CN107039877A - A kind of high stability optical pulse generator - Google Patents

Abstract

A high-stability optical pulse generator of the present invention belongs to the technical field of optical communication devices, and its main structure includes a pump light source (1), a wavelength division multiplexer (2), a first optical coupler (3), An active mode-locked fiber laser resonator composed of a polarization controller (4) and other devices, a passive mode-locked fiber laser system composed of a dispersion compensating fiber (23), a graphene saturable absorber (24) and other devices, and two automatic Pulse optimization system composed of feedback control loop. The invention adopts the active-passive hybrid mode-locking technology, uses the optical detector to receive part of the output laser, and uses the single-chip microcomputer and the amplifier circuit to process the received signal, controls the piezoelectric ceramics to realize the optimization of the output pulse of the whole system, and finally makes the whole system generate stable The ultra-short high-speed light pulse is easy to operate and can achieve precise control.

Description

A High Stability Optical Pulse Generator

technical field

The invention belongs to the technical field of optical communication devices, and in particular relates to an optical pulse generator which utilizes an active-passive combined mode-locking technology to realize high-stability pulse output.

Background technique

With the rapid development of the national economy and the arrival of the information age, optical fiber communication technology has penetrated into various communication and information networks. Fiber lasers are ideal light sources for fiber optic communications and have many advantages over traditional solid-state lasers, and have been extensively studied in recent years. Mode-locked fiber lasers in fiber lasers are ideal for pulsed light sources in optical communication systems.

Common structures of mode-locked fiber lasers include active mode-locked and passive mode-locked fiber lasers. Among them, the active mode-locked fiber laser has narrow output pulse width, small frequency chirp and tunable frequency, so it has great application prospects in ultra-high-speed optical fiber communication.

The prior art closest to the present invention is an active mode-locked fiber laser system as shown in accompanying drawing 2, a sinusoidal voltage signal acts on a lithium niobate (LiNbO ₃ ) modulator, and the modulator will produce periodic phase changes or Loss, the periodic variation acts on the pulses circulating in the resonator, and the interaction between them makes a mode-locked sequence. _The LiNbO3 modulator is polarization sensitive, and a polarization controller is usually placed in front of the modulator to adjust the polarization state of the light field of the modulator. The center wavelength is adjusted by a tunable filter.

However, the output laser spectrum of active mode-locked fiber lasers is relatively narrow, and it is difficult to obtain ultra-narrow pulses. Moreover, the cavity length of active mode-locked fiber lasers is generally long, which is easily affected by the outside world, resulting in poor stability.

Passively mode-locked fiber lasers are simple in structure, low in cost and high in reliability. They are true all-fiber devices. Using the nonlinear effect of optical fibers, they can generate the shortest optical pulses. However, their output pulse repetition frequency has poor stability and cannot be adjusted externally.

To sum up, the existing active or passive mode-locked fiber laser systems have their own inherent shortcomings, especially because the existing mode-locked fiber laser systems do not adopt effective automatic control, which makes the stability of the output optical pulse poor .

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of mode-locked fiber lasers in the background technology, and provide a high-stability optical pulse generator using active-passive hybrid mode-locking technology for the purpose of generating stable ultra-high-speed pulses.

Technical scheme of the present invention is as follows:

A high-stability optical pulse generator, the structure of which is that the pump light source 1 is connected to the 980nm end of the wavelength division multiplexer 2, and the 1550nm end of the wavelength division multiplexer 2 is connected to the input end of the first optical coupler 3 The 10% output end of the first optical coupler 3 is connected with one end of the polarization controller 4, and the other end of the polarization controller 4 is connected with the input end of the lithium niobate modulator 5 driven by the microwave source 6; lithium niobate modulation The output end of the device 5 is connected to one end of the optical fiber wound on the first PZT piezoelectric ceramic 7; the other end of the optical fiber wound on the first PZT piezoelectric ceramic 7 is connected to an input of the second optical coupler 8 The other input end of the second optical coupler 8 is connected with the input end of the first optical isolator 9; the output end of the first optical isolator 9 is connected with one end of the first erbium-doped optical fiber 10, and the first erbium-doped fiber The other end of the optical fiber 10 is connected to the common end of the wavelength division multiplexer 2;

It is characterized in that the structure also has the input end of the third optical coupler 11 connected to the 90% output end of the first optical coupler 3, and the 40% output end of the third optical coupler 11 is connected to the input end of the fourth optical coupler 12 The 60% output end of the third optical coupler 11 is used as the output port of the high stability optical pulse generator; a 50% output end of the fourth optical coupler 12 is connected with the input of the first photodetector 13 The other 50% output is connected with the input of the second photodetector 18; the output of the first photodetector 13 is connected with the input of the analog/digital converter 14, and the output of the analog/digital converter 14 End links to each other with single-chip microcomputer 15, and single-chip microcomputer 15 links to each other with the input terminal of digital/analog converter 16, and the output terminal of digital/analog converter 16 links to each other with the input terminal of the first piezoelectric ceramic driver 17, and the input terminal of the first piezoelectric ceramic driver 17 The output end is connected with the first PZT piezoelectric ceramic 7; the output end of the second photodetector 18 is connected with the input end of the amplifying circuit 19, and the output end of the amplifying circuit 19 is connected with the input end of the second piezoelectric ceramic driver 20. The output end of the two piezoelectric ceramic drivers 20 is connected with the second PZT piezoelectric ceramic 21, and one end of the optical fiber wound on the second PZT piezoelectric ceramic 21 is connected with a 50% output end of the second optical coupler 8, and the second Another 50% output end of optical coupler 8 is connected with the input end of second optical isolator 22, and the output end of second optical isolator 22 is connected with one end of dispersion compensation optical fiber 23, and the other end of dispersion compensation optical fiber 23 is connected with graphite One end of graphene saturable absorber 24 is connected; the other end of graphene saturable absorber 24 is connected with one end of single-mode fiber 25, and the other end of single-mode fiber 25 is connected with one end of second erbium-doped fiber 26, and the second doped fiber The other end of the erbium fiber 26 is connected to the other end of the fiber wound on the second PZT piezoelectric ceramic 21 .

Beneficial effect:

1. The present invention uses active-passive hybrid locking technology to generate high-speed ultra-short optical pulse output, which can overcome the shortcomings of the passive mode-locked fiber laser system that cannot control the output pulse repetition frequency and the poor stability of the repetition frequency, and make full use of the passive mode-locked fiber laser system. The advantages of second-level optical pulses; at the same time, it can overcome the shortcomings of poor output stability of the active mode-locked fiber laser system, and take advantage of the adjustable output repetition frequency of the active mode-locked fiber laser system, so that the entire system can generate stable ultra-short high-speed optical pulses.

2. The present invention uses the feedback signal to control the piezoelectric ceramic to stabilize the length of the resonant cavity in the active mode-locked fiber laser, overcomes the drift of the cavity length, and stabilizes the system output; at the same time, the feedback signal is used to control the piezoelectric ceramic in the passive mode-locked fiber laser, so that The optical pulses in the passively mode-locked fiber laser system are more optimized, which ultimately enables the entire system to generate stable ultrashort and high-speed optical pulses.

3. The present invention uses the novel two-dimensional material graphene as a saturable absorber to generate ultra-short high-speed light pulses. The graphene-based saturable absorber has ultra-short recovery time, high anti-damage threshold, and wide bandwidth response wavelength range. With the advantages of low saturation absorption loss, it can generate femtosecond ultrashort pulses.

4. In the present invention, an erbium-doped fiber is added to the resonant cavity of the passive mode-locked fiber laser, which can generate a gain amplification effect on the optical signal transmitted in it, and further increase the optical pulse energy output by the system.

5. The present invention has a simple structure, uses two photodetectors to receive part of the output laser light respectively, and uses a single-chip microcomputer and an amplifier circuit to process the received signal, controls the piezoelectric ceramics to realize the optimization of the output pulse of the entire system, and is easy to operate and can achieve accurate control.

Description of drawings:

Fig. 1 is a functional block diagram of a high-stability optical pulse generator of the present invention.

Figure 2 is a block diagram of a traditional active mode-locked fiber laser system.

detailed description

The specific structure of each part of the optical path of the present invention will be described below in conjunction with the accompanying drawings. In the embodiments, the preferred parameters of the present invention are marked in brackets behind the components, but the protection scope of the present invention is not limited by these parameters.

Embodiment 1: Concrete structure of the present invention

A kind of optical pulse generator structure based on piezoelectric ceramic feedback control of the present invention is as shown in accompanying drawing 1, and its structure has, pump light source 1 (980nm laser device, maximum output power is 1W) and wavelength division multiplexer 2 ( 980/1550nm wavelength division multiplexer) connected to the 980nm terminal, the 1550nm terminal of the wavelength division multiplexer 2 is connected to the input of the first optical coupler 3 (1×2 standard single-mode optical coupler, the splitting ratio is 10:90) The 10% output end of the first optical coupler 3 is connected with one end of the polarization controller 4 (pigtail type mechanical polarization controller), and the optical pulse of its output continues to run in the cavity of the active mode-locked fiber laser, The 90% output end of the first optical coupler 3 is connected with the input end of the third optical coupler 11 (1 * 2 standard single-mode optical coupler, splitting ratio is 40:60); The input end of the lithium niobate modulator 5 (the MX-LN-20 optical intensity modulator of Shanghai Hanyu Optical Fiber Communication Technology Co., Ltd.) driven by the microwave source 6 is connected; the output end of the lithium niobate modulator 5 is connected to the first One end of the optical fiber on the PZT piezoelectric ceramic 7 is connected; the other end of the optical fiber wound on the first PZT piezoelectric ceramic 7 is connected to the second optical coupler 8 (2 * 2 standard single-mode optical coupler, splitting ratio The other input end of the second optical coupler 8 is connected with the input end of the first optical isolator 9 (1550nm polarization-independent optical isolator), and the first optical isolator 9 makes the system The optical pulse in the unidirectional operation, direction is the clockwise direction of accompanying drawing 1; ) is connected to one end, and the other end of the first erbium-doped optical fiber 10 is connected to the common end of the wavelength division multiplexer 2. The above structure constitutes a traditional actively mode-locked fiber laser resonator.

On the basis of the traditional active mode-locked fiber laser resonator, the present invention also has a passive mode-locked fiber laser system based on a graphene saturable absorber and a pulse optimization system composed of two automatic feedback control loops. The structure is as follows: The 40% output end of three optical couplers 11 is connected with the input end of the fourth optical coupler 12 (1×2 standard single-mode optical coupler, splitting ratio is 50:50), and the 60% output of the third optical coupler 11 terminal as the output port of the high-stability optical pulse generator, the optical pulses produced by the system are output from this port; a 50% output terminal of the fourth optical coupler 12 is connected with the first photodetector 13 (Beijing Minguang Technology Co., Ltd. The input end of the company's LSIPD-LD50 type light detector) is connected, and another 50% output is connected with the input end of the second light detector 18 (the LSIPD-LD50 type light detector of Beijing Minguang Technology Co., Ltd.); the first The output end of photodetector 13 links to each other with the input end of analog/digital converter 14 (MAX197), and the output end of analog/digital converter 14 links to each other with single-chip microcomputer 15 (STC89C51 single-chip microcomputer), and single-chip microcomputer 15 receives digital quantity and carries out calculation processing; 15 is connected to the input end of the digital/analog converter 16 (AD7541), and the output end of the digital/analog converter 16 is connected to the first piezoelectric ceramic driver 17 (a device made by our research group, see patent ZL200710055865.8 for the specific structure) The input end is connected, and the output end of the first piezoelectric ceramic driver 17 is connected with the first PZT piezoelectric ceramic 7 (cylindrical piezoelectric ceramic, outer diameter 50mm, inner diameter 40mm, high 50mm), to control the length of the resonant cavity; The output end of the photodetector 18 is connected to the input end of the amplifying circuit 19, and the output end of the amplifying circuit 19 is connected to the input end of the second piezoelectric ceramic driver 20 (a device made by our research group, see patent ZL200710055865.8 for the specific structure) , the output end of the second piezoelectric ceramic driver 20 is connected with the second PZT piezoelectric ceramic 21, and one end of the optical fiber wound on the second PZT piezoelectric ceramic 21 is connected with a 50% output end of the second optical coupler 8, Another 50% output end of the second optical coupler 8 is connected with the input end of the second optical isolator 22 (1550nm polarization-independent optical isolator), and the second optical isolator 22 allows the light pulse passing direction to be the reverse of accompanying drawing 1 Clockwise direction; the output end of the second optical isolator 22 links to each other with an end of dispersion compensation fiber 23 (DCF38 type dispersion compensation fiber of U.S. THORLABS company), and the other end of dispersion compensation fiber 23 is connected with graphene saturable absorber 24 (multiple A layer of graphene is made on the end face of the optical fiber connector on one side, and the connector is connected to the optical fiber connector on the other side with an optical fiber connector. The optical fiber connector can use the standard FC/PC optical fiber produced by Shanghai Hanyu Optical Fiber Communication Technology Co., Ltd. connector) connected to one end; the other end of the graphene saturable absorber 24 is connected to one end of the single-mode fiber 25 (standard single-mode fiber), and the other end of the single-mode fiber 25 is connected to the second erbium-doped optical fiber One end of fiber 26 (SM-ESF-7/125 erbium-doped fiber produced by U.S. Nufern Company) is connected, and the other end of the second erbium-doped fiber 26 is connected with the other end of the fiber wound on the second PZT piezoelectric ceramic 21.

Embodiment 2 Working process of the present invention and the effect of each main component

In the structure shown in Figure 1, the pump light source 1 is used as the laser pump source of the whole system, and the pump light source 1 enters the system through the wavelength division multiplexer 2; the first optical coupler 3 with a splitting ratio of 10:90 The laser light running in the cavity is divided into two parts, one part (90%) is output to the third optical coupler 11, and the other part (10%) continues to run in the resonant cavity of the active mode-locked fiber laser; the splitting ratio is 40:60 The third optical coupler 11 divides the laser light output by the first optical coupler 3 into two parts, one part (60%) is used as the laser output of the whole system, and the other part (40%) is output to the fourth optical coupler 12 as the laser output of the system. Feedback signal; polarization controller 4 is used to control the polarization state in the system; the first optical isolator 9 is used to ensure the unidirectional operation of light in the resonator cavity of the active mode-locked fiber laser; the first erbium-doped fiber 10 generates gain in the system function, to ensure that the energy of the running laser in the resonator does not attenuate; the second optical coupler 8 with a splitting ratio of 50:50 is connected with two parts of active mode-locking and passive mode-locking structures, so that the passive mode-locking fiber laser system based on graphene It is organically combined with the active mode-locked fiber laser system to realize active-passive hybrid mode-locking; the graphene saturable absorber 24 is made of graphene material into a saturable absorber for the generation of mode-locked ultrashort pulses. The second erbium-doped optical fiber 26 performs gain amplification on the optical signal transmitted therein, so that the energy of the optical pulse output by the system is further increased.

The fourth optical coupler 12 divides the received light into two paths, one path is output to the first photodetector 13, the first photodetector 13 converts the optical signal into a current, and the analog/digital converter 14 receives the first photodetector 13 output electrical signal, and convert the analog signal into a digital signal to make it suitable for subsequent control; the single-chip microcomputer 15 receives the digital signal output by the analog/digital converter 14 for calculation and processing, and generates a control signal; the digital/analog converter 16 will The control signal output by the single-chip microcomputer 15 is converted into an analog signal and output to the first piezoelectric ceramic driver 17, and the first piezoelectric ceramic driver 17 amplifies the received control signal to drive the first PZT piezoelectric ceramic 7, and then controls the winding of the first piezoelectric ceramic driver 17. The length of the optical fiber on the PZT piezoelectric ceramic 7 performs cavity length compensation on the resonant cavity of the active mode-locked fiber laser to overcome cavity length drift and ensure the reliability of system mode-locking.

The other output of the fourth optical coupler 12 is output to the second photodetector 18, which is converted into an electrical signal by the second photodetector 18 and then amplified by the amplifier circuit 19 and then sent to the second piezoelectric ceramic driver 20. The second piezoelectric ceramic driver 20 amplifies the received control signal to drive the second PZT piezoelectric ceramic 21, and then controls the length of the optical fiber wound on the second PZT piezoelectric ceramic 21, so as to ensure the graphene-based saturable absorption The soliton type generated by the passive mode-locked fiber laser system of the body automatically matches the soliton type generated by the active mode-locked fiber laser resonator, thereby optimizing the ultrashort high-speed optical pulse output by the entire system.

Claims (1)

1. a kind of high stability optical pulse generator, its structure has, pump light source (1) and the 980nm ends phase of wavelength division multiplexer (2) Even, the 1550nm ends of wavelength division multiplexer (2) are connected with the input of the first photo-coupler (3)；The 10% of first photo-coupler (3) Output end is connected with the one end of Polarization Controller (4), the other end of Polarization Controller (4) and the niobic acid driven by microwave source (6) The input of lithium modulator (5) is connected；The output end of lithium niobate modulator (5) is with being wrapped on the first PZT piezoelectric ceramics (7) One end of optical fiber is connected；The other end and the second photo-coupler of the described optical fiber being wrapped on the first PZT piezoelectric ceramics (7) (8) a input is connected；The input phase of another input of the second photo-coupler (8) and the first optoisolator (9) Even；The output end of first optoisolator (9) is connected with one end of the first Er-doped fiber (10), the first Er-doped fiber (10) it is another End is connected with the common port of wavelength division multiplexer (2)；

Characterized in that, structure also has the input of the 3rd photo-coupler (11) and 90% output end of the first photo-coupler (3) It is connected, 40% output end of the 3rd photo-coupler (11) is connected with the input of the 4th photo-coupler (12), the 3rd photo-coupler (11) 60% output end as described high stability optical pulse generator output port；The one of 4th photo-coupler (12) Individual 50% output end is connected with the input of the first photo-detector (13), another 50% output end and the second photo-detector (18) Input be connected；The output end of first photo-detector (13) is connected with the input of A/D converter (14), analog/digital conversion The output end of device (14) is connected with single-chip microcomputer (15), and single-chip microcomputer (15) is connected with the input of D/A converter (16), D/A The output end of converter (16) is connected with the input of the first piezoelectric ceramic actuator (17), the first piezoelectric ceramic actuator (17) Output end be connected with the first PZT piezoelectric ceramics (7)；The output end of second photo-detector (18) and the input of amplifying circuit (19) End is connected, and the output end of amplifying circuit (19) is connected with the input of the second piezoelectric ceramic actuator (20), the second piezoelectric ceramics The output end of driver (20) is connected with the 2nd PZT piezoelectric ceramics (21), is wrapped in the optical fiber on the 2nd PZT piezoelectric ceramics (21) One end be connected with 50% output end of the second photo-coupler (8), another 50% output end of the second photo-coupler (8) It is connected with the input of the second optoisolator (22), the output end of the second optoisolator (22) and the one of dispersion compensating fiber (23) End is connected, and the other end of dispersion compensating fiber (23) is connected with one end of graphene saturable absorber (24)；Graphene can satisfy It is connected with the other end of absorber (24) with one end of single-mode fiber (25), the other end of single-mode fiber (25) and the second er-doped light The one end of fine (26) is connected, and the other end of the second Er-doped fiber (26) is wrapped on the 2nd PZT piezoelectric ceramics (21) with described Optical fiber the other end be connected.