This type of sensor is manufactured by using the KF-FBT type fusion taper machine to uniformly pull the same single mode optical fiber. Double tapered section cascade type singles mode fiber. When the signal light passes through the concatenation fiber cone, the cladding mode is excited after passing through the first stage cone region. After a certain distance transmission, the second stage cone region interferes with the core mode. The change of the waveform is seen from the spectrometer. When the two cones are bent by 90, the article explores a double-cone-section cascading sensor that is easy to operate and easy to perform multi-point measurements from both theory and experiment. The spectral peak-to-valley contrast of the interference fringe is more obvious, and it can serve as a sensor head to test the ambient temperature. The sensor has a temperature sensitivity of 60 pm/°C.
In order to improve the measurement accuracy of the angle and signal processing speed of operation, this paper proposes a novel method of second harmonic measurement of multi-beam laser heterodyne for the angle, which based on the combination of Doppler effect and heterodyne technology, loaded the information of the angle to the frequency difference of second harmonic of the multi-beam laser heterodyne signal by frequency modulation of the oscillating mirror, which is in the light path. Heterodyne signal frequency can be obtained by fast Fourier transform, and can obtain values of the angle accurately after the multi-beam laser heterodyne signal demodulation. This novel method is used to simulate measurement for incident angle of standard mirror by Matlab, the obtained result shows that the relative measurement error of this method is just 0.5213%.
The gain flatness of an L-band erbium-doped fiber amplifier (EDFA) is still an open issue. We improve the conventional single-pass two-stage configuration by placing a fiber Bragg grating (FBG) with the center wavelength at 1529.4 nm. Then, a weak lasing resonance cavity is formed by this FBG and a fiber isolator, which is able to increase the pump conversion efficiency by reflecting the residual amplified spontaneous emission and compressing the raised gain around 1570 nm based on the gain-clamped effect. The experimental results show that by adopting the proposed scheme, the gain un-flatness of the L-band EDFA is controlled within ±0.4 dB in the range of 1570 to 1610 nm, and an ∼29 dB average gain is simultaneously maintained.
This paper proposes a novel method of multi-beam laser heterodyne measurement for Young modulus. Based on Doppler effect and heterodyne technology, loaded the information of length variation to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by mass variation after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can obtain length variation accurately, and eventually obtain value of Young modulus of the sample by the calculation. This novel method is used to simulate measurement for Young modulus of wire under different mass by MATLAB, the obtained result shows that the relative measurement error of this method is just 0.3%.
Fiber grating-pair is one of the efficient methods for gain stabilization of erbium doped fiber amplifier (EDFA) but with a gain-reduction of signals, especially in C-band. In order to overcome it, in this article, we establish a configuration of EDFA based uniform fiber grating-pair and conduct a comprehensive study on gain stabilization by varying the reflectivity, center wavelength and 3dB bandwidth of grating, and by varying the channel number and pump power. The numerical results show that under the optimal parameters of grating the gain stabilization at 1550nm is ±0.044dB with high gain and large dynamic range.
Utilizing the fused-taper technology, a fiber coupler with sensitive to wavelength and strain is obtained. This type
coupler is fabricated after Nth coupling period. They are usually called overcoupled devices, N is the number of coupling
period, N>>1. The relation between wavelength and coupling ratio of the coupler is analyzed. The maximum sensitive
wavelength can be control by the fused-taper technology. When a Bragg wavelength of the fiber Bragg grating (FBG) is
agreed with the maximum sensitive wavelength of the coupler, the shift of the Bragg wavelength is can be detected. In
this paper we demodulate one FBG which Bragg wavelength is at 1564.69 with the coupler. So the coupler with sensitive
to wavelength can be used to demodulate the FBG. And the sensitive to strain of the coupler is also analyzed. The
experimental data is present as the theory value, sinusoidal curve. So the coupler can also be used to detect the strain and
the temperature with the packaging of the thermal sensitive. The overcoupled couplers have a potential application to the