A push-pull optical amplitude modulator

A push-pull optical amplitude modulator is described, and some experimental results are presented. The modulator is an interferometer with phase modulators in each arm. The design gives good temperature stability and allows a reduced modulating voltage by using a transverse modulating field. The use of a Köster's beamsplitting prism provided a compact practical design for the experimental KDP modulator. The modulator held a null in the output of 20 dB below the input for periods of one hour. The frequency response out to 30 MHz and the pulse response of the modulator were measured. Strong piezoelectric resonances were observed. The advantages of the push-pull modulator design for use with LiNbO3or LiTaO3are pointed out.     

DWDM optical millimeter-wave generation for radio-over-fiber using an optical phase modulator and an optical interleaver

We have proposed and experimentally demonstrated a novel scheme to generate a dense wavelength-division multiplexing (DWDM) optical millimeter-wave source by using an optical phase modulator and an optical interleaver. The stability of the DWDM optical millimeter wave generation is largely improved because we use an optical phase modulator without a dc-bias controller and an optical interleaver is subsequently employed to suppress the optical carrier of the DWDM source, which is not as temperature sensitive as a fiber Bragg grating. Moreover, the limitation of chromatic dispersion is greatly reduced due to avoiding the generation of higher order sidebands via driving the phase modulator with optimized RF signal.     

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     

An optical homodyne technique for measurement of amplitude and phase of subangstrom ultrasonic vibrations

An optical homodyne technique is utilized to measure sub-angstrom dynamic mechanical deformations. For measurement in the frequency domain, where synchronous detection is used both the amplitude and phase of the mechanical signal can be measured with a high sensitivity; displacements less than 10^-2Å were measured with normal environment acoustic noise. Measurement in the time domain is also feasible with reduced sensitivity.     

测量光学非线性的4f相位相干成像技术研究进展

4f相位相干成像技术是一种简单有效的测量材料三阶非线性的方法,文中具体介绍了它的基本原理、发展现状及应用前景.设计了一种改进的4f相位相干成像系统,通过改进传统4f相位相干成像系统的参考光路,使得原来用以监设计测脉冲能量浮动的参考光斑同时具备了监测入射脉冲空间分布的功能,实现了4f相位干成像系统在光斑空间分布不稳定情况下的非线性折射测量.报道了4f相位相干成像技术的最新进展一基于4f相位相干成像系统的泵浦探测系统.用这个新系统进行泵浦一探测实验方便快捷,并可同时研究出材料的激发态吸收与折射.     

Arrayed-waveguide grating with built-in interferometer for measuring amplitude and phase distribution

We propose an arrayed-waveguide grating with a built-in interferometer that enables us to evaluate the amplitude and phase distribution in the arrayed waveguides easily and precisely. We fabricated the proposed optical circuit with silica waveguides, and successfully confirmed its operational principle in experiments.     

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.     

A novel optical bistable multiple-quantum-well phase modulator

The authors present a new type of optically bistable phase modulator utilizing a self electrooptic effect device (SEED) integrated with an electrooptic wavelength modulator. An electrically bistable SEED, operating on the principle of the quantum-confined Stark effect, controls the bias voltage across an electrooptic waveguide phase modulator to produce optical bistability. A control signal at 0.848 μm, corresponding to the first electron to heavy hole exciton transition in GaAs/AlGaAs multiple-quantum-well is used to switch 1.152 μm light propagating through a waveguide in a direction normal to the control beam     

Half-octave bandwidth traveling-wave X-band optical phase modulator

Multiple interactions of optical and microwave fields in an electrooptical crystal have yielded low-power optical phase modulation over a 4.6-GHz bandwidth.     

Field probe for measuring both amplitude and phase of antenna radiation patterns

Small probe antennas are often used for measuring the amplitude and phase of antenna radiation patterns. Phase measurements are complicated by the need for an accurate r.f. phase reference to be conveyed to or from the mobile probe. The letter describes a scheme for simplifying such measurements by the use of a probe unit which backscatters incident energy after subjecting it to a single sideband frequency translation. The scheme has application to both compact ranges and to the measurement of profile errors in reflector antennas by phase measurements within the aperture plane.     

A simple bidirectional hybrid optical link for alternatively providing wired and wireless accesses based on an optical phase modulator

A simple bidirectional hybrid optical link based on an optical phase modulator (OPM) is proposed to alternatively provide wired and wireless accesses. At the optical line terminal, only an OPM along with an optical band-pass filter is employed to generate the data-bearing four-tone downlink optical signal. At the hybrid optical network unit (HONU), both the downlink wired and wireless access electrical signals are simply generated based on the direct detection. Meanwhile, since the optical carrier for the uplink can be abstracted from the downlink, the HONU is free from the light source. To demonstrate the feasibility of our proposed scheme, a proof-of-concept bidirectional hybrid optical access link based on the OptiSystem platform is built. The simulation results indicate that after 30-km-long standard single-mode fiber transmission, the proposed bidirectional hybrid optical link still maintains good performance.     

Optical generation and distribution of continuously tunable millimeter-wave signals using an optical phase modulator

In this paper, we propose an approach to generate and distribute two wide bands of continuously tunable millimeter-wave (mm-wave) signals using an optical phase modulator and a fixed optical notch filter. We demonstrate theoretically that the odd-order electrical harmonics are cancelled and even-order electrical harmonics are generated at the output of a photodetector when the optical carrier is filtered out from the phase-modulated optical spectrum. Analysis shows that dispersion compensation is required in order to maintain the suppression of the odd-order electrical harmonics, in order to eliminate signal fading of the generated electrical signal when the optical signal is distributed using conventional single-mode optical fiber. It is experimentally demonstrated that, when the electrical drive signal is tuned from 18.8-25 GHz, two bands of mm-wave signals from 37.6 to 50 GHz and from 75.2 to 100 GHz with high signal quality are generated locally and remotely. This approach does not suffer from the direct current (dc) bias-drifting problem observed when an optical intensity modulator is used.     

A novel optical phase modulator design suitable for phased arrays

A new design of optical phase modulator in SIMOX has been demonstrated, which allows duplication of active waveguides with a minimum requirement for external contacts and metallization. The device is based on a common cathode configuration and requires 56.5 mA at 1.65 V to produce a π-phase shift. To confirm the experimental results, the same device structure has been modeled, and provided good agreement, with V_π calculated to 1.70 V and 52.6 mA     

2.75-4.75 GHz QPSK modulator with low amplitude and phase errors

A QPSK modulator with a 2.75-4.75 GHz operating frequency range is presented. The modulator is realised using a broadband power divider, microstrip-slotline-microstrip transitions and Lange couplers. Computer optimised matching circuits are used to maintain a phase error less than 5 degrees and an amplitude phase imbalance error across the band of less than 0.5 dB. The modulator is suitable for MMIC implementation.<>     

Heterodyne reception of millimeterwave-modulated optical signalswith an InP-based transistor

High-frequency transistors are known for their ability to efficiently perform signal processing functions that reach beyond mere amplification. Among such functions are oscillation, signal mixing, frequency multiplication, and optical signal detection. The current investigation focuses specifically on these four functions as they pertain to retrieving signal information impressed on optical carriers of 1.3-μm wavelength. The main demonstration object is a 40-GHz hybrid-integrated heterodyne receiver circuit that employs an InP-based HEMT in a four-function role to simultaneously provide carrier demodulation, self-generation of a local oscillation signal, internal frequency doubling thereof, and signal downconversion to a lower intermediate frequency band     

Low detection penalty in an optical DPSK heterodyne system using asaturated optical amplifier as phase modulator

A model established from the rate equations of a near traveling-wave optical amplifier (NTWOA) used as a phase modulator shows that the modulation rate is limited by the carrier lifetime to 500 Mb/s and that the worst-case detection penalty is about 0.7 dB. It is then experimentally demonstrated that close control of the injected light polarization can reduce the detection penalty in a DPSK (differential phase-shift keying) heterodyne system, using an NTWOA phase modulator instead of an LiNbO₃ modulator, to 0.6 dB. This device and a balance receiver have allowed the implementation of 282-Mb/s DPSK link operating at 1.522 μm over 242 km of fiber with a 3-dB margin     

Alignment monitoring technique for pulse carver and data modulator in RZ-DPSK systems using an optical frequency discriminator

A technique for monitoring the timing alignment between a pulse carver and a phase modulator in return-to-zero differential phase-shift keying systems is proposed. An optical frequency discriminator and a microwave detector centered at a half of the phase modulation data rate are used to monitor the spectrum broadening caused by timing misalignment. The proposed method has a large detection dynamic range and is polarization-independent.     

并行PM生成的12倍频毫米波RoF系统研究

提出了一种利用4并行相位调制器(PM)结构调制生成12倍频毫米波的方法,详细介绍了该方法的原理,并通过公式推导证明了其可行性.采用软件搭建了相应的RoF仿真系统,检测到12倍频后毫米波的频谱图和通过系统传输后的眼图.理论分析和仿真结果表明,10GHz的射频信号可产生120GHz的毫米波,5Gb/s的数据可在光纤中传输30km以上,功率代价小于0.9dB.     

基于相位调制器倍频技术产生56GHz毫米波的光载无线通信系统

提出并实验研究了一种基于光相位调制器(PM)倍频技术产生56GHz毫米波的光载无线通信(RoF)系统。在中心站,通过28GHz射频(RF)信号驱动PM产生了56GHz光毫米波,并将下行的2.8Gb/s开关键控(OOK)信号调制到该光载波上,然后经过20km标准单模光纤(SSMF)传输至基站,最后由天线进行发射。用户终端接收后,采用相干解调恢复出基带信号。实验结果表明,56GHz光载毫米波信号经SSMF传输20km后其功率代价小于1dB,通过无线方式传输1.1m后其功率代价小于2.5dB。     

AlGaAs-GaAs quantum-well electrooptic phase modulator with disorderdelineated optical confinement

Waveguide phase modulators, with 0.5- and 1-μm quantum-well (QW) active regions which are defined by impurity induced disordering are investigated theoretically. By controlling the extent of the interdiffusion in the lateral claddings, the refractive index difference between the core and claddings is used to provide single-mode operation. Strong optical confinement, which is required to produce single-mode high-efficiency modulation, requires the peak impurity concentration to be at the center of the QW active region. Moreover, the annealing time needs to be optimized so that single mode can be maintained at the desired bias field. A low dopant concentration is also expected to minimize the destruction of the modulator structure. The results show that since the core/cladding interface is graded, the width of the metal contact is important. A comparison of modulation efficiency for active layer thicknesses of 0.5 and 1.0 μm shows that the 0.5-μm one is a more efficient structure and its absorption loss can be reduced by increasing the applied field from 50 to 100 kV/cm