Abstract: The optical transmission circuit of the present invention has an optical modulator 12 which modulates continuous light at wavelength ?o with a signal at repetition frequency fo Hz and outputs alternating phase-inverted pulse light; a bias voltage applying unit 14 which applies a bias voltage to the optical modulator 12; an optical power spectrum measuring unit 17 having frequency resolution of less than fo Hz which measures the optical power spectrum of light output from the optical modulator 12; and a control circuit which controls the bias voltage via the bias voltage applying unit 14 based on measurements of the power spectrum of the output light of the optical modulator 12, so as to minimize the power intensity of the carrier spectrum component of wavelength ?o, or to maximize the power intensity of the spectrum component in both side bands.

Abstract: In a multiplexing repeater a transmitting part is provided with: GbE receiving circuits 101 and 102 of two channels for receiving GbE signals; FIFO memories 105 and 106 which are connected thereto, respectively, and which can be written and read out by independent clocks of two channels; a multiplexing circuit 109 for multiplexing read-out signals of two channels; an OTU frame generating circuit 111 for mapping the multiplexed two-channel signals over an OTU payload of an OTU frame; and an optical transmitting circuit 115 for transmitting a transmission signal of an OTU frame structure.

Abstract: The optical transmission circuit of the present invention has an optical modulator 12 which modulates continuous light at wavelength &lgr;o with a signal at repetition frequency fo Hz and outputs alternating phase-inverted pulse light; a bias voltage applying unit 14 which applies a bias voltage to the optical modulator 12; an optical power spectrum measuring unit 17 having frequency resolution of less than fo Hz which measures the optical power spectrum of light output from the optical modulator 12; and a control circuit which controls the bias voltage via the bias voltage applying unit 14 based on measurements of the power spectrum of the output light of the optical modulator 12, so as to minimize the power intensity of the carrier spectrum component of wavelength &lgr;o, or to maximize the power intensity of the spectrum component in both side bands.