Multiobject spectroscopy is applied in numerous modern astronomical facilities conducting observations of a large number of targets per pointing. Assigning the maximum number of targets to these instruments requires efficient algorithms. We present a simple and effective algorithm, the averaging (Aver) algorithm, to maximize the number of assigned targets for the first few visits of a given field. In comparison to the draining (Dra) algorithm, our algorithm increases the target completeness by 1% to 2% by employing Poisson distributed and real catalogs from the Large Sky Area Multiobject Fiber Spectroscopic Telescope survey. Moreover, our algorithm performs ∼375 times faster than the conventionally applied simulated annealing algorithm and yields a slightly higher completeness. We further optimize the Aver and Dra algorithms by combining the genetic algorithm (GA) and the differential evolution method. The Aver is slightly optimized by this method, whereas the Dra algorithm is improved by 0.9% to 1.6%, suggesting that our proposed Aver algorithm approaches maximum completeness. Furthermore, we find that the GA can optimize the rotation angle with a specially designed fitness function in the case of focal-plane rotation that is expected to be realized in the future, achieving a 1.8% increase in the number of the targets observed. In particular, our Aver algorithm assigns the maximum number of targets within the first few visits.
The regenerative wavelength conversion of the picosecond short pulse with repetition rate of 10GHz is demonstrated employing a SOA based interferometer. Both up-conversion and down-conversion can be realized with wavelength range from 1535nm to 1555nm. The regenerative capability of this wavelength convertor is also demonstrated with degradated signal.
We experimentally demonstrate the generation of supercontinuum (SC) with a 12.5GHz DFB/EAM ultrashort optical pulse broadened in the high nonlinear fiber (HNLF). Through longitudinal mode-carving of the SC spectrum, a novel multiwavelength continuous wave (CW) optical source with precise 25GHz channel spacing is realized. The bit error rate (BER) curve and eye diagram show that the multiwavelength CW optical source is promising for dense wavelength division multiplexing (DWDM) systems.
We demonstrate a simple method of generating time division multiplexed pulse trains with correlated and controlled phase, only using low-cost birefringent crystals and polarizers. As an illustration of this method, we achieve carriersuppressed RZ (CS-RZ) pulse trains at 20GHz and 40GHz respectively by multiplexing 10GHz ultrashort pulse train. Furthermore, by numerical simulations, it is verified that the suitable phase-modulated pulse train generated by our method can be applied to high speed optical transmission system for suppressing intrachannel nonlinear effects.
We experimentally demonstrate multiple wavelength continuous wave (CW) sources based on longitudinal mode carving of the supercontinuum (SC) generated in optical fibers. The 10GHz SC with -20dB bandwidth of 63nm was generated with the actively modelocked fiber laser (AML-EDFL). By longitudinal mode carving of the SC we can generate more than 100 channels CW optical frequency chain.
A novel method to suppress the waveform distortion and compress frequency chirp in SOAs as in-line amplifiers in WDM networks is proposed and experimented. The results show that the signal distortion and pattern effect are reduced significantly and over 5dB expansion of input dynamic range is achieved.
Protection and restoration issues in optical networks especially DWDM networks are attracting significant attention for future high-capacity transport applications. In this paper a flexible protection scheme of BWLSR/2 (Two-fiber Bi-directional Wavelength Line Switched Ring)/1/ is demonstrated, this protection system can function automatically without the interference of the network management system. In the case of fiber broken or single channel transport problem it can protect the optical signal. It is implemented successfully in the NSFCNET.
10Gb/s optical internet network (NSFCnet) in china with protection switching function and performance monitoring is introduced in this paper. 16x10Gb/s Transmission is demonstrated over 400km SMF with 3 network elements consisting of multiplxers and demultiplxers. The power penalties for all 16 channels are measured to be less than 2dB (BER=10-10).
To compensate for the imperfections of endoscopic mechanical structure and limitations of working space, in paper, a new approach based on recursive minimum-maximum method is proposed to enlarge images of medical electronic endoscopic. This method can be used repeatedly to realize 2n times image enlargement through optimizing the neighborhood information of the interesting pixels in adjustable windows. In order to ensure the best evaluation of the pixel, the algorithm criterion is presented to decide whether the pixel accept new value. Experimental results on applying the method to the endoscopic images are presented in this paper. The results demonstrate that the recursive minimum-maximum method for enlarging images can succeed in images blowing-up at the same time it preserves the fine details with rich edge-information.
The laser scattering particle size measurement technique is studied in this paper. An improved projection iterative algorithm is proposed to retrieve the particle size distribution from the scattering light energy. Experiments are made with spray droplet and standard multi-peak particles, which demonstrate the effectiveness of the measurement technique.
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