Building a Swept-Wavelength System

A swept-wavelength system is similar to the traditional step-and-measure system in that you’ll need a tunable laser source, the device you want to test, some photoreceivers or power sensors (the number depends on the number of output ports in your device) such as the Model 2103, and a data-acquisition and display system. The swept-wavelength system differs from the step-and-measure system only in the specific requirements of the source and photoreceivers. In the step-and-measure system, the source is “stepped” through the wavelength range, dwelling for a period of time at a number of specified wavelengths while data is taken. In the swept-wavelength system, the source is tuned continuously through the wavelength range of interest at a constant speed. Data is acquired continuously throughout the sweep.

The most critical component in the system, the source must be able to tune linearly and mode-hop free over the wavelength range. The accuracy of the measurement is directly coupled to the linearity of the laser sweep.

Traditional power meters are too slow for this technique so photoreceivers or power sensors are the best choice. Be sure you choose one with large enough bandwidth to handle the fast sweep of the TLB-6600 (like the 2011-FC, or the 2103).

Data from the photoreceivers is sent into a DAQ card and displayed on your computer. Alternatively, the photoreceivers’ outputs can be displayed directly on a multichannel oscilloscope.