Wavelength-tunable add/drop optical filter

A new type of add/drop optical filter discretely tunable along equally spaced channels is presented. This device may have very useful applications in WDM optical networks.     

Tunable polymer optical add/drop filter for multiwavelength networks

We present a polymer optical add/drop filter with a channel cross-talk of -18.5 dB, a free spectral range of 12.8 nm and a channel spacing of 400 GHz (4 channels) as well as a tunable optical filter with a free spectral range of 50 nm. Both filter designs are based on a synthesis which provides the minimum number of filter stages for a given channel crosstalk and number of channels. Wavelength tunability over the entire free-spectral range (FSR) is demonstrated with applied heating powers of 500 mW. For the narrow bandwidth filter we used a fluorinated high temperature stable polymer as the waveguiding material, which has proven to exhibit losses as low as 0.25 dB/cm at a wavelength of 1.55 /spl mu/m.     

Interferometric crosstalk-free optical add/drop multiplexer usingMach-Zehnder-based fiber gratings

Mach-Zehnder interferometers with fiber Bragg gratings (MZ-FG) are investigated as promising devices for wavelength-selectable optical add-and-drop multiplexers (OADM). A wavelength reused OADM performance is demonstrated for the first time to our knowledge in a six-channel, 10 Gb/s WDM experiment using a single-stage MZ-FG. We discuss both theoretically and experimentally the interferometric crosstalk induced by imperfect Bragg-reflectivity. Two methods are proposed to solve the interferometric crosstalk issues. The first one is wavelength offset scheme. It is experimentally confirmed that there is no interference when the wavelength of crosstalk is away from that of the signal at least two times of bit-rate. In order to separate each wavelength, the master-slave wavelength control method is proposed with Fabry-Perot interferometer made of a set of fiber gratings. The second one is a cascaded MZ-FG scheme eliminating the crosstalk itself. The calculation indicates that a Bragg-reflectivity of only 93% can suppress the crosstalk to be -35 dB. Cascaded MZ-FG's have been fabricated to show that the interferometric crosstalk can be successfully reduced to -50 dB for the add signal, and -71 dB for the drop signal, respectively. The eight-wavelength 10 Gb/s OADM experiment is carried out to demonstrate the low interferometric crosstalk performance     

一种新型的可重构光分插复用器件的设计

设计了一种带四根单模尾纤的光纤准直器,基于这种四光纤准直器及介质薄膜滤波器,提出了一种新型的可重构光分插复用器件的设计方案.该器件只用一个四光纤准直器,输入光纤、输出光纤和分下/插入光纤都分布在器件的同侧,具有体积小、成本低、信道隔离度高等优点.     

PLC-based optical add/drop switch with automatic level control

A novel switch configuration for an optical add/drop multiplexer is proposed. By utilizing a certain Mach-Zehnder interferometer both as a component of a double-gate switch and as a level equalizer, we reduced the number of Mach-Zehnder interferometers from five in a conventional switch configuration to three. The add/drop switch simultaneously provides high-isolation switching and polarization-independent automatic level control. The use of planar lightwave circuit (PLC) technology enables this switch to be fabricated with three thermooptic switches (TOSWs) and a monitor tap. High isolation of more than 44 dB and automatic level control accuracy of better than 0.3 dB are achieved. Bit error rate (BER) measurements confirmed switch's usability in the optical add/drop multiplexer     

Design considerations in optical add/drop multiplexers based ongrating-assisted null couplers

The performance of a fully optimized optical add/drop multiplexer (OADM), based on null couplers and tilted Bragg gratings, is studied in detail. It is shown that maximization of the device performance involves three main optimization steps. First, the waveguide asymmetry (V₂ /V₁ ratio) should be optimized in order to minimize the extinction ratio of the unwanted mode at the null coupler waist. Second, the coupler taper shape should he optimized in order to further minimize the aforementioned extinction ratio. Third, the grating tilt angle and relative width can be also optimized to give negligible backreflections at the input port and minimize radiation losses. The results show that the proposed high-performance OADM configuration can meet stringent telecom specifications     

Design and performance of a reconfigurable liquid-crystal-based optical add/drop multiplexer

The authors describe a reconfigurable optical add-drop multiplexer designed for 50-GHz channel spacing over either the C- or L-bands. The system may also function as a variable optical attenuator. The design features a reflective liquid-crystal modulator, a compact free-space spectrometer, polarization diversity, and fine-scale attenuation control.     

The design and assembly of surface-micromachined optical switch for optical add/drop multiplexer application

An assembly process including: flip-chip bonding, microelectromechanical (MEMS) structure release, and atomic layer deposition (ALD) is proposed to integrate a surface micromachined optical switch for optical add/drop multiplexer (OADM) applications. In the current optical switch designs, pre-stressed beams were used to pop up the micromirror and an electrode (substrate) under the beams was designed to perform ON/OFF function of the optical switch. In order to achieve desired popped-up angle for precise optical switching, a flip-chip bonding technique is applied to a mechanical stopper with an accurate joint height that can be used to constrain the movement of the micromirror. A conformal thin layer of dielectric material (Al/sub 2/O/sub 3/) coated on the surfaces of device through an ALD coating process is used to improve vertical actuation force, as well as electrical isolation. Experiments indicate that the micromirrors fabricated by the present assembly process can achieve desired angle that meet the requirements of the proposed OADM configuration.     

Ion-exchanged waveguide add/drop filter

An add/drop filter is fabricated using ion-exchanged waveguides and photowritten Bragg gratings. The device exhibits 20 dB extinction ratios and 3 dB bandwidths of 0.4 nm (100 GHz)     

一种基于锥光纤微球腔的光分插复用器

利用锥光纤倏逝波与微球腔回廊模的耦合原理制成一种锥光纤-微球腔-锥光纤(TRT)型光分插复用器(OADM),可用于密集波复用(DWDM)光纤通信系统光节点中.设计制作了一种三锥光纤双微球结构的TRT型OADM.采用在硅片上光刻腐蚀制作V槽,双面光刻腐蚀制成固定微球上光纤柄的小通孔,将锥光纤与微球集合在硅片上成为OADM器件.对所制作的器件用光波测试系统进行了测试,对结果进行了分析.制作的器件对与微球谐振的光信号具有分出与插入功能,而不谐振的信号损耗很小.     

Ultrashort optical pulse transmission characteristics of verticallycoupled microring resonator add/drop filter

The ultrashort optical pulse transmission characteristics of a vertically coupled microring resonator (VCMRR) filter were measured at 1.55 μm wavelength, and the transmission capacity per channel was evaluated. The pulsewidth at the output was measured to be 3.4 ps, when 1.2 ps input pulse with a sech pulse shape from a fiber laser was incident on the microring resonator filter with a fullwidth at half-maximum (FWHM) of 0.75 nm (94 GHz). From this result, the maximum transmission capacity of the filter was estimated to be approximately 50 Gb/s. The pulse broadening through the filter was theoretically analyzed, and it was confirmed that the pulse broadening evaluated from the bandwidth of the filter spectrum response were in good agreement with the measured results     

Eight-channel bidirectional WDM add/drop multiplexer

The authors propose and demonstrate an eight-channel reconfigurable bidirectional wavelength division multiplexed (WDM) add-drop multiplexer in which all channels can be added/dropped independently in either direction. The performance of the bidirectional WDM add/drop multiplexer is experimentally studied for a data rate of 10 Gbit/s per channel, providing an overall capacity of 80 Gbit/s. It is found that the performance of the add/drop multiplexer is not degraded by a backward propagating signal     

Highly stable optical add/drop multiplexer using polarization beam splitters and fiber Bragg gratings

We demonstrate a novel wavelength-division add/drop multiplexer employing fiber Bragg gratings and polarization beam splitters. The multiplexer is easy to fabricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5-Gb/s-per-channel wavelength-division multiplexing (WDM) transmission system.     

带光纤光栅的MZI型全功能光分插复用器的研究(本期优秀论文)

提出了一种结合光纤Bragg光栅(FBG)和级联马赫-曾德尔干涉仪(MZI)的全功能光分插复用器(OADM).应用扭转梁对光栅对的中心波长实施同步调谐,使两级MZI单元的反射波长错位或动态一致,实现全通和动态上/下路功能.在0.8nm波长间隔、8波长的波分复用系统中,对其输出响应进行了数值模拟,并分析了两光栅相对位置差和两干涉臂长差对响应波形及隔离度的影响.     

一种新型的OADM上/下路(Add/Drop)实现方案

设计了一种新型的基于声光可调谐滤波器(AOTF)的光分插复用器(OADM)上/下路实现方案.该方案用于可重构型OADM中,实现信号的上载与下载.设计内容主要包括上/下路功能模块的组成和具体实现原理,即上/下路的光源产生信号以及电光调制过程.     

使用模式兼容OADM的双LP11模CO-OFDM信号传输方法

介绍了一种使用模式兼容的OADM(光分插复用器)的双LP11模相干OFDM(正交频分复用)信号传输方法。该OADM采用薄膜滤波器和双反射机制实现模式复用的光信号的插分功能。实验结果表明,对于3×318Gbit/s的OFDM信号,OADM在插、分与直通端口的功率代价分别为2.6、2.4和0.7dB。     

Fiber-grating add–drop reconfigurable multiplexer with multichannel using in bi-directional optical network

A bi-directional reconfigurable scheme of multichannel-selective optical add–drop multiplexer (OADM) is proposed in this paper. With only small wavelength channel tuned range, the proposal applies fiber Bragg gratings (FBGs) and multiport optical circulators (MOCs) to build a bi-direction reconfigurable OADM which can deal with full channels without the receiving signal having wavelength-interleaved. Moreover, it is easier and more flexible to extend wavelength channels by cascading additional FBGs. The magnitudes of homodyne and heterodyne crosstalks are analyzed for evaluating the performance of the proposed BOADM. Also, the power equalization of each signal in the add–drop and output ports is managed properly by implementing filters. As a result, the BOADM will be found in wide applications in dense wavelength-division multiplexing (DWDM) optical networks and in multiwavelength crossconnects (WXCs).     

Novel add/drop filters for wavelength-division-multiplexing optical fiber systems using a Bragg grating assisted mismatched coupler

We have demonstrated a novel add/drop filter for use in wavelength-division-multiplexing (WDM) optical fiber systems based on a Bragg grating assisted mismatched coupler. The device is potentially easy to fabricate and stable, because it is not interferometric, unlike all similar devices demonstrated so far, and, therefore, does not need fine tuning of the interferometers during fabrication and does not have to maintain the balance of the interferometers during its lifetime.