CN102636337A - Method for measuring optical fiber dispersion - Google Patents

Method for measuring optical fiber dispersion Download PDF

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Publication number
CN102636337A
CN102636337A CN2012101251188A CN201210125118A CN102636337A CN 102636337 A CN102636337 A CN 102636337A CN 2012101251188 A CN2012101251188 A CN 2012101251188A CN 201210125118 A CN201210125118 A CN 201210125118A CN 102636337 A CN102636337 A CN 102636337A
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China
Prior art keywords
optical fiber
light
sample
pump light
transient state
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CN2012101251188A
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Chinese (zh)
Inventor
许孝芳
李宏刚
高永锋
吕柳
任乃飞
周明
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Jiangsu University
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Jiangsu University
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Abstract

The invention discloses a method for measuring optical fiber dispersion, relating to the field of measurement of optical fiber loss. The method disclosed by the invention is based on a femtosecond laser pumping detection technology and is realized through a femtosecond laser system, a beam splitter, a reflecting mirror, a time delay wire, a wave chopper, a photoelectric detector, a phase-locked amplifier, an optical fiber, a sample and a computer system. The photoelectric detector is used for respectively detecting the change conditions of transient reflected light on the surface of the sample before and after the optical fiber is loaded, so that the moments for the sudden change of transient reflectivity under two conditions can be obtained, and the optical fiber dispersion is calculated. The method disclosed by the invention is suitable for measuring the optical fiber dispersion of different materials and is simple in device structure and good in repeatability.

Description

A kind of method of measuring optical fiber chromatic dispersion
Technical field
The present invention relates to the loss measurement of optic fibre field, refer in particular to a kind of method of measuring optical fiber chromatic dispersion, be applicable to the measurement of any kind fibre-optical dispersion.
Background technology
As everyone knows; The development of optical communication be unable to do without the development of optoelectronic device; Many transmission apparatuss in the optical communication require to have good dispersion characteristics, and warbling that the high-order dispersion of optical fiber causes directly has influence on the transmission of light pulse, also have influence on the formation of optical soliton and the compression of light pulse simultaneously.In addition, the growth at full speed of worldwide traffic impels optical fiber communication capacity and speed all need increase substantially, and this just requires CHROMATIC DISPERSION IN FIBER OPTICS is controlled.Because because the existence of chromatic dispersion not only can make output laser light pulse generation broadening, particularly in the ROF optical communication, can cause the cyclical variation of output light amplitude, cause the output energy unstable, the increase of output error rate with the variation of fiber lengths.Usually adopt fiber grating, the chromatic dispersion that dispersion compensator spares such as waveguide micro-ring resonator come compensated optical fiber.Therefore along with to optical fiber research day by day deeply with practicability widely, the test of optical fiber correlation parameter become has been badly in need of the technical matters that solves.And the appearance of the appearance of laser, especially femtosecond laser, for various measuring technology development provide strong tool.Femtosecond laser has the characteristic of ultrafast time response and superelevation peak value; The existence and the influence of thermal diffusion in the time of can fundamentally avoiding light in optical fiber, to transmit on the one hand; On the other hand; The nonlinear interaction of laser and material is occupied an leading position, so femtosecond laser have high precision, characteristics such as the controllability of three-dimensional.After femtosecond laser and the material effect; Excite and the relaxation of charge carrier all are ultrafast processes; The starting point of femtosecond spectroscopic technique is the relevant action effect of the transient state of ultra-short pulse laser and material; Utilize amplitude that it can the detectable signal light field, position mutually and wave vector, also can measurement of species and relevant other information that act on of Laser Transient, like the information of the aspects such as variation, electron motion and atomic nucleus vibration of excited state population number.Patent of invention " a kind of optical fiber optical device chromatic dispersion measurement apparatus and method " (Chinese patent; Number of patent application: 201110268543.8) a kind of fiber optics chromatic dispersion test system and method based on microwave light electronics method is provided; The method of testing of using is based on optical interference; Mainly be to make lightwave signal through having the optical fiber optical device of chromatic dispersion; And in the certain optical path difference of transmission course acquisition, interfere through latter two microwave signal of detector, judge the size of chromatic dispersion through the relation of interference signal and chromatic dispersion.The present invention utilizes femtosecond laser to use light source as measuring, and a kind of brand-new chromatic dispersion measurement method that need not to interfere is provided, and easy to operate, data processing is simple, can measure the chromatic dispersion of various types of optical fiber.
Summary of the invention
The technical matters that the present invention will solve is to have proposed a kind of method based on the technological measuring optical fiber chromatic dispersion of femtosecond laser pump probe.Utilize ultrafast energy density of femtosecond laser and the characteristics of ultrafast time response,, can measure CHROMATIC DISPERSION IN FIBER OPTICS accurately in conjunction with the pump probe technology.This method principle is simple, easy to operate, favorable repeatability, and the chromatic dispersion of energy measurement various types of optical fiber, range of application is very extensive.
The technical scheme that the present invention adopted is, a kind of method of measuring optical fiber chromatic dispersion is provided, and uses the pump light excited sample, and the Electron absorption in the sample produces the non-equilibrium relaxation of electronics behind laser energy, shows as and surveys undergoing mutation of light transient state emissivity.Survey the radiative variation that light is used to characterize sample surfaces.Pass through detector; Lock-in amplifier and computer system to sample surfaces transient state reflectivity signals gather, de-noising, processing; Drawn out transient state reflectance varies (△ R/R) curve, gone out CHROMATIC DISPERSION IN FIBER OPTICS according to the △ R/R value corresponding step size computation of undergoing mutation.
The method based on the technological measuring optical fiber chromatic dispersion of femtosecond laser pump probe that the present invention proposes mainly comprises following content:
(1) is divided into pump light and surveys light two bundles behind the femto-second laser pulse process beam splitter that titanium jewel fs-laser system sends; Both energy density ratios are controlled at about 10:1; Pump light gets into the pump light transmission channel, surveys light and gets into the detection transmission line.
(2) in the pump light transmission channel, continuous pump light is modulated into interrupted square wave train pulse by chopper.If what measure is to load the preceding transient state reflected signal of optical fiber, then interrupted square wave pump light pulse directly transfers to condenser lens.If what measure is the transient state reflected signal behind the loading optical fiber, the pump light pulse of then from chopper, exporting is focused into Optical Fiber Transmission through condenser lens earlier, from optical fiber, transfers to condenser lens after the outgoing.
(3) will survey light via a corner cube mirror after, enter into the time delay light path, mainly be the time delay of surveying light through step motor control, so that form an optical path difference between pump light and the detection light.
(4) pump light with survey light respectively from separately transmission channel outgoing after condenser lens converges to the sample surfaces same point, surface reflection is received by detector, gets into lock-in amplifier and computer system.
(5) draw film transient state reflectance varies curve through computer software, and draw CHROMATIC DISPERSION IN FIBER OPTICS according to the corresponding constantly step size computation of reflectivity sudden change in the curve.
This method is with highly sensitive; The femtosecond laser pump probe technology that antijamming capability is strong is used for CHROMATIC DISPERSION IN FIBER OPTICS is tested; Optical fiber dispersion measurement system is placed under the conventional environment of laboratory; Ultrafast reflectance varies process to material sample surface (normally metallic film, like chromium, nickel etc.) is carried out detection study, thereby calculates the chromatic dispersion of testing fiber.Obtain experimental data degree of accuracy height, good reliability through this technology, and method of testing is easy, good reproducibility is applicable to the measurement of various types of optical fiber chromatic dispersion.
Description of drawings
The structured flowchart and the description of drawings of practical implementation of the present invention are following:
Fig. 1 optical fiber dispersion measurement system synoptic diagram;
Fig. 2 pump light transmission channel synoptic diagram;
Fig. 3 surveys the optical transmission pathway synoptic diagram;
Sample surfaces transient state reflectance varies curve under the effect of Fig. 4 femtosecond laser;
Among the figure, 1. titanium jewel fs-laser system 2. beam splitters 3. pump light transmission channels 4. condenser lenses 5. samples 6. catoptrons 7. are surveyed optical transmission pathway 8. computing machines 9. lock-in amplifiers 10. detectors 11. choppers 12. focus lamps 13. optical fiber 14. time delay lines 15. catoptrons 16. catoptrons.
Embodiment
1, adopting peak power output is the pumping source of the Vedi CW laser instrument of 5W as ti sapphire laser; Its operation wavelength is 532nm; The centre wavelength of the titanium jewel femtosecond laser that behind locked mode, obtains is 800nm; Repetition frequency is 82 MHz, single pulse width 30fs, and the output laser energy is controlled at about 330mW.
2, be divided into pump light and survey light two bundles behind the femtosecond laser beam process beam splitter 2 that fs-laser system 1 sends, the about 300mW of the luminous power of pump light, energy is higher, is mainly used in excited sample; Survey the about 30mW of light luminous power, be mainly used in and survey the variable signal that is swashed sample surfaces transient state reflectivity.
3, pump light at first passes through chopper 11; Is that 2000 Hz modulate to pump light with frequency; Continuous pump light is modulated into the interrupted square wave train pulse that dutycycle is 1:1; Then pumping pulse line focus lens 12 back is focused on and gets into optical fiber 13 transmission, from optical fiber 13 outgoing after lens 4 act on sample 5 surfaces after converging.
4, survey light and at first pass through catoptron 6 and catoptron 15; The entry time lag line 14 then, and the time delay line mainly is made up of a stepper motor, 1 step of kinematic accuracy; Per step is 10 μ m; Being converted into temporal resolution is 66.7fs, surveys light through catoptron 16 outgoing of warp again behind the stepper motor, after lens 4 are assembled, acts on sample 5 surfaces equally then.
5, the pump light focused light spot on sample 5 surfaces and detection optical convergence hot spot must overlap, and hot spot is more little good more.
6, the transient state reflected signal of surveying on the sample 5 with detector 10; And convert it into electric signal; Import lock-in amplifier 9 then and carry out denoising Processing, be input to computing machine 8 at last, draw transient state reflectivity (Δ R/R) change curve of sample surfaces with the computing machine special software.
7, calculate the dispersion values of testing fiber.Fibre-optical dispersion; Be that the time delay that produces behind the optical fiber is passed through in light pulse, the expression with .In sample surfaces transient state reflectance varies curve, the horizontal ordinate of curve representes to survey the corresponding concrete moment of light generation transient state reflex time, and with step-length (step) expression, 1 step-length equals 66.7 femtoseconds.Measure and not add step-length corresponding when sample surfaces transient state reflectance varies is undergone mutation before the optical fiber in the pump light transmission channel; And loading step-length corresponding when sample surfaces transient state reflectivity is undergone mutation behind the optical fiber in the pump light transmission channel, the time delay that fibre-optical dispersion causes is represented to be with step-length: .Define according to chromatic dispersion: , can obtain CHROMATIC DISPERSION IN FIBER OPTICS .

Claims (3)

1. the method for a measuring optical fiber chromatic dispersion is characterized in that, concrete steps are following:
A, employing peak power output are the pumping source of the Vedi CW laser instrument of 5W as ti sapphire laser; Its operation wavelength is 532nm; The centre wavelength of the titanium jewel femtosecond laser that behind locked mode, obtains is 800nm; Repetition frequency is 82 MHz, single pulse width 30fs, and the output laser energy is controlled at about 330mW;
Be divided into pump light behind the femtosecond laser beam process beam splitter (2) that B, fs-laser system (1) send and survey light two bundles, the luminous power 300mW of pump light is used for excited sample; Survey light luminous power 30mW, be used to survey the variable signal that is swashed sample surfaces transient state reflectivity;
C, pump light at first pass through chopper (11); Is that 2000 Hz modulate to pump light with frequency; Continuous pump light is modulated into the interrupted square wave train pulse that dutycycle is 1:1; Then pumping pulse line focus lens (12) backs is focused on and gets into optical fiber (13) transmission, from optical fiber (13) outgoing after lens (4) act on sample (5) surface after converging;
D, detection light at first pass through catoptron (6) and catoptron (15); Entry time lag line (14) then, the time delay line mainly is made up of a stepper motor, 1 step of kinematic accuracy; Per step is 10 μ m; Being converted into temporal resolution is 66.7fs, surveys light through a warp catoptron (16) outgoing again behind the stepper motor, after lens (4) are assembled, acts on sample (5) surface equally then;
The pump light focused light spot on E, sample (5) surface overlaps with detection optical convergence hot spot;
F, survey the transient state reflected signal on the sample (5) with detector (10); And convert it into electric signal; Import lock-in amplifier (9) then and carry out denoising Processing; Be input to computing machine (8) at last, draw transient state reflectivity (Δ R/R) change curve of sample surfaces with the computing machine special software;
The dispersion values of G, calculating testing fiber; Fibre-optical dispersion; Be that the time delay that produces behind the optical fiber is passed through in light pulse; The expression with ; Measure and not add step-length corresponding when sample surfaces transient state reflectance varies is undergone mutation before the optical fiber in the pump light transmission channel; And loading step-length corresponding when sample surfaces transient state reflectivity is undergone mutation behind the optical fiber in the pump light transmission channel, the time delay that fibre-optical dispersion causes is represented to be with step-length: .
2. the method for a kind of measuring optical fiber chromatic dispersion according to claim 1; It is characterized in that; Calculate the dispersion values of testing fiber, in sample surfaces transient state reflectance varies curve, the horizontal ordinate of curve representes to survey the corresponding concrete moment of light generation transient state reflex time; With step-length (step) expression, 1 step-length equals 66.7 femtoseconds.
3. the method for a kind of measuring optical fiber chromatic dispersion according to claim 2; It is characterized in that CHROMATIC DISPERSION IN FIBER OPTICS .
CN2012101251188A 2012-04-26 2012-04-26 Method for measuring optical fiber dispersion Pending CN102636337A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104849027A (en) * 2015-05-14 2015-08-19 河南师范大学 Laser-beat-frequency-based method for chromatic dispersion measurement
CN107271146A (en) * 2017-06-02 2017-10-20 广州广电计量检测股份有限公司 The calibrating installation and equipment of optical fibre dispersion tester
CN107449738A (en) * 2017-06-20 2017-12-08 江苏大学 A kind of dual-beam pump probe experimental system
CN109374134A (en) * 2018-10-30 2019-02-22 北京工业大学 Superfast time resolution transient state reflectance spectrum imaging system

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CN102045109A (en) * 2011-01-19 2011-05-04 武汉虹拓新技术有限责任公司 Optical fiber link online dispersion measuring device

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104849027A (en) * 2015-05-14 2015-08-19 河南师范大学 Laser-beat-frequency-based method for chromatic dispersion measurement
CN104849027B (en) * 2015-05-14 2017-08-15 河南师范大学 A kind of method that dispersion is measured based on laser beat frequency
CN107271146A (en) * 2017-06-02 2017-10-20 广州广电计量检测股份有限公司 The calibrating installation and equipment of optical fibre dispersion tester
CN107449738A (en) * 2017-06-20 2017-12-08 江苏大学 A kind of dual-beam pump probe experimental system
CN109374134A (en) * 2018-10-30 2019-02-22 北京工业大学 Superfast time resolution transient state reflectance spectrum imaging system

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Application publication date: 20120815