OFC '00 Postdeadline: Modular 8 x 8 Optical Switch Provides Scalability for High Data Rates

By: Yvonne Carts-Powell

Using arrays of eight-element gain-clamped silicon optical amplifiers (GC-SOAs), researchers have demonstrated a modular and scaleable 8 x 8 optical switch. F. Dorgeuille and others at Alcatel Data Networks (Marcoussis, France) reported on the work during the postdeadline paper sessions at the Optical Fiber Communications conference (OFC '00; Baltimore, MD; March 5-10).¹

The non-blocking architecture for this switch consists of eight input 1:8 splitters connected to eight output 8 x 1 switches through a 64-fiber perfect shuffle. Although the design is based on arrays of eight GC-SOAs, the design would work for arrays of more or fewer amplifiers. Alternatively, this system could be used as a building block for a larger switch.

Design
For demonstration purposes, four input 1:8 splitters were connected to one output 8 x 1 space switch module through a perfect shuffle interconnect so that each input port of the 8 x 1 SOA was fed a signal (see Figure 1). This module consists of an 8 GC-SOA gate array flip chip mounted on an silicon oxide/silicon (SiO₂/Si) motherboard. The device's insertion loss is between 1 and 2.5 dB for a 100-mA injected current, with a polarization sensitivity of less than 1 dB from 1525 to 1575 nm, and negligible gain ripple.

Figure 1. 8 X 8 experimental optical switch

Transmission
Dorgeuille's group demonstrated 16 10-Gbit/s channels (with channels spaced at 200 GHz, from 1535 to 1559 nm) launched into the switch. Insertion loss through the switch ranges from 12 to 14 dB, with about 10 dB contributed by the 1:8 splitter. Polarization-dependent losses ranged from 0.5 to 0.9 dB, depending on the port. The extinction ratio of the switch ranged between 32 and 38 dB, including contributions of all the eight input ports.

The current injected in the selected optical gate was 200 mA. The total 8 x 78 input power was +4 dBm, and the input signal-to-noise ratio (SNR) was about 30 dB/0.1 nm. The worst output SNR was 24 dB/0.1 nm.

Based on these experiments using one input splitter, the researchers believe that this architecture could handle switching using all eight splitters originally envisioned. This would lead to eight splitters handling 16 channels of 10 Gbit/s data, or a data rate of 1.28 Tbit/s.

Reference
F. Dorgeuille, et. al., "1.28 Tbit/s throughput 8 X 8 optical switch based on arrays of Gain-Clamped Semiconductor Optical Amplifier gates," Optical Fiber Communications Conference, paper #PD18, Baltimore, MD (2000).

About the author…
Yvonne Carts-Powell is a freelance science and technology writer based in Belmont, MA.