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The Study Of Some Problems Of Optical Fiber Amplifier

Posted on:2002-09-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:J S LeiFull Text:PDF
GTID:1118360122996232Subject:Communications and electronic systems
Abstract/Summary:PDF Full Text Request
Fiber amplifiers with high-power, big-gain bandwidth and low-noise figure are required for their application to DWDM system, fiber CATV system and space laser communication system. High-power, big-gain bandwidth, optimal parameters and low-noise figure are becoming the goals the fiber amplifier pursues for and the focus both at home and abroad. They are also the hot topics today in the development of fiber amplifier. This paper makes an attempt to explore these hot, difficult and key problems. Erbium doped fiber amplifier(EDFA) is studied theoretically and experimentally in this dissertation. Double-cladding fiber amplifier and Raman fiber amplifier pumped by double-cladding fiber Raman laser are mainly under investigation theoretically. Several key problems of space laser communication system, especially the application of high power fiber amplifier in transmitter and low noise figure amplifier in receiver, are also studied.First of all, EDFA model is set up by using rate equations and propagation equations for signals, pumps, and ASE. Experiments for C band EDFA have been made by using 980nm pumping and 1480nm pumping, respectively. The experimental results show that output power spectrum density between 1500~1600nm agrees well with calculated results based on the model. EDFA noise characteristic is analyzed, too.Secondly, EDFA designing software is studied. Low noise preamplifier is designed by using optimization method.Thirdly, the effect of different inner cladding section shape on pump absorb efficiency has been studied using ray-optics. Someinstructive conclusions for double-cladding fiber designing are obtained. Pump methods of double-cladding fiber amplifier are also studied. Dividing the fibre into sections, a novel semi-numeral model for double-cladding fibre amplifier is set up according to the principle of photon balance. Then double-cladding fibre amplifier design has been optimized according to this model.Fourthly, some key problems of space laser communication are studied including the selection of working wavelength, laser and modulation technology, as well as the calculation of optical link for inter-satellite optical communication. Two experiment designs have been studied, which are about MOPA transmitter using high-power fiber amplifier as power amplifier and the receiver using low-noise fiber amplifier as preamplifier.Finally, Raman fiber amplifier pumped by double-cladding fiber Raman laser has been studied. A simplified theoretical model of double-cladding fiber laser is presented. The relationship between multimode pumping power threshold and fiber length has been obtained according to this model. When the threshold pumping power reaches its minimum, the cavity length of fiber laser is then optimized. High-power output of Yb3+doped double-cladding fiber laser is injected into single mode frequency-shift fiber, through, and the energy of pumping laser could be transferred to the expected wavelength in cascaded way. The times of cascade are decided by the quantity of frequency-shift and the expected wavelength and they are realized by the number of fiber grating. The conclusion is that High-power double-cladding fiber Raman laser can be the appropriate pumping source of fiber Raman laser.
Keywords/Search Tags:Erbium doped fiber amplifier, Double-cladding fiber amplifier Raman fiber amplifier, Space laser communication
PDF Full Text Request
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