Wide-range adjustable dispersion implementation structure and implementation method based on frequency domain resolution

Abstract

The application provides a wide-range adjustable dispersion implementation structure and method based on frequency domain resolution, the wide-range adjustable dispersion implementation structure based on frequency domain resolution comprises a light source, a fiber loop and an optical filter; the fiber loop comprises a frequency shifter, an optical amplifier, a coupler and a dispersion device which are connected in sequence; and the light source is connected with the optical filter through the coupler. Compared with the adjustable dispersion implementation method realized by using stress characteristics, temperature characteristics and piezoelectric characteristics, the wide-range adjustable dispersion implementation structure and method based on frequency domain resolution provided by the application can realize adjustable dispersion processing by multiplexing a single dispersion device and using cyclic frequency shift and frequency domain resolution, and the dispersion quantity that can be realized is several times of the dispersion quantity provided by a single dispersion device, so that the dispersion adjustment range is larger.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave photonics, in particular to a wide-range tunable dispersion implementation structure and method based on frequency domain resolution. BACKGROUND

[0002] Dispersion refers to the change of refractive index of a material with frequency, and the propagation speed of electromagnetic waves of different frequencies in the material is different, thus introducing a delay related to frequency. Due to this characteristic, dispersion medium has important applications in the field of optical signal processing such as optical signal transmission and pulse compression. In the process of dispersing the signal, the dispersion medium is often required to have a tunable dispersion amount. Chirped fiber grating has the advantages of small size and low insertion loss, and is an important device for realizing optical signal dispersion processing. At the same time, due to the sensitive characteristics of chirped fiber grating to stress, pressure and temperature, the tunable dispersion processing can be realized by adjusting these parameters.

[0003] The tunable dispersion can be realized by the stress characteristics of the grating. For a chirped fiber grating, the resonant wavelength can be expressed as λ B = 2n(z)Λ(z), where n(z) represents the average effective refractive index of the fiber grating at z, and Λ(z) represents the grating period of the fiber grating at z. It can be seen that the Bragg wavelength of the optical fiber depends on the optical path length in each period, and further depends on the period and refractive index coefficient of the grating. Therefore, when stress is applied along the axis of the optical fiber, the spatial Bragg period of the fiber grating can be increased, and the optical path length in one period is also increased, and the resonant wavelength of each point on the fiber grating will change. The change of stress causes the change of the resonant wavelength distribution of the chirped fiber grating, thereby realizing the change of the dispersion amount.

[0004] The tunable dispersion can be realized by the temperature characteristics of the grating. The temperature characteristics of the grating are that the change of the temperature of the grating can change the grating period through the expansion coefficient, and change the effective refractive index of the grating through the thermo-optic coefficient. As can be seen from the above formula, when the effective refractive index of the grating changes, the resonant wavelength distribution and the dispersion amount of the grating will also change correspondingly. Therefore, when a thin film heater is used on the surface of the grating to change the temperature of the grating, the change of the temperature gradient along the axis of the grating will change the chirp amount of the grating, thereby realizing the change of the dispersion amount.

[0005] The tunable dispersion can also be realized by piezoelectricity. Piezoelectricity refers to the discharge or polarization of dielectric crystals caused by mechanical pressure, or the application of voltage to cause pressure in electrolyte crystals. When a uniform fiber grating is placed on a piezoelectric stack, by synchronously controlling each piezoelectric stack to contract or stretch, a stress gradient can be generated on the grating, thereby obtaining a chirped fiber grating, and the adjustment of the chirp amount of the chirped fiber grating can be realized by changing the pressure of each piezoelectric stack.

[0006] The above methods can realize the change of the dispersion amount of the chirped fiber grating by adjusting different parameters. However, due to the limitation of the characteristics of the optical fiber material, the range of the change of the dispersion amount realized by these methods is limited, and the maximum range is usually several thousand ps / nm. In some cases, we often need a larger range of adjustable dispersion. The adjustable dispersion realized by the prior art using stress characteristics, temperature characteristics, and piezoelectric characteristics cannot meet this requirement. SUMMARY

[0007] The present application aims to provide a frequency domain resolution-based large-range adjustable dispersion implementation structure and implementation method to solve the problem that the adjustable dispersion implementation method using stress characteristics, temperature characteristics, and piezoelectric characteristics cannot meet the large-range adjustable dispersion processing of optical signals.

[0008] The present application provides a frequency domain resolution-based large-range adjustable dispersion implementation structure, which comprises an optical source, an optical fiber loop, and an optical filter.

[0009] The present application provides a frequency domain resolution-based large-range adjustable dispersion implementation structure, which comprises an optical source, an optical fiber loop, and an optical filter.

[0010] Preferably, the frequency shifter is a double parallel Mach-Zehnder modulator.

[0011] Preferably, the frequency domain resolution-based large-range adjustable dispersion implementation structure further comprises a microwave source connected to the double parallel Mach-Zehnder modulator.

[0012] Preferably, the dispersion device is a chirped fiber grating.

[0013] Preferably, the optical source is a pulsed optical source.

[0014] The present application also provides a frequency domain resolution-based large-range adjustable dispersion implementation method, which comprises:

[0015] S1, the optical source generates an optical signal which is input into the optical fiber loop through the coupler;

[0016] S2, in the optical fiber loop: the dispersion device realizes the dispersion processing of the optical signal in the optical fiber loop, the frequency shifter realizes the frequency shift of the optical signal in the optical fiber loop, the optical amplifier realizes the amplification in the optical fiber loop, and the coupler realizes the coupling of the input optical signal and the optical signal in the optical fiber loop;

[0017] S3, after the optical signal propagates in the optical fiber loop for several times, the optical signal output by the coupler contains several frequency components in the frequency domain;

[0018] S4, after each frequency component passes through the optical filter, the optical signal after a specific number of cycles is selected.

[0019] As a preference, the frequency shifter is driven by a microwave source.

[0020] In summary, due to the adoption of the technical solutions described above, the present application has the following beneficial effects:

[0021] Compared with the adjustable dispersion implementation method realized by using stress characteristics, temperature characteristics and piezoelectric characteristics, the wide-range adjustable dispersion implementation structure and implementation method based on frequency domain resolution provided by the present application realizes adjustable dispersion processing by multiplexing a single dispersion device and using cyclic frequency shifting and frequency domain resolution, and the dispersion amount that can be realized is several times the dispersion amount provided by a single dispersion device, so the present application has a larger dispersion adjustment range. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and other related drawings can also be obtained by those of ordinary skill in the art without creative labor on the basis of these drawings.

[0023] Figure 1 The figure is a schematic diagram of the wide-range adjustable dispersion implementation structure based on frequency domain resolution of the present application.

[0024] Figure 2 The figure is a structural schematic diagram of the wide-range adjustable dispersion implementation structure based on frequency domain resolution in the embodiments of the present application.

[0025] Figure 3 The figure is a schematic diagram of the time-domain stretching output of the pulse optical signal in the wide-range adjustable dispersion implementation method based on frequency domain resolution in the embodiments of the present application. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art on the basis of the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0028] EMBODIMENT

[0029] AsFigure 1 As shown, this embodiment proposes a wide-range tunable dispersion realization structure based on frequency domain resolution, including a microwave source, a light source, an optical fiber loop, and an optical filter; the optical fiber loop includes a frequency shifter, an optical amplifier, a coupler, and a dispersion device connected in sequence from beginning to end; the frequency shifter is also connected to the microwave source; the light source is connected to the optical filter via the coupler.

[0030] like Figure 2 As shown, in this embodiment, the light source is a pulsed light source with a spectral bandwidth of 40 GHz. The dispersive device is a chirped fiber grating with a passband bandwidth of 3.5 nm, which corresponds to a bandwidth of approximately 437.5 GHz at 1550 nm, providing a second-order dispersion of 10000 ps / nm. The frequency shifter is a dual parallel Mach-Zehnder modulator driven by a microwave source, with a frequency shift of 50 GHz.

[0031] Therefore, the frequency-domain-resolved large-range tunable dispersion realization method using the aforementioned frequency-domain-resolved large-range tunable dispersion realization structure includes:

[0032] S1, the light signal generated by the light source is input into the optical fiber loop via the coupler;

[0033] S2, in an optical fiber loop, such as Figure 3 As shown: a dispersive device performs dispersion processing on the optical signal in the fiber optic loop, introducing a dispersion of 10000 ps / nm; a frequency shifter performs frequency shift on the optical signal in the fiber optic loop, introducing a frequency shift of 50 GHz; an optical amplifier amplifies the optical signal in the fiber optic loop to compensate for fiber optic loop loss; and a coupler couples the input optical signal with the optical signal in the fiber optic loop, allowing the coupled optical signal to continue propagating in the fiber optic loop.

[0034] S3, after the optical signal propagates several times in the optical fiber loop, the optical signal output by the coupler contains several frequency components in the frequency domain. Each frequency component is formed by the dispersion processing of the original pulse optical signal after the corresponding number of cycles.

[0035] S4, after each frequency component passes through the optical filter, the optical signal after a specific number of cycles is selected. This optical signal represents the original pulse optical signal after the dispersion processing of the corresponding number of cycles, thereby realizing the time-domain stretching output of the pulse optical signal.

[0036] As can be seen from the above implementation method:

[0037] In the implementation method of the application, firstly, multiple dispersion processing of the input optical signal is realized through the optical fiber loop, and multiple copies in the frequency domain are realized, forming multiple frequency components, and different frequency components correspond to different dispersion processing times; then, the multiple sets of frequency components formed are screened in the frequency domain, and the frequency components meeting the requirements are selected to obtain the optical signal after specific cycle dispersion processing. Through the joint regulation and control of the frequency shift amount in the optical fiber loop and the passband position of the optical filter outside the optical fiber loop, large-range adjustable optical signal dispersion processing is realized.

[0038] In the implementation method of the application, after the optical signal to be processed enters the optical fiber loop, it will be dispersed by the dispersion device every time it passes through the optical fiber loop, and a fixed frequency shift will be introduced and coupled with the input optical signal to be processed, and then continue to propagate in the optical fiber loop. After several loop propagations, the optical signal to be processed will be copied multiple times in the frequency domain, and the optical signal output by the optical fiber loop will have multiple frequency components with fixed frequency intervals in the frequency domain, and different frequency components correspond to different dispersion processing times.

[0039] In the implementation method of the application, for the optical signal after multiple optical fiber loop frequency shifting and dispersion processing, it has multiple frequency components with fixed frequency intervals in the frequency domain, and different frequency components correspond to different dispersion processing times, so that different dispersion processing times can be realized when a certain frequency component is obtained through frequency domain resolution.

[0040] In summary, compared with the adjustable dispersion implementation method realized by using stress characteristics, temperature characteristics and piezoelectric characteristics, the large-range adjustable dispersion implementation structure and implementation method based on frequency domain resolution provided by the application realize adjustable dispersion processing through multiplexing of a single dispersion device and using cyclic frequency shifting and frequency domain resolution, and the dispersion amount that can be realized is several times the dispersion amount provided by a single dispersion device, so the dispersion adjustment range is larger.

[0041] The above only describes the preferred embodiments of the application and is not used to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A structure for realizing a large-range tunable dispersion based on frequency-domain resolution, characterized in that, It comprises a light source, a fiber loop and an optical filter; the fiber loop comprises a frequency shifter, an optical amplifier, a coupler and a dispersion device connected in sequence; the light source is connected with the optical filter through the coupler; the light source is a pulse light source; the adjustable dispersion processing is realized by multiplexing a single dispersion device and using cyclic frequency shift and frequency domain resolution.

2. The frequency-domain-resolved wide-range tunable dispersion implementation structure according to claim 1, characterized in that, The frequency shifter is a double parallel Mach-Zehnder modulator.

3. The frequency-domain-resolved wide-range tunable dispersion implementation structure according to claim 1, characterized in that, It further comprises a microwave source connected with the double parallel Mach-Zehnder modulator.

4. The frequency-domain-resolved wide-range tunable dispersion implementation structure according to claim 1, characterized in that, The dispersion device is a chirped fiber grating.

5. The frequency-domain-resolved wide-range tunable dispersion implementation structure according to claim 1, characterized in that, The light source is a pulse light source.

6. A method for realizing a large-range tunable dispersion based on frequency domain resolution, characterized in that, It comprises: S1, a light source generates an optical signal which is input into the fiber loop through a coupler; the light source is a pulse light source; S2, in the fiber loop: the dispersion device realizes the dispersion processing of the optical signal in the fiber loop, the frequency shifter realizes the frequency shift of the optical signal in the fiber loop, the optical amplifier realizes the amplification in the fiber loop, and the coupler realizes the coupling of the input optical signal and the optical signal in the fiber loop; S3, after the optical signal is propagated in the fiber loop for several times, the optical signal output by the coupler contains several frequency components in the frequency domain; S4, after each frequency component passes through the optical filter, the optical signal after a specific cycle is selected; the adjustable dispersion processing is realized by multiplexing a single dispersion device and using cyclic frequency shift and frequency domain resolution.

7. The method of claim 6, wherein, The frequency shifter is driven by a microwave source.

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