685 results about "Mach–Zehnder interferometer" patented technology

A photonic crystal optical switch having a periodic dielectric structure including at least one input waveguide. First and second waveguide arms branch from the input waveguide in which the relative optical path lengths of electromagnetic radiation within the arms are controlled by stimuli. At least one output waveguide that combines the electromagnetic radiation propagating within the first and second waveguide arms.

The invention provides novel “folded” Mach-Zehnder interferometers (“folded” MZI's), methods for making folded MZI's, and systems and devices incorporating them. The novel folded MZI's are elaborated from conventional MZI structures by cutting across the interferometer arms of a conventional MZI structure and creating reflectors on the exposed ends of the interferometer arms to form two “folded” MZI's from a single conventional Mach-Zehnder interferometer structure. The novel folded MZI's show promise as sensors having a reduced size and enhanced sensitivity relative to sensors incorporating conventional Mach-Zehnder Interferometers.

Data carrying optical signals are subjected to equalization or pulse shaping of the optical signal waveform. A plurality of optical tap signals derived from the optical signal are used to control a modulator operating on an input signal to provide an output signal having the desired waveform. A Mach-Zehnder interferometer having semiconductor optical amplifiers in each arm provides modulation by the effect of cross modulation induced by propagating the respective tap signals through a selected one of the semiconductor optical amplifiers. Various forms of transversal filter are provided by selecting the number of optical taps, assigning positive or negative weights and appropriate delays. The effects of dispersion in optical signals can be mitigated by utilizing optical taps with negative weights to subtract tail portions from the leading and trailing edges of a signal pulse. The invention has application to systems with high bit rates where equalization or pulse shaping in the electrical domain is difficult to implement.

The invention refers to electrically controlled optical switching devices which are based on the use of a layer of dielectric and transparent viscoelastic material (G) located between transparent first (ES1) and transparent second (ES2) electrode structures. According to the invention, the first (ES1) and second (ES2) electrode structures are arranged in a manner that the thickness of the layer of the viscoelastic material (G) can be electrically altered maintaining the thickness of said layer substantially equal. This makes it possible to realize a generic, electrically controlled variable thickness plate (30). The generic variable thickness plate (30) can be further used to create optical switching devices based on a Fabry Perot Interferometer or a Mach-Zehnder Interferometer.

An apparatus includes a single or dual output port, dual-drive Mach-Zehnder Interferometer configured to generate a first optical signal in one path, and to generate a second optical signal in a different path. The apparatus also includes an optical spectrum analyzer configured to receive output from at least one port of the dual-drive Mach-Zehnder Interferometer. A method includes causing radio frequency signals from two different antennae to modulate an optical carrier at a corresponding drive of a dual-drive Mach-Zehnder Interferometer, and causing output from at least one port of the Mach-Zehnder Interferometer to be directed to an optical spectrum analyzer. The method further comprises determining arrival angle at each of a plurality of frequencies in the radio frequency signals based on output from the optical spectrum analyzer.

Systems and methods for modulating light with light in high index contrast waveguides clad with graphene. Graphene exhibits a large nonlinear electro-optic constant χ3. Waveguides fabricated on SOI wafers and clad with graphene are described. Systems and methods for modulating light with light are discussed. Optical logic gates are described. Waveguides having closed loop structures such as rings and ovals, Mach-Zehnder interferometer, grating, and Fabry-Perot configurations, are described. Optical signal processing methods, including optical modulation at Terahertz frequencies, are disclosed. Optical detectors are described. Microelectromechanical and nanoelectromechanical systems using graphene on silicon substrates are described.

Methods and systems for encoding multi-level pulse amplitude modulated signals using integrated optoelectronics are disclosed and may include generating a multi-level, amplitude-modulated optical signal utilizing an optical modulator driven by two or more electrical input signals. The optical modulator may include optical modulator elements coupled in series and configured into groups. The number of optical modular elements and groups may configure the number of levels in the multi-level amplitude modulated optical signal. Unit drivers may be coupled to each of the groups. The electrical input signals may be synchronized before communicating them to the unit drivers utilizing flip-flops. Phase addition may be synchronized utilizing one or more electrical delay lines. The optical modulator may be integrated on a single substrate, which may include one of: silicon, gallium arsenide, germanium, indium gallium arsenide, polymers, or indium phosphide. The optical modulator may include a Mach-Zehnder interferometer or one or more ring modulators.

An arrangement for actively controlling, in two dimensions, the manipulation of light within an SOI-based optical structure utilizes doped regions formed within the SOI layer and a polysilicon layer of a silicon-insulator-silicon capacitive (SISCAP) structure. The regions are oppositely doped so as to form an active device, where the application of a voltage potential between the oppositely doped regions functions to modify the refractive index in the affected area and alter the properties of an optical signal propagating through the region. The doped regions may be advantageously formed to exhibit any desired “shaped” (such as, for example, lenses, prisms, Bragg gratings, etc.), so as to manipulate the propagating beam as a function of the known properties of these devices. One or more active devices of the present invention may be included within a SISCAP formed, SOI-based optical element (such as, for example, a Mach-Zehnder interferometer, ring resonator, optical switch, etc.) so as to form an active, tunable element.

An integrated control system for a laser and Mach-Zehnder interferometer are disclosed and may include configuring a bias point for low-speed control of an optical modulator utilizing control circuitry integrated on the same CMOS die. The optical modulator may be differentially monitored. A laser source for the modulator may be controlled utilizing monitor photodiodes via optical taps on outputs of the modulator, or utilizing a monitor photodiode on one output port of the modulator, which may comprise a Mach-Zehnder interferometer. An error signal may be generated by subtracting monitor photodiode signals from optical taps on output ports of the modulator. The bias point of the modulator may be adjusted by minimizing the error signal. Calibration time of the bias point may be reduced utilizing electronic data inversion. An output of the modulator may comprise a Y-junction and a single monitor photodiode may measure both branches of the modulator.

Optical waveguide devices are disclosed which utilize an optical waveguide having a waveguide bend therein with a width that varies adiabatically between a minimum value and a maximum value of the width. One or more connecting members can be attached to the waveguide bend near the maximum value of the width thereof to support the waveguide bend or to supply electrical power to an impurity-doped region located within the waveguide bend near the maximum value of the width. The impurity-doped region can form an electrical heater or a semiconductor junction which can be activated with a voltage to provide a variable optical path length in the optical waveguide. The optical waveguide devices can be used to form a tunable interferometer (e.g. a Mach-Zehnder interferometer) which can be used for optical modulation or switching. The optical waveguide devices can also be used to form an optical delay line.

Optical logic gates are constructed from Mach-Zehnder Interferometer (MZI) optical circuits. A multi-mode interference (MMI) splitter divides a continuous-wave input into two branches of the interferometer. Each branch has a semiconductor optical amplifier (SOA). When a logic input having a logic-high power level is applied to one of the SOA's, cross-phase modulation occurs in the SOA. The phase shift increases through the SOA. The branch coupled to the logic input has a relative phase shift of pi compared with the other branch. When two branches with the pi phase difference are combined, destructive interference occurs, producing a logic low. An MMI combiner or an equivalent phase shifter is used to combine the two branches. The MMI splitter adds a phase shift of pi / 2 to the upper branch but not to the lower branch, while the MMI combiner also adds pi / 2 shifts.

The invention provides a space division multiplexing Mach-Zehnder cascade fiber interferometer and a measurement method thereof. The space division multiplexing Mach-Zehnder cascade fiber interferometer is composed of a wide-spectrum light source, a photodetector, a coupler, a single-mode connection optical fiber, an optical fiber sensor, a continuous-variable optical delay device, and a reflector, wherein the optical fiber sensor is composed of a Mach-Zehnder interferometer and forms a cascade optical fiber sensor array or a network. The wide-spectrum light source and a photodetector are connected with the optical fiber sensor through the coupler to form a sensor network; and the sensor network is connected with the continuous-variable optical delay device and the reflector through the coupler and is used for enquiring and demodulating the optical fiber sensor. The space division multiplexing Mach-Zehnder cascade fiber interferometer solves the problem of breakage of the optical fiber sensor array, improves the anti-damage characteristics of the optical fiber sensor array and the network and solves the temperature compensation problem in the measurement process. The space division multiplexing Mach-Zehnder cascade fiber interferometer has the advantages of simple interferometer structure, easy implementation, improved measurement reliability and low cost, and better facilitates the technology generalization and popularization.

A method for modulating the E-field of an optical carrier signal utilizes a Mach-Zehnder modulator having a pair of independently controllable branches. A pair of independent branch drive signals VL(t) and VR(t) are derived. Each branch of the MZ modulator is driven with a respective one of the independent branch drive signals. By this means, a low cost conventional MZ modulator (interferometer) can be used to perform complex modulation of the E-field of the optical carrier. In some embodiments, this functionality is used to facilitate precompensation of optical impairments of an optical communications system.

An optical modulator that includes a resonator near one arm of a Mach-Zehnder interferometer and that increases the optical length of that arm so as to introduce a phase-shift in an optical signal propagating in that arm when compared to an optical signal propagating in the other arm of the interferometer. The resonator also increases the electro-optic interaction between an electrical signal (i.e., the source of information in a modulated signal) and the optical devices (e.g., waveguides). A modulator constructed in accordance with the present invention is thus physically small than prior art modulators and requires a significantly reduced drive voltage to impart information on an optical signal.

An optical transmitter generates a transmission signal having a frame as a unit, the frame including a single optical pilot signal with a constant optical phase and a plurality of phase-modulated optical data signals, and outputs the transmission signal into a transmission line. In a receiver, a splitter splits the optical signal input from the transmission line. On a second arm of a Mach-Zehnder interferometer, an optical gate transmits the optical pilot signal and a duplicator duplicates the optical pilot signal output from the optical gate at predetermined time intervals. A balanced optical receiver converts the interfered optical signal output from the interferometer into an electrical signal. A gate and a discriminator extract the data from the electrical signal output from the receiver.

Methods and systems for a polarization immune wavelength division multiplexing demultiplexer are disclosed and may include, in an optoelectronic transceiver having an input coupler, a demultiplexer, and an amplitude scrambler: receiving input optical signals of different polarization via the input coupler, communicating the input optical signals to the amplitude scrambler via waveguides, configuring the average optical power in each of the waveguides utilizing the amplitude scrambler, and demultiplexing the optical signals utilizing the demultiplexer. The amplitude scrambler may include phase modulators and a coupling section. The phase modulators may include sections of P-N junctions in the two waveguides. The demultiplexer may include a Mach-Zehnder Interferometer. The demultiplexed signals may be received utilizing photodetectors. The input coupler may include a polarization splitting grating coupler. The average optical power may be configured above which demultiplexer control circuitry is able to control the demultiplexer to process incoming optical signals.

A method and apparatus for implementing a colorless polarization independent Mach-Zehnder-interferometer (MZI)-based tunable dispersion compensator (TDC) that has only three MZI stages (two in a reflective MZI-TDC) and two adjustable couplers which are responsive to one control voltage, making it compact, low power, and simple to fabricate, test, and operate. Polarization independence is obtained by using a half-wave plate positioned across the midpoints of the two path lengths of middle stage MZI of the three stage MZI-TDC and by using a quarter-wave plate in front of a reflective facet of the reflective MZI-TDC. A cascaded MZI-TDC arrangement with also only a single control is formed by cascading two MZI-TDC arrangements and driving all adjustable couplers with the same control signal.

Methods and systems for encoding multi-level pulse amplitude modulated signals using integrated optoelectronics are disclosed and may include generating a multi-level, amplitude-modulated optical signal utilizing an optical modulator driven by two or more electrical input signals. The optical modulator may include optical modulator elements coupled in series and configured into groups. The number of optical modular elements and groups may configure the number of levels in the multi-level amplitude modulated optical signal. Unit drivers may be coupled to each of the groups. The electrical input signals may be synchronized before communicating them to the unit drivers utilizing flip-flops. Phase addition may be synchronized utilizing one or more electrical delay lines. The optical modulator may be integrated on a single substrate, which may include one of: silicon, gallium arsenide, germanium, indium gallium arsenide, polymers, or indium phosphide. The optical modulator may include a Mach-Zehnder interferometer or one or more ring modulators.

A subwavelength terahertz (THz) switch using an artificially designed conductor metamaterial is discussed in this invention. Theoretically, slow-light EM wave propagating at THz speed imitates the strongly localized surface plasmon modes and henceforth is called Spoof Surface Plasmon Polariton (SSPP) mode in this invention. The SSPP mode of slow-light EM propagation can be easily tailored by changing the refractive index of the dielectric materials inside the metallic gap structure engineered as a periodic array of grooves. Thus, the incorporation of electro-optical material which has birefringence such as a nematic liquid crystal (N-LC) or multiple-refractive indices into the metallic gap leads to a highly compact and efficient terahertz switch being controlled by a low-voltage signal. The optimal design of the SSPP switch enabled by this novel method shows many interesting properties including 1) strong subwavelength localization; 2) relatively high extinction (On / Off switching) ratio; and 3) small damping attenuation. The THz dynamic switches can be used to construct linear switches, Y junction switches and Mach-Zehnder interferometers by using micromachining and other fabrication techniques.

An electro-optical modulator with two electrodes as part of a transmission line of a first phase modulator and two electrodes as part of a transmission line of a second phase modulator included in two arms of a Mach-Zehnder-interferometer. An electrical controller applies a first electrical high-frequency-modulated voltage signals between the first and second electrodes and applies a second electrical high-frequency-modulated signals between the fourth and third electrodes. The electrical controller applies signals such that voltages applied to the first and fourth electrodes have substantially a same high-frequency content, and voltages applied to the second and third electrodes have substantially the same high-frequency content. In such configuration, a constant voltage offset is produced by either the voltages applied to the first and fourth electrodes or, the second and third electrodes. Thereby, cross-talk between electrodes, electrical losses, device size and fabrication costs may be reduced.

A transmitter (3) for generating a DQPSK-modulated optical signal, comprising: a splitter (7) for dividing an optical carrier signal into a first and second branch (8a, 8b), a first and second Mach-Zehnder interferometer (9, 10) in the first and second branch (8a, 8b), respectively, a phase shifter (11) in one of the branches (8b) generating a nominal phase shift of π / 2, and a combiner (7′) for combining the optical output signals of the two branches (8a, 8b). The transmitter (3) has a feedback circuit (12) generating at least a first and second bias signal (15.1 to 15.3) for adjusting a bias of at least the first and second Mach-Zehnder interferometers (9, 10), the feedback circuit (12) comprising: a detector for generating at least a first and second feedback signal from a sample signal extracted from the optical signal after the combiner (7′), and for each bias signal: a local oscillator generating an auxiliary signal modulating the bias signal (15.1 to 15.3) at a pre-defined frequency (f1, f2, f3), a lock-in detector determining a phase difference between the feedback signal and the auxiliary signal, and a bias circuit for generating the bias signal (15.1 to 15.3) from an output signal of the lock-in detector, wherein the pre-defined frequencies of the auxiliary signals (f1, f2, f3) are different from one another (f1≠f2≠f3) and preferably no integer multiples of each other.

Apparatus and methods for fluorescence imaging using radiofrequency multiplexed excitation. One apparatus splits an excitation laser beam into two arms of a Mach-Zehnder interferometer. The light in the first beam is frequency shifted by an acousto-optic deflector, which is driven by a phase-engineered radiofrequency comb designed to minimize peak-to-average power ratio. This RF comb generates multiple deflected optical beams possessing a range of output angles and frequency shifts. The second beam is shifted in frequency using an acousto-optic frequency shifter. After combining at a second beam splitter, the two beams are focused to a line on the sample using a conventional laser scanning microscope lens system. The acousto-optic deflectors frequency-encode the simultaneous excitation of an entire row of pixels, which enables detection and de-multiplexing of fluorescence images using a single photomultiplier tube and digital phase-coherent signal recovery techniques.

The encoder / decoder design for spectrum-encoded optical CDMA systems uses waveguide circuits monolithically integrated on one chip to fulfill essential encoding and decoding functions. The integrated device functions as a 1x2 wavelength selective Mach-Zehnder interferometer switch to encode the input broadband light source and to decode the transmitted spectrally encoded signals. The device comprises a frontal 3-dB coupler, a double-ended arrayed-waveguide grating (AWG), and arrays of thermooptic phase shifters and attenuators, together with their symmetric images reflected from the high-reflection coated facet, to realize all required functionality. The thermooptic phase shifters and attenuators are programmable through electronic interface to realize programmable encoding and decoding capabilities. The attenuators are used to equalize the powers and to increase the ON / OFF extinction ratio of all spectral chips.

The invention discloses a distributed optical fiber vibration sensor. The distributed optical fiber vibration sensor is characterized in that: on the basis of the optimized combination of the interference principles of a Sagnac interferometer and a Mach-Zehnder interferometer, the distributed optical fiber vibration sensor comprises a signal processing device, a first sensing optical fiber, a second sensing optical fiber, a third sensing optical fiber, a wideband light source, a narrowband light source, an optical circulator, a first optical wavelength division multiplexer, a second optical wavelength division multiplexer, a first coupler, a second coupler, a third coupler, a fourth coupler, a Faraday rotating mirror, a first photodetector, a second photodetector, a third photodetector and an optoisolator. The distributed optical fiber vibration sensor has a simple structure and can be used for monitoring outside disturbance and positioning multi-point interferences in real time; the demodulation work is relative simple and polarization maintaining optical fibers can be prevented from being used; and by adopting the Faraday rotating mirror, the phenomenon of polarization state fading due to double refraction can be also compensated.

An optical equalizer / dispersion compensator (E / CDC) comprises an input / output for receiving a multiplexed channel signal comprising a plurality of channel signals of different wavelengths. An optical amplifier may be coupled to receive, as an input / output, the multiplexed channel signals which amplifier may be a semiconductor optical amplifier (SOA) or a gain clamped-semiconductor optical amplifier (GC-SOA). A variable optical attenuator (VOA) is coupled to the optical amplifier and a chromatic dispersion compensator (CDC) is coupled to the variable optical attenuator. A mirror or Faraday rotator mirror (FRM) is coupled to the chromatic dispersion compensator to reflect the multiplexed channel signal back through optical components comprising the chromatic dispersion compensator, the variable optical attenuator and the optical amplifier so that the multiplexed channel signal is corrected partially for equalization and chromatic dispersion compensation with respect to each pass through these optical components. The E / CDC components may be integrated in a photonic integrated circuit (PIC) chip. In several embodiments, a photonic integrated circuit (PIC) chip comprises an input into the chip that receives at least one channel signal having experienced chromatic dispersion, a chromatic dispersion compensator (CDC) that separates the at least one channel signal into separate wavelength components over a free spectral range (FSR) spanning only a signal channel width and subjects the wavelength components to a phase shift to change the wavelength group delay in the wavelength components and that recombines the wavelength components to reconstitute the at least one channel signal, and an output from the chip for the recombined at least one channel signal having reduced chromatic dispersion compared to the same channel signal received at the chip input. The CDC device may include a tuning section to vary the phase shift of wavelength components as they propagate through the device. Such a CDC device may include a Mach-Zehnder interferometer (MZI) or a cascaded group of Mach-Zehnder interferometers, or at least one arrayed waveguide grating (AWG) or at least one Echelle grating.

An optical resonant modulator includes an optical ring resonator and an optical loop that is coupled to the optical ring resonator by two couplers. The optical ring resonator can have a hybrid design in which the ring resonator is formed on an electro-optically passive material and the optical loop is formed on an electro-optically active material. An amplification section can be inserted between the electro-optically passive and the electro-optically active sections. In analog applications, an optical resonator includes a Mach Zehnder interferometer section having an input and an output, with a feedback path coupling the output to the input. Applications of the optical modulator of the invention, and a method for modulating an optical signal also are disclosed.