Continued demands for increased bandwidth have re-sulted in deployment of fiber optic-based networks. The fiber optic lines, driven by solid state lasers, are capable of
very high information density. Highly packed data schemes such as DWDM (dense wavelength division multiplexing) utilize multiple lasers driving a fiber to obtain large multi-
channel data streams. The narrow channel spacing relies on laser wavelength being controlled within 0.1nm (na-nometer). Lasers are capable of this but temperature variation influences operation. Figure 1 shows that laser output peaks sharply vs wavelength, implying that laser wavelength must be controlled well within 0.1nm to main- tain performance. Figure 2 plots typical laser wavelength vs temperature. The 0.1nm/°C slope means that although temperature facilitates tuning laser wavelength, it must not vary once the laser has been peaked. Typically, tem- perature control of 0.1°C is required to maintain laser operation well within 0.1nm.