Optical Performance Analysis Research Articles

Analysis of laser beam propagation properties with the Collins formula in a focused laser system

A Collins formula method with a scaling factor between the target and source plane is proposed for laser propagation in optical system design, which can be used to evaluate laser optical system performance and tolerance analysis. The laser propagation in optical systems can be calculated by the Collins integral formula, and an angular spectrum method is derived by coordinate substitution. It is introduced a scaling factor m, making the choice of the observation plane more flexible and the calculation more accurate. A laser optical system is designed, and its tolerance analysis is conducted by the angular spectrum method. The evaluation criterion is the laser spot radius in the far-field, which is defined by 86.5% power in bucket. The radius of the laser spot in 90 m distance is from 0.8 to 1.4 mm by the tolerance analysis, which the ideal expectation is 0.92 mm and the experimental result is 1.01 mm. In the distance of 47 m, the radius is from 0.42 to 0.73 mm by the tolerance analysis, which the ideal expectation is 0.48 mm and the experimental result is 0.46 mm. The experimental results agree with the results of the tolerance analysis well. The focal shift for laser propagation in optical systems is validated. The experimental results confirm the calculation and they prove the use of the method in laser focus optical system design.

Optical Flow-Switched Transport Layer Protocol Design and Performance Analysis

We explore transport layer protocol design for a scheduled optical flow-switched network. The design guarantees the reliable delivery of large data files (“elephant” flows) over an all-optical end-to-end flow-switched network that can be modeled as a burst-error channel. We describe a good first-order channel model for optical flow-switched networks with optical amplifier transients. First, we show that transmission control protocol (TCP) performs poorly in such networks. Specifically, flow control and fair resource allocation with windowing in TCP are unnecessary since they are done via scheduling. Instead, we propose a transport protocol that uses file segmentation and reassembly, interleaving with forward error correction, and frame retransmission to combat burst errors. We analyze the protocol performance using standard results from information theory and probability theory and optimize throughput efficiency and delay, find practical frame lengths, and optimize flow durations.

Optical performance analysis of a HCPV solar concentrator yielding highly uniform cell irradiance

Here we analyze the optical performance of a novel solar concentrator design suitable for high-concentration photovoltaic (HCPV) modules. In the design, a pair of confocal parabolic reflectors and a Fresnel lens with matching focal length are employed to achieve high irradiance uniformity on the solar cell in an HCPV module. To evaluate the sunlight concentrating characteristics of this concentrator design, its peak concentration ratio (PCR) on the solar cell, overall optical efficiency, and acceptance angle are calculated numerically. Moreover, the dependence of these performance indices on the geometrical concentration ratio (GCR) and aspect ratio (AR) of the concentrator also is investigated, so as to identify the “optimal” concentrator geometry. It is thus demonstrated that, at a GCR of 800× for example, the concentrator design can limit the PCR below 1200× for all ARs greater than unity. Also, test data for a sample concentrator with 800× GCR and an optimized AR of 1.6 indicate that the enhanced cell irradiance uniformity enables an HCPV module to achieve an increased photovoltaic conversion efficiency of 28.6%.

DSSC-Integrated Glassblocks for the Construction of Sustainable Building Envelopes

The paper shows the first results of the optical performance analysis carried out on the DSSC integrated glassblock, an innovative building product developed at the Department of Architecture of the University of Palermo. In the field of a research that is being conducted in order to define innovative solutions for the construction of photovoltaic and energy efficient translucent building envelopes, different hypotheses of integration of DSSC into the glassblock have been foreseen. The integration of glassblock with third generation PV systems allows to define a novel building-PV product that meets the current requirements of the BIPV (Building Integrated Photovoltaics) market. By means of OptiCAD® software, several numerical simulations were conducted to analyse the solar factor, the light transmittance and the shading coefficient of the device.

Optical characterization of nonimaging dish concentrator for the application of dense-array concentrator photovoltaic system

Optimization of the design of a nonimaging dish concentrator (NIDC) for a dense-array concentrator photovoltaic system is presented. A new algorithm has been developed to determine configuration of facet mirrors in a NIDC. Analytical formulas were derived to analyze the optical performance of a NIDC and then compared with a simulated result obtained from a numerical method. Comprehensive analysis of optical performance via analytical method has been carried out based on facet dimension and focal distance of the concentrator with a total reflective area of 120 m2. The result shows that a facet dimension of 49.8 cm, focal distance of 8 m, and solar concentration ratio of 411.8 suns is the most optimized design for the lowest cost-per-output power, which is US$1.93 per watt.

Impact of the Phosphors on the Conformal Coating LED by Optical Simulation

The conformal coating phosphor converted light emitting diode (LED) is one of the important high power white LED. The thickness, concentration and concentration distribution of the phosphor layer has a critical influence on the LED optical performance. Previous literature mainly focus on the luminous flux of the LED. Few are involved with the relationship between the concentration and the correlated color temperature (CCT), and angular color uniformity (ACU) of LED. Based on the ray-tracing simulation, the luminous flux, CCT and ACU affected by the phosphor thickness, concentration and concentration distribution were obtained and studied. The results provide effective references for the phosphor coating process design and optical performance analysis of conformal coating LED.

Design of High Power RGB White Light Emitting Diodes

In this paper, thermal performance of RGB white LED packages was optimized by thermal simulation using the Finite Volume method. A Monte Carlo photon simulation method was utilized for the analysis of optical performance of LED in quantitative terms. It was found that the distribution of RGB chips has great effect both on the thermal and optical performance of the RGB white LEDs. The tilted angle, material of the reflection cup, and the shape of encapsulant were found to be the key factors which determine the extraction efficiency of LED package. It is demonstrated that the combination of optical and thermal simulation provides a comprehensive optimization approach for a design of high efficient RGB white LED package.

Free space optical communication performance analysis with focal plane based wavefront measurement

In order to decrease the Bit Error Rate (BER) and increase coupling efficiency of free space optical (FSO) communication system, we compute and compensate the wavefront aberrations of the laser signal with the wavefront measurement method based on the focal plane proposed in this paper. The aberrations of laser signal are calculated based on the two images which are respectively generated from focal plane (PF) channel and the defocused plane (DF) channel. Assuming the On–Off Keying (OOK) modulation is used under the condition of weak turbulence, the fundamental of wavefront measurement method based on focal plane is introduced. By numerical simulation, we analyze the variation trend of coupling efficiency and BER, using the method we proposed to measure and compensate the wavefront aberrations for the FSO communication system. The experiment results show that the wavefront measurement error can reach nearly 0.004 wavelengths, the average coupling efficiency increases from 10.32% to 63.82%, and the average BER of FSO communication system decreases from 10−5 to 10−13.

A study on the heat dissipation of high power multi-chip COB LEDs

In this study, the heat dissipation efficiencies of high power multi-chip COB (Chip-on-Board) LEDs with five different chip gaps were compared by assessing their junction temperature (Tj) and thermal resistance (Rth). Junction temperatures were measured using an IR camera and were also simulated by computational fluid dynamics (CFD) software. The effects of heat sinks with different surface areas, heat slugs made of different materials and different injection currents (different wattages) on high power LED junction temperatures are discussed. In addition, the optical characteristics of the LED, such as its lumens and luminous efficiency are evaluated. The experimental results show that a chip with a smaller gap has a higher junction temperature and more thermal resistance, and the junction temperature difference between the LEDs with the smallest and largest chip gaps is 3.12°C. Optical performance analyses show that the LED with a larger chip gap has higher lumens and higher luminous efficiency. Thus, higher junction temperatures reduce the optical performance of high power LEDs.

基于传输矩阵法的聚合物太阳能电池光学性能分析

基于传输矩阵法的聚合物太阳能电池光学性能分析

硅基有机太阳能电池光学性能分析

The effects of active layer thickness,capping layer thickness and transport layer thickness on the optical absorption of active layer have been investigated by employing MATLAB and an optical model based on the transfer matrix method.The results reveal that the absorption of active layer is mainly attributed to its thickness which could be optimized by the microcavity effect.Furthermore,it demonstrates that active layer optical absorption can be effectively improved by adjusting the thickness of capping layer and transport layer.At last,the results show that the solar cells with 10 nm thick transport layer have superior optical and electrical performance than those without transport layer;the optimized thickness of ZnS layer and the thickness of Alq3 layer are 30 nm and 60 nm,respectively.The research of optical properties of organic solar cell on Si substrate provides a theoretical basis to its future structural design and application.

Modeling and analysis of quadruple optical ring resonator performance as optical filter using Vernier principle

Vernier principle based modeling and analysis of an optical ring resonator structure that includes four asymmetric rings are introduced in this paper to obtain very wide free spectral range (FSR). Delay line signal processing approach in Z-domain modeling is used for analysis of waveguide based novel quadruple optical ring resonator (QORR). Two QORR architectures made of SOI and SiN waveguides have been compared, which produce FSR of 343.4 THz 264.6 THz respectively. Apart from obtaining wider FSR and adequate suppression of spurious interstitial modes close to -30 dB, this work presents group delay and dispersion characteristics for QORR made of materials with different effective refractive indices.

Optical performance analysis of V‐trough PV concentrators

AbstractThis paper proposes a method for the analysis of the optical losses that take place inside PV concentrators, which is useful in the design of such systems. The study is focused in V‐trough concentrators with two‐axis tracking. Those are low concentration systems that use nearly conventional flat PV modules. Optical losses are shown to depend on the cavity angle, the mirrors spectral and angular reflectance and the surfaces dirtiness. Final effective concentration ratio and relative cost should consider all these analysed factors. This will help in the search of the most efficient solution in each case. Copyright © 2008 John Wiley & Sons, Ltd.

LED照明的光栅光调制器光学特性分析与实验

LED照明的光栅光调制器光学特性分析与实验

Analysis of graded-index polymer optical fiber link performance under fiber bending

Bending effects on bandwidth and loss of a graded-index polymer optical fiber (GI POF) were investigated, and those influences on the optical link performance were discussed simultaneously for the first time. The numerical apertures (NAs) of the GI POFs were deliberately varied from 0.154 to 0.292. A bending radius larger than 10 mm induced little mode coupling and little change in the bandwidth of the GI POF. A bending radius smaller than 10 mm caused degradation in the bandwidths of the higher NA GI POFs. On the other hand, in the lower NA GI POFs, even more severe bending could cause little change in their bandwidths. Thus, the lower NA GI POF seemed preferable in suppressing the bandwidth change. However, the higher NA GI POF exhibited the lower bending loss. The preferable NAs for both characteristics were completely opposite. Moreover, the bending loss under underfilled launch (UFL) could be lower than that under overfilled launch (OFL). On the other hand, the bending loss was equivalent to the bandwidth degradation in view of the link power penalty. Therefore, the bandwidth change and loss caused by the bending were the critical factors to optimize the optical link considering the link power budget. The high-NA GI POF with almost ideal refractive-index profile could provide stable high performance in overgigabit communication even under any bending conditions.

Analysis of ShuffleNets with limited number of wavelength converters employing deflection routing

Optical node performance analysis in terms of number of wavelength converters for a multihop optical ShuffleNet under deflection routing is presented. From the computed results for a given number of wavelengths, it is found that in order to achieve the minimum deflection probability at full load, the number of wavelength converters required is at most 60% of the number of wavelengths. Any additional wavelength converters would not be necessary in reducing the overall deflection probability. These upper-bound findings are indeed helpful for network engineers designing a cost-effective network node.

100 Mbit/s IrDA optical wireless throughput performance analysis

Existing IrDA standard optical wireless links operate at data rates up to 16 Mbit/s. Such links are incorporated into millions of products such as mobile phones, personal digital assistants, laptop and palmtop PCs. Longer term, IrDA is destined to create standards for links at even higher data rates. The performance of such links depends crucially on the efficient operation of the IrDA IrLAP protocol. The authors examine the IrDA IrLAP protocol performance at data rates up to 100 Mbit/s. Using a mathematical analysis based on the concept of ‘window transmission time’, the throughput equation of IrLAP is derived. Subsequently, optimum values for important design parameters of the link layer such as window size and frame length are derived, for maximum IrLAP throughput as a function of BER. The results indicate that the IrLAP protocol offers excellent performance even at 100 Mbit/s. High link layer throughput even at high data bit error rates is possible provided the IrLAP window size and frame length values are adapted to optimum values for the corresponding BER. Results are presented on link performance limited due to the turnaround time. Such results are important to hardware manufacturers of high speed optical wireless links.

Analysis of Wavelength-Routed Optical Burst-Switched Network Performance

This paper studies a novel scalable network architecture combining optical burst switching (OBS) with dynamic wavelength allocation to guarantee quality of service (QoS), forming a wavelength-routed optical burst-switched network. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Different burst aggregation mechanisms are evaluated for a range of traffic statistics in terms of delay and packet loss rate. New network performance parameters in an analytical model quantify the advantages of dynamic wavelength allocation. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength routed optical networks.

Fabrication of large-aperture lightweight diffractive lenses for use in space

We describe the advantages of using diffractive (Fresnel) lenses on thin membranes over conventional optics for, among others, future space telescope projects. Fabrication methods are presented for lenses on two types of freestanding membrane up to 50 cm in size. The first is a Fresnel lens etched into a thin (380-microm) glass sheet, and the second is an approximately 50-microm-thick polymer membrane containing a Fresnel lens made by replication process from a specially made fused-silica master. We show optical performance analysis of all the lenses that are fabricated, including a diffraction-limited Airy spot from a 20-m- focal-length membrane lens in a diffractive telescope system.

Geometric analysis of optical fiber EFPI sensor performance

In this note, the geometric analysis of an optical fiber EFPI sensor performance is presented to establish a relationship between the geometric parameters of an EFPI sensor and its output characteristics due to environmental perturbations. Based on the theoretical analysis, two EFPI sensors have been constructed and their temperature and pressure responses have been tested. The experimental results were in good agreement with the analysis. The obtained conclusions provide general guidance for the geometric design and optimization of an optical fiber EFPI sensor for given application requirements.