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A new contact method to measure vibrations with a frequency range of about 30–110 Hz by a distributed Bragg reflector (DBR) fiber laser sensor, based on a beat frequency modulation, has been proposed. In order to demonstrate the plausibility for a DBR fiber sensor to detect vibrations lower than 110 Hz without any complex structures, it is encapsulated in a rectangular slice composed of an epoxy resin glue, with a Young’s modulus of about 2.9 GPa. In experiments, the packaged DBR fiber sensor is placed on a vibration platform to sense the vibration, with a commercial magnet-electrical vibration velocity transducer as a reference. Experimental results indicate that the single DBR fiber laser is able to measure the low-frequency vibration with a few tens of Hertz and several microns of amplitude, offering potential for a low-frequency vibration measurement. [ABSTRACT FROM AUTHOR]

A low-frequency vibration measurement based on a camera-projector system is proposed and verified by experiment at several hertz. A CCD camera gathered deformed fringes modulated by a vibrating trumpet at a constant sampling rate. Information on amplitude and frequency are contained in a series of observed images. The height value of each pixel point in the image can be restored by using Fourier transform profilometry. Connecting the height value of every sampling frame into a motion trajectory, the frequency and amplitude of the vibrating object can be obtained from the trajectory curve. The experiment restored the vibration process of a trumpet in half a cycle while the vibrating frequency was 3 Hz. Subsequently, the measurement of different frequencies and different amplitudes are comparatively studied. The results show that slight vibration at 35 µm and above can be detected by the system, which confirms the feasibility of the proposed system in the field of industrial vibration measurement. [ABSTRACT FROM AUTHOR]

The self Q-switched characteristic of the single longitudinal-mode distributed Bragg reflector (DBR) erbium-doped fiber laser (EDFL) with narrow linewidth pulse output is demonstrated without any extra saturable absorber or electro-optic and acoustic-optic modulator, and it is provided with a simpler structure and lower cost. The proposed pulse laser operates at approximately 1550.33 nm with a 20 dB bandwidth of 0.56 nm and signal-to-noise ratio of about 55 dB. By increasing the 980 nm pump power from 80–330 mW, the repetition rate of the output pulse increases from 73.53–147.1 kHz while the pulse width decreases from 1.4–0.2 µs, which shows the feature of the narrow linewidth ideally. The maximum pulse energy of 0.379 nJ and peak power of 1897.2 µW are generated with a repetition rate and pulse width of 147.1 kHz and 0.2 µs, respectively. The result shows that the self Q-switched pulse of the DBR EDFL is obviously dependent on the applied pump power and possesses the characteristic of the single longitudinal mode and the narrow linewidth, offering potential utilization in industrial processing and scientific research. [ABSTRACT FROM AUTHOR]