Due to the expected capacity crunch in DWDM optical networks, advanced optical modulation formats which offer high spectral efficiency are being increasingly deployed [1]. At the same time, a trend towards greater reconfigurability in the network is also taking place. Rapid reconfiguration of the optical network using dynamic circuit switching or optical packet switching allows the amplification bandwidth of the fiber to be used more efficiently while also enabling networking functions such as protection and restoration and dynamic bandwidth provisioning. A key component in reconfigurable optical networks, the tunable laser, is required to exhibit a wide tuning range, operate with high output power and high side mode suppression, and to switch quickly and accurately between wavelengths. A number of suitable lasers have been presented [2] including the Sampled Grating Distributed Bragg Reflector (SG-DBR) laser, which we consider in this work. Wavelength switching times of less than 5ns have been demonstrated using the SG-DBR [3] making it suitable for optical packet switching, however its relatively broad linewidth (which is related to phase noise) may reduce its suitability if phase-shift-keying based advanced optical modulation formats are employed in the optical packet switched network. As shown in [4], the linewidth of an SG-DBR laser can broaden significantly during switching and can require up to 3s to return to its steady state value. It was unclear from [4] whether this linewidth broadening was a characteristic of the SG-DBR laser itself, or if it was caused by the drive and control circuitry of the laser. © 2011 IEEE.