| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress the effect on telephone speech signals, which call for particularly rigorous S/N quality requirements, due to S/N deterioration caused by beat noise, which is constant even when a modulation index decreases and decreases only the signal level, and is generated between optical signals in a CMTS due to proximity of optical transmission wavelengths of upstream signals of CMs, in a transmission equalization scheme, which controls the level of electric signals of the CMs and is adopted in upstream signals of an RFOG system, where the optical modulation index is controlled in terms of optical signals of an R-ONU, that is, the modulation index of the R-ONU at a high reception level is decreased in the CMTS. <P>SOLUTION: A transmission path loss L is calculated by detecting a reception level of an optical downstream signal. An R-ONU controls a bias current Ib of a semiconductor laser according to the transmission path loss L, so as to make an OMI constant. Thereby, C/N deterioration of an upstream signal due to increase in the effect of optical heterodyne interference during occurrence of OBI is prevented. <P>COPYRIGHT: (C)2013,JPO&INPIT |
