The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented Discussed also are critical technologies that are essential to progress in this field >

Dense wavelength division multiplexing networks: principles and applications

An overview of emerging all-optical networks is given. The characteristics and alternative architectures for single-hop systems are discussed. The characteristics of lightwave technology that facilitate the design of wavelength-division-multiplexing (WDM) networks are reviewed, and it is explained how WDM local networks can be built based on the single-hop and multihop approaches. Various categories of single-hop systems are discussed: experimental systems, systems based on no pretransmission coordination, and systems based on pretransmission coordination, which also require a separate control channel. A simple classification for single-hop systems is provided. >

WDM-based local lightwave networks. I. Single-hop systems

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.

All-optical label swapping networks and technologies

An overview is given of the direct modulation performance of high-speed semiconductor lasers. The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.

High-speed modulation of semiconductor lasers

The unitraveling-carrier photodiode (UTC-PD) is a novel photodiode that utilizes only electrons as the active carriers. This unique feature is the key for its ability to achieve excellent high-speed and high-output characteristics simultaneously. To date, a record 3-dB bandwidth of 310 GHz and a millimeter-wave output power of over 20 mW at 100 GHz have been achieved. The superior capability of the UTC-PD for generating very large high-bit-rate electrical signals as well as a very high RF output power in millimeter/submillimeter ranges can lead to innovations in various systems, such as broadband optical communications systems, wireless communications systems, and high-frequency measurement systems. Accomplishments include photoreceivers of up to 160 Gb/s, error-free DEMUX operations using an integrated UTC-PD driven optical gate of up to 320 Gb/s, a 10-Gb/s millimeter-wave wireless link at 120 GHz, submillimeter-wave generation at frequencies of up to 1.5 THz, and photonic frequency conversion with an efficiency of -8 dB at 60 GHz. For the practical use, various types of modules, such as a 1-mm coaxial connector module, a rectangular-waveguide output module, and a quasi-optic module, have been developed. The superior reliability and stability are also confirmed demonstrating usefulness of the UTC-PD for the system applications.

/pdf/high-speed-and-high-output-inp-ingaas-unitraveling-carrier-2psspr7mz2.pdf

High-speed and high-output InP-InGaAs unitraveling-carrier photodiodes

Microwave subcarrier multiplexing (SCM) is an important approach to the design of lightwave systems for broadband distribution. Recent progress in the design and performance of both analog and digital multichannel SCM systems is reviewed. The application of broadband SCM systems to both passive and optically amplified distribution networks is discussed. The discussion covers the general features of SCM systems; the electrooptic components that have been used in the system experiments described here, including laser intensity noise and noise due to intermodulation products; the carrier-to-noise ratio requirements; some multichannel FM systems experiments; and a 20-channel digital systems experiment; and a hybrid system carrying 60 FM SCM channels plus a 100-Mb/s baseband digital channel. Several approaches to broadband subscriber distribution networks are analyzed. >

Subcarrier multiplexed lightwave systems for broad-band distribution

Measurements of the longitudinal-mode spectra of 1.3 μm InGaAsP buried-heterostructure lasers are used to determine the form and magnitude of the nonlinear gain. It is shown that nonlinear gain is responsible for the anomalous longitudinal-mode spectra which appear to be universally observed in InGaAsP lasers, and also for the anomalously strong damping of the relaxation oscillations observed in pulse-modulated lasers.

Strong influence of nonlinear gain on spectral and dynamic characteristics of InGaAsP lasers

Very high-speed packet networks will be required in the near future to efficiently integrate data, video, and voice into a common telecom-munications fabric. Many existing and proposed packet networks fail to take advantage of the multigigabit bandwidths provided by optical fiber and semiconductor optoelectronics. Much of the disparity between the data transfer rate of traditional packet networks (≤1 Gbit/s) and the link transmission rates for conventional lightwave systems (as high as 10 Gbit/s) lies in the amount of electronic processing that occurs at each node. A number of methods have been suggested to overcome this bottleneck. Many of these solutions rely on providing optical connectivity through the network without full optical-to-electronic (OE) and electronic-to-optical (EO) conversion of the packet at each node.

Multigigabit optical packet switch for self-routing networks with subcarrier addressing

Hole drift velocities in n‐type In0.53Ga0.47As have been determined experimentally for the first time. Measured values of the frequency response of transit‐time‐limited InGaAs p‐i‐n photodiodes were fit with the theoretical response using hole velocity as the only free parameter. Measurements over field strengths from 54 to 108 kV/cm showed the drift velocity to be relatively constant at (4.8±0.2) 106 cm/s, indicating that velocity saturation has occurred at field levels below 54 kV/cm.

Measurement of hole velocity in n-type InGaAs

An optical polarization multiplexing system using BPSK coherent heterodyne detection to transmit 4 Gb/s over a 45-km standard single-mode fiber optical link at a receiver sensitivity of -35 dBm is described. The 4-Gb/s system has a potential receiver sensitivity of -40 dBm while using 2-Gb/s baseband electronics. >

Robert Olshansky

Papers

Subcarrier multiplexed lightwave systems for broad-band distribution

Strong influence of nonlinear gain on spectral and dynamic characteristics of InGaAsP lasers

Multigigabit optical packet switch for self-routing networks with subcarrier addressing

Measurement of hole velocity in n-type InGaAs

Optical polarization division multiplexing at 4 Gb/s