7. Conclusion

numerical simulation. Our experimental results (Figure 7) corroborate well functionally. Two resolutions are also confirmed σBG for each local sensor: low resolution σenv and high resolution σint. Both resolutions depend on noise system, cavity length, instrumentation, sen-

A twin-grating fiber optic sensor and an optical fiber sensor based on a single Bragg grating will have the same resolution if and only if FDPA algorithm cannot eliminate the 2πP ambiguity. In this case, the twin-grating sensor has only low resolution because the FDPA algorithm evaluates the Bragg wavelength shift with the enveloped function [11]. However, if the optical sensing system has small noise, then the twin-grating sensor has high resolution, since the Bragg wavelength shift was evaluated combining the enveloped and modulated functions [3, 11]. Additionally, three twin-grating sensors have approximately the same resolution because three wavelength channels are very close and all interferometer sensors have the same cavity length. In conclusion, the sensor´s resolution is high while the FDPA algorithm can

The presented study optimizes the quasi-distributed sensor which was shown in Figure 3. Combining our study (this work) and the analysis presented in Ref. [3], the experimental sensing system described by Shlyagin et al. [4, 5] can be optimized. The optimization will be on signal processing, local sensor properties, sensitivity, resolution and instrumentation

Our future work has the following direction: a theoretical analysis and practical application. In the theoretical analysis, frequency-and-wavelength division multiplexing can be implemented based on the twin-grating interferometer; resolution is another direction. In the practical

parameters. Additionally, the cost per sensing point is considerably reduced.

sor properties, and the digital demodulation algorithm.

acceptably demodulate the optical signal.

192 Numerical Simulations in Engineering and Science

Figure 7. Numerical results obtained from the numerical experiments.

In this work, a quasi-distributed fiber optic sensor was numerically simulated. The sensor was based on twin-grating sensors and wavelength-division multiplexing. The numerical results show the resolution for each local twin-grating sensor. Local sensors have approximately the same resolution because all twin-grating sensors have the same cavity length and the wavelength channels are close. Two resolutions were obtained for each local sensor. Our numerical results show that the quasi-distributed sensor has potential industrial application: temperature measurement, strain measurement, pressure measurement, humidity monitoring, and security system.
