Mirror quality and the performance of reflective arrayed-waveguide grating multiplexers

This paper discusses an investigation of the effects of mirror quality on the performance of reflecting arrayed-waveguide-grating multiplexers. Using specially designed external mirrors as external reflectors, the optimum flatness and microroughness of the reflecting surface are determined. The experiments discussed in the paper indicate that a reflecting-surface flatness of /spl lambda//4 is sufficient to obtain high-performance reflective multiplexers. Extrinsic mirror-related phase and intensity errors were found to be negligible for surfaces polished with diamond lapping films with a grain size smaller than 1 /spl mu/m. These experimental results were found to be in excellent agreement with simulations based on mirror-related changes in the waveguide-grating-length increment.     

阵列波导光栅复用器的原理,设计及应用

介绍了阵列波导光栅复用器的原理，设计及在ＷＤＭ通信系统中的应用，并对其最新的研究成果作了介绍。     

Athermal silica-based arrayed-waveguide grating (AWG)multi/demultiplexers with new low loss groove design

A new low loss groove design for athermal silica-based AWG multi/demultiplexers is proposed. The insertion loss was <3.2 dB with an excess loss of 0.4 dB. The temperature dependence of the channel wavelength change was suppressed to be below 2.5 GHz in the 0-85°C range     

Digitally controlled, conductance tunable active filters

The use of digitally controlled variable conductances (DCVC's) to control the center frequency and selectivity of an active state variable filter is described theoretically and experimentally. Advantages of this approach are: zero sensitivity of selectivity with respect to the control conductances, excellent tuning linearity (1 percent over one decade) can be achieved with 1 percent part accuracies, a common digital control can be used to drive simple three-element variable conductances, and the input signal can be very low (about 0.5 mV) without any adverse effect on the tuning accuracy or linearity.     

Colorless tunable optical dispersion compensator based on a silica arrayed-waveguide grating and a polymer thermooptic lens

We present a colorless tunable optical dispersion compensator (TODC) comprised of a silica arrayed-waveguide grating (AWG) directly coupled to a polymer thermooptic lens. Using silica for the AWG allows it to be low loss and manufactured by a standard process, and using polymer for the thermooptic lens allows it to have a large tuning range and low electrical power consumption. This hybrid TODC is fully solid-state and scales to a large figure-of-merit (dispersion range times bandwidth squared). We demonstrate a version with 100-GHz free-spectral range and 1300-ps/nm tuning range with a 3-dB bandwidth >39 GHz and a lens power consumption <74 mW.     

Digitally tunable channel dropping filter/equalizer based onwaveguide grating router and optical amplifier integration

We demonstrate a novel and powerful device that permits individual and simultaneous control of all the wavelength channels in a WDM system. The device is based on the monolithic integration of two identical waveguide grating routers with semiconductor optical amplifiers. By biasing appropriately the individual amplifier, each WDM channel can be amplified, detected or modulated. The device exhibits a channel bandwidth of 60 GHz, a channel spacing of 195 GHz and a crosstalk of -19 dB     

Microoptic grating multiplexers and optical isolators for fiber-optic communications

As new optical devices for increasing further the utility of and to expand the application of fiber-optic communications, grating multiplexers and isolators have been developed for 0.8 μm band employing microoptic approach. The development of these devices is the subject of this paper. The devices have desirable features of small size, compactness, high optical performances, and high reliability. The grating multiplexer consists of a graded-index rod, a blazed reflection grating replicated onto the graded-index rod slanting facet or a wedge facet, and an input-output fiber array. Simple calculations have been done to determine necessary element parameters for a given channel spacing. Experimental results are presented for five-channel multiplexers devised using a SELFOC^®lens. Around 3 dB insertion loss and less than -30 dB crosstalk have been obtained for about 35 nm channel spacing in overall device size of18 times 13 times 50mm. Faraday rotation optical isolators for 0.8 μm band have been miniaturized by employing an efficient paramagnetic glass Faraday rotator, a magnet with a through hole and a folded optics in the Faraday rotator. The path number in the folded optics has been optimized in terms of trading-off between the magnet size and the insertion loss. A 0.9 dB insertion loss including fiber coupling loss and 36 dB isolation have been obtained in overall device size of24 times 24.5 times 42mm. Results on the temperature and wavelength dependence of the isolation are also presented. In addition, fundamental properties of optical circulators for 0.8 μm band and optical isolators and circulators both for 1.3 μm band, developed as extended modifications of the optical isolators for 0.8 μm band, are briefly described.     

Repetition rate and center wavelength-tunable optical pulse generation using an optical comb generator and a high-resolution arrayed-waveguide grating

Optical pulse generation using an optical comb generator and a high-resolution arrayed-waveguide grating with 30 integrated phase and amplitude modulators is successfully demonstrated. The repetition rate and the center wavelength of the Gaussian pulse train can be controlled from 9.7 to 10.3 GHz and from 1527 to 1565 nm, respectively.     

Second- and third-order dispersion compensator using ahigh-resolution arrayed-waveguide grating

We have proposed a dispersion compensation scheme that uses a high-resolution arrayed-waveguide grating (AWG). When the diffraction order of the AWG is 59 and the number of waveguides in an arrayed-waveguide is 340, the calculated maximum second- and third-order dispersion compensation range is 18.0 ps/nm and ±6.0 ps/nm² , and 1100 ps/nm and ±937.5 ps/nm², for a 1 ps-pulse and a 12.5 ps-pulse, respectively. In experiments, second-order dispersion (-0.8 to +5.2 ps/nm) is effectively compensated for 1,1-ps pulses; and. Pulse compression by third-order dispersion compensation is successfully demonstrated     

可调谐光滤波器的研究

可调谐滤波器在光纤通信和光纤光栅传感中发挥了重要的作用.分别介绍了几种常用的可调谐光滤波的原理、结构和性能,分析了其发展趋势.     

FDM-channel selection filter using arrayed-waveguide gratingmultiplexer with input and output switches

A novel configuration is reported for a tunable channel-selection filter that employs an arrayed-waveguide grating (AWG) multiplexer and optical switches. The filter requires only 2(√N-1) 1×2 switch elements to select one of N frequency-division-multiplexed (FDM) channels. A filter for 100 GHz-spaced 16 FDM channels is demonstrated with an AWG 16×16 multiplexer and six 1×2 switches     

用布拉格相移光纤光栅实现光标记交换的方法

提出了用布拉格相移光纤光栅中相移来实现低功率的光标交换的新方法。设计了一个基于该方法的光标记交换实验。实验所用的布拉格光纤光栅是在通信用的标准光纤内刻写而成,通过强泵浦脉冲作用在低强度的探测信号上。光标记交换是基于交叉相位调制来完成的。     

阵列波导光栅器件的发展与应用

密集波分复用（ＤＷＤＭ）是光纤通信中的关键技术,而阵列波导光栅（ＡＷＧ）在波分复用系统中有 广泛的应用。本文综述了ＡＷＧ的原理以及它的发展和光纤通信系统中的应用。     

Efficient electromagnetic optimization of microwave filters and multiplexers using rational models

A method is presented for the efficient optimization of microwave filters and multiplexers designed from an ideal prototype. The method is based on the estimation of a rational function adjusted to a reduced number of samples of the microwave device response obtained either through electromagnetic analysis or measurements. From this rational function, a circuital network having the previously known topology of the microwave device is synthesized and compared to a circuital network with the desired response but including nonidealities. All of the process of analysis and model extraction can be seen as a model function that relates the physical parameters of the microwave device with the extracted circuital network parameters. Then, the error vector of the circuital parameters is used to generate a correction vector of the physical parameters through an estimation of the inverse of the Jacobian matrix of the complete model function. The Jacobian estimation is updated at each iteration of the optimization process with no need for additional evaluations of the model function. Two numerical examples of the proposed technique corresponding to the synthesis of a filter and a diplexer are presented, demonstrating the increased efficiency of the proposed technique with respect to direct electromagnetic optimization.     

Demultiplexing using an arrayed-waveguide grating for frequency-interleaved DWDM millimeter-wave radio-on-fiber systems

The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme.     

Crosstalk reduction in arrayed-waveguide grating multiplexer/demultiplexer using cascade connection

This paper proposes a cascade-connected arrayed-waveguide grating (AWG) as a solution to the problem of crosstalk accumulation in a large-scale AWG multiplexer/demultiplexer (MUX/DEMUX) and demonstrates a 64-channel cascaded AWG module with a very low background crosstalk of less than -80 dB and a total crosstalk of about -34 dB. In this paper, the authors densely integrate 64 additional compactly designed crosstalk-suppressing AWGs whose bandwidths were carefully optimized and directly attach them to a conventional 64-channel AWG. Consequently, in addition to a very low crosstalk, a low insertion loss and a compact size without passband shape distortion are achieved with this module. Based on the performance of the cascaded AWG module, it is then estimated that it is possible to realize a 1000-channel AWG MUX/DEMUX that is free from the problem of crosstalk accumulation.     

超窄带宽可调光滤波器的研究

为了降低可调光滤波器的带宽,采用双光栅结构和基于微机电系统的反射镜相结合的方法,构建了具有波长连续可调谐的超窄带宽滤波器,并进行了理论分析和实验验证,取得了滤波带宽小于0.4nm的数据。结果表明,双光栅结构的光滤波器具有性能稳定、重复性优良的性能特点,并且很好地满足了带宽需求。这种结构显著降低了可调谐光滤波器的滤波带宽,提高了系统的稳定性。     

Miniature and tunable filters using MEMS capacitors

Microelectromechanical system (MEMS) bridge capacitors have been used to design miniature and tunable bandpass filters at 18-22 GHz. Using coplanar waveguide transmission lines on a quartz substrate (/spl epsiv//sub r/ = 3.8, tan/spl delta/ = 0.0002), a miniature three-pole filter was developed with 8.6% bandwidth based on high-Q MEMS bridge capacitors. The miniature filter is approximately 3.5 times smaller than the standard filter with a midband insertion loss of 2.9 dB at 21.1 GHz. The MEMS bridges in this design can also be used as varactors to tune the passband. Such a tunable filter was made on a glass substrate (/spl epsiv//sub r/ = 4.6, tan/spl delta/ = 0.006). Over a tuning range of 14% from 18.6 to 21.4 GHz, the miniature tunable filter has a fractional bandwidth of 7.5 /spl plusmn/ 0.2% and a midband insertion loss of 3.85-4.15 dB. The IIP/sub 3/ of the miniature-tunable filter is measured at 32 dBm for the difference frequency of 50 kHz. The IIP/sub 3/ increases to >50 dBm for difference frequencies greater than 150 kHz. Simple mechanical simulation with a maximum dc and ac (ramp) tuning voltages of 50 V indicates that the filter can tune at a conservative rate of 150-300 MHz//spl mu/s.     

Digitally tunable wavelength filter and laser

A novel nonmechanical, digitally tunable, polarization insensitive and optically transparent wavelength filter using holograms electro-optically written on a ferroelectric liquid crystal (FLC) spatial light modulator (SLM) has been constructed and operated to tune to discrete wavelengths spaced by 1.3 nm. The filter has been incorporated in a ring laser which is tunable over a range of 38.5 nm across the erbium window, giving output powers of 10 mW. Both wavelength filter and tunable laser are suitable for wavelength division multiplexing (WDM) applications.     

Dielectric-waveguide filters using parallel-coupled grating resonators

Results for a new class of dielectric-waveguide bandpass filters are presented. The filters use pairs of gratings on a guide to make a resonator, and the resonators are coupled by side-by-side placement. Attenuation is by reflection around the passband and by absorption elsewhere.