Wideband planar lightwave circuit type variable optical attenuator using phase-generating coupler

A novel wideband planar lightwave circuit type variable optical attenuator (VOA) that incorporates a phase-generating coupler is proposed. The proposed VOA was fabricated on a 1.5%-/spl Delta/ silica-based waveguide, and obtained a low insertion loss of less than 1.2 dB and a low wavelength dependent loss of less than 0.8 dB at attenuation levels of 0 to 25 dB over the C- and L-band wavelength range.     

基于二氧化硅平面光波导的强度均衡的光脉冲对的产生

提出了一种基于平面光波导工艺的带有可调定向耦合器的非对称MZI结构.模拟结果显示,当定向耦合器的两个耦合臂的折射率独立改变时,定向耦合器的调制效果较好;当调制电极与耦合区的波导间距为0时,两个耦合臂的温度差达到最大.测试得到,AMZI的插入损耗为2.05 dB,延迟时间为151.4 ps,脉冲对的功率比近似为1.该器件有助于提高集成QKD器件的性能.     

Time-spreading wavelength-hopping optical CDMA system using EWO and TCM

In this paper, time-spreading wavelength-hopping optical CDMA system using trellis coded modulation scheme is investigated. The carrier hopping prime code and its shifted version are employed as signature sequences. Since the carrier hopping prime code is a symmetric code, the out of phase autocorrelation is zero. Applying the orthogonality of the signature sequences, the ternary transmission mechanism can be achieved. The proposed coding scheme is simple in both transmitter and receiver. As the multiple access interference and beat noise are the major deterioration of system performance, using coding scheme is an effective way to reduce the error floor. The numerical results reveal that the proposed coding scheme can significantly improve the system performance.     

Polarization-insensitive planar lightwave circuit dual-rate Mach-Zehnder delay-interferometer

We demonstrate a silica waveguide Mach-Zehnder delay-interferometer that uses integrated switches to demodulate either 10- or 40-Gb/s differential phase-shift keyed signals. We achieved polarization insensitivity by using a half-wave plate and reducing polarization crosstalk in the couplers.     

Highly-integrated planar lightwave circuit wavelength selective switch

The first demonstration of large-scale integration of AWG filters and thermo-optic switches and attenuators in 2% delta silica-on-silicon waveguides is reported. A compact high performance wavelength selective switch is demonstrated.     

Guided-wave laser based on erbium-doped silica planar lightwave circuit

The Er-doped silica guided-wave laser operating around 1.6 mu m was realised using a low-scattering-loss planar lightwave circuit with an Er-doped silica core which was fabricated by flame hydrolysis deposition and reactive ion etching techniques on an Si substrate. CW lasing was achieved successfully with an incident threshold power of 49 mW for pumping at 0.98 mu m.<>     

Planar lightwave circuit design for programmable complementaryspectral keying encoder and decoder

A planar lightwave circuit design for implementing complementary spectral keying encoders and decoders is presented. The design uses only one arrayed-waveguide grating integrated with arrays of thermo-optic phase shifters and attenuators in a reflective structure. The result is a compact, low component count, programmable spectral keying switch that can implement a variety of spectral encoding/decoding functions     

单纤三向器件平面光波导芯片结构优化设计

文章对采用平面光波导技术的单纤三向器件(Triplexer)芯片结构的参数进行了优化设计,对单元结构的光谱响应进行了模拟计算,通过数值模拟分析了结构的工艺容差性.结果表明,采用双模耦合器和M-z干涉仪结构可以得到工艺容差性高、光谱响应优良的适用的Triplexer器件.     

Lattice-form CWDM interleave filter using silica-based planar lightwave circuit

We demonstrate an eight-channel coarse wavelength-division-multiplexing interleave filter that employs a silica-based lattice-form filter. The filter incorporates phase-generating couplers to convert a conventional frequency interleave filter into a wavelength interleave filter with a constant channel spacing with respect to wavelength. We fabricated the designed interleave filter on a 1.5%-/spl Delta/ silica-based waveguide and realized a constant channel spacing of 20 nm with a wavelength displacement of within /spl plusmn/0.5 nm and an insertion loss of less than 1.7 dB over eight channels.     

Dispersion slope equalizer for dispersion shifted fiber using alattice-form programmable optical filter on a planar lightwave circuit

This paper reports an integrated-optic dispersion slope (third-order dispersion) equalizer for dispersion shifted fiber which employs a lattice-form programmable optical filter on a planar lightwave circuit (PLC). This dispersion slope equalizer consists of nine symmetrical interferometers interleaved with eight asymmetrical interferometers. The performance of the equalizer is evaluated numerically. We confirm experimentally that this equalizer is effective in reducing the pulse waveform deterioration caused by the dispersion slope. In addition, the equalizer improves the power penalty of a 200-Gb/s, 100-km, time-division multiplexed optical transmission experiment     

Compact bi-directional optical CDMA encoder/decoder with low power dissipation

One decoding structure with power saving ability is proposed for spectral-amplitude-coding (SAC) optical code-division multiple access (OCDMA) system. This decoding structure can avoid unnecessary power loss in the decoder based on fiber Bragg gratings, thus thermal noise in the photodiodes of the decoder is suppressed. In addition, this decoding structure can cooperate with the encoding structure based on arrayed-waveguide grating (AWG) routers with power saving ability to enhance the system performance. Code families generated from cyclic difference sets (CDSs) can be used in this encoding/decoding pair based on AWG routers due to their cyclic properties. Therefore network application such as passive optical network can adopt OCDMA with simper coder configuration and accommodate the same number of users with lower source power.     

A 1.3/1.55-μm wavelength-division multiplexing optical moduleusing a planar lightwave circuit for full duplex operation

We developed a hybrid integrated optical module for 1.3/1.55-μm wavelength-division multiplexing (WDM) full-duplex operation. The optical circuit was designed to suppress the optical and electrical crosstalk using a wavelength division multiplexing filter, and an optical crosstalk of -43 dB and an electrical crosstalk of -105 dB were achieved with a separation between the transmitter laser diode and the receiver photodiode of more than 9 mm. We used the optical circuit design to fabricate an optical module with a bare chip preamplifier in a package. This module exhibited a full duplex operation of 156 Mbit/s with a minimum sensitivity of -35.2 dBm at a bit error rate of 10^-10     

Low loss fully reconfigurable wavelength-selective optical 1/spl times/N switch based on transversal filter configuration using silica-based planar lightwave circuit

A low loss wavelength-selective switch is proposed and demonstrated. The switch has a 1/spl times/4 transversal filter configuration that includes arrayed waveguide gratings and thermooptic phase shifters, and can route arbitrary wavelength input light to arbitrary outputs with no loss variation. We confirmed its operating principle and obtained an average loss of 2.7 dB and a worst extinction ratio of more than 20 dB.     

III-nitride-based planar lightwave circuits for long wavelength optical communications

Planar lightwave circuits based on III-nitride wide-bandgap semiconductors are proposed and the feasibility of developing III-nitride-based novel photonic integrated circuits for applications in fiber-optical communications is discussed. III-nitrides have low attenuation in the near-infrared wavelength region because of their wide bandgaps, while as semiconductors their refractive indexes can be modulated by carrier injection. III-nitrides are also well known for their ability to operate at high temperatures, high power levels and in harsh environments. These characteristics make III-nitrides ideal candidates for tunable optical phased-array (PHASAR) devices for optical communications. We have characterized the optical properties of Al/sub x/Ga/sub 1-x/N epilayers in the 1550-nm wavelength region, including the refractive indexes and the impact of Al concentrations. Single-mode ridged optical waveguide devices using GaN-AlGaN heterostructures have been designed, fabricated and characterized for operation in the 1550-nm wavelength window. The birefringence of wurtzite GaN grown on sapphire substrate has been observed. Refractive indexes were found to be different for signal optical field perpendicular and parallel to the crystal c axis (n/sub /spl perp// /spl ne/ n/sub ///). More importantly, we found an approximately 10% change in the index difference /spl Delta/n=n/sub ///-n/sub /spl perp// with varying the waveguide orientation within the c plane, and a 60/spl deg/ periodicity was clearly observed. This is attributed to the hexagonal structure of the nitride materials. Various functional waveguide devices have been realized, including 2/spl times/2 directional couplers and eight-wavelength array-waveguide gratings. Theoretical predictions of temperature sensitivity and the efficiency of carrier-induced refractive change are provided.     

Laser-diode pumping of waveguide laser based on Nd-doped silica planar lightwave circuit

The authors describes an improvement in the lasing threshold in Nd-doped silica planar-lightwave-circuit (PLC)-type lasers fabricated on Si substrates in which the scattering loss was reduced by an improved fabrication technique. Lasers with core widths from 6 to 30 mu m were fabricated by flame hydrolysis deposition and reactive ion etching techniques. Based on an investigation of the lasing threshold dependence on core width, a minimum lasing threshold was obtained in a waveguide laser with an 8 mu m wide core. A threshold of 25 mW and a slope efficiency of 1.2% for laser-diode pumping at 805 nm were obtained in the waveguide laser.<>     

Highly linear-polarized external cavity lasers hybrid integrated on planar lightwave circuit platform

We propose and demonstrate, for the first time, a highly linear-polarized external cavity laser (ECL) integrated on planar lightwave circuit (PLC) with an in-PLC polarizer designed to improve polarization extinction ratio (PER). The in-PLC polarizer based on a 45/spl deg/-tilted grating was simply formed in the laser cavity composed of a Fabry-Pe/spl acute/rot laser diode and a Bragg grating. The proposed ECL exhibited a PER value as high as 30 dB and single longitudinal mode oscillation with a high sidemode suppression ratio of 50 dB at 1310 nm.     

Low-loss planar lightwave circuit OADM with high isolation and nopolarization dependence

A passive optical add-drop multiplexer with 1 dB of insertion loss and 36 dB of isolation is fabricated by writing Bragg gratings in a waveguide Mach-Zehnder interferometer using ArF excimer laser light. The spectral properties and bit-error-rate performance of the device are fully characterized using polarized light     

OCDMA通信系统编/解码器技术

介绍了光延迟线编／解码器，给出了两种光延迟线变址方案并分析了它们的性能。提出了三种新的编／解码器设计方案：基于步进啁啾FBG(光纤布喇格光栅)的光谱编码器、二维光延迟线编／解码器和多FBG编/解码器。     

AlGaAs-based two-dimensional photonic crystal slab with defectwaveguides for planar lightwave circuit applications

An AlGaAs-based near-infrared 2-D photonic crystal (PC) with an air-bridge structure featuring defect waveguides has been developed. For the sample without defect waveguides, measurements of the optical transmission characteristics in the wavelength range from 850 nm to 1100 nm showed a deep attenuation due to a bandgap with 30-35 dB attenuation and transmittance of nearly 100% for the guided modes. Optical propagation properties of defect waveguides were obtained by two methods: measurements of transmission spectra and plan-view observations of the optical beam trace along the waveguide with an infrared-vidicon camera. 3-D finite-difference time-domain simulations for the band structure and transmission spectra in the air-bridge slab with and without defect waveguides have revealed the appearance of four defect propagation modes specific to the defect waveguide, between two slab modes for the defect-free photonic crystal slab. These defect modes were experimentally identified in the measured transmission spectra     

WDM-PON module using a planar lightwave circuit with a coated WDM filter

We have presented a new configuration of a planar lightwave circuit (PLC) module coated directly with a filter which divides 1310/1550-nm wavelength bands for a wavelength-division-multiplexing passive optical network module in order to improve the conventional insertion process of thin film filter into the narrow trench located at the Y-junction of a PLC platform. The broadly tapered output facet width of a V-shaped waveguide was designed to be 12 /spl mu/m to minimize the reflected loss. The receiver module integrated with a PIN-photodiode on a silicon optical bench was fabricated. Data transmission of 2.5-Gb/s was demonstrated with clear eye diagrams.