A highly sensitive fiber optics twist sensor is proposed and experimentally demonstrated using elliptical-core few-mode fiber (e-FMF). With the help of a fixed-phase plate for conversion from LP₁₁ to LP₀₁ mode, the twist angle can be linearly mapped to the spatial rotation of LP₁₁ mode profile and consequently discriminated by monitoring the optical power variation at the standard single-mode fiber (SSMF) output. When the optical power at the e-FMF output is 10 mW, the twist angle within the range of ±39° can be successfully detected with a sensitivity of more than 20 μW/°. Meanwhile, the twist direction can be identified simultaneously. In particular, when the twist angle ranges from -12.5° to 20.1°, the sensitivity is higher than 100 μW/°. Both temperature-insensitive operation from 20°C to 150°C and e-FMF length insensitive operation are experimentally verified.

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With the development of display technology, several new displays have attracted much attention such as OLED display, QLED display, Laser display and Mini/MicroLED display. Displays with high brightness, wide color gamut, high efficiency and long lifetime are our ultimate goal. Defect inspections and color measurements are important for us to evaluate display quality. To obtain wide color gamut, we usually use narrow spectral bandwidth light source. However, it's not easy for traditional color camera or filter camera to measure narrow bandwidth light source because the accuracy is limited. In this paper, we simulate color measurement accuracy by color camera and filter camera. We analyze the influence of bandwidth effect on the color measurement and carry out bandwidth effect correction method. With the correction, the measurement accuracy improves obviously. In addition, different displays with different spectral bandwidth have been measured to validate the corrections. The results show significant improvement in color measurement accuracy. Our bandwidth effect correction can be used for wide color gamut display measurement.

We characterize the phase-modulation-dependent loss (PMDL) arising from the commercial liquid crystal on silicon (LCOS) and find that it severely degrades the fidelity of mode-selective conversion and orbital-angular-momentum (OAM) generation, as well as the performance of LCOS-based wavelength-selective switch (WSS). For the LP₁₁ mode conversion, an offset-launch technique is proposed to mitigate such effect. For the LP_l,m (l>1) mode conversion, the superposition of OAMs with conjugation vortices is demonstrated to achieve perfect mode conversion. Experimental outcomes verify that both solutions are able to improve the fidelity quality factor by at least 15 dB.