mechanical energy exists extensively in our daily life, such as vibration, wind, and waves. [3] However, most of this energy is wasted and long-neglected. For one thing, environmental mechanical energy is random in amplitude, low in frequently, widely distributed, unstable, and random. Therefore, the design of effective and environmental-friendly energy harvesters still has lots of technical and economic challenges. [4] Besides, IoT has made a great progress with the development of sensor, wireless communication, and micro/nanotechnology. [5] IoT enables collecting and processing data among the whole network, which consists of huge numbers of widely distributed sensors or smart devices. But how to supply adaptive and sustainable energy for nodes of IoT is a big task even though each node only needs a tiny power. According to the characteristic of wide distribution, harvesting environmental mechanical energy is an attractive approach to powering the nodes of IoT. [6]

An ultra-long phase-sensitive optical time domain reflectometry (Φ-OTDR) that can achieve high-sensitivity intrusion detection over 131.5km fiber with high spatial resolution of 8m is presented, which is the longest Φ-OTDR reported to date, to the best of our knowledge. It is found that the combination of distributed Raman amplification with heterodyne detection can extend the sensing distance and enhances the sensitivity substantially, leading to the realization of ultra-long Φ-OTDR with high sensitivity and spatial resolution. Furthermore, the feasibility of applying such an ultra-long Φ-OTDR to pipeline security monitoring is demonstrated and the features of intrusion signal can be extracted with improved SNR by using the wavelet detrending/denoising method proposed.

In this paper, we reported the realization of 2nd-order random lasing in a half-opened fiber cavity, which is formed by a FBG with central wavelength at the 1st-order Raman Stokes wavelength and a single-mode fiber (SMF) performing as a random distributed feedback mirror. Using this proposed method, the threshold of 1st-order (2nd-order) random lasing is reduced to 0.7 (2.0) W, which is nearly 2 times lower than that observed in a completely-opened cavity.

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Recent development of interactive motion-tracking and positioning technologies is attracting increasing interests in many areas, such as wearable electronics, intelligent electronics, and the internet of things. For example, the so-called somatosensory technology can afford users strong empathy of immersion and realism due to their consistent interaction with the game. Here, we report a noncontact self-powered positioning and motion-tracking system based on a freestanding triboelectric nanogenerator (TENG). The TENG was fabricated by a nanoengineered surface in the contact-separation mode with the use of a free moving human body (hands or feet) as the trigger. The poly(tetrafluoroethylene) (PTFE) arrays based interactive interface can give an output of 222 V from casual human motions. Different from previous works, this device also responses to a small action at certain heights of 0.01-0.11 m from the device with a sensitivity of about 315 V·m, so that the mechanical sensing is possible. Such a distinctive noncontact sensing feature promotes a wide range of potential applications in smart interaction systems.

We find that the random fiber laser (RFL) without point-reflectors is a temperature-insensitive distributed lasing system for the first time. Inspired by such thermal stability, we propose the novel concept of utilizing the RFL to achieve long-distance fiber-optic remote sensing, in which the RFL offers high-fidelity and long-distance transmission for the sensing signal. Two 100 km fiber Bragg grating (FBG) point-sensing schemes based on RFLs are experimentally demonstrated using the first-order and the second-order random lasing, respectively, to verify the concept. Each sensing scheme can achieve >20 dB optical signal-to-noise ratio (OSNR) over 100 km distance. It is found that the second-order random lasing scheme has much better OSNR than that of the first-order random lasing scheme due to enhanced lasing efficiency, by incorporating a 1455 nm FBG into the lasing cavity.

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