Cascaded acoustooptic/fiber Fabry-Perot filter with finesse over2000

A compound optical filter consisting of an integrated acoustooptic filter in series with a fiber Fabry-Perot filter possesses a very high effective finesse of over 2000 as well as the unique multichannel passband capability of the acoustooptic filter. The fine-grain element in this pair is a narrow (0.5-Å) passband Fabry-Perot filter, and the coarse-grain element is a wide tuning range (130-nm) polarization-independent integrated acoustooptic filter. The composite device has the narrow passband of the Fabry-Perot, the wide tuning range of the acoustooptic filter and the tuning speed of the faster acoustooptic filter (5 μs)     

Wide passband grating multiplexer for multimode fibers

A grating multiplexer in Littrow-configuration is presented, whose passband width-normalized to channel spacing-is comparable with grating demultiplexers. As shown by calculation, a wide passband is attainable by very small input fiber spacing. Using a standard-(50/125 mum)-GI-fiber as transmission fiber, a 1-dB pass-band of 30 nm with a channel spacing of 46 nm is achieved in an 8- channel device. The insertion losses for each channel are in the range 1.4-2.5 dB for 8- or 10-channel devices.     

A ±1.5-V, 4-MHz CMOS continuous-time filter with asingle-integrator based tuning

A 4-MHz, fifth-order elliptic low-pass Gm-C filter is described whose characteristics are tuned by an on-chip automatic tuning circuit. The tuning circuit uses only one integrator as the master of tuning instead of problematic voltage controlled oscillator (VCO) and voltage controlled filter (VCF). MOS transistors in linear operation region perform the voltage-to-current conversion in an operational transconductance amplifier, and thereby we achieved ±1.5 V operation. A prototype filter was implemented in a 0.8-μm double-poly, double-metal CMOS process. The filter exhibits the dynamic range of 57.6 dB and dissipates 10 mW with ±1.5-V supply. The stopband attenuation is better than 45.0 dB and the passband ripple is smaller than 1.0 dB     

Experimental demonstration of thin-film dispersion compensation for 50-GHz filters

Dispersion management is critical for next-generation high-bandwidth-utilization fiber-optical networks. Square-top thin-film bandpass filters for 50-GHz dense wavelength-division multiplexing inherently have high chromatic dispersion (CD) in transmission. The imparted dispersion power penalty on the network is undesirable. However, a second thin-film filter, operating in reflection, can be designed to compensate the CD of the bandpass filter. In this paper we demonstrate experimentally the reduction of the intrinsic CD of a 50-GHz thin-film coupler from /spl plusmn/170 ps/nm to /spl plusmn/50 ps/nm over a 30-GHz passband, through the use of such a cascaded thin-film compensator. Network simulations based on filter performance confirm the reduced dispersion power penalty of the cascade over the individual filter.     

Electronically tunable liquid-crystal-etalon filter forhigh-density WDM systems

A 1.5-μm high-density wavelength-division-multiplexed (HD-WDM) system experiment is demonstrated using a novel Fabry-Perot etalon filter with a liquid-crystal electrical tuning element. The filter has a narrow passband (0.4 nm) and is continuously tunable over a wavelength range of >60 nm with a drive voltage from 1 to 5 V. Bit-error-rate measurements with an 8-channel (1539-1556 nm), 622 Mb/s WDM system confirms that the crosstalk penalty is negligible for an optical channel spacing of 2 nm     

Reconfigurable Add–Drop Optical Filter Based on Arrays of Digital Micromirrors

We demonstrate a universal reconfigurable add-drop optical filter based on arrays of digital micromirrors. Our approach allows for reconfiguration of the device parameters for operation in different sets of channel wavelengths, even or uneven channel-to-channel separation, adjustable channel passband, and dynamic add-drop of optical signals. The proposed device shows insertion loss at the center wavelength in the all-pass configuration of 7.6 dB, extinction ratio of 35 dB, channel isolation better than 24dB, negligible loss ripple, and possibility of reconfiguration time in the order of microseconds. Although designed for demonstration on optical telecommunication frequencies, the high-flexibility features of the proposed add-drop filter allow it to be used for other optical wavelength-based filtering/switching applications.     

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.     

A 2.7-V, 200-kHz, 49-dBm, stopband-IIP3, low-noise, fully balancedgm-C filter IC

This 2.7 V low-distortion, low-noise, fourth order gm-C filter adopts real resistors for terminations and transconductors of wide common mode input range. Degradation in passband ripple due to mismatch between termination resistors and transconductors is alleviated by design centering. The filter achieves a stopband third-order intermodulation intercept point (IIP3) of 49 dBm, a passband IIP3 of 14 dBm, an input-referred noise of 28 nV/√(Hz) and a common mode rejection ratio of 70 dB. The cutoff frequency is tuned to 200 kHz using a reference resistor. The filter consumes 11.5 mA/channel. It operates even at 2.2 V with a stopband IIP3 of 40 dBm     

基于多节SIRs的新型四通带滤波器设计

提出了一种基于多节1/2波长SIRs的具有通带可控的紧凑型四通带滤波器。该滤波器由上下两个谐振器A和B组成,谐振器A由两节1/2波长SIRs中心加载一段短路枝节组成,控制第二和第三通带;谐振器B由三节1/2波长SIRs中心加载一段短路枝节组成,控制第一和第四通带,最终得到了尺寸为8.09 mm×14.12 mm(0.10λ_g×0.17λ_g)的四频带通滤波器。实验结果表明,该滤波器的通带可控并且满足低损耗的要求,4个通带的中心频率分别为2.22/3.66/5.63/7.52 GHz,插入损耗分别为0.32/0.41/1.38/0.43 dB,每个通带的回波损耗都优于20 dB,实验结果与理论分析一致。     

Mixed analog/digital, FIR/IIR realization of a linear-phase lowpassfilter

A 5 kHz linear-phase lowpass filter is implemented in a 2-μm BiCMOS technology as a combination of sigma-delta front-end, a digital shift register, a switched capacitor (SC) summer circuit with 50 input capacitors, and an SC biquad running at a 1 MHz clock. The measured group delay variation in the passband is less than 1 μs and the measured total harmonic distortion (THD) is -80 dB for an input sine wave amplitude of 0.7 V at 1 kHz. The circuit consumes 80 mW from ±5 V supply and measures 8.12 mm² without pads     

A low-jitter 1.9-V CMOS PLL for UltraSPARC microprocessorapplications

A phase-locked loop (PLL) for CMOS UltraSPARC microprocessor applications uses a loop filter referenced to a quiet power supply and achieves measured clock period jitter of ±25 ps at 360 MHz. The fully integrated CMOS PLL uses a charge-pump phase/frequency detector, a single-capacitor loop filter, and a feedforward error correction architecture. Loop characteristics are analyzed and verified by measurements. The measured sensitivity of clock period jitter to supply voltage is 2.6 ps/100 mv over an analog supply-voltage range of 1.6-2.1 V; the measured output operating frequency range is 8.5-660 MHz. Fabricated in an area of 310×280 μm² in a 0.25-μm CMOS process, the PLL dissipates 25 mW from a 1.9-V supply     

Broad-band dynamic dispersion compensation in nonlinear fiber-based device

In this paper we report on the design, numerical simulation and experimental testing of a novel dynamic dispersion compensation device based on self-phase modulation (SPM) in nonlinear fiber. The proposed all-fiber device is inherently simple and presents several unique advantages, most notably the potential for a broad-band operation covering all wave-length division multiplexing (WDM) channels of a system and the ability to address variable amounts of residual dispersion in each individual channel. Dynamic compensation ranges of up to 140 ps/nm for a single-stage and 240 ps/nm for a two-stage device are demonstrated with 40 Gb/s CS-RZ signal. It is shown that the device can operate with a minimum channel spacing of 200 GHz. For a two-stage device with inter-stage spectral filtering, simultaneous dynamic dispersion compensation (130 ps/nm for 1 dB penalty) and 2R regeneration (2 dB receiver sensitivity improvement) are demonstrated.     

Practical realization of a high density diode-coupled wavelengthdemultiplexer

The design, development, and optical performance of a novel demultiplexer in which a photodiode array replaces the array of fibers at the output is described. The prototype diode-coupler high-density wavelength demultiplexer has 16 channels with 4-nm channel spacing. Its optical performance, with respect to insertion loss, optical passband, total optical crosstalk, and polarization response and taking into account expected component and manufacturing tolerances is good. In particular, an optical passband between ±0.7 nm and ±0.9 nm can be tolerated without deterioration in performance, reducing the need for precise laser wavelength control. In addition, the diode leakage currents achieved, although relatively large, do not constitute a significant penalty in receiver sensitivity for applications at 560 Mb/s or higher, and the diode capacitance is very low. It is concluded that this is an attractive solution for high-density wavelength-division multiplexing     

A low-power CMOS time-to-digital converter

A time-to-digital converter, TDC, with 780 ps lsb and 10-μs input range has been integrated in a 1.2-μm CMOS technology. The circuit is based on the interpolation time interval measurement principle and contains an amplitude regulated crystal oscillator, a counter, two pulse-shrinking delay lines, and a delay-locked loop for stabilization of the delay. The TDC is designed for a portable, low-power laser range-finding device. The supply voltage is 5±0.5 V, and the operating temperature range is -40 to +60°C. Single-shot accuracy is 3 ns and accuracy after averaging is ±120 ps with input time intervals 5-500 ns. In the total input range of 10 μs, the final accuracy after averaging is ±200 ps. Current consumption is 3 mA, and the chip size is 2.9 mm×2.5 mm     

A monolithic ΣΔ A/D and D/A converter with filter forbroad-band speech coding

The authors present a 5-V-only 14-b, 16 ksamples/s linear codec suitable as the audio part of a CCITT G722 codec. The device uses second-order sigma-delta modulation for both analog/digital (A/D) and digital/analog (D/A) conversion at 2.048 Msamples/s. A time-continuous modulator with integrated antialias filtering is used at the A/D side, obviating the need for an external antialiasing filter. The digital filters for decimation and interpolation are implemented with both a custom digital signal processor (DSP) and specialized hardware. The device was realized with 74000 transistors on a 31-mm² die in a 3-μm SACMOS technology. A dynamic range of more than 80 dB and a passband ripple of 0.3 dB were attained with A/D and D/A paths in cascade     

A Mechanical Filter Channel Bank

The channel modem is encountered in carrier telephone systems in far greater quantities than any other equipment unit. Measures for improving the productivity with regard to this basic unit of equipment will thus be particularly effective. The newly developed channel modem uses mechanical filters for both the speech channel and the outband signaling. The channel filter has its passband at about 50 kHz and consists of 12 flexural vibrators with longitudinal coupling. Using the premodulation principle, only a single type of channel filter is required. Because of the simple setup of these mechanical filters, they are well-suited for automatic production. An improvement in the electrical characteristics is also achieved. The attenuation distortion in the passband of the loop-connected channel is within 1/10 of the International Telephone and Telegraph Consultative Committee (CCITT) tolerance scheme number 1 without any attenuation equalization. In addition, an essential size reduction has been accomplished. The customary bay volume will accommodate instead of the present 120 channels the channel modems for 600 voice circuits including power and carrier supplies.     

Si-based guided-mode resonance filter on a micro-optical bench

An out-of-plane guided-mode resonance filter on a single Si chip using a two-layer polysilicon surface micromachining process has been proposed. To the best of the authors' knowledge, this is the first time that a monolithic optical filter has been integrated on a silicon micro-optical bench. This device can be used as a bi-directional transceiver filter. The extinction ratio between 1550 and 1310 nm could be as low as 40 dB and the channel passband at 1550 nm was 20 nm.     

A 128-kHz mechanical channel filter with finite-frequency attenuation poles

The paper describes the design and manufacture of a miniaturized 128-kHz pole-type mechanical channel filter for FDM communication systems. By introducing a new phase inversion structure to realize the finite attenuation poles, and by minimizing sensitivity in the circuit design, we have designed and manufactured a miniaturized high-performance mechanical channel filter. The filter volume is 10.7 cm³, which is about ⅙ that of conventional LC channel filters. The passband response satisfies the 1/20 CCITT Recommendation. With this filter, we have developed a channel modem compact enough to mount 900 channel units per standard bay. Manufacturing steps and material characteristics are described in some detail. We also briefly discuss some future considerations in further miniaturizing the channel filter.     

基于SOA的L波段多波长锁模光纤环形激光器

报道了一种基于半导体光放大器(SOA)的L波段多波长光纤环形激光器,采用自制的100GHz信道间隔的光纤Mach-Zehnder(M-Z)干涉仪作为梳状滤波器,电吸收调制器(EAM)实现主动锁模,在1593.6nm附近获得了11个波长的同步锁模脉冲序列,脉冲重复频率为10GHz,半高全宽约为24ps,不同波长间功率不平坦度小于1dB。激光器具有工作稳定、输出光谱较宽和不同波长间功率波动小的特性。     

An image-rejecting mixer and vector filter with 55-dB imagerejection over process, temperature, and transistor mismatch

This paper describes an image-rejecting mixer and vector filter for use in radio systems with channel bandwidths in the range of 1 MHz. The circuit replaces the SAW filter and second downconverter commonly used in this style of radio. Because the output of the circuit is at an IF of 5 MHz, traditional demodulation methods including limiting and FM discrimination can still be used. The circuit is based on a quadrature mixer that guarantees good performance despite device mismatches and process variation. The circuit consumes 29 mA at 3.3 V,and achieves better than 55-dB image rejection despite device mismatches and process variation and is implemented in a single-poly triple metal 0.5 μm CMOS process with linear capacitor implants. The circuit is designed for input signals from 125 to 250 MHz. Input referred voltage noise is 900 μVrms. The in-band IP3 is 18 dBm. By changing an external reference frequency, the passband width of the filter can be varied from 3 to 0.5 MHz