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Experimental Study On Ultra-narrow Linewidth Dual-wavelength Fiber Lasers

Posted on:2017-07-15Degree:MasterType:Thesis
Country:ChinaCandidate:B M ZhangFull Text:PDF
GTID:2348330503465571Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Dual-wavelength fiber lasers with ultra-narrow linewidth find wide applications in high-speed optical communications, fiber optic sensors, high resolution measurements and medical instruments and microwave or terahertz generation systems. In the field of optical communications, ultra-narrow linewidth multi-wavelength fiber laser can greatly improve the communication capacity, communication quality and communication distance, while reducing the cost of the communication system; in multi-parameters light sensing, multi-wavelength optical fiber laser with ultra-narrow linewidth can effectively improve the precision and accuracy, while avoiding the high cost and instability introduced by multi light source; and particularly, a narrow linewidth dual-wavelength SLM fiber laser is a good candidate for highly pure microwave or terahertz source since narrower linewidth leads to lower high-frequency phase noise for the beating signal. Based on the linewidth compression mechanism due to Rayleigh backscattering, theoretical study and experiments on dual-wavelength fiber lasers with ultra-narrow linewidth are taken done in this thesis. The main contents of this thesis are as follows:(1) Several techniques for obtaining ultra-narrow linewidth fiber lasers and dual-wavelength fiber lasers have been theoretically studied, and according to the principle analysis and comparison, the laser linewidth compression mechanism based on Rayleigh backscattering is the only technique that can compress laser linewidth effectively, as the Rayleigh bandwidth is relatively narrow, the pump bandwidth in the cavity could become narrower and narrower after several million times of resonance, and finally an ultra-narrow linewidth laser is formed and output. Due to the none-wavelength-selectivity characteristic of Rayleigh scattering, it is very suitable for compressing multi-wavelength laser linewidth in theory.(2) Based on the linewidth compression mechanism due to Rayleigh backscattering, a typical ring resonant cavity cooperated with two fiber Bragg gratings centered at 1550 nm and 1530 nm is adopted, by carefully adjusting the variable optical attenuator and polarization controller to make a good balance between the loss and gain of the two wavelength lasers, a stable dual-wavelength laser output is achieved, and the laser linewidth is compressed by the Rayleigh backscattering in 110 m micro-tapered fiber with high stimulated Brillouin threshold. The output laser linewidth is detected by self-heterodyne method, ultra-narrow linewidth of 670 Hz and 650 Hz are obtained for 1530 nm laser and 1550 nm laser respectively when the pump power is 200 m W, with the SNR of 52 d B and 51 d B respectively, and the output laser shows good stability.(3) Comparative experiments to study the linewidth compression effect based on Rayleigh backscattering is conducted by removing the 110 m micro-tapered fiber, dual-wavelength laser with linewidth of 12.93 k Hz and 13.4 k Hz for 1530 nm laser and 1550 nm laser is obtained respectively, the experimental results show that the laser linewidth is suppressed from tens of k Hz to hundreds of Hertz successfully based on the Rayleigh backscattering compression mechanism, and the compression effect is indiscriminate for the two wavelength lasers, which indicates that there is no wavelength selectivity to compress laser linewidth based on Rayleigh backscattering between the two wavelength.(4) Tuning the center wavelength of the 1550 nm FBG by applying micro-strain while the 1530 nm FBG keeps unchanged, tunable wavelength laser output is obtained, the linewidth of the tunable wavelength laser keeps 700 Hz, and the wavelength can be tuned in a range of about 3nm. This experimental result further indicates that laser linewidth compression mechanism based on Rayleigh backscattering can be applied in multi-wavelength laser, and in this experiment, the laser wavelength is determined by the two FBGs, hence, the wavelength can be expanded from the ultraviolet to the far infrared by utilizing proper filters and gain medium. This method has great potential in the application of wide wavelength range linewidth compression from the ultraviolet to the far infrared.
Keywords/Search Tags:Dual-wavelength Fiber Lasers, Linewidth Compression, Rayleigh Scattering, Ultra-narrow Linewidth, Wavelength Tunable
PDF Full Text Request
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