CN108683064A - An all-fiber laser oscillator based on a longitudinally graded gain fiber with core size - Google Patents

Abstract

An all-fiber laser oscillator based on a longitudinally graded gain fiber with a core size, comprising a longitudinally graded gain fiber with a core size (1), a high-reflection fiber grating (2), a low-reflection fiber grating (3), and a fiber-coupled semiconductor laser ( 4), pump beam combiner (5), signal energy transmission fiber (6), pump energy transmission fiber (7), cladding light filter (8), fiber end cap (9); among them, high reflection fiber The grating, fiber core size longitudinally variable gain fiber, and low-reflection fiber grating are sequentially connected through the signal energy transmission fiber to form a fiber laser resonator; the output laser light of the fiber-coupled semiconductor laser is injected into the pump beam combiner through the pump energy transmission fiber, and then passed through the signal transmission fiber. The energy fiber is injected into the fiber laser resonator; the output laser light of the fiber laser resonator passes through the cladding light filter, and is output by the fiber end cap; wherein the core diameter of the fiber core size longitudinally gradient gain fiber is along the length of the fiber The direction becomes larger first and then smaller.

Description

An all-fiber laser oscillator based on a longitudinally graded gain fiber with core size

technical field

The present invention generally relates to the field of fiber lasers, in particular to an all-fiber laser oscillator based on a longitudinally graded gain fiber with a core size.

Background technique

Compared with the fiber laser with the main oscillation power amplification structure, the all-fiber laser oscillator has the advantages of low cost, compact structure, simple control logic, stable performance, and strong anti-reflection ability, and has been widely used in industrial processing. With the expansion of application fields, the power requirements of fiber laser oscillators are getting higher and higher. At present, the main physical limiting factors affecting the output power of all-fiber laser oscillators include mode instability effects and stimulated Raman scattering effects. Generally speaking, in order to suppress mode instability, it is generally necessary to use a gain fiber with a smaller core diameter and mode field area and a lower normalized frequency to suppress the generation of high-order modes, thereby increasing the output power of the laser. However, in order to suppress the nonlinear effect and increase the threshold of stimulated Raman scattering, it is necessary to use a gain fiber with a larger core diameter and mode field area.

Therefore, in general, the requirements for suppressing transverse mode instability and stimulated Raman scattering are contradictory to the mode field area of the gain fiber. It is difficult for an all-fiber laser with a common structure to balance this contradiction and further increase the power of an all-fiber laser oscillator. Encountered an obvious technical bottleneck.

At present, most all-fiber laser oscillators use a gain fiber whose core diameter varies uniformly along the fiber length direction as the gain medium of the laser. It is difficult to balance the contradiction between the mode instability effect and the suppression of the stimulated Raman scattering effect.

It is publicly reported that a laser with a longitudinally graded fiber core diameter is used to form a laser, mainly using a tapered fiber placed in a laser resonator: Patent CN201310069242.1 uses a tapered region with an axial length of 1.5-2 cm and two adjacent tapered regions A multi-taper optical fiber with a distance of 4 to 6 meters between the axial centers and a total length greater than or equal to 80 m can realize stable single-frequency laser operation in a ring cavity laser; patent CN201410106212.8 uses a tapered fiber with a taper diameter of 4 The tapered optical fiber with a length of ~10 microns and a length of 0.5 ~ 2 cm is fixed on the tunable device, and different stresses are applied to the tapered fiber through the adjustment device to achieve tuning output of different wavelengths in the ring laser; patent CN201610567283.7 uses modulation The tapered fiber with a period of 6.8-7.2 nanometers and a tapered waist of 7.0-7.5 microns stretches the length of the tapered fiber through the micro-displacement fiber clamp, and realizes the suppression of the laser longitudinal mode competition and the realization of the wavelength in the thulium-doped fiber ring cavity. The tuning achieved the tunable 2-micron band dual-wavelength mode-locked fiber laser output based on the tapered fiber.

When using tapered fiber to build lasers, the tapered fiber is single-mode fiber, and the length of the tapered area is less than 2 cm. The wavelength tuning or line width control is mainly achieved by controlling the length or stress of the tapered area. Because these lasers Both the core and the cladding of the medium fiber change with the length of the fiber, and the pump light has a large loss when it is transmitted through the cladding. In severe cases, the laser may burn out, which is not suitable for the application of high-power fiber lasers; Shaped fiber lasers, without transverse mode control and stimulated Raman scattering suppression.

Contents of the invention

For above-mentioned deficiencies in the prior art, the present invention provides a kind of all-fiber laser oscillator based on fiber core size longitudinally graded gain fiber, utilizes the gain fiber that core diameter changes gradually along the fiber length direction (referred to as longitudinal) as all-fiber laser The gain medium of the oscillator can take into account the suppression of mode instability and stimulated Raman scattering at the same time, breaking through the power limit of the fiber laser oscillator whose core size is constant along the fiber length, and improving the output of the all-fiber laser oscillator power while maintaining good beam quality.

The technical solution of the present invention is an all-fiber laser oscillator based on a longitudinally graded gain fiber with a core size, which is characterized in that it includes a longitudinally graded gain fiber with a core size, a high-reflection fiber grating, a low-reflection fiber grating, a fiber coupling Semiconductor lasers, pump beam combiners, signal energy transmission fibers, pump energy transmission fibers, cladding light filters, fiber end caps; the high reflection fiber Bragg grating, core diameter longitudinally graded gain fiber, low reflection fiber Bragg grating The fiber laser resonator is formed by sequential connection through the signal energy transmission fiber; the output laser of the fiber-coupled semiconductor laser is injected into the pump beam combiner through the pump energy transmission fiber, and then output from the pump beam combiner, injected into the pump beam combiner through the signal energy transmission fiber into the fiber laser resonator; the output laser from the fiber laser resonator passes through the cladding optical filter, and then is output by the fiber end cap; , the inner cladding wraps the fiber core, and the outer cladding wraps the inner cladding to form a gain fiber as a whole. The cross section of the core and the outer cladding is circular, and the cross section of the inner cladding is circular or regular octagonal. The diameter of the core is Along the length direction of the fiber, it first becomes larger and then becomes smaller, the cross-section of the inner cladding and its corresponding circumscribed circle diameter are constant along the length of the fiber, and the diameter of the outer cladding is constant along the length of the fiber.

Further, the above fiber core includes two sections of small diameter area, one section of large diameter area and two sections of transition diameter area, the small diameter area, transition diameter area, large diameter area, transition diameter area and small diameter area are sequentially connected to form a diameter along the The fiber core becomes larger first and then smaller in the direction of the fiber.

Furthermore, the diameters of the above two sections of small-diameter regions are the same and constant along the length of the optical fiber, the lengths are both in the range of 1-10 meters, and the normalized frequency is less than 3.8; The length direction is a fixed value and not less than 30 microns; the lengths of the two transitional diameter regions are both within the range of 0.01 to 1 meter, the diameter gradient rates of the two are the same, and the diameter and normalized frequency change along the length of the fiber, and the size of the small end and normalized frequency not less than the size and normalized frequency of the small diameter region, and the size and normalized frequency of the big end not greater than the size and normalized frequency of the large diameter region.

The all-fiber laser oscillator of the present invention based on the fiber core size longitudinally graded gain fiber can also include a backward pumping signal beam combiner, and the backward pumping signal beam combiner is arranged on the low-reflection fiber grating and cladding optical filter Between the dividers; the backward pump signal combiner includes a signal input arm, a signal output arm, one or more pump input arms; the output signal arm of the backward pump signal combiner and The low-reflection fiber grating is connected through a signal energy transmission fiber, its signal input arm is connected to the cladding optical filter through a signal energy transmission fiber, and its pump input arm is connected to another group of fiber-coupled semiconductor lasers through a pump energy transmission fiber.

Further, the above-mentioned core size longitudinally graded gain fiber is a gain fiber doped with rare earth ions, which is used for laser generation and transmission; and the cross-sectional structure of the optical fiber is selected from the cross-sectional structure of the optical fiber with double-clad or triple-clad structure When the cross-sectional structure of the core size longitudinally graded gain fiber is a double-clad structure, the diameter of the inner cladding or the diameter of the circumscribed circle of the inner cladding is between 100 and 1000 microns; the diameter of the outer cladding is between 250 and 2000 microns between.

Further, the above-mentioned high-reflection fiber grating is a high-reflection device of the laser resonator, and its reflectivity is greater than 90%. The diameter of the laser beam is matched to reflect most of the signal laser light into the resonant cavity.

Further, the reflectivity of the above-mentioned low-reflection fiber grating is in the range of 4% to 50%, and the diameter of the fiber core matches the diameter of the signal energy transmission fiber, which is the low reflection and output end of the laser resonator, and is used to reflect part of the signal Inside the resonator, most of the laser light is output outside the resonator.

Further, the above-mentioned fiber-coupled semiconductor laser is the excitation source for the upper-level particles produced by the core diameter longitudinally graded gain fiber, and it includes semiconductor lasers of various bands that match the absorption peaks of the core diameter longitudinally graded gain fiber, and the wavelengths of each band Semiconductor lasers include one or more combinations of wavelength bands of 808 nm, 915 nm, 940 nm, 976 nm, and 1550 nm.

Further, the above-mentioned pump signal combiner has single or multiple pump arms and a signal output arm, and a group of fiber-coupled semiconductor lasers are connected to the pump arm of the pump signal combiner through the pumping energy-transmitting optical fiber, so as to The pump light emitted by the fiber-coupled semiconductor laser is coupled to the inner cladding of the optical fiber of the signal output arm of the pump signal combiner through the pump arm, and finally realizes the transmission of the pump light in the pump signal combiner; The signal energy transmission fiber is a non-doped rare earth ion fiber used for laser transmission, and its cross-sectional structure is a double-clad or triple-clad structure; its core diameter is 10-1000 microns, and the inner cladding diameter is between 100-2000 microns The diameter of the outer cladding is between 250 and 3000 microns; the pump energy transmission fiber is a non-doped rare earth ion fiber used for pumping laser transmission, and its cross-sectional structure is a single cladding structure; its core diameter is between 10 and 3000 microns. 1000 microns, the cladding diameter is between 100 and 2000 microns.

Further, the above-mentioned cladding optical filter is used to filter the residual pump light and high-order modes in the signal fiber, and its geometric size is consistent with the geometric size of the signal energy transmission fiber; the optical fiber end cap is used for the signal energy transmission fiber The beam expansion of the signal light in the output reduces the power density of the output end face and improves the reliability of the laser.

The following technical effects can be achieved by adopting the present invention:

1. Effectively suppress the mode instability in the fiber oscillator: using the small diameter area of the fiber core with longitudinal gradient gain, only support less than 2 modes, and at the same time, by controlling the bending diameter of the single-mode gain fiber to be less than a certain value, it can effectively suppress The high-order mode generation in the oscillator ensures single-mode operation and effectively suppresses the transverse mode instability effect in fiber lasers.

2. Effective suppression of stimulated Raman scattering in fiber oscillators: the use of the large-diameter region of the fiber with longitudinally graded gain in core size can reduce the effective power density in the fiber core and increase the threshold of stimulated Raman scattering.

3. Obtain high-power and high-beam-quality laser output: Utilizing the free-flowing effect of the laser resonator, it can take into account the suppression of mode instability and stimulated Raman scattering at the same time, breaking through the fiber with a constant core size along the length of the fiber. Power limiting, maintaining good beam quality while increasing the output power of all-fiber laser oscillators.

Description of drawings

These and/or other aspects and advantages of the present invention will become clearer and easier to understand from the following detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, wherein:

1 is a schematic diagram of an all-fiber laser oscillator based on a fiber core size longitudinally graded gain fiber according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of the structure of an optical fiber with a longitudinally graded gain in core size in Embodiment 1 of the present invention;

Fig. 3 is a schematic diagram of a dual-end pumped all-fiber laser oscillator based on a longitudinally graded gain fiber with core size according to an embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

An all-fiber laser oscillator based on a longitudinally graded gain fiber with a core size, the structural diagram is shown in Figure 1, including a fiber with a core diameter with a longitudinally graded gain fiber 1, a high-reflection fiber grating 2, a low-reflection fiber grating 3, and a fiber-coupled semiconductor Laser 4, pump beam combiner 5, signal energy transmission fiber 6, pump energy transmission fiber 7, cladding light filter 8, fiber end cap 9; among them, high reflection fiber grating 2, fiber core diameter longitudinal gradient gain fiber 1. The low-reflection fiber grating 3 is sequentially connected through the signal energy transmission fiber 6 to form a fiber laser resonator, and the output laser light of the fiber-coupled semiconductor laser 4 is injected into the pump beam combiner 5 through the pump energy transmission fiber 7, and then passed through the pump beam combiner 5 is injected into the fiber laser resonator, and the output laser light from the fiber laser resonator passes through the cladding optical filter 8, and then is expanded and output by the fiber end cap 9.

In the all-fiber laser oscillator based on the core size longitudinally graded gain fiber of this embodiment, the core diameter longitudinally graded gain fiber 1 includes a core 1-1, an inner cladding 1-2, and an outer cladding 1-3 from the inside to the outside , the inner cladding 1-2 wraps the fiber core 1-1, the outer cladding 1-3 wraps outside the inner cladding 1-2, and constitutes a gain fiber as a whole, the cross section of the fiber core 1-1 and the outer cladding 1-3 is circular, The cross-section of the inner cladding 1-2 is circular or regular octagonal. The diameter of the core 1-1 first increases and then becomes smaller along the length of the fiber. The direction is constant, and the diameter of the outer cladding layer 1-3 is constant along the length direction of the optical fiber.

The specific design that the size of the fiber core 1-1 becomes larger first and then smaller along the length of the fiber is as follows: the fiber core 1-1 includes two small diameter regions 1-4, 1-8, one large diameter region 1-5 and two Segment transition diameter area 1-6, 1-7; small diameter area 1-4, transition diameter area 1-6, large diameter area 1-5, transition diameter area 1-7, small diameter area 1-8 of the fiber core in order Connection; the dimensions of the inner cladding 1-2 and the outer cladding 1-3 are constant along the length of the optical fiber. Small diameter regions 1-4, 1-8 have a length of 10 meters, a diameter of 15 microns, and a numerical aperture of 0.055; large diameter regions 1-5 have a length of 10 meters, a diameter of 50 microns, and a numerical aperture of 0.065; transitional diameter regions 1-6 , 1-7 have a length of 1 meter, the diameter of the small end is 15 microns, and is connected with the small diameter areas 1-4, 1-8, and the diameter of the large end is 50 microns, and is connected with the large diameter area 1-5.

In a specific implementation, since the normalized frequency in the small-size region 1-4 of the core size longitudinally graded gain fiber (1) is less than 2.4, the small-diameter region 1-4 gain fiber is a strict single-mode fiber and only supports the fundamental mode Operating in a laser resonator, no special fiber bending is required for effective mode instability suppression.

Example 2

A kind of fiber core size longitudinally graded gain fiber 1, its structure is shown in Figure 2, comprises fiber core 1-1, inner cladding 1-2, outer cladding 1-3 from inside to outside; Wherein fiber core 1-1 comprises two A section of small diameter area 1-4, 1-8, a section of large diameter area 1-5 and two transitional diameter areas 1-6, 1-7, the above-mentioned small diameter area 1-4, transitional diameter area 1-6, large diameter Areas 1-5, transition diameter areas 1-7, and small diameter areas 1-8 are sequentially connected, and the dimensions of the inner cladding 1-2 and the outer cladding 1-3 are constant along the length of the fiber, but the core 1-1 is overall The diameter is longitudinally gradual: the length of the small-diameter areas 1-4 and 1-8 is 1-10 meters, the diameter is constant along the length of the fiber and not greater than 20 microns, and the normalized frequency is less than 3.8; the large-diameter areas 1-5 The length is 10 meters, the diameter is constant along the length of the fiber and not less than 30 microns; the length of the transition diameter areas 1-6 and 1-7 is 0.01-1 m, the diameter and normalized frequency change along the length of the fiber, and the transition area 1- 6. The diameter gradient rate of 1-7 can be the same or different, and the diameter and normalized frequency of the small end are not less than the diameter and normalized frequency of the small diameter area 1-4, 1-8, and the diameter and normalized frequency of the big end The normalized frequency is not greater than the diameter and normalized frequency of the large diameter regions 1-5.

Example 3

A double-end pumped all-fiber laser oscillator based on a longitudinally graded gain fiber with a core size, the structural diagram is shown in Figure 3, including a fiber with a longitudinally graded core size gain fiber 1, a high-reflection fiber grating 2, and a low-reflection fiber grating 3 , fiber-coupled semiconductor laser 4, forward pump combiner 5, signal energy transmission fiber 6, pump energy transmission fiber 7, cladding optical filter 8, fiber end cap 9, backward pump signal combiner 10. The structure of the laser oscillator is basically the same as that in Embodiment 1, except that a backward pumping signal beam combiner 10 is inserted between the low-reflection fiber grating 3 and the cladding optical filter 8, The backward pump signal combiner 10 includes a signal input arm, a signal output arm, and one or more pump input arms. High-reflection fiber grating 2, core diameter longitudinally variable gain fiber 1, and low-reflection fiber grating 3 are sequentially connected through the signal energy transmission fiber 6 to form a fiber laser resonator, and the output laser of the fiber-coupled semiconductor laser 4 is injected into the pump through the pump energy transmission fiber 7 The pump beam combiner 5 is then injected into the fiber laser resonator via the pump beam combiner 5, and the output laser light from the fiber laser resonator passes through the cladding light filter 8, and is output by the fiber end cap 9 beam expansion; the other group of optical fibers The laser output from the coupling semiconductor laser 4 is injected into the pump signal beam combiner 10 through the pump energy transmission fiber 7 , and then injected into the fiber laser resonator through the pump signal beam combiner 10 .

The core size longitudinally graded gain fiber 1 in this embodiment includes a core 1-1, an inner cladding 1-2, and an outer cladding 1-3 from the inside to the outside; the core 1-1 includes two sections of small diameter regions 1-4 , 1-8, a large diameter area 1-5 and two transitional diameter areas 1-6, 1-7; small diameter area 1-4, transitional diameter area 1-6, and large diameter area 1 of the fiber core 1-1 -5. The transition diameter area 1-7 and the small diameter area 1-8 are sequentially connected; the size of the inner cladding layer 1-2 and the outer cladding layer 1-3 is constant along the length of the optical fiber, and the specific design of the longitudinal gradient of the core diameter is as follows: The small diameter regions 1-4, 1-8 have a length of 10 meters, a diameter of 20 microns, and a numerical aperture of 0.06, and the large diameter regions 1-5 have a length of 10 meters, a diameter of 50 microns, and a numerical aperture of 0.065; transitional diameter regions 1-6 , the length of 1-7 is 1 meter, the size of the small end is 20 microns, the small end is connected with the small diameter areas 1-4, 1-8, the size of the large end is 50 microns, and the large end is connected with the large diameter area 1-5.

In this specific implementation, the normalized frequency of the small diameter region 1-4 of the core size longitudinally graded gain fiber (1) is between 2.4 and 3.8, supporting two modes of LP01 and LP11, and the small diameter region 1-4 needs to be 4 Bend into a circular ring with a diameter of less than 12 cm to increase the loss of the higher-order mode, suppress the mode instability effect, and realize the effective operation of the fundamental mode LP01.

Having described various embodiments of the present invention, the foregoing description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and alterations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (10)

1. a kind of full optical fiber laser oscillator based on core size longitudinal direction gradual change gain fibre, which is characterized in that it includes fibre The gain fibre (1) of core size longitudinal direction gradual change, high reflection fiber grating (2), low light reflectivity fibre grating (3), fiber coupling are partly led Body laser (4), pump combiner (5), signal energy-transmission optic fibre (6), pumping energy-transmission optic fibre (7), cladding light stripper (8), light Fine end cap (9)；

The high reflection fiber grating (2), core size longitudinal direction gradual change gain fibre (1), low light reflectivity fibre grating (3) pass through letter Number energy-transmission optic fibre (6) is sequentially connected, and forms optical fiber laser resonant cavity；

Fiber coupled laser diode (4) the output laser injects pump combiner (5) by pumping energy-transmission optic fibre (7), Then it spreads out of from pump combiner (5), is injected into the optical fiber laser resonant cavity by signal energy-transmission optic fibre (6)；

Optical fiber laser resonant cavity exports laser after cladding light stripper (8), and output is expanded by end caps (9)；

The gain fibre (1) of core size longitudinal direction gradual change includes fibre core (1-1), inner cladding (1-2), surrounding layer (1-3), institute State inner cladding (1-2) and wrap fibre core (1-1), surrounding layer (1-3) packet inner cladding (1-2) outside, be integrally formed gain fibre, it is fine Core (1-1) and the cross section surrounding layer (1-3) are round, the cross section inner cladding (1-2) is round or octagon, fibre core (1-1) Size first become larger along fiber length and become smaller afterwards, the inner cladding (1-2) is along the cross section of fiber length and transversal The circumscribed circle diameter in face is invariable along fiber length, and the diameter of the surrounding layer (1-3) is constant along fiber length It is constant.

2. the full optical fiber laser oscillator as described in claim 1 based on core size longitudinal direction gradual change gain fibre, feature It is, the fibre core (1-1) includes that two sections of small diameter areas (1-4,1-8), one section of large-diameter region (1-5) and two sections of transition are straight Diameter region (1-6,1-7), the small diameter area (1-4), transitional diameter region (1-6), large-diameter region (1-5), transition are straight Diameter region (1-7), small diameter area (1-8) are in turn connected to form diameter and first become larger along optical fiber direction the fibre core (1-1) to become smaller afterwards.

3. the full optical fiber laser oscillator as claimed in claim 2 based on core size longitudinal direction gradual change gain fibre, feature It is, the diameter of two sections of small diameter areas (1-4,1-8) is identical and constant along fiber length, and length is 1~10 Rice range is interior, normalized frequency is less than 3.8；1~10 meter of the length of large-diameter region (1-5), diameter are along fiber length Definite value and be not less than 30 microns；The length of two sections of transitional diameter regions (1-6,1-7) within the scope of 0.01~1 meter, the two Diameter Gradual Change rate is identical and diameter and normalized frequency change along fiber lengths, and the size and normalized frequency of small end are not less than Size and normalized frequency, the size of big end and normalized frequency of small diameter area (1-4,1-8) are not more than large-diameter region The size and normalized frequency of (1-5).

4. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, special Sign is, further includes backward pump signal bundling device (10), and the backward pump signal bundling device (10) is arranged in low light reflectivity Between fine grating (3) and cladding light stripper (8)；The backward pump signal bundling device (10) include a signal input arm, One signal output arm, one or more pumping input arm；The output signal arm of the backward pump signal bundling device (10) with Low light reflectivity fibre grating (3) is connected by signal energy-transmission optic fibre (6), and signal input arm passes through letter with cladding light stripper (8) The connection of number energy-transmission optic fibre (6), pumping input arm passes through with another set fiber coupled laser diode (4) pumps that pass can light Fine (7) connection.

5. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, special Sign is, the gain fibre (1) of core size longitudinal direction gradual change is rare-earth-ion-doped gain fibre, generated for laser and The optical fiber of transmission；And one kind in cross section of optic fibre structure of the cross-sectional structure of optical fiber selected from double clad or triple clad structure； When the cross-sectional structure of the core size longitudinal direction gradual change gain fibre (1) be double-clad structure when, inner cladding (1-2) diameter or Circumscribed circle diameter is between 100~1000 microns；The diameter of surrounding layer (1-3) is between 250~2000 microns.

6. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, special Sign is that the high reflection fiber grating (2) is the high reflection device of laser resonator, and reflectivity is more than 90%, in reflection Cardiac wave length is matched with the centre wavelength of the low light reflectivity fibre grating (3), the fibre core diameter of high reflection fiber grating (2) and The diameter matches of signal energy-transmission optic fibre (6), in the overwhelming majority reflection meeting resonant cavity by signal laser.

7. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, special Sign is that for the reflectivity of the low light reflectivity fibre grating (3) in 4%~50% range, core diameter is passed with signal can light The diameter matches of fine (6) are low reflection and the output end of laser resonator, are used to reflect part signal in meeting resonant cavity, greatly Fraction of laser light is output to outside resonant cavity.

8. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, special Sign is that the fiber coupled laser diode (4) is energy level grain in gain fibre (1) generation of core size longitudinal direction gradual change The driving source of son, it includes the semiconductor with the matched each wave band of the gain fibre of core size longitudinal direction gradual change (1) absorption peak Laser, the semiconductor laser of each wave band include wave band be 808 nanometers, 915 nanometers, 940 nanometers, 976 nanometers, One or more of 1550 nanometers of combination.

9. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, special Sign is that the pump signal bundling device (5) has single or multiple pumping arms, a signal output arm, one group of fiber coupling half Conductor laser (4) is connected to the pumping arm of pump signal bundling device (5) by pumping energy-transmission optic fibre (7), so that fiber coupling The pump light that semiconductor laser (4) is sent out is coupled to the light of the signal output arm of pump signal bundling device (5) by pumping arm In fine inner cladding, the final middle transmission for realizing pump light in pump signal bundling device (5)；The signal energy-transmission optic fibre (6) is to use In the non-rare-earth-doped fiber of laser transmission, cross-sectional structure is double clad or triple clad structure；Its core diameter is 10 ~1000 microns, inner cladding diameter is between 100~2000 microns；Outer cladding diameter is between 250~3000 microns；The pump Pu energy-transmission optic fibre (7) be for pumping laser transmit it is non-mix rare earth sub-optical fibre, cross-sectional structure is list cladding structure；It is fine Core diameter is at 10~1000 microns, and cladding diameter is between 100~2000 microns.

10. the full optical fiber laser oscillator according to claim 3 based on core size longitudinal direction gradual change gain fibre, It is characterized in that, geometric dimension and the signal energy-transmission optic fibre geometric identity of the cladding light stripper (8), for filtering out signal Residual pump light in optical fiber and higher order mode；The end caps (9) are used to expand the signal light in signal energy-transmission optic fibre (6) Beam exports, and reduces the power density of output end face, improves the reliability of laser.