EVEN DARK PULSES

Even dark pulses,[#!KA!#,#!WA!#] which are symmetric functions of time centered around the pulse, can be simply generated by driving the MZI with a short electric pulse. In this case, only an intensity modulation that gives a dip of optical power under the constant background is required.

The propagation characteristics of even dark pulses are different from those of odd dark solitons. Generally, even dark pulses split into pairs of secondary dark solitons without the formation of a primary dark soliton. The energy of the input dark pulse is then redistributed into a certain number of paired secondary dark solitons. Secondary dark solitons, which are called gray solitons[#!TB!#] have nonzero intensity of pulse centers. ...

If we define the amplitudes of the secondary soliton pairs as

κn = κ0 - Δn,     (10)

then the nth order secondary pulse shape (n = 1, 2, 3, ...) has the form
un(z, t) = κ0$\displaystyle {(\lambda_n - i \nu_n )^2 - \nu_n \,{\rm exp} [ 2 \nu_n (t-t_{n0}... ...lambda_{n} z)] \over 1 + \nu_n\, {\rm exp} [ 2 \nu_n (t-t_{n0} - \lambda_n z)]}$eiz,     (11)

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