We describe a simple and inexpensive inline optical power monitor (OPMo) for polymer optical fibre (POF) links that are transmitting visible light carriers. The OPMo is non-invasive in the sense that it does not tap any guided light from the fibre core; rather, it collects and detects the spontaneous side-scattered light. Indeed, the OPMo indicates whether a POF transmission link has dark or live status and measures the average optical power level of the propagating signals without disconnecting the fibre link. This paper demonstrates the proof-of-principle of the device for one wavelength at a time, selected from a set of previously calibrated wavelength channels which have been found in the 45 dB dynamic range, with 50 dBm sensitivity or insensitivity by the use or non-use of a mode scrambler. Our findings are very promising milestones for further OPMo development towards the marketplace.

This article shows the development of a photonic detector of low-frequency ultrasonic signals. These signals latter reach a sensitive single-mode optical fiber as an acoustic guide conveying the signals (around 43 kHz) over 70 cm to a distant and protected in-fiber Bragg grating. The grating reflects a spectrum centered around 1550 and 2.6 nm bandwidth and is interrogated by a tunable laser in their linear and most sensitive region. As a result, real-time passive demodulation of communication or monitoring of ultrasonic signals propagating through solid materials is possible. The detector may also be applied to other physical media. In this study, a new passive technique to thermally desensitize the fiber-Bragg gratings (FBG) is also proposed, though the proposed technique is not experimentally tested. K E Y W O R D S acoustic communications, acoustic guide, acoustic monitoring, fiber Bragg grating, optical fiber, ultrasound AbstractThis article presents a novel multi-band rectifier utilizing modified hybrid structure for radio frequency (RF) energy harvesting. The proposed multi-band rectifier consists of a modified hybrid junction and three rectifying branches. The rectifying branches are placed inside the modified hybrid to reduce the layout size. The proposed multi-band rectifier is designed for GSM-1800, UMTS-2100, and Wi-Fi bands. Measured peak efficiency of the proposed rectifier reaches 61.7% at 9 dBm input power level. The results show a good overall performance on operation bands, LI ET AL. | 817

Resumo-Neste trabalho, descrevemos um monitor de potência óptica OPMo de construção simples, compacto e incluindo o uso de um modelo de foto-detector amplamente disponível no mercado. Com o presente protótipo, pode-se notar uma nãosaturação para valores de potência >-5 dBm e um aumento de até 10 dB na sensibilidade com um simples aumento da impedância de carga do foto-detector.

This paper shows for the first time, to the best of our knowledge, the design of a simple, non-invasive, bidirectional and inexpensive optical power monitor (OPMo) for WDM over PMMA-based polymer optical fibre (POF) links transmitting 470 nm and 650 nm wavelengths light carriers. Low-cost cellophane plastic optical filters were used for each WDM channel aiming to demonstrate the OPMo operational principle. The OPMo is non-invasive because it does not tap any guided light from the fibre core; rather, it collects and detects the spontaneous side-scattered light. A sensitivity of  −32 dBm and dynamic range of 38.8 dB were measured. A crosstalk rejection better than 25 dB was achieved when both light carriers are of the same power.

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