Photonic crystal-based permutation switch for optical networks

We present, for the first time, the design of a low-cross talk scalable permutation switch employing photonic crystal ring resonators in an optical network. Through this novel approach, the transition between different states of the \(2 \times 2\) optical switch, as the basic element, is achieved by applying different operating wavelengths. Subsequently, the shuffling mechanisms in \(3 \times 3\) and \(4 \times 4\) optical networks are realized by controlling the position of photonics crystal ring resonators. Lowest cross talk levels of 6 and 5% are obtained for “bar” and “cross” switching states, respectively.     

Photonic notch filter without optical coherence limitations

A new topology for a photonic notch filter that can solve the coherent interference problem in photonic signal processors is presented in this paper. It is based on a double-pass modulation technique. The key advantage of this new structure is that it completely removes the dominant phase noise limitation, which is a fundamental problem with existing incoherent processor approaches. It also enables arbitrary narrow-linewidth telecommunication-type lasers to be used with stable and robust filter operation. Extensions to obtain tunable notch frequency and wide-passband notch filter operation are presented. Results demonstrate robust notch filter operation with a narrow-linewidth source, no phase-induced intensity noise, and a vastly superior signal-to-noise ratio performance (i.e., a nearly 60-dB increase) compared with the conventional delay line notch filter. Tunable coherence-free operation of the notch filter is also shown. Finally, a new structure that not only operates without coherence limitations but also realizes a notch filter with a wide passband of more than 50% of the free spectral range is demonstrated.     

Liquid crystal-based optical space switches fordwdm networks

This paper addresses the issue of using conventional liquid crystal materials as reconfigurable holographic or diffractive phase elements within optical space switches and the resulting constraints in their choice and use in a telecommunication environment. We discuss the advantage of this technology for implementing holographic-based approaches with respect to other techniques. As an illustration we give two examples which illustrate two generic architectures and complementary use of liquid crystal to implement them. Finally, we give some trends on implementations of high channel capacity space switches based on this technology.     

Photonic crystal-based circulators with three and four ports for sub-terahertz region

Three- and four-port circulators based on resonators in 2D photonic crystals with square unit cell possessing a low symmetry are investigated. The three-ports are described by only one specific element named antiplane of symmetry. On the other hand, the four-port circulators formed by cascading these two three-ports can have one of the two symmetries. One of them is described by the antiplane of symmetry, and the other symmetry corresponds to a twofold rotational axis. The theoretical part of our paper concerns scattering matrix analysis of the devices with different symmetries and also the operation of the four-port circulator as a single-pole triple-throw switch. Finally, the calculated frequency responses of two circulators are presented.     

Liquid crystal-based optical control of phased array antennas

Nematic liquid crystal (NLC) technology-based optical systems for controlling phased array antennas are presented. These systems can provide low-cost, high-quality (>6-b), phase-based antenna control for very large phased arrays (e.g. 5000 elements). An experiment demonstrating NLC-based antenna phase control is performed, with 0-3π phase shift measured for a 60-MHz carrier. A novel time-multiplexed radar beam scanning approach is introduced to counter the slow response of the NLCs, allowing fast 200 beams/s antenna scanning rates     

Liquid crystal-based optical time delay units for phased arrayantennas

Novel two-dimensional (2-D) spatial light modulator (SLM)-based optical time delay units (OTDU's) using freespace/solid optics and fiber delays are introduced for phased array antenna and wideband signal processing applications. In particular, the mature nematic liquid crystal (NLC) SLM technology is considered for the proposed architectures. A 1×2 optical switch is demonstrated using a parallel-rub birefringent-mode NLC cell, a bulk optics cube polarizing beamsplitter, and a sheet polarizer. Switch measurements taken at 633 nm show a >3400:1 or >35 dB output port optical isolation. The 1×2 NLC switch is used to build a 1-bit, 3.33-ns-duration, free-space OTDU using mirrors and total internal reflection corner prisms. The unit demonstrated a >30 dB optical (or >60 dB electrical) signal-to-noise ratio for both delay and no-delay positions. A 1500 pixel NLC SLM is built, and a 128:1 or 21 dB on/off isolation is demonstrated limited by the digital drive electronics of thin-film transistor (TFT)-based pixel control     

Photonic bandgap dielectric waveguide filter

The application of photonic bandgap (PBG) structures as the sidewall of the printed circuit board (PCB) dielectric waveguide filter is investigated. The effect of different PBG parameters on the Q-value of PBG dielectric waveguide resonator is evaluated. A PBG dielectric waveguide three-pole Chebyshev bandpass filter is realized. The measured performance matched well with the calculated results. The newly proposed I/O coupling structure makes the filter much easier for mass production     

基于FBG传感系统的可调光滤波器非线性研究

采用光纤布拉格光栅(FBG)传感系统研究压电陶瓷(PZT)驱动法布里-珀罗(F-P)型可调谐光滤波器(TOF)的非线性特性。基于多光束干涉理论建立了TOF的非线性模型,推导了透射带波长和自由光谱范围(FSR)对驱动电压的非线性响应;基于FBG传感系统测试了F-P型TOF的波长非线性,并采用多项式拟合对其进行描述,实测F-P型TOF波长的非线性误差最大为1.006 nm;基于F-P型TOF的非线性模型,研究了其波长定位误差,并提出采用参考光栅的方法降低波长定位误差。实验表明,F-P型TOF的波长随机误差可由73～81 pm降至12 pm以下。     

Photonic microwave tunable single-bandpass filter based on a Mach-Zehnder interferometer

The authors present the theoretical analysis and experimental demonstration of a novel single-bandpass tunable microwave filter. The filter is based on a broadband optical source and a fiber Mach-Zehnder interferometer and shows a high Q factor over a tuning range of 5-17 GHz. A generalized analysis considering that the optical signal propagates along optical delay lines with a dispersion slope different from zero is presented.     

Photonic crystal fibre optical attenuators

Photonic crystal fibre-based attenuators ranging from 0-31 dB per component are demonstrated. The devices are simple to produce and have little if any external fibre diameter variations.     

Photonic reconfigurable microwave filter with negative coefficients

A photonic implementation of a reconfigurable microwave transversal filter is proposed. The implementation allows the filter taps to be both positive and negative. This allows for greater flexibility in the design of the filter so that bandpass and lowpass filters with flatter passbands could be realised. A four-tap version of the filter is demonstrated.     

超窄带光学滤波器

叙述了超窄带光学滤波器的基本原理,总结了目前超窄带光学滤波器的发展现状,指出这两种光学滤波器的不足,并提出今后的发展前景。     

滤波器技术简要回顾

开关电容滤波器技术允许使用片外或片内时钟调整滤波器截止频率,时钟频率是截止频率的倍数.这个本来非常方便的特性,却总是被这类滤波器的"采样数据"的本质弄得不方便.即这种技术总需要一个时钟,一个在纯模拟电路中的数字部分.     

Photonic nano-device for optical signal processing

Micro/nanostructure photonic devices offer a variety of enabling properties,including low powerconsumption,cost-efficient,compact size,and reliability.These distinctive features have been exploited in a wealth of applications ranging from telecommunication and optical interconnect to photonic network on chip.In this paper,we review two main classes of micro/nanostructure photonic devices,to provide the kinds of functions for optical signal processing.     

Photonic FDM multichannel selector using coherent opticaltransversal filter

This paper describes a photonic frequency-division-multiplexing (FDM) multichannel selector using a coherent optical transversal filter and discusses its application to a photonic FDM highway switch. The selector can select several arbitrary channels out of several multiplexed frequency channels. The selector function takes advantage of the fact that the filter can express arbitrary frequency characteristics. An experimental 16-tap filter is fabricated according to silica-based-waveguide technology, which can monolithically integrate a variety of optical components. Arbitrary channel selection and signal transmission characteristics are confirmed by measuring the frequency characteristics of the selector and the bit-error-rate performance     

DBR-based tunable optical filter

A device structure for implementing a continuously tunable optical filter is described. The proposed filter relies on the creation of a resonant optical cavity between a high-reflectivity mirror and a periodic grating, with a phase control section in between. The filter has only one transmission peak over the entire frequency range, can be tuned in a few nanoseconds, and is suitable for integration with the receiver in a photonic circuit     

Narrow-band optical channel-dropping filter

Waveguide couplers are combined with λ/4 shifted distributed feedback (DFB) resonators to produce narrowband channel dropping filters. The bandwidth of the filter can be made much narrower than the stopband of the grating. It is possible to remove the spurious responses of the grating filter by appropriate dispersion characteristics for the coupled waveguides. However, in some practical applications it may not be necessary to do this, if all channels can be accommodated within half the grating bandwidth of the filters     

An optical decision filter

This paper presents the basic concepts, design details, and construction techniques used in the development of an advanced type of self-organised image filter. The filter has the capability of recognizing and classifying three-dimensional objects regardless of their size and orientation with respect to the viewing mechanism. The applications of the techniques include reconnaissance, photo interpretation, and star field recognition for space probes. Self-organization was used as a design tool only; the decision filter itself is not adaptive. Design principles described here are directly applicable to an even wider variety of problems in the broad areas of communication and data processing. A natural selection process of eliminating elements of marginal utility enables a significant reduction of network size without adversely affecting its classification capability. Full advantage was taken of the self-organization process to minimize the engineering design task involved. Many of the features described have not previously been reported in the literature.     

Photonic transport networks based on optical paths

This paper explores the technologies that will enable a further leap forward in transport network evolution. First, requirements of the future transport network are elucidated. Existing network cost is evaluated and the viable means to reduce transport network cost are identified. It is demonstrated that optical path technologies such as WP (wavelength path) and VWP (virtual wavelength path) will play a key role in this. They enhance not only transmission capacity but also cross-connect node throughput cost-effectively by capitalizing on the wavelength routeing scheme. Optical path realization technologies focusing on optical path cross-connect systems are examined. Requirements for the optical path cross-connect system are then elucidated, and a new cross-connect system architecture is evaluated. The architecture exploits PLC (planar lightwave circuit) and other commercially available technologies suitable for large-scale production. The evaluations include cross-connect node upgradability, modular growth capability, total node cost, optical loss and switching power consumption. It is proved that the architecture has significant advantages over existing switch architectures. The optical path technologies provided in this paper will pave the way for a new transport network paradigm, a ubiquitous, bandwidth-abundant and affordable broadband ISDN.     

Interleave filter based on coherent optical transversal filter

The principle of the transversal interleave filter previously proposed as a novel class of interleave filter is described. The principle of a conventional 1 /spl times/ 1 coherent optical transversal filter is reviewed. Then, the fundamental operating principle and the three design conditions required for the novel interleave filter are explained. As examples, three types of filter design, namely 1) a general/transposed design; 2) an asymmetric design; and 3) a symmetric design, are presented, and their interleave filter characteristics are discussed. The designed interleave filters with a free spectral range of 100 GHz was fabricated using silica-based planar lightwave circuit (PLC) technology. The asymmetric design achieved a wide 3-dB passband width of 55 GHz, whereas an ordinary lattice-form interleave filter could not realize a 3-dB passband width larger than 50 GHz because of the halfband property. A small polarization-dependent wavelength shift of 0.01 nm is demonstrated by inserting a single half waveplate in the middle of the circuit. The general/transposed and symmetric designs realized a practical interleave filter with a boxlike transmission spectrum and low chromatic dispersion. The two-stage interleave filter formed by cascading the general and transposed designs has the advantages of a low crosstalk of less than -46 dB and a wide 20-dB stopband width of 40 GHz, whereas the single-stage symmetric design has an extremely small chromatic dispersion of within /spl plusmn/5 ps/nm. In addition, the design concept to realize a 1/spl times/N transversal interleave filter is extended.