Investigation Of Key Components For All-Optical Network And Few Mode Fiber

The next generation network communication system is being developed towards all-optical network.Compared with the currently widely used OEO-based network,it has the important advantages of high security,large capacity,small congestion,etc.The technical challenges faced by all-optical network include adapting light source at the transmitting front,enlarging the communication capacity of the transmission network,and all-opticalizing the network switching nodes.Aimed at the above-mentioned key technologies,this paper correspondingly studied and elaborated on a number of items.On the transmitting front,two types of multi-wavelength fiber lasers and one type of narrow linewidth single longitudinal mode fiber laser were built;on the transmission network side,a mode-resolved characterization method was proposed for few-mode fibers widespread in mode division multiplexing systems,and following that,extensive theoretical and simulation work as well as experimental studies were conducted on the fiber's underlying characteristics change under external disturbance;in terms of switching nodes,the collaborative work on the development of optical switching devices and the construction of all-optical switching systems was demonstrated.In this paper,the research highlights and innovations are as follows:1.A multi-parameter characterization method for all modes in the fiber under perturbation based on spatial and spectral scanning was proposed.The effect of external bending and twisting perturbations on the characteristics of higher order modes including mode intensity,modal delay difference,intensity distribution and modal dispersion was investigated.The experiment results agreed with simulation,which revealed the relation between external disturbance and characteristics of higher order modes in few mode fibers and proved the feasibility of the method.The proposed method allows comprehensive characterization of any specific higher order mode,and it provides accurate mode-resolved analysis data only through a single measurement,which further enables real-time characterization of propagating modes under external perturbations.2.A simultaneous torsion and displacement sensor based on few mode fiber was proposed and assembled.The measurement principle of the sensor was demonstrated,and by combining image detection with fiber sensing,wide-range and high-sensitivity synchronous sensing of torsion and displacement was achieved.The trade-off between the measurement range and sensitivity of the sensor and its mediation methods were discussed in detail,which provides the foundation for designing and building a fiber sensor of specific requirement.3.Multi-wavelength switchable fiber lasers based on chirped grating and on sampled polarization-maintaining grating were designed and built respectively.The stability,polarization characteristics and switchability of the multi-wavelength output out of these two lasers were tested and discussed.4.A narrow linewidth single longitudinal mode fiber laser based on asymmetrical cavity of chirped grating was designed and built.High bandwidth(?0.1 nm)chirped gratings were used to achieve the ultra-narrow linewidth of the longitudinal mode.An output with a 20dB linewidth of 8.1 kHz was achieved,and its stability and polarization characteristics were examined.