| 摘要 |
It is an object of the present invention to provide a method for processing optical signals showing real improvement for the transmission of optical signals over long distance at high bit rate but without implying to high costs. This is achieved by the use of a new modulation format (BL-FSK) based on the generation of a frequency modulated signal. It is obtained by driving an electro-optical modulator (e.g. LiNbO3) with a 1-bit delay pre-coded signal (or some other differential pre-coding) in a similar way as for generating DPSK. But unlike for DPSK, it is advantageously make use of the bandwidth limitation of the electrical and electro-optical components, chosen close to a half of the bit rate (B). A ramp-electrical signal is generated that produces the FSK modulation. As a direct consequence of such modulation, a higher spectral efficiency and a lower cost construction of the transmitter is achieved. |
