We present an analysis of crosstalk in aligned and misaligned free-space optical interconnect (FSOI) systems. On the basis of a generalized diffraction integral formula, an analytical expression of irradiation distribution for FSOI systems and a convenient approach to calculate crosstalk noise signal ratios (CNSR) are proposed. Simulations are performed to analyze the factors affecting the CNSR. The analyses indicate that small beam quality factor and wide channel pitch will significantly improve performance of the FSOIs. Furthermore, the displacement of the transmitter microlens array will affect the interconnection distance much more significantly than that of the receiver microlens array.

Subpixel centroid estimation is the most important star image location method of star tracker. This paper presents a theoretical analysis of the systematic error of subpixel centroid estimation algorithm utilizing frequency domain analysis under the consideration of sampling frequency limitation and sampling window limitation. Explicit expression of systematic error of centroid estimation is obtained, and the dependence of systematic error on Gaussian width of star image, actual star centroid location and the number of sampling pixels is derived. A systematic error compensation algorithm for star centroid estimation is proposed based on the result of theoretical analysis. Simulation results show that after compensation, the residual systematic errors of 3-pixel-and 5-pixel-windows' centroid estimation are less than 2×10 −3 pixels and 2×10 −4 pixels respectively. star tracker, star image location, subpixel centroid estimation, centroid algorithm, frequency domain analysis, systematic error compensation Citation:Jia H, Yang J K, Li X J, et al. Systematic error analysis and compensation for high accuracy star centroid estimation of star tracker.

Received Month X, XXXX; revised Month X, XXXX; accepted Month X, XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX Though new affordable high power laser technologies make possible many processing applications in science and industry, depth control remains a serious technical challenge. Here we show that inline coherent imaging, with line rates up to 312 kHz and microsecond-duration capture times, is capable of directly measuring laser penetration depth in a process as violent as kWclass keyhole welding. We exploit ICI's high speed, high dynamic range and robustness to interference from other optical sources to achieve fully automatic, adaptive control of laser welding as well as ablation, achieving micron-scale sculpting in vastly different heterogeneous biological materials.

We demonstrate the evolution of picosecond pulses in silicon nanowire waveguides by sum frequency generation cross-correlation frequency-resolved optical gating (SFG-XFROG) and nonlinear Schrödinger equation (NLSE) modeling. Due to the unambiguous temporal direction and ultrahigh sensitivity of the SFG-XFROG, which enable observation of the pulse accelerations, the captured pulses' temporal and spectral characteristics showed remarkable agreement with NLSE predictions. The temporal intensity redistribution of the pulses through the silicon nanowire waveguide for various input pulse energies is analyzed experimentally and numerically to demonstrate the nonlinear contributions of self-phase modulation, two-photon absorption, and free carriers. It indicates that free carrier absorption dominates the pulse acceleration. The model for pulse evolution during propagation through arbitrary lengths of silicon nanowire waveguides is established by NLSE, in support of chip-scale optical interconnects and signal processing.