Author Affiliations
Abstract
Key Laboratory of Intelligent Optical Sensing and Manipulation, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
With the increasing demand for space optical communication security, space chaotic optical communication has attracted a great amount of attention. Compared with traditional space optical communication, a chaotic optical communication system has a higher bit error rate (BER) for its complex system design. In order to decrease the BER of space chaotic optical communication systems, we introduce two diffractive optical elements (DOEs) at a transmitting terminal (Tx). That is because the commonly used reflective optical antenna at Tx blocks the central part of the transmission beam, which leads to a great amount of power consumption. Introducing the DOEs into the optical subsystem at Tx can reshape the transmission beam from a Gaussian distribution to a hollow Gaussian distribution so that the block of the secondary mirror in the reflective optical antenna can be avoided. In terms of the DOE influence on communication quality, we give a BER model based on a minimum-shift-key (MSK) space uplink chaotic optical communication system to describe the DOE function. Based on the model, we further investigate the effect of the DOEs through analyzing the BER relationship versus basic system parameters based on the BER model. Both different mismatch conditions of chaotic systems and different atmospheric turbulence conditions are considered. These results will be helpful for the scheme design of space uplink chaotic optical communication systems.
chaotic-encrypted communication space uplink optical communication atmospheric turbulence effects diffractive optical element design minimum-shift-key bit error rate Chinese Optics Letters
2020, 18(7): 070601
Author Affiliations
Abstract
We propose and demonstrate a tunable optical filter based on a tapered silica microcylinder, whose diameter is gradually varied along its longitudinal axis. The tapered microcylinder comprises a slowly varying transition zone fabricated through the fiber drawing technique. Given the tapered diameter of the microcylinder, the resonant wavelengths can be tuned by displacing the tapered microcylinder. This tunable filter exhibits a high Q-factor (～106) and a large tuning range (>1 free spectral range (FSR)).
230.7408 Wavelength filtering devices 230.3990 Micro-optical devices 230.4685 Optical microelectromechanical devices 230.5750 Resonators Chinese Optics Letters
2013, 11(8): 082302
南京大学光通信工程研究中心, 江苏 南京 210093
将4阶回音壁谐振模式(WGM)应用于折射率传感器的检测中。实验中以壁厚为4.8 μm的微毛细管构建折射率传感器，验证了不同WGM的传感器灵敏度有显著差异。实验获得的最高灵敏度达到48.74 nm/RIU(折射率单位)，对应的探测极限达6.2×10-6 RIU。通过与模拟结果对比，清晰地识别出4阶WGM共振峰，并且4阶WGM在传感灵敏度方面有明显的优势。此外，分析了环境温度的扰动对不同径向阶数WGM共振波长的影响，发现与其他低阶模相比4阶WGM表现出低温度响应的优势。为实现实用的高灵敏度、抗热噪声折射率传感器提供了理论和实验基础。
光学器件 折射率传感器 微环谐振腔 回音壁谐振模 倏逝波
Author Affiliations
Abstract
We propose and demonstrate broadband Brillouin slow light using a multiple-longitudinal-mode tunable fiber laser as Brillouin pump. A tunable broadband Brillouin pump with a tuning range from 1 520 to 1 555 nm is generated using a fiber ring laser with a semiconductor optical amplifier (SOA) as its gain medium. The pump spectrum consists of a large number of longitudinal modes separated by 6 MHz. The 3-dB bandwidth is about 11.5 GHz, and its fluctuation is less than 100 MHz within the tuning range. An 8-Gb/s data signal can be delayed by up to 83.0 ps (bit error rate < 10 9) at 17-dBm pump power.
140.3280 Laser amplifiers 140.3510 Lasers, fiber 290.5900 Scattering, stimulated Brillouin Chinese Optics Letters
2012, 10(8): 081401
Author Affiliations
Abstract
The nonlinear effects that limit the performance of the multi-frequency probe (MFP) based coherent optical time domain reflectometry (C-OTDR) are investigated. Based on theoretical analysis and experimental results, compared with conventional C-OTDR, when the probe pulse has power gradient within the pulse width, self-phase modulation (SPM) and cross-phase modulation (XPM) are strengthened in the new C-OTDR scheme. The generation of four-wave mixing (FWM) is dependent on SPM and XPM, and with modulation frequency of phase modulator higher than 40 MHz, the stimulated Brillouin scattering (SBS) threshold can be enhanced by more than 5 dB, which benefits the maximum dynamic range of the MFP C-OTDR.
060.2370 Fiber optics sensors 120.4825 Optical time domain reflectometry Chinese Optics Letters
2012, 10(4): 040604
南京大学光通信工程研究中心, 江苏 南京 210093
提出一种利用四波混频增强多波长布里渊掺铒光纤激光器的方法，在激光器中使用色散位移光纤作为布里渊增益介质，通过布里渊多波长之间四波混频效应提供的参变增益展宽激光器的有效增益谱，产生高阶斯托克斯光和反斯托克斯光，增加多波长的数目并改善输出功率。分析了激光器中掺铒光纤放大器功率和布里渊抽运功率对四波混频增强效果的影响，在980 nm抽运为105 mW，外部注入1559 nm布里渊抽运为8 dBm的条件下，在1557.56~1560.78 nm之间得到了稳定的39个波长的输出。
光纤激光器 多波长 四波混频 受激布里渊散射
南京大学光通信工程研究中心, 江苏 南京 210093
提出并实现了一种单纵模窄线宽输出、波长可开关的光纤激光器。该激光器采用环形腔结构, 利用一段未抽运的掺铒光纤(EDF)的饱和吸收效应来实现光纤激光器的单纵模运转与窄线宽输出; 同时利用1×2光开关和2个并联的不同中心波长的光纤光栅(FBG)的选波作用, 通过控制光开关的电压信号, 实现2个输出波长的可开关功能。在17.5 dBm的掺铒光纤放大器(EDFA)输出功率下, 获得了2.5 dBm峰值功率,3 kHz线宽的单纵模激光输出; 并且输出光的波长在控制电压的作用下可在1545.2 nm和1556.4 nm两个波长之间任意选择。
激光器 光纤激光器 单纵模 光开关 饱和吸收体
南京大学光通信工程研究中心, 江苏 南京 210093
提出并实现了一种单纵模输出、波长可开关的光纤激光器。该激光器采用线性法布里-珀罗(F-P)腔结构,利用980 nm抽运的掺铒光纤(EDF)作为增益介质,并且通过腔内另一段未抽运的掺铒光纤的饱和吸收效应来实现光纤激光器的单纵模运转; 同时利用1×N光开关和N个并联的不同中心波长的光纤光栅(FBG)的选波作用,通过控制光开关的电压信号,实现N个输出波长的可开关功能。在90 mW的抽运功率下,获得了-0.5 dBm峰值功率,3.6 kHz线宽的单纵模激光输出; 输出光的波长在控制电压的作用下可在1574.6 nm,1579.7 nm,1584.8 nm和1589.9 nm四个波长之间任意选择。
激光器 光纤激光器 单纵模 光开关 饱和吸收体
南京大学光通信工程研究中心, 南京 江苏 210093
提出并实现了一种脉冲幅度可均匀化的有理谐波锁模光纤激光器。该激光器采用主动有理谐波锁模机制,可获得重复频率为整数倍调制频率的锁模脉冲信号。通过在光纤激光器谐振腔中添加非线性光纤放大环镜,并利用其反射率对输入信号强度的开关特性,实现对锁模脉冲信号的整幅。在1 GHz的调制频率下,分别获得了4 GHz和5 GHz重复频率的锁模脉冲信号输出,并且在一定的980 nm抽运功率下,可通过调节电光调制器的直流偏置电压大小以及调制信号的调制深度,使得脉冲幅度具有较好的均匀性。
光纤激光器 主动谐波锁模 有理谐波锁模 非线性光纤放大环镜
