scholarly journals Quantitative characteristic of phase signal with changed pulse in the coherent PHI-OTDR system

2020 ◽  
Author(s):  
Zhen Zhong ◽  
Xuping Zhang
Keyword(s):  
Pulse Width ◽  
Peak Power ◽  
Optical Pulse ◽  
Quantitative Characteristic ◽  
Maximum Amplitude ◽  
Observation Point ◽  
Electrical Signal ◽  
Rayleigh Backscattering ◽  
Phase Signal ◽  
Measured Phase

In the coherent PHI-OTDR system, the phase signal is retrieved based on the reference point and the observation point which are off and closer to the two sides of step of the phase change. In the experiment, the optical pulse with the changed peak power, width or shape is injected into the fiber for interrogating the change of the quantitative characteristic of the measured phase signal. When the pulse width is fixed at 200 ns and its peak power is adjusted from 14 dBm to -23 dBm, the amplitude is slightly increased from 17.3575 rad to 17.4411 rad as long as the Rayleigh backscattering signal can be found in the electrical signal. Changing the pulse width from 260 ns to 80 ns when the peak power is fixed at 14 dBm, the maximum amplitude and the minimum amplitude of the measured phase signal are 17.4625 rad to 17.4509 rad, respectively. When the arbitrary shape of the optical pulse generated from the MZI structure with a changed delay fiber from 3 m to 6 m, the amplitude varies from 17.4558 rad to 17.4819 rad. For every measurement, the change of frequency is also small. And the small value of standard deviation supports the accuracy of the measurement. All the measurements show that the changed pulse nearly has no impact on the quantitative characteristic of the measured phase signal in the coherent PHI-OTDR system. Moreover, we also find that the phase signal of external event can be correctly extracted as long as the Rayleigh backscattering signal can be detected.<br>

scholarly journals Quantitative characteristic of phase signal with changed pulse in the coherent PHI-OTDR system

2020 ◽  
Author(s):  
Zhen Zhong ◽  
Xuping Zhang
Keyword(s):  
Pulse Width ◽  
Peak Power ◽  
Optical Pulse ◽  
Quantitative Characteristic ◽  
Maximum Amplitude ◽  
Observation Point ◽  
Electrical Signal ◽  
Rayleigh Backscattering ◽  
Phase Signal ◽  
Measured Phase

In the coherent PHI-OTDR system, the phase signal is retrieved based on the reference point and the observation point which are off and closer to the two sides of step of the phase change. In the experiment, the optical pulse with the changed peak power, width or shape is injected into the fiber for interrogating the change of the quantitative characteristic of the measured phase signal. When the pulse width is fixed at 200 ns and its peak power is adjusted from 14 dBm to -23 dBm, the amplitude is slightly increased from 17.3575 rad to 17.4411 rad as long as the Rayleigh backscattering signal can be found in the electrical signal. Changing the pulse width from 260 ns to 80 ns when the peak power is fixed at 14 dBm, the maximum amplitude and the minimum amplitude of the measured phase signal are 17.4625 rad to 17.4509 rad, respectively. When the arbitrary shape of the optical pulse generated from the MZI structure with a changed delay fiber from 3 m to 6 m, the amplitude varies from 17.4558 rad to 17.4819 rad. For every measurement, the change of frequency is also small. And the small value of standard deviation supports the accuracy of the measurement. All the measurements show that the changed pulse nearly has no impact on the quantitative characteristic of the measured phase signal in the coherent PHI-OTDR system. Moreover, we also find that the phase signal of external event can be correctly extracted as long as the Rayleigh backscattering signal can be detected.<br>

Study on Recast Phenomenon in Processing of Micro-Hole with Millisecond Laser

2012 ◽  
Vol 459 ◽  
pp. 315-319 ◽  
Author(s):  
Ke Dian Wang ◽  
Wen Qiang Duan ◽  
Xue Song Mei ◽  
Wen Jun Wang
Keyword(s):  
Stainless Steel ◽  
Titanium Alloy ◽  
Pulse Width ◽  
Peak Power ◽  
Recast Layer ◽  
Hole Depth ◽  
Maximum Peak ◽  
Blind Hole ◽  
Micro Hole ◽  
Millisecond Laser

The experiments of micro-hole ablation are conducted firstly on titanium alloy Ti-6Al-4V with Nd: YAG millisecond laser. A significant factor which affects the depth of blind hole is found: the depth of recast material. This paper closely examines the regularity of recast depth varying with laser parameters, discovering that the ratio of recast depth to the entire hole depth decreases as pulse width decreases, and increases as peak power decreases. Verification experiment is conducted on stainless steel 1Cr13, eventually micro-hole with very thin recast layer is drilled when the maximum peak power and the minimum pulse width of the present millisecond laser are used.

Stable continuous-wave mode-locked laser from a 1645 nm Er:YAG ceramic oscillator

2022 ◽  
Author(s):  
Yangyu Liu ◽  
Xue Cao ◽  
AnHua Xian ◽  
Guangmiao Liu ◽  
Wei zhou ◽  
...  
Keyword(s):  
Solid State ◽  
Pulse Width ◽  
Peak Power ◽  
Continuous Wave ◽  
Modulation Depth ◽  
Average Power ◽  
Mode Locking ◽  
Wave Mode ◽  
Semiconductor Saturable Absorber ◽  
Continuous Wave Mode

Abstract We demonstrate stable continuous-wave mode-locking (CWML) pulses around 1645nm by employing the home-made Er:YAG ceramic. By using a fiber laser and semiconductor saturable absorber mirror (SESAM) with modulation depth of 1.2%, we get ML pulses with the output average power up to 815 mW, the pulse width shortened as ~4 ps, and the peak power of 1.8 kW. With the SESAM of modulation depth of 2.4%, the second-order harmonic ML pulses were also obtained. As far as we know, this is the first report of CWML from Er3+-doped ceramics and also the shortest pulse duration in Er3+-doped solid-state oscillators.

Study on Laser Welding of Phone Nuts

2013 ◽  
Vol 815 ◽  
pp. 778-781
Author(s):  
Xiao Hong Wu
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Laser Pulse ◽  
Laser Welding ◽  
Pulse Energy ◽  
Pulse Width ◽  
Peak Power ◽  
Laser Pulse Energy ◽  
304 Stainless Steel ◽  
Power Pulse

Used YAG pulse laser to weld 304 stainless steel nuts, studied about the parameters such as peak power, pulse width, defocus distance impacting on the performance of the joints welded by laser. The studies showed that the tensile strength and torque of the nuts increased as the peak power and the pulse width increased.Burn through in welding easy occur when laser pulse energy is too big, pulse width is too wide or defocus distance is too low.

scholarly journals Graphene slurry based passive Q-switcher in erbium doped fiber laser

2019 ◽  
Vol 8 (4) ◽  
Author(s):  
Siti Nur Fatin Zuikafly ◽  
Nor Farhah Razak ◽  
Rizuan Mohd Rosnan ◽  
Sulaiman Wadi Harun ◽  
Fauzan Ahmad
Keyword(s):  
Pump Power ◽  
Fiber Laser ◽  
Pulse Width ◽  
Peak Power ◽  
Signal To Noise Ratio ◽  
Pulsed Laser ◽  
Laser Cavity ◽  
Signal To Noise ◽  
Maximum Pulse Energy ◽  
Erbium Doped

In this work, a Graphene slurry based passive Q-switcher fabricated from Graphene-Polylactic acid (PLA) filament which is used for 3D printing. To produce the Graphene slurry, the diameter of the filament was reduced and Tetrahydrofuran (THF) was used to dissolve the PLA. The Graphene-THF suspension was drop cast to the end of a fiber ferrule and the THF then evaporated to develop Graphene slurry based SA which is integrated in fiber laser cavity. At threshold input pump power of 30.45 mW, a Q-switched Erbium-doped fiber laser (EDFL) can be observed with the wavelength centered at 1531.01 nm and this remained stable up to a pump power of 179.5 mW. As the pump power was increased gradually, an increase in the repetition rates was recorded from 42 kHz to 125 kHz, while the pulse width was reduced to 2.58 μs from 6.74 μs. The Q-switched laser yielded a maximum pulse energy and peak power of 11.68 nJ and 4.16 mW, respectively. The proposed Graphene slurry based saturable absorber also produced a signal-to-noise ratio of 44 dB indicating a stable Q-switched pulsed laser.

scholarly journals All-fiber passively Q-switched ytterbium doped double-clad fiber lasers: experiment And modeling.

2021 ◽  
Author(s):  
Yi Lu
Keyword(s):  
Pulse Energy ◽  
Traveling Wave ◽  
Pulse Width ◽  
Fiber Lasers ◽  
Peak Power ◽  
Wave Model ◽  
Core Size ◽  
The Core ◽  
Q Switching ◽  
Output Characteristics

All-fiber passively Q-switched lasers were demonstrated using ytterbium-doped double cladding fiber (YDF) as an active medium. The laser was pumped by three 25W, 975nm fiber coupled diodes and Q-switching was initiated when the amplified spontaneous emission generated in the core of the gain fiber bleached the saturable absorber (SA). A piece of samarium-doped fiber was used as SA in first configuration and pulses with 68μJ pulse energy and 210ns pulse width were obtained. In second configuration, a piece of ytterbium-doped fiber with much smaller core size was used as SA to produce pulse energy of 86μJ. The last configuration incorporated a 9m-long YDF as gain fiber. The far end from pump was acting as SA in this case and pulses with 82μJ pulse energy and 148ns pulse width were observed. The peak power was estimated at 554W. Traveling wave model was implemented to numerically simulate the output characteristics versus pump power.

Parametric Analysis of Laser Beam Percussion Drilling for Thin Titanium Alloy Sheet Using Yb: Yag Fiber Laser

2021 ◽  
pp. 1-24
Author(s):  
Mohit Singh ◽  
Sanjay Mishra ◽  
Vinod Yadava ◽  
J. Ramkumar
Keyword(s):  
Laser Beam ◽  
Fiber Laser ◽  
Pulse Width ◽  
Peak Power ◽  
Laser Pulses ◽  
Pulse Frequency ◽  
Alloy Sheet ◽  
Power Pulse ◽  
The Individual ◽  
Percussion Drilling

Laser beam percussion drilling (LBPD) can create high density holes in aerospace materials with the repeated application of laser pulses at a single spot. In this study, one-parameter-at-a-time approach has been used to investigate the individual effect of peak power, pulse width and pulse frequency on geometrical accuracy and metallurgical distortion during LBPD of 0.85[Formula: see text]mm thick Ti–6Al–4V sheet using 200[Formula: see text]W Yb:YAG fiber laser. It has been found that the output parameters behave differently at the higher and lower values of a particular input process. The increase of pulse width from 1 to 1.50[Formula: see text]ms increases hole taper by 20% whereas the same corresponding change from 1.50 to 2.00[Formula: see text]ms reduces the taper by 20%. The increase of pulse frequency from 10 to 50[Formula: see text]Hz reduces hole circularity by 40% but the same proportionate change from 50 to 90[Formula: see text]Hz reduces circularity by 79%. Increase of peak power from 1.70 to 2.0[Formula: see text]kW increases hole taper by 8% but the corresponding increase from 2 to 2.30[Formula: see text]kW is 143%.

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