Investigation Of Novel Special Optical Fibers And Their Applications

With the rapid development of large capacity,high speed and long distance optical fiber communication,the novel special optical fibers and their devices are attracting more and more attention.With the development of Internet of Things(IoT)technology,users' demand for access bandwidth is growing.The traditional ADSL broadband access has been unable to meet users' requirements.The fiber to the home(FTTH)has been becoming the final form for telecom operators to solve the "Last One Kilometer",which requires high bending loss performance of the fiber.Nowadays,the 400G optical network is gradually deployed and one of the technology requirements is the light source.The multiwavelength optical fiber lasers have become a research hotspot due to the advantages of compact structure and low cost.Works in this thesis are supported by projects of the laboratory,including the National 973 Project,the National 863 Project,and National Natural Science Foundation of China.The main research achievements are as follows:(1)The various steps in the fiber manufacturing process are discussed separately,and the possible problems are analyzed.Two kinds of novel optical fibers:multicladding large mode area single mode fiber(MC-LMA-SMF)and Er-doped flat optical fiber(ED-FOF),fabricated by using MCVD method,are analyzed.For the fabricated MC-LMA-SMF,at wavelength 1550nm,the mode field area is 332?m2 and the cutoff wavelength is 1350nm,which guarantees the single-mode transmission.We proposed the ED-FOF initiatively and stated the manufacturing process which provides a guiding significance for the fabrication of optical fiber with special geometrical core.(2)The bending loss of the bending insensitive fiber is deduced by the perturbation method.We measured the bending loss of commercial bending insensitive fiber and compared with the calculated results and showed good agreement.The parameters of large mode area bending insensitive optical fiber with parabolic core are optimized.When the bending radius is 5mm under the optimized parameters,the bending loss can be as low as 0.052dB/turn at 1550nm and the mode area is 260?m2.The bending performance of trench-assisted bending insensitive fiber(TA-BIF)is optimized by the particle swarm optimization method.When the bending radius is 3mm,the bending loss can be as low as 0.044dB/turn at 1550nm,and the mode field diameter can reach 8.9?m when the cutoff wavelength is 1260nm.A kind of TA-BIF is fabricated.As for this TC-BIF,the cutoff wavelength is 1263nm.At 1550nm,the mode field diameter,dispersion,bending loss at bending radius 5mm are 10.7?m,17.69 ps/nm-km,0.05dB/turn,respectively.The results show the performance of fabricated TA-BIF agrees with recommendation of ITU-T.The bending loss of TA-BIF can be reduced by 1?3 orders of magnitude in the same condition as the commercial Corning SMF,G657A,and G657B and the comprehensive performance are completely dominant.(3)A tunable multiwavelength fiber laser based on Er-doped twin-core fiber(ED-TCF)and nonlinear polarization rotation(NPR)effect is proposed.1-4 wavelength oscillations can be achieved at room temperature.The number and position of wavelength can be adjusted by adjusting the polarization controllers.The interval between adjacent wavelengths is 1.1 nm,the signal-to-noise ratio is higher than 43dB,the 3-dB bandwidth is less than 0.06nm,and the peak power difference of each wavelength is within 2dB.The proposed laser shows good stability in 30 minutes with wavelength shift less than 0.01nm and peak power fluctuation less than 5dB(4)A multiwavelength fiber laser based on Er-doped twin-core fiber(ED-TCF)and nonlinear optical loop mirror(NOLM)is proposed.Stable output of 8 wavelengths can be achieved at room temperature.The adjacent wavelength interval is 1.5nm,the signal-to-noise ratio of each wavelength is higher than 45dB,the 3-dB bandwidth is 0.09nm,and the difference of peak power between wavelengths is within 2dB.The output laser shows good stability in 30 minutes of the test time.The peak power fluctuations of all wavelengths are less than 0.4dB and the wavelengths shift are within 0.015nm.