基于差频原理的声光移频器

描述了声光移频器的特点及应用,依据一般声光移频器移频频率大于20MHz的局限性,提出了一种基于差频原理的声光移频器,介绍了其工作原理、光路设计及电路设计,在1 550nm波长下,得到了衍射效率>60%,移频频率±1MHz,频率稳定度优于10-6/2h的测试结果。     

利用声光差频抑制集成光学陀螺背散噪声研究

研究了利用两个声光移频器间的差频抑制谐振式集成光学陀螺中的背向散射噪声.测试了声光移频器的输出特性,结果表明声光移频器输出功率随调制频率变化.测试并说明了两路声光移频器的功率不平衡会影响环形谐振器的谐振曲线深度和陀螺解调曲线的斜率,并最终导致陀螺的测量误差.实验中通过补偿声光移频器的输出功率,有效地克服了声光移频器功率带宽的影响,陀螺零漂从补偿前的0.28 mV降低为0.095 mV.     

微型光学陀螺仪中声光移频器的设计与分析

微型光学陀螺仪是基于Ｓａｇｎａｃ效应，采用先进的集成光学技术研制的新型光学陀螺仪。研制微型光学陀螺仪的关键在于用频率调制来实现频率伺服，对主要误差进行有效抑制，以及实现高精度Ｓａｇｎａｃ频差测量。声光移频器是解决这一系列技术关键的一个核心器件。针对微型光学陀螺仪中对声光移频器所提出的百万分之一相对频移精度，调制带宽不低于１０ＭＨｚ，有效声功率大于１８０ｍＷ的特殊要求，对微型光学陀螺仪的核心器件——声光移频器进行了理论分析与设计，研究了它在实现上的主要技术难点，提出采用直接数字频率合成技术来代替一般的压控振荡器激励方案     

声光频移通信系统中接收技术研究

设计了基于声光频移技术的激光通信系统接收端系统,针对声光频移激光通信传输信号特点,利用LC谐振回路实现模拟选频,采用D触发器实现载波的数字下变频,最终通过现场可编程门阵列实现信号解调。最后对设计的模块进行测试,测试结果符合设计要求,实现了100MHz载波幅移键控信号的下变频以及基带信号的解调。     

利用双晶体实现的低频保偏光纤声光移频器

该文介绍了一种低频保偏光纤声光移频器的设计、制作、性能参数及典型应用。采用双晶体反向级联设计,将两片晶体工作频率的差值作为器件的移频频率,避免了单片声光晶体难以实现低频声光移频的问题。样品获得的性能参数为:工作波长1 053nm,移频频率10 MHz,插入损耗3.3dB,光上升时间33ns,输出偏振态线偏振。     

用于多普勒激光雷达系统的光纤声光移频器

介绍了应用于多普勒激光雷达系统中起频移作用的光纤声光移频器的设计及应用,描述了光纤声光移频器的工作原理,着重介绍光纤声光移频器的关键指标插入损耗、消光比、频率精度和稳定度的设计方法,得到了工作波长1.55 μm,插入损耗1.8 dB,消光比45 dB,频率稳定度优于频率×10 -7的实验结果。     

基于DDS的激光频率高精度控制系统及其应用

在诸如激光冷却原子、光频标和冷原子干涉等实验中,通常采用压控振荡器（VCO）技术对激光移频,但是移频精度和稳定性不能满足实验要求。本文提出并研制了一种直接数字频率合成器（DDS）及其专用高精度时序控制系统用于激光的移频。DDS基于AD9852芯片,配合微控制器（MCU）控制其参数,输出经功率放大后直接驱动声光调制器以调...     

声表面波声光移频器的工艺与实验研究

在微型光学陀螺仪中，声表面波声光移频器是实现系统闭环控制的核心执行器件。本文在理论分析与设计的基础上，以Ｋ８玻璃为基片，采用相应工艺成功地研制出声表面波声光移频器样片。经测试，其主要技术指标已初步满足微型光学陀螺仪的设计要求     

多光束傅里叶望远镜的移频设计

多光束傅里叶望远镜(MFT)对运动的深空暗目标快速成像有着独特的优势,但光学、电学、机械、软件等未突破的关键技术制约着其发展。根据傅里叶望远镜的成像原理和戈洛姆法则(Golomb ruler),分析选取了多光束成像下每束光的移频量,并设计了符合系统要求的声光移频器。结果表明,采用Golomb ruler时,31束光系统下的最大相对移频量为7.47MHz,设计的声光移频器通光孔径为8mm,全频带下最低衍射效率为0.9021,各指标都能满足系统需求。因此,多光束傅里叶望远镜的移频技术可行。     

用10.6μm光外差稳频提高接收机中频的分析

本文论述了提高CO_2激光外差雷达接收机中频对测量目标多普勒频移的意义,及采用声光移频器和外差频率跟踪技术,可使本振和发射频率保持恒定,使接收机中频的声光移频量提高2～3倍,从而使接收机探测动目标多普勒频移提高到±160MHz以上(相当于2.5Ma的目标运动速度).本文还分析了影响中频误差的因素,以及检测目标多普勒最小分辨率.     

A new heterodyne fiber-optic gyroscope using electrooptic frequency shifter

In this paper, a novel heterodyne detection technique of rotation rate is described. This technique uses highly birefringent single-mode fiber and an electrooptic frequency shifter for a heterodyne interferometric system, and thus releases the use of acoustooptic devices and also the nonreciprocity which usually exists in a heterodyne fiberoptic gyroscope. Initial experimental results show a good linearity of the scale factor.     

Continuous-wave frequency synthesis of a laser diode based ondiscrete-time negative frequency feedback: II. Theory

For part I, see, ibid., vol. 31, no.6, p. 1038, 1995. In this paper, we present the theory for a novel lightwave frequency synthesis system demonstrated recently. The system is composed of a frequency stabilized master laser, a frequency tunable slave laser, and an active optical feedback loop with an acoustooptic frequency shifter. The reference frequency is synthesized by circulating the optical pulse from the master laser around the loop and one output pulse with the desired frequency shift is used to stabilize the frequency of the slave laser. The theoretical aspects of the frequency synthesis system are explained based on the control theory for discrete-time negative feedback. We evaluate the frequency stability numerically by means of the Allan variance for different sampling periods, and reveal the relation between the frequency fluctuation characteristics of the slave laser in its free running condition. The numerical results agree with those of the reported experiments     

A novel integrated acoustooptic frequency shifter

An integrated optical frequency shifter that utilizes guided-wave acoustooptic Bragg diffractions in cascade from two tilted- and counterpropagating-surface acoustic waves is reported. The doubly and frequency-shifted diffracted light propagates in a fixed direction, but spatially resolved from the incident light, irrespective of the magnitude of frequency tuning. A device fabricated in a Y-cut LiNbO₃ planar waveguide has demonstrated desirable characteristics, including single-sideband suppressed-carrier properties, a frequency shift centered at 1 GHz, a tunable bandwidth of 165 MHz, a linear dynamic range greater than 41 dB, and high efficiency at the optical wavelength of 0.63 μm. These preliminary results suggest that a compact integrated acoustooptic frequency shifter module capable of multigigahertz center frequency and gigahertz bandwidth can be realized in a common LiNBO₃ substrate 0.2 cm×1.0 cm×1.5 cm in size     

Propagation and optical interaction of guided acoustic waves intwo-mode optical fibers

Acoustic modes propagating in cylindrical solid rods are considered. A review of the properties of several mode groups is given, and computed results are shown for a wide range of material properties. The lower mode of each group is relevant for an all-fiber-optic frequency shifter recently demonstrated. For these modes, dispersion relations, mode patterns, power relations, and acoustooptic coupling strength are calculated. Some experimental results are compared with the calculations, and alterations to improve the frequency shifter are proposed     

A method for measuring the frequency response of photodetector modules using twice-modulated light

In this paper, a novel method is proposed for measuring the frequency response of a photodetector (PD) and its associated amplifier, which is called a PD module in this paper, by using light whose intensity is modulated twice. A distinctive feature of the twice-modulated light is that it contains two frequency components that essentially have equal intensities. A measurement system was constructed consisting of an He-Ne laser source and two acoustooptic modulators to verify the method. This study shows the resolution to a problem caused by the use of acoustooptic modulators (AOMs). This method can be readily used for determining the frequency responses of a PD module in the frequency range of up to tens of megaHertz.     

Nonlinearity-Compensation-Free Optical Frequency Domain Reflectometry Based on Electrically-Controlled Optical Frequency Sweep

A nonlinearity-compensation-free optical frequency domain reflectometry (OFDR) scheme is proposed and experimentally demonstrated based on the electrically-controlled optical frequency sweep. In the proposed scheme, the linear frequency sweep light is generated by propagating an ultra-narrow-linewidth continuous-wave (CW) light through an electro-optic frequency shifter which consists of a dual-parallel Mach-Zehnder modulator (DPMZM) and an electronic 90° hybrid, where the electro-optic frequency shifter is driven by a linear frequency modulated signal generated by a direct digital synthesizer (DDS). Experimental results show that the spatial resolution and signal-to-noise ratio (SNR) of the proposed OFDR scheme without the nonlinear phase compensation are comparable to those of OFDR employing a commercial tunable laser source (TLS), an auxiliary interferometer, and a software-based nonlinear phase compensation method. The proposed OFDR scheme is helpful to reduce the complexity of the optical structure and eliminate the difficulty of developing the nonlinear phase compensation algorithm.     

普通单膜光纤声光频率偏移装置的研究

本文介绍为实现全光纤功能型传感系统而研制的一种新颖光纤偏频装置。分析了此装置的设计理论和设计方法,在实验基础上给出了实验研究结果,并确定了某些重要设计参数。     

Realization of a 10-µm homodyne receiver

We have realized a homodyne receiver for phase-modulated laser radiation atlambda = 10.6 mum, based on a dc-coupled optical phase-locked loop (PLL). A control loop maintains the output power of the CO2laser local oscillator at 0.7 mW. Fine frequency tuning of this laser is achieved by an acoustooptic frequency shifter whose inherent time delay has been taken into account in the design of both the PLL and the power control loop. The PLL rms phase error is some 3° for a received optical power of 4 nW. The HgCdTe photodiode serving as phase detector and as demodulator, as well as the preamplifier are operated at 80 K by means of a Stirling cooler. Clear domination of shot noise is achieved for the data rate of 140 Mbit/s. A microcomputer performs dc-offset compensation and frequency acquisition. The system is part of a breadboard of an intersatellite data link.     

在信号发生器中DDS/FPGA的应用

直接数字频率合成(DDS)技术是近年来迅速发展起来的新的频率合成方法,在很多领域得到了广泛应用。根据DDS原理及应用现状,介绍了DDS芯片AD9854与可编程门阵列(FPGA)相结合,设计开发了一种信号发生器,该系统具有灵活可变、可由用户控制的特点,用户可通过选择不同控制模块得到各种不同的线形调频(LFM)信号。     

Short pulse generation by use of an active multipass interferometer

The operation of a simple device that converts continuous-wave (CW) laser light into a short-pulse train is reported. The setup is based on a passive ring cavity in which an acoustooptic frequency shifter takes the place of one of the mirrors. Temporal filtering and pulse compression of laser light was demonstrated. The experimental results obtained by injecting a CW CO₂ laser light in such a device are in agreement with the theoretical analysis. The device's application in external pulse compression of mode-locked pulses is also demonstrated