Robert Lewén

Segmented transmission-line electroabsorption modulators

We present segmented transmission-line (TML) electroabsorption modulators (EAMs) with characteristic impedance close to 50 /spl Omega/. The segmented TML approach allows us to design a traveling-wave EAM with 50 /spl Omega/ impedance and very high bandwidth. The devices show low return loss (<-15 dB) and excellent frequency response up to 50 GHz, and exhibit a maximum model-extrapolated 3 dBe bandwidth (BW) of 90 GHz. An effective modeling tool based on Bloch-wave analysis is derived. Design considerations and TML properties for periodic TML-EAMs are discussed.

80 Gb/s ETDM transmitter with a traveling-wave electroabsorption modulator

We have demonstrated non-return-to-zero data transmission at 80 Gb/s using an ETDM (electronic time division multiplexing) fiberoptic transmitter consisting of a segmented traveling-wave electroabsorption modulator with integrated termination resistor and a SiGe electronic multiplexer.

Ultra high-speed segmented traveling-wave electroabsorption modulators

We present segmented traveling-wave electroabsorption modulators matched to 50 /spl Omega/. The devices show excellent high frequency performance up to 50 GHz, and exhibit a maximum model-extrapolated 3dBe bandwidth of 95 GHz. Clear eye openings at 50 Gbit/s are presented.

Design of inductive p-i-n diode matching for optical receivers with increased bit-rate operation

We have studied matching of a p-i-n photodiode (PD) with a single serial inductive element for broadband operation. The bit rate and rise time may be significantly improved, compared to a device without inductor for nonreturn-to-zero (NRZ) modulation. The matched device offers improved pulse equalization leading to increased receiver sensitivity, and reduces the need for an additional pulse-equalizing filter. The material is presented so that it can serve as a guideline of how the inductor can be included when choosing the thickness of the absorption layer and/or area for a p-i-n PD design, and ends with typical design examples.

Influence of electrode width on high-speed performance of traveling-wave electroabsorption modulators

InP/InGaAs traveling-wave electro-absorption modulators for 1.55 /spl mu/m were fabricated with on-chip integrated termination resistors. The influence of the electrode width on their microwave properties and modulation bandwidth is measured and analyzed. Reduction of microwave losses and velocity mismatch can be demonstrated for wider electrodes, offering the potential for modulation bandwidth >100 GHz.

Design and fabrication of electroabsorption modulators for data rates up to 100 Gb/s

We present segmented transmission-line (TML) electroabsorption modulators (EAM) matched to 50 /spl Omega/. The devices show excellent high frequency performance up to 50 GHz, and exhibit a maximum model-extrapolated 3 dBe bandwidth of 90 GHz. Design considerations and optimization techniques for periodic segmented TML-EAM are discussed. Also methods used for the device fabrication are presented.

High-speed electro-absorption modulators for fiber optic communications

Features such as large bandwidth, low drive voltage, compact size, and feasibility for monolithic laser integration make electro-absorption modulators (EAM) attractive candidates for ultra high-speed fiber-optical time division multiplexing (TDM). EAM with traveling-wave (TW) electrodes have successfully been demonstrated as a way to considerably increase the modulation bandwidth without sacrificing modulation efficiency. However, for reasonable modulation efficiency a low characteristic impedance (≈25Ω) has to be accepted. Termination with a matched load is necessary to benefit from the TW configuration. Thus, TWEAM with continuous impedance-matched transmission lines (TML) provide very high bandwidths, but suffer from high electrical return loss when using a 50Ω driver. A solution to this problem is to split up the modulator and insert passive TML segments between the active parts. The passive segments can be designed for a higher characteristic impedance than the active modulator parts with their inherently low impedance. In this way, the impedance seen at the electrical modulator input can be tailored for values that deliver optimum performance in combination with the available driving electronics (usually 50Ω). Only little bandwidth is sacrificed with the segmented design. Recently, we have demonstrated state-of-the-art performance of segmented TWEAM. These devices exhibit low electrical return loss (<-15dB) and a flat small signal modulation response in the characterized frequency range of 0.04 to 50GHz. 50Gb/s operation is demonstrated. An extinction of 10dB with 3Vp-p is achieved at 40Gb/s.