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In this paper, we report a simulation study on the performance enhancement of Praseodymium doped silica fiber amplifiers (PDFAs) in O-band (1270-1350 nm) in terms of small signal gain, power conversion efficiency (PCE), and output optical power by employing bidirectional pumping. The PDFA performance is examined by optimizing the length of Praseodymium doped silica fiber (PDF), its mode-field diameter (MFD) and the concentration of Pr3+. A small-signal peak gain of 56.4 dB, power conversion efficiency (PCE) of 47%, and output optical power of around 1.6 W (32 dBm) is observed at optimized parameters for input signal wavelength of 1310 nm. Minimum noise figure (NF) of 4.1 dB is observed at input signal wavelength of 1310 nm. Moreover, the effect of varying the pump wavelength and pump power on output optical power of the amplifier and amplified spontaneous emission (ASE) noise is also investigated, respectively. Finally, the impact of ion-ion interaction (up-conversion effect) on small-signal gain of the amplifier is also studied by considering different values of up-conversion coefficient. [ABSTRACT FROM AUTHOR]

Photonic signal processing is a suitable alternative of electronics based processing for wideband frequency detection. We propose a novel technique for the detection of a wide range of frequencies based on photonic signal processing. The unknown frequency to be measured is used to modulate a tunable optical source by implementing single sideband suppressed carrier modulation. The modulated signal is combined with two fixed frequency optical carriers to perform heterodyne detection. The frequency of the tunable laser source is swept until significant power of the beat signal is observed after photodetection. A mathematical expression is presented that can be used to measure the frequency of the unknown electrical signal based on value of the center frequency of tunable laser source. The effect of increasing laser linewidth up to 100 MHz and instantaneous shift in laser center frequency up to 200 MHz has also been demonstrated. It has been shown that the proposed technique can measure almost any radio frequency by simply varying the frequency of the tunable laser source. [ABSTRACT FROM AUTHOR]

Microwave photonic filters have the advantages of wide tunability, low loss, and ease of reconfiguration. In this article, we propose a simple and cost‐efficient technique for the implementation of microwave photonic filter through simulations. This technique for the implementation of microwave photonic filter is employing a multiwavelength source and dispersive fiber. The multiwavelengths have been generated by employing optical carrier suppression based modulation. It has been shown that the free spectral range (FSR) of the filter may be tuned from 4.26 to 3.55 GHz by simply varying the frequency of the RF sinusoidal signal being used for modulation from 25 to 30 GHz, respectively. Furthermore, the bandwidth of the filter may be tuned by varying the number of filter taps. [ABSTRACT FROM AUTHOR]

As a key technique of supporting the fixed backbone network, radio over fiber (RoF) systems transmit the radio frequency signals over optical fiber in order to take advantage of their large available bandwidth. In this context, optical fiber aided phased antenna array (PAA) based beamforming techniques have attracted substantial research interest with the goal of improving the cell-edge coverage of cellular base stations. In this paper, we conceive a novel optical fiber aided beamforming technique based on the fiber's nonlinearity to be applied in cloud radio access network (C-RAN). In our proposed technique, the PAA elements are fed by the phase-shifted signals introduced by our highly nonlinear fiber (HNLF) aided phase-shifting solution, which results in an angular beamsteering range of around 90◦.This can be exploited by sectorization in cellular networks to reduce the cochannel interference imposed. Furthermore, we exploit the proposed RoF-aided phase shifting technique in C-RAN, where our proposed system takes advantage of the centralized signal processing capability of the RoF system to conceive an all-optical processing based tunable beamforming system. While our flexible HNLF-aided phase-shifting process is confined to the central office of the C-RAN, the end users in the C-RAN cellular networks are capable of flexibly choosing the serving remote radio heads and employing diverse wireless transmission techniques. Through integrating our HNLF-aided phase-shifting design into the proposed C-RAN, we impose as little as 0.1 dB signal-to-noise ratio degradation compared to its traditional electronic counterpart, which requires extra phase-shifters. [ABSTRACT FROM AUTHOR]