Volkan Kaman

All-optical label swapping networks and technologies

All-optical label swapping is a promising approach to ultra-high packet-rate routing and forwarding directly in the optical layer. In this paper, we review results of the DARPA Next Generation Internet program in all-optical label swapping at University of California at Santa Barbara (UCSB). We describe the overall network approach to encapsulate packets with optical labels and process forwarding and routing functions independent of packer bit rate and format. Various approaches to label coding using serial and subcarrier multiplexing addressing and the associated techniques for label erasure and rewriting, packet regeneration and packet-rate wavelength conversion are reviewed. These functions have been implemented using both fiber and semiconductor-based technologies and the ongoing effort at UCSB to integrate these functions is reported. We described experimental results for various components and label swapping functions and demonstration of 40 Gb/s optical label swapping. The advantages and disadvantages of using the various coding techniques and implementation technologies are discussed.

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.

High extinction ratio and saturation power traveling-wave electroabsorption modulator

An InGaAsP multiquantum-well traveling-wave electroabsorption modulator is demonstrated with high extinction ratio and modulation efficiency. By designing a strain-compensated quantum-well active region with traveling-wave design, high saturation power (>14 dBm) for >20-GHz high-speed performance (1.5 dB drop at 20 GHz) is achieved. Due to high modulation efficiency (>30 dBN for 0 to 1 V 40-dB extinction ratio in 2 V), error free 10-Gb/s operation with 1 V/sub p-p/ driving voltage is obtained. By comparing codirections and counterdirections of optical and microwave interactions, pulse generation at 40 GHz shows that the traveling-wave performance has an advantage for short pulses with high-power output, where pulsewidth as short as 4.5 ps is obtained in this kind of device.

A 32-element 8-bit photonic true-time-delay system based on a 288 x 288 3-D MEMS optical switch

A large-scale three-dimensional microelectromechanical-system optical switch is used for the first time to realize a true-time-delay (TTD) beamformer for phased-array radar applications, with a capacity of 32 antenna elements and eight bits of delay. The 288 /spl times/ 288 optical switch has a median loss of 1.4 dB and all measured 82 944 paths exhibit less than 2.3 dB loss at 1310 nm. The TTD beamformer exhibits a loss variation of 1.5 dB, which is equalized using a mirror-offset technique.

Applications of large-scale optical 3D-MEMS switches in fiber-based broadband-access networks

Applications of non-blocking large-scale optical switches based on three-dimensional micro-electro-mechanical system (3D-MEMS) technology with small size and low power consumption are described for fiber-based broadband access networks. The low-loss and fast-switching 3D-MEMS switches offer remotely reconfigurable and automated operational solutions for access networks such as fiber management, preventative maintenance, monitoring, testing, and troubleshooting of a large number of end customers. Furthermore, the wavelength, data rate, and protocol-transparent nature of 3D-MEMS switches results in a future-proof optical distribution network design for future higher speed and higher capacity wavelength division multiplexing overlay upgrades over the passive optical network (PON). We show that large-scale 3D-MEMS switches deployed in PON environments can offer over an order of magnitude in capital and operational savings in comparison to manual patch panels (in deployed fiber hardware, real estate, and manual labor) with minimal impact on the overall network design.

Integrated tandem traveling-wave electroabsorption modulators for >100 Gbit/s OTDM applications

Integrated tandem traveling-wave electroabsorption modulators are demonstrated as high-speed optical short pulse generators and demultiplexers for >100 Gbit/s optical time-division-multiplexed systems. The tandem significantly increases the extinction ratio and further compresses the optical pulses in comparison to a single modulator. An extinction ratio of /spl sim/50 dB is achieved while optical pulses of 4-6 ps width at 30-40 GHz are generated.

Distributed effects model for cascaded traveling-wave electroabsorption modulator

A distributed model based on the large-signal electrooptic conversion is proposed to analyze cascaded traveling-wave electroabsorption modulators (TWEAMs) for high-speed optical switching applications. The microwave propagation loss, velocity mismatch, as well as frequency chirping are included. The model predicts that a cascaded TWEAM structure has the advantage of a high design tolerance to various distributed effects and an improved extinction ratio and optical loss in comparison to a single device of same total length. The agreement between experimental and calculated results indicates that the cascaded structures can be implemented for efficient TWEAM design.

Simultaneous OTDM demultiplexing and detection using an electroabsorptioa modulator

A traveling-wave electroabsorption modulator is used to simultaneously demultiplex and electrically detect a single 10-Gb/s channel from a 20-Gb/s optical time-division multiplexed data stream while transmitting the other channel in an optically transparent manner. A bit-error-rate penalty of 0.5 dB and an error floor were observed for the dropped channel due to residual absorption of the other channel. Error-free operation was achieved for the transparent channel.

Compact and scalable three-dimensional microelectromechanical system optical switches [Invited]

Feature Issue on Nanoscale Integrated Photonics for Optical Networks We review the performance and applications of compact (20cm3) and large-scale (320×320) three-dimensional microelectromechanical system (3-D MEMS) based optical switches. The low loss (<3dB for all 102,400 paths) and variable attenuation capable optical switch performs penalty-free for cascaded operation at 40Gbits/s. Scalability and performance of integrated wavelength-selective cross-connects based on 3-D MEMS with an unprecedented 12.8Tbit/s switching capacity for next-generation all-optical networks are also presented.

A cyclic MUX-DMUX photonic cross-connect architecture for transparent waveband optical networks

A novel photonic cross-connect (PXC) configuration with cyclic multiplexers and demultiplexers (DMUXs) is proposed for realizing dynamic switching and transparent add-drop in waveband dense wavelength-division-multiplexed networks. The PXC architecture allows for a flexible operation while maintaining low optical losses for express wavebands and add-drop wavelengths. The drop functionality of this architecture is demonstrated using an integrated cyclic optical DMUX and four 10-Gb/s PIN receivers with an average receiver sensitivity of -34 dBm as a compact and cost-effective solution.