Study On Fabry-Perot Cavity Based On Fiber Bragg Grating

Fiber grating functional devices based on Fabry-Perot(F-P)structure have attracted a lot of attention in recent years,which have important application prospects.The outstanding features of F-P fiber grating devices are multi-functions and various forms,the parameters of the fiber grating composed of F-P cavity can be varied,the parameters of the interfering cavity can also be varied.By changing these parameters,many unique designs and functions can be derived.In this paper,coupled mode theory and the transfer matrix method are used to systematically research and simulation analysis the changes of various properties of F-P resonant cavity consisting of two uniform FBGs and the F-P resonator cavity composed of two chirped FBG under different parameters.The main work is as follows:(1)For the F-P cavity consisting of two uniform FBGs,when the three parameters of the length of two uniform FBGs,F-P cavity length and refractive index modulation depth were individually changed,we simulated the change of the free spectral range(FSR)of F-P cavity,transmission spectrum,reflection spectrum,phase,delay,dispersion by MATLAB.A special uniform fiber grating F-P cavity is discussed,one of the reflectivity of the two uniform gratings consisted of the F-P cavity is small and the other is extremely large(almost 100%),which is called the uniform fiber grating Gires-Tournois(G-T)cavity.(2)According to the cascaded direction and position of two linear chirped gratings consisted of F-P cavity,the F-P cavity consisting of two chirped gratings is divided into four categories:1)Both cascaded linear chirped grating periods are from small to large;2)Both cascaded linear chirped grating periods are from large to small;3)Two linear chirped grating cascade,the first chirped grating period is from small to large,the second is from large to small;4)Two linear chirped grating cascade,the first chirped grating period is from large to small,the second is from small to large.For the above four cases,the transmission spectra,reflection spectra,phase,delay,dispersion and FSR of F-P cavity were simulated by MATLAB when the three parameters of grating length,refractive index modulation depth and chirp ratio were changed individually,and discussed the impact of various parameters on these characteristics.A special chirped fiber grating F-P cavity was discussed,one of the reflectivity of the two chirped gratings consisted of the F-P cavity is small and the other is extremely large(almost 100%),which is called the chirped fiber grating G-T cavity.A special type of chirped grating F-P cavity is discussed,Two chirped gratings are overlapped and written into the fiber with a certain position offset to form a chirped Moire fiber grating.