A novel method is proposed for measuring the frequency response of photodiodes. This method calculates the frequency response of the photodiode based on the gain peaks of the phase-modulated interferometric detection using a microwave network analyzer, and the half-wave voltage of the phase modulator, which is calibrated by measuring the intensity ratio of the modulated optical side-bands with the optical spectrum analyzer. The experimental results show a good match between the frequency response of photodiode measured by phase-modulated interferometric detection and by Mach-Zehnder intensity-modulated direct demodulation, as well as the data provided by the photodiode manufacturer. It provides an easy way to quickly sweep the frequency response of the photodiode, and the bias-control is not needed when calibrating half-voltage of the phase modulator.

This paper proposes a frequency-doubling optoelectronic oscillator employing a novel three-arm dualoutput Mach-Zehnder modulator (MZM). One output of the MZM generates the fundamental-frequency signal which is recycled by the microwave optical fiber link for oscillation, and the other output can generate the frequency-doubled signal. Experiment was conducted using a commercial two-arm MZM, a phase modulator, and an optical fiber link of 89 meters in length. A 19-GHz frequency-doubled signal was successively obtained with fundamental signal suppression more than 36 dB.

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a school of electronics and information engineering, Jinling institute of technology, nanjing, china; b school of electronic science and engineering, southeast university, nanjing, china ABSTRACT Microwave photonic links can provide many advantages over traditional coaxial due to its low loss, small size, lightweight, large bandwidth and immunity to external interference. In this paper, a novel phase noise measurement system is built, since the input signal and the power supply noise can be effectively cancelled by a two-arm configuration without the phase locking. Using this approach, the phase noise performance of the 10-GHz phase modulation photonic link has been measured for the first time, evaluated the values of −124 dBc/Hz at 1 kHz offset and −132 dBc/Hz at 10 kHz offset is obtained. Theoretical analysis on the phase noise measurement system calibration is also discussed. KEYWORDSMicrowave photonic links; phase modulation; phase noise ARTICLE HISTORY

<p>Groundwater plays a vital role in improving the efficiency of natural water resource management and protecting and restoring water related ecosystems (SDG 6). Additionally, understanding the importance of groundwater for general public and proper management of the interactions between surface waters and their underlying aquifers is a prerequisite to maintaining their cultural and ecological value and services.</p><p>Nowadays, decisions around groundwater in Australia are out of the reach of the general people owing to a lack of awareness and technical knowledge within the field. By including people in the decision making process through an integrated groundwater surveillance platform, communities will be empowered to contribute to the resilience of water resources, safeguarding them for future generations (SDG 11).</p><p>This abstract introduces and proposes a program that is designed to raise awareness and involve the public in groundwater distribution. By using the simple concept of groundwater flow direction and interactions with surface water features, individuals can monitor and report the abnormal flow of water that may affect surface water resources. This will also enable people to raise questions about local water management plans, promoting the sustainable management of natural water resources.</p><p>The program will have a direct impact on regions suffering from the degradation of surface water features that may relate to insufficient groundwater discharge. It also serves as a preventative measure, protecting groundwater storage in regions that heavily rely on groundwater. To sum up, groundwater is a crucial link of water cycle and the sustainable management of groundwater can lead to efficient water management and improve water usage sustainability.</p>