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Dynamic Range Improvement of IM-DD Optical Link using Dual-Wavelength Dual-Parallel Modulation
Li Xianghua,Zhou Zhenghua,Chong Yuhua,Yang Chun 한국광학회 2014 Current Optics and Photonics Vol.18 No.4
In this paper, we present an incoherent dual-parallel modulation linearized optical link employing two different optical wavelengths. Comparing with previous dual-parallel modulation, this linearization method prevents the recreation of distortion products and can be readily implemented. Furthermore, a dual-wavelength dual-parallel modulation linearized optical link constructed with the commercially available devices is experimentally demonstrated with a spurious-free dynamic range of 122.5 dB.Hz4/5. More than 25 dB suppression of the intermodulation distortion, 15.6 dB improvement of spurious-free dynamic range and 1.5 dB improvement of compression dynamic range are achieved after linearization.
Cross-Correlation Measurements of Phase Noise Induced by Relative Intensity Noise in Photodetectors
Zhewei Cao,Chun Yang,Zhenghua Zhou 한국광학회 2016 Current Optics and Photonics Vol.20 No.6
Up-converted phase noise, which is induced by the low-frequency relative intensity noise (RIN) of alaser through AM-PM conversion within a photodetector (PD), is first measured here by means of across-correlation method. Our proposed measurement system can isolate the RIN-induced phase noise fromnoise contributions of other components, such as amplifiers, modulators, and mixers. In particular, shotnoise and thermal noise generated from the PD are also suppressed by this method, so that standalonecharacteristics of the RIN-induced phase noise can be obtained. Experimental results clearly show thequantitative relationship between the RIN-induced phase noise and the incident optical power of the PD. Our findings indicate that the least RIN-induced phase noise appeared at the saturation point of the PD,which is about -162 dBc/Hz at 10 kHz offset.
Li Xianghua,Ye Quanyi,Chong Yuhua,Zhou Zhenghua,Yang Chun 한국광학회 2014 Current Optics and Photonics Vol.18 No.3
This paper presents a new method for measuring the half-wave voltage Vπ of an electro-optic phase modulator based on a phase-modulated photonic link with interferometric demodulation. By using this method, the Vπ can be obtained with the RF voltage amplitude input required to achieve 1-dB gain compression of link and the differential delay of a Mach-Zehnder interferometer. We measure the Vπ of a commercial phase modulator by using the presented method and the carrier/the first sideband intensity ratio method. Furthermore, we compare the two measurements with the typical value provided by the manufacturer. The experiment shows that this novel measurement method is feasible, straightforward, and accurate.
Optimization of a double crystal monochromator
Jiang Zheng,Wang Eryan,Song Ruiqiang,Guo Siming,Wu Jinjie,Hou Dongjie,An Zhenghua,Zhou Pengyue 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.8
The double crystal diffraction structure based on Bragg diffraction is the core component of the monochromator that is widely used in synchrotron radiation beam lines and monochromatic X-ray radiation devices. The stability of monochromatic X-rays produced by using the T-structure double crystal monochromator at National Institute of Metrology was investigated experimentally. Due to its structural defects, the X-ray flux of the T-structured double crystal monochromator shows poor long-term stability. Inspired by the Channel-cut monochromator structure, we designed a new double crystal monochromator structure to improve the long-term stability of the X-ray flux. Experiments showed that the stability of the monochromatic X-ray flux for the new double crystal monochromator structure was better than 1.0%@1 h, and the energy region and flux rate of the monochromatic X-rays are significantly improved. This work provides a stable and reliable monochromatic X-ray source for the calibration of X/γ detectors such as satellite load detectors, which will contribute to the development of X/γ detection technology.