Setting optical power for an optical communications network channel

A method of controlling an optical power of one or more optical channels of a wavelength division multiplexed communications network, the method comprising:

• obtaining a power correction factor for a said optical channel;
• generating a control signal for transmitting the power correction factor to an optical power regulation device of the network operable to control the optical power of said optical channel;
• and
• at the optical power regulation device, obtaining a desired optical power value for the optical channel, and
• determining an operational power value for the optical power regulation device to regulate the optical power of said optical channel to, the operational power value being equal to the desired optical power value plus the power correction factor,
• wherein the power correction factor is obtained using a power correction factor method of determining a power correction factor for an optical power of an optical channel of a wavelength division multiplexed communications network, the power correction factor method comprising:
• configuring an optical source of the communications network to generate an unmodulated optical carrier signal for the optical channel;
• determining the optical power of the unmodulated optical carrier signal PHIGH;
• configuring the optical source to apply a test modulation pattern to the optical carrier signal to thereby generate a modulated optical carrier signal for the optical channel;
• determining the optical power of the modulated optical carrier signal PMOD;
• and
• determining a power correction factor for the optical channel by determining the difference between the optical power of the unmodulated optical carrier signal and the optical power of the modulated optical carrier signal.

A network element of a wavelength division multiplexed communications network, the network element comprising:

• an optical source operable to generate an optical carrier signal for an optical channel;
• optical power measurement apparatus arranged to receive a portion of the optical carrier signal and to determine the optical power of the optical signal;
• and
• control apparatus operable to:
• i. receive from the optical signal power measurement apparatus an optical power measurement (PHIGH) of an unmodulated optical carrier signal received from the optical source;
• ii. receive from the optical signal power measurement apparatus an optical power measurement (PMOD) for a modulated optical carrier signal received from the optical source;
• and
• iii. determine a power correction factor for the optical channel by determining the difference between the received optical power of the unmodulated optical carrier signal and the received optical power of the modulated optical carrier signal.

A channel monitoring unit for a wavelength division multiplexed communications network, the channel monitoring unit comprising:

• optical power measurement apparatus arranged to receive a portion of an optical carrier signal from an optical source of an optical channel of the network and to determine the optical power of the optical carrier signal;
• and
• a processor unit operable to:
• i. receive from the optical signal power measurement apparatus an optical power measurement (PHIGH) of an unmodulated optical carrier signal received from the optical source;
• ii. receive from the optical signal power measurement apparatus an optical power measurement (PMOD) for a modulated optical carrier signal received from the optical source;
• and
• iii. determine a power correction factor for the optical channel by determining the difference between the received optical power of the unmodulated optical carrier signal and the received optical power of the modulated optical carrier signal.

A non-transitory data carrier having computer readable instructions embodied therein for providing access to resources available on a processor, the computer readable instructions comprising instructions to cause the processor to perform the steps of a method of determining a power correction factor for an optical power of an optical channel of a wavelength division multiplexed communications network, the method comprising:

• configuring an optical source of the communications network to generate an unmodulated optical carrier signal for the optical channel;
• determining the optical power of the unmodulated optical carrier signal PHIGH;
• configuring the optical source to apply a test modulation pattern to the optical carrier signal to thereby generate a modulated optical carrier signal for the optical channel;
• determining the optical power of the modulated optical carrier signal PMOD;
• and
• determining a power correction factor for the optical channel by determining the difference between the optical power of the unmodulated optical carrier signal and the optical power of the modulated optical carrier signal.