Two-dimensional grating unit cell demultiplexer for thin-film optical waveguides

An optical wavelength demultiplexer has been constructed on a planar waveguide using a pair of crossed gratings which have the same spatial frequency. The device is tunable and can separate spatially two channels 1.6 nm apart at 594.8 nm. Channel crosstalk is very low and the device can readily be cascaded.     

Demonstration of grating demultiplexer in GaAs/AlGaAs suitable for integration

Based on Rowland circle construction, a grating spectrometer integrated with 90 degrees curved output waveguides was designed and fabricated in a GaAs/AlGaAs waveguide structure. By incorporating curved waveguides, a larger separation between output facets was obtained.<>     

A novel resonance-type optical receiver for high-speed opticalheterodyne transmission systems

A wideband resonance-type optical receiver (WROR) is proposed. It is based on inserting inductance in the feedback path of transistors to improve the frequency bandwidth and noise characteristics of the ROR in the high-frequency range. The noise characteristics of conventional and resonance-type optical receivers are evaluated by considering the series resistance of photodiodes. The double-balanced wideband resonance-type optical receiver is also evaluated. Its frequency bandwidth is 5-12 GHz. Finally, a 5-Gb/s optical CPFSK modulation and demodulation experiment is carried out using this optical receiver     

Demonstration of a 1*2 multichannel grating cavity laser for wavelength division multiplexing (WDM) application

A new form of diode laser source for wavelength-division multiplexing (WDM) applications is reported. The source has been designed to operate in systems requiring wavelength separations between channels of more than 1 nm and provides exact control of channel separation with low crosstalk. Simultaneous multiwavelength generation is also possible.<>     

A terahertz optical asymmetric demultiplexer (TOAD)

A device capable of demultiplexing Tb/s pulse trains that requires less than 1 pJ of switching energy and can be integrated on a chip is presented. The device consists of an optical nonlinear element asymmetrically placed in a short fiber loop. Its switching time is determined by the off-center position of the nonlinear element within the loop, and therefore it can use the strong, slow optical nonlinearities found in semiconductors, which all other fast demultiplexers seek to avoid. The switch's operation at 50 Gb/s is demonstrated, using 600-fJ control pulses     

光栅多通道光学双稳性系统的理论分析

本文提出了一种由两个平行放置的正弦位相光栅构成的混合型多通道光学双稳性系统。理论上推导出了描述此系统的调制性和双稳性的数学模型。基于此模型,对不同参数情况下,此系统的调制性和双稳性进行了数字模拟。最后,对数字模拟结果进行了分析和总结.此系统有可能应用于光通信和光信息处理等领域。     

Demonstration of multilevel multichannel optical frequency shift keying (FSK) with cleaved-coupled-cavity (C3) semiconductor lasers

We report the first demonstration of multilevel multichannel (4-level, 2-channel) optical frequency shift keying (FSK) using a newly developed cleaved-coupled-cavity (C3) GaInAsP semiconductor laser operating at ~1.3 ?m. This is made possible because of the very large frequency tuning rate (~10 A/mA) and frequency tuning range (~150 A) achievable with these new lasers. In addition, such a laser is also shown to operate in a highly stable single-longitudinal mode even under high-speed direct frequency modulation.     

Demonstration of all-optical Mach-Zehnder demultiplexer

Recently, Kang et al. reported the demonstration of an all-optical Mach-Zehnder demultiplexer (see ibid., vol.31, no.9, pp.749-50, 1995). In their paper, Kang et al. drew what we believe is an invalid comparison with work previously published by ourselves (see S. Nakamura et al., Appl. Phys. Lett., vol.65, no.3, pp.283-5, 1994). They described the device proposed by us, the symmetric Mach-Zehnder (SMZ) all-optical switch, as a Mach-Zehnder version of the terahertz optical asymmetric demultiplexer (TOAD). The SMZ and TOAD are in fact different independently-developed devices, each of which has its advantages and disadvantages. A reply by Kang et al. to this comment is included     

A monolithic GaAs receiver for optical interconnect systems

A monolithic GaAs optical receiver which includes a photodetector and preamplifier was designed and fabricated using a common 1.0-μm GaAs MESFET technology. The optical receiver operates at the data rate of 1 Gb/s. The transimpedance value can be continuously tuned from 1 to 10 kΩ. The metal-semiconductor-metal photodiode shows a 35% efficiency. Several design factors are considered to achieve high-bandwidth and low-noise operation. An array of the integrated receivers can be compactly implemented in a single chip for high-speed interconnection networks and photonic signal processing     

Broad-passband-width optical filter for multi/demultiplexer using a diffraction grating and a retroreflector prism

The letter describes the experimental results of a novel optical filter for a multi/demultiplexer using a diffraction grating and a retroreflector prism. A broader passband width, which is proportional to the difference between the prism base length and the input fibre core diameter, is obtained. The minimum insertion loss is 2.2 dB.     

Analysis of a tunable multichannel two-mode-interferencewavelength-division-multiplexer/demultiplexer

An integrated optical multichannel wavelength-division multiplexer/demultiplexer for a single-mode fiber system is investigated by the beam propagation method (BPM). Important wavelength characteristics of dual-channel two-mode-interference (TMI) multiplexer/demultiplexer waveguide with and without electrode are studied and general design guidelines for realizing multichannel multiplexer/demultiplexer are given. Design and simulation of four-channel TMI multiplexer/demultiplexer are discussed     

Effect of intermodulation in multichannel optical heterodyne systems

It is shown that large numbers of optical heterodyne channels may be frequency multiplexed over a single-mode optical fibre without the intermodulation byproducts of the photodetection process becoming a problem, provided the channels are spaced at five times their optical bandwidth, or greater.     

Mitigation of polarization-mode dispersion in optical multichannel systems

Simulations of first-order polarization-mode dispersion (PMD) mitigation, based on the electrical power spectrum has been performed. We show that, although first-order compensation significantly improves the signal quality for PMD values of a few tenths of the bit-slot, the improvement still is deficient for telecom purposes when the PMD value neighbors a third of the bit-slot. We, therefore, propose and analyze a novel concept for PMD mitigation in optical multichannel systems, which increases the systems reliability at the expense of the total capacity for the same system. With the proposed method, which uses switching to redundant channels based on measurements of signal quality of all channels in the actual system, the PMD value can be increased to a half of the bit-slot while still keeping the probability for signal outage at acceptable low levels. In the appendixes we simulate the statistical impact of different PMD-emulator models and we show that static bit sequences may induce notches in the electrical power spectrum. These notches may obstruct the extraction of feedback signals for PMD-mitigator schemes based on electrical power spectrum.     

Optical receiver for VHF multichannel video transmission

Optical receivers for multichannel TV transmission in the VHF band are analyzed and tested from the viewpoints of linearity, sensitivity, and frequency response. Photodiodes and avalanche photodiodes are compared for use as a front-end detector. Optimization of the preamplifiers is studied in terms of both configurations and biasing conditions. Improvement of frequency characteristics, using a Percival coil, is also investigated. It is concluded that a receiver using a photodiode can attain as high a sensitivity as and a greater linearity (around 5 dB) than one using an avalanche photodiode     

一种新型前馈自动增益控制光接收机的研究

自动增益控制模拟光接收机广泛应用于光纤有线电视、光纤直播卫星电视、无线通讯及雷达等射频微波信号光传输,是实现大动态范围光载波信号高质量接收必不可少的一项技术.我们采用一种入射光功率电平检测与处理的新方法,对模拟光接收机的增益进行控制,将接收机输出电平控制在要求的范围内,实现了一种新型的无射频反馈电路的自动增益控制光接收机.     

Random access optical heterodyne receiver for coherent FDM broadcasting systems

A random access optical heterodyne receiver for a coherent FDM broadcasting system has been developed, using a wavelength tunable local DBR LD, polarisation diversity technique and a random access automatic frequency controller. In a 10-channel FDM experimental system, 114 GHz capture range, 80 GHz lock range and arbitrary channel selection within less than 1 ms were realised.<>     

Wideband guided-wave periodic multi/demultiplexer with a ringcavity for optical FDM transmission systems

A guided-wave periodic multi/demultiplexer with a ring cavity for optical frequency-division-multiplexing (FDM) transmission systems is demonstrated. The frequency spacing is 5 GHz at the 1.55 μm wavelength region and the bandwidth is 1.8 times as wide as that of conventional periodic filters with simple Mach-Zehnder interferometer structure     

新型WDMA-EPON系统OLT端光接收机的研究

文章介绍了一种新型粗波分复用（CWDM）阵列式光接收模块,用于波分多址（WDMA）基于以太网的无源光网络（EPON）的光线路终端（OLT）侧。谊接收模块采用新颖有源、无源混合集成的光电子器件,最终实现了多个波长通道的接收单元电路一体化,因而具有高可靠性、低成本和体积小的特点。在155Mbit／s速率时谊接收机的接收灵敏度优于-34．0dBm。     

Arrayed-waveguide grating for wavelength division multi/demultiplexer with nanometre resolution

A novel diffraction grating based on arrayed channel waveguides has been proposed for nanometre-spaced wavelength division multiplexing. A grating with a diffraction order of 20 has been fabricated using a composite glass waveguide. A wavelength resolution of 0.63 nm has been achieved in the 1.3 mu m wavelength band.<>     

信道串扰对多信道混沌通信的影响

构建了基于垂直腔面发射激光器(VCSELs)的多信道全光混沌通信系统模型,通过描述其特性的数率方程,研究了信道串扰对系统混沌同步及解码性能的影响。在数值模拟中,使用一个改进型的参数——相似指数作为参考标准来评价同步性能。结果表明,相对注入强度越小,信道间隔越大,系统同步的性能越好;双信道系统的同步质量相比主从式单信道系统会有明显下降,而进一步增加信道数量,同步品质并不发生显著改变。以2.5Gb/s伪随机数字调制下的混沌掩藏方式为例,分析了不同信道条件下系统解码性能。在同步质量足够高时,信号可以得到较好的恢复。