End surface grating by direct inscribing an
index modulation pattern on optical waveguide surface to
control amplitude and direction of the diffracted light is
fabricated. Direct inscribing an index modulation pattern by
femto-laser is simple, agile and the pattern is steady and
durable. We control power and direction of diffracting orders
by inscribing different modulation patterns and the
controllability may well offer opportunities for various kinds
of applications such as beam splitter, beam deflector, and
beam shape controller.
A novel electric current sensor based on a high-birefringence fiber loop mirror(HBFLM) and a kind of magnetostrictive material rod(MMR) is demonstrated theoretically and experimentally. Part of the high-birefringence fiber(HBF) is pasted onto the MMR which is placed in the central part of a solenoid. The HBFLM is used as the sensor head and the linear filter simultaneously. Part of the high-birefringence fiber(HBF) is pasted onto the MMR which is placed in the central part of a solenoid. The rod will have elastic lengthening along the direction of the magnetic field when the uniform magnetic field changes, which will lead to a change of transmission intensity of the HBFLM filter, thus the variation of the electric current can be determined via the laser wavelength within the quasi-linear transmission range of the HBFLM filter. The sensitivity reaches 0.0153/100mA, the resolution reaches 10mA. Comparing with the previous fiber-optic electric current sensor, it has nothing with the linear birefringence based on Faraday effects in the previous fiber-optic electric current sensor. Comparing with the expensive and complex FBG electric current, the sensing signal can be directly detected by a photodiode(PD) and complicated demodulation devices are avoidable. The advantages of the electric current include optical power detection, simple and smart structure, high sensitivity, low cost, and good repeatability, etc.
A novel high-birefringence fiber loop mirror(HBFLM) force sensor based on a freely supported beam(FSB) is
demonstrated theoretically and experimentally. Part of the high-birefringence fiber(HBF) is pasted onto the central
surface of the FSB. The force is applied to the center of the FSB, which leads to the pre-demarcated wavelength shift of
the transmission spectrum of the HBFLM. The sensitivity reaches 8.9N/nm, the resolution is 0.049N, and the linear
measurement range is 0.049N~0.392N.There is a good linear relationship between the force and the wavelength shift.
The advantages of the sensor include simple structure, high sensitivity, low cost, and good repeatability, etc.
An acousto-optic programmable ultrashort optical pulse shape modulator (AO-PPSM) is presented, which can
compensate for large amounts of dispersion over large spectral bandwidths while at the same time provide amplitude
shaping with high contrast. The analytical expression relating the group delay and amplitude at the output of the
AO-PPSM to the input acoustic signal is obtained with coupled-wave theory in the case of collinear acousto-optic
interactions. With these relations, the acoustic signal that will induce an arbitrary group-delay variation with frequency
can be easily obtained.
A technique for temperature-insensitive displacement measurement using a single fiber Bragg grating (FBG) based on
strain-gradient-induced reflection spectrum bandwidth modulation and optical power detection is demonstrated. Linear
displacement measurement up to 20mm with displacement resolution of 0.054 mm and thermal stability of < 0.8 % F.S.
for temperature range from 20 °C to 80 °C are respectively achieved without any temperature compensation.i
Temperature-insensitive pressure measurement using a single fiber Bragg grating (FBG) based on reflection spectrum
bandwidth modulation and optical power detection is proposed. A specially designed double-hole cantilever beam
(DHCB) is used to provide pressure induced axial strain gradient along the sensing FBG and further modulate the
reflection bandwidth of the grating. The bandwidth modulation immunes to spatially uniform temperature effect and the
pressure can be unambiguous determined by reflected optical power measurement, avoiding the complex wavelength
interrogation system. The thermal fluctuate of the system is less than 1.2 % F.S. for temperature range from -10°C to 80
°C without any temperature compensation.
The design and development of a digital liquid level sensor system based on parallel fiber sensor heads are presented. A
novel parallel fiber sensor heads based on side-polished common single-mode optical fiber is designed and applied.
When the sensor head contacts with the liquid, we observe a sharp decrease in the output intensity. The digital liquid
level sensor system based on 16 sensor points is operated by using an optical source with limited power. The
measurement resolution and range of the liquid level sensor can be selected by adjusting the distance between the sensor
heads. The advantages of this sensor system include low cost, high sensitivity, simple structure, excellent real-time
character, high stability, and temperature-insensitiveness in normal temperature and pressure.
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