可高效利用光谱资源的高精度高速光谱解调技术研究

In modern intelligent optical-fiber sensor network, spectrum interrogation technology should not only extract sensing data with high speed and high wavelength resolution, but also should be compatible with the extension and survival ability of sensor network. That is to say, the limited spectrum resource should be allocated efficiently and dynamically. Nowadays spectrum interrogation technologies are difficult to meet the three requirements mentioned above at the same time. A new spectrum interrogation technology that can efficiently use spectrum resource with high speed and high wavelength resolution will be studied in this project, which includes: ① The speed of interrogation will be increased by sampling the segmented spectrum synchronously. The spectrum to be sampled is divided into N-1 segments by the N comb wavelengths output by a multiwavelength optical source. The segmented spectrum is then synchronously scanned by an electro-optical component driven by radio frequency signal; ②The resolution and repeatability will be improved by spectrum scanning controlled by radio frequency driven signal. Since optical component is electronically controlled instead of traditional mechanism driven, the system will has good stability and repeatability. Meanwhile the wavelength resolution will be exactly improved while reducing the requirements of components in the system; ③ The spectrum will be efficiently used by converting sampled data format in real time. The comb spectrum signals extracted from each sensing sub link are converted into optical time division multiplexing (OTDM) signals on a single wavelength by a high speed electro-absorption modulator. The OTDM signals are sent into the bus network. Since the rest of spectrum resources occupied by each link are relaxed, the spectrum resources will then be able to shared and dynamically allocated among the other sub links in the same bus network. An advanced and comprehensive spectrum interrogation with hundreds of KHz scanning frequency and sub pm wavelength resolution in several tens of nm is expected to be realized. The requirements of unification of spectrum interrogation and intelligently using spectrum resources are expected to be satisfied by using this technology.

现代智能光纤传感网中的光谱解调技术除了要高速、高精度提取传感数据，还要兼顾网络延拓性和强生存能力，实现光谱资源共享和动态分配。现有技术难以兼顾上述要求。本项目研究高效利用谱资源的高速高精度光解调新方法，特点为：①解调速度成倍提高：用多波长光源的N个梳状谱把采样频带分成N－1段，再由射频电信号驱动电光器件对各段光谱同步扫描采样，解调速度提高N－1倍；②射频电控扫描精度高、重复性好：完全脱离传统的机械扫描，解调精度提高时对器件的要求不升反降；③实时转换光谱数据格式，光谱利用率高：用高速响应的电吸收调制器，将传感子链路采样得到的各帧梳状谱信号，实时转换为单一波长上的时分复用信号，进入网络总线传输，节省出的谱资源由同一总线上其他子链路共享并动态分配。最终实现十几nm波长范围内，以百 kHz光谱扫描频率、亚pm波长分辨率为标志的先进、全面的光解调，迎合传感网光解调方式统一化和谱资源利用智能化的需求。

现代智能光纤传感网中的光谱解调技术除了要高速、高精度提取传感数据，还要兼顾网络延拓性和强生存能力，实现光谱资源共享和动态分配。现有技术难以兼顾上述要求。项目研究了一种能灵活高效利用光谱资源的高精度高速光谱解调新方法。用多波长光源的N 个梳状谱把采样频带分成N－1 段，再由射频电信号驱动电光器件对各段光谱同步扫描采样，解调速度提高N－1 倍，在常用光纤传感光谱范围内获得~200KHz 水平的扫描频率，波长分辨率达到亚pm 量级，并在10MHz-20GHz范围内任意可调；研究了对N只DFB激光器并联输出的梳状载波进行并行扫频实验，实现3个DFB种子光的并行扫频，获得扫频光谱平坦度±1.5dBm、扫频范围3nm内扫频速率200kHz、线性度0.99991的扫频输出；实现4个DFB并联，扫频步长为20pm时的四波长并行阶跃扫频输出，光谱平坦度为±2.65dB，扫频范围为1.6nm，扫描频率为133.3kHz。利用扫频光源对FBG分别进行了温度传感、静态应变传感和动态应变传感的光谱信息采集和解调，实现 FBG应变灵敏度1.566 pm/μ，中心波长随应力变化线性度0.99944；温度灵敏度为10.004pm/°C，温度线性度0.99946；实现了对FBG高频振动的实时测量，获得5Hz~11kHz动态应变的解调结果，并测得瞬时响应时间约25s的频率突变；对传感链路中级联的多只FBG并行进行温度、应变传感的光谱信息采集和解调，实现光源扫频步长为0.04nm和0.02nm时，分别获得了平均温度灵敏度10.055±0.005pm/℃，线性度0.99789和平均静态应变灵敏度系数1.614±0.002pm/με，线性度0.9975的传感解调结果。对采样得到的光谱数据，再利用用高速响应的电吸收调制器，将传感子链路采样得到的各帧波分复用信号，实时转换为单一波长上的时分复用信号，实验实现有效信号工作波长范围可达到45nm，为传感网组网提供了统一、高效且灵活的光谱解调新方法。项目研究的光源及其光谱分段采样技术，同时兼具了宽光谱范围、分段采样、扫频速率高、分辨率高、线性度高等优势，可以同时满足不同物理量的传感要求，能够统一各种异构传感器的光解调方法。项目研究的光谱数据格式实时转换，能够实现组网时各个子链路共用相同的光谱资源，并实时动态优化调配光谱资源，有可能应用于未来的智能光纤传感网中。