High-precision optical fiber link delay measuring device and method

Abstract

The invention discloses a high-precision optical fiber link delay measuring device and method, and belongs to the technical field of optical fiber transmission. The device comprises a first signal source for outputting a sinusoidal signal; the second signal source outputs a 1pps pulse signal; the atomic clock is used for synchronizing the signals; the optical signal transmitting module mixes the two signals, modulates the two signals into an optical signal and transmits the optical signal to an optical fiber link; the tunable optical delay line is used for compensating delay jitter of the optical fiber link; the Faraday polariscope is used for reflecting light signals; the photoelectric detector is used for converting optical signals into electric signals; a first band-pass filter separating a sinusoidal signal from the electrical signal; the feedback control module is used for controlling the tunable optical delay line; the first data acquisition and processing module is used for obtaining a wide-range delay result; and the second data acquisition and processing module is used for obtaining a small quantity of high-precision delay results. According to the invention, the high-precision time delay of the optical fiber link can be obtained by obtaining a wide-range time delay result and obtaining a small amount of a high-precision time delay result.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber transmission technology, and in particular to a high-precision optical fiber link delay measurement device and method. Background Art

[0002] The delay of an optical fiber link is an important parameter in optical fiber communications. However, due to the limitations of existing technologies, it is difficult to achieve high-precision measurement when measuring delay. In 2008, a research group from Peking University proposed and demonstrated a new method for measuring optical fiber delay using a free-running laser. The optical fiber to be measured was spliced onto an erbium-doped fiber to form a ring cavity laser. The mode beat frequency of the laser was measured and the round-trip time delay was determined. This method has achieved a fiber length reduction from 100 km to a few meters with an accuracy of 10 -8 -10 -6 , and resolutions from tens of nanoseconds to tens of picoseconds.

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

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

[0005] The present invention provides a high-precision optical fiber link delay measurement device and method, in order to at least partially solve the above technical problems.

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

[0007] The optical signal transmission module includes a laser, a Mach-Zehnder intensity modulator, a fourth mixer and a first electrical amplifier; the signals of 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 10 MHz signal via a single-sideband modulation circuit board and amplified by a second electrical amplifier.

[0009] Wherein, the atomic clock is a rubidium clock.

[0010] The length of the optical fiber link is not less than 10 km.

[0011] The length of the optical fiber link is 20 km.

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

[0013] As a second aspect of the present invention, a method is also provided, a high-precision optical fiber link delay measurement method, characterized in that it includes the following steps: A sinusoidal signal with a frequency of not less than 1 GHz output by the first signal source and a 1 pps pulse signal output by the second signal source are synchronized with a 10 MHz signal from an atomic clock, and then mixed and modulated with an optical signal output by the laser of the optical signal generating unit. The optical signal is then transmitted to the optical fiber link through a polarization beam splitter. The optical signal of the optical fiber link passes through the tunable optical delay line and is reflected by the Faraday rotator back to the tunable optical delay line, the optical fiber link and the polarization beam splitter, and then converted into an electrical signal; Separating a sinusoidal signal from the electrical signal of the photodetector using a first bandpass filter, and mixing the sinusoidal signal with the signal of the first signal source to generate a signal that controls the tunable optical delay line through a feedback control module; The first data acquisition and processing module mixes the signal of the photodetector with the signal of the first signal source, and then uses a low-pass filter to restore the 1pps signal to compare with the signal of the second signal source to obtain a wide range of delay results; The second data acquisition and processing module mixes the 10MHz signal of the first signal source modulated by the single-sideband modulation circuit board with the signal of the first bandpass filter, and then separates the 10MHz signal through the second bandpass filter and compares it with the signal of the atomic clock to obtain a small amount of high-precision delay result.

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

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

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

[0017] 3. This invention controls a tunable optical delay line by processing the voltage signal from the feedback control module. This tunable optical delay line can quickly and accurately compensate for delay jitter caused by various factors, such as temperature changes and external vibrations, over a wide range, thereby stabilizing the delay jitter of optical fiber links. This eliminates the need to consider the effects of temperature changes and other factors when measuring delay, simplifying the solution and improving reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments.

[0019] Figure 1 This is a framework diagram of the high-precision optical fiber link delay measurement of the present invention. DETAILED DESCRIPTION

[0020] In order to better understand the technical solutions of the embodiments of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0021] It should be clear that the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the embodiments of the present invention.

[0022] like Figure 1 As shown, an embodiment of the present invention discloses a high-precision optical fiber 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 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 a 5 GHz, 10 GHz, 20 GHz, 50 GHz, or 100 GHz signal.

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

[0025] The atomic clock synchronizes the first signal source and the second signal source using a 10 MHz signal. In this embodiment, the atomic clock is a rubidium clock.

[0026] The optical signal transmission 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 transmission module modulates the mixed signal from the first and second signal sources onto the optical signal output by the laser through the Mach-Zehnder intensity modulator. This achieves the mixing of the sinusoidal signal output by the first signal source and the 1 pps pulse signal output by the second signal source, which are then modulated onto an optical carrier.

[0027] The optical signal is transmitted by the polarization beam splitter to an optical fiber link. The length of the optical fiber link is not less than 10 km. In this embodiment, the length of the optical fiber link is 20 km.

[0028] The tunable optical delay line connects the optical fiber link and compensates for the delay jitter of the optical fiber link, thereby eliminating the delay jitter of the stable optical fiber link and reducing the impact of the delay jitter of the optical fiber link on the signal.

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

[0030] The photodetector is connected to the polarization beam splitter, receiving the reflected light signal from the polarization beam splitter and converting it into an electrical signal. This electrical signal is then split into two paths: one for measuring wide-range delay and the other for high-precision delay.

[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 of the first signal source and the sinusoidal signal separated by the first bandpass filter are mixed by the first mixer to generate a signal as the input of the feedback control module, which controls the tunable optical delay line after signal processing.

[0033] The output signal of the photodetector is divided into two channels. One channel, which measures wide-range delay, is mixed with the signal from the first signal source through a second mixer and then filtered through a low-pass filter to restore a 1pps signal. The first data acquisition and processing module compares this restored 1pps signal with the signal from the second signal source to obtain a wide-range delay result. The first data acquisition and processing module uses a pulse delay measurement method to compare the restored second pulse with the second pulse from the transmitter in the time domain to obtain a coarse-precision delay measurement.

[0034] Depend on Figure 1 It can be seen that the 10HMz signal of the atomic clock on the single-sideband modulation circuit board is single-sideband modulated by the first signal source, amplified by the second electrical amplifier, mixed with the sinusoidal signal separated by the first bandpass filter in the third mixer, and then separated out by the second bandpass filter to obtain a 10MHz signal, which is 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 pulse-second pulse and a sinusoidal signal at the local end, mixes them, and modulates them into a single-wavelength optical signal. The pulse-second pulse and high-frequency sinusoidal signal are then transmitted through the optical link. The optical signal is detected and demodulated at the receiving end, where the pulse-second pulse and sinusoidal signal are both detected. Both signals carry information about the optical signal's perception of fiber optic link delay jitter. The recovered sinusoidal signal has a phase delay compared to the transmitting end's sinusoidal signal, which can be expressed as 2kπ + ∆φ. However, due to period ambiguity, 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 full-cycle portion of the coarse-precision delay to the high-precision small delay.

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

[0037] The high-precision fiber optic link delay measurement device of the present invention can achieve femtosecond-level measurement accuracy. Furthermore, by controlling the tunable optical delay line through a feedback control module, the tunable optical delay line can automatically, over a wide range, with high precision, and quickly compensate for delay jitter caused by various factors, such as temperature changes and external vibrations, thereby stabilizing fiber optic link delay jitter. This eliminates the need to consider the impact of various factors, such as temperature changes, when measuring delay, simplifying the solution and improving reliability.

[0038] This embodiment further discloses a high-precision optical fiber link delay measurement method, which is used in the above-mentioned high-precision optical fiber link delay measurement device. The method includes the following steps: A sinusoidal signal with a frequency of not less than 1 GHz output by the first signal source and a 1 pps pulse signal output by the second signal source are synchronized with a 10 MHz signal from an atomic clock, and then mixed and modulated with an optical signal output by the laser of the optical signal generating unit. The optical signal is then transmitted to the optical fiber link through a polarization beam splitter. The optical signal of the optical fiber link passes through the tunable optical delay line and is reflected by the Faraday rotator back to the tunable optical delay line, the optical fiber link and the polarization beam splitter, and then converted into an electrical signal; Separating a sinusoidal signal from the electrical signal of the photodetector using a first bandpass filter, and mixing the sinusoidal signal with the signal of the first signal source to generate a signal that controls the tunable optical delay line through a feedback control module; The first data acquisition and processing module mixes the signal of the photodetector with the signal of the first signal source, and then uses a low-pass filter to restore the 1pps signal to compare with the signal of the second signal source to obtain a wide range of delay results; The second data acquisition and processing module mixes the 10MHz signal of the first signal source on the single-sideband modulation circuit board with the signal of the first bandpass filter, and then separates the 10MHz signal through the second bandpass filter and compares it with the signal of the atomic clock to obtain a high-precision delay small amount result.

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

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

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

Claims

1. A high-precision optical fiber link delay measurement device, characterized in that: include: A first signal source outputs a sinusoidal signal with a frequency not less than 1 GHz; The second signal source outputs a 1pps pulse signal; An atomic clock synchronizes the first signal source and the second signal source with a 10 MHz signal; An optical signal transmitting module, which mixes and modulates the signals of the first signal source and the second signal source into an optical signal output by the laser, and then transmits the optical signal to the optical fiber link through a polarization beam splitter; Tunable optical delay line to compensate for delay jitter of optical fiber link; A Faraday rotator reflects the optical signal to the tunable optical delay line, so that the optical signal is then transmitted to the polarization beam splitter via the optical fiber link; a photodetector, which receives the reflected light signal from the polarization beam splitter and converts it into an electrical signal; a first bandpass filter for separating a sinusoidal signal from an electrical signal from the photodetector; A feedback control module controls the tunable optical delay line after processing a signal obtained by mixing a signal from the first signal source and a signal separated by the first bandpass filter; The first data acquisition and processing module mixes the signal of the photodetector with the signal of the first signal source and then compares the 1pps signal restored by the low-pass filter with the signal of the second signal source to obtain a wide range delay result; The second data acquisition and processing module mixes the 10MHz signal of the atomic clock on the single-sideband modulation circuit board of the first signal source with the signal of the first bandpass filter, and then compares the 10MHz signal separated by the second bandpass filter with the signal of the atomic clock to obtain a small amount of high-precision delay result.

2. The high-precision optical fiber link delay measurement device according to claim 1, characterized in that: The optical signal transmission module includes a laser, a Mach-Zehnder intensity modulator, a fourth mixer and a first electrical amplifier; the signals of the first signal source and the second signal source are mixed by the fourth mixer, amplified by the first electrical amplifier, and modulated by the Mach-Zehnder intensity modulator to the optical signal output by the laser.

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

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

5. The high-precision optical fiber link delay measurement device according to claim 1, characterized in that: The length of the optical fiber link is not less than 10 km.

6. The high-precision optical fiber link delay measurement device according to claim 1, characterized in that: The length of the optical fiber link is 20 km.

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

8. A high-precision optical fiber link delay measurement method, characterized in that: The steps include: A sinusoidal signal with a frequency of not less than 1 GHz output by the first signal source and a 1 pps pulse signal output by the second signal source are synchronized with a 10 MHz signal from an atomic clock, and then mixed and modulated with an optical signal output by the laser of the optical signal generating unit. The optical signal is then transmitted to the optical fiber link through a polarization beam splitter. The optical signal of the optical fiber link passes through the tunable optical delay line and is reflected by the Faraday rotator back to the tunable optical delay line, the optical fiber link and the polarization beam splitter, and then converted into an electrical signal; Separating a sinusoidal signal from the electrical signal of the photodetector using a first bandpass filter, and mixing the sinusoidal signal with the signal of the first signal source to generate a signal that controls the tunable optical delay line through a feedback control module; The first data acquisition and processing module mixes the signal of the photodetector with the signal of the first signal source, and then uses a low-pass filter to restore the 1pps signal to compare with the signal of the second signal source to obtain a wide range of delay results; The second data acquisition and processing module mixes the 10MHz signal of the first signal source modulated by the single-sideband modulation circuit board with the signal of the first bandpass filter, and then separates the 10MHz signal through the second bandpass filter and compares it with the signal of the atomic clock to obtain a small amount of high-precision delay result.

9. The high-precision optical fiber link delay measurement method according to claim 8, characterized in that: The signal of the first signal source is modulated into a 10 MHz signal by a single-sideband modulation circuit board and amplified by a second electrical amplifier. The 10 MHz signal is a 10 MHz signal provided by an atomic clock.

10. The high-precision optical fiber link delay measurement method according to claim 8, characterized in that: The frequency of the first signal source is 5 GHz, 10 GHz, 20 GHz, 50 GHz or 100 GHz.

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