Abstract: An apparatus and method are provided for communicating data between a first and a second terminal unit, wherein at least one of the terminal units is a mobile terminal unit. The apparatus comprises a base station and a number of antenna units each linked to the base station and operable to transmit, wirelessly, modulated data signals received from the base station, and to forward modulated data signals, received wirelessly, to the base station. The base station has a transmitter for transmitting modulated data signals to each of the antenna units for wireless transmission, a receiver for receiving modulated data signals forwarded by at least one of the antenna units and a demodulator for demodulating received modulated data signals that have been modulated according to a predetermined modulation scheme.

Abstract: This invention relates to optical delay lines, particularly to modifying an optical signal passing through an optical delay line. A method of applying a Doppler shift to an optical signal as it passes through an optical delay line is provided, the method comprising the step of progressively altering a property of the optical delay line during passage of the optical signal therethrough such that the time taken for the optical signal to pass therethrough is progressively lengthened or progressively shortened for successive portions of the optical signal. In addition, an optical delay line is provided that may be used in accordance with the above method.