Patent ID: 9350446
Filing Date: 2016-05-24
CPC Classification: H04B

Claim Text:
1. A method of selecting an optical signal power for an optical signal carrying traffic encoded on the optical signal in a modulation format, the optical signal to be transmitted across an optical path in an optical communications system, the method comprising: a. providing a probe optical signal at a probe signal power, the probe optical signal carrying test traffic encoded on the probe optical signal in said modulation format; b. transmitting the probe optical signal across the optical path; and c. receiving the probe optical signal at an end of the optical path and measuring a quality indicator corresponding to the probe optical signal, wherein the method comprises implementing steps a. to c. for each of a plurality of different probe signal powers and the method further comprises selecting one of said plurality of probe optical signals based on the measured quality indicators corresponding to the probe optical signals and selecting as the optical signal power for the optical signal an optical signal power substantially the same as the probe signal power of the selected probe optical signal power, wherein said one of the probe optical signals has an optical signal to noise ratio and the method further comprises adding a noise signal to said one of the probe optical signals, the noise signal being arranged to reduce the optical signal to noise ratio, and wherein traffic is encoded on the optical signal at a first bit rate, and test traffic is encoded on one of the plurality of probe optical at a second, lower bit rate.