Theoretical investigation of 8 /spl times/ 10-Gb/s WDM signal transmission performance based on gain-equalized SOAs using backward Raman pumping at DCF

We have theoretically investigated 8 /spl times/ 10-Gb/s wavelength-division multiplexing (WDM) signal transmission characteristics based on semiconductor optical amplifiers (SOAs) with equalized gain using discrete Raman amplification (DRA). Gain equalization and low noise figures have been obtained by adjusting the backward Raman pumping power and wavelength at a dispersion compensating fiber (DCF) for each span. Bit-error-rate characteristics were calculated for 8 /spl times/ 10-Gb/s WDM signal transmission over 6 /spl times/ 40-km single-mode fiber (SMF) + DCF links with gain-equalized SOAs using DRAs at DCF. Approximately a 2.5-dB improvement of the receiver sensitivity was achieved by using SOAs and DRAs with optimized Raman pumping. One can easily upgrade the transmission length of a link based on SOAs with an appropriate backward pump laser at each DCF.     

FDTD simulation of radiation characteristics of half-volume HEM and TE-mode dielectric resonator antennas

Cylindrical and rectangular dielectric resonator antennas (DRAs) using HEM_11δ, TE_11δ, and TE_01δ mode were examined to see the radiation pattern, impedance, field distribution and resonant frequency that were achieved when the DRAs were bisected through an image plane by a conducting sheet. The resultant half DRAs are smaller in volume and have a more directional radiation pattern. The elevation angle of maximum radiation was lowered in some cases. Finite-difference time-domain simulation techniques were used     

Raman-amplifier-based submarine transmission systems

The broad bandwidth and low noise figure of a distributed Raman amplifier (DRA) makes it attractive for use in high-capacity, long-haul transmission systems. This paper discusses key technologies for such systems using Raman amplifiers (RAs), such as a method to expand the signal bandwidth for hybrid DRA/EDFAs and all-RAs. The combination of two different types of optical amplifiers enables them to compensate for each other's gain profiles through adjustment of the RA's pump wavelength allocation to reduce the accumulated gain deviation. A variable gain equalization scheme is also described. Furthermore, we have developed a form of dispersion management suitable for a system using DRAs. The overall system performance with this management during a transmission experiment was 1.6 dB better than that with conventional management. Using these techniques, we successfully demonstrated 2.1-Tb/s 7221-km transmission in a system using hybrid DRA/EDFAs and 2.4-Tb/s 7404-km transmission in a system using DRAs.     

Comparative study on the mutual coupling between different sized cylindrical dielectric resonators antennas and circular microstrip patch antennas

A systematic comparative study on the mutual coupling (S/sub 21/) between dielectric resonator antennas (DRAs) and microstrip patch antennas is presented. The mutual coupling between two cylindrical probe-fed DRAs is studied for different radius to height (a/L) ratios. It is found that the mutual coupling decreases with the radius to height ratio. Comparison between mutual coupling of probe-fed cylindrical DRAs and circular microstrip patch antennas with different dielectric substrates are also studied. The mutual coupling between DRAs is 2 dB stronger than between microstrip patch antennas when the patch is etched on a dielectric substrate of a dielectric constant close to the permittivity of the DRA. The mutual coupling of the circular patch antennas reduces with the dielectric constant of the substrate.     

Broadband dielectric resonator antennas excited by L-shaped probe

Dielectric resonator antennas (DRAs) designed for broadband applications and excited by L-shaped probe are presented. The L-probe is housed under an air-filled groove between the DRA and the ground plane. A 32% matching bandwidth (S/sub 11/<-10 dB) is achieved with broadside radiation patterns. The new structure is constructed from the same dielectric materials. Thus, it is mechanically better than other wideband DRAs that consist of more than one dielectric material such as the stacked DRA. Some results are verified experimentally. The performance of this DRA and those fed by traditional probes and slots are investigated numerically. In addition, comparisons between L-probe excited DRAs and L-probe excited microstrip patch antennas are discussed.     

Numerical comparison between distributed and discrete amplificationin a point-to-point 40-Gb/s 40-WDM-Based transmission system with threedifferent modulation formats

We describe a detailed numerical investigation on the relative merits of gain flattened distributed Raman amplification (DRA) and discrete gain flattened amplifiers. We simulate a system with forty 40-Gb/s channels spaced at 100 GHz and compare the performance of three different modulation formats nonreturn-to-zero (NRZ), return-to-zero (RZ) and carrier-suppressed RZ (CS-RZ). Three types of amplifiers, multifrequency backward- and forward-pumped DRAs, and an idealized discrete gain flattened amplifier are examined for various signal powers and transmission distances. For the backward-pumped DRA, we also describe calculated tolerance limits imposed by incomplete dispersion slope compensation and polarization mode dispersion (PMD) level     

Bandwidth improvement for a microstrip-fed series array ofdielectric resonator antennas

The impedance and pattern bandwidth of an array of dielectric resonator antennas series fed by a microstrip line was significantly improved by replacing individual DRAs with paired DRAs. The DRAs in each pair are spaced slightly <λ_g/4 apart so that their input reflections cancel. An array of eight DRA pairs was designed and fabricated, and its performance was compared to an array of eight single elements. The 10 dB return loss bandwidth improved from 2 to 18% and the 3 dB gain pattern bandwidth improved from 12 to 17%     

Mutual coupling between millimeter-wave dielectric-resonatorantennas

The mutual coupling between aperture coupled cylindrical dielectric-resonator antennas (DRAs) is analyzed using the finite-difference time domain method. The perfectly matched layer is used as absorbing boundary conditions. The voltage excitation source of microstrip structure is based on the Zhao's model, in which the source plane or the terminal plane can be moved very close to the discontinuity so that the computational domain can be reduced substantially. The numerical results are verified by measurements and reasonable agreement between theory and experiment is obtained. It is shown that this method is highly efficient for the analysis of DRAs     

Performance Analysis of Dielectric Resonator Antennas

Compact, lightweight and low cost electronics components are attracting much attention because of the rapid growth of the wireless communication systems. The antenna designers are thus in continuous search for new advanced design of miniaturized antennas. One solution is to use a dielectric resonator antenna (DRA) which provides various benefits in terms of the performance. This paper presents fundamental concepts, theory and review study carried out on DRAs. The achievable performance of DRAs designed for wide impedance bandwidth, low profiles, circular polarization, compactness, and high gain are illustrated. The latest techniques for improving the results are also covered.     

Wideband simple cylindrical dielectric resonator antennas

Bandwidths of the coaxial fed and aperture coupled cylindrical dielectric resonator antennas (DRAs) with broadside radiation patterns are enhanced by exciting the HEM/sub 11/spl Delta// (1相似文献   

基于拉曼放大对色散渐减光纤的绝热压缩效果的优化

数值研究了光纤损耗对色散渐减光纤中基孤子脉冲的绝热压缩的影响,并分析了利用分布式的拉曼放大来提高DDF的绝热压缩效果的方案.结果表明:光纤损耗严重破坏了DDF对基孤子绝热压缩的效果;采用分布式的拉曼放大能对DDF的绝热压缩起到很好的优化效果,获得更高的压缩因子和脉冲能量;当拉曼增益系数选取优化值0.27/LD时,脉宽为10 ps的基孤子脉冲压缩后可得到脉宽仅417fs、脉冲能量增至5.9倍、峰值功率增至136.3倍、基座能量比仅为2.8%的输出脉冲.     

一种采用同轴探针馈电的半球形介质谐振天线

介质谐振天线具有一些突出的优点,如:体积小、效率高、带宽很宽等。本文仿真设计了一种采用同轴馈电的半球形介质谐振天线,并研究了其探针长度、馈电点位置和介电常数对天线性能的影响。     

Low profile equilateral-triangular dielectric resonator antenna ofvery high permittivity

An aperture-coupled equilateral-triangular dielectric resonator antenna (DRA) of very high permittivity (ϵ_r=82) is investigated experimentally. The triangular DRA is more compact in size than rectangular and circular disk DRAs operating at the same frequency. The impedance matching, radiation patterns and antenna gain of the triangular DRA are presented     

Input impedance of aperture-coupled dielectric resonator antennas

Dielectric resonator antennas (DRAs) excited by a narrow-slot aperture in a conducting ground plane are analyzed using a numerical technique based upon a surface-integral equation formulation for bodies of revolution (BORs) coupled to non-BOR geometries. An efficient matrix-solution algorithm, together with a simple microstrip transmission-line model or a delta-source model are used to compute the antenna input impedance. Input impedances obtained with this technique show favorable agreement to those obtained via another numerical technique, as well as to those obtained by measurement     

Perforated dielectric resonator antennas

A dielectric resonator antenna (DRA) is formed by perforating a dielectric substrate with a lattice of holes. The performance of several perforated DRA prototypes is compared to a conventional DRA and the results demonstrate better gain and cross-polarisation levels. This technique of fabricating DRAs using perforations is intended for array applications, eliminating the need to position and bond individual elements.     

Numerical modeling of dielectric-resonator antennas in a complexenvironment using the method of moments

Aperture coupled dielectric resonator antennas (DRAs) that reside above a layered background are analyzed using the method of moments (MoM). Dyadic Green's functions for the layered medium are derived in a simple and effective manner and the Rao-Wilton-Glisson (RWG) function is used to expand both electric and magnetic currents. A transmission-line technique is used to compute the antenna-input impedance. Numerical results obtained for both hemispheric and rectangular DRAB agree well with published measurement results     

Frequency-adjustable circularly polarised dielectric resonator antenna with slotted ground plane

Circularly polarised (CP) dielectric resonator antennas (DRAs) with a slotted ground plane are proposed. The proposed CP design is achieved by embedding two pairs of unequal slots in the finite ground plane of the feed substrate, which results in the excitation of two near-degenerate orthogonal modes and leads to CP radiation. For the proposed design, a large CP bandwidth, determined from 3 dB axial ratio, as high as 2.7% is also obtained. The resonant frequency can be tuned by changing the slot length. This proposed design is applicable to DR antennas where post-manufacturing trimming is required. Details of the proposed designs and experimental results of the constructed prototypes are presented.     

Compact circular sector and annular sector dielectric resonatorantennas

We investigate circular sector and annular sector dielectric resonator antenna (DRA) geometries. The advantage these geometries offer, compared to conventional circular cylindrical DRAs are significant reductions in volume, making them potential candidates for use in compact applications such as mobile communication handsets. Approximate theory, simulation, and experimental results are provided to support the findings. In particular, a sector DRA is demonstrated to have 75% less volume than a conventional cylindrical DRA, with the same resonant frequency. The DRA volume minimization for compact antenna design is also discussed and a design is proposed and tested for a mobile telephone handset suitable for the DCS1800 system     

Noise analysis of an amplified fiber-optic recirculating-ring delayline

We present the first theoretical and experimental noise analysis of a fiber-optic recirculating-ring delay line (RDL) including a doped fiber amplifier to compensate for the roundtrip loss. Both thermal-like sources and laser sources are considered. The output source induced noise (signal-signal beat noise), signal-spontaneous (s-sp) beat noise, and spontaneous-spontaneous (sp-sp) beat noise spectra for a thermal-like source are calculated from the autocorrelation function of the output detector current. It is shown that all three electrical beat noise spectra can be expressed as correlations of the output optical signal and ASE spectra. The source-induced noise will normally be the dominating noise source, but in some applications, the other noise terms also will be of importance. We use our theory to define the maximum number of recirculations in an amplified RDL with a pulsed source, where the fundamental noise floor is determined by the sp-sp beat noise     

Phase Noise in Millimeter Wave Phase-Locked Loop with Mixer

In order to estimate the phase noise of millimetre wave (MMW) phase-locked oscillator (PLO), the phase noise relation of signals in MMW phase-locked loop (PLL) with frequency conversion is analyzed. The signals include output of MMW PLO, intermediate frequency (IF) output of harmonic mixer and output of microwave oscillator serving as local oscillator (LO). A method to estimate the phase noise of MMW PLO is presented, which is based on the phase noise of LO and IF. At the same time, a W-band PLO is achieved, and the phase noise values of the three signals are measured. It is shown that the experimental result is well coincident with the analysis of phase noise relation.