InP integrated wavelength selector suits packet-switching applications


An indium phosphide (InP) monolithic 16-channel wavelength selector has been shown to be capable of optical packet switching. Sabry Khalfallah and others at Alcatel (Marcoussis, France) demonstrated switching time below 5 ns, wide input power, dynamic range of 15 dB, average polarization-dependent loss below 2 dB, and error-free transmission. The module's fast wavelength selection and suppression makes it suitable for a range of optical packet-switching applications for metropolitan and backbone networks.

To keep up with the growth in data traffic from Internet applications, metropolitan and backbone networks need a fast optical switching technology that works with the constraints of packet applications. Optical packet-switching systems must be able to switch wavelengths (as well as space) in nanoseconds. Integrating InP semiconductor optical amplifiers (SOAs) with multiplexers results in WDM channel selectors, which fit the switching constraints. The researchers made the device using metal-organic vapor-phase epitaxy and gas-source molecular-beam epitaxy (for layers of the SOA). By butt-coupling the two phased-array wavelength multiplexers and 16 SOAs, the device provides zero-loss operation at a low driving current, low polarization sensitivity, and low crosstalk in a compact package (see figure). The InP chip containing the optics was flip-chip mounted to a silicon submount to which the SOA electrodes were soldered.

It has low propagation loss of about 3 dB/cm for the passive sections, as well as low and reproducible coupling loss and low reflectivity at the transitions with the active sections. The polarization-dependent loss is only 1.8 ±1 dB. Crosstalk is below -40 dB while the 3-dB bandwidth is about 85 GHz.

The Alcatel researchers tested the chip in a 10-Gbit/s system with an NRZ signal and 215 - 1-long PRBS. The sensitivity at a 10-9 bit-error rate was --14.3 dBm. The group did a further test with 1.6-µs-long optical packets separated by 32-ns guard bands to see if the device could select one out of two packets for switching. The input optical power was -3 dBm. They found that with the 32-ns guard bands, the packet's beginning and end were not corrupted by switching, and that switching occurred in less than 7 ns. Direct measurement of the switching times showed that the SOAs were switched within less than 5 ns.

For more information contact Sabry Khalfallah at

Yvonne Carts-Powell


  1. S. Khalfallah et al., ECOC 2001, postdeadline paper PD.B.1.7.
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