Together with the progress in telecommunications, the high quality multicore fiber (MCF) and few-mode fiber (MCF) are developed with reliable spatial-division multiplexer/demultiplexers for innovative fiber devices and sensing applications. We will review our recent progress in the spatial-division-multiplexed (SDM) fiber devices and their applications in discrete and distributed fiber sensing, such as integrated parallel LPG, MZI, MI and the distributed curvature and 3D shape sensing. The simultaneous multi-parameter measurement using discrete/distributed technologies are also introduced.

Super-resolution focused light spots are always expected in scanning optical microscopy. There are bright focused light spots and dark focused spots in stimulated emission depletion (STED) microscopy. The latter dark spot is normally generated by focusing a linearly polarized beam with spiral phase. In this work, we generated a super-resolution optical tube by tightly focusing a binary phase modulated azimuthally polarized laser beam. The binary phase modulation is achieved by a glass substrate with multi-belt concentric ring grooves. We also characterized the 3D beam profile by using a cross-shaped knife-edge fabricated on a silicon photo-detector. The size of the super-resolution dark spot in the tube is 0.32λ, which remains unchanged for ~4λ within the tube. This optical tube may find applications in super-resolution microscopy, optical trapping and particle acceleration.

Conventional surface-enhanced Raman scattering (SERS) has a poor surface reproducibility, which led to measurement repeatability becoming unreliable, therefore, it is not suitable for quantitative analysis. With the rapid development of nanotechnology in recent years, highly ordered and controllable SERS substrates have been realised, so as to ensure the accuracy of measurements, and SERS signal enhancement factor has also greatly increased.  In this research we have undertaken two step innovative research on Nano structured arrays for Raman signal enhancement; and channel waveguide evanescent field emission Raman signal, followed by further exploring and developing in to a high-sensitivity integrated optical SERS sensing device with practical value, which can be used in the fields of detecting contaminants, medical diagnostics, gene research and rapid identification applications.

Distributed optical fibre sensors based on Brillouin scattering have find many applications in different application areas. In particular, there have been significant interest in BOTDA based system in recent years. The performance of such systems is often limited by signal to noise ratio of detected signal which in turn is limited by limited pump and probe power due to fibre nonlinearity and nonlocal effect. The detection speed is often limited by the need for large number of averaging and the number of pulses that can be sent over a round trip time. In this talk, work on attempting to address these issues are discussed. In particular, the use of machine learning technique such as artificial neural network(ANN) and principal component analysis(ANN) for improving measurement accuracy and measurement speed is discussed. Results obtained using coherent detection for improving noise performance as well as the use of electronic generated multicarrier probe signal with amplitude and phase detection for improving measurement speed are presented.

We will review the latest progress of the improvement of supercontinuum (SC) characteristics in highly nonlinear fibers. We will present our results on the use of the CW trigger to control the SC generation with different pump sources. A weak CW trigger can manipulate the behaviors of optical rogue waves in the SC regime. For the proposed CW triggering technique which requires only wavelength tuning and is a handy approach for the active control of SC, the resultant spectrum can be greatly broadened, and the noise properties of the SC can be significantly improved in terms of both of the coherence and intensity stability.

Gas stimulated scattering has been demonstrated to be an effective method to obtain tunable, narrow linewidth light sources of otherwise unobtainable wavelengths, especially in the ultra-violet and infrared spectral range. In traditional gas cells the effective interaction length is very short and the system can be bulky and cumbersome, limiting the applications of these lasers. The advent of anti-resonance hollow core fibers and their properties of long effective interaction length, high optical confinement, and the possibility of control of the effective gain spectrum make it possible to develop a novel type of laser, fiber gas Raman lasers, which combines the advantages of both fiber and gas lasers. By properly designing the transmission bands of hollow-core fibers, selecting active gases and pump sources, fiber gas Raman lasers can potentially provide a wide range of emission wavelengths from the UV to the IR. Owing to the nature of transitions in atomic and molecular gases, fiber gas Raman lasers are spectrally narrow even without additional linewidth limiting measures. We have demonstrated nanosecond, hundred kilowatt peak-power, gigahertz linewidth, 1.5μm and 2μm fiber gas Raman lasers using the anti-resonance hollow-core fibers made by Bath University in UK. Our work provides a very possible way to obtain mid-infrared fiber lasers by gas stimulated Raman scattering in hollow-core fiber designed specially pumped with normal fiber lasers.

Waste streams containing volatile fatty acids (VFAs) can be used for polyhydroxyalkanoate (PHA) production by mixed microbial cultures (MMCs) and most of the operating strategy for MMCs PHA production includes moderate organic loading and nitrogen limitation. However, waste streams in reality commonly contain different concentration of carbonand nitrogen (for example COD=24.0 g/L, Ammonia N=6.58 mg/L for fermented paper mill wastewater and COD=5978.17 mg/L, Ammonia N=398.18 mg/L for sludge fermentation liquid). This paper aims to investigate whether there is an optimal strategy for MMCs PHA production that appeal to a wide carbon and nutrient level spectrum.

Three typical sequence batch reactors (SBRs) submitted to aerobic dynamic feeding (ADF) mode were operated under the same C/N ratio, VFAs composition and hydraulic retention time (HRT) but different combination of sludge retention time (SRT), organic load rate (OLR) and cycle length (CL) to enrich PHA accumulating MMCs from municipal activated sludge. The PHA production capacity of SBRs under nutrient excess, limitation and starvation conditions (Cmol/Nmol ratio equals to 8, 40 and ∞, respectively) was evaluated in batch assays. The succession of microbial communities in SBRs and batch assays was analyzed by the method of terminal restriction fragment length polymorphism (T-RFLP). Batch assays of SBR#1 (long SRT, low OLR, long CL), SBR2# (short SRT, high OLR, long CL) and SBR#3 (short SRT, high OLR, short CL) showed similar results under nutrient starvation condition, with PHA content of 46.60 wt% (g PHA/g VSS), 46.46 wt% and 47.12 wt% achieved respectively after 7.5 h reaction, while batch assay of SBR#3 reached the maximum PHA content (54.85 wt%) under nutrient excess condition, compared to that of SBR#1 and SBR#2 of 49.99 wt% and 50.04 wt%, respectively. Regarding active biomass growth, batch assays of SBR#2 and SBR#3 showed an increase of 20.61% (g Biomass/g Initial Biomass) and 38.92% under nutrient limitation, 19.80% and 24.79% under nutrient excess, respectively, while no apparent growth occurred in batch assay of SBR#1 (8.92% and 4.15% under nutrient limitation and excess respectively). Negative growth were observed under nutrient starvation of all SBRs because of sampling loss. Due to the inhibition of free ammonia under nutrient excess condition, biomass growth was less compared to that under nitrogen limited condition. The results showed that SBR#3 had the best overall PHA production performance considering its relatively high PHA content and productivity in all nutrient conditions, which will guarantee the production performance with adaptability for a wide range of VFA-rich waste streams. Nitrogen has great impact on the biomass yield especially when OLR is high, the presence of nitrogen results in the increase of biomass consequently increases the final PHA productivity that can be calculated from .

Micropollutants represent a broad category of chemicals, which were previously unrecognized but are being of concern due to their potential risks to environmental and human health. Because the majority of micropollutants are released into wastewater treatment plants (WWTPs), which is a final barrier preventing the spread of micropollutants into the environment, the removal of micropollutants is highly desired in WWTPs (e.g., activated sludge system) to reduce the potential toxicity in the environment. In this talk, I will present whether or not micropollutants are sufficiently removed in activated sludge processes and, if so, what mechanisms underlie the removal of micropollutants. Further, this talk will discuss what activated sludge microorganisms are responsible for the biodegradation/biotransformation of micropollutants, which has implications for predicting the fate of micropollutants in WWTPs and developing an appropriate remediation strategy for treating micropollutants-bearing waste streams.

Membrane filtration has been increasingly used in water purification and wastewater treatment and reuse. However, membrane fouling is still a major problem to the membrane filtration process. Membrane fouling occurs in the boundary layer at the membrane surface where impurities rejected by the membrane accumulate and form a dynamic fouling layer. Owing to the lacking of experimental means, this dynamic fouling process that has not been well characterized. In this study, the micro-particle image velocimetry (MicroPIV) technique was utilized to achieve in-situ investigation of the membrane fouling dynamics near the membrane surface during the crossflow ultrafiltration in a flat-sheet membrane cell. A membrane sheet was placed on the bottom of the crossflow filtration cell. Fluorescent latex nanoparticles sizing 600 nm were used as particulate impurities or tracers in the feed solution. When excited by laser, the nanoparticles can emit fluorescent light. A high-speed scientific CCD camera equipped with a microscopic objective lens was employed to take photos of the flow field over the membrane surface during the ultrafiltration process, while the fluorescent signals from the nanoparticles were captured by the camera. With the MicroPIV technique, the dynamic process of fouling layer formation was directly observed. By further image processing, the thickness and the concentration of the dynamic fouling layer were well determined.

Anaerobic digestion is sensitive to a wide range of toxicants, and when they are present in inhibitory concentrations in wastewater, digester upset or failure can occur. Although many off-line monitoring of toxicants have been developed and widely used, measurement delays result in slow responses to these shocks. Such delayed feedback responses can lead to difficulties in preventing anaerobic digestion system failure. Microfluidic droplet reactors have many potential uses, from analytical to synthesis. In our project, a real-time biosensor based on microfluidic was fabricated to monitor the biotoxicity in anaerobic digestion.

Firstly, a rapid fluorescence-based assay was developed and applied for the detection of toxicants/inhibitors to anaerobic digestion metabolism. The technique revealed PCP’s toxicity to Enterococcus faecalis at a concentration of only 0.05 mg/L in 8 minutes. By extending this technique to a mixed anaerobic sludge, not only could the effect of 0.05-100 mg/L PCP be determined on anaerobic digestion metabolism within 10 minutes, but also its rate of biogas production. Using this bioassay, and based on its change in rate over time, we evaluated inhibition/stimulatory effect nickel (II), and cobalt (II), and their mixture, in just 6 hours.

Secondly, we introduced the developed bioassay into a Poly (methyl Methacrylate) (PMMA) microfluidics whose surface was modified by silica nanoparticle (SiNP) and dodecyltrichlorosilane (DTS) layers to enhance its wetting properties. Without surfactant addition, this SiNP-DTS modified chip has been used to monitor bacterial viability with a resazurin reduction bioassay. The whole process involving sequential reagents injection, and multiplexed droplet fluorescence intensity monitoring is carried out on chip. Metabolic inhibition of the anaerobe Enterococcus faecalis by 30 mg L^-1 of NiCl₂ was detected in 5 minutes.