S. G. Aliushina, P. E. Denisenko, O. G. Morozov, I. R. Sadykov, O. A. Stepuschenko
To achieve high resolution in different FBG based sensor systems either FBG or more complex configurations, such as Fabry-Perot interferometer that is based on two FBG with very narrow resonance are used. Based on this approach π-shifted FBG which is the simplest of the FPI with a cavity length not exceeding λВ for creating measurement fiber optic sensors may be used. The half-width of the resonance peak of this type grating may reach 0.005 nm, indicating a possible increase in the resolution of measurements by two orders compared with the sensor on the FBG.
The problem of triangular spectrum FBG implementation as adaptable and linear spectrum measurement instrument for measurement channels establishing is actual. In telecommunication channels spectral area with triangular spectrum may be used for their central wavelenght monitoring system implementation. Introduction of the phase structuring by the normalization method allowed us to develop a triangular spectrum FBG with symmetrical, asymmetrical and rectangular forms. On this basis, respectively, measuring channels with multifrequency sensing and telecommunication channel with built-in system monitoring of its center frequency position was constructed and simulated.
Discrete π-shifted FBG offer the prospects of using multi-grids windows with successive transparency and reflection. Group-delay characteristic for each window is equal to the group delay of the original π-shifted FBG, also at the center of each reflection band there is a narrow-band transmission window. Thus, in the FBG of this type π-shifted FBG and triangular spectrum advantages may be implemented.
We first considered a discretization according to Cantor dust law and the possibility of establishing a structure of parallel channels with identical parameters for distributed systems.