CN116316004A - Gain fiber structure, adjustable grating package structure and frequency-locked signal transmission system - Google Patents

Abstract

The application discloses gain fiber structure, adjustable grating packaging structure and frequency locking signal transmission system relates to fiber laser technical field, the last optical fiber Bragg grating that writes two at least different wavelengths of gain fiber structure, it changes to carve a plurality of gratings synchronization, the single frequency laser of output multiple wavelength after the excitation is applicable to the frequency locking signal transmission, adjustable grating packaging structure based on above-mentioned gain fiber structure can realize the synchronous stretching of grating through temperature regulation, realize the synchronous locking of grating wavelength on the adjustable grating packaging structure, the frequency locking signal transmission system based on above-mentioned adjustable grating packaging structure can realize the transmission of the cross wavelength of frequency locking signal, and is simple in structure, the technical degree of difficulty and the cost of realizing the transmission of frequency locking signal have been reduced.

Description

Gain fiber structure, adjustable grating package structure and frequency-locked signal transmission system

technical field

This application relates to the field of fiber laser technology, more specifically, it relates to a gain fiber structure, an adjustable grating packaging structure and a frequency-locked signal transmission system.

Background technique

The transmission of frequency-locked signals occurs between optical signals of different wavelengths, which means that when an optical signal of one wavelength is frequency-locked, optical signals of other wavelengths are also locked accordingly.

In the prior art, it can be realized mainly by means of high-precision auxiliary equipment such as optical frequency combs or ultra-stable cavities. The optical system composed of ultra-stable cavities has a complex structure, usually consisting of F-P cavity, vacuum chamber, ion pump, temperature controller and Composed of multiple modules such as the PDH frequency stabilization module, the optical path and the spatial mode of the cavity need to be precisely matched. The system is expensive, bulky, sensitive to environmental parameters, and difficult to lock. An optical frequency comb is a broadband spectral light source composed of many discrete frequency spectra with strictly equal frequency intervals. It is similar to a ruler for measuring frequency, so it is also called an optical frequency ruler. However, the optical system composed of optical frequency combs is also expensive, huge in size, sensitive to spatial physical jitter, difficult to lock, and complicated in actual use steps.

Contents of the invention

Aiming at the problem that the existing frequency-locked signal transmission system in practical application has a complex structure, high difficulty and high cost, the first purpose of this application is to propose a gain fiber structure, and write multiple gratings on the same gain fiber to achieve synchronization change, and output multi-wavelength single-frequency laser after being excited, which is suitable for frequency-locked signal transmission; based on the above-mentioned gain fiber structure, the second purpose is to provide an adjustable grating packaging structure, which can achieve synchronous stretching of the grating through temperature adjustment; based on The third purpose of the above-mentioned adjustable grating package structure is to protect a frequency-locked signal transmission system, which has a simple structure and reduces the technical difficulty and cost of realizing frequency-locked signal transmission.

The specific plan is as follows:

A gain fiber structure, including a fiber body, on which at least two fiber Bragg gratings of different wavelengths are written, and output multi-wavelength single-frequency laser after being excited

By adopting the above technical solution, two or more fiber Bragg gratings with different wavelengths are written on the core of the fiber. The wavelengths of the fiber Bragg gratings are all within the gain bandwidth of the fiber, and at least two single-frequency lasers can be output simultaneously. And the wavelength changes synchronously.

Preferably, at least two of the fiber Bragg gratings are arranged vertically or overlappingly on the fiber body.

By adopting the above-mentioned technical scheme, different distribution modes of the fiber Bragg grating on the optical fiber can output single-frequency laser light whose wavelength changes synchronously.

Preferably, the gain fiber is configured as an erbium-doped, ytterbium-doped, erbium-ytterbium co-doped, thulium-doped or other rare earth-doped gain fiber or highly nonlinear fiber.

By adopting the above technical scheme, writing multiple fiber Bragg gratings on gain fibers doped with different rare earth elements can achieve different technical effects, corresponding to the characteristics of various gain fibers. Based on the characteristics of various types of gain fibers, it is necessary to The parameters of the grating are adaptively adjusted.

Preferably, the number of gratings on the fiber body is configured as two, which are respectively set as a first Fiber Bragg Grating and a second Fiber Bragg Grating;

The first fiber Bragg grating and the second fiber Bragg grating are distributed overlappingly.

By adopting the above-mentioned technical scheme, the two fiber Bragg gratings overlapped and distributed occupy less space on the optical fiber, and only need to stretch a shorter length of optical fiber to modulate it, and the wavelength can be changed synchronously, with higher adjustment accuracy and easier operation. More convenient and easier to implement.

An adjustable grating packaging structure, comprising the aforementioned gain fiber structure, and an adjustment component for adjusting the stretched length of the fiber body in the gain fiber structure.

By adopting the above technical scheme, the adjustment component can adjust the length of the optical fiber through the influence of the external environment or human operation. By adjusting the length of the optical fiber, the stretching of the grating on the optical fiber can be realized. Since there are multiple fiber Bragg gratings written on the optical fiber, it can be Realize synchronous adjustment and synchronous change of multiple fiber Bragg grating wavelengths.

Preferably, the adjustment assembly includes a fixed base arranged along the length direction of the fiber body for fixing the grating, and the fixed base is made of metal or ceramic material.

By adopting the above technical solution, metal and ceramics have higher thermal conductivity, and the fixed base made of metal or ceramics is more sensitive to temperature, when the adjustment component of the grating is fixed.

Preferably, the adjustment assembly further includes a piezoelectric ceramic base, one end of the optical fiber body is fixedly connected to the piezoelectric ceramic base, and the other end is fixedly connected to the fixed base;

Wherein, the piezoelectric ceramic base changes its own length by adjusting the voltage.

By adopting the above technical solution, using the voltage signal as the adjustment signal of the adjustment component, the precise and controllable adjustment of the fiber length can be realized, that is, the precise adjustment of the output laser wavelength can be realized, and the frequency locking of the specific wavelength laser can be realized conveniently.

A frequency-locked signal transmission system is characterized in that it comprises:

A multi-wavelength single-frequency fiber laser, including the aforementioned adjustable grating package structure, used to output multi-wavelength single-frequency laser;

An optical splitting module, receiving the output multi-wavelength single-frequency laser output from the multi-wavelength single-frequency fiber laser, and outputting a first split signal and a second split signal;

The frequency locking module receives the first split signal, outputs a frequency locking signal to the multi-wavelength single-frequency fiber laser, performs frequency locking on the single-frequency laser with a set wavelength, and realizes frequency locking on other wavelength single-frequency lasers at the same time.

By adopting the above technical solution, the optical splitting module separates the single-frequency laser of a specific wavelength from the multi-wavelength single-frequency laser output by the fiber laser, and inputs it into the frequency locking module as a feedback adjustment signal, and the frequency locking module performs feedback adjustment based on the specific wavelength of the laser , and input the frequency-locking signal into the fiber laser, so that the frequency of the single-frequency laser output by the fiber laser is locked. Since the multiple gratings on the grating package structure are stretched synchronously, the frequency of the remaining wavelengths of the single-frequency laser in the multi-wavelength single-frequency laser It is also locked, so as to realize the cross-wavelength transmission of the frequency-locked signal.

Preferably, the multi-wavelength single-frequency fiber laser also includes a pump source for emitting pump light, a wavelength division multiplexing module for receiving and introducing the pump light, and an output isolator, and the adjustable grating The package structure is provided with an input port for receiving the frequency locking signal.

By adopting the above technical solution, the wavelength division multiplexing module guides the pump light from the pump source into the gain fiber, and generates multi-wavelength single-frequency laser in multiple fiber Bragg gratings, and the output isolator is used to isolate the reverse input and filter noise , to ensure the frequency-locking adjustment accuracy of the frequency-locking module.

Compared with the prior art, the beneficial effects of the present application are as follows:

(1) By writing multiple fiber Bragg gratings on the same section of suitable gain fiber, multiple distributed feedback fiber lasers can simultaneously realize single-frequency laser output with different wavelengths on the same section of fiber, and are simultaneously affected by the fiber itself and The influence of the external environment makes the laser wavelength change synchronously, and the change trend is the same;

(2) Stretch the grating by stretching the fiber to tune the wavelength of the single-frequency laser. When the real-time feedback of the wavelength is performed for a single-frequency laser of a certain wavelength and the wavelength is locked by fast tuning, the rest of the wavelengths on the gain fiber The wavelength of the single-frequency laser is also synchronously locked, so that the transmission of the laser frequency-locked signal can be directly realized. Compared with the traditional method of using an optical frequency comb and an ultra-stable cavity to realize frequency-locked signal transmission, this system has low technical requirements and does not need to rely on high-end high-end Precision auxiliary equipment simplifies the system structure and reduces the cost and difficulty of operation.

Description of drawings

Figure 1 is a schematic diagram of a distribution method of the grating on the gain fiber of the present application (upper and lower distribution);

Figure 2 is a schematic diagram of another distribution method of the grating on the gain fiber of the present application (overlapping distribution);

Fig. 3 is a schematic diagram of the package structure of the adjustable grating of the present application;

FIG. 4 is a schematic diagram of the frequency-locking signal transmission system of the present application.

Reference signs: 1. Tunable grating packaging structure; 11. Fiber Bragg grating; 12. Fixed base; 13. Piezoelectric ceramic base; 2. Pump source; 3. Wavelength division multiplexing module; 4. Optical splitting module; 5 , Frequency locking module; 6, Multi-wavelength single-frequency fiber laser.

Detailed ways

The present application will be further described in detail below in conjunction with the embodiments and figures, but the implementation of the present application is not limited thereto.

As shown in FIG. 1 and FIG. 2 , a gain fiber structure, on which at least two fiber Bragg gratings 11 of different wavelengths are written, outputs multi-wavelength single-frequency laser after being excited. Multiple fiber Bragg gratings 11 located in the same segment of the gain fiber will be affected by the fiber itself and the external environment synchronously, so that the laser wavelength will change synchronously, and the change trend will be the same. At this time, fast temperature tuning and other methods are used to quickly pull the grating and tune the wavelength of the single-frequency laser. Single-frequency laser wavelengths of different wavelengths are also synchronously locked.

A plurality of fiber Bragg gratings 11 are distributed up and down or overlappingly distributed on the gain fiber body. As shown in FIG. The fiber Bragg gratings 11 of b2 are distributed overlappingly. In practical applications, the fiber Bragg gratings 11 of different wavelengths can also be distributed in other ways, as long as the simultaneous stretching of the wavelengths of multiple fiber Bragg gratings 11 can be achieved.

Fiber Bragg grating 11 is formed by introducing periodic modulation of the refractive index into the fiber core. The wavelength reflected by the grating is determined by the refractive index modulation period in the fiber core and the refractive index of the fiber, that is, when the light satisfying the Bragg condition passes through the grating will be distributed reflection, the specific expression of the Bragg condition is, where is the laser wavelength, is the effective refractive index of the fiber core, and is the period of the refractive index modulation in the fiber core. The basic principle of this condition is that in the adjacent refractive index The phase difference of the reflected light during the modulation period is 2π, which can achieve coherence and phase growth. When the modulation period of the refractive index is large enough, the effective reflection of light can be realized. In addition, when a certain phase shift is introduced into certain positions in the fiber Bragg grating 11 to form a phase-shifted fiber Bragg grating 11, a transmission peak with a certain width can be introduced into the grating to bring about a narrow-band filtering effect. At this time, the multi-wavelength single-frequency fiber laser 6 formed by the phase-shifted fiber Bragg grating 11 written on the gain fiber can realize single-frequency laser output, and the wavelength of the output laser is the central wavelength of the grating transmission peak.

When two or more phase-shifted Bragg gratings with different periods are written in the fiber core, and the wavelengths of these gratings are all within the gain bandwidth of the gain fiber, as long as the parameters of each wavelength grating are rationally optimized, two or more Multi-wavelength single-frequency laser output at the same time, and the wavelength changes synchronously.

In the embodiment of the present application, the number of fiber Bragg gratings 11 on the gain fiber is set to two, which are respectively set as the first fiber Bragg grating and the second fiber Bragg grating, and the first fiber Bragg grating and the second fiber Bragg grating overlap distributed.

The gain fiber is configured as an erbium-doped, ytterbium-doped or erbium-ytterbium co-doped gain fiber, and can also be set as a gain fiber doped with other rare earth elements such as thulium, preferably an erbium-ytterbium co-doped gain fiber, which has high output power and energy The advantages of high conversion efficiency, high peak power, and high beam quality.

An adjustable grating package structure, as shown in Figure 3, includes the aforementioned gain fiber structure and an adjustment component for adjusting the stretched length of the gain fiber. When the adjustment component is affected by the ambient temperature or artificially adjusted, the gain Fiber stretching will change the refractive index modulation period of the grating to achieve a change in the wavelength of the single-frequency laser, and since all the gratings are on the same section of fiber, all wavelengths change synchronously when the grating is stretched. Encapsulation and temperature control of the gain grating can isolate the influence of external vibration to a certain extent and ensure the realization of frequency-locked signal transmission.

In detail, the adjustment assembly includes a fixed base 12 for fixing the grating arranged along the length direction of the fiber body, the fixed base 12 is made of metal or ceramic material, the thermal conductivity of metal and ceramic material is relatively high, and the temperature It is more sensitive and will expand and contract with the influence of temperature, which is convenient for temperature tuning of the gain fiber.

The adjustment assembly also includes a piezoelectric ceramic base 13, the piezoelectric ceramic base 13 changes its own length by adjusting the voltage, therefore, the voltage signal can be used as the adjustment signal of the grating, and the voltage can be adjusted by adjusting the voltage on the piezoelectric ceramic. The grating is stretched, and the refractive index modulation period of the grating is changed to realize the change of the laser wavelength. Since all the gratings are on the same section of optical fiber, all wavelengths change synchronously when the grating is stretched. As shown in FIG. 3 , one end of the gain fiber with the grating written on it is fixedly connected to the piezoelectric ceramic base 13 , and the other end is fixedly connected to the fixed base 12 .

A frequency-locked signal transmission system, as shown in Figure 4, includes a multi-wavelength single-frequency fiber laser 6 for outputting multi-wavelength single-frequency laser light, and a light splitting module that receives the output laser light from the multi-wavelength single-frequency fiber laser 6 and splits it 4 and a frequency-locking module 5 for frequency-locking a single-frequency laser with a set wavelength. The frequency-locking module 5 monitors, feeds back and locks the laser with a set wavelength in real time, because the wavelengths of lasers with different wavelengths are synchronously locked , frequency-locked signals can be transmitted between lasers of different wavelengths. Compared with the traditional method of using optical frequency combs and ultra-stable cavities to achieve frequency-locked signal transmission, this system has low technical requirements and does not need high-end and high-precision auxiliary equipment. The system structure is simplified, and the cost and operation difficulty are reduced.

Among them, the multi-wavelength single-frequency fiber laser 6 includes the tunable grating packaging module 1 as mentioned above, the pumping source 2 for emitting pumping light, and the wavelength division multiplexing module for receiving and introducing the pumping light 3. In the embodiment of the present application, the pumping source 2 is configured as a pumping laser diode, and the wavelength division multiplexing module 3 includes a wavelength division multiplexer, which outputs multi-wavelength single-frequency laser, and the wavelength division multiplexer is then set as an optical splitting module 4, It is configured as an optical splitter for splitting a single-frequency laser with a set wavelength, and an output isolator is provided between the optical splitting module 4 and the wavelength division multiplexer for isolating reverse input and filtering noise signals.

The wavelength division multiplexer guides the pump light emitted by the pump source 2 into the gain fiber, generates multi-wavelength single-frequency laser light in multiple fiber Bragg gratings 11, and outputs it to the optical splitter, and the optical splitter converts the single-frequency laser light of the set wavelength The signal is split, and the first split signal and the second split signal are respectively output. The second split signal is used as the main output optical path output system. The first split signal corresponds to the single-frequency signal of the set wavelength and is input to the frequency locking module as a feedback control signal. 5. The frequency locking module 5 receives the first split signal and converts it into a voltage signal, and outputs it to the adjustable grating packaging structure 1 of the multi-wavelength single-frequency fiber laser 6. The adjustable grating packaging structure 1 is provided with a device for receiving the lock The input port of the frequency signal is used to receive the voltage signal, and perform frequency locking for the real-time feedback adjustment of the single-frequency signal of the set wavelength, that is, wavelength locking. The corresponding multi-wavelength single-frequency signal is also frequency-locked, that is, the wavelength is locked, so as to realize the cross-wavelength transmission of the frequency-locked signal.

The above descriptions are only preferred implementation modes of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present application belong to the protection scope of the present application. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present application should also be considered as the scope of protection of the present application.

Claims (9)

1. A gain fiber structure, comprising a gain fiber body, characterized in that at least two fiber Bragg gratings (11) of different wavelengths are written on the gain fiber body, and output multi-wavelength single-frequency lasers after being excited. 2. The gain fiber structure according to claim 1, characterized in that at least two of the fiber Bragg gratings (11) are arranged vertically or overlappingly on the gain fiber body. 3. The gain fiber structure according to claim 2, characterized in that the gain fiber is configured as an erbium-doped, ytterbium-doped, erbium-ytterbium co-doped, thulium-doped or other rare earth-doped gain fiber or highly nonlinear fiber. 4. gain fiber structure according to claim 3, is characterized in that, the number of gratings on the gain fiber body is configured as two, which are respectively set as a first Fiber Bragg Grating (11) and a second Fiber Bragg Grating (11) ); The first fiber Bragg grating (11) and the second fiber Bragg grating (11) are distributed overlappingly. 5. An adjustable grating packaging structure, characterized in that it includes the gain fiber structure according to any one of claims 1-4, and an adjustment component for adjusting the stretched length of the fiber body in the gain fiber structure . 6. The adjustable grating packaging structure according to claim 5, wherein the adjustment assembly includes a fixed base (12) for fixing the grating arranged along the length direction of the gain fiber body, the fixed base ( 12) Made of metal or ceramic material. 7. The package structure of adjustable grating according to claim 6, characterized in that, the adjustment assembly further comprises a piezoelectric ceramic base (13), and one end of the optical fiber body is fixedly connected to the piezoelectric ceramic base (13) , the other end is fixedly connected to the fixed base (12); Wherein, the piezoelectric ceramic base (13) changes its own length by adjusting the voltage. 8. A frequency-locked signal transmission system, characterized in that, comprising: A multi-wavelength single-frequency fiber laser (6), including the adjustable grating package structure (1) according to any one of claims 5-7, for outputting multi-wavelength single-frequency laser; A splitting module (4), receiving the output multi-wavelength single-frequency laser output from the multi-wavelength single-frequency fiber laser (6), and outputting a first split signal and a second split signal; A frequency locking module (5), which receives the first splitting signal, outputs a frequency locking signal to the multi-wavelength single-frequency fiber laser (6), performs frequency locking on the single-frequency laser with a set wavelength, and realizes single-frequency laser light on other wavelengths at the same time. frequency locking of the laser. 9. frequency-locked signal delivery system according to claim 8, is characterized in that, described multi-wavelength single-frequency fiber laser (6) also comprises the pumping source (2) that is used to launch pumping light and is used for receiving and A wavelength division multiplexing module (3) for introducing the pump light, and an input port for receiving the frequency-locked signal is arranged on the adjustable grating package structure (1).

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