Study On Design Method Optimization And Key Technologies Of Large Fiber-based Integral Field Unit

3D spectral imaging technology in astronomy can sample the 2D target,then send the energy of each unit into the spectrometer,and obtain the 3D information of the source through single exposure.Integral field unit(IFU)is the key device for 3D spectral imaging technology in astronomy,which slices the celestial target,transmits the optical signal and reformates the optical construction.The application of optical fiber in astronomy provides a new technique to improve the performance of astronomical instruments,miniaturize and integrate them and reduce the cost.Fiber-based IFU is a typical application of astronomical optical fiber technology.Fiber-based IFU has attracted wide attention of astronomers for its unique advantages.Compared with the traditional spectral imaging technology,the 3D spectral imaging technology based on fiber-based IFU has many advantages on large field of view,high spatial resolution and a large number of spectral resolution units.It has been widely used in astronomical researches,including the distribution of star-forming regions in neighboring galaxies or clusters,the dynamics of moderate redshift galaxies,the estimation of distances at moderate redshift scales,the reconstruction of galaxies subject to gravitational lensing effects,the nuclear area structure of active galactic nuclei,planetary nebulae and supernova remnants,etc.Since the 20th century,10 m level ground optical and infrared telescopes have installed or been planned to install the fiber-based IFUs.In addition,the majority of existing small and medium sized telescopes over 2 m level will equip or renovate with fiber-based IUF in the upgrade plan.In this thesis,a large fiber-based IFU with 8064 fibers was designed to satisfy the scientific requirement of Fiber Arrayed Solar Optical Telescope(FASOT),which has high spatial resolution,high spectral resolution and high spatial repetition accuracy.This IFU considered the key techniques such as the design parameters of the telescope system,the cost of the project,and so on.The fiber used in the IFU with the core size 35?m and the coating size 125 ?m.The transmission efficiency is better than 75%and the output focal ratio within EE90 is larger the F/7 between the wavelength form 400nm to 900 nm.The field of view(FOV)of the FASOT system with this IFU is 29.9×26.4 arcsec2,the spatial resolution is 0.95 arcsec and the spectral resolution is 110000 at the wavelength 520 nm.It will become a pair of IFUs with the largest number of optical fibers in the world.An IFU with 242 fibers for FASOT-1B was fabricated to verify the feasibility of the design theory,fabrication technology and detection method of large fiber-based IFU.FASOT-1B is the upgraded prototype of the FASOT.After installing and debugging on FASOT-1B telescope,the polarization data of MgI chromosphere in solar NOAA12738 active region were obtained successfully.The polarization sensitivity of FASOT-1B is better than 10-3 and the resolution is 3.3×104 at the wavelength 518nm.The test results show that the technical specifications of IFU meet the technical requirements of FASOT-1B.This IFU was the first self-developed IFU system,which used successfully for observation in China.The main topics of this thesis are as follows:1.According to the basic structure of fiber-based IFU,and considering the scientific objective of FASOT,the interaction mechanism between relevant parameters of the around optical system and fiber-based IFU was studied.The overall structure of the IFU with 8064 optical fibers for FASOT was optimized,including fiber geometry,arrangement type,optical parameters of microlens and mechanical structure parameters.2.Based on the encircled energy of fiber output,the rapid measurement system for transmission characteristics of astronomical fibers was investigated.The system can simultaneously measure output focal ratio,transmission efficiency and fiber end-face quality.At the same time,this system provided feedback compensation to reduce the influence of incident light source fluctuation and realize the closed-loop real-time measurement of the optical fiber transmission characteristics.This system had the characteristics of fast measurement speed,high accuracy and good repeatability.3.The morphology of optical fibers in cables was analyzed and the focal ratio degradation(FRD)characteristics of fibers in the traditional stranded optical cable based on microtubule structure were studied.An external colloidal fiber bundle with uniform transmission characteristics was designed as the basic unit of FASOT-IFU cable.By detecting the transmission characteristics of optical fibers in different states of external colloidal fiber bundles,it shows that the external colloidal fiber bundle has uniform transmission characteristics and can resist a certain external stress.It is suitable for making high-density optical cable for astronomy.A high-density optical cable structure with 350 fibers was proposed for large fiber-based IFU.A high strain sensitivity long period fiber grating(LPFG)was used to monitor the changes of internal stress when the cable state changes4.The key fabrication technology of large IFU was studied,and the performance test method and device for large fiber-based IFU were designed.By fabricating,testing,installing and debugging the IFU with 242 fibers for FASOT-1B,the feasibility of the key technology of large fiber-based IFU was verified.