Optical fiber sensors based on Michelson interferometers (MIs) have potential applications in condition monitoring and measurement systems. We propose an optoelectronic oscillator (OEO)-based interrogation system with MI. The interrogation system has a high interrogation resolution and large measurement scale. The sinusoidal nature of the MI spectrum results in a single-passband microwave photonic filter (MPF), whose central frequency is determined by the dispersion parameters of the employed dispersive element and the free spectral range (FSR) of the MI. When the external environmental or physical factors change, the FSR of the MI varies and leads to the frequency shift o f the MPF, ultimately contributing to the frequency shift of the OEO-generated signal. We verify that the variation of temperature and strain can be demodulated by tracking the frequency of the OEO. We also employ an infinite impulse response (IIR)- MPF based on a fiber ring resonator (FRR) for fine oscillation mode selection and evaluate the interrogation resolution and the measurement accuracy of the interrogation system. Different from conventional interrogation systems tracking the wavelength shift of the MI spectrum, our scheme demodulates the sensing information in the electrical domain utilizing an OEO, providing a potential way to implement high-resolution sensing for conventional optical fiber sensors. Moreover, thanks to the wavelength-to-frequency mapping and the wide frequency tunable range of the OEO, our scheme would support large-scale sensing because it can avoid the overlap of MI periodic spectrum in wavelength demodulation.
To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, FBG on sleeve compactly single model fiber with two typical different kind of connection such as fiber splicing and optical fiber connector are researched. Influence of the different connection to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, experimental program of influence on FBG reflection spectrum characteristics is designed. Then, a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG with two typical different connections under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different single-mode optical fiber connection dropped to -196 ̊C from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 ̊C temperature cycle).
To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, two different kinds of sleeve compactly single model fiber covered by acrylate and polyimide are researched. Influence of the cover to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, transmission characteristic of single model fiber in high vacuum thermal environment is analyzed by solve the equation of heat conduction. Then, experimental program of influence on FBG reflection spectrum characteristics is designed and a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG in different coating single-mode transmission fiber under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different coating single-mode transmission fiber dropped to -196 ° from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the theoretical and experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 ° ∼ 25 ° temperature cycle) .
FOV separation (between VNIR sensor and SWIR sensor) and motion compensation imaging modes are introduced into the pushbroom imaging spectrometer to increase the SNR of the imaging data sometimes. Besides the higher SNR, the two imaging modes result in some bad effects on the imaging data, such as the additional misregistration. In the paper, a digital simulator for pushbroom Offner hyperspectral imaging spectrometer is used to analyze the misregistration caused by the FOV separation and the motion compensation imaging modes. Based on the imaging process, the simulator consists of a spatial response module, a spectral response module, and a radiometric response module. The FOV separation is simulated in the imaging position calculation process of the spatial response module, and the motion compensation is considered in both the imaging position simulation and the radiometric response module. Using the simulator, the imaging position data is created to quantify the misregistration. The result shows that the imaging track deviation, caused by the FOV separation, between the VNIR sensor and SWIR sensor keeps a constant quantity in the latitude direction. However, the deviation will increase along with the imaging time in the longitude direction. When the two imaging modes are both considered, the deviation is symmetrical relative to the nadir point in the latitude direction. However, the deviation is not symmetrical in the longitude. In order to analyze the misregistration effect on the imaging data, simulation data with different imaging modes on Dongtianshan remote sensing testing field is created using the simulator. And the misregistration effect on the spectra of flat ground pixel and rugged ground pixel are analyzed.
With the rapid development of China's space industry, digitization and intelligent is the tendency of the future. This report is present a foundation research about guidance system which based on the HSV color space. With the help of these research which will help to design the automatic navigation and parking system for the frock transport car and the infrared lamp homogeneity intelligent test equipment.
The drive mode, steer mode as well as the navigation method was selected. In consideration of the practicability, it was determined to use the front-wheel-steering chassis. The steering mechanism was controlled by the stepping motors, and it is guided by Machine Vision. The optimization and calibration of the steering mechanism was made. A mathematical model was built and the objective functions was constructed for the steering mechanism.
The extraction method of the steering line was studied and the motion controller was designed and optimized. The theory of HSV, RGB color space and analysis of the testing result will be discussed
Using the function library OPENCV on the Linux system to fulfill the camera calibration. Based on the HSV color space to design the guidance algorithm.
In order to verify the performance of space deployable structures before launch, separation and deployment tests should be carried out in large space environment simulation chamber, in which a simulated on-orbit environment can be achieved. In separation and deployment tests, high-speed camera system is often employed to capture the test image. The high-speed camera system is also exposed to the cryogenic and vacuum environment in large space environment simulation chamber. Consequently, cryogenic and vacuum adaptability of the system should be very strong to withstand the extreme environment in space environment simulation chamber. A common solution is using optical chamber. The equipment was set in a pressurized chamber which can insulate inner environment from the outer vacuum environment, and the gas in the chamber can also help to heat convection, therefore heat generated by the device can be transferred to the chamber wall. This paper aims to explore the thermal design of optical chamber for high-speed camera or other special equipment used in extreme environment. Using rule number analysis method, Heat transfer model in vacuum and ambient environment had been built to analyze the characteristics of heat transfer under different thermal power, characteristic length, and environment. recommended limits were delivered by the rule number analysis. CFD method was applied to verify the rule number analysis above. The two methods above reached a similar result, which demonstrated the effectiveness of the analysis.
The high air-tightness multicore fiber optic penetration connector is a core component for the optical fiber sensing and communication technologies applied in the space environment simulator under the vacuum thermal environment. High air-tightness and insertion loss are the two key indexes of the fiber optic penetration connector. The air-tightness and insertion loss on-line synchronous detection method was proposed. First, established hardware-in-the-loop testing platform by using the vacuum pumping system, the vacuum vessel, the helium mass spectrometer leak detector and optical time-domain reflectmeter, then, described the air tightness and insertion loss on-line detection principle, finally, designed a detection test scheme and air-tightness and insertion loss were tested. Experimental results indicate that the leakage rate is lower than 1.0×10-7Pa•L/S, the minimum of which is1.0×10-10Pa•L/S and the insertion loss at wave length window 1550 nm is ±0.07db, which is less than ±0.1db. It can lay the data basis for the design of opto-mechanical combination and later period fine processing.
Optical fiber sensor has great advantage for applications dealing with extreme environment. We developed a high
precision optical pressure sensor for aviation industry. The optical pressure sensor is based on two-beam interference of
microcavity and is fabricated with Micro-electromechanical systems (MEMS) and laser fusion technology. The cavity
length variation resulting from external pressure is demodulated with spatial polarization low coherence interference unit
and a high stable phase demodulation algorithm. The effect of light source output parameter is also investigated. We
carried out research on optical fiber strain, temperature and acoustic vibration sensor for aerospace application. The
optical fiber sensors for strain and temperature measurement are based on fiber Bragg grating(FBG).Both bare FBG and
packaged FBG performances under cryogenic temperature and high vacuum are investigated. An eight-channel parallel
FBG wavelength interrogator is developed. The optical fiber acoustic vibration sensor is based on two-beam interference
of microcavity and use intensity demodulation method for high speed response. The mutiple-parameter and multiplepoint
measurement instrument is successfully applied to status monitoring of water sublimator.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.