Fig. 1. Experiments with 1 m and 5 km of GRIN MMF, 1.4 ps pulses at 1550 nm, 100 pJ pulse energy, lateral shift of 4 μm. (a) Measured near field at 1 m. (b) Measured near field at 5 km. (c) Instantaneous power at 5 km (measured and reconstructed). (d) Reconstructed near field at 5 km.

Fig. 2. (a) Mean power fractions for test with 1.4 ps, 5 km, 100 pJ, shift 4 μm. (b) Test with 70 fs, 830 m, 100 pJ, shift 15 μm. (c) T and μ for the test of case (a) versus pulse energy. (d) T and μ for the test of case (b) versus lateral shift.

Fig. 3. Experiment with 6 and 830 m of GRIN MMF, 70 fs pulses at 1550 nm, 100 pJ pulse energy, and lateral input beam offset of 15 μm. (a) Measured near field at 6 m. (b) Measured near field at 830 m. (c) Instantaneous power at 830 m (measured and reconstructed). (d) Reconstructed near field at 830 m.

Fig. 4. Experiments with 1 m, 830 m, and 5 km of GRIN fiber, with input CW beam at 1460 nm, 1 μW power, an input beam diffuser, and a lateral shift of 15 μm.

Fig. 5. Experiments with 5 km of GRIN MMF, 70 fs pulses at 1550 nm, lateral shift of 10 μm. (a)–(c) Measured near field, output power, and mean modal power fraction for input pulse energy of 200 pJ. (d)–(f) Measured near field, output power, and mean modal power fraction for input pulse energy of 1.3 nJ, corresponding to the formation of a multimode soliton.