A triple frequency- and phase-tunable optoelectronic oscillator based on stimulated Brillouin scattering effect and carrier phase-shifted single sideband (CPS-SSB) modulation is proposed and theoretically analyzed. In the structure, three pump lights are used to generate an oscillator signal in which the frequency is equal to triple the Brillouin frequency shift through the Brillouin gain–loss compensation. Benefiting from the wavelength-dependent characteristic of Brillouin shift, the triple frequency-tunable signal can be realized by directly tuning the laser source. The CPS-SSB modulation signal lies in the combination of a dual-parallel Mach–Zehnder modulator (DPMZM) and a tunable bandpass filter. The phase of the output microwave signal is changed by controlling the direct current bias voltage of DPMZM. Ultimately, a microwave signal, with a tunable frequency range from 26.3925 to 28.3425 GHz and a tunable phase from 0 deg to 360 deg, is obtained in theory. In addition, the theoretical simulation of the phase noise is below −110 dBc / Hz at the 10-kHz offset when tunable laser source is set at 1550 nm.
A bandwidth reconfigurable and passband switchable filter is proposed and experimentally demonstrated. Based on the same structure, the filter can realize a single broadened response, two passbands with tunable bandwidth or multiband filter. A single broadened response adopts binary phase-shift keying modulation, in which the bandwidth is related to the modulation data pattern. By using the programmable single-sideband suppression carrier signals, the position of the optical lines can be settled down properly and the corresponding arbitrary passbands are constructed. The proposed filter is flexible, which offers possibilities to process multitype microwave signals simultaneously.
TiO2 and Mn0.2Ti0.8O2thin films were prepared by sol-gel process and their structural and optical properties were examined. The structural properties of samples were investigated by the X-ray diffraction (XRD) and auto force microscope (AFM). The XRD results showed that TiO2 thin film calcined at 650°C was anatase phase, and Mn0.2Ti0.8O2 thin films calcined at the same temperature was rutile. The AFM results of both samples showed quite a smooth surface. Optical properties of samples were examined by UV absorption spectrum. The absorption edge of Mn0.2Ti0.8O2 red-shifted.
The variable optical attenuator (VOA) has played very important roles in wavelength division multiplexed (WDM) systems, it is an essential optical component aimed to continuously adjust the optical power transmitting in optical networks. In this paper, we began to study a new type of variable optical attenuator using polymer liquid crystal material. We hanged the liquid crystal technologies and MEMS technologies together to design variable optical attenuator. This paper describes the methods and process of the preparation of polymer liquid crystal material, presents some experimental results obtained in laboratory.
TiO2 thin films were prepared at various calcinations temperatures by sol-gel process and their structural and optical properties were examined. The influence of calcinations temperature on the structural properties of the prepared TiO2 thin films was investigated by the X-ray diffraction (XRD) and atomic force microscope (AFM). The XRD results showed that TiO2 thin film was transformed into the anatase phase at 350°C, and further into rutile phase at 850°C. The AFM results show quite a smooth surface and are in reasonably well agreement with the crystallite sizes estimated by XRD peak broadening. The influence of calcinations temperature on the optical properties of the prepared TiO2 thin films was investigated by UV-Vis spectrum and variable angle incidence spectroscopic ellipsometer (VASE). The results showed the both anatase phase and rutile phase of the TiO2 thin films prepared have good optical properties in UV region.
Indium tin oxide (ITO) films as transparent conductors have caused a great deal of interest due to their prominent electro-optical behavior. This paper describes a study of the properties of ITO thin films that are used for a new type variable optical attenuator using polymer network liquid crystal (PNLC). The mechanism of PNLC optical attenuator operation is that the light from the input fiber is scattered when no voltage is applied, and the light passes through the attenuator when sufficient voltage is applied. So the ITO thin films can provide transparent electrodes for PNLC. They were deposited under various preparation conditions using the radio-frequency (rf) magnetron sputtering technique. Here discuss the results of the structural, electrical and optical properties of the ITO films. The paper presents some experimental results obtained in laboratory.
Micromechanical optical switch has a good quality for free-space optical cross connects, particularly in terms of the low insertion loss, low crosstalk, low polarization dependent loss (PDL), wavelength-independence, and bit-rate transparency. In research of micromechanical optical switches, the electrostatic torsion beam actuator is widely used. But this actuator needs high-applied voltage. In this paper, the actuator with the slant counter electrode was proposed and fabricated with tilted 3° (111) silicon wafer.
The diffraction characteristics are analyzed for a polymer arrayed-waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. The diffraction loss and diffraction efficiency in the input and the output slab waveguide are investigated and discussed for different values of parameters, such as the core width, pitch of adjacent waveguides, the number of arrayed waveguides, taper end width of waveguides, and number of output wavelength. Finally, we give a set of parameters which have been optimized in this device.
The optical variable attenuators (VOA) play important roles in wavelength division multiplexing (WDM) transmutation systems, this paper describes a new type variable optical attenuator made by using fiber U-grooves in silicon wafer and polymer-network liquid crystal. Fibers are placed in the U-grooves of silicon wafer, and the
polymer-network liquid crystal is filled in the gaps between the ends of the docking fibers. The paper explains the principle of the attenuator operation and presents experimental method in laboratory.
Micromechanical optical switches have good quality for free-space optical cross connects, particularly in terms of the low insertion loss, low crosstalk, polarization and wavelength-independence, and bit-rate transparency. In micromechanical optical switches, the electrostatic torsion beam actuator is widely used. But this actuator needs high-applied voltage. In this paper, using mechanical and electric characteristic, the relation between the translocation at the end of upper electrode and the applied voltage was derived. The applied voltage is in direct proportion to the cube of the torsion beam thickness, and reduces with the shorten of original distance between two adjacent electrodes. The actuator with the inclined under electrode was proposed and fabricated with certain tilting angle (111) silicon. Theoretical analysis indicates that the drive voltage based on the slant under electrode actuator can decrease half of that based on the flat under electrode.
Using pure aqueous KOH solution and a one-level mask, the reflective micromirror in the direction <100> and the fibers self-aligned V-grooves in the direction <110> were fabricated on the (100) silicon. Reflective micromirror is a part of {100} family; the surface of the mirror is perpendicular at the optical axes. The deviation brought by manual assemble can be decreased by crystal orientation self-aligned between the micromirror and fibers. Using Atomic Force Microscope (AFM), the measured the surface roughness of the reflective micromirror is below 40nm, at a wavelength of 1550nm the reflectivity ofthe micromirror was measured to be higher than 80%.
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