CN114584210A - Distributed mode crosstalk measurement method and device - Google Patents
Distributed mode crosstalk measurement method and device Download PDFInfo
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Abstract
The invention provides a distributed mode crosstalk measurement method and a distributed mode crosstalk measurement device. The device includes: an optical signal generating unit that provides a chirp optical signal; a first optical power splitter that splits the chirped optical signal into a main arm optical signal and a reference arm optical signal; the first mode conversion unit is used for converting the mode of the main arm optical signal from a fundamental mode in the single-mode optical fiber into a first mode of the few-mode optical fiber to be detected and then transmitting the main arm optical signal to the few-mode optical fiber to be detected; the second mode conversion unit is used for converting the mode of the main arm optical signal transmitted by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber; the single-mode fiber reference arm transmits a reference arm optical signal; the second optical power splitter mixes the main arm optical signal transmitted by the second mode conversion unit and the reference arm optical signal transmitted by the single-mode fiber reference arm and outputs the mixed optical signal; the acquisition unit acquires an electric signal of the mixed optical signal; and the detection unit acquires the distributed mode crosstalk information in the detected few-mode optical fiber according to the electric signal.
Description
Technical Field
The present invention relates to the field of transmission and IP technologies, and in particular, to a distributed mode crosstalk measurement method and apparatus.
Background
With the continuous increase of network users and the continuous emergence of new types of network data services, the demand for network capacity is continuously increased. Currently, an optical communication system based on a common single mode fiber cannot meet the vigorous network capacity requirement, and a mode in a few-mode fiber (Few-mode fiber, FMF) receives wide attention worldwide as a novel optical multiplexing dimension.
For a Mode Division Multiplexing (MDM) optical transmission system, the level of crosstalk between Mode channels in a few-Mode optical fiber greatly affects the performance of the MDM optical transmission system. Therefore, how to accurately measure the distributed mode crosstalk in the few-mode optical fiber is urgent. The existing distributed mode crosstalk measurement methods are mainly an Optical Time Domain Reflectometer (OTDR) method based on backward rayleigh scattering, an OTDR method based on backward brillouin scattering, and a measurement method based on an Optical Frequency Domain Reflectometer (OFDR), but none of the methods can accurately measure distributed mode crosstalk in a few-mode Optical fiber.
Disclosure of Invention
The invention aims to provide a distributed mode crosstalk measuring method and a distributed mode crosstalk measuring device, which are used for solving the problem that the distributed mode crosstalk in a few-mode optical fiber cannot be accurately measured in the prior art.
To achieve the above object, an embodiment of the present invention provides a distributed mode crosstalk measuring apparatus, including:
an optical signal generating unit for providing a chirped optical signal;
a first optical power splitter connected to the optical signal generation unit, and configured to split the chirped optical signal into a main arm optical signal and a reference arm optical signal;
the first mode conversion unit is respectively connected with the first optical power splitter and the to-be-tested few-mode fiber, and is used for converting the mode of the main arm optical signal from a fundamental mode in a single-mode fiber to a first mode of the to-be-tested few-mode fiber and then transmitting the main arm optical signal to the to-be-tested few-mode fiber;
the second mode conversion unit is connected with the tested few-mode optical fiber and used for converting the mode of the main arm optical signal transmitted by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber;
the single-mode fiber reference arm is connected with the first optical power splitter and is used for transmitting the reference arm optical signal;
the second optical power splitter is respectively connected with the second mode conversion unit and the single-mode fiber reference arm, and is used for mixing a main arm optical signal transmitted by the second mode conversion unit and a reference arm optical signal transmitted by the single-mode fiber reference arm and outputting the mixed optical signal;
the acquisition unit is connected with the second optical power splitter and is used for acquiring an electric signal converted from the mixed optical signal;
and the detection unit is connected with the acquisition unit and used for acquiring the distributed mode crosstalk information in the measured few-mode optical fiber according to the electric signal.
Optionally, the optical signal generating unit includes:
a light source unit for providing linearly polarized light;
the linear frequency modulation wave generating unit is used for generating a linear frequency modulation electric signal;
the IQ modulator is respectively connected with the light source unit and the linear frequency modulation wave generation unit and is used for modulating the linear frequency modulation electric signal to linearly polarized light provided by the light source unit to obtain a linear frequency modulation optical signal;
and the optical amplifier is connected with the IQ modulator and the first optical power splitter and is used for amplifying the linear frequency modulation optical signal and outputting the amplified linear frequency modulation optical signal to the first optical power splitter.
Optionally, the acquisition unit includes:
the balance optical detector is connected with the second optical power splitter and used for detecting the mixed optical signal, converting the mixed optical signal into an electric signal and transmitting the electric signal to the time domain electric signal acquisition unit;
and the time domain electric signal acquisition unit is connected with the balance light detector and is used for acquiring the electric signal.
Optionally, the detection unit is configured to obtain distributed mode crosstalk in the measured few-mode optical fiber through the following formula;
wherein, Δ βAB,1The differential group delay between the modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the measured few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p is0The optical power emitted from the measured few-mode optical fiber is measured; t is the time length of the electric signal; t is0Is the relative time delay of the first mode and the signal in the single mode fiber reference arm;<ρB(z)>the average value of the smooth traversal random process of the polarization fading of the second mode conversion unit is obtained;<γB(z)>averaging a smooth ergodic random process of the mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
Optionally, the second optical power splitter is a 50:50 optical power splitter.
An embodiment of the present invention further provides a distributed mode crosstalk measurement method, which is applied to the above-described distributed mode crosstalk measurement apparatus, and includes:
dividing the linear frequency modulation optical signal into a main arm optical signal and a reference arm optical signal;
transmitting a first main-arm optical signal to the tested few-mode optical fiber, and converting a mode of a second main-arm optical signal output by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main-arm optical signal, wherein the first main-arm optical signal is an optical signal obtained by converting the mode of the main-arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the tested few-mode optical fiber;
mixing the optical signal of the third main arm and the optical signal of the reference arm to obtain a mixed optical signal, and converting the mixed optical signal into an electric signal;
and acquiring distributed mode crosstalk information in the tested few-mode optical fiber according to the electric signal.
Optionally, the obtaining, according to the electrical signal, distributed mode crosstalk information in the measured few-mode optical fiber includes:
obtaining distributed mode crosstalk in the tested few-mode optical fiber through the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is0Relative time delay of the first mode and a signal in a single mode fiber reference arm;<ρB(z)>for smooth traversal of the random course of polarization fading of the second mode conversion unitMean value;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BRepresenting distributed modal crosstalk coefficients of the first mode versus the second mode.
An embodiment of the present invention further provides a distributed mode crosstalk measurement apparatus, which is applied to the distributed mode crosstalk measurement apparatus described above, and includes: a transceiver and a processor:
the processor is used for dividing the linear frequency modulation optical signal into a main arm optical signal and a reference arm optical signal; transmitting a first main arm optical signal to the measured few-mode optical fiber, and converting a mode of a second main arm optical signal output by the measured few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main arm optical signal, wherein the first main arm optical signal is an optical signal obtained by converting the mode of the main arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the measured few-mode optical fiber; mixing the third main arm optical signal and the reference arm optical signal to obtain a mixed optical signal; and converting the mixed optical signal into an electric signal, and acquiring distributed mode crosstalk information in the tested few-mode optical fiber according to the electric signal.
Optionally, the processor is configured to obtain distributed mode crosstalk in the measured few-mode optical fiber according to the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is a unit of0Relative time delay of the first mode and a signal in a single mode fiber reference arm;<ρB(z)>the average value of the smooth traversing random process of the polarization fading of the second mode conversion unit is obtained;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
An embodiment of the present invention further provides a distributed mode crosstalk measurement apparatus, including: a transceiver, a processor, a memory, and a program or instructions stored on the memory and executable on the processor; the processor, when executing the program or instructions, implements the steps in the distributed mode crosstalk measurement apparatus method as described above.
To achieve the above object, an embodiment of the present invention provides a readable storage medium on which a program or instructions are stored, which when executed by a processor implement the steps in the distributed mode crosstalk measurement method as described above.
The technical scheme of the invention has the following beneficial effects:
in the distributed mode crosstalk measuring device of the embodiment of the invention, a first optical power splitter divides a chirp optical signal into a main arm optical signal and a reference arm optical signal; the first mode conversion unit converts the mode of a main arm optical signal from a fundamental mode in a single-mode fiber to a first mode of the tested few-mode fiber, and then transmits the main arm optical signal to the tested few-mode fiber; the second mode conversion unit converts the mode of the main arm optical signal transmitted by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber; the second optical power splitter mixes the main arm optical signal transmitted by the second mode conversion unit and the reference arm optical signal transmitted by the single-mode fiber reference arm and outputs the mixed optical signal; the acquisition unit acquires an electric signal of the mixed optical signal; and the detection unit acquires the distributed mode crosstalk information in the detected few-mode optical fiber. The measuring device can simply and accurately measure the distributed mode crosstalk in the few-mode optical fiber.
Drawings
Fig. 1 is a schematic structural diagram of a distributed mode crosstalk measuring apparatus according to an embodiment of the present invention;
fig. 2 is a time delay-relative intensity graph obtained after fast fourier transform of 20 paths of electric signals obtained by respectively combining five collected modes in pairs;
fig. 3 is a schematic flow chart of a distributed mode crosstalk measurement method according to an embodiment of the present invention;
fig. 4 is a second schematic structural diagram of a distributed mode crosstalk measuring apparatus according to an embodiment of the present invention;
fig. 5 is a third schematic structural diagram of a distributed mode crosstalk measuring apparatus according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
In various embodiments of the present invention, it should be understood that the sequence numbers of the following processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
In addition, the terms "system" and "network" are often used interchangeably herein.
In the embodiments provided herein, it should be understood that "B corresponding to a" means that B is associated with a from which B can be determined. It should also be understood that determining B from a does not mean determining B from a alone, but may be determined from a and/or other information.
As shown in fig. 1, a distributed mode crosstalk measuring apparatus according to an embodiment of the present invention includes:
an optical signal generation unit 101 for providing a chirped optical signal.
A first optical power splitter 102, where the first optical power splitter 102 is connected to the optical signal generating unit 101, and is configured to split the chirped optical signal into a main arm optical signal and a reference arm optical signal.
The first optical power splitter is a 50:50 optical power splitter, that is, the main arm optical signal and the reference arm optical signal have the same power. Preferably, the first optical power splitter is an optical fiber type coupler manufactured by a fused biconical taper method, an optical fiber type coupler manufactured by a side polishing method, a silicate glass substrate-based coupler manufactured by a 3D laser direct writing method, a planar optical waveguide type coupler or a spatial light modulator-based power splitter.
A first mode conversion unit 103, connected to the first optical power splitter 102 and the few-mode fiber 104, respectively, and configured to convert the mode of the main arm optical signal from a fundamental mode in a single-mode fiber to a first mode of the few-mode fiber, and then transmit the main arm optical signal to the few-mode fiber.
The few-mode fiber is an optical fiber that supports a plurality of guided wave modes. Its length L1Between 5km and 100 km.
And a second mode conversion unit 105, connected to the measured few-mode fiber, and configured to convert the mode of the main arm optical signal transmitted by the measured few-mode fiber into a fundamental mode in a single-mode fiber.
In an embodiment of the present invention, the first mode conversion unit and the second mode conversion unit may be one or more of an optical fiber type mode selective coupler manufactured by a fused biconical taper method, an optical fiber type mode selective coupler manufactured by a side polishing method, a mode selective coupler manufactured by a 3D laser direct writing method and based on a silicate glass substrate, a planar optical waveguide type mode selective coupler, a long period optical fiber grating type mode converter, a mechanical phase plate type mode converter, a mode converter based on a spatial light modulator, a multi-planar optical converter, or a photonic lantern.
And a single-mode fiber reference arm 106 connected to the first optical power splitter 102 for transmitting the reference arm optical signal.
Preferably, the single-mode fiber reference arm is a single-mode fiber supporting only the lowest-order fundamental mode in the test band.
And a second optical power splitter 107, connected to the second mode conversion unit 104 and the single-mode fiber reference arm 105, respectively, and configured to mix the main arm optical signal transmitted by the second mode conversion unit 104 and the reference arm optical signal transmitted by the single-mode fiber reference arm 105, and output the mixed optical signal.
Optionally, the second optical power splitter is a 50:50 optical power splitter. Preferably, the second optical power splitter is an optical fiber type coupler manufactured by a fused biconical taper method, an optical fiber type coupler manufactured by a side polishing method, a silicate glass substrate-based coupler manufactured by a 3D laser direct writing method, a planar optical waveguide type coupler or a spatial light modulator-based power splitter.
The collecting unit 108, where the collecting unit 107 is connected to the second optical power splitter 106, and is configured to obtain an electrical signal converted from the mixed optical signal;
and the detection unit 109 is connected with the acquisition unit 107 and is used for acquiring the distributed mode crosstalk information in the measured few-mode optical fiber according to the electrical signal.
The distributed mode crosstalk refers to mode crosstalk generated when each mode is transmitted in an optical fiber, and is different from discrete mode crosstalk generated on a single point by a discrete mode device.
In the distributed mode crosstalk measuring device of the embodiment of the invention, a first optical power splitter divides a chirp optical signal into a main arm optical signal and a reference arm optical signal; the first mode conversion unit converts the mode of the main arm optical signal from a fundamental mode in a single mode fiber to a first mode of the few-mode fiber to be tested, and then transmits the main arm optical signal to the few-mode fiber to be tested; the second mode conversion unit converts the mode of the main arm optical signal transmitted by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber; the second optical power splitter mixes the main arm optical signal transmitted by the second mode conversion unit and the reference arm optical signal transmitted by the single-mode fiber reference arm and outputs the mixed optical signal; the acquisition unit acquires an electric signal of the mixed optical signal; and the detection unit acquires the distributed mode crosstalk information in the detected few-mode optical fiber. The measuring device can simply and accurately measure the distributed mode crosstalk in the few-mode optical fiber.
Optionally, the optical signal generating unit includes:
a light source unit for providing linearly polarized light;
the linear frequency modulation wave generating unit is used for generating a linear frequency modulation electric signal;
the IQ modulator is respectively connected with the light source unit and the linear frequency modulation wave generation unit and is used for modulating the linear frequency modulation electric signal to linearly polarized light provided by the light source unit to obtain a linear frequency modulation optical signal;
and the optical amplifier is connected with the IQ modulator and the first optical power splitter and is used for amplifying the linear frequency modulation optical signal and outputting the amplified linear frequency modulation optical signal to the first optical power splitter.
In the embodiment of the invention, the working wavelength and the laser power of the light source unit are adjustable, and the light source unit is used for providing the narrow-linewidth continuous laser. The working wavelength range of the light source unit is continuously adjustable between 850-1650nm, the width of the laser fiber is less than 5MHz, and the laser power is continuously adjustable between 0 and 1W; the IQ modulator can be a lithium niobate modulator or a silicon-based modulator; the chirp generation unit can be an Arbitrary Waveform Generator (AWG), a Waveform Generator based on a Field Programmable Gate Array (FPGA), or a Waveform Generator based on an Application Specific Integrated Circuit (ASIC), and the frequency sweep range and the frequency sweep rate of the chirp generation unit are adjustable; the Optical Amplifier may be a Semiconductor Optical Amplifier (SOA), an Optical Parametric Amplifier (OPA), an Erbium-Doped Fiber Amplifier (EDFA), an Ytterbium-Doped Fiber Amplifier (YDFA), a Praseodymium-Doped Fiber Amplifier (PDFA), or an Erbium-Ytterbium co-Doped Fiber Amplifier (E/YDFA).
Optionally, the acquisition unit includes:
the balance optical detector is connected with the second optical power splitter and used for detecting the mixed optical signal, converting the mixed optical signal into an electric signal and transmitting the electric signal to the time domain electric signal acquisition unit;
and the time domain electric signal acquisition unit is connected with the balance light detector and is used for acquiring the electric signal.
The balanced light detector can be a balanced light detector based on a PIN photodiode or a balanced light detector based on an avalanche photodiode.
The time domain electric signal acquisition unit can be a real-time oscilloscope, a real-time electric signal collector based on a Field Programmable Gate Array (FPGA), or a real-time electric signal collector based on an Application Specific Integrated Circuit (ASIC); the detection unit obtains a time domain electric signal of a detected optical signal under the working wavelength, and calculates distributed mode crosstalk in the few-mode optical fiber according to the time domain electric signal.
Optionally, the detection unit is configured to obtain distributed mode crosstalk in the measured few-mode optical fiber through the following formula;
wherein, Delta betaAB,1Is the inter-mode dgd between a first mode and a second mode, the first modeThe first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBAn insertion loss for the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is0Relative time delay of the first mode and a signal in a single mode fiber reference arm;<ρB(z)>the average value of the smooth traversal random process of the polarization fading of the second mode conversion unit is 1/2 for all the modes;<γB(z)>the mean value of the smooth traversal random process of the mode field orientation fading of the second mode conversion unit is represented by 1 for the circularly symmetric mode and 1/2 for the non-circularly symmetric mode; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
The operation method of the distributed mode crosstalk measuring apparatus according to the present invention will be described with reference to specific embodiments.
In this embodiment, the light source unit includes a narrow linewidth continuous laser light source, a polarizer, and a single-mode optical fiber; the narrow-linewidth continuous laser light source is used for providing narrow-linewidth continuous laser, the working wavelength range is between 850 and 1650nm, the width of the continuously adjustable laser fiber is less than 5-MHz, and the laser power is continuously adjustable between 0W and 1W; the polarizer is used for converting laser emitted by the narrow-linewidth continuous laser light source into linearly polarized light, and is preferably an optical fiber polarizer; the single-mode optical fiber conducts laser output by the wide-spectrum continuous laser light source and forms a basic mode, the input end of the single-mode optical fiber is used for inputting light and is preferably connected with the polarizer, the output end of the single-mode optical fiber is used for outputting the light to the IQ modulator, and the preferred output end is provided with a connector; the single mode fiber is a bare fiber or a jumper.
The chirp generation unit is configured to generate a chirp electrical signal, preferably an arbitrary waveform generator, and an output of the chirp generation unit is configured to output the electrical signal to the IQ modulator, preferably, the output is a radio frequency connector.
The IQ modulator is configured to modulate a chirp signal generated by the chirp generation unit onto laser light emitted by the light source unit, and is preferably a lithium niobate-type modulator, an optical input end of which is configured to be optically input and is preferably connected to the light source unit, an optical output end of which is configured to output light to an optical amplifier, and an optical input end of which is configured to be optically input and output and is provided with a connector, and an electrical input end of which is configured to be electrically input and is preferably connected to the chirp generation unit.
The optical amplifier is used for amplifying laser signal power, preferably an erbium-doped optical fiber amplifier, and the input end and the output end of the optical amplifier are respectively provided with an optical fiber connector based on a jumper wire.
The first optical power splitter is used for splitting a laser signal into two paths of laser signals with equal power, preferably an optical fiber type coupler manufactured by a fused biconical taper method, and the input end and the output end of the first optical power splitter are provided with optical fiber connectors based on jumper wires.
The first mode conversion unit is used for converting the main arm optical signal from a fundamental mode in a single-mode optical fiber to a certain mode in a few-mode optical fiber to be tested, and is preferably an optical fiber mode selection coupler manufactured by a fused biconical taper method.
The second mode conversion unit is used for converting the main arm optical signal into a fundamental mode in a single-mode optical fiber, preferably an optical fiber type mode selection coupler manufactured by a fused biconical taper method, and the input end and the output end of the second mode conversion unit are provided with optical fiber connectors based on jumpers.
The single-mode fiber reference arm is used for transmitting a laser reference signal, preferably a G.652D standard single-mode fiber, and the input end and the output end of the single-mode fiber reference arm are both provided with fiber connectors.
And the second optical power splitter is used for mixing the main-arm optical main signal and the reference-arm optical signal in the single-mode fiber reference arm. The optical fiber type coupler is preferably manufactured by a fused biconical taper method, and the input end and the output end of the optical fiber type coupler are provided with optical fiber connectors based on jumper wires.
The balanced optical detector is used for detecting two paths of mixed laser signals transmitted by the second optical power splitter, preferably the balanced optical detector based on the PIN photodiode, the optical input end of the balanced optical detector is provided with an optical fiber connector based on a jumper wire, the electrical output end of the balanced optical detector is preferably connected with the time domain electrical signal acquisition unit, and the electrical output end of the balanced optical detector is preferably a radio frequency connector.
The time domain electric signal acquisition unit is used for acquiring electric signals transmitted by the balanced light detector, and is preferably a real-time oscilloscope.
The detection unit obtains the time domain electric signals collected by the time domain electric signal collection unit and calculates the distributed mode crosstalk in the detected few-mode optical fiber.
Based on this, the working method of the distributed crosstalk measurement apparatus of the embodiment of the present invention includes:
1) selecting a length L1The measured few-mode optical fiber is arranged between a first mode conversion unit and a second mode conversion unit of the distributed mode crosstalk measuring device provided by the invention;
the few-mode optical fiber to be detected is an annular six-mode optical fiber and supports LP01、LP11、LP21、LP02、LP31、LP12A total of six degenerate modes, in which LP01And LP02Mode is circularly symmetric degenerate mode, LP11、LP21、LP31、LP12Is a non-circularly symmetric degenerate mode; this test LP01、LP11、LP21、LP02、LP31Five modes, the length L of the measured optical fiber1The input end and the output end of the antenna are provided with connectors, and the length of the antenna is 21.31 km.
2) Selecting a length L2The single-mode fiber reference arm of the invention is arranged between a first optical power splitter and a second optical power splitter of the distributed mode crosstalk measuring device provided by the invention;
the single-mode fiber reference arm is G.652D standard single-mode fiber, and the length L of the single-mode fiber reference arm2The input end and the output end of the sensor are provided with joints, and the input end and the output end of the sensor are 21.24 km.
3) And adjusting the optical path to enable the distributed mode crosstalk measuring device to be in a corresponding measuring state, and returning the measured distributed mode crosstalk of the few-mode optical fiber to be measured.
The method for measuring the distributed mode crosstalk in the few-mode optical fiber comprises the following specific steps:
(1) placing a first mode conversion unit corresponding to an excitation mode A (namely, the first mode) and a second mode conversion unit corresponding to a detected crosstalk mode B (namely, the second mode) in a working light path of the distributed mode crosstalk measurement device, and adjusting the output working wavelength and the output power of the light source unit to be a preset working wavelength and preset output power;
(2) configuring the sweep frequency range of the linear frequency modulation wave generating unit as a preset sweep frequency range, wherein the sweep frequency speed is a preset sweep frequency speed; adjusting the IQ modulator to enable the light source unit to emit laser to be modulated into a single-carrier fiber core frequency modulation optical signal; configuring the output power of the optical amplifier to be preset output power;
(3) obtaining distributed mode crosstalk coefficient h of excitation mode A to crosstalk mode B in the detected few-mode optical fiber under preset working wavelength and calculated by the detection unitA→BThe specific calculation formula is as follows:
the parameters of the formula are described in the above description and will not be described in detail here.
Repeating (1) - (3), measuring and calculating the distributed mode crosstalk between all other modes and the excited mode.
Wherein the collected LP01、LP11、LP21、LP02、LP31The time delay-relative intensity graph obtained after the 20 paths of electric signals obtained by combining the five modes in pairs are subjected to fast fourier transform is shown in fig. 2. As shown in Table 1, LP01For LP11Distributed mode crosstalk of-28.5 dB/km, LP01For LP21Distributed mode crosstalk of-34.6 dB/km, LP01For LP02Distributed mode crosstalk of-35.8 dB/km, LP01For LP31Distributed mode crosstalk of-36.7 dB/km, LP11For LP01Distributed mode crosstalk of-29.9 dB/km, LP11For LP21Distributed mode crosstalk of-31.3 dB/km, LP11For LP02Distributed mode crosstalk of-33.7 dB/km, LP11For LP31Distributed mode crosstalk of-35.5 dB/km, LP21For LP01Distributed mode crosstalk of-36.9 dB/km, LP21For LP11Distributed mode crosstalk of-33 dB/km, LP21For LP02Distributed mode crosstalk of-31.7 dB/km, LP21For LP01Distributed mode crosstalk of-33.4 dB/km, LP02For LP01Distributed mode crosstalk of-37.4 dB/km, LP02For LP11Distributed mode crosstalk of-35.4 dB/km, LP02For LP21Distributed mode crosstalk of-34.7 dB/km, LP02For LP31Distributed mode crosstalk of-32.2 dB/km, LP31For LP01Distributed mode crosstalk of-39.1 dB/km, LP31For LP11Distributed mode crosstalk of-37.1 dB/km, LP31For LP21Distributed mode crosstalk of-33.4 dB/km, LP31For LP02The distributed mode crosstalk was-34.8 dB/km.
TABLE 1
The distributed mode crosstalk measuring device abandons the method of simultaneously measuring the extinction ratio of the mode and other crosstalk modes, avoids the problem that the insertion loss of the mode demultiplexer cannot be determined, and realizes the direct and accurate measurement of the mode crosstalk by measuring the absolute optical power of other crosstalk modes.
As shown in fig. 3, an embodiment of the present invention further provides a distributed mode crosstalk measuring method, where the distributed mode crosstalk measuring method is applied to the distributed mode crosstalk measuring apparatus, and the method includes:
step 301: the chirped optical signal is split into a main arm optical signal and a reference arm optical signal.
Wherein the main arm optical signal and the reference arm optical signal have the same power.
Step 302: transmitting a first main-arm optical signal to the tested few-mode optical fiber, and converting a mode of a second main-arm optical signal output by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main-arm optical signal, wherein the first main-arm optical signal is an optical signal obtained by converting the mode of the main-arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the tested few-mode optical fiber;
step 303: and mixing the optical signal of the third main arm and the optical signal of the reference arm to obtain a mixed optical signal, and converting the mixed optical signal into an electric signal.
Step 304: and acquiring distributed mode crosstalk information in the tested few-mode optical fiber according to the electric signal.
The few-mode optical fiber is an optical fiber that supports a plurality of guided wave modes. Its length L1Between 5km and 100 km.
Distributed mode crosstalk refers to mode crosstalk occurring when each mode is transmitted in an optical fiber, and is different from discrete mode crosstalk generated by a discrete mode device on a single point.
Optionally, the obtaining, according to the electrical signal, distributed mode crosstalk information in the measured few-mode optical fiber includes:
obtaining distributed mode crosstalk in the tested few-mode optical fiber through the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber;t is the time length of the electric signal; t is0Is the relative time delay of the first mode and the signal in the single mode fiber reference arm;<ρB(z)>the average value of the smooth traversal random process of the polarization fading of the second mode conversion unit is obtained;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
It should be noted that, for the measurement method applied to the distributed mode crosstalk measurement apparatus, a specific implementation process of the distributed mode crosstalk measurement method has been described in detail in the embodiment of the distributed mode crosstalk measurement apparatus, and is not described herein again to avoid repetition.
According to the distributed mode crosstalk measurement method, a linear frequency modulation optical signal is divided into a main arm optical signal and a reference arm optical signal; transmitting a first main-arm optical signal to the tested few-mode optical fiber, and converting a mode of a second main-arm optical signal output by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main-arm optical signal, wherein the first main-arm optical signal is an optical signal obtained by converting the mode of the main-arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the tested few-mode optical fiber; mixing the optical signal of the third main arm and the optical signal of the reference arm to obtain a mixed optical signal, and converting the mixed optical signal into an electric signal; and acquiring distributed mode crosstalk information in the measured few-mode optical fiber according to the electric signal, thereby achieving the purpose of simply and accurately measuring the distributed mode crosstalk in the few-mode optical fiber.
According to the measuring method provided by the embodiment of the invention, the method for simultaneously measuring the extinction ratios of the mode and other crosstalk modes is abandoned, the problem that the insertion loss of the mode demultiplexer cannot be determined is avoided, and the method for measuring the absolute optical power of other crosstalk modes is used to realize accurate measurement of the distributed mode crosstalk.
As shown in fig. 4, an inter-mode crosstalk measuring apparatus 400 according to an embodiment of the present invention includes: transceiver 420 and processor 410:
the processor 410 is configured to divide the chirped optical signal into a main arm optical signal and a reference arm optical signal; transmitting a first main-arm optical signal to the tested few-mode optical fiber, and converting a mode of a second main-arm optical signal output by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main-arm optical signal, wherein the first main-arm optical signal is an optical signal obtained by converting the mode of the main-arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the tested few-mode optical fiber; mixing the third main arm optical signal and the reference arm optical signal to obtain a mixed optical signal; and converting the mixed optical signal into an electric signal, and acquiring distributed mode crosstalk information in the tested few-mode optical fiber according to the electric signal.
Optionally, the processor 410 is configured to obtain distributed mode crosstalk in the measured few-mode optical fiber according to the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is0Is the relative time delay of the first mode and the signal in the single mode fiber reference arm;<ρB(z)>the average value of the smooth traversal random process of the polarization fading of the second mode conversion unit is obtained;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v being the chirp productGenerating the sweep frequency speed of the unit; h is a total ofA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
The distributed mode crosstalk measuring device of the embodiment can simply and accurately measure the distributed mode crosstalk in the measured few-mode optical fiber, and solves the problem that the distributed mode crosstalk in the measured few-mode optical fiber cannot be accurately measured at present.
The distributed mode crosstalk measurement apparatus can implement all implementation manners in the above described embodiments of the distributed mode crosstalk measurement method, and details are not described here to avoid repetition.
Another embodiment of the present invention provides a distributed mode crosstalk measurement apparatus, as shown in fig. 5, including a transceiver 510, a processor 500, a memory 520, and a program or instructions stored in the memory 520 and executable on the processor 500; the processor 500, when executing the program or instructions, performs the steps of the distributed mode crosstalk measurement method described above.
The transceiver 510 is used for receiving and transmitting data under the control of the processor 500.
Wherein in fig. 5, the bus architecture may include any number of interconnected buses and bridges, with one or more processors, represented by processor 500, and various circuits, represented by memory 520, being linked together. The bus architecture may also link together various other circuits such as peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further herein. The bus interface provides an interface. The transceiver 510 may be a number of elements including a transmitter and a receiver that provide a means for communicating with various other apparatus over a transmission medium. For different user devices, the user interface 530 may also be an interface capable of interfacing externally to a desired device, including but not limited to a keypad, display, speaker, microphone, joystick, etc.
The processor 500 is responsible for managing the bus architecture and general processing, and the memory 520 may store data used by the processor 500 in performing operations.
The readable storage medium of the embodiment of the present invention stores a program or an instruction thereon, and the program or the instruction when executed by the processor implements the steps in the distributed mode crosstalk measurement method described above, and can achieve the same technical effects, and the details are not repeated here in order to avoid repetition.
It is further noted that the terminals described in this specification include, but are not limited to, smart phones, tablets, etc., and that many of the functional components described are referred to as modules in order to more particularly emphasize their implementation independence.
In embodiments of the present invention, modules may be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be constructed as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different bits which, when joined logically together, comprise the module and achieve the stated purpose for the module.
Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.
When a module can be implemented by software, considering the level of existing hardware technology, a module implemented by software may build a corresponding hardware circuit to implement a corresponding function, without considering cost, and the hardware circuit may include a conventional Very Large Scale Integration (VLSI) circuit or a gate array and an existing semiconductor such as a logic chip, a transistor, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.
The exemplary embodiments described above are described with reference to the drawings, and many different forms and embodiments of the invention may be made without departing from the spirit and teaching of the invention, therefore, the invention is not to be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of elements may be exaggerated for clarity. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Unless otherwise indicated, a range of values, when stated, includes the upper and lower limits of the range and any subranges therebetween.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (11)
1. A distributed modal crosstalk measurement apparatus, comprising:
an optical signal generating unit for providing a chirped optical signal;
a first optical power splitter connected to the optical signal generation unit, and configured to split the chirped optical signal into a main arm optical signal and a reference arm optical signal;
the first mode conversion unit is respectively connected with the first optical power splitter and the to-be-tested few-mode fiber, and is used for converting the mode of the main arm optical signal from a fundamental mode in a single-mode fiber to a first mode of the to-be-tested few-mode fiber and then transmitting the main arm optical signal to the to-be-tested few-mode fiber;
the second mode conversion unit is connected with the tested few-mode optical fiber and used for converting the mode of the main arm optical signal transmitted by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber;
the single-mode fiber reference arm is connected with the first optical power splitter and is used for transmitting the reference arm optical signal;
the second optical power splitter is respectively connected with the second mode conversion unit and the single-mode fiber reference arm, and is used for mixing a main arm optical signal transmitted by the second mode conversion unit and a reference arm optical signal transmitted by the single-mode fiber reference arm and outputting the mixed optical signal;
the acquisition unit is connected with the second optical power splitter and is used for acquiring an electric signal converted from the mixed optical signal;
and the detection unit is connected with the acquisition unit and used for acquiring the distributed mode crosstalk information in the measured few-mode optical fiber according to the electric signal.
2. The distributed mode crosstalk measurement apparatus according to claim 1, wherein said optical signal generation unit comprises:
a light source unit for providing linearly polarized light;
a chirp generation unit for generating a chirp electrical signal;
the IQ modulator is respectively connected with the light source unit and the linear frequency modulation wave generating unit and is used for modulating the linear frequency modulation electric signal to linearly polarized light provided by the light source unit to obtain a linear frequency modulation optical signal;
and the optical amplifier is connected with the IQ modulator and the first optical power splitter and is used for amplifying the linear frequency modulation optical signal and outputting the amplified linear frequency modulation optical signal to the first optical power splitter.
3. The distributed mode crosstalk measurement apparatus according to claim 2, wherein said acquisition unit comprises:
the balance optical detector is connected with the second optical power splitter and used for detecting the mixed optical signal, converting the mixed optical signal into an electric signal and transmitting the electric signal to the time domain electric signal acquisition unit;
and the time domain electric signal acquisition unit is connected with the balance light detector and is used for acquiring the electric signal.
4. The distributed mode crosstalk measurement apparatus according to claim 3, wherein the detection unit is configured to obtain the distributed mode crosstalk in the tested few-mode optical fiber according to the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBAn insertion loss for the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is0Relative time delay of the first mode and a signal in a single mode fiber reference arm;<ρB(z)>is the firstThe mean value of the stable traversing random process of the polarization fading of the two mode conversion units;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h is a total ofA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
5. The distributed mode crosstalk measurement apparatus of claim 1 wherein the second optical power splitter is a 50:50 optical power splitter.
6. A distributed mode crosstalk measurement method applied to the distributed mode crosstalk measurement apparatus according to any one of claims 1 to 5, comprising:
dividing the linear frequency modulation optical signal into a main arm optical signal and a reference arm optical signal;
transmitting a first main-arm optical signal to the tested few-mode optical fiber, and converting a mode of a second main-arm optical signal output by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main-arm optical signal, wherein the first main-arm optical signal is an optical signal obtained by converting the mode of the main-arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the tested few-mode optical fiber;
mixing the optical signal of the third main arm and the optical signal of the reference arm to obtain a mixed optical signal, and converting the mixed optical signal into an electrical signal;
and acquiring distributed mode crosstalk information in the tested few-mode optical fiber according to the electric signal.
7. The method according to claim 6, wherein the obtaining distributed mode crosstalk information in the measured few-mode fiber according to the electrical signal comprises:
obtaining distributed mode crosstalk in the tested few-mode optical fiber through the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of converting the mixed optical signal into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is0Relative time delay of the first mode and a signal in a single mode fiber reference arm;<ρB(z)>the average value of the smooth traversal random process of the polarization fading of the second mode conversion unit is obtained;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BA distributed mode crosstalk coefficient representing the first mode versus the second mode.
8. A distributed mode crosstalk measuring apparatus applied to the distributed mode crosstalk measuring apparatus according to any one of claims 1 to 5, comprising: a transceiver and a processor:
the processor is used for dividing the linear frequency modulation optical signal into a main arm optical signal and a reference arm optical signal; transmitting a first main-arm optical signal to the tested few-mode optical fiber, and converting a mode of a second main-arm optical signal output by the tested few-mode optical fiber into a fundamental mode in a single-mode optical fiber to obtain a third main-arm optical signal, wherein the first main-arm optical signal is an optical signal obtained by converting the mode of the main-arm optical signal from the fundamental mode in the single-mode optical fiber into a first mode of the tested few-mode optical fiber; mixing the third main arm optical signal and the reference arm optical signal to obtain a mixed optical signal; and converting the mixed optical signal into an electric signal, and acquiring distributed mode crosstalk information in the tested few-mode optical fiber according to the electric signal.
9. The distributed mode crosstalk measurement apparatus according to claim 8, wherein the processor is configured to obtain the distributed mode crosstalk in the measured few-mode optical fiber according to the following formula;
wherein, Delta betaAB,1The differential group delay between modes is a first mode and a second mode, and the first mode and the second mode are both modes supported by the tested few-mode optical fiber; kappa is the photoelectric conversion rate of the mixed optical signal converted into an electric signal; etaBInsertion loss of the second mode conversion unit for the second mode; p0The optical power emitted from the measured few-mode optical fiber; t is the time length of the electric signal; t is0Relative time delay of the first mode and a signal in a single mode fiber reference arm;<ρB(z)>the average value of the smooth traversal random process of the polarization fading of the second mode conversion unit is obtained;<γB(z)>averaging a stationary traversal random process of mode field orientation fading of the second mode conversion unit; f (t) represents the electrical signal, v is the sweep frequency speed of the chirp generation unit; h isA→BRepresenting distributed modal crosstalk coefficients of the first mode versus the second mode.
10. A distributed modal crosstalk measurement apparatus comprising: a transceiver, a processor, a memory, and a program or instructions stored on the memory and executable on the processor; characterized in that the processor implements the steps in the distributed mode crosstalk measurement apparatus method according to any of claims 8 to 9 when executing the program or instructions.
11. A readable storage medium on which a program or instructions are stored, which program or instructions, when executed by a processor, implement the steps in the distributed mode crosstalk measurement method according to any one of claims 8 to 9.
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