Design and analysis of widely tunable sampled grating DFB laser diode integrated with sampled grating distributed Bragg reflector

A new widely tunable laser diode structure that requires only two tuning currents is proposed. The laser diode consists of a sampled grating distributed feedback (SGDFB) laser diode monolithically integrated with a sampled grating distributed Bragg reflector (SGDBR). The phase control sections are properly inserted between the grating bursts of the SGDBR and SGDFB sections for the discrete and continuous tuning. To confirm the feasibility of the new structure, the split-step time domain model is used. The simulation result for a particular design shows that the tuning range as wide as 27 nm is possible with side-mode suppression ratio exceeding 35 dB. Furthermore, the output power is larger than that from SGDBR laser diodes with similar parameters.     

Fabrication of Butt‐Coupled SGDBR Laser Integrated with Semiconductor Optical Amplifier Having a Lateral Tapered Waveguide

We have demonstrated a high‐power widely tunable sampled grating distributed Bragg reflector (SGDBR) laser integrated monolithically with a semiconductor optical amplifier (SOA) having a lateral tapered waveguide, which is the first to emit a fiber‐coupled output power of more than 10 dBm using a planar buried heterostructure (PBH). The output facet reflectivity of the integrated SOA using a lateral tapered waveguide and two‐layer AR coating of TiO₂ and SiO₂ was lower than 3 × 10^?4 over a wide bandwidth of 85 nm. The spectra of 40 channels spaced by 50 GHz within the tuning range of 33 nm were obtained by a precise control of SG and phase control currents. A side‐mode suppression ratio of more than 35 dB was obtained in the whole tuning range. Fiber‐coupled output power of more than 11 dBm and an output power variation of less than 1 dB were obtained for the whole tuning range.     

2GHz低功耗差分控制的CMOS单片LC压控振荡器

设计了工作在2GHz,差分控制的单片LC压控振荡器,并利用0.18μm CMOS工艺实现.利用模拟和数字(4位二进制开关电容阵列)调频技术,压控振荡器的调频范围达到16.15%(1.8998～2.2335GHz).在2.158GHz工作频率下,在1MHz频偏处的相位噪声为-118.17dBc/Hz.应用给出的开关设计,相位噪声在不同的数字位控制下变化不超过3dB.由于利用pn结二级管作为变容管,在调频范围内,相位噪声仅改变约2dB.压控振荡器在1.8V电源电压下消耗2.1mA电流并能够在1.5V电源电压下正常工作.     

基于氮化硅微环和载波分离的可重构微波光子带通滤波器

基于Add-Drop型氮化硅微环滤波器,利用光学单边带调制和光载波分离的方法,实现可重构微波光子带通滤波器。滤波器带宽和带外抑制比分别达到726 MHz和37.0dB。并且通过改变光载波波长实现1.64~23.41GHz的滤波器频率调谐;通过调节微环耦合系数实现0.683~2.246GHz的滤波器带宽调谐,在带宽调谐范围内带外抑制比大于26dB。     

Improved design of tuned optical receivers

We present new design principles for improved heterodyne tuned optical receivers where several tuning inductances reduce the influence of thermal receiver noise over a broad frequency range. A theoretical example for a 600 MHz tuning bandwidth shows a reduction of thermal receiver noise (and thus in required local oscillator power) of up to 13dB. The example is tested experimentally for the so-called mixed tuning configuration. We obtain good agreement with the theoretical predictions. The experimental RMS noise current is <5pA/?(Hz) over a 580 MHz bandwidth with the lowest value of 3-5 pA/?(Hz) at 950MHz.     

A low phase noise silicon 18-GHz push-push VCO

The design and measurement of a push-push voltage controlled oscillator (VCO) at 18.66-18.3 GHz are presented in this paper. The circuit includes two packaged silicon transistors (Siemens BFP 540F) and a microstrip resonator tuned by two GaAs varactor diodes (M/A-COM ML46580). A 360-MHz tuning range is obtained with an output power of 0-3.1 dBm. The fundamental rejection is around 17 dB for a wide range of collector bias current. The phase noise is below -103 dBc/Hz at 100-kHz offset and below -122 dBc/Hz at 1 MHz for the entire tuning bandwidth.     

5-GHz Low Phase-Noise CMOS VCO Integrated With a Micromachined Switchable Differential Inductor

A 5-GHz CMOS voltage-controlled oscillator (VCO) integrated with a micromachined switchable differential inductor is reported in a 0.18 mum radio frequency-CMOS-based microelectromechanical system technology. The power consumption of the core is about 8 mW at the supply voltage of 1.8 V. A total tuning range of 470 MHz (from 5.13 GHz to 5.60 GHz) is achieved as the tuning voltage ranging from 0 V to 1.8 V. In the practical tuning range, the measured phase noise performances at 1 MHz offset are less than -125 dBc/Hz and -126 dBc/Hz when the inductor switch is turned on and off, respectively. The figure-of-merit is better than -190 dB. When compared with a contrast VCO circuit that utilizes a standard switchable differential inductor, this oscillator reaches a phase noise improvement of around 3 dB as the switch is turned on. Around 1-dB on-off phase noise difference can be achievable.     

A compact external cavity wavelength tunable laser without an intracavity etalon

We propose a novel external cavity wavelength tunable laser (ECTL) configuration without an etalon inside the cavity. ECTL consists only of a semiconductor optical amplifier with an integrated phase section, and a liquid crystal tunable mirror. We successfully demonstrated excellent performances of the ECTL with fiber coupled output power of more than 50 mW over a 40-nm tuning range, sidemode suppression ratio of better than 45 dB, relative intensity noise of better than -148 dB/Hz, and linewidth of narrower than 2.3 MHz.     

Analog performance of an ultrafast sampled-time all-optical fiber XPM wavelength converter

Analog performance of an all-optical ultrafast wavelength converter is measured and reported for the first time. The wavelength-conversion process is based on nonlinear cross-phase modulation in an optical fiber combined with an optical filter to convert phase modulation to amplitude modulation. The spurious-free dynamic range (SFDR) of the converter is measured to be 82 dB/spl middot/Hz/sup 2/3/. We define a new metric called the SFDR power penalty, which measures the degradation in SFDR relative to baseline the back-to-back analog optical link. The SFDR power penalty was measured to be 5 dB/spl middot/Hz/sup 2/3/ and is shown to be a function of the input optical power. This metric is used to characterize the linear region of the optical wavelength converter.     

A 1.48-mW low-phase-noise analog frequency modulator for wireless biotelemetry

This paper presents a low-phase-noise, hybrid LC-tank, analog frequency modulator for wireless biotelemetry employing on-chip NMOS varactors in the inversion region as the frequency tuning element. We demonstrate that a correct estimate for the destination signal-to-noise ratio, which quantifies the quality of the wirelessly received signal in a frequency-modulated biotelemetry system, is only achieved after taking into account the large-signal oscillation effect on the tank varactor. A prototype chip is fabricated using AMI 1.5-microm double-poly double-metal n-well CMOS process, and exhibits a measured gain factor of 1.21 MHz/V in the mid-range of the tuning voltage and a phase noise of -88.6 dBc/Hz at 10-kHz offset from the 95.1-MHz carrier while dissipating 1.48 mW from a 3 V power supply leading to a figure of merit (FOM) of -166.5 dBc/Hz. The VCO is successfully interfaced with a penetrating silicon microelectrode with 700 microm2 iridium recording sites for wireless in vitro recording of a 50 Hz simulated normal sinus rhythm signal from saline over a distance of approximately 0.25 m. Given a typical gain of approximately 40 dB for fully integrated front-end bioamplifiers, a wireless recording microsystem employing this VCO would be capable of detecting input biopotentials down to the submilivolt range.     

Optical Microring Resonators in Fluorine-Implanted Lithium Niobate for Electrooptical Switching and Filtering

We present a new approach for the fabrication of electrooptically tunable microring resonators in lithium niobate. Planar optical waveguides for vertical light confinement (Deltan o = 0.17) are produced by fluorine ion implantation. Optical microrings and bus waveguides are then formed by laser lithography masking and Ar⁺ plasma etching. Electrodes are optically isolated from the optical microrings by a polyvinyl alcohol buffer layer with a high dielectric constant (epsiv ~ 70 at 10 Hz) to improve electrooptic tuning. The microrings with a radius of 80 mu m exhibit optical resonances with a modulation depth of 11 dB, a free spectral range of 2 nm, and an electrooptical tunability of 10 pm/V.     

窄线宽低噪声可调谐非平面环形激光器

针对空间相干光通信和探测等应用,对非平面环形激光器的线宽、噪声和调谐特性进行了系统的实验研究。单频输出功率达到752mW,光光效率42%,斜率效率54%。采用延时自外差拍频法测试了激光线宽,其随泵浦功率的增加而增大,输出功率小于200 mW 时,线宽小于1 kHz,在最高输出功率下线宽为2.3 kHz。激光强度噪声主要由弛豫振荡引起,相对强度噪声（RIN）随着泵浦功率的提高而降低。在1.78W 泵浦功率下,RIN 达到-93 dB/Hz。采用温度和压电两种方式进行了激光调谐。温度调谐范围达到62 GHz。压电调谐范围达到130MHz,响应带宽100 kHz。     

Broad-band electronic linearizer for externally modulated analogfiber-optic links

Linearization of analog fiber-optic links using a novel CMOS linearization circuit is reported. A 17-dB suppression of the third-order intermodulation product (IMP3) has been achieved at the modulation index of 49.6 % and over a broad-band frequency range from dc to 1.3 GHz. In an experimental link with a noise floor of -124 dBm/Hz, the spurious free dynamic range (SFDR) is improved by 14 dB from 85 dB/Hz^2/3 to 99 dB/Hz^2/3     

A 0.83-2.5-GHz continuously tunable quadrature VCO

A quadrature VCO with /spl plusmn/50% continuous 0.83-2.5-GHz tuning range is presented. It is based on a core LC-QVCO with /spl plusmn/20% tuning range, a single sideband mixer (SSBM), two frequency dividers and a multiplexer. The circuit has been implemented in a 0.13-/spl mu/m 1.2-V CMOS technology. The additional area with respect to the core LC-QVCO is 100 /spl mu/m/spl times/100 /spl mu/m. Quadrature error is less than 2/spl deg/; the phase noise is less than -120 dBc/Hz @ 1 MHz over the whole tuning range and is mainly due to the LC-QVCO. Spurs are more than 34 dB below the fundamental in the worst case.     

A low-voltage 40-GHz complementary VCO with 15% frequency tuning range in SOI CMOS technology

The design of a low-voltage 40-GHz complementary voltage-controlled oscillator (VCO) with 15% frequency tuning range fabricated in 0.13-/spl mu/m partially depleted silicon-on-insulator (SOI) CMOS technology is reported. Technological advantages of SOI over bulk CMOS are demonstrated, and the accumulation MOS (AMOS) varactor limitations on frequency tuning range are addressed. At 1.5-V supply, the VCO core and each output buffer consumes 11.25 mW and 3 mW of power, respectively. The measured phase noise at 40-GHz is -109.73 dBc/Hz at 4-MHz offset from the carrier, and the output power is -8 dBm. VCO performance using high resistivity substrate (/spl sim/300-/spl Omega//spl middot/cm) has the same frequency tuning range but 2 dB better phase noise compared with using low resistivity substrate (10 /spl Omega//spl middot/cm). The VCO occupies a chip area of only 100 /spl mu/m by 100 /spl mu/m (excluding pads).     

1.5 μm phase-controlled distributed feedback wavelength tunableoptical filter

A 1.5-μm phase-controlled distributed feedback wavelength-tunable optical filter is studied. This is the first optical filter which controls the transmissivity (gain) and the transmission wavelength independently. Wavelength tuning range as wide as 43 GHz (3.4 Å) with high constant gain of 27 dB has been achieved. A five-channel wavelength selection with less than -10 dB crosstalk is expected with this filter. This device also operates as a wavelength tunable laser, and the wavelength tuning range as a laser is larger than as a filter. The reason is studied, and it is shown that suppression of the submodes is important to expand the wavelength tuning range     

Peripheral-coupled-waveguide MQW electroabsorption modulator for near transparency and high spurious free dynamic range RF fiber-optic link

Peripheral coupled waveguide (PCW) design has been deployed in InGaAsP multiple quantum-well (MQW) electroabsorption modulator (EAM) at 1.55-/spl mu/m wavelength. PCW enhances the optical saturation power and reduces the optical insertion loss and the equivalent V/sub /spl pi// simultaneously. A radio-frequency link using a 1.3-mm-long lumped-element PCW EAM has achieved experimentally a link gain of -3 dB, at 500 MHz and at input optical power of 80 mW. The corresponding two-tone multioctave spurious-free dynamic range (SFDR) at the same bias is measured at 118 dB/spl middot/Hz/sup 2/3/. The single-octave SFDR at the third-order null bias is 132 dB/spl middot/Hz/sup 4/5/.     

Low-loss and compact V-band MEMS-based analog tunable bandpass filters

This paper presents compact V-band MEMS-based analog tunable bandpass filters with improved tuning ranges and low losses. For compact size and wide tuning range, the two-pole filters are designed using the lumped-elements topology with metal-air-metal (MAM) bridge-type capacitors as tuning elements. Capacitive inter-resonator coupling has been employed to minimize the radiation loss, which is the main loss contributor at high frequencies. Two filters have been demonstrated at 50 and 65 GHz. The 65-GHz analog tunable filter showed a frequency tuning bandwidth of 10% (6.5 GHz) with low and flat insertion losses of 3.3 /spl plusmn/ 0.2 dB over the entire tuning range.     

Relative intensity noise measurements of a widely tunablesampled-grating DBR laser

The intensity noise of a sampled-grating distributed Bragg reflector laser with 50-nm tuning range and 45-dB side-mode suppression ratio has been measured. The resonance frequency, damping factor, and modified Schawlow-Townes linewidth are extracted from the noise spectra. At high output power, the relative intensity noise (RIN) of the laser is below the photodiode shot noise limit, which is -160 dB/Hz. The laser has uniform shot noise limited RIN properties along the whole tuning range. The maximum resonance frequency is 5.4 GHz at a bias current of 120 mA and the K factor is 0.58 ns     

Frequency dependence on bias current in 5 GHz CMOS VCOs: impact on tuning range and flicker noise upconversion

The tuning curve of an LC-tuned voltage-controlled oscillator (VCO) substantially deviates from the ideal curve 1//spl radic/(LC(V)) when a varactor with an abrupt C(V) characteristic is adopted and the full oscillator swing is applied directly across the varactor. The tuning curve becomes strongly dependent on the oscillator bias current. As a result, the practical tuning range is reduced and the upconverted flicker noise of the bias current dominates the 1/f/sup 3/ close-in phase noise, even if the waveform symmetry has been assured. A first-order estimation of the tuning curve for MOS-varactor-tuned VCOs is provided. Based on this result, a simplified phase-noise model for double cross-coupled VCOs is derived. This model can be easily adapted to cover other LC-tuned oscillator topologies. The theoretical analyses are experimentally validated with a 0.25 /spl mu/m CMOS fully integrated VCO for 5 GHz wireless LAN receivers. By eliminating the bias current generator in a second oscillator, the close-in phase noise improves by 10 dB and features -70 dBc/Hz at 10 kHz offset. The 1/f/sup 2/ noise is -132 dBc/Hz at 3 MHz offset. The tuning range spans from 4.6 to 5.7 GHz (21%) and the current consumption is 2.9 mA.