The growth of Internet traffic has led to a dramatic increase of data transmission capability in telecommunication networks. This can be satisfied by using optical communication systems exploiting the almost unlimited transmission bandwidth of optical fibres. In particular, wavelength-division multiplexing (WDM) technology offers an attractive means to increase network capacities. Unfortunately, it remains the essential problem of the limited speed of the electronic switching components. This issue has inspired active research in all optical switching systems. Among several proposed technologies to realize optical switches, the acousto-optic technology seems to be attractive because it presents some interesting characteristics such as short configuration time and no moving parts. Consequently, optical switch sensitivity to the wavelength must be very low in order to ensure efficient temporal demultiplexing for WDM applications. For a few years, we have worked on the development of a 2X2 switch based on an acousto-optic Bragg cell for telecommunication applications. This acousto-optic switch is designed to have a low crosstalk level (< -50 dB) and a short switching time (< 200 ns) @ 1550 nm. The Bragg cell is made of piezoelectric phased array transducers bonded to a crystalline material (TeO2). In order to realize the 2X2 switch, we create two Bragg gratings in the same crystal by driving the transducers with two RF signals f1 and f2 simultaneously. Each diffraction grating acts as a deflector for one of the inputs, and should have no influence on the other. One of the gratings must be tilted with respect to the other one. The tilt is done by driving the transducer elements separately by equal amplitude RF signals (f2) whose phases are increased by an amount of fe degree per element. The switch is a fibered system using two coupling systems, one at the input of the acousto-optic cell and another one at the output made of a Fourier lens and a microlens array. In this paper, we present the wavelength dependence of the acousto-optic switch developed in our laboratory. We characterise both the diffraction efficiency and the coupling efficiency as a function of the optical wavelength over the 1500 - 1600 nm range. First, the diffraction efficiency has been measured when only one and then two Bragg gratings were simultaneously generated in the crystal in order to observe the influence of nonlinear effects. In our experimental configuration, the diffraction efficiency dependence on the wavelength is less than 2 dB over the wavelength range. Moreover, the diffraction efficiency reaches down to -7 dB in the worse case for an acousto-optic power consumption of 1.6 W. Those experimental measurements are well correlated to simulation results. We also measured the coupling efficiency in optical single mode fibre array according to the wavelength. The optical coupling losses increase when the wavelength moves away from the central value 1550 nm because the diffraction direction slightly changes. We show that these coupling losses reduce a lot the bandwidth performance of the switch. The switch bandwidth defined at -1.5 dB is then about 50 nm around 1550 nm.