Longer Fiber Length Research Articles

All-fiber integrated 10 GHz repetition rate femtosecond laser source based on Raman compression of pulses generated through spectral masking of a phase-modulated diode

We report the development of a 10 GHz repetition rate all-fiber integrated femtosecond source tunable around 1.55 μm. A phase modulator and sharp spectral filter are used to convert the output of a tunable CW diode to a 10 GHz pulse train. These pulses are compressed using Raman soliton adiabatic compression in a 21 km long length of fiber to generate sub-300-fs duration pulses at a 10 GHz repetition rate. By tuning the wavelength of the diode and appropriate filtering, similar performance was achieved over a 20 nm bandwidth.

Lateral Load Measurements Based on a Distributed Sensing System of Optical Frequency-Domain Reflectometry Using Long-Length Fiber Bragg Gratings

In this paper, we demonstrate the measurements of lateral loads in a distributed manner using long-length fiber Bragg gratings (FBGs) based on optical frequency-domain reflectometry (OFDR). Birefringence is induced at specific areas of the long-length FBGs by lateral compression. The distributions of the Bragg peaks were monitored by the OFDR sensing system, from which we calculated the applied lateral loads. Theoretical calculation results confirmed the validity of the experimental results. In addition, position-wise beat signals of the power of the obtained spectra were observed with smaller lateral loads that were not sufficient to provide two distinguished Bragg peaks. This unique phenomenon for the frequency-domain reflectometry scheme is explained theoretically. We proposed a method for utilizing the beat cycle to calculate smaller lateral loads.

Enhanced 1.5 μm luminescence lifetime of vacuum deposited erbium-doped organic thin films for optical amplification applications

ABSTRACTInorganic erbium-doped glasses are widely used in telecommunications due to the sharp intra-atomic 4I13/2 → 4I15/2 transition in the 4f orbital of erbium resulting in an emission at ∼ 1.5 μm, which is the low loss window of silica optical fibres. The limited erbium concentration of about 1020 ions/cm3 in inorganic erbium-doped glasses and the low absorption coefficient of the Er3+ ions, imply that relatively long lengths of fibre are required. Organic erbium complexes present higher absorption cross sections due to the photosensitization of erbium by the organic conjugated ligands and broader emission bands than those of the free Er3+ ions. Such properties open the possibility to develop compact, low power and broadband infrared emitting devices. We present the study of an organic fluorinated erbium complex exhibiting 1.5 μm luminescence lifetime of several hundreds of microseconds measured on thin film. The organic complex has been deposited by vacuum sublimation technique. This deposition method allows the realization of an erbium-doped thin film without the help of an organic polymer matrix, which is a potential source of vibrationnal luminescence quenching. We report the synthesis, the sublimation process, and the characterization of the thin films. The chemical structure of the complex is assessed by FTIR, NMR and MALDI-TOF. Chemical integrity of the thin film after vacuum deposition is determined by FTIR. The morphology of the thin film is characterized by X-ray diffraction experiments. The optical properties of the thin film are determined by spectroscopic ellipsometry, UV-Vis-NIR absorption spectroscopy and time resolved NIR photoluminescence spectroscopy.

CLONAL AND PLANTING DENSITY EFFECTS ON SOME PROPERTIES OF RUBBER WOOD (HEVEA BRASILIENSIS MUELL. ARG.)

Inter-clonal and intra-clonal wood properties and their variations from pith to bark were evaluated for wood density and anatomical features on rubber wood (Hevea brasiliensis Muell. Arg) from a 9-year-old plantation with planting densities of 500 and 2000 trees per hectare comprised of clones RRIM 2020 and RRIM 2025. Planting density had uneven effects on wood density and wood cell features. Intra-clonal and inter-clonal variations were significant for wood density in both clones and planting densities. Wood density demonstrated an increasing trend in the radial direction. However, at the lower planting density wood density near the bark decreased slightly. Fiber diameter, lumen diameter, and cell wall thickness showed an increasing trend from pith to bark. Best average fiber characteristics were observed at the lower planting density in clone RRIM 2025. Vessel frequency had a direct relationship with planting density in that it was higher in the higher planting density of 2000 trees per hectare. Overall, planting density had a significant effect on wood quality. The properties of clone RRIM 2025 were found to be comparatively better with longer fiber length and higher wood density than those of RRIM 2020.

Air-Bar cotton Lint Cleaner

Saw-type lint cleaners are now the most common lint cleaners used at gins because of their higher cleaning efficiency. Saw-type lint cleaning improves the grade of the fiber and increases the market value for the farmer. However, during the cleaning process the saw-type lint cleaners damage fiber in creating short fibers and neps. An innovative air-bar lint cleaner (ABLC) was designed and built. The ABLC used pressurized air to clean non-lint materials from cotton fiber while the cotton fiber batt was on a rotating saw cylinder. Thus, non-lint materials attached to the fiber were removed by the interaction of blowing force of compressed airflow and centrifugal force created by the rotating cylinder without the fiber making mechanical contact with a solid object, such as a grid bar. The fiber quality could be preserved by reducing the damage from mechanical impact of the fiber against the grid bar during the lint cleaning process. Preliminary testing of the ABLC prototype was conducted. Compared with cotton cleaned using the conventional saw-type lint cleaner, cotton cleaned using the ABLC had better fiber quality properties, including less short fiber content, less trash content, longer fiber length by number, less immature fiber content, lower yellowness, and less lint content in the lint waste.

Solving the Near-Far Problem in Dynamic Frequency Hopping-Optical Code Division Multiple Access using Power Control

In this study, a distributed power control algorithm is proposed for Dynamic Frequency Hopping Optical-CDMA (DFH-OCDMA) system. In general, the DFH-OCDMA can support higher number of simultaneous users compared to other OCDMA techniques. However, the performance of such system degrades significantly as the received power does lower than its minimum threshold. This may obviously occur in a DFH-OCDMA network with near-far problem which consist of different fiber lengths among the users, that resulting to unequal power attenuation. The power misdistribution among simultaneous active users at the star coupler would degrade the Bit Error Rate (BER) performance for users whose transmitting signals with longer fiber lengths. In order to solve these problems, we propose an adaptive distributed power control technique for DFH-OCDMA to satisfy the target Signal to Noise Ratio (SNR) for all users. Taking into account the noise effects of Multiple Access Interference (MAI), Phase Induced Intensity Noise (PIIN) and shot noise, the system can support 100% of users with power control as compared to 33% without power control when the initial transmitted power was −1dBm with 30 simultaneous users.

Solving the Near-Far Problem in Dynamic Frequency Hopping-Optical Code Division Multiple Access using Power Control

In this study, a distributed power control algorithm is proposed for Dynamic Frequency Hopping Optical-CDMA (DFH-OCDMA) system. In general, the DFH-OCDMA can support higher number of simultaneous users compared to other OCDMA techniques. However, the performance of such system degrades significantly as the received power does lower than its minimum threshold. This may obviously occur in a DFH-OCDMA network with near-far problem which consist of different fiber lengths among the users, that resulting to unequal power attenuation. The power misdistribution among simultaneous active users at the star coupler would degrade the Bit Error Rate (BER) performance for users whose transmitting signals with longer fiber lengths. In order to solve these problems, we propose an adaptive distributed power control technique for DFH-OCDMA to satisfy the target Signal to oise Ratio (S R) for all users. Taking into account the noise effects of Multiple Access Interference (MAI), Phase Induced Intensity oise (PII ) and shot noise, the system can support 100% of users with power control as compared to 33% without power control when the initial transmitted power was -1dBm with 30 simultaneous users.

Clonal and planting density effects on some properties of rubber wood (Hevea brasiliensis Muell. Arg.)

Inter-clonal and intra-clonal wood properties and their variations from pith to bark were evaluated for wood density and anatomical features on rubber wood (Hevea brasiliensis Muell. Arg) from a 9-year-old plantation with planting densities of 500 and 2000 trees per hectare comprised of clones RRIM 2020 and RRIM 2025. Planting density had uneven effects on wood density and wood cell features. Intra-clonal and inter-clonal variations were significant for wood density in both clones and planting densities. Wood density demonstrated an increasing trend in the radial direction. However, at the lower planting density wood density near the bark decreased slightly. Fiber diameter, lumen diameter, and cell wall thickness showed an increasing trend from pith to bark. Best average fiber characteristics were observed at the lower planting density in clone RRIM 2025. Vessel frequency had a direct relationship with planting density in that it was higher in the higher planting density of 2000 trees per hectare. Overall, planting density had a significant effect on wood quality. The properties of clone RRIM 2025 were found to be comparatively better with longer fiber length and higher wood density than those of RRIM 2020.

Multiplexing of Long-Length Fiber Bragg Grating Distributed Sensors Based on Synthesis of Optical Coherence Function

Long-length fiber Bragg grating (FBG) distributed sensors are multiplexed, and measurement of Bragg wavelength distribution along the gratings are demonstrated. This sensing system adopts synthesis of optical coherence function (SOCF) as a reflectometry technique to measure the distribution of the local reflection spectra inside the long-length FBGs. Simulations have been carried out to determine appropriate FBG reflectivity for the multiplexing. In the proposed system, which is a heterodyne interferometer, heterodyne beat frequency for each FBG gets different from those for the others, when the measurement speed becomes higher. By introducing a way for compensating the difference, three long-length distributed FBG sensors, which are originally uniform and have the same Bragg wavelength, are successfully multiplexed with 1 kHz sampling rate.

Wide-Range Tunable Optical Delay Line Using Dual Concentric Core Fiber With Dispersion Coefficient of ${-} $2800 ps/nm/km

There is great interest in finding a way to control the propagation speed of optical pulses through a medium. A pulse delay control technique that uses a dispersive medium and wavelength conversion has attracted a lot of attention because it is transparent as regards the format or bit rate of incoming signals. However, a long length of fiber is needed to obtain a sufficient delay in the delay line. In this paper, we propose a tunable optical delay line with a highly dispersive dual concentric core fiber (DCCF) that enables us to obtain a large time delay efficiently. The fabricated DCCF has a minimum dispersion of - 2800 ps/nm/km, and has the potential to generate a 54 ns/km delay by employing wavelength conversion within the C-band. We also evaluate the signal quality by measuring the bit error rate characteristics of the delayed signals through the proposed delay line.

A Long-Distance Remote Sensing Technique Using a Multiwavelength Raman Fiber Laser Based on Fiber Bragg Gratings Embedded in a Quartz Tube

A long-distance remote sensing technique using a multiwavelength Raman fiber laser with fiber Bragg gratings (FBGs) embedded in a quartz tube is proposed. A Raman linear cavity for multiwavelength generation was configured by using a long length of single mode fiber and FBGs. To discriminate concurrent sensitivities, such as temperature and strain sensitivities, FBG2 was etched to reduce the cladding diameter. Then, two FBGs with different cladding diameters put in a quartz capillary tube and FBG1 with a large diameter (125 μm) was firmly attached in a quartz capillary tube with UV curable epoxy. Since the two FBGs have identical material composition, the multiwavelength Raman fiber laser outputs have the same temperature sensitivities. However, since the FBG1 with a diameter of 125 μm was substantially fixed in a quartz capillary tube, the strain-induced wavelength shift was effectively suppressed. Since the FBG2 with a small cladding diameter of 60 μm only responds to the external strain change, the multiwavelength Raman fiber laser outputs have different strain sensitivities. Therefore, it is possible to simultaneously measure temperature and strain over a long distance of more than 75 km by using the proposed multiwavelength Raman fiber laser without additional input sources.

Vacuum Deposited Erbium-Doped NIR Luminescent Organic Thin Films For 1.5 μm Optical Amplification Applications

AbstractInorganic erbium-doped glasses are widely used in telecommunications due to the sharp intra-atomic 4I13/2 → 4I15/2 transition in the 4f orbital of erbium resulting in an emission at ∼ 1.5 μm, which is the low loss window of silica optical fibres. The limited erbium concentration of about 1020 ions.cm−3 in inorganic erbium-doped glasses and the low absorption coefficient of the Er3+ ions, imply that relatively long lengths of fibre are required. The organic erbium complexes present higher absorption cross sections due to the photosensitization of erbium by organic conjugated ligands and broader emission bands than those of the free Er3+ ion. Such properties open the possibility to develop compact, low power and broadband infrared emitting devices. We present the study of a highly doped organic thin film obtained from organic erbium complexes deposited by a vacuum sublimation technique. This deposition method allows the realization of an erbium-doped thin film without the help of an organic polymer matrix, which is a potential source of vibrationnal luminescence quenching. The ligands used in the present study are fluorinated in order to limit the vibrationnal quenching of the ligand itself, and to increase the volatility of the complexes. In this paper, we report the synthesis, the sublimation process and the characterization of the thin films.

A novel genetic variant of the goat Six6 gene and its association with production traits in Chinese goat breeds

We looked for novel genetic variations within the Six6 gene by PCR-SSCP, DNA sequencing and forced RFLP-PCR and estimated their associations with production traits in 2132 goats of eight indigenous Chinese breeds. A novel single nucleotide polymorphism (NM_001104993.1: g.232T>C) within the goat Six6 gene was identified. The frequencies of allele "C" varied from 0.8621 to 1.000, which were in Hardy-Weinberg equilibrium. Genotype and allele frequencies were found to be significantly different in the breeds. Association analysis revealed a significant relationship between genotypes and cannon circumference in Hainan black goats (P = 0.047); adult individuals with genotype CT showed higher cannon circumference than those with genotype CC. Another significant association of genotypes with five-year-old fiber length was found in Inner Mongolia white cashmere goats (P = 0.002). In addition, individuals with genotype CT had longer fiber length than those with genotype CC. The data revealed that the Six6 gene positively affects growth traits and cashmere traits. Polymorphism of Six6-PstI could be useful as a DNA marker for goat breeding and genetics via marker-assisted selection.

J044021 分布型光ファイバセンサを用いた接着継手内部のひずみ計測([J04402]知的材料・構造システム(2))

We have developed the distributed strain measurement system based on optical frequency domain reflectometry (OFDR) system. It can measure a strain distribution with the high spatial resolution at an arbitrary position along long-length fiber Bragg grating (FBG) sensors. In this study, we embedded the long-length FBG sensors into the adhesive of a single-lap joint. We could successfully measure the strain distribution at the interface between the adhesive and the adherend in the tensile test.

Self-referenced characterization of optical frequency combs and arbitrary waveforms using a simple, linear, zero-delay implementation of spectral shearing interferometry

We discuss a simple, linear, zero-delay implementation of spectral shearing interferometry for amplitude and phase characterization of optical frequency comb sources and arbitrary waveforms. We demonstrate this technique by characterizing two different high repetition rate (approximately 10 GHz) frequency comb sources, generated respectively by strong external and intracavity phase modulation of a continuous-wave laser. This technique is easy to implement, requiring only an intensity modulator and an optical spectrum analyzer (OSA), and is demonstrated to work at average power levels down to 100 nW (10 aJ/pulse at 10 GHz). By exploiting the long coherence lengths of these frequency combs and the self-referenced nature of the measurement, we also demonstrate a simple single-ended measurement of dispersion and dispersion slope in long lengths of fiber (>25 km).

Effect of different locations on the morphological, chemical, pulping and papermaking properties of Trema orientalis (Nalita)

The chemical compositions and fiber morphology of stem and branch samples from Trema orientalis at three different sites planted in Bangladesh were determined and their pulping, bleaching and the resulting pulp properties were investigated. A large difference between the stem and branch samples was observed. The stem samples have consistently higher α-cellulose and lower lignin content, and longer fibers than the branch samples in all sites. T. orientalis from the Dhaka and Rajbari region had higher α-cellulose content and longer fiber length, resulting in higher pulp yield and better papermaking properties. The T. orientalis pulp from Rajbari region also showed the best bleachability.

Anatomical Structures and Fiber Morphology of New Kenaf Varieties

Kenaf plant is claimed as one of the fast-growing herbaceous plants with the high potential as a fiber material or lignocellulosic material. Nine kenaf varieties i.e., Q-Ping, KK60, V12, V19, V36, V132 and NS V133 and TK were introduced recently by Taman Pertanian Universiti, Universiti Putra Malaysia as one of the potential plant to replace tobacco plantation. Since, these nine kenaf varieties are new to Malaysia, therefore, there is a need to study their anatomical structures and fiber morphology as well as microscopic appearances to understand their different and similarity. Cell morphology and anatomical appearances were observed and evaluated under the image analysis system (Leitz DMRB). From the results, V19 and V12 had the wider ray among the nine varieties, whereas other varieties in their microscopic appearance were almost similar to those observed in many diffuse-porous hardwoods. The longest fiber length was observed in variety TK (2.96 mm) followed by V36. Q-ping showed the widest fiber diameter and lumen diameter amongst the nine varieties, with value of 28.64 μm in bast fiber and 28.06 μm in core diameter. However, Q-ping had the thinnest core cell wall with the thickness of 3.34 μm. In term of fiber length, all the kenaf varieties bast fiber has longer fiber than core fiber. The kenaf core of nine varieties has wider fiber diameter and fiber lumen diameter than the bast fiber. Conclusively, although kenaf exhibit similarity in some fiber morphology and anatomical structures, however, there still some distinction that can be used to differentiate these kenaf variety.

Solving the Near-Far Problem in Dynamic Frequency Hopping-Optical Code Division Multiple Access using Power Control

Problem statement: In this study, a distributed power control algorithm is proposed for Dynamic Frequency Hopping Optical-CDMA (DFH-OCDMA) system. Approach: In general, the DFH-OCDMA can support higher number of simultaneous users compared to other OCDMA techniques. However, the performance of such system degrades significantly as the received power does lower than its minimum threshold. Results: This may obviously occur in a DFH-OCDMA network with near-far problem which consist of different fiber lengths among the users, that resulting to unequal power attenuation. The power misdistribution among simultaneous active users at the star coupler would degrade the Bit Error Rate (BER) performance for users whose transmitting signals with longer fiber lengths. In order to solve these problems, we propose an adaptive distributed power control technique for DFH-OCDMA to satisfy the target Signal to Noise Ratio (SNR) for all users. Conclusion: Taking into account the noise effects of Multiple Access Interference (MAI), Phase Induced Intensity Noise (PIIN) and shot noise, the system can support 100% of users with power control as compared to 33% without power control when the initial transmitted power was -1dBm with 30 simultaneous users.

Fabrication and Applications of Low Loss Nonlinear Holey Fibers

We present the important fabrication issues involved with the realization of low loss, low water peak, nonlinear holey fibers based on the Stack and Draw technique. We have realized fibers with loss performances in the 1.38 μm spectral region that are limited by the intrinsic losses of the raw materials, opening up the possibility of using long lengths of such fibers to demonstrate phenomenon such as Raman amplification and supercontinuum generation using continuous wave pump sources.

Simulations and experiments on polarization squeezing in optical fiber

We investigate polarization squeezing of ultrashort pulses in optical fiber, over a wide range of input energies and fiber lengths. Comparisons are made between experimental data and quantum dynamical simulations to find good quantitative agreement. The numerical calculations, performed using both truncated Wigner and exact $+P$ phase-space methods, include nonlinear and stochastic Raman effects, through coupling to phonon variables. The simulations reveal that excess phase noise, such as from depolarizing guided acoustic wave Brillouin scattering, affects squeezing at low input energies, while Raman effects cause a marked deterioration of squeezing at higher energies and longer fiber lengths. We also calculate the optimum fiber length for maximum squeezing.