Recent developments in IC design technology for high-speed communications have led to highly improved
optoelectronic (O/E) system design. Specifically, signal integrity management is a specific area of communications
circuit design that is promising in playing a role in optoelectronic packaging and component cost. This paper explores
the potential of these techniques in impacting O/E component design and possibilities for cost reduction. It is argued that
a judicious tradeoff in system parameters such as link length and component bandwidth could impact overall cost
In this tutorial overview, we survey some of the challenging problems facing Optical Transport and their solutions using new semiconductor-based technologies. Advances in 0.13um CMOS, SiGe/HBT and InP/HBT IC process technologies and mixed-signal design strategies are the fundamental breakthroughs that have made these solutions possible. In combination with innovative packaging and transponder/transceiver architectures IC approaches have clearly demonstrated enhanced optical link budgets with simultaneously lower (perhaps the lowest to date) cost and manufacturability tradeoffs. This paper will describe:
*Electronic Dispersion Compensation broadly viewed as the overcoming of dispersion based limits to OC-192 links and extending link budgets,
*Error Control/Coding also known as Forward Error Correction (FEC),
*Adaptive Receivers for signal quality monitoring for real-time estimation of Q/OSNR, eye-pattern, signal BER and related temporal statistics (such as jitter).
We will discuss the theoretical underpinnings of these receiver and transmitter architectures, provide examples of system performance and conclude with general market trends. These Physical layer IC solutions represent a fundamental new toolbox of options for equipment designers in addressing systems level problems. With unmatched cost and yield/performance tradeoffs, it is expected that IC approaches will provide significant flexibility in turn, for carriers and service providers who must ultimately manage the network and assure acceptable quality of service under stringent cost constraints.
Fine-grained polymer dispersed liquid crystals have recently become available for electrically switchable holographic elements. We explore applications of this novel material to switchable focus diffractive lenses. Several fabrication approaches, holographic and non-holographic, are demonstrated and compared with respect to design flexibility, diffraction efficiency, switching dynamic range, and optical quality. It appears possible to shift optical power between widely separated focal points with a modulation ratio 100:1 on a 10 - 50 microsecond(s) time scale.
In this paper we report novel high contrast, high reflectivity n+-AlGaAs/GaAsAl/Ag asymmetric Fabry-Perot (ASFP) optical modulators and self-electro-optic devices (SEED) using the Franz-Keldysh (FK) electroabsorption in bulk GaAlAs layer. These modulators exhibit `normally off' and `normally on' optical modulation at and below the band edge with contrast ratios in the range of 25:1 to 200:1 and reflectivities of about 30% to 50%. We show that our experimental data is consistent with a model of electroabsorption that includes unbound excitons. The FK-SEED, exhibiting contrast rations of approximately 90:1 and reflectivities of 27% at 11 V, operates based on the combined effects of negative electroabsorption and the `normally off' properties of the device. In addition to these devices operating in the 10 nm vicinity of the GaAs band gap (872 nm), we also report a high contrast modulator with Ga0.975Al0.025As FK layer operating at the standard 850 nm wavelength. These devices demonstrate the feasibility of using the bulk Franz-Keldysh effect as an alternative to quantum confined stark effects (QCSE) for efficient optical switching and modulation for many applications.
Foster-Miller is developing a new family of SLM devices, based on the Franz-Keldysh (FK) effect in bulk III-V semiconductors, for several applications in optical signal processing and switching. Spatial light modulators constructed using the FK effect offer contrast ratios and switching energies rivalling state-of-the-art devices. However, our devices require typically only 2 or 3 bulk epilayers (available commercially), significantly reducing the materials and fabrication cost. Using the FK effect in an asymmetric Fabry-Perot geometry, we demonstrate high contrast (120:1 best, 50:1 typical) with drive voltages roughly 10 - 20 V and 2 - 3 nm optical bandwidth. We demonstrate high-contrast reflection mode optical modulation at a number of wavelengths in the 800 - 950 nm band.