Eric Shih-Tse Hu

SUCCESS: a next-generation hybrid WDM/TDM optical access network architecture

In this paper, the authors propose a next-generation hybrid WDM/TDM optical access network architecture called Stanford University aCCESS or SUCCESS. This architecture provides practical migration steps from current-generation time-division multiplexing (TDM)-passive optical network (PONs) to future WDM optical access networks. The architecture is backward compatible for users on existing TDM-PONs, while simultaneously capable of providing upgraded high-bandwidth services to new users on DWDM-PONs through advanced WDM techniques. The SUCCESS architecture is based on a collector ring and several distribution stars connecting the CO and the users. A semipassive configuration of the Remote Nodes (RNs) enables protection and restoration, making the network resilient to power failures. A novel design of the OLT and DWDM-PON ONUs minimizes the system cost considerably: 1) tunable lasers and receivers at the OLT are shared by all ONUs on the network to reduce the transceiver count and 2) the fast tunable lasers not only generate downstream data traffic but also provide DWDM-PON ONUs with optical CW bursts for their upstream data transmission. Results from an experimental system testbed support the feasibility of the proposed SUCCESS architecture. Also, simulation results of the first SUCCESS DWDM-PON MAC protocol verify that it can efficiently provide bidirectional transmission between the OLT and ONUs over multiple wavelengths with a small number of tunable transmitters and receivers.

Performance demonstration of a fast-tunable transmitter and burst-mode packet receiver for HORNET

We demonstrate error-free packet-over-WDM transmission using a fast-tunable transmitter and novel packet receiver. The transmitter tunes fine (0.8 nm) and. wide (/spl sim/30 nm) within 15 ns, while the receiver receives unframed packets by bit-synchronizing in 40 ns.

4-level direct-detection polarization shift-keying (DD-PolSK) system with phase modulators

We propose and demonstrate a novel 4-level DD-PolSK system with LiNbO/sub 3/-based phase modulator and alternative allocation of constellations, which lead to a greatly simplified transceiver architecture. A 5 Gb/s (2.5 GS/s) testbed has been build to demonstrate the feasibility of the 4-PolSK transceiver.

Demonstration and system analysis of the HORNET architecture

The HORNET architecture is a packet-over-wavelength-division-multiplexing ring network that utilizes fast-tunable packet transmitters and wavelength routing to enable it to scale cost-effectively to ultrahigh capacities. In this paper, we present the HORNET architecture and a novel control-channel-based media access control protocol. The survivability of the architecture is demonstrated with an experimental laboratory testbed. Mathematical analysis of the architecture shows that the wavelength routed network can scale to relatively large sizes ranging between 30 and 50 nodes, depending on the component performance. This is true even for arrangements that do not contain high-power optical amplifiers in every node.

Gain-clamped S-band discrete Raman amplifier

In summary, we have demonstrated, for the first time to our knowledge, a gain-clamped discrete Raman amplifier in the S-band. The device achieves peak net gain over 22 dB, and a gain variation of only 0.3 dB for signal input power ranging from -20 dBm to 2.7 dBm. Unlike conventional gain-clamping designs, an extinction ratio between signal and lasing wavelength of over 30 dB is achieved. This new technique suppresses instability due to randomly-polarized ASE and double Rayleigh scattering (DRS) (hence noise figure) for small signal input power under high pump power, as well as power surges due to transient effects in Raman amplifiers. This promises a viable technology to provide gain bands not currently available from traditional doped fiber amplifiers.

Novel in-service wavelength-band upgrade scheme for fiber Raman amplifier

To reduce the initial introduction cost of fiber Raman amplifiers, a novel in-service wavelength-band upgrade scheme is proposed. In this scheme, new pump lasers are added to an existing Raman amplifier already carrying wavelength-division-multiplexing (WDM) signals, and all the pump laser driving currents are changed synchronously through the transient period, keeping the WDM signal gain unchanged, while increasing the gain in the new band. We experimentally proved the principle of the proposed scheme in both discrete and distributed Raman amplifiers, even with the existence of signal-gain saturation, nonlinear pump interaction, and pump power loss. We also confirmed error-free wavelength-band upgrade in an eight-channel-WDM transmission system.

Fast transient response of L-band tellurite-based EDFAs and their optically gain-clamped behavior

We reported on the fast transient response of EDTFAs. The transient time of EDTFAs can be one-ninth as short as that of the EDSFAs with similar gain shape in L-band. We also demonstrated optically gain-clamped EDTFAs and showed that the power excursion due to SHB is comparable to or smaller than that in EDSFAs. The relaxation oscillation frequencies also give us information about the fast dynamics within EDTFAs. In summary, EDTFAs show superior controllability over EDSFAs for automatic gain control via either electrical or optical schemes. Further research will include modeling of the dynamic behavior of EDTFAs.

Opposite-parity orthonormal function expansion for efficient full-vectorial modeling of holey optical fibers.

An improved full-vectorial method exploiting the opposite-parity property of eigenmodes based on orthonormal-functions expansion is proposed to solve the wave equation for holey optical fibers. By use of the parity property of eigenmodes in symmetric structures, the number of orthonormal function integrals involved in the calculation is reduced, and the computation efficiency is greatly enhanced. The coupling between the two transverse field components is considered, and both dominant and minor field components can be calculated for the accurate modeling of fiber modes. This method is useful for efficiently modeling holey fibers, especially those with large air holes, in which the coupling effect that is due to refractive-index discontinuities is strong.

A full-vectorial method for efficient holey optical fiber modeling

Summary form only given. A vectorial algorithm (Monro et al. J. Lightwave Technol., vol.18, p.50-6, 2000) has been proposed to analyze large-hole structures. This algorithm, however, assumes the decoupling of the two transverse field components and should really be classified as a semi-vectorial algorithm. Here we propose a full-vectorial algorithm, which solves the wave equations exactly, without the assumption of decoupling of the two transverse fields. The algorithm based on Hermite-Gaussian function expansions is efficient because only relatively few terms are necessary to obtain good results. Our algorithm simplifies the refractive index representation of Monro, is better suited to various holey fiber structures, and provides better approximations around the core region. Compared with Monro, our proposed algorithm considers both transverse field components, and it is an accurate modeling for strongly guiding structures like holey fibers. The full-vectorial algorithm has been checked against analytical results in analytically solvable structures, and experimental results. Very good agreement is obtained in both cases.

XPM cancellation in tellurite and silica EDFAs by complementary modulation of twin carriers

Cross-phase modulation cancellation of more than 15dB in various lengths of telluriteand silica-based erbium-doped fiber amplifiers is achieved by using complementary modulation of two closely-spaced optical carriers in WDM systems.