| Long period fiber grating(LPFG) has broad application prospects in the field of optical fiber communications and optical sensors because of its great benefits. And in recent years, it’s one of the fastest growing optical passive components. Mechanically induced long period fiber grating(M LPFG) overcome the disadvantages of traditional method, such as UV exposure method, that only with fixed period, loss peak amplitude grating and the grating length during the production period of LPFG. It can be used to realize the simple-produced, easy tunable, low-cost, reconfigurable LPFG.Firstly, this paper proposes a design of new series LPFG band-pass band-stop filter. In order to avoid the inefficiency problem of coupling through the evanescent in the structure of concatenation LPFG coupler, it achieves the band-pass and band-stop result at the same time, by welding the hollow-core optical fiber(HOF) with a reflective end surface in series between these two same LPFG.Secondly, this paper uses a method to produce pressure by an ordinary spring to obtain the MLPFG. It focuses on the research of the band-stop filter characteristics of MLPFG, including relationship between transmission spectrum and pressure, relationship between the pressure per unit length and the resonance wavelength fiber, the relationship between transmission transmittance and FWHM. In the result, the MLPFG gets the lowest transmittance of the resonant wavelength, 0.01 um. Its FWHM is low to 29 nm and achieves a tuning in the 1540-1580 nm range. It also has the following characteristics: Firstly, loss peak amplitude of the resonance wavelength can change with the change of pressure. Secondly, it has the flexibility to change the resonant wavelength by changing the spring pitch. Because it will not bring a permanently changing of the grating structure and physical properties of the fiber, the device has a reconfigurable ability to be expected as an optical fiber filter in the optical communication and optical sensing fields. |
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