Modeling and characterization of a new three-stage quadruple pass EDFA

Variation in cotton fiber length impacts processability at the mill and the quality of spun yarns. The High Volume Instrument (HVI) and Advanced Fiber Information System (AFIS) are cotton fiber quality assessment instruments able to quickly assess a myriad of fiber quality characteristics. HVI testing provides the fiber length parameters most widely utilized by the cotton industry, Upper Half Mean Length and Uniformity Index. However, HVI fiber length parameters do not account for the complete within-sample variation in fiber length, such as the shortest fibers in the sample. AFIS testing is able to characterize the complete within-sample distribution of fiber length within a sample of cotton by evaluating individual fibers. Within-sample variation in fiber length is an important cotton fiber quality concern because it impacts processing performance and yarn quality. In this paper, the fiber length for 9127 commercial cotton bales was evaluated on both HVI and AFIS. The AFIS length distributions are used to characterize the complete distribution of fiber length within each bale. A novel statistical technique is introduced and is used to characterize a set of multivariate axes that characterize the total within-bale variation in fiber length among the complete set of commercial bales. These results suggest that less than half of the variation in cotton fiber length captured by the AFIS length distributions is captured by the two length parameters provided by HVI testing. If an experimental factor has no significant impact on an HVI fiber quality parameter, an alternative cotton fiber length measurement such as the AFIS length distribution should be considered.

This work analyses gain property of an erbium doped fibre (EDF) pumped at 830 nm. Particularly, gain at 1550 nm obtained from an EDF is numerically investigated by solving a number of rate and propagation equations incorporating the effect of amplified spontaneous emission (ASE). In addition, the impact of forward and backward ASE on the propagation of pump and signal powers along the fibre length is studied. ASEs are observed to increase if pump power or signal power or EDF length is increased. However, the impact of ASE on gain is very much sensitive with fibre length and power levels. For instance, gain at 1550 nm is found to be more affected by ASE at lower pump and signal powers. It is observed that, gain difference (AG) between gain estimated with ASE effect and without ASE effect is higher for pump powers lower than 50 mW at 830 nm. Thus, the analysis of gain properties in EDF under 830 nm pump are significant to model and design amplifiers using EDF.

We propose a novel optimization method that combines two design criteria to reduce the differential modal gain (DMG) in few-mode cladding-pumped erbium-doped fiber amplifiers (FM-EDFAs). In addition to the standard criterion that considers the mode intensity and dopant profile overlap, we introduce a second criterion that ensures that all doped regions have the same saturation behavior. With these two criteria, we define a figure-of-merit (FOM) that allows the design of FM-EDFAs with low DMG without high computational cost. We illustrate this method with the design of six-mode erbium-doped fibers (EDFs) for amplification over the C-Band targeting designs that are compatible with standard fabrication processes. The fibers have either a step-index or a staircase refractive index profile (RIP), with two ring-shaped erbium-doped regions in the core. With a staircase RIP, a fiber length of 29 m and 20 W of pump power injected in the cladding, our best design leads to a minimum gain of 22.6 dB while maintaining a DMGmax under 0.18 dB. We further show that the FOM optimization achieves a robust design with low DMG over a wide range of variations in signal power, pump power and fiber length.

Within-sample variation in cotton fiber length is a major factor influencing the production and quality of yarns. The textile industry has been searching for approaches of improving the long fiber fraction and minimizing the short fiber fraction within a cotton sample to produce superior fiber and yarn quality. USTER® High Volume Instrument (HVI) has been widely used for a rapid assessment of cotton fiber length traits from a fiber bundle. However, its effectiveness for genetic studies has been questioned due to the indirect estimations of the cotton fiber traits that cannot be measured from a fiber bundle. To overcome the limits of the HVI fiber length traits, we utilized the Advanced Fiber Information System (AFIS) measuring fiber length traits directly from individual fibers based on weight or number. Comparative fiber length analyses showed AFIS provided higher sensitivity in detecting the fiber length variations within and among cotton samples than HVI. The weight-based AFIS length traits were strongly correlated with the corresponding HVI lengths, whereas the number-based AFIS mean length showed a relatively weaker correlation with the HVI lengths. Integrations of the weight based-length traits with genome-wide association studies (GWAS) enabled classifying the QTLs specifically associated with long, mean, or short fiber length traits and identified a false positive associated with the indirectly estimated HVI short fiber trait. Unlike the weight based-AFIS length traits, the number-based AFIS length trait did not show a negative correlation with a weight related-HVI property, and identified a single QTL that was not detected by the corresponding HVI trait. These results suggested that integrating the AFIS method with GWAS helped discoveries of the genome loci involved in the within-sample variation in cotton fiber length and characterizations of the fiber length QTLs.

An implicit analytical solution for the gain and output signal power of a realistic erbium doped fibre amplifier is given as a function of pump power, fibre length, input signal power and various fibre and material parameters. This solution is shown to accurately predict the gain variation with fibre length and pump power, and the saturation behaviour with increasing signal power. It is a useful building block for accurately modelling multiamplifier systems while minimising computation time.

In this research, Amplified Spontaneous Emission (ASE) spectrum characteristics for a highly Yb3+ doped glass fiber with different pump powers and pump wavelengths are scrutinized. ASE spectral profile and wavelength shift corresponding to different optical fiber lengths are measured. Highly-doped Yb3+ fiber lasers in a linear-cavity are both experimentally and analytically investigated. Rate equations are solved using quasi-numerical models. Numerical results are reported for wide range of operating conditions to enable design optimization. The model takes into account the scattering loss and the distributed laser loss power density in strongly pump condition. The effects of various parameters such as pump power, pump wavelength, signal wavelength and fiber length on the output power and laser threshold are studied. Theoretical results are shown to be in good agreement with the experimental data.

The establishment of fast-growing teak plantations in Indonesia provides opportunities for shorter harvesting periods. However, it also poses challenges on wood utilization due to juvenility and growth stress-related defects. This study investigated growth stress levels and some wood properties of 10-year-old fast-growing teak grown in Gunungkidul Regency, Yogyakarta. The strain gauge method was used to measure longitudinal surface released-strains (LRS), tangential surface released-strains (TRS), and longitudinal internal residual strains (IRS). Wood specimens were also collected near each strain measurement point for the analysis of wood properties. The results showed LRS values ranging from −1243 to 320 με, TRS values ranging from −779 to 382 με, and IRS values ranging from −589 to 786 με. Meanwhile, radial variations in fiber length, modulus of elasticity, and lignin content were observed. Significant correlations were found between IRS values and microfibril angle, fiber length, modulus of elasticity, lignin content, and hemicellulose content, while no significant correlations were observed between LRS and TRS values and wood properties. These findings suggest a moderate level of growth stress. Additionally, the results also indicate that this 10-year-old fast-growing teak is still in the juvenile stage. Therefore, its utilization should be performed with caution.

Predicting the modulus of short fiber‐reinforced composites is complicated by simultaneous variations in fiber length, orientation, and volume fraction during processing. This work refines the classical modified rule of mixtures (MROM) by introducing two concentration‐dependent weighting functions, and , which capture the evolution of effective fiber length, fiber‐fiber interactions, fiber orientation, and loading‐angle effects. A microstructural efficiency coefficient is further incorporated to describe reinforcement degradation from dilute to crowded fiber conditions. The model was validated using ethylene‐vinyl acetate/short carbon fiber composites with fiber volume fractions of 1.37%–16.80%. Young's modulus measured at loading angles of 0°, 45°, and 90° showed excellent agreement with predictions, with the refined formulation outperforming the classical MROM, particularly at higher loading angles. Overall, the refined framework provides a compact and physically grounded framework for accurately predicting stiffness and supports the design and optimization of short fiber‐reinforced polymer systems.

We develop a simulation tool for an all-optical gain-clamped erbium-doped fiber amplifier (GC-EDFA) based on an amplified spontaneous emission (ASE) reflector and thoroughly verify its validity by comparing simulation data with experimental ones. We carry out simulation work as changing conditions like reflection ratio and bandwidth of the ASE reflector, EDF length, and pump power. From this work, we have an exact understanding about the gain clamping principle that a reflected ASE acts like an intensity reservoir against input signal intensity variation. In general, as a reflected ASE power becomes higher, both a dynamic range and a noise figure (NF) increase; on the other hand, a clamped gain value decreases. The ASE reflector-based gain clamping scheme can be used for EDFAs with low NF characteristics at small input signal range in case a reflected ASE power is set at a level much lower than powers required for normal gain clamping function.

It is proposed that in high fiber-fraction composites with relatively weak matrices, final fracture and toughness may be more dependent upon architectural details than upon crack behavior in the matrix phase. Specifically, implications of statistical variations in fiber length are considered. A simple analytical model for the stress-strain behavior of a fiber dominated composite is described. Characteristics of the model are discussed with regard to existing experimental data.

ケヤキ材の繊維長,繊維壁厚,早材道管内腔面積の髄から樹皮にかけての変動と成長状態との関連を調べた。繊維長は供試木の肥大成長に関わらず,平均して髄からの年輪数で約10年輪,距離で約2cmぐらいまで急速に伸長する。繊維壁厚はほとんど一定の傾向がみられないものと,年齢とともに約10年ぐらいまでわずかに増大するものがみられた。早材道管の内腔面積は初期の肥大成長の影響が強く,肥大成長が悪いと増大率が減少する。しかし,髄から約7cmまでは急速に増大する。ケヤキの構成要素の寸法変動からみて,木材の性質は髄から約10年,距離で約7cmの範囲はきわめて不安定と考えられる。

Core samples collected from 30–31 year old Tectona grandis (teak) clones from CSO raised in 1974 at Maredumilli, Rajahmundry, Andhra Pradesh were evaluated for different wood quality parameters. Based on mean annual increment (MAI) computed from tree growth and volume of wood, the trees were categorized in three groups—best (B), average (A) and poor (P) performing clones. Variation in fibre length, fibre diameter, wall thickness; increment growth rate, moisture content and specific gravity were studied using core samples taken from two opposite sides at breast height of stem of each clone. Comparisons were made between these categories based on the wood quality parameters. The objective of study was to generate base line information on wood quality of teak clones which are source material for plantations and further research programs. This will also help the tree breeders and forest managers in selecting best quality planting stock based on the inherent wood quality traits for further propagation. The results of the study indicated that different wood quality parameters such as anatomical structure, growth rates, percentage of moisture content and specific gravity varied within as well as between the categories and exhibited to have greater relevance as reference information for quality improvement and value addition than MAI alone. Some of clones having average MAI exhibited comparatively better wood quality parameters. Similarly, some of best clones showed slightly inferior values to certain wood quality parameters. It is thus suggested that in any large scale species improvement programs taken up by the plantation industries including Forest Departments, more emphasis should be given to wood quality parameters during progeny trials of such commercially important species for different end use applications as value addition.

This paper presents a novel fiber spraying process for the manufacturing of short fiber bundle‐reinforced Nextel™ 610/Al 2 O 3 ‐ZrO 2 oxide fiber composites (SF‐OFC) and its characterization. First, the influence of varying fiber lengths (7, 14, and 28 mm, continuous fibers) and fiber orientations (unidirectional 0°, quasi‐isotropic, ±45°) was investigated using hand‐laid SF‐OFC. Due to the weak matrix, the hand‐laid material exhibited a strongly fiber‐dominated material behavior, that is, variations in fiber length and orientation had a strong influence on the material properties. Second, the automated sprayed SF‐OFC, however, exhibited a random orientation of the fiber bundles, which resulted in in‐plane isotropic material properties. Average bending strengths of up to 177 MPa, strains of .39%, and a quasi‐ductile fracture behavior were achieved. The strain was, therefore, in the range of fabric‐reinforced OFC. While the bending strength of the SF‐OFC was somewhat lower than that of fabric‐reinforced OFC with the fiber orientation parallel to the loading direction, it was more than two times higher than the strength in 45° direction relative to the fabric reinforcement. Combined with good drapability and lower material costs compared to fabric‐reinforced OFC, SF‐OFC is, therefore, a promising material for industrial applications.

A amplification model of Er/Yb co-doped fiber amplifiers (EYDFAs), considering Er-bands amplified spontaneous emission (ASE), is proposed to optimize the parameters of EYDFAs in space applications. The impact of pump wavelength, fiber length, and input signal power on the performance of EYDFAs are investigated numerically.

Summary form only given. Many applications require high power good beam quality lasers with fiber delivered output. Very often, the necessary powers are above the damage threshold and nonlinear effects threshold of single mode (SM) fibers. This may be overcome by two approaches. A first approach is to use either large mode area fibers or photonic crystal fibers (PCFs), which have a very large and nearly SM cores. Nevertheless, this approach is limited by the achievable nearly SM core size, which is 40 μm for a flexible PCF. A second possible approach is to impose a Gaussian mode in a highly multimode (MM) step-index fiber with very large core diameter. In this approach, it was found that in passive highly MM fibers the fundamental mode can be maintained over short distances (~20 cm) in the case of straight fibers [1], or over longer distances in the case of coiled fibers [2]. Additionally, off-centered coupling of the fundamental mode into highly MM (100-400 μm core diameter), 2 m long, passive fibers was studied [4], along with its effect on the output beam quality [3]. Finally, SM excitation in active MM fibers, as means for achieving high quality output in an amplifier configuration, was also reported [2].Additionally, offcentered coupling of the fundamental mode into highly MM (100-400 m core diameter), 2 m long, passive fibers was studied [4], along with its effect on the output beam quality [3]. Finally, SM excitation in active MM fibers, as means for achieving high quality output in an amplifier configuration, was also reported [2]. Here we experimentally investigate propagation of the fundamental mode in highly MM passive and active fibers. We resorted to well controlled, free-space coupling of a Gaussian beam to the MM fiber, instead of tapering or other complex ways of mode coupling. The experimental setup in the case of a passive fiber consists of a 1 μm CW Gaussian seed source, coupling optics, and a commercially available highly MM passive fiber with 50 μm core diameter and 0.15 numerical aperture (NA). This fiber supports ~200 spatial modes and can handle almost 1 MW of peak power. The measured effect of the fiber length and coiling radius on the beam quality (M2) is shown in Fig 1 (left). As evident, the beam quality improves with larger coiling radius and with shorter fiber length. In addition, a clear minimum of the M2 parameter (<;1.2) is observed at a coiling radius of 7.5 cm for all fiber lengths. This demonstrates fundamental mode propagation in highly passive MM fiber for more than 15 m without significant degradation. In the case of an active double-clad fiber, the experimental setup is similar but includes a 2 m long fiber and a pump source with suitable coupling optics in a counter propagating pump configuration. In these experiments our active fiber is extremely MM (supports ~340 spatial modes), with 140 μm core diameter and 0.07 NA, which can handle up to 7.5 GW peak power. To the best of our knowledge, this is the largest active core diameter that was used for preservation and amplification of the fundamental mode. Our experimental results, which are presented in Fig. 1 (right), show successful preservation of the fundamental mode in this fiber with M2<;2. Additionally, the amplification results show some degradation in beam quality with increasing pump power that corresponds to the increase in amplified spontaneous emission (ASE). Since the fundamental mode field diameter is significantly smaller than the active core diameter, highly multimode ASE is generated, degrading the beam quality. A more detailed discussion as well as additional experimental results will be presented.