The invention concerns a method for characterizing mode group properties of multimodal light traveling through an optical component, comprising: providing a Mode Group Separating optical fiber in an optical path between a light source and said optical component; launching reference pulses of light with a wavelength t from said light source through said Mode Group Separating optical fiber into said optical component at discrete intervals between a core center and a core radius of said fiber.

The Mode Group Separating optical fiber is a multimode fiber with an -profile graded index core with an -value chosen such that said fiber satisfies the following criterion at the wavelength t:

[00001]$\frac{.Math..Math..Math.L}{.Math..Math.T_{\mathrm{REF}}}>4$

where: is a time delay difference between consecutive mode groups; L is a length of said fiber; T.sub.REF is a Full Width at Quarter Maximum of said reference pulses.

An optical amplifier assembly for determining a parameter of an optical fiber configured to amplify an optical signal being propagated therethrough, the assembly comprising: at least one amplifier pump light source assembly configured to transmit light at a plurality of wavelengths into the optical fiber; a receiver configured to receive light that has propagated through at least part of the optical fiber; and a processor configured to determine the parameter of the optical fiber based on the received light.

An estimation method includes estimating, using a relational equation, a measurement variation in a group delay from one or both of a loss in a target optical fiber and a power of a target light source. The group delay occurs when light generated by the target light source is inputted into the target optical fiber.

There is provided a chromatic dispersion measurement method and system for characterizing an optical fiber link under test. From a proximal end of the optical fiber link, at least one OTDR acquisition is performed, wherein each OTDR acquisition is performed by propagating in the optical fiber link under test, at least one test signal comprising a plurality of light pulses in accordance with a known sequence of pulses and detecting corresponding return light signal from the optical fiber link so as to obtain a trace representing backscattered and reflected light as a function of distance in the optical fiber link under test, and wherein said test signals have mutually different wavelengths. For each test signal and corresponding wavelength, a position of the reflective peak associated with a remote end of the optical fiber link is extracted from the return light signal by calculating a cross-correlation between the known sequence of pulses and the acquired trace. A value of a chromatic dispersion coefficient associated with said optical fiber link is then calculated from values of the extracted positions and corresponding wavelengths.

A digital processor (DP) is configured to obtain a temporal sequence of digital phase distortion measurements of a first optical signal received by a coherent optical receiver (COR) from an optical fiber link, where the first optical signal co-propagates with a second, power-modulated, optical signal in different frequency channels. The DP is configured to estimate a cross-correlation between the temporal sequence of digital measurements and a temporal sequence of powers of the second optical signal for a plurality of relative time shifts between the sequences, and to identify a location along the optical fiber link based on a magnitude of the cross-correlation exceeding a threshold for a particular time shift.

A characteristics estimation device estimates characteristics of an optical fiber transmission line in an optical transmission system in which an optical signal is transmitted from first node to second node via the optical fiber transmission line. The characteristics estimation device includes a processor. The processor generates, based on electric field information indicating an electric field of the optical signal received by the second node via the optical fiber transmission line, a power profile indicating a relationship between power of the optical signal and dispersion amount corresponding to a transmission distance from the first node or the second node. The processor detects a span forming the optical fiber transmission line by using the power profile. The processor calculates, for the detected span, a dispersion coefficient of the optical fiber transmission line by dividing the dispersion amount estimated based on the power profile by a corresponding span length.

An apparatus for generating group velocity dispersion comprising: a group velocity dispersion module composed of an optical fiber, the group velocity dispersion module applying group velocity dispersion to at least one channel signal in which information is encoded to adjust a time difference between adjacent two channel signals; and a controller configured to receive optical fiber length information and control the group velocity dispersion module based on the optical fiber length information, wherein the group velocity dispersion module includes: a group velocity dispersion generation line connected to the input line, separating the input quantum signal into a plurality of channel signals in which information is encoded using a plurality of filters, and generating group velocity dispersion according to a line length difference for each channel signal passing through each channel line to adjust a time difference between the channel signals.