Yuichi Akage

Low Chirp Operation of 40 Gbit/s Electroabsorption Modulator Integrated DFB Laser Module With Low Driving Voltage

We clarified experimentally that an EA-DFB laser in which the EAM and DFB parts are coupled with a passive waveguide provides a large bandwidth, even when a large reverse bias is applied to the EAM. This allows the chip to operate in a negative-chirp condition. We fabricated an EA-DFB module terminated with a 50 Omega resistor through a dc-block capacitor to suppress the increase in dc current as the reverse bias increases. A module equipped with our new EA-DFB chip successfully transmitted data over a distance of 3 km at a rate of 40 Gbit/s and at a driving voltage as low as 2 V.

High-speed electroabsorption modulators buried with ruthenium-doped SI-InP

InGaAlAs-InAlAs electroabsorption modulators are successfully fabricated using ruthenium (Ru)-doped semi-insulating (SI)-InP burying technology. A comparison of measured and calculated microwave characteristics reveals that there is no additional microwave loss because zinc diffusion is inhibited by the use of Ru-doped SI-InP layers. A small-signal electrooptical response with a -3-dB electrical bandwidth of over 50 GHz is demonstrated.

High-performance InP-based optical modulators

We demonstrate two types of high-speed semiconductor optical modulators operating at 40 Gbit/s with reduced driving voltage. One is a compact Mach-Zehnder modulator module that achieves error-free operation in a push-pull configuration with a peak-to-peak voltage of 1.3 V. The other is an electroabsorption modulator integrated with microwave coplanar waveguides and driven by a voltage as low as 0.79 V

High-Performance Electroabsorption Modulators Utilizing Microwave Reflection Control Technique

A microwave reflection control technique that improves the performance of electroabsorption modulators (EAMs) is presented. The technique exploits the superposition of incident and reflected electrical signals as a modulation signal to enhance the modulation signal voltage applied to EAMs and therefore differs from conventional impedance matching techniques in terms of operating principle. A nearly flat electrical-to-optical frequency response up to 50 GHz and significant improvement in eye openings at 40 Gbit/s have been achieved with the technique. The effects of the technique are demonstrated through both experimental and computational investigations.

Return-loss-suppressed electroabsorption modulator with novel transmission line electrodes on conductive substrate

An electroabsorption modulator with transmission line electrodes on an n-InP substrate has been newly designed and fabricated. We demonstrate clear eye opening at 40 Gbit/s with well-suppressed electrical return loss of less than -20 dB.

Low driving-voltage (1.1 Vpp) electroabsorption modulators operating at 40 Gbit/s

40 Gbit/s InGaAlAs/InAlAs electroabsorption modulators driven by a Vpp as low as 1.1 V have been successfully fabricated. This low driving voltage is achieved by means of a sophisticated device design that optimizes the extinction and bandwidth.

High-speed electroabsorption modulators using ruthenium-doped SI-InP: impact of interdiffusion-free burying technology on E/O modulation characteristics

InGaAlAs/InAlAs electroabsorption (EA) modulators are successfully fabricated using ruthenium (Ru)-doped semi-insulating (SI)-InP burying technology. A comparison between measured and calculated microwave characteristics reveals that no additional microwave loss due to Zn diffusion occurred because of the use of Ru-doped SI-InP layers. A small-signal E/O response with a -3 dB electrical bandwidth of over 50 GHz is demonstrated.

Low Driving-Voltage 40-Gbit/s Electroabsorption Modulator Integrated DFB Laser Module with Low Chirp Characteristics

We demonstrated successful 3-km transmission using a 40-Gbit/s EA-DFB laser module with driving voltage as low as 2 V. The installed EA-DFB chip has an optimized device structure which is operatable under low chirp condition