Abstract: A fiber optic communications network includes multiple transmitters and multiple receivers connected by an optical WDM transmission link, the receivers having output channels for providing signals to terminal devices, each receiver including a demodulator to detect and recover a received signal, and the network includes at least one optical amplifier having a shutdown input for actuating the safety shut down of the network upon detecting a disconnect in the transmission line. The system includes circuitry connected to the output of each of the demodulators for sensing the presence of a valid signal and for determining whether a predetermined number of valid signals are present at the demodulators. If the number of valid signals detected is less than the predetermined majority number, the safety shutdown function is actuated.

Abstract: Optical supervisory channels are provided in an optical fiber network by receiving, in a first network element (10), a first optical supervisory channel signal (12) at a first wavelength (&lgr;1) from a first direction (14) on a first optical fiber (16), and by transmitting, from the first network element (10), a second optical supervisory channel signal (18) at a second wavelength (&lgr;2) in a second direction (20) and also on the first optical fiber (16). An amplified optical wavelength division multiplexed transmission system utilizing these supervisory signals divides a revenue-traffic amplifying region of an optical amplifier, with a lower portion being used for transmission in the first direction and an upper portion being used for transmission in the second direction. Both the first and second wavelengths are located outside of a flat-gain amplifying region of the optical amplifier.

Abstract: An optical channel regulator (46) is provided. The optical channel regulator (46) includes a tapped optical coupler (60) receiving an optical line carrying an optical signal. The tapped optical coupler (60) provides substantially all of the optical signal as an output. An electrically variable optical attenuator (64) receives the output of the tapped optical coupler (60) and attenuates the optical signal responsive to a feedback control signal. A second tapped optical coupler (66) receives an output of the attenuator (64). The second coupler (66) provides substantially all of the received optical signal as an output and provides a remaining portion of the optical signal as a tapped output. An optical detector (68) then receives the tapped output and provides an output signal representing the optical signal. A comparator (70) receives the output signal of the optical detector (68) and a reference signal.

Abstract: An optical channel regulator (46) is provided. The optical channel regulator (46) includes a tapped optical coupler (60) receiving an optical line carrying an optical signal. The tapped optical coupler (60) provides substantially all of the optical signal as an output. An electrically variable optical attenuator (64) receives the output of the tapped optical coupler (60) and attenuates the optical signal responsive to a feedback control signal. A second tapped optical coupler (66) receives an output of the attenuator (64). The second coupler (66) provides substantially all of the received optical signal as an output and provides a remaining portion of the optical signal as a tapped output. An optical detector (68) then receives the tapped output and provides an output signal representing the optical signal. A comparator (70) receives the output signal of the optical detector (68) and a reference signal.

Abstract: Various optical amplifier configurations are disclosed. In one configuration, an optical amplifier provides an amplified output signal through use of a pumping device. The output signal is split to an output and a feedback input. The feedback signal is converted to a current which is sensed by a controller. The controller adjusts the amount of current to the pumping device in various instances. In one instance, the current is controlled to prevent overdriving the pumping device. In another instance, the current is controlled to maintain the output signal at a substantially constant level. In another configuration, the optical amplifier is coupled to a ratio computation block which measures the operating efficiency of the pumping device. Additional components detect an undesirable efficiency and provide a warning of the same.

Abstract: Current regulating apparatus for connecting a plurality of different impedance loads in series across a high voltage power source with protection means in the event of the failure in the shorted or open condition of the series connected load portions.

Abstract: An optical channel regulator (46) is provided. The optical channel regulator (46) includes a tapped optical coupler (60) receiving an optical line carrying an optical signal. The tapped optical coupler (60) provides substantially all of the optical signal as an output. An electrically variable optical attenuator (64) receives the output of the tapped optical coupler (60) and attenuates the optical signal responsive to a feedback control signal. A second tapped optical coupler (66) receives an output of the attenuator (64). The second coupler (66) provides substantially all of the received optical signal as an output and provides a remaining portion of the optical signal as a tapped output. An optical detector (68) then receives the tapped output and provides an output signal representing the optical signal. A comparator (70) receives the output signal of the optical detector (68) and a reference signal.