High speed wavelength conversion utilising an integrated amplifier/DFB laser

Devices with all-optical wavelength conversion capabilities are likely to be essential elements in future wavelength division multiplexed (WDM) systems. The wavelength converter can help increase the efficiency of a WDM network by overcoming the problems of wavelength contention, simplifying network management (wavelengths can be assigned locally rather than globally) and by aiding the achievement of rapid link restoration. Wavelength converters can also be used very efficiently in connection with space switching and are expected to be useful in the joining of separate WDM networks. Wavelength conversion in the 1.55 μm regime has been achieved for the first time in an integrated semiconductor optical amplifier/distributed feedback (SOA/DFB) laser by modulating the output power of the laser with a light beam of a different wavelength externally injected into the SOA section. The advantage of using such a device is that the presence of the integrated SOA helps boost the input signal to high power levels before injection into the laser, affording fast, high extinction ratio switching of the laser light for very low chip input powers via optical modulation of the carrier density within the laser section. Thus the wavelength converted signal is inverted with respect to the input. It is expected that the integration of an amplifier with a multi-section DFB laser will allow the wavelength of the converted signal to be tuned easily, thus affording an enhanced functionality