A device and method for measuring inter-mode parameters based on tunable electrical delay

Abstract

The present invention provides an intermodal parameter measurement device and method based on tunable electrical time delay, which relates to the technical field of optical communication measurement, and solves the problem that the current differential group delay measurement method for few-mode fibers cannot distinguish the differential group delay DMGD with negative values. Two fundamental mode optical signals are generated at the transmitting end, and a tunable electrical time delay Δτ1 is loaded on one of the fundamental mode optical signals. The two fundamental mode optical signals are converted into optical signals with different spatial modes by the first photon lantern and transmitted to the few-mode fiber under test, and then are converted into fundamental mode signals again by the second photon lantern. The analysis module acquires the spectra of the fundamental mode optical signals, records the absolute power difference between the +1st order and -1st order sidebands in the spectra, determines the value of the tunable electrical time delay Δτ1 based on the absolute power difference, and obtains the differential group delay DMGD of the few-mode fiber under test based on the value of the tunable electrical time delay Δτ1, realizing the distinction of the differential group delay DMGD with positive or negative values and broadening the measurement range of the differential group delay DMGD.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communication measurement, and in particular to an inter-mode parameter measurement device and method based on tunable electrical delay. Background Art

[0002] With the rapid growth of bandwidth demand for technologies such as 5G, Internet of Things, big data, Internet+, and cloud computing, people's demand for the transmission capacity of optical fiber communication systems has increased exponentially. In order to increase the maximum transmission capacity of single-mode optical fiber communication systems, people have adopted time division multiplexing, wavelength division multiplexing, polarization multiplexing, and orthogonal amplitude modulation technologies. Although these capacity expansion technologies have been fully explored and the transmission capacity of single-mode optical fiber communication systems has been very close to the nonlinear Shannon limit, they still cannot meet the growing system capacity requirements. Therefore, mode division multiplexing technology based on few-mode fiber has become an effective solution to significantly increase the transmission capacity of long-distance optical communication systems.

[0003] The few-mode optical fiber used in mode division multiplexing technology uses a limited number of mutually orthogonal spatial modes to carry signals, providing multiple independent transmission channels in a single-core optical fiber, thereby significantly improving the transmission capacity of the optical fiber communication system.

[0004] However, due to the increase in the number of modes, the unique inter-mode parameters in few-mode fiber will greatly affect the transmission performance of the mode division multiplexing system, such as differential modal group delay (DMGD). Differential group delay refers to the transmission time difference between any two modes in a unit length of few-mode fiber. The unit is usually ps / m. It is a unique inter-mode parameter in few-mode fiber and can evaluate the power consumption of the mode division multiplexing transmission system. When the fiber length is the same, the larger the DMGD value, the greater the transmission time difference of the signals carried by different spatial modes to the receiving end, which will increase the number of taps of the multi-input multi-output equalization algorithm at the receiving end, thereby greatly increasing the computational complexity of the digital signal processing at the receiving end, and seriously increasing the power consumption of the digital signal processing at the receiving end. Therefore, in order to evaluate the power consumption of the mode division multiplexing transmission system, the measurement and characterization of the DMGD of few-mode fiber is particularly important. The prior art discloses a method for measuring differential group delay of a few-mode optical fiber. Through inter-mode interference of frequency-modulated continuous optical signals of different modes, the traditional amplitude-frequency response measurement is converted into detection of the difference frequency term generated by the inter-mode interference, and the difference frequency component is obtained. The difference frequency component is demodulated to obtain DMGD, and the calculation complexity is low. However, since two DMGDs with equal values ​​but opposite signs will result in the same difference frequency component, this method has the disadvantage of being unable to distinguish negative DMGD values. Summary of the invention

[0005] In order to solve the problem that the current few-mode fiber differential group delay measurement method cannot distinguish negative DMGD, the present invention proposes an inter-mode parameter measurement device and method based on tunable electrical delay, which can distinguish positive or negative DMGD and broaden the range of DMGD measurement.

[0006] In order to achieve the above technical effects, the technical solution of the present invention is as follows:

[0007] A device for measuring inter-mode parameters based on tunable electrical delay, which is used for measuring differential group delay (DMGD) of few-mode optical fiber, and comprises a transmitting end, a first photon lantern, a second photon lantern and an analysis module;

[0008] The few-mode optical fiber to be tested is connected between the first photon lantern and the second photon lantern. The transmitting end generates two fundamental mode optical signals with multi-tone signals, one of which is loaded with a tunable electrical delay. , the two fundamental mode optical signals are converted into different spatial mode optical signals by the first photon lantern and transmitted to the few-mode optical fiber to be tested, the second photon lantern converts the different spatial mode optical signals output from the few-mode optical fiber to be tested into the fundamental mode signal, the analysis module obtains the spectrum of the fundamental mode optical signal, records the power difference between the +1st order and -1st order sidebands in the spectrum, and sets the absolute value of the difference to be the absolute power difference, at any two RF frequencies of the fundamental mode optical signal , The tunable electrical delay is determined when the absolute power difference between the +1st and -1st order sidebands is zero at the same time. The value of the tunable electrical delay The differential group delay DMGD of the few-mode fiber to be tested is calculated based on the value of

[0009] In this technical solution, first, the transmitter generates two fundamental mode optical signals with multi-tone signals, and a tunable electrical delay is added to one of the fundamental mode optical signals with multi-tone signals. , which compensates for the time delay of another fundamental mode optical signal. Then, the two fundamental mode optical signals with multi-tone signals realize the conversion of different spatial mode optical signals through the first photon lantern, and transmit the different spatial mode optical signals to the few-mode optical fiber to be tested. Then, the different spatial mode optical signals in the few-mode optical fiber to be tested are converted into fundamental mode signals through the second photon lantern, and the mode conversion of the optical signal is realized again. The spectrum of the fundamental mode optical signal is further obtained by the analysis module, and the power difference between the +1st and -1st order sidebands is calculated. The absolute value of the difference is obtained to obtain the absolute power difference between the +1st and -1st order sidebands. At any two RF frequencies of the fundamental mode optical signal , The tunable electrical delay is determined when the absolute power difference between the +1st and -1st order sidebands is zero at the same time. The value of can be judged that DMGD is a positive value at this time; if any two RF frequencies , The absolute power difference between the +1st and -1st order sidebands cannot be zero at the same time, then it can be judged that the DMGD at this time is a negative value. By loading another fundamental mode optical signal with multi-tone signals, the value of DMGD can also be measured; this realizes the distinction between positive or negative DMGD values ​​and broadens the range of DMGD measurement.

[0010] Preferably, the transmitting end includes a continuous laser, a first coupler, an arbitrary waveform generator and two photoelectric intensity modulators. The continuous laser emits a continuous optical signal and transmits it to the first coupler. The first coupler splits the continuous optical signal into two optical signals and transmits them to the two photoelectric intensity modulators respectively. The arbitrary waveform generator loads the two generated multi-tone signals onto the optical signals in the two photoelectric intensity modulators respectively, wherein one multi-tone signal is loaded with a tunable electrical delay. , each photoelectric intensity modulator outputs a beam of fundamental mode light signal at the output end.

[0011] Preferably, the photoelectric intensity modulator is a Mach-Zehnder modulator, which plays a role in generating a carrier suppressed double sideband modulation signal.

[0012] Preferably, the analysis module includes a second coupler and a spectrum analyzer, the second coupler combines two fundamental mode optical signals output from the second photon lantern, the combined light enters the spectrum analyzer, and the spectrum of the combined light is obtained using the spectrum analyzer.

[0013] Preferably, a method for measuring inter-mode parameters based on tunable electrical delay is implemented based on the inter-mode parameter measuring device, and at least comprises:

[0014] S1. Connect the few-mode optical fiber to be tested between the first photon lantern and the second photon lantern, and use the transmitting end to generate two fundamental mode optical signals with multi-tone signals, one of which is loaded with a tunable electrical delay. ;

[0015] S2. The two fundamental mode optical signals are transmitted to the first photon lantern, converted into different spatial mode optical signals by the first photon lantern and transmitted to the few-mode optical fiber to be tested;

[0016] S3. The second photon lantern converts different spatial mode optical signals output from the few-mode fiber to be tested into fundamental mode signals;

[0017] S4. Obtain the spectrum of the fundamental mode optical signal through the analysis module, record the power difference between the +1-order and -1-order sidebands in the spectrum, and set the absolute value of the difference to the absolute power difference;

[0018] S5. Set the tunable electrical delay in S1 The initial value of S4 determines any two RF frequencies of the fundamental mode optical signal , Is the absolute power difference between the +1st and -1st order sidebands zero at the same time? If so, determine the tunable electrical delay value, execute S6; otherwise, change the adjustable electrical delay value, continue to judge any two RF frequencies , Whether the absolute power difference between the +1st and -1st order sidebands is zero at the same time;

[0019] S6. Utilization The differential group delay DMGD of the tested few-mode fiber is calculated. The specific calculation formula is as follows:

[0020]

[0021] in, is the length of the few-mode fiber to be tested.

[0022] Preferably, in step S1, parameter calibration is required before accessing the few-mode optical fiber to be tested, and the parameters include the electrical delay difference inherent in the inter-mode parameter measurement device. The transmission time difference between the optical signal transmission link and the , the specific steps of calibration are:

[0023] S11. Connect the transmitting end of the tunable electrical delay to the analysis module to form a first calibration device to calibrate the electrical delay difference inherent in the inter-mode parameter measurement device. ;

[0024] S12. A first photon lantern and a second photon lantern are connected between the transmitting end of the tunable electrical delay and the analysis module to form a second calibration device, and the transmission time difference of the optical signal transmission link in the inter-mode parameter measurement device is calibrated back-to-back. ;

[0025] Here, the electrical delay difference The transmission time difference of the optical signal transmission link The DMGD measurement of the few-mode fiber has an impact on the DMGD measurement. The construction of the first calibration device can calibrate the electrical delay difference. The first photon lantern and the second photon lantern are added to the first calibration device to build a second calibration device. The second calibration device plays the role of the transmission time difference of the optical signal transmission link. The calibration of the two parameters can eliminate interference for the differential group delay DMGD measurement of few-mode optical fibers, making the measurement results of the differential group delay DMGD of subsequent mode optical fibers more accurate.

[0026] Preferably, the transmitting end includes a continuous laser, a first coupler, an arbitrary waveform generator and two photoelectric intensity modulators. The continuous laser emits a continuous optical signal and transmits it to the first coupler. The first coupler splits the continuous optical signal into two optical signals and transmits them to the two photoelectric intensity modulators respectively. The arbitrary waveform generator loads the generated two multi-tone signals onto the optical signals in the two photoelectric intensity modulators respectively, wherein one multi-tone signal is loaded with a tunable electrical delay. , each photoelectric intensity modulator outputs a beam of fundamental mode light signal at the output end.

[0027] Preferably, in step S11, the electrical delay difference is calibrated The steps are:

[0028] First, the tunable electrical delay is set by using the first calibration device The initial value of is obtained by analyzing the module (4) to obtain the spectrum of the two fundamental mode optical signals generated by the transmitting end (1) after they are combined, and the absolute power difference of the +1-order sideband in the spectrum is recorded. The absolute power difference satisfies the following relationship:

[0029]

[0030] in, Any two RF frequencies in the multi-tone signal , The absolute power difference between the +1st order sidebands, is the value of the tunable electrical delay, is the electrical time delay difference inherent in the inter-mode parameter measurement device;

[0031] Then determine any two RF frequencies , Is the absolute power difference between the +1-order sidebands zero? If so, determine the tunable electrical delay , and The value of electrical delay difference The calibration is completed; otherwise, change the adjustable electrical delay The initial value of continues to determine any two RF frequencies , The absolute power difference between the +1st order sidebands is zero.

[0032] Preferably, in step S12, the transmission time difference existing in the optical signal transmission link is calibrated The specific steps are:

[0033] First, the tunable electrical delay is set by using the second calibration device The initial value of is obtained by analyzing the module (4) to obtain the spectrum of the fundamental mode optical signal, and the absolute power difference between the +1st order and -1st order sidebands in the spectrum is recorded. The absolute power difference satisfies the following relationship:

[0034]

[0035] in, is the angular frequency of the optical signal emitted by the continuous laser (11), is the RF frequency in the multi-tone signal The absolute power difference between the +1st and -1st order sidebands, is the RF frequency in the multi-tone signal The absolute power difference between the +1st and -1st order sidebands, It is the transmission time difference existing in the optical signal transmission link;

[0036] Then determine any two RF frequencies , Is the absolute power difference between the +1st and -1st order sidebands zero at the same time? If so, determine the tunable electrical delay , and The value is set to the transmission time difference of the optical signal transmission link The calibration is completed; otherwise, change the adjustable electrical delay The initial value of continues to determine any two RF frequencies , Whether the absolute power difference between the +1st and -1st order sidebands is zero at the same time.

[0037] Preferably, in step S5, the absolute power difference satisfies the following relationship:

[0038]

[0039] in, is the transmission time difference between any two modes in the few-mode fiber to be tested;

[0040] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0041] The present invention proposes a device and method for measuring inter-mode parameters based on tunable electrical delay. First, the transmitting end generates two fundamental mode optical signals with multi-tone signals, and a tunable electrical delay is loaded on one of the fundamental mode optical signals with multi-tone signals. , which plays a role in compensating the time delay of another fundamental mode optical signal. Then, the two fundamental mode optical signals are converted into different spatial mode optical signals through the first photon lantern and input into the few-mode optical fiber to be tested. The different spatial mode optical signals are converted into fundamental mode signals through the second photon lantern, and the mode conversion of the optical signal is realized again. Then, the spectrum of the fundamental mode optical signal is obtained by the analysis module, and the power difference between the +1-order and -1-order sidebands is calculated. The absolute value of the difference is taken to obtain the absolute power difference between the +1-order and -1-order sidebands. When the absolute power difference between the +1-order and -1-order sidebands of any two RF frequencies of the fundamental mode optical signal is zero at the same time, the tunable electrical delay is obtained. If the absolute power difference between the +1st and -1st order sidebands of any two RF frequencies cannot be zero at the same time, it can be judged that the DMGD is a negative value. By loading another fundamental mode optical signal with multi-tone signals, the value of DMGD can also be measured; this realizes the distinction between positive or negative DMGD values ​​and broadens the range of DMGD measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A structural diagram showing an inter-mode parameter measurement device based on tunable electrical delay proposed in Embodiment 1 of the present invention;

[0043] Figure 2 A schematic flow chart showing a method for measuring inter-mode parameters based on tunable electrical delay proposed in Embodiment 2 of the present invention;

[0044] Figure 3 The tunable electrical delay of embodiment 2 of the present invention is shown in FIG. The simulation result diagram of

[0045] Figure 4 A structural diagram showing a first calibration device proposed in Embodiment 3 of the present invention;

[0046] Figure 5 A structural diagram showing a second calibration device proposed in Embodiment 3 of the present invention;

[0047] 1. Transmitter; 11. Continuous laser; 12. First coupler; 13. Arbitrary waveform generator; 14. Photoelectric intensity modulator; 2. First photon lantern; 3. Second photon lantern; 4. Analysis module; 41. Second coupler; 42. Spectrum analyzer; 5. Few-mode optical fiber to be tested. DETAILED DESCRIPTION

[0048] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0049] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent actual sizes. The description of the directions of parts such as "upper" and "lower" does not limit the present patent;

[0050] It is understandable to those skilled in the art that some well-known contents may be omitted in the drawings;

[0051] The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present patent.

[0052] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0053] Example 1

[0054] like Figure 1 As shown, a device for measuring inter-mode parameters based on tunable electrical delay is used for measuring differential group delay DMGD of few-mode optical fiber. The device comprises: a transmitting end 1, a first photon lantern 2, a second photon lantern 3 and an analysis module 4;

[0055] The first photon lantern 2 and the second photon lantern 3 are connected to the tested few-mode optical fiber 5, and the transmitting end 1 generates two fundamental mode optical signals with multi-tone signals, one of which is loaded with a tunable electrical delay , the two fundamental mode optical signals are converted into different spatial mode optical signals by the first photon lantern 2 and transmitted to the few-mode optical fiber 5 to be tested, the second photon lantern 3 converts the different spatial mode optical signals output from the few-mode optical fiber 5 to be tested into the fundamental mode signal, the analysis module 4 obtains the spectrum of the fundamental mode optical signal, records the power difference between the +1 order and -1 order sidebands in the spectrum, and assumes that the absolute value of the difference is the absolute power difference, at any two RF frequencies of the fundamental mode optical signal , The tunable electrical delay is determined when the absolute power difference between the +1st and -1st order sidebands is zero at the same time. The value of the tunable electrical delay The differential group delay DMGD of the tested few-mode fiber 5 is calculated based on the value of .

[0056] First, the transmitter generates two fundamental mode optical signals with multi-tone signals, and loads a tunable electrical delay on one of the fundamental mode optical signals with multi-tone signals. , which compensates for the time delay of another fundamental mode optical signal. Then, the two fundamental mode optical signals with multi-tone signals realize the conversion of different spatial mode optical signals through the first photon lantern, and transmit the different spatial mode optical signals to the few-mode optical fiber to be tested. Then, the different spatial mode optical signals in the few-mode optical fiber to be tested are converted into fundamental mode signals through the second photon lantern, and the mode conversion of the optical signal is realized again. The spectrum of the fundamental mode optical signal is further obtained by the analysis module, and the power difference between the +1st and -1st order sidebands is calculated. The absolute value of the difference is obtained to obtain the absolute power difference between the +1st and -1st order sidebands. At any two RF frequencies of the fundamental mode optical signal , The tunable electrical delay is determined when the absolute power difference between the +1st and -1st order sidebands is zero at the same time. If the absolute power difference between the +1st and -1st order sidebands of any two RF frequencies cannot be zero at the same time, it can be judged that the DMGD is a negative value. By loading another fundamental mode optical signal with multi-tone signals, the value of DMGD can also be measured; this realizes the distinction between positive or negative DMGD values ​​and broadens the range of DMGD measurement.

[0057] See also Figure 1 The transmitting end 1 includes a continuous laser 11, a first coupler 12, an arbitrary waveform generator 13 and two photoelectric intensity modulators 14. The continuous laser 11 emits a continuous optical signal and transmits it to the first coupler 12. The first coupler 12 splits the continuous optical signal into two optical signals and transmits them to the two photoelectric intensity modulators 14 respectively. The arbitrary waveform generator 13 loads the generated two multi-tone signals onto the optical signals in the two photoelectric intensity modulators 14 respectively, wherein one multi-tone signal is loaded with a tunable electrical delay. Each output end of the photoelectric intensity modulator 14 outputs a beam of fundamental mode light signal. The photoelectric intensity modulator 14 is a Mach-Zehnder modulator. The analysis module 4 includes a second coupler 41 and a spectrum analyzer 42. The second coupler 41 combines the two beams of fundamental mode light signals output from the second photon lantern 3. The combined light enters the spectrum analyzer 42, and the spectrum of the combined light is obtained by the spectrum analyzer 42.

[0058] Example 2

[0059] See also Figure 2 , a method for measuring inter-mode parameters based on tunable electrical delay, the method is implemented based on the inter-mode parameter measurement device, and at least comprises:

[0060] S1. Connect the few-mode optical fiber 5 to be tested between the first photon lantern 2 and the second photon lantern 3, and use the transmitting end 1 to generate two fundamental mode optical signals with multi-tone signals, one of which is loaded with a tunable electrical delay. ;

[0061] In S1, the DMGD of the connected few-mode fiber 5 to be tested is 1.9 ps / m , length is 10 m ;

[0062] S2. The two fundamental mode optical signals are transmitted to the first photon lantern 2, which are converted into different spatial mode optical signals by the first photon lantern 2 and transmitted to the few-mode optical fiber 5 to be tested;

[0063] S3. The second photon lantern 3 converts different spatial mode optical signals output from the few-mode fiber 5 to be tested into fundamental mode signals;

[0064] S4. Obtain the spectrum of the fundamental mode optical signal by analyzing module 4, record the difference between the +1-order and -1-order sidebands in the spectrum, and set the absolute value of the difference to the absolute power difference;

[0065] S5. Set the tunable electrical delay in S1 The initial value of S4 determines any two RF frequencies of the fundamental mode optical signal , Is the absolute power difference between the +1st and -1st order sidebands zero at the same time? If so, determine the tunable electrical delay value, execute S6; otherwise, change the adjustable electrical delay value, continue to judge any two RF frequencies , Whether the absolute power difference between the +1st and -1st order sidebands is zero at the same time;

[0066] In step S5, the absolute power difference satisfies the following relationship:

[0067]

[0068] in, is the angular frequency of the optical signal emitted by the continuous laser 11, is the RF frequency in the multi-tone signal The absolute power difference between the +1st and -1st order sidebands, is the RF frequency in the multi-tone signal The absolute power difference between the +1st and -1st order sidebands, is the transmission time difference between any two modes in the few-mode optical fiber 5 to be tested;

[0069] See also Figure 3 , with tunable electrical delay The value of the horizontal axis, any two RF frequencies =2π*10 GHz , =2π*19 GHz The simulation result diagram is obtained by taking the absolute power difference as the ordinate. Figure 3 The coordinates corresponding to the absolute power difference between the +1st and -1st order sidebands of the two RF frequencies are confirmed to be zero at the same time. The coordinates are (19, 0), which is the common zero point of the absolute power difference between the +1st and -1st order sidebands of the two RF frequencies. At this time, the tunable electrical delay corresponding to the horizontal coordinate The value is 19 p s;

[0070] S6. Utilization The differential group delay DMGD of the tested few-mode optical fiber 5 is calculated, and the specific calculation formula is as follows:

[0071]

[0072] in, is the length of the few-mode optical fiber 5 to be tested;

[0073] See also Figure 2 and Figure 3 In step S6, The value is 19 ps , the value of L is 10 m Substituting the above formula into calculation, the differential group delay DMGD of the tested few-mode fiber 5 is obtained to be 1.9 ps / m.

[0074] Example 3

[0075] See also Figure 2 In step S1, parameter calibration is required before connecting the few-mode optical fiber 5 to be tested, see Figure 4 and Figure 5 The parameters include the electrical delay difference inherent in the inter-mode parameter measurement device The transmission time difference between the optical signal transmission link and the , the specific steps of calibration are:

[0076] S11. Connect the transmitting end 1 to the analysis module 4 to form a first calibration device to calibrate the electrical delay difference inherent in the inter-mode parameter measurement device. ;

[0077] S12. A first photon lantern 2 and a second photon lantern 3 are connected between the transmitting end 1 and the analysis module 4 to form a second calibration device, and the transmission time difference existing in the optical signal transmission link in the inter-mode parameter measurement device is calibrated back-to-back. .

[0078] In step S11, the electrical delay difference is calibrated The steps are:

[0079] First, the tunable electrical delay is set by using the first calibration device The initial value of is obtained by analyzing the module (4) to obtain the spectrum of the two fundamental mode optical signals generated by the transmitting end (1) after the combination of the two fundamental mode optical signals, and record the absolute power difference of the +1 order sidebands of different radio frequency frequencies in the spectrum. The absolute power difference satisfies the following relationship:

[0080]

[0081] in, Any two RF frequencies in the multi-tone signal , The absolute power difference between the +1st order sidebands, is the value of the tunable electrical delay, is the electrical time delay difference inherent in the inter-mode parameter measurement device;

[0082] Then determine any two RF frequencies , Is the absolute power difference between the +1-order sidebands zero? If so, determine the tunable electrical delay , and The value of electrical delay difference The calibration is completed; otherwise, change the adjustable electrical delay The initial value of continues to determine any two RF frequencies , The absolute power difference between the +1st order sidebands is zero.

[0083] In step S12, the transmission time difference of the optical signal transmission link is calibrated. The specific steps are:

[0084] First, the tunable electrical delay is set by using the second calibration device The initial value of is obtained by analyzing the module (4) to obtain the spectrum of the fundamental mode optical signal, and the absolute power difference between the +1st order and -1st order sidebands in the spectrum is recorded. The absolute power difference satisfies the following relationship:

[0085]

[0086] in, is the angular frequency of the optical signal emitted by the continuous laser (11), is the RF frequency in the multi-tone signal The absolute power difference between the +1st and -1st order sidebands, is the RF frequency in the multi-tone signal The absolute power difference between the +1st and -1st order sidebands, It is the transmission time difference existing in the optical signal transmission link;

[0087] Then determine any two RF frequencies , Is the absolute power difference between the +1st and -1st order sidebands zero at the same time? If so, determine the tunable electrical delay , and The value is set to the transmission time difference of the optical signal transmission link The calibration is completed; otherwise, change the adjustable electrical delay The initial value of continues to determine any two RF frequencies , Whether the absolute power difference between the +1st and -1st order sidebands is zero at the same time.

[0088] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A device for measuring inter-mode parameters based on tunable electrical delay, It is characterized in that The measuring device is used for measuring the differential group delay (DMGD) of a few-mode optical fiber, and comprises: a transmitting end (1), a first photon lantern (2), a second photon lantern (3) and an analysis module (4); A few-mode optical fiber (5) to be tested is connected between the first photon lantern (2) and the second photon lantern (3), and the transmitting end (1) generates two fundamental mode optical signals with multi-tone signals, one of which is loaded with a tunable electrical delay Δτ. 1 , the two fundamental mode optical signals are converted into different spatial mode optical signals by the first photon lantern (2) and transmitted to the few-mode optical fiber to be tested (5), the second photon lantern (3) converts the different spatial mode optical signals output from the few-mode optical fiber to be tested (5) into fundamental mode signals, the analysis module (4) obtains the spectrum of the fundamental mode optical signal, records the power difference between the +1st order and -1st order sidebands in the spectrum, and assumes that the absolute value of the difference is the absolute power difference. At any two radio frequency frequencies ω of the fundamental mode optical signal i ,ω j The tunable electrical delay Δτ is determined when the absolute power difference of 1 The value of the tunable electrical delay Δτ 1 The differential group delay DMGD of the tested few-mode optical fiber (5) is calculated by using the value of 2. The device for measuring inter-mode parameters based on tunable electrical delay according to claim 1, It is characterized in that The transmitting end (1) comprises a continuous laser (11), a first coupler (12), an arbitrary waveform generator (13) and two photoelectric intensity modulators (14); the continuous laser (11) emits a continuous optical signal and transmits it to the first coupler (12); the first coupler (12) splits the continuous optical signal into two optical signals and transmits them to the two photoelectric intensity modulators (14) respectively; the arbitrary waveform generator (13) loads the generated two multi-tone signals onto the optical signals in the two photoelectric intensity modulators (14) respectively; one of the multi-tone signals is loaded with a tunable electrical delay Δτ 1 The output end of each photoelectric intensity modulator (14) outputs a beam of fundamental mode optical signal.

3. The inter-mode parameter measurement device based on tunable electrical delay according to claim 2, It is characterized in that The photoelectric intensity modulator (14) is a Mach-Zehnder modulator.

4. The device for measuring inter-mode parameters based on tunable electrical delay according to claim 1, It is characterized in that The analysis module (4) comprises a second coupler (41) and a spectrum analyzer (42) connected to the second coupler (41); the second coupler (41) combines two fundamental mode optical signals output from the second photon lantern (3); the combined light enters the spectrum analyzer (42); and the spectrum of the combined light is obtained by using the spectrum analyzer (42).

5. A method for measuring inter-mode parameters based on tunable electrical delay, the method being implemented based on the inter-mode parameter measuring device according to claim 1, It is characterized in that At least: S1. Connect the few-mode optical fiber (5) to be tested between the first photon lantern (2) and the second photon lantern (3), and use the transmitting end (1) to generate two fundamental mode optical signals with multi-tone signals, one of which is loaded with a tunable electrical delay Δτ. 1 ; S2. The two fundamental mode optical signals are transmitted to the first photon lantern (2), converted into different spatial mode optical signals by the first photon lantern (2) and transmitted to the few-mode optical fiber to be tested (5); S3. The second photon lantern (3) converts different spatial mode optical signals output from the few-mode optical fiber (5) to be tested into fundamental mode signals; S4. Obtain the spectrum of the fundamental mode optical signal through the analysis module (4), record the power difference between the +1-order and -1-order sidebands in the spectrum, and set the absolute value of the difference to the absolute power difference; S5. Set the tunable electrical delay Δτ in S1 1 The initial value of S4 is used to determine the two RF frequencies ω of the fundamental mode optical signal in S4. i ,ω j Is the absolute power difference between the +1st and -1st order sidebands zero at the same time? If so, determine the tunable electrical delay Δτ 1 value, execute S6; otherwise, change the tunable electrical delay Δτ 1 The value of ω is used to determine the value of any two RF frequencies. i ,ω j Whether the absolute power difference between the +1st and -1st order sidebands is zero at the same time; S6. Using Δτ 1 The differential group delay DMGD of the tested few-mode optical fiber (5) is calculated, and the specific calculation formula is as follows: DMGD=Δτ 1 / L Wherein, L is the length of the few-mode optical fiber (5) to be tested.

6. The method for measuring inter-mode parameters based on tunable electrical delay according to claim 5, It is characterized in that In step S1, parameter calibration is required before accessing the few-mode optical fiber (5) to be tested, wherein the parameters include the electrical delay difference Δτ inherent in the inter-mode parameter measurement device. 0 The transmission time difference Δτ between the optical signal transmission link and 2 , the specific steps of calibration are: S11. Connect the transmitting end (1) to the analysis module (4) to form a first calibration device to calibrate the electrical delay difference Δτ inherent in the inter-mode parameter measurement device 0 ; S12. A first photon lantern (2) and a second photon lantern (3) are connected between the transmitting end (1) and the analysis module (4) to form a second calibration device, and a transmission time difference Δτ existing in the optical signal transmission link in the inter-mode parameter measurement device is calibrated back-to-back by light. 2 .

7. The method for measuring inter-mode parameters based on tunable electrical delay according to claim 6, It is characterized in that The transmitting end (1) comprises a continuous laser (11), a first coupler (12), an arbitrary waveform generator (13) and two photoelectric intensity modulators (14); the continuous laser (11) emits a continuous optical signal and transmits it to the first coupler (12); the first coupler (12) splits the continuous optical signal into two optical signals and transmits them to the two photoelectric intensity modulators (14) respectively; the arbitrary waveform generator (13) loads the generated two multi-tone signals onto the optical signals in the two photoelectric intensity modulators (14) respectively; one of the multi-tone signals is loaded with a tunable electrical delay Δτ 1 The output end of each photoelectric intensity modulator (14) outputs a beam of fundamental mode optical signal.

8. The method for measuring inter-mode parameters based on tunable electrical delay according to claim 7, It is characterized in that In step S11, the electrical delay difference Δτ is calibrated 0 The steps are: First, the tunable electrical delay Δτ is set by using the first calibration device 1 The initial value of is obtained by analyzing the module (4) to obtain the spectrum of the two fundamental mode optical signals generated by the transmitting end (1) after being combined, and the absolute power difference between the +1st order sidebands of different radio frequency frequencies in the spectrum is recorded. The absolute power difference satisfies the following relationship: Where |ΔP| is any two RF frequencies ω in the multi-tone signal i ,ω j The absolute power difference between the +1st order sidebands, Δτ 1 is the value of the tunable electrical delay, Δτ 0 is the electrical time delay difference inherent in the inter-mode parameter measurement device; Then determine any two RF frequencies ω i ,ω j Is the absolute power difference between the +1-order sidebands zero? If so, determine the tunable electrical delay Δτ 1 The value of Δτ 1 The value of is set to the electrical delay difference Δτ 0 The calibration is completed; otherwise, change the tunable electrical delay Δτ 1 The initial value of continues to determine any two RF frequencies ω i ,ω j The absolute power difference between the +1st order sidebands is zero.

9. The method for measuring inter-mode parameters based on tunable electrical delay according to claim 8, It is characterized in that In step S12, the transmission time difference Δτ existing in the optical signal transmission link is calibrated. 2 The specific steps are: First, the tunable electrical delay Δτ is set by using the second calibration device 1 The initial value of is obtained by analyzing the module (4) to obtain the spectrum of the fundamental mode optical signal, and record the absolute power difference between the +1st order and -1st order sidebands in the spectrum. The absolute power difference satisfies the following relationship: Among them, ω o is the angular frequency of the optical signal emitted by the continuous laser (11), |ΔP i | is the RF frequency ω in the multi-tone signal i The absolute power difference between the +1st and -1st order sidebands, |ΔP j | is the RF frequency ω in the multi-tone signal j The absolute power difference between the +1st and -1st order sidebands, Δτ 2 It is the transmission time difference existing in the optical signal transmission link; Then determine any two RF frequencies ω i ,ω j Is the absolute power difference between the +1st and -1st order sidebands zero at the same time? If so, determine the tunable electrical delay Δτ 1 The value of Δτ 1 The value of is set to the transmission time difference Δτ in the optical signal transmission link 2 The calibration is completed; otherwise, change the tunable electrical delay Δτ 1 The initial value of continues to determine any two RF frequencies ω i ,ω j Whether the absolute power difference between the +1st and -1st order sidebands is zero at the same time.

10. The method for measuring inter-mode parameters based on tunable electrical delay according to claim 9, It is characterized in that In step S5, the absolute power difference satisfies the following relationship: Among them, Δτ 3 is the transmission time difference between any two modes in the few-mode optical fiber (5) to be tested.

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