Suppression of wavelength-dependent polarization fading using hybrid-polarization scheme in OFDR.

What we believe to be a new hybrid-polarization diversity scheme which can eliminate the polarization state variation caused by wavelength tuning of laser in optical frequency domain reflectometry is proposed in the paper. In the scheme, a 45° polarizer is used to maintain the polarization of signals. It decreases the polarization angle fluctuation to 2.

Beyond a 10 range-resolution product in an OFDR based on a periodic phase noise estimation method.

We present and demonstrate a method based on a periodic phase noise estimation in an optical frequency domain reflectometry (OFDR) capable of a beyond 10 range-resolution product (RRP) for the first time, which corresponds to 2.5 × improvement compared with the state-of-the-art. The moving average filter is employed to suppress the amplification of noise in the derivation process.

Phase noise elimination in frequency sweeping interferometry based on a common-path interferometer.

We propose a common-path interferometer (CPI) method to suppress the ambient and laser phase noise in frequency sweeping interferometry. The CPI realizes the multiplexing of the main and auxiliary interferometer to ensure the common-mode characteristic of the interference phase noise, which can be eliminated by signal mixing. In experiments, we obtain a dynamic range of up to 110 dB.

Strain distribution characteristics of sensing fiber and influence on sensitivity of a fiber-optic disk accelerometer.

In a fiber-optic disk accelerometer, the strain distribution of sensing fiber is crucial for the improvement of sensitivity. The distribution characteristics of axial and radial strain in the sensing fiber are analyzed by the finite-element method, and the influence of strain distribution on the sensitivity of accelerometer is studied. Sensors with different outer radii of sensing fiber coils are designed and manufactured, and their performance is tested.

Evaluating imaging quality of optical dome affected by aero-optical transmission effect and aero-thermal radiation effect.

The imaging quality of the aerodynamically heated optical dome was evaluated under the comprehensive influence of aero-optical transmission effect and aero-thermal radiation effect. The ray propagating algorithm based on the fourth order Runge-Kutta method was used to trace the target ray and the thermal radiation ray of the optical dome. Three imaging quality evaluation parameters were proposed to evaluate aero-optical effect: Modulation transfer function (MTF), irradiance, peak signal-to-noise ratio (PSNR) of distorted images.

Influence of altitude on aero-optic imaging quality degradation of the hemispherical optical dome.

We investigated the influence of altitude on aero-optic imaging quality degradation of the hemispherical optical dome. Boundary conditions for the aerodynamic heating effect of the optical dome were calculated by solving the Reynolds-averaged Navier-Stokes equations provided by FLUENT. The finite element model and the thermal-structure simulation results of the optical dome were obtained using ANSYS.

Optimized design method for the inner surface of a conformal dome based on the ray tracing approach.

Traditional optical domes are spherical, which introduces constant aberrations with look angle. However, spherical domes are not optimum for reducing aerodynamic drag. Conformal domes deviate from spherical to reduce drag but they generate dynamic aberrations varying significantly with look angle in the field of regard.

Basic geometry and aberration characteristics of conicoidal conformal domes.

This paper investigated the geometry and aberration characteristics of conicoidal conformal domes. First, on the basis of previous research, we got the expression that was suitable for describing the external surface of the conicoidal conformal dome. Based on the theory of differential geometry, this paper first proved that the Dupin index line of a quadric surface was an ellipsoid and the radius of curvature had extreme values in the meridian plane and sagittal plane.

Extending depth of field for hybrid imaging systems via the use of both dark and dot point spread functions.

In this paper, we propose one method based on the use of both dark and dot point spread functions (PSFs) to extend depth of field in hybrid imaging systems. Two different phase modulations of two phase masks are used to generate both dark and dot PSFs. The quartic phase mask (QPM) is used to generate the dot PSF.