The Study Of Ultra-high Resolution Coherent Spectral Analysis System Based On Heterodyne Interference

In the areas of optical communication, biomedical detection, laser quality analysis and optical frequency comb, more and more high demand for resolution of spectral details analysis and development in the d irection of the lower than 1 pm. Traditional spectral analysis cannot effectively monitor the transmission signal due to the low resolution, F-P spectral analysis technique has high resolution, but its measurement range is narrow, so it is only suitable fo r dedicated demodulation equipment. Although new type of spectral analysis technology can achieve very high resolution, resolution proportional to the length of the fiber, high resolution must use a long fiber, resolution vulnerable to environmental impact.In the view of the above problems, this paper puts forward a ultra-high resolution coherent spectral demodulation technology based on heterodyne interference. The spectrum has high resolution and wide measuring range, not involving the use of optical fiber long, not easily being affected by the environment. This article mainly aims at the principle of heterodyne interference coherent spectroscopic analysis, putting forward a scheme of heterodyne interference coherent spectral analysis, build an experimental system of heterodyne interference coherent spectral analysis, realizing the spectrum demodulation of the optical signal. The main research content is divided into the following several parts:1. Scheme design based on heterodyne interference coherent sp ectrum analysis system. According to the principle of heterodyne interference in coherent spectroscopic analysis using electrical filter achieving wide range narrow line-width filtering, designing heterodyne coherent spectrum analysis program, including the design of two modules: the spectrum analysis module and the real-time wavelength calibration module, the spectrum analysis module is divided into two sub module beat frequency optical path module and beat frequency signal processing module.2. Performance analysis and optimization of coherent spectrum analysis system based on heterodyne interference. For design scheme of heterodyne interference in coherent spectrum analysis system, establish mathematical model to analyze the performance of heterodyne interference coherent spectrum analysis. First set for metering to single frequency light, the whole process of heterodyne interference coherent spectrum analysis is analyzed. The parameters of Affecting heterodyne interference coherent spectral analysis syst em performance is analyzed. Through optimizing the parameters of heterodyne coherent spectrum analysis system can improve the properties of heterodyne coherent spectrum analysis system. The model of broadband optical detection is established and the proces s of broadband optical detection is analyzed3. The design of hardware and software of coherent spectrum analysis system based on heterodyne interference. Hardware design mainly includes the balanced detector, RBW band pass filter, the power detector, VBW filter and signal processing circuit. Software design mainly includes the tunable laser output wavelength adjustment procedure, digital acquisition card control program, data processing algorithms of Real-time wavelength calibration module.4. The performance test of coherent spectrum analysis system based on heterodyne interference. The performance of each module of heterodyne interference coherent spectral analysis system is tested, mainly including RBW band pass filter module, power detector module and real-time wavelength calibration module. Establishing heterodyne interference coherent spectrum analysis system, the performance based on heterodyne interference coherence spectrum analysis system is tested, mainly including the Power accuracy, the dynamic range and resolution of spectrum analysis system. The experimental results show that spectral analysis system’s resolution is 48 fm, dynamic state range is 38 d B,wave-length accuracy is ±0.4pm.After the performance testing, the spectral analysis system was used to detect the reflection spectrum of the Phase-shift grating, the optical frequency comb and the output spectrum Mach-Zehnder interferometer, the detection results were compared with ordinary spectrum analyzer.This article mainly through constructing heterodyne interference ultra-high resolution spectrum analysis system achieve high resolution, high dynamic range, high precision and wide range measuring. To solve the defects in the existing spectrum analysis system.