CN107968311A - A kind of MOPA pulse optical fibers and its method of work - Google Patents

A kind of MOPA pulse optical fibers and its method of work Download PDF

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CN107968311A
CN107968311A CN201711396888.5A CN201711396888A CN107968311A CN 107968311 A CN107968311 A CN 107968311A CN 201711396888 A CN201711396888 A CN 201711396888A CN 107968311 A CN107968311 A CN 107968311A
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laser
frequency
signal
state
power
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CN107968311B (en
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魏东
卓壮
郭松振
王云征
田桂霞
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Celox Photonics Tech Co ltd
Shandong University
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Celox Photonics Tech Co ltd
Shandong University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10084—Frequency control by seeding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

The present invention relates to a kind of MOPA pulse optical fibers and its method of work.After the governor circuit of optical fiber laser of the present invention receives trigger signal, first signal disappear and tremble processing, after confirmation signal is effective, set corresponding table that pulsewidth is set according to PW signals and pulsewidth, the signal of the corresponding pulsewidth of output, control peripheral chip produce the electric pulse of corresponding pulsewidth；Electric pulse obtains corresponding optical signal by seed source control circuit.MOPA pulse optical fibers of the present invention, by optimizing the pulse shape of seed source, pulse front edge amplifies too fast situation caused by avoiding conventional laser seed source pulse shape, optimizes the output characteristics of laser.

Description

MOPA pulse fiber laser and working method thereof
Technical Field
The invention relates to an MOPA pulse fiber laser and a working method thereof, belonging to the technical field of pulse lasers.
Background
With the economic development and technological progress, the laser plays an increasingly prominent role in industrial processing and is widely applied to the fields of electronic 3C products, machinery, food, packaging and the like. The fiber laser has the advantages of high conversion efficiency, simple structure, high beam quality, long service life and the like. Since the fiber laser also controls the pulse repetition frequency and the pump source power while obtaining ultrashort pulses (nanosecond or picosecond), a stable and reliable control procedure is very important.
The traditional Q-switched fiber laser has the advantages of wide application range, low cost and reliable performance, but when precise materials (such as thin aluminum oxide materials) are processed, the material is deformed due to the fact that the width of the optical pulse is too wide. Therefore, the MOPA laser with narrower pulse width has the advantages of more obvious metal surface processing, narrower pulse width (nanosecond or even subnanosecond) and high peak power. In addition, parameters such as the optical pulse width, the power and the frequency of the MOPA optical fiber laser are adjustable, the defect that the pulse width of a traditional Q-switched laser is fixed is overcome, multiple purposes of one machine are realized, and the MOPA optical fiber laser more conforms to the development trend of industry 4.0.
However, the conventional MOPA fiber laser has the problem that the leading edge of the optical pulse rises too fast, so that the quality of the output laser is reduced.
Chinese patent publication No. 106785875A discloses a pulse width adjustable MOPA fiber laser, which utilizes a program control delay circuit to regulate and control the delay time of two acousto-optic modulators, wherein the first acousto-optic modulator is used as a switch device of a linear pulse Q-switched fiber laser, and the Q-switched fiber laser outputs high-power wide-pulse laser; the second acousto-optic modulator is used as an optical switch to realize the clipping of the output laser pulse, and the delay time of the second acousto-optic modulator is controlled, so that the laser output with adjustable pulse width can be obtained. Therefore, the pulse light signals with the pulse width adjusted by the double acousto-optic modulator are effectively amplified by the optical fiber amplifier to obtain high-power laser output, and the laser pulse width is adjustable.
For the traditional MOPA fiber laser, Q-switched fiber laser and various fiber lasers which obtain pulses in a Q-switched mode, the shape of the light pulse is single, and the shape of the pulse cannot be controlled. Single pulse shape lasers have not been able to meet the ever increasing demands of the metal surface machining industry.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a MOPA pulse fiber laser.
The invention also provides a working method of the pulse fiber laser.
Summary of the invention:
after receiving the trigger signal, the main control circuit firstly carries out jitter elimination processing on the signal, sets the pulse width according to the PW signal and the pulse width setting corresponding table after confirming that the signal is effective, outputs the signal corresponding to the pulse width and controls the peripheral chip to generate an electric pulse corresponding to the pulse width; the electric pulse obtains corresponding optical signals through a seed source control circuit.
The technical scheme of the invention is as follows:
an MOPA pulse fiber laser comprises a main control board and a seed source board which are respectively connected with a power supply; the main control board and the seed source board are respectively connected with the pumping source, and the main control board is connected with the seed source board; the main control board is provided with a main control chip; a seed source is arranged on the seed source plate; the master control chip is provided with a DB-25 interface;
the DB-25 interface function is defined as shown in the following table:
when the multiplexing function is used, the definitions of pins 2, 3, and 22 above are changed, as shown in the following table:
according to the control protocol of the DB-25 interface, a corresponding program is compiled, so that the laser works in a state set by a user, and meanwhile, a state signal of the laser is reported to an upper computer, and the safety and the reliability are ensured.
According to the optimization of the invention, the main control chip is provided with an embedded control system based on CPLD and realized based on VHDL language.
According to the optimization of the invention, the main control chip comprises an input signal processing module, a frequency detection module, a pulse width setting module, a power setting module, an output current control module, a seed source board communication module, an abnormality detection module and a state control module.
Further preferably, the power setting module changes the power of the laser by setting the power; the state control module controls the working state of the switching laser; the working states of the laser comprise a starting state, a shutdown state, a standby state, an alarm non-light-emitting state, a pre-starting state and a light-emitting state;
the laser power supply enters a starting-up state when working;
after the laser is started, entering a standby state, carrying out initialization setting, and after the initialization setting is finished, allowing to enter other working states;
when the laser detects abnormal alarm information, the laser enters an alarm light-out state, sends out an alarm signal and closes laser output;
when the initialization of the laser is finished and abnormal alarm information does not exist, the laser enters a pre-starting state;
when the pre-starting signal of the 18 pins is effective, the laser enters a pre-starting state and is allowed to enter a light emitting state;
when the power starting signal of the pin 19 is effective, the laser enters a light emitting state;
when the power supply of the laser is turned off, the laser machine enters a shutdown state.
A working method of the pulse fiber laser comprises the following steps:
the trigger signal generates an electric pulse after passing through the main control chip, the electric pulse controls a seed source in the seed plate to generate seed light with certain pulse width and frequency, and the seed light generates laser after being amplified by a pumping source; the main control chip sets the laser power by setting the working current of the pumping source.
1) Inputting a trigger signal to a 20 th pin of the DB-25, and processing the trigger signal by an input signal processing module; if the trigger signal is kept stable in the holding time, judging the trigger signal to be an effective signal, and sending the trigger signal to a frequency detection module for frequency detection; if the trigger signal can not be kept stable in the holding time, judging the trigger signal to be an invalid signal, and waiting for the input of the next trigger signal;
due to the interference of the power supply of the equipment and the space coupling, the trigger signal output by the upper computer can generate deformation and distortion after reaching the DB-25 interface through the transmission line, and the stable state of the system is ensured by processing the signal.
2) The frequency detection module detects the frequency of the trigger signal and inputs the frequency into the pulse width setting module; the frequency detection module detects the frequency of the 20-pin trigger signal; if the frequency of the trigger signal is lower than the lowest protection frequency, the seed light is output at the lowest protection frequency; if the input frequency of the trigger signal is higher than the highest protection frequency, the seed light is output at the highest protection frequency; if the input frequency is within the available frequency range, the seed light is output at a frequency set by a user; if no signal is input into the 20 pins, the frequency detection module sets the frequency of the seed light to be a default value; wherein, the available frequency range is the frequency between the highest protection frequency and the lowest protection frequency; the control of the upper limit and the lower limit of the seed light output pulse frequency is realized through a frequency detection module.
3) The pulse width setting module changes the pulse width of the seed light; a high level signal is sent to a pin 22 of the DB-25, and pins 2 and 3 enter a multiplexing state; DB-25 reads the serial port signals of the pin 2 and the pin 3; the 3 pins are used as clock signals, when the level of the 3 pins is turned over, the data of the 2 pins are read, and meanwhile, the reading bits are counted; due to the fact that the number of selectable pulse widths is large and the number of interfaces is limited, the pulse width of the seed light is changed in a serial communication mode instead of a parallel communication mode.
The specific process of reading the 2-pin data comprises the steps of firstly reading a check code of the 2-pin data, comparing and verifying the read check code with a preset check code 1010 0101 0000 0001, if the read check code is consistent with the preset check code, verifying the check code, starting to read serial data after the check code, and if not, continuously reading the check code; until the check code is verified to pass;
when the serial data conforms to a preset certain data, the pulse width setting module sets the pulse width of the seed light to a corresponding value; in the process of changing the pulse width, the enabling signal is always kept effective, and after the pulse width is changed, the enabling signal is changed into a low level; the enable signal remains active at all times preventing interruption of the pulse width setting process.
4) The main control circuit transmits the pulse width signal processed by the pulse width setting module to the seed source board in a 4-bit 2-system data form PW0-PW3 and transmits a synchronous trigger signal; the seed source board controls the seed source to generate a seed source synchronous with the frequency of the trigger signal;
5) The power setting module sets the power of the laser; setting the power value of the laser through pins 1-8 of the DB-25, wherein pin 1 is the least significant bit and pin 8 is the most significant bit;
output power = set power × C + X
Wherein X is a power linearization parameter; c is a power parameter; the system determines a power parameter C according to the pulse width and frequency of the trigger signal.
Set power = (D8 × 128+ D7 × 64+ D6 × 32+ D5 × 16+ D4 × 8+ D3 × 4+ D2 × 2+ D1 × 1)/255 × 100%, that is, the set power corresponding to 11111111 is 100%, and the set power corresponding to 00000000 is 0%;
in order to ensure the consistency of peak power, the invention innovatively adopts a power continuous adjustment scheme. The power level is controlled by the current set frequency and pulse width.
Due to the nonlinear corresponding relation between the output power of the pumping source and the current, the output power increases exponentially with the increase of the current, which brings difficulty to laser processing control and makes prediction of specific output power difficult; the invention innovatively adopts a power compensation mode, a power linearization parameter X is preset in a control program, and the system adjusts the power linearization parameter X according to a power setting value.
According to the invention, preferably, when the frequency f of the trigger signal is greater>PRF 0 When, C =1; when frequency f of the trigger signal<PRF 0 When, C = f/PRF 0 Wherein PRF 0 For reducing power frequency, it is artificially constant, and different pulse widths correspond to different PRFs 0 ；
X＝KI-(e I-a + b), where I is the operating current of the pump source; K. a and b are intrinsic parameters of the pumping source; the higher the power, the smaller X; the smaller the power, the larger X.
According to the invention, the working method of the laser further comprises the step of adjusting the laser by the output current control module;
6.1 The output current control module adjusts the equivalent current of the seed source according to the pulse width and the frequency of the trigger signal;where t is the pulse width of the trigger signal, f is the frequency of the trigger signal, I R Is the effective value of the working current of the seed source, W is the output power of the seed source, c and I 0 Is an inherent parameter of the seed source; in order to ensure the output power of the seed source to be consistent, the equivalent current I output by adopting CPLD control is innovatively adopted R Setting the equivalent current I as the pulse width t is wider and the frequency f of the trigger signal is higher R The smaller; the narrower the pulse width and the lower the frequency, the equivalent current I is set R The larger.
6.2 Output current control moduleOptimizing the frequency fluctuation; according to equation i = e -at + b, transmitting the working current of the seed source to a digital-to-analog converter (DAC), transmitting an analog signal to an operational amplifier by the DAC, and driving the seed source to generate a seed light pulse shape meeting the requirement by the operational amplifier; wherein i is real-time working current, t is time, and a and b are experimental parameters; since an external signal may have an influence on the frequency of the synchronization trigger signal; according to the experimental result of optical amplification, the frequency fluctuation is optimized through the buffering treatment of a control program, and a new current waveform is obtained so as to improve the stability of output current. The DAC and the operational amplifier belong to the seed driving circuit and are well known to those skilled in the art.
6.3 Equivalent current I) of the seed source in step 6.1) R The corresponding relation with the real-time working current i in the step 6.2) is as follows:
according to the invention, preferably, after the laser is powered on, the abnormality detection module detects the temperature of the laser, and when the temperature of the laser exceeds the specified temperature, the abnormality detection module cuts off the power supply of the laser; when the laser works in a light emitting state and the power is larger than a set value, the PD protection is started, and the abnormality detection module monitors the light emitting state of the laser in real time; and if the light emitting power is smaller than the set power in the light emitting state or no laser is output, judging that the laser is abnormal, and cutting off the power supply of the laser by the abnormality detection module after the time for maintaining the abnormal state exceeds the specified time.
When the laser works, if the laser is abnormal or dust enters the laser, the optical fiber is easy to be blown, and the laser, a processed object and an operator are very dangerous. In order to avoid the situation, the invention innovatively adds a PD protective measure, when the laser is in a light-emitting state, the PD starts detection, transmits a detected signal to a main control program in real time, and judges the current working state; when the abnormity is judged to occur, the power supply of the laser needs to be cut off in time, so that accidents are avoided.
Preferably, the abnormality detection module feeds back a working state signal of the laser to the upper computer in a 4-bit signal form in real time, and the upper computer judges the working state of the laser; the specific process is that 4-bit working state signals are transmitted to an upper computer through pins 11, 12, 16 and 21 of a DB-25; when the 4-bit working state signal is 0001, judging that the laser works normally; when the 4-bit working state signal is 0000, judging that the temperature of the laser is too high; when the four-bit working state signal is 0010, judging that the light emitting state of the laser is abnormal; and other 4-bit signals are in a reserved state and are used for later expansion and upgrading of the system.
According to a preferred embodiment of the present invention, in the step 3), the serial data and pulse width setting correspondence relationship is as shown in the following table:
according to the present invention, preferably, the PW signal and pulse width setting correspondence table in step 4):
the invention has the beneficial effects that:
1. according to the MOPA pulse fiber laser, the condition that the pulse front edge is amplified too fast due to the pulse shape of a seed source of a traditional laser is avoided by optimizing the pulse shape of the seed source, and the output characteristic of the laser is optimized;
2. according to the MOPA pulse fiber laser, the jitter elimination processing is carried out on the trigger signal, so that the interference of deformation and distortion signals is avoided; in addition, a user sets the power of the amplification laser, and the system adjusts the output power according to the pulse width and the frequency, so that the adjustment of the output frequency and the pulse width of the laser pulse is realized;
3. the MOPA pulse fiber laser is controllable in pulse shape, can obtain a better processing effect by controlling the pulse shape, and can customize the pulse shape according to the requirements of users; can meet the increasing requirements of the metal surface processing industry.
Drawings
FIG. 1 is a schematic circuit diagram of a DB-25 interface in a main control chip;
FIG. 2 is a flow chart of the working state of the MOPA pulse fiber laser;
FIG. 3 is a flowchart illustrating the operation of the input signal processing module to process the trigger signal according to the present invention;
FIG. 4 is a flowchart illustrating the operation of the pulse width setting module to change the pulse width of the trigger signal according to the present invention;
FIG. 5 is a flowchart illustrating the operation of the frequency detection module detecting the frequency of the trigger signal according to the present invention;
FIG. 6 is a flowchart illustrating the operation of the power setting module setting the power of the trigger signal according to the present invention;
fig. 7 is a flowchart illustrating a process of the main control circuit sending a trigger signal to the seed source control circuit through the seed source board communication module according to the present invention;
FIG. 8 is a flowchart illustrating the operation of the anomaly detection module in real-time monitoring the operating state of the laser according to the present invention;
FIG. 9 is a flowchart illustrating the operation of the output current control module adjusting the operating current of the seed source control circuit according to the present invention;
fig. 10 is a flowchart illustrating a process of controlling the working state of the switching laser by the light emitting state control module according to the present invention.
Fig. 11 is a schematic diagram of the overall circuit structure of the laser according to the present invention.
Detailed Description
The invention is further described below, but not limited thereto, with reference to the following examples and the accompanying drawings.
Example 1
As shown in fig. 1, 2 and 11.
An MOPA pulse fiber laser comprises a main control board and a seed source board which are respectively connected with a power supply; the main control board and the seed source board are respectively connected with the pumping source, and the main control board is connected with the seed source board; the main control board is provided with a main control chip; a seed source is arranged on the seed source plate; the master control chip is provided with a DB-25 interface;
the DB-25 interface function is defined as shown in the following table:
when the multiplexing function is used, the definitions of pins 2, 3, and 22 above change, as shown in the following table:
according to the control protocol of the DB-25 interface, a corresponding program is compiled, so that the laser works in a state set by a user, and meanwhile, a state signal of the laser is reported to an upper computer, and the safety and the reliability are ensured.
The master control circuit adopts an LCMXO2-4000HC-4TG144I chip of a MachXO2 series CPLD of Lattice company, has the advantages of sufficient resources (4320 lookup tables), multiple input and output pins (115I/O), short propagation delay (7.24 ns) and wide working temperature range (-40 ℃ -100 ℃), and is suitable for being used as a master control chip; the seed source control circuit adopts an EPM240T100I5N chip of MAXII series CPLD of Altera corporation, has the advantages of sufficient resources (192 lookup tables), moderate input and output pins (80I/O), short propagation delay (7.5 ns) and wide working temperature range (-40 ℃ -100 ℃), and is suitable for being used as a control chip of an additional circuit.
The main control chip is provided with an embedded control system based on CPLD and realized based on VHDL language.
The main control chip comprises an input signal processing module, a frequency detection module, a pulse width setting module, a power setting module, an output current control module, a seed source board communication module, an abnormality detection module and a state control module.
The power setting module changes the power of the laser by setting the power; the state control module controls the working state of the switching laser; the working state of the laser comprises a starting state, a shutdown state, a standby state, an alarm non-light-emitting state, a pre-starting state and a light-emitting state;
the laser power supply enters a starting state when working;
after the laser is started, entering a standby state, carrying out initialization setting, and after the initialization setting is finished, allowing to enter other working states;
when the laser detects abnormal alarm information, the laser enters an alarm light-out state, sends out an alarm signal and closes laser output;
when the initialization of the laser is finished and abnormal alarm information does not exist, the laser enters a pre-starting state;
when the pre-starting signal of the 18 pins is effective, the laser enters a pre-starting state and is allowed to enter a light emitting state;
when the power starting signal of the pin 19 is effective, the laser enters a light emitting state;
when the power supply of the laser is turned off, the laser enters a shutdown state.
Example 2
The working method of the pulse fiber laser according to embodiment 1 includes the following steps:
the trigger signal generates an electric pulse after passing through the main control chip, the electric pulse controls a seed source in the seed plate to generate seed light with certain pulse width and frequency, and the seed light generates laser after being amplified by a pumping source; the main control chip sets the laser power by setting the working current of the pumping source.
1) Inputting a trigger signal to a 20 th pin of the DB-25, and processing the trigger signal by an input signal processing module; if the trigger signal is kept stable in the holding time, the trigger signal is judged to be an effective signal, and the trigger signal is sent to a frequency detection module for frequency detection; if the trigger signal can not be kept stable in the holding time, judging the trigger signal to be an invalid signal, and waiting for the input of the next trigger signal; as shown in fig. 3.
Due to the interference of the power supply and the space coupling of the equipment, the trigger signal output by the upper computer can be deformed and distorted after reaching the DB-25 interface through the transmission line, and the stable state of the system is ensured by processing the signal.
2) As shown in fig. 5. The frequency detection module detects the frequency of the trigger signal and inputs the frequency into the pulse width setting module; the frequency detection module detects the frequency of the 20-pin trigger signal; if the frequency of the trigger signal is lower than the lowest protection frequency, the seed light is output at the lowest protection frequency; if the input frequency of the trigger signal is higher than the highest protection frequency, the seed light is output at the highest protection frequency; if the input frequency is within the available frequency range, the seed light is output at the frequency set by the user; if no signal is input into the 20 pins, the frequency detection module sets the frequency of the seed light to be a default value; wherein, the available frequency range is the frequency between the highest protection frequency and the lowest protection frequency; the control of the upper limit and the lower limit of the seed light output pulse frequency is realized through a frequency detection module.
3) As shown in fig. 4; the pulse width setting module changes the pulse width of the seed light; a high level signal is sent to a pin 22 of the DB-25, and pins 2 and 3 enter a multiplexing state; DB-25 reads the serial port signals of the pin 2 and the pin 3; the 3 pins are used as clock signals, when the level of the 3 pin signal is turned over, the data of the 2 pins are read, and meanwhile, the reading digit is counted; due to the fact that the number of selectable pulse widths is large and the number of interfaces is limited, the pulse width of the seed light is changed in a serial communication mode instead of a parallel communication mode.
The serial data to pulse width setting correspondence is shown in the following table:
the specific process of reading the 2-pin data comprises the steps of firstly reading a check code of the 2-pin data, comparing and verifying the read check code with a preset check code 1010 0101 0000 0001, if the read check code is consistent with the preset check code, verifying the check code, starting to read serial data after the check code, and if not, continuously reading the check code; until the check code is verified to pass;
when the serial data is consistent with a preset certain data, the pulse width setting module sets the pulse width of the seed light to a corresponding value; in the process of changing the pulse width, the enabling signal is always kept effective, and after the pulse width is changed, the enabling signal is changed into low level; the enable signal remains active at all times preventing interruption of the pulse width setting process.
4) As shown in fig. 7. The main control circuit transmits the pulse width signal processed by the pulse width setting module to the seed source board in a 4-bit 2-system data form PW0-PW3 and transmits a synchronous trigger signal; the seed source board controls the seed source to generate a seed source synchronous with the frequency of the trigger signal;
PW signal and pulse width setting correspondence table:
5) As shown in fig. 6. The power setting module sets the power of the laser; setting the power value of the laser through pins 1-8 of the DB-25, wherein pin 1 is the least significant bit and pin 8 is the most significant bit;
output power = set power × C + X
Wherein X is a power linearization parameter; c is a power parameter; the system determines a power parameter C according to the pulse width and frequency of the trigger signal.
Set power = (D8 × 128+ D7 × 64+ D6 × 32+ D5 × 16+ D4 × 8+ D3 × 4+ D2 × 2+ D1 × 1)/255 × 100%, that is, the set power corresponding to 11111111 is 100%, and the set power corresponding to 00000000 is 0%;
in order to ensure the consistency of peak power, the invention innovatively adopts a power continuous adjustment scheme. The power level is controlled by the current set frequency and pulse width.
Due to the nonlinear corresponding relation between the output power of the pumping source and the current, the output power increases exponentially with the increase of the current, which brings difficulty to laser processing control and makes it difficult to predict the specific output power; the invention innovatively adopts a power compensation mode, a power linearization parameter X is preset in a control program, and the system adjusts the power linearization parameter X according to a power setting value.
When frequency f of the trigger signal>PRF 0 When, C =1; when the frequency f of the trigger signal<PRF 0 When, C = f/PRF 0 Wherein PRF 0 For reducing power frequency, it is artificially constant, and different pulse widths correspond to different PRFs 0 ；
X＝KI-(e I-a + b), wherein I is the working current of the pump source; K. a and b are intrinsic parameters of a pumping source; the higher the power, the smaller X; the smaller the power, the larger X.
The embodiment realizes the aims of pulse width of 4-200ns, repetition frequency of 1KHz-1MHz, and accurate control of power and pulse, works stably, and achieves the expected functions.
Example 3
As shown in fig. 9.
The working method of the pulse fiber laser according to embodiment 2, further comprising a step of adjusting the laser by an output current control module;
6.1 Delivery ofThe current output control module adjusts the equivalent current of the seed source according to the pulse width and the frequency of the trigger signal;where t is the pulse width of the trigger signal, f is the frequency of the trigger signal, I R Is the equivalent current of the seed source, W is the output power of the seed source, c and I 0 Is an inherent parameter of the seed source; in order to ensure the output power of the seed source to be consistent, the equivalent current I output by adopting CPLD control is innovatively adopted R Setting the equivalent current I as the pulse width t is wider and the frequency f of the trigger signal is higher R The smaller; the narrower the pulse width and the lower the frequency, the equivalent current I is set R The larger.
6.2 Output current control module optimizes frequency fluctuations; according to equation i = e -at + b, transmitting the working current of the seed source to a digital-to-analog converter (DAC), transmitting an analog signal to an operational amplifier by the DAC, and driving the seed source to generate a seed light pulse shape meeting the requirement by the operational amplifier; wherein i is real-time working current, t is time, and a and b are experimental parameters; since the external signal may have an influence on the frequency of the synchronization trigger signal; according to the experimental result of optical amplification, the frequency fluctuation is optimized through the buffering treatment of a control program, and a new current waveform is obtained so as to improve the stability of output current. The DAC and the operational amplifier belong to the seed driving circuit and are well known to those skilled in the art.
6.3 Equivalent current I of the seed source in step 6.1) R The corresponding relation with the real-time working current i in the step 6.2) is as follows:
example 4
As shown in fig. 8.
The operating method of the pulse optical fiber laser according to embodiment 2, further comprising detecting a temperature of the laser by the abnormality detecting module after the laser is powered on, and cutting off power supply to the laser by the abnormality detecting module when the temperature of the laser exceeds a predetermined temperature; when the laser works in a light emitting state and the power is larger than a set value, the PD protection is started, and the abnormality detection module monitors the light emitting state of the laser in real time; and if the light emitting power is smaller than the set power in the light emitting state or no laser is output, judging that the laser is abnormal, and cutting off the power supply of the laser by the abnormality detection module after the time for maintaining the abnormal state exceeds the specified time.
When the laser works, if the laser is abnormal or dust enters the laser, the optical fiber is easy to be blown, and the laser, a processed object and an operator are very dangerous. In order to avoid the situation, the invention innovatively adds a PD protection measure, when the laser is in a light emitting state, the PD starts detection, transmits a detected signal to a main control program in real time, and judges the current working state; when the abnormity is judged to occur, the power supply of the laser needs to be cut off in time, so that accidents are avoided.
The abnormality detection module feeds back a working state signal of the laser to the upper computer in a 4-bit signal mode in real time, and the upper computer judges the working state of the laser; the specific process is that 4-bit working state signals are transmitted to an upper computer through pins 11, 12, 16 and 21 of a DB-25; when the 4-bit working state signal is 0001, judging that the laser works normally; when the 4-bit working state signal is 0000, judging that the temperature of the laser is too high; when the four-bit working state signal is 0010, judging that the light emitting state of the laser is abnormal; and other 4-bit signals are in a reserved state and are used for later expansion and upgrading of the system.

Claims (10)

1. An MOPA pulse fiber laser is characterized by comprising a main control board and a seed source board which are respectively connected with a power supply; the main control board and the seed source board are respectively connected with the pumping source, and the main control board is connected with the seed source board; the main control board is provided with a main control chip; a seed source is arranged on the seed source plate; the master control chip is provided with a DB-25 interface;
the DB-25 interface function is defined as shown in the following table:
when the multiplexing function is used, the definitions of pins 2, 3, and 22 above change, as shown in the following table:
2. the MOPA pulse fiber laser device according to claim 1, wherein the main control chip comprises an input signal processing module, a frequency detection module, a pulse width setting module, a power setting module, an output current control module, a seed source board communication module, an abnormality detection module and a state control module.
3. The MOPA pulsed fiber laser according to claim 2, wherein the power setting module changes the power of the laser by setting the power; the state control module controls the working state of the switching laser; the working state of the laser comprises a starting state, a shutdown state, a standby state, an alarm non-light-emitting state, a pre-starting state and a light-emitting state;
the laser power supply enters a starting-up state when working;
after the laser is started, entering a standby state, carrying out initialization setting, and after the initialization setting is finished, allowing to enter other working states;
when the laser detects abnormal alarm information, the laser enters an alarm light-out state, sends out an alarm signal and closes the laser output;
when the initialization of the laser is finished and abnormal alarm information does not exist, the laser enters a pre-starting state;
when the pre-starting signal of the 18 pins is effective, the laser enters a pre-starting state and is allowed to enter a light emitting state;
when the power starting signal of the pin 19 is effective, the laser enters a light emitting state;
when the power supply of the laser is turned off, the laser enters a shutdown state.
4. A method of operating a pulsed fiber laser as claimed in any of claims 1 to 3, comprising the steps of:
1) Inputting a trigger signal to a 20 th pin of the DB-25, and processing the trigger signal by an input signal processing module; if the trigger signal is kept stable in the holding time, judging the trigger signal to be an effective signal, and sending the trigger signal to a frequency detection module for frequency detection; if the trigger signal can not be kept stable in the holding time, judging the trigger signal to be an invalid signal, and waiting for the input of the next trigger signal;
2) The frequency detection module detects the frequency of the trigger signal and inputs the frequency into the pulse width setting module; the frequency detection module detects the frequency of the 20-pin trigger signal; if the frequency of the trigger signal is lower than the lowest protection frequency, the seed light is output at the lowest protection frequency; if the input frequency of the trigger signal is higher than the highest protection frequency, the seed light is output at the highest protection frequency; if the input frequency is within the available frequency range, the seed light is output at a frequency set by a user; if no signal is input into the 20 pins, the frequency detection module sets the frequency of the seed light to be a default value; wherein, the available frequency range is the frequency between the highest protection frequency and the lowest protection frequency;
3) The pulse width setting module changes the pulse width of the seed light; a high level signal is sent to a 22 pin of the DB-25, and 2 and 3 pins enter a multiplexing state; DB-25 reads the serial port signals of the pin 2 and the pin 3; the 3 pins are used as clock signals, when the level of the 3 pin signal is turned over, the data of the 2 pins are read, and meanwhile, the reading digit is counted;
the specific process of reading the 2-pin data comprises the steps of firstly reading a check code of the 2-pin data, comparing and verifying the read check code with a preset check code 1010 0101 0000 0001, if the read check code is consistent with the preset check code, verifying the check code, starting to read serial data after the check code, and if not, continuously reading the check code; until the check code is verified to pass;
when the serial data conforms to a preset certain data, the pulse width setting module sets the pulse width of the seed light to a corresponding value; in the process of changing the pulse width, the enabling signal is always kept effective, and after the pulse width is changed, the enabling signal is changed into low level;
4) The main control circuit transmits the pulse width signal processed by the pulse width setting module to the seed source board in a 4-bit 2-system data form PW0-PW3 and transmits a synchronous trigger signal; the seed source board controls the seed source to generate a seed source synchronous with the frequency of the trigger signal;
5) The power setting module sets the power of the laser; setting the power value of the laser through pins 1-8 of the DB-25, wherein the pin 1 is the least significant bit, and the pin 8 is the most significant bit;
output power = set power × C + X
Wherein X is a power linearization parameter; c is a power parameter;
set power = (D8 × 128+ D7 × 64+ D6 × 32+ D5 × 16+ D4 × 8+ D3 × 4+ D2 × 2+ D1 × 1)/255 × 100%, that is, the set power corresponding to 11111111 is 100%, and the set power corresponding to 00000000 is 0%.
5. The method of claim 4, wherein the frequency f of the trigger signal is the same as the frequency f of the trigger signal>PRF 0 When, C =1; when the frequency f of the trigger signal<PRF 0 When, C = f/PRF 0 Wherein PRF 0 For reducing power frequency, it is artificially constant, and different pulse widths correspond to different PRFs 0 ；
X＝KI-(e I-a + b), where I is the operating current of the pump source.
6. The working method of the pulse fiber laser according to claim 4, further comprising the step of adjusting the laser by an output current control module;
6.1 The output current control module adjusts the equivalent current of the seed source according to the pulse width and the frequency of the trigger signal;where t is the pulse width of the trigger signal, f is the frequency of the trigger signal, I R Is the effective value of the working current of the seed source, W is the output power of the seed source, c and I 0 Is an inherent parameter of the seed source;
6.2 Output current control module optimizes frequency fluctuations; according to equation i = e -at + b, transmitting the working current of the seed source to a digital-to-analog converter (DAC), transmitting the analog signal to an operational amplifier by the DAC, and driving the seed source to generate a seed optical pulse shape meeting the requirement by the operational amplifier; wherein i is real-time working current, t is time, and a and b are experimental parameters;
6.3 Equivalent current I) of the seed source in step 6.1) R The corresponding relation with the real-time working current i in the step 6.2) is as follows:
7. the method according to claim 4, characterized in that after the laser is powered on, the abnormality detection module detects the temperature of the laser, and when the temperature of the laser exceeds a specified temperature, the abnormality detection module cuts off the power supply of the laser; when the laser works in the light emitting state and the power is larger than a set value, the PD protection is started, and the abnormality detection module monitors the light emitting state of the laser in real time; and if the light emitting power is smaller than the set power in the light emitting state or no laser is output, judging that the laser is abnormal, and cutting off the power supply of the laser by the abnormality detection module after the time for maintaining the abnormal state exceeds the set time.
8. The working method of the pulse fiber laser device according to claim 7, wherein the abnormality detection module feeds back a working state signal of the laser device to an upper computer in a form of a 4-bit signal in real time, and the upper computer judges the working state of the laser device; the specific process is that 4-bit working state signals are transmitted to an upper computer through pins 11, 12, 16 and 21 of DB-25; when the 4-bit working state signal is 0001, judging that the laser works normally; when the 4-bit working state signal is 0000, judging that the temperature of the laser is too high; when the four-bit working state signal is 0010, judging that the light emitting state of the laser is abnormal; and other 4-bit signals are in a reserved state and are used for later expansion and upgrading of the system.
9. The method for operating a pulsed fiber laser according to claim 4, wherein in step 3), the serial data and pulse width setting correspondence is as shown in the following table:
10. the working method of the pulse fiber laser according to claim 4, wherein the PW signal and pulse width setting correspondence table in step 4) is as follows:
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