Abstract: In a CWDM optical transmission system of the present invention, in place of an optical signal of at least one wave among a plurality of optical signals corresponding to a CWDM system, a DWDM light output from an additional light transmission unit of a DWDM system is given to a multiplexer via a variable optical attenuator, and multiplexed with the optical signals corresponding to CWDM, to be sent out to a transmission path. At this time, the total power of the DWDM light sent out to the transmission path, is attenuated by the variable optical attenuator, so as to be approximately equal to the power per one wavelength of the CWDM light. On an optical reception terminal, the light propagated through the transmission path is demultiplexed by a demultiplexer, and the DWDM light corresponding to the additional wavelengths is amplified by an optical amplifier and thereafter, received by an additional light reception unit.

Abstract: In a CWDM optical transmission system of the present invention, in place of an optical signal of at least one wave among a plurality of optical signals corresponding to a CWDM system, a DWDM light output from an additional light transmission unit of a DWDM system is given to a multiplexer via a variable optical attenuator, and multiplexed with the optical signals corresponding to CWDM, to be sent out to a transmission path. At this time, the total power of the DWDM light sent out to the transmission path, is attenuated by the variable optical attenuator, so as to be approximately equal to the power per one wavelength of the CWDM light. On an optical reception terminal, the light propagated through the transmission path is demultiplexed by a demultiplexer, and the DWDM light corresponding to the additional wavelengths is amplified by an optical amplifier and thereafter, received by an additional light reception unit.

Abstract: A circuit for generating a discrimination voltage level V.sub.ref which is used as a reference voltage to discriminate between two adjacent logic levels or an input signal which can have a plurality of different voltage levels generally corresponding to a plurality of respective, different logic levels. The frequency at which the levels of the input signals lie in the upper half of the vicinity (i.e., the voltage range from the level V.sub.ref -.DELTA.V to the level V.sub.ref +.DELTA.V) of the discrimination voltage level (i.e., the "upper half" thereof being the voltage range from V.sub.ref to V.sub.ref +.DELTA.V, ".DELTA.V" being a predetermined off-set value) and the frequency at which the levels of the input signals lie in the lower half of the vicinity (i.e., as above defined) of the discrimination level (i.e., the "low half" thereof being the voltage range from V.sub.ref -.DELTA.V to V.sub.ref) are compared, and the discrimination level is controlled so that the above two frequencies are the same.

Abstract: A phase shift circuit used in a regenerating repeater, includes a separating unit for separating an input signal into two separate signals having a phase difference of a phase angle of 90.degree. therebetween, one separated signal having a "0" phase and the other separated signal having a ".pi./2" phase. A distributing unit distributes the "0" phase separated signal and ".pi./2" phase separated signal as three distributed signals having phase difference of phase angles of 90.degree. and 180.degree. therebetween, one distributed signal having a "0" phase and the others being a ".pi./2" phase distributed signal and a ".pi." phase distributed signal. A weighting/compounding unit analyzes the "0" phase distributed signal, ".pi./2" phase distributed signal, and ".pi.

Abstract: Disclosed is a drop/insert processing circuit connected to, for example, a broadband subscriber network including a high speed data loop. The circuit is formed in one body comprising a single shift register, a single clock signal generator, a low speed data insertion control circuit, and a low speed data dropping circuit, whereby the circuit scale is reduced and the control is simplified.