The invention concerns a method for characterizing mode group properties of multimodal light traveling through an optical component, comprising: launching a reference pulse of light with a wavelength .sub.t from a light source into said optical component, collecting light signal output by said optical component into a Mode Group Separating optical fiber; detecting light signal output by said Mode Group Separating optical 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 .sub.t:

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

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 pulse.

Methods for estimating the Effective Modal Bandwidth (EMB) of laser optimized Multimode Fiber (MMF) at a specified wavelength, S, based on the measured EMB at a first reference measurement wavelength, M. In these methods the Differential Mode Delay (DMD) of a MMF is measured and the Effective Modal Bandwidth (EMB) is computed at a first measurement wavelength. By extracting signal features such as centroids, peak power, pulse widths, and skews, as described in this disclosure, the EMB can be estimated at a second specified wavelength with different degrees of accuracy. The first method estimates the EMB at the second specified wavelength based on measurements at the reference wavelength. The second method predicts if the EMB at the second specified wavelength is equal or greater than a specified bandwidth limit.

A method of selecting a group of multimode optical fibers, includes comparing a first effective modal bandwidth at a first wavelength of a multimode optical fiber with a first effective modal bandwidth threshold at the first wavelength, the multimode optical fiber being in a group of multimode optical fibers meeting a first OM standard, wherein the first wavelength is from 844 nm to 863 nm; and categorizing the multimode optical fiber as passing a transmission distance requirement if the first effective modal bandwidth of the first multimode optical fiber is greater than or equal to the first effective modal bandwidth threshold; wherein the transmission distance is defined in a transceiver specification, wherein the transceiver specification is one or more of: (a) an 800G bidirectional (BiDi) transceiver specification, or (b) a 100G/lane based MM VCSEL transceiver specification, or (c) a 25Gbaud based transceiver specification, or (d) 50G PAM4 based transceiver specification.

A method for selecting wide-band multimode optical fibers from a single wavelength, the method comprising the following steps of, for each multimode optical fiber obtaining a first DMD plot using a measurement of DMD carried out at a first single wavelength, obtaining from the first DMD plot, a first multimode fiber specification parameter; and for each fiber: obtaining from the first DMD plot, a curve representative of a radial offset delay, called ROD curve, as a function of the radial offset value; applying a linear fit on the ROD curve for at least two radial offset value ranges; obtaining from the linear fit and for each radial offset value range, an average radial offset delay slope, called ROD slope; selecting the multimode optical fibers meeting a first predetermined specification criterion for the first multimode fiber performance parameter, and for which the at least two computed ROD slopes meet a predetermined slope criterion.

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: $\frac{.Math..Math..Math.L}{T_{\mathrm{REF}}}>4$
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.

A method of qualifying an effective bandwidth of a multimode optical fiber at a first wavelength .sub.1, using DMD data of the fiber measured a second wavelength .sub.2. Data representative of a Radial Offset Delay, a Radial Offset Bandwidth and a Relative Radial Coupled Power of the fiber are derived from the DMD data at the second wavelength .sub.2. A transformation is performed on the ROD data and ROB data at the second wavelength .sub.2 to obtain corresponding ROD data and ROB data at the first wavelength .sub.1. An effective bandwidth of the fiber at the second wavelength .sub.2 is computed using the ROD data and the ROB data at the first wavelength .sub.1 and the {tilde over (P)}.sub.DMD data at the second wavelength .sub.2.

A dispersion measuring device includes a pulsed laser light source, a pulse forming unit, a correlator, and an arithmetic operation unit. The pulse forming unit forms an optical pulse train from an optical pulse output from the pulsed laser light source. The correlator detects a temporal waveform of correlated light formed from the optical pulse train. The arithmetic operation unit estimates a wavelength dispersion amount of an optical component disposed between the pulsed laser light source and the correlator, based on the temporal waveform of the correlated light. A dispersion medium gives a group delay dispersion to the optical pulse train to increase the peak intensity of the correlated light to be equal to or greater than a threshold value of the correlator. The pulse forming unit gives a group delay dispersion having a sign opposite to the group delay dispersion given to the optical pulse train to the optical pulse.

A dispersion measuring device includes a pulse forming unit, a light detection unit, a control unit, and an arithmetic operation unit. The control unit selectively outputs a first phase pattern and a second phase pattern. The pulse forming unit forms an optical pulse train from initial pulsed light, the optical pulse train including a plurality of optical pulses having a time difference from each other and having different center wavelengths from each other. The light detection unit detects a temporal waveform of the optical pulse train. The arithmetic operation unit estimates a wavelength dispersion amount of a measurement object based on a feature amount of the temporal waveform of the optical pulse train. When the first phase pattern is output, a pulse having a long center wavelength is generated first. When the second phase pattern is output, a pulse having a short center wavelength is generated first.

A differential mode delay (DMD) measurement system for an optical fiber is provided. The system includes an optical test fiber with a plurality of modes; a single mode light source that provides a continuous light wave signal to a modulator; and a pulse generator that provides an electrical pulse train signal to the modulator and a triggering signal to a receiver. The modulator is configured to generate a modulated optical test signal through the optical fiber based at least in part on the received light wave and pulse train signals, and the receiver is configured to receive the test signal transmitted through the fiber and evaluate the test signal based at least in part on the triggering signal. The system can be employed to create DMD waveform and centroid charts to obtain minEMBc bandwidth information for a fiber within a wavelength range.

The invention relates to a method of measuring time delays with respect to differential mode delay of a multi-mode fiber or a few-mode fiber for at least two different wavelengths. The time delays for each wavelength are measured before the single mode fiber is translated to a next radial offset.