Application Note 89
April 2001
A Thermoelectric Cooler Temperature Controller
for Fiber Optic Lasers
Climatic Pampering for Temperamental Lasers
Jim Williams
INTRODUCTION
Continued demands for increased bandwidth have resulted 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 multichannel data streams. The narrow channel spacing relies
on laser wavelength being controlled within 0.1nm (nanometer). 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 maintain performance. Figure 2 plots typical laser wavelength
vs temperature. The 0.1nm/В°C slope means that although
temperature facilitates tuning laser wavelength, it must
not vary once the laser has been peaked. Typically, temperature control of 0.1В°C is required to maintain laser
operation well within 0.1nm. Temperature Controller Requirements
The temperature controller must meet some unusual
requirements. Most notably, because of ambient temperature variation and laser operation uncertainties, the controller must be capable of either sourcing or removing heat
to maintain control. Peltier-based thermoelectric coolers …