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s The Brillouin frequency shift in single-mode fiber is linear to the temperature change around the sensing fiber, so on-line temperature monitoring of three-phase cables could be realized through measuring the Brillouin frequency shift of contained fiber used for fiber communication. Electrifying 100 m compound transmission lines with different time, and monitoring the temperature variation, experimental results shows that the temperature along the lines increases generally with the time lengthening, presenting monotonic increasing property. Moreover, the temperature distribution across the line section is analyzed, and the temperature difference between the cable line and the fiber is 0.018 °C. All the results shows that the BODTR sensing system could be used for the on-line temperature monitoring on the power transmission lines and provide technical support for the smart grid.

This paper describes experimental investigation of copper-clad aluminum (CCA) tubing as a replacement for copper tubing to connect the indoor and outdoor units of split air conditioners. Experiments conducted on three specifications of CCA tubes ( φ 6.35 × 0.6 mm 2 , φ 9.52 × 0.7 mm 2 , and φ 12.7 × 0.8 mm 2 ) indicate good performance in terms of mechanical properties, processing properties, corrosion resistance, and pressure resistance; this means CCA tubes meet the installation and operation safety requirements for connecting tubes of air conditioners. Additionally, experimental results under two specifications – air conditioners in cooling and heating conditions – reveal no obvious difference in cooling or heating performance when CCA tubes, instead of copper tubes, connect the indoor and outdoor units of air conditioners. Furthermore, compared to copper tubes, CCA tubes can reduce the weight by 36.5%–46.3% and the material cost by 23.0%–34.8%. There is great potential for weight and cost reduction in the widespread application of CCA tubing as the connecting tubes in air conditioners.

We demonstrate a narrow-linewidth laser source for high spatial resolution distributed optical sensing by utilizing the high-order modulation sidebands injection locking. A pair of phase-locked lasers with arbitrary frequency offset from 5 GHz to 50 GHz is generated. Meanwhile, a linearized frequency sweep covering range of 15 GHz in 6 ms with frequency errors of 240 kHz from linearity is also achieved using the same scheme, the instantaneous linewidth of the frequency-swept laser is measured to be ~2.5 kHz.

Polarization fading is a phenomenon observed often in BOTDR distributed sensors, which greatly reduces signal-to-noise ratio of the detected signal. We proposed a scheme based on injecting optical pulse probes with orthogonal polarization states, which is generated by a delay Mach-Zehnder interferometer (MZI) composed of two polarization beam splitters (PBS). The principle is analyzed and the effect of reducing polarization fading is demonstrated experimentally. The method uses simple and passive components and is suitable for practical applications.

A phase-sensitive optical time domain reflectometer (-OTDR) based on a 120°-phase-difference Michelson interferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the phase difference between the Rayleigh scattering from two sections of the fiber. A new demodulation method called the inverse transmission matrix demodulation scheme is utilized to demodulate the distributed phase from the backward scattering along the long fiber. The experimental results show that the 120°-phase-difference interferometer -OTDR can detect the phase along the 3km fiber, and the acoustic signal within the whole human hearing range of 20 Hz–20 kHz is reproduced accurately and quickly.

A distributed fiber vibration sensor based on 3 * 3 Michelson interferometer is proposed, and a 3 * 3 interferometer is used to build the structure of a phase sensitive optical time domain reflectometer (phi-OTDR) based on homodyne coherent detection. With transfer matrix phase demodulation algorithm and through the basic parameters of the 3*3 interferometer transmission matrix, the corresponding relationship between differential phase and interferometer output light intensity is established. The simple and efficient software computing programs are used to demodulate the differential phase of Rayleigh scattering light in optical fiber, so as to realize the optical fiber distributed disturbance detection. The system is also used to detect the vibration along the fiber, and the experimental results show that the sensing system can accurately locate for the vibration and restore the frequencies of audio and radio frequency drivers, of which the effective sensing distance is 10 km.

In conventional Brillouin optical time domain reflectometry (BOTDR),mutual restraint between the spatial resolution and the width of spontaneous Brillouin scattering spectrum can not be avoided. To solve this problem, we ameliorated the approach using double ultra-short pulses as probe light. By detecting spectral envelope, the spatial resolution of BOTDR can be extracted. This method improves the spatial resolution of the BOTDR system and meanwhile avoids the influence of Brillouin gain spectrum broadening caused by narrowing pulse on measurement accuracy. The experimental results show that with this novel BOTDR system, the temperature measurement can be realized at a 0.5 m spatial resolution, and the large broadening of the spontaneous Brillouin scattering spectrum can be avoided.

With the development of the electronics and information technology, the requirement of people toward the resolution of images become higher. However, the resolution of acquired images can’t meet our needs because of the different imaging system from a variety of factors. And it will cost too much to improve image resolution via using the physical hardware. So it requires a new method to solve this problem. Super-resolution is emerged in this context. This technique uses a software approach to enhance the resolution based on the existing images. Thus it has aroused widespread concern when it appeared. In this paper, on the basis of previous studies, a new super-resolution reconstruction method based on linear regression of scale-space which could obtain higher resolution image is proposed and the experiments indeed show the higher resolution image could be obtained after using the method.