An apparatus includes a single photonic crystal fiber including a first end, a propagation length, and a second end. The single photonic crystal fiber includes a varying dispersion that varies along the propagation length. The single photonic crystal fiber includes a varying mode field diameter that varies along the propagation length. The first end includes a first dispersion at a pump wavelength, the first dispersion being normal. The second end includes a second dispersion at the pump wavelength, the second dispersion being anomalous. The first end includes a first mode field diameter at the pump wavelength. The second end includes a second mode field diameter at the pump wavelength, the second mode field diameter being smaller than the first mode field diameter.