Patent ID: 8175454

Claim:
A system comprising: a first device to: generate a first optical signal at a first wavelength, generate a second optical signal at a second wavelength, combine the first optical signal and the second optical signal to form a first combined signal, and transmit the first combined signal on a first fiber optic link in a first direction; and a second device to: receive, from the first device, the first combined signal, extract, from the first combined signal, the first optical signal at the first wavelength and the second optical signal at the second wavelength, transmit the extracted first optical signal toward a target, receive a reflection of the transmitted first optical signal, from the target, as a reflected first optical signal, combine the reflected first optical signal and the extracted second optical signal to form a second combined signal, and transmit the second combined signal to the first device, on a second fiber optic link in a second direction opposite the first direction, where the first device is further to: receive, from the second device, the second combined signal; and split the second combined signal to separate the reflected first optical signal at the first wavelength and the second optical signal at the second wavelength, where the first device and the second device operate in a fiber optic network that includes multiple optical amplifiers along the first fiber optic link and the second fiber optic link, and where the second optical signal prevents automatic laser shutdown of at least one of the multiple optical amplifiers.