Study Of C+L Band Broadband ASE Fiber Source

Broadband super-fluorescence fiber source (SFS) with low spectral ripplesand high spectral intensity based on the amplified spontaneous emission (ASE) hasbeen not only intensively studied as an essential source for passive opticalnetworks and wavelength-division multiplexing (WDM) communication systems,but also used in various fields such as the optical sensor systems and fiber-opticgyroscopes. SFS is superior to other broadband sources for it can produce higherpower and wider band. With the requirement of fiber communication for broadbandwidth, the research of C+L-band flat broad bandwidth sources have causescholars much attentions. The researching of extending L-band source and relatingto component is very important. Meanwhile, to satisfiy the application of large areaand dense multi-points distributed fiber sensors, a high power and broad bandwidthASE source was needed.In this thesis, C+L band bandwidth ASE source was investigated. The mainworks related to the application in dense wavelength division multiplexing(DWDM) fiber communication system toward broad bandwidth and to satisfy theapplication of in a larger area and dense multi-points distributed fiber gratingsensors, a high power and broad bandwidth ASE source will be studied. Theresearch work can be divided into five parts as following:The first part is introduction. On the basis of reading a great deal datumabout broadband source, the research and development about Er-dopedsuperfluorescent fiber source was summarized. The actuality and direction of theexternal and internal broadband source in history, today and the future wasdiscussed.The reason on broadband source caused scholars much atentions atinternationality in 1990s was analyzed at first. Comparing with the SLD, thebroadband fiber source was applied widly in gyro sensors, component testing,signal processing, optic layer analyse, medical diagnosis, fiber sensor, fiberdetecting and WDM optic communication system. Moreover, whole system'sfiberization can be realized being this kind source's compatibility. Throughcomparing and analyzing various configurations, the double-pumped two-stage anddouble-pass erbium doped superfluorescent fiber source was adopted.The second part is the theoretical analysis of the Er-doped fiber broadbandASE source. The characteristic of the erbium was summaried from atom, ion to theenergy level in this part. The spontaneous emission and the amplified spontaneousemission were discussed. The various ASE source configurations, the propagationequations and the rate equations were summarized. Finally, the outputcharacteristics of the EDF-SFS were disccused from three aspects: meanwavelength, output width and output power. The stablily of the EDF-SFS areinfluenced by the change of mean wavelength, pump wavelength and power, whichwere changed by temperature. In a word, Er-doped fiber broadband ASE sourcewas analyzed in theory comprehensively.In the third part, the characteristic of the two-stage dual-pass structure C+Lband broadband ASE source was analyzed. For example, the important componentsoptic fiber reflector and pump source related to this structure were introuduced.The basic specific of two-stage dual-pass structure was chiefly analysed. Theconclusion is followed: (1) Based on this configuration, L-band or C+L-band highoutput power was obtained by using the other configuration's advantage which cansatisfy the applications of various occasion;(2) This configuration has higher pumpefficiency than the stability sigle-pass backward one;(3) The output of stabletwo-stage double-pass SFS can be changed with the pumping power andreflectivity of the reflector. Finally, the principle of C+L-band ASE source wasclarified in this configuration.The fourth part is software simulation of C+L band broadband ASE source.Two-stage, two-pass structure was simulated in this part. The affections on thecharacteristics of Er-doped superfluorescent fiber sources that caused by the pumpwavelength,pump power,fiber length, Er-ion density and optic reflectivity werestudied.The fifth part is the experiment of C+L-band broad bandwidth ASE source.Double-pumped, two-stage and double-pass erbium doped superfluorescent fibersource was presented. Low and heavy erbium-doped fibers pumped by two 980nmlaser diodes in backward and forward were utilized in the experiment, an isolatorand broad bandwidth fiber refector was selected. By using a broad bandwidth fiberreflector to feedback and amplify the forward L-band ASE generated by therear-stage erbium doped fiber in the former-stage. The power of L-band ASE wasimproved efficiently and C-band ASE power was reduced slightly. Therefore, a flatC+L-band broad bandwidth ASE source with about 66.82nm (from 1533.80nm to1600.62nm) flat bandwidth and 7.06dBm total output power were obtained.Meanwhile, experimental results were analysed. At the last the 20 channels aroundC-band (from 1542 to 1559 nm) with mean spacing of 1.7±1nm were obtained byusing a multi-medium filter.