Study On Relative Intensity Noise Characteristics Of Broadband Light Sources

Broadband light sources are widely used in low-coherence systems such as fiber optic gyroscope systems,optical coherence tomography systems,and fiber optic sensor systems.With the continuous improvement of production and scientific research needs,low-coherence detection systems are developing in the direction of high precision.It is very urgent to research and improve the system's performance indicators.Shot noise,thermal noise,and relative intensity noise(RIN)constitute the optical noise of the system.Among them,RIN is the most in-depth understanding and the most important factor that limits the minimum detectable performance of low-coherence systems.Therefore,a thorough understanding of RIN of a broadband light source is essential to maximize system performance.To date,the research on the relative intensity noise characteristics of broadband light sources is generally focused on the light-emitting characteristics.The noise of different broadband sources varies greatly,and no one has studied the RIN distribution characteristics of various positions in the broadband light source yet.In this thesis,tunable fiber Bragg gratings and dense wavelength division multiplexing(DWDM)are used to perform spectral segmentation and filtering on broadband light sources.The overall RIN of broadband light sources and the distribution characteristics of RIN at different wavelength positions along the spectrum are studied.It is mainly divided into two parts.At the same time,two commonly used typical broadband light sources were selected: amplified spontaneous emission(ASE)and superluminescent diode(SLD)for comparative experimental research.Firstly,the overall relative intensity noise characteristics of broadband light sources are studied,and the variation characteristics of RIN with spectral width and pump are mainly completed.The effect of spectral width on the broadband light source RIN was verified by experimental tests,and it was revealed that RIN of the ASE and SLD light sources have different changing rules when the pump increases.Secondly,the RIN characteristics of the distribution of ASE and SLD along the spectral are mainly studied.The RIN test of the filtered light source at different wavelength positions of the broadband light source using tunable fiber Bragg gratings is performed to obtain the distribution of ASE and SLD light sources along the spectral RIN.It was first observed that the RIN of the ASE light source was related to its spectral shape.This is very different from the uniformly distributed SLD,which illustrates the fundamental difference between the two broadband light sources,which has guiding significance for designing high-performance broadband light source based measurement systems.