CN101476978B - Method for measuring geometric parameter of single mode fiber - Google Patents
Method for measuring geometric parameter of single mode fiber Download PDFInfo
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- CN101476978B CN101476978B CN2009100775894A CN200910077589A CN101476978B CN 101476978 B CN101476978 B CN 101476978B CN 2009100775894 A CN2009100775894 A CN 2009100775894A CN 200910077589 A CN200910077589 A CN 200910077589A CN 101476978 B CN101476978 B CN 101476978B
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Abstract
The invention relates to a method for measuring geometric parameters of monomode optical fiber. The method utilizes a common laser as a light source, couples lights into optical fiber through a precise five-dimensional adjusting rack with a lens and an optical fiber griping handle, utilizes CCD or other imaging systems for data acquisition, analyzes the obtained data by a computer, uses a Mathematica mathematical software to process and calculate the measured light intensity distribution graph under visible light and uses a nonlinear least square fitting method to calculate the geometric parameters of the optical fiber, which comprises fiber core refractive index n1, cladding refractive index n2 and fiber core radius a. The method utilizes the common semiconductor laser as a light source,has convenient use, needs little equipment and low cost, and has no strict requirement on environment. The method utilizes visible light wave band for mensuration, avoids using an infrared detector and an infrared laser source with high price, is convenient to adjust by naked eyes at the same time and also convenient to acquire information of light intensity, utilizes CCD to detect the light intensity distribution of the output end of the optical fiber, can carry out full-field mensuration, acquire total data once and avoid using mechanical movable scanning equipment.
Description
Technical field
The present invention relates to a kind of method of measuring geometric parameter of single mode fiber, belong to areas of information technology.
Background technology
Geometric parameter of single mode fiber comprises fiber core refractive index n
1, cladding index n
2, fiber core radius a.They are the most basic parameters of optical fiber, and other characterisitic parameters of optical fiber such as optical property parameter, transmission characteristic parameter all depend on geometric parameter.Therefore the geometric parameter of measuring single-mode fiber is significant.The method of traditional measurement optical fibre refractivity is a near-field scanning technique, need use highly exquisite optical device, the instrument and equipment costliness, and the measuring process complexity, Measuring Time is long.The method of traditional measurement fiber core radius is the back scattering method, only is suitable for the measurement in the optical fiber manufacture process.
Summary of the invention
The invention provides a kind of geometric parameter of measuring single-mode fiber and (comprise fiber core refractive index n
1, cladding index n
2, fiber core radius method a).This method comprises the semiconductor laser light source, the nothing of directive optical fiber lining input end face in such a way, optimum is to be parallel to the incident of the described optical fiber longitudinal axis, make the light distribution image As soon as possible Promising Policy experiment measuring requirement of output, calculate the geometric parameter of single-mode fiber then according to the light distribution of the fiber-optic output that records.
The object of the present invention is achieved like this: a kind of method of measuring geometric parameter of single mode fiber, contain following steps;
Do light source with the general semiconductor laser instrument, optical source wavelength is at visible light wave range;
With the light distribution of CCD detection optical fiber output terminal, carry out measurement of full field;
Use a kind of high-order mode filtering device, make the high-order mode of transmitting in the optical fiber by filtering, only basic mode arrives fiber-optic output;
The image that obtains is handled with computing machine,, calculated the geometric parameter of single-mode fiber, comprise fiber core refractive index n by match is carried out in light distribution
1, cladding index n
2With fiber core radius a;
Carry out match with nonlinear least square method, treat that fitting parameter is fiber core refractive index n
1, cladding index n
2With fiber core radius a; According to Light Wave Guide Theory, calculate the formula I (n of fiber-optic output basic mode light distribution
1, n
2, a), from being extracted the light distribution data point the altimetric image, (n1, n2 a) carry out match to data point, obtain best n with formula I
1, n
2, a value.
Utilize common lasers as light source, optical fiber is advanced in optically-coupled, utilize CCD or other imaging systems to carry out data acquisition, the data that obtain are analyzed with computer, obtain the intensity distributions of image by the precision five dimension adjustment racks and the fibre clip of band lens.With the Mathematica mathematical software of U.S. Wolfram company, the surface of intensity distribution under the visible light that measures is handled and calculated,
Computing method are as follows:
According to Light Wave Guide Theory, operation wavelength is the general single mode fiber of 1310nm, will be operated in the multimode state when visible light injects.The condition of optical fiber single mode transport is:
V＜2.405；
Wherein V is a normalized frequency, is determined by the optical fiber structure parameter:
N in the formula
1Be fiber core refractive index, n
2Be cladding index, a is a fiber core radius.If injecting wavelength is the visible light of 635nm, can calculate operation wavelength by above two formulas is the general single mode fiber of the 1310nm condition that V is satisfied when working under the 635nm wavelength:
V＜4.9615；
Because LP
31The cut-off condition of mould is V=5.316, so LP
31Mould and LP
31Later mould all ends, and may transmit four mould: LP in the optical fiber
01, LP
11, LP
02, LP
21, the cutoff frequency of each mould is respectively 0,2.405,3.832,3.832.
If n
1, n
2, a is known, the field distribution of each mould all can be calculated so, total field distribution is the coherence stack of each mould light field in the optical fiber.
The near field distribution of basic mode is carried out Hankel transform, obtain far-field intensity distribution, it distributes and optical fiber parameter n
1, n
2, a, optical source wavelength λ and light stray fiber axis angle theta relevant, remember that its expression formula is P (n
1, n
2, a; λ; θ).If experiment measuring goes out the far-field distribution figure of optical fiber basic mode, use expression formula P (n so
1, n
2, a; λ; θ) data point that measures is carried out match, just can obtain best n
1, n
2, a.
Calculate the geometric parameter of optical fiber with the nonlinear least square fitting method, comprise fiber core refractive index n
1, cladding index n
2, fiber core radius a.
Described light source is the general semiconductor laser light source, satisfies power greater than 10mW, and wavelength gets final product at visible light wave range.
Described imaging system is that CCD or other can be used for gathering the equipment of intensity signal, and spectral response characteristic will coincide with the semiconductor laser light source.
The beneficial effect that the present invention produces is:
1, the present invention utilizes the general semiconductor laser instrument as light source, and easy to use, devices needed is few, and is with low cost, and environment is not had strict requirement.
2, the present invention utilizes visible light wave range to measure, and avoids using expensive infrared eye and infrared laser light source, is convenient to simultaneously with the naked eye adjust, and also is convenient to the collection of intensity signal.
3, the present invention utilizes the light distribution of CCD detection optical fiber output terminal, can carry out measurement of full field, and the disposable total data of evening up is avoided the scanning device that uses machinery to move.
Description of drawings
Fig. 1 is a schematic diagram of the present invention.
The invention will be further described below in conjunction with drawings and Examples.
Embodiment
Embodiment 1: as shown in Figure 1, in the present embodiment, patent measurement mechanism of the present invention comprises light source, optic fiber coupling unit, high-order mode filtering unit, image acquisition units, graphics processing unit.In the present embodiment, light source is the general semiconductor laser instrument.
In the present embodiment, optic fiber coupling unit comprises precision five dimension adjustment rack and the fibre clip of being with lens, and accurate five dimension adjustment rack models are OM-TZ-112, and the fibre clip model is F1-109, produces by Shanghai friendship ties optical-fiber laser apparatus factory.
In the present embodiment, high-order mode filtering unit is the certain right cylinder of radius.Radius is 3mm-5mm, optical fiber on this right cylinder around one the circle more than.
In the present embodiment, image acquisition units is utilized commercially available common CCD and image pick-up card, can be data transmission to computing machine.
In the present embodiment, graphics processing unit is a common computer, and related software is housed.Comprise software kit (this software and image pick-up card are supporting, obtain this software when buying image pick-up card simultaneously), Mathematica mathematical software that ccd image is gathered.
Principle of work of the present invention and operation steps are:
The first step is pressed Fig. 1 with optical fiber and is connected.
Second step, open light source, adjust accurate five dimension adjustment racks, make the light intensity maximum that is coupled into optical fiber.
The 3rd step, adjust the position of fiber-optic output and image receiving unit, make the photosurface center of fiber-optic output perpendicular alignmnet image receiving unit, fiber-optic output to the distance of photosurface in the 5mm-20mm scope.
In the 4th step, regulate the background light intensity.With the red light emitting diodes irradiation image receiving unit of adjustable brightness, adjust brightness, the image that makes image receiving unit receive has uniform bias light, and the light intensity maximal value is less than the saturation threshold of image receiving unit.
The 5th step, the distance of record fiber-optic output and image capturing system.Images acquired, and the image that collects imported computing machine by image pick-up card, handle with supporting program (software kit and the Mathematica mathematical software of ccd image collection), just can arrive the geometric parameter of optical fiber.This program is to write on the Mathematica mathematical software platform base of U.S. Wolfram company, utilizes the nonlinear least square fitting algorithm to calculate the geometric parameter of optical fiber according to the surface of intensity distribution, and specific algorithm is as described in the top computing method part.
Though at this to be envisioned for the most practical and illustrated embodiments is showed the present invention and described; But should admit, can change within the scope of the invention thus, so the present invention should not be limited to details disclosed herein, but the four corner of its claims be should follow so that comprise any equivalent method.
Claims (4)
1. the method for a photo measure geometric parameter of single mode fiber is characterised in that may further comprise the steps:
Do light source with the general semiconductor laser instrument, optical source wavelength is at visible light wave range;
With the light distribution of CCD detection optical fiber output terminal, carry out measurement of full field;
Use a kind of high-order mode filtering device, make the high-order mode of transmitting in the optical fiber by filtering, only basic mode arrives fiber-optic output;
The image that obtains is handled with computing machine,, calculated the geometric parameter of single-mode fiber, comprise fiber core refractive index n by match is carried out in light distribution
1, cladding index n
2With fiber core radius a;
Carry out match with nonlinear least square method, treat that fitting parameter is fiber core refractive index n
1, cladding index n
2With fiber core radius a; According to Light Wave Guide Theory, calculate the formula I (n of fiber-optic output basic mode light distribution
1, n
2, a), from being extracted the light distribution data point the altimetric image, with formula I (n
1, n
2, a) data point is carried out match, obtain best n
1, n
2, a value.
2. method according to claim 1 is characterised in that: used light detection device can carry out measurement of full field, the light intensity value of disposable measuring optical fiber output terminal each point, thus can obtain the space two-dimensional surface of intensity distribution.
3. method according to claim 1 is characterised in that: used high-order mode filtering device is the certain right cylinder of radius, optical fiber on this right cylinder around a fixing turn.
4. method according to claim 1, be characterised in that: CCD directly links to each other with computing machine by image pick-up card, can show the light distribution image that measures on computers in real time, and can be fast, in real time image is handled, calculate the geometric parameter of optical fiber.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100775894A CN101476978B (en) | 2009-01-23 | 2009-01-23 | Method for measuring geometric parameter of single mode fiber |
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|---|---|---|---|
| CN2009100775894A CN101476978B (en) | 2009-01-23 | 2009-01-23 | Method for measuring geometric parameter of single mode fiber |
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102207375A (en) * | 2010-03-31 | 2011-10-05 | 梁红 | Novel device for measuring diameter of optical fiber |
| CN102297655B (en) * | 2010-06-24 | 2013-04-03 | 上海电缆研究所 | Testing method for performing bidirectional positioning and synchronous testing on fiber end face |
| CN102435986A (en) * | 2011-09-16 | 2012-05-02 | 北方民族大学 | Single-mode fiber automatic coupling system of all-fiber laser radar |
| CN105428982A (en) * | 2015-12-14 | 2016-03-23 | 中国科学院西安光学精密机械研究所 | Semiconductor direct pumping optical fiber laser |
| CN106991249B (en) * | 2017-04-25 | 2020-06-02 | 中国民航大学 | Method for evaluating transverse light intensity distribution of high-order vector mode of optical fiber |
| CN109900215A (en) * | 2019-03-15 | 2019-06-18 | 武汉睿芯特种光纤有限责任公司 | A kind of optical fiber geometric parameter test device |
| CN110455205A (en) * | 2019-08-08 | 2019-11-15 | 上海理工大学 | A kind of fiber end face size detecting method based on Halcon |
| CN110672303B (en) * | 2019-10-31 | 2021-01-22 | 中国电子科技集团公司第四十一研究所 | Optical fiber end face geometric parameter measuring device and method based on annular LED illumination |
| CN112697393A (en) * | 2020-12-25 | 2021-04-23 | 长飞光纤光缆股份有限公司 | Control method for fiber core injection light source in geometric test of optical fiber end face |
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