High-Speed Optical 1 × 4 Switch Based on Generalized Mach–Zehnder Interferometer With Hybrid Configuration of Silica-Based PLC and Lithium Niobate Phase-Shifter Array

We demonstrate a high-speed optical switch based on a generalized Mach-Zehnder interferometer with a hybrid configuration consisting of a silica-based planar lightwave circuit and lithium niobate phase shifters. The novel switch demonstrated here has one input and four output ports and a switching time of less than 0.1 mus, thanks to the fast response of the electrooptic phase shifters on the LN chip. The insertion loss and extinction ratio of the switch are 4.2 dB and more than 17 dB, respectively     

Multiple-chip precise self-aligned assembly for hybrid integratedoptical modules using Au-Sn solder bumps

We have developed a novel three-dimensional high precision self-aligned assembly using stripe-type Au-Sn solder bumps and a micro-press solder bump formation method. This produces a high bonding precision of 1 μm for optical device assembly in both lateral and vertical directions without the need for time-consuming optical axes alignment. Furthermore, we tested a hybrid integrated 4×4 optical matrix switch, in which multiple SSC-SOAG arrays were simultaneously positioned and optical fibers were passively positioned on a silica based PLC platform using this technology. Four optical chips and seven wiring chips are assembled on a planar lightwave circuit (PLC) platform. The insertion loss for each of these paths at an injection current of 40 mA was within a range of 9±4 dB. The average extinction ratio was 40 dB. This self-aligned assembly technology was shown to be useful for building hybrid-integrated multichannel optical network components     

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     

Spot-size converted polarization-insensitive SOA gate with avertical tapered submicrometer stripe structure

To develop polarization-insensitive semiconductor optical amplifier (SOA) gates into more efficient and functional optical components by using hybrid integration with a planer lightwave circuit (PLC) platform, vertical tapered spot-size converters were integrated into a SOA gate with a narrow mesa-stripe structure of submicrometer width leading to low coupling loss (2.6 dB). Very-low polarization dependence of gain (<0.2 dB) and high extinction ratio (>30 dB) were achieved in a wide wavelength range (40 nm). High-speed (<1 us) gate operation was also demonstrated. These results indicate that the spot-size converted SOA integrated on a PLC platform will perform well in wavelength-division-multiplexing (WDM) applications     

Planar lightwave circuit platform with coplanar waveguide foropto-electronic hybrid integration

We propose a planar lightwave circuit (PLC) platform constructed on a silica-on-terraced-silicon (STS) substrate for opto-electronic hybrid integration. This platform consists of an embedded silica PLC region, a terraced silicon region for optical device assembly, and a high-speed electrical circuit region. In the electrical circuit region, the coplanar waveguides (CPW) are prepared on a thick-silica/silicon substrate. This structure reduces the propagation loss of the CPW drastically to 2.7 dB/cm at 10 GHz, because the loss tangent (tan δ) of the dielectric constants of silica is much smaller than that of silicon. In order to study the feasibility of this PLC-platform for multi-gigabit operation, we used it to fabricate an LD module in which an LD chip and LD-driver integrated circuits (IC) are assembled on the PLC-platform. A bit error rate measurement of this LD module in a 2.5 Gb/s NRZ showed that this platform is applicable to multi-gigabit optical signal processing     

Hybrid-integrated 4×4 optical gate matrix switch usingsilica-based optical waveguides and LD array chips

The fabrication and characteristics of a hybrid-integrated optical gate matrix switch were studied. The switch was composed of a silica-based single-mode guided-wave circuit and two InGaAsP gate array chips, each of which comprised eight laser diode optical gates. The gate array chips were assembled on the guided-wave circuit using a hybrid integration technique. The insertion loss of the fabricated 4×4 matrix switch was scattered among switching paths and ranged from 26 to 33 dB. The switch was applicable to a 400 Mb/s signal system with a bit error rate of 10^-9. The numerical analysis shows that the residual reflectivity at the LD gate and waveguide facets caused the loss scattering among the paths and that reduction of the residual reflectivity is essential for improving the switch characteristics     

新颖的掺铒光纤放大器无源复合组件的研究

报道了一种将光波分复用器与光隔离器集于一体的适用于掺铒光纤放大器的新颖复合组件。根据复合组件的性能指标对组件的结构参数进行了优化设计。实际制作的复合组件，得到泵浦光插入损耗＜０．６ｄＢ，信号光的插入损耗＜１．５ｄＢ，反向隔离度＞４２ｄＢ，体积为９×４５ｍｍ３。将复合组件用于掺铒光纤放大器中（前向泵浦方式）得到约３０ｄＢ的小信号增益，１０ｄＢｍ的饱和输出功率。     

Low loss GaAs optical waveguides

To realize an optical integrated circuit, various losses in the semiconductor waveguide such as absorption loss, waveguide loss, bending loss, and coupling loss, have to be minimized. Theoretical and experimental considerations for the reduction of these losses have been presented. A propagation loss of less than 0.5 dB/cm has been observed for a well-designed GaAs ridge waveguide. Moreover its coupling loss with a polarization-maintaining optical fiber decreased below 1.5 dB.     

Low loss GaAs optical waveguides

To realize an optical integrated circuit, various losses in the semiconductor waveguide such as absorption loss, waveguide loss, bending loss, and coupling loss, have to be minimized. Theoretical and experimental considerations for the reduction of these losses have been presented. A propagation loss of less than 0.5 dB/cm has been observed for a well-designed GaAs ridge waveguide. Moreover its coupling loss with a polarization-maintaining optical fiber decreased below 1.5 dB.     

Low radiation loss branching/combining of optical circuits using high-silica channel waveguides

A new branching/combining optical circuit structure using high-silica channel waveguides was proposed to reduce radiation loss where branching occurs. In this structure, an additional low-refractive-index layer was formed at the junction surface between the main and branching channels. The loss in a conventional circuit could be successfully reduced by over 0.4 dB in the through channel and 0.1 dB in the reflecting channel. The allowable conditions for a low-refractive-index layer were obtained through experimental and theoretical studies.     

Design and performance of a planar star mixer

This paper describes the realization of a hybrid star mixer as a planar circuit. The mixer has a minimum conversion loss of 5 dB and, for a conversion loss of less than 9 dB, spans over 2.2 GHz in IF bandwidth and 8 GHz in RF/LO bandwidth. The mixer employs a novel, planar balun structure, similar to conductor-backed CPW, that is suitable for realization as a monolithic circuit     

Monolithic millimeter wave optical receivers

A single stage monolithic millimeter wave optical receiver circuit was designed and fabricated using a metal-semiconductor-metal (MSM) photodetector and a pSeudomorphic Modulation Doped Field Effect Transistors (SMODFET) on a GaAs substrate for possible applications in chip-to-chip and free space communications. The MSM photodetector and the SMODFET epitaxial material were grown by molecular beam epitaxy (MBE). Device isolation was achieved using an epitaxially grown buffer between the MSM detector layers and SMODFET. The photodetector was designed for maximum absorption at optical wavelength of 770 nm light and the SMODFET impedance matching network was optimized for 44 GHz. The monolithic millimeter wave optical receiver circuit achieved 3 dB gain over a photodetector at 39 GHz, which was the limit of the measurement system. TOUCHSTONE model of the circuit indicated 6.6 dB gain over the photodetector and 5.7 dB total gain including the insertion loss of the photodetector at 44 GHz     

Distributed fiber Raman amplifiers with localized loss

Backward pumped C- and L-band distributed fiber Raman amplifiers are described, where discrete losses from 0-8 dB were added at various positions to examine the effect of localized loss. Below 3-dB additional loss, the overall optical performance degraded similarly, regardless of loss position in a hybrid Raman and erbium-doped fiber amplifier. Above 3 dB, the performance degradation worsened as the loss position became closer to the signal output. The spectral shape change of the fiber output against loss variation was made tolerable within /spl plusmn/0.4 dB simply by balancing the output power of L band with that of C band, unless the loss was close to pump input. The tolerance provides design flexibility for hybrid optical amplifiers and allows the use of fixed gain-flattening filters.     

140Mb/s光接收混合集成AGC主放大模块

本文介绍了140Mb/s光通信系统接收机中所用的AGC主放大模块。此模块采用厚膜电路混合集成形式,将AGC电路、主放大器制作在29.1×13.9mm~2的陶瓷片上,封装在DHM24绝缘子壳内,带宽为200MHz(3dB),增益为50dB,AGC范围大于25dB。在四次群光纤通信系统试验中,接收机灵敏度为-39dBm(误码率10~(-9)),眼图清晰。     

High-performance compact optical WDM transceiver module for passivedouble star subscriber systems

High-performance transceiver-type optical WDM interface modules with a volume of only 36 cc have been developed for PDS subscriber systems. The new module comprises an optical WDM sub-module, hybrid-integrated transmitter and receiver circuits. In the WDM sub-module, a planar lightwave circuit chip was hermetically sealed together with laser and photodiode chips in order to minimize the size of the transceiver module. The lightwave circuit was formed on an optical-waveguide chip by adopting a high-silica based optical-waveguide technology. The circuit has a 3-dB directional coupler for bi-directional transmission with a 1.3-μm wavelength through a single fiber and a wavelength division multiplexer between both 1.3-μm and 1.55-μm wavelengths. The overall characteristics of the fabricated WDM sub-module achieved were a responsitivity of 0.25±0.05 A/W, an insertion loss approximately 3 dB at 1.55 μm and an isolation of 35 dB between both wavelengths. Optical output power of the fabricated transceiver module was -3.8 dBm. Also, receiver sensitivity of less than -35 dBm with an overload of over -14 dBm were obtained by introducing high-speed automatic gain and threshold control techniques. Thus, an allowable span loss of over 30 dB and an optical dynamic range of over 20 dB were attained. The preamble bit length required to reach stable receiver operation was confirmed to be within three bits     

A Wide-Band 12-GHz 12-Way Planar Power Divider/Combiner (Short Paper)

A 12-way, low-loss, wide-band planar electrically symmetric hybrid power divider/combiner for the X-band is described. It is a two-stage fork, 12-way hybrid realized completely in microstrip. A circuit design is given to maximize the match and isolation at band center. Over a frequency band of 10-13 GHz, this divider/combiner has an insertion loss of less than 1 dB and an isolation between output ports of better than 17 dB.     

多功能插损回损测量仪的设计

为了快速精确测量光连接器件的插入损耗和回波损耗,在传统测量方法的基础上设计了一种新型的多功能差损回损测量仪。该测量仪系统由光路和电路两部分组成。光路部分利用光耦合器得到待测器件的损耗功率,经探测器接收并转换为电流;电流送到电路进行放大和A/D转换,并由单片机进行处理,测量结果由LCD显示输出。实验结果表明,该系统能够实时显示待测器件的差损和回损,达到0.05dB的精度。进一步测试结果表明,该测量系统可以达到70dB的高精度动态范围。     

X-band integrated circuit mixer with reactively terminated image

AnX-band mixer using GaAS Schottky barrier diodes with a thin-film 500-MHz IF preamplifier was developed using hybrid microwave integrated circuit techniques. The balanced mixer had filters to provide a short circuit at the image frequency. The entire mixer preamplifier occupied an area of only 0.38 square inches and had a noise figure of 6.7 dB which corresponded quite closely to the theoretical noise figure considering all losses. The thin-film IF amplifier alone had a 2.2-dB noise figure and the mixer IF amplifier coupling network had a loss of 0.4 dB.     

X-Band Integrated Circuit Mixer with Reactively Terminated Image

An X-band mixer using GaAs Schottky barrier diodes with a thin-film 500-MHz IF preamplifier was developed using hybrid microwave integrated circuit techniques. The balanced mixer had filters to provide a short circuit at the image frequency. The entire mixer preamplifier occupied an area of only 0.38 square inches and had a noise figure of 6.7 dB which corresponded quite closely to the theoretical noise figure considering all losses. The thin-film IF amplifier alone had a 2.2-dB noise figure and the mixer IF amplifier coupling network had a loss of 0.4 dB.     

X-Band Integrated Circuit Mixer with Reactively Terminated Image

An X-band mixer using GaAs Schottky barrier diodes with a thin-film 500-MHz IF preamplifier was developed using hybrid microwave integrated circuit techniques. The balanced mixer had filters to provide a short circuit at the image frequency. The entire mixer preamplifier occupied an area of only 0.38 square inches and had a noise figure of 6.7 dB which corresponded quite closely to the theoretical noise figure considering all losses. The thin-film IF amplifier alone had a 2.2-dB noise figure and the mixer IF amplifier coupling network had a loss of 0.4 dB.