AWG chip automatic test system based on photodiode array

Abstract

The invention discloses an AWG chip automatic test system based on a photodiode array, and the system comprises a light source transmitting module which is used for transmitting laser and finally coupling the laser to an input waveguide of an AWG chip; the six-axis control platform controls the single-mode optical fiber FA to be accurately coupled to the AWG chip by adjusting the position of the single-mode optical fiber FA; the light source detection module comprises a PD array composed of a plurality of photodiodes, and the PD array obtains information of an output waveguide of the AWG chip; data acquired by the upper computer and the data acquisition system are transmitted to the upper computer to be processed and displayed, and by taking a CWDM chip as an example, insertion loss, central wavelength, bandwidth, crosstalk and the like of the chip can be calculated by respectively acquiring optical power of four channels in the chip, so that whether the chip reaches the standard or not is judged. In the process, as the AWG chip is a passive device, input and output waveguides at the two ends of the chip carry out optical transmission in an alignment mode, and if alignment is wrong, large loss is likely to be generated.

Description

Technical Field

[0001] The invention relates to the field of AWG chip testing devices, and in particular to an AWG chip automatic testing system based on a photodiode array. Background Art

[0002] Arrayed Waveguide Grating (AWG) is a key optical device used in wavelength division multiplexing (WDM) systems. It can combine and separate multiple optical signals at different wavelengths, so that multiple signals can be efficiently transmitted in the same optical fiber. AWG chips are widely used in optical communications, optical networks, data centers and other fields. They have become the core components of modern optical communication systems due to their superior performance and high integration. The performance of AWG chips directly affects the overall efficiency and stability of optical communication systems. In optical communication systems, the failure of AWG chips may cause problems such as signal attenuation, increased bit error rate or service interruption. Therefore, in the production process of AWG chips, testing is a key link to ensure product quality. By testing AWG chips, key parameters such as wavelength selectivity, insertion loss, crosstalk and bandwidth can be verified to ensure that they meet design specifications and standards.

[0003] Current AWG chip test equipment usually requires more manual settings and operations, which increases the complexity and time cost of the test, and is also prone to introducing human errors, affecting the reliability of the test results. Although the traditional automatic AWG chip test system reduces the human factor, the consistency of the test results may still be poor due to reasons such as equipment accuracy and environmental influences.

[0004] At present, most of the AWG chip automatic test systems on the market use bilateral six-axis adjustment frames to achieve channel alignment of AWG chips. During the test process, the adjustment frames on the left and right sides need to be adjusted continuously to reach the position with the maximum optical power, which takes a long time. When switching different test objects or wavelengths, the configuration time of automatic adjustment may still be long, affecting the test efficiency. In addition, long-term use of the six-axis adjustment frame may cause component wear, thereby affecting the accuracy and stability of the adjustment.

[0005] In addition, most automatic test systems are designed for specific products or test standards, such as CWDM, DWDM, Lan-WDM, etc. They are not compatible with the testing of multiple WDM chips and lack the ability to adapt to new devices or new technologies. In response to the above problems, a solution is proposed below. Summary of the invention

[0006] The invention aims to provide an automatic AWG chip testing system based on a photodiode array, which has the advantage of being able to quickly and conveniently couple and align the AWG chip.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions: An automatic test system for AWG chips based on photodiode arrays, comprising: A light source transmitting module, which is used to transmit laser light and polarize the laser light, and finally couple the polarized light to the input waveguide of the AWG chip through the single-mode optical fiber FA; A six-axis control platform, including three linear motion axes X, Y, and Z and three rotation axes θx, θy, and θz. A fixture for clamping the single-mode optical fiber FA is installed on the six-axis control platform. The six-axis control platform controls the single-mode optical fiber FA to be accurately coupled to the AWG chip by adjusting the position of the fixture. A light source detection module, comprising a plurality of photodiodes, each of which can independently receive an optical signal, and a plurality of the photodiodes form a PD array, and the PD array is connected to a data acquisition system through a multiplexing switch to obtain optical power information and position information of different photodiodes, thereby obtaining information of an output waveguide of an AWG chip; The host computer, the light source transmitting module, the six-axis control platform and the light source detecting module are all connected to the host computer, and the data collected by the data acquisition system is transmitted to the host computer for processing and display.

[0008] Preferably, the light source emission module comprises a tunable laser and a polarization controller, the tunable laser is used to emit laser light with a fixed wavelength and fixed optical power, and the polarization controller converts the laser light into polarized light with different polarization states.

[0009] Preferably, a reading circuit is provided on the rear side of each of the photodiodes, and the reading circuit reads the optical signal. The PD array draws an optical power diagram of the AWG output waveguide at that moment according to the optical signal received by the photodiode at each position, thereby identifying the output waveguide position of the AWG in the diagram and calculating the optical power at each position.

[0010] Preferably, the reading circuit includes a voltage reading circuit and an address reading circuit, the voltage reading circuit includes an optical signal detection circuit, a transimpedance amplifier circuit and a differential gain amplifier circuit, and the optical signal outputs a voltage signal within the collection voltage range after passing through the two amplifier circuits; the address reading circuit includes a light intensity detection judgment circuit and an address encoding circuit, and each photodiode outputs an optical signal carrying position information by position encoding each photodiode.

[0011] A testing method for an AWG chip automatic testing system based on a photodiode array comprises the following steps: S1: Preparation before testing, check that all instruments are connected correctly and initialized; S2: Adjust the six-position adjustment bracket on the left to align the optical fiber with the waveguide; S3: Identify and record the light spot position corresponding to each waveguide of the AWG chip through the photodiode array on the right; S4: The laser emits continuous wavelength light for scanning testing to calculate parameters such as insertion loss and crosstalk.

[0012] The beneficial effects of the present invention are: 1. It can achieve fast response and real-time monitoring. The design of the photodiode array can monitor the changes in optical power in real time. Compared with the traditional bilateral six-axis adjustment of optical fiber alignment, the photodiode array can work effectively without the need for precise alignment, thereby reducing the cumbersome steps in the test process and improving test efficiency.

[0013] 2. Improved test accuracy. The photodiode array uses multi-point acquisition and can collect optical signals from multiple locations at the same time. This acquisition method significantly improves measurement accuracy. Secondly, through the design of the array, the distribution of optical power at different locations can be analyzed to provide more comprehensive measurement results.

[0014] 3. Improved system stability. Photodiode arrays usually have better background noise suppression capabilities and can effectively filter environmental interference, which allows stable test results to be maintained in environments with large light interference. Secondly, the high integration design of photodiode arrays and other circuits reduces the use of mechanical alignment components, thereby improving the stability and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a system framework diagram of an embodiment; Figure 2 is a schematic diagram of the PD array of the embodiment; Figure 3 A circuit diagram of a single photodiode of an embodiment; Figure 4 The voltage reading circuit diagram of the embodiment; Figure 5 is a structural diagram of an address reading circuit in an embodiment; Figure 6 This is a structural diagram of the six-axis control platform of the embodiment.

[0016] Figure numerals: 1. single-sided six-position adjustment frame; 2. single-mode optical fiber FA; 3. AWG chip; 4. stage; 5. PD array. DETAILED DESCRIPTION

[0017] The following is only a preferred embodiment of the present invention, and the protection scope is not limited to this embodiment. All technical solutions under the concept of the present invention should belong to the protection scope of the present invention. The same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "bottom" and "top", "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively.

[0018] like Figures 1 to 6 As shown, an automatic test system for an AWG chip based on a photodiode array includes a light source transmitting module, a six-axis control platform, a light source detection module and a host computer. The light source transmitting module includes a tunable laser and a polarization controller. The tunable laser emits a laser with a fixed wavelength and a fixed optical power, which is converted into polarized light with different polarization states by the polarization controller. The polarized light is coupled to the input waveguide of the AWG chip through a single-mode optical fiber FA.

[0019] The six-axis control platform includes three linear motion axes X, Y, and Z and three rotation axes θx, θy, and θz. The six-axis control platform is equipped with a fixture for clamping the single-mode optical fiber FA. By continuously adjusting the position of the fixture, the single-mode optical fiber FA is controlled to be accurately coupled to the AWG chip to minimize the loss.

[0020] The light source detection module includes a PD array composed of multiple photodiodes, each of which can independently receive light signals. In this application, the PD array is composed of 200 micro photodiodes with a size of 50um×50um arranged in 20×10. A reading circuit is provided on the back side of each photodiode, which is used to read the voltage and position information in the light signal, and can output the voltage signal and the position of the photodiode in real time. The PD array is connected to the data acquisition system through a multiplexing switch to obtain the optical power information and position information of different photodiodes, so as to obtain the insertion loss, center wavelength, bandwidth, crosstalk and other information of the output waveguide of the AWG chip. The PD array draws the optical power diagram of the AWG output waveguide at this moment according to the optical signal received by the photodiode at each position, thereby identifying the output waveguide position of the AWG in the figure and calculating the optical power at each position.

[0021] The reading circuit includes a voltage reading circuit and an address reading circuit. The voltage reading circuit includes an optical signal detection circuit, a transimpedance amplifier circuit and a differential gain amplifier circuit. After the optical signal passes through the two amplifier circuits, it can output a voltage signal within the acquisition voltage range. The transimpedance amplifier circuit receives and amplifies the weak current from the photodiode, and outputs an enable signal through the optical signal detection circuit, which facilitates the address reading circuit to encode and output. The differential amplifier circuit is used for secondary amplification and denoising of the electrical signal to reduce the interference of the dark current generated in the absence of optical power. The address reading circuit mainly includes a light intensity detection judgment circuit and an address encoding circuit. By encoding the position of each photodiode, each photodiode outputs an optical signal carrying address information.

[0022] All devices are connected to the host computer for control, and the collected data is transmitted to the host computer for processing and display Working principle: The structure of the AWG chip is an arrayed waveguide grating made on the chip substrate using PLC technology. The following test process description takes the CWDM chip as an example. The test principle is to input a wide light source. Due to the internal structure of the CWDM chip, this wide light source can be divided into lights with central wavelengths of 1271nm, 1291nm, 1301nm and 1331nm. By collecting the optical power of these four channels respectively, the insertion loss, central wavelength, bandwidth, crosstalk, etc. of the CWDM chip can be calculated to determine whether the chip meets the standard. In this process, since the CWDM chip is a passive device, the input and output waveguides at both ends of the chip are aligned for optical transmission. If the alignment is wrong, it is easy to cause large losses.

[0023] First, make preparations before the test to ensure that all test equipment is working properly, including tunable lasers, polarization controllers, PD arrays, six-axis control platforms, etc. Connect all equipment to the host computer, initialize all axes of the six-axis control platform and move them to the test initial point, install the CWDM chip on the middle stage of the six-axis control platform, and fix the single-mode fiber FA on the fixture of the left six-axis adjustment frame. Set the test parameters in the test software, including scanning wavelength range, scanning step length, scanning speed, etc.

[0024] Secondly, the single-mode optical fiber FA on the left needs to be aligned with the output waveguide of the CWDM chip. The specific method is that the single-mode optical fiber FA is constantly approaching the CWDM chip, and the distance information between the two is monitored in real time through the displacement sensor on the fixture to prevent the two from squeezing and colliding and causing the CWDM chip to break. Then the rotation angle axis θx axis and θy axis are continuously adjusted. When the displacement sensor feedback value is the largest, it means that the output plane of the single-mode optical fiber FA is parallel to the input waveguide plane of the CWDM chip. Then, the scanning range in the X and Y directions is set according to the waveguide spacing of different AWG chips. For example, the scanning range of CWDM is Y axis ±75um, and the X axis moves 50um at a spacing of 5um. This ensures that a signal similar to a Gaussian beam can be obtained on the photodiode array. The maximum value position of the signal is the aligned X and Y positions. The optimal position of the alignment is obtained and returned to complete the coupling alignment on the left.

[0025] After the left side is aligned, the optical signal is output to the output waveguide through the internal structure of the AWG chip. At this time, the wavelengths of the first and last channels are switched. When the wavelength of the first channel is switched, the light emitted from the first channel of the chip is displayed as a light spot with the highest optical power on the photodiode array. The specific process is that when the photodiode receives a light signal, it is converted into a current signal. The anode of the photodiode is connected to the inverting input terminal of the operational amplifier. The feedback resistor is connected between the output terminal and the inverting input terminal of the operational amplifier. By selecting a suitable feedback resistor and setting the required gain, the weak current signal can be amplified by the transimpedance amplifier circuit and converted into a larger voltage signal. In order to avoid the output of dark current in the absence of photocurrent, a differential gain amplifier is added for processing, thereby enhancing the clarity and anti-interference ability of the optical signal. At the same time, the optical signal is judged by the light intensity detection judgment circuit whether each photodiode receives the optical signal, and an enable signal is generated. The implementation process is to compare the output signal of the photodiode with a set threshold through a comparator. The threshold is the electrical signal V generated in the light-free probability environment. ref If the output signal is greater than the threshold, it is determined that the optical signal exists. At this time, the comparator outputs a high level, the enable signal = 1, otherwise the enable signal = 0.

[0026] When the enable signal = 1, the address encoding circuit is activated to encode each diode in the photodiode array, thereby outputting a binary representation of its position. Since the size of the photodiode array is 20×10, a 5-bit binary number is used to represent the row number, a 4-bit binary number is used to represent the column number, and a total of 9 bits of binary numbers represent the position of each photodiode. For the output of rows and columns, an encoder is used to determine the currently activated row. According to the output of the photoelectric detection judgment circuit, the corresponding row and column signals are activated, and then the outputs of the row number and column number are merged through the logic gate circuit to form a 9-bit binary signal, indicating the position information of a specific photodiode in the photodiode array. Since the light spot is circular and the optical power signal is Gaussian distributed, the optical power of the photodiode covered by the light spot can be integrated to obtain the optical power of the channel.

[0027] By switching the first and last wavelengths of the AWG chip and obtaining the optical power diagrams of the first and last channels, the photodiode positions corresponding to the light spots output by the first and last channels can be identified, thereby inferring the positions of each evenly distributed middle channel and recording them. After the recording is completed, the system considers that the next step of scanning test can be carried out.

[0028] Finally, the tunable laser sends a trigger signal to the acquisition module, and then emits incident light to the input waveguide of the AWG chip according to the set scanning information. The photodiode array on the right collects and calculates the corresponding optical power according to the recorded positions of each channel, thereby obtaining the output optical power of each channel at different wavelengths. The software calculates parameters such as insertion loss, center wavelength, bandwidth, and crosstalk based on the collected optical power signal to determine whether the current chip meets the standard.

[0029] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit 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. An automatic test system for AWG chips based on photodiode array, characterized in that: include A light source transmitting module, which is used to transmit laser light and polarize the laser light, and finally couple the polarized light to the input waveguide of the AWG chip through the single-mode optical fiber FA; A six-axis control platform, including three linear motion axes X, Y, and Z and three rotation axes θx, θy, and θz. A fixture for clamping the single-mode optical fiber FA is installed on the six-axis control platform. The six-axis control platform controls the single-mode optical fiber FA to be accurately coupled to the AWG chip by adjusting the position of the fixture. A light source detection module, comprising a plurality of photodiodes, each of which can independently receive an optical signal, and a plurality of the photodiodes form a PD array, and the PD array is connected to a data acquisition system through a multiplexing switch to obtain optical power information and position information of different photodiodes, thereby obtaining information of an output waveguide of an AWG chip; The host computer, the light source transmitting module, the six-axis control platform and the light source detecting module are all connected to the host computer, and the data collected by the data acquisition system is transmitted to the host computer for processing and display.

2. The AWG chip automatic testing system based on a photodiode array according to claim 1, characterized in that: The light source emission module comprises a tunable laser and a polarization controller. The tunable laser is used to emit laser light with a fixed wavelength and fixed optical power, and the polarization controller converts the laser light into polarized light with different polarization states.

3. The AWG chip automatic testing system based on photodiode array according to claim 1, characterized in that: A reading circuit is provided on the rear side of each of the photodiodes, and the reading circuit reads the optical signal. The PD array draws an optical power diagram of the AWG output waveguide at that moment according to the optical signal received by the photodiode at each position, thereby identifying the output waveguide position of the AWG in the diagram and calculating the optical power at each position.

4. The AWG chip automatic testing system based on photodiode array according to claim 3, characterized in that: The reading circuit includes a voltage reading circuit and an address reading circuit. The voltage reading circuit includes an optical signal detection circuit, a transimpedance amplifier circuit and a differential gain amplifier circuit. The optical signal outputs a voltage signal within the collection voltage range after passing through the two amplifier circuits. The address reading circuit includes a light intensity detection and judgment circuit and an address encoding circuit. By encoding the position of each photodiode, each photodiode outputs an optical signal carrying position information.

5. The testing method of the AWG chip automatic testing system based on the photodiode array according to any one of claims 1 to 4, characterized in that: The following steps are included: S1: Preparation before testing, check that all instruments are connected correctly and initialized; S2: Adjust the six-position adjustment bracket on the left to align the optical fiber with the waveguide; S3: Identify and record the light spot position corresponding to each waveguide of the AWG chip through the photodiode array on the right; S4: The laser emits continuous wavelength light for scanning testing to calculate parameters such as insertion loss and crosstalk.

Images