A fiber optic phase stabilization device based on tunable laser

Abstract

The invention discloses an optical fiber phase stabilization device based on a tunable laser. The laser is used to emit a signal to be measured in a continuous optical signal, which passes through a first optical circulator, an adjustable optical fiber delay line and an optical fiber to be measured in sequence. After being reflected by a second optical circulator, the signal passes through the optical fiber to be measured and the adjustable optical fiber delay line, enters the first optical circulator, and enters a first photodetector together with a reference optical signal in the continuous optical signal, generates interference beat frequency, which is displayed by an oscilloscope, and performs discrete Fourier spectrum analysis and spectrum refinement through a digital signal processor to obtain a delay standard value. At the same time, a proportional-integral-differential controller controls the adjustable optical fiber delay line to compensate for the delay change of the optical fiber to be measured, thereby maintaining the delay stability of the optical fiber. The structure is simple, and highly stable optical fiber transmission of radio frequency signals can be easily realized.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber phase stabilization, and in particular to an optical fiber phase stabilization device based on a tunable laser. Background Art

[0002] Applications such as deep space networks, distributed synthetic aperture radar systems, high-precision clock distribution, and particle accelerators often require that the RF signal maintain a very stable phase after transmission, that is, the phase jitter of the RF signal is as small as possible, which requires the support of a corresponding phase stabilization system. Initially, the RF signal stabilization system generally processes the RF signal in the electrical domain, such as using a phase detector to analyze the phase of the RF signal, and then continuously adjusts the phase shifter in the link through a feedback loop to ultimately achieve RF signal phase stability. With the emergence of RF signal fiber transmission, a new idea has been provided for phase stabilization technology. RF signal fiber transmission technology modulates the RF signal onto an optical carrier and transmits it through an optical fiber. It has the inherent advantages of large bandwidth, low loss, and high rate in the optical domain. However, due to environmental interference, the effective length of the transmission fiber will fluctuate, which will cause the phase jitter of the RF signal loaded on the optical carrier. In order to achieve stable RF signal fiber transmission, people have proposed a variety of fiber optic phase stabilization methods, which are generally divided into two categories: passive and active. The existing passive fiber optic phase stabilization method uses multi-stage mixing to achieve phase correction. Due to mixing in the electrical domain, the link has the disadvantage of limited bandwidth. The active fiber phase stabilization method uses a light source phase-locked loop to extract the fiber delay jitter, and then uses a tunable fiber delay line to compensate for it. The compensation structure of this type of method is often more complex, and it is difficult to achieve high-stability RF signal fiber transmission. Summary of the invention

[0003] The object of the present invention is to provide an optical fiber phase stabilization device based on a tunable laser, which has a simple structure and is easy to realize highly stable optical fiber transmission of radio frequency signals.

[0004] To achieve the above-mentioned object, the present invention provides an optical fiber phase stabilization device based on a tunable laser, wherein the optical fiber phase stabilization device based on a tunable laser comprises a laser, a first optical circulator, an adjustable optical fiber delay line, an optical fiber to be tested, a second optical circulator, a first photodetector, an oscilloscope, a digital signal processor and a proportional integral differential controller, wherein the laser is connected to the first optical circulator and is located on one side of the first optical circulator, the adjustable optical fiber delay line is connected to the first optical circulator and is located away from the laser, and the optical fiber to be tested is connected to the adjustable optical fiber delay line and is located away from the first optical circulator. On one side of the optical circulator, the second optical circulator is connected to the optical fiber to be tested and is located away from the side of the adjustable optical fiber delay line, the first photodetector is connected to the first optical circulator and is located on one side of the first optical circulator, the oscilloscope is connected to the first photodetector and is located away from the side of the first optical circulator, the digital signal processor is connected to the oscilloscope and is located away from the side of the first photodetector, and the proportional-integral-differential controller is connected to the digital signal processor and the adjustable optical fiber delay line and is located between the digital signal processor and the adjustable optical fiber delay line.

[0005] Wherein, the optical fiber phase stabilization device of the laser further includes a wavelength division multiplexer, and the wavelength division multiplexer is connected to the laser and the first optical circulator, and is located between the laser and the first optical circulator.

[0006] Wherein, the optical fiber phase stabilization device of the laser further includes a splitter, which is connected to the wavelength division multiplexer and the laser and is located between the wavelength division multiplexer and the laser.

[0007] The optical fiber phase stabilization device of the laser further comprises a wavelength division multiplexer, which is connected to the optical fiber to be tested and the second optical circulator and is located between the optical fiber to be tested and the second optical circulator.

[0008] Wherein, the optical fiber phase stabilization device of the laser further comprises a second photodetector, and the second photodetector is connected to the wavelength division multiplexer and is located at one side of the second optical circulator.

[0009] The optical fiber phase stabilization device of the laser further comprises a combiner, which is connected to the splitter, the first optical circulator and the first photodetector, and is located between the first optical circulator and the first photodetector.

[0010] The invention discloses an optical fiber phase stabilization device based on a tunable laser. The optical fiber phase stabilization device based on a tunable laser comprises a laser, a first optical circulator, an adjustable optical fiber delay line, an optical fiber to be tested, a second optical circulator, a first photodetector, an oscilloscope, a digital signal processor and a proportional integral differential controller. The optical signal to be tested in a continuous optical signal emitted by the laser passes through the first optical circulator, the adjustable optical fiber delay line and the optical fiber to be tested in sequence, passes through the optical fiber to be tested and the adjustable optical fiber delay line after being reflected by the second optical circulator, enters the first optical circulator, and enters the first photodetector together with a reference optical signal in the continuous optical signal, generates interference beat frequency, which is displayed by the oscilloscope, and performs discrete Fourier spectrum analysis and spectrum refinement by the digital signal processor to obtain a delay standard value. At the same time, the proportional integral differential controller controls the adjustable optical fiber delay line to compensate for the delay change of the optical fiber to be tested, thereby maintaining the delay stability of the optical fiber. The structure is simple and highly stable radio frequency signal optical fiber transmission can be easily realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 It is a structural schematic diagram of an optical fiber phase stabilization device based on a tunable laser provided by the present invention.

[0013] 1-laser, 2-first optical circulator, 3-adjustable optical fiber delay line, 4-optical fiber to be tested, 5-second optical circulator, 6-first photodetector, 7-oscilloscope, 8-digital signal processor, 9-proportional integral differential controller, 10-first laser, 11-second laser, 12-wavelength division multiplexer, 13-splitter, 14-wavelength demultiplexer, 15-second photodetector, 16-combiner. DETAILED DESCRIPTION

[0014] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0015] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0016] See also Figure 1 The present invention provides an optical fiber phase stabilization device based on a tunable laser, the optical fiber phase stabilization device based on a tunable laser comprises a laser 1, a first optical circulator 2, an adjustable optical fiber delay line 3, an optical fiber to be tested 4, a second optical circulator 5, a first photodetector 6, an oscilloscope 7, a digital signal processor 8 and a proportional integral differential controller 9, the laser 1 is connected to the first optical circulator 2 and is located on one side of the first optical circulator 2, the adjustable optical fiber delay line 3 is connected to the first optical circulator 2 and is located away from the side of the laser 1, the optical fiber to be tested 4 is connected to the adjustable optical fiber delay line 3 and is located away from the first optical circulator 2 side, the second optical circulator 5 is connected to the optical fiber to be tested 4 and is located on the side away from the adjustable optical fiber delay line 3, the first photodetector 6 is connected to the first optical circulator 2 and is located on the side of the first optical circulator 2, the oscilloscope 7 is connected to the first photodetector 6 and is located on the side away from the first optical circulator 2, the digital signal processor 8 is connected to the oscilloscope 7 and is located on the side away from the first photodetector 6, the proportional-integral-differential controller 9 is connected to the digital signal processor 8 and the adjustable optical fiber delay line 3, and is located between the digital signal processor 8 and the adjustable optical delay line 3.

[0017] In this embodiment, it is assumed that the frequency of the continuous optical signal emitted by the laser 1 is f=f0+αt, wherein f0 is the starting frequency of the adjustable laser, and α is the frequency tuning rate. Before passing through the first optical circulator 2, the continuous optical signal is divided into two parts, one part is used as a reference signal, and the other part is used as a measurement optical signal. The optical signal passes through the adjustable optical fiber delay line 3 and the optical fiber to be measured 4 with a transmission distance of L in sequence, and enters the second optical circulator 5, wherein the length of the optical fiber to be measured 4 is 100m. The optical signal is then reflected back by the second optical circulator 5, and the reflected signal passes through the optical fiber to be measured 4 and the adjustable optical fiber delay line 3 with a transmission distance of L, enters the first optical circulator 2, and is transmitted into the first photodetector 6 together with the reference optical signal, and interference beat occurs. The signal after interference beat is displayed by the oscilloscope 7, and discrete Fourier spectrum analysis is performed by the digital signal processor 8, and spectrum refinement is performed to obtain an accurate spectrum of the electrical signal, and the center frequency is obtained as f m When the adjustable laser frequency scanning speed is constant, the delay of the optical fiber 4 to be tested is τ = f m / (α), where α is the laser frequency tuning rate. When the optical fiber is affected by environmental changes, it will cause changes in the optical fiber refractive index and length, which is reflected in the time domain as a change in the optical delay, and the change is recorded as Δτ. The phase jitter caused by the change in the RF signal phase with the optical delay is 2πf R Δτ, where f R By constructing the proportional integral differential (PID) controller feedback loop, the feedback signal controls the delay of the optical delay line, thereby offsetting Δτ, so as to achieve stable optical delay of the optical fiber. The simulation results show that when the ambient temperature of the optical fiber changes, the optical delay change of the RF signal after being transmitted through 100m of optical fiber is 90fs, and the phase change of the RF signal with a transmission frequency of 32GHz is 1°, which can achieve highly stable optical fiber transmission of RF signals.

[0018] Furthermore, the optical fiber phase stabilization device of the laser further includes a wavelength division multiplexer 12 , which is connected to the laser 1 and the first optical circulator 2 and is located between the laser 1 and the first optical circulator 2 .

[0019] In this embodiment, the output end of the laser 1 is connected to the input end of the wavelength division multiplexer 12, and the wavelength division multiplexer 12 is used to synthesize the multiple optical signals generated by the laser 1 into one optical fiber for transmission.

[0020] Furthermore, the laser 1 includes a first laser 10 and a second laser 11, wherein the first laser 10 and the second laser 11 are both connected to the wavelength division multiplexer 12 and are located away from the first optical circulator 2.

[0021] In this embodiment, the first laser 10 is a tunable swept frequency laser that generates a measurement optical signal, and the second laser 11 is a fixed frequency laser that generates a service optical signal. The radio frequency signal with a frequency of 32 GHz directly modulates the service optical signal, and the measurement optical signal is not modulated by the radio frequency signal. The measurement optical signal and the service optical signal generated by the first laser 10 and the second laser 11 are synthesized by the wavelength division multiplexer 12 and transmitted into one optical fiber.

[0022] Furthermore, the optical fiber phase stabilization device of the laser further includes a splitter 13 , which is connected to the wavelength division multiplexer 12 and the laser 1 , and is located between the wavelength division multiplexer 12 and the laser 1 .

[0023] In this embodiment, the first laser 10 emits a frequency-sweeping optical signal, which is divided into two paths by the splitter 13 (the splitting ratio can be determined according to actual needs). One path enters the wavelength division multiplexer 12 as a measurement signal and is combined with the business signal emitted by the second laser 11 to the same optical fiber for transmission, and the other path enters the first photodetector 6 as a reference signal and beats the frequency together with the returned measurement signal.

[0024] Furthermore, the optical fiber phase stabilization device of the laser further includes a wavelength division multiplexer 14 , which is connected to the optical fiber 4 to be tested and the second optical circulator 5 , and is located between the optical fiber 4 to be tested and the second optical circulator 5 .

[0025] In this embodiment, the demultiplexed optical signal is divided into a service optical signal and a measurement optical signal by using the wavelength division multiplexer 14, wherein the measurement optical signal returns to the wavelength division multiplexer 14 through the second optical circulator 5, and then returns to the optical fiber to be tested 4, and reaches the first optical circulator 2 after transmission.

[0026] Furthermore, the optical fiber phase stabilization device of the laser further includes a second photodetector 15 , which is connected to the wavelength division multiplexer 14 and is located on one side of the second optical circulator 5 .

[0027] In this embodiment, the second photodetector 15 is used to perform photoelectric conversion on the service optical signal decomposed in the wavelength division multiplexer 14 to demodulate the radio frequency signal.

[0028] Furthermore, the optical fiber phase stabilization device of the laser further includes a combiner 16 , which is connected to the splitter 13 , the first optical circulator 2 and the first photodetector 6 , and is located between the first optical circulator 2 and the first photodetector 6 .

[0029] In this embodiment, the reference optical signal and the optical measurement signal are sent together to the first photodetector 6 by using the combiner 16 for beat frequency.

[0030] The invention discloses an optical fiber phase stabilization device based on a tunable laser. The optical fiber phase stabilization device based on a tunable laser comprises a laser 1, a first optical circulator 2, an adjustable optical fiber delay line 3, an optical fiber to be tested 4, a second optical circulator 5, a first photodetector 6, an oscilloscope 7, a digital signal processor 8 and a proportional integral differential controller 9. The optical signal to be tested in a continuous optical signal emitted by the laser 1 passes through the first optical circulator 2, the adjustable optical fiber delay line 3 and the optical fiber to be tested 4 in sequence, passes through the second optical circulator 5, passes through the optical fiber to be tested 4 and the adjustable optical fiber delay line 3, enters the first optical circulator 2, and enters the first photodetector 6 together with a reference optical signal in the continuous optical signal, generates interference beat frequency, which is displayed by the oscilloscope 7, and performs discrete Fourier spectrum analysis and spectrum refinement by the digital signal processor 8 to obtain a delay standard value. At the same time, the proportional integral differential controller 9 controls the adjustable optical fiber delay line 3 to compensate for the delay change of the optical fiber to be tested 4, thereby maintaining the delay stability of the optical fiber. The structure is simple and it is easy to realize highly stable optical fiber transmission of radio frequency signals.

[0031] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. An optical fiber phase stabilization device based on a tunable laser, characterized in that: The optical fiber phase stabilization device based on a tunable laser comprises a laser, a first optical circulator, an adjustable optical fiber delay line, an optical fiber to be tested, a second optical circulator, a first photodetector, an oscilloscope, a digital signal processor and a proportional integral differential controller, wherein the laser is connected to the first optical circulator and is located at one side of the first optical circulator, the adjustable optical fiber delay line is connected to the first optical circulator and is located at a side away from the laser, the optical fiber to be tested is connected to the adjustable optical fiber delay line and is located at a side away from the first optical circulator, the second optical circulator is connected to the optical fiber to be tested and is located at a side away from the adjustable optical fiber delay line, the first photodetector is connected to the first optical circulator and is located at one side of the first optical circulator, the oscilloscope is connected to the first photodetector and is located at a side away from the first optical circulator, the digital signal processor is connected to the oscilloscope and is located at a side away from the first photodetector, the proportional integral differential controller is connected to the digital signal processor and the adjustable optical fiber delay line and is located between the digital signal processor and the adjustable optical fiber delay line; The optical fiber phase stabilization device of the laser further comprises a wavelength division multiplexer, which is connected to the laser and the first optical circulator and is located between the laser and the first optical circulator; The optical fiber phase stabilization device of the laser further comprises a splitter, which is connected to the wavelength division multiplexer and the laser and is located between the wavelength division multiplexer and the laser; The optical fiber phase stabilization device of the laser further comprises a combiner, which is connected to the splitter, the first optical circulator and the first photodetector, and is located between the first optical circulator and the first photodetector; The frequency of the continuous optical signal emitted by the laser is f=f0+αt, wherein f0 is the starting frequency of the adjustable laser, and α is the frequency tuning rate. Before passing through the first optical circulator, the continuous optical signal is divided into two parts, one part is used as a reference signal, and the other part is used as a measurement optical signal. The two parts sequentially pass through the adjustable optical fiber delay line with a transmission distance of L and the optical fiber to be measured, and enter the second optical circulator, wherein the length of the optical fiber to be measured is 100m. The optical signal is then reflected back by the second optical circulator, and the reflected signal passes through the optical fiber to be measured with a transmission distance of L and the adjustable optical fiber delay line again, enters the first optical circulator, and is transmitted into the first photodetector together with the reference optical signal, generating interference beat frequency.

2. The optical fiber phase stabilization device based on tunable laser according to claim 1, characterized in that: The optical fiber phase stabilization device of the laser further comprises a wavelength division multiplexer, which is connected to the optical fiber to be tested and the second optical circulator and is located between the optical fiber to be tested and the second optical circulator.

3. The optical fiber phase stabilization device based on tunable laser according to claim 2, characterized in that: The optical fiber phase stabilization device of the laser further comprises a second photoelectric detector, which is connected to the wavelength division multiplexer and is located at one side of the second optical circulator.

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