Variable Fiber-optic Attenuator Research Articles

Optically controllable variable fiber optical attenuator integrated in conventional optical fiber

New type of optically controllable variable fiber optical attenuator based on thermo-optical effect in liquid cladding of optical fiber is described. The thermo-optical effect in liquid cladding optical fiber causes refractive index contrast changes in core–cladding interface, what enables to change the propagating optical signal power with temperature. The temperature change is achieved by fiber based heating element using laser radiation. Attenuation up to −12dB was achieved in static dependence and dynamic response confirmed rise time up to 24ms.

Flat Spectral Response Digital Micromirror Device-Based Variable Fiber Optic Attenuator

To the best of our knowledge, for the first time, an all-digital broadband variable fiber optic attenuator (VFOA) is demonstrated using the Texas Instruments' digital micromirror device (DMD) that does not use any narrowband or polarization-sensitive components. Simulations show that the proposed VFOA has a truly flat spectral response with a wavelength-dependent loss (WDL) of <;0.01 dB over the C-band 1530-1560 nm with a DMD designed to operate in the infrared. Experimental results show a WDL of ± 0.13 dB and a dynamic range of 38.6 dB with a visible DMD.

Variable Liquid-Core Fiber Optical Attenuator Based on Thermo-Optical Effect

We present variable fiber optical attenuator based on shaped and metal-coated liquid core optical fiber filled with index matching liquid. Variable attenuation of 60 dB was achieved by thermo-optical effect, where focused laser beam with optical power of 2 mW was used as a local heating source. Dynamic response shows rise time of 30 ms.

Experimental demonstration of an all‐fiber variable optical attenuator based on liquid crystal infiltrated photonic crystal fiber

AbstractThe application of a nematic liquid crystal infiltrated solid core photonic crystal fiber as a novel all‐fiber in‐line electronically controlled broadband fiber optic attenuator in the wavelength range from 1500 to 1600 nm is demonstrated.The device based on photonic bandgap transmission is electronically controlled and, due to its compact configuration, can be easily incorporated into an optical network. A low‐insertion loss at zero attenuation state and a high‐extinction ratio of ∼40 dB are obtained between the high and low transmission states of the attenuator. The device works on the application of a varying voltage applied perpendicular to the fiber axis. The attenuation varies linearly with an increase in voltage, with a ∼3.5 V increment required for 1 dB attenuation. The device is shown to have a flat spectral response for all attenuation states in the wavelength range. The device can be used as the core of a highly efficient in‐line electronically controlled variable fiber optic attenuator. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:539–543, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25789

Properties of novel variable optical attenuator based on electrowetting microprisms

A novel variable fiber optical attenuator (VFOA)using an electrowetting microprisms (EMPs) and and two self-focusing lenses is proposed . EMPs can change the wetting angle of solid-liquid interface technology by electronic control methods. The attenuation of the VFOA is analyzed by the theory and experimental measurements . Theoretical analysis and experimental results show that a good control effect of light attenuation in the small voltage range (such as 135—139 V),and the optical attenuation range can achieve in 2—60dB. With the merits of novel conception, easy production, low cost and simple structure, the device will be widely used in communications fields after the optimized design. Disadvantage of this device is high voltage, in order to reduce the operating voltage to achieve the purpose of actual use, screening of high dielectric constant material as the dielectric layer material is topic of future research.

High Dynamic Range Variable Fiber-Optical Attenuator Using Digital Micromirrors and Opto-Fluidics

To the best of the authors knowledge, proposed is the first variable fiber-optical attenuator (VFOA) using a digital micromirror device (DMD) and an opto-fluidic electronically controlled variable focus lens (ECVFL). The hybrid VFOA uses individually controllable two-state micromirrors of the DMD and the variable focal length capability of the ECVFL to control the amount of light coupled between two fiber ports leading to a high dynamic range VFOA. The demonstrated VFOA at 1545 nm has a 63.5-dB dynamic range, <0.1-dB resolution, 0.2-dB polarization-dependent loss, 4.9-dB optical loss, and < 100-ms switching time. Applications for the proposed VFOA include use in test and measurement systems.

A liquid lens-based broadband variable fiber optical attenuator

To the best of our knowledge, proposed is the first variable fiber optical attenuator (VFOA) using an electronically controlled variable focus liquid lens. The approach uses the changes in the radius of curvature of the liquid lens edge to enable an electronically controlled optical wedge that produces a varying beam tilt angle. In effect, changing beam tilt within a single mode fiber (SMF) lens free space coupling assembly leads to a polarization independent broadband VFOA design. The demonstrated VFOA experiment shows broadband operation over the 1530–1560 nm C-Band with a 40 dB dynamic range, <0.5 dB resolution, 0.3 dB polarization dependant loss, 4.3 dB fiber-to-fiber optical loss, 3 dB optical bandwidth from 1510 nm to 1700 nm, and switching time of <100 ms. Applications for this VFOA include use in hand held test and measurement equipment.

Broadband All-Digital Variable Fiber-Optic Attenuator Using Digital Micromirror Device

To the best of our knowledge, we propose the first broadband variable fiber-optic attenuator (VFOA) using a digital micromirror device (DMD). The VFOA design is based on a unique double reflection geometry structure that counters the strong spectral attenuation inherent when implementing single-mode-fiber light coupling via a pixelated blazed grating device such as a DMD. The demonstrated VFOA features ~C-band 1530- to 1560-nm broadband attenuation operation with a plusmn0.17-dB in-band variation and a 25-dB attenuation dynamic range. This high repeatability all-digital VFOA can be useful in broadband optical source controls, test instrumentation, telecommunications, signal processing, and sensor systems.

Micro-electromechanical systems variable optical attenuator based on nonsilicon surface micromachining technology

A novel, electromagnetically driven variable fiber optic attenuator based on micro-electromechanical system (MEMS) technology is described. The attenuation level is adjusted by changing the microshutter position in the optical path. A new technique, termed "nonsilicon surface micromachining," is used to fabricate the shutter, in which a copper layer was used as the sacrificial layer, and the electroplated FeNi as the structure layer. This scheme provides another way to fabricate the optical microstructure. The optical characteristics of the attenuator are theoretically analyzed, and the result is verified by experiments. The MEMS attenuator has fiber-to-fiber insertion loss less than 3 dB at 1550-nm wavelength, dynamic range greater than 40 dB, 0.2-dB repeatability, and return loss better than 40 dB.

High-dynamic-range high-optical-isolation wavelength-sensitive thin film filter-based variable fiber optic attenuator

A wavelength-sensitive variable fiber optic attenuator (VFOA) is introduced by incorporating the movable optical mirror with a fixed desired thin film filter (TF) in a compact in-line reflective architecture. Our TF-based wavelength-sensitive VFOA features low component count, high attenuation dynamic range, and high optical isolation. Experimental proof of concept using an off-the-shelf measured 1545.71-nm TF and a mechanically movable mirror shows a 4.64-dB optical loss, and a low polarization-dependent loss of 0.12 dB at the output port. A high optical attenuation dynamic range of >43 dB with a better than 30-dB optical isolation is obtained. Several proposed reflective wavelength-sensitive TF-based VFOAs can also be cascaded to form a low-cost, compact, multiwavelength amplitude controller.

A Thin-Film Filter-Based 1$, times,$2 Reconfigurable Fiber-Optic Add–Drop Module With a Quadruple Fiber-Optic Collimator

Due to a limited optical crosstalk in most thin-film filter (TF)-based fiber-optic modules, we propose and experimentally verify a low optical crosstalk TF-based 1/spl times/2 reconfigurable fiber-optic add-drop structure. Our key idea is to employ a passive noise rejection scheme by introducing a double reflection on the TF as well as a spatial separation through a combination of a quadruple and a single fiber-optic collimators. Our experimental results show a much improved <-39.1-dB optical crosstalk at the Thru port. In addition, the measured average optical losses at the Drop and the Thru ports are 1.40 and 1.23 dB, respectively, when the TF is in the optical path. When the mirror is in the optical path, all wavelength optical beams are directed to the Thru port with a measured average 2.50-dB optical loss. A low polarization-dependent loss of <0.17 dB is also determined. Furthermore, our design concept can be used to form a low optical crosstalk fixed three-port add-drop filter and a high dynamic-range wavelength-sensitive variable fiber-optic attenuator.

Super-resolution variable fiber optic attenuator instrument using digital micromirror device (DMD™)

Demonstrated is a super resolution, low loss, 100% repeatable and fast response digital variable fiber-optic attenuator instrument using a digital micromirror device. The attenuator design exploits beam expansion optics and a retroreflective architecture to achieve super-resolution with digital repeatability. The proof-of-concept attenuator at 1550nm demonstrates a 41.5dB optical attenuation range, optical insertion loss of 3.8dB, a 1ms maximum attenuation reset time, an optical polarization dependant loss of less than 0.07dB, and an optical resolution range of 2.9–0.0517mdB. The demonstrated attenuator is appropriate for fiber-optic test and instrumentation applications.

Wavelength-Sensitive Thin-Film Filter-Based Variable Fiber-Optic Attenuator With an Embedded Monitoring Port

A wavelength-sensitive three-port variable fiber-optic attenuator (VFOA) is introduced by incorporating the movable optical mirror with a fixed desired thin-film filter (TF). Experimental proof of concept using an off-the-shelf measured 1545.60-nm TF and a mechanically movable mirror shows a low 0.47-dB optical loss, a low polarization-dependent loss of 0.6 dB at maximum optical attenuation setting, and a 15.9-dB dynamic range measured at the output port. Several proposed wavelength-sensitive three-port VFOAs can also be cascaded to form a low cost compact multiwavelength amplitude controller.

Fault-tolerant variable fiber-optic attenuator using three-dimensional beam spoiling

A variable fiber-optic attenuator (VFOA) in a compact folded optical structure is introduced using the basic principles of optical beam misalignment via three-dimensional (3-D) beam spoiling. Key features include high resolution of control, the ability to tune the attenuation response, and the fault tolerant attenuator design. Experimental proof of concept demonstration using one dual fiber collimator and a three-axis controlled mirror as a 3-D beam spoiling element shows a high 52.4 dB dynamic range and a very low optical loss of 0.12 dB at 1550 nm wavelength. The measured polarization dependent loss is 0.02 dB. In addition, multiwavelength VFOA performance indicates an average 52.4 dB maximum optical attenuation with a ±0.04 dB fluctuation over a 70 nm bandwidth. A wavelength dependent loss of 0.10 dB is also measured with a fluctuation of ±0.04 dB.

Versatile multi-wavelength fiber-optic switch and attenuator structures using mirror manipulations

Compact frequency-selective fiber-optic switch (FOS) and attenuator structures are proposed based on the use of 2N hinge-type flapping micromirrors in a linear array geometry and piston-type micromirrors in a two dimensional (2D) array format. The flapping micromirrors are designed to be positioned in a compact low-loss in-line geometry that provides ease in optical alignment. The results of an experimental 4-wavelength proof of concept FOS using two macro-mirrors shows an average optical interchannel crosstalk of <−33 dB and an average total loss of <10.8 dB. Both numbers are limited by other devices in our self-aligning structure, as the unique in-line mirror placement design provides a low 0.4 dB free-space coupling average optical loss. Using sub-micrometer motion of 2D piston-type micromirrors, an alternate higher speed FOS based on the Michelson interferometer structure is proposed. Experimental proof of concept data for this FOS indicates an average optical loss of 9.81 dB and a loss fluctuation of ±0.06 dB within a 50 nm bandwidth. This optical loss value is again limited by the WDM devices, fiber adapters, three-port optical circulators, and free-space coupling efficiency. An average optical interchannel crosstalk of −24.4 dB is measured, limited by the resolution of the translation stage used in the experiment. Using these FOS architectures, variable fiber-optic attenuator structures are also introduced. An average maximum optical attenuation of 24.38 dB is measured within a 50 nm bandwidth for our attenuator using the interferometric FOS design.

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.