A calibration structure and calibration method of optical fiber probe

Abstract

The embodiments of the present application provide a calibration structure and a calibration method for an optical fiber probe, wherein the calibration structure of the optical fiber probe comprises: at least two grating couplers having different expected coupling angles for a specific working wavelength, at least one coupler, a light detection device, and an optical waveguide sequentially connecting the gratings in the at least two grating couplers, at least one coupler, and the light detection device; the at least two grating couplers include a grating coupler to be calibrated; each grating coupler is used to sequentially receive a first optical signal output by the optical fiber probe in a preset order and output a second optical signal to the optical waveguide; at least one coupler is used to sequentially receive the second optical signal in the preset order and output a third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal; and the light detection device is used to sequentially receive and respond to the third optical signal in a preset order and output an optical detection signal corresponding to each grating coupler.

Description

Technical Field

[0001] The present application relates to optical coupling and silicon optical device testing technology, and in particular to a calibration structure and calibration method of an optical fiber probe. Background Art

[0002] In related technologies, the coupling angle of the grating design value is usually used for testing (for example, the commonly used 8° (degrees) and 10°). When the process error is too large, the coupling efficiency at the working wavelength will drop sharply due to the drift of the peak wavelength, increasing the insertion loss and test error during the test. Even if the grating coupling angle needs to be adjusted, it is usually adjusted blindly to increase or decrease the coupling angle. There is no response reference value, which leads to low calibration efficiency and low accuracy. Summary of the invention

[0003] The embodiments of the present application are intended to provide a calibration structure and a calibration method for an optical fiber probe.

[0004] In a first aspect, an embodiment of the present application provides a calibration structure of an optical fiber probe, comprising: at least two grating couplers having different desired coupling angles for a specific working wavelength, at least one coupler, a light detection device, and an optical waveguide sequentially connecting the gratings in the at least two grating couplers, the at least one coupler, and the light detection device; the at least two grating couplers include a grating coupler to be calibrated;

[0005] Each of the grating couplers is used to sequentially receive the first optical signal output by the optical fiber probe according to a preset order and output a second optical signal to the optical waveguide;

[0006] The at least one coupler is used to sequentially receive the second optical signals according to the preset order and output the third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal;

[0007] The optical detection device is used to receive and respond to the third optical signal in sequence according to the preset order, and output an optical detection signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal, thereby realizing the calibration of the optical fiber probe.

[0008] In a second aspect, an embodiment of the present application provides a calibration method for an optical fiber probe, which is applied to any of the calibration structures of the optical fiber probe described above, and the method comprises:

[0009] Each of the at least two grating couplers sequentially receives the first optical signal output by the optical fiber probe according to a preset sequence and outputs a second optical signal to the optical waveguide;

[0010] At least one coupler receives the second optical signal in sequence according to the preset order and outputs a third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal;

[0011] The optical detection device receives and responds to the third optical signal in sequence according to the preset order, and outputs an optical detection signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal, thereby realizing the calibration of the optical fiber probe.

[0012] In a third aspect, an embodiment of the present application further provides a method for calibrating an optical fiber probe, the method comprising:

[0013] Acquiring, under the condition of a specific working wavelength and a specific optical fiber probe angle, a light detection signal corresponding to each of the at least two grating couplers arranged in a preset order;

[0014] Determine a first target light detection signal with the largest optical power or photocurrent from the light detection signals corresponding to each grating coupler;

[0015] Determining the specific optical fiber probe angle as the actual coupling angle of the first grating coupler corresponding to the first target light detection signal;

[0016] Determining an actual coupling angle range of the grating coupler to be tested based on the actual coupling angle of the first grating coupler;

[0017] The actual coupling angle of the grating coupler to be calibrated is determined based on the actual coupling angle range.

[0018] In the implementation mode of the present application, the grating coupler to be calibrated is arranged in at least two grating couplers with different expected coupling angles for a specific working wavelength, each grating coupler receives the first optical signal input by the optical fiber probe in sequence according to a preset order, outputs the second optical signal to at least one coupler, obtains the third optical signal at the output end of at least one coupler, and finally obtains the optical detection signal of the third optical signal corresponding to each first optical signal through the detection device, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal. Since the difference in optical power between the third optical signal and the corresponding first optical signal is equal, the optical detection signal detected by the optical detection device is more accurate, and the coupling angle of the grating coupler determined based on the optical detection signal is more accurate, that is, the calibration accuracy is lower, and it does not adopt a blind adjustment method such as increasing or decreasing the coupling angle, and the calibration efficiency is higher.

[0019] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present invention and, together with the specification, are used to explain the technical solutions of the present invention.

[0021] Figure 1 A schematic diagram of the composition of a calibration structure of an optical fiber probe provided in an embodiment of the present application;

[0022] Figure 2 A schematic diagram of the composition of another optical fiber probe calibration structure provided in an embodiment of the present application;

[0023] Figure 3 A schematic diagram of the composition of another optical fiber probe calibration structure provided in an embodiment of the present application;

[0024] Figure 4 A schematic diagram of a calibration structure including two calibrators on the left and right provided in an embodiment of the present application;

[0025] Figure 5 A schematic diagram of another calibration structure including two left and right calibrators provided in an embodiment of the present application;

[0026] Figure 6 A schematic diagram of an implementation flow of a calibration method for an optical fiber probe provided in an embodiment of the present application;

[0027] Figure 7 A schematic diagram of the implementation flow of another optical fiber probe calibration method provided in an embodiment of the present application;

[0028] Figure 8 A schematic diagram of the effect of grating etching depth on grating coupling efficiency spectrum provided in an embodiment of the present application;

[0029] Fig. 9 A schematic diagram of a grating coupling efficiency spectrum under different duty cycles provided in an embodiment of the present application;

[0030] Fig.10 A schematic diagram of a grating coupling efficiency spectrum at different coupling angles provided in an embodiment of the present application;

[0031] Fig.11 A schematic diagram of a grating coupling efficiency spectrum at different coupling angles provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments provided herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the embodiments provided below are partial embodiments for implementing the present invention, rather than providing all embodiments for implementing the present invention. In the absence of conflict, the technical solutions recorded in the embodiments of the present invention can be implemented in any combination.

[0033] It should be noted that, in the embodiments of the present invention, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a method or apparatus including a series of elements includes not only the elements explicitly recorded, but also includes other elements not explicitly listed, or also includes elements inherent to the implementation of the method or apparatus. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other related elements (such as steps in a method or units in a device, for example, a unit may be a part of a circuit, a part of a processor, a part of a program or software, etc.) in the method or apparatus including the element.

[0034] The term "and / or" herein is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, U and / or W can represent the three situations that U exists alone, U and W exist at the same time, and W exists alone. In addition, the term "at least one" herein represents any combination of at least two of any one or more of a plurality of. For example, including at least one of U, W, and V can represent including any one or more elements selected from the set consisting of U, W, and V.

[0035] For silicon-based photonic integrated chips, a key issue that cannot be ignored is the input and output of optical signals. The two commonly used coupling methods generally adopt end-face horizontal coupling structure or on-chip vertical coupling structure, among which vertical coupling generally uses a grating coupler. A grating coupler refers to the diffraction effect of a grating, which couples the diffracted light into an optical waveguide for propagation, enabling real-time upload and download of signals, greatly enhancing the flexibility of the system. The grating coupler can be made at any position on the substrate, so light can be input and output at any waveguide position that needs to be tested. It has the advantages of easy on-chip testing, no need for wafer or chip preprocessing, and no strict space restrictions.

[0036] The grating coupler consists of a grating structure with a period of nanometer scale, a waveguide layer and a substrate. The incident light is coupled from the fiber probe to the waveguide through the grating. During the propagation of this light, there are many factors that affect the grating coupling efficiency. Since the grating design size is smaller than the wavelength of the incident light, any change of 1nm (nanometer) in any design parameter may affect the performance of the grating coupler.

[0037] When a wafer fab is producing wafers, there will be process errors between different wafers or different areas of the same wafer, and the performance of the devices will also vary. For grating couplers, the impact of process errors on their performance is often the drift of peak wavelength, reduction in coupling efficiency, and reduction in optical bandwidth.

[0038] In order to reduce the second-order reflection and improve the coupling efficiency, the diffraction direction of the grating coupler needs to avoid being completely perpendicular to the chip as much as possible, usually at an angle of about 10° (degrees). The grating coupling angle is often considered when designing a grating coupler. Different grating coupling angles can also cause changes in the peak wavelength. Similarly, the coupling angle during testing is also one of the important conditions that affect the test accuracy. The drift of the peak wavelength of the grating coupler caused by process errors can be improved by adjusting the coupling angle during testing and packaging.

[0039] Usually, the coupling angle of the grating design value is used for testing (such as the commonly used 8° and 10°). When the process error is too large, the coupling efficiency at the working wavelength will drop sharply due to the drift of the peak wavelength, increasing the insertion loss and test error during the test. Even if the grating coupling angle needs to be adjusted, it is usually adjusted blindly to increase or decrease the coupling angle. There is no response reference value, which leads to low calibration efficiency and low accuracy.

[0040] At the same time, the fiber coupling fixtures used in most coupling stations cannot determine the coupling angle on site. Even if there is no process error, the coupling angle cannot be guaranteed to be 8° or 10° before testing. It is very necessary to calibrate the coupling angle of the fiber probe before testing. This is the most commonly used function of the calibrator, and its importance is no less than correcting the test error caused by process error.

[0041] Figure 1 FIG. 1 is a schematic diagram of a vertical grating coupling test device in the related art. Figure 1 As shown, the optical signal emitted by the light source 101 is incident on the incident grating 103 on the surface of the first grating coupler through the optical fiber 102, and the incident grating 103 transmits the optical signal to the exit grating 105 on the surface of the second grating coupler through the waveguide 104. The optical signal on the exit grating 105 is output to the power meter through the optical fiber 106. The optical power of the optical signal output from the optical fiber 106 can be calculated by the power meter.

[0042] Based on the above technical problems, the present application embodiment provides a calibration structure of an optical fiber probe, such as Figure 2As shown, the calibration structure 20 of the optical fiber probe includes: at least two grating couplers 201 with different expected coupling angles for a specific working wavelength, at least one coupler 202, a light detection device 203, and an optical waveguide 204 sequentially connecting the gratings in the at least two grating couplers 201, the at least one coupler 202 and the light detection device 203; the at least two grating couplers 201 include the grating coupler to be calibrated;

[0043] Each of the grating couplers is used to sequentially receive the first optical signal output by the optical fiber probe according to a preset order and output a second optical signal to the optical waveguide 204;

[0044] The at least one coupler 202 is used to sequentially receive the second optical signals according to the preset order and output a third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal;

[0045] The optical detection device 203 is used to receive and respond to the third optical signal in sequence according to the preset order, and output an optical detection signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal, thereby realizing the calibration of the optical fiber probe.

[0046] Here, the optical fiber probe may be a preset initial angle, that is, during the calibration of the optical fiber probe, the coupling angle of the grating coupler is a preset initial angle.

[0047] It is understandable that the expected coupling angle refers to the coupling angle determined based on the preset etching depth, duty cycle, period and other parameters of the grating coupler in the design or manufacture of the grating coupler. Since the grating coupler is designed according to the preset etching depth, duty cycle, period and other parameters of the grating coupler during the manufacturing process, there are errors in the actual manufacturing. For example, the preset etching depth of the grating coupler is 70nm, but the actual etching depth may be 65nm or 75nm, and a change of 1nm may affect the performance of the grating coupler. Therefore, the expected coupling angle is the coupling angle of the grating coupler determined by the theoretical parameter design, not the actual coupling angle.

[0048] In some possible embodiments, the specific working wavelength may be 1550 nm; the at least two grating couplers 201 having different expected coupling angles for the specific working wavelength may be at least two grating couplers 201 having expected coupling angles for the specific wavelength that conform to a preset rule; wherein the at least two grating couplers 101 are arranged in sequence according to a preset order.

[0049] In a possible implementation, the preset rule may be any pre-set rule. For example, the preset rule may be that the coupling angle increases or decreases by a preset angle Δθ in sequence. When at least two grating couplers are the 1st to Nth grating couplers (N grating couplers) and the corresponding desired coupling angles are θ1 to θN, respectively, the preset rule may be θ1<θ2<θ3<……<θN; and there is no specific limitation on Δθ, and Δθ may be equal or unequal. If △θ is to be equal, the difficulty of simulation design will be greatly increased. The preset order may be the 1st grating coupler, the 2nd grating coupler, the 3rd grating coupler…the N-1th grating coupler, the Nth grating coupler.

[0050] It is understandable that the grating coupler has insertion loss. The first optical signal outputs the second optical signal through the grating coupler, the optical power of the second optical signal is different from that of the first optical signal, the optical power of the first optical signal is greater than that of the second optical signal, and the difference between the optical power of the first optical signal and the optical power of the second optical signal corresponds to the insertion loss.

[0051] In some possible implementations, the insertion loss of each of the at least two grating couplers 201 is the same.

[0052] In one embodiment, when at least two grating couplers 201 include N grating couplers, at least one coupler 202 may include a 1×N coupler (N input ends and 1 output end), or may include multiple 1×2 couplers (two input ends and one output end).

[0053] It is understandable that the coupler also has a specific insertion loss. The second optical signal input to the coupler outputs a third optical signal through the coupler; the optical power of the third optical signal is different from that of the second optical signal, the optical power of the second optical signal is greater than that of the third optical signal, and the difference between the optical power of the second optical signal and the optical power of the third optical signal corresponds to the specific insertion loss.

[0054] In some possible implementations, the light detection signal may be an optical power signal or a photocurrent signal. Correspondingly, the light detection device 203 may be a grating or a photodetector (PD).

[0055] It can be understood that, when the optical fiber probe is at a preset initial angle, the output optical power of each grating coupler is different in at least two grating couplers 201 with different expected coupling angles for a specific working wavelength, and the optical power of each optical signal output by the corresponding coupler is also different. Therefore, the actual coupling angle of the grating coupler to be calibrated included in the at least two grating couplers can be determined according to the optical signal corresponding to each grating coupler.

[0056] In the implementation mode of the present application, the grating coupler to be calibrated is arranged in at least two grating couplers with different expected coupling angles for a specific working wavelength, each grating coupler receives the first optical signal input by the optical fiber probe in sequence according to a preset order, outputs the second optical signal to at least one coupler, obtains the third optical signal at the output end of at least one coupler, and finally obtains the optical detection signal of the third optical signal corresponding to each first optical signal through the detection device, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal. Since the difference in optical power between the third optical signal and the corresponding first optical signal is equal, the optical detection signal detected by the optical detection device is more accurate, and the coupling angle of the grating coupler determined based on the optical detection signal is more accurate, that is, the calibration accuracy is lower, and it does not adopt a blind adjustment method such as increasing or decreasing the coupling angle, and the calibration efficiency is higher.

[0057] In some possible implementations, the coupler includes two input ports and one output port; the insertion losses of a first channel and a second channel formed by the two input ports and one output port are equal; and the at least one coupler includes at least two identical couplers.

[0058] In some possible embodiments, the coupler includes N input ports and one output port; the insertion losses of the 1st to Nth channels formed by the N input ports and one output port are equal; the at least one coupler includes 1 coupler; and N represents the number of the at least two grating couplers.

[0059] Figure 3 A schematic diagram of the composition of another optical fiber probe calibration structure provided in an embodiment of the present application, such as Figure 3 As shown, the calibration structure 30 of the optical fiber probe includes: at least two grating couplers 301 with different expected coupling angles for a specific working wavelength, at least one coupler 302, a PD 303, and an optical waveguide 304 sequentially connecting the gratings in the at least two grating couplers 301, the at least one coupler 302, and the PD 303; the at least two grating couplers 301 include the grating coupler to be calibrated;

[0060] Each of the grating couplers is used to sequentially receive the first optical signal output by the optical fiber probe according to a preset order and output a second optical signal to the optical waveguide;

[0061] The at least one coupler 302 is used to sequentially receive the second optical signals according to the preset order and output a third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal;

[0062] The PD 303 is used to receive and respond to the third optical signal in sequence according to the preset order, and output the photocurrent signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the photocurrent signal, thereby realizing the calibration of the optical fiber probe.

[0063] In the embodiment of the present application, since PD is more suitable for monitoring the photocurrent of the optical signal, the accuracy of the photocurrent signal corresponding to each grating coupler detected by PD is higher, and the coupling angle of the grating coupler determined based on the photocurrent signal is more accurate, that is, the calibration accuracy is lower, and it does not adopt blind adjustment methods such as increasing or decreasing the coupling angle, and the calibration efficiency is higher.

[0064] Figure 4 A schematic diagram of the composition of another optical fiber probe calibration structure provided in an embodiment of the present application is shown in FIG. Figure 4 As shown, the calibration structure 40 of the optical fiber probe includes: at least two grating couplers 401 with different expected coupling angles for a specific working wavelength, at least one coupler 402, a grating 403, and an optical waveguide 404 sequentially connecting the gratings in the at least two grating couplers 401, the at least one coupler 402, and the grating 403; the at least two grating couplers 401 include the grating coupler to be calibrated;

[0065] Each of the grating couplers is used to sequentially receive the first optical signal output by the optical fiber probe according to a preset order and output a second optical signal to the optical waveguide;

[0066] The at least one coupler 402 is used to sequentially receive the second optical signals according to the preset order and output a third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal;

[0067] The grating 403 is used to receive and respond to the third optical signal in sequence according to the preset order to obtain the optical output power signal corresponding to each of the grating couplers, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical output power signal to achieve calibration of the optical fiber probe.

[0068] In the embodiment of the present application, since the optical output power signal corresponding to each grating coupler can be obtained through the grating, the optical output power signal corresponding to each grating coupler detected by the grating is more accurate, and the coupling angle of the grating coupler determined based on the optical power signal is more accurate, that is, the calibration accuracy is lower, and blind adjustment methods such as increasing or decreasing the coupling angle are not adopted, and the calibration efficiency is higher.

[0069] In some possible implementations, the at least two grating couplers include 1st to Nth grating couplers arranged in sequence according to the preset order; wherein the expected coupling angles of the 1st to Nth grating couplers conform to a preset rule.

[0070] In some possible implementations, the desired coupling angle of each of the grating couplers is related to parameters such as grating etching depth, period, and duty cycle of the grating coupler.

[0071] The purpose of the embodiment of the present application is to assist in calibrating the test fiber probe angle before large-scale testing, confirm the optimal coupling angle of the grating coupler, reduce the insertion loss caused by the grating coupler during the test, reduce the difference between the insertion loss of the output ports, and improve the drift of the peak wavelength of the grating coupler caused by process errors. It provides a coupling angle reference for packaging and can also be used to evaluate the process errors of the grating coupler.

[0072] To achieve the above objectives, the technical solution adopted by the embodiment of the present application is: a fiber probe calibration structure for vertical grating coupling. The calibration structure includes multiple grating couplers with different optimal coupling angles as the light input end, wherein one grating coupler is a standard grating coupler used by various devices in this batch; multiple 1×2 couplers (or one 1×N coupler) for injecting the light coupled from the gratings of each grating coupler into the photodetector with the same insertion loss; a photodetector for detecting the coupling efficiency of the grating coupler; a straight waveguide connecting the grating, the 1×2 coupler (or the 1×N coupler) and the photodetector, etc.

[0073] Among them, the grating coupler, 1×2 coupler, 1×N coupler, photodetector, optical waveguide, etc. are manufactured on a SOI (Silico N-ON-INsulator, silicon on insulating substrate) wafer and are compatible with silicon-based photonic processes.

[0074] In some embodiments, the standard grating coupler is a standard grating coupler used as the optical input end of various grating coupling devices in the batch of chips, and the standard grating coupler has fixed parameters such as etching depth, period, and duty cycle.

[0075] In some embodiments, the multiple 1×2 couplers are 1×2 couplers of the same specification, and the incident light is incident through one of the 2 ports of the coupler and output from port 1. It is necessary to ensure that laser light with the same optical power is incident from any one of the 2 ports, and the optical power output from port 1 is the same, that is, the insertion loss of the two ports is consistent.

[0076] In some embodiments, the 1×N coupler, the incident light is incident through one of the N ports of the coupler and output from port 1, ensuring that laser light with the same optical power is incident from any port of the N ports and the optical power output from port 1 is the same, that is, the insertion loss of the N ports is consistent.

[0077] In some embodiments, one of the N grating couplers with different optimal coupling angles is consistent with all parameters of the standard input grating coupler, and is a standard grating coupler in this batch of chips as the light output end of various grating coupling devices; the remaining multiple grating couplers are grating couplers whose parameters such as grating etching depth, period, duty cycle, etc. are modified, resulting in a slight difference in the optimal coupling angle under the same wavelength of incident light from the standard grating coupler and the difference is known (or under the same coupling angle, there is a slight difference in the peak wavelength and the difference is known); the optimal coupling angles of the N grating couplers are all different, and are arranged in order from the smallest to the largest optimal coupling angle.

[0078] In some embodiments, the vertical grating coupled fiber probe calibration structure can be divided into two left and right calibrators, which are used to calibrate the fiber probes on the left and right sides respectively. The photodetector can be one for each left and right calibrator, or one photodetector can be shared.

[0079] The embodiments of the present application can assist in calibrating the test fiber probe angle before large-scale testing, confirm the optimal coupling angle of the grating coupler, reduce the insertion loss caused by the grating coupler during the test, reduce the difference in insertion loss between the output ports, and improve the drift of the peak wavelength of the grating coupler caused by process errors.

[0080] The grating couplers are all equal-period gratings.

[0081] In one embodiment, the grating coupler may include all grating couplers that require tilt angle coupling and can determine the optimal coupling angle and be sorted according to a preset rule, including but not limited to uniform gratings (the unit period, duty cycle, and etching depth of the grating are all constant values), non-uniform gratings (variable period, variable duty cycle, variable etching depth), two-dimensional gratings, blazed gratings, etc.

[0082] In some embodiments, the plurality of 1×2 couplers are 1×2 couplers of the same specification, and their insertion losses incident from any port are the same; the plurality of 1×N couplers have the same insertion losses incident from any port.

[0083] In some embodiments, the operating peak wavelength of the standard grating coupler should be designed according to actual usage, such as 1310 nm, 1550 nm, etc.

[0084] In some embodiments, when the standard grating coupler is designed, the standard coupling angle is a fixed value, such as 10°, and the peak wavelength is the designed working wavelength.

[0085] In some embodiments, the optimal coupling angle of the standard grating coupler is the angle between the optical fiber probe and the SOI in the perpendicular direction when the coupling efficiency is the highest at a specific wavelength.

[0086] Figure 5 A schematic diagram of a calibration structure including two left and right calibrators provided in an embodiment of the present application is shown in FIG. Figure 5 As shown, the calibrator 50 on the left and the calibrator 51 on the right can be exactly the same, wherein the calibrator 50 on the left includes the 1st to the 4th grating couplers 501, the 1st to the 3rd couplers (1×2 couplers) 502 and the optical detection device 503, and the connecting lines in the figure can be regarded as connected optical waveguides.

[0087] It can be understood that, in an actual calibration structure, the calibrator 50 on the left and the calibrator 51 on the right may each include 8, 16 or more grating couplers.

[0088] Figure 6 A schematic diagram of another calibration structure including two left and right calibrators provided in an embodiment of the present application is shown in FIG. Figure 6 As shown, the etalon 60 on the left and the etalon 61 on the right can be exactly the same, wherein the etalon 60 on the left includes the 1st to Nth grating couplers 601, 1×N coupler 602 and PD 603, and the connecting lines in the figure can be regarded as connected optical waveguides.

[0089] On the basis of the above-mentioned embodiments, the present application embodiment provides a calibration method for an optical fiber probe, which is applied to the calibration structure of the optical fiber probe described above, such as Figure 7 As shown, the method includes:

[0090] Step S701: each of the at least two grating couplers receives the first optical signal output by the optical fiber probe in sequence according to a preset order and outputs the second optical signal to the optical waveguide;

[0091] Step S702: at least one coupler receives the second optical signals in sequence according to the preset order and outputs a third optical signal to the optical waveguide; the difference in optical power between each of the first optical signals and the corresponding third optical signal is equal;

[0092] Step S703: The optical detection device receives and responds to the third optical signal in sequence according to the preset order, and outputs an optical detection signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal, thereby realizing the calibration of the optical fiber probe.

[0093] Figure 8 A schematic diagram of the implementation flow of another optical fiber probe calibration method provided in an embodiment of the present application is shown in FIG. Figure 8 As shown, the process includes:

[0094] Step S801: acquiring a light detection signal corresponding to each of at least two grating couplers arranged in a preset order under a specific working wavelength and a specific optical fiber probe angle;

[0095] It is understandable that, under the condition of a specific working wavelength and a specific fiber probe angle, the size of the optical detection signal corresponding to each grating coupler is different. The optical detection signal corresponding to each grating coupler is related to the desired coupling angle of each selected grating coupler.

[0096] Here, the optical detection signal may be a photocurrent signal or an optical power signal.

[0097] Step S802: determining a first target light detection signal having the largest optical power or photocurrent from the light detection signals corresponding to each grating coupler;

[0098] In some possible implementations, determining the first target light detection signal with the largest light power or photocurrent from the light detection signals corresponding to each grating coupler can be performed by querying the light detection signal with the largest light power or photocurrent among the light detection signals corresponding to each grating coupler, and determining the queried light detection signal with the largest light power or photocurrent as the first target light detection signal.

[0099] Step S803: determining the specific optical fiber probe angle as the actual coupling angle of the first grating coupler corresponding to the first target light detection signal;

[0100] Step S804: determining an actual coupling angle range of the grating coupler to be tested based on the actual coupling angle of the first grating coupler;

[0101] In some possible embodiments, the actual coupling angle range of the grating coupler to be tested is determined based on the actual coupling angle of the first grating coupler, including determining the actual coupling angle range of the grating coupler to be tested according to the angle difference between the expected coupling angles of the first target grating coupler and the grating coupler to be tested and the actual coupling angle of the first grating coupler.

[0102] Step S805: determining the actual coupling angle of the grating coupler to be calibrated based on the actual coupling angle range.

[0103] In one implementation, the actual coupling angle of the grating coupler to be calibrated is determined based on the actual coupling angle range, and any actual coupling angle is selected from the determined actual coupling angle range to be determined as the actual coupling angle of the grating coupler to be calibrated.

[0104] In another embodiment, the actual coupling angle of the grating coupler to be calibrated is determined based on the actual coupling angle range. The expected coupling angle range can be reset based on the determined actual coupling angle range as at least two grating couplers of the actual coupling angle range, and the above steps S801 to S805 are re-executed to obtain a more accurate coupling angle of the grating coupler to be calibrated.

[0105] In practical applications, steps S801 to S805 can be implemented using a control unit, and the above-mentioned control unit can be at least one of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), an FPGA, a central processing unit (CPU), a controller, a microcontroller, and a microprocessor.

[0106] In the embodiment of the present application, when the difference between the desired coupling angles of two adjacent grating couplers in at least two grating couplers is the first angle accuracy, the accuracy of the actual grating coupling angle determined by the above method will be less than the first angle accuracy.

[0107] The present application further provides a method for calibrating an optical fiber probe, the method comprising:

[0108] Step 90: obtaining a light detection signal corresponding to each of the at least two grating couplers arranged in a preset order under a specific working wavelength and a specific optical fiber probe angle; the expected coupling angle of each of the grating couplers conforms to a preset rule;

[0109] Step 91: determining a first target light detection signal having the largest optical power or photocurrent from the light detection signals corresponding to each grating coupler;

[0110] Step 92: determining the specific optical fiber probe angle as the actual coupling angle of the first grating coupler corresponding to the first target light detection signal;

[0111] Step 93: Obtain the preset rule;

[0112] Step 94: determining an actual coupling angle range of the grating coupler to be tested based on the preset rule and the actual coupling angle of the first grating coupler;

[0113] Step 95: Determine the actual coupling angle of the grating coupler to be calibrated based on the actual coupling angle range.

[0114] In an embodiment of the present application, since the expected coupling angle of each of the at least two grating couplers conforms to a preset rule, when the preset rule is obtained, the actual coupling angle range of the grating coupler to be tested can be accurately determined based on the preset rule and the actual coupling angle of the first grating coupler.

[0115] In the embodiment of the present application, at least two grating couplers include grating couplers GC1, GC2, GC3 to GCn, and GC1, GC2, GC3 to GCn are designed to have different optimal coupling angles (expected coupling angles) at a specified working wavelength, and when each grating coupler is at the optimal coupling angle, its coupling efficiency is almost the same. At least one coupler is a 1×n coupler; and the light detection device is a PD.

[0116] Among them, the grating CGnorm in the middle of all gratings is the standard grating coupler used by various devices in this batch. All the grating optimal coupling angles at the specified working wavelength are θ1, θ2, θ3 to θn, and are designed as θ1<θ2<θ3<……<θn. The difference between two adjacent optimal coupling angles is △θ, which is a known value. △θ is the minimum resolution of the calibration structure. The calibration accuracy can be improved by increasing the number of grating couplers and reducing △θ.

[0117] Start calibrating the left fiber probe, and the initial angle of the fiber probe is θ. First, provide a reverse bias for the PD, and use a commercial laser tube to input DC light of a fixed wavelength, which is the working wavelength of various optical devices in this batch. The laser is coupled to the N grating couplers on the left side of the calibration structure through the fiber probe in turn. The light coupled into the optical waveguide is injected into the photodetector with the same insertion loss through the 1×N coupler. The photodetector records the optical power coupled into the photodetector by the N grating couplers in the form of photocurrent, which are I1, I2, I3 to IN in turn. Since the insertion loss values ​​incident on each port of the 1×N coupler are the same, it can be considered that the order of the photocurrent is the order of the coupling efficiency of each grating coupler.

[0118] After the test is completed, compare the size of each photocurrent. For example, if Im is the maximum photocurrent, the fiber coupling angle θ at this time can be considered to be the optimal coupling angle of GCm at the working wavelength. It can be easily calculated that θ+(norm-m)△θ is the optimal coupling angle of the standard grating coupler CGnorm. At this time, it is only necessary to increase the coupling angle of the fiber coupler by (norm-m)△θ, that is, adjust the fiber probe to the optimal coupling angle of the standard grating coupler. To avoid errors, the calibration process can be performed once or multiple times to ensure that Inorm is calibrated to the maximum value. The calibration is completed. At this time, the optimal coupling angle of the fiber probe is less than △θ compared to the theoretical value.

[0119] It will be appreciated that the right fiber optic probe may be calibrated in the same manner.

[0120] Fig. 9 A schematic diagram of the effect of grating etching depth on grating coupling efficiency spectrum provided in an embodiment of the present application, such as Fig. 9 As shown, the abscissa is the wavelength in nm, and the ordinate is the coupling efficiency in dimensionless units; wherein curves 900 to 909 correspond to curves representing the grating coupling efficiency with grating etching depths of 65 to 74 nm, respectively. It can be seen that the grating coupling efficiency curves for different grating etching depths (1 nm difference) are completely different, and the wavelength corresponding to the highest point of the grating coupling efficiency increases with the increase of the grating etching depth.

[0121] Fig.10 A schematic diagram of a grating coupling efficiency spectrum under different duty cycles provided in an embodiment of the present application, such as Fig.10 As shown, the horizontal axis is wavelength in nm, and the vertical axis is coupling efficiency in dimensionless units; wherein curves 1000 to 1006 correspond to curves representing grating coupling efficiency when duty cycles are 48%, 49%, 49.5%, 50%, 50.5%, 51%, and 52%, respectively. It can be seen that the grating coupling efficiency curves for different light duty cycles (with a difference of 0.5%) are completely different, and the wavelength corresponding to the highest point of the grating coupling efficiency increases with the increase of duty cycle.

[0122] Fig.11 A schematic diagram of a grating coupling efficiency spectrum at different coupling angles provided in an embodiment of the present application, such as Fig.11As shown, the abscissa is the wavelength in nm, and the ordinate is the coupling efficiency in dimensionless units; wherein curves 1100 to 1104 correspond to curves representing the grating coupling efficiency when the coupling angle is 8 to 12 degrees. It can be seen that the grating coupling efficiency curves for different coupling angles (1 degree difference) are completely different, and the wavelength corresponding to the highest point of the grating coupling efficiency decreases as the coupling angle increases.

[0123] In some embodiments, the functions or modules included in the device provided in the embodiments of the present application can be used to execute the method described in the above method embodiments, and its implementation can refer to the description of the above method embodiments. For the sake of brevity, it will not be repeated here.

[0124] The above description of various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other, and for the sake of brevity, they will not be repeated herein.

[0125] The methods disclosed in the various method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0126] The features disclosed in the various product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

[0127] The features disclosed in the various method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0128] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0129] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned implementation modes. The above-mentioned implementation modes are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, which are all within the protection of the present application.

Claims

1. A calibration structure for an optical fiber probe, characterized in that: include: At least two grating couplers having different desired coupling angles for a specific operating wavelength, at least one coupler, a light detection device, and an optical waveguide sequentially connecting the gratings in the at least two grating couplers, the at least one coupler, and the light detection device; the at least two grating couplers include a grating coupler to be calibrated; Each of the grating couplers is used to sequentially receive the first optical signal output by the optical fiber probe according to a preset order and output a second optical signal to the optical waveguide; The at least one coupler is used to sequentially receive the second optical signals according to the preset order and output the third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal; The optical detection device is used to receive and respond to the third optical signal in sequence according to the preset order, and output an optical detection signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal, thereby realizing the calibration of the optical fiber probe.

2. The optical fiber probe calibration structure according to claim 1, characterized in that: The coupler comprises two input ports and one output port; the insertion losses of a first channel and a second channel formed by the two input ports and one output port are equal; and the at least one coupler comprises at least two identical couplers.

3. The calibration structure of the optical fiber probe according to claim 1, characterized in that: The coupler includes N input ports and one output port; the insertion losses of the 1st to Nth channels formed by the N input ports and one output port are equal; the at least one coupler includes one coupler; N represents the number of the at least two grating couplers.

4. The optical fiber probe calibration structure according to any one of claims 1 to 3, characterized in that: The light detection device includes a photodetector PD; the light detection signal includes a photocurrent signal; Correspondingly, the PD is used to receive and respond to the third optical signal in sequence according to the preset order, and output the photocurrent signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the photocurrent signal, thereby realizing the calibration of the optical fiber probe.

5. The optical fiber probe calibration structure according to any one of claims 1 to 3, characterized in that: The optical detection device includes a grating; the optical detection signal includes an optical output power signal; Correspondingly, the grating is used to receive and respond to the third optical signal in sequence according to the preset order, and obtain the optical output power signal corresponding to each of the grating couplers, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical output power signal, thereby realizing the calibration of the optical fiber probe.

6. The optical fiber probe calibration structure according to any one of claims 1 to 3, characterized in that: The at least two grating couplers include the first to Nth grating couplers arranged in sequence according to the preset order; wherein the expected coupling angles of the first to Nth grating couplers conform to a preset rule.

7. The calibration structure of the optical fiber probe according to any one of claims 1 to 3, characterized in that: The desired coupling angle of each of the grating couplers is related to parameters such as the grating etching depth, period, and duty cycle of the grating coupler.

8. A method for calibrating an optical fiber probe, characterized in that: The method applied to the calibration structure of the optical fiber probe according to any one of claims 1 to 7 comprises: Each of the at least two grating couplers sequentially receives the first optical signal output by the optical fiber probe according to a preset sequence and outputs the second optical signal to the optical waveguide; At least one coupler receives the second optical signal in sequence according to the preset order and outputs a third optical signal to the optical waveguide; the difference in optical power between each first optical signal and the corresponding third optical signal is equal; The optical detection device receives and responds to the third optical signal in sequence according to the preset order, and outputs an optical detection signal corresponding to each grating coupler, so that the actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signal, thereby realizing the calibration of the optical fiber probe.

9. A method for calibrating an optical fiber probe, characterized in that: The method comprises: Acquiring, under the condition of a specific working wavelength and a specific optical fiber probe angle, a light detection signal corresponding to each of the at least two grating couplers arranged in a preset order; Determine a first target light detection signal with the largest optical power or photocurrent from the light detection signals corresponding to each grating coupler; Determining the specific optical fiber probe angle as the actual coupling angle of the first grating coupler corresponding to the first target light detection signal; Determining an actual coupling angle range of the grating coupler to be calibrated based on the actual coupling angle of the first grating coupler; An actual coupling angle of the grating coupler to be calibrated is determined based on the actual coupling angle range.

10. The method according to claim 9, characterized in that The expected coupling angle of each of the grating couplers complies with a preset rule; and the actual coupling angle range of the grating coupler to be calibrated is determined based on the actual coupling angle of the first grating coupler, comprising: Obtaining the preset rule; The actual coupling angle range of the grating coupler to be calibrated is determined based on the preset rule and the actual coupling angle of the first grating coupler.

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