A transmission apparatus includes a signal power detector configured to detect signal power of a wavelength-multiplexed optical signal to be transmitted to a transmission line, a variable optical attenuator configured to attenuate the wavelength-multiplexed optical signal, and a processor configured to control an attenuation amount of the variable optical attenuator according to the signal power and whether a Raman amplifier in which pumping light is inputted to the transmission line exists.

An apparatus may include a plurality of wavelength selective switches (WSSs). The apparatus may include a plurality of transmitters. The transmitters may transmit a plurality of super-channels. The apparatus may include a plurality of passive power splitters corresponding to the plurality of transmitters. The plurality of passive power splitters may receive the plurality of super-channels. The plurality of passive power splitters may generate a respective set of power-split super-channels for each super-channel of the plurality of super-channels. The plurality of passive power splitters may transmit each power-split super-channel of the respective set of power-split super-channels to a corresponding WSS of the plurality of WSSs. A WSS, of the plurality of WSSs, may receive a plurality of power-split super-channels, of the respective sets of power-split super-channels, from the plurality of passive power splitters. The WSS may selectively route a portion of the plurality of power-split super-channels toward a receiver.

Methods and systems for superchannel power pre-emphasis based on transmission criteria may determine a guardband used when transmitting multiple superchannels over an optical transport network. The guardband values may depend on various transmission criteria, such as a reach distance for the superchannels and a number of reconfigurable add-drop multiplexer nodes over a given optical path. An amount of power pre-emphasis for each superchannel may then be determined based on the actual guardband values used. Certain values used for superchannel power pre-emphasis based on transmission criteria may be pre-calculated and stored in advance.

Methods and systems for replicating current outputs from a photodetector include using a transimpedance (TIA) amplifier to directly generate a TIA output voltage that is linear with optical power at the photodetector. Additionally, a first logarithmic amplifier is used to generate a first output voltage from the photodetector current and a second logarithmic amplifier is used to generate a second voltage from a copy of the photodetector current. The first voltage and the second voltage may be linear in some cases with the optical power in decibels.

Methods and systems for replicating current outputs from a photodetector include using a transimpedance (TIA) amplifier to directly generate a TIA output voltage that is linear with optical power at the photodetector. Additionally, a first logarithmic amplifier is used to generate a first output voltage from the photodetector current and a second logarithmic amplifier is used to generate a second voltage from a copy of the photodetector current. The first voltage and the second voltage may be linear in some cases with the optical power in decibels.

A method includes collecting values for a plurality of optical parameters from a first reconfigurable optical add/drop multiplexer and a second reconfigurable optical add/drop multiplexer connected by an optical link of an optical network, wherein the first reconfigurable optical add/drop multiplexer and the second reconfigurable optical add/drop multiplexer are provided by different vendors, comparing the values to previously collected values for the plurality of optical parameters, determining, based on the comparing, that a change has been detected in a power value of at least one channel of at least one of: the first reconfigurable optical add/drop multiplexer or the second reconfigurable optical add/drop multiplexer, and sending an instruction to at least one of: the first reconfigurable optical add/drop multiplexer or the second reconfigurable optical add/drop multiplexer to adjust a transmit power of the at least one of: the first reconfigurable optical add/drop multiplexer or the second reconfigurable optical add/drop multiplexer.