A novel grating-assisted wavelength selective switch (WSS) is proposed. Its operating principle is experimentally confirmed with strong coupling strength, negligible birefringence, and low channel crosstalk. A WSS-based cross-connect device is demonstrated.

An all-optical switch for future computer optical interconnect systems based on an optical cavity with a high quality factor and a nonlinear material is computionally investigated in two dimensional with a finite-difference time domain method. The signal and control bus are perpendicular to each other and can couple into a high-Q cavity consisting of a nonlinear material. It is designed in such a way that the control bus switches the signal bus on and off. Owing to the nonlinearity in the cavity, the resonance is shifted in frequency when increasing the power in the control bus so that the signal can pass through the resonator. The high Q of the cavity maximizes the interaction with the nonlinear material, and the symmetry of the cavity mode is designed in such a way that the cross talk between the signal bus and the control bus is minimized.

In short-distance optical links, the development of driving circuits for vertical-cavity surf ace-emitting lasers (VCSELs) requires precise and computationally efficient VCSEL models. A small-signal model of a VCSEL is computationally efficient and simple to implement; however, it does not take into account the nonlinear output behavior of the VCSEL. In contrast, VCSEL models that are highly based on first principles cannot be implemented in standard circuit device simulators, because the simulation of eye diagrams becomes too time consuming. We present another approach using VCSEL models, which are based on the 1-D rate equations. Our analysis shows that they combine efficient extraction and short simulation time with an accurate calculation of eye diagrams over a wide range of ambient temperatures. As different implementations of the rate equations exist, tradeoffs between three different versions are presented and compared with measured GaAs oxide-confined VCSELs. The first model has a linear and the second a logarithmic function of the gain versus the carrier density. The third model considers the additional transport time for carriers to reach the active region with quantum wells. For parameter extraction, a minimum set of parameters is identified, which can be determined from fundamental measurements. (c) 2005 society of Photo-Optical Instrumentation Engineers.

A quad-optical transceiver in 80nm CMOS transmits 10Gb/s/ channel over a multi-mode fiber at a BER of <10/sup -12/. Each driver consumes 2mW from a 0.8V supply and a VCSEL requires 7mA from a 2.4V supply. The receiver excluding the output buffer consumes 6mW from a 1.1V supply per channel and features a transimpedance gain of 10.1 k/spl Omega/.

This paper describes a quad optical transceiver for low-power high-density short-distance optical data communication. Each channel transmits 10 Gb/s over a multimode (MM) fiber and features a link margin of 5.2 dB at a bit error rate (BER) of 10/sup -12/. The transmit and receive amplifying circuits are implemented in an 80-nm digital CMOS process. Each driver consumes 2 mW from a 0.8-V supply, and each vertical cavity surface-emitting laser (VCSEL) requires 7 mA from a 2.4-V supply. The receiver excluding the output buffer consumes 6 mW from a 1.1-V supply per channel and achieves a transimpedance gain of 80.1 dB/spl Omega/. The isolation to the neighboring channels is >30dB including the bond wires and optical components. A detailed link budget analysis takes the relevant system impairments as losses and power penalties into account, derives the specifications for the electrical circuits, and accurately predicts the link performance. This work presents the highest serial data rate for CMOS transceiver arrays and the lowest power consumption per data rate reported to date.

Static and dynamic measurements are performed with GaAs oxide-confined vertical-cavity surface-emitting lasers (VCSELs), using multimode fibers with a core diameter of 50 and 62.5 /spl mu/m and different numerical apertures (NAs). They show that a small NA can have a severe impact on the eye opening and thus also on the bit-error rate. The measurements are analyzed with a spatiotemporal two-dimensional (2-D) multimode VCSEL model. The required parameter extraction for the model is verified with small- and large-signal measurements. The analysis shows that the change of the eye opening can be explained by the interaction between the mode- and the current-injection profile, carrier diffusion, and intermodal gain compression (IGC). IGC increases differences in the modal power distribution caused by the interaction between the mode profiles and the current-injection profile. Carrier diffusion is able to compensate these increased differences of the modal power distribution. Its impact, however, on dynamic changes caused by IGC is moderate.

Optically pumped organic polymer lasers are fabricated by spin coating a thin polymer film onto a nanopatterned SiO2 circular-grating surface-emitting distributed Bragg reflector. For certain grating parameters, we observe a peak inside the stop band that leads to lasing with a reduced threshold. An analytical model, based on the transfer-matrix method, has been developed to investigate the origin of this peak. The theoretical results are in good agreement with the experimental findings.

The development of optical interconnects in printed circuit boards (PCBs) is driven by the increasing bandwidth requirements in servers, supercomputers and switch routers. At higher data rates, electrical connections exhibit an increase in crosstalk and attenuation; which limits channel density and leads to high power dissipation. Optical interconnects may overcome these drawbacks, although open questions still need to be resolved. We have realized multimode acrylate-polymer-based waveguides on PCBs that have propagation losses below 0.04 dB/cm at a wavelength of 850 nm and 0.12 dB/cm at 980 nm. Transmission measurements at a data rate of 12.5 Gb/s over a 1-m-long waveguide show good eye openings, independent of the incoupling conditions. In the interconnect system, the transmitter and receiver arrays are flip-chip-positioned on the top of the board with turning mirrors to redirect the light. The coupling concept is based on the collimated-beam approach with microlenses in front of the waveguides and the optoelectronic components. As we aim for large two-dimensional waveguide arrays, optical crosstalk is an important parameter to be understood. Accordingly, we have measured optical crosstalk for a linear array of 12 optical channels at a pitch of 250 um. The influence of misalignment at the transmitter and the receiver side on optical crosstalk will be presented as a function of the distance between waveguide and transmitter/receiver.

The temporal coupled mode theory is applied on the design of filters and waveguide crossings that feature a resonator with a high quality factor. To determine the transmission properties of the device we calculate the decay rate of the resonator. The analysis using the decay rates requires far less computational effort than conventional FDTD transmission calculations and therefore the optimum device properties can be determined quickly.

We investigated bends for photonic crystals with triangular arrays of holes theoretically by employing two-dimensional band-structure and transmission calculations. We find that the guided mode of the bend is frequency-shifted compared with that of a straight waveguide. Decreasing the size of the holes in the immediate vicinity of the bend shifts the frequency of the mode back. These optimized bends can guide light in the frequency region of very low group velocities around corners.

The temporal-coupled-mode theory is directly applied to the design of devices that feature a resonator with a high quality factor. For the temporal-coupled-mode theory we calculate the decay rate of the resonator to determine the transmission properties of the device. The analysis using the decay rates requires little computational effort, and therefore the optimum device properties can be determined quickly. Two examples, a wavelength filter and a resonator crossing, are presented to illustrate the use of the analysis.

Organic two-dimensional photonic bandgap structures (2D PBG) have been fabricated by spin-coating a thin polymer film onto a nano-patterned SiO2 circular-grating surface-emitting distributed Bragg reflectors (CG-SE-DBR). When optically pumped and for certain grating parameters, these structures exhibit a peak inside the stop band that leads to lasing with a reduced threshold. An analytical model based on the transfer-matrix method has been developed to investigate the origin of this peak. The theoretical results are in excellent agreement with the experimental findings.

This paper describes methods to control and manipulate birefringence in SiliconOxyNitride waveguides and devices. Each method is demonstrated by measurements on example devices. The methods and devices that will be covered are:Reduction of heater induced birefringence in a dynamic gain equalizer by heater design or etched trenches.Reduction of polarization mode dispersion in a tunable dispersion compensator by UV trimming of residual waveguide birefringence.Polarization conversion using integrated optical half-wave-plates, fabricated by etching trenches at one side of a waveguide.Polarization splitting using waveguide sections with specified birefringence, obtained by etched trenches at both sides of the waveguide.

The effective refractive index of dielectric waveguides can be tuned using the thermooptic effect. In general, the tuning efficiency is polarization-dependent owing to temperature-induced stress in the layers, which causes polarization-dependent loss in optical devices. These stress issues are analyzed and tested for a high-index-contrast waveguide structure based on a silicon-oxynitride core. Experimental results are in agreement with simulations. The relative difference in tuning efficiency for transverse electric and transverse magnetic polarized light can be tuned from -3% to +3% by appropriate waveguide technology control. The optimized thermooptic phase shifters show tuning efficiency differences below 0.25%, which are reproducible from wafer to wafer.

The evolution of optical networks towards flexible many-wavelength systems with high data rates creates the need for a variety of novel optical devices. Reconfigurable optical components are required to re-route wavelength channels, and tunable compensating filter devices are necessary to control the optical properties of the signal carriers such as power, chromatic dispersion (CD) and polarization-mode dispersion (PMD). Silica-on-silicon planar waveguide technologies offer an ideal platform for the realization of such tunable components because of the excellent optical properties and compatibility with IC manufacturing tools. However, with increasing complexity, devices can become large with respect to the wafer size, which increases device cost. This can be overcome by a high-index-contrast silica technology. The small minimum bending radius leads to a reduced device size, and the overall reduction in waveguide dimensions results in a reduced processing time for deposition and etching. In this paper, we describe our high-index contrast technology based on silicon-oxynitride (SiON), and present two device examples.

We present a tunable dispersion compensator, based on a sixth-order finite impulse response lattice filter. The filter has a free spectral range of 100 GHz and can be tuned for linear group delay slopes between -100 and 100 ps/nm with less than 1-ps ripple over a usable bandwidth of more than 60 GHz. Within this usable bandwidth, the average polarization-mode dispersion is low, reaching 2.4 ps only for extreme group delay slopes. The filter can also generate higher order group delay curves, for example for dispersion slope compensation.

We identify applications for optics-enabled printed circuit boards, together with a list of requirements that have to be met for real-world products. We draw conclusions for the technology choices, and present our approaches and experiments.

We report on the fabrication of a grating-based add–drop filter in SiON planar waveguide technology. We achieved apodization of the Bragg grating by concatenating subgratings with various duty cycles. We present the theoretical and experimental dependence of the coupling coefficient on the duty cycle, which leads to a minimum coupling coefficient of 30%. With a breeder genetic algorithm we were able to find optimal apodization profiles within this limited coupling coefficient range. The final device is compatible with a 100-GHz channel spacing and has a bandwidth utilization factor of 36%.

Planar optical waveguides for applications in communication networks can be fabricated using conventional chip-manufacturing techniques. We present a planar optical waveguide technology that is based on a silicon-oxynitride (SiON) core and silicon-oxide cladding layers. In addition to more compact, conventional optical devices, it also enables enhanced optical functions such as dynamically reconfigurable planar integrated optical devices. Examples of adaptive devices realized in this technology include finite and infinite impulse response (FIR and IIR) filters.