Multiple quantum well optical modulator structures using surfaceacoustic wave induced Stark effect

Multiple-quantum-well (MQW) optical modulator structures using the quantum-confined Stark effect (QCSE) manifested by the application of an electric field induced by a propagating surface acoustic wave (SAW) are proposed. The magnitudes of the parallel E_∥ and perpendicular E_⊥ electric-field components are computed to determine the electroabsorption and change of index of refraction for the AlGaAs-GaAs system. The proposed structures are shown to be less cumbersome than conventional p-i-n configurations used to impress E. In addition, an enhanced performance Bragg modulator/switch which utilizes the QCSE as well as the acoustic phase grating produced by the SAW beam is described     

Third-order dispersion compensation using a phase modulator

Compensation of third-order dispersion in a fiber-optic transmission system using a phase modulator is studied both theoretically and experimentally. A sinusoidal signal is used as modulation function, where the amplitude and phase delay are optimized. The 2-ps input pulses (160-Gb/s compatible) were transmitted through a 626-km fiber link, where the characteristic oscillating tail was measured with a 1.6-ps resolution optical sampling system. When applying the phase modulation, the oscillating tail was significantly suppressed. The pulses were also used in a 160-Gb/s transmission experiment, where the eye diagrams were measured with the sampling system. Numerical simulations and practical experiments showed excellent agreement.     

Wide-frequency fiber-optic phase modulator using piezoelectricpolymer coating

The highly sensitive response of a fiber-optic phase modulator that is coated with 80-90-μm-thick vinylidene fluoride/trifluoroethylene copolymer on an 80-μm-diameter single-mode fiber and made piezoactive by radial poling is demonstrated over a wide frequency range, from 500 Hz to 50 MHz. In the range of 10 kHz up to 2 MHz, a relatively flat response is measured, whereas at high frequencies between 6 and 50 MHz, the phase modulation exhibits multiple peaks dominated by radial resonances of the fiber-jacket composite. Theoretical considerations on the phase shift and experimental results are given     

利用相位和强度调制器产生高消光比超短光脉冲

提出了一种产生高消光比超短光脉冲的新方法.利用相位调制器调制连续光生成啾啁光,而后利用M-Z强度调制器的倍频调制抑制对压缩不利的啁啾部分的影响,再通过等效啁啾光纤光栅进行压缩产生光脉冲.理论和仿真结果表明,该方法可以很好地消除光脉冲的基底及减小旁辦,产生消光比大于30 dB、波形理想的光脉冲,具有很强的可实现性.最后利用实际制作的色散系数为-380 ps/nm的等效啁啾光纤光栅对该方法进行了实验验证,结果表明,在重复频率为2.5 GHz、相位调制系数为9时,可产生脉宽小于18 ps的高质量光脉冲.     

Optical fibre phase modulator using coaxial PZT films

Experimental and theoretical investigations of optical phase modulation induced by thick piezoelectric lead zirconate titanate (PZT) film coated coaxially on single mode optical fibres are presented for the first time. PZT film thicknesses up to 120 μm have been realised by a sol-gel based process. The measured phase modulation ranges from hundreds of kilohertz to several megahertz     

Direct quadrature phase shift keying modulator using six-port technology

A direct quadrature phase shift keying modulator based on six-port technology is presented. The modulator comprises a six-port circuit, a switch matrix and open and short terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technology has the advantage of signal integrity, low power consumption and physical scalability to attain different frequencies of operation and extendibility to M-ary phase shift keying. Experiment results demonstrate performance with an output phase difference from 0.8 to 4.5/spl deg/ and an amplitude difference from 0.5 to 2.7 dB. A data throughput of 200 Mbits was attained.     

Optical waveguide phase modulator in GaInAsP using depletion edgetranslation

Under reverse bias a phase shift per unit length of up to 500°/mm is observed in a GaInAsP/InP inverted rib waveguide embedded in a double-heterostructure pin diode. The waveguides were fabricated by wet chemical etching and subsequent liquid phase epitaxy. Diodes were formed by selective Zn diffusion in the InP cladding layer. The planar structure is favourable for integration with other electronic or optoelectronic devices     

Optical-fibre phase modulator

A clip-on piezoelectric transducer is described which may be easily attached to a plastics-coated optical fibre and used to phase modulate signals within the glass fibre. The technique is applicable to a 1-way optical telemetry highway.     

Fiber-optic magnetic-force phase modulator

A fiber-optic magnetic-force phase modulator using an aluminium-jacketed current-carrying fiber coil placed in a uniform external magnetic field is presented. The modulator has a center frequency of 30 kHz with a modulation efficiency of 2.4 rad/mA and a Q of 4.6. A theoretical model is developed for the modulator, and its predictions are compared with experimental results. An accurate and simple method of characterizing the phase modulator response is described     

2.4 GHz direct-digital binary phase shift keying modulator using MEMS switch

A novel MEMS-based binary phase shift keying direct-digital modulator operating at a carrier frequency of 2.4 GHz is presented. The circuit is composed of a rat-race coupler and a single-pole double-throw MEMS switch controlled by a digital baseband signal. The coupler divides the input waveform into two signals that are 180/spl deg/ out of phase and the MEMS switch is used to select between these two signals. This circuit has been experimentally verified and results are reported.     

Bridge phase modulator with great phase deviation

A bridge phase modulator is described, with an RLC circuit in one branch of the bridge, having the possibility of eliminating parasitic amplitude modulation. One can obtain with this modulator large phase deviation with good linearity. The phenomena in the quasisteady and dynamic states are analysed.     

A new FM modulator using phase unstable PLL (PU-PLL)

A phase-locked loop (PLL) with a second-order low-pass filter can oscillate with the frequency nearly equal to the filter cutoff. By modulating the amplitude of the oscillation, a stable frequency modulated signal can be obtained at the output of a voltage-controlled oscillator (VCO).     

相位调制器实现光标记交换的新方案

提出了一种利用相位调制器实现一阶边带抑制的光标记交换(OLS)技术的新方案,在中心载波和其余生成的多个副边带分别进行强度调制,实验产生10Gb/s非归零(NRZ)光载荷和2.5Gb/s垂直频分复用(OFDM)光标记信号,并分别在单模光纤中传输了50km。分析了基本原理,进而建立了一简单的系统理论模型,最后通过仿真和实验相结合的方法验证了方案的可行性。     

Standing-wave EO phase modulator using nonperiodic domain inversionfor large modulation index

A deep microwave EO phase modulator using a standing-wave electrode structure together with nonperiodic domain inversion is presented. The calculation and experimental results show that the maximum modulation index obtained by this modulator is 30% higher than the best result obtained for a travelling-wave EO phase modulator with periodic domain inversion     

High-efficiency all-fiber phase modulator using an annular zinc oxide piezoelectric transducer

We present a high-efficiency in-fiber phase modulator, which consists of an annular ZnO piezoelectric transducer deposited on a gold-coated optical fiber by reactive RF planar magnetron sputtering. The deposited film is highly oriented and uniform in thickness and structure, which results in highly efficient acoustooptic interaction in the fiber core. Experimental results show modulator performance significantly exceeding previously reported devices.     

Semidigital multiplication by discrete convolution using surfaceacoustic wave (SAW) devices

The computation of the product of two digital numbers by discrete convolution by a surface acoustic wave (SAW) convolver is described. The principal limitations of the method are discussed as well as realistic performance numbers that can be achieved by using available SAW device technology. The multiplication is done by convolving the 2-b streams that represent two digital input operands in a SAW convolver at a rate of 100 MHz. The convolver output is the product in mixed binary representation. It consists of one analog value per digit with a resolution of 0.5%. These values are digitized at a rate of 200 MHz by an 8-b flash analog-to-digital converter and added up to form the digital result. It is shown that such a device has a very high computing power that can be adapted to special applications. One extreme is the multiplication of 256-b integer numbers, corresponding to a dynamic range of 1:10⁷⁷, at a rate of 0.2 MIPS. The other extreme is the computation of matrix products where computing speeds of 12000 MIPS can be achieved for 8-b operands, as required, for example, in image filtering applications     

ZnO-coated fiber acoustooptic phase modulator

We have developed an approximate theory of all-fiber acoustooptic phase modulator using ZnO coating. The induced axial and radial strains by acoustic waves dominantly affect low- and high-frequency modulation, respectively. The prediction of the optical phase modulation agrees well with the experimental published data.     

Actively stabilised electro-optic phase modulator

The authors show that a simple undoped LiNbO₃ monocrystal may be used as a highly performing electro-optic phase modulator in an actively stabilised holographic recording setup regardless of thermal and optical damage effects. The performance of this modulator in a typical time-averaged holographic interferometry experiment is described     

All-optical phase controlled amplitude modulator

Based on the cascading of second-order nonlinearities, the authors propose a novel scheme for all-optical processing exploiting the tensorial nature of the second-order susceptibility. A weak phase modulated signal can efficiently modulate the amplitude of a frequency-degenerate orthogonally polarised intense beam through coherent interaction via the generated second-harmonic. Device feasibility in lithium niobate is addressed     

A phase modulator with variable maximum phase deviation

A phase modulator, constructed with three Armstrong modulators, is presented. In this modulator, the maximum phase deviation can be extended up to π without frequency multiplication. Numerical results of the signal distortion are given for several values of the maximum phase deviation and compared to other Armstrong type phase modulators