Mr. Guanru Lyu Profile

Guanru Lyu

at National Astronomical Observatories

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Publications (3)

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Proceedings Article | 3 January 2020 Paper

The impact of fiber fusion splicing on the focal ratio degradation and transmission of LAMOST fiber system

Jian Li, Guanru Lyu, Shuqing Wang, Yonghui Hou

Proceedings Volume 11203, 112031G (2020) https://doi.org/10.1117/12.2549835

KEYWORDS: Fusion splicing, Optical fibers, Spectroscopy, Telescopes, Polishing, Spectrographs, Light sources, Beam splitters, Astronomy, Free space optics

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We report results of the impact of fiber fusion splicing on Focal Ratio Degradation (FRD) and transmission loss of Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) fiber system. We test at f/5 input f-ratio conditions, the influence of fiber fusion splicing on FRD and transmission respectively in the laboratory. A precision test system was designed to reduce the system error and human error. The measurement accuracy of the system reaches micron scale. The fiber end surface was prepared by large core fiber cutter, grinder and fusion splicing workstation. The fiber surface roughness is less than 1 micron and the surface angle is less than 0.5°. By optimize the cutting and polish process, adjusted the fusion parameters, a satisfactory results of optical fiber fusion obtained in the laboratory. The maximum transmission increase caused by the fiber fusion is less than 3%, average value is about 1%; while the maximum FRD increase is about 0.12°. We repaired 14 damaged optical fibers of LAMOST fiber system by use fiber fusion method, and the average peak light intensity of the repaired fiber reaches more than 90% of the peak light intensity of the normal use fiber in action. Our results indicate that fiber fusion technology can be adopted for repair failure optical fiber, replace the fiber clips and astronomical instrument construction.

Proceedings Article | 9 September 2019 Paper

Design and improvements of the control system for LAMOST spectrographs

Guanru Lyu, Jian Li, Yonghui Hou, Shuqing Wang

Proceedings Volume 11115, 1111517 (2019) https://doi.org/10.1117/12.2526878

KEYWORDS: Spectrographs, Control systems, Field programmable gate arrays, Switches, Cameras, Camera shutters, Mirrors, Sensors, Control systems design, Logic

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LAMOST is a special Schmidt telescope with 16 spectrographs. Through these spectrographs, it can detect 4000 stellar spectra via optical fibers. Before the year of 2017 LAMOST’s spectrograph only work on low resolution spectrograph(LRS) mode, and recently we have finished the update of optical, mechanical structure and control system of these 16 spectrographs which could switch working mode between low resolution and middle resolution spectrograph(MRS) to meet the needs of LAMOST Phase II Sky Survey. Due to the strict optical performance requirements and the close arrangement of the optical equipment on the spectrograph platform, the control system must be quite accurate, stable and reliable. In this paper, we mainly describe the design and improvements of the spectrograph control system of the LAMOST’s spectrographs, including shutter sub-system control, back-illuminate sub-system control, LRS/MRS switch sub-system control, camera lens electric focus sub-system control, and some other sub-systems in LAMOST’s spectrograph control system. What’s more, there are also some connections between different sub-systems. As a result, we use FPGA chip as the main spectrograph controller, and make some improvements not only on host-computer software program, but also on slave-FPGA controller software and hardware design. The FPGA controller does some logical judgements according to the feedback information provided by the position sensor and the working mode designed to suit for different working condition. In this way, we make the spectrograph work more accurate and stable, and make it more safety and reliable especially on switching between LRS mode and MRS mode. Through those design and improvements on spectrograph’s control system mentioned in this paper, LAMOST could get more high-quality star spectral data from its 16 spectrographs.

Proceedings Article | 9 September 2019 Paper

The impact of fiber fusion on the focal ratio degradation and transmission

Jian Li, Guanru Lyu, Shuqing Wang, Yonghui Hou

Proceedings Volume 11115, 1111516 (2019) https://doi.org/10.1117/12.2525141

KEYWORDS: Fusion splicing, Optical fibers, Polishing, Telescopes, Spectrometers, Astronomy, Surface finishing, Light sources, Spectroscopy, Optical testing

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We report results of the impact of fiber fusion splicing on Focal Ratio Degradation and transmission loss. Experiment use formed beam methods at wavelengths between 400 and 1000nm of Polymicro fiber. We test at five input f-ratio (f/2.5, f/3.75, f/5, f/75, f/10) conditions, the influence of fiber fusion splicing on FRD respectively, and test at f/5 input fratio condition, the influence of fiber fusion splicing on fiber transmission loss. A precision test system was designed to reduce the system error and human error. The measurement accuracy of the system reaches micron scale. The fiber end surface was prepared by large core fiber cutter, grinder and fusion splicing workstation. The fiber surface roughness is less than 1 micron and the surface angle is less than 0.5 deg. By optimize the cutting and polish process, adjusted the fusion parameters, a satisfactory results of optical fiber fusion obtained in the laboratory. The maximum transmission increase caused by the fiber fusion is less than 2%, average value is less than 1%; while the maximum FRD increase is less than 0.16 degrees. Our results indicate that fiber fusion technology can be adopted for repair failure optical fiber, replace the fiber clips and astronomical instrument construction.

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