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The navigable percutaneous disc decompression (PDD) device L'DISQ is an effective and safe option for the treatment of lumbar discogenic pain. However, few studies have evaluated the prognostic factors of successful PDD using this device.This study aimed to evaluate the prognostic factors associated with the successful outcome of PDD using the L'DISQ for treating lumbar discogenic pain by following up patients before and one, 2, 3, and 6 months after the procedure.Retrospective cohort study.Tertiary university hospital.A successful outcome was defined as a= 50% reduction in the numeric rating scale scores for pain and a= 40% reduction in the Oswestry Disability Index scores at 6 months after the procedure. Clinical parameters and patient demographics, including pain duration, history of surgery, number of treatment levels, and the radiographic findings of lumbar magnetic resonance imaging (MRI), were also examined.Of the 106 patients included, 80 (75.5%) had successful outcomes at 6 months. Multivariable logistic regression analysis revealed that the presence of high-intensity zones (HIZs) (P = 0.016) was an independent positive predictor of successful PDD outcomes; conversely, migration of the herniated disc (P = 0.017) and bilaterally herniated discs (P = 0.001) were negative predictors.The limitations of this study were its retrospective design, absence of a control group, and difficulty in predicting the effect when multiple levels were involved because of the use of MRI characteristics of the disc as a predictor.The presence of HIZs, the absence of migration of herniated discs, and the presence of unilaterally herniated discs are positive predictors of successful outcomes of PDD using the L'DISQ.

Incidences of brain death due to nicotine overdose by e-cigarettes have been increasing. In such cases, liver donation has been not reported because of the secondary damage to the liver due to metabolism of large amounts of nicotine. However, kidneys have been considered acceptable for transplant. Here, we present a successful case of liver transplant from a brain-dead donor due to intentional nicotine ingestion who did not have extensive steatosis. To the best of our knowledge, this is the first report of such a case.

In this paper, a generalized switching modification method is proposed to reduce the root-mean-square (rms) current flowing into a dc-link capacitor in a dc–dc–ac structure consisting of a boost converter and a three-phase inverter. To analyze the current flowing into the capacitor, we analyze the currents at the respective converter and inverter sides. Based on this analysis, we derive an analytical method to find the modification time between the converter and inverter pulsewidth modulation (PWM) carriers through a Fourier series and approximation to facilitate real-time implementation. Real-time implementation of the modification time calculated by the derived method is described. To verify the validity of the proposed method, experimental results are presented based on a 1-kVA dc–dc–ac prototype. The proposed method has a better capacitor rms current reduction performance than the conventional method in various inverter power factors and PWM strategies. Especially, it has an excellent performance in mid-power factor level (0.95–0.1).

2'-Fucosyllactose (2-FL), one of the most abundant oligosaccharides in human milk, has been spotlighted for its neutraceutical and pharmaceutical potentials. Microbial production of 2-FL is promising since it is efficient as compared to other production methods. In 2-FL microbial production via the salvage pathway for biosynthesis of guanosine 5'-diphosphate (GDP)-l-fucose from fucose, the conversion yield from fucose is important because of the high price of fucose. In this study, deletion of the genes (araA and rhaA) coding for arabinose isomerase (AraA) and rhamnose isomerase (RhaA) was attempted in engineered Escherichia coli for improving 2-FL production by using fucose, lactose, and glycerol. The engineered E. coli constructed previously is able to express fucokinase/GDP-l-fucose pyrophosphorylase (Fkp) from Bacteroides fragilis and the α-1,2-fucosyltransferase (FucT2) from Helicobacter pylori and deficient in β-galactosidase (LacZ), fucose isomerase (FucI), and fuculose kinase (FucK). The additional double-deletion of the araA and rhaA genes in the engineered E. coli enhanced the product yield of 2-FL to 0.52 mole 2-FL/mole fucose, and hence the concentration of 2-FL reached to 47.0 g/L, which are 44% and two-fold higher than those (23.1 g/L and 0.36 mole 2-FL/mole fucose) of the control strain in fed-batch fermentation. Elimination of sugar isomerases exhibiting promiscuous activities with fucose might be critical in the microbial production of 2-FL through the salvage pathway of GDP-l-fucose.

This paper demonstrates wavelength reused bidirectional transmission for a reflective coherent passive optical network (R-Co-PON). By reusing the downstream optical signal as the upstream optical carrier, the proposed R-Co-PON enhances the optical spectral efficiency. In an experimental demonstration, the proposed R-Co-PON achieved a symmetrical bidirectional transmission rate of 12 Gb/s using a 73-km-long fiber loopback architecture. The experiments confirmed the potential applicability of the proposed system in future optical access networks, particularly those using wavelength-division multiplexing.

Monolayer doping (MLD) has been regarded as the most suitable doping method for future semiconductor devices. MLD based on surface functionalization can be seriously affected by the surface states, including the orientations, crystallinities, and defects. We report for the first time the effect of surface states on boron-MLD (B-MLD) process and discuss the applicability of MLD for a fin structures. Depending on the surface states, the monolayer formation reaction is restricted, which causes more than five-fold differences in the doping level. Therefore, the surface states should be gravely considered before applying MLD and are crucial constraints in the MLD process on non-planar structures that have different surface states depending on its structural position. The B-MLD process on as-cleaned (100) and (110) silicon surfaces provides doping levels of 4.69 × 1020 and 2.48 × 1020 atoms/cm3, respectively. The MLD efficiency on the (110) orientation is degraded by insufficient reaction sites for the hydrosilylation reaction on the monohydride-terminated (110) silicon surface. Additionally, the surface damage interrupts the formation of a dopant-containing monolayer, causing a poor doping level and dose uniformity. Our research provides new insights into the development of wet-chemical doping methods for non-planar devices by studying the effect of surface states on MLD efficiency.

Photo-thermal processing assisted by laser irradiation is proposed as a novel method to control the phase of nickel silicide with reduction in the diffusion of nickel into the silicon substrate. The third harmonics of Nd3+:Y3Al5O12 laser (wavelength, 355 nm) is used for photo-thermal processing. Optical and thermal simulations are performed to obtain an optimum thickness (30 nm) of the nickel film for photo-thermal processing and to predict the temperature profile of the nickel-silicon interface during laser irradiation. It is confirmed that Ni2Si, NiSi and NiSi2 phase are effectively formed at the laser energy densities of 15, 20–40, and 50 mJ/cm2, respectively. We demonstrate that the phases of nickel silicide determined by Raman spectroscopy and X-ray diffraction analyses are in good agreement with those predicted by the heat transfer simulation. In addition, undesirable diffusion of nickel into silicon substrate is considerably reduced by instantaneous photo-thermal processing using the nano-second laser (pulse duration, 6 ns).

Channel equalization and phase noise compensation are required in coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission systems for reliable performance. In general, redundant data such as training symbols and pilot tones are necessary for channel and phase noise estimation in quadrature amplitude modulation (QAM) based CO-OFDM systems, which reduces the spectral efficiency of the system. Especially, in the coherent passive optical network (PON), the redundancy increases as the number of subscribers increases. In this letter, we propose a differential amplitude shift keying (DAPSK)-based CO-OFDM transmission for PON system, which does not require channel equalization and phase noise compensation processes. The proposed DAPSK-based CO-OFDM transmission was experimentally demonstrated, and the performance according to receiver launched power and the number of subcarriers was compared with QAM-based CO-OFDM.

In this paper, thermal stability of a one-dimensional metallodielectric photonic crystal (1D MDPhC) structure based on W and SiO2 for thermophotovoltaic systems is reported. The thermal degradation mechanism of the structure, in its operating temperature range, is thoroughly investigated by using energy dispersive spectroscopy (EDS) with transmission electron microscope (TEM) and depth-profiling X-ray photoelectron spectroscopy (XPS). It is found that the structure is entirely destroyed under 1400 K by an inter-diffusion process forming a mixture of W and SiO2 without measurable oxidization of W. But, long-term annealing results in oxidization of W layer even at a lower temperature of 1300 K. During the long-term annealing, oxygen atoms in outside atmosphere are believed to cause oxidation of the upper W layer below the top SiO2 layer. Additionally, delaminated spots are observed over the surface. These thermal behaviors are potential clues to prevent or minimize thermal degradation of the multilayer structure under high temperature operation.

2'-Fucosyllactose (2-FL) is one of most abundant oligosaccharides in human milk, which is involved in many biological functions for infant health. Since 2-FL has a great potential in application to functional food materials and pharmaceuticals, several microbial systems for mass production of 2-FL have been developed in recent years. Microbial production of 2-FL was suggested to be influenced by a number of factors including fucosylation activity of α-1,2-fucosyltransferase. In the present study, the wcfB gene coding for α-1,2-fucosyltransferase from Bacteroides fragilis was screened from eleven candidates of putative α-1,2-fucosyltransferase. Introduction of the wcfB gene allows the lacZ-deleted strain of E. coli expressing the genes for guanosine 5'-diphosphate (GDP)-l-fucose biosynthetic enzymes to produce 2-FL. As a result of fed-batch fermentation, 15.4g/L extracellular concentration of 2-FL with 2-FL yield of 0.858g/g lactose and productivity of 0.530g/L/h were obtained. In addition, the feasibility of industrial production of 2-FL using this microbial system was demonstrated by performing fed-batch fermentation in a 75L bioreactor.

We investigate the effect of the number of laser pulses on the formation of p+/n silicon ultra-shallow junctions during non-melt ultra-violet laser (wavelength, 355 nm) annealing. Through surface peak temperature calculating by COMSOL Multiphysics, the non-melt laser thermal annealing is performed under the energy density of 130 mJ/cm2. We demonstrate that increasing the number of laser pulses without additional pre-annealing is an effective annealing method for achieving good electrical properties and shallow junction depth by analyzing sheet resistance and junction depth profiles. The optimal number of laser pulses is eight for achieving a high degree of activation of dopant without further increase of junction depth. We have also explained the improved electrical characteristics of the samples on the basis of fully recovered crystallinity as revealed by Raman spectroscopy. Thus, it is suggested that controlling the number of laser pulses with moderate energy density is a promising laser annealing method without additional pre-annealing.

Optical interference noise (OIN), including optical beating interference and Rayleigh back-scattering noise, severely degrades transmission performance in self-coherent reflective passive optical network uplink transmission systems. A simple, cost-effective, and optical interferometry-based optical carrier cancelation method is proposed to reduce OIN. In this experiment, we demonstrate the cancelation of optical carriers, which is a major cause of OIN, up to 29 dB. Under the conditions of higher fiber input power and longer transmission distance, a remarkable improvement in transmission performance in terms of the eye-pattern and bit-error-rate was achieved.

We propose and demonstrate a novel all-optical virtual private network (VPN) using a microwave photonic filter, which enables inter-communications among optical network units in a passive optical network system. In our scheme, an optical coupler based recirculating delay line is used at optical line terminal as an optical subsystem to implement a microwave photonic-bandpass filter (MP-BPF). The periodic passbands of an MP-BPF are used to transmit VPN signal, whereas stopbands are used for conventional upstream transmission. The proposed system has two critical issues, optical phase-induced intensity noise in the MP-BPF and Rayleigh back-scattering interference by a single-fiber loop back link. To overcome the issues, an RF clipping tone based spectrum-broadening technique is applied to uplink transmitter. The proposed all-optical VPN system is tolerant to wavelength of VPN optical carrier, and enables multi-VPN data transmission using multi-passbands of MP-BPF.

Phase diversity of coherent optical communication provides spectrally efficient higher-order modulation for optical communications. However, in-phase/quadrature (IQ) imbalance in coherent optical communication degrades transmission performance by introducing unwanted signal distortions. In a coherent optical orthogonal frequency division multiple access (OFDMA) passive optical network (PON), IQ imbalance-induced signal distortions degrade transmission performance by interferences of mirror subcarriers, inter-symbol interference (ISI), and inter-channel interference (ICI). We propose parallel-channel discrete multitone (DMT) transmission to mitigate transceiver IQ imbalance-induced signal distortions in coherent orthogonal frequency division multiplexing (OFDM) transmissions. We experimentally demonstrate the effectiveness of parallel-channel DMT transmission compared with that of OFDM transmission in the presence of IQ imbalance.

Emissivity-tunable metamaterials of layered refractory metal and dielectric have great potentials as a simple thermophotovoltaic (TPV) selective emitter due to its near-omnidirectional, polarization-independent, and broadband selective emissivity. However, it is known that the stability of the layered structure is limited by the oxidation of metals. While there still exists ambiguity concerning the main source of oxygen between adjacent oxide layers and external residual oxygen, most reports focus on the adjacent layers. In this report, thermal stability of a tungsten-based layered metamaterial is investigated under a high-vacuum environment with great care to reduce residual oxygen. The results show unprecedented thermal stability up to 1200 °C for 3 h without any measurable oxidation of metal. This implies that the interlayer diffusion of oxygen from adjacent oxide layers is not exclusively responsible for the oxidation of metal. At such a high temperature, the layered metamaterial theoretically yields a high convertible radiative power density of 3.04 W/cm2 with comparable spectral efficiency of 40.2%. Finally, after performing series of thermal tests under higher thermal loads, we propose a novel high-temperature degradation model for layered metamaterials, the stability of which is ultimately limited by the agglomeration of thin metal layers.

L-Fucose (6-deoxy-L-galactose) is a major constituent of glycans and glycolipids in mammals. Fucosylation of glycans can confer unique functional properties and may be an economical way to manufacture L-fucose. Research can extract L-fucose directly from brown algae, or by enzymatic hydrolysis of L-fucose-rich microbial exopolysaccharides. However, these L-fucose production methods are not economical or scalable for various applications. We engineered an Escherichia coli strain to produce L-fucose. Specifically, we modified the strain genome to eliminate endogenous L-fucose and lactose metabolism, produce 2'-fucosyllactose (2'-FL), and to liberate L-fucose from 2'-FL. This E. coli strain produced 16.7 g/L of L-fucose with productivity of 0.1 g·L-1 ·h-1 in a fed-batch fermentation. This study presents an efficient one-pot biosynthesis strategy to produce a monomeric form of L-fucose by microbial fermentation, making large-scale industrial production of L-fucose feasible.

3-Fucosyllactose (3-FL), one of the major oligosaccharides in human breast milk, is produced in engineered Escherichia coli. In order to search for a good α-1,3-fucosyltransferase, three bacterial α-1,3-fucosyltransferases are expressed in engineered E. coli deficient in β-galactosidase activity and expressing the essential enzymes for the production of guanosine 5'-diphosphate-l-fucose, the donor of fucose for 3-FL biosynthesis. Among the three enzymes tested, the fucT gene from Helicobacter pylori National Collection of Type Cultures 11637 gives the best 3-FL production in a simple batch fermentation process using glycerol as a carbon source and lactose as an acceptor. In order to use glucose as a carbon source, the chromosomal ptsG gene, considered the main regulator of the glucose repression mechanism, is disrupted. The resulting E. coli strain of ∆LP-YA+FT shows a much lower performance of 3-FL production (4.50 g L-1 ) than the ∆L-YA+FT strain grown in a glycerol medium (10.7 g L-1 ), suggesting that glycerol is a better carbon source than glucose. Finally, the engineered E. coli ∆LW-YA+FT expressing the essential genes for 3-FL production and blocking the colanic acid biosynthetic pathway (∆wcaJ) exhibits the highest concentration (11.5 g L-1 ), yield (0.39 mol mol-1 ), and productivity (0.22 g L-1 h) of 3-FL in glycerol-limited fed-batch fermentation.

We propose a novel technique for mitigating the optical-beat-induced multi-user-interference (MUI) between the upstream multiple access signals in an orthogonal frequency division multiple access (OFDMA) passive optical network (PON). To provide upstream multiple access on a single-wavelength orthogonal frequency division multiplexing optical access network, optical beating interference and polarization diverseness are critical issues that severely degrade system performance. By using the proposed total intensity aggregation with self-homodyne coherent detection, we experimentally demonstrated stable transmission performance by reducing MUI in OFDMA PON upstream multiple access transmission.

A self-homodyne coherent detection technique using gain-saturated SOA (GS-SOA) is proposed. In the proposed system, local oscillator (LO) for optical coherent detection is extracted from the optical signal which is sent from the transmitter using the fact that the modulated downlink data can be erased with SOA operation in saturation region. Therefore, carrier frequency offset noise does not occur because LO light which is extracted from the received optical signal has totally same wavelength with the optical signal. In order to operate SOA operates in deep saturation region, high optical input power is needed. The proposed scheme was experimentally demonstrated, and the feasibility was discussed with the experimental results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:561–565, 2016

We propose window shaping based inter-band interference suppression technique in multi-band orthogonal frequency division multiple access (MB-OFDMA) based passive optical network (PON) system. Conventional MB-OFDMA and raised-cosine (RC) windowed MB-OFDMA were compared in QPSK transmission and adaptive modulation scenario. The effect of OFDM clipping ratio is analyzed, which is used to mitigate peak to average power ratio (PAPR) problem at the transmitter. Also, the MB-OFDMA based multiple access performance is investigated according to the different roll-off factor of RC window in terms of error vector magnitude (EVM) and effective bit rate. Compared with the conventional MB-OFDMA which is rectangular windowed, the RC-windowed MB-OFDMA shows better performance by suppressed sidelobe which leads to IBI. The maximum effective bit rate of 10 Gbps was achieved for 20 km transmission scenario at optimum roll-off factor, while it was 9 Gbps in the conventional MB-OFDMA transmission.

Whole-cell biotransformation of fatty acids can be influenced by the activities of catalytic enzymes and by the efficiency of substrate transport into host cells. Here, we improved fatty acid hydration activity of the recombinant Escherichia coli expressing an oleate hydratase of Stenotrophomonas maltophilia by targeting the catalytic enzyme into the periplasm instead of the cytoplasm. Recombinant E. coli producing OhyA in the periplasm under guidance of the PelB signal sequence (E. coli OhyA_PP) exhibited significantly greater hydration activity with oleic acid and linoleic acid compared to a recombinant E. coli producing OhyA in the cytoplasm (E. coli OhyA_CS). For example, the oleate double bond hydration rate of E. coli OhyA_PP was >400 μmol/g dry cells/min (400 U/g dry cells), which is >10-fold higher than that of E. coli OhyA_CS. As the specific activities of the enzymes targeted into the cytoplasm and periplasm were comparable, we assumed that targeting OhyA into the periplasm could accelerate fatty acid transport to the catalytic enzymes by skipping the major mass transport barrier of the cytoplasmic membrane. Our results will contribute to the development of whole-cell biocatalysts for fatty acid biotransformation.

In this report, a selective interface laser annealing (SILA) process is applied to the atomic-layer-deposited Al2O3 film/p-type silicon interface using an Nd3+: YAG laser with a wave-length of 532 nm. The absorptivity of the laser wavelength confirms a full absorption of the laser power to the Al2O3/Si interface without any loss through the Al2O3 film, which results in a successful selective annealing of the interface. Compared with conventional forming gas annealing (FGA), the SILA is found to build a thinner SiO2 interface layer and lead to a less reduction of capacitance. It is also revealed that the laser-annealed sample exhibits a surface blister density of 31 counts/mm2 which is much lower than the value of 250 counts/mm2 obtained from FGA. The suppression of the surface blister is attributed to the much shorter processing time of lasing (

Fucosyllactoses (FLs), present in human breast milk, have been reported to benefit human health immensely. Especially, 3-fucosyllactose (3-FL) has numerous benefits associated with a healthy gut ecosystem. Metabolic engineering of microorganisms is thought to be currently the only option to provide an economically feasible route for large-scale production of 3-FL. However, engineering principles for α-1,3-fucosyltransferases (1,3-FTs) are not well-known, resulting in the lower productivity of 3-FL than that of 2'-fucosyllactose (2'-FL), although both 2'-FL and 3-FL follow a common pathway to produce GDP-L-fucose. The C-terminus of 1,3-FTs is composed of heptad repeats, responsible for dimerization of the enzymes, and a peripheral membrane anchoring region. It has long been thought that truncation of most heptad repeats, retaining just 1 or 2, helps the soluble expression of 1,3-FTs. However, whether the introduction of truncated version of 1,3-FTs enhances the production of 3-FL in a metabolically engineered strain, is yet to be tested. In this study, the effect of these structural components on the production of 3-FL in Escherichia coli was evaluated through systematic truncation and elongation of the C-terminal regions of three 1,3-FTs from Helicobacter pylori. Although these three 1,3-FTs contained heptad repeats and membrane-anchoring regions of varying lengths, they commonly exhibited an optimal performance when the number of heptad repeats was increased, and membrane-binding region was removed. The production of 3-FL could be increased 10-20-fold through this simple strategy.

A new technique, which can increase the data rate in optical orthogonal frequency division multiplexed access link, is proposed in this paper. An adaptive sampling based on a compressive sensing (CS) technique is implemented in order to save channel bandwidth. The CS tells us that all signals with high sparsity, which is sampled below the Nyquist/Shannon limit, can be reconstructed successively using sufficient measurement. In this paper, it is reported that the compression ratio of 40 % is observed within the error free optical transmission (FEC limit: BER of 10−3) in case of QPSK symbols. It means that its data rate can be increased by 1.7 times (from 1.56 to 2.3 Gbps) using the proposed technique without the use of optical and electrical devices with higher physical bandwidth.

Objective: Some studies have evaluated the prognostic indicators associated with acute paraquat (PQ) poisoning. In this study, we externally validated the Yamaguchi index, which showed a good prognostic relevance in predicting the outcome of PQ poisoning. Methods: A retrospective analysis of 297 patients was performed. The Yamaguchi index was calculated using the following equation: Eq1 = (K+ × HCO3−)/(Creatinine × 0.088)(mEq/L) against time from PQ ingestion ( T). The patients were divided into three groups: group A: Eq1 > 1500 − 399 × log T, group B: 930 − 399 × log T < Eq1 ≤ 1500 − 399 × log T, and group C: Eq1 ≤ 930 − 399 × log T). Results: The overall mortality rate was 65.3% (194 of 297). The mortality rates of the three groups stratified by the Yamaguchi index were 7.1% (2 of 28), 22.4% (15 of 67), and 87.6% (177 of 202). The area under the receiver–operating characteristic curve for predicting mortality from the external validation of the Yamaguchi index was 0.842 (95% confidence interval: 0.795–0.882). Conclusion: The Yamaguchi index is a reliable prognostic factor and could be helpful in predicting mortality due to PQ poisoning.

We propose a scalable support WDM-based orthogonal frequency division multiple access-passive optical network uplink transmission system using an injection-locked Fabry–Perot laser diode (IL-FP-LD). This system uses an injection-locking technique to enhance the usable bandwidth by making stable channel states. By properly controlling the IL-FP-LD operation, the number of optical network units (ONU) within a wavelength can be increased, which improves the optical bandwidth efficiency for the uplink transmission. The experimental results show an enhanced modulation bandwidth of 3.5 GHz. Compared with a conventional RSOA which has a modulation bandwidth of 1.5 GHz, our scheme improves the number of ONUs that can be accommodated within a wavelength more than two times. The total discrete multitone signal received from the ONUs, with QPSK mapping on the subcarriers was 6.77 Gbps over a 23-km standard single mode fiber transmission. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1727–1732, 2015

Orthogonal frequency-division multiplexing (OFDM) is susceptible to multiple access interference and synchronization errors due to sidelobes, which hinder the integration of various applications and multiple access in OFDM-based optical transmission. In this letter, an adaptively modulated optical filter bank multicarrier with offset quadrature amplitude modulation-based sidelobe suppression is proposed in a wired/wireless converged optical network. We experimentally verified both the improvements in signal performance and spectral efficiency compared with OFDM in a multisender-supported optical network after a 50-km transmission.

The authors have proposed and experimentally demonstrated a novel slow adaptive orthogonal frequency division multiple access (OFDMA)-based passive optical network (PON) uplink transmission scheme using a 1-GHz reflective semiconductor optical amplifier operating as an optical network unit (ONU) in combination with Rayleigh backscattering (RB) mitigation in a 20-km single fibre loopback link. This RB mitigation, which can dramatically stabilise the channel state information and enhance the total throughput so that the OFDMA-PON transmitters can operate in the slow adaptive concept and provides beyond 15-Gbit/s uplink transmission, is achieved by employing 10-MHz low-frequency dithering of an optical seed carrier cooperating with a gain-saturated semiconductor optical amplifier at an optical line terminal. In doing so, the proposed scheme could guarantee a 50% total throughput enhancement with a proof-of-concept multiple access scenario for two ONUs, compared to its counterpart that does not apply the RB mitigation technique.

Multi-band OFDMA PON with windowing technique is proposed for asynchronous multiple access. In the asynchronous multiple access system, frequency orthogonality is not maintained among OFDM bands, and it leads to inter-band interference arisen from OFDM sidelobe. To mitigate this effect, raised cosine window is applied to suppress the sidelobe. The proposed system is experimentally compared with conventional Multi-band OFDMA PON according to different roll-off factor of raised cosine window.

Orthogonal frequency division multiple access-based passive optical network (OFDMA-PON) is considered as a strong candidate for next-generation optical access network. In intensity modulation/direct detection system, OFDMA-PON downlink transmission is relatively stable, but critical issues exist in uplink multiple access. Because of different optical paths, optical beat interference (OBI) and timing offset effect are generated, which seriously disturb signal detection. We propose optical pulse division multiplexing-based OBI reduction. By considering both the spectrum broadening effect and the time domain near orthogonality, OBI could be reduced. We demonstrate that the spectral efficiency can be improved from 0.37 to 3.8 bit/s/Hz in 1-GHz signal bandwidth. (C) 2016 Optical Society of America