A fiber-based laser transmitter has been designed for active remote-sensing spectroscopy. The transmitter uses a master-oscillator- power-amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodically poled nonlinear crystal. The utility of this singlefrequency, wavelength-tunable, power-scalable laser has been demonstrated in a spectroscopic measurement of the diatomic oxygen A-band.

The problem that needed to be addressed was how to measure atmospheric state parameters (like temperature and pressure) from space to get local measurements and global coverage. The only successful laser transmitter that had been used for this type of measurement (remote sensing from an airplane) used dye and alexandrite lasers. These devices were both spectroscopically and mechanically unstable and very inefficient. This transmitter design offers many advantages over this technology.

Fiber-based technology vastly improves mechanical alignment issues because optical path is inside a waveguide that is spliced together and no longer contingent on the relative alignment of bulk optical parts. Many of the components are built to telecommunications industry reliability standards.

This work was done by Mark A. Stephen and James B. Abshire of Goddard Space Flight Center. For further information, contact the Goddard Innovative Partnerships Office at (301) 286-5810. GSC-15710-1

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