The experiment results of two kinds of FBG temperature sensors in identical conditions were compared by analyzing the variety properties of center wavelength from-70℃ to 0℃.
From the experimental results,it is shown that the center wavelength of FBG temperature sensor with thin stainless steel tube package falls sharply at-60℃;
while there is a very good linearity and preferable repeatability between the center wavelength of FBG with gold package in the temperature change from-70℃ to 0℃,and almost no hysteresis effect.
doing an experiment in calibrating FBG center wavelength by three methods of piecewise linear interpolation, Lagrangeinterpolation and cubic spline interpolation, the two latter methods of which have very high precision of ± 1 pm~ ± 3 pm and stability.
The relation between the central wavelength of reflection wave of FBG and pressure was given,and the expression of the pressure sensitivity coefficient was also given.
The detailed research contents are as following:(1) Based on molecule spectrum theory and experimental data, presented are fine parameters of CH4 combined frequency band v2+v3 and wide frequency band 2v3, including absorption spectrum central wavelength, line space, intensity distribution, line type and line width. These fine parameters have played solid foundation for measurement wavelength selection, and effectively eliminated cross sensitivity.
For di- fferent light resource, system designs for harmonic detection have great differences, but all of them are based on derivative spectrum characteristics and even symmetric gas absorption line (or F-P chamber multiple vertical pattern symmetry). With ground wave as feedback signal, the central wavelength can be precisely locked on the location of gas absorption central position.
The effects of central wavelength variation of the optical source due to temperature fluctuation upon the output of the system through the dispersions of the RIR, LB and Verdet constant are studied.
An OCT system is designed through selecting single-mode LED with 1.3μm central wavelength and 20μW optic fiber emitting power used for communication as light source. Its minimum detectable reflectance is less than -92dB. A measurement for skin is carried out on human body.
Due to the birefringence effect of the fiber Bragg grating, the splitting of the two Bragg wavelengths corresponding to the fast axis and slow axis is observed, and the maximum of the splitting is 0.66nm.
The research results showed that the Bragg wavelength has a good line sexual behavior with the strain and the temperature, and the experimental results of the 11.5pm/℃ and 1.12pm/με fit together with the theories analyses.
In the temperature range 20～100 ℃ and pressure range 0～7.8 N, the precisions of temperature measure and pressure measure are ±1.1 ℃ and ±0.18 N respectively. The response curves of FBG have good linearity which are higher than 99.6%.
Due to the birefringence effect of the fiber Bragg grating, the splitting of the two Bragg wavelengths corresponding to the fast axis and slow axis is observed, and the maximum of the splitting is 066nm.
For a center wavelength of FBG of about 1550 nm and a 40 nm shift range of its reflection wavelength, the relative error of measurement is only ± 0.001.
The wavelength of the light source is modulated at a frequency of 10?kHz, and the center wavelength is stabilized at the center of the 2ν3 band R(3) line of methane (1.65372?μm).
Variations in the intensity of the solar radiation are measured in the six spectral intervals of the multi-channel photometer: 350, 500, 650, 850, 1100, and 1500 nm, with the bandwidths being about 10% of the central wavelength of each interval.
The RATAN-600 Zenith Field (RZF) catalog was obtained at the central wavelength of 7.6 cm, and contains 437 radio sources, virtually all of which have been identified with NVSS objects.
This effect reduces unwanted variations in the central wavelength, as well as fluctuations of the delay time of the frequency-shifted soliton with respect to the input pulse.
By slightly tuning the central wavelength of the narrowband FBG, SLM lasing at 1549.658 or 1549.563 nm (corresponding to the two transmission peaks of the FBG-FPF) is achieved with a laser output power of ～4 mW, when the pump power is ～75 mW.
PID-temperature control system based on single chip computer and semiconductorrefrigerator has been developed.This system has high precision and stability. In roomtemperature region,its control precision is≤±0.1℃. With this system,the authors study thetemperature dependence of the light source(LED) of IM85-1 optical-fiber pressure sensor.Theresults show that,under the conditions of constant temperature,controller and operating,thelight source’s temperature stability is improved.
In many optical fiber sensors, any drifts in the wavelength of the source which are due to changes in ambient temperature will induce errors. By theoretical analysis and experiment, this error can be reduced using software compensatory method.
The concept of tree topology Bragg Optical Fiber Grating (BOFG) distribution sensing array is introduced. Comparing with the serial topology array, this type of arrays has the following advantages. First, it is not necessary that the central reflecting wavelengths of all the BOFG sensors must be different. In general, they can be identical. Thus, the cost of producing the sensors can be cheaper and they will easily be commercialized; Secondly, for this type of arrays, it is likely that a large number of sen...
中心波长
center wavelength 
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