Electroabsorption modulators (EA) are attractive components for very high speed digital links (up to 40 Gbit/s). The objective of the present work has been to evaluate the analog performance and use of a Franz Keldysh modulator (FK) monolithically integrated with a DFB laser (DFB/FK-modulator) operating at 1550 nm. This DFB/FK-modulator is a combination of a directly modulated laser diode and an external modulator in one chip. The analog performance is therefore depending on both the modulator bias voltage and DFB-laser bias current. The normal optical output characteristic from an EA-modulator has a strongly nonlinear behavior. The modulator described in this paper shows for low bias voltage and/or high laser current a linear bahavior. This linear behavior is mainly due to the hole pile-up effect at the p/i-interface of the modulator. In digital transmission system this hole pile-up effect is a disadvantage, but in an analog transmission system it can be used to achieve better analog performance. Measurements (and simulations) on the DFB/FK-modulator show that its analog performance competes well with direct modulated FP and DFB lasers, especially if the modulator is biased for optimum analog performance.
KEYWORDS: Fiber optics, Receivers, Stars, Transmitters, Local area networks, Connectors, Signal detection, Light emitting diodes, Space operations, Hybrid fiber optics
The major part of the studies for introducing photonics in space are performed in the USA, but a few years ago, Saab Ericsson Space AB started a study project under a European Space Agency (ESA) contract with Ericsson Microwave Systems AB as a subcontractor. The main objectives of the project were to investigate the requirements on photonics systems and hardware for space applications and to develop space qualifiable fiber optic hybrids for a spacecraft data network. The system analysis, as well as the specifications for the fiber optic hybrids, was performed to meet the performance and environmental requirements of the Columbus Data Management System (DMS) (the fiber optic version of 10 Mbps ISO 8802-4 Token Bus). The requirements, design, and performance of these fiber optic transmitter and receiver hybrids are presented. The most important characteristics are: optical output peak power of -8.5 dBm, receiver sensitivity of -44 dBm, acquisition time of 2 microsecond(s) and a dynamic range of 27 dB.
Conference Committee Involvement (1)
Micro-Optics, VCSELs, and Photonic Interconnects: Fabrication, Packaging, and Integration
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