Henrik N. Poulsen

Three-dimensional MEMS photonic cross-connect switch design and performance

Photonic cross-connects (PXC) play a key role in all-optical transparent networks. In this paper, the optical design and modeling of a three-dimensional microelectromechanical system (3-D MEMS) based optical switch are discussed. Basic design rules and considerations are reviewed and used to determine the optimum configuration for free-space optical switches with more than 300 ports. The optical performance of a 256 /spl times/ 256 PXC system, including a 347 /spl times/ 347 nonblocking core switch and auxiliary 2 /spl times/ 2 optical switches for 1:1 protection and optical taps for power monitoring, is presented. The core switch has 1.4-dB median insertion loss, 1.5-dB wavelength dependent loss across a broadband of 1260-1625 nm, and a typical polarization dependent loss of 0.1 dB. Environmental tests including temperature and vibration are described.

All-optical wavelength conversion of short pulses and NRZ signals based on a nonlinear optical loop mirror

Wavelength conversion of short pulses at 10 GHz based on a nonlinear optical loop mirror (NOLM) is experimentally and numerically investigated for the case of small group velocity dispersion and walkoff between the control pulses and continuous lightwaves. Experimental and numerical simulation results show that the pulsewidths of the converted signals at different wavelengths are almost the same, and the pulsewidths are compressed when the peak power of the control pulse is smaller than a certain value. An RZ optical source containing eight wavelengths having a high sidemode suppression ratio, equal amplitudes and almost the same pulsewidths is obtained by using wavelength conversion in a NOLM consisting of a common dispersion shifted fiber. 10 Gb/s NRZ wavelength conversion based on the NOLM is demonstrated for the first time and certain conclusions in some of the references are confirmed by our experimental results.

Toward wide-scale all-optical transparent networking: the ACTS optical pan-European network (OPEN) project

The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N/spl times/10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4/spl times/4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s.

All-optical regenerative OTDM add-drop multiplexing at 40 Gb/s using monolithic InP Mach-Zehnder interferometer

We present a novel method for all-optical add-drop multiplexing having regenerative capability for 40-Gb/s optical time-division multiplexed (OTDM) data using a semiconductor optical amplifier (SOA) based, monolithic Mach-Zehnder interferometer (MZI). Simultaneous dropping of one 10-Gb/s channel out of 10-Gb/s OTDM data and perfect clearing of the corresponding time slot in the remaining 3/spl times/10 Gb/s data stream is demonstrated. Bit-error-rate measurements show a low penalty of 2 dB for each 10 Gb/s channel. No extra penalty was observed introducing a 10-Gb/s add channel through the device into the cleared time slot.

Integrated Photonics for Low-Power Packet Networking

Communications interconnects and networks will continue to play a large role in contributing to the global carbon footprint, especially in data center and cloud-computing applications exponential growth in capacity. Key to maximizing the benefits of photonics technology is highly functional, lower power, and large-scale photonics integration. In this paper, we report on the latest advances in the photonic integration technologies used for asynchronous optical packet switching using an example photonic integrated switched optical router, the label switched optical router architecture. We report measurements of the power consumed by the photonic circuits in performing their intended function, the electronics required to bias the photonics, processing electronics, and required cooling technology. Data is presented to show that there is room (potentially greater than 10 ×) for improvement in the router packet-forwarding plane. The purpose of this exercise is not to provide a comparison of all-optical versus electronic routers, rather to present a data point on actual measurements of the power contributions for various photonic integration technologies of an all-optical packet router that has been demonstrated and conclude, where the technology can move to reduce power consumption for high-capacity packet routing systems.

Photonic integrated circuit optical buffer for packet-switched networks

A chip-scale optical buffer performs autonomous contention resolution for 40-byte packets with 99% packet recovery. The buffer consists of a fast, InP-based 2 x 2 optical switch and a silica-on-silicon low loss delay loop. The buffer is demonstrated in recirculating operation, but may be reconfigured in feed-forward operation for longer packet lengths. The recirculating buffer provides packet storage in integer multiples of the delay length of 12.86 ns up to 64.3 ns with 98% packet recovery. The buffer is used to resolve contention between two 40 Gb/s packet streams using multiple photonic chip optical buffers.

Raman-enhanced regenerative ultrafast all-optical fiber XPM wavelength converter

The Raman gain enhancement of a regenerative ultrafast all-optical cross-phase modulation (XPM) wavelength converter (WC) is quantitatively investigated and experimentally demonstrated to operate error free at 40 and 80 Gb/s. The regenerative nature of the converter is shown by experimentally demonstrating a negative 2-dB power penalty at 80 Gb/s. It is also shown that the Raman gain greatly enhances the wavelength conversion efficiency at 80 Gb/s by 21 dB at a Raman pump power of 600 mW using 1 km of highly nonlinear fiber. An analytical theory based on nonlinear phase-shift enhancement of the fiber-effective length is presented and shows the relationship between a nonlinear enhancement and Raman gain as a function of pump power and fiber design parameters. Measured parameters are used in the analytical model, and a good fit between experiment and theory is shown for two different types of fiber: one dispersion-shifted and one highly nonlinear fiber. The ultrafast response time of Raman gain makes this technique applicable to fiber-based ultrafast WCs. In addition, the applicability to other nonlinear fiber wavelength conversion techniques is discussed.

40-Gb/s Widely Tunable Low-Drive-Voltage Electroabsorption-Modulated Transmitters

We present the first 40-Gb/s widely tunable electroabsorption modulator (EAM)-based transmitters. The sampled-grating Distributed Bragg Reflector (SG-DBR) laser/EAM devices were fabricated using a multiple-band-edge-quantum-well-intermixing (QWI) technique, which requires only simple blanket regrowth and avoids disruption of the axial waveguide. Devices were fabricated from two different multiple quantum well (MQW) active-region designs for direct comparison. The SG-DBR lasers demonstrated 30 nm of tuning with output powers up to 35 mW. The integrated QW EAMs provided 3-dB optical modulation bandwidths in the 35-39 GHz range, low-drive voltage (1.0-1.5 VPtoP), and low/negative-chirp operation. Bit-error-rate measurements at 40 Gb/s demonstrated 0.2-1.1 dB of power penalty for transmission through 2.3 km of standard fiber

40-Gb/s all-optical wavelength conversion based on a nonlinear optical loop mirror

All-optical wavelength conversion based on a nonlinear optical loop mirror (NOLM) at 40 Gb/s is demonstrated for the first time. The effect of walkoff time between control beam and signal beams is investigated when the NOLM is used as an all-optical wavelength converter or an all-optical demultiplexer.

SOA Gate Array Recirculating Buffer for Optical Packet Switching

A compact recirculating buffer using an InP-based 2×2 switch with gain and a fiber delay line is demonstrated at 40 Gb/s. Packet throughput of 98% is measured for up to 8 circulations, or 0.18 μs.