Non-intrusive optical fiber optical power measuring system

Abstract

The invention relates to the technical field of optical fiber communication, and discloses a non-intrusive optical fiber optical power measuring system. According to the method, leakage light is generated through micro bending of an optical fiber, high-sensitivity amplification is performed on leakage light current by adopting an AD8304 logarithmic amplifier, and the measurement range of micro current is expanded in combination with an intercept adjustment technology; leakage optical signals in two directions at the micro-bend position are collected through a left-right dual-channel analog-to-digital converter (ADC), and accurate real-time monitoring of optical power is achieved through a digital processing module and a remote control module. The system comprises an optical fiber clamp module, a photoelectric conversion module, a logarithmic amplification circuit, a dual-channel ADC module and a remote control unit, and measurement is completed on the premise that normal communication of optical fibers is not affected at all. The problem that a communication link is interfered by traditional intrusive measurement is solved, the dynamic range of the measured actual optical power reaches 50dB, the measurement error is low, and a high-reliability solution is provided for performance monitoring and maintenance of an optical communication system.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communication, and more particularly to a non-invasive optical power measurement system based on optical fiber leakage light detection. Background Art

[0002] Optical fiber communication has become the core of modern communication networks due to its high bandwidth, low loss, and strong anti-interference ability. The accurate measurement of optical power in optical fibers is an important link in communication quality monitoring and maintenance. In traditional optical power measurement, invasive measurement is used, which destroys the integrity of the optical fiber and affects the normal communication of the optical fiber; while non-invasive measurement is used, although it does not affect the normal communication of the optical fiber, due to the low proportion of leakage light and inaccurate amplification, the measured optical power range is narrow or inaccurate.

[0003] In view of the above technical bottlenecks, the present invention innovatively proposes a non-invasive optical fiber optical power measurement system. Through an optimized optical fiber fixture, a 1%-level leakage light signal is accurately captured while ensuring the transmission quality; an AD8304 logarithmic amplifier is used to construct a signal processing link with adaptive bias compensation, and an intercept adjustment method is used to reduce the intercept of 100 pA in the traditional scheme to less than 1 pA, significantly expanding the measurement dynamic range; and a parameter correction algorithm is set up to realize remote real-time monitoring in combination with a human-computer interaction system. Summary of the Invention

[0004] The object of the present invention is to provide a non-invasive optical fiber optical power measurement system that uses the leakage light signal generated by optical fiber bending to measure optical power, which avoids damage to the optical fiber; and realizes accurate real-time measurement through high-sensitivity photoelectric conversion and high-performance logarithmic amplification technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] Step 1: Use an optical fiber fixture to make the optical fiber generate a micro-bending structure, causing it to generate a high proportion of leakage and generate leakage light. When the InGaAs PIN photodiode is accurately embedded in the matching hole of the fixture, the leakage light can be efficiently captured and photoelectric conversion is completed, thus constituting a complete photoelectric conversion module;

[0007] Step 2: The AD8304 logarithmic amplifier highly sensitively amplifies the leakage photocurrent, combines the intercept adjustment technology to expand the measurement range of tiny currents, and then realizes digital sampling through an analog-to-digital converter ADC, and finally constructs a complete processing link including signal conditioning and analog-to-digital conversion;

[0008] Step 3: The digital signal output by the analog-to-digital conversion ADC is processed by digital signal processing and digital filtering algorithms to obtain the actual optical power parameters. A two-way communication is established with the host monitoring platform through wireless communication, and finally a complete optical power analysis system with a human-computer interaction interface and remote monitoring and control functions is constructed.

[0009] The non-intrusive optical fiber optical power measurement system includes:

[0010] A voltage conversion circuit, an optical fiber fixture, an InGaAs PIN photodiode, an AD8304 logarithmic amplifier circuit, and a microcontroller STM32F103RCT6 ADC acquisition and remote control circuit; the optical fiber fixture, the InGaAs PIN photodiode, the AD8304 logarithmic amplifier circuit, the voltage conversion circuit, and the microcontroller STM32F103RCT6 ADC acquisition and remote control circuit are connected in sequence. The voltage of the AD8304 logarithmic amplifier circuit is connected to +5V, and the voltage of the microcontroller STM32F103RCT6 ADC acquisition and remote control circuit is connected to +3.3V.

[0011] Among them, the optical fiber fixture is composed of an optical fiber clamping component and a sensor fixing seat; the optical fiber clamping component uses a fixed structural pressing piece to press the measured optical fiber against the photosensitive sensor with a certain pressure to form a micro-bend to generate leakage light; the sensor fixing seat has a high-precision angle positioning structure for fixing the photosensitive sensor to ensure that the included angle between the two photosensitive sensors can be stably maintained.

[0012] Among them, the InGaAs PIN photodiode has high responsivity and low noise characteristics and is matched with the diode hole of the optical fiber fixture to process weak leakage light signals.

[0013] Among them, the AD8304 logarithmic amplifier circuit includes a logarithmic amplifier U1, a capacitor C1, a resistor R1, a capacitor C2, a capacitor C3, a resistor R A 、a resistor R B 、a resistor R Z 、a capacitor C4, a capacitor C5, a resistor R2, and a capacitor C6; the power supply terminal of the logarithmic amplifier U1 is connected to the capacitor C4 and the capacitor C5 and connected to the power supply +5V; the input terminal of the logarithmic amplifier U1 is connected to the capacitor C1 and the resistor R1 to ground; the bias input terminal of the logarithmic amplifier U1 is connected to the capacitor C3 to ground; the input protection terminal of the logarithmic amplifier U1 is connected to the capacitor C2 to ground; the three ground terminals of the logarithmic amplifier U1 are grounded; the logarithmic amplifier voltage pin of the logarithmic amplifier U1 is connected to the positive input terminal of the buffer amplifier and connected to the resistor R Z and connected to the 2V bias pin of the logarithmic amplifier; the reverse input terminal of the buffer amplifier of the logarithmic amplifier U1 and the resistor R BConnected to ground and to the resistor R A is connected to the output terminal of U1; the output terminal of the logarithmic amplifier U1 is connected to the resistor R2 and the capacitor C6 and is connected to ground.

[0014] Among them, the microcontroller STM32F103RCT6 ADC acquisition and remote control circuit includes a minimum system chip of a single chip microcomputer, a remote control chip ESP8266 U5, a capacitor C 15 , a capacitor C 17 , a capacitor C 16 , an inductor L1, a capacitor C 18 and a crystal oscillator X2; the power supply terminal of the remote control chip U5 is connected to +3.3V; the input protection pin of the remote control chip U5 is connected to the capacitor C 16 , the capacitor C 15 and the inductor L1 are connected to ground; the crystal oscillator pin of the remote control chip U5 is connected to the crystal oscillator X2, and is connected to the capacitor C 17 and the capacitor C 18 and is connected to ground; the serial communication pin of the remote control chip U5 is cross-connected with the serial communication pin of the minimum system chip of the single chip microcomputer.

[0015] The present invention has achieved two major breakthroughs through a non-invasive fiber optical power measurement: First, a non-invasive measurement is constructed based on the fiber microbending principle, fundamentally avoiding affecting the normal transmission of the optical fiber; Second, an intercept-adjusted wide-range logarithmic AD8304 amplification and dual-ADC collaborative sampling strategy is adopted, which can measure leakage photocurrent as low as 1 pA, enabling the system to maintain a linearity index better than ±0.2 dB within a 50 dB dynamic range. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flowchart of a non-invasive fiber optical power measurement system in a specific embodiment.

[0017] Figure 2 is a schematic diagram of a voltage conversion circuit of a non-invasive fiber optical power measurement system in a specific embodiment.

[0018] Figure 3 is a schematic diagram of the non-invasive fiber principle of a non-invasive fiber optical power measurement system in a specific embodiment.

[0019] Figure 4 is a schematic diagram of the non-invasive fiber fixture structure of a non-invasive fiber optical power measurement system in a specific embodiment.

[0020] Figure 5Amplification circuit diagram with high sensitivity for reducing the intercept and increasing the slope of AD8304 in a non-invasive fiber optic optical power measurement system in a specific embodiment.

[0021] Figure 6 Remote control circuit diagram for a non-invasive fiber optic optical power measurement system in a specific embodiment.

[0022] Figure 7 Flow chart of a non-invasive fiber optic optical power measurement system in a specific embodiment. Detailed implementation manners

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and through embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0024] Refer to Figure 1 , which is an embodiment of the present invention, and provides a non-invasive fiber optic optical power measurement system, including:

[0025] In this embodiment, a non-invasive fiber optic optical power measurement system, refer to Figure 2 , its power supply module adopts a low dropout linear voltage regulator architecture to achieve power supply, and realizes the mutual conversion of 5V voltage and 3.3V voltage.

[0026] For the 5V driving requirement of the optoelectronic conversion module and the 3.3V low voltage characteristic of the digital processing unit, the integrated AMS1117 voltage regulator chip is used as the voltage conversion circuit. This chip realizes the efficient conversion from 5V to 3.3V through precise feedback control, which not only meets the strict requirements of the logarithmic amplifier AD8304 for power supply noise, but also ensures the reliable operation of the dual-channel ADC sampling circuit and the microcontroller. It effectively solves the power supply interference problem caused by the coexistence of multiple voltage domains in the mixed signal system, and lays a hardware foundation for the low-noise transmission of the optoelectronic signal link.

[0027] Among them, the grounding end of the voltage conversion voltage regulator chip AMS1117 is grounded, the input end is connected to the 5V power supply, and a 10μF capacitor C6 and a 0.1μF capacitor C7 are connected in parallel to the ground, which plays a role in reducing the ripple coefficient of the power supply; the output end of the voltage regulator chip is connected with a 10μF capacitor C8 and a 1μF capacitor C9 in parallel, and is connected to one end of a 0Ω resistor R8 and a 0.1μF capacitor C 10 are connected in parallel to the ground together and are connected to the output voltage of 3.3V; the converted voltage of 3.3V is connected in series with a 1K resistor R9 and an LED lamp to the ground to test the stability of the power supply module.

[0028] In this embodiment, in a non-invasive fiber optic optical power measurement system, Figure 3 The following is the principle structure of the non-invasive fiber optic, and the specific structure refers to Figure 4。

[0029] Refer to Figure 3 , when the optical fiber is bent, the light originally transmitted inside the core may no longer satisfy the total reflection condition, thus generating bending loss. If the curvature radius of the bend is too small, the light will penetrate from the core into the cladding and even leak outwards. Among them, micro-bending refers to some random distortions with a curvature radius similar to the cross-sectional size of the optical fiber. By artificially controlling the optical fiber to generate micro-bending, part of the light will radiate from the core. Utilizing the characteristics of these leaked lights, the signal in the optical fiber can be measured.

[0030] In addition, in order to accurately measure the leaked light, the angle of the optical fiber fixture should be such that the leakage ratio reaches the maximum; and the leaked light is related to the bending radius of the optical fiber. The formula used is as follows:

[0031]

[0032]

[0033]

[0034] Δn = n core -n clad

[0035] Among them, α c and A c are the optical fiber bending loss coefficient and the bending loss mode coefficient respectively; R is the optical fiber bending radius; U is the exponential factor of the optical fiber bending loss; a and Δn are the core radius and the refractive index difference between the core and the cladding respectively, u, W, and V are the radial normalized phase constant, the radial normalized attenuation constant, and the normalized frequency respectively; k1(W) is the first kind of modified Bessel function of the second kind; n core and n clad represent the core refractive index and the cladding refractive index as constants respectively; n2, that is, n clad is the cladding refractive index.

[0036] After calculation, it is determined that when the optical fiber bending radius R = 0.75 mm and the bending angles at both ends are 169°, the leakage light ratio is the largest, reaching 1% of the optical fiber leakage ratio.

[0037] Among them, during the measurement process, two InGaAs photosensitive sensors In1 and In2 are respectively installed on two planes with a specific included angle. The optical fiber to be measured is fixed by a mechanical device and is in close contact with the photosensitive sensors on these two planes, and the optical fiber generates micro-bending under the action of mechanical pressure. When the optical signal is transmitted in the optical fiber, due to the difference in the transmission direction of the optical signal, the intensity of the leaked optical signal measured by In2 will be greater than that measured by In1.

[0038] Figure 4Among them, the structural parameters of the optical fiber fixture are as follows: the low center of gravity layout with a base width of 11 mm ensures uniform force distribution, the adjustable fixed bracket with a width of 26 mm adapts to the clamping requirements of various types of optical fibers, the multi-stage buffer layer with a clamping height of 21 mm and a thickness of 12 mm is matched, and the angle is maintained at 169°. On both sides of the fixture base, InGaAs PIN photodiodes with a photosensitive surface of 1 mm are placed.

[0039] Among them, the InGaAs photodetector 1 and the InGaAs photodetector 2 need to be accurately installed at the predetermined positions on the sensor base to ensure that the distance between their planes and the optical fiber contact points meets the design requirements. During installation, first install the sensor on the base, precisely calibrate the position using the fixture, and then carefully place the optical fiber between the fixed structural pressing piece and the photosensitive sensor. Adjust the position of the pressing piece to make the optical fiber have a moderate micro-bend, which not only ensures that there is enough leaked light for measurement but also does not affect the normal communication of the optical fiber due to excessive bending. This design avoids the drawbacks of interrupting the optical path in traditional measurement methods, and the selected angle has a leaked light generation ratio of 1%, ensuring the continuous and stable operation of the optical fiber communication system.

[0040] Among them, in order to measure weak leaked light signals, the InGaAs PIN photodiode selects a photodiode with a large photosensitive surface (1 mm) and high responsivity. This diode can quickly respond to the changes in light signals and provide an output signal with a high signal-to-noise ratio, reducing the noise interference in the signal and improving the clarity and accuracy of the signal.

[0041] The indium gallium arsenide material of the InGaAs PIN photodiode has a wavelength range of 900 nm to 1700 nm, covering the two transmission bands of 1310 nm and 1550 nm in optical fiber communication.

[0042] In this embodiment, in a non-intrusive optical fiber optical power measurement system Figure 5 It is a high-sensitivity logarithmic amplifier circuit diagram with reduced intercept and increased slope in this measurement system.

[0043] Figure 5 Among them, through optimizing the circuit design, the measurement sensitivity of the amplifier is reduced from 100 pA to below 1 pA, and at the same time, the amplification gain slope is increased to the order of 300 mV / dB, significantly enhancing the response ability to low-power optical signals. The output signal amplitude of the improved amplifier shows a highly linear relationship with the optical power, effectively matching the quantization interval of the subsequent ADC module, solving the problem that weak signals are easily submerged by noise in the traditional scheme, and providing a stable and reliable signal basis for high-precision optical power analysis.

[0044] Among them, the 1 interface, 2 interface and 14 interface of the chip U1 of the logarithmic amplifier are grounded. The 10th interface and 12th interface of the U1 are connected to the power supply +5V and are connected to the ground through a 100nF capacitor C4 and a 4.7μF capacitor C5 to filter out the noise at the power supply end. The input pin of the U1 is connected in series with a 1nF capacitor C1 and a 750Ω resistor R1 to the ground to form a low-pass filter to filter out the high-frequency noise at the input end. The adaptive bias interface of the U1 is connected to a 10nF capacitor C3 to the ground. The two input protection pins of the U1 are connected to a 10nF capacitor C2 to the ground. The 2V bias pin of the U1 is connected to a 25K resistor R Z to the 8th and 9th interfaces of the U1. The 13th interface of the U1 is connected to the ground through a 12.4K resistor R B . One end of R B is connected to the ground through a 10K resistor R A , R A . One end of R A is connected to the output pin of the U1. Through R B and R Z , the adjustment of the logarithmic amplification slope and intercept is realized through 3 resistors. The output pin of the U1 is connected in series with a 100Ω resistor R2 and a 100nF capacitor C6 to the ground to form a low-pass filter.

[0045] The circuit of the logarithmic amplification affects its amplification as the slope and intercept. Its logarithmic output voltage pin is the 8th pin of the chip U1 of the logarithmic amplifier. It is connected to the 11th pin through a buffer amplifier with a voltage amplification gain of G, and uses R Z and the 7th pin of the U1 to introduce a 2V bias and a resistor to reduce its intercept to improve the sensitivity and measurement dynamic range. After calculation, the slope of the logarithmic amplifier is 300mV / dB and the intercept is 1pA, which can measure weaker currents. The specific formula is:

[0046]

[0047]

[0048] Among them, G is the voltage amplification gain; R LOG is the internal resistance of the logarithmic amplification, which is 5K. V REF is the reference bias voltage, which is 2V; V Y is the proportionality coefficient, with the unit of V / decade, which determines the logarithmic voltage change ratio; I PD is the photocurrent generated by the photodiode; I Z is the reference current of the logarithmic amplification, which is 100pA. V OUT is the final output voltage; R Z , R A, R B constitute a circuit for increasing gain and reducing intercept.

[0049] Refer to Figure 6 , which is the remote control circuit diagram of the measurement system.

[0050] It connects the voltage signal amplified by the logarithmic amplifier AD8304 to the built-in ADC module of the microcontroller STM32F103RCT6 for analog-to-digital conversion and data processing.

[0051] Among them, after obtaining the voltage signal through dual-channel ADC synchronous sampling, the system selects the effective channel data based on the amplitude optimization mechanism, and constructs the optical power data processing through the pre-calibrated 1% micro-bending leakage optical coupling coefficient. This algorithm eliminates the dark current drift error through the dynamic baseline correction module, and finally outputs the temperature-compensated optical power quantization value to achieve the accurate traceability from the leakage optical signal to the original optical power.

[0052] After establishing the optical power error compensation model using the least squares fitting algorithm, the system conducts remote control through the cross-connection of the microcontroller STM32F103RCT6 and the ESP8266 module. The microcontroller uses the Direct Memory Access (DMA) mode to achieve the lossless transmission and dynamic calibration of dual-ADC data, encapsulates the calibration data into floating-point format packets through the lightweight TCP / IP protocol stack, and the host computer finally displays the optical power value.

[0053] Refer to Figure 7 , which is the working flowchart of a non-intrusive optical fiber optical power measurement system.

[0054] Among them, the fiber optic fixture is used to generate leakage light by micro-bending the optical fiber. The InGaAs PIN photodiode is used for photoelectric conversion to generate photocurrent. The photocurrent is logarithmically amplified by the AD8304 with intercept adjustment and a wider dynamic range. Then, the microcontroller STM32F103RCT6 conducts analog-to-digital conversion and data processing. Finally, the esp8266 uploads the measured data to the host computer using the TCP / IP protocol.

Claims

1. A non-invasive optical fiber optical power measurement system, characterized in that, It includes the following steps: Step 1: Use an optical fiber fixture to make the optical fiber generate a micro-bending structure, which causes a high proportion of leakage to generate leakage light. When the InGaAs PIN photodiode is precisely embedded in the matching hole of the fixture, the leakage light energy can be efficiently captured and the photoelectric conversion is completed, thus forming a complete photoelectric conversion module; Step 2: The AD8304 logarithmic amplifier highly sensitively amplifies the leakage photocurrent, combines the intercept adjustment technology to expand the measurement range of tiny currents, and then realizes digital sampling through the analog-to-digital converter ADC, and finally constructs a complete processing link including signal conditioning and analog-to-digital conversion; Step 3: The digital signal output by the analog-to-digital converter ADC obtains the actual optical power parameter through digital signal processing and digital filtering algorithms, establishes two-way communication with the host computer monitoring platform through wireless communication, and finally constructs a complete optical power analysis system with a human-computer interaction interface and remote monitoring and control functions.

2. A non-intrusive optical fiber optical power measurement system according to claim 1, wherein: The system includes a voltage conversion circuit, an optical fiber fixture, an InGaAs PIN photodiode, an AD8304 logarithmic amplifier circuit, and a microcontroller STM32F103RCT6 ADC acquisition and remote control circuit; the optical fiber fixture, the InGaAs PIN photodiode, the AD8304 logarithmic amplifier circuit, the voltage conversion circuit, and the microcontroller STM32F103RCT6 ADC acquisition and remote control circuit are connected in sequence. The voltage of the AD8304 logarithmic amplifier circuit is connected to +5V, and the voltage of the microcontroller STM32F103RCT6 ADC acquisition and remote control circuit is connected to +3.3V.

3. A non-intrusive optical fiber optical power measurement system according to claim 2, wherein: The voltage conversion circuit includes a linear voltage regulator chip U2, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a capacitor C 10 , a resistor R8, a resistor R9, and a light-emitting diode LED1; one end of the input terminal of the linear voltage regulator chip U2 is connected to the voltage +5V, and the other end is connected in parallel with the capacitor C6 and the capacitor C7 and connected to the ground; one end of the output terminal of the linear voltage regulator chip U2 is connected in parallel with the capacitor C8 and the capacitor C9, and is also connected in parallel with the resistor R8 and the capacitor C 10 and is connected to the ground to generate a voltage of 3.3V; the ground terminal of the linear voltage regulator chip U2 is grounded; the linear voltage regulator chip U2 generates a voltage of 3.3V and is connected to the ground through the resistor R9 and the light-emitting diode LED1.

4. A non-intrusive optical fiber optical power measurement system according to claim 2, wherein: The optical fiber fixture consists of an optical fiber clamping component and a sensor fixing seat; the optical fiber clamping component uses a fixed structural pressing piece to press the measured optical fiber on the photosensitive sensor with a certain pressure to form a micro-bending to generate leakage light; the sensor fixing seat has a high-precision angle positioning structure for fixing the photosensitive sensor to ensure that the included angle between the two photosensitive sensors can be stably maintained.

5. A non-intrusive optical fiber optical power measurement system according to claim 2, wherein: The InGaAs PIN photodiode has the characteristics of high responsivity and low noise, and is matched with the diode hole of the optical fiber fixture to process weak leakage light signals.

6. A non-intrusive optical fiber optical power measurement system according to claim 2, wherein: The AD8304 logarithmic amplifier circuit includes a logarithmic amplifier U1, a capacitor C1, a resistor R1, a capacitor C2, a capacitor C3, a resistor R A , a resistor R B , a resistor R Z , a capacitor C4, a capacitor C5, a resistor R2, and a capacitor C6; the power supply terminal of the logarithmic amplifier U1 is connected to the capacitor C4 and the capacitor C5 and connected to the power supply +5V; the input terminal of the logarithmic amplifier U1 is connected to the capacitor C1 and the resistor R1 to ground; the bias input terminal of the logarithmic amplifier U1 is connected to the capacitor C3 to ground; the input protection terminal of the logarithmic amplifier U1 is connected to the capacitor C2 to ground; the three ground terminals of the logarithmic amplifier U1 are grounded; the logarithmic amplifier voltage pin of the logarithmic amplifier U1 is connected to the positive input terminal of the buffer amplifier and connected to the resistor R Z and connected to the 2V bias pin of the logarithmic amplifier; the negative input terminal of the buffer amplifier of the logarithmic amplifier U1 is connected to the resistor R B and connected to ground and connected to the resistor R A and connected to the output terminal of U1; the output terminal of the logarithmic amplifier U1 is connected to the resistor R2 and the capacitor C6 and connected to ground.

7. A non-intrusive optical fiber optical power measurement system according to claim 2, wherein: The STM32F103RCT6 ADC acquisition and remote control circuit of the microcontroller includes a minimum system chip of the single-chip microcomputer, a remote control chip ESP8266 U5, a capacitor C 15 , a capacitor C 17 , a capacitor C 16 , an inductor L1, a capacitor C 18 and a crystal oscillator X2; the power supply terminal of the remote control chip U5 is connected to +3.3V; the input protection pin of the remote control chip U5 is connected to the capacitor C 16 , the capacitor C 15 and the inductor L1 are connected to the ground; the crystal oscillator pin of the remote control chip U5 is connected to the crystal oscillator X2, and is connected to the ground through the capacitor C 17 and the capacitor C 18 ; the serial communication pins of the remote control chip U5 and the single-chip microcomputer minimum system chip are cross-connected.

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