CN111106514A

CN111106514A - Double-wavelength fiber laser capable of switching output of bright pulse and dark pulse and method

Info

Publication number: CN111106514A
Application number: CN201911294368.2A
Authority: CN
Inventors: 姚勇; 吴乾超; 刘楚彦; 淦亚苹; 傅艳萍; 田佳峻
Original assignee: Shenzhen Graduate School Harbin Institute of Technology
Current assignee: Shenzhen Graduate School Harbin Institute of Technology
Priority date: 2019-12-16
Filing date: 2019-12-16
Publication date: 2020-05-05

Abstract

The invention provides a double-wavelength fiber laser and a method capable of switching output of bright pulses and dark pulses, wherein the double-wavelength fiber laser comprises an annular fiber laser, the annular fiber laser comprises a laser diode, a wavelength division multiplexer, an erbium-doped fiber, a polarization dependence isolator, a polarization controller, a high nonlinear fiber, an optical coupler and a tunable optical filter which are sequentially connected, the polarization state of the pulses is adjusted through the polarization controller, the bright pulses and the dark pulses are mutually switched and output by utilizing different polarization states, and the wavelengths corresponding to the bright pulses and the pulses are respectively separated by adopting the tunable optical filter. The invention has the beneficial effects that: the invention can realize the switching between bright and dark pulses in the same optical fiber laser, thereby enhancing the performance of the laser and saving the cost.

Description

Double-wavelength fiber laser capable of switching output of bright pulse and dark pulse and method

Technical Field

The invention relates to the technical field of fiber lasers, in particular to a double-wavelength fiber laser and a method capable of switching output of bright pulses and dark pulses.

Background

The existing optical fiber laser can only output bright pulses or dark pulses generally, and can not realize the switching output of the two pulses. In addition, the existing optical fiber laser is generally single wavelength, and the wavelength corresponding to the bright and dark pulses is not adjustable.

Disclosure of Invention

The invention provides a dual-wavelength fiber laser capable of switching output of bright pulses and dark pulses, which comprises an annular fiber laser, wherein the annular fiber laser comprises a laser diode, a wavelength division multiplexer, an erbium-doped fiber, a polarization dependence isolator, a polarization controller, a high nonlinear fiber, an optical coupler and a tunable optical filter which are sequentially connected, the polarization state of the pulses is adjusted through the polarization controller, the bright pulses and the dark pulses are switched and output by utilizing different polarization states, and the wavelengths corresponding to the bright pulses and the pulses are separated by adopting the tunable optical filter.

As a further improvement of the invention, the dispersion parameter of the erbium-doped fiber is-16.3 ps/(Km nm).

As a further improvement of the invention, the energy intensity of the wave band is changed by rotating the polarization controller, and the conversion between the bright pulse output and the dark pulse output is realized by rotating the polarization controller.

As a further improvement of the invention, the wavelengths corresponding to the bright pulse and the dark pulse are respectively adjustable.

As a further improvement of the invention, the wavelength of the dark pulse is adjustable from 1554nm to 1560 nm.

As a further refinement of the present invention, the dark pulse pair repetition frequency is 196.8 kHz.

As a further improvement of the invention, the wavelength of the bright pulse is adjustable between 1552.7nm and 1560 nm.

As a further refinement of the invention, the time interval and repetition frequency of the sequence of pairs of bright pulses are 5.08s and 196.8kHz, respectively.

The invention also provides a method for switching output of bright pulses and dark pulses, which uses a ring-shaped optical fiber laser, firstly rotates a polarization controller to change the energy intensity of a wave band, secondly separates the wavelengths respectively corresponding to the bright pulses and the pulses through a tunable optical filter, and realizes the conversion between the bright pulse output and the dark pulse output through rotating the polarization controller.

As a further improvement of the invention, the wavelength of the dark pulse is adjustable from 1554nm to 1560nm, and the repetition frequency of the dark pulse is 196.8 kHz; the wavelength of the bright pulse is adjustable from 1552.7nm to 1560nm, and the time interval and the repetition frequency of the bright pulse pair sequence are respectively 5.08s and 196.8 kHz.

The invention has the beneficial effects that: the invention can realize the switching between bright and dark pulses in the same optical fiber laser, thereby enhancing the performance of the laser and saving the cost.

Drawings

FIG. 1 is a schematic diagram of the principles of the present invention;

fig. 2 is a schematic view of the measurement of the present invention.

Detailed Description

As shown in fig. 1, the present invention discloses a dual-wavelength fiber laser capable of switching output of bright pulses and dark pulses, which includes a laser diode LD, a wavelength division multiplexer WDM, an erbium-doped fiber EDF, a polarization-dependent isolator PD-ISO, a polarization controller PC, a high nonlinear fiber HNLF, an optical coupler OC, and a tunable optical filter TOF, which are connected in sequence.

As shown in FIG. 1, a length of erbium doped fiber EDF about 12 meters long is used as the gain medium, and a laser diode (Amonics, ALD-980-. A polarization-dependent isolator PD-ISO is adopted in the cavity to ensure laser unidirectionality. The polarization state of the pulses is adjusted by means of an in-line polarization controller PC. A section of 1000 m zero-dispersion high-nonlinearity fiber HNLF is a key component for generating a dual-wavelength bright-dark pulse pair, and the zero-dispersion high-nonlinearity fiber HNLF can also prevent the pulse from widening after the pulse is transmitted to the 1000 m fiber. The pulse is output using a 10% optical coupler OC. A further 39m section of Single Mode Fibre (SMF) was used to connect the various devices within the cavity. The SMF dispersion parameter is 18ps/(Km nm), and the EDF dispersion parameter is-16.3 ps/(Km nm), so that the total net dispersion in the cavityIs-0.65 ps². At the output, the wavelengths corresponding to the bright pulses and the pulses are separated by using the tunable optical filter TOF. In the measurement, a spectrum analyzer (AQ6370C), a 1GHz oscilloscope (TekMDO3104) and a 1GHz AC-coupled photodetector (Newfocus:1611) were used to monitor both the laser spectrum and the pulse shape.

As shown in fig. 2(a), (d), (g), the black dashed line indicates the wavelength of 1554 nm; the solid black line represents the 1560nm wavelength. Careful comparison analysis shows that fig. 2 shows a new method for achieving the switching of the light and sound pulses and the wavelength adjustment. Bright and dark pulses are switched and output by utilizing different polarization states, and dark pulses and bright pulses are switched and output by comparing graphs (b) and (h) and in the vicinity of 1554nm of wavelength; comparing fig. (c) and (i), the light pulse and dark pulse switchable output is realized at a wavelength of 1560 nm. The bright pulse wavelength can be adjusted from 1552.7nm to 1560nm, and the dark pulse wavelength can be adjusted from 1554nm to 1560 nm. Comparing the spectra (a), (d), (g), we find that the intensity of the short wavelength is higher than the long wavelength band, then equal to the long wavelength band, and finally lower than the long wavelength band, and the intensity of the long wavelength band varies just in reverse. Comparing the pulse outputs (b), (e) and (h) corresponding to the short wavelength, it can be found that the dark pulse output is when the short wavelength band intensity is high, the quasi-square wave output is equal to the long wavelength band, and the bright pulse output is lower than the long wavelength band. Also, the comparison of (c), (f), (i) shows that the output pulse of the long wavelength band is changed from a bright pulse to a dark pulse. For an explanation of the above phenomenon, we compare (a), (b), (c) and (g), (h), (i) and find that the high energy wavelength corresponds to a dark pulse and the low energy wavelength corresponds to a bright pulse. Experimental results show that the energy of the dark pulse is higher than that of the light pulse. First, we can change the energy intensity of the band by rotating the polarization controller PC. Secondly, the required wavelength is filtered out through the tunable optical filter TOF, and the conversion between the bright pulse output and the dark pulse output can be realized through rotating the PC. Comparing (b) and (i) and then (c) and (h), we find that the wavelength of the dark pulse and the wavelength of the light pulse are adjustable, so we not only prove that the light and dark pulses can switch output, but also can adjust the pulse wavelength.

A dual-wavelength optical fiber ring laser with tunable wavelength and switchable dark and light pulses. And mode-locked dual-wavelength output is realized by adding a high nonlinear optical fiber HNLF into the optical fiber annular cavity. Dark and bright pulse switching output is realized through the tunable optical filter TOF and the polarization controller PC, and the wavelengths corresponding to the bright pulse and the dark pulse are respectively tunable. The dark pulse has a repetition frequency of 196.8kHz and a wavelength of 1554nm to 1560 nm. The wavelength of the bright pulse is adjustable from 1552.7nm to 1560nm, and the time interval and the repetition frequency of the bright pulse pair sequence are respectively 5.08s and 196.8 kHz. And the bright and dark pulses of the dual-wavelength fiber laser can be switched and output under the same wavelength or different wavelengths.

The invention also discloses a method for switching output of the bright pulse and the dark pulse, which uses a ring-shaped optical fiber laser, firstly rotates the polarization controller PC to change the energy intensity of the wave band, secondly separates the wavelengths respectively corresponding to the bright pulse and the pulse through the adjustable optical filter TOF, and realizes the conversion between the bright pulse output and the dark pulse output through rotating the polarization controller PC.

The wavelength of the dark pulse is adjustable from 1554nm to 1560nm, and the repetition frequency of the dark pulse is 196.8 kHz; the wavelength of the bright pulse is adjustable from 1552.7nm to 1560nm, and the time interval and the repetition frequency of the bright pulse pair sequence are respectively 5.08s and 196.8 kHz.

The invention has the beneficial effects that: firstly, the invention provides a new method for realizing the fiber laser with tunable wavelength and switchable pulse. Second, the light and dark pulses can be generated at two tunable wavelengths, which can be used for Wavelength Division Multiplexing (WDM) and fiber sensing technologies. Finally, the switching between bright and dark pulses is realized in the same optical fiber laser, which can enhance the performance of the laser and save the cost.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims

1. A dual-wavelength fiber laser capable of switching output of bright pulses and dark pulses is characterized in that: the ring-shaped fiber laser comprises a laser diode, a wavelength division multiplexer, an erbium-doped fiber, a polarization dependence isolator, a polarization controller, a high nonlinear fiber, an optical coupler and a tunable optical filter which are sequentially connected, wherein the polarization controller is used for adjusting the polarization state of pulses, bright and dark pulses are mutually switched and output by utilizing different polarization states, and the tunable optical filter is used for separating the wavelengths corresponding to the bright pulses and the pulses respectively.

2. The dual-wavelength fiber laser of claim 1, wherein: the dispersion parameter of the erbium-doped fiber is-16.3 ps/(Km & nm).

3. The dual-wavelength fiber laser of claim 1, wherein: the energy intensity of the wave band is changed by rotating the polarization controller, and the conversion between the bright pulse output and the dark pulse output is realized by rotating the polarization controller.

4. The dual-wavelength fiber laser of claim 1, wherein: the wavelengths corresponding to the bright pulse and the dark pulse are respectively adjustable.

5. The dual-wavelength fiber laser of claim 1, wherein: the wavelength of the dark pulse is adjustable from 1554nm to 1560 nm.

6. The dual-wavelength fiber laser of claim 5, wherein: the dark pulse pair repetition frequency was 196.8 kHz.

7. The dual-wavelength fiber laser of claim 1, wherein: the wavelength of the bright pulse is adjustable between 1552.7nm and 1560 nm.

8. The dual-wavelength fiber laser of claim 7, wherein: the time interval and repetition frequency of the sequence of pairs of bright pulses are 5.08s and 196.8kHz, respectively.

9. A method for switching output of bright pulses and dark pulses is characterized in that: the ring-shaped optical fiber laser is used, firstly, the energy intensity of a wave band is changed by rotating the polarization controller, secondly, the wavelengths corresponding to the bright pulse and the pulse are separated by the adjustable optical filter, and the conversion between the bright pulse output and the dark pulse output is realized by rotating the polarization controller.

10. The method of claim 9, wherein: the wavelength of the dark pulse is adjustable from 1554nm to 1560nm, and the repetition frequency of the dark pulse is 196.8 kHz; the wavelength of the bright pulse is adjustable from 1552.7nm to 1560nm, and the time interval and the repetition frequency of the bright pulse pair sequence are respectively 5.08s and 196.8 kHz.