Abstract: A vehicle is provided including an electronic power steering system, an electronic throttle control system, and a stability control system.

Abstract: A single silica optical fiber (4) is formed in a Sagnac interferometer (2) by forming a fused, dichroic optical fiber coupler (8) having four ports (10, 12, 14 and 16). A 1.3 .mu.m optical data signal is coupled to the port (10) via a dichroic optical fiber coupler (18) which combines it with a 1.53 .mu.m c-w probe signal from laser (16). The coupler (8) splits the 1.53 .mu.m probe signal into two equal intensity, counter-propagating portions and couples the 1.3 .mu.m data signal so it propagates in one direction round the loop (6). The loop (6) exhibits a non-linearity such that the data signal provides a relative phase shift of the counter-propagating c-w probe portions causing a portion of the 1.53 .mu.m signal is switched to port (12). This 1.53 .mu.m switched output provides tapping of the data signal without affecting its intensity.

Abstract: An optical apparatus including a first optical coupling having a first and a second pair of optical communication ports in which substantially equal portions of an optical signal received at a port of one pair of ports are coupled to each port of the other pair of ports; an optical waveguide optically coupling the second pair of ports such that an optical signal leaving either one of the second pair of ports in a first polarization state; a second optical coupling for coupling an optical signal at a second wavelength to the optical waveguide so as to propagate along at least a portion of it in one direction only; and first and second polarizing beam splitters optically coupled to a respective one of the first pair of ports.

Abstract: An all-optical fibre Sagnac antiresonant interferometer (2) is formed from an optical fibre having a non-linear refractive index. The coupler (8) is a dichroic coupler coupling equal portions of a cw optical signal at 1.53 .mu.m from laser (16) to ports (14 and 16) and all of a pulsed optical signal from laser (20 ) to port (14). The intensity of the pulsed optical signal is sufficient to provide a relative phase shift in the counter propagating 1.53 .mu.m signals. The loop (6) is longer than the inverse of the absolute difference in group delays of the cw and pulsed optical so causing a square optical pulse at 1.53 .mu.m to be switched to port (12) of the coupler.

Abstract: An optical coupler comprises at least two waveguides (4,5) arranged so that light couples from one to the other. The waveguides are dissimilar and support different mode fields, and the composition or geometry of the waveguides is varied to determine the particular critical phenomenon characteristic that is required.