Author Affiliations
Abstract
National Key Laboratory of Microwave Photonics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
High accuracy and time resolution optical transfer delay (OTD) measurement is highly desired in many multi-path applications, such as optical true-time-delay-based array systems and distributed optical sensors. However, the time resolution is usually limited by the frequency range of the probe signal in frequency-multiplexed OTD measurement techniques. Here, we proposed a time-resolution enhanced OTD measurement method based on incoherent optical frequency domain reflectometry (I-OFDR), where an adaptive filter is designed to suppress the spectral leakage from other paths to break the resolution limitation. A weighted least square (WLS) cost function is first established, and then an iteration approach is used to minimize the cost function. Finally, the appropriate filter parameter is obtained according to the convergence results. In a proof-of-concept experiment, the time-domain response of two optical links with a length difference of 900 ps is successfully estimated by applying a probe signal with a bandwidth of 400 MHz. The time resolution is improved by 2.78 times compared to the theoretical resolution limit of the inverse discrete Fourier transform (iDFT) algorithm. In addition, the OTD measurement error is below ±0.8 ps. The proposed algorithm provides a novel way to improve the measurement resolution without applying a probe signal with a large bandwidth, avoiding measurement errors induced by the dispersion effect.
optical transfer delay measurement time resolution enhancement incoherent OFDR adaptive filtering 
Chinese Optics Letters
2024, 22(1): 013901
Author Affiliations
Abstract
Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
We demonstrate microwave photonic radar with post-bandwidth synthesis, which can realize target detection with ultra-high range resolution using relatively small-bandwidth radio frequency (RF) frontends. In the proposed radar, two temporal-overlapped linear frequency-modulated (LFM) signals with the same chirp rate and different center frequencies are transmitted. By post-processing the de-chirped echoes in the receiver, a signal equivalent to that de-chirped from an LFM signal with the combined bandwidth is achieved. In a proof-of-concept experiment, two LFM signals with bandwidths of 8.4 GHz are exploited to achieve radar detection with an equivalent bandwidth of 16 GHz, and a range resolution of 1 cm is obtained.
microwave photonics ultra-high resolution synthetic bandwidth 
Chinese Optics Letters
2020, 18(7): 072501
Author Affiliations
Abstract
Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Optoelectronic components and subsystems such as optically controlled phased array antennas, distributed radar networks, interferometric optical fiber hydrophones, and high-speed optoelectronic chips demand high-accuracy optical time delay measurement with large measurement range and the capability for single-end and wavelength-dependent measurement. In this paper, the recent advances in the optical time delay measurement of a fiber link with high accuracy are reviewed. The general models of the typical time delay measurement technologies are established with the operational principle analyzed. The performance of these techniques is also discussed.
060.2300 Fiber measurements 120.5050 Phase measurement 280.3400 Laser range finder 
Chinese Optics Letters
2019, 17(6): 060601
作者单位
摘要
南京大学光通信工程研究中心, 江苏 南京 210093
基于瑞利散射效应的相干探测光时域反射技术(COTDR)因具有高动态范围、高灵敏度等特性,而成为超长距离连续分布式传感监测的重要手段。在介绍COTDR技术的原理和发展现状基础上,对COTDR传感系统的设计及关键技术包括抑制相干衰落噪声、提高传感速度以及多机理融合传感系统等进行了研究,并对COTDR在超长通信线缆链路监测、温度和应变传感等方面的应用进行了探讨。
光纤光学 连续分布式光纤传感 瑞利散射 相干探测 光时域反射计 fiber optics fully distributed optical fiber sensor Rayleigh scattering coherent detection optical time domain reflectometry 
中国激光
2016, 43(7): 0700002
作者单位
摘要
南京大学光通信工程研究中心, 江苏 南京 210093
布里渊光时域反射测量(BOTDR)系统空间分辨率和传感距离存在相互制约的关系。相关序列脉冲编码技术可用于解决这一矛盾,但直接对编码脉冲的布里渊散射采样信号进行解码,会因采样时间间隔小于编码单位脉冲宽度而导致解码信号的失真,从而降低了系统空间分辨率和测量精度。分析了直接互相关解码对BOTDR系统空间分辨率的影响,提出一种基于重采样的互相关解码方法,该方法解决了直接相关运算造成的系统性能降低问题。实验中用512 bit 20 ns的互补序列在20 km光纤末端获得2 m的空间分辨率。实验结果表明,与直接互相关的解码方法相比,基于重采样的互相关方法是一种有效的序列脉冲BOTDR信号解码方法。
光纤传感 布里渊光时域反射 相关序列 编码脉冲 采样率 optical fiber sensor Brillouin optical time domain reflectometry correlation sequence coded pulse sampling rate 
光学学报
2011, 31(10): 1006002
作者单位
摘要
1 南京大学 光通信工程研究中心,南京 210093
2 南京大学 工程管理学院,南京 210093
对光纤振动的频率和幅度与受振动影响的偏振光在某一方向上的强度信息之间的关系进行了分析,发现波动光信号的基波频率与振动频率相同,同时在光信号的频域上会存在许多谐波分量,随着振动幅度的增加或光纤弯曲的横向长度的减小,谐波分量的个数越来越多,高次谐波的幅度也越来越大;光波偏振态与检偏器之间初始角也会对光强信息产生影响,当初始角为0°和90°时,谐波的个数最少。在理论分析的基础上,通过实验验证了上述结论。
振动测量 光纤双折射 偏振态 光纤传感器 vibration measurement fiber birefringence polarization optical fiber sensor 
光电子技术
2009, 29(3): 186

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