Method for testing pump absorption coefficients of double-coated gain fiber

Abstract

The invention provides a method for testing pump absorption coefficients of a double-coated gain fiber. The method comprises the following steps: (S1) welding an LD pump light source tail fiber with a fiber combiner pump tail fiber by virtue of a hectowatt-order LD pump light source needing to be subjected to wavelength testing, coupling pump light into high reflection grating by virtue of a fiber combiner, outputting the pump light from a high reflection grating tail fiber, and recording an output power value as pump coupling power; (S2) selecting a to-be-tested double-coated gain fiber with an initial length L0 less than or equal to 40m, and building a hectowatt-order vibration structure fiber laser device; (S3) recording power values of a fiber output end by virtue of a truncation method when the lengths of the to-be-tested fiber are L0, L1......LN and power values of an input end when a 45-degree dichroic mirror is inserted into the input end, so as to obtain corresponding surplus pump light power under each fiber length; and (S4) carrying out calculation and statistics so as to obtain the pump absorption coefficients of the double-coated gain fiber. According to the method, the influence caused by ASE upon a testing result can be omitted, a testing platform is stable and safe, and the accurate measurement of the pump absorption coefficients of a double-coated gain fiber is realized.

Description

Technical field [0001] The invention relates to the technical field of fiber lasers, in particular to a method for testing the absorption coefficient of a double-clad gain fiber pump. Background technique [0002] Most of the existing test methods use a low-power pump light source to directly couple into the double-clad gain fiber, and use the physical mechanism that "the gain fiber absorbs the pump light will generate spontaneous radiation, and the pump light output is not completely absorbed". Obtain the remaining pump light, calculate the absorption coefficient, and select a more reasonable value as the effective pump absorption coefficient of the fiber under test by repeatedly cutting and repeating the test. [0003] Existing technology 1 (CN105222998B. National University of Defense Technology 2015) This method injects a broadband light source into the fiber under test with full numerical aperture through spatial coupling, cuts the fiber under test multiple times, obtains the ...

AI Technical Summary

Problems solved by technology

The disadvantages of this method are: the steps of adjusting the full numerical aperture injection are too cumbersome, and the spatial optical path makes the test structure not stable enough

The disadvantages of this method are: 1. The ASE spectrum is very wide and has a certain intensity. The dichroic film cannot guarantee 100% high transparency to ASE light, so the measured absorption coefficient is likely to be too small

2. It is biased to use the output at 1 cm behind the doped fiber as the total pump light coupled into the fiber, because the fiber absorbs a lot in a short distance from the pump end face, which may cause the measured value of the absorption coefficient to be biased. Big

3. In the process of continuous truncation, there is a possibility of self-excitation. This scheme uses a two-color chip to eliminate the influence of self-excited oscillating light on the measured value of the remaining pump light, but it brings safety hazards to the platform.

[0008] Generally speaking, there are more or less design defects in the existing technology. First, the low-power pump itself puts forward extremely high requirements on the power meter or spectrometer; The impact of the influence, it is likely to cause the test value of the absorption coefficient to be too large; for example, when the fiber length is selected too short, the mode in the fiber is not stable may cause the test value of the absorption coefficient to be too large; and if the fiber length is selected too long, the test value may be too large. Too small, it is easy to generate self-excited oscillation in the fiber, which poses a threat to the test platform

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