A hybrid optimal algorithm, named the SAA-PA in brief, based on the simulated annealing algorithm （SAA） and the Powell algorithm （PA） is proposed. The proposed algorithm puts the random search strategy of the SAA ...A hybrid optimal algorithm, named the SAA-PA in brief, based on the simulated annealing algorithm （SAA） and the Powell algorithm （PA） is proposed. The proposed algorithm puts the random search strategy of the SAA into the PA, which can prevent optimizing courses from trapping in local optima. The SAA-PA can effectively solve multimodal optimization in the distributed multi-pump Raman amplifier （DMRA）. Optimal results show that, under the conditions of the on-off gain of 10 dB, the gain bandwidth of larger than 80 nm and the fiber length of 80 km, the gain ripple of less than 1.25 dB can be designed from the DMRA with only four backward pumps after the optimization of the proposed SAA-PA. Compared with the pure SAA, the SAA-PA can attain a lower gain ripple with the same number of pumps. Also, the relationship between the optimal signal bandwidth and the number of pumps can be simulated numerically with the SAA-PA.展开更多
A novel technique to suppress stimulated Raman scattering in a high power narrow-band fiber amplifier is reported. By seeding with a comSination of a broadband amplified spontaneous emission seed and a narrowband mast...A novel technique to suppress stimulated Raman scattering in a high power narrow-band fiber amplifier is reported. By seeding with a comSination of a broadband amplified spontaneous emission seed and a narrowband master oscillator seed, the Raman Stokes components can be reduced about 16dB at a total output power of i kW. Ratnan suppression results are depicted in a different wavelengths seeding case and the same wavelength seeding ease, respectively, with different seed power ratios.展开更多
The amplification effect on stimulated Brillouin scattering （SBS） and Rayleigh scattering in the backward pumped G652 fibers Raman amplifier have been researched. The signal source is a tunable narrow spectral bandw...The amplification effect on stimulated Brillouin scattering （SBS） and Rayleigh scattering in the backward pumped G652 fibers Raman amplifier have been researched. The signal source is a tunable narrow spectral bandwidth （〈10 MHz） ECL laser and is pumped by the tunable power 1427.2 nm fiber Raman laser. The Rayleigh scattering lines are amplified by fiber Raman amplifier, and Stokes stimulated Brillouin scattering lines are amplified by fiber Raman amplifier and fiber Brillouin amplifier. The SBS lines total gain is a production of the gain of Raman and the gain of Brillouin amplifier. In experiment, the gain of SBS is about 42 dB and the saturation gain of 25 Ion G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.展开更多
For distributed fiber Raman amplifiers（DFRAs）, stimulated Brillouin scattering（SBS） can deplete the pump once occurring and consequently generate gain saturation. On the basis of such a theory, theoretical gain sa...For distributed fiber Raman amplifiers（DFRAs）, stimulated Brillouin scattering（SBS） can deplete the pump once occurring and consequently generate gain saturation. On the basis of such a theory, theoretical gain saturation powers in DFRAs with various pump schemes are obtained by calculating SBS thresholds in them, and the experimental results show that they are in excellent agreement with the calculation results. The saturation power of the DFRA with a 300 m W forward pump is as low as 0 d Bm, which needs to be enhanced by phase modulation, and the effect is quantitatively studied. A simple model taking both modulation frequency and index into consideration is presented by introducing a correction factor to evaluate the effect of phase modulation on the enhancement of saturation power. Experimentally, it is shown that such a correction factor decreases as the modulation frequency increases and approaches zero when the modulation frequency becomes high enough. In particular, a phase modulation with a modulation frequency of 100 MHz and a modulation index of 1.380 can enhance the saturation power by 4.44 d B, and the correction factor is 0.25 d B, in which the modulation frequency is high enough. Additionally, the factor is 1.767 d B for the modulation frequency of 25 MHz. On this basis,phase modulations with various indexes and a fixed frequency of 25 MHz are adopted to verify the modified model, and the results are positive. To obtain the highest gain saturation power, the model is referable. The research results provide a guide for the design of practical DFRAs.展开更多
Stimulated Raman scattering in a double cladding optical fiber is studied with a continuous wave laser used as a pump source. Under various launch conditions, pump modes are differently excited. Considering the mode c...Stimulated Raman scattering in a double cladding optical fiber is studied with a continuous wave laser used as a pump source. Under various launch conditions, pump modes are differently excited. Considering the mode coupling effect among the pump modes, the evolution of the power in the Stokes modes is studied. The results show that the scattered waves （the Stokes waves） in the fiber core with 9%tm diameter and 0.14 NA could propagate predominantly in the fundamental mode of the fiber by carefully adjusting the pump light launching conditions.展开更多
The double Rayleigh backscatter （DRB） effect in long distance CATV systems using fiber Raman amplifiers （FRAs） is investigated theoretically in the paper. As a comparison, performance of a system with erbium doped...The double Rayleigh backscatter （DRB） effect in long distance CATV systems using fiber Raman amplifiers （FRAs） is investigated theoretically in the paper. As a comparison, performance of a system with erbium doped fiber amplifier （EDFA） is also evaluated. According to the simulation results, it is found that, in case of FRA, the increase of carrier-to-noise ratio （CNR） due to the DRB effect will not impair the performance more than that using EDFA.展开更多
In this paper, a new theoretical model for Rayleigh backscattering (RB) analysis of fiber Raman amplifiers is proposed. The model includes all the interactions among the pumps, signals, and all orders of RB. The resul...In this paper, a new theoretical model for Rayleigh backscattering (RB) analysis of fiber Raman amplifiers is proposed. The model includes all the interactions among the pumps, signals, and all orders of RB. The results show that the higher order RB has a negligible influence on the performance of the amplifier. The co-propagating and counterpropagating RB power of the signal grow quadratically with the net-gain of the amplifier. The signal to double Rayleigh backscattering noise ratio (OSNRDRB ) of backward-pumped FRAs is better than that of the forward-pumped ones at high net-gain level (＞ 13 dB), while at low net-gain level the OSNRDrb of the forward-pumped FRAs is slightly better than that of the backward-pumped ones.展开更多
The Stokes spectrum in the stimulated Raman scattering (SRS) is very complicated. In this article, we use both Gaussian and Lorentz approximation to investigate the gain properties of multi pumping broadband Raman amp...The Stokes spectrum in the stimulated Raman scattering (SRS) is very complicated. In this article, we use both Gaussian and Lorentz approximation to investigate the gain properties of multi pumping broadband Raman amplifier, and present some schemes for flattening the gain. All the results show that the flatness of the gain spectrum is closely related to the pumping frequency grid. By researching the gain properties of Raman amplifiers of such ITU-T fibers as G.652, G.653, G.655 and large effective area non zero dispersion flattening fiber, we find that the Raman gain is associated with the fiber type and its transmission characteristics, especially it decreases with the increase of the effective core area.展开更多
We present an experimental study on low-threshold broadband spectrum generation mainly due to the amplirfication of the cascaded stimulated Raman scattering （SRS） effect in a four-stage fiber master oscillator power...We present an experimental study on low-threshold broadband spectrum generation mainly due to the amplirfication of the cascaded stimulated Raman scattering （SRS） effect in a four-stage fiber master oscillator power amplifier system. The cascaded SRS is achieved by using a long passive fiber pumped by a pulsed fiber laser cen： tered at wavelength 1064 nm. The amplified spontaneous emission during the amplification process is efficiently suppressed by cutting the length of the passive fiber and by using a double-clad ytterbium-doped fiber amplifier. The generated broadband spectrum spans from 960nm to 1700nm with maximum average output 13.6 W and average spectral power density approximately 17. 7 mW/nm.展开更多
We investigate a silica-based thulium-doped fibre amplifier, which is a promising candidate for an amplifying device in the S band, in detail using a single wavelength upconversion pumping scheme centred at 1064nm. Ou...We investigate a silica-based thulium-doped fibre amplifier, which is a promising candidate for an amplifying device in the S band, in detail using a single wavelength upconversion pumping scheme centred at 1064nm. Our experimental results show that in terms of gain and noise figure, the bi-directional pumping scheme is the best one in the three pumping schemes, named forward, backward and hi-directional pumping schemes. The amplifier has a gain not only in the S band, but also in the C band, even in the L band. The gain is above 3dB from 1525nm to 1580nm with a peak of 7.SdB.展开更多
Impact of amplified spontaneous emission(ASE)noise on the stimulated Raman scattering(SRS)threshold of highpower fiber amplifiers is demonstrated numerically through a spectral evolution approach.The simulation result...Impact of amplified spontaneous emission(ASE)noise on the stimulated Raman scattering(SRS)threshold of highpower fiber amplifiers is demonstrated numerically through a spectral evolution approach.The simulation results confirm that ASE noise in the Raman wavelength band could reduce the SRS threshold of high-power fiber amplifiers significantly.As for ASE noise originated the main amplifier,it becomes stronger and reduces the SRS threshold at shorter operation wavelength below 1052 nm.As for ASE noise originated from the seed laser,it reduces the SRS threshold at different operation wavelength under the condition that the Raman ratio is over-90 dB in the seed laser.The theoretical method and results in this work could provide a well reference to extend the operation wavelength of high-power fiber lasers.展开更多
This paper describe a numerical simulation method for the interaction between laser pulses and low density plasmas based on hydrodynamic approximation. We investigate Backward Raman Amplifying （BRA） experiments and ...This paper describe a numerical simulation method for the interaction between laser pulses and low density plasmas based on hydrodynamic approximation. We investigate Backward Raman Amplifying （BRA） experiments and their variants. The numerical results are in good agreement with experiments.展开更多
The competition between the stimulated resonance Raman scattering （SRRS） of Rhodamine B （RhB） and the stimulated Raman scattering （SRS） of ethanol （C2H50H） is observed at the RhB in C2H5OH solution. For differ...The competition between the stimulated resonance Raman scattering （SRRS） of Rhodamine B （RhB） and the stimulated Raman scattering （SRS） of ethanol （C2H50H） is observed at the RhB in C2H5OH solution. For different concentrations of the solution, the peak wavelengths of the SRRS, the amplified spontaneous emission （ASE）, the fluorescence and the absorption of RhB are different. The SRRS of RhB and the SRS of C2H50H are simultaneously generated when the concentration of the solution is 10-5 mol/L and the energy of the excitation laser is 20.4 mJ. Otherwise, only either the SRRS of RhB or the SRS of C2H5OH is generated. The SRRS can be amplified by the ASE gain when the SRRS is near the peak of the ASE, and the peak wavelength of the SRRS coincides with the wavelength of the maximal intensity ASE.展开更多
基金The Start-Up Research Foundation of Nanjing Uni-versity of Information Science and Technology (No.QD60)
文摘A hybrid optimal algorithm, named the SAA-PA in brief, based on the simulated annealing algorithm （SAA） and the Powell algorithm （PA） is proposed. The proposed algorithm puts the random search strategy of the SAA into the PA, which can prevent optimizing courses from trapping in local optima. The SAA-PA can effectively solve multimodal optimization in the distributed multi-pump Raman amplifier （DMRA）. Optimal results show that, under the conditions of the on-off gain of 10 dB, the gain bandwidth of larger than 80 nm and the fiber length of 80 km, the gain ripple of less than 1.25 dB can be designed from the DMRA with only four backward pumps after the optimization of the proposed SAA-PA. Compared with the pure SAA, the SAA-PA can attain a lower gain ripple with the same number of pumps. Also, the relationship between the optimal signal bandwidth and the number of pumps can be simulated numerically with the SAA-PA.
基金Supported by the National High Technology Research and Development Program of China under Grant No 2014AA041901the NSAF Foundation of National Natural Science Foundation of China under Grant No U1330134the National Natural Science Foundation of China under Grant No 61308024
文摘A novel technique to suppress stimulated Raman scattering in a high power narrow-band fiber amplifier is reported. By seeding with a comSination of a broadband amplified spontaneous emission seed and a narrowband master oscillator seed, the Raman Stokes components can be reduced about 16dB at a total output power of i kW. Ratnan suppression results are depicted in a different wavelengths seeding case and the same wavelength seeding ease, respectively, with different seed power ratios.
基金supported by the National Natural Science Foundation under Grant No. 60608009Zhejiang Science Foundation under Grant No. Y107091.
文摘The amplification effect on stimulated Brillouin scattering （SBS） and Rayleigh scattering in the backward pumped G652 fibers Raman amplifier have been researched. The signal source is a tunable narrow spectral bandwidth （〈10 MHz） ECL laser and is pumped by the tunable power 1427.2 nm fiber Raman laser. The Rayleigh scattering lines are amplified by fiber Raman amplifier, and Stokes stimulated Brillouin scattering lines are amplified by fiber Raman amplifier and fiber Brillouin amplifier. The SBS lines total gain is a production of the gain of Raman and the gain of Brillouin amplifier. In experiment, the gain of SBS is about 42 dB and the saturation gain of 25 Ion G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.
基金Project supported by the National Natural Science Foundation of China(Grant No.61177073)the Major Application Basic Research Project of National University of Defense Technology,China(Grant No.ZDYYJCYJ20140701)
文摘For distributed fiber Raman amplifiers（DFRAs）, stimulated Brillouin scattering（SBS） can deplete the pump once occurring and consequently generate gain saturation. On the basis of such a theory, theoretical gain saturation powers in DFRAs with various pump schemes are obtained by calculating SBS thresholds in them, and the experimental results show that they are in excellent agreement with the calculation results. The saturation power of the DFRA with a 300 m W forward pump is as low as 0 d Bm, which needs to be enhanced by phase modulation, and the effect is quantitatively studied. A simple model taking both modulation frequency and index into consideration is presented by introducing a correction factor to evaluate the effect of phase modulation on the enhancement of saturation power. Experimentally, it is shown that such a correction factor decreases as the modulation frequency increases and approaches zero when the modulation frequency becomes high enough. In particular, a phase modulation with a modulation frequency of 100 MHz and a modulation index of 1.380 can enhance the saturation power by 4.44 d B, and the correction factor is 0.25 d B, in which the modulation frequency is high enough. Additionally, the factor is 1.767 d B for the modulation frequency of 25 MHz. On this basis,phase modulations with various indexes and a fixed frequency of 25 MHz are adopted to verify the modified model, and the results are positive. To obtain the highest gain saturation power, the model is referable. The research results provide a guide for the design of practical DFRAs.
文摘Stimulated Raman scattering in a double cladding optical fiber is studied with a continuous wave laser used as a pump source. Under various launch conditions, pump modes are differently excited. Considering the mode coupling effect among the pump modes, the evolution of the power in the Stokes modes is studied. The results show that the scattered waves （the Stokes waves） in the fiber core with 9%tm diameter and 0.14 NA could propagate predominantly in the fundamental mode of the fiber by carefully adjusting the pump light launching conditions.
基金Project supported by the National Natural Science Foundation of China (Grant No.61077018)the Shanghai Leading Academic Discipline Project (Grant Nos.S30108, SKLFSO200901)
文摘The double Rayleigh backscatter （DRB） effect in long distance CATV systems using fiber Raman amplifiers （FRAs） is investigated theoretically in the paper. As a comparison, performance of a system with erbium doped fiber amplifier （EDFA） is also evaluated. According to the simulation results, it is found that, in case of FRA, the increase of carrier-to-noise ratio （CNR） due to the DRB effect will not impair the performance more than that using EDFA.
文摘In this paper, a new theoretical model for Rayleigh backscattering (RB) analysis of fiber Raman amplifiers is proposed. The model includes all the interactions among the pumps, signals, and all orders of RB. The results show that the higher order RB has a negligible influence on the performance of the amplifier. The co-propagating and counterpropagating RB power of the signal grow quadratically with the net-gain of the amplifier. The signal to double Rayleigh backscattering noise ratio (OSNRDRB ) of backward-pumped FRAs is better than that of the forward-pumped ones at high net-gain level (＞ 13 dB), while at low net-gain level the OSNRDrb of the forward-pumped FRAs is slightly better than that of the backward-pumped ones.
文摘The Stokes spectrum in the stimulated Raman scattering (SRS) is very complicated. In this article, we use both Gaussian and Lorentz approximation to investigate the gain properties of multi pumping broadband Raman amplifier, and present some schemes for flattening the gain. All the results show that the flatness of the gain spectrum is closely related to the pumping frequency grid. By researching the gain properties of Raman amplifiers of such ITU-T fibers as G.652, G.653, G.655 and large effective area non zero dispersion flattening fiber, we find that the Raman gain is associated with the fiber type and its transmission characteristics, especially it decreases with the increase of the effective core area.
基金Supported by the National Natural Science Foundation of China under Grant No 11404404the Outstanding Youth Fund Project of Hunan Provincethe Fund of Innovation of National University of Defense Technology under Grant No B120701
文摘We present an experimental study on low-threshold broadband spectrum generation mainly due to the amplirfication of the cascaded stimulated Raman scattering （SRS） effect in a four-stage fiber master oscillator power amplifier system. The cascaded SRS is achieved by using a long passive fiber pumped by a pulsed fiber laser cen： tered at wavelength 1064 nm. The amplified spontaneous emission during the amplification process is efficiently suppressed by cutting the length of the passive fiber and by using a double-clad ytterbium-doped fiber amplifier. The generated broadband spectrum spans from 960nm to 1700nm with maximum average output 13.6 W and average spectral power density approximately 17. 7 mW/nm.
文摘We investigate a silica-based thulium-doped fibre amplifier, which is a promising candidate for an amplifying device in the S band, in detail using a single wavelength upconversion pumping scheme centred at 1064nm. Our experimental results show that in terms of gain and noise figure, the bi-directional pumping scheme is the best one in the three pumping schemes, named forward, backward and hi-directional pumping schemes. The amplifier has a gain not only in the S band, but also in the C band, even in the L band. The gain is above 3dB from 1525nm to 1580nm with a peak of 7.SdB.
基金the National Natural Science Foundation of China(Grant Nos.62005313 and 62061136013).
文摘Impact of amplified spontaneous emission(ASE)noise on the stimulated Raman scattering(SRS)threshold of highpower fiber amplifiers is demonstrated numerically through a spectral evolution approach.The simulation results confirm that ASE noise in the Raman wavelength band could reduce the SRS threshold of high-power fiber amplifiers significantly.As for ASE noise originated the main amplifier,it becomes stronger and reduces the SRS threshold at shorter operation wavelength below 1052 nm.As for ASE noise originated from the seed laser,it reduces the SRS threshold at different operation wavelength under the condition that the Raman ratio is over-90 dB in the seed laser.The theoretical method and results in this work could provide a well reference to extend the operation wavelength of high-power fiber lasers.
文摘This paper describe a numerical simulation method for the interaction between laser pulses and low density plasmas based on hydrodynamic approximation. We investigate Backward Raman Amplifying （BRA） experiments and their variants. The numerical results are in good agreement with experiments.
基金Project supported by the National Natural Science Foundation of China (Gant No. 10974067)the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 11104106)+1 种基金the Science and Technology Planning Project of Jilin Province, China (Gant Nos. 20101508 201101037 and 201115033)China Postdoctoral Science Foundation (Grant No. 20100481062)
文摘The competition between the stimulated resonance Raman scattering （SRRS） of Rhodamine B （RhB） and the stimulated Raman scattering （SRS） of ethanol （C2H50H） is observed at the RhB in C2H5OH solution. For different concentrations of the solution, the peak wavelengths of the SRRS, the amplified spontaneous emission （ASE）, the fluorescence and the absorption of RhB are different. The SRRS of RhB and the SRS of C2H50H are simultaneously generated when the concentration of the solution is 10-5 mol/L and the energy of the excitation laser is 20.4 mJ. Otherwise, only either the SRRS of RhB or the SRS of C2H5OH is generated. The SRRS can be amplified by the ASE gain when the SRRS is near the peak of the ASE, and the peak wavelength of the SRRS coincides with the wavelength of the maximal intensity ASE.
