Integrated optical attenuator based on mechanical deformation of an elastomer layer

We propose an optical attenuator concept based on a polymer waveguide coupled to an elastomer thin film. The thickness of the elastomer layer can be controlled by Coulomb force-induced squeezing in a capacitor geometry. Thereby resonant coupling between the light modes in the waveguide and the elastomer layer is achieved. We predict close to 100% modulation contrast and about 40% transmission for an about 200 μm long device. In addition, we demonstrate experimentally a proof-of-principle of the attenuator device.     

Polymer waveguide thermo-optic switches with −70 dB optical crosstalk

To reduce the crosstalk of the polymer waveguide optical switches, waveguide attenuators are integrated with the switch on the same substrate. The switch and attenuator shares a single connected electrode which is controlled by a single current source. Due to the simple structure of the integrated attenuator, the device length is reduced to 10 mm so as to provide low insertion loss of 0.8 and 1.1 dB for 1300 and 1550 nm, respectively. Further radiation of the remained optical signal on the switch-off branch is induced by the integrated attenuator so that the switching crosstalk is reduced to −70 dB with an applied electrical power of 200 mW. The low crosstalk is maintained for the environmental temperature range of −10 to 55 °C.     

Analysis and optimization of an InGaAsP/InP waveguide variable optical attenuator

An InGaAsP/InP waveguide variable optical attenuator (VOA) is proposed in this paper. The device consists of straight input and output waveguides and an S-bend waveguide. An electrode is deposited on a portion of the waveguide to form an active region so that its refractive index can be modified by a current injection, resulting in the variation of the transmitted optical power. The beam propagation method is employed in the numerical simulation and the device structure is optimized using a genetic algorithm. The optimized VOA has a low excess loss (<1 dB) and a large dynamic range of about 40 dB.     

Polymeric PLC-type thermo-optic optical attenuator fabricated by UV imprint technique

A planar lightwave circuit-type polymer thermo-optic optical attenuator was fabricated via a UV imprint technique. In order to reduce the step for filling of cores and minimize the detrimental residual slab waveguide, convex ridge-type micro cores for guidance of light were defined with an accuracy of ±0.5 μm on the under-clad by a single step of imprinting. The voltage-controlled polymer optical attenuator showed 30-dB attenuation with 80-mW electrical input power at a wavelength of 1.55 μm. The rise and fall times are less than 5 ms. It displays about 0.2- and 1-dB polarization dependence at 0- and 10-dB attenuations, respectively.     

S弯曲聚合物热光型可变衰减器的特性

提出一种热光聚合物可变光衰减器(VOA)的设计分析,利用S弯曲的波导提高衰减效率,BPM法模拟中验证其衰减动态范围可达60 dB,实现60 dB的衰减计算功耗为60 mW,附加弯曲损耗小于0.3 dB.并且具有很好的极化独立性,串扰低,尺寸小,易于集成.     

Digitally controlled fault-tolerant multiwavelength programmable fiber-optic attenuator using a two-dimensional digital micromirror device

A digitally controlled multiwavelength variable fiber-optic attenuator using a two-dimensional digital micromirror device (DMD) is introduced. The results from an experimental four-wavelength (i.e., 1546.92, 1548.52, 1550.12, and 1551.72 nm) proof-of-concept attenuator indicate a 26-dB dynamic range and 11-bit resolution. The measured attenuator average coherent optical cross talk per wavelength channel is -38 dB , limited by the additive noise resulting from the nonideal isolation of the optical circulator and the attenuator module. The average optical loss for our experimental attenuator is 15 dB and is limited mainly by the visible-mode DMD that is used as a 1550-nm infrared window device. Our theoretical estimate of a <8-dB loss optimized attenuator can be used for equalization in multiwavelength fiber-optic communications with as many as 108 wavelengths.     

Variable photonic crystal fiber optical attenuator combining air hole reduction induced radiation and bending loss

Recently, an optical attenuator has been important in fiber optic communication systems, because a transmission power in fiber has become higher due to a channel increment in wavelength division multiplexing transmission. A photonic crystal fiber (PCF) optical attenuator is fabricated by air hole diameter reduction in a part of PCF in which radiations are caused in the air hole diameter reduced part of PCF. A PCF optical attenuator has a high power resistance feature due to its radiation-induced operation of optical attenuation. In this paper, we proposed a variable PCF optical attenuator in which a bend was applied to the air hole diameter reduced part in PCF optical attenuator that was fabricated by CO₂ laser irradiation. In PCF optical attenuator fabrication, the attenuation was adjusted by the reduced air hole diameter with laser irradiation time control. It was demonstrated that 10.6–13.5 dB of variable attenuation was obtained at 1550 nm-wavelength with 0°–90° bending angle applied to the air hole diameter reduced part in PCF optical attenuator.     

The thermo-optical variable optical attenuator based on SOI

A thermo-optical variable optical attenuator was studied based on silicon on insulator (SOI) substrate waveguide. It is composed by the single-mode waveguide, taper waveguide, multi-mode waveguide, and inclined electrode. By adjusting the applied voltage on the inclined electrode it can achieve continuously variable attenuation of the output light. The results we studied show that when the applied voltage is about 4.7 V (the corresponding power is 233 mW), the variation of the waveguide's core temperature is about 33 °C, the refractive index changes more than 5.0 × 10⁻³ and the attenuation will reach 35 dB, and the response time is only 35 μs.     

Loss in a rectangular optical waveguide induced by the crossover of a second waveguide

We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design.     

Stable dual-wavelength erbium-doped fiber ring laser with switchable spacing employing controllable channel loss

A stable dual-wavelength erbium-doped fiber ring laser with switchable spacing is proposed and experimentally demonstrated. An arrayed waveguide grating (AWG) incorporating two fiber optic switches (OS) is used to as the wavelength selector. The ring cavity is divided into two cavities by a 30:70 optical coupler. Equalized dual-wavelength outputs are achieved by controlling the variable optical attenuator (VOA) inserted in the lower loss cavity. The wavelength spacing can be tuned from 0.80 to 12.05 nm. The fiber laser has good optical quality with maximum power fluctuation of 1.5 dB and side mode suppression ratios (SMSRs) higher than 71 dB.     

Photonic Crystal Fiber Attenuator

We propose a novel fiber attenuator based on photonic crystal fibers. The difference in the modal field diameters of a conventional single mode fiber and a photonic crystal fiber was used. A variable optical attenuator was also achieved by applying macro-bending on the PCF part of the proposed attenuator     

High-speed electrooptical VOA integrated in silicon-on-insulator

In this paper, we present simulation results of an electrooptical variable optical attenuator (VOA) integrated in silicon-on-insulator waveguide. The device is functionally based on free carriers absorption to achieve attenuation. Beam propagation method (BPM) and two-dimensional semiconductor device simulation tool PISCES-II were used to analyze the dc and transient characteristics of the device. The device has a response time (including rise time and fall time) less than 200 ns, much faster than the thermooptic and micro-electromechanical systems (MEMSs) based VOAs.     

新型可变光衰减器的温度特性研究

介绍一种新型光衰减器的工作原理、结构及温度特性.实验中采用在线温度特性测试法得到了新型光衰减器的插入损耗随温度变化的特性曲线.提出通过改进工艺的办法来优化新型光衰减器结构和提高光衰减器温度稳定性的方案.     

Coupled-resonator optical waveguide: a proposal and analysis

We propose a new type of optical waveguide that consists of a sequence of coupled high-Q resonators. Unlike other types of optical waveguide, waveguiding in the coupled-resonator optical waveguide (CROW) is achieved through weak coupling between otherwise localized high-Q optical cavities. Employing a formalism similar to the tight-binding method in solid-state physics, we obtain the relations for the dispersion and the group velocity of the photonic band of the CROW's and find that they are solely characterized by coupling factor k(1) . We also demonstrate the possibility of highly efficient nonlinear optical frequency conversion and perfect transmission through bends in CROW's.     

The 650-nm variable optical attenuator based on polymer/silica hybrid waveguide

Visible light variable optical attenuators(VOA) are essential devices in the application of channel power regulation and equalization in wavelength-division multiplexing cross-connect nodes in plastic optical fiber(POF) transmission systems.In this paper, a polymer/silica hybrid waveguide thermo–optic attenuator based on multimode interference(MMI) coupler is designed and fabricated to operate at 650 nm. The single-mode transmission condition, MMI coupler, and transition taper dimensions are optimized through the beam propagation method. Thermal analysis based on material properties provides the optimized heater placement angle. The fabricated VOA presents an attenuation of 26.5 dB with a 21-mW electrical input power at 650 nm. The rise time and fall time are 51.99 and 192 μs, respectively. The time–stability measurement results prove its working reliability.     

Microwave System for BEPCⅡ-Linac

Specifications of microwave system for BEPCⅡ-Linac were enhanced by a wide margin in comparison with those of the microwave system for BEPC-Linac. For this reason many RF components must be developed and improved. This paper introduces the developments of SLED detuning system, accelerating section, high power waveguide valve, high power dummy-load, and medium & high power waveguide attenuator/phase shifters. High power operation of the microwave system has been carried out.     

毫米波大功率脉冲衰减器渐变结构的匹配研究

首先提出一种适合于毫米波大功率脉冲衰减器的结构形式，然后，用里兹－瑞利法分析了它的截面阻抗值，根据阻抗值，提出渐变线的一种优化方法。经实验验证，这种渐变结构的衰减器具有很低的驻波，同时也可有很高的功率容量。     

Field enhancement of gold optical nanoantennas mounted on a dielectric waveguide

In this paper, we investigate the localized field enhancement of optical nanoantennas consisting of different types of coupled gold nanoparticles and fed by a silicon nitrite slab waveguide. The optical nanoantenna is mounted on the surface of the waveguide, and the incident blue-violet light is guided in the slab waveguide and then reflected to the nanoatenna at the end of the waveguide. We also study the performance of the slab waveguide with different optimized parameters and also the field enhancement achieved by different shapes of nanoantennas.     

Fabrication and study of a metal-clad planar waveguide based biosensor

A metal-clad planar optical waveguide biosensor having five layer structure has been fabricated to study the detection of Pseudomonas and Pseudomonas-like bacteria. This waveguide is designed to increase the overlap of the evanescent field extension from the sensor face with the micro-scale biological objects in the bulk solution, to place most of the entire volume of the bacteria within the evanescent field. The results presented here leads to a significant optimization of the important design parameters to sense micro-scale biological objects. We have compared our computed results with the results obtained by similar non-metallic clad biosensor. The effect of affinity-layer refractive index on the sensitivity of these planar waveguides is also studied. We have shown this for some special cases by obtaining reflection dips at the particular angle of incidence. Our observations show that the metal-clad planar optical waveguide biosensor having higher affinity refractive index will give better sensitivity than other similar non-metallic clad biosensor. The validation of metal-clad planar optical waveguide sensor for the detection of Pseudomonas aeruginosa bacterium is also made.     

Comparative study of asymmetric versus symmetric planar slab dielectric optical waveguides

In this paper we have studied the asymmetric versus symmetric planar waveguide in terms of their usefulness in optical fiber communication systems. We have explored the thin waveguide versus thick waveguide first. Later on usefulness of asymmetric versus symmetric waveguide is carried out to target for WDM optical network application. All kinds of optical network components are fabricated on Si substrate with the point of view of their application. Here asymmetric planar structure may be more useful compared to symmetric waveguide in terms of their non-uniform power confinement properties. However, the symmetric waveguide structure may be more useful for their high power confinement properties. It is well known that the thin symmetric waveguide supports at least one mode. However the thick waveguide may support many even as well as odd modes. We study the power confinement properties for symmetric as well as asymmetric waveguide structure. We conclude that higher order modes show the nonlinear power variations. Mode field profile for various cases is discussed as well. Comparative study between asymmetric versus symmetric waveguide has a lot of significance in optical network area. It has been shown through analysis that in asymmetric waveguide, the power flows more through film region in the case of fundamental mode. Power confinement properties for asymmetric waveguide versus symmetric waveguide have been studied.