Low-drive-voltage MQW electroabsorption modulator for opticalshort-pulse generation

This paper reports on InGaAsP-InGaAsP tensile strained MQW electroabsorption (EA) modulators with a high modulation efficiency of 35 GHz/V that generate optical short pulses. We studied and optimized the multiple-quantum-well (MQW) structural parameters, barrier height, and well number, thickness, and strain in the absorption layer to ensure high attenuation efficiency and generate low duty cycle pulses. Low TE/TM polarization sensitivity was obtained by controlling strain. Stable, nearly transform-limited optical pulse trains with a narrow pulsewidth of 3.6 ps are generated by applying a 20-GHz sinusoidal modulation voltage (6 V_pp) to the EA modulator. This achieves a very small pulse duty cycle of 7.2%     

MQW EA调制器用于短脉冲光子源驱动条件的优化设计

本文分析了多量子阱电吸收调制器（MQW EAM）的非线性损耗特性,从时域和频域两个方面讨论了MQW EAM驱动条件与输出光脉冲特性的关系.数值计算结果证明EAM产生的脉冲形状比较接近Gauss脉冲,具有较小的啁啾,接近于变换限的光脉冲,十分适用于高速时分复用系统.     

Optimizing driving conditions of a MQW EA modulator for solitongeneration

A detailed analysis of the pulses generated with a multiple quantum well (MQW) electroabsorption (EA) modulator used as a soliton source is performed. The pulse temporal and spectral shape are simulated and a good agreement is obtained with the experimental results. An irregular holed spectrum shape is observed under certain operating conditions and its existence is attributed to parasitic phase modulation. This type of spectrum could be observed even for pulses having a time bandwidth τΔν product below 0.4 which makes them usually considered as nearly transform limited. However it is not the case. The influence of the pulse spectral shape on transmission performances is investigated by means of a realistic simulation of soliton pulse propagation at 10 Gb/s. It is shown that for 9000 km propagation distance and for pulses presenting this irregular spectral shape a signal degradation occurs as the timing jitter is above 10 ps and the quality factor Q is below 2, which results in an increase of the transmission bit error rate. In order to avoid the generation of this kind of pulses when operating a MQW modulator as a soliton source, a mapping is realized giving the adequate voltages to apply to the diode for acceptable soliton generation     

Strongly improved frequency response at high-optical input powersfrom InGaAsP compensated strain MQW electroabsorption modulators

InGaAsP MQW electroabsorption modulators with and without compensated strain were fabricated and tested. Compensated strain was employed to reduce the valence band discontinuity between the well and barrier, which decreased the heavy-hole carrier escape time. A short optical pulse coupled into the modulator was used to measure the enhancement in carrier escape time from strained compensated InGaAsP quantum wells, for the first time. As a result, the strained MQW sample demonstrated an improved frequency response when operated at high optical input powers and low fields     

NRZ operation at 40 Gb/s of a compact module containing an MQW electroabsorption modulator integrated with a DFB laser

NRZ operation at 40 Gb/s has been successfully performed using a very compact module of a multiple-quantum-well (MQW) electroabsorption modulator integrated with a distributed-feedback (DFB) laser. While the DFB laser is injected with a constant current, the integrated MQW electroabsorption modulator is driven with a 10-Gb/s electrical NRZ signal. A clearly opened eye diagram has been observed in the modulated light from the modulator. And a receiver sensitivity of -27.2 dBm at 10/sup -9/ has been experimentally confirmed in the bit-error-rate (BER) performance.     

Anisotropic electroabsorption and optical modulation in InGaAs/InAlAs multiple quantum well structures

The first measurements to be made of large anistropic electroabsorption and modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported. Photocurrent response of waveguide p-i-n diodes is studied for incident light polarization parallel and perpendicular to the MQW layers. Photocurrent increase with reverse bias throughout the entire photoresponse spectrum is observed for both polarizations. The MQW p-in optical modulator shows a capacitance-limited pulse response of 250 ps and the modulation depth is 14 percent.     

100 ps waveguide multiple quantum well (MQW) optical modulator with 10:1 on/off ratio

By incorporating two quantum wells into a capillary waveguide, we have made the first MQW optical modulator with an on/off ratio of at least 10:1. Furthermore, this device was used to generate an optical pulse less than 100 ps long, the fastest to date with an MQW device.     

80 Gbit/s wavelength conversion using MQW electroabsorption modulator in delayed-interferometric configuration

Absorption recovery time and cross-phase modulation characteristics of an MQW electroabsorption modulator (EAM) were experimentally analysed. 80 Gbit/s error-free operation of a wavelength converter using the MQW EAM in a delayed-interferometer configuration was demonstrated for the first time.     

Efficient electroabsorption in InGaAsP/InGaAsP MQW optical waveguide

Efficient electroabsorption in an InGaAsP/InGaAsP MQW optical waveguide modulator structure is reported. A 17 dB extinction ratio is obtained by applying a 3.5 V drive voltage to a 78 mu m long waveguide operating at 1.54 mu m under TE-polarisation mode. The on-state attenuation is only 2 dB.<>     

High-speed tandem of MQW modulators for coded pulse generation with 14-dB fiber-to-fiber gain

We report on a tandem of electroabsorption modulators integrated with an amplifier by the identical active layer (IAL) approach. A 14 dB fiber-to-fiber is obtained by the use of constant As-P ratio MQW active layer and operation at 10 Gb/s is demonstrated. A record modulator saturation power of 35 mW is also reported.     

Experimental optimisation of MQW electroabsorption modulators withup to 40 GHz bandwidths

Three MQW electroabsorption modulator structures made of 7, 13 and 20 wells are reported. The bandwidth is shown to increase linearly with intrinsic region thickness up to 40 GHz, with negligible penalty on the drive voltage which remains at less than 2 V. It is suggested that 100 GHz bandwidth should be reached with low drive voltage     

20 Gbit/s, 1.55 μm strained-InGaAsP MQW modulator integrated DFBlaser module

The high-speed (20 Gbit/s) and highly efficient (2 V peak to peak for a 22 dB on/off ratio) operation of an MQW integrated electroabsorption modulator/DFB laser module is demonstrated. Output power from the module is over +3 dBm in the pigtailed singlemode fibre. To the authors' knowledge, this is the first report of 20 Gbit/s operation with a monolithically integrated light source     

10 Gbit/s high performance MQW tandem modulator for solitongeneration and coding

Soliton generation and coding are obtained using a novel, and simple tandem integrated electroabsorption (EA) MQW modulator structure. Negligible electrical crosstalk (<40 dB) is obtained due to the integration between the modulators, of an optical amplifier based on the same active layer. This also allowed a very low fibre to fibre insertion loss of 9 dB. The device was operated at 10 Gbit/s     

Monolithic integration on InP of a Wannier Stark modulator with astrained MQW DFB 1.55-μm laser

We present the technical approach and the preliminary device results on the first integration of a Wannier Stark (WS) electroabsorption (EA) modulator with a DFB laser on InP. The WS modulator active layer consists of a lattice matched InGaAs-InAlAs superlattice (SL) grown by solid source MBE. It is butt-coupled to a laser grown by AP-MOVPE whose active layer includes a strained InGaAsP-InGaAsP MQW stack. Device results cover static performances of integrated lasers and modulators, and measurements of high frequency characteristics (small signal bandwidth and 10 Gb/s eye diagram)     

MQW wavelength-tunable DBR lasers with monolithically integrated external cavity electroabsorption modulators with low-driving voltages fabricated by selective-area MOCVD

The design and operation of multiple-quantum-well (MQW) wavelength-tunable distributed Bragg reflector (DBR) InGaAs QW lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area MOCVD are presented. Uncoated devices exhibit CW threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices also exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibited high extinction ratios of 40 dB at a modulator bias of 1.25 V.     

Polarization and wavelength insensitive MQW electroabsorption optical gates for WDM switching systems

We propose using MQW electroabsorption (EA) modulators as optical gates in wavelength-division-multiplexing (WDM) switching systems. A fabricated MQW-EA gate with integrated waveguides showed a high extinction ratio (>30 dB), a low polarization-dependent loss (0.3 dB), and a low wavelength-dependent loss (1.1 dB) within the gain band (1545-1560 nm) of erbium doped fiber amplifiers (EDFAs). Ultra-high-speed (<40 ps) switching of a WDM signal was demonstrated.     

选择区域生长高质量InGaAsP多量子阱材料

采用LP-MOVPE在SiO2掩膜的InP衬底上实现了高质量的InGaAsP多量子阱(MQW)的选择区域生长(SAG).通过改变生长温度和生长压力,MQW的适用范围由C波段扩展至L波段,即MQW的光致发光波长从1546nm延展至1621nm.光致发光（PL）测试表明：在宽达75nm的波长范围内,MQW的质量与非选择生长的MQW质量相当,并成功制作出电吸收调制DFB激光器（EML）.     

Picosecond pulse generation with high extinction ratio employing electroabsorption modulator, fibre compressor, and self-phase-modulation-based pulse reshaper

A wavelength-tunable 3.5 ps pulse generator, which employs an electroabsorption modulator (EAM), a fibre pulse compressor, and a self-phase-modulation (SPM)-based pulse reshaper, is developed. An EAM directly generates 21 ps pulses at a repetition rate of 10 GHz, which are compressed to 6 ps by a fibre pulse compressor. An SPM-based pulse reshaper then eliminates the large pedestal of the compressed pulses. Thus, 3.5 ps pulses with extinction ratio larger than 27 dB and timing jitter as small as 150 fs are obtained.     

The distributed feedback waveguide modulator

A novel waveguide electroabsorption modulator structure is proposed. In this structure, the resonator properties of a quarter-wave phase-shifted grating are combined with the electroabsorption properties of a multiple-quantum-well (MQW) waveguide. The theory and design considerations for such a distributed feedback MQW modulator are discussed. The performance characteristics of this structure are studied theoretically and compared with conventional MQW waveguide modulators. It is found that increased modulation bandwidth and reasonable optical bandwidths can be obtained over a device without feedback, and design tradeoffs are identified and explored     

Proposal and demonstration of a symmetrical npipn electroabsorptionmodulator

We propose a new type of electroabsorption modulator based on a npipn diode structure. Its transmission curve versus applied bias should be symmetrical with respect to zero bias. A npipn InGaAs-InAlAs multiple-quantum-well (MQW) modulator has been fabricated to experimentally demonstrate two applications for optical fiber transmission systems: pulse generation with adjustable duty cycle for optical time division multiplexing and harmonic generation up to 40 GHz for millimeter radiowave transport on optical fiber