Future high-speed optical communications systems could benefit from wideband sources that produce high-repetition-rate, chirp-free pulses with high extinction ratios. Systems have been designed to deliver such pulses, but few meet all the requirements.
Jonas Hansryd and Peter A. Andrekson at Chalmers University of Technology (Göteborg, Sweden) developed a pulse source that is wavelength-tunable, robust, and works at 40 GHz with RZ data.1 The system is based on a sinusoidally intensity-modulated fiber optical parametric amplifier (OPA), a nonlinear process in which the gain is exponentially dependent on the pump power (when phase matching is maintained along the length of the fiber).
The researchers used 500 m of highly nonlinear fiber (HNLF), with a signal from a laser tunable between 1480 and 1575 nm, and a modulated pump operating at 1562.4 nm (see figure). The fiber parameters allow the gain slope to be 50 dB/W, with an expected pulse width of 3 ps when the pump source is modulated at 40 GHz. At a signal wavelength of 1547.4 nm and 840-mW average pump power at 1562.7 nm, the system generated stable 40-GHz RZ 2-ps-wide pulses at the signal wavelength.
The spectral width of the pulses at the signal wavelength is 2 nm, and the average output power is up to 15 dBm. The output is tunable over a 37-nm-wide wavelength span, including 1535 to 1555 nm (in the C-band) and 1568 to 1585 nm (in the L-band).
For more information contact Jonas Hansryd at email@example.com.
- J. Hansryd and P. A. Andrekson, Elect. Lett. 37, 584 (Apr. 26, 2001).