Disclosure of Invention
The invention provides a novel optical power automatic calibration system and a novel optical power automatic calibration method in order to well overcome the problems that in the prior art, multiple devices are needed for calibration, the operation is inconvenient, the test process is complicated, and a large amount of manual operation is needed;
an optical power automatic calibration system, characterized in that: the system comprises a light source module 1, an electrical modulation attenuator 2, a one-in-two-out light beam splitter 3, a micro control unit MCU4, an output photoelectric detector 5, an input photoelectric detector 6, a system serial interface 7, an ADC analog-to-digital conversion module 8, a temperature detection control circuit 9, a current drive circuit 10 and an analog voltage control circuit 14; the optical output end 11 of the module to be tested is connected with the input optical detector 6, the input optical detector 6 is connected to the micro control unit MCU4 through the ADC analog-to-digital conversion module 8, the first end of the micro control unit MCU4 is connected with the temperature detection control circuit 9, the second end of the micro control unit MCU4 is connected with the current driving circuit 10 to control the wavelength of the light source module 1, the light source module 1 is connected with the electrical modulation attenuator 2, the third end of the micro control unit MCU4 is connected with the analog voltage control circuit 14, the electrical modulation attenuator 2 is controlled by the analog voltage control circuit 14 to control the power of output light, the output end of the electrical modulation attenuator 2 is connected to the inlet of the one-in two-out optical beam splitter 3, one output port of the one-in two-out optical beam splitter 3 is connected to the optical input end 12 of the module to be tested, and the other end is, the output photoelectric detector 5 is connected to the MCU4 through the ADC module 8, the 4 th end of the MCU4 is connected to the system serial interface 7, and the other end of the system serial interface 7 is connected to the serial interface 13 of the module to be tested.
Further, the system for automatically calibrating optical power is characterized in that: the detection ranges of the output photoelectric detector 5 and the input photoelectric detector 6 should cover the wavelength range of the light source module 1 and the power attenuation range of the electric modulation attenuator 2.
A method for calibrating optical power using the automatic optical power calibration system, comprising:
the first step is as follows:
the micro control unit MCU4 acquires the current temperature through the temperature detection control circuit 9, and according to the current detected temperature value, the micro control unit MCU4 controls the light source module 1 to output light with a set wavelength through the current driving circuit 10;
the second step is that:
the micro control unit MCU4 controls the attenuation value of the electric modulation attenuator 2 through the analog voltage control circuit 14, thereby changing the power of the output light of the electric modulation attenuator 2;
the third step:
the electric modulation attenuator 2 inputs light into the one-in two-out light beam splitter 3, the split light, the b path light is collected as light power, and the a path light is output as main path light; the optical power split from the two output ports of the beam splitter is determined according to the splitting ratio of the device, and the splitting formula is as follows:
wherein P is1outThe light output power of the path a of the beam splitter is K1Is the light splitting ratio of path a of the beam splitter, PinThe incident light power of the beam splitter is P2outThe light output power of the path b of the beam splitter is K2The light splitting ratio of the path b of the beam splitter; combining the above formula yields:
the output optical power of the other path can be calculated from the formula;
the fourth step:
b-path light used for collecting optical power is collected by an output photoelectric detector 5, converted into a digital signal by an ADC (analog-to-digital converter) module 8 and then enters a micro control unit MCU4 to calculate the optical power and calculate the output optical power value of the system;
output photoelectric detectorThe conversion function of the detector 5 is fLThe ADC analog-to-digital conversion module 8 converts the analog signal of the output photoelectric detector 5 into a digital signal, and the MCU4 collects the digital signal converted by the ADC analog-to-digital conversion module 8, and calculates the optical power value input to the output photoelectric detector 5 according to the following formula:
Pout=fL(A0)
wherein P isoutFor the value of the light power input to the output photodetector 5, fLAs a conversion function of the photodetector, A0The digital signal value is acquired by the micro control unit MCU4 through the output photoelectric detector 5 and processed by the ADC analog-to-digital conversion module 8;
can be derived from the above formula
Pout=fL(A0)*K2/K1
Wherein P isoutIs the value of the optical power output by the system, fLAs a conversion function of the photodetector, A0Digital signal values, K, collected by the output photoelectric detector 5 and processed by the ADC module 8 for the MCU42Low b-path splitting ratio, K, of beam splitter1The splitting ratio of the path a of the optical splitter;
the fifth step:
the micro control unit MCU4 performs a first group matching on the system output light power value and the sampling value through the sampling value of the module to be tested read by the system serial interface 7;
and a sixth step:
the MCU4 changes the attenuation value by adjusting the attenuator 2 a number of times, and repeats the previous step a number of times, matching the data a number of times, and fitting the data into a formula:
fout(Pout[N],Kx[N])=0
wherein P isout[N]Light power value, K, for N system light sourcesx[N]Reading external module sampling values for N serial ports, foutIs composed of Pout[N]And Kx[N]Function fitted outThe curve is transmitted to an external module through a serial port, and the input of the external module is calibrated; after completion, the micro control unit MCU4 writes the calibration value into the flash memory of the module to be tested through the system serial interface 7;
the seventh step:
the input optical power is converted into a current signal by an input photoelectric detector 6, and the conversion function is fLThe digital signal value collected by the input photoelectric detector 6 and processed by the ADC analog-to-digital conversion module 8 and collected by the micro control unit MCU4 can obtain the value of the optical power input to the detector, and the formula is:
Pin=fL(A1)
wherein, PinOptical power value, f, input to a system optical power meterLIs a photoelectric conversion function of the input photoelectric detector, A1The values are acquired by the input photoelectric detector 6 and processed by the ADC module 8;
meanwhile, the micro control unit MCU4 reads the sampling value of the external module through the serial port, and carries out a first group matching on the system input optical power value and the sampling value;
eighth step:
the micro control unit MCU4 adjusts the drive current of the module to be tested many times through the serial port to change the output power of the module to be tested, and obtains the detection input power of the automatic calibration system through the system serial interface 7, and repeats the above steps, matches data many times, and fits the data into a formula:
fin(Pin[N],Kx[N])=0
wherein P isin[N]Optical power values, K, input for N system light sourcesx[N]Reading external module sampling values for N serial ports, finIs composed of Pin[N]And Kx[N]Fitting the function curve, and transmitting the curve to an external module through a serial port, wherein the output of the external module is calibrated; after the comparison is completed, the MCU4 writes the calibration value into the flash memory of the module to be tested via the serial interface 7.
The novel automatic calibration system and method for the optical power have the advantages that the PID system with built-in control detection is adopted, so that the output optical power is free from drifting and distortion; according to the invention, through full-automatic adjustment of the output and the input of the optical power, the manual adjustment time is greatly shortened, and the input and the output can be measured only by once plugging and unplugging in the calibration; the invention integrates the functions of a light source, a power meter, an attenuator and the like into a set of system, and is controlled by a micro control unit, so that the occupied space is small, and the device to be measured can be measured only by connecting the device to be measured into equipment; the invention can automatically output multi-wavelength by using the tunable light source module, and the test process is controlled by the microcontroller.
Detailed Description
The structure of the novel optical power automatic calibration system provided by the invention is shown in fig. 1, and the novel optical power automatic calibration system is composed of a light source module 1, an electric modulation attenuator 2, a one-in-two-out light beam splitter 3, a micro control unit MCU4, an output photoelectric detector 5, an input photoelectric detector 6, a system serial interface 7, an ADC analog-to-digital conversion module 8, a temperature detection control circuit 9, a current drive circuit 10 and an analog voltage control circuit 14.
The optical output end 11 of the module to be tested is connected with the input photoelectric detector 6, the input photoelectric detector 6 is connected to the micro control unit MCU4 through the ADC analog-to-digital conversion module 8, the first end of the micro control unit MCU4 is connected with the temperature detection control circuit 9, the second end of the micro control unit MCU4 is connected with the current drive circuit 10 to control the wavelength of the light source module 1, the light source module 1 is connected with the electric modulation attenuator 2, the third end of the micro control unit MCU4 is connected with the analog voltage control circuit 14, the electric modulation attenuator 2 is controlled by the analog voltage control circuit 14 to control the power of output light, the output end of the electric modulation attenuator 2 is connected to the inlet of the one-in-two-out optical beam splitter 3, one output port of the one-in-two-out optical beam splitter 3 is connected to the optical input end 12 of the module to be tested, the other end, the 4 th end of the micro control unit MCU4 is connected to the system serial interface 7, and the other end of the system serial interface 7 is connected to the serial interface 13 of the module to be tested.
When the light source module 1 is designed, the type and the adjustable range of the light source should be selected according to the actually required wavelength range and power range of the light, the attenuation range of the electrical modulation attenuator 2 can also be selected according to the actually required requirements, and the detection ranges of the output photoelectric detector 5 and the input photoelectric detector 6 should cover the wavelength range and power range of the light source module 1 and the attenuation range of the electrical modulation attenuator 2.
The detection method based on the automatic optical power calibration system of the invention comprises the following steps.
The flow of the test is as follows,
the first step is as follows:
the micro control unit MCU4 collects the current temperature through the temperature detection control circuit 9, and according to the current detected temperature value, the micro control unit MCU4 controls the light source to output light with set wavelength through the current drive circuit.
The second step is that:
the MCU4 controls the attenuation value of the electric modulation attenuator 2 through the analog voltage control circuit 14, thereby changing the output light power of the electric modulation attenuator
The third step:
the electric modulation attenuator 2 inputs the light into the one-in two-out light beam splitter 3, the split light, the b-path light as the light power collection, and the a-path light as the main path light output. The optical power split from the two output ports of the beam splitter is determined according to the splitting ratio of the device, and the splitting formula is as follows:
wherein P is1outThe light output power of the path a of the beam splitter is K1Is the light splitting ratio of path a of the beam splitter, PinThe incident light power of the beam splitter is P2outThe light output power of the path b of the beam splitter is K2The splitting ratio of the path b of the beam splitter. Combining the above formula yields:
the output power of the other path can be calculated by knowing the output power of the path b
The fourth step:
the b-path light used for collecting the optical power is collected by the output photoelectric detector 5, converted into a digital signal by the ADC analog-to-digital conversion module 8, and then enters the micro control unit MCU4 to calculate the optical power and calculate the output optical power value of the system.
The output photodetector 5 functions to convert the optical power signal into a current signal with a conversion function fLThe ADC analog-to-digital conversion module 8 converts the analog signal of the output photoelectric detector 5 into a digital signal, and the MCU4 collects the digital signal converted by the ADC analog-to-digital conversion module 8, and calculates the optical power value input to the output photoelectric detector 5 according to the following formula:
Pout=fL(A0)
wherein P isoutFor the optical power input to the output photodetector 5Value fLAs a conversion function of the photodetector, A0The digital signal values collected by the output photoelectric detector 5 and processed by the ADC analog-to-digital conversion module 8 are collected by the micro control unit MCU 4.
Can be derived from the above formula
Pout=fL(A0)*K2/K1
Wherein P isoutIs the value of the optical power output by the system, fLAs a conversion function of the photodetector, A0Digital signal values, K, collected by the output photoelectric detector 5 and processed by the ADC module 8 for the MCU42Low 2-way splitting ratio, K, of beam splitter1The 1 st splitting ratio of the optical splitter.
The fifth step:
the micro control unit MCU4 performs a first group matching on the system output light power value and the sampling value of the module to be tested, which is read through the system serial interface 7.
And a sixth step:
the MCU4 changes the attenuation value by adjusting the attenuator 2 a number of times, and repeats the previous step a number of times, matching the data a number of times, and fitting the data into a formula:
fout(Pout[N],Kx[N])=0
wherein P isout[N]Light power value, K, for N system light sourcesx[N]Reading external module sampling values for N serial ports, foutIs composed of Pout[N]And Kx[N]And fitting the function curve, and transmitting the curve to an external module through a serial port, wherein the input of the external module is calibrated. After completion, the micro control unit MCU4 writes the calibration value into the flash memory of the module to be tested through the system serial interface 7.
The seventh step:
input optical power is converted into a current signal by an input photoelectric detector 6, and the conversion function is fLThe signal collected by the MCU4 is collected by the input photoelectric detector 6 and processed by the ADC module 8The digital signal value of (a) can obtain the optical power value input to the detector, and the formula is as follows:
Pin=fL(A1)
wherein, PinOptical power value, f, input to a system optical power meterLIs a photoelectric conversion function of the input photoelectric detector, A1Is the value collected by the input photoelectric detector 6 and processed by the ADC module 8.
Meanwhile, the micro control unit MCU4 reads the sampling value of the external module through the serial port, and carries out a first group matching on the system input optical power value and the sampling value.
Eighth step:
the micro control unit MCU4 adjusts the drive current of the module to be tested many times through the serial port to change the output power of the module to be tested, and obtains the detection input power of the automatic calibration system through the system serial interface 7, and repeats the above steps, matches data many times, and fits the data into a formula:
fin(Pin[N],Kx[N])=0
wherein P isin[N]Optical power values, K, input for N system light sourcesx[N]Reading external module sampling values for N serial ports, finIs composed of Pin[N]And Kx[N]And fitting the function curve, transmitting the curve to an external module through a serial port, and finishing the calibration of the output of the external module. After the comparison is completed, the MCU4 writes the calibration value into the flash memory of the module to be tested via the serial interface 7.
In the process, all the steps are connected for the first time and wait for the completion of calibration, so that the plugging error and the manual reading error of the devices are avoided, the calibration accuracy can be automatically calibrated and improved, and 2 functions of the light source and the optical power meter are integrated.
The present invention will be further illustrated by the following specific examples.
The system is used for carrying out power calibration on optical communication equipment with a communication waveband (C waveband) of 1525nm-1565 nm. In order to realize the automatic calibration function, the light source module used in the system needs to have a wavelength tunable function, and a common laser cannot realize wavelength tuning in a 40nm range.
In this embodiment, the light source module 1 uses a DBR semiconductor laser as a light source, and the effective refractive index of the grating region is changed by changing the concentration of carriers through current injection, so as to complete wavelength tuning. The module adopts a DS-DBR type laser, utilizes the vernier effect of front and back sampling gratings and introduces a phase grating, thereby realizing the wavelength tuning range of dozens of nanometers. Meanwhile, the tuning of the wavelength and the power of the light source is completed by matching with the temperature detection control circuit 9 and the current driving circuit 10.
The output photoelectric detector 5 and the input photoelectric detector 6 adopt a high-precision power detection module and an InGaAs type photoelectric detector as a core, are low-noise and high-response photoelectric detectors, have high spectral responsivity in the wave band of 800-1700 nm, and can reach 0.8A/W. Compared with a detector based on an Avalanche Photodiode (APD), the high-voltage bias circuit does not need to be designed independently, and the test requirement of the optical fiber communication waveband can be met. Based on factors such as dark current, rise time, bias voltage, bandwidth and the like, the InGaAs type photoelectric detector is adopted, system noise can be obviously reduced, and measurement linearity, sensitivity and optical power measurement range of the whole machine are improved. The photoelectric conversion amplifying circuit in the power detection module is a key part for guaranteeing indexes such as the measurement range, linearity and measurement precision of the optical power meter. The pre-amplifier and the post-amplifier in the circuit adopt operational amplifier chips with low noise, low bias current and wide frequency band, and adopt the scheme of an impedance transformation type amplifying circuit; the resistor is a low-noise metal film resistor, and the capacitor is a mica capacitor and a ceramic chip capacitor with low loss; in addition, in order to shield the interference of an external electromagnetic field, a small resistor is connected in series to the ground end at the suspended floating ground end. Through the noise reduction technologies such as impedance matching design and optimized electric signal transmission circuit, the high-sensitivity detection of the optical power meter can be realized.
The electric modulation attenuator 2 adopts an MEMS type VOA, is different from the traditional mechanical VOA, has the characteristics of large attenuation range, low power consumption, good linearity and the like, and has small volume, easy multi-channel integration and high response speed.
The detection range of the system is-60 dBm- +20dBm, and the selected VOA electric modulation attenuator needs to reach at least an attenuation range of 80 dB.
The optical power automatic calibration system formed by the embodiment is used for testing the performance of the light source, the output wavelengths of the light source are respectively set to 1530nm, 1540nm and 1550nm through the liquid crystal screen, and then the light source is sequentially connected to the spectrometer AQ6370D, so that the obtained spectrograms are shown in fig. 3 to 5. The test result shows that the light source can realize the purpose of controlling the wavelength of the output light through the temperature detection control circuit 9 and the current drive circuit 10. And the side mode suppression ratio of output light is more than 50dB, the line width is less than 1MHz, the relative intensity noise is low, and the output quality is good.
The power performance of the automatic calibration system is tested, a ThorLabs standard power meter PM400, a calibrated LD laser light source, an adjustable attenuator and a 50:50 beam splitter are used as test instruments, and input light with 1550nm wavelength of an input PM400 module and a power meter module of the system is adjusted through the adjustable attenuator. The PM400 is taken as a standard, the standard is adjusted from-60 dBm to +20dBm, the recording is carried out once every 10dBm, the recording result is shown in the table 1, and the result shows that the accuracy and the measurement range of the power meter module of the system are basically consistent with those of a ThorLabs standard power meter PM 400.
Table 11550 nm wavelength accuracy test data
And testing the automatic calibration function of the automatic calibration system, accessing the optical fiber amplifier module to be tested into the calibration system, setting the calibration flow to start, and setting the calibration time to be about 60 s. After calibration was completed, calibration was performed using standard test equipment and the highest composite error was found to be no more than 0.08 dB.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein are intended to be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.