Non-contact inspection for inner surface of small-diameter pipes based on laser-PSD

A new non-contact inspection technique based on laser-PSD （position sensitive detector） to inspect the inner surface of small-diameter pipe is proposed,and the corresponding sensor has been developed. After being reflected by two mirrors in series,a laser beam is projected onto the inner wall of a pipe as a small light spot and is read by a two-dimensional PSD. Based on the signals from the PSD and the structure parameters of the sensor,the spot position on the wall can be calculated in a local 3D coordinate system. The spot controlled by the micro-motor driven mirrors will scan a closed section ring on the inner wall of the pipe to obtain the relative coordinates of all the sampled points. The data will be then processed through data segmentation and least square fitting,to reconstruct the section curve used for obtaining the radius and the defect description of the section. Driven by a micro-pipe robot,the sensor can inspect a long curved pipe and obtain its 3-D reconstruction. An inspection system based on this technique can detect the mini-diarneter pipe with an inner diameter of 9.5 mm-10.5 mm and a curvature radius larger than 100 mm at a measurement accuracy of the inner surface defect of ±0.1 mm.

ZTE's Perspective on Applying OFDM-PON in Next Converged Optical and Wireless Networks

Driven by ZTE and other telecom vendors and operators in order to meet the ever increasing bandwidth demand from fixed optical network users and mobile backhaul/fronthaul services, the latest next generation passive optical network （NG- PON2） is being standardized by Full Service Access Network （FSAN） and International Telecommunication Union （ITU-T） which consists of two separated sub-systems, hybrid time- and wavelength-division multiplexing PON （TWDM-PON） and point-to-point wavelength- division multiplex （PtP WDM）. The TWDM-PON will be used for traditional residential, business and wireless backhaul services which are not sensitive to time delay and delay variation, whereas the PtP WDM is mainly used for emerging wireless fronthaul service which is very sensitive to the time delay and time delay variation. However, as a main international standards＇ contributor, ZTE thinks for those operators who offer multiple-level of services to both residential, business and mobile backhaul/fronthaul users, this obviously raises significant economic and power concerns by demanding to deploy two separated systems. Therefore, in this paper, for the first time, ZTE proposes a new converged optical and wireless integrated network architecture and topology by applying orthogonal frequency division multiplexing（OFDM） PON technology, which is able to simultaneously support residential, business and mobile backhaul/fronthaul services in terms of meeting the requirements of both time delay sensitive and non-sensitive services, and also address the economic and power concerns compared with conventional technologies. This architecture is further investigated and analyzed in depth on functional block, Quality-of-service （QoS）, synchronization and deployment considerations. Also ZTE reports in this paper the first 40Gbps OFDM- PON prototype in which eight wavelengths each with 5Gbps Ethernet data via 10G-PON encapsulation method （X-GEM） and 10G-PON transmission convergence （X-GTC） framing are demonstrated.

Condition Assessment of Oil-Paper Transformer Insulating System

Damages of power transformers are caused partly by construction setting but also by operation （i. e., due to operational and degradation parameters）. A long-term operation and exceeding of the limit values of transformer abbreviate the lifetime of this device very dramatically. A condition of insulating system oilpaper is principal diagnostic indicator that has its essential influence to failure-free operation of power transformers. The paper deals with a description of the experience with developed monitoring system, which is focused mainly on a control of oil filling of experimental transformer. Relative humidity, amount of dissolved gases and increased temperature are observed, as they have decisive influence on insulating system of transformer. Monitoring of these characteristics is completed with analysis of oil samples by infrared spectroscopy in mode of Attenuated Total Reflection technique.

Terahertz emission from localized modes in one-dimensional disordered systems [Invited]

We demonstrate terahertz(THz) frequency laser emission around 3.2 THz from localized modes in one-dimensional disordered grating systems. The disordered structures are patterned on top of the double-metal waveguide of a THz quantum cascade laser. Multiple emission peaks are observed within a frequency range corresponding to the bandgap of a periodic counterpart with no disorder, indicating the presence of mode localization aided by Bragg scattering. Simulations and experimental measurements provide strong evidence for the spatial localization of the THz laser modes.