Research On Programmable OADM And Multiwavelength Fiber Laser In DWDM Communication System

With the advent of information era, human society's increasing demand for communication capacity causes the introduction of Wavelength-Division Multiplexing (WDM). In present, WDM communication system is developed towards two directions. On one hand, WDM system is transforming from the point to point system to all optical networks. Optical Add/Drop Multiplexer (OADM), which has a capacity of add/drop signals in the optical formation and then avoids the drawback of electronic bottleneck demonstrated in traditional technology, becomes the pivot to realize all optical WDM networks. On the other hand, the number of signal channels keeps increasing with the development of WDM communication system. Due to their economic cost, it is an indispensable way to utilize multiwavelength lasers as signal emitters in communication system in order. Multiwavelength Erbium-doped fiber lasers (MW-EDFLs) become the research focus out of various types of multiwavelength lasers for their attracting merits. This dissertation emphasizes on the study of fiber Bragg grating (FBG) based Programmable OADM and Multiwavelength erbium-doped fiber lasers, and includes the detail descriptions on the following subjects:1. The spectra characteristics of both the single mode fiber Bragg grating and the hi-birefringence fiber Bragg grating are analyzed and simulated with coupled-mode theory. The reflection wavelength tuning of FBGs by applying axial strain and lateral strain is discussed, and the theoretic results in both of the above situations are presented.2. The development status and structures of programmable OADMs are generalized in brief. Programmable OADM's future application is prospected after analyzing merits and shortcomings of several typical POADM schemes3. A POADM based on FBG and optical circulator is developed. By tuning the FBG glued on a piezoelectric transducer, and monitoring the spectra at download ports by an optical spectra analyzer through computer management, we realize a programmable OADM. Tested by Four-wavelength laser, its add/drop wavelengths are 1550.02nm, 1550.82nm, 1551.62nm, 1552.42nm with wavelength space of 0.8nm, tuning speed reaches about 1s, and isolation between adjacent channels is 21.5dB. Monitor and control can be easily executed from the system interface.4. The fundamental principles of both the linear cavity fiber laser and the ring cavity fiber laser and the stability criterion for multiwavelength oscillations are introduced. Several kinds of techniques to achieve mulitwavelength oscillations are summarized.