Characteristics Of F-P Cavity Based On Dynamic Grating In Er-doped Fiber And Fiber Bragg Grating

Researches for dynamic grating and fiber Bragg grating have been very mature.The characteristics of fiber Bragg grating are very advantageous,such as small size,light weight,high flexibility,high temperature resistance,anti-electromagnetic interference and chemical stability,so fiber Bragg gratings are attractive for different applications.On the other hand,dynamic gratings recorded in Er-doped fibers(EDF)attracted attention in connection with their possible applications in optical fiber sensors,adaptive interferometers and optical memory elements.Also,dynamic gratings possess some unique advantages that the wavelength,refractive index modulation depth and bandwidth are tunable.Using the advantages of fiber Bragg grating and dynamic grating,we designed a F-P cavity based on dynamic grating in Er-doped fiber and fiber Bragg grating and researched its optical characteristics.First we calculate the reflection and transmission of the grating and further more we propose a scheme of Fabry-Perot(F-P)cavity based on the above-mentioned DBG recorded in EDF and a normal UV-written fiber Bragg grating(FBG).An important feature of the proposed F-P cavity is that the transmission characteristics can be dynamically tunable.This performance of F-P cavity is advantageous comparing with that of the F-P cavity based on two FBGs.Since the resonance responses of F-P cavity based on two FBGs are un-adjustable once the recorded FBGs and cavity length are fixedly fabricated.A tunable device is always much more flexible than a fixed one.In our proposed F-P cavity based on a tunable DBG and a FBG,the transmission and reflection characteristics can also be dynamically tunable by modulating the Rabi frequency c? of the coherent fields and other parameters.On the other hand,the F-P cavity based on two FBGs are not perfect when the two inscribed UV-written gratings at two ends are not symmetrical because of restricted manufacturing process.In another words,two fiber Bragg gratings have different grating parameters,such as different Bragg periods(43)B and different refractive index modulation depths ?n.This asymmetry of the two gratings is a disadvantage for mode selection of the F-P cavity.While using the F-P cavity based on a tunable DBG and a FBG can overcome the asymmetrical drawback by simply changing the wavelength c? and Rabi frequency c? of the coherent fields.The main results of this research are as follows:1.Theoretical and experimental researches on dynamic fiber gratings in two level system in Er-doped fiber.We calculated the reflection and transmission of the dynamic grating which are based on semiclassical interactional theory and Coupled mode method.We observed dynamic grating which was recorded in Er-doped Fiber in experiment.Then we obtain the numerical results of the reflection properties.We can get parameters of more effective dynamic grating to conduct the experimental observation.2.The reflection and transmission characteristics of the F-P cavity formed by a dynamic grating and a fiber Bragg grating by using method of transfer matrix.We calculated and analyzed reflection spectra by changing the parameters for the three parts of the F-P cavity separately.The parameters include Rabi frequency of the coherent field in the dynamic fiber,the refractive index modulation depth of the fiber Bragg grating and the cavity length of the F-P cavity.In conclusion,we research the characteristics of formed by dynamic grating and fiber Bragg grating,which has reference value for further experiment and practical application of dynamic F-P cavity.