Abstract: An optical modulator includes a phase modulator configured to drive light with an NRZI-coded drive signal for phase modulation and an intensity modulator to modulate the intensity of a phase-modulated NRZI-coded optical signal received from the phase modulator. The operating point of the intensity modulator is set such that the output of the intensity-modulated optical signal is eliminated when the NRZI-coded optical signal is not varied.

Abstract: To provide a phase modulator for introducing a topological phase, which is designed to produce any desired phase shift between zero and 360°, the phase modulator has means, at least one double-refractive, electrooptical delay element having a rotatable indicatrix, which is/are used to direct the polarization of the light, during transmission through the modulator, over at the light one closed path on the Poincaré sphere, the indicatrix rotating in accordance with the predefined phase shift, and the total encircled surface on Poincaré sphere being equal in terms of absolute value to ?.

Abstract: A method of, and apparatus for, setting an operating (control) voltage of a voltage controllable optical component, such as a Mach-Zehnder optical modulator, having a periodic voltage/optical parameter (optical power) characteristic include an up/down counter and a digital to analog converter operable to set the voltage applied to the component to a predetermined initial value, a device for measuring the optical parameter, and another device for sequentially progressively increasing and decreasing the voltage (incrementing/decrementing the counter) with respect to the predetermined value, and for determining respective voltage values which produce maximum and minimum values of the optical parameter. The voltage is set to a value intermediate the maximum and minimum voltage values. Further, the apparatus determines the sense of the slope of that portion of the periodic characteristic lying between the maximum and minimum values for use by a control loop during subsequent operation of the optical component.

Abstract: An opto-electronic oscillator including a modulator for outputting modulated light and a tunable filter for receiving modulated light output from the modulator.

Abstract: A method and device for stabilizing operation point and optical output of an external optical modulator. A low-frequency signal below a lower limit of signal frequency band of an input signal inputted to optical modulator is superimposed onto direct current bias. A low-frequency component included in detector output is extracted. On the basis of the low-frequency signal, output of the low-frequency component is normalized, and output-light of light source is controlled in accordance with normalized low-frequency component. Means of controlling optical output of light source, in control of output-light of light source, detects the output-light, compares the value of detected output-light to a standard value of primary optical output, and adjusts the output-light. The standard value is modified according to a ratio of primary value of normalized low-frequency component to a subsequent value, and means controlling optical output of light source is operated on the basis of modified standard value.

Abstract: An optical transmitter architecture has a return-to-zero (RZ) laser modulator coupled in cascade with a non-return-to-zero (NRZ) laser modulator. Modulator bias and electronic phase delay bias are controlled using dither-based feedback, so as to align the phase of the RZ clock signal with that of the NRZ data. A first method uses an RZ quadrature AM dither or an RZ “hillclimber” bias dither, to apply a relatively low frequency dither signal to a variable RF delay for the RZ clock signal applied to the RZ modulator or NRZ data signal applied to the NRZ modulator. A second method is an RZ quadrature AM dither or “hillclimber” bias dither scheme that applies equal amplitude and opposite phase dither signals to perform complementary modulation of both the RZ and NRZ MZ modulators simultaneously.

Abstract: A modulation quality detection system is disclosed for determining the modulation quality of an illumination modulator in an imaging system. The modulation quality detection system includes a modulator adjustment unit for providing a test pattern on the illumination modulator, a detector for receiving a modulated illumination field from the illumination modulator, a sampling unit for determining at least three sample values (A, B and C) for each of three areas of the modulated illumination field respectively, and an evaluation unit for determining whether the value ( A + C 2 ) - B is greater than a threshold value.

Abstract: A pulse shaping apparatus for shaping an input optical pulse into an output optical pulse having substantially constant optical power, includes a modulator that acts upon the input optical pulse in response to a control signal. A sampling unit samples a portion of the input or output pulse and generates a sample signal that corresponds to the optical power of the input or output optical pulse. In a preferred embodiment, the sampling unit includes a power splitter that splits off sample portion of the input or output pulse, and directs the sample portion to the photodetector which generates the sample signal. Processing of the sample signal may be performed in either an analog or digital form.

Abstract: Electro-optical modulator (100), comprising at least one electrical port (918, 919) and an input circuit (915, 916, 917) for the application of a modulating electrical signal to the said at least one electrical port. The said modulator also comprises a linear processing circuit (250) capable of generating a compensation signal. This linear processing circuit comprises a first terminal connected to the input circuit for taking a fraction of the said modulating electrical signal, at least one filtering element (2, 3) for eliminating predetermined spectral components from the said fraction of the modulating electrical signal, and at least one phase-shifting element (4, 6) for inverting the phase of the said fraction of the modulating electrical signal. The said linear processing circuit also comprises a second terminal capable of being connected to the said at least one electrical port for applying the compensation signal to the said electro-optical modulator.

Abstract: In one embodiment, a laser refraction system includes a refracting unit to refract light emitted from a laser. A refracting unit control procedure configures a charge on an OPC according to an image by sending a signal to the refracting unit to control refraction degree and timing.

Abstract: An RF power controller arrangement prevents excessive RF power-based thermal loading of an RF signal processing device, such an as acousto-optic modulator, by controllably constraining the product of the average on-duration of a baseband modulation signal and RF input power to realize no more than a prescribed value of RF energy supplied to the modulator.

Abstract: A diagnostic system (24) for a PEM (20) provides optically determined information about the retardance characteristics induced by the PEM (20). The diagnostic system (24) is integrated with the PEM (20) so that the PEM (20) performance may be diagnosed or monitored during operation of the PEM (20). Specifically, the diagnostic system (24) is used alongside an optical setup (22) that employs a primary light beam (28) for conventional purposes such as polarimetry, optical metrology, etc. The diagnostic system (24) includes its own diagnostic light source (50) that is directed through the optical element (32) of the PEM (20) at a location remote from the primary aperture (38) of the PEM (20). Thus, the diagnostic system (24) and the primary PEM (20) operation can be undertaken simultaneously, with one not interfering with the other. The output of the diagnostic system reflects the actual retardance characteristic provided by the PEM (20) and can be used as feedback to adjust the PEM control as needed.

Abstract: With the normal modulation method, it is difficult to construct a Hilbert transform device because it is complicated. To solve the problem, a single sideband modulated optical pulse train is generated by driving a Mach-Zehnder optical modulator for optical pulse generation with a laser source's sine wave clock signals that have been rendered 90 degrees out of phase from each other. The generated pulse train is applied to an optical modulator, modulated with an NRZ (nonreturn-to-zero) data signal, and filtered by a narrow-band optical filter to obtain one of two sidebands.

Abstract: An illumination modulator correction system is disclosed for adjusting the operational parameters of an illumination modulator in an imaging system. The correction system includes a modulator pattern unit for providing a test pattern on the illumination modulator, a modulator adjustment unit for permitting an actuation voltage on the illumination modulator to be changed through a range of actuation voltage values, a detector for receiving a modulated illumination field from the illumination modulator, a sampling unit for determining at least one sample value for at least one area of the modulated illumination field, and an evaluation unit for determining a minimum sample value within the range of actuation voltage values of the illumination modulator.

Abstract: The optical transmitter comprises a light source which inputs continuous optical signal and a driving circuit which inputs driving signal to an optical modulator of Mach-Zehnder type. A photo coupler separates a part of the output of the optical modulator. A photo diode converts this part into electric signal. A band-pass filter and a pre-amplifier extract a frequency component of the driving signal contained in the electric signal. A mixer conducts synchronous detection between the driving signal and the extracted frequency component. Finally, a bias voltage control circuit controls a bias voltage based on a result of the phase comparison.

Abstract: Methods are disclosed for row and column addressing of an array of microelectromechanical (MEM) devices. The methods of the present invention are applicable to MEM micromirrors or memory elements and allow the MEM array to be programmed and maintained latched in a programmed state with a voltage that is generally lower than the voltage required for electrostatically switching the MEM devices.

Abstract: The present invention aims at providing a control technique for an optical modulator, which can accurately detect a phase shift between signals of a drive system of an optical modulator, to feedback control. To this end, a control apparatus of the present invention comprises, for example, in an optical modulator which generates a signal light corresponding to the CS-RZ modulation method by two LN modulators connected in series: a monitor section that extracts a specific frequency component from a spectrum of the CS-RZ signal light output from a latter LN modulator to detect the optical intensity thereof, and a control CPU that determines a phase shift between first and second drive signals corresponding to a clock signal supplied to the latter LN modulator based on the optical intensity detected by the monitor section, and controls a phase difference between the drive signals so that the phase shift is minimized.

Abstract: Disclosed are a light modulation apparatus including a liquid crystal device; and a polarizing plate disposed in an optical path of light made incident on said liquid crystal device; wherein said liquid crystal device is of a guest-host type using a negative type liquid crystal as a host material, an image pickup apparatus using the light modulation apparatus, and methods of driving the light modulation apparatus and image pickup apparatus.

Abstract: The purpose of present invention is to provide the method and device for stabilizing the operation point and optical output of external optical modulator, which can control the wave pattern deformation of electrical signal array and set up stably the operation point of modulation curve of optical modulator and the optical output from optical modulator, even in case there is an optical output variation of the light source itself or a transmission factor variation in optical modulator.

Abstract: An optical modulation apparatus includes an optical signal input section, an optical signal propagation path, an optical modulator that modulates the phase of optical signals in at least two of a plurality of optical paths, and a wavelength selective filter that selectively reflects and transmits. Optical signals input via the input section are divided into a plurality of optical paths at a branching point and phase modulated by the phase modulator, that divides the optical path into a plurality of optical paths. Light transmitted by the filter is output via the output section, while light reflected by the filter travels back along the optical path and is again phase modulated by the phase modulator combined at the branching point and output from the input section as an intensity modulated optical signal.

Abstract: One or more single mode waveguide devices are fiber coupled such that signals to an optical element affect the coupling of the waveguide device to one or more modulators and to an optical fiber. The optical element or additional optical elements are controlled to adjust the coupling of the waveguide device to a modulator and to an optical fiber.

Abstract: Optical pulses at a given repetition rate (f) are obtained by modulating an optical signal by means of a Mach-Zehnder modulator. The modulator is driven by means of a driving signal including, in addition to a sinusoidal component at a frequency (f/2) half the repetition rate (f) of the pulses, at least one odd harmonic of the sinusoidal component. Very short optical pulses can thus be generated without giving rise to undesired side effects such as ringing in pulse tails.

Abstract: An image production apparatus, an image display apparatus and an image display method are disclosed which can reduce the ununiformity in luminance and color which appears on a display screen and can be formed compact. Also optical modulation device adjustment apparatus is disclosed which can detect and correct the ununiformity in modulation characteristic of a modulation device. The image display apparatus includes a light detection apparatus in addition to a light source section, an illumination optical system, an optical modulation section, a spatial filter, a light projection section and a screen. The light detection apparatus detects the dispersion of a modulation characteristic of each pixel element of GLV devices and the ununiformity in luminance and color displayed in accordance with an illumination condition. An optimum driving voltage for minimizing the ununiformity in color and luminance to be displayed is determined based on a signal detected by the light detection apparatus.

Abstract: A control circuit designed to control driving voltages applied to the actuating electrodes of a MEMS mirror. The control circuit is interfaced with a mirror position sensor and includes a variable gain amplifier whose output depends on a desired mirror equilibrium angle and a current mirror tilt angle determined by the sensor. The desired equilibrium angle can be changed by varying a reference signal applied to the amplifier. The control circuit can stabilize the mirror at relatively large tilt angles and, as a result, extend the available angular range beyond the snap-down angle. Since the number of MEMS mirrors that can be arrayed in an optical cross-connect is a function of the available angular range, the number of channels in a cross-connect may be substantially increased.

Abstract: Opto-electronic oscillators having a frequency locking mechanism to stabilize the oscillation frequency of the oscillators to an atomic frequency reference. Whispering gallery mode optical resonators may be used in such oscillators to form compact atomic clocks.

Abstract: An illumination modulation system for producing modulated illumination for an imaging system is disclosed. The illumination modulation system includes a first modulator and a second modulator. The first modulator receives illumination from an illumination source and produces modulated illumination. The second modulator receives modulated illumination and produces corrected modulated illumination for imaging. In various embodiments the second modulator may be passive or active.

Abstract: A method for suppressing distortion in a multi-wavelengths system which uses a Mach Zehnder optical modulator includes adjusting an internal path length mismatch of the modulator and changing an applied voltage, Vb, such that the combination biases the modulator to the required &pgr;/2 phase bias.

Abstract: Opto-electronic oscillators having a frequency locking mechanism to stabilize the oscillation frequency of the oscillators to an atomic frequency reference. Whispering gallery mode optical resonators may be used in such oscillators to form compact atomic clocks.

Abstract: A device (16) in a system (10) modulates an optical signal (13) and tunes the duty cycle of the optical signal (13) for optimizing system performance as a response of the duty cycle. The device (16) includes a tunable duty-cycle Mach-Zehnder interferometer (MZI) acting as a pulse-width shaper (160) for modulating the optical signal (13) and tuning the duty cycle of the optical signal (13). The MZI (160) has a transmittance transfer function of the interferometer (160). At least one electrode structure (163) generates a DC voltage and an AC voltage for biasing and controlling the swing of the Mach-Zehnder interferometer (160) with the respective amplitudes of the DC and AC voltages such that the maximum power transmittance point on the transfer function is less than 100% for tuning the duty cycle of the optical signal (13) such that system performance is optimized.

Abstract: A Mach-Zehnder Modulator (MZM) pulse generator is provided having an increased power output. Power carved from the output signal in creating the pulses is recycled back to the input of the pulse generator via a feedback arm. Careful design of the length of the feedback arm such that a feedback signal has a propagation time of (2n+1)T/2 to complete one loop (n being a non-negative integer and T being the pulse period) allows a 50% duty cycle to be obtained using a driving frequency of only one half of the pulse frequency.

Abstract: A method and apparatus for providing tunable second-order polarization mode dispersion with constant mean first-order differential group delay for fiber optic transmission systems are provided. A section of fixed high birefringent optical fiber, a polarization controller, and a variable differential group delay module are provided. The polarization controller is connected to the high birefringent optical fiber section, and the variable differential group delay module is connected to the polarization controller. The variable differential group delay module is controlled to vary the second-order polarization mode dispersion values at an output of the high birefringent optical fiber section. The polarization controller is controlled to hold the mean first-order differential group delay substantially constant at the output of the high birefringent optical fiber section for each value of the second-order polarization mode dispersion at the output of the high birefringent optical fiber section.

Abstract: A control device for controlling an electro-optic modulator which receives an optical input signal, modulates the optical input signal with an electrical input signal and a bias voltage signal, and outputs the modulated optical signal is provided. The control device includes: a light source for providing the optical input signal used for the optical modulation to the electro-optic modulator; an optical input measuring unit for measuring the intensity of the optical input signal outputted by the light source; an optical output measuring unit for measuring the intensity of the optical output signal outputted by the electro-optic modulator; and a controller for adjusting the bias voltage signal and the gain of the electrical input signal depending on the intensity of the optical input signal and the optical output signal measured respectively by the optical input measuring unit and the optical output measuring unit.

Abstract: There is provided a pulse shaping apparatus for shaping an input optical pulse (500) into an output optical pulse having substantially constant optical power (100, in FIG. 1). The apparatus includes a modulator, which acts upon the input optical pulse (500) under the control of a control signal, and a sampling means, which takes a sample of the incoming optical pulse for further processing. In a feedback configuration, the modulator acts on the incoming pulse under the control of an error signal, the incoming pulse is then sampled, the sample processed and the error signal generated from the processed sample. In a feed-forward configuration, the incoming pulse is sampled first, the sample processed and the modulator acts on the incoming pulse under the control of an error signal resulting from the processing steps.

Abstract: A method and system of detecting whether the intensity of light incident a spatial light modulator varies periodically. One embodiment provides a method of operating a spatial light modulator, the method comprising: determining a peak level of light incident the modulator over a period of time; setting a threshold level equal to a fraction of the peak level; monitoring a current level of light incident the modulator; comparing the current level of light and the threshold level; and disabling the modulator based on the comparison. Another embodiment provides a modulator array.

Abstract: An electro-optical assembly, consisting of an optical sub-assembly and a transmission line. The optical sub-assembly consists of an electro-optical component having an optical region and a first and a second electrode coupled thereto, and a conductive optical bench in contact with the second electrode of the electro-optical component, the optical bench being adapted to permit optical alignment of the electro-optical component while making such contact. The transmission line consists of a live conductor, a ground conductor insulated from the live conductor, and a port adapted to receive a signal. The live and ground conductors are coupled to the first and second electrodes of the electro-optical component so as to convey the signal between the port and the electro-optical component and to provide a direct current (DC) bias level to the electro-optical component independent of the signal.

Abstract: The present invention aims at providing a control technique for an optical modulator, which can accurately detect a phase shift between signals of a drive system of an optical modulator, to feedback control. To this end, a control apparatus of the present invention comprises, for example, in an optical modulator which generates a signal light corresponding to the CS-RZ modulation method by two LN modulators connected in series: a monitor section that extracts a specific frequency component from a spectrum of the CS-RZ signal light output from a latter LN modulator to detect the optical intensity thereof, and a control CPU that determines a phase shift between first and second drive signals corresponding to a clock signal supplied to the latter LN modulator based on the optical intensity detected by the monitor section, and controls a phase difference between the drive signals so that the phase shift is minimized.

Abstract: An adaptive pulse compressor is described, especially for use with ultrashort pulses, wherein the input pulses are modified in an iterative fashion, according to a feedback signal obtained from measurement of the output pulses. The feedback signal is programmed, by means of a programmable spatial light modulator, to allow for independent control of the individual spectral components of the incoming pulses, such that almost arbitrary phase functions can be realized to accomplish efficient compression. One of the main disadvantages associated with prior art pulse compressors, namely, the need for characterization of the uncompressed pulses, is thus eliminated. The compressor is thus capable of handling completely uncharacterized or partially characterized input pulses, or pulses from time varying sources.

Abstract: An optical communication system (10), a method (100) for parallel modulation of an optical spectrum and a method (200) for parallel demodulation of the optical spectrum of modulated optical frequencies by the system (10) are described. The optical frequencies are provided in parallel to a modulation section (14) for modulating with data bits from a data signal source (16). The data bits are associated with an optical modulator (58) that controls passage of the optical spectrum at a plurality of predetermined optical frequencies based upon the data bits. The optical frequencies of the optical spectrum, modulated by the data bits, are then transmitted via a communication section (18) to an optical receiver (20) that is coupled to a demodulation section (22) of the system (10). Modulated optical frequencies are received as a modulated optical spectrum and demodulated in parallel by an optical demodulator (92) to derive the data bits.

Abstract: A method of dynamically adjusting at least one optical module in an optical system including a plurality of transmission channels includes the following steps:

Abstract: Techniques for reducing frequency shifts in an oscillating frequency of an opto-electronic oscillator by having at least two separate optical delay elements in an optical portion of an opto-electronic feedback loop.

Abstract: Method of modulating an optical light source to maintain stability with time, temperature and any variation in the source's electrical connections.

Abstract: An optical transmitter includes a light source emitting input light; and a modulator modulating the input light in accordance with an input electric signal to generate an optical transmission signal. The transmitter also includes a monitor which detects frequency fluctuation of the optical transmission signal. The modulator is controlled so as to optimize the amount of frequency fluctuation of the optical transmission signal.

Abstract: A method and apparatus for transmitting a modulated optical signal includes a continuous source of light, a first optical modulator for generating an optical pulse stream in response to a radio frequency (RF) driving signal and a DC bias signal, and a second modulator for modulating the optical pulse stream with an electrical data signal. A processor dithers the phase of the RF driving signal using a first dither signal and the level of the DC bias signal using a second dither signal. The processor detects the first and/or second dither signals in the modulated optical signal and adjusts the phase of the RF driving signal and/or level of the DC bias signal to null the detected first and/or second dither signal.

Abstract: A control method and apparatus used for a bias controller of automatic bias correction on an optical modulator of optical emitter of external modulation type is a close-loop control system, composed of a base signal generator, an optical receiver, a second-order harmonic signal generator, a second-order harmonic signal detector, a DC amplifier, and a temperature automatic correction device. The bias voltage point of the optical modulator can remain a constant, whereby the optical power can be exported in stable level and distortion of transmission is reduced. It can be avoided about the effect of the environmental temperature, resulting in the change of optical output and the additional signal distortion of the transmission signal.

Abstract: The amplitude of an input laser beam is modulated by a two-dimensional array of Michelson interferometers comprised of a phase spatial light modulator, a mirror and a 50/50 light beamsplitter. The array of Michelson interferometers is calibrated by adjusting the path length of one of the interferometer arms. The calibration is maintained with the aid of feedback. The amplitude-modulated beam is then directed successively through a field imaging telescope, a polarization beamsplitter, and a quarter-wave plate before impinging a second phase spatial light modulator. The second spatial light modulator is adjusted to apply the desired phase profile. The beam, which at this point has the desired amplitude and phase profiles, is then again directed through the quarter-wave plate and subsequently reflected off of the polarization beamsplitter, out of the apparatus, and into free space.

Abstract: An electro absorption modulator in which the photocurrent generated by the absorption of light is monitored and the bias voltage applied to the electro absorption modulator is varied in order to vary the photocurrent and thence the extinction ratio of the electro absorption modulator.

Abstract: An apparatus and a method for modulating the optical intensity, with the noises suppressed by using a linear optical modulator, are disclosed, so that the characteristics of signals transmitted from an optical communication system can be improved, and that the resolution of the measured physical quantities can be improved in an optical measuring instrument. The method is carried out in the following manner. That is, the magnitude of frequency is measured by utilizing pilot signals and electrical signals to transfer negatively fed-back signals to an optical intensity modulator. The phase is delayed by generating pilot signals so as to suppress an amplitude noise from the pilot signal caused by nonlinear modulation at the optical intensity modulator. A linear modulation is carried out on the phase-delayed signals and on optical signals from an external source to provide a linear component.

Abstract: Conventional retroreflection mirrors in the form of right angle prisms are quite sensitive to beam position and beam angle errors. Manufacturing and assembly tolerances are also a cause of concern in conventional devices. Accordingly, the present invention solves these aforementioned problems by providing a retroreflection device comprising: a beam director, preferably in the form of a Wollaston prism; a polarization rotator, preferably in the form of a quarter wave plate; and a flat reflective surface, such as a plane mirror. The device of the present invention is far less sensitive to beam angle alignment and is completely independent of the beam position. The present invention is particularly useful as a beam splitter for directing orthogonally polarized beams of light back along parallel paths in an interleaver apparatus.

Abstract: A multi-user optical fiber communications system uses spread spectrum code division multiple access techniques to achieve better bandwidth utilization. Each channel of the system is provided with light source that is temporally and spectrally modulated by an encoder. Modulation is accomplished by first passing the data through a pulse modifier to obtain a stream of shortened pulses with a reduced duty cycle. The modulated light is coupled to a fiber and data are recovered by the decoder. The source includes a superluminescent fiber source that is split multiple times and amplified in a hierarchical manner to produce a plurality of like sources. The like sources are decorrelated by adding delays to the different sources. Each of the encoders includes an encoding mask having a first code that encodes the optical signal. Light, spatially encoded by the mask and temporally modulated with data, is transmitted over a fiber link with the signals of other users and received by a decoder.

Abstract: An apparatus and method for filtering an optical input is disclosed. In an illustrative embodiment, an optical input is split into polarization components along separate paths. The polarization components are then fed into a first electro-optic device that includes a set of electrodes across which a voltage is applied to adjust a wavelength transmission characteristic of the device. A section of the first device positioned between the electrodes preferably has a birefringence that is adjusted depending on the voltage applied across the electrodes. The adjusted components of the optical input are thereafter combined to produce an optical output. Accordingly, the optical input can be attenuated based on the voltage applied to electrodes of the first electro-optic device.