Simulation and optimization of a polymer directional coupler electro-optic switch with push-pull electrodes

Humidity remains in the atmosphere even on bright days. Water of all three states can be found naturally in the atmosphere: liquid (rain, fog, and clouds), solid (snowflakes, ice crystals), and gas (water vapour). Water in any state is an obstacle in the link of the electromagnetic wave. When the wave passes through the water particles, a part of its energy is absorbed and a part is scattered. Therefore the electromagnetic wave is attenuated. Prediction of the influence of these factors is very important in radio system design. Attenuation due to rain, fog, and clouds can lead to the perturbations of the wireless, mobile, satellite and other communications. Another problem is the refractive index of the atmosphere, which affects the curvature of the electromagnetic wave path and gives some insight into the fading phenomenon. The anomalous electromagnetic wave propagation can cause disturbances to radar work, because variation of the refractive index of the atmosphere can induce loss of radar coverage. Accurate prediction of losses due to these factors can ensure a reliability of the radio system, decrease an equipment cost, furthermore, the radio systems can become less injurious to health of people. When there are no possibilities to gather data for calculations of the specific attenuation due to rain, clouds and fog, and atmospheric refractive index, the values recommended by the International Communication Union’s Radiocommunication sector (ITU-R) can be used. But the recommended values are not always exact. In design of the radio links, the most desirable operating frequencies are below 10 GHz, because in such cases atmospheric absorption and rainfall loss may generally be neglected (Freeman, 2007). However, in most countries, the frequency-band below 10 GHz is highly congested. In addition, high frequencies provide larger bandwidth, narrower beam width, good resolution and smaller component size (Bhattacharyya et al., 2000). Therefore, the operating frequencies of 10 GHz and above are often used in design of radio systems. The higher the operating frequency, the greater attenuation due to hydrometeors (rain, cloud, fog, snow, and etc.) is observed (Tamosiūnaitė et al., 2010a). In (Ishimaru, 1978), it was mentioned that the electromagnetic wave attenuation due to snow is less than attenuation due to rain, and that the attenuation due to dry snow may be neglected

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Atmospheric Attenuation due to Humidity

A new S-type of IR integrated waveguide amplifiers, based on erbium-ytterbium co-doped phosphate glass integrated with medium thin film filter, is proposed. The intrinsical gain spectrum of the proposed amplifier is obtained by solving rate and power propagation equations, a thin film filter flattening this intrinsical gain spectrum is designed by genetic algorithm, and fabricated. An average gain >10dB is obtained between 1530nm and 1560nm, and the average gain about 18dB between 1531nm and 1550nm with gain difference of <3dB is achieved.

Thin Film Filter for Broadband IR Integrated Waveguide Amplifiers

A novel optical microwave and millimeter generation by using single mode fiber FP cavity (SMFFPC) with pulse laser injection is proposed and experimentally demonstrated. The frequency of output signal is determined by the birefringence degree of the SMFFPC, a general relationship between output signal frequency of SMFFPC and birefringence degree of single mode fiber is derived. The proof of concept device consists of a light source, a polarizer controller, a modulator, a RF generator, a single mode fiber Fabry-Perot cavity, a strain inspector, an erbium doped fiber amplifier, a filter, a polarizer, and a digital communication analyzer. The results demonstrate the new concept of optical microwave and millimeter generation and the technical feasibility.

Optical Microwave and Millimeter Generation by Using Birefringent Fiber FP Cavity with Pulse Laser Injection

A novel broadband IR integrated Er-Yb codoped phosphate glass waveguide amplifier with a long-period waveguide grating is proposed. The long-period waveguide grating, which is used as a gain equalizer, is directly fabricated in the waveguide. The amplifier model is based on propagation and population-rate equations and includes both uniform and pair-induced up-conversion mechanisms. It is solved numerically by combining overlapping integral and Runge-Kutta(RK) algorithm. The intrinsical gain spectrum of the proposed amplifier is obtained by solving a set of rate and power propagation equations and, the deleterious gain peaking is reduced by the long-period waveguide grating filter. The effects of transmission spectrum of the proposed long-period grating on flattening gain are discussed. An average gain  ~ 20dB between 1532 nm and 1565 nm with gain difference of  < 3dB is achieved.

Design and Simulation of Broadband IR integrated Waveguide Amplifiers with Long - Period Waveguide Grating Filter

The effect of fog and clouds in millimeter communication is discussed, and the attenuation caused by fog and clouds is reviewed. Signal-to-noise ratio (SNR) of image is derived using relating models of fog and clouds attenuation. According to the relation of image quality and its signal-to-noise ratio, the system behavior is forecasted theoretically. It is shown that the signal-to-noise ratio of receiver at certain transmitter power is inverse with radio wave frequency, from about 70dB at 10GHz to 48dB for fog and 49dB for clouds. The image quality of received signal at certain transmitter power is inverse with radio wave frequency, from about 7 grade at 10GHz to 5.27 grade for fog and 5.37 grade for clouds. The above calculated results are consistent with experimental results.

Effect of Fog and Clouds on the Image Quality in Millimeter Communications

IR integrated photonic amplifiers at 1.55μm operation will have good foreground in optical phased‐array radars for splitters and signal processing. The saturation gain characteristics of IR integrated photonic waveguide amplifiers (taken Er3+‐Yb3+ co-doped phosphate glass waveguide amplifiers as an example) are studied theoretically. For the home‐made laser glass materials the calculated saturation intensities are 2.22kw /cm2 for signal and 10.15kw/cm2 for pump. The effects of absorption saturation of signal and pump lights on the gain of amplifiers are discussed.

Modeling and Simulation of Saturation Gain of IR Integrated Photonic Amplifiers

Using a method of conformal finite-difference time domain (CFDTD), we present the analysis results of attenuation that may occur on the CPW with complicated cross-section up to 200GHz. The CPW is fabricated on lithium niobate which is an anisotropic material. The simulative result is more accurate than that of quasi-static method and shows good agreement with experiment data. It also shows that the radiation loss is not negligible in total power loss when frequency is up to millimeter wave band.

Yongzhi Liu

Papers

Thin Film Filter for Broadband IR Integrated Waveguide Amplifiers

Effect of Fog and Clouds on the Image Quality in Millimeter Communications

Modeling and Simulation of Saturation Gain of IR Integrated Photonic Amplifiers

Computation of Microwave Attenuation on Coplanar Waveguide (CPW) with Complicated Cross-Section