隔离电阻对集成光源特性的影响分析

提出了一种分布反馈(DFB)激光器与电吸收(EA)调制器集成光源(EML)的等效电路模型。该模型考虑了由于隔离电阻不够大而导致的激光器与调制器之间的电耦合,通过对电路模型进行仿真可以看出,对于不同隔离电阻的EML,激光器的阈值电流、调制器的频率响应带宽、集成器件的小信号调制和脉冲调制等多方面特性均有明显不同。分析得到,EML的隔离电阻阻值只有达到10kQ量级,才能够忽略电泄漏对器件特性的影响。并指出EML在更高的偏置下,将对隔离电阻提出更高的要求。     

DFB半导体激光器的频移和色散脉冲崎变

根据分布反馈（ＤＦＢ）半导体激光器的耦合波理论和电吸收调制器模型，推导出了描述ＤＦＢ／ＥＡ集成器件中调制器的端面反射造成的激光器的静态频移和动态频移的解析表达式，动态频移（“反射啁啾”）正比于调制器的有效端面反射率。利用动态频移模型对光脉冲经过反常色散光纤传输后的波形进行了计算机仿真，取得了与实验一致的结果。结果表明：无论脉冲的初始啁啾的正负如何，“反射啁啾”总是使得传输后的脉冲变窄，当反射啁啾为正时，脉冲的上升沿出现“过冲”，而下降沿变缓；当反射啁啾为负时，情况与之相反。     

高速光通信用的光电子器件的进展

人类社会的信息化建设正在加速进行,即使是在全球经济发展不景气的情况下,通信和信息行业也十分红火。光通信呈现着蓬勃发展的新局面,正朝着高速、超高速光纤传输、超大容量的ＷＤＭ、ＯＴＤＭ以及全光网等方向发展。但这些系统的实现还依赖于相应的光电子技术的进步。一系列的光电子器件将在未来的通信网中起着重要的作用,因而各国从事光电子器件的研究者都在奋力开发各种高性能器件,研究其材料及工艺,并取得了丰硕成果。１．ＤＦＢ激光器／ＥＡ调制器集成光源ＤＦＢ激光器／ＥＡ调制器集成光源具有低啁啾、低驱动电压（Ｖｐｐ：２～３ｖ,ＬｉＮｂＯ３调制器的Ｖｐｐ：４～５ｖ）、低功耗、容易与激光器或其它波导器件集成、耦合损耗低、调制效率高、且体积小（一般长０．２ｃｍ左右,而ＬｉＮｂＯ３调制器长８ｃｍ）等优点,特别是含有增益耦合的ＤＦＢ激光器因为具有动态单模和调制啁啾小等特性,有助于减小集成器件线宽,而且它还具有较强的抗端面反射能力,从而减小因端面反射引起的啁啾,改善集成器件的啁啾特性等。该光源现已广泛用于２．５Ｇｂｉｔ／ｓ、１０Ｇｂｉｔ／ｓ等高速传输系统,其中２.５Ｇｂｉｔ／ｓＤＦＢ激光器／ＥＡ调制器集成器件已成为干线光纤通信系统的主要光源。１０...     

日本半导体光电子器件研究与开发的新进展

根据对日本九所研究所和大学的实地考察,综述了这些研究机构在光电子器件方面的研究和开发进展,这些光电器件主要包括多波长光源和滤长可选择光源、电吸收调制器与分布反馈激光器的集成、泵浦用大功率激光器、大功率ＧａＮ激光器和平面光波回路等。同时,介绍了日本半导体光电产业的发展现状和趋势。     

光网络与光子集成的发展(下)

光网络体系中的有源光子集成 高速响应、低啁啾、单稳频集成光子源 半导体分布反馈(DFB)激光器作为光通信的光子源器件已占据不可替代的重要地位,然而DwDM光网络对光子源却提出更高的要求.直接调制DFB激光器受到固有张弛振荡效应的限制,响应速率难以越过5Gb/s,同时在高速率下,频移啁啾效应已比较严重,因此必须采用外调制技术,从光网络体系考虑,调制器宜结构简单并能与DFB激光器实现单片集成.     

10Gbit/s高T0无制冷分布反馈激光器

与折射率耦合分布的分布反馈(DFB)激光器相比,不管界面反射率是多少,增益耦合DFB激光器都能稳定地单纵模工作,而且具有高速、低啁啾的特性.本课题组用AlGaInAs/InP材料,采用增益耦合DFB结构,进行了单纵模激光器研发,并对器件特性进行了测试分析.     

GaAlAs／GaAs欧量子阱增益耦合型DFB激光器电吸收型调制器单片光子…

我们在国际上率先提出将增益耦合分布反馈式（ＧＣ－ＤＦＢ）半导体激光器作为激光器／调制器单片集成器件的光源，为了简化制作工艺，进一步提出激光器的有源层与调制器波动共用同一组分和同一结构，本理论上分析了新型器件的可行性，优化设计了器件结构，在此基础上，采用金属有机化合物化学汽相外延技术（ＭＯＣＶＤ）在国际上首次研制成功了该种增益耦合型ＤＦＢ激光器／电吸收型调制器单片光子集成器件，器件电流为３５ｍＡ。     

10Gbit／s传输用的低驱动电压调制器DFB激光器集成器件

电场吸收型光调制器／ＤＦＢ激光集成器件作为低啁啾、小型、高输出功率的高速工调制光源是很有吸引力的。从减轻驱动电路负担和降低功耗的观点，要求降低１０Ｇｂｉｔ／ｓ以上的超高速系统用器件的驱动电压。因此，通过增大电场吸收型光调顺和蔗和吸收系数变化率，使调制器和ＤＦＢ激光器集成的器件实现了低驱动电压。其结果，在驱动电压变化幅度１Ｖ以下可得到１０ｄＢ以上的动态消光比，没有使它特性恶变，并且在１００ｋｍ的单模     

啁啾管理调制格式在高速接入网中传输分析

物联网、虚拟现实及人工智能等技术的发展加大了对光纤接入无源光网络带宽的需求,其中调制器成为制约无源光网络带宽的关键因素。结合了直接调制激光器和外调制器各自优势的啁啾管理激光器以产生结构简单、便于集成等特点受到了广泛关注。采用耦合速率方程理论研究了啁啾管理激光器的动力学特性,分析了40 Gbit/s啁啾管理调制格式的产生原理及时频域特性,并在高速无色散补偿接入网中与由外调制器产生的40 Gbit/s非归零调制格式进行了性能对比。结果表明,带宽为48.5 GHz的40 Gbit/s啁啾管理调制格式在1 dB灵敏度代价下所对应的色散容限为215 ps/nm,与非归零调制格式相比其无色散补偿传输距离增加了1.6倍,表现出了强的抗色散能力,在高速接入网中也体现了较高的应用价值。相关结果可为实际系统设计提供理论参考。     

10Gbit/s高T0无制冷分布反馈激光器

与折射率耦合分布的分布反馈（DFB）激光器相比,不管界面反射率是多少,增益耦合DFB激光器都能稳定地单纵模工作,而且具有高速、低啁啾的特性．本课题组用AlGaInAs/InP材料,采用增益耦合DFB结构,进行了单纵模激光器研发,并对器件特性进行了测试分析．     

Chirp characteristics of 10-Gb/s electroabsorption modulatorintegrated DFB lasers

We present a complete large-signal dynamic model of electroabsorption modulator integrated (EAMI) distributed feedback (DFB) lasers using the time-dependent transfer matrix method. With this model, it is possible to analyze dynamic characteristics depending on optical feedback and spatial hole burning. Also, we can separately calculate the laser and modulator chirp including the voltage-dependent modulator chirp parameter, the grating phase at the end of the laser section, the length of the waveguide region, and electrical coupling. Therefore, our model can provide better predictions regarding the laser and modulator chirp. The calculated large-signal chirp using our model has similar characteristics to the measured large-signal chirp for 10-Gb/s EAMI-DFB lasers     

Design and performance of externally modulated 1.5-μm lasertransmitter in the presence of chromatic dispersion

Key laser and modulator characteristics that impact the use of externally modulated lasers in the presence of chromatic dispersion, excluding effects due to fiber nonlinearities, are reviewed. After a brief consideration of transmission performance with directly modulated 1.5-μm DFB lasers which have limited application of up to 80 km at 2.5 Gb/s, the key design characteristics of externally modulated transmitters are discussed. Experimental results showing the effects of modulator chirp and laser linewidth at a 2.5-Gb/s transmission rate are presented. It is found that lasers with CW linewidth under 100 MHz have less than 2-dB dispersion penalty for 600 km of non-dispersion-shifted fiber. Lower dispersion penalties can be realized if the modulator chirp is tuned so as to narrow the transmitted pulses. Excellent modulator stability is demonstrated for 60 days of error- and degradation-free 2.5-Gb/s operation     

Analysis of large-signal dynamic characteristics of 10-Gb/s tunable distributed Bragg reflector lasers integrated with electroabsorption modulator and semiconductor optical amplifier based on the time-dependent transfer matrix method

We investigate large-signal dynamic characteristics of tunable distributed Bragg reflector (DBR) lasers with different structures. Because of high chirp and complex structures of tunable DBR lasers, it is difficult to accurately analyze large signal chirp and output pulse shapes with analytical models. Therefore, we apply a numerical model based on the time-dependent transfer matrix method to tunable DBR lasers integrated with electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA). Using this model, we find a suitable /spl alpha/-parameter range in the Bragg grating section (/spl alpha//sub Bragg/-parameter) that produces the tolerable wavelength chirp while maintaining a proper tuning range. To employ the tunable lasers in wavelength division multiplexed networks and improve flexibility of the networks, the tunable lasers should have high output power and low wavelength chirp. According to our simulation results, the EAM section had better be located in between SOA and DBR laser sections to obtain high output power and low wavelength chirp.     

Semiconductor 1.55 μm laser source with gigabit/secondintegrated electroabsorptive modulator

A 1.55 μm laser source with low chirp and high speed can be achieved when a single-mode DFB laser is modulated by an integrated quantum-confined Stark effect electroabsorptive modulator. The dynamic characteristics of such a device are simulated by a time domain, large signal dynamic model. The simulation demonstrates that the frequency chirp has two components: 1) changes of the refractive index induced by variation of the absorption coefficient during the modulation and 2) changes in the lasing frequency caused by changes in the effective residual facet reflection as the external modulator is switched on and off. Optimization by choice of the operating wavelength and coupling coefficient in the lasing section is discussed     

Characteristics of 10-Gb/s Electroabsorption Modulator Integrated Distributed Feedback Lasers for Long-Haul Optical Transmission Systems

In this study, we review the characteristics of 10-Gb/s electroabsorption modulator integrated (EAMI) distributed feedback (DFB) lasers for long-haul optical transmission systems. The recent progress and issue of extinction ratio, chirp, and frequency response are described, which are important parameters to improve transmission performance. Except for the extinction ratio, frequency response and chirp characteristics are discussed further. The frequency response of packaged EAMI-DFB lasers has been improved using the novel impedance matching technique. The large signal chirp characteristics are calculated with varying bias voltage, facet reflectance, grating phase, and a coupling coefficient (κL) to predict the measured chirp characteristics. Finally, transmission performance (BER, eye margin, and eye opening penalty) is measured and estimated using the calculated chirp characteristics.     

In search of a linear electrooptic amplitude modulator

An electrooptic modulator which offers high linearity and low intermodulation distortion (IMD) is proposed. The modulation characteristics, harmonic and intermodulation distortions, are calculated. In the two-tone test with an optical modulation depth of 16% for each channel, the third-order IMD is expected to be as low as -95 dB. Such a linearized electrooptic modulator used in conjunction with diode-pumped solid-state lasers can be expected to outperform directly modulated injection lasers for CATV transmission systems.<>     

Yield estimation of 10-Gb/s electroabsorption modulator-integratedDFB lasers due to chirp

We investigate the yield of 10-Gb/s electroabsorption modulator integrated-distributed feedback (EAMI-DFB) lasers for 40- and 60-km transmissions due to the chirp. The yield has been estimated from the effective positive chirp (EPC) capable to transmit signals over 40 and 60 km within 2-dB dispersion power penalty. The signals with EPC of 0.48 and 0.24 Å can be transmitted over 40 and 60 km with less than 2-dB power penalty, respectively. The chirp is calculated from a large signal dynamic model of EAMI-DFB lasers using the time-dependent transfer matrix method (TMM). The results suggest that the yield is mostly dependent on coupling constant (κL) and should be set around 1.3 for high yield while maintaining low facet reflectivity at modulator     

Multisectional modeling of high-speed electrooptic modulators integrated in a microwave circuit CAD environment

We present a new multisectional model for high-speed electrooptic modulators, fully integrated within the framework of a microwave circuit computer-aided design (CAD) suite (MWOFFICE). Starting from geometrical and layout parameters, the model allows both simple (traveling-wave) and complex (phase reversal, periodically loaded) structures to be assembled, analyzed, and optimized from the standpoint of the electrical and electrooptic response (including chirp effects) both in small-signal (analog) and in large-signal (digital) operation, exploiting standard simulator tools. At no additional effort, parasitic and passive elements (such as optical or electrical delay paths) can be directly included in the modulator schematic, and the effect of transitions and package parasitics can be readily accounted for at a circuit level. Moreover, model integration within a circuit CAD suite enables one to seamlessly perform driver and modulator design and optimization within the same monolithic or hybrid circuit environment. Comparisons with experimental and literature data and design examples are presented to validate the approach and stress its potential in the design of high-speed electrooptic modulators.     

Effects of filter concatenation for directly modulated transmissionlasers at 2.5 and 10 Gb/s

We report computer simulation results of the effects on optical signal quality of passage through a cascade of wavelength division multiplexing (WDM) filters-multiplexers and demultiplexers-for directly modulated lasers with different chirp characteristics. In particular, lasers with transient or adiabatic chirp characteristics at 2.5 Gb/s and 10 Gb/s are investigated, and we find clear differences between the laser types with respect to filter concatenation effects. Filters with an optical bandwidth suitable for a 200-GHz channel-spacing system are considered, and we evaluate the system behavior as a function of laser frequency offset for a fixed number of filters. The reference network architecture used for the simulations is an optically transparent metropolitan scale network in which the WDM signals may be demultiplexed and then multiplexed again at multiple optical network elements. The signal quality is evaluated in terms of a distortion-induced eye-closure penalty as well as the excess attenuation or loss suffered. We find that transient chirp-dominated lasers show a generally symmetric distortion penalty response to laser frequency offset, whereas the response for adiabatic chirp dominated lasers is highly asymmetric. Furthermore, the extinction ratio for the latter class of lasers can be improved, in some cases, by the appropriate offset between laser and filter center frequencies     

Measurement-based model for the modulation properties of an integrated laser modulator and its application to systems with tight optical filtering

An efficient and accurate model of a distributed feedback laser integrated with an electroabsorption modulator (integrated laser modulator) is presented. The model is based on an experimental characterization of the absorption, adiabatic chirp, transient chirp, and intensity modulation (IM) frequency response. Agreement between calculated and measured results for the large-signal modulation dynamics (intensity and chirp) is obtained. By implementing the model in a system simulation tool, it is shown that the adiabatic chirp due to reflection from the modulator facet must be considered to accurately assess the performance of systems with dispersive fiber and tight optical filtering.