average to be small to avoid impairment of transmission of data by the laser diode. An optical attenuator opposite an output of a laser diode resolves this problem by maintaining the average power emitted by the laser diode within acceptable operating limits.

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 temperature control apparatus comprises a light-emitting device, a light-emitting device controller, a Peltier device for controlling the temperature of the light-emitting device to a target temperature, a temperature detector for the light-emitting device, a first reference voltage holding unit for holding a voltage corresponding to the target temperature, a reference voltage controller for outputting a holding signal and a switching signal, a second reference voltage holding unit for holding the output voltage of the temperature detector on the basis of the holding signal, a reference voltage switching unit for selecting either the output of the first reference voltage holding unit or the output of the second reference voltage holding unit as a reference voltage, and a Peltier controller for controlling the Peltier device so as to minimize a difference between the output voltage of the temperature detector and the output voltage of the reference voltage switching unit.

Abstract: A simply structured apparatus according to the present invention corrects an overdrive power level. A main controller allows an overdrive power generator to set an overdrive power current to zero, allows a base power controller to control a base power current with the target value of a base power monitor level set to a desired overdrive power level. When the base power monitor level has reached the target value, the main controller allows said overdrive power generator to increase the overdrive power current until a base power control signal monitored by a base power control signal monitor reaches a value corresponding to a desired base power level.

Abstract: Methods and system are provided for automatic power control of a laser diode, e.g., in a laser driver. In accordance with an embodiment of the present invention, a power controller includes a detector circuit adapted to detect the output of the laser diode and to produce a measured output therefrom. A comparator compares a desired output to the measured output, and produces an error signal therefrom. The error signal is provided to an integrator circuit that produces an integrated error signal. At least one digital-to-analog converter (DAC) uses the integrated error signal to produce a current drive signal that drives the laser diode.

Abstract: An optical communication system suitable for full duplex optical communication between a first and a second optical transceiver units. connected with each other by a single-core optical fiber. The first and second transceiver units may have different types of light emitting elements emitting light having different loss rates in the single-core optical fiber. The system enables stable full duplex communication without setting up large scale or costly transmission units by relatively reducing the optical crosstalk involved. The first optical transceiver unit provides transmission light to be coupled with the single-core optical fiber with the intensity in the range of TAmin–TAmax. The amount of light emitted from the light emitting element of the optical transceiver unit to be coupled with the single-core optical fiber is in the range TBmin–TBmax, which amount may be adjusted by a light emission adjusting unit provided in the optical transceiver unit.

Abstract: A method and apparatus for generating multiple levels of optical signals. A plurality of electrical currents is produced. The magnitudes of the electrical currents are independent of each other. Optical signals are produced using the electrical currents. Each optical signal has an amplitude corresponding to one of the multiple levels. The amplitudes of the optical signals corresponding to a level are adjustable by independently adjusting a respective electrical current. Amplitudes of optical signals corresponding to other levels may be adjusted independently.

Abstract: An automatic gain control circuit in the feedback path for a laser wavelength control circuit is described herein. This gain control circuit automatically adjusts the amplification of the analog signals output from a photodetector array, where the array detects a fringe pattern created by a laser beam. Another feature of the preferred embodiment feedback circuit is the automatic setting of a DC offset voltage that compensates for errors in the feedback path and enables an accurate determination of a dark level signal in the fringe pattern signal. This dark level signal provides a reference for measuring the magnitude of the fringe pattern signal. Varying photodetector outputs may now be more accurately measured. The preferred embodiment feedback circuit also employs a very fast amplifier anti-saturation circuit using LED's connected in a clamp circuit.