Optical Characteristics Analysis Of Long Period Fiber Gratings And Femtosecond Laser Directly Writing Manufacturing Method

Fiber grating is a new type of fiber devices developed recent years and is wildly applied in the fields of fiber communication and sensors. With the development of manufacturing techniques, many manufacturing methods were provided for manufacturing high performance fiber gratings. Femtosecond laser technique is a kind of recently developed technique, with which high temperature resistance fiber gratings could be gained.In the manufacturing process of the femtosecond laser directly writing Long Period Fiber Grating (LPFG) method, the manufacture errors can directly cause the variation of grating parameters, which would affect the transmission spectrum of the LPFG and thus making the gained LPFG transmission spectrum different from what we expected originally. In order to better understand the affected degree of the transmission spectrum caused by the grating parameter errors and use which to guide the parameters and precision control in the manufacturing process, the following content of research were included:1. Based on the Coupled-Mode Theory, transmission spectrum simulation with the variation of grating period, grating length, duty cycle, cladding refractive index and refractive index modulation depth were done to better understand the transmission spectrum varying patterns along with the variation of these fiber grating parameters.2. For the manufacturing process of femtosecond laser directly writing Long Period Fiber Grating, possible manufacturing errors that could cause the variation of grating parameters were considered. Analysis focus was put on the variation of transmission characteristics of LPFG along with the variation of grating period and refractive index modulate depth cooperated with manufacturing errors. These varying patterns could provide guidance into the experiment setup parameters and precision control in the manufacture process.3. The mechanisms for femtosecond laser processing fiber gratings were studied and experiments with femtosecond laser directly writing LPFG were done, from which we learned the key factors for good fiber gratings process.