EAM-DFB集成光源典型参数特性的电路级分析

针对电吸收型调制器和分布反馈激光器集成光源(EAM-DFB)的光电混合特征,建立了包含自发辐射、俄歇复合、寄生效应以及隔离电阻的等效电路模型。分析了在不同驱动电流和自发辐射因子下,该模块的输出、调制及噪声特性,并与直接调制DFB作了对比。结果表明,EAM-DFB可生成超短脉冲(小于25 ps);随着驱动电流的增加,输出功率增大、脉冲展宽,噪声增强且峰值点向高频移动;减小自发辐射因子和增加驱动电流均使其调制带宽增加;与DFB相比,EAM-DFB增加了少量噪声,但具有更陡峭的功率-电流特性和更大的调制带宽。     

Electrical and Optical Coupling in an Electroabsorption Modulator Integrated With a DFB Laser

Electrical and optical coupling in an electroabsorption (EA) modulator integrated with a distributed feedback (DFB) laser have been investigated. The integrated device is treated as a three-port optoelectronic device with two electrical ports and one optical output port. The scattering parameters of this three-port device have been measured in the designed experiment. The measured results indicate that there exists the electrical coupling between the DFB laser and EA modulator of the integrated light source whenever the current applied to the laser section is below or above the threshold current, and the optical coupling will have stronger influence on the frequency responses than the electrical coupling when the bias current is above the threshold. A small-signal equivalent circuit model for the integrated device is established considering both the electrical and internal optical coupling. Experiments show that the equivalent circuit model is reasonable and the determined element values are correct. Based on the measurement and modeling, the influences of the electrical and optical coupling on the high-frequency responses are investigated and the effective measure to eliminate the additional modulation in the DFB laser are discussed.     

Monolithically Integrated 100 GHz DFB-TWEAM

A monolithically integrated distributed feedback (DFB) laser and traveling-wave electro-absorption modulator (TWEAM) with ${geq} 100$ GHz ${-}3$ dBe bandwidth suitable for Non-return-to-zero (NRZ) operation with on-off keying (OOK) is presented. The steady-state, small-signal modulation response, microwave reflection, chirp characteristic, and both data operation and transmission were investigated. The DFB-TWEAM was found to be an attractive candidate for future short distance communication in high bitrates systems.      

Monolithic integration of multiple quantum well DFB lasers and electroabsorption modulators

Advanced fibre optics telecommunication systems rely on high performance components amongst which photonic integrated circuits (PICs) play a major role. In particular, there has been a growing need for low chirp optical sources, such as externally modulated distributed feedback (DFB) lasers. In this paper, the various monolithic integration schemes of multiple quantum well DFB lasers and electro-absorption modulators are reviewed and typical applications of these devices are briefly presented.     

1064-nm DFB laser diode modules applicable to seeder for pulse-on-demand fiber laser systems

Semiconductor DFB (Distributed feedback) laser diodes with an operating wavelength of 1064 nm, which is suitable for pulse-on-demand fiber laser, have been developed. The stable performance of CW and nanosecond/picosecond pulsed operation is reviewed. By applying gain-switching operation with a simple direct modulation technique, 50-ps pulse generation with a stable spectral single-mode property was obtained. For the efficient amplification of the obtained 50-ps pulse, a monolithic semiconductor optical amplifier (SOA) was integrated into the DFB lasers. An improved peak power of 300 mW at 50-ps pulse was observed with limited optical noise injection when the synchronous modulation technique of the DFB and the SOA was employed. Short cavity lasers showed a high-frequency response compared to the original DFB lasers and achieved a short pulse width of 13 ps by standard gain-switched operation.     

1.55-μm wavelength-selectable microarray DFB-LD's withmonolithically integrated MMI combiner, SOA, and EA-modulator

We developed compact (1.136 mm²) eight-channel wavelength-selectable microarray distributed feedback laser diodes (DFB-LD's) with a monolithically integrated 8×1 multimode-interference (MMI) optical combiner, a semiconductor optical amplifier (SOA), and an electro-absorption (EA) modulator. By using ±10°C thermal tuning, an addressable wavelength range of 15.3 nm with uniform device characteristics and 2.5-Gb/s modulation performance were successfully demonstrated     

Measurement and Characterization of Microwave Interaction between Integrated Distributed Feedback Laser Diode and Electro-Absorption Modulator

Integrated electro-absorption-modulated distributed feedback laser diodes (EMLs) are attracting much interest in optical communications for the advantages of a compact structure, low power consumption, and high-speed modulation. In integrated EML, the microwave interaction between the distributed feedback laser diode (DFB-LD) and the electro-absorption modulator (EAM) has a nonnegligible influence on the modulation performance, especially at the high-frequency region. In this paper, integrated EML was investigated as a three-port network with two electrical inputs and a single optical output, where the scattering matrix of the integrated device was theoretically deduced and experimentally measured. Based on the theoretical model and the measured data, the microwave equivalent circuit model of the integrated device was established, from which the microwave interaction between DFB-LD and EAM was successfully extracted. The results reveal that the microwave interaction within integrated EML contains both the electrical isolation and optical coupling. The electrical isolation is bidirectional while the optical coupling is directional, which aggravates the microwave interaction in the direction from DFB-LD to EAM.     

Influence of facet reflection on the performance of a DFB laserintegrated with an optical amplifier/modulator

The influence of output facet reflection on characteristics of a monolithically integrated optical device consisting of a distributed feedback (DFB) laser and an optical amplifier/modulator is analyzed. Basic equations used for the analysis are the characteristic equation for a DFB laser and the rate equations. As a result, it is known that static and dynamic properties of such optical integrated devices are seriously degraded by the optical feedback from the output facet. It is concluded that the power reflectivity of the output facet should be reduced to at least less than 0.1% for the integrated region to work as an optical amplifier and less than 0.01% as an intensity modulator     

Monolithically integrated InGaAsP/InP composite-cavity distributedfeedback lasers

Linewidth reduction to 1 MHz for monolithically integrated extended-cavity DFB lasers that are designed to achieve high optical coupling to a low-loss extended cavity is described. Since a high-efficiency extended cavity at the same time degrades the frequency-modulation (FM) response, an active gain section is integrated at the end of the extended cavity, and its use as a modulator section that maintains a flat FM response at 0.7 GHz/mA is shown. The linewidth and FM characteristics of this DFB extended-passive/active-cavity laser are compared to those of the conventional DFB extended-passive-cavity laser and a two-section DFB laser     

单片集成电吸收调制分布反馈激光器

提出一种选择区域外延双有源区叠层(SAG-DSAL)结构新技术,基于此技术设计研制了单片集成电吸收调制激光器(EML),SAG-DSAL-EML管芯的阈值电流为20mA,工作电流为100mA时的出光功率为10mw,由吸收调制器(EAM)加-3V偏压时的消光比为12dB,实现了简化制作工艺并提高器件性能的预期目的,有望用...     

Electrical and optical interactions between integrated InGaAsP/InPDFB lasers and electroabsorption modulators

Electrical and optical interactions occurring in InGaAsP/InP integrated light sources composed of DFB lasers and electroabsorption modulators have been studied. Static measurements indicated that an isolation resistance between the laser and the modulator should be as large as 100 kΩ or more in order to reduce a lasing wavelength shift associated with biasing the modulator. The useful guided light out of the modulator was about 1-2 percent of the laser output. At high frequency modulation, asymmetric sidebands were observed in dynamic spectra measured at the modulator facet, which were caused by additional modulation of the laser part. Such additional modulation was relatively large at the relaxation oscillation frequency of the laser, but it was reduced by connecting an RF bypass condenser in parallel to the laser diode and by depositing an antireflection coating at the modulator facet. After eliminating the additional modulation, an integrated device showed a high frequency response of 5.7-GHz 3-dB bandwidth and a small linewidth enhancement factor of α=0.8     

高消光比超短脉冲产生的实验研究

实验研究了一种高消光比短脉冲的产生技术。利用色散补偿光纤线性压缩由增益开关分布反馈激光器出射的光脉冲。而后利用电吸收调制器的非线性吸收特性同步调制光脉冲。利用这种方法在实验上产生了重复频率为10GHz，脉宽为10．4ps，抖动小，高消光比，无基座的短脉冲。此种技术可以应用于40Gbit／s的光时分复用系统中，同时也说明电吸收调制器具有同号脉冲整形功能。     

Optical feedback on linearity performance of 1.3-μm DFB andmultimode lasers under microwave intensity modulation

Under large signal modulation and quantitatively controlled optical feedback (from about -50 dB to -25 dB, from the end of ~2-m pigtails), the linearity performance of both a 1.3-μm distributed-feedback (DFB) and a multimode laser is examined. Under proper bias levels and modulation frequencies, both lasers exhibit good linearity even with strong optical feedback. The DFB laser exhibits good linearity because of its coherence reduction, resulting from modulation-induced frequency chirping     

Theory and experiment of high-speed cross-gain modulation insemiconductor lasers

We present theory and experiment for the high-speed modulation response of a quantum-well (QW) laser in the presence of an external microwave modulated optical pump in the gain region. The model includes the effects of pump-induced stimulated recombination and cross-gain saturation. Expressions for the small-signal modulation response of the test laser under gain modulation are derived. We also present experimental results using a multiple-QW InGaAlAs Fabry-Perot (FP) laser at 1.552 μm as the test laser and an external pump by a 1.542 μm DFB laser. Comparison between electrical modulation and optical cross-gain modulation (XGM) of the test laser is also presented, which shows improvement of the modulation bandwidth by optical XGM. Our data show a reduction of carrier lifetime with increasing optical pumping, a shift of the test-laser threshold current, a change in the K factor, and a variation of the relaxation frequency with different pump powers. The experimental results agree very well with the theoretical results     

A Passive Broadband Impedance Equalizer for Improving the Input Return Loss of Electro-Absorption Modulators

Based on the context of an electro-absorption modulator integrated laser and the industry's standard 7-pin package having a RF connector, a complete module design that incorporates a simple yet effective broadband impedance equalizer to improve the input return loss of electro-absorption modulators (EAM) is proposed. The passive broadband impedance equalizer effectively reduces the input return loss of the EAM from between -9.84 and -5.26 dB to between -11.5 and -9.35 dB over a frequency range from 4.4 to 12.2 GHz without having to add a resistor in series with the EAM or reducing the EAM absorption-layer capacitance from the value that was optimized for optimal optical performance.     

40 Gbit/s all-optical clock recovery using two-section gain-coupledDFB laser and semiconductor optical amplifier

40 Gbit/s wavelength and polarisation insensitive all-optical clock recovery using a two-section distributed feedback (DFB) laser has been demonstrated. The polarisation sensitivity of the two-section DFB laser was solved by converting incoming data onto a local laser through cross-gain modulation using a semiconductor optical amplifier. The scheme has a sensitivity of -13 dBm     

Suppression of external cavity modes in DFB lasers with a highendurance against optical feedback

This paper clarifies that the external cavity modes deform optical output response in the DFB lasers by enhancing the relaxation oscillation under NRZ modulation. It is shown that a DFB laser with an asymmetric structure in reflectivity of facets and in position of a λ/4 phase shift can suppress the influence of the external cavity modes     

5 Gbit/s direct optical DPSK modulation of a 1530-nm DFB laser

5 Gb/s direct optical differential-phase-shift-keying (DPSK) modulation of a 1530-nm distributed feedback (DFB) laser is demonstrated using injection current modulation with a bipolar signal format. Delay demodulation is performed using an interferometer with a delay time T equal to the duration of one bit. The input and differentially encoded nonreturn to zero (NRZ) signals are shown. The bipolar modulation current signal is basically the time derivative of the NRZ signal. There was no degradation of the optical DPSK signal due to thermal frequency modulation of the laser. The direct DPSK modulation technique avoids the insertion loss and systems complexity of external DPSK modulators     

Characterisation of frequency response of 1.5 ?m InGaAsP DFB laser diode and InGaAs PIN photodiode by heterodyne measurement technique

The frequency response of an InGaAs PIN photodiode and the ratio of the frequency modulation (FM) index to the intensity modulation (IM) index of a 1.5 ?m InGaAsP vapour-phase-transported DFB laser diode have been measured by an optical heterodyne measurement technique. From the response of the photodiode to the laser radiation beat frequency, a 20 GHz detector bandwidth is determined. The ratio of the FM and IM indices at 3 mW laser output power per facet decreases from 60 at 100 MHz modulation frequency to 3.3 above 2 GHz.     

具有纯频率调制和啁啾抑制的幅度调制的三电极DFB LD

二电极和三电极(多电极或多节)分布反馈激光器是超长传输距离和超大传输容量光纤通信系统的关键器件。本文详细地讨论了三电极分布反缋(DFB)激光器的重要特性,其中包括调谐理论、频率调制响应以及纯频率调制和啁啾抑制的辐度调制。