SOLITON COMPRESSION AND SPLITTING IN DOUBLE-CORE NONLINEAR-OPTICAL FIBERS

We consider compression of higher-order solitons in asymmetric and sym metric dual-core fibers (couplers) by means of numerical simulations o f the corresponding coupled nonlinear Schrodinger equations. We demons trate that an asymmetric coupler with different dispersion coefficient s in its two cores provides almost the same degree of compression for the soliton tunneling from the core with a larger dispersion into the one with a smaller dispersion as the single-core fiber with the same j ump of the dispersion coefficients, The pedestal around the compressed soliton is smaller when using the coupler; however, the necessary com pression length is larger for the coupler than for the single-core fib er. An advantage of using the coupler is that it allows one to avoid a junction between two pieces of the fiber with different dispersions, which is inevitable if one uses the single-core fiber. Next, we consid er compression of a higher-order soliton in a symmetric coupler. We de monstrate that, using the so-called soliton effect, one can achieve a record compression ratio (approximately 20), which is larger than that for any other known soliton compressor, with a very small share of th e total energy in the pedestal. The corresponding compression length i s still larger than for the single-core fiber, but the compression qua lity is much better. Lastly, the symmetric coupler allows, in some cas es, to split the incoming pulse into two nearly identical compressed p ulses outcoming from the two cores.