Permanent attachment of single-mode fiber arrays to waveguides

We report on coupling arrays of SM fibers in siliconV- grooves to waveguides. Arrays with up to 12 fibers have been permanently attached to waveguides with an average excess loss of 0.3 dB per interface. We discuss a subtle, heretofore unreported effect of polarization on fiber-waveguide insertion loss and we describe the first measurements of waveguide-mode position as a function of polarization. In general, the modes of a Ti:LiNbO3waveguide peak at different positions. This results in different optimum positions for coupling and thus leads to an unavoidable excess loss when attaching fibers. For low-loss waveguides, we predict a minimum excess loss of 0.25 dB per interface.     

Deterministic, analytically complete measurement ofpolarization-dependent transmission through optical devices

Polarization dependence of the loss or gain of an optical device has been difficult to measure in a consistent and reproducible manner because it has been necessary to search for the extrema of transmission over a two-dimensional polarization space. It is shown that the global variation of the transmission through any linear, time-invariant optical device, over all states of polarization, can be found in a strictly deterministic, analytically complete manner by measuring the polarization responses to only three input polarizations. A series of fast, automated measurements of two test devices yielded standard deviations of 0.017 and 0.033 dB and agreement with manual measurements     

Zn indiffusion waveguide polarizer on a Y-cut LiNbO3 at1.32-μm wavelength

A polarization-dependent loss measurement of Zn indiffusion (ZI) waveguide on a Y-cut LiNbO₃ substrate is firstly reported. The measured results show that the waveguides support either a single extraordinary polarization or both extraordinary and ordinary polarizations depending on the fabrication process parameters. For the single extraordinary polarization waveguide, the measured propagation loss at 1.32-μm wavelength is 0.9 dB/cm and the best measured polarization extinction ratio is 44 dB at a distance of 1.5 cm from the input end, which are quite good for being a waveguide polarizer. Moreover, the voltage-length product measured for the ZI Mach-Zehnder modulator shows that the substrate electrooptic coefficient is not degraded     

SOA-Assisted Data-Polarization-Insensitive Wavelength Conversion in a PPLN Waveguide

We demonstrate a novel method of wavelength conversion in a periodically poled lithium niobate (PPLN) waveguide using polarization modulation and amplitude modulation of its pump. Polarization-insensitive, all-optical, intensity-to-polarization conversion in a semiconductor optical amplifier (SOA) is used to reduce the waveguide's polarization sensitivity from >30 dB to <1 dB. We demonstrate BER measurements of the converted signal at 2.5 Gb/s. We also demonstrate polarization modulation of the PPLN waveguide pump using cross-polarization modulation in highly nonlinear fiber (HNLF) at 10 Gb/s.     

Design of a 1 × 2 novel optical switch based on polarization converters and splitters

In this paper, a 1?×?2 optical switch based on two TE/TM polarization converters, one 1?×?2-polarization beam splitter and a hybrid 2?×?2-polarization beam splitter/combiner is designed and discussed. The novelty of this work resides in the design of a 2?×?2-hybrid polarization beam combiner/splitter, operating as a 2?×?2 polarization optical switch through the combining and the splitting of polarized signals issued from two TE/TM polarization controllers. The novel hybrid splitter/combiner can route an optical signal either to a bar or a cross port with an extinction ratio higher than 90 dB, thanks to the feature of polarization splitting used in this device to suppress undesired polarization states and minimize the polarization-dependent loss. We have used polarization beam converters to switch between two orthogonal modes in order to facilitate the routing of these signals through the 2?×?2-hybrid polarization splitter/combiner. We changed the polarization states of signals, in our simulation via OptiSystem, through polarization controllers, by modifying only their phase shifts between 0 rad and π rad. The proposed 1?×?2 optical switch presents an average insertion loss of 3.5 dB.

     

980/1 550保偏光纤波分复用器

从耦合模理论出发,分析了980／1550熔融拉锥（FBT）型保偏光纤（PMF）波分复用器（WDM）的工作原理,设计了WDM的制作方法。在FBT台上,通过控制火焰的温度和宽度以及拉伸速度,有效控制WDM的拉伸长度和耦合区结构,用1550nm的PMF和H11060单模光纤（SMF）成功研制了高性能的980／1550PMFWDM。测试结果表明：在1550nm波长上,该WDM具有0．2dB的插入损耗、32dB的隔离度和22．8dB的消光比偏振特性;在980nm波长上,具有0．2dB的插入损耗、14_8dB的隔离度。该器件除了具有SMFWDM的特性外,1550nm端口还具有偏振保持特性,它将促进PMF激光器和放大器快速发展。     

Measuring the propagation properties of a forest canopy using apolarimetric scatterometer

A truck-mounted 1.6-GHz polarimetric scatterometer was used from a 19-m high platform to measure the backscattering from a dense canopy of pine trees at an incidence angle of 40°. Two sets of measurements were made at each of many spatial locations, one set with and the other without a trihedral corner reflector present on the ground surface underneath the canopy. From the two sets of polarimetric measurements, it was possible to determine the mean values and the statistical distributions of the canopy attenuation factors for horizontal and vertical polarizations. The mean values of the one-way attenuation factors were found to be 9.31 dB for horizontal polarization and 9.16 dB for vertical polarization. The precision associated with the values of the canopy loss factor measured using the polarimetric technique is estimated to be on the order of ±0.3 dB     

Development of a Submillimeter Double-Ridged Waveguide Ortho-Mode Transducer (OMT) for the 385–500 GHz Band

We present design and evaluations of a submillimeter double-ridged waveguide ortho-mode transducer (OMT) for ALMA Band 8 (385–500 GHz) cartridge receiver. The measured transmission loss of the OMT at 4 K was 0.4–0.5 dB according to noise measurements with an SIS mixer. The polarization isolation was measured to be larger than 29 dB from quasioptical measurements. The OMT consists of a Bϕifot junction and a double-ridged guide. A robust design with allowable mechanical errors of 20 μm has been demonstrated.     

Accurate spectral characterization of polarization-dependent loss

Building on previous work, a rapid automated nonmechanical measurement system for spectral characterization of polarization-dependent loss (PDL) has been developed. A deterministic fixed-states Mueller-Stokes method in conjunction with realtime calibrated spectral information is used to derive wavelength-dependent Mueller matrix elements. Voltage-modulated liquid-crystal variable retarders set the input polarization states. A narrow voltage-tuned filter provides a wavelength sweep following a broadband source; the sweep wavelength is calibrated in realtime by hydrogen cyanide reference lines. This rapid measurement system can measure PDL over a wavelength range of 15 nm in 5 s. A complete uncertainty analysis has been conducted for PDL in the range of 0.05 to 0.3 dB with an expanded uncertainty of 0.0098 dB over the range of 1535 to 1560 nm. Performance was verified using a Fresnel reference. Finally, design and performance results from all-fiber artifact calibration standards are presented.     

A quasi-optical universal polarizer

This paper describes the design and measurement of a quasi-optical universal polarizer for use in the 100–170 GHz frequency range. The instrument may be configured to convert an arbitrary elliptical polarization state into a linearly polarized stale suitable for feeding a fixed waveguide receiver. A transmission loss of 0.15 dB was measured at 140 GHz and the rejection of the orthogonal polarization state was greater than 50 dB.     

Compact polarization-insensitive InGaAsP-InP 2 /spl times/ 2 optical switch

We demonstrate a simple, compact, high-contrast ratio, and low-loss polarization-insensitive InGaAsP-InP 2 /spl times/ 2 optical switch with an operational wavelength range from 1520 to 1580 nm. The switch is 1.3 mm long by 160 /spl mu/m wide. The on-off contrast ratio is within (21/spl plusmn/2) dB over the temperature range from 16/spl deg/C to 64/spl deg/C, the polarization sensitivity is <2 dB, and the propagation loss is (3/spl plusmn/2) dB in both the ON and OFF states, making it potentially useful for optical cross-connects, delay lines, and add-drop multiplexers.     

Wavelength add-drop switching using tilting micromirrors

This paper describes a single-mode optical fiber switch which routes individual signals into and out of a wavelength multiplexed data stream without interrupting the remaining channels. The switch uses free-space optical wavelength multiplexing and a column of micromechanical tilt-mirrors to switch 16 channels at 200 GHz spacing from 1531 to 1556 nm. The electrostatically actuated tilt mirrors use an 80 V peak-to-peak 300 KHz sinusoidal drive signal to switch between ±10° with a 20 μs response. The total fiber-to-fiber insertion loss for the packaged switch is 5 dB for the passed signals and 8 dB for added and dropped signals, with 0.2 dB polarization dependence. Switching contrast was 30 dB or more for all 16 channels and all input and output states. We demonstrate operation by switching 622 Mb/s data on eight wavelength channels between the two input and output ports with negligible eye closure     

A Novel Design for Polarization-Independent Single-Pump Fiber-Optic Parametric Amplifiers

We propose a novel scheme for designing fiber-optic parametric amplifiers whose operation does not depend on the input signal polarization. In our scheme, four-wave mixing takes place inside a birefringent fiber pumped at 45deg from a principal axis. We show numerically that output power varies by <0.1 dB for arbitrary states of input polarization under practical conditions     

Polarization-selective mode coupling in two-mode Hi-Bi fibers

We propose and demonstrate a mode coupler which converts either of the LP₀₁ polarization states in a two-mode high-birefringence (Hi-Bi) fiber to the LP₁₁ mode with the same polarization. We use coupled-mode theory to develop design rules based on the polarization splitting of the beat length between the two lower-order modes. The device can be operated either as a narrow-band device in a region with large intermodal group delay difference or as a broadband device in a region with zero group delay difference. We use this novel device as a key component in a two-mode Hi-Bi fiber polarizer. In this configuration either of the polarization eigenstates can be selected and transmitted with an adjustable extinction ratio which can be as large as 30 dB. The coupling loss in the transmitted state of polarization can be less than 0.2 dB. In the broadband polarizer we demonstrate -20 dB extinction over 42 nm with a potential for considerable improvement. We also propose and experimentally investigate an increased differential group delay obtained by propagating one polarization state in the LP₁₁ mode instead of in the LP₀₁ mode. The largest differential group delay measured in this configuration is 14.5 ps/m which is seven times larger than the differential group delay between the polarization modes. We discuss several possible uses in fiber sensors and measure the transmission of a proposed two-coupler configuration     

Study of MPI measurement conditions and MPI characteristic in BIF

We investigated the measurement conditions for measuring multipath interference (MPI) occurring between fundamental and higher order modes. We considered the sampling interval as a function of the free spectral range (FSR) as a measurement condition. We also investigated the effect of randomized polarization states when measuring the MPI characteristics. We then confirmed the MPI characteristic, which we measured using three methods with a suitable sampling interval over FSR value and a suitable number of repetitions of randomized polarization states. Furthermore, we describe the MPI characteristic of bending loss insensitive fibers (BIFs) with offset connections and tight bends. We discuss the MPI degradation factor in an access network employing BIF.     

共面微波探针在片测试技术研究

本文描述了使用共面微波探针的半导体芯片在片测试技术.设计研制出的多种微波探针性能参数稳定,使用寿命在十万次以上,用于在片检测各种GaAs共面集成电路芯片.触头排列为GSG的微波探针,-3dB带宽及反射损耗分别为14GHz和小于-10dB.     

Preliminary Report on Measurements of Forest Canopies with C-Band Radar Scatterometer at NASA/NSTL

This paper presents preliminary results of C-band radar scatterometer measurements of forest canopies of southeastern forests in the vicinity of NASA/NSTL. The results are as follows: 1) radar backscattering coefficients (BSC's) of deciduous forests such as oak, maple, blackgum, and cypress are higher than those of coniferous forests such as slash pine plantation and natural pine; 2) at a large incidence angle, where polarization effect is significant, and by ranging measurement, the VV polarization BSC's obtain peak value at the first few meters from the canopy top and decrease rather quickly, while the HH polarization BSC's obtain peak value at longer distances from the canopy top and decrease rather slowly through the canopy; 3) using the active radar calibrator for tree canopy attenuation measurement of a dense and a sparse live oak, it is found that the tree canopies with higher attenuations have higher BSC's for all three polarizations, with VV polarization containing the largest differential (2.2 dB).     

Extinction ratio improvement using the nonlinear optical loopmirror

We have investigated the nonlinear optical loop mirror operating as an extinction ratio (ER) improvement device. ER improvement and bit-error-rate measurements were made in a polarization insensitive mode. An ER of 3.8 dB can be improved to 10.8 dB with an improvement of the receiver power penalty from 4.1 dB to 1.6 dB     

用偏振模色散模拟器加偏振片实现带内光信噪比检测

提出了一种基于偏振模色散(PMD)模 拟器加偏振片的带内检测光信噪比(OSNR)的方法,理论分析了检测方 法的工作原理,证明了方法不受光纤链路色散和PMD的影响,并且与信号偏振态 、调制格式及传输 速率无关。测试结果表明:在9dB到34dB的测量范围 内,本文检测方 法的测量误差在0.5dB内;在1dB的测量误差范围内,对偏振相关损 耗(PDL)的容忍范围为1dB。     

Phase-stepping an all-fiber Sagnac loop for full characterization of femtosecond PMD

A novel phase-stepping technique is demonstrated in a Sagnac loop for measuring femtosecond first-order polarization-mode dispersion (PMD) spectra and wavelength-dependent principal states of polarization without the polarization-dependent loss impairing the measurement. The technique allows full characterization of the second-order PMD. The measurements agree well with the ones obtained using the /spl pi/-shifted Sagnac loop previously proposed by the authors.