Long-period grating(LPG) which has a grating period of more than 100μm is a new kind of fiber gratting and its principle is that optical power is coupled from the forward transmission fundamental core mode to the forward transmission cladding modes and is attenuated after some distance. Transmission spectrum of LPG has a range close to linearity in both side of the peak. This range can be use as double edge filter on this property. Cascaded LPGs have special spectrum which is used as filters in multiple technology.
For high resolution application in seismic detection, the geophone should be smaller in size, more reliable and sensitive.
So a kind of photo-electronic integrated acceleration seismic detecting technology, which is novel and precise based on
waveguide M-Z interference, is presented. The principle of the photo-electronic integrated acceleration seismic geophone
is introduced in this paper. The seismometer is composed of a waveguide M-Z interferometer, a sensing element, a
modulation LD and signal processing system. The silicon crystal is adopted as the substrate. The core of the photoelectronic
integrated acceleration is the silicon harmonic oscillator, which is supported by four silicon beams and
integrated on the signal beam of the M-Z interferometer . The harmonic oscillator translates the acceleration information
of the external vibrational signal into phase variation of optical signal in the sensing arm, which is converted into optical
signal by M-Z interferometer, then PIN converts the optical signal into electric signal to process by the signal processing.
The experimental curve of seismometer frequency response is achieved.
For simultaneously detecting multi-parameters of blood in the clinical diagnosis, the analysis apparatus should be smaller
in size, more reliable and sensitive. So a kind of integrated bio-sensor for blood analysis based on Micro Total Analysis
System (μTAS) is presented. It provides modern bio-sensor prospect with a novel technology.
A multi-parameters of blood analysis integration sensor is μTAS bio-sensor based on 4 groups of interdigital array (IDA)microelectrodes. The IDA microelectrodes are fabricated on glass substrates by photography, film deposition and
other microfabrication techniques. Thin-film gold microelectrode with a thickness of 250nm is deposited on a chromium-adhesion
layer. The finger microelectrode width and space are both 10μm. The work space is 2×2cm2. The concentration
of Blood sugar, Total Cholesterol, Acetone body and Lactic acid is measured by detecting steady-state limiting
currents in IDA microelectrodes modified with enzymes on the "generate-collect" mode. Blood distribution structure is
designed and fabricated, to distribute blood and isolate reaction areas. By contrasting two kinds of process flow based on
lift-off and etching, etching is adopted to preparation method of microelectrode.
A multi-channel apparatus for current measurement is accompleted. The system characteristics of the bio-sensor are
tested. The curve of the apparatus time to current response is achieved by testing on real-time. The relationships between
parameter concentration and current are analyzed in detail. The experimental data indicates: current measurement
dimension 0~40μA, certainty of measurement 0.1μA, the performances of the bio-sensor meets design requirement.
A direct current sensor based on all-fiber Mach-Zehnder interferometer is demonstrated in this paper. The phases of interferometric lights in the interferometer is modulated by heat effect when current flowing through a thin metal tube. The charactersistics of current sensing are studied experimentally. Adopting the wavelength scale method, in the case of elimination of environmental perturbation, the wavelength changing range is 32nm when the current changes from 0 to 1.8A. The shifting wavelength is linear to the power and the linear fitting is 0.9987. The tuning efficiency is approximately 19.47nm/W.
A new approach for displacement sensing based on chirp effect of fiber Bragg grating under strain-gradient is proposed and demonstrated in this paper. Strain gradient chirp of fiber Bragg grating is realized by attaching the grating slantways on a side face of a simple cantilever beam. The strain gradient, which is formed along the grating when the free of the beam is curved, produces a linear variation in the grating pitch .The theoretical formulae are derived and the experimental results are given. Because bandwidth of the grating is temperature-insensitive, the cross talk between displacement and temperature is avoided. This device has many characteristics, such as simple configuration, good noise immunity, and good linearity (about 0.9992). It is promising to be used into in-process displacement measurement.
A novel of bend sensor is demonstrated firstly. The device uses a simple support beam composing of two beams with a metal line winded on each beam and multimode fiber of a few meters in length which is placed between two beams having metal teeth profile such that the fiber experiences multiple bends. The experiment shows that the microbend loss of the multimode optical fiber is sensitive to the simple support beam bend curvature. The microbend loss with curvatures from 0 to 4.4m-1 is examined. The microbend loss with curvature is nonlinear, with a minimum detectable curvature change of 0.0175m-1.
A cascaded M-Z fiber interferometer has been analyzed,which is made of several 3dB couplers in series. Theoretical analysis and numerical simulation indicate that a good comb-like curve will be obtained when the length difference ? L of interference arms is given a certain value in order. Side-mode suppression ratio (SSR) will increase as adding of the number of interference arms.
In this paper, a new physical model is proposed. For a uniform Bragg grating, the index modulation distribution is a cosine profile. We slice the grating into many slabs and each slab can be looked as a thin surface. A slab has higher or lower index modulation than its adjacent slabs. A slab with high index modulation and its adjacent slab with different index modulation can be taken as a Fabry-Perot cavity. Thus a grating can be looked as a system that consists of a series of a coupled Fabry-Perot cavities. A matrix method is introduced, which relies on the calculation of the reflected and transmitted fields at an interface between two slabs of dissimilar refractive indexes. The simulation results can explain the properties of fiber grating well and show good consistency with previous conclusion.
A direct current voltage sensor based on all-fiber Mach- Zehnder interferometer is demonstrated, which utilizes electrostriction effect of Piezoelectric Translator. The character of voltage sensing is studies experimentally. Adopting the wavelength scale method, in the case of elimination of environmental perturbation, the wavelength changing range is 3.86nm when the voltage changes from -58v to 58v. The tuning sensitivity and the linear fitting are 0.033nm/v and 0.9985, respectively.