136 results about "Optical modulation amplitude" patented technology

The invention provides an active optical module multi-channel automatic test system and a method. optimal signals emitted by a tested optical module are monitored, and indexes of the incident light power, emission current, bias current, temperature, voltage, extinction ratio, eye diagram allowance, crossing point, OMA (optical modulation amplitude) etc. are measured and calculated; if the above indexes are all in accordance with the standard, the sensitivity of the optical module is tested, the emission optical power of the tested module is enabled to reach the sensitivity of the test standard via the adjustment of an attenuator, and error code tests are conducted; and if there is no error code, indexes of alarm value and alarm recovery etc. of the optical module are tested. According to the test system, an error detector, an optical module test board, an optical power meter, and the attenuator employed by the test system are all multi-channel devices, an optical switch and an optical splitter are combined for time-sharing multiplexing of one oscilloscope, at least 8 modules can be simultaneously tested, the utilization rate of the oscilloscope and the test efficiency of the optical module are greatly optimized, the equipment cost and the manual cost are reduced, and automatic and batch production of the optical modules is realized.

A method and circuit for measuring the optical modulation amplitude in the operating region of a laser diode is described. The method utilises two measurements of OMA, each measurement being related to the slope in a specific portion of the operating region of the power / current characteristic curve of the laser diode. By combining the two measurement values, the invention provides a 1 measurement for OMA in the operating region of the laser diode that allows for the presence of a non-linear response in the region.

The invention provides a method and a system for testing a high-speed optical module. The method comprises the steps of receiving an optical signal sent by the tested high-speed optical module, measuring the OMA (Optical Modulation Amplitude) and optical power of the optical signal, obtaining an extinction ratio by virtue of calculation, if the extinction ratio complies with the product specification, performing error code testing on the tested high-speed optical module, adopting a standard receiving tube test unit to receive an optical signal with a pseudo-random signal from the tested high-speed optical module while testing error codes, and carrying out demodulation on the optical signal by use of the standard receiving tube test unit and then carrying out comparison, thereby finishing the error rate testing.

A control method for a laser diode is conducted such that optical output and OMA (optical modulation amplitude) or extinction ratio of the laser diode are controlled while modulating the optical output of the laser diode by applying a bias current and a modulation current to the laser diode. The method has: a first step of measuring the optical output of the laser diode; a second step of measuring a slope efficiency or a corresponding value of the slope efficiency while conducting APC (automatic power control) to adjust the bias current such that the optical output coincides with a predetermined value; and a third step of adjusting the modulation current by AAC (automatic amplitude control) according to the slope efficiency or the corresponding value of the slope efficiency such that the OMA or extinction ratio coincides with a predetermined value.

The invention discloses a static Fourier transform interference imaging spectrum full-polarization detector, which comprises a fronting optical telescope system, a static all-optical modulation module, a static Fourier transform interference imaging spectrometer, an imaging lens group, an area-array detector which are arranged in sequence along the light transmission direction, wherein the area-array detector is connected with a signal acquiring and processing system; light emitted by a target source is collimated by the fronting optical system, and then is modulated by the static all-optical modulation module; after the modulated transmission light passes through the static Fourier transform interference imaging spectrometer, emergent light is changed into two beams of coherent light; the two beams of light pass through the imaging lens group and then are convergent on the area-array detector for imaging and interference; and a signal received by the area-array detector is sent to the signal acquiring and processing system for processing. The static Fourier transform interference imaging spectrum full-polarization detector has the characteristics of simple and compact structure, no moving parts, high luminous flux, and acquisition of target two-dimensional spacial images, one-dimensional spectral information and complete polarization information at one time.

An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.

A method for an optical transmitter, receiver or transceiver allowing determination of a signal property of a first binary signal such as the modulation amplitude. The method applies a reference stage which is modulated by the signal content of the first binary signal to allow the determination.

A system for stabilizing an output optical power from a laser source against drifts induced by temperature and / or aging, said output optical power including a target optical modulation amplitude around a target average value includes: a power sensor for sensing the output optical power from the laser source and generating a power sensing signal indicative thereof, and a controller sensitive to the power sensing signal and configured for selectively adjusting the bias (IB) and modulation (IM) currents of the laser source by: detecting an error between the actual average output optical power from the laser source and the target average value,comparing the error against a given error threshold, and when the error reaches the threshold adjusting the bias (IB) and modulation (IM) currents to bring the output optical power from the laser source (1) back to the target average value (Ptarget) and the target optical modulation amplitude (OMAtarget) around the target average value (Ptarget).

The invention relates to a passive optical network comprising an optical exchange linked by at least one optical fiber to at least one line termination device of said network, able to transmit a downlink optical signal phase-modulated in NRZ-DPSK format and to receive an uplink optical signal.According to the invention, said line termination device comprises means of converting the transmitted downlink optical signal phase-modulated in NRZ-DPSK format into an optical data signal amplitude-modulated in duobinary modulation format and means of generating an uplink optical signal phase-modulated in NRZ-DPSK format from the downlink optical signal phase-modulated in NRZ-DPSK format. The optical exchange is able to convert the uplink optical signal phase-modulated in NRZ-DPSK format into an optical data signal amplitude-modulated in duobinary modulation format.

The invention discloses a frequency hopping signal generator and a frequency hopping method. The frequency hopping method includes: after a modulation type is determined, a phase modulation code for a phase adder is selected according to a configured phase control word to achieve phase modulation, and a modulation amplitude is selected according to a configured amplitude control word to achieve amplitude modulation; the phase adder enables a sum of an accumulated value obtained through accumulation of frequency control words and the phase modulation code to be used as a read address of a carrier memory; the carrier memory reads a carrier amplitude according to the read address to achieve phase-amplitude conversion; and the carrier amplitude and the modulation amplitude multiply and are sent to a digital to analog converter (DAC) to complete digital to analog conversion. The frequency hopping signal generator and the frequency hopping method can support various modulation types and are good in flexibility, and other modulation types can be added easily.

An optical modulation unit included in an optical transmitter includes two optical modulators that modulate each of two light beams based on applied bias voltages and input modulation signals, and an optical phase regulator that is connected to either of the two optical modulators, and regulates a phase of the light beam incident on the optical modulator. In a state where no modulation signal is input to the two optical modulators, while keeping bias voltages to be applied to one optical modulator and the optical phase regulator constant, the controller determines a first initial bias voltage such that an output light beam from the other optical modulator becomes zero. Thereafter, the controller determines a second initial bias voltage such that an output light beam from the one optical modulator becomes zero, while applying the first initial bias voltage to the other optical modulator.

The present invention relates to an optical modulation method and optical modulation system of a wavelength locked Fabry Perot-Laser Diode (FP-LD) by injecting a broadband light source (BLS) using mutual injection of FP-LDs. More specifically, the present invention relates to a novel modulation technology which embodies a wavelength locked FP-LD capable of being used as an economic light source in an optical network based on a wavelength-division multiplexing passive optical network (WDM-PON). According to the present invention, a light modulation system is suggested comprising: BLS being constructed by mutual injection between two FP-LDs and an optical fiber being used for light transmission; first AWG for filtering light from a plurality of oscillation modes of the BLS into n group; n FP-LDs outputting wavelength locked light which is divided through the first AWG; an encoder being provided at a transmitting end of a subscriber to which the output from the first AWG is transmitted; a circulator outputting light which is inputted through the first AWG; second AWG de-multiplexing WDM signals from the first AWG into n group; and a decoder being provided at a receiving end to which the output from the second AWG is transmitted. Therefore, the present invention makes it possible to provide a more economic light source for WDM-PON subscribers by embodying a wavelength locked FP-LD by injecting a low-cost BLS.

The power control system utilizing a normal average power control loop to control average power and modulation level of an optic signal generated by an optic signal generator. The target average power is adjusted by a small percentage, and the corresponding change in bias current needed to adjust the average power level is monitored. The change in average power divided by the change in bias current is a measure of the optic signal generator's slope efficiency. Modulation current is adjusted up or down based on the change in slope efficiency compared to the slope efficiency stored at the time of module calibration. By adjusting the modulation current, the desired optic signal output from the transmitter may be maintained.

An optical modulation apparatus including: a Mach-Zehnder optical modulator having two optical waveguides, two output optical waveguides and a join-and-branch portion; a phase adjustment circuit configured to output a phase control signal to phase adjustment electrodes provided respectively on the two optical waveguides; a drive circuit configured to output a modulation signal to modulation electrodes provided respectively on the two optical waveguides as a differential signal, the modulation signal modulating lights propagated in the two optical waveguides; and a signal polarity reversal circuit configured to reverse a polarity of the differential signal to be output from the drive circuit.

To provide an optical phase modulation circuit and an optical phase modulation method capable of achieving a high-speed operation without increasing the power consumption. An optical phase modulation circuit according to the present invention includes an optical modulation unit 50 that includes a plurality of division electrodes 12 to 15 connected in tandem and generates a modulation signal by summing up optical signals modulated by using respective division electrodes, drive circuits 8 to 11 that drive the plurality of division electrodes, and a modulation timing control unit 60 that controls timings at which the optical signals are modulated in the plurality of division electrodes 12 to 15, by controlling an operation timing of the drive circuits 8 to 11.

Systems and methods for controlling the modulation current of a laser included as a component of an optical transmitter, such as an optical transceiver module, are disclosed. Control of the modulation current, which affects various laser operational parameters, including extinction ratio and optical modulation amplitude, enables operation of the laser to be optimized, thereby enabling reliable transceiver performance to be achieved. In one embodiment, a method for modifying the modulation current in an optical transceiver module includes first sensing analog voltage data that proportionally relates to an actual modulation current of the laser. Once sensed, the analog voltage data are converted to digital voltage data. Using the digital voltage data, the actual modulation current of the laser is determined, then a desired modulation current is determined. Should a discrepancy exist between the actual and desired modulation currents, the actual modulation current is modified to match the desired current.

The invention relates to a preparation method of a WO3 film. An ion-beam sputtering deposition technique and a subsequent annealing treatment technique are combined to prepare the electrochromic WO3 film with favorable optical properties, and the strength of the anaerobic phase in the WO3 film is controlled to regulate the optical modulation properties. By using ITO (indium tin oxide) conducting glass as the substrate, the ion-beam sputtering deposition technique is utilized to prepare the WOx film; and by using 99.999% pure O2 as an annealing atmosphere, the WOx film is subjected to annealing treatment at different temperatures for different time periods to prepare the WO3 film containing anaerobic phase. When the WO3 film is subjected to Li<+> electrochemical coloring / discoloring reaction, after the discoloring voltage is applied, the prepared electrochromic WO3 film has the advantages of low coloring-stage integral transmittivity, adjustable anaerobic phase strength, large optical modulation amplitude and favorable controllability. The WO3 film is simple in preparation technique and is hopeful to be applied to the fields of smart windows, electronic information display devices, no-glare reflectors and the like.

The invention provides a display device. The display device is characterized in that the display device comprises a backlight unit which comprises a light guide plate, and is used for providing a backlight for the display device, a transmittance and reflectance controllable film which comprises a number of array units, and is used for carrying out regional control on the backlight, an optical modulation layer which has a number of pixel units, and is used for modulating a light from the transmittance and reflectance controllable film, and a control unit which is connected with a number of array units of the transmittance and reflectance controllable film, and is used for controlling the array units of the transmittance and reflectance controllable film to switch between different states according to a display content. The transmittance and reflectance controllable film is located between the backlight unit and the optical modulation layer. Through the configuration, the display device provided by the invention can dynamically control the backlight to realize backlight regional control, which enhances the dynamic contrast, reduces power consumption and improves the image quality.

The embodiment of the invention discloses an optical modulation device, an optical modulation method and a dispersion pre-compensation transmitter. The optical modulation device comprises a branching unit, an optical power regulating unit, an electro-optical modulation unit and a combining unit, wherein the branching unit is used for dividing an input optical signal into a first branch optical signal and a second branch optical signal and outputting the first branch optical signal and the second branch optical signal; the optical power regulating unit is used for regulating the power of at least one of the first branch optical signal and the second branch optical signal output by the branching unit and then outputting the first branch optical signal and the second branch optical signal; the electro-optical modulation unit is used for receiving an input pre-compensation electrical signal and modulating the first branch optical signal and the second branch optical signal output by the optical power regulating unit according to the pre-compensation electrical signal so as to generate a first modulation signal and a second modulation signal; and the combining unit is used for combining the first modulation signal and the second modulation signal into a path of modulated signal. Under the condition of high speed, the embodiment of the invention does not need a driver with great difficulty of realization, and meanwhile, power regulation is easier to realize so as to more accurately regulate the power of the output modulated signal.

An optical modulation apparatus includes a first modulator, a second modulator, a multiplexer, a calculator and an adjustor. The first modulator configured to modulate light emitted by a light source using a first input signal and output a first modulated signal. The second modulator configured to modulate the light using a second input signal and output a second modulated signal. The multiplexer configured to multiplex the first and second modulated signals and output a multiplexed signal. The calculator configured to calculate a power difference between a higher-side frequency component having a frequency higher than a center frequency of the multiplexed signal and a lower-side frequency component having a frequency lower than the center frequency. The adjustor configured to adjust delays of the first and second input signals based on the power.

An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.

The optical modulator includes optical modulation units. The plurality of optical modulation units is disposed in parallel on the same substrate. One input waveguide branches off to be connected to the Mach-Zehnder type optical waveguide of each optical modulation unit, and an entire optical waveguide is formed such that outputs from the Mach-Zehnder type optical waveguides are combined and output through one output waveguide. A modulation signal with the same intensity is applied to a modulation electrode of each optical modulation unit. In at least some of the optical modulation units, mechanical structures including the modulation electrodes of the optical modulation units are configured such that an amplitude value of an optical output modulated by the modulation signal of the optical modulation unit is ½n (n is a natural number) of a maximum amplitude value in other optical modulation units.

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. An average amplitude measurement value may also be obtained using an average amplitude measurement device that processes the OMA detection signal produced by the high-speed amplitude detector to obtain the average amplitude measurement value. The laser controller receives the average amplitude measurement value and processes it to obtain a bias current control signal, which is then output to the laser driver to cause it to adjust the amplitude of the bias current to obtain a desired or optimum average laser output power level.

Techniques for measuring optical modulation amplitude (OMA) are disclosed. For example, a technique for measuring an OMA value associated with an input signal includes the following steps / operations. The input signal is applied to a photodetector, wherein the photodetector is calibrated to have a given responsivity value R, and further wherein the photodetector generates an output signal in response to the input signal. The output signal from the photodetector is applied to a radio frequency (RF) power meter, wherein the RF power meter measures the root mean squared (RMS) power value of the output signal received from the photodetector. The OMA value associated with the input signal is determined in response to the root mean squared (RMS) power value measured by the RF power meter. The OMA value may be determined as a function of a factor F derived from a relationship between an amplitude of a data signal and the RMS value of the data signal.

The invention relates to a modulation amplitude closed-loop control system and method of a photoelastic modulator based on second harmonics. The modulation amplitude closed-loop control system comprises three parts including a laser intensity sterilization module, a detection optical module and a closed-loop control module, wherein the laser intensity sterilization module is composed of a laser device, a controllable phase delayer, a polarizer, a polarization beam splitter, a first photoelectric detector and a light intensity controller and is used for stabilizing main path laser to a pre-set value; the detection optical module is composed of a sample to be detected, a quarter-wave plate, the photoelastic modulator, a polarization analyzer and a second photoelectric detector and is used for realizing conversion of main path laser photoelectric signals; and the closed-loop control module is composed of a lock phase amplifier, a signal processor and a photoelastic modulator driving circuit and is used for demodulating second harmonic signal feedback to control the modulation amplitude of the photoelastic modulator. According to the modulation amplitude closed-loop control system and method of the photoelastic modulator based on the second harmonics, modulation amplitude fluctuation of the photoelastic modulator, caused by changes of environment factors, can be effectively inhibited, so that long-period stability of a detection system is improved.

According to an aspect of an embodiment, an optical modulation device includes a Mach-Zehnder modulator and a controller. The Mach-Zehnder modulator is supplied a drive signal and a bias voltage. The Mach-Zehnder modulator modulates inputted light on the bases of the drive signal and the bias voltage. The drive signal selectively is superimposes a predetermined frequency signal. The bias voltage selectively is superimposes the predetermined frequency signal. The controller selects a superimposing target which is the drive signal or the bias voltage so as to change modulation formats.