Embedded Research On Hybrid Fiber Amplifier In High Speed And Ultra Haul Long WDM System

High speed and ultra long haul wavelength division multiplexing is a key technologyin optical communication, which becomes the hotpot of research.Wavelength divisionmultiplexing can increase optical system capacity through transmitting multichanneloptical signal in one optical fiber. Wavelength division multiplexing has significantadvantage in uograding network capacity and developing new business and is of greatsignificance in achieving high speed、high capacity and telecommunication. With rapiddeveloping of ultra long haul wavelength division multiplexing, there are morerequirements and performance to optical amplifier, sole erbium-doped optical fiberamplifer or raman fiber amplifier could not meet requirements of modern communication.Erbium-doped fiber amplifer(EDFA) ide high output power and high gain; with opticalfiber as medium, raman fiber amplifier(RFA) can amplify arbitrary wavelength signal withappropriate pump wavelength and power and has low noise figure. So hybrid fiberamplifier emerged which combines the advantage of EDFA and RFA, which can satisfyrequirement of optical amplifier.At present, hybrid fiber amplifier is researched and used which has a variable opticalattenuator(VOA) owned EDFA of variable gain at home and abroad. RFA and EDFA iscontrolled solely, and with fixed raman gain, EDFA changes gain through controlling theattenuation of VOA, at last hybrid fiber amplifier changes gain. Because of VOA,amplifier has a larger noise figure, especially when EDFA has a low gain. At the same time,the attenuation of VOA wastes power of pump. So in ordering to improving performanceof amplifier and saving cost, this paper designes a new hybrid fiber amplifier which cancontrol gain and gain tilt of RFA and EDFA simultaneously in one unified control platformto made gain and gain tilt of RFA and EDFA mutul offset respectively. The hybrid fiberamplifier has a flat gain bandwidth.At first, this paper analyzes and studies fundamental of EDFA and RFA, andintroduces their gain and noise characteristics. Secondly, this paper studies the relationship of gain and gain tilt of EDFA qualitatively and quantificationally, and studies influence ofpump wavelength and power to gain and gain tilt of RFA, then according to gain and gaintilt characterisitics of EDFA and RFA, the paper proposes three methods to change hybriedfiber amplifier gain. Threely the paper designs hybried fiber amplifier entirely, includingthree parts, opticator, hardware and software, and descripe every part in detail. At last, thepaper verifies feasibility of three merhods of changing gain through testing, and make acomparison with hybrid fiber amplifier owning VOA.The hybrid fiber amplifier owns wide gain range, low noise figure,great gain flatnessand low cost,which is fit for high speed and ultra long haul wavelength divisionmultiplexing system.