CN107976302B - Device and method for detecting absorption spectrum of optical fiber cladding based on all-fiber structure - Google Patents
Device and method for detecting absorption spectrum of optical fiber cladding based on all-fiber structure Download PDFInfo
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- 238000005253 cladding Methods 0.000 title claims abstract description 72
- 238000000862 absorption spectrum Methods 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000001514 detection method Methods 0.000 claims abstract description 45
- 238000001228 spectrum Methods 0.000 claims abstract description 22
- 238000010521 absorption reaction Methods 0.000 claims description 37
- 238000004804 winding Methods 0.000 claims description 19
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- 230000003595 spectral effect Effects 0.000 claims description 5
- 238000012360 testing method Methods 0.000 abstract description 36
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 31
- 150000002910 rare earth metals Chemical class 0.000 abstract description 31
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- 239000007924 injection Substances 0.000 description 1
- 238000004372 laser cladding Methods 0.000 description 1
- 238000003698 laser cutting Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
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Abstract
The invention discloses an optical fiber cladding absorption spectrum detection device and method based on an all-fiber structure, comprising a supercontinuum light source, a first connecting optical fiber, a to-be-detected rare earth doped optical fiber, a second connecting optical fiber and a spectrometer, wherein broadband single-mode laser output by the supercontinuum light source is coupled to a cladding mode through the first connecting optical fiber, is led into the spectrometer after passing through the to-be-detected rare earth doped optical fiber, and is compared with spectra before and after interception to obtain the cladding absorption spectrum of the rare earth doped optical fiber based on a interception method. The detection device and the detection method are based on an all-fiber structure, the device is stable and reliable in structure, the method is simple and efficient, the detection device and the detection method can be widely applied to the cladding absorption spectrum test of double-cladding and multi-cladding optical fibers, and the detection device and the detection method have the potential of being applied to the development and integration of cladding absorption spectrum test equipment.
Description
Technical Field
The invention relates to the technical field of lasers, in particular to an optical fiber cladding absorption spectrum detection device and method based on an all-fiber structure.
Background
Compared with the traditional solid laser, the fiber laser adopts the rare earth doped fiber as the gain medium, so that the fiber laser has the characteristics of good heat dissipation effect, compact structure, easy maintenance and easy realization of high-power single-mode laser output, and has an attractive application prospect in the fields of material processing (laser drilling, laser marking, laser cutting, laser cladding, laser welding and the like), medical treatment, communication, remote sensing, military and the like. Currently, fiber lasers have been industrially applied, and the average annual increase in the market output value exceeds 30% in recent five years, and the fiber lasers are the first of various types of lasers.
The absorption coefficient of the optical fiber is an important performance parameter of the rare earth doped double-cladding optical fiber, can reflect the rare earth doping concentration of the optical fiber, sensitively and conveniently reflect the production condition of the optical fiber preform, and guide the adjustment and improvement of the production process. Furthermore, the length of the rare earth doped fiber used in a fiber laser is determined by the absorption coefficient of the fiber. The optical fiber is overlong, and the nonlinear effect is enhanced; the optical fiber is too short, the pump light absorption is incomplete, the beam quality is poor. Therefore, an appropriate optical fiber length is one of the key factors in designing and manufacturing an optical fiber laser with excellent performance. In summary, the absorption coefficient of the optical fiber and the accurate measurement of the absorption coefficient of the optical fiber are of great significance in the development and use processes of the optical fiber.
In the prior art, the absorption coefficient of an optical fiber is tested on the basis of a cut-off method, a semiconductor pump light or a supercontinuum light source is adopted to be injected into a rare earth doped optical fiber of the optical fiber to be tested, the power before and after the cut-off of the optical fiber is recorded by a power meter or a spectrometer, and the absorption coefficient is obtained through calculation.
In the prior art 1 (CN 105222998A, national defense science and technology university 2015), pump light is injected into an optical fiber to be detected with the length of 1-2 m in a space coupling mode, so that absorption spectra under different length conditions are obtained. The absorption coefficient under a specific wavelength condition is obtained by a linear fitting mode. The disadvantages of this method are: (1) The length of the optical fiber is greatly different from that of the optical fiber laser (generally more than 10 meters), and the data obtained by the test are difficult to directly reference; (2) The specific wavelengths need to be linearly fitted one by one, so that the broadband absorption spectrum is difficult to accurately obtain; (3) The cutting times are more than or equal to 7 times, the cutting times and the welding times are more, the test process is complex and the test period is long.
In the prior art 2 (CN 107238485 a), a semiconductor laser with a wavelength to be measured is connected with a tail fiber of a beam combiner, amplified Spontaneous Emission (ASE) is suppressed by a high-reflection grating, a dichroic mirror separates pump light and laser light, each time, 1 meter is intercepted, at least 6 times of testing is performed, and an absorption coefficient of the fiber is obtained through calculation. The disadvantage of this method is that: (1) A semiconductor laser with a specific wavelength is used as a test light source, so that only the absorption coefficient of a certain specific wavelength can be obtained, and a broadband absorption spectrum cannot be obtained; (2) The method of searching the stable test point by multiple times of measurement is adopted to improve the test precision, but the test steps are complex and the test period is long.
The related prior art also includes (Fu Yongjun, test of pumping absorption of rare earth doped double clad fiber, china laser 37.1 (2010): 166-170).
The above prior art has corresponding drawbacks, including: (1) In the prior art, a beam combiner tail fiber with a fiber core is usually selected, or a test light source is directly injected into a double-clad optical fiber to be tested, so that a light field mode entering the optical fiber to be tested is not a complete cladding mode, and therefore, the measured absorption coefficient cannot accurately reflect the cladding absorption coefficient, but is a weighted sum of the cladding absorption coefficient and the fiber core absorption coefficient; (2) In the prior art, a double-clad optical fiber to be measured is directly connected into a spectrometer or a power meter, the bending curvature of the optical fiber is inconsistent, and the test result of the thin layer absorption coefficient is easy to influence; (3) The prior art generally does not require a coiling mode of the optical fiber, and the bending or stress of the optical fiber is equivalent to the application of an additional refractive index to the optical fiber, so that the accuracy and the stability of the absorption test of the double-clad optical fiber are easily and negatively affected; (4) In the prior art, a space optical path coupling mode is generally adopted at a test light source injection end or a test light source optical signal output end, and the stability of a test device system manufactured based on the technology is insufficient, so that the system maintenance cost of the test device is increased.
Disclosure of Invention
The invention aims at: aiming at the problems, the device and the method for accurately, efficiently and stably detecting and acquiring the rare earth doped double-clad optical fiber cladding absorption spectrum are provided, wherein the front end of the double-clad optical fiber to be detected is connected in a matched manner by adopting a first connecting optical fiber, the rear end of the double-clad optical fiber to be detected is connected with a second connecting optical fiber, the light energy in the double-clad optical fiber to be detected is transmitted to a spectrometer, and the cladding absorption spectrum of the rare earth doped clad optical fiber is acquired by comparing the spectra before and after interception based on an interception method. The technical scheme provided by the invention adopts an all-fiber structure, the device has a stable structure, the method is simple and efficient, the device has the potential of being applied to development and integration of cladding absorption spectrum detection or test equipment, and the coreless fiber and the cylindrical fiber winder are introduced to effectively improve the test accuracy and stability of the fiber, and reduce the cost of the detection device.
The technical scheme adopted by the invention is as follows:
in one aspect, the invention provides an optical fiber cladding absorption spectrum detection device based on an all-fiber structure, which comprises a supercontinuum light source, a first connecting optical fiber, a double-cladding optical fiber to be detected, a second connecting optical fiber and a spectrometer, wherein the supercontinuum light source, the first connecting optical fiber, the double-cladding optical fiber to be detected, the second connecting optical fiber and the spectrometer are respectively connected in sequence.
Further, the double-clad optical fiber to be measured is uniformly and non-overlapped coiled and fixed on a fiber winder, and the fiber winder is a disk-shaped fiber winder, a cylindrical fiber winder or other coiled structure for fixing the optical fiber.
Further, the first connecting optical fiber and the second connecting optical fiber are energy-transmitting optical fibers or coreless optical fibers.
Further, the first connecting optical fiber and the second connecting optical fiber are respectively connected with the cut double-clad optical fiber to be tested; the cut-off length of the double-cladding optical fiber to be measured is determined according to the absorption condition of the optical fiber, and the absorption loss at the observation wavelength is more than or equal to 10dB.
Further, the diameter of the cylindrical fiber winding device is determined according to the diameter of the inner cladding of the double-cladding optical fiber to be measured, and the diameter of the fiber winding device is larger than or equal to 1000.
On the other hand, the invention provides an optical fiber cladding absorption spectrum detection method based on an all-fiber structure, which comprises the following steps:
step S1, selecting a suitable detection device, said device comprising: the device comprises a supercontinuum light source, a first connecting optical fiber, a second connecting optical fiber and a spectrometer;
step S2, the supercontinuum light source, the first connecting optical fiber, the double-clad optical fiber to be tested, the second connecting optical fiber and the spectrometer are connected in sequence respectively;
step S3, turning on the supercontinuum light source and the spectrometer, and recording the length of the double-clad optical fiber to be measured as L after the supercontinuum light source and the spectrometer are stable 0 Spectrum P at the time 0 (λ), where λ is the spectral range of interest for detection.
S4, turning off the supercontinuum light source, intercepting the length of the optical fiber to be detected, and connecting the optical fiber to be detected with the first connecting optical fiber and the second connecting optical fiber again after intercepting the optical fiber to be detected, so as to measure the absorption spectrum of the double-clad optical fiber to be detected when the lengths are different;
re-turning on the super-continuum spectrum light source, measuring and recording the length L after the super-continuum spectrum light source is stable 1 Is defined by the optical fiber spectrum P 1 (λ)；
Step S5, calculating an absorption coefficient alpha according to a formula (1) by using the length of the optical fiber to be measured and the corresponding spectrum:
further, the first connecting optical fiber and the second connecting optical fiber are energy-transmitting optical fibers or coreless optical fibers.
Further, the length of the optical fiber to be tested is intercepted, and the optical fiber to be detected is cut off and then is connected with the first connecting optical fiber and the second connecting optical fiber again, and the method specifically comprises the following steps:
disconnecting a welding point (A) of the front end of the double-clad optical fiber to be tested and the first connecting optical fiber, intercepting the double-clad optical fiber to be tested with the length L from the disconnected point (A) to the rear, cutting the disconnected first connecting optical fiber and the optical fiber to be tested, and then welding the cut first connecting optical fiber and the cut optical fiber to be tested together again with the length L1 of the residual optical fiber;
or disconnecting the fusion point (B) of the rear end of the double-clad optical fiber to be tested and the second connecting optical fiber, cutting the double-clad optical fiber to be tested with the length of L forwards from the disconnection point of the fusion point (B), and the length of the rest optical fiber is L 1 And re-welding the disconnected second connecting optical fiber and the optical fiber to be tested together.
Further, step S2 further includes uniformly and non-overlapping coiling and fixing the double-clad optical fiber to be measured on a fiber winder, where the fiber winder is a disk-shaped fiber winder, a cylindrical fiber winder or other coiled structure for fixing the optical fiber.
Further, the cut-off length L of the double-clad optical fiber to be measured is determined according to the absorption condition of the optical fiber, the cut-off length L satisfies that the absorption loss at the observation wavelength is not less than 10db, and l=l 0 -L 1 ，L 1 /L 0 ≤1/10。
In summary, due to the adoption of the technical scheme, the beneficial effects of the invention are as follows:
compared with the mode of the prior art, the patent has at least one of the following advantages:
1. the technical scheme provided by the invention can be suitable for parameter measurement of double-clad optical fibers with various core-clad sizes, and the obtained cladding absorption spectrum has wide spectral range, and the acquired absorption data information is rich, so that the method is suitable for cladding absorption spectrum test of rare earth doped double-clad optical fibers with various types.
2. According to the technical scheme provided by the invention, the detection device is simple in structure, and detection devices are all common devices and are easy to obtain; the detection method is simple and easy to learn and use; the detection steps are simple, only one time of cutting is needed, and the test period is short.
3. According to the technical scheme provided by the invention, the double-clad fiber cladding with an all-fiber structure is adopted for carrying out absorption spectrum detection, the light field mode injected into the to-be-detected rare earth doped double-clad fiber is the cladding mode, so that the accurate cladding absorption coefficient can be obtained, and the stable and reliable double-clad fiber cladding absorption spectrum detection equipment is easy to integrate.
4. According to the technical scheme provided by the invention, the winding type fiber winder is introduced, and the rare earth doped optical fiber to be detected is fixed in a uniformly winding manner, so that the optical fiber is not easily affected by bending and stress in the detection process, and the detection result is high in accuracy and good in stability.
Drawings
The invention will now be described by way of example and with reference to the accompanying drawings in which:
fig. 1 is a schematic view of an embodiment of a detection device provided by the present invention.
Fig. 2 is a schematic diagram of another embodiment of the detection device provided by the present invention.
FIG. 3 is a schematic diagram of the structure of a double-clad fiber and coreless fiber to be tested.
Fig. 4 is a schematic view of a fiber winder provided by the present invention.
FIG. 5 shows the results of detection of the absorption spectrum of a 20/400 Yb-DCF fiber under different cut lengths.
FIG. 6 shows the result of the reproducibility of the absorption coefficient at 915/976nm provided by the present invention.
Detailed Description
In order to make the technical solution of the present invention better understood by those skilled in the art, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, and based on the embodiments in the present application, other similar embodiments obtained by those skilled in the art without making creative efforts should fall within the scope of protection of the present application.
Example 1
The embodiment is a rare earth doped double-cladding optical fiber cladding absorption spectrum detection device based on an all-fiber structure, and as shown in fig. 1, the device consists of a supercontinuum light source, a first connecting optical fiber, a fiber winder wound with the rare earth doped double-cladding optical fiber to be detected, a second connecting optical fiber and a spectrometer. In this embodiment, the first and second connection fibers are coreless fibers, i.e., first and second coreless fibers, respectively.
The first coreless optical fiber is connected with the supercontinuum light source and the to-be-measured rare earth doped double-clad optical fiber on the fiber winder through the fusion points A1 and A2 respectively.
In another embodiment, as shown in fig. 2, the first coreless fiber may also be connected to the supercontinuum light source and the to-be-measured rare-earth doped double-clad fiber on the fiber winder through a first bare fiber adapter and a fusion point a, respectively.
The second coreless optical fiber is respectively connected with the to-be-measured rare earth doped double-clad optical fiber on the fiber winder and the spectrometer through the fusion point B and the second bare fiber in an adapting way.
The supercontinuum light source and spectrometer should be selected according to the doping element type and the cladding absorption spectrum test range of interest, and the supercontinuum light source and spectrometer should contain the cladding absorption spectrum test range. For example: the test device of Yb-doped double-clad optical fiber should select a supercontinuum light source and a spectrometer with the spectral range at least comprising 900 nm-1000 nm.
The diameter of the cylindrical fiber winding device is determined according to the diameter of the inner cladding of the double-cladding optical fiber to be measured, and in a preferred embodiment, the diameter of the fiber winding device is equal to or larger than 1000 times the diameter of the inner cladding. For example: the winding diameter of the double-clad optical fiber with the diameter of 400 mu m is more than or equal to 40cm, the winding diameter of the double-clad optical fiber with the diameter of 125 mu m is more than or equal to 12.5cm, the winding diameter of the double-clad optical fiber with the diameter of 250 mu m is more than or equal to 25cm, and the winding diameter of the double-clad optical fiber with the diameter of 600 mu m is more than or equal to 60cm.
The first coreless optical fiber and the second coreless optical fiber are respectively connected with the cut-off rare earth doped double-clad optical fiber to be measured; cut-off length L of double-clad optical fiber to be measured 1 The absorption loss at the observation wavelength is more than or equal to 10dB according to the absorption condition of the optical fiber. For example: the absorption coefficient of the commercial Yb-doped double-clad fiber is about 1.2dB/m, and the length of the fiber is more than or equal to 8.33m. In addition, the length of the rare earth doped fiber remaining after cleaving (L 1 ) And the cutoff length L of the rare earth doped optical fiber should satisfy the relation L 1 L is less than or equal to 1/9, that is, the length (L) 1 ) And the total length of the rare-earth doped fiber (L 0 ) Should satisfy the relation L 1 /L 0 ≤1/10。
The coreless fiber should be selected from the same matrix material as the inner cladding of the rare earth doped double-clad fiber to be measured, and the same or similar numerical aperture, which refers to a numerical range that can be determined by one skilled in the art. For example: the rare earth doped silica fiber has an inner cladding diameter of 400 μm and an inner cladding numerical aperture na=0.46, and the coreless fiber selected should be a silica matrix material, the silica cladding diameter being 400 μm, and the numerical aperture na=0.46 between the silica cladding and the coating layer material.
The bare fiber adapter is determined according to the fiber size, and the coreless fiber can be ensured to smoothly pass through the jack of the bare fiber adapter. The welding points are suggested to be processed by a high-performance welding machine, so that better welding quality is ensured.
It should be noted that, in the present embodiment, the optical fiber to be measured is a rare-earth doped double-clad optical fiber, while in other embodiments the optical fiber to be measured may be a multi-clad optical fiber, measurement of the absorption spectrum of the fiber cladding can also be achieved using any of the embodiments of the present invention.
Example 2
A rare earth doped double-cladding optical fiber cladding absorption spectrum detection method based on an all-optical fiber structure comprises the following steps:
step S1, selecting a testing device suitable for the core package size, the numerical aperture, the matrix material, the doping element type and the like of the rare earth doped double-clad optical fiber to be tested, wherein the testing device comprises: the device comprises a supercontinuum light source, a first connecting optical fiber, a second connecting optical fiber, a cylindrical fiber winder and a spectrometer.
Step S2, connecting each optical fiber with an optical device according to a schematic diagram of a detection device: uniformly winding the rare earth doped double-cladding optical fiber to be measured on a cylindrical fiber winder. And cutting and flattening optical fibers at two ends of the fusion joint for connection by adopting an optical fiber cutting knife, and connecting the fusion joint by adopting an optical fiber fusion splicer. And cutting the end face of the optical fiber of the bare fiber adapter in the schematic diagram to be smooth or cutting the end face of the optical fiber of the bare fiber adapter to be 6-10 degrees of bevel angle by adopting an optical fiber cutting knife.
Step S3, turning on the supercontinuum light source and the spectrometer, and recording the length of the double-clad optical fiber to be measured as L after the supercontinuum light source and the spectrometer are stable 0 Spectrum P at (unit m) 0 (λ) (in dBm), where λ is the spectral range of interest for detection.
And S4, turning off the supercontinuum light source. Disconnecting the front-end welding point A of the double cladding to be tested, and intercepting the front-end welding point A from the disconnected part of the welding pointDouble-clad optical fiber to be measured with length L and residual optical fiber length L 1 Cutting the cut coreless optical fiber and the optical fiber to be measured, and then welding the cut coreless optical fiber and the optical fiber to be measured together again; or disconnecting the rear-end fusion point B of the double-clad optical fiber to be tested, cutting the double-clad optical fiber to be tested with the length of L forwards from the fusion point disconnection point, and ensuring that the length of the residual optical fiber is L 1 . Re-welding the cut coreless optical fiber/energy-transmitting optical fiber and the double-clad optical fiber to be measured together, turning on the supercontinuum light source, and recording the cut surplus length as L after the supercontinuum light source is stable 1 Spectrum P at the time 1 (λ)。
The length of the double-clad optical fiber to be measured is cut for measuring optical fiber spectra under different lengths, the cut length L is selected to be an optimal value according to an actual detection test or theoretical analysis, and in a preferred embodiment, the length relation before and after the optical fiber is cut meets L=L 0 -L 1 ，L 1 /L 0 ≤1/10。
S5, calculating an absorption coefficient alpha according to a formula (1) by using the measured length of the to-be-measured double-clad optical fiber and the corresponding spectrum:
fig. 5 shows two types of fiber winding devices with different structures, namely a disc-shaped fiber winding device and a cylindrical fiber winding device, on which the optical fibers to be measured are uniformly wound without overlapping or crossing. It should be noted that in other embodiments, the winder may be a modified structure based on a disk shape and a column shape.
Example 3
The embodiment is to detect 20/400 Yb-DCF cladding absorption spectrum by using a rare earth doped double-cladding optical fiber cladding absorption spectrum detection device based on an all-optical fiber structure.
Step (1) selection of optical fibers and optical devices:
the parameters of the 20/400 Yb-DCF optical fiber to be measured are as follows: the doping element is Yb, the quartz matrix, the fiber core diameter is 20 μm, the inner cladding diameter (edge-to-edge) is 400 μm, the coating diameter is 530 μm, and the inner cladding numerical aperture is 0.46.
The coreless optical fiber and the optical device selected according to the optical fiber to be measured have the following performance parameters: the model of the supercontinuum light source is SC-5, the coverage spectrum range is 400-2400 nm, and the total power is 1W; a bare fiber adapter with a jack diameter of 550 μm; the coreless fiber is quartz substrate, the diameter of the inner cladding is 400 μm, the numerical aperture of the inner cladding is 0.46, and the lengths of the front end and the rear end are 2 meters; the length of the Yb-DCF optical fiber is 13 meters; the diameter of the cylindrical fiber winding device is 50cm; the model of the spectrometer is AQ-6370D, and the coverage wavelength range is 600-1700 nm.
Step (2) winding Yb-DCF optical fiber:
and uniformly winding 13m Yb-DCF optical fibers on a cylindrical fiber winder by adopting an optical fiber rewinder, and fixing by using an adhesive tape.
And (3) connecting the optical fiber with a device:
the coreless optical fiber passes through the FC type bare fiber adapter, the flat angle end face is cut by a cutting knife, the large-core-diameter bare fiber adapter plug is manufactured, the front end is connected with a supercontinuum light source tail fiber jumper wire through a flange plate, and the rear end is connected with a spectrometer. Cutting the other free end face of the two coreless optical fibers and the two free end faces of the 20/400 Yb-DCF optical fiber to be tested, and connecting the two ends of the 20/400 Yb-DCF optical fiber to be tested and the coreless optical fiber by adopting an optical fiber fusion splicer. The 20/400 Yb-DCF and part of coreless optical fibers are wound on a cylindrical fiber winder, and the optical paths are arranged so that the optical fibers are connected naturally without obvious stress and sharp bending.
Step (4) testing the spectrum before truncation:
and (3) turning on an SC-5 supercontinuum light source and an AQ-6370D spectrometer, and setting parameters of the SC-5 supercontinuum light source and the AQ-6370D spectrometer, including light source power, spectrometer resolution, wavelength scanning range, scanning step length, scanning mode and the like. After the SC-5 supercontinuum light source and AQ-6370D work stably, the spectrum when the length of the optical fiber connected into the optical path before the test cut-off is 13 meters is P 0 (λ)。
To verify the stability of the cladding absorption test, a 0.5m length of Yb-DCF fiber was cut from the fusion point B and the coreless fiber was re-fusion spliced. Repeating the above steps for 4 times, and connecting the optical fibers with lengths of L respectively 0i (12.5 m,12m,11.5m,11m,10.5m,10 m) and recording the corresponding spectrum as P 0i (i＝2,3,4,5,6)。
Step (5) testing the cut spectrum:
after the test in step (4) is completed, cutting off the optical fiber to be tested so that the length of the residual optical fiber is L 1 (0.5 m), after the cut optical fiber to be tested is welded with the coreless optical fiber again, repeating the step (4), and recording the spectrum P when the length of the connected optical fiber is 0.5m 1 (λ)。
(6) Calculating the absorption coefficient alpha of Yb-DCF optical fibers under different length conditions:
wherein: p (P) 0i (lambda) is the length L of the optical fiber before cutting 0i (L 0i =13 m,12.5m,12m,11.5m,11m,10.5 m), P 1 (lambda) is the length L of the cut-off connected optical fiber 1 (L 1 =0.5m).
Absorption spectrum of 20/400 Yb-DCF fiber and Yb under different length test 3+ The absorption coefficient at the position of the characteristic absorption peak (915 nm/976 nm) is shown in fig. 5-6, wherein fig. 5 shows the absorption spectrum of 20/400 Yb-DCF optical fiber under the condition of different cut lengths, and fig. 6 shows the repeatability detection result of the absorption coefficient of 915/976nm optical fiber to be detected.
The detection result shows that the rare earth doped optical fiber detection method based on the all-fiber structure provided by the invention is used for actually detecting the 20/400 Yb-DCF optical fiber absorption spectrum:
(1) Can obtain covered Yb 3+ The characteristic peak (915 nm/976 nm) and the water peak (1383 nm) are clad and absorbed, and the obtained test result information is rich;
(2) The detection result accords with Yb3+ absorption spectrum characteristics, the accuracy of the detection result is high;
(3) After 6 times of repeatability detection, the detection values of absorption coefficients of 976nm and 915nm are stable, and the detection repeatability is good.
All of the features disclosed in this specification, or all of the steps in a method or process disclosed, other than mutually exclusive features and/or steps may be combined in any manner.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (3)
1. The optical fiber cladding absorption spectrum detection method based on the all-fiber structure is realized by using an optical fiber cladding absorption spectrum detection device, and is characterized in that the optical fiber cladding absorption spectrum detection device comprises a supercontinuum light source, a first connecting optical fiber, a double-cladding optical fiber to be detected, a second connecting optical fiber and a spectrometer, wherein the supercontinuum light source, the first connecting optical fiber, the double-cladding optical fiber to be detected, the second connecting optical fiber and the spectrometer are respectively connected in sequence;
the first connecting optical fiber is a coreless optical fiber, and the second connecting optical fiber is an energy-transmitting optical fiber or a coreless optical fiber; the first connecting optical fiber and the second connecting optical fiber are respectively connected with the cut double-clad optical fiber to be tested; the cut-off length L of the double-cladding optical fiber to be detected is determined according to the absorption condition of the optical fiber, and the absorption loss at the observation wavelength is more than or equal to 10dB;
the optical fiber cladding absorption spectrum detection method comprises the following steps:
s1, selecting an optical fiber cladding absorption spectrum detection device;
step S2, the supercontinuum light source, the first connecting optical fiber, the double-clad optical fiber to be tested, the second connecting optical fiber and the spectrometer are connected in sequence respectively;
step S3, turning on the supercontinuum light source and the spectrometer, and recording the length of the double-clad optical fiber to be measured as L after the supercontinuum light source and the spectrometer are stable 0 Spectrum P at the time 0 (lambda), where lambda is the spectral range of interest for detection；
S4, turning off the supercontinuum light source, intercepting the length of the double-clad optical fiber to be detected, and connecting the intercepted double-clad optical fiber to be detected with the first connecting optical fiber and the second connecting optical fiber again for measuring the absorption spectrum of the double-clad optical fiber to be detected with different lengths;
re-turning on the super-continuum spectrum light source, measuring and recording the length L after the super-continuum spectrum light source is stable 1 Is defined by the optical fiber spectrum P 1 (λ)；
Step S5, calculating an absorption coefficient according to a formula (1) by utilizing the length of the double-clad optical fiber to be measured and the corresponding spectrum:
the length of the double-cladding optical fiber to be detected is intercepted, and the double-cladding optical fiber to be detected is connected with the first connecting optical fiber and the second connecting optical fiber again after being intercepted, specifically:
disconnecting the fusion point (A) of the front end of the double-clad optical fiber to be tested and the first connecting optical fiber, and intercepting the double-clad optical fiber to be tested with the length of L from the disconnection point (A) backwards, wherein the length of the rest optical fiber is L 1 Cutting the disconnected first connecting optical fiber and the to-be-detected double-clad optical fiber and then welding the cut first connecting optical fiber and the to-be-detected double-clad optical fiber together again;
or disconnecting the fusion point (B) of the rear end of the double-clad optical fiber to be tested and the second connecting optical fiber, cutting the double-clad optical fiber to be tested with the length of L forwards from the disconnection point of the fusion point (B), and the length of the rest optical fiber is L 1 And re-welding the disconnected second connecting optical fiber and the double-cladding optical fiber to be tested together.
2. The method for detecting the absorption spectrum of the optical fiber cladding according to claim 1, wherein the optical fiber of the double cladding to be detected is uniformly and non-overlapped coiled and fixed on a fiber winder, and the fiber winder is a disk-shaped fiber winder and a cylindrical fiber winder; the diameter of the fiber winding device is determined according to the diameter of the inner cladding of the double-cladding optical fiber to be measured, and the diameter of the fiber winding device is more than or equal to 1000.
3. The method for detecting the absorption spectrum of an optical fiber cladding according to claim 2, wherein the cutoff length l=l of the double-clad optical fiber to be detected 0 -L 1 ，L 1 /L 0 ≤1/10。
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| CN116539279B (en) * | 2023-03-13 | 2023-10-20 | 中国工程物理研究院激光聚变研究中心 | Measuring system and measuring method for absorption coefficient of cladding pumping light |
| CN117554034B (en) * | 2024-01-12 | 2024-05-28 | 中国工程物理研究院激光聚变研究中心 | Method, system and device for measuring coupling coefficient of distributed side pumping optical fiber |
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