Abstract
In this paper, we present a study of the crosstalk level of an
acousto-optic tunable filter (AOTF) operating with ultrashort light
pulses (2 ps). Initially, we consider the performance of the device,
with several lengths, operating in the linear and nonlinear regime without loss. Given low pump power (P-O = 1 W), the crosstalk level (XL)
of this device always increases with the length of the AOTF, for three
different device configurations: the soliton regime, the dispersionless
regime, and the linear regime. For shorter devices (L/10 < xi(1.) < L),
the soliton regime presents the lower XL. However, this behavior is
reversed for longer devices, where the filter bandwidth is much shorter
than the pulse bandwidth. For the dispensionless regime and low pump power, tire device with length of xi(L)= L/10 presents the lowest XL. As
one starts increasing the pump power, the XL is increases as a
consequence of the increase of the switched pulse's bandwidth. One would
expect that the presence of nonlinearity leads to the broadening of the
pulse bandwidth associated with the self-phase modulation and, consequently, with the increase of tire XL. For high power (P-O = 9 W),
the switched pulse is also presenting pulse break up. However, in the
limit of high pump powers, all the devices present almost the same XL of
around -1.5 dB. For the soliton regime, in all the devices there is a
decrease of the XL for pump powers around 1 W, which is the energy of
the fundamental soliton. For high pump powers, all devices present a
second peak, where again a decrease of the XL is detected. For the xi(L) = L/10 device, the minimum is around 8 W. The increase of the pump power
results in high-order solitons and pulse compression; in this situation,
the bandwidth of the pulse increases and we can extrapolate the
bandwidth of the device, the XL as increases. The study of the effect of
the XL on the AOTF, operating with ultra-short optical solitons,
provides possibilities for achieving high efficiency in ultrafast
all-optical signal processing, especially for optical switches, filters,
and optical transistors. The acoustic-optic tunable filter (AOTF) has
attracted great attention in recent years, in part because it appears to
be a suitable basis for multiwavelength optical cross-connects. It is
probably the only known tunable falter that is capable of selecting
several wavelengths simultaneously. This capability can be used to
construct a multiwavelength router. (C) 2002 Wiley Periodicals, Inc.
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