Out of band fiber characterization using optical amplifier light sources

In an optical transmission system having a plurality of optical sources connected to a first end of an optical transmission fiber and wherein each of said plurality of optical sources is operable at a particular wavelength and in which traffic signals are transmitted from a second end of the optical transmission fiber to the first end, a method of characterizing the optical transmission fiber comprising:

• operating the plurality of optical sources so as to launch a plurality of optical signals into the first end of the optical transmission fiber;
• detecting at the second end of the optical transmission fiber a plurality of residual optical signals resulting from the plurality of optical signals launched into the first end of the optical transmission fiber;
• and
• characterizing the optical transmission fiber on the basis of the plurality of residual optical signals detected at the second end of the optical transmission fiber;
• whereby the optical signals and traffic signals may exist simultaneously allowing the optical transmission fiber to be characterized both in the presence and absence of said traffic signals on the optical transmission fiber.

In an optical transmission system in which at least one Raman pump laser is connected to a receive end of an optical transmission fiber, a method of characterizing the optical transmission fiber comprising:

• operating the at least one Raman pump laser so as to launch Raman pump light into the receive end of the optical transmission fiber;
• detecting at a transmit end of the optical transmission fiber residual Raman pump light resulting from the Raman pump light launched into the receive end of the optical transmission fiber;
• and
• characterizing the optical transmission fiber on the basis of the residual Raman pump light detected at the transmit end of the optical transmission fiber;
• whereby the Raman pump light and traffic signals may exist simultaneously allowing the optical transmission fiber to be characterized both in the presence and absence of said traffic signals on the optical transmission fiber.

In an optical transmission system in which at least one OSC laser source is connected to a first end of an optical transmission fiber and in which traffic signals are transmitted from a second end of the optical transmission fiber to the first end, a method of characterizing the optical transmission fiber comprising:

• operating the at least one OSC laser source so as to launch an optical signal into the first end of the optical transmission fiber;
• detecting at the second end of the optical transmission fiber a residual optical signal resulting from the optical signal launched into the first end of the optical transmission fiber;
• and
• characterizing the optical transmission fiber on the basis of the residual optical signal detected at the second end of the optical transmission fibers;
• whereby the optical signal and traffic signals may exist simultaneously allowing the optical transmission fiber to be characterized both in the presence and absence of said traffic signals on the optical transmission fiber.

In an optical transmission system for transmitting multi-channel optical signals over an optical transmission path, the optical transmission path comprising an optical transmission fiber interposed between a first node and a second node and where in normal operation the multi-channel optical signals are transmitted over the optical transmission fiber from the first node to the second node, a method for characterizing the optical transmission fiber comprising:

• injecting a plurality of counter-propagating Raman pump wavelengths into the optical transmission fiber at the second node for transmission to the first node;
• collecting a phase and power measurement for each of said plurality of counter-propagating Raman pump wavelengths at the first node;
• and
• processing the phase and power measurements collected at the first node for each of said plurality of counter-propagating Raman pump wavelengths so as to compute an estimate of the attenuation profile for the optical transmission fiber;
• whereby the Raman pump wavelengths and traffic signals may exist simultaneously allowing the optical transmission fiber to be characterized both in the presence and absence of said traffic signals on the optical transmission fiber.

An optical transmission system for transmitting multi-channel optical signals over an optical transmission path, the optical transmission path including an optical transmission fiber interposed between a first node and a second node wherein the multi-channel optical signals are transmitted over the optical transmission fiber from the first node to the second node, the system comprising:

• at least one optical light source provided at the second node operable to inject an optical signal into the optical transmission fiber for transmission to the first node;
• at least one photodetector at the first node for detecting a residual optical signal resulting from the optical signal injected into the optical transmission fiber at the second node;
• and
• a processing agent for characterizing the optical transmission fiber on the basis of the optical signal injected at the second node and the residual optical signal detected at the first node;
• whereby the optical signal and traffic signals may exist simultaneously allowing the optical transmission fiber to be characterized both in the presence and absence of said traffic signals on the optical transmission fiber.