Abstract: A system and method of protecting all the amplifiers in a link between wavelength routing network elements of an optical network. According to the invention, an optical control channel is added before a plurality of optical amplifier, preferably the first amplifier, in a link. To prevent improper loading of downstream links, the control channel is stripped off at the next wavelength routing network element. The power of the control channel is automatically adjusted using a fast feedback circuit to hold substantially constant the total power of the signal channels and the control channel at the input of the first amplifier following the feedback loop. In this manner, channel loading of all optical amplifiers in the link is maintained substantially constant, and the incidence of error bursts, as might otherwise result when one or more channels are added or dropped due to a network fault or reconfiguration, is substantially reduced.

Abstract: An optical fiber communications system with a plurality of bidirectional channels and a protection channel is disclosed. Each channel has a respective identity which is transmitted in the traffic of that channel and in the event of a protection switch is identified in the protection channel traffic. A protection switch is effected by detecting a channel failure at the receive end of a span, transmitting a protection request on the return channel back to the transmit end of the span, and using this request in a controller for the channel to effect a protection switch, using an individual selector for the channel, if a priority scheme allows. The controllers are enabled or disabled under software control following a protection switch in accordance with the prevailing priority scheme. The arrangement provides for rapid protection switching.

Abstract: An optical fiber communications system with a plurality of bidirectional channels and a protection channel is disclosed. Each channel has a respective identity which is transmitted in the traffic of that channel and in the event of a protection switch is identified in the protection channel traffic. A protection switch is effected by detecting a channel failure at the receive end of a span, transmitting a protection request on the return channel back to the transmit end of the span, and using this request in a controller for the channel to effect a protection switch, using an individual selector for the channel, if a priority scheme allows. The controllers are enabled or disabled under software control following a protection switch in accordance with the prevailing priority scheme. The arrangement provides for rapid protection switching.

Abstract: A method and apparatus for deriving thirteen distinct parameters of a telephone line from current and charge flow measurements on each side of the line, taken during only three successive voltage states applied to both sides thereof through known tip and ring resistors. The derivations enable calculation of any spurious a-c volages, d-c voltages, leakage resistances, and line capacitances between tip and ground, ring and ground, and tip and ring, as well as the frequency of the spurious a-c voltages.

Abstract: A method and apparatus for deriving thirteen distinct parameters of a telephone line from current and charge flow measurements on each side of the line, taken during only three successive voltage states applied to both sides thereof through known tip and ring resistors. The derivations enable calculation of any spurious a-c voltages, d-c voltages, leakage resistances, and line capacitances between tip and ground, ring and ground, and tip and ring, as well as the frequency of the spurious a-c voltages.