Wenxiang Jiao

Investigation of the EDFA effect on the BER performance in space uplink optical communication under the atmospheric turbulence

In a ground-to-satellite communication system with a preset EDFA, the EDFAs performance will be affected by space environment. With 250 Gy radiation, the EDFAs gain decreases by 2 dB from 19.97 dB at 20 °C. The BER increases by 2.5 orders of magnitude from 10(-10), and increases more with more radiation. The situation aggravates when the temperature rises by 73 °C. The lasers divergence-angle and transmitter radius have optimal values to make the lowest BER and increasing receiver diameter makes lower BERs, so setting these parameters with appropriate values will compensate the degradation caused by EDFA.

Self-Adaptive High Anti-Radiation EDFA for Space Optical Communication Systems

In a space optical communication system with an amplification sub-system, the performance of the erbium-doped fiber amplifier (EDFA) will worsen due to the effect of space radiation. Consequently, the EDFA will not work under its optimal state which has been already designed on the ground. To fix this problem, a study on the basic characteristics of EDFA under radiation is conducted. In the simulation tests, the gain of EDFA and the optimal length of the erbium-doped fiber both decrease with the dose of radiation. To dynamically adapt to such effects, a new self-adaptive system is established and makes an improvement of 7 dB in the gain when the radiation dose reaches 5000 Gy. This paper can practically benefit the design of the space optical communication systems.

An Algorithm for Determining the Peak Frequency of BOTDR Under the Case of Transient Interference

An algorithm based on spectra splicing is proposed to determine the peak frequency of Brillouin spectrum under a transient interference. The peak frequency calculated is only 0.79 MHz lower than that obtained based on the whole Brillouin spectrum when the frequency interval is 5 MHz. Discussions on the performance of our algorithm with and without spectral shift are conducted in light of the practical situation. Imposing a random shift on the primal Brillouin spectrum between -5 and 5 MHz, only 200 incomplete Brillouin spectra are required for splicing to gain a reliable value of the peak frequency with a frequency interval of 5 MHz. Moreover, the efficiency can be significantly improved by increasing the frequency interval, but the improvement is limited since higher frequency interval means more information loss of the whole Brillouin spectrum. This method is helpful in deciding the Brillouin frequency shift when the external interference lasts for a very short time, such as sound barriers and wind tunnel tests. It provides guidelines for the design of distributed optical fiber sensing systems.

Extraordinary Optical Transmission in a Hybrid Plasmonic Waveguide

Extraordinary optical transmission in free space through nanohole arrays has been widely investigated over the past two decades. However, because of its intrinsic nature of periodicity, it suffers from poor integration with nano-/micro-systems. Here, by folding a periodic grating into a compact cavity, we propose a waveguide-based structure within subwavelength, which also exhibits extraordinary optical transmission. Thus, lots of promising applications realized in metallic films can now be migrated onto integrated waveguides in an ultracompact way. Comparing the characteristics of the proposed integrated device and the conventional periodic structure, we reveal the nature of the unexpected transmission spectrum. Based on this principle, a collinear broadband (~500 nm) polarizer with extinction ratio of >17.8 dB is proposed, with an ultrashort length of 450 nm. Furthermore, this structure has the potential in biological applications when integrated into lab-on-a-chip or microfluidic system. As an example, a biosensor with enhanced sensitivity of 775 nm/RIU is presented.

A Method for Peak Seeking of BOTDR Based on the Incomplete Brillouin Spectrum

Distributed fiber sensing technology based on a Brillouin optical time domain reflectometer is widely applied for health monitoring in engineering. However, it cannot perceive quick external interference. In this paper, we propose to use polynomial fitting on the inverse of an incomplete Brillouin spectrum and find the peak frequency by statistical analysis. Simulation results show that the peak frequency obtained by our method is only 1.096 MHz higher than that by using the Lorenz fitting method on a whole discrete Brillouin spectrum. The method has high accuracy, good repetitiveness, and high stability and is helpful in health monitoring for situations with interference that lasts for a short time.

Plasmonic non-concentric nanorings array as an unidirectional nano-optical conveyor belt actuated by polarization rotation

We report a nano-optical conveyor belt containing an array of gold plasmonic non-concentric nanorings (PNNRs) for the realization of trapping and unidirectional transportation of nanoparticles through rotating the polarization of an excitation beam. The location of hot spots within an asymmetric plasmonic nanostructure is polarization dependent, thus making it possible to manipulate a trapped target by rotating the incident polarization state. In the case of PNNR, the two poles have highly unbalanced trap potential. This greatly enhances the chance of transferring trapped particles between adjacent PNNRs in a given direction through rotating the polarization. As confirmed by three-dimensional finite-difference time-domain analysis, an array of PNNRs forms an unidirectional nano-optical conveyor belt, which delivers target nanoparticles or biomolecules over a long distance with nanometer accuracy. With the capacity to trap and to transfer, our design offers a versatile scheme for conducting mechanical sample manipulation in many on-chip optofluidic applications.

Switching of nanoparticles in large-scale hybrid electro-optofluidics integration

We numerically demonstrate the scheme of independent optofluidic switching of nanoparticles on a silicon-based lab-on-a-chip system, using an electronic logic activated ring-assisted Mach-Zehnder interferometer (RAMZI). By using the carrier injection method with a tiny refractive index change of 8.00×10-4 to adjust the phase delay of a ring resonator sitting on one arm of the MZI, the light passing through could be switched to any output port of MZI followed by a directional coupler (DC). Meanwhile, the trapping force and scattering force of the guided lightwave could provide the actuation for sample delivery. Therefore, the switching logic of the guided mode is mapping to its loaded sample of nanomaterials. Our structure possesses high compactness, scalability, and time-effectiveness and, thereby, it is very appropriate for on-chip optical manipulation. The introduction of the RAMZI and cascaded RAMZIs in an optofluidic chip can form a scalable switching module with an independent electronic logic trigger signal, and make the chip dynamically configurable and scalable, which is very critical and opens a new horizon for the large-scale hybrid electro-optofluidics integration of a lab-on-a-chip system.

The Numerical Modeling of 3D Microfiber Couplers and Resonators

We numerically investigate the optical properties of three-dimensional (3D) microfiber/nanofiber (MNF) couplers and resonators, by using the finite-difference time domain method. It is the first time that the polarization-dependent transmission properties of 3D MNF couplers and resonators are investigated numerically. For the knot coupler, the twisted structure contributes to the inter-polarization coupling, and the envelope of intraand inter-polarization coupling coefficients, respectively, has the trend as a (cosc)2 or (sinc)2 function. For the loop resonator, the inter-polarization coupling coefficients are relatively small. However, the coupling coefficients for both polarization states are discriminated obviously. The high Q-factor resonance spectrum in one polarized state may be overwhelmed by that of the other. We also investigate the mechanism of resonance spectrum splitting, and find out that the inter-polarization coupling at the coupler region degenerates the resonance spectrum and gives rise to the splitting. The results provide guidance to design 3-D MNF devices, for example, high Q-factor resonators.

Optofluidic Switching of Nanoparticles Based on a WDM Tree Splitter

We demonstrate a silicon-based wavelength-division multiplexing (WDM) tree splitter for optofluidic switching of nanoparticles in a lab-on-a-chip or nanofluidic system. The gradient force and scattering force induced by the evanescent field can, respectively, lead to trapping and transportation of colloidal polystyrene (PS) spheres directly above the waveguide. Guiding of PS into any designated branch within a cascaded tree splitter is achieved by switching of the excitation wavelength. As compared to that based on microrings, an optimized design of the reported tree splitter approach offers a number of advantages in terms of device compactness, wavelength tolerance, response speed, and trap stability, while maintaining the inherent low-loss and low-power performance features of WDM splitters. A network of such splitters can readily lead to a platform for high-throughput and large-scale particle manipulation in nanofluidic systems.

Optical switch for particle manipulation using a ring-assisted Mach-Zehnder interferometer

Ring-assisted Mach-Zehnder interferometer (RAMZI) is proposed for particles switching and manipulation in micro- nanofluidics applications. Simulations shows that significant modulation can be achieved by tunning effective index of the ring up to only ~7×10-4.