A method and system is described. A signal indicative of a failure of a first channel within a plurality of channels of a transmission signal traversing a signal working path in a network is received. The signal working path has a headend node, a tail-end node and an intermediate node. The first channel has a frequency band and a power level prior to failing. The signal working path is associated with a protection path. The protection path includes the intermediate node, optical cross-connects, and a transmitter supplying (ASE) light. The transmitter is activated to supply the ASE light within a frequency band and having a power level corresponding to the frequency band and power level associated with the first channel. The ASE light is supplied to a cross-connect, such that the cross-connect provides a transmission signal including the ASE light.

Disclosed are a control method and an optical fiber amplifier. The optical fiber amplifier is configured to execute the control method. The method comprises: initially correcting a target gain on the basis of a first compensation gain to obtain an initially corrected target gain; when the actual power of the pump laser reaches target power determined on the basis of the initially corrected target gain obtaining, on the basis of a first signal optical power and a second signal optical power, a second compensation gain and a first compensation slope through calculation; correcting the initially corrected target gain again according to the second compensation gain to obtain a corrected target gain; and correcting a target slope according to the first compensation slope to obtain a corrected target slope. This solution can provide high precision control for the gain and the slope of the optical fiber amplifier.

Disclosed are a control method and an optical fiber amplifier. The optical fiber amplifier is configured to execute the control method. The method comprises: initially correcting a target gain on the basis of a first compensation gain to obtain an initially corrected target gain; when the actual power of the pump laser reaches target power determined on the basis of the initially corrected target gain obtaining, on the basis of a first signal optical power and a second signal optical power, a second compensation gain and a first compensation slope through calculation; correcting the initially corrected target gain again according to the second compensation gain to obtain a corrected target gain; and correcting a target slope according to the first compensation slope to obtain a corrected target slope. This solution can provide high precision control for the gain and the slope of the optical fiber amplifier.

Provided is a method for reducing the impact of transient effects in an optical network. The optical network includes at least one span, and an optical signal having a plurality of sub-bands travels through at least one span of the at least one span of the optical network. Each of the at least one span has associated amplifiers and the associated amplifiers are connected to launch optical signals into a remainder of a corresponding optical transmission line. Respectively one of the sub-bands of the optical signal traveling through the span is amplified by one of these associated amplifiers. Each of the associated amplifiers includes at least one control element for controlling gain and tilt of the corresponding amplifier. The method includes the steps of for each span, acquiring an actual value of at least one performance parameter; for each span, respectively computing actual settings for each of the control elements included in the amplifiers associated to the corresponding span based on the actual value of the at least one performance parameter of the corresponding span; and for each span, respectively adjusting the settings of each of the control elements included in the amplifiers associated to the corresponding span based on the computed actual settings for the corresponding control element, in order to reduce the impact of transient effects.

An optical transmission device includes: a selector configured to select a wavelength of a signal to be transmitted to an optical transmission line and output a wavelength-multiplexed signal; an adjustor configured to control a power level of the wavelength-multiplexed signal; and a controller configured to control the adjustor or the selector, wherein the selector selects a wavelength of an optical signal in a second wavelength band different from an existing first wavelength band, and when the second wavelength band is added to or removed from the optical transmission line, the controller controls power of the wavelength-multiplexed signal in the second wavelength band at a slower speed than power control in the first wavelength band.

An optical transmission device includes: a selector configured to select a wavelength of a signal to be transmitted to an optical transmission line and output a wavelength-multiplexed signal; an adjustor configured to control a power level of the wavelength-multiplexed signal; and a controller configured to control the adjustor or the selector, wherein the selector selects a wavelength of an optical signal in a second wavelength band different from an existing first wavelength band, and when the second wavelength band is added to or removed from the optical transmission line, the controller controls power of the wavelength-multiplexed signal in the second wavelength band at a slower speed than power control in the first wavelength band.

The disclosed systems and methods support addition of bands to a multi-band optical interface. The systems and methods can include a multi-band interface device for optical networks. The device can include a multi-band optical amplifier, a C-Band Add/Drop multiplexer, an L-Band Add/Drop multiplexer and an amplifier noise source. The multi-band optical amplifier can be connected to the C-Band Add/Drop multiplexer and connected to the L-Band Add/Drop multiplexer through the amplifier noise source. The amplifier noise source be configured to generate a combination of bulk noise and an input transmission received from the L-Band Add/Drop multiplexer. The gain of the amplifier noise source can depend on the power of the received input transmission. The power of the received input transmission can be increased over a period of time, transitioning the amplifier noise source from acting as a bulk noise source to acting an amplifier.

Disclosed is a method of Controlling a gain of an optical amplifier comprising a gain medium and at least one pumping device. The method comprises the following steps: determining or predicting a change of input signal power to the amplifier, changing the pump power from an initial pump power level to a new pump power level at a first time instant, the initial pump power level being the pump power level applied to the amplifier prior to the change in input signal power, setting the pump power to a second pump power level at a second time instant, wherein the pump power level is varied in an oscillatory manner for at least one period of time starting at a third time instant and ending at a fourth time instant, wherein said third time instant is identical with or later than said first time instant and said fourth time instant is identical with or earlier than said second time instant.

A method (10) of changing operating mode of an optical amplifier in an amplifier chain in an optical network, the optical amplifier initially configured to operate in a first mode to apply a substantially constant first gain to an optical signal comprising a plurality of optical channels, the method comprising, after a time period unique to the optical amplifier within the amplifier chain (12), configuring the optical amplifier to operate in a second mode to apply a second gain to the optical signal so that the optical power of the optical signal is maintained at a target optical power dependent on a current plurality of optical channels in the optical signal (14).

A method (10) of changing operating mode of an optical amplifier in an amplifier chain in an optical network, the optical amplifier initially configured to operate in a first mode to apply a substantially constant first gain to an optical signal comprising a plurality of optical channels, the method comprising, after a time period unique to the optical amplifier within the amplifier chain (12), configuring the optical amplifier to operate in a second mode to apply a second gain to the optical signal so that the optical power of the optical signal is maintained at a target optical power dependent on a current plurality of optical channels in the optical signal (14).