MODULATED AND DEPOLARIZED OPTICAL SIGNAL TRANSMISSION SYSTEM

摘要

An optical communication system is described which comprises an optical source; an optical modulator, receiving a transmission signal having frequencies included within a signal band and adapted to emit a modulated optical signal of a predetermined optical bandwidth; an optical transmission line comprising an optical fibre portion; an optical receiver adapted to receive the optical signal in the presence of a predetermined SNR in the signal band, measured in a 5 MHz band. The telecommunication system further comprises, optically connected between the optical modulator and the optical transmission line, a depolarizer comprising two polarization-maintaining optical fibre portions, optically connected with each other in such a manner that the respective polarization axes form an angle of 45.degree., in which the optical bandwidth, lengths and birefringence of the polarizationmaintaining optical fibres are operatively selected so that the SNR at the receiver in the signal band does not differ more than 1 dB from the SNR at the receiver measured in a band of 5 MHz by substituting the optical fibre portion of the transmission line with a passive attenuator of same attenuation.