A simple wireless-fiber laser sensor is proposed base on directly photonic generation
of microwave beat signal. In this scheme, a multi-longitudinal modes fiber laser is formed by two fiber Bragg gratings and a section of erbium-doped fiber. Two same 2G-GSM mobile antennas are used as wireless transmitter and receiver. By this method, the real-time monitoring of fiber laser sensors can be achieved through over ultra-long distance. This technique offers a simple, all-electrical and cheap way for fiber sensor information accessing wireless net. The experiment result shows the root mean square deviations of the sensor are about 4.7 με and 6.7 με at 2.38 GHz before and after wireless transmission, respectively.
A multilongitudinal mode fiber ring laser sensor is proposed and experimentally demonstrated by measuring the strain applied on the laser sensor head. The ring cavity of the laser is formed by a 3-dB coupler, a section of erbium-doped fiber, and one fiber Bragg grating. Photonic generation of beat signals and strain measurement theory are discussed in detail. The strain applied on the fiber ring cavity is obtained by measuring the beat frequency shift. The selection way of the optimal beat signal for strain measurement is obtained by experimental research and discussion. The root-mean-square deviation of the strain and the response of beat frequency to the strain are 2.7 μɛ and 1.5 kHz/μɛ at 1993 MHz, respectively. The proposed sensor scheme offers a cost-effective and high-stability device for strain measurement.
A special sampling structure based on the double exposure technology is proposed to achieve dual-wavelength lasing in
the distributed feedback (DFB) fiber laser. This structure is composed of two grating pitches in one sampling period,
which could be realized by changing the fiber's length in the fabrication. And through employing an equivalent phase
shift, only a submicrometer-level precision is required for precise phase control. Then a stable dual-wavelength laser
with the spacing of 400pm is obtained in the experiment successfully. The output power is 30.46uW and the SMSR is
46dB under a pumped power of 146mw.
A multi-longitudinal-mode fiber laser sensor is proposed and experimentally
demonstrated base on beat frequency demodulation method. A novel laser cavity is formed by a
FBG, a section of erbium-doped fiber and a broadband reflector. The proposed laser sensor has
ultra-stable frequency information due to self-phase matching of FBG, and high signal to noise
We propose and experimentally demonstrate a novel FBG dual-wavelength fiber laser sensor based on the beat
frequency demodulation technology. The dual-wavelength beat frequency sensing signal of about 5.224 GHz has been
obtained in a photodetector and observed by a radio-frequency spectrum analyzer (RFSA). Furthermore, by employing a
LiNbO3 modulator, the high-frequency beating signal can be tuned arbitrarily to tens or hundreds of MHz without
distortions. Thus a very cheap and low-frequency RF spectrum analyzer can be used in frequency signal detection. When
a strain is applied on the sensor, the beating signal will shift with a stain sensitivity of about (-3.92) kHz/με.
A two-wavelength fiber laser with two π-equivalent phase shifts (EPSs) is studied and fabricated. The π-EPS is obtained
through extending one sampling period by 50% in a fiber sampled Bragg grating (SBG). To get a two-wavelength fiber
laser lasing in the -1st channel, two π-EPSs are introduced in the position of L/3 and 2L/3 in the SBG, where L is the total
length of the SBG. A stable 22-pm-spaced dual wavelength DFB fiber laser is achieved in the experiment.
Instead of real phase shifts, equivalent phase shifts (EPS) are adopted to construct ultra narrow phase-shifted band-pass
filer in sampled Bragg gratings (SBG). Two optimized distributions of multiple equivalent phase shifts, using 2 and 5
EPSs respectively, are given in this paper to realize flat-top and ripple-free transmission characteristics simultaneously.
Also two demonstrations with 5 EPSs both on hydrogen-loaded and photosensitive fibers are presented and their
spectrums are examined by an optical vector analyzer (OVA). Given only ordinary phase mask and sub-micrometer
precision control, ultra-narrowband flat-top filters with expected performance can be achieved flexibly and cost-effectively.