Abstract: An ISDN alarm notification (fault locating) system in subscriber transmission equipment is connected to switching equipment conforming to TR-303 standard, in particular. The system includes a controller for setting switch options in subscriber transmission equipment externally, in addition to a digital switch and subscriber transmission equipment. The subscriber transmission equipment is provided with a switching equipment interface unit, a control path unit, and an ISDN subscriber interface unit. The controller sets the switch options provided in the switching equipment interface unit, the control path unit, and the ISDN subscriber interface unit. Thereby each switch option performs identical function, corresponding to each digital switch connected to the subscriber transmission equipment.

Abstract: In each node of an optical transmission system: an optical preamplifier has an ALC function for maintaining an optical output level constant and an AGC function for maintaining the gain constant; the operational mode of the optical preamplifier is changed from an ALC mode to an AGC mode after the gain is set in the ALC mode; an optical postamplifier has an AGC function; an optical switch unit performs an optical crossconnect operation; and a thru-light-shutoff control unit makes a switch setting so as to shut off pass-through light in the optical switch unit and stop transmission of an optical signal having an unstable level to a next stage when the optical preamplifier operates in the ALC mode, and clears the switch setting when the operational mode of the optical preamplifier is changed to the AGC mode.

Abstract: A WDM optical transmission apparatus is disclosed utilizing ASE light. The WDM optical transmission apparatus includes a pre-amplifier having two control modes consisting of ALC mode in which the gain of an optical amplifier is controlled such that the total output of the optical amplifier is constant for a multiplexed wavelength number n, and of AGC mode which is a control mode maintaining constant the ratio of an optical input level to an optical output level for the multiplexed wavelength number n; and a post-amplifier having two control modes consisting of ASE mode in which the gain of the post-amplifier is set higher than that in the AGC mode and is set such that the output level of ASE light corresponds to the multiplexed wavelength number n, and of the AGC mode; wherein in the ASE mode, the gain of the pre-amplifier in the WDM optical transmission apparatus at the next node is set under an ALC control utilizing ASE light output from the post-amplifier.

Abstract: The gain control circuit controls the amplification ratio of EDFA based on the results of having measured the input power monitor which monitors the EDFA input optical level which amplifies light and of having measured the output power monitor which monitors the output optical level. The optical pre-amplifier receives a notice of the number of wavelengths from a fore node and a notice of whether the optical post-amplifier of a fore node is in normal operation by a supervisory control signal, and changes over the gain control circuit to either the ALC or AGC mode. When the number of wavelengths changes while the optical pre-amplifier is operating in the ALC mode, the optical pre-amplifier is controlled in the AGC mode using the backed-up amplifier gain. Also, the gain value when the optical pre-amplifier is in routine operation is backed up in an amplifier gain back-up unit and an back-up unit.

Abstract: An apparatus for transmission between subscriber terminals and digital switches that employ a 4:1 time-division-multiplexing scheme includes a main path for carrying signals between the subscriber terminals and digital switches, a control path which is separate from said main path and carries control information for maintenance purpose, and an interface-&-control unit which converts the control information so as to conform to specifications of the said digital switches wherein the conversion of the control information is based on switch settings made to said interface-&-control unit.

Abstract: In each node of an optical transmission system: an optical preamplifier has an ALC function for maintaining an optical output level constant and an AGC function for maintaining the gain constant; the operational mode of the optical preamplifier is changed from an ALC mode to an AGC mode after the gain is set in the ALC mode; an optical postamplifier has an AGC function; an optical switch unit performs an optical crossconnect operation; and a thru-light-shutoff control unit makes a switch setting so as to shut off pass-through light in the optical switch unit and stop transmission of an optical signal having an unstable level to a next stage when the optical preamplifier operates in the ALC mode, and clears the switch setting when the operational mode of the optical preamplifier is changed to the AGC mode.

Abstract: A WDM optical transmission apparatus is disclosed utilizing ASE light. The WDM optical transmission apparatus includes a pre-amplifier having two control modes consisting of ALC mode in which the gain of an optical amplifier is controlled such that the total output of the optical amplifier is constant for a multiplexed wavelength number n, and of AGC mode which is a control mode maintaining constant the ratio of an optical input level to an optical output level for the multiplexed wavelength number n; and a post-amplifier having two control modes consisting of ASE mode in which the gain of the post-amplifier is set higher than that in the AGC mode and is set such that the output level of ASE light corresponds to the multiplexed wavelength number n, and of the AGC mode; wherein in the ASE mode, the gain of the pre-amplifier in the WDM optical transmission apparatus at the next node is set under an ALC control utilizing ASE light output from the post-amplifier.

Abstract: The gain control circuit controls the amplification ratio of EDFA based on the results of having measured the input power monitor which monitors the EDFA input optical level which amplifies light and of having measured the output power monitor which monitors the output optical level. The optical pre-amplifier receives a notice of the number of wavelengths from a fore node and a notice of whether the optical post-amplifier of a fore node is in normal operation by a supervisory control signal, and changes over the gain control circuit to either the ALC or AGC mode. When the number of wavelengths changes while the optical pre-amplifier is operating in the ALC mode, the optical pre-amplifier is controlled in the AGC mode using the backed-up amplifier gain. Also, the gain value when the optical pre-amplifier is in routine operation is backed up in an amplifier gain back-up unit and an back-up unit.

Abstract: At an optical node, variable attenuators VAT 1 to VAT n, TAP 11-1 to TAP 11-n, and photo detectors PD 1 to PD n are disposed corresponding to paths of optical signal components of individual wavelengths that are demultiplexed from a WDM optical signal and that are switched. The TAP 11-1 to TAP 11-n monitor output optical levels of the variable attenuators VAT 1 to VAT n, respectively. The monitored results are processed by a feed-back circuit and output as control signals of the variable attenuators VAT 1 to VAT n.

Abstract: An ISDN alarm notification (fault locating) system in subscriber transmission equipment is connected to switching equipment conforming to TR-303 standard, in particular. The system includes a controller for setting switch options in subscriber transmission equipment externally, in addition to a digital switch and subscriber transmission equipment. The subscriber transmission equipment is provided with a switching equipment interface unit, a control path unit, and an ISDN subscriber interface unit. The controller sets the switch options provided in the switching equipment interface unit, the control path unit, and the ISDN subscriber interface unit. Thereby each switch option performs identical function, corresponding to each digital switch connected to the subscriber transmission equipment.

Abstract: An apparatus for transmission between subscriber terminals and digital switches that employ a 4:1 time-division-multiplexing scheme includes a main path for carrying signals between the subscriber terminals and digital switches, a control path which is separate from said main path and carries control information for maintenance purpose, and an interface-&-control unit which converts the control information so as to conform to specifications of the said digital switches wherein the conversion of the control information is based on switch settings made to said interface-&-control unit.