Multi-channel polarized low-coherence interference synchronous demodulation system based on a matrix charge-coupled device

A multi-channel synchronous demodulation system of a polarized low-coherence interferometer(PLCI) based on a matrix charge-coupled-device(CCD) is proposed and demonstrated. By using special designs, the system allows the signals from different channels to be received and demodulated synchronously. Multichannel air pressure experiments were implemented to verify the effectiveness of the proposed system. The experiment results showed that the Fabry–Perot(F–P) sensors could be demodulated synchronously with a high tolerance for light sources and sensors, which indicated that any sensor and light source that can be demodulated by PLCI were allowed to be employed, leading to a wide application in the field of multichannel synchronous measurement.

Measurement of ocular axial length using full-range spectral-domain low-coherence interferometry

We demonstrate a system for measuring the ocular axial length （AL） with high sensitivity and high speed using spectral-domain low-coherence interferometry （SD-LCI）. To address the limit in measuring such a large range by using SD-LCI, we propose a full-range method to recognize the positive and negative depths. The reference arm length is changed synchronously with the shift of the focal point of the probing beam. The system provides a composite depth range that is sufficient to cover the whole eye. We demonstrate the performance of the presented system by measuring the ALs of five volunteers. This system can provide the A-scan ocular biometric assessment of the corneal thickness and AL in 0.1 s.

Blood equivalent phantom vs whole human blood, a comparative study

Preclinical research of biomedical optoelectronic devices is often performed with the use of blood phantoms-a simplified physical model of blood.The aim of this study is the comparison and distinction between blood phantoms as well as whole human blood measurements.We show how the use of such phantoms may in°uence the incorrect interpretation of measured signal.On the other hand,we highlight how the use of blood phantoms enables to investigate the phenomena that otherwise are almost impossible to be noticed.

Quasi-distributed sensing network based on coherence multiplexing and spatial division multiplexing for coal mine security monitoring

A low-cost fiber Bragg grating(FBG) sensing system for coal-mine security monitoring is proposed in this paper.Based on the coherence multiplexing(CM) and spatial division multiplexing(SDM) techniques,this hybrid sensing network can support more than 40 sensors for quasi-distributed detection.It is demonstrated experimentally that the multiplexed sensing signal of each sensor can be clearly distinguished by an optical low-coherence reflectometry(OLCR).Methane concentration is detected with maximum sensitivities of an intensity variation of 10.92% and a concentration variation of 1%,using a well-designed sensor structure.Strain and temperature are also detected by this system,which also exhibits good results in the experiment.

Cost-Effective Fiber Multiplexing System Based on Low Coherence Interferometers and Application to Temperature Measurement

Based on the low-coherence interferometric principles, a cost-effective all-fiber Mach-Zehnder multiplexing system is proposed and demonstrated. The system consists of two interferometers： sensing interferometer and demodulation interferometer. By scanning an optical tunable delay line back and forth constantly with a stable speed, sensing fibers with different optical paths can be temporal interrogated. The system is experimentally proved to have a high performance with a good stability and low system noises. The multiplexing capacity of the system is also investigated. An experiment of measuring the surrounding temperature is carried out. A sensitivity of 12 gm/℃ is achieved within the range of 20 ℃ to 80 ℃. This low cost fiber multiplexing system has a potential application in the remote monitoring of temperature and strain in building structures, such as bridges and towers.