CN101476877A - Method and structure for precisely measuring optical fiber length - Google Patents
Method and structure for precisely measuring optical fiber length Download PDFInfo
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- CN101476877A CN101476877A CNA2009101149031A CN200910114903A CN101476877A CN 101476877 A CN101476877 A CN 101476877A CN A2009101149031 A CNA2009101149031 A CN A2009101149031A CN 200910114903 A CN200910114903 A CN 200910114903A CN 101476877 A CN101476877 A CN 101476877A
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Abstract
The invention discloses a method and a structure for precisely measuring the length of optical fibers, and belongs to the field of precision measuring instruments. The method is to measure the length of the optical fibers by utilizing the relation that the period of stable mode-locking pulse sequences generated by a passive mode-locking optical fiber laser is directly proportional to the length of a cavity of the laser. The structure consists of an erbium-doped optical fiber, a 980/1,550 nm wavelength division multiplexer, 980 nm pumping laser, a polarization dependent isolator, two polarization controllers and a 10 dB coupler. The optical fiber to be measured is connected with the laser through an optical fiber access port; the polarization controllers are adjusted to acquire stable fundamental-frequency mode-locking pulses; and the length of the optical fiber to be measured can be directly calculated by reading out the pulse period on an oscilloscope. The measurement precision of the method and the structure can reach centimeter order, and the method and the structure can be used for measuring the length of hundreds of kilometers of optical fibers.
Description
The technology neighborhood
The present invention relates to fine measuring instrument and fiber optic communication field, a kind of method and structure of precisely measuring optical fiber length particularly is provided.
Background technology
Optical fiber has high anti-jamming capacity, high transfer rate and extremely low advantages such as transmission error rates in signals transmission, therefore optical fiber communication has become the main transmission mode of various communication networks, is playing the part of vital role in the information highway construction.The optical fiber of laying in land, the ocean is connecting numerous countries and regions, is closely related with our daily life.In each side such as test optical fiber, optical cable laying, trouble shootings, all can relate to the measurement of fiber lengths.In all kinds of Experiments in Fibre Optical, also often involve the problem of choosing suitable fiber lengths.We can say that optical fiber length measuring is all particularly important in nearly all optical fiber communication and optical fiber sensing system accurately.
Since M.K.Barnoski in 1976 and S.M.Jensen propose the notion of optical time domain reflectometer (OTDR), OTDR just is widely applied to the fiber optic network communications field and comes measuring optical fiber length, detects optical cable breakpoint location etc.It is made according to Rayleigh scattering and Fresnel reflection are theoretical dorsad, and measuring accuracy can reach the magnitude of rice, and test specification reaches as high as kilometers up to a hundred.Yet, the OTDR method exists many factors that inevitably cause error, comprise inherent errors such as the graduation error of instrument and Resolution Error, optical fiber group index, back scattering loss factor and optical cable stranding coefficient be isoparametric to be provided with error of calculation that is produced etc.Simultaneously, because the OTDR equipment volume is huger, also limited its application to a certain extent.Subsequently, the someone proposes to use weak coherent light reflection (OLCR) principle to realize the method for high-precision optical fiber length measuring again.OLCR has the not available lot of advantages of OTDR, and it is simple in structure, conveniently makes portable instrument, and its measuring accuracy is higher, can reach 10 μ m.The shortcoming of OLCR is that its dynamic range is smaller, and Maximum Measurable Range has only several centimetres; And owing to OLCR is based upon on the coherent interference condition, its requirement is wanted and can be mated from the polarization state of the signal that interferometer two arms reflect, and in actual conditions, the unmatched situation of polarization may occur, interference will weaken, and this just will influence the OLCR accuracy of test.
The ultimate principle of optical frequency domain reflectometry measurement instrument (OFDR) measuring optical fiber length is to adopt light source is carried out frequency modulation (PFM), and then the signal beat frequency on the detector can increase with the increase of scattering point distance, and the energy on the detector is proportional to this scattering point size.The measuring accuracy of OFDR can reach a millimeter magnitude than OTDR height; Measurement range is bigger than OLCR, can reach several kms, has advantages of high practicability.But OFDR can not record back-scattering light effectively, and will reach good coherence and stability, and system is also very high to the requirement of LASER Light Source; In addition, the coherence of light source can carry out uncertain modulation to receiving spectrum, thereby makes the spatial variations of the scattered signal that will observe produce distortion, has destroyed real spatial information; Add the phase noise of the non-linear and interferometer of frequency sweep, therefore it use and be restricted.
Light coherent field reflection measurement (OCDR) also is a kind of method of high-precision measuring optical fiber length commonly used.Its measuring accuracy is higher, can reach 10 μ m, and it is bigger to measure dynamic range, and signal to noise ratio (S/N ratio) is greater than 100dB, and sensitivity is also higher.But similar to the problem of OFDR, guarantee the coherence that system is good, there is very high requirement in system to light source, is unsuitable for measuring long optical fibers.
The present invention proposes a kind of novel optical fibre length measurement method and structure based on the passive mode-locking principle, this method principle and structure are all very simple, utilize cycle of the stable mode-locking pulse that mode-locked laser produces and laser chamber to grow up to this relation of direct ratio and come measuring optical fiber length, locked mode method measuring optical fiber length ratio of precision is higher, can reach a centimetre magnitude, and can be used for measuring the fiber lengths of kms up to a hundred, simple in structure.
Summary of the invention
The object of the present invention is to provide a kind of method and structure of the precisely measuring optical fiber length based on passive mode-locking fiber laser.Passive mode-locking fiber laser is made of following device: as the Er-doped fiber (1) of gain media, 980/1550nm wavelength division multiplexer (2) is used for a 980nm pumping laser (3) and is coupled into Er-doped fiber, the relevant isolator (4) of the polarization of two ends magnetic tape trailer fibre guarantees that the laser instrument folk prescription is to work with simultaneously as the polarizer, two Polarization Controllers (5,6) be used for controlling polarization state, testing fiber is from optical fiber incoming end (7,8) insert, 10% port (10) the output light mode locking pulse signal of 10dB coupling mechanism (9), photodetector (11) is used for the opto-electronic conversion of light signal, uses oscillograph (12) to observe then.After testing fiber inserts laser cavity, regulate Polarization Controller and be easy to make laser instrument to produce the mode locking pulse sequence.This fiber laser locked mode principle is as follows, the only linear polarization of coming out from the relevant isolator of polarization, by becoming elliptical polarization behind the Polarization Controller, and elliptically polarized light can be thought the stack of two polarized components of left-handed and right-circularly polarized light that intensity is different.When transmitting, this two circular component produces the nonlinear phase shift that varies in size owing to understood by the nonlinear effect effect (comprising) of optical fiber from phase modulation (PM) and cross-phase modulation in optical fiber, thereby the pulse polarization state is changed, and it is not that peak value of pulse place polarization state is rotated greater than the both wings place uniformly that the polarization state of whole pulse different piece changes.Regulate the orientation of fiber-optic output half-wave plate, make that the high strength part of pulse central authorities can be through the polarizer thereafter, and the low-intensity part of both wings is prevented from, and has so just formed equivalent saturable absorber, pulse has obtained compression, forms to stablize the passive mode-locking pulse.
The principle of optical fiber length measuring is to utilize the cycle and the relevant principle of laser cavity inner fiber length of mode locking pulse in the mode locked fiber laser, be L=qcT/n, generally we get vacuum light speed c=299792458m/s, optical fibre refractivity n=1.4680, when integer q=1, pairing T is the mode locking pulse cycle of basic chamber under frequently.The long L of laser chamber is directly proportional with the period T of mode locking pulse, and when the length changes delta L=1m of chamber, the recurrence interval changes Δ T ≈ 4.89672ns.That is to say that as long as the mode locking pulse cycle can be stablized and be reached the ns magnitude, then this optical fiber length measuring instrument degree of accuracy just can reach the magnitude of rice.If accurate again, when Δ T=0.1ns, Δ L ≈ 0.02m=2cm.That is to say that then the degree of accuracy of optical fiber length measuring can reach a centimetre magnitude as long as oscillograph can accurately identify the recurrence interval of 0.1ns to be changed, and the oscillograph that uses in the actual experiment is easy to reach the time precision of 0.1ns.As long as therefore can obtain the stable mode locking pulse cycle, just can accurately extrapolate fiber lengths.When measuring short fiber, can measure the length of segment length's optical fiber in advance, then with this long optical fibers as reference optical fiber, be welded together with tested optical fiber, by measuring the variable quantity of welding front and back fiber lengths, can obtain the length of tested short fiber accurately.
Description of drawings
Fig. 1 is a structural principle synoptic diagram of the present invention.。
Among the figure: 1, Er-doped fiber, 2,980/1550nm wavelength division multiplexer, 3, the 980nm pumping laser, 4, the relevant isolator of polarization, 5, Polarization Controller, 6, Polarization Controller, 7, the testing fiber access interface, 8, the testing fiber access interface, 9,10dB coupling mechanism, 10,10dB coupling mechanism 10% output terminal, 11, photodetector, 12, oscillograph.
Embodiment
With one section known length single-mode fiber that is 12.65km from optical fiber access interface (7,8) connect in the passive mode-locking laser ring cavity, Er-doped fiber length is 12m in the known device, other connects fiber lengths is 15m, so the chamber of whole laser instrument is long is 12.677km, regulate Polarization Controller and pump power, the passive mode-locking laser pulse is stabilized on the fundamental frequency, at this moment repeatedly average on the oscillograph and obtain mode locking pulse period T=62.07878 μ s, be stabilized in the 4th of radix point back, according to formula formula L=qcT/n, if we get c=299792458m/s, n=1.4680 is during q=1, recording fiber lengths is L ≈ 12.6776km, conforms to the optical fiber physical length.
Claims (3)
1, a kind of method and structure of precisely measuring optical fiber length is characterized in that, this device utilizes cycle of the stable mode-locking pulse that mode locked fiber laser produces and laser chamber to grow up to this relation of direct ratio to come measuring optical fiber length.This structure comprises the Er-doped fiber (1) as gain media, 980/1550nm wavelength division multiplexer (2) is used for a 980nm pumping laser (3) and is coupled into Er-doped fiber, the relevant isolator (4) of the polarization of two ends magnetic tape trailer fibre guarantees that the laser instrument folk prescription is to work with simultaneously as the polarizer, two Polarization Controllers (5,6) be used for controlling polarization state, testing fiber is from optical fiber incoming end (7,8) insert, from 10% port (10) the output locked mode light pulse signal of 10dB coupling mechanism (9), after photodetector (11) opto-electronic conversion, observe with oscillograph (12).
2, as right 1 described optical fibre length measurement method and structure, it is characterized in that, passively mode-locked fiber ring laser produces stable fundamental frequency mode locking pulse, observing the mode locking pulse cycle just can calculate total fiber lengths in the laser instrument, deduct original known fiber optic length, thereby obtain tested optical fiber length.
3, as right 1 described optical fibre length measurement method and structure, it is characterized in that, adopt passive mode-locking fiber laser structure measurement fiber lengths, simple in structure, the degree of accuracy height, measurable range is big.
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101944990A (en) * | 2010-09-02 | 2011-01-12 | 吉林大学 | Passive mode-locking fiber laser delay feedback chaotization system based on graphene |
| CN102121851B (en) * | 2010-01-08 | 2012-02-08 | 深圳新飞通光电子技术有限公司 | Method for measuring length difference of array fibers |
| CN102494617A (en) * | 2011-12-09 | 2012-06-13 | 华中科技大学 | Single mode fiber length measuring system |
| CN102636121A (en) * | 2012-03-09 | 2012-08-15 | 中国科学院西安光学精密机械研究所 | High-precision optical fiber length measuring system |
| CN103591895A (en) * | 2013-11-07 | 2014-02-19 | 中国电子科技集团公司第四十一研究所 | Optical fiber length measuring system and measuring method |
| CN104677287A (en) * | 2015-03-05 | 2015-06-03 | 哈尔滨工业大学 | Micro-scale measurement device and method adopting three-core optical fiber grating probe and based on optical fiber ring laser |
| CN104677288A (en) * | 2015-03-05 | 2015-06-03 | 哈尔滨工业大学 | Micro-scale measurement device and method adopting dual-core optical fiber grating probe and based on optical fiber ring laser |
| CN106247949A (en) * | 2016-08-23 | 2016-12-21 | 中国航空工业集团公司西安飞行自动控制研究所 | A kind of full optical fiber interference formula optical fibre length measurement method and device |
| CN106969714A (en) * | 2017-05-02 | 2017-07-21 | 中国航空工业集团公司北京长城计量测试技术研究所 | A kind of method of the fine length of precise measuring |
| CN107289978A (en) * | 2017-06-09 | 2017-10-24 | 南京大学 | A kind of system and method for the survey disturbance based on POTDR |
| CN111595246A (en) * | 2020-07-24 | 2020-08-28 | 武汉昊衡科技有限公司 | Wavelength division multiplexer channel length measuring device and method |
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2009
- 2009-02-03 CN CNA2009101149031A patent/CN101476877A/en active Pending
Cited By (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102121851B (en) * | 2010-01-08 | 2012-02-08 | 深圳新飞通光电子技术有限公司 | Method for measuring length difference of array fibers |
| CN101944990A (en) * | 2010-09-02 | 2011-01-12 | 吉林大学 | Passive mode-locking fiber laser delay feedback chaotization system based on graphene |
| CN101944990B (en) * | 2010-09-02 | 2013-01-16 | 吉林大学 | Passive mode-locking fiber laser delay feedback chaotization system based on graphene |
| CN102494617A (en) * | 2011-12-09 | 2012-06-13 | 华中科技大学 | Single mode fiber length measuring system |
| CN102494617B (en) * | 2011-12-09 | 2014-01-01 | 华中科技大学 | Single mode fiber length measuring system |
| CN102636121A (en) * | 2012-03-09 | 2012-08-15 | 中国科学院西安光学精密机械研究所 | High-precision optical fiber length measuring system |
| CN103591895A (en) * | 2013-11-07 | 2014-02-19 | 中国电子科技集团公司第四十一研究所 | Optical fiber length measuring system and measuring method |
| CN103591895B (en) * | 2013-11-07 | 2017-06-27 | 中国电子科技集团公司第四十一研究所 | A kind of optical fiber length measuring system and measuring method |
| CN104677288A (en) * | 2015-03-05 | 2015-06-03 | 哈尔滨工业大学 | Micro-scale measurement device and method adopting dual-core optical fiber grating probe and based on optical fiber ring laser |
| CN104677287A (en) * | 2015-03-05 | 2015-06-03 | 哈尔滨工业大学 | Micro-scale measurement device and method adopting three-core optical fiber grating probe and based on optical fiber ring laser |
| CN106247949A (en) * | 2016-08-23 | 2016-12-21 | 中国航空工业集团公司西安飞行自动控制研究所 | A kind of full optical fiber interference formula optical fibre length measurement method and device |
| CN106247949B (en) * | 2016-08-23 | 2019-01-25 | 中国航空工业集团公司西安飞行自动控制研究所 | A kind of full optical fiber interference formula optical fibre length measurement method and device |
| CN106969714A (en) * | 2017-05-02 | 2017-07-21 | 中国航空工业集团公司北京长城计量测试技术研究所 | A kind of method of the fine length of precise measuring |
| CN107289978A (en) * | 2017-06-09 | 2017-10-24 | 南京大学 | A kind of system and method for the survey disturbance based on POTDR |
| CN107289978B (en) * | 2017-06-09 | 2019-05-07 | 南京大学 | A kind of system and method for the survey disturbance based on POTDR |
| CN111595246A (en) * | 2020-07-24 | 2020-08-28 | 武汉昊衡科技有限公司 | Wavelength division multiplexer channel length measuring device and method |
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