A tone wheel for generating electrical pulses at a rate proportional to the rotational speed of a road wheel. Two terminal-fixing bases to fix the two-wired conducting strip and connected electric cables are provided at both ends of the two-wired conducting strip, respectively. 5 to 20 parts by weight of a polyamine-based crosslinking agent with respect to 100 parts by weight of a nitrile rubber including an \u03b1,\u03b2-ethylenically unsaturated nitrile unit and an \u03b1,\u03b2-ethylenically unsaturated dicarboxylic acid monoester unit, and with iodine value of 120 or less. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter andor receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc. The middle, or second semiconductor layer provides a two dimensional electron gas.