Preparation Of Er³⁺,Ho³⁺-doped Fluorotellurite Glass Fibers For Broadband Optical Fiber Amplifiers

With the rapid development of mobile Internet,Internet of things,cloud computing and high-definition video,the worldwide network data traffic has increased dramatically.However,for the existing single mode optical fiber transmission system based on wavelength division multiplexing,its working band is mainly C band(1530?1565 nm).Due to the influence of amplified noise and Kerr nonlinearity,the continuous increase of transmission capacity becomes more difficult.Therefore,the contradiction between the slow growth of optical fiber transmission capacity and the sharp increase of network data traffic will lead to the"capacity crisis"problem.Broad band optical fiber transmission technology is an effective solution to the above problems.For example,extending the working band of the single-mode optical fiber transmission system from the current C band to the L band(1565?1625nm)or even wider band,the transmission capacity can be increased by more than several times.Broadband optical amplification technology is the core technology to realize broadband optical fiber transmission system.Compared with commercial Er³⁺-doped silica fiber amplifiers,Er³⁺-doped tellurite glasses have wider and larger stimulated emission cross sections and are expected to be used for broadband optical amplifiers.In our previous work,the erbium doped tellurite fiber was used as the gain medium to build a broadband optical amplifier.The broadband optical amplification with a working bandwidth of 113 nm(1524?1637 nm)was achieved,but its gain value was low,and the thermal mechanical stability of the gain optical fiber needs to be improved.In view of the above problems,during the doctoral degree,the author carried out research work around high temperature mechanical stability,low loss rare earth doped tellurite glass fiber design and preparation,and broadband optical fiber amplifier and laser.1.A low loss Er³⁺-doped fluorotellurite glass fiber with high thermal mechanical stability is designed and fabricated.In the experiment,Er³⁺-doped fluorotellurite glass with high chemical,thermal and mechanical stability was prepared by melt cooling method.Further,it was used as matrix material and optimized optical fiber preparation parameters combined with precision machining technology.A series of Er³⁺-doped fluorotellurite glass fibers have been developed.The concentration of Er³⁺ions is?4000 ppm,and the optical fiber loss is?0.5 d B/m@1980 nm.2.Using the Er³⁺-doped fluorotellurite glass fiber as the gain medium,a broadband optical amplifier with a gain value of 18 d B and a wavelength coverage of1560?1618 nm has been developed.In the experiment,a 2.1 m long Er³⁺-doped fluorotellurite glass fiber with a core diameter of 7?m was used as the gain medium,and a broadband Er³⁺-doped fiber amplifier was built using a Raman fiber laser with a wavelength of 1480 nm as the pump source.When the pump power is 800 m W and the signal power is 0 d Bm,a broadband optical amplifier with a gain of 18 d B and a working wavelength range of 1560?1618 nm is obtained.The maximum gain of the amplifier is increased by 3.2 d B by using C-band auxiliary pumping technology.The above results show that the Er³⁺-doped fluorotellurite glass fiber can be developed as a broadband fiber amplifier.3.The Ce³⁺/Er³⁺co-doped tellurite glass fiber is designed and fabricated.Using it as a gain medium,a broadband optical fiber amplifier with a gain of more than 18 d B and a working wavelength range of 1559?1620 nm is obtained.It is found that the introduction of proper Ce³⁺ions can not only enhance the?1.5?m emission of Er³⁺-doped fluorotellurite glasses,but also broaden the bandwidth of the emission spectrum.Based on this,a series of Ce³⁺/Er³⁺co-doped fluorotellurite glass fibers are designed and fabricated.The 2.8 m long Ce³⁺/Er³⁺co-doped fluorotellurite glass fiber is used as gain medium,and the Raman fiber laser with working wavelength of 1480nm is used as pump source to build a broadband Ce³⁺/Er³⁺co-doped fiber amplifier.When the pump power is 500 m W and the signal power is 0 d Bm,a broadband optical amplifier with a gain of 18 d B and a wavelength range of 1559?1620 nm is obtained.Compared with the single Er³⁺-doped tellurite glass fiber amplifier,its working bandwidth extends to 3 nm.4.Ho³⁺-doped fluorotellurite glass fiber was prepared and used as a gain medium to build the laser.For the first time,a ten watt?2.1?m laser output was achieved in the Ho³⁺-doped fluorotellurite glass fiber laser.In the experiment,a 30 cm long Ho³⁺-doped fluorotellurite glass fiber was used as the gain medium.The fiber laser was built by using a laser with a wavelength of 1980 nm as the pump source.When the pump power is 10.56 W,the output of?2.1?m laser with a maximum unsaturated output power of 8.08 W is obtained,and the corresponding slope efficiency is about77.21%.The above results indicate that Ho³⁺-doped fluorotellurite glass fiber can be used to develop high efficiency?2.1 m laser and broadband amplifier.