Fluorescent fiber sensors fluoresce when light of various wavelengths is absorbed by the fiber. Fluorescent fiber sensors that fluoresce along the length of the fiber offer an advantage for detecting partial discharge (which generates UV and visible light), since light absorbed from any angle, along the entire length of the fiber, may be detected. However, other limitations have reduced the attractiveness of fluorescent fiber sensors for partial discharge detection, including short signal transmission range and constraints on fiber lengths due to high fiber attenuation, inability to pick up discharges internal to insulation, and the lack of multi-functional sensor capability. We describe the use of power over fiber as a means to enable multi-function sensors to be located near the source of partial discharge, and we explore the possibility of a hybrid power over fiber and fluorescent fiber sensor solution. This hybrid solution offers the potential to overcome the limitations of fluorescent fiber sensors. Furthermore, we expand the analysis to include the benefits of merging power over fiber with other fiber sensors. We find that new fiber sensor capabilities are created by combining these two technologies, and therefore enabling potential new applications, and market opportunities.
Continuing improvements in the cost and power of laser diodes have been critical in launching the emerging fields of power over fiber (PoF), and laser power beaming. Laser power is transmitted either over fiber (for PoF), or through free space (power beaming), and is converted to electricity by photovoltaic cells designed to efficiently convert the laser light. MH GoPower’s vertical multi-junction (VMJ) PV cell, designed for high intensity photovoltaic applications, is fueling the emergence of this market, by enabling unparalleled photovoltaic receiver flexibility in voltage, cell size, and power output. Our research examined the use of the VMJ PV cell for laser power transmission applications. We fully characterized the performance of the VMJ PV cell under various laser conditions, including multiple near IR wavelengths and light intensities up to tens of watts per cm<sup>2</sup>. Results indicated VMJ PV cell efficiency over 40% for 9xx nm wavelengths, at laser power densities near 30 W/cm<sup>2</sup>. We also investigated the impact of the physical dimensions (length, width, and height) of the VMJ PV cell on its performance, showing similarly high performance across a wide range of cell dimensions. We then evaluated the VMJ PV cell performance within the power over fiber application, examining the cell’s effectiveness in receiver packages that deliver target voltage, intensity, and power levels. By designing and characterizing multiple receivers, we illustrated techniques for packaging the VMJ PV cell for achieving high performance (> 30%), high power (> 185 W), and target voltages for power over fiber applications.