All-fiber Structure Optical Bistability And Application

Optical bistability is an important nonlinear optical phenomenon in the field of optoelectronics. Optical bistability and its achievements have constituted a major theme of modern optics. Optical bistable device with logic and storage functions is an important basis device to achieve optical switching, optical limiting, optical wavelength conversion, light shaping, optical modulation and other functions. It is strongly promoted by rapid development of photonic crystal technology, fiber technology and microelectronics that research and development of new structure of optical bistable device and its applications in optical communications, optical sensing and optical signal processing. In this paper, it was carried out that application of hybrid optical bistable in all-fiber structure, and optical bistable operation was obtained respectively by using fiber Bragg grating, fiber overcoupler, amplified spontaneous emission source in erbium-doped fiber and non-symmetric Mach-Zehnder fiber filter. On this basis, application of optical bistability was carried out in optical fiber sensing, optical wavelength conversion, optical power stabilizer and so on. The main research is as follows:Utilizing nonlinear characteristics of FBG reflection spectrum, electro-optical hybrid optical bistable operation was obtained which was modulated by wavelength. And the relationship between optical bistable characteristic curve and transform parameters was studied, respectively, in three cases, that is transform bias voltage, gain of amplification loop and input intensity. Demodulation method for FBG sensor was proposed based on the principle of optical bistability and the mechanism of its demodulation were clarified. Using sensing fiber Bragg grating as nonlinear modulation components of optical bistable system, the corresponding experimental system was set up. As transform of bias voltage to demodulate FBG, 0.706 pm could be obtained for demodulation resolution; as transform of amplification loop gain to demodulate FBG, 0.332 pm could be obtained for demodulation resolution. This method is fully applicable to the multi-fiber grating sensing network demodulation.A method to achieved optical bistable operation was proposed by utilizing nonlinear transmission power spectrum of fiber overcoupler. Fiber overcoupler which was needed in experiment was produced by fused biconical taper and corresponding experiment system was designed. For the better cycle of transmission power spectrum of fiber overcoupler, it was easily to obtain optical multi-stable operation by using this characteristic. We proposed wavelength conversion method based on optical multi-stable principle. Corresponding theoretical analysis and experimental research were completed, and experimental results were agreed with theoretical analysis.It was proposed that optical bistability was obtained in ASE source of erbium-doped fiber by using its nonlinear power spectrum at 1525 nm~1535 nm. Three kind of optical bistable operation were respectively analyzed in theory and researched in experiment, and experimental results were agreed with simulations. Base on angalysis of relationship between optical bistable curve and transform parameters in all kinds of operations, the method to obtain stable light power output by dual-fed optical bistable system at 1525 nm~1535 nm band was discussed and its effectiveness was proved.Utilizing non-symmetric Mach-Zehnder fiber filter, optical bistability was obtained. And it was proposed that strain was detected by using a non-symmetric Mach-Zehnder fiber filter as sensor, which eliminated cross sensitivity between strain and temperature and at the same time still had the advantage of wavelength code. Two sensing systems of it were designed and researched in experiment and then the factors which had influence on the results of experiment were analyzed.