CN108400813A - A kind of optical fiber link detecting system and method based on linear FM signal - Google Patents
A kind of optical fiber link detecting system and method based on linear FM signal Download PDFInfo
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- CN108400813A CN108400813A CN201810130477.XA CN201810130477A CN108400813A CN 108400813 A CN108400813 A CN 108400813A CN 201810130477 A CN201810130477 A CN 201810130477A CN 108400813 A CN108400813 A CN 108400813A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
Abstract
A kind of optical fiber link detecting system based on linear FM signal, is related to fiber optic communication field, including：Laser, linear frequency modulation transmitter, circulator and receiver, laser send out continuous optical signal；Linear frequency modulation transmitter generates the repetition pulse signal for including linear frequency modulation optical signal, as detection optical signal；The detection optical signal is input in tested optical fiber by circulator, and receives the backscatter signals from tested optical fiber；Receiver extracts the tested optical fiber feature carried in the backscatter signals, exports detectable signal curvilinear path.The present invention improves the dynamic range of measurement under the premise of the same time, improves distance resolution.
Description
Technical field
The present invention relates to fiber optic communication field, in particular to a kind of optical fiber link detection based on linear FM signal
System and method.
Background technology
Optical time domain reflection technology is made with principle of reflection according to the backscattering of light, is produced when being transmitted in a fiber using light
Raw back-scattering light obtains dampening information, can be used for measuring optical fiber attenuation, splicing loss, fiber failure point location, and
Understand loss distribution situation etc. of the optical fiber along length.Due to fiber optic materials Density inhomogeneity, doping component is uneven and optical fiber
The defect of itself, when light pulse is transmitted in optical fiber, can due to the property of optical fiber itself, connector, junction, bending or its
Its similar event and generate scattering, reflection.The scattering of a portion and reflected light return to optical time domain reflectometer
In (Optical Time Domain Reflectometer, OTDR), the useful information of return by optical time domain reflectometer detection
Device measures, they just as on different location in optical fiber time or curve segment.Return letter is transmitted signals to by measuring
Time used in number, and determining light is in the speed of optical fiber, so that it may to calculate corresponding distance.
With the reduction of introducing and the fibre loss of fiber amplifier, Optical Fiber Transmission distance is continuously increased, detector detection
Signal it is very faint, it is desirable that detector have higher sensitivity and bigger dynamic range.In order to solve detector signal
Faint problem, conventional method one is that repeated sampling is averaged to improve detectivity, second is that increasing the energy of transmitting signal.
Repeated sampling can improve the dynamic range of measurement, but expend more times.Due to the power limited of laser, to improve
The energy of incoming signal can only increase the pulsewidth of transmitting signal, but this can reduce distance resolution again.
Invention content
In view of the deficiencies in the prior art, the purpose of the present invention is to provide a kind of light based on linear FM signal
Fine link detecting system and method improves the dynamic range of measurement under the premise of the same time, improves distance resolution.
To achieve the above objectives, the present invention takes a kind of optical fiber link detecting system based on linear FM signal, including：
Laser is used to send out continuous optical signal；
Linear frequency modulation transmitter is used to generate the repetition pulse signal for including linear frequency modulation optical signal, as detection light
Signal；
Circulator is used to the detection optical signal being input in tested optical fiber, and receives the back of the body from tested optical fiber
To scattered signal；
Receiver, is used to extract the tested optical fiber feature carried in the backscatter signals, and output detectable signal is bent
Line tracking.
Based on the above technical solution, the linear frequency modulation transmitter includes：
Electric signal generator is used to generate linear frequency modulation electric signal and clock sync pulse signal, and the two repeats
Cycle phase is same；
Optical modulator is used to linear frequency modulation electric signal being modulated to the continuous optical signal that the laser is sent out, raw
At continuous linear frequency modulation optical signal；
Photoswitch is used to from continuous linear frequency modulation optical signal intercept linear frequency modulated light signal according to same period,
As detection optical signal.
Based on the above technical solution, the repetition week of the linear frequency modulation electric signal and clock sync pulse signal
Phase T meets：Wherein c is the light velocity in vacuum, and L is the length of tested optical fiber, and n is mean refractive index.
Based on the above technical solution, the receiver includes：
Signal receiving unit is reflected, is used to receive the backscatter signals, and be converted to digital signal；
Digital signal processing unit is used to receive the digital signal, extracts tested optical fiber feature.
Based on the above technical solution, the reflection signal receiving unit includes：
Photodetector is used to backscatter signals being converted to analog electrical signal；
Filtering and amplifying circuit is used to be amplified analog electrical signal and filters out partial noise；
Analog-digital converter is used to analog electrical signal being converted to digital electric signal.
Based on the above technical solution, the reflection signal receiving unit is photodiode.
Based on the above technical solution, the electric signal generator is electrical waveform generator, and the optical modulator is
Photoelectricity intensity modulator.
Based on the above technical solution, the circulator is the optical circulator of C+L wave bands.
The optical fiber link detection method based on linear FM signal that the present invention also provides a kind of, including step：According to linear
FM signal modulated light source sends out continuous optical signal, forms continuous linear frequency modulation optical signal, is linearly adjusted described in periodic intercepts
Frequency optical signal inputs tested optical fiber as detection optical signal by circulator；The back of the body from tested optical fiber is received by circulator
To scattered signal；The tested optical fiber feature carried in the backscatter signals is extracted, detectable signal curvilinear path is exported, as
Testing result.
Based on the above technical solution, the linear FM signal is generated by electric signal generator, electric signal hair
Raw device also generates repetition period identical clock sync pulse signal, described linear according to clock sync pulse signal interception
Frequency modulated light signal.
The beneficial effects of the present invention are：
It is used as detection optical signal by periodic intercepts linear frequency modulation optical signal, since linear FM signal is in fractional order Fu
In leaf domain there is fabulous energy accumulating characteristic, and noise and NLFM signal will not after Fourier Transform of Fractional Order
Assemble, therefore can be divided linear FM signal and noise by digital signal processing algorithm in backscatter signals
It opens, extracts linear FM signal, more accurately therefrom extract the tested optical fiber feature of carrying, detection is being improved to improve
Range (dynamic range of measurement) and detectivity (i.e. distance resolution), and the more time will not be expended.
Description of the drawings
Fig. 1 is the schematic diagram of optical fiber link detecting system of the embodiment of the present invention based on linear FM signal；
Fig. 2 is the time domain schematic diagram of linear frequency modulation electric signal in the present invention；
Fig. 3 is the schematic diagram that the embodiment of the present invention reflects signal receiving unit；
Fig. 4 is optical fiber link detection method flow chart of the embodiment of the present invention based on linear FM signal；
Fig. 5 is distribution schematic diagram of the unlike signal Jing Guo Digital Signal Processing in the present invention.
Reference numeral：
Laser 1, linear frequency modulation transmitter 2, electric signal generator 21, optical modulator 22, photoswitch 23, circulator 3 connect
Receipts machine 4 reflects signal receiving unit 41, photodetector 411, filtering and amplifying circuit 412, analog-digital converter 413, number
Signal processing unit 42.
Specific implementation mode
Invention is further described in detail with reference to the accompanying drawings and embodiments.
As shown in Figure 1, the present invention is based on the optical fiber link detecting system of linear FM signal, including laser 1, linear tune
Channel transmitter 2, circulator 3 and receiver 4.Wherein, laser 1 is for sending out continuous optical signal.Linear frequency modulation transmitter 2 is used
In generating the repetition pulse signal for including linear frequency modulation optical signal, as detection optical signal.Circulator 3 will be for that will detect optical signal
It is input in tested optical fiber (i.e. Transmission Fibers), and receives the backscatter signals from tested optical fiber.Receiver 4 is for extracting
The tested optical fiber feature carried in backscatter signals exports detectable signal curvilinear path, the testing result as output.It is preferred that
, circulator 3 can be the optical circulator of C+L wave bands, such as the circulator CIR-3-1550-A-025-1- of the fast science and technology production of light
APC。
Specifically, linear frequency modulation transmitter 2 includes electric signal generator 21, optical modulator 22 and photoswitch 23.Electric signal
Generator 21 is for generating linear frequency modulation electric signal and clock sync pulse signal, the period of linear frequency modulation electric signal and clock
The repetition period of synchronization pulse is identical, is all cycle T, and cycle T is limited by tested optical fiber length, and cycle T meets：Wherein, c is the light velocity in vacuum, and L is the length of tested optical fiber, and n is mean refractive index.Lock-out pulse is duty ratio
The electric signal of very little, pulse width is related with the spatial resolution of optical time domain reflection, if the width of lock-out pulse is Δ t,
Then the spatial resolution Δ L of optical time domain reflection is：
The mathematic(al) representation of the linear frequency modulation electric signal of a cycle is：
Wherein, t is time independent variable, and A is impulse amplitude, the length of τ linear FM signals, f0Centered on frequency, μ be adjust
Frequency slope；As shown in Fig. 2, for the time-domain diagram of linear frequency modulation electric signal.Electric signal generator 21 can be electrical waveform generator.
Optical modulator 22 is used to the linear frequency modulation electric signal that electric signal generator 21 generates being modulated to what laser 1 was sent out
On continuous optical signal, continuous linear frequency modulation optical signal is generated.Optical modulator 22 can be photoelectricity intensity modulator, such as
Lithium niobate intensity modulator MX-LN-10 of Photline etc..
Photoswitch 23 according to synchronization pulse by continuous linear frequency modulation optical signal according to same period T for blocking
At the linear frequency modulation optical signal that one section of a period of time width is Δ t, it is sent into circulator 3 as detection optical signal.Due to linear
Frequency modulation electric signal is identical with the cycle T of synchronization pulse, therefore it is the repetition pulse signal for being T in the period to detect optical signal, no
It is identical with the linear frequency modulation optical signal for including in recurrent pulse.Photoswitch 23 can be acousto-optic modulator, such as CTI companies
AO3165-1 etc..
Receiver 4 includes reflection signal receiving unit 41 and digital signal processing unit 42, reflects signal receiving unit 41
For receiving the backscatter signals from circulator 3, and digital data transmission is converted to digital signal processing unit 42.Number
Word signal processing unit 42 is used to receive the digital signal that reflection signal receiving unit 41 is converted, and extracts in linear FM signal
The optical fiber link feature of the tested optical fiber of carrying, to obtain and export detectable signal curvilinear path, as optical time domain reflection
Export result.Photodiode (APD) may be used to realize, as Thorlabs companies produce in reflection signal receiving unit 41
Avalanche photodide APD110C.The realization of Digital Signal Processing (DSP) chip may be used in digital signal processing unit 42, such as
The dsp chip C6652 of TI companies production.
Specifically, the realization method of digital signal processing algorithm is in digital signal processing unit 42：
Wherein, x (t) is the signal that signal receiving unit 6 receives, and t is time independent variable, Xp(u) it is in score grade Fu
Signal after leaf transformation, u are the horizontal axis independents variable of transform domain, and p is the exponent number of algorithm, and it is integer to have α=p pi/2s, k.
Specifically, as shown in figure 3, reflection signal receiving unit 41 includes photodetector 411, filtering and amplifying circuit 412
With analog-digital converter 413, photodetector 411 is used to the backscatter signals from circulator 3 being converted to simulation electricity
Signal.Filtering and amplifying circuit 412 filters out a part and makes an uproar for being amplified to the analog electrical signal that photodetector 411 exports
Sound.Analog-digital converter 413 is used to analog electrical signal being converted to digital electric signal, to carry out at subsequent digital signal
Reason.
The present invention is based on the optical fiber link detection methods of linear FM signal, including step：
Continuous optical signal is sent out according to linear FM signal modulated light source, forms continuous linear frequency modulation optical signal, period
Property the interception linear frequency modulation optical signal, tested optical fiber is inputted by circulator as detection optical signal；It is received by circulator
Backscatter signals from tested optical fiber；Extract the tested optical fiber feature carried in the backscatter signals, output detection
Signal curve track, as testing result.
As shown in figure 4, illustrate the optical fiber link detection method based on linear FM signal by embodiment, specifically include as
Lower step：
S1. linear frequency modulation electric signal and clock sync pulse signal are generated by electric signal generator 21, laser 1 is sent out
Go out continuous optical signal.
S2. optical modulator 22 modulates laser 1 according to linear frequency modulation electric signal and sends out continuous optical signal, generates continuous line
Property frequency modulated light signal.
S3. photoswitch 23 blocks linear frequency modulation optical signal according to clock sync pulse signal, and is passed by circulator 3
It is defeated in tested optical fiber.
S4. circulator 3 receives the backscatter signals from tested optical fiber, and is transmitted to reflection signal receiving unit 41.
S5. backscatter signals are converted to digital signal by reflection signal receiving unit 41.
S6. digital signal processing unit 42 receives the digital signal of conversion, extracts the optical fiber link feature of tested optical fiber, defeated
Go out detectable signal curvilinear path, the output result as optical time domain reflection.
As shown in figure 5, for distribution schematic diagram of the unlike signal after digital signal processing algorithm in the present invention, wherein horizontal
Axis is the independent variable in fractional order domain, and the longitudinal axis indicates the relative value of unlike signal energy.Fig. 5 illustrates linear FM signal in score
The energy accumulating characteristic of rank Fourier, it is seen that the energy accumulating of linear FM signal is in very narrow range, and noise power
Then approaches uniformity is distributed in the range of entire independent variable.If the gross energy phase of the gross energy of linear FM signal and noise
Together, it then peak value of the linear FM signal in the transform domain can be far longer than noise peak, helps to so quick and precisely
The optical fiber link characteristic information of linear FM signal and its carrying is extracted from noise in ground.
The present invention is not limited to the above-described embodiments, for those skilled in the art, is not departing from
Under the premise of the principle of the invention, several improvements and modifications can also be made, these improvements and modifications are also considered as the protection of the present invention
Within the scope of.The content not being described in detail in this specification belongs to the prior art well known to professional and technical personnel in the field.
Claims (10)
1. a kind of optical fiber link detecting system based on linear FM signal, which is characterized in that including：
Laser is used to send out continuous optical signal；
Linear frequency modulation transmitter is used to generate the repetition pulse signal for including linear frequency modulation optical signal, as detection optical signal；
Circulator is used to the detection optical signal being input in tested optical fiber, and receives dissipating backwards from tested optical fiber
Penetrate signal；
Receiver is used to extract the tested optical fiber feature carried in the backscatter signals, exports detectable signal curve rail
Mark.
2. the optical fiber link detecting system based on linear FM signal as described in claim 1, which is characterized in that described linear
Frequency modulation transmitter includes：
Electric signal generator is used to generate linear frequency modulation electric signal and clock sync pulse signal, and the two repetition period
It is identical；
Optical modulator is used to linear frequency modulation electric signal being modulated to the continuous optical signal that the laser is sent out, the company of generation
Continuous linear frequency modulation optical signal；
Photoswitch is used to from continuous linear frequency modulation optical signal intercept linear frequency modulated light signal according to same period, as
Detect optical signal.
3. the optical fiber link detecting system based on linear FM signal as claimed in claim 2, which is characterized in that described linear
Repetition period T of frequency modulation electric signal and clock sync pulse signal meets：Wherein c is the light velocity in vacuum, and L is
The length of tested optical fiber, n are mean refractive index.
4. the optical fiber link detecting system based on linear FM signal as claimed in claim 2, which is characterized in that the reception
Machine includes：
Signal receiving unit is reflected, is used to receive the backscatter signals, and be converted to digital signal；
Digital signal processing unit is used to receive the digital signal, extracts tested optical fiber feature.
5. the optical fiber link detecting system based on linear FM signal as claimed in claim 4, which is characterized in that the reflection
Signal receiving unit includes：
Photodetector is used to backscatter signals being converted to analog electrical signal；
Filtering and amplifying circuit is used to be amplified analog electrical signal and filters out partial noise；
Analog-digital converter is used to analog electrical signal being converted to digital electric signal.
6. the optical fiber link detecting system based on linear FM signal as claimed in claim 4, it is characterised in that：The reflection
Signal receiving unit is photodiode.
7. such as optical fiber link detecting system of the claim 2-6 any one of them based on linear FM signal, it is characterised in that：
The electric signal generator is electrical waveform generator, and the optical modulator is photoelectricity intensity modulator.
8. the optical fiber link detecting system as claimed in any one of claims 1 to 6 based on linear FM signal, it is characterised in that：
The circulator is the optical circulator of C+L wave bands.
9. a kind of optical fiber link detection method based on linear FM signal, which is characterized in that including step：
Continuous optical signal is sent out according to linear FM signal modulated light source, continuous linear frequency modulation optical signal is formed, periodically cuts
The linear frequency modulation optical signal is taken, tested optical fiber is inputted by circulator as detection optical signal；
The backscatter signals from tested optical fiber are received by circulator；
The tested optical fiber feature carried in the backscatter signals is extracted, detectable signal curvilinear path is exported, is tied as detection
Fruit.
10. the optical fiber link detection method based on linear FM signal as claimed in claim 9, it is characterised in that：The line
Property FM signal generated by electric signal generator, electric signal generator also generates repetition period identical clock sync pulse letter
Number, the linear frequency modulation optical signal is intercepted according to the clock sync pulse signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201810130477.XA CN108400813A (en) | 2018-02-08 | 2018-02-08 | A kind of optical fiber link detecting system and method based on linear FM signal |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810130477.XA CN108400813A (en) | 2018-02-08 | 2018-02-08 | A kind of optical fiber link detecting system and method based on linear FM signal |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112702114A (en) * | 2020-12-16 | 2021-04-23 | 上海交通大学 | Device for acquiring optical fiber side scattering signals and detection method |
| WO2024078013A1 (en) * | 2022-10-12 | 2024-04-18 | 华为技术有限公司 | Optical fiber link fault detection method, communication system and apparatus |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101043273A (en) * | 2006-03-02 | 2007-09-26 | 昂科公司 | Directly modulated laser optical transmission system with phase modulation |
| CN102226703A (en) * | 2011-03-29 | 2011-10-26 | 宁波诺驰光电科技发展有限公司 | Distributed fiber multi-parameter sensor and multi-parameter measuring method |
| CN103674082A (en) * | 2013-12-06 | 2014-03-26 | 何祖源 | High-spatial-resolution optical frequency domain reflectometer system based on four-wave mixing process |
-
2018
- 2018-02-08 CN CN201810130477.XA patent/CN108400813A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101043273A (en) * | 2006-03-02 | 2007-09-26 | 昂科公司 | Directly modulated laser optical transmission system with phase modulation |
| CN102226703A (en) * | 2011-03-29 | 2011-10-26 | 宁波诺驰光电科技发展有限公司 | Distributed fiber multi-parameter sensor and multi-parameter measuring method |
| CN103674082A (en) * | 2013-12-06 | 2014-03-26 | 何祖源 | High-spatial-resolution optical frequency domain reflectometer system based on four-wave mixing process |
Non-Patent Citations (1)
| Title |
|---|
| J. PASTOR-GRAELLS: "Single-shot distributed temperature and strain tracking using direct detection phase-sensitive OTDR with chirped pulses", 《OPTICS EXPRESS》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112702114A (en) * | 2020-12-16 | 2021-04-23 | 上海交通大学 | Device for acquiring optical fiber side scattering signals and detection method |
| WO2024078013A1 (en) * | 2022-10-12 | 2024-04-18 | 华为技术有限公司 | Optical fiber link fault detection method, communication system and apparatus |
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Application publication date: 20180814 |