SLD light source power control method

Abstract

The invention discloses an SLD light source power control method, which is characterized in that the output of an SLD light source is connected with the input of one end of a coupler, the output of the coupler is connected with the input of a waveguide, two output ends of the waveguide are connected with two input ends of an optical fiber ring, and the other output end of the coupler is connected with the input of a detector; the output end of the detector is connected with the low-pass filter, the low-pass filter is connected with the A / D converter, the A / D converter is connected with the main control chip, the main control chip is connected with the D / A converter, the D / A converter is connected with the constant-current driver, and the constant-current driver is connected with the SLD light source; according to the invention, the output power of the SLD light source is directly controlled, the light source can be rapidly started, and the phenomenon of current overshoot does not exist.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology, and in particular relates to a SLD light source power control method. Background Art

[0002] The SLD (superluminescent diode) light source is a broadband light source with extremely low coherence based on the spontaneous radiation effect, and is one of the key components of the fiber optic gyroscope. The driving current drives the SLD light source to provide the fiber optic gyroscope with a stable power light wave. The fluctuation of the light wave power will directly lead to the fluctuation of the fiber optic gyroscope output. Therefore, the power stability of the light wave output by the SLD light source directly affects the performance of the fiber optic gyroscope. The factors affecting the stability of the SLD light source are mainly the driving current and the internal temperature of the light source. Changes in both will cause fluctuations in the optical power of the SLD light source. The greater the driving current, the greater the output optical power of the light source, and the higher the temperature, the lower the output optical power.

[0003] At present, temperature control is widely used in China to keep the internal temperature of the light source constant, and constant current drive is used to keep the driving current constant. This solution is relatively mature. However, in actual use, the high power consumption and high heat generation of the light source refrigerator of the temperature control system itself will lead to an increase in the power consumption of the fiber optic gyroscope. When working in high and low temperature environments, the temperature control system has a large delay, and the fiber optic gyroscope cannot work normally immediately when it starts, and the startup time is long. In addition, in a low temperature environment, the light output power of the SLD light source is high, and there will be a driving current overshoot phenomenon at startup, which is easy to damage the light source. Summary of the invention

[0004] In view of this, the present invention provides a SLD light source power control method, which directly controls the output power of the SLD light source, can enable the light source to start quickly, and does not have a current overshoot phenomenon.

[0005] The technical solution for implementing the present invention is as follows:

[0006] The invention discloses a power control method for an SLD light source. The output of the SLD light source is connected to the input of one end of a coupler, the output of the coupler is connected to the input of a waveguide, two output ends of the waveguide are connected to two input ends of an optical fiber ring, and the other output end of the coupler is connected to the input of a detector; the output end of the detector is connected to a low-pass filter, the low-pass filter is connected to an A / D converter, the A / D converter is connected to a main control chip, the main control chip is connected to a D / A converter, the D / A converter is connected to a constant current driver, and the constant current driver is connected to the SLD light source.

[0007] Furthermore, the light waves generated by the SLD light source are divided into two light waves through the coupler and waveguide and propagate in opposite directions in the optical fiber ring, resulting in interference phenomenon; the interference light waves are transmitted back to the detector through the waveguide and coupler, and the detector converts the power of the interference light waves into electrical signals.

[0008] Furthermore, a modulated square wave is added to the waveguide control end, and the peak-to-peak value of the modulated square wave voltage is equal to the waveguide half-wave voltage, so that the interference phase difference and the interference light wave power converted by the detector are sinusoidally related; the modulated square wave has the same frequency and phase as the modulation clock.

[0009] Furthermore, the detector converts the interference light wave power P modulated by the square wave into an electrical signal, filters out the high-frequency noise of the electrical signal through low-pass filtering, and collects the electrical signal through A / D conversion under the control of the modulation clock to obtain the digital value D of the power of the interference light wave. P The main control chip modulates the digital value D of the positive and negative half cycles of the clock A The DC component of the interference light wave power is obtained by adding them together; then the control amount of the SLD light source is calculated, and the control amount is converted into an analog voltage V by D / A. P , the constant current driver converts the analog voltage into the driving current of the SLD light source.

[0010] Furthermore, the main control chip generates a modulation clock and collects digital quantities D in the positive and negative half cycles of the modulation clock. P The two digital quantities are added to obtain the DC component of the interference light wave power, which is subtracted from the target value Pt of the light source power to obtain the power error e P , and through the power error e P Calculate the driving current I of the SLD light source P , through D / A conversion and constant current drive feedback to the SLD light source, completing the closed-loop control of the SLD light source output power; the solution process includes PID and advance correction.

[0011] Furthermore, the low-pass filtering adopts active / passive analog filtering or digital filtering.

[0012] Beneficial effects:

[0013] 1. The present invention controls the power of the SLD light source by controlling the driving current of the light source, thereby avoiding the large delay phenomenon of the temperature control scheme and improving the start-up time of the fiber optic gyroscope.

[0014] 2. The present invention can reduce the driving current IP of the SLD when starting at low temperature, thereby solving the current overshoot phenomenon when starting at low temperature.

[0015] 3. The present invention also solves the problem of gradual aging of the light source due to long-term use, the attenuation of output power, and the problem of unstable light source power under complex environments such as heat, magnetism, and force. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the SLD light source power control method of the present invention.

[0017] Figure 2 This is the constant current drive schematic. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0019] The present invention provides a method for controlling the power of an SLD light source, as shown in the schematic diagram Figure 1 To achieve SLD light source output power control and maintain power stability, the present invention adopts the following solution:

[0020] The SLD light source output is connected to the input of one end of the coupler, the coupler output is connected to the waveguide input, the two output ends of the waveguide are connected to the two input ends of the optical fiber ring, and the other output end of the coupler is connected to the detector input.

[0021] The detector output end is connected to the low-pass filter, the low-pass filter is connected to the A / D converter, the A / D converter is connected to the main control chip, the main control chip is connected to the D / A converter, the D / A converter is connected to the constant current driver, and the constant current driver is connected to the SLD light source.

[0022] The light waves generated by the SLD light source are divided into two light waves through the coupler and waveguide and propagate in opposite directions in the optical fiber ring. The two light waves propagating in opposite directions in the optical fiber ring produce interference phenomenon. The power of the interference light wave P g Phase difference with interfering light waves The cosine relationship is

[0023]

[0024] Where P 出 is the optical power output by the SLD light source, and k is the attenuation coefficient of the optical path.

[0025] The interference light wave is transmitted back to the detector through the waveguide and coupler, and the detector converts the interference light wave power P g Converted into electrical signals.

[0026] The power of the interference light wave is in a cosine relationship with the phase difference of the interference light wave, and the linearity is poor near the zero position. A modulated square wave is added to the control end of the waveguide, and the peak-to-peak value of the modulated square wave voltage is equal to the half-wave voltage of the waveguide, so that the phase difference of the interference light wave is in a sinusoidal relationship with the power of the interference light wave.

[0027] When in the positive half cycle of the modulation clock

[0028]

[0029] When in the negative half cycle of the modulation clock

[0030]

[0031] Near the zero position, the phase difference of the interference light wave is linearly related to the power of the interference light wave. The modulated square wave and the modulation clock have the same frequency and phase, and the modulated square wave and the modulation clock are generated by the main control chip.

[0032] The detector will be square wave modulated interference light wave power P g Converted into electrical signal V F ,

[0033] V F =K F P g

[0034] In the formula, K F is the detector responsivity.

[0035] Low-pass filter removes the electrical signal V F The low-pass filter can use active / passive analog filtering or digital filtering in the main control chip.

[0036] Under the control of the modulation clock, the A / D conversion collects the electrical signal and obtains the digital value D of the positive and negative half cycles of the modulation clock. A+ , D A- ,

[0037] D A+ =K A V F+

[0038] D A- =K A V F-

[0039] Where V F+ When the electrical signal V is in the positive half cycle F , V F- When the electric signal V is in the negative half cycle F , K A is the conversion factor of the A / D converter.

[0040] The main control chip modulates the digital quantity D collected in the positive and negative half cycles of the clock A+ , D A- Add together to get the DC component D of the light wave power.

[0041] D=D A+ +D A- =K A V F+ +K A V F- =K A K F (P g- +P g+ )=2kK A KF P 出

[0042] According to the above formula, the output optical power P of the SLD light source can be obtained 出 .P 出 Subtract the target value Pt of the light source power to get the power error e P , and through the power error e P Calculate the driving current I of the SLD light source P The digital quantity D d The solution process can include but is not limited to PID, advance correction, etc. Digital quantity D d The D / A converter output value V is obtained by D / A conversion p .

[0043] V p =K D D d

[0044] In the formula, K D is the conversion factor of the D / A converter.

[0045] Constant current drive D / A converter output value V p Converted into the driving current I of the SLD light source P The constant current driver is composed of an op amp, resistors, capacitors and transistors to achieve V p To I P The conversion of constant current drive is shown in the following figure. Figure 2 As shown. Drive current I P for

[0046] I P =V P / R c

[0047] In the formula, R c is the sampling resistor, V P It is the analog voltage output by D / A conversion.

[0048] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A SLD light source power control method, characterized in that: The output of the SLD light source is connected to the input of one end of the coupler, the output of the coupler is connected to the input of the waveguide, the two output ends of the waveguide are connected to the two input ends of the optical fiber ring, and the other output end of the coupler is connected to the input of the detector; the output end of the detector is connected to the low-pass filter, the low-pass filter is connected to the A / D converter, the A / D converter is connected to the main control chip, the main control chip is connected to the D / A converter, the D / A converter is connected to the constant current driver, and the constant current driver is connected to the SLD light source.

2. The SLD light source power control method according to claim 1, characterized in that: The light waves generated by the SLD light source are divided into two light waves through the coupler and waveguide and propagate in opposite directions in the optical fiber ring, resulting in interference phenomenon; the interference light waves are transmitted back to the detector through the waveguide and coupler, and the detector converts the power of the interference light waves into electrical signals.

3. The SLD light source power control method according to claim 2, characterized in that: A modulated square wave is added to the waveguide control end, and the peak-to-peak value of the modulated square wave voltage is equal to the waveguide half-wave voltage, so that the interference phase difference and the interference light wave power converted by the detector are in a sinusoidal relationship; the modulated square wave has the same frequency and phase as the modulation clock.

4. The SLD light source power control method according to claim 3, characterized in that: The detector converts the square wave modulated interference light wave power P into an electrical signal, filters out the high-frequency noise of the electrical signal through low-pass filtering, and collects the electrical signal through A / D conversion under the control of the modulation clock to obtain the digital value D of the power of the interference light wave. P The main control chip modulates the digital value D of the positive and negative half cycles of the clock A The DC component of the interference light wave power is obtained by adding them together; then the control amount of the SLD light source is calculated, and the control amount is converted into an analog voltage V by D / A. P , the constant current driver converts the analog voltage into the driving current of the SLD light source.

5. The SLD light source power control method according to any one of claims 1 to 4, characterized in that: The main control chip generates a modulation clock and collects digital quantity D in the positive and negative half cycles of the modulation clock. P The two digital quantities are added to obtain the DC component of the interference light wave power, which is subtracted from the target value Pt of the light source power to obtain the power error e P , and through the power error e P Calculate the driving current I of the SLD light source P , through D / A conversion and constant current drive feedback to the SLD light source, completing the closed-loop control of the SLD light source output power; the solution process includes PID and advance correction.

6. The SLD light source power control method according to claim 1, characterized in that: Low-pass filtering uses active / passive analog filtering or digital filtering.

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