Method of computing an effective bandwidth of a multimode fiber

Patent metadata

Field	Value
Publication number	US-9377579-B2
Application number	US-201213652627-A
Country	US
Kind code	B2
Filing date	Oct 16, 2012
Priority date	Oct 20, 2011
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

A method of assessing the power penalty at a given bit error rate of a multimode fiber including measuring a set of elementary fiber responses corresponding to different offset launches of light over the core radius into the multimode fiber, generating a global fiber response by applying, to the set of elementary fiber responses, a set of weighting coefficients and delays depending on the different offset launches of the elementary fiber responses, and computing a parameter representative of a fiber power penalty from the global fiber response, wherein the set of weighting coefficients includes several subsets of weighting coefficients time delayed relative to one another, wherein at least one relative time delay is not set to zero, and wherein weighting coefficients of each subset depend on the different offset launches of the elementary fiber responses.

First claim

What is claimed is:

1. A method of assessing chromatic and modal dispersions in a multimode fiber for assessing a fiber power penalty at a given bit error rate of the multimode fiber to predict multimode fiber behavior in an optical communication system, the method comprising:
providing the multimode fiber and an artificial light source before a first step;
applying artificial light from the artificial light source to the multimode fiber before the first step;
the first step of measuring differential mode delay by utilizing a test machine to measure a set of elementary fiber responses corresponding respectively to different offset launches of the artificial light over a core radius into the multimode fiber;
a second step of generating a global fiber response by applying, to the set of elementary fiber responses, a set of weighting coefficients and time delays respectively depending on the different offset launches of the elementary fiber responses; and
a third step of computing a parameter representative of the fiber power penalty from the global fiber response;
wherein, in the second step of generating a global fiber response, the set of weighting coefficients includes several subsets of weighting coefficients that are time delayed relative to one another,
wherein at least one relative time delay is not set to zero, and wherein the weighting coefficients of each subset respectively depend on the different offset launches of the elementary fiber responses,
wherein fiber selection is made based on the computed parameter being at least an effective bandwidth and the fiber selection includes fibers having the effective bandwidth between 3000 MHz-km and 6000 MHz-km at 850 nm; and
wherein the method achieves a correlation between predicted values and actual values of the multimode fiber in the optical communication system.

2. The method according to claim 1 , wherein the computed parameter representative of a fiber power penalty is an effective bandwidth of the multimode fiber.

3. The method according to claim 1 , wherein:
each subset of weighting coefficients is applied, to a same set of elementary fiber responses, to generate a partial fiber response corresponding to only one transverse mode of a laser source;
a time delay is applied to each partial fiber response corresponding to only one transverse mode of a laser source; and
the global fiber response is built as a sum of a different delayed partial fiber responses.

4. The method according to claim 1 , wherein respective time delays are computed as products of the respective differences between wavelengths of a laser source and central wavelength of the laser source multiplied by the chromatic dispersion of the fiber.

5. The method according to claim 4 , wherein weighting coefficients and time delays are such that a spectrum width Root Mean Square (RMS) of the laser source is more than 0.2 nm.

6. The method according to claim 4 , wherein a difference between a maximum wavelength and a minimum wavelength of the laser source is more than 0.6 nm.

7. The method according to claim 4 , wherein a weighting function corresponding to the interpolation, between discreet weighting coefficients, of a subset of weighting coefficients, areas under the respective weighting functions are respectively proportional to powers of their corresponding wavelengths of the laser source.

8. The method according to claim 1 , wherein the set of weighting coefficients includes at least four subsets of weighting coefficients.

9. The method according to claim 1 , wherein the set of weighting coefficients includes at most ten subsets of weighting coefficients.

10. The method according to claim 1 , wherein weighting coefficients obtained through numerical optimization including an iteration of calculation steps, for each transverse mode of launched light corresponding to a subset of weighting coefficients, of a difference between simulated and measured launched light power distribution among fiber modes, performed until minimization of weighted sum of calculated differences, relative weighting of calculated differences corresponding to relative emitting power of corresponding transverse modes launched light.

11. The method according to claim 1 , wherein the differential mode delay measurements are performed with a 1 μm step.

12. The method according to claim 1 , wherein a fiber core radius is more than 10 μm.

13. The method according to claim 1 , wherein an additional fiber selection is performed in which only fibers are kept that present an effective modal bandwidth of more than a predetermined threshold.

14. The method according to claim 13 , wherein an additional fiber selection is performed in which only fibers are kept that present an effective modal bandwidth of more than 4700 MHz-km at 850 nm.

Assignees

• Draka Comteq Bv

Inventors

• Molin Denis
• Sillard Pierre
• Bigot-Astruc Marianne

Classifications

• H04B10/079

  using measurements of the data signal · CPC title

• G02B6/0288 Primary

  Multimode fibre, e.g. graded index core for compensating modal dispersion · CPC title

• G02B6/262

  Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements · CPC title

• H04B10/2581

  Multimode transmission · CPC title

• H04B10/073

  using an out-of-service signal (H04B10/071 takes precedence) · CPC title