Hybrid optical amplifier uses PPLN to eliminate Kerr nonlinearity

Hybrid optical amplifier uses PPLN to eliminate Kerr nonlinearity

Researchers at the University of Southampton (England) and the University of Maryland (College Park, MD) have constructed a hybrid Ononlinearity-freeO optical amplifier using

periodically poled lithium niobate (PPLN) and an erbium-doped fiber amplifier (EDFA). The device compensates for Kerr-induced nonlinearity by taking advantage of cascaded nonlinearity in the PPLN. The researchers will describe their experimental device this month in a presentation at the Optical Fiber Communication conference (San Diego, CA).

The first stage of the two-step experiment consisted of amplifying 1.2-ps, bandwidth-limited pulses from a passively modelocked fiber laser in a 2-m-long EDFA and resulted in significant spectral broadening of the input signal. In the second stage of the experiment, the pulse train was passed through a 4-mm-long bulk PPLN crystal with a pitch of 18.3 ?m prior to amplification. The tuning curve for the crystal indicated a negative effective nonlinear refractive index at temperatures in excess of the phase-matching point at 165!C, and the crystal was maintained at about 10!C above phase-matching during the experiment. When the signal was passed through the PPLN prior to amplification, input and output spectra appeared almost identical. Contact Anatoly Grudinin at [email protected].