We report, to our knowledge, for the first time on humidity-induced Brillouin frequency shifts in perfluorinated graded index polymer optical fibers. A linear relation between Brillouin frequency shift and humidity was observed. Furthermore, the humidity coefficient of the Brillouin frequency shift is demonstrated to be a function of temperature (-107 to -64 kHz/%r.h. or -426 to -49 kHz m/g in the range of 20 to 60 °C). An analytical description proves temperature and humidity as two mutually independent effects on the Brillouin frequency shift.

We demonstrate (and are the first to do so) 63 km Brillouin Optical Frequency-Domain Analysis (BOFDA) for temperature and strain monitoring using a 100 km fiber loop. The use of BOFDA for long-range applications can be considered a novel approach, as previous investigations focused on the utilization of Brillouin Optical Time-Domain Reflectometry and Analysis (BOTDR and BOTDA, respectively). At 51.7 km, a 100 m hotspot (37 ∘C) was detected without using distributed Raman amplification or image processing.

No abstract

This paper studies the multi-wavelength capability of our recently developed tracking and beam-steering fiber-wirelessfiber (FWF) terminals for simultaneous, full-duplex optical wireless communication over telecommunication bands widely used in optical access networks. Tracked terminal-to-terminal concurrent data transmission over O and C bands is demonstrated.

We present a miniaturised free-space quantum key distribution (QKD) system which allows key exchange between a handheld transmitter and a fixed terminal. The QKD system requires to be optically aligned emphasising the need of a beamsteering unit for later applications. To maintain within the size, weight and power restrictions, the active beamsteering hardware is exclusively located inside the receiver. Our target is consumer use so we present rigorous characterisation against a range of background light levels to show anticipated performance outside of a laboratory environment.Experimental results show a reduction in the raw count rate commensurate with the transmission of the added components (74.5%) and a small degradation of the error rate (0.5 percentage points) due to the worse signal-to-noise ratio. These combine to a 50% reduction in estimated secret key rate of the system with the additional components for beam steering.