Patent ID: 7450860

Claim:
An apparatus for optical transmission using an FSK scheme, the apparatus comprising: a light generator arranged to generate a first tone signal having a first frequency f 1 and a second tone signal having a second frequency f 2 ; and a light modulator including an asymmetric mach-zehnder modulator containing a first and a second arm of different lengths and arranged to selectively output one of the first tone signal and the second tone signal input from the light generator according to input data, wherein a difference between the first frequency f 1 and the second frequency f 2 corresponds to a clock frequency f d of the data, a length difference between the first arm and the second arm corresponds to ½ bit of the data, and transmittance of the asymmetric mach-zehnder modulator shows a sine waveform repeating a rise and fall with a 2 bit duration according to a wavelength change, and wherein the asymmetric mach-zehnder modulator has a wavelength response characteristic wavelength-shifted according to an applied voltage level, the asymmetric mach-zehnder modulator selectively outputs the first tone signal when a bit of the input data is ‘0’, and the asymmetric mach-zehnder modulator selectively outputs the second tone signal when the bit of the input data is ‘1’.