Sensing the internal temperature of lithium-ion batteries is particularly useful for reliable battery operation as both electrochemistry and mass transport are dictated by local temperature. In this article, we review in operando techniques to monitor the internal temperature of lithium-ion batteries during charging and discharging. We categorize existing techniques into two groups: invasive and non-invasive approaches. Invasive techniques include optical fibers, thermocouples, and resistance temperature detectors as a thermometer. Non-invasive methods cover the temperature estimation techniques, namely electrochemical impedance spectroscopy as well as X-ray thermometry. For both approaches, we review working principle of thermometry, pros and cons of each thermometry, and recent studies to tackle relevant technical challenges. This review provides useful information for internal temperature measurements, offering chances for thermally reliable battery operation.

In this study, beam divergence through an optical fiber has been controlled through shaping of the optical fiber tip using a CO₂ laser, which make the beam divergence smaller than the conventional diamond wheel cleaving method. Precise length cleaving of an optical fiber inserted in a ferrule using a femtosecond laser has also been investigated with respect to changes of the laser pulse energy. A ribbon fiber composed of 12 optical fibers could be cut precisely at different lengths in a micrometer scale.

The Internet protocol television (IPTV) service enables people to enjoy various Internet-based services via conventional TV watching. In the IPTV system, a set-top box (STB) is the key since it works as a terminal device that can relay real-time multimedia content from the Internet. However, the current IPTV STB functions as an attached device in a local area network although the actual IPTV network is usually served by an optical fiber-based network such as fiber-to-the-home (FTTH). Therefore, we introduce a novel fiber channel (FC)-embedded IPTV STB to fully use the sufficient optical fiber-based network bandwidth such as 1 Gbps. To verify the IPTV network capabilities by impact of the FC-embedded STB, we evaluate the performance of the FC-embedded STB-attached IPTV network architecture via extensible simulations in terms of an average startup-delay, an average reject ratio, and the number of concurrent users. Surprisingly, the suggested IPTV system demonstrates superior average startup-delay (less than 15 msec), an acceptable average reject-ratio less than 3%, and an almost linear increasing number of concurrent users, which reveals that the FC-embedded STB significantly affects the entire FC-AL-based IPTV network performance by efficiently facilitating the broadband optical fiber bandwidth.