A high-precision optical fiber link delay measurement device and method

Abstract

A high-precision optical fiber link delay measurement device and method belong to the field of optical fiber transmission technology. The device includes a first signal source outputting a sinusoidal signal; a second signal source outputting a 1pps pulse signal; an atomic clock for signal synchronization; an optical signal transmission module that mixes and modulates the two signals into an optical signal before transmitting it to the optical fiber link; a tunable optical delay line to compensate for optical fiber link delay jitter; a Faraday rotator to reflect the optical signal; a photodetector to convert the optical signal into an electrical signal; a first bandpass filter to separate the sinusoidal signal from the electrical signal; a feedback control module to control the tunable optical delay line; a first data acquisition and processing module to obtain a wide-range delay result; and a second data acquisition and processing module to obtain a high-precision delay result. This invention measures the high-precision delay of the optical fiber link by obtaining a wide-range delay result and a high-precision delay result.

Description

Technical Field

[0001] This invention relates to the field of optical fiber transmission technology, and specifically to a high-precision optical fiber link delay measurement device and method. Background Technology

[0002] Optical fiber link delay is a crucial parameter in optical fiber communication. However, due to limitations in current technology, achieving high-precision delay measurements is difficult. In 2008, a research group at Peking University proposed and demonstrated a novel method for measuring optical fiber delay using a free-running laser. The fiber under test was spliced ​​onto an erbium-doped fiber to form a ring cavity laser. The laser's mode beat frequency was measured, and the round-trip time delay was determined. This method was successfully implemented for fiber lengths ranging from 100 km to a few meters, achieving an accuracy of 10⁻⁶. -8 -10 -6 And resolutions ranging from tens of nanoseconds to tens of picoseconds.

[0003] In 2010, a research group at Tsinghua University theoretically analyzed the delay measurement system of phase-sensitive low-coherence optical interferometry (OLCR) and built an OLCR measurement device based on an unbalanced Michelson interferometer. The light source used was spontaneous broadband light from an erbium-doped fiber amplifier (EDFA). The delay of photonic crystal fiber (PCF) was measured at wavelengths of 1540~1560nm with a measurement accuracy of about 0.14ps.

[0004] In 2014, a research group at the PLA University of Science and Technology conducted research on high-precision fiber optic transmission time measurement based on the peak scanning method using single-photon detection. By adjusting the delay and width of the gate signal of the single-photon detector, under the condition of optimal matching between the reflected light pulse and the gate signal, the measurement accuracy of 125km of fiber optic cable reached 35ps. Summary of the Invention

[0005] This invention provides a high-precision fiber optic link delay measurement device and method, aiming to at least partially solve the above-mentioned technical problems.

[0006] As a first aspect of the present invention, a high-precision fiber optic link delay measurement device is provided, comprising: The first signal source outputs a sine wave signal with a frequency of not less than 1 GHz; The second signal source outputs a 1pps pulse signal; An atomic clock synchronizes the first and second signal sources using a 10MHz signal. The optical signal transmitting module mixes and modulates the signals from the first and second signal sources into the optical signal output by the laser, and then transmits the optical signal to the optical fiber link via a polarization beam splitter. Tunable optical delay lines compensate for delay jitter in fiber optic links; A Faraday rotator reflects the optical signal to a tunable optical delay line, so that the optical signal can be transmitted to a polarization beam splitter via an optical fiber link. A photodetector receives reflected light signals from a polarization beam splitter and converts them into electrical signals. The first bandpass filter separates the sinusoidal signal from the electrical signal of the photodetector; The feedback control module controls the tunable optical delay line by mixing the signal from the first signal source and the signal separated by the first bandpass filter. The first data acquisition and processing module mixes the signal from the photodetector with the signal from the first signal source and then restores the 1pps signal through a low-pass filter. It then compares the 1pps signal restored by the low-pass filter with the signal from the second signal source to obtain a wide-range delay result. The second data acquisition and processing module mixes the 10MHz signal from the atomic clock on the single-sideband modulation circuit board of the first signal source with the signal from the first bandpass filter, and then compares the 10MHz signal separated by the second bandpass filter with the signal from the atomic clock to obtain a high-precision delay result.

[0007] The optical signal transmitting module includes a laser, a Mach-Zehnder intensity modulator, a fourth mixer, and a first electrical amplifier; the signals from the first signal source and the second signal source are mixed by the fourth mixer and amplified by the first electrical amplifier, and then modulated by the Mach-Zehnder intensity modulator to the optical signal output by the laser.

[0008] The signal from the first signal source is modulated to a 10MHz signal by a single-sideband modulation circuit board and then amplified by a second amplifier.

[0009] The atomic clock is a rubidium clock.

[0010] The length of the optical fiber link shall be no less than 10 km.

[0011] The fiber optic link is 20km long.

[0012] The frequency of the first signal source is 5GHz, 10GHz, 20GHz, 50GHz or 100GHz.

[0013] As a second aspect of the present invention, a method for measuring high-precision fiber optic link delay is also provided, characterized by comprising the following steps: The first signal source outputs a sinusoidal signal with a frequency of not less than 1 GHz and the second signal source outputs a 1 pps pulse signal. After synchronizing with the atomic clock's 10 MHz signal, the signal is then mixed and modulated with the optical signal output by the laser of the optical signal generation unit. The optical signal is then transmitted to the optical fiber link by the polarization beam splitter. The optical signal of the fiber optic link is reflected back to the tunable optical delay line, the fiber optic link, and the polarization beam splitter by a Faraday rotator after passing through the tunable optical delay line. The optical signal is then converted into an electrical signal. The first bandpass filter separates the sinusoidal signal from the electrical signal of the photodetector, and the signal generated after mixing with the signal of the first signal source is controlled by the feedback control module to control the tunable optical delay line. The first data acquisition and processing module mixes the signal from the photodetector with the signal from the first signal source, and then the 1pps signal restored by the low-pass filter is compared with the signal from the second signal source to obtain a wide range of delay results. The second data acquisition and processing module mixes the 10MHz signal from the first signal source, which is modulated by the single-sideband modulation circuit board, with the signal from the first bandpass filter. Then, the 10MHz signal separated by the second bandpass filter is compared with the signal from the atomic clock to obtain a high-precision delay result.

[0014] The signal from the first signal source is modulated to a 10MHz signal by a single-sideband modulation circuit board and amplified by a second amplifier. This 10MHz signal is provided by an atomic clock.

[0015] The frequency of the first signal source is 5GHz, 10GHz, 20GHz, 50GHz or 100GHz. Based on the above solution, it can be seen that the high-precision fiber optic link delay measurement device and method of the present invention have at least one of the following advantages over the prior art: 1. This invention measures a small amount of delay data to obtain a wide range of delay results and high-precision delay results, thereby obtaining high-precision delay of the fiber optic link.

[0016] 2. The high-precision fiber optic link delay measurement device of the present invention can achieve femtosecond-level measurement accuracy.

[0017] 3. This invention controls the tunable optical delay line by processing the voltage signal of the feedback control module. The tunable optical delay line can be used to compensate for delay jitter caused by various factors such as temperature changes and external vibrations over a wide range, with high precision and rapid speed, thereby stabilizing the delay jitter of the fiber optic link. When measuring delay, the influence of factors such as temperature changes does not need to be considered, simplifying the process and improving reliability. Attached Figure Description

[0018] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0019] Figure 1 This is a framework diagram of the high-precision fiber optic link delay measurement of the present invention. Detailed Implementation

[0020] To better understand the technical solutions of the embodiments of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, this embodiment of the invention discloses a high-precision fiber optic link delay measurement device, including a first signal source, a second signal source, an atomic clock, an optical signal transmission module, a tunable optical delay line, a Faraday rotator, a photodetector, a first bandpass filter, a feedback control module, a first data acquisition and processing module, and a second data acquisition and processing module.

[0023] The first signal source outputs a sinusoidal signal with a frequency of not less than 1 GHz. Specifically, in this embodiment, the first signal source outputs a 10 GHz signal. The first signal source can be selected to output signals of 5 GHz, 10 GHz, 20 GHz, 50 GHz, or 100 GHz.

[0024] The second signal source outputs a 1pps pulse signal (1 Pulse Per Second Signal).

[0025] An atomic clock is used to synchronize the first and second signal sources using a 10MHz signal. In this embodiment, the atomic clock is a rubidium clock.

[0026] The optical signal transmitting module includes a laser, a Mach-Zehnder intensity modulator, a fourth mixer, and a first electrical amplifier. The signals from the first and second signal sources are mixed by the fourth mixer and then amplified by the first electrical amplifier. The optical signal transmitting module modulates the mixed signal from the first and second signal sources onto the optical signal output from the laser via the Mach-Zehnder intensity modulator, thus achieving the mixing and modulation of the sinusoidal signal output from the first signal source and the 1pps pulse signal output from the second signal source onto the optical carrier.

[0027] The optical signal is transmitted to the optical fiber link via a polarization beam splitter. The length of the optical fiber link is no less than 10 km; in this embodiment, the length of the optical fiber link is 20 km.

[0028] Tunable optical delay lines connect to fiber optic links and compensate for delay jitter in the fiber optic links, thereby eliminating delay jitter in stable fiber optic links and reducing the impact of delay jitter on signals.

[0029] The Faraday rotator reflects the optical signal to a tunable optical delay line, so that the optical signal can be transmitted to the polarization beam splitter via an optical fiber link.

[0030] The photodetector is connected to the polarization beamsplitter. It receives the reflected light signal from the polarization beamsplitter and converts it into an electrical signal through photoelectric conversion. This electrical signal is split into two paths: one for measuring a wide range of time delays and the other for measuring high-precision time delays.

[0031] The first bandpass filter separates a 10 GHz sinusoidal signal from the electrical signal generated by the photoelectric conversion of the photodetector.

[0032] The sinusoidal signal from the first signal source and the sinusoidal signal separated by the first bandpass filter are mixed by the first mixer to generate a signal that serves as the input to the feedback control module. After signal processing, the signal controls the tunable optical delay line.

[0033] The output signal of the photodetector is divided into two paths. One path, which measures a wide-range delay, is mixed with the signal from the first signal source via a second mixer, and then filtered by a low-pass filter to reconstruct a 1pps signal. The first data acquisition and processing module compares this reconstructed 1pps signal with the signal from the second signal source to obtain the wide-range delay result. This first data acquisition and processing module uses a pulse delay measurement method to compare the reconstructed second pulse with the second pulse from the transmitting end in the time domain to obtain the delay amount. This delay amount is a coarse-precision delay amount.

[0034] Depend on Figure 1 It can be seen that the 10MHz signal of the atomic clock on the first signal source is modulated by the single-sideband modulation circuit board, amplified by the second amplifier, and then mixed with the sinusoidal signal separated by the first bandpass filter in the third mixer. The 10MHz signal is then separated by the second bandpass filter and compared with the 10MHz signal of the atomic clock to obtain a high-precision delay result.

[0035] In summary, the high-precision fiber optic link delay measurement device of the present invention transmits a second pulse and a sine wave at the local end, mixes them, and modulates them into an optical signal with only one wavelength. The second pulse and the high-frequency sine wave are transmitted through the fiber optic link. At the receiving end, the optical signal is detected and the second pulse and the sine wave are demodulated. Both signals carry information about the fiber optic link delay jitter. The reconstructed sine wave has a phase delay compared to the transmitting sine wave, which can be expressed as 2kπ + ∆φ. However, there is periodic ambiguity, and only ∆φ can be measured during comparison. Therefore, the delay calculated using ∆φ is actually a high-precision small delay. The final delay is obtained by adding the integer period portion of the coarse-precision delay to the high-precision small delay.

[0036] The high-precision fiber optic link delay measurement device of the present invention effectively doubles the path length because the optical signal is transmitted twice in the fiber optic link. By adding a small amount of the obtained wide-range delay result and the obtained high-precision delay result, the high-precision delay of the fiber optic link can be obtained.

[0037] The high-precision fiber optic link delay measurement device of this invention can achieve femtosecond-level measurement accuracy. Furthermore, by controlling a tunable optical delay line through a feedback control module, it can automatically, with high precision and rapid compensation over a wide range, for delay jitter caused by various factors such as temperature changes and external vibrations, thereby stabilizing fiber optic link delay jitter. The device simplifies the measurement process by eliminating the need to consider the effects of temperature changes and other factors, thus improving reliability.

[0038] This embodiment also discloses a high-precision fiber optic link delay measurement method for use with the aforementioned high-precision fiber optic link delay measurement device. The method includes the following steps: The first signal source outputs a sinusoidal signal with a frequency of not less than 1 GHz and the second signal source outputs a 1 pps pulse signal. After synchronizing with the atomic clock's 10 MHz signal, the signal is then mixed and modulated with the optical signal output by the laser of the optical signal generation unit. The optical signal is then transmitted to the optical fiber link by the polarization beam splitter. The optical signal of the fiber optic link is reflected back to the tunable optical delay line, the fiber optic link, and the polarization beam splitter by a Faraday rotator after passing through the tunable optical delay line. The optical signal is then converted into an electrical signal. The first bandpass filter separates the sinusoidal signal from the electrical signal of the photodetector, and the signal generated after mixing with the signal of the first signal source is controlled by the feedback control module to control the tunable optical delay line. The first data acquisition and processing module mixes the signal from the photodetector with the signal from the first signal source, and then the 1pps signal restored by the low-pass filter is compared with the signal from the second signal source to obtain a wide range of delay results. The second data acquisition and processing module mixes the 10MHz signal from the first signal source, which is modulated by the single-sideband modulation circuit board, with the signal from the first bandpass filter. Then, the 10MHz signal separated by the second bandpass filter is compared with the signal from the atomic clock to obtain a high-precision delay result with a small amount of delay.

[0039] The signal from the first signal source is modulated to a 10MHz signal by a single-sideband modulation circuit board and amplified by a second amplifier. This 10MHz signal is provided by the atomic clock.

[0040] The frequency of the first signal source is 5GHz, 10GHz, 20GHz, 50GHz or 100GHz.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-precision fiber optic link delay measurement device, characterized in that, include: The first signal source outputs a sine wave signal with a frequency of not less than 1 GHz; The second signal source outputs a 1pps pulse signal; An atomic clock synchronizes the first and second signal sources using a 10MHz signal. The optical signal transmitting module mixes and modulates the signals from the first and second signal sources into the optical signal output by the laser, and then transmits the optical signal to the optical fiber link via a polarization beam splitter. Tunable optical delay lines compensate for delay jitter in fiber optic links; A Faraday rotator reflects the optical signal to a tunable optical delay line, so that the optical signal can be transmitted to a polarization beam splitter via an optical fiber link. A photodetector receives reflected light signals from a polarization beam splitter and converts them into electrical signals. The first bandpass filter separates the sinusoidal signal from the electrical signal of the photodetector; The feedback control module controls the tunable optical delay line by mixing the signal from the first signal source and the signal separated by the first bandpass filter. The first data acquisition and processing module mixes the signal from the photodetector with the signal from the first signal source and then restores the 1pps signal through a low-pass filter. It then compares the 1pps signal restored by the low-pass filter with the signal from the second signal source to obtain a wide-range delay result. The second data acquisition and processing module mixes the 10MHz signal from the atomic clock on the single-sideband modulation circuit board of the first signal source with the signal from the first bandpass filter, and then compares the 10MHz signal separated by the second bandpass filter with the signal from the atomic clock to obtain a high-precision delay result. The optical signal transmitting module includes a laser, a Mach-Zehnder intensity modulator, a fourth mixer, and a first electrical amplifier; the signals from the first signal source and the second signal source are mixed by the fourth mixer and amplified by the first electrical amplifier, and then modulated by the Mach-Zehnder intensity modulator to the optical signal output by the laser.

2. The high-precision fiber optic link delay measurement device according to claim 1, characterized in that, The signal from the first signal source is modulated to a 10MHz signal by a single-sideband modulation circuit board and amplified by a second amplifier.

3. The high-precision fiber optic link delay measurement device according to claim 1, characterized in that, The atomic clock is a rubidium clock.

4. The high-precision fiber optic link delay measurement device according to claim 1, characterized in that, The length of the optical fiber link shall not be less than 10 km.

5. The high-precision fiber optic link delay measurement device according to claim 1, characterized in that, The fiber optic link is 20km long.

6. The high-precision fiber optic link delay measurement device according to claim 1, characterized in that, The frequency of the first signal source is 5GHz, 10GHz, 20GHz, 50GHz or 100GHz.

7. A high-precision fiber optic link delay measurement method, characterized in that, Includes the following steps: The first signal source outputs a sinusoidal signal with a frequency of not less than 1 GHz and the second signal source outputs a 1 pps pulse signal. After synchronizing with the atomic clock's 10 MHz signal, the signal is then mixed and modulated with the optical signal output by the laser of the optical signal generation unit. The optical signal is then transmitted to the optical fiber link by the polarization beam splitter. The optical signal of the fiber optic link is reflected back to the tunable optical delay line, the fiber optic link, and the polarization beam splitter by a Faraday rotator after passing through the tunable optical delay line. The optical signal is then converted into an electrical signal. The first bandpass filter separates the sinusoidal signal from the electrical signal of the photodetector, and the signal generated after mixing with the signal of the first signal source is controlled by the feedback control module to control the tunable optical delay line. The first data acquisition and processing module mixes the signal from the photodetector with the signal from the first signal source, and then the 1pps signal restored by the low-pass filter is compared with the signal from the second signal source to obtain a wide range of delay results. The second data acquisition and processing module mixes the 10MHz signal from the first signal source, which is modulated by the single-sideband modulation circuit board, with the signal from the first bandpass filter. Then, the 10MHz signal separated by the second bandpass filter is compared with the signal from the atomic clock to obtain a high-precision delay result.

8. The high-precision fiber optic link delay measurement method according to claim 7, characterized in that, The signal from the first signal source is modulated by a single-sideband modulation circuit board to provide a 10MHz signal from an atomic clock, and then amplified by a second amplifier.

9. The high-precision fiber optic link delay measurement method according to claim 7, characterized in that, The frequency of the first signal source is 5GHz, 10GHz, 20GHz, 50GHz or 100GHz.

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