We propose and demonstrate a reconfigurable microwave photonic filter (MPF) based on tunable dispersion-induced power fading (DIPF) in a dispersive element A multi-wavelength optical signal is used to generate the multi-taps of the MPF. A polarization modulator (PolM), a polarization controller (PC), and a polarizer are cascaded to build a new modulator which can be regarded as an intensity modulator, a phase modulator, or an intensity and phase hybrid modulator by adjusting the PC. A dispersive element is followed after the PC to generate the DIPF which is controllable by tuning the PC. In this way, the MPF is reconfigurable and tunable. The proposed method is theoretically analyzed and experimentally verified. The simulated results fit well with the experimental ones. (C) 2014 Elsevier B.V. All rights reserved.

The coherent ultra-dense wavelength division multiplexed passive optical network (UDWDM-PON) has been widely studied recently, in which the envelop detection based coherent reception of on-off keying (00K) signal has been shown to possess both high receiver sensitivity and tolerance against laser linewidth/chirp. In order to increase the spectral efficiency (SE) to 2 bit/s/Hz, researchers formulated a hybrid DBPSK/ASK-2 modulation using the silicon Mach-Zehnder modulator (MZM), where both amplitude and phase modulation are employed. The experimental result shows that the proposed DBPSK/ASK-2 modulation is of better performance than PAM-4 at the same SE of 2 bit/s/Hz. When the low-cost silicon MZM and DFB laser of 4-MHz linewidth are employed, the receiver sensitivity of DBPSK/ASK-2 exceeds that of the PAM-4 by about 5.7 dB. This work can achieve about 46 dBm receiver sensitivity at 2.5 GBaud after transmission over 80-km standard single mode fiber (SSMF). The proposed DBPSK/ASK-2 modulation using low-cost silicon MZM and DFB laser is considered as a practical and reliable method for the future UDWDM-PON at the SE of 2 bit/s/Hz. (C) 2016 Elsevier B.V. All rights reserved.

Visible light communication (VLC) is a promising candidate for short-range broadband access due to its integration of advantages for both optical communication and wireless communication, whereas multi-user access is a key problem because of the intra-cell and inter-cell interferences. In addition, the non-flat channel effect results in higher losses for users in high frequency bands, which leads to unfair qualities. To solve those issues, we propose a power adaptive multi-filter carrierless amplitude and phase access (PA-MF-CAPA) scheme, and in the first step of this scheme, the MF-CAPA scheme utilizing multiple filters as different CAP dimensions is used to realize multi-user access. The character of orthogonality among the filters in different dimensions can mitigate the effect of intra-cell and inter-cell interferences. Moreover, the MF-CAPA scheme provides different channels modulated on the same frequency bands, which further increases the transmission rate. Then, the power adaptive procedure based on MF-CAPA scheme is presented to realize quality fairness. As demonstrated in our experiments, the MF-CAPA scheme yields an improved throughput compared with multi-band CAP access scheme, and the PA-MF-CAPA scheme enhances the quality fairness and further improves the throughput compared with the MF-CAPA scheme. (c) 2017 Elsevier B.V. All rights reserved.

A novel scheme to determine frequency sweep nonlinearity using atomic saturated absorption spectroscopy is proposed and demonstrated. The frequency modulation rate is determined by directly measuring the interference fringe number and the frequency gap between two atomic transition peaks of rubidium atom. An experimental setup is established, and test results show that the frequency sweep nonlinearity is similar to 10%, with an average frequency modulation rate of similar to 1.12 THz/s. Moreover, the absolute optical frequency and optical path difference between two laser beams are simultaneously determined with this method. This low-cost technique can be used for optical frequency sweep nonlinearity correction and real-time frequency monitor. (C) 2017 Elsevier B.V. All rights reserved.