A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission re- sponses and the Mach-Zehnder interferometers （MZIs）, this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a freauencv ranee from 0.1 to 5.3 GHz.
We propose a third-order intermodulation distortion （IMD3） compensation scheme based on the bidirec- tional modulation of 2-Ch phase modulator （PM）. We realize the destructive combination of IMD3 by using different modulation efficiencies and appropriately adjusting the input optical power ratio to satisfy a fixed relationship with modulation efficiency. The primary advantage of this scheme is that out-of-phase IMD3 is introduced using only one 2-Ch PM, thereby resulting in the cancellation of IMD3. Up to 27-dB suppression in IMD3 is experimentally demonstrated--a feature that will be useful in low-distortion analog or）tical transrni^sirm.
We present a network-level signaling mechanism for user access and service setup in light emitting diode （LED）-based visible light communication （VLC） networks and define the corresponding signaling messages. In this mechanism, lamp selection is an important step for realizing flexible user access and efficient resource allocation. Two basic selection schemes are proposed, and an enhanced bandwidth-based scheme is presented. Simulation results show the different advantages among these schemes.
We propose a blind quadrature imbalance （QI） compensation algorithm based on the statistical properties of I and Q signals in a receiver. The algorithm estimates the QI parmneters of a receiver by calculating the mean, variance, and correlation coefficient of I and Q components. Then, the estimated imbalance parameters are adopted to compensate for the QI in the receiver. Simulation results show that the Q factor is considerably optimized by the application of the QI compensation algorithm in an 80-Gb/s Pol- Mux coherent optical quadrature phase-shift keying （CO-QPSK） system. Compared with conventional algorithms, the proposed algorithm exhibits better performance when the phase deviation from QI exceeds ±15°.
Microwave photonics(MWPs)uses the strength of photonic techniques to generate,process,control,and distribute microwave signals,combining the advantages of microwaves and photonics.As one of the main topics of MWP,radio-over-fiber(RoF)links can provide features that are very difficult or even impossible to achieve with traditional technologies.Meanwhile,a considerable number of signal-processing subsystems have been carried out in the field of MWP as they are instrumental for the implementation of many functionalities.However,there are still several challenges in strengthening the performance of the technology to support systems and applications with more complex structures,multiple functionality,larger bandwidth,and larger processing capability.In this paper,we identify some of the notable challenges in MWP and review our recent work.Applications and future direction of research are also discussed.
Kun XuRuixin WangYitang DaiFeifei YinJianqiang LiYuefeng JiJintong Lin
Transport network paths are typically bidirectional and symmetrical, In multi-protocol label switching （MPLS） and generalized MPLS （GMPLS） mechanisms, independent labels are distributed for bidirectional paths. Thus, the requirement of the MPLS transport profile （MPLS-TP）, which is a new transport technology, could not be satisfied efficiently. A novel label distribution mechanism for bidirectional paths in MPLS-TP networks is proposed. Labels distributed by the mechanism are symmetrical and can reflect the pairing relationship of the forward and backward directions of the transport path.
The effects of optical losses oil a directly-modulated radio-over-fiber （RoF） system used for distributed antenna networks are determined. The results show that with a properly designed bidirectional amplifier, the RoF link can tolerate over 20 and 16 dB of optical losses for down- and up-links, respectively. Simulation results are also consistent with the experimental data. These findings can contribute to tile design of RoF distributed antenna systems with different topologies.
