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Interchannel crosstalk on the acousto‐optic tunable filter (AOTF) for network applications

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 (P0 = 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 < ξL < 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 dispersionless regime and low pump power, the device with length of ξL = 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 the XL. For high power (P0 = 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 ξL = 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 filter that is capable of selecting several wavelengths simultaneously. This capability can be used to construct a multiwavelength router. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 230–235, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10565