A novel high-order FIR photonic signal processor

A new topology for realizing a high-order FIR RF photonic filter is presented. It is based on a novel structure that uses wavelength conversion and a routing technique to enable a multiple-pass transmission of the signal to be obtained through a single photonic sub-filter. The sub-filter can be of low order, however the routing of the output of the sub-filter back to itself several times together with some additional coefficients, realizes a high-order filter. Experimental results are presented which demonstrate a high-order FIR photonic filter realization comprising 39 taps.     

导模共振效应光子晶体滤波器光谱检测稳定性的研究

由于光子晶体滤波器带宽窄和高灵敏度的特点,检测抗体含量极限可以达到ng·mL-1。可以应用于生物传感器监测生物大分子内部反应过程。一维光子晶体滤波器作为生物传感器换能元件将生物信息转化为可检测的光电信号信息,主要反应在光谱仪测得共振波峰所在波长的变化。精确测试时,检测传感系统的稳定性是首要考虑的关键因素。稳定性决定实验数据的有效性。该工作对所制备的基于导模共振效应的一维光子晶体滤波器结构进行形貌和光谱测试,介绍了实验室所搭建的实时检测传感系统。由于系统集成度、 耦合损耗等因素的影响,光谱信息出现一定的噪声信号。因此,重点提出利用Lab VIEW编程实时监控光子晶体滤波器共振波峰值随时间的变化,由光谱变化情况来反应本套检测系统的稳定性和测试数据的有效性。同时这种实时监控程序也可用来监控其他基于导模共振生物传感系统的稳定度。该检测系统由于震动,光源抖动等问题产生的共振峰值漂移为0.25 nm,通过与模拟计算结果比较可以判定系统稳定性可以达到试剂检测的要求。     

Opto-VLSI-based tunable photonic RF filter

In this paper, an Opto-Very-Large-Scale-Integrated (Opto-VLSI) based tunable photonic radio frequency (RF) filter structure is proposed and numerically simulated. The structure comprises a reconfigurable Opto-VLSI processor capable of arbitrarily steering optical beams of different wavelengths, a diffraction grating for wavelength division demultiplexing, and high-dispersion fibres for true-time delaying RF-modulated wavebands. The proposed structure has the ability to generate arbitrary wavebands and weights for realizing any RF filter responses. The proof-of-concept of the tunable photonic RF signal processor is also experimentally demonstrated by tuning its free-spectral range and altering its shape factor through optical beam steering.     

Wideband versatile radio-frequency spectrum analyzer

Operation of a wideband, versatile optical spectrum analyzer for radio-frequency (RF) signals is demonstrated. The device is based on spectral hole burning (SHB). The demonstration features 2.3-GHz instantaneous bandwidth, 500-kHz resolution, and a 32-dB dynamic range. A true RF signal, transferred to the optical carrier with the help of a Mach-Zehnder modulator, is analyzed with optical carrier suppression and zooming capabilities. This is to the authors' knowledge the largest instantaneous bandwidth ever demonstrated for a SHB-based processor in rare-earth-doped crystals.     

基于光子晶体光纤中受激布里渊散射的光载波抑制

设计了一种基于光子晶体光纤中受激布里渊散射的载波滤波器.该滤波器利用两个环形器和一段光子晶体光纤构成了一个环形腔,这种腔结构有效地降低了光纤中受激布里渊散射的阈值.理论分析了光子晶体光纤载波滤波器对提高光调制深度和射频增益的影响.利用25 m的高非线性光子晶体光纤作为受激布里渊增益介质,当入射载波功率为70 mW时,微波光子信号的射频增益为5.38 dB,实验结果与理论计算相吻合.     

基于半导体光放大器和光学滤波器的同相波长转换理论研究

采用半导体光放大器(SOA)级联滤波器的方案可以实现高速全光波长转换,其中,滤波器实质上是对SOA输出信号的光谱进行优化操作.文中利用带通滤波器(BPF)和延时干涉仪(DI)组成的光谱优化器,不仅实现了80Gbit/s同相波长转换,而且基于遗传算法设计光谱优化器的参数,极大地提高了输出信号的质量.同时,也从理论上分析了SOA中超快带内效应对信号光谱的影响以及光谱优化器中BPF和DI的消光比对输出信号质量的影响.     

Detection and spectral measurement of single photons in communication bands using up-conversion technology

Quantum information systems are commonly operated in conventional communication bands (1310 and 1550 nm) over an optical fiber to take advantage of low transmission loss. However, the detection and spectral measurement of single photons in these communication bands are limited due to high noise and low sensitivity of single photon detectors in the wavelength ranges. To demonstrate high efficiency detection and high sensitivity spectral measurement, we have implemented a single photon detector and a spectrometer based on frequency up-conversion technology. This detector and spectrometer uses a 5-cm periodically poled lithium niobate (PPLN) waveguide and a tunable pump laser around 1550 nm, to convert signal photons around 1310 to 710 nm. The converted photons are then detected by a silicon-based avalanche photodiode (APD). The overall detection efficiency of the single photon detector is as high as 32%, which is three times higher than commercial InGaAs APDs. The sensitivity of the spectrometer is measured to be −126 dBm, which is at least three orders-of-magnitude better than any commercial optical spectrum analyzer in this wavelength range.     

基于微波频差转换的光学拍频研究

光学拍频是大学物理和光学实验教学中的重要内容.由于激光器存在中心波长漂移问题,实验中不易产生可观测的拍频信号.受到微波光子技术中微波波段和光波波段相互作用机理的启发,提出了基于微波频差转换的光学拍频方法.借助强度调制和相位调制将两个频差较小的微波信号调制到同一光载波上,结合光学滤波器获得了两个频差极小的稳定光信号,利用...     

Spectral hole burning for wideband, high-resolution radio-frequency spectrum analysis

We present experimental results for what is to our knowledge the first spectral-hole-burning based rf spectrum analyzer to cover 10 GHz of rf analysis bandwidth. The rf signal of interest is modulated onto an optical carrier, and the resultant optical sidebands are burned into the inhomogeneously broadened absorption band of a Tm3+:YAG crystal. At the same time a second, frequency-swept laser reads out the absorption profile, which is a double-sideband replica of the rf spectrum, and thus the rf spectrum can be deduced after spectral calibration of the nonlinear readout chirp. This initial demonstration shows spectral analysis covering 10 GHz of bandwidth with >5500 spectral channels and provides 43 dB of dynamic range.     

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) is demonstrated to operate stably with a simple configuration. By forward injecting an easily-generated external pulse train, the mode-locked fiber laser can generate an optical-pulse sequence with pulsewidth about 6 ps and average output power about 7.9 mW. The output pulses show an ultra-low RMS jitter about 70.7 fs measured by a RF spectrum analyzer. The use of the proposed forward-injection configuration can realize the repetition-rate tunability from 1 to 15 GHz for the generated optical-pulse sequences. By employing a wavelength-tunable optical band-pass filter in the laser cavity, the operation wavelength of the designed SOA-based actively mode-locked fiber laser can be tuned continuously in a wide span between 1528 and 1565 nm. The parameters of external-injection optical pulses are studied experimentally to optimize the mode-locked fiber laser.     

光子晶体超窄带滤波器

本文利用光学传输矩阵法研究了一种类似于谐振腔结构的光子晶体.研究发现在这种光子晶体的光子带隙的中央存在一个极窄的透光窗口,窗口的宽度在红外波段1500nm附近可以做到0.0001nm以下,窗口内的透光率峰值可以接近100%,窗口以外的区域的透光率可以做到0.01%以下.通过改变所研究结构中的周期厚度、中间夹层厚度、两边光子晶体的周期重复数和波的入射角可以改变窄带透过窗口的位置和窄带的宽度.这种光子晶体可以用来制作超窄带滤波器,有望在光通信超密度波分复用技术和光学信息精密测量技术当中获得应用.     

Angle of arrival estimation using spectral interferometry

We have developed a correlative signal processing concept based on a Mach-Zehnder interferometer and spatial-spectral (S2) materials that enables direct mapping of RF spectral phase as well as power spectral recording. This configuration can be used for precise frequency resolved time delay estimation between signals received by a phased antenna array system that in turn could be utilized to estimate the angle of arrival. We present an analytical theoretical model and a proof-of-principle demonstration of the concept of time difference of arrival estimation with a cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm.     

Microwave Photonic Phase Shifter Based on an Integrated Dual-polarization Dual-parallel Mach-Zehnder Modulator without Optical Filter

ABSTRACT

A frequency-doubled microwave photonic phase shifter (MPPS) without optical filter is proposed. The MPPS is based on an integrated dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM) and a polarization modulator (PolM). The DP-DPMZM with a 90° polarization rotator in one arm is used to generate an optical carrier suppressed double sideband (OCS-DSB) signal with orthogonal polarization, and the PolM with two modes opposite phase modulation is used to introduce the optical phase shift between the two orthogonally polarized tones. Simulations show that the MPPS can realize a continuously tunable phase shift of 360° with only one DC bias voltage, and is not sensitive to the optical carrier wavelength and microwave signal frequency since no optical filter is used.     

顶部反射镜对GaN基共振腔发光二极管性能的影响研究

本文在Ga N基共振腔发光二极管(RCLED)顶部设计制备了高反膜结构分布式布拉格反射镜(DBR)和滤波器结构DBR,对比分析了两种反射镜的反射率曲线特征以及对应的RCLED器件的光输出纵模模式、光谱线宽和输出光强等性能差异,详细研究了顶部反射镜的光反射特性对RCLED器件输出光谱性能的影响机理.研究结果表明,顶部反射镜是RCLED的重要组成部分,其反射率曲线特征决定器件的光输出性能.常规高反膜结构DBR顶部反射镜的反射率曲线具有较宽的高反射带,将其作为顶部反射镜可有效压窄RCLED发光纵模线宽,但是发光光谱仍呈现多纵模光输出特征.滤波器结构DBR顶部反射镜的反射率曲线在中心波长处具有较窄的透光凹带,利用透光凹带对输出光的调制作用,器件可实现单纵模光输出,在光通信、光纤传感等领域展示了广阔的应用前景.通过进一步设计RCLED顶部反射镜结构,可以改变其反射率曲线特性,进而优化RCLED器件的输出光谱特性,以满足器件在多个领域的应用需求.     

A novel tunable cascaded IIR microwave photonic filter

A new tunable cascaded infinite impulse response (IIR) microwave photonic filter is presented, based on a novel configuration in which a semiconductor optical amplifier (SOA) is inserted between two active recirculating delay line (RDL) loops. Due to wavelength conversion with cross-gain modulation (XGM) in SOA, interferences between light beams traveling different paths are canceled, ensuring a stable transmission. By employing this configuration, a cascaded IIR microwave photonic filter is firstly achieved. The free spectral range (FSR) and the Q factor are both increased significantly by adopting “vernier effect” technique in the IIR filter. The structure is also tunable by adjusting the length of one RDL loop.     

Six-bit all-optical quantization using photonic crystal fiber with soliton self-frequency shift and pre-chirp spectral compression techniques

In this paper,we propose an optical quantization scheme for all-optical analog-to-digital conversion that facilitates photonics integration.A segment of 10-m photonic crystal fiber with a high nonlinear coefficient of 62.8 W 1/km is utilized to realize large scale soliton self-frequency shift relevant to the power of the sampled optical signal.Furthermore,a 100-m dispersion-increasing fiber is used as the spectral compression module for further resolution enhancement.Simulation results show that 317-nm maximum wavelength shift is realized with 1550-nm initial wavelength and 6-bit quantization resolution is obtained with a subsequent spectral compression process.     

有限冲击响应滤波器在四频激光陀螺中的应用

针对目前四频差动激光陀螺光学解调方案可靠性和温度特性差的特点,介绍一种基于FPGA的数字拍频解调方案。分析了四频差动激光陀螺数字拍频解调对电路系统的需求,对数字拍频解调的关键部件低通滤波器进行了设计与实现。根据四频差动激光陀螺的特性参数计算滤波器的通带截止频率及阻带截止频率,使用MATLAB的滤波器设计和分析工具FDATool完成了有限冲击响应（FIR）数字滤波器的参数设计,并利用Xilinx公司的FPGA集成开发环境ISE实现FIR数字滤波器的片上系统设计。仿真和实验结果表明,所设计的FIR数字滤波器对四频差动激光陀螺的和频分量衰减达到-66 dB,满足四频差动激光陀螺拍频解调的需求,并有助于实现四频差动激光陀螺的小型化和数字化。     

All-fiber incoherent frequency-to-time mapping method for microwave signal generation with baseband transmission and multicasting support

We present a proof-of-principle experiment for achieving simultaneous distribution of baseband radio-frequency data and up-conversion with broadcasting support over a passive optical network. The technique is based on an incoherent frequency-to-time mapping method for pulse shaping. Specifically, we synthesize the spectral density function of sliced ASE noise from an EDFA with a periodic Mach–Zehnder fiber interferometer optical filter. By using external intensity modulation combined with propagation in an optical fiber, after photodetection, the resultant averaged temporal pulse profile resembles the shape of the incoherent source. The photodetected signal contains both the baseband data and an up-frequency converted copy with central wavelength for the microwave carrier into the ultra-wideband range and tuning capability by selection of the fiber length.     

95 GHz millimeter wave signal generation using an arrayed waveguide grating dual wavelength semiconductor laser

We report the generation of a 95?GHz carrier frequency by optical heterodyning of two wavelengths from adjacent channels from an arrayed waveguide grating-based multiwavelength laser. The extended cavity structure of the device provides low phase noise and narrow optical linewidth, further enhanced by the intracavity filter effect of the arrayed waveguide grating. We demonstrate that the generated RF beat note, at 95?GHz, has a -3 dB linewidth of 250?kHz. To the best of our knowledge, this is the narrowest RF linewidth generated from a free-running dual-wavelength semiconductor laser. The device is realized as a photonic integrated circuit using active-passive integration technology, and fabricated on a multiproject wafer run, constituting a novel approach for a compact, low-cost dual-wavelength heterodyne source.     

A Reconfigurable Microwave Photonic Channelized Receiver Based on Dense Wavelength Division Multiplexing Using an Optical Comb

A photonic approach to implementing a microwave channelized receiver based on dense wavelength division multiplexing using an optical comb is proposed. In the approach, a flat optical comb with 11 comb lines is generated using two cascaded Mach-Zehnder modulators. Frequency analysis of a microwave signal with multiple-frequency components is realized by using the optical comb together with an optical etalon with a periodic transfer function, a wavelength division multiplexer (WDM) and a photodetector array. The system is investigated numerically. Frequency measurement of a multi-frequency signal with a measurement range from 0.5-11.5 with an accuracy of ± 0.5 GHz is achieved. The reconfigurability of the system realized by tuning the comb-line spacing and the peak positions of the etalon is also evaluated. The improvement of the dynamic range of the system using an optimized periodic filter is also discussed.