CN208111909U - Random Fiber Laser Based on Sagnac Ring and Oppositely Chirped Fiber Bragg Grating Strings - Google Patents

Abstract

The utility model discloses a kind of random fiber laser based on Sagnac ring and opposite chirped fiber grating string, including pump laser, 980/1550nm wavelength division multiplexer, Y type coupler, polarization maintaining optical fibre, Polarization Controller, weak reflection chirp erbium-doped nonlinear fiber grating string, 980/1550nm wavelength division multiplexer, spectrometer and light power meter.The utility model provides random distribution feedback using the chirped fiber grating string being scribed on erbium-doped fiber, using Er-doped fiber as gain media.The distance of each chirped fiber grating random distribution between 30-100mm in the chirp erbium-doped nonlinear fiber grating string that the utility model uses.The chirp of two neighboring chirped fiber grating is contrary, increases the randomness of feedback.By adjusting Polarization Controller, the changeable stable output of wavelength is realized.The features such as random fiber laser described in the utility model has tunable wave length range wide, and stability is good, has huge application potential in the fields such as Fibre Optical Sensor and optic communication.

Description

Random Fiber Laser Based on Sagnac Ring and Oppositely Chirped Fiber Bragg Grating Strings

technical field

The invention belongs to the technical field of lasers, in particular to a random fiber laser based on Sagnac rings and oppositely chirped fiber grating strings.

Background technique

Random fiber laser is a new cavity-free structure laser based on the fact that the scattered light in the disordered medium is continuously amplified during transmission. It has the advantages of simple structure and high conversion efficiency. It is used in nonlinear optics, optical sensing and optical communication. , biomedical imaging, remote sensing and many other fields have great application value.

In 2010, the distributed Rayleigh scattering fiber random laser with Raman effect as the gain mechanism was reported for the first time, and its basic working principle was clarified. applied research. Therefore, in the field of fiber lasers, using the Rayleigh scattering and Raman scattering effects caused by the intrinsic disorder in the fiber as the mechanism for generating random phenomena has become the mainstream of current research and development. However, due to the weak Rayleigh scattering caused in the fiber, this kind of fiber laser has the disadvantages of high threshold, low power conversion efficiency and so on.

In 1913, the Sagnac effect was discovered for the first time and verified by experiments. On the basis of this effect, a filter can be formed by adding a polarization-maintaining fiber and a polarization controller. Compared with other filter devices, its filtering characteristics have the characteristics of simple structure, flexible adjustment, and comb filtering.

A chirped fiber grating is an important optical component. Since different grating positions correspond to different reflection wavelengths, a chirped fiber grating can form a reflection range with a large bandwidth. Applying chirped fiber grating strings to random fiber lasers to replace Rayleigh scattering in fibers and provide distributed feedback can greatly save fiber length and improve laser conversion efficiency and output power.

Contents of the invention

The present invention proposes a random fiber laser based on Sagnac rings and oppositely chirped fiber grating strings, and writes chirped fiber grating strings with opposite chirping directions and random spacing between two adjacent chirped fiber gratings on an erbium-doped fiber. The laser is continuously fed back by gain in the chirped erbium-doped fiber grating string, and the stable laser output is realized by adjusting the polarization controller in the Sagnac ring.

The technical solution adopted by the present invention to solve the technical problems is as follows:

A random fiber laser based on Sagnac rings and oppositely chirped fiber grating strings, characterized in that it consists of a pump laser 1, a first 980/1550nm wavelength division multiplexer 2, a Y-coupler 3, a polarization-maintaining fiber 4, and a polarization controller 5. Weak reflection chirped erbium-doped fiber grating series 6, second 980/1550nm wavelength division multiplexer 7, spectrometer and optical power meter 8; pump laser 1 and first 980/1550nm wavelength division multiplexer 2 980nm The ends are connected, the common end of the first 980/1550nm wavelength division multiplexer 2 is connected to the Y-type coupler 3, and the other end of the Y-type coupler is respectively connected to the polarization-maintaining fiber 4 and the polarization controller 5 to form a closed end; the first 980/1550nm wavelength division multiplexer 2 The 1550nm end of the 1550nm wavelength division multiplexer 2 is connected to the weak reflection chirped erbium-doped fiber grating string 6, and the other end of the weak reflection chirped erbium-doped fiber grating string 6 is connected to the 1550nm end of the second 980/1550nm wavelength division multiplexer 7 The common end of the second 980/1550nm wavelength division multiplexer 7 is connected to the spectrometer and the optical power meter 8; wherein, the chirp directions of two adjacent chirped fiber gratings in the weak reflection chirped erbium-doped fiber grating string 6 Instead, the pitch of each chirped fiber grating is randomly distributed.

Further according to the random fiber laser based on Sagnac ring and oppositely chirped fiber grating strings according to the present invention, it is characterized in that the number of chirped fiber gratings in the weak reflection chirped erbium-doped fiber grating string 6 is 30-50, The bandwidth range of each chirped fiber grating is 1-10nm, the reflectivity of each chirped fiber grating is 1%-10%, and the central wavelength is consistent.

Working principle of the present invention is:

Turn on the pump laser 1, the pump light is coupled into the linear cavity through the first 980/1550nm wavelength division multiplexer 2, and in the weak reflection chirped erbium-doped fiber grating string 6, after Er3+ absorbs the energy of the pump light, it transitions from the ground state to a high energy level state, and transition to a metastable energy level in a non-radiative manner, Er3+ continuously absorbs the pump light energy and accumulates at the upper energy level, and finally realizes the inversion of the number of particles between the energy levels, thereby generating stimulated radiation. For the C-band The light is amplified with optical gain. At the same time, due to the Anderson localization phenomenon in the weakly reflective chirped erbium-doped fiber grating string 6, the light is reflected multiple times in the weakly reflective chirped erbium-doped fiber grating string 6, resulting in a closed ring cavity similar to a resonant cavity. Light is continuously amplified by gain in weakly reflected trains. Since the chirp directions of two adjacent chirped fiber gratings are opposite and the distances between the chirped fiber gratings are randomly distributed. Therefore, random lasing occurs when the gain in the cavity is greater than the loss. By adjusting the polarization controller 5 in the Sagnac ring, the wavelength-selective and stable output is realized.

The present invention has the following innovative advantages:

The chirped fiber grating series used in the present invention is written on the erbium-doped optical fiber and provides distributed feedback. Compared with the traditional distribution feedback provided by Rayleigh scattering, the length of the optical fiber is greatly reduced, and the output efficiency of the laser is effectively improved. , which reduces the output threshold of the laser. Compared with the fiber Bragg grating, the chirped fiber grating used in the present invention has a larger bandwidth of the chirped fiber grating, which increases the optional range of the generated random laser; The direction of the chirp is opposite, which greatly improves the randomness of the feedback. In the present invention, a Sagnac ring is added to a random fiber laser, and the stable output of single wavelength, double wavelength and multiple wavelengths can be realized by adjusting the polarization controller 5 .

Description of drawings

Fig. 1 is a schematic structural diagram of a random fiber laser based on Sagnac rings and oppositely chirped fiber grating strings.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments, but is not limited thereto.

A kind of random fiber laser based on Sagnac ring and oppositely chirped fiber grating series, its structural schematic diagram is as shown in Figure 1, comprises pumping laser 1, first 980/1550nm wavelength division multiplexer 2, Y-type coupler 3, Polarization maintaining fiber 4, polarization controller 5, weak reflection chirped erbium-doped fiber grating series 6, second 980/1550nm wavelength division multiplexer 7, spectrometer and optical power meter 8, characterized in that the pump laser 1 and the first 980nm The 980nm end of the /1550nm wavelength division multiplexer 2 is connected, the common end of the first 980/1550nm wavelength division multiplexer 2 is connected to the Y-type coupler 3, and the other end of the Y-type coupler is respectively connected to the polarization-maintaining fiber 4 and the polarization control The device 5 forms a closed end; the 1550nm end of the first 980/1550nm wavelength division multiplexer 2 is connected to the weak reflection chirped erbium-doped fiber grating string 6, and the other end of the weak reflection chirped erbium-doped fiber grating string 6 is connected to the second 980/1550nm wavelength division multiplexer 2. The 1550nm terminal of the 1550nm wavelength division multiplexer 7 and the common terminal of the second 980/1550nm wavelength division multiplexer 7 are connected to a spectrometer and an optical power meter 8 to detect the spectrum and power output characteristics of the laser respectively.

The weak reflection chirped erbium-doped fiber grating series 6 of the present invention, the number of chirped fiber gratings is 30-50, the bandwidth of each chirped fiber grating is 1-5nm, and the reflectivity of each chirped fiber grating is 1%- 10% and the center wavelength is consistent, and the spacing of each chirped fiber grating is randomly distributed; the chirp directions of two adjacent chirped fiber gratings in the weak reflection chirped erbium-doped fiber grating string 6 are opposite to increase the randomness of feedback .

The writing process of the weak reflection chirped erbium-doped fiber grating string 6 of the present invention: firstly carry out the hydrogen-carrying technology on the erbium-doped fiber to be written, and then use the phase mask to carry out continuous writing under the laser. During the writing process, it is necessary to constantly change the front and rear directions of the phase mask to realize that the chirp directions of two adjacent chirped fiber gratings are opposite.

Claims (2)

1. based on the random fiber laser of Sagnac ring and oppositely chirped fiber grating string, it is characterized in that by pumping laser (1), the first 980/1550nm wavelength division multiplexer (2), Y type coupler (3), Polarization maintaining fiber (4), polarization controller (5), weak reflection chirped erbium-doped fiber grating string (6), second 980/1550nm wavelength division multiplexer (7), spectrometer and optical power meter (8); The pump laser (1) is connected to the 980nm end of the first 980/1550nm wavelength division multiplexer (2), and the common end of the first 980/1550nm wavelength division multiplexer (2) is connected to the Y-type coupler (3), The other end of the Y-shaped coupler is respectively connected to the polarization maintaining fiber (4) and the polarization controller (5) to form a closed end; the 1550nm end of the first 980/1550nm wavelength division multiplexer (2) is connected to the weak reflection chirped erbium-doped optical fiber Grating series (6), the other end of weak reflection chirped erbium-doped fiber grating series (6) connects the 1550nm end of the second 980/1550nm wavelength division multiplexer (7), the second 980/1550nm wavelength division multiplexer ( 7) The common end connects the spectrometer and the optical power meter (8); Wherein, the chirp directions of two adjacent chirped fiber gratings in the described weak reflection chirped erbium-doped fiber grating string (6) are opposite, each chirped optical fiber The pitch of the grating is randomly distributed. 2. the random fiber laser based on Sagnac ring and opposite chirped fiber grating string according to claim 1, it is characterized in that, the chirped fiber grating quantity of described weak reflection chirped erbium-doped fiber grating string (6) is 30 -50, the bandwidth range of each chirped fiber grating is 1-10nm, the reflectivity of each chirped fiber grating is 1%-10%, and the center wavelength is consistent.