A method and system for accurately measuring fiber dispersion and its temperature coefficient

Abstract

The application discloses a method and system for precisely measuring fiber dispersion and its temperature coefficient, and relates to the technical field of fiber communication and measurement. The application comprises a transmitting end, a receiving end, a fiber link and a time delay measurement module; the signal output by the receiving end is phase-locked to the reference signal of the transmitting end by utilizing the stable phase transmission of the fiber frequency signal; in each measurement period, the wavelength of the optical signal of the transmitting end is changed and the transmission time delay is measured, the fiber dispersion coefficient is calculated according to the influence of the dispersion on the transmission time delay; and then the temperature of the temperature control box is changed, and the temperature coefficient of the dispersion is calculated according to the change rate of the time delay with the temperature. The application has the advantages of high measurement precision and low cost, and can efficiently realize the precise measurement of the fiber dispersion and its temperature coefficient.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication and measurement technology, specifically relating to a method and system for accurately measuring optical fiber dispersion and its temperature coefficient. Background Technology

[0002] Fiber dispersion refers to the phenomenon where light propagates through an optical fiber, and different frequency components exhibit different group velocities due to the wavelength dependence of the material's refractive index and waveguide structure, resulting in pulse broadening and time delay variations. Furthermore, the drift in dispersion parameters caused by environmental temperature fluctuations further increases system uncertainty. Therefore, accurate measurement of fiber dispersion and its temperature coefficient is fundamental to the design of high-performance fiber optic systems.

[0003] In fiber optic communication, dispersion directly limits signal transmission rate and system bandwidth, and pulse broadening caused by dispersion generates inter-symbol interference. Especially in ultra-high-speed, long-distance transmission, pulse broadening is exacerbated, significantly reducing system transmission rate and signal quality. Dispersion drift caused by temperature changes further degrades link performance with environmental variations; therefore, accurate measurement of dispersion and its temperature coefficient is a prerequisite for achieving all-weather dynamic compensation and ensuring long-term link stability. In quantum communication, dispersion disrupts the precise temporal overlap of photons, leading to quantum state decoherence and severely impacting system security and reliability. In fiber optic sensing, fiber dispersion directly affects pulse positioning accuracy, signal demodulation results, and sensitivity. Therefore, measuring fiber dispersion and its temperature coefficient can improve sensor accuracy and stability, helping to maintain high spatial resolution in long-distance sensing. In fiber optic time-frequency transmission, group delay variations caused by dispersion and temperature directly translate into time errors and phase noise, affecting high-precision time-frequency comparison and long-term stability. Therefore, precise measurement and dynamic compensation of dispersion and its temperature coefficient are crucial for ensuring the stability and accuracy of time-frequency transmission systems.

[0004] Currently, methods for measuring fiber dispersion mainly include the phase-shift method, the pulse delay method, and methods based on fiber dispersive analyzers. The phase-shift method injects sinusoidal modulation signals of different wavelengths into the fiber under test, measures the phase shift of the output signal as a function of wavelength, and calculates the dispersion parameters using the group delay difference; this is currently the most widely used method. The pulse delay method obtains dispersion parameters by comparing the arrival time differences of light pulses of different wavelengths; its principle is intuitive and it is suitable for measuring large dispersion quantities. Fiber dispersive analyzers obtain the dispersion coefficient by directly measuring the group delay or group velocity dispersion of the fiber; this method is relatively direct.

[0005] However, existing methods still have certain limitations. On the one hand, they are highly dependent on test conditions and instrument performance, requiring high costs and complex equipment; on the other hand, their accuracy is limited in short fiber, low dispersion, or wide-spectral measurement scenarios. Furthermore, most traditional methods are mainly used for measurements under static or quasi-static conditions, which cannot fully meet the demands for high-precision, real-time, and long-term stable dispersion characterization in fields such as optical communication, time-frequency transfer, and quantum communication. Therefore, it is necessary to explore new methods for measuring fiber dispersion and its temperature coefficient. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a method and system for accurately measuring optical fiber dispersion and its temperature coefficient.

[0007] The technical problem to be solved by this invention is achieved through the following technical solution:

[0008] This invention provides a method for accurately measuring the dispersion and temperature coefficient of optical fibers, comprising:

[0009] S1. During the current measurement cycle, a reference signal and a frequency signal are transmitted through the transmitter, and the frequency signal is modulated into a first optical signal after fiber phase noise compensation. The first optical signal is then transmitted to the receiver through the optical fiber located in the temperature control box.

[0010] S2. The received first optical signal is converted into a first electrical signal by the receiving end and then modulated into a second optical signal, which is then transmitted to the transmitting end through the optical fiber.

[0011] S3. The received second optical signal is converted into a second electrical signal through the transmitting end, and the delay difference of the current measurement period and the phase compensation parameters required for the next fiber phase noise compensation are determined based on the first electrical signal and the second electrical signal, respectively.

[0012] S4. Return to S1 and continue execution to complete the measurement of the next measurement cycle, wherein in the current measurement cycle, the first optical signal has a first wavelength and the second optical signal has a second wavelength, and in the next measurement cycle, the first optical signal has a third wavelength and the second optical signal has a fourth wavelength.

[0013] S5. Change the temperature of the temperature control box, and then return to S1 to continue to complete the measurement of the next measurement cycle. In the next measurement cycle, the first optical signal has a first target wavelength and the second optical signal has a second target wavelength.

[0014] S6. Calculate the fiber dispersion coefficient based on the time delay difference between the two measurement cycles, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the fiber dispersion coefficient.

[0015] S7. Calculate the dispersion temperature coefficient based on the time delay difference between the two measurement cycles, the temperature change of the temperature control box, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the dispersion temperature coefficient.

[0016] The present invention also provides a system for accurately measuring fiber dispersion and its temperature coefficient, for implementing the above-mentioned method for accurately measuring fiber dispersion and its temperature coefficient, the system comprising:

[0017] The system comprises a transmitter, a receiver, a delay measurement module, and a coefficient calculation module. The transmitter and receiver are connected via optical fiber, which is placed in a temperature-controlled chamber with adjustable temperature. The transmitter includes a signal source, an optical fiber noise measurement and compensation module, a first electro-optical conversion module, a first photoelectric conversion module, and a first dense wavelength division multiplexing module. The receiver includes a second electro-optical conversion module, a second photoelectric conversion module, and a second dense wavelength division multiplexing module.

[0018] The signal source is used to transmit a reference signal in each measurement cycle and transmit the reference signal to the time delay measurement module and the fiber optic noise measurement and compensation module, respectively.

[0019] The fiber optic noise measurement and compensation module is used to transmit a frequency signal in each measurement cycle, and transmit the frequency signal to the first electro-optic conversion module after performing fiber optic phase noise compensation.

[0020] The first electro-optic conversion module is used to convert the compensated frequency signal into a first optical signal and then transmit it to the first dense wavelength division multiplexing module. The first optical signal has a first wavelength or a third wavelength.

[0021] The first dense wavelength division multiplexing module is used to perform dense wavelength division multiplexing on the first optical signal and then transmit it to the optical fiber;

[0022] The second dense wavelength division multiplexing module is used to densely wavelength divide the first optical signal transmitted by the optical fiber and then transmit it to the second photoelectric conversion module;

[0023] The second photoelectric conversion module is used to convert the first optical signal into a first electrical signal and then transmit it to the time delay measurement module and the second electro-optic conversion module;

[0024] The time delay measurement module is used to determine the phase difference between the first electrical signal and the reference signal, and convert the obtained phase difference into a time delay difference to obtain the time delay difference for each measurement cycle.

[0025] The second electro-optic conversion module is used to convert the first electrical signal into a second optical signal and then transmit it to the second dense wavelength division multiplexing module;

[0026] The second dense wavelength division multiplexing module is also used to transmit the second optical signal to the optical fiber after dense wavelength division multiplexing;

[0027] The first dense wavelength division multiplexing module is further configured to perform dense wavelength division multiplexing on the second optical signal transmitted by the optical fiber and then transmit it to the first photoelectric conversion module; the second optical signal has a second wavelength or a fourth wavelength;

[0028] The first photoelectric conversion module is used to convert the second optical signal into a second electrical signal and then transmit it to the fiber optic noise measurement and compensation module;

[0029] The fiber optic noise measurement and compensation module is also used to determine the phase compensation parameters required for the next fiber optic phase noise compensation based on the second electrical signal, the frequency signal, and the reference signal.

[0030] The coefficient calculation module is used to calculate the fiber dispersion coefficient based on the time delay difference between two measurement cycles, the wavelength difference between the first optical signal and the second optical signal, the length of the optical fiber, and an expression for the fiber dispersion coefficient; and to calculate the dispersion temperature coefficient based on the time delay difference between two measurement cycles, the temperature change of the temperature control box, the wavelength difference between the first optical signal and the second optical signal, the length of the optical fiber, and an expression for the dispersion temperature coefficient.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The method and system for measuring fiber dispersion and its temperature coefficient provided by this invention achieve accurate measurement of fiber dispersion and its temperature coefficient by measuring the asymmetry of transmission delay and combining it with precise mathematical calculations. The measurement accuracy is not entirely dependent on test conditions and instrument performance, and it is low in cost and high in accuracy. It can achieve accurate measurement of fiber dispersion and its temperature coefficient in short fiber, low dispersion, or wide spectrum measurement scenarios, combining the advantages of high measurement accuracy and low cost. In addition, the measurement method provided by this invention can achieve accurate measurement of fiber dispersion and its temperature coefficient in at least two measurement cycles under the working conditions of the transmitter and receiver, which can meet the needs of optical communication, time-frequency transmission, and quantum communication for high-precision, real-time, and long-term stable dispersion characterization.

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the method for accurately measuring fiber dispersion and its temperature coefficient provided in an embodiment of the present invention.

[0035] Figure 2This is a schematic diagram of the architecture of the fiber optic microwave phase-stable transmission system provided in an embodiment of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0037] Figure 1 This is a flowchart illustrating a method for accurately measuring fiber dispersion and its temperature coefficient provided in an embodiment of the present invention. Figure 1 As shown, the method includes:

[0038] S1. During the current measurement cycle, a reference signal and a frequency signal are transmitted through the transmitter. The frequency signal is then modulated into a first optical signal after fiber phase noise compensation. The first optical signal is transmitted to the receiver through the optical fiber located in the temperature control box.

[0039] Here, the phase compensation parameters determined last time are used to perform fiber phase noise compensation on the frequency signal transmitted in the current measurement period. The compensated frequency signal is then converted into a first optical signal. The first optical signal is then densely wavelength division multiplexed (DWDM) and transmitted to the optical fiber located in the temperature control box, so as to transmit the first optical signal to the receiving end through the optical fiber.

[0040] It should be noted that the phase compensation parameter refers to the phase difference, and how to use the phase difference for phase noise compensation is existing technology, which will not be elaborated upon in this invention. During the current measurement cycle, the temperature control chamber has a temperature, for example, denoted as... .

[0041] S2. The first optical signal received is converted into a first electrical signal by the receiving end and then modulated into a second optical signal, which is then transmitted to the transmitting end through an optical fiber.

[0042] Here, the first optical signal transmitted through the optical fiber is densely wavelength divided (DWDM) and then converted into a first electrical signal. The first electrical signal is then converted into a second optical signal, which is then DWDM-multiplexed again before being transmitted back to the optical fiber. This allows the second optical signal to be transmitted to the transmitting end via the optical fiber. It should be noted that the second optical signal and the first optical signal have different wavelengths.

[0043] S3. The received second optical signal is converted into a second electrical signal through the transmitter. Based on the first electrical signal and the second electrical signal, the time delay difference of the current measurement period and the phase compensation parameters required for the next fiber phase noise compensation are determined respectively.

[0044] In this invention, the phase difference between the first electrical signal and the reference signal is determined, and the obtained phase difference is converted into a time delay difference according to the relationship between time delay and phase, thereby obtaining the time delay difference of the current measurement period.

[0045] In this invention, the phase compensation parameters required for the next fiber optic phase noise compensation are determined based on the phase relationship between the second electrical signal, the frequency signal, and the reference signal. Specifically, two phase-conjugate signals are generated based on the reference signal. One of the two phase-conjugate signals is mixed with the second electrical signal to obtain a sum-frequency component and a difference-frequency component. Simultaneously, the other of the two phase-conjugate signals is mixed with the frequency signal to obtain a sum-frequency component and a difference-frequency component. The two difference-frequency components are then mixed to obtain phase noise, which is the phase compensation parameter required for the next fiber optic phase noise compensation.

[0046] It should be noted that completing S3 indicates the end of the current measurement cycle. It should also be noted that the fiber optic phase noise compensation cycle is completely independent of the measurement cycle.

[0047] S4. Return to S1 and continue execution to complete the measurement of the next measurement cycle. In the current measurement cycle, the first optical signal has a first wavelength and the second optical signal has a second wavelength. In the next measurement cycle, the first optical signal has a third wavelength and the second optical signal has a fourth wavelength.

[0048] It should be noted that the specific values ​​of the first wavelength, second wavelength, third wavelength and fourth wavelength can be set according to actual needs, and the present invention does not limit them.

[0049] S5. Change the temperature of the temperature control box, and then return to S1 to continue the execution to complete the measurement of the next measurement cycle. In the next measurement cycle, the first optical signal has the first target wavelength and the second optical signal has the second target wavelength.

[0050] It is understood that in this invention, the current measurement cycle, the next measurement cycle, and the measurement cycle after that refer to the first, second, and third measurement cycles in three consecutive measurement cycles, respectively. The temperature of the temperature control chamber is the same in the current and next measurement cycles, but different in the next and the measurement cycle after that. The amount of temperature change in the temperature control chamber can be set according to actual needs, and this invention does not limit this.

[0051] S6. Calculate the fiber dispersion coefficient based on the time delay difference between the two measurement cycles, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the fiber dispersion coefficient.

[0052] S7. Calculate the dispersion temperature coefficient based on the time delay difference between the two measurement cycles, the temperature change of the temperature control box, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the dispersion temperature coefficient.

[0053] In some embodiments, the expression for the fiber dispersion coefficient is as follows:

[0054] (1);

[0055] in, Indicates the time delay difference. Represents the absolute value of the wavelength difference. Represents the fiber dispersion coefficient. Indicates the length of the optical fiber. This represents the base latency, and... and All of these are unknowns.

[0056] In some embodiments, S6 is implemented via S61 to S62:

[0057] S61. Determine the first wavelength Second wavelength The absolute value of the difference between them is used to obtain the absolute value of the first wavelength difference. and determining the third wavelength and the fourth wavelength The absolute value of the difference between the two wavelengths is used to obtain the absolute value of the second wavelength difference. .

[0058] S62. Based on the time delay difference of the current measurement period The length of the optical fiber and the absolute value of the first wavelength difference. The time delay difference in the next measurement cycle The absolute value of the difference between the second and second wavelengths The fiber dispersion coefficient is determined by using the expression for the fiber dispersion coefficient.

[0059] Specifically, the time delay difference of the current measurement period The absolute value of the difference between the length of the optical fiber and the first wavelength. Substituting the expression for the fiber dispersion coefficient, we obtain a linear equation in two variables; the time delay difference of the next measurement cycle is then used. The length of the optical fiber and the absolute value of the difference between the second wavelength. Substituting the expression for the fiber dispersion coefficient, we obtain another linear equation in two variables. By solving these two equations simultaneously, we can determine the fiber dispersion coefficient. and .

[0060] In some embodiments, the first target wavelength is a first wavelength. And the second target wavelength is the second wavelength. Based on this, the above S7 is implemented through S71~S74:

[0061] S71. Determine the first wavelength Second wavelength The absolute value of the difference between them is used to obtain the absolute value of the first wavelength difference. .

[0062] S72. Determine the time delay difference for the next measurement cycle. Time delay difference with the current measurement period The absolute value of the difference between them yields the first time delay difference change. .

[0063] S73. Determine the temperature value of the temperature control box for the next measurement cycle. Temperature value of the temperature control box during the current measurement cycle The absolute value of the difference between them yields the first temperature change. .

[0064] S74, at least based on the length of the optical fiber and the first time delay difference variation First temperature change The absolute value of the first wavelength difference And the expression for the dispersion temperature coefficient, determine the dispersion temperature coefficient. .

[0065] In some embodiments, the first target wavelength is the third wavelength. And the second target wavelength is the fourth wavelength. Based on this, the above S7 is implemented through S701~S704:

[0066] S701, Determine the third wavelength and the fourth wavelength The absolute value of the difference between the two wavelengths is used to obtain the absolute value of the second wavelength difference. .

[0067] S702. Determine the time delay difference for the next measurement cycle. Time delay difference with the next measurement cycle The absolute value of the difference between them yields the second time delay difference change. .

[0068] S703. Determine the temperature value of the temperature control box for the next measurement cycle. Temperature value of the temperature control chamber in the next measurement cycle The absolute value of the difference between them yields the second temperature change. .

[0069] S704, at least based on the length of the optical fiber and the second time delay difference variation Second temperature change The absolute value of the second wavelength difference And the expression for the dispersion temperature coefficient, determine the dispersion temperature coefficient. .

[0070] Change in fiber temperature Temperature can be determined using the above formula (1). The partial derivatives are used to calculate the result, which is expressed as:

[0071] (2);

[0072] in The dispersion temperature coefficient is This is the coefficient of thermal expansion of the optical fiber, which reflects the change in the physical length of the fiber with temperature. Represents the fiber dispersion coefficient Temperature rate of change, Indicates the length of the optical fiber Temperature rate of change, It represents the amount of temperature change.

[0073] According to the above formula (2), it can be seen that, given... , and Based on the measurement and Then it can be calculated .

[0074] Furthermore, because the dispersion temperature coefficient of optical fiber is much greater than its thermal expansion coefficient... With fiber dispersion coefficient The product ( , Indicates much greater than, (This indicates taking the absolute value), therefore, the above formula (2) can be simplified to a linear relationship:

[0075] (3);

[0076] According to the above formula (3), it can be seen that when only the known Based on the measurement , and It can also be calculated Therefore, either formula (2) or (3) above can be used to calculate... .

[0077] In some embodiments, S74 above can be implemented as: the change in the length of the optical fiber and the change in the first time delay difference. First temperature change The absolute value of the first wavelength difference Substituting into the expression for the dispersion temperature coefficient, we can calculate... In some embodiments, S74 above can also be implemented as: the change in the length of the optical fiber and the change in the first time delay difference. First temperature change The absolute value of the first wavelength difference and Substituting into the expression for the dispersion temperature coefficient, we can calculate... This leads to a more accurate result. .

[0078] Similarly, in some embodiments, S704 above can be implemented as: the change in the length of the optical fiber and the change in the second time delay difference. Second temperature change The absolute value of the second wavelength difference Substituting into the expression for the dispersion temperature coefficient, we can calculate... In some embodiments, S704 above can also be implemented as: the change in the length of the optical fiber and the change in the second time delay difference. Second temperature change The absolute value of the second wavelength difference and Substituting into the expression for the dispersion temperature coefficient, we can calculate... This leads to a more accurate result. .

[0079] The present invention also provides a system for accurately measuring fiber dispersion and its temperature coefficient. This system includes a fiber optic microwave phase-stabilized transmission system and a coefficient calculation module. For example, Figure 2 This is a schematic diagram of the architecture of the fiber optic microwave phase-steady transmission system. (For example...) Figure 2 As shown, the system includes: a transmitter, a receiver, and a time delay measurement module. The transmitter and receiver are connected via optical fiber, which is placed in a temperature-controlled chamber with adjustable temperature. The transmitter includes a signal source (…). Figure 2 (not shown in the image), fiber optic noise measurement and compensation module, first electro-optic conversion module ( Figure 2 LD1), the first photoelectric conversion module ( Figure 2 PD1 in the first dense wavelength division multiplexing module (PD1) Figure 2 The DWDM is located at the transmitting end. The receiving end includes a second electro-optical conversion module. Figure 2 LD2 in the middle), the second photoelectric conversion module ( Figure 2PD2 in the middle), the second dense wavelength division multiplexing module ( Figure 2 The DWDM located at the receiving end is mentioned. It should be noted that the fiber optic noise measurement and compensation module, the first electro-optic conversion module, the first optoelectronic conversion module, the first dense wavelength division multiplexing module, the second electro-optic conversion module, the second optoelectronic conversion module, and the second dense wavelength division multiplexing module all adopt existing modules or devices in the prior art. Therefore, the specific structure of these modules and devices will not be described in detail in this invention.

[0080] The signal source is used to transmit a reference signal in each measurement cycle and transmit the reference signal to the time delay measurement module and the fiber optic noise measurement and compensation module, respectively.

[0081] The fiber optic noise measurement and compensation module is used to transmit frequency signals using an internal voltage-controlled oscillator (VCO) in each measurement cycle, and then use the VCO to perform fiber optic phase noise compensation on the frequency signals before transmitting them to the first electro-optic conversion module.

[0082] The first electro-optical conversion module is used to convert the compensated frequency signal into a first optical signal and then transmit it to the first dense wavelength division multiplexing module. The first optical signal has a first wavelength. Or the third wavelength .

[0083] The first dense wavelength division multiplexing module is used to perform dense wavelength division multiplexing on the first optical signal and then transmit it to the optical fiber.

[0084] The second dense wavelength division multiplexing module is used to densely wavelength divide the first optical signal transmitted by optical fiber and then transmit it to the second photoelectric conversion module.

[0085] The second photoelectric conversion module is used to convert the first optical signal into a first electrical signal and then transmit it to the time delay measurement module and the second electro-optical conversion module.

[0086] The time delay measurement module is used to determine the phase difference between the first electrical signal and the reference signal, and convert the obtained phase difference into a time delay difference to obtain the time delay difference for each measurement cycle.

[0087] The second electro-optic conversion module is used to convert the first electrical signal into a second optical signal and then transmit it to the second dense wavelength division multiplexing module.

[0088] The second dense wavelength division multiplexing module is also used to transmit the second optical signal to the optical fiber after dense wavelength division multiplexing.

[0089] The first dense wavelength division multiplexing module is also used to densely wavelength divide the second optical signal transmitted through the optical fiber and then transmit it to the first photoelectric conversion module; the second optical signal has a second wavelength. or fourth wavelength .

[0090] The first photoelectric conversion module is used to convert the second optical signal into a second electrical signal and then transmit it to the fiber optic noise measurement and compensation module.

[0091] The fiber optic noise measurement and compensation module is also used to determine the phase compensation parameters required for the next fiber optic phase noise compensation based on the phase relationship between the second electrical signal, the frequency signal, and the reference signal, using the internal fiber optic noise measurement module. Specifically, the fiber optic noise measurement module includes: a conjugate signal generation device, a mixer, and a loop filter. The conjugate signal generation device generates two phase-conjugate signals based on the reference signal. The mixer mixes one of the two phase-conjugate signals with the second electrical signal to obtain a sum-frequency component and a difference-frequency component. Simultaneously, it mixes the other of the two phase-conjugate signals with the frequency signal to obtain a sum-frequency component and a difference-frequency component. The two difference-frequency components are then mixed to obtain the phase noise. The loop filter transmits the phase noise to the VCO inside the fiber optic noise measurement and compensation module.

[0092] The coefficient calculation module is used to calculate the fiber dispersion coefficient based on the time delay difference between two measurement cycles, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the fiber dispersion coefficient; and to calculate the dispersion temperature coefficient based on the time delay difference between two measurement cycles, the temperature change of the temperature control box, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the dispersion temperature coefficient.

[0093] The method and system for accurately measuring fiber dispersion and its temperature coefficient provided by this invention achieve precise measurement of fiber dispersion and its temperature coefficient by measuring the asymmetry of transmission delay and combining it with precise mathematical calculations. The measurement accuracy is not entirely dependent on test conditions and instrument performance, and it is low in cost and high in accuracy. It can achieve precise measurement of fiber dispersion and its temperature coefficient in short fiber, low dispersion, or wide spectrum measurement scenarios, combining the advantages of high measurement accuracy and low cost. In addition, the measurement method provided by this invention can achieve precise measurement of fiber dispersion and its temperature coefficient in at least two measurement cycles under the working conditions of the transmitter and receiver, which can meet the needs of optical communication, time-frequency transmission, and quantum communication for high-precision, real-time, and long-term stable dispersion characterization.

[0094] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0095] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0096] In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple instances. While different embodiments may describe certain measures, this does not mean that these measures cannot be combined to produce a good effect.

[0097] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for accurately measuring the dispersion and temperature coefficient of optical fibers, characterized in that, include: S1. During the current measurement cycle, a reference signal and a frequency signal are transmitted through the transmitter, and the frequency signal is modulated into a first optical signal after fiber phase noise compensation. The first optical signal is then transmitted to the receiver through the optical fiber located in the temperature control box. S2. The received first optical signal is converted into a first electrical signal by the receiving end and then modulated into a second optical signal, which is then transmitted to the transmitting end through the optical fiber. S3. The received second optical signal is converted into a second electrical signal through the transmitting end, and the delay difference of the current measurement period and the phase compensation parameters required for the next fiber phase noise compensation are determined based on the first electrical signal and the second electrical signal, respectively. S4. Return to S1 and continue execution to complete the measurement of the next measurement cycle, wherein in the current measurement cycle, the first optical signal has a first wavelength and the second optical signal has a second wavelength, and in the next measurement cycle, the first optical signal has a third wavelength and the second optical signal has a fourth wavelength. S5. Change the temperature of the temperature control box, and then return to S1 to continue to complete the measurement of the next measurement cycle. In the next measurement cycle, the first optical signal has a first target wavelength and the second optical signal has a second target wavelength. S6. Calculate the fiber dispersion coefficient based on the time delay difference between the two measurement cycles, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the fiber dispersion coefficient. S7. Calculate the dispersion temperature coefficient based on the time delay difference between the two measurement cycles, the temperature change of the temperature control box, the wavelength difference between the first and second optical signals, the length of the optical fiber, and the expression for the dispersion temperature coefficient. The expression for the fiber dispersion coefficient is as follows: , Indicates the time delay difference. Represents the absolute value of the wavelength difference. This represents the dispersion coefficient of the optical fiber. Indicates the length of the optical fiber. This represents the basic latency, and... and All are unknowns; S6 includes: S61. Determine the first wavelength Second wavelength The absolute value of the difference between them is used to obtain the absolute value of the first wavelength difference. and determining the third wavelength and the fourth wavelength The absolute value of the difference between the two wavelengths is used to obtain the absolute value of the second wavelength difference. ; S62, the time delay difference of the current measurement period The length of the optical fiber The absolute value of the difference between the first wavelength and the second wavelength Substituting the expression for the fiber dispersion coefficient, a linear equation in two variables is obtained; the time delay difference of the next measurement cycle is then used. The length of the optical fiber The absolute value of the difference between the second and second wavelengths Substituting the expression for the fiber dispersion coefficient, another linear equation in two variables is obtained; by solving the two linear equations simultaneously, the fiber dispersion coefficient is determined. and the aforementioned basic delay ; Wherein, when the first target wavelength is the first wavelength And the second target wavelength is the second wavelength. When, S7 includes: S71. Determine the first wavelength Second wavelength The absolute value of the difference between them is used to obtain the absolute value of the first wavelength difference. ; S72. Determine the time delay difference of the next measurement cycle. Time delay difference with the current measurement period The absolute value of the difference between them yields the first time delay difference change. ; S73. Determine the temperature value of the temperature control box for the next measurement cycle. The temperature value of the temperature control box during the current measurement cycle The absolute value of the difference between them yields the first temperature change. ; S74, at least according to the length of the optical fiber First time delay difference change First temperature change The absolute value of the first wavelength difference Based on the expression for the dispersion temperature coefficient, the dispersion temperature coefficient is determined. ; Wherein, when the first target wavelength is the third wavelength And the second target wavelength is the fourth wavelength. When, S7 includes: S701, Determine the third wavelength and the fourth wavelength The absolute value of the difference between the two wavelengths is used to obtain the absolute value of the second wavelength difference. ; S702, Determine the time delay difference of the next measurement cycle. Time delay difference with the next measurement cycle The absolute value of the difference between them yields the second time delay difference change. ; S703. Determine the temperature value of the temperature control box for the next measurement cycle. The temperature value of the temperature control box in the next measurement cycle The absolute value of the difference between them yields the second temperature change. ; S704, at least according to the length of the optical fiber Second time delay difference change Second temperature change The absolute value of the second wavelength difference Based on the expression for the dispersion temperature coefficient, the dispersion temperature coefficient is determined. .

2. The method for accurately measuring fiber dispersion and its temperature coefficient according to claim 1, characterized in that, S3 includes: S31. The received second optical signal is converted into a second electrical signal through the transmitting end; S32. Determine the phase difference between the first electrical signal and the reference signal, and convert the obtained phase difference into a time delay difference to obtain the time delay difference of the current measurement period; S33. Determine the phase compensation parameters required for the next fiber optic phase noise compensation based on the second electrical signal, the frequency signal, and the reference signal.

3. The method for accurately measuring fiber dispersion and its temperature coefficient according to claim 1, characterized in that, The expression for the dispersion temperature coefficient is as follows: ； in, This represents the change in time delay difference. It represents the amount of temperature change.

4. The method for accurately measuring fiber dispersion and its temperature coefficient according to claim 1, characterized in that, The expression for the dispersion temperature coefficient is as follows: ； in, The coefficient of thermal expansion of optical fiber is used to reflect the change in the physical length of the fiber with temperature. This represents the change in time delay difference. It represents the amount of temperature change.

5. A system for accurately measuring the dispersion and temperature coefficient of optical fibers, characterized in that, The system for implementing the method for accurately measuring fiber dispersion and its temperature coefficient according to any one of claims 1 to 4, the system comprising: The system comprises a transmitter, a receiver, a delay measurement module, and a coefficient calculation module. The transmitter and receiver are connected via optical fiber, which is placed in a temperature-controlled chamber with adjustable temperature. The transmitter includes a signal source, an optical fiber noise measurement and compensation module, a first electro-optical conversion module, a first photoelectric conversion module, and a first dense wavelength division multiplexing module. The receiver includes a second electro-optical conversion module, a second photoelectric conversion module, and a second dense wavelength division multiplexing module. The signal source is used to transmit a reference signal in each measurement cycle and transmit the reference signal to the time delay measurement module and the fiber optic noise measurement and compensation module, respectively. The fiber optic noise measurement and compensation module is used to transmit a frequency signal in each measurement cycle, and transmit the frequency signal to the first electro-optic conversion module after performing fiber optic phase noise compensation. The first electro-optic conversion module is used to convert the compensated frequency signal into a first optical signal and then transmit it to the first dense wavelength division multiplexing module. The first optical signal has a first wavelength or a third wavelength. The first dense wavelength division multiplexing module is used to perform dense wavelength division multiplexing on the first optical signal and then transmit it to the optical fiber; The second dense wavelength division multiplexing module is used to densely wavelength divide the first optical signal transmitted by the optical fiber and then transmit it to the second photoelectric conversion module; The second photoelectric conversion module is used to convert the first optical signal into a first electrical signal and then transmit it to the time delay measurement module and the second electro-optic conversion module; The time delay measurement module is used to determine the phase difference between the first electrical signal and the reference signal, and convert the obtained phase difference into a time delay difference to obtain the time delay difference for each measurement cycle. The second electro-optic conversion module is used to convert the first electrical signal into a second optical signal and then transmit it to the second dense wavelength division multiplexing module; The second dense wavelength division multiplexing module is also used to transmit the second optical signal to the optical fiber after dense wavelength division multiplexing; The first dense wavelength division multiplexing module is further configured to perform dense wavelength division multiplexing on the second optical signal transmitted by the optical fiber and then transmit it to the first photoelectric conversion module; the second optical signal has a second wavelength or a fourth wavelength; The first photoelectric conversion module is used to convert the second optical signal into a second electrical signal and then transmit it to the fiber optic noise measurement and compensation module; The fiber optic noise measurement and compensation module is also used to determine the phase compensation parameters required for the next fiber optic phase noise compensation based on the second electrical signal, the frequency signal, and the reference signal. The coefficient calculation module is used to calculate the fiber dispersion coefficient based on the time delay difference between two measurement cycles, the wavelength difference between the first optical signal and the second optical signal, the length of the optical fiber, and an expression for the fiber dispersion coefficient; and to calculate the dispersion temperature coefficient based on the time delay difference between two measurement cycles, the temperature change of the temperature control box, the wavelength difference between the first optical signal and the second optical signal, the length of the optical fiber, and an expression for the dispersion temperature coefficient.

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