CN110829164A - All-fiber ultrashort pulse light source capable of simultaneously generating soliton and noise-like pulses - Google Patents

Abstract

An all-fiber ultrashort pulse light source capable of simultaneously generating soliton and noise-like pulses belongs to the field of optical information technology. pump source, first wavelength division multiplexer, second wavelength division multiplexer, erbium-doped fiber, first coupler, high nonlinear fiber, second coupler, first polarization controller, polarization dependent isolator, Optical circulator, reflective adjustable optical attenuator and second polarization control, the present invention adopts a mode-locking structure with controllable attenuation and a double-coupler light splitting structure, in the same laser resonant cavity structure, the soliton pulse and The simultaneous output of noise-like pulses with high pulse energy increases the practicability of the all-fiber ultrashort pulse light source, greatly reduces the cost, and can be applied to optical communication, sensing, imaging, nonlinear frequency conversion and other fields.

Description

An all-fiber ultrashort pulse light source capable of simultaneously generating soliton and noise-like pulses

technical field

The invention relates to an all-fiber ultra-short pulse light source capable of simultaneously generating soliton and noise-like pulses, and belongs to the technical field of optical information.

Background technique

Ultrashort pulsed light source refers to the time-domain width of the pulse is less than picosecond laser. Ultrashort pulsed light source has important applications in medical, military, communication, ranging, mid-infrared light source generation and other fields, and has become the most promising development today. One of the laser technologies. The use of all-fiber resonator structure to generate ultra-short pulse laser has the characteristics of small size, good heat dissipation, and simple manufacturing process. Therefore, all-fiber ultra-short pulse laser has high reliability and low cost, and is suitable for mass production and application. . In addition, by properly controlling the parameters such as the total dispersion value and nonlinear effect of the fiber resonator, several working states of traditional soliton pulse, dispersion-managed soliton pulse, self-similar pulse and noise-like pulse can be realized respectively.

At present, the generation of all-fiber ultrashort pulse lasers is mostly realized by the multi-longitudinal mode phase locking method, mainly using two-dimensional material saturable absorbers such as graphene and black scale, or fiber ring mirrors, nonlinear polarization rotation and other fiber mode locking structures. . However, the above solutions still have a common problem, that is, the output ultra-short pulses are usually maintained in a single working state. In practical applications, if two or more ultra-short pulses in different operating states are required at the same time, two different laser resonators need to be built. , which greatly increases the complexity and cost of the system.

The Chinese Patent Publication No. "CN105977784A" discloses "a noise-like pulse generator". As shown in Figure 1, the generator includes a pump source and an optical fiber annular cavity, which is characterized in that: the optical fiber annular cavity includes a A wavelength division multiplexer, a doped fiber, an optical isolator, a polarizer, a polarization controller and a fiber coupler in which the optical fibers are connected in turn and form a closed-loop structure, the pump source and the pump of the wavelength division multiplexer port connection, the fiber coupler includes a loop output port, a target output port and an input port, the input port and the common port of the wavelength division multiplexer pass through the doped fiber, the optical isolator , the polarizer and the polarization controller are connected in turn to form a connection loop segment connection, the loop output port is connected with the signal port of the wavelength division multiplexer, and the target output port is used for Output "noise-like" pulses.

The patent adopts a standard annular cavity structure, uses a polarizer and a polarization controller to achieve mode locking, uses the Raman effect of the fiber to assist in generating broadband noise-like pulses, and uses a 10% energy output coupler to generate broadband-like noise in the total positive dispersion region. noise pulse. However, after the mode-locking pulse starts automatically in this patent, the output ultra-short pulse can only work in a state of noise-like pulse due to the limitation of the resonator structure, and it cannot output conventional soliton pulses with more stable performance at the same time.

SUMMARY OF THE INVENTION

In order to solve the technical problem that the output pulse of the existing all-fiber ultra-short pulse light source has a single working state, the invention proposes an all-fiber ultra-short pulse light source that can simultaneously generate soliton and noise-like pulses. It can greatly reduce the complexity of the system, and further promote the application of all-fiber mode-locked pulse light sources in more cutting-edge fields while reducing costs.

The present invention adopts following technical scheme:

An all-fiber ultrashort pulse light source capable of simultaneously generating soliton and noise-like pulses, characterized in that the first pump source is connected to the a-end of the first wavelength division multiplexer, and the second pump source is connected to the second wavelength division multiplexer The d end of the first wavelength division multiplexer and the f end of the second wavelength division multiplexer are respectively connected to both ends of the erbium-doped fiber, and the e end of the second wavelength division multiplexer is connected to the first The h end of the coupler is connected, the i end of the first coupler is connected to the high nonlinear fiber, the other end of the high nonlinear fiber is connected to the k end of the second coupler, and the l end of the second coupler is connected to the first polarization control The other end of the first polarization controller is connected to the input end of the polarization dependent isolator, the output end of the polarization dependent isolator is connected to the n end of the optical circulator, and the o end of the optical circulator is connected to the reflective adjustable optical attenuation The p end of the optical circulator is connected to the second polarization controller to form a nonlinear polarization rotation mode locking structure with controllable attenuation, and the other end of the second polarization controller is connected to the b end of the first wavelength division multiplexer , forming an all-fiber ring resonator structure;

Turn on the first pump source and the second pump source at the same time and adjust the pump power appropriately. The total pump power is in the range of 400-550mW, and the pump light passes through the first wavelength division multiplexer and the second wavelength division multiplexer respectively. The erbium-doped fiber is injected into the erbium-doped fiber to generate clockwise and counterclockwise gains. The counterclockwise gain is isolated by the polarization-dependent isolator. Conventional soliton mode-locked pulses, in which 5% of the total power of the soliton pulses are output from the j port of the first coupler, and the remaining 95% of the soliton pulses are injected into the highly nonlinear fiber from the i end of the first coupler, and the soliton collapse effect Under the action of , the soliton pulse gradually evolves into a noise-like pulse during the transmission process in the highly nonlinear fiber. The noise-like pulse accounting for 50% of the total power is output from the m port of the second coupler, and the remaining 50% of the noise-like pulse passes through in turn. After the first polarization controller and the polarization-dependent isolator, it is incident on the n-port of the optical circulator, and the o-port of the circulator is incident on the reflective adjustable optical attenuator, and the attenuated optical pulse is incident on the p-port of the circulator. to a second polarization controller and amplified in an erbium-doped fiber, where it is reduced to a regular soliton pulse.

Beneficial effects of the present invention:

The invention adopts a mode-locking structure with controllable attenuation and a double-coupler optical splitting structure, and in the same laser resonant cavity structure, the soliton pulse with stable performance and the noise-like pulse with high pulse energy can be output at the same time, and the all-fiber ultra-short pulse is increased. The practicability of the light source greatly reduces the cost, and can be applied to the fields of optical communication, sensing, imaging, nonlinear frequency conversion, etc.

The invention adopts an all-fiber ring resonant cavity structure, with simple structure, low threshold value, strong anti-interference ability, narrow output laser pulse width and stable performance. Industrial processing, scientific research and other fields.

Description of drawings

FIG. 1 is a schematic structural diagram of an all-fiber ultrashort pulse light source capable of simultaneously generating soliton and noise-like pulses according to the present invention.

Figure 2(a) is the output spectrum of the soliton pulse; 2(b) is the time domain sequence diagram of the soliton pulse; 2(c) is the autocorrelation curve of the soliton pulse; (d) is the spectrum of the soliton pulse.

Figure 3(a) is the output spectrum of the noise-like pulse; 3(b) is the autocorrelation curve of the noise-like pulse; 3(c) is the enlarged peak of the autocorrelation curve of the noise-like pulse;

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings.

As shown in Figure 1, an all-fiber ultrashort pulse light source that can generate soliton and noise-like pulses at the same time includes a first pump source 1, a second pump source 2, a first wavelength division multiplexer 3, a second wavelength division multiplexer Multiplexer 4, erbium-doped fiber 5, first coupler 6, high nonlinear fiber 7, second coupler 8, first polarization controller 9, polarization-dependent isolator 10, optical circulator 11, reflective adjustable Optical attenuator 12 and second polarization control 13 .

In the resonator part, the pump light is injected into both ends of the gain fiber to form a bidirectional pump structure. The first pump source 1 is connected to the a terminal of the first wavelength division multiplexer 3, the second pump source 2 is connected to the d terminal of the second wavelength division multiplexer 4, and the c terminal of the first wavelength division multiplexer 3 is connected. end, the f end of the second wavelength division multiplexer 4 are respectively connected with both ends of the erbium-doped fiber 5, the e end of the second wavelength division multiplexer 4 is connected with the h end of the first coupler 6, and the first coupler The i end of 6 is connected to the high nonlinear fiber 7, the other end of the high nonlinear fiber 7 is connected to the k end of the second coupler 8, the l end of the second coupler 8 is connected to the first polarization controller 9, and the first The other end of the polarization controller 9 is connected to the input end of the polarization dependent isolator 10, the output end of the polarization dependent isolator 10 is connected to the n end of the optical circulator, and the o end of the optical circulator 11 is connected to the reflective adjustable optical attenuation connected to the optical circulator 12, the p end of the optical circulator is connected to the second polarization controller 13 to form a nonlinear polarization rotation mode locking structure with controllable attenuation, and the other end of the second polarization controller 13 is connected to the first wavelength division multiplexer 3 The b end is connected to form an all-fiber ring resonator structure. All of the above components are welded by pigtails.

In the mode locking structure part, the first polarization controller 9, the polarization dependent isolator 10, and the second polarization controller 13 together constitute a nonlinear polarization rotation mode locking structure, which is used to realize the phase locking of the multi-longitudinal modes in the resonant cavity. The resonant cavity loss control structure composed of the optical circulator 11 and the reflective adjustable optical attenuator 12 achieves a dynamic balance between nonlinear effects and losses in the resonant cavity, and by setting two output couplers at different positions, the Solitons and noise-like pulses are output simultaneously.

The wavelength of the first pump source 1 and the second pump source 2 is 976 nm, and the maximum output power is both 400 mW. The erbium-doped fiber 5 selects a single-mode erbium-doped fiber with high doping concentration as the gain fiber, the output band is 1550 nm band, and the length is 15 cm. If a gain fiber with other doped particles is used in the resonator, the output laser band can be changed without affecting the mode-locked pulse type, which should be within the protection scope of the present invention.

The splitting ratio of the j end to the i end of the first coupler 6 is 5/95. The splitting ratio between the l end and the m end of the second coupler 8 is 50/50. If a coupler with other split ratio is selected to change the output soliton pulse power without affecting the mode-locked pulse type, it should be within the protection scope of this patent.

The length of the high nonlinear optical fiber 7 is selected as 30m. If other fiber lengths are selected, or similar types of nonlinear fibers such as dispersion compensating fibers are selected as substitutes, the structure of the resonator will be slightly changed without affecting the basic generation mechanism of the mode-locked pulse, which should be within the protection scope of the present invention.

The loss control structure of the resonator formed by the optical circulator 11 and the reflective adjustable optical attenuator 12 achieves a dynamic balance between the nonlinear effect and the loss in the resonator, thereby realizing the simultaneous output of soliton and noise-like pulses.

Turn on the first pump source 1 and the second pump source 2 at the same time and adjust the pump power appropriately. When the total pump power is in the range of 400-550mW, a stable fundamental frequency mode-locked pulse output can be achieved. The pump light is injected into the erbium-doped fiber 5 through the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4, respectively, to generate gains in both clockwise and counterclockwise directions, wherein the gain in the counterclockwise direction is polarization dependent The isolator 10 isolates, and the gain in the clockwise direction forms a stable conventional soliton mode-locked pulse under the action of the nonlinear polarization rotation effect. 95% of the soliton pulses are injected into the high nonlinear fiber 7 from the i end of the first coupler 6. Under the action of the soliton collapse effect, the soliton pulses gradually evolve into noise-like pulses during the transmission process in the high nonlinear fiber 7, accounting for The noise-like pulse with 50% of the total power is output by the m port of the second coupler 8, and the remaining 50% of the noise-like pulse passes through the first polarization controller 9 and the polarization-dependent isolator 10 in sequence, and then is incident on the n of the optical circulator 11. port, and the o port of the circulator 11 is incident to the reflective tunable optical attenuator 12, the attenuated optical pulse is incident to the second polarization controller 13 from the p port of the circulator 11, and is absorbed in the erbium-doped fiber 5 Amplified and thus reduced to regular soliton pulses. Therefore, the entire structure can simultaneously output conventional soliton pulses and noise-like pulses.

Figure 2(a) is the spectrum of the conventional soliton pulse. The central wavelength of the output laser is 1560 nm, and the 3dB spectral bandwidth is 3.7 nm. There are Kelly sidebands with symmetrical positions and small intensity difference on both sides of the spectrum, indicating that mode locking is present at this time. The pulse works in the regular soliton state.

Figure 2(b) is the time domain sequence diagram of the soliton pulse. The soliton pulse keeps running continuously in the time domain range of 300ns, and no loss of lock occurs, and the pulse interval is 29ns.

Figure 2(c) is the autocorrelation curve of the soliton pulse. The hyperbolic secant function can be used to perfectly fit the experimental data, and the time domain width of the soliton pulse is calculated to be 850 fs.

Figure 2(d) is the spectrum diagram of the soliton pulse. In the 300MHz sweep range, the soliton pulse has a very flat frequency spectrum distribution, and the signal-to-noise ratio of each frequency curve can reach 40dB, indicating that the soliton pulse works at a lower noise level. Environment.

Figure 3(a) shows the spectrum of the noise-like pulse. Affected by nonlinear effects, during the evolution of the soliton pulse into a noise-like pulse, the 3dB spectral bandwidth is broadened to 26.9 nm, and the central wavelength shifts to 1620 nm.

Figure 3(b) is the autocorrelation curve of the noise-like pulse. The curve has a wide base, and there is a peak with a width of the order of fs above the base, which is a standard characteristic of noise-like pulses.

Figure 3(c) is an enlarged view of the peak of the autocorrelation curve of the noise-like pulse. The peak width is 289fs. The noise-like pulse is essentially a pulse envelope formed by a large number of ultra-short pulses bound to each other in the time domain. The width of the peak is a single pulse. Average width of ultrashort pulses.

An all-fiber ultra-short pulse light source that can generate soliton and noise-like pulses at the same time. During use, only the first pump source 1 and the second pump source 2 need to be turned on to the specified pump power, and the reflective tunable light attenuation is properly controlled. By adjusting the attenuation value of the device 12, the simultaneous output of the soliton pulse and the noise-like pulse can be realized, and the output power is in the order of mW, and the stable operation of the mode-locked pulse will not be destroyed during the adjustment process. Among them, the soliton pulse has high stability. During the transmission process, it will not be distorted by factors such as dispersion. The noise-like pulse has a high peak power. Under the condition of the output power of the order of mW, the peak power can reach 1kW. above. Therefore, the present invention has important application prospects in the fields of communication, sensing, nonlinear frequency conversion and the like.

Claims (5)

1. The all-fiber ultrashort pulse light source capable of generating soliton and noise-like pulses simultaneously is characterized in that a first pumping source (1) is connected with an a end of a first wavelength division multiplexer (3), a second pumping source (2) is connected with a d end of a second wavelength division multiplexer (4), a c end of the first wavelength division multiplexer (3) and an f end of the second wavelength division multiplexer (4) are respectively connected with two ends of an erbium-doped fiber (5), an e end of the second wavelength division multiplexer (4) is connected with an h end of a first coupler (6), an i end of the first coupler (6) is connected with a high nonlinear fiber (7), the other end of the high nonlinear fiber (7) is connected with a k end of a second coupler (8), and an l end of the second coupler (8) is connected with a first polarization controller (9); the other end of the first polarization controller (9) is connected with the input end of a polarization-dependent isolator (10), the output end of the polarization-dependent isolator (10) is connected with the n end of an optical circulator, the o end of the optical circulator (11) is connected with a reflective variable optical attenuator (12), the p end of the optical circulator (11) is connected with a second polarization controller (13) to form an attenuation-controllable nonlinear polarization rotation mode locking structure, and the other end of the second polarization controller (13) is connected with the b end of the first wavelength division multiplexer (3) to form an all-fiber annular resonant cavity structure;

simultaneously starting a first pump source (1) and a second pump source (2) and properly adjusting the pump power, wherein the total pump power is 400-550mW, pump light is respectively injected into an erbium-doped fiber (5) through a first wavelength division multiplexer (3) and a second wavelength division multiplexer (4) to generate running gains in both clockwise and counterclockwise directions, wherein the gain in the counterclockwise direction is isolated by a polarization-dependent isolator (10), the gain in the clockwise direction forms a stable conventional soliton mode-locked pulse under the action of a nonlinear polarization rotation effect, wherein a soliton pulse accounting for 5% of the total power is output from a j port of a first coupler (6), the remaining 95% of the soliton pulse is injected into a high nonlinear fiber (7) from an i end of the first coupler (6), and the soliton pulse gradually evolves into a noise-like pulse in the transmission process of the high nonlinear fiber (7) under the action of the soliton effect, the noise-like pulses accounting for 50% of the total power are output from the port m of the second coupler (8), the remaining 50% of the noise-like pulses sequentially pass through the first polarization controller (9) and the polarization-dependent isolator (10), then are incident to the port n of the optical circulator (11), and are incident to the reflective variable optical attenuator (12) from the port o of the circulator (11), and the attenuated optical pulses are incident to the second polarization controller (13) from the port p of the circulator (11), and are amplified in the erbium-doped fiber (5), so that the optical pulses are reduced to conventional soliton pulses.

2. The all-fiber ultrashort pulse light source capable of generating soliton and noise-like pulses simultaneously as claimed in claim 1, wherein the erbium-doped fiber (5) is a single-mode erbium-doped fiber with high doping concentration, and the output waveband is 1550 nm.

3. The all-fiber ultrashort pulse light source capable of generating soliton and noise-like pulses simultaneously as claimed in claim 1, wherein the splitting ratio of the first coupler (6) is 5/95, and the splitting ratio of the second coupler (8) is 50/50.

4. The all-fiber ultrashort pulse light source capable of simultaneously generating soliton and noise-like pulses according to claim 1, wherein the length of the high nonlinear optical fiber (7) is 30 m.

5. The all-fiber ultrashort pulse light source capable of generating soliton and noise-like pulses simultaneously as claimed in claim 1, wherein a resonator loss control structure formed by the circulator (11) and the reflective variable optical attenuator (12) achieves dynamic balance between nonlinear effect and loss in the resonator, thereby realizing simultaneous output of soliton and noise-like pulses.

Images