单脊条形可调谐电吸收调制DFB激光器

报道了一种波长可热调谐的电吸收调制分布反馈激光器(Electroabsorptionmodulateddistributedfeedbacklaser,EML)。在激光器条形的侧面淀积一薄膜加热器,EML实现了 2 2nm的连续调谐。在调谐范围内,激光器输出功率的变化小于 3dB。采用端面有效反射率方法和耦合波理论的计算表明:采用相调制方法,可实现调谐范围达3 2nm的EML。如果热调谐与相调谐方法结合,可在较宽范围内实现波长快速调谐的EML     

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.     

40 Gb/s Traveling‐Wave Electroabsorption Modulator‐Integrated DFB Lasers Fabricated Using Selective Area Growth

In this paper, we present the fabrication of 40 Gb/s traveling‐wave electroabsorption modulator‐integrated laser (TW‐EML) modules. A selective area growth method is first employed in 40 Gb/s EML fabrication to simultaneously provide active layers for lasers and modulators. The 3 dB bandwidth of a TW‐EML module is measured to be 34 GHz, which is wider than that of a lumped EML module. The 40 Gb/s non‐return‐to‐zero eye diagram shows clear openings with an average output power of +0.5 dBm.     

低波长漂移的电吸收调制DFB激光器

采用端面有效反射率法,从理论上计算了单片集成电吸收调制DFB激光器（Electroabsorption Modulated DFB Laser,EML）的腔面反射率、耦合强度（κL）对其波长漂移的影响.同时在实验中通过改变腔面的反射率来验证计算结果.理论与实验的结果表明：为提高EML的模式稳定性,必须减小调制器一端的反射率,同时增加DFB激光器的κL.最终我们采用选择区域生长（Selective Area Growth,SAG）的方法,制作了低光反馈出光面的单脊条形EML,在2.5Gb/s的非归零(NRZ)码调制下,经过280km的标准光纤传输后,没有发现色散代价.     

Chirp and system performance of integrated laser modulators

Time-resolved chirp measurements and laser-threshold measurements are used to understand the chirp performance of integrated laser electroabsorption modulators. The different effects of the intrinsic modulator chirp component and chirp caused by optical feedback, from reflection at the output facet into the laser, are observed. A figure of merit is introduced to assess the chirp performance, which shows good correlation with dispersion penalty measurements. The effect of reflection-induced chirp is considerably reduced by operating the modulator with negative chirp. An optimized device is reported, which delivers purely negative chirp with reasonable optical power     

A Four‐Channel Laser Array with Four 10 Gbps Monolithic EAMs Each Integrated with a DBR Laser

A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non‐return to zero operation with 12 dB extinction ratio is obtained. A four‐channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.     

选区外延制作单片集成单脊条形电吸收调制DFB激光器

报道了采用选区外延生长技术制作的可实用的单脊条形电吸收调制DFB激光器。激光器的阈值为 2 6mA ,最大光功率可达 9mW ,消光比可达 16dB。减小端面的光反馈后 ,从自发发射谱上观察不到波长随调制电压的变化 ,调制器部分的电容为 1 5pF ,初步筛选结果显示阈值、隔离电阻、消光比基本没有变化 ,可应用在 2 5Gb/s的长途干线光纤传输系统上。     

High-power ultralow-chirp 10-Gb/s electroabsorption modulator integrated laser with ultrashort photocarrier lifetime

A high-power, ultralow-chirp electroabsorption modulator (EAM) integrated with a distributed-feedback laser diode (EML) having ultrashort lifetime of photogenerated holes in the EAM quantum-well (QW) structure is reported for the first time. A shallow QW structure having a small valence band offset to enhance the sweepout of photogenerated holes was employed as EAM absorption layer. The measured hole lifetimes were 7-11 ps, and the measured frequency chirp (/spl alpha/-parameter) was low or negative at low EAM reverse bias voltages even under high optical output power conditions. Successful 10-Gb/s 80-km normal-dispersion single-mode fiber transmission (chromatic dispersion D=1600 ps/nm) and the record average fiber optical output power (P/sub f/) of +5.3 dBm were achieved at 25/spl deg/C. In addition, semicooled operation of EML at enhanced bit rates has been demonstrated for application in small-form-factor protocol-agnostic optical transceivers. A 10.7-Gb/s 1600-ps/nm transmission was achieved at 45/spl deg/C and P/sub f/=+3.0 dBm.     

Novel and simple model of 10-Gb/s electroabsorption modulated lasers and its experimental validation of transmission performance due to overshoot of optical signals

We have experimentally and theoretically investigated the transmission performance of 10-Gb/s electroabsorption modulated lasers (EMLs) due to the overshoot of optical pulses. When a highly negative bias voltage is applied to EMLs, the overshoot becomes larger due to nonlinear transfer curves of EMLs. In order to further understand the overshoot effect of optical pulses from EMLs on transmission performance, we propose a novel and simple EML model based on the frequency response (magnitude and phase) and the transfer curves (P-V and /spl alpha/-V) of EMLs. Although the model does not solve the rate equations and the wave equations, it can accurately predict output pulse shapes and the frequency chirp as well as the transmission performance with reducing simulation time. Using the EML model, we can calculate the overshoot and dispersion power penalty due to modulation bandwidth and group delay difference in 10-Gb/s EMLs. Our results suggest that the overshoot should be considered to accurately predict the transmission performance of 10-Gb/s EMLs.     

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     

Narrow-band resonant optical reflectors and resonant optical transformers for laser stabilization and wavelength division multiplexing

We propose a new way of making highly resonant integrated optical circuits based on weak side-by-side coupling between waveguides and highQdistributed Bragg resonators. This method can be used to design a resonant optical reflector which, when used as a feedback element to a laser, will result in a compact structure that has both extremely narrow line width and very low chirp. By coupling the resonator to two waveguides, one on either side, an optical analog of the resonant transformer can be made. This device can be used for wavelength division multiplexing. Such multiplexer elements will both resonantly transform optical power from the laser to a common output channel and also provide feedback which locks the laser to the channel wavelength.     

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.     

A novel way to improve the dispersion-limited transmission distance of electroabsorption modulated lasers

We propose and demonstrate a way to improve the dispersion-limited reach of electroabsorption modulated lasers (EMLs). We generate continuous-phase frequency-shift keying/amplitude-shift keying (ASK) signals with the EML by applying a small current modulation to the laser diode (LD) on top of electroabsorption-modulated ASK signals. The amount of frequency deviation induced by the current modulation is adjusted to have the EML output signals experience /spl pi/ phase shift at every space. The experimental demonstration shows that with the proposed scheme we can increase the dispersion-limited transmission distance of the EML-based transmitter by 25%-75%, and it can be further improved by employing an LD with flat frequency-modulation response.     

从等效电路模型分析激光光源的啁啾特性

在已有的分布反馈激光器的电路模型中引入位相回路,从而使这种电路模型能够携带出射光的位相信息,进而反映激光器的啁啾特性.对修正后的模型进行仿真,结果与已报道的结果十分吻合.进一步将这种带位相回路的激光器模型与电吸收调制器的电路模型相结合,构成分布反馈激光器与电吸收调制器集成光源的等效电路模型.该模型同时考虑了激光器与调制器之间的电耦合.这种由于隔离电阻不够大而导致的电耦合将导致激光器激射波长发生漂移,即产生啁啾.通过对电路模型进行仿真,给出不同隔离电阻时的啁啾特性曲线,并对啁啾大小与隔离电阻的关系进行讨论.结果显示了集成光源相比于直接调制激光器在啁啾特性方面的显著改善.     

基于重叠光栅和啁啾光栅的双波长光纤激光器

研究光寻址电位传感器(LAPS)的器件噪声特性 。通过对LAPS半导体场效应器件的结构分析,建 立LAPS的理论模型,并进一步分析LAPS器件噪声信号的来源、种类及特性。以 pH缓冲液中H离子 浓度为检测对象,搭建基于NI采集卡和Labview环境的LAPS测试系统,对影响LAPS信号噪声 特性的光源 波长、光源调制频率、光源强度和Si衬底厚度等因素进行了仿真和实验研究。结果表明,增 大光源波长和光源强度 是提高输出信号幅值和信噪比(SNR)的最有效方法。     

Electroabsorption modulated laser for long transmission spans

Strain-compensated AlGaInAs quantum-well electroabsorption modulated lasers (EMLs) transmit at 10 Gbits/s on uncompensated transmission spans of >75 km of standard fiber and >225 km of MetroCor fiber. Details of the design, fabrication, and testing are presented. A complex-coupled distributed feedback (DFB) grating is used to enable high output power. The epitaxy and chip structure are described. The paper studies what is needed to accomplish long-span transmission in terms of minimum physical requirements for laser mode control, facet reflection, index grating strength, laser-modulator matching, laser-modulator electrical isolation, modulator extinction ratio, modulator capacitance, linewidth enhancement factor, etc. The interaction of the modulator with the laser is analyzed and a requirement for this structure is computed for the electrical isolation resistance between modulator and laser contacts. Stability of the laser source is discussed and a method is derived for determining the grating's gain-coupling coefficient at operating power. Chirp due to the modulator is analyzed. Nonzero chirp of the modulator is shown to have beneficial impact on the quality of the signal after transmission. The effect of a bias-dependent alpha parameter is analyzed. Because bit-error rate is a strong function of mean alpha parameter and not a strong function of the range of alpha during nonreturn-to-zero modulation, we determine that tuning the chirp of the EML modulator to suit different fiber types (MetroCor, SMF-28, etc.) is practical. Specific tradeoffs are also required. Experimental results verify the analysis     

4$,times,$25-Gb/s 40-km PHY at 1310 nm for 100 GbE Using SOA-Based Preamplifier

We present extensive numerical simulations of an optical link deploying four electroabsorption modulated lasers (EMLs) at 25 Gb/s over up to 40 km of standard single-mode fiber. The receiver comprises a semiconductor optical amplifier (SOA) as a preamplifier. We analyze the bit error ratio (BER) along different link lengths under varying conditions such as output power and extinction ratio of the EML transmitters, the noise figure of the SOA preamplifier and the bit and word alignment of the four wavelength channels. We demonstrate that the EML transmitters require a minimum extinction ratio of 8 to 10 dB and a minimum output power of +2 to +4 dBm in order to meet the BER requirements for 100 Gigabit Ethernet (100 GbE) using 4 times 25-Gb/s physical media dependent (PMD) devices. Furthermore, we show that single-channel performance analyses can be used to estimate the behavior for multichannel amplification in the SOA preamplifier.     

A 10-Gb/s Monolithically Integrated Filterless InGaAsP/InP Widely Tunable Wavelength Converter With Conversion Gain

In this paper, we present the details of a monolithically integrated filterless wavelength converter based on photocurrent-driven technology. The device consists of an integrated tunable laser transmitter and an optical receiver. The transmitter includes a sampled-grating distributed-Bragg-reflector laser, an electroabsorption modulator, and a semiconductor optical amplifier. The optical receiver employs two semiconductor optical amplifiers and a quantum-well p-i-n photodetector. The wavelength converter is characterized at 10 Gb/s over a variety of bias conditions at various input-power levels in various digital-system experiments. Bit-error-rate measurements at 10 Gb/s over an output tuning range of 32 nm between 1531 and 1563 nm show power penalties less than 1 dB. Similar experiments over an input wavelength range of 25 nm from 1535 to 1560 nm show a power penalty less than 2.5 dB. For a wavelength conversion from 1548 nm to a range of output wavelengths between 1531 and 1563 nm, the facet-to-facet gain ranges from 9 to 13 dB, neglecting fiber coupling losses.     

Physical Media Dependent Prototype for 10‐Gigabit‐Capable PON OLT

In this work, we study the physical layer solutions for 10‐gigabit‐capable passive optical networks (PONs), particularly for an optical link terminal (OLT) including a 10‐Gbit/s electroabsorption modulated laser (EML) and a 2.5‐Gbit/s burst mode receiver (BM‐Rx) in a novel bidirectional optical subassembly (BOSA). As unique features, a bidirectional mini‐flat package and a 9‐pin TO package are developed for a 10‐gigabit‐capable PON OLT BOSA composed of a 1,577‐nm EML and a 1,270‐nm avalanche photodiode BM‐Rx, including a single‐chip burst mode integrated circuit that is integrated with a transimpedance and limiting amplifier. In the developed prototype, the 10‐Gbit/s transmitter and 2.5‐Gbit/s receiver characteristics are evaluated and compared with the physical media dependent (PMD) specifications in ITU‐T G.987.2 for XG‐PON1. By conducting the 10‐Gbit/s downstream and 2.5‐Gbit/s upstream transmission experiments, we verify that the developed 10‐gigabit‐capable PON PMD prototype can operate for extended network coverage of up to a 40‐km fiber reach.     

Waveguiding Effect in Electroabsorption Modulators: Passivation Layers and Their Impact on Extinction Ratios

Waveguide structures of the stand‐alone electroabsorption (EA) modulator and the electroabsorption modulated laser (EML) are investigated using the 3D beam propagation method. The EA waveguide structures with InP‐based passivation layers show saturation in the extinction ratio (ER) due to the stray light traveling through the passivation layers. This paper demonstrates that narrower passivation layers suppress stray‐light excitation in the EA waveguide, increasing the ER. A taper structure in the isolation section of the EML waveguide can reduce the mode mismatch and suppress the excitation of the stray light, increasing the ER further. Low‐index‐polymer passivation layers can confine the mode more tightly in the active waveguide, yielding an even higher ER.