This paper reviews advanced optical burst switching (OBS) and optical packet switching (OPS) technologies and discusses their roles in the future photonic Internet. Discussions include optoelectronic and optical systems technologies as well as systems integration into viable network elements (OBS and OPS routers). Optical label switching (OLS) offers a unified multiple-service platform with effective and agile utilization of the available optical bandwidth in support of voice, data, and multimedia services on the Internet Protocol. In particular, OLS routers with wavelength routing switching fabrics and parallel optical labeling allow forwarding of asynchronously arriving variable-length packets, bursts, and circuits. By exploiting contention resolution in wavelength, time, and space domains, the OLS routers can achieve high throughput without resorting to a store-and-forward method associated with large buffer requirements. Testbed demonstrations employing OLS edge routers show high-performance networking in support of multimedia and data communications applications over the photonic Internet with optical packets and bursts switched directly at the optical layer

Optical Packet and Burst Switching Technologies for the Future Photonic Internet

After over two decades of exploration, tunable diode lasers are beginning to find significant applications, driven largely by the huge demand for bandwidth that is guiding many developments in the optical fiber communication business today. In the paper, some of the history and key developments that have led to the technologies available today are reviewed from the perspective of the author. After discussion of some of the early work, the focus shifts to widely tunable diode lasers, which would appear to be key enablers for future dense wavelength-division multiplexing and optical switching and networking systems. The distinguishing characteristics of the current technological alternatives are summarized.

Monolithic tunable diode lasers

The different approaches being considered to build high-capacity lightwave networks are described. Two kinds of lightwave network architectures are examined: broadcast-and-select networks and wavelength-routing networks. A comparison of the two shows that broadcast-and-select networks may be more suitable for local area networks (LANs) and metropolitan area networks (MANs), while wavelength-routing networks are suitable for wide area networks (WANs). The overall network may then be a combination of broadcast subnets interconnected by a point-to-point wavelength-routing network. >

Multiwavelength lightwave networks for computer communication

A 40 mm long optical fibre grating superstructure is written by translating an ultraviolet writing beam along a fibre and phase-mask assembly while its intensity is periodically varied. The grating reflects at multiple wavelengths, equally spaced by 0.13 nm, over a range of more than 1.0 nm. This grating structure has applications in signal processing and tunable fibre lasers.<
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Long periodic superstructure Bragg gratings in optical fibres

A broad tuning range is demonstrated in tunable DBR lasers with a novel superstructure grating (SSG). These SSG reflectors were fabricated by electron-beam lithography, and grating performance was evaluated by measuring the transmittance characteristics of a ridge-type SSG reflector. Incorporating this SSG reflector into distributed-Bragg-reflector (DBR) laser results in lasers that can be tuned over a wide wavelength range by using coarse and fine tuning mechanisms. Wavelength-tunable SSG DBR lasers were fabricated and operated under low-threshold CW conditions. Wavelength tuning ranges of 50 and 100 nm were designed and experimentally measured to be 50 and 83 nm, respectively, with single-mode operation. >

Broad-range wavelength-tunable superstructure grating (SSG) DBR lasers

We propose and demonstrate a new monolithic laser structure in which the fractional tuning range Δλ/λ can be more than an order of magnitude larger than the fractional index change Δμ/μ in one section. The key idea involves using grating mirrors with grating elements removed in a periodic fashion. These ‘‘sampled gratings’’ have reflection spectra with periodic maxima. By using two such mirrors with identical grating pitch but mismatched sampling periods, it is possible to tune among the various reflectivity maxima. Our initial experimental results show 29.3 nm of tuning in an InGaAsP laser.

V. Jayaraman

Papers

Demonstration of broadband tunability in a semiconductor laser using sampled gratings

Extended tuning range in a distributed feedback InGaAsP laser with sampled gratings