Antifungal activity of chitosan against Fusarium oxysporum f. sp. cubense.

The in vitro antifungal activity of chitosan against Fusarium oxysporum f. sp. cubense Race 4 (FocR4) the causal agent of banana wilt was investigated. Chitosan at all concentrations tested reduced the hyphal growth of FocR4 on potato dextrose agar media and recording maximum inhibition of 76.36% at 8 mg/mL. The inhibitory effect was found to increase as chitosan concentration increases. The 50% effective concentration value was estimated by probit analysis, and it was 1.4 mg/mL. Chitosan was more effective in potato dextrose broth where it completely inhibited the mycelial growth of FocR4 at all concentrations tested. Chitosan inhibited the sporulation of FocR4 by a maximum of 96.53% at 8 mg/mL chitosan, and 100% inhibition for spore germination was recorded at all concentrations tested. Chitosan at concentrations of more than 1.6 mg/mL was also found to induce morphological changes in FocR4 characterized by agglomeration of hyphae, abnormal shapes, vesicles, or empty cells devoid of cytoplasm in the mycelia

Performance evaluation for optical backhaul and wireless front-end in hybrid optical-wireless access network

The hybrid optical-wireless access network (HOWAN) is a promising broadband access network. In this paper, the new architecture of the HOWAN is proposed and designed based on both a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul and a wireless fidelity (WiFi) technology at the wireless front-end. The power budget of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length of 23 km from the central office (CO) to a 54 Mb/s access points (APs) along a 50 m outdoor wireless link is analyzed

Multimode interference photonic switches

Photonic switches are becoming key components in advanced optical networks due to their various applications in optical communication. One of the key advantages of photonic switches is the fact that they redirect or convert light without any optical to electronic conversions and vice versa. As one type of optical switch, multimode interference (MMI) switches have received more attention in recent years due to their significant role. The structure and operation principle of various types of MMI switches are introduced, and the recent progresses of MMI switches are also discussed

A ridge waveguide for thermo-optic application

A thermal analysis and structure of a ridge single mode waveguide with a metal heater are presented. The steady-state temperature increases linearly and the thermal response becomes slower at the same power consumption, when the under-etched depth in the lower cladding increases. When the upper cladding thickness decreases, the thermal response becomes faster. This shows that a thinner upper cladding and a deeper etching are preferred to achieve a faster thermal response and lower power consumption, respectively. The numerical simulation also shows the power consumption of the present ridge waveguide is almost third of that for conventional one and the response time is half of that of the conventional one

Fabrication and characterization of polymer thermo-optic switch based on MMI coupler

The 2×2 polymer thermo-optic switch based on MMI coupler is realized. This device is fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of -36.2 dB is achieved at cross and bar states. A power consumption of 1.85 mW is applied to change the state of the switch from the cross to the bar state. A switching time of less than 0.7 ms is traced to change a state of the realized switch

Fixed wireless service coexistence with IMT-A system within UHF band

Coexistence analysis is exceedingly important in investigating the possibility for spectrum sharing between IMT-A system and existing wireless services. The 470-862 MHz frequency band is currently allocating to several services such fixed wireless access (FWA). International telecommunication union-radio (ITU-R) sector has allocated sub-bands within 470-862 MHz for IMT-A system. This concurrent operation causes a destructive interference that influences the coexisting feasibility between IMT-A and this existing service, FWA. This paper addresses a timely and topical problem dealing with spectrum sharing and coexistence between an IMT-A systems and FWA service within 790-862 MHz. Co-channel and adjacent channel with an overlapping band and with or without guard band are intersystem interference scenarios investigated. The deterministic analysis is carried out by spectral emission mask (SEM) technique. Different significant factors such as channel bandwidths, propagation path lengths, and clutter loss which influence the feasibility of coexistence are examined. Feasible coexistence coordination procedures in terms of separation distance, frequency offset, and guard band are suggested

Thermo-optic multimode interference switches with air and silicon trenches

A novel thermo-optic multimode interference (MMI) switch with air and silicon trenches was proposed, and the performance of the switch was simulated. In the design, one heating electrode is used to alter the refractive index at a spot image which changes the phase of this image to realize the switching function. The simulation results clearly indicate that the MMI switch can satisfy −39 dB crosstalk at two states. The electric power consumption for the MMI switch with these trenches is less than half of that of a conventional MMI switch

Bandwith efficient hybrid wireless-opical broadband-access network (WOBAN) based on OFDM transmission

In this paper, a simple and bandwidth efficient hybrid wireless-optical broadband access network (WOBAN) based on orthogonal frequency division multiplexing (OFDM) is pro- posed and designed. It is an optimal combination of an optical backhaul and a wireless front-end for an e±cient access network. The bandwidth e±cient WOBAN based on OFDM provides an effective solution to eliminate intersymbol interference (ISI) caused by dispersive channels. There are two factors considered important here; multipath fading in wireless link and dispersion effects in fiber link. The physical layer performance is analyzed in terms of bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR). An 8 Gb/s data rate has been achieved by the optical backhaul along optical ¯ber length of 20 km. The wireless front-end access point supports data rate up to 240 Mb/s along an outdoor wireless link

Low loss 1x2 optical coupler based on cosine s-bend with segmented waveguides

This paper presents an optimization of 1x2 polymer Y-junction optical coupler. The optimized optical coupler comprises straight polymer waveguide as the input waveguide, tapered waveguide, modified cosine S-bend and linear waveguide. At the branching point, N short waveguides with small width are introduced to reduce evanescent field. At operating wavelength of 1550 nm the excess loss of the coupler is ~0.18 dB. In term of polarization dependence loss (PDL), the proposed coupler also shows a good performance with PDL value of less than 0.015 dB for wavelength range of 1470 nm-1550 nm. The proposed coupler could reduce excess loss more than 25% compared to conventional Y junction optical coupler