Starting-up mode hopping detection and correction method for external cavity laser

Abstract

The invention relates to the technical field of laser mode hopping detection, in particular to an external cavity laser startup mode hopping detection and correction method, which comprises the following steps: a test stage: in the production test process of a laser, recording power values and temperatures corresponding to different wavelengths of the laser as standard power values W and standard temperatures T, and generating a corresponding table; in the using stage, the laser is adjusted to the standard temperature T corresponding to the expected wavelength, the current power of the laser is detected, the current power is compared with the standard power value W of the expected wavelength in the corresponding table, whether the current power is within the standard power range of the expected wavelength or not is judged, if yes, normal operation is conducted, and if not, mode hopping is judged, and the automatic correction stage is entered; in the automatic correction stage, the power and the temperature of the laser are adjusted to the standard power value W and the standard temperature T range corresponding to the needed wavelength, correction is completed, the production link that the laser must be screened with the help of a special instrument is omitted, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser mode hopping detection, and in particular to a method for detecting and correcting mode hopping when an external cavity laser is turned on. Background Art

[0002] The problem of mode hopping when the external cavity laser is turned on means that the laser does not enter the expected mode after it is turned on and stabilized, resulting in the wavelength and power being different from the expected values, making the system unusable. The problem of mode hopping when the external cavity laser is turned on is a complex technical problem. The fundamental reason is that the laser itself has three modes, which overlap with each other. The same temperature point may correspond to two different modes. There is a certain randomness in which mode the laser enters after it is turned on, which brings great difficulties to the normal application of the laser.

[0003] At present, the main method to prevent external cavity laser mode hopping is to screen the laser before installation through instruments and equipment, but this method cannot simulate various complex use environments. In actual application, there is a certain probability that the laser will mode hop when it is turned on due to ambient temperature, current fluctuations, etc., and it is impossible to determine whether it has mode hopped without using instruments such as wavelength meters and power meters after the mode hopping. Especially in the fields of underwater detection and space free optical communication, the laser use environment is special. After the equipment is installed, personnel cannot enter the working environment for testing, and there is no clear basis for judging whether the laser is adjusted after it is turned on. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for detecting and correcting mode hopping when an external cavity laser is turned on.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows: the method for detecting and correcting the mode hopping when the external cavity laser is turned on includes a testing stage, a use stage and an automatic correction stage;

[0006] Testing stage: During the production test of the laser, the power values ​​and temperatures corresponding to different wavelengths of the laser are recorded as standard power values ​​W and standard temperatures T, and a corresponding table is generated;

[0007] Use stage: adjust the laser to the standard temperature T corresponding to the expected wavelength, detect the current power of the laser, compare the current power with the standard power value W of the expected wavelength in the corresponding table, and determine whether the current power is within the standard power range of the expected wavelength. If so, it operates normally. Otherwise, it is determined as laser mode hopping and enters the automatic correction stage;

[0008] Automatic calibration stage: adjust the power and temperature of the laser to the standard power value W and standard temperature T range corresponding to the required wavelength to complete the calibration.

[0009] In the test phase, when the laser is tested after production, the laser wavelength is obtained by a wavelength meter, and the corresponding thermistor value and PD power feedback value are obtained by an A / D converter;

[0010] Calculate the corresponding temperature based on the thermistor value;

[0011] The PD power feedback value and temperature are matched with the corresponding wavelength one by one, and saved in the corresponding table as the standard power value W and standard temperature T of the wavelength. In this process, the test can be repeated many times to ensure the accuracy of the correspondence between the wavelength and the standard power value W and the standard temperature T.

[0012] The use phase includes the following sub-steps:

[0013] 2-1: Determine the laser wavelength to be used, recorded as the expected wavelength A;

[0014] 2-2: Set the laser temperature to the standard temperature T corresponding to the desired wavelength A;

[0015] 2-3: Collect the laser temperature through the A / D converter, and after the laser temperature reaches the standard temperature fluctuation range and stabilizes, detect the current laser power value;

[0016] 2-4: Compare the current power of the laser with the standard power value W corresponding to the expected wavelength A in the corresponding table. If the current power value is within the fluctuation range of the standard power value W corresponding to the expected wavelength A, it is determined that the laser has entered the expected mode segment and operates normally. Otherwise, it is determined to be mode hopping and enters the automatic correction stage.

[0017] The automatic correction stage includes the following sub-steps:

[0018] 3-1: After the laser enters the calibration stage, the laser temperature is adjusted up or down by k based on the standard temperature T to obtain the adjusted temperature. After the laser temperature stabilizes at the adjusted temperature, the laser temperature is adjusted to the standard temperature T and enters 3-2;

[0019] 3-2: Wait for the laser temperature to stabilize within the standard temperature fluctuation range, and detect the current laser power value. If the current power value is within the standard power value fluctuation range, it is determined that the laser has entered the desired mode segment and the calibration is terminated. Otherwise, it goes to 3-3.

[0020] 3-3: Based on the last adjusted temperature, adjust the laser temperature by k to obtain a new adjusted temperature. After the laser temperature stabilizes at the new adjusted temperature, adjust the laser temperature to the standard temperature T and return to 3-2.

[0021] The standard temperature fluctuation range is T±0.1℃.

[0022] The standard power value fluctuation range is W±0.5mW.

[0023] The k value is 0.5°C.

[0024] The laser temperature can be adjusted within the range of T±5℃.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Reduce the production process that requires the use of special instruments to screen lasers and improve production efficiency;

[0027] 2. Lasers can be used on a large scale without screening, saving costs;

[0028] 3. In an environment where personnel cannot test, the system automatically determines the mode hopping and performs self-correction of the mode hopping to improve system reliability. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] The method for detecting and correcting the mode hopping when the external cavity laser is turned on includes a test phase, a use phase and an automatic correction phase;

[0032] Testing stage: During the production test of the laser, the power values ​​and temperatures corresponding to different wavelengths of the laser are recorded as standard power values ​​W and standard temperatures T, and a corresponding table is generated;

[0033] Use stage: When put into use, adjust the laser to the standard temperature T corresponding to the expected wavelength, detect the current power of the laser, compare the current power with the standard power value W of the expected wavelength in the corresponding table, and determine whether the current power is within the standard power range of the expected wavelength. If so, it operates normally. Otherwise, it is determined to be a laser mode hopping and enters the automatic correction stage;

[0034] Automatic calibration stage: adjust the power and temperature of the laser to the standard power value W and standard temperature T range corresponding to the required wavelength to complete the calibration.

[0035] In the test phase, when the laser is tested after production, the laser wavelength is obtained by a wavelength meter, and the corresponding thermistor value and PD power feedback value are obtained by an A / D converter;

[0036] Calculate the corresponding temperature based on the thermistor value;

[0037] The PD power feedback value and temperature are matched with the corresponding wavelength one by one, and saved in the corresponding table as the standard power value W and standard temperature T of the wavelength. In this process, the test can be repeated many times to ensure the accuracy of the correspondence between the wavelength and the standard power value W and the standard temperature T.

[0038] The calculation process for the temperature value based on thermistor is as follows:

[0039] 1) The sampled voltage value V can be obtained through the A / D converter (ADC) output IN , which is the voltage value collected by ADC.

[0040]

[0041] V TREF is the reference voltage, which is set to 2.56V here;

[0042] V IN is the sampling voltage value, unit is V.

[0043] 2) The thermistor resistance R can be obtained by the following formula T ;

[0044]

[0045] R T is the resistance value of thermistor;

[0046] R D is the resistance value of the matching resistor in the circuit, which is set to 10KΩ here;

[0047] V TREF is the reference voltage, which is set to 2.5V here.

[0048] 3) The actual temperature T1 measured by the thermistor can be calculated by the following formula;

[0049]

[0050] R T : Thermistor resistance;

[0051] R: Thermistor nominal resistance, here set to 10KΩ;

[0052] B: thermal resistance coefficient, here set to 3900;

[0053] T2=273.15+25.

[0054] The use phase includes the following sub-steps:

[0055] 2-1: Determine the laser wavelength to be used, recorded as the expected wavelength A;

[0056] 2-2: Set the laser temperature to the standard temperature T corresponding to the desired wavelength A;

[0057] 2-3: Collect the laser temperature through the A / D converter, and after the laser temperature reaches the standard temperature fluctuation range and stabilizes, detect the current laser power value;

[0058] 2-4: Compare the current power of the laser with the standard power value W corresponding to the expected wavelength A in the corresponding table. If the current power value is within the fluctuation range of the standard power value W corresponding to the expected wavelength A, it is determined that the laser has entered the expected mode segment and operates normally. Otherwise, it is determined to be mode hopping and enters the automatic correction stage.

[0059] The automatic correction stage includes the following sub-steps:

[0060] 3-1: After the laser enters the calibration stage, the laser temperature is adjusted up or down by k based on the standard temperature T to obtain the adjusted temperature. After the laser temperature stabilizes at the adjusted temperature, the laser temperature is adjusted to the standard temperature T and enters 3-2;

[0061] 3-2: Wait for the laser temperature to stabilize within the standard temperature fluctuation range, and detect the current laser power value. If the current power value is within the standard power value fluctuation range, it is determined that the laser has entered the desired mode segment and the calibration is terminated. Otherwise, it goes to 3-3.

[0062] 3-3: Based on the last adjusted temperature, adjust the laser temperature by k to obtain a new adjusted temperature. After the laser temperature stabilizes at the new adjusted temperature, adjust the laser temperature to the standard temperature T and return to 3-2.

[0063] The standard temperature fluctuation range of this application is T±0.1°C, the standard power value fluctuation range is W±0.5mW, and the k value is 0.5°C.

[0064] The laser temperature can be adjusted within the range of T±5℃.

[0065] Example 2

[0066] Based on the embodiment, taking a laser as an example, assuming that the standard temperature T corresponding to the desired wavelength A is 24.7° C. and the standard power value W is 11.7 mW, the mode hopping detection and correction thereof includes the following steps:

[0067] After the device is powered on, first set the laser temperature to 24.7℃, wait for the ADC temperature value to stabilize at 24.7℃±0.1℃, and then turn on the laser after 3S. Wait for 10S, and use PD monitoring to feedback the current power value. If the current power value is 11.7±0.5mW, it is considered that the laser has entered the expected mode.

[0068] If the laser power exceeds 11.7±0.5mW after it is turned on and stabilized, the laser temperature is adjusted to 25.2°C. After the ADC collected temperature value stabilizes at 25.2°C±0.1°C, the laser temperature is adjusted to 24.7°C.

[0069] After the ADC collected temperature value stabilizes at 24.7℃±0.1℃, the current power value is fed back through PD monitoring. If the current power value is 11.7±0.5mW, it is considered that the laser has entered the desired mode segment.

[0070] If the current power exceeds the range of 11.7±0.5mW, adjust the laser temperature to 25.7°C, then adjust the temperature to 24.7°C and repeat step 3.

[0071] In this embodiment, the laser temperature is adjusted up or down in steps of 0.5°C, and then the temperature is restored to the set value until the laser power value is consistent with the reference value. The upper and lower limits of the laser temperature adjustment are set value ±5°C, and this temperature range can completely cover a module segment to ensure that the laser enters the module segment.

[0072] With a step of 0.5°C, efficiency is improved while ensuring that the temperature range in which the middle mold section does not overlap with the mold sections on both sides is entered during adjustment.

[0073] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for detecting and correcting mode hopping when an external cavity laser is turned on, characterized in that: It includes the testing phase, the use phase and the automatic correction phase; Testing stage: During the production test of the laser, the power values ​​and temperatures corresponding to different wavelengths of the laser are recorded as standard power values ​​W and standard temperatures T, and a corresponding table is generated; Use stage: adjust the laser to the standard temperature T corresponding to the expected wavelength, detect the current power of the laser, compare the current power with the standard power value W of the expected wavelength in the corresponding table, and determine whether the current power is within the standard power range of the expected wavelength. If so, it operates normally. Otherwise, it is determined as laser mode hopping and enters the automatic correction stage; Automatic calibration stage: adjust the power and temperature of the laser to the standard power value W and standard temperature T range corresponding to the required wavelength to complete the calibration.

2. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 1, characterized in that: In the test phase, when the laser is tested after production, the laser wavelength is obtained by a wavelength meter, and the corresponding thermistor value and PD power feedback value are obtained by an A / D converter; Calculate the corresponding temperature based on the thermistor value; The PD power feedback value and temperature are matched one by one with the corresponding wavelength, and saved in the corresponding table as the standard power value W and standard temperature T of the wavelength.

3. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 1, characterized in that: The use phase includes the following sub-steps: 2-1: Determine the laser wavelength to be used, recorded as the expected wavelength A; 2-2: Set the laser temperature to the standard temperature T corresponding to the desired wavelength A; 2-3: Collect the laser temperature through the A / D converter, and after the laser temperature reaches the standard temperature fluctuation range and stabilizes, detect the current laser power value; 2-4: Compare the current power of the laser with the standard power value W corresponding to the expected wavelength A in the corresponding table. If the current power value is within the fluctuation range of the standard power value W corresponding to the expected wavelength A, it is determined that the laser has entered the expected mode segment and operates normally. Otherwise, it is determined to be mode hopping and enters the automatic correction stage.

4. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 1, characterized in that: The automatic correction stage includes the following sub-steps: 3-1: After the laser enters the calibration stage, the laser temperature is adjusted up or down by k based on the standard temperature T to obtain the adjusted temperature. After the laser temperature stabilizes at the adjusted temperature, the laser temperature is adjusted to the standard temperature T and enters 3-2; 3-2: Wait for the laser temperature to stabilize within the standard temperature fluctuation range, and detect the current laser power value. If the current power value is within the standard power value fluctuation range, it is determined that the laser has entered the desired mode segment and the calibration is terminated. Otherwise, it goes to 3-3. 3-3: Based on the last adjusted temperature, adjust the laser temperature by k to obtain a new adjusted temperature. After the laser temperature stabilizes at the new adjusted temperature, adjust the laser temperature to the standard temperature T and return to 3-2.

5. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 4, characterized in that: The standard temperature fluctuation range is T±0.1℃.

6. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 4, characterized in that: The standard power value fluctuation range is W±0.5mW.

7. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 4, characterized in that: The k value is 0.5°C.

8. The method for detecting and correcting mode hopping when an external cavity laser is turned on according to claim 4, characterized in that: The laser temperature can be adjusted within the range of T±5℃.

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