Method for measuring absorption coefficient of few-mode erbium-doped optical fiber

Abstract

The invention discloses a method for measuring an absorption coefficient of a few-mode erbium-doped optical fiber. The method comprises the following steps of: under the pumping condition of a fundamental mode optical fiber, acquiring the gain of fundamental mode signal light by measuring the power of input and output signal light and pump light of the few-mode erbium-doped optical fiber, and calculating a particle number inversion number; then changing the power of the pump light, measuring a change curve of the gain reversing along with the population, fitting the gain G0 according to a curve when rho l is equal to 0, and calculating an absorption coefficient of a fundamental mode optical signal; and finally, calculating mode field distribution of each mode according to the erbium ion concentration and refractive index distribution of the few-mode erbium-doped optical fiber, and further calculating an absorption coefficient of a high-order mode signal light of the few-mode erbium-doped optical fiber according to the measured fundamental mode absorption coefficient.

Description

technical field [0001] The invention belongs to the technical field of optical communication, and more specifically relates to a method for measuring the absorption coefficient of a few-mode erbium-doped optical fiber. Background technique [0002] At present, based on technologies such as wavelength division multiplexing, polarization multiplexing, and multi-level modulation, the transmission capacity of a single fiber can reach 100 Tbit / s, and the transmission capacity of single-mode fiber (SMF) is close to Shannon's limit. To further increase the transmission capacity of optical fibers, it is necessary to utilize a new optical fiber dimension—spatial mode. The mode-division multiplexing (MDM) technology based on few-mode fiber has great potential in improving transmission capacity, and has continuously attracted attention at home and abroad. [0003] The WDM long-distance transmission system based on single-mode fiber is inseparable from the traditional erbium-doped fibe...

AI Technical Summary

Problems solved by technology

Traditionally, the insertion method or the shearing method is used to experimentally measure the absorption coefficient of the erbium-doped fiber. For the few-mode fiber, when the optical signal of the mode to be tested is injected into the few-mode erbium-doped fiber, other crosstalk modes are usually excited, resulting in the insertion method inaccurate measurements

The shearing method will cause loss to the optical fiber and increase the cost of the experiment, especially at the present stage, the price of the few-mode erbium-doped fiber is still very expensive, about 30-50 times that of the single-mode erbium-doped fiber

More importantly, due to the absorption effect of erbium ions in the few-mode erbium fiber, the measurement results of these traditional methods will further introduce errors

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