CN114323592A

CN114323592A - Calibration structure and calibration method of optical fiber probe

Info

Publication number: CN114323592A
Application number: CN202111672797.6A
Authority: CN
Inventors: 吴定益; 胡晓; 肖希; 王磊; 冯朋
Original assignee: Wuhan Optical Valley Information Optoelectronic Innovation Center Co Ltd
Current assignee: Wuhan Optical Valley Information Optoelectronic Innovation Center Co Ltd
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-04-12

Abstract

The embodiment of the application provides a calibration structure and a calibration method of an optical fiber probe, and the calibration structure of the optical fiber probe comprises: at least two grating couplers having different desired coupling angles for a specific operating wavelength, at least one coupler, an optical detection device, and an optical waveguide sequentially connecting the grating, the at least one coupler, and the optical detection device of the at least two grating couplers; the at least two grating couplers comprise grating couplers to be calibrated; each grating coupler is used for sequentially receiving a first optical signal output by the optical fiber probe according to a preset sequence and outputting a second optical signal to the optical waveguide; the coupler is used for sequentially receiving the second optical signals according to the preset sequence and outputting third optical signals to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal; and the optical detection device is used for receiving and responding to the third optical signals in sequence according to a preset sequence and outputting optical detection signals corresponding to each grating coupler.

Description

Calibration structure and calibration method of optical fiber probe

Technical Field

The present disclosure relates to optical coupling and silicon optical device testing technologies, and in particular, to a calibration structure and a calibration method for an optical fiber probe.

Background

In the related art, a coupling angle of a grating design value is usually used for testing (for example, 8 ° (degree) and 10 °), and when a process error is too large, the coupling efficiency at an operating wavelength of the grating is sharply reduced due to a drift of a peak wavelength, so that insertion loss and a test error in a testing process are increased. Even if the grating coupling angle is required to be adjusted, a blind tuning mode is usually adopted, the coupling angle is increased or reduced, no response reference value exists, the calibration efficiency is low, and the precision is low.

Disclosure of Invention

The embodiment of the application is expected to provide a calibration structure and a calibration method of an optical fiber probe.

In a first aspect, an embodiment of the present application provides a calibration structure of a fiber probe, including: at least two grating couplers having different desired coupling angles for a particular operating wavelength, at least one coupler, an optical detection device, and an optical waveguide sequentially connecting a grating of the at least two grating couplers, the at least one coupler, and the optical detection device; the at least two grating couplers comprise grating couplers to be calibrated;

each grating coupler is used for sequentially receiving the first optical signals output by the optical fiber probes according to a preset sequence and outputting second optical signals to the optical waveguide;

the at least one coupler is used for sequentially receiving the second optical signals according to the preset sequence and outputting third optical signals to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal;

the optical detection device is configured to sequentially receive and respond to the third optical signals according to the preset sequence, and output an optical detection signal corresponding to each grating coupler, so that an actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signals, and the calibration of the optical fiber probe is achieved.

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

each grating coupler in the at least two grating couplers sequentially receives a first optical signal output by the optical fiber probe according to a preset sequence and outputs a second optical signal to the optical waveguide;

at least one coupler sequentially receives the second optical signals according to the preset sequence and outputs third optical signals to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal;

and the optical detection device sequentially receives and responds to the third optical signals according to the preset sequence and outputs optical detection signals 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 signals, and the calibration of the optical fiber probe is realized.

In a third aspect, an embodiment of the present application further provides a calibration method for an optical fiber probe, where the method includes:

under the condition of obtaining a specific working wavelength and a specific optical fiber probe angle, acquiring an optical detection signal corresponding to each grating coupler in at least two grating couplers arranged according to a preset sequence;

determining a first target optical detection signal with the maximum optical power or photocurrent from the optical detection signals corresponding to each grating coupler;

determining the specific optical fiber probe angle as an actual coupling angle of a first grating coupler corresponding to the first target optical detection signal;

determining an actual coupling angle range of the grating coupler to be tested based on the actual coupling angle of the first grating coupler;

determining an actual coupling angle of the grating coupler to be calibrated based on the actual coupling angle range.

In the embodiment of the application, the grating couplers to be calibrated are arranged in at least two grating couplers with different expected coupling angles for specific working wavelengths, each grating coupler sequentially receives the first optical signals output by the optical fiber probe according to a preset sequence, outputs the second optical signals to at least one coupler, obtains the third optical signals at the output end of at least one coupler, and finally obtains the optical detection signals of the third optical signals corresponding to each first optical signal through the detection device, so that the actual coupling angles of the grating couplers to be calibrated can be determined based on the optical detection signals. Because the difference of the 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 even coupler determined based on the optical detection signal is more accurate, that is, the calibration precision is lower, and the calibration efficiency is higher without adopting blind tuning modes such as increasing or reducing the coupling angle.

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, as claimed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

Fig. 1 is a schematic composition diagram of a calibration structure of an optical fiber probe according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of another calibration structure of a fiber-optic probe according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of another calibration structure of a fiber-optic probe according to an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of an exemplary calibration structure including a left calibrator and a right calibrator;

FIG. 5 is a schematic diagram of another exemplary calibration structure including a left calibrator and a right calibrator;

fig. 6 is a schematic flow chart illustrating an implementation of a calibration method for an optical fiber probe according to an embodiment of the present disclosure;

FIG. 7 is a schematic flow chart illustrating an implementation of another method for calibrating an optical fiber probe according to an embodiment of the present disclosure;

fig. 8 is a schematic diagram illustrating an influence of a grating etching depth on a grating coupling efficiency spectrum according to an embodiment of the present disclosure;

FIG. 9 is a schematic diagram of a grating coupling efficiency spectrum at different duty ratios according to an embodiment of the present disclosure;

FIG. 10 is a graph illustrating grating coupling efficiency spectra at different coupling angles according to an embodiment of the present disclosure;

fig. 11 is a schematic diagram of grating coupling efficiency spectra at different coupling angles according to an embodiment of the present disclosure.

Detailed Description

The present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the examples provided herein are merely illustrative of the present invention and are not intended to limit the present invention. In addition, the following embodiments are provided as partial embodiments for implementing the present invention, not all embodiments for implementing the present invention, and the technical solutions described in the embodiments of the present invention may be implemented in any combination without conflict.

It should be noted that, in the embodiments of the present invention, the terms "comprises", "comprising" or any other variation thereof are intended to cover a non-exclusive inclusion, so that a method or apparatus including a series of elements includes not only the explicitly recited elements but also other elements not explicitly listed or inherent to the method or apparatus. Without further limitation, the use of the phrase "including a. -. said." does not exclude the presence of other elements (e.g., steps in a method or elements in a device, such as portions of circuitry, processors, programs, software, etc.) in the method or device in which the element is included.

The term "and/or" herein is merely an association relationship describing an associated object, and means that there may be three relationships, e.g., U and/or W, which may mean: u exists alone, U and W exist simultaneously, and W exists alone. In addition, the term "at least one" herein means any one of a plurality or any combination of at least two of a plurality, for example, including at least one of U, W, V, and may mean including any one or more elements selected from the group consisting of U, W and V.

One key issue that cannot be ignored for silicon-based photonic integrated chips is the input and output of optical signals. Two commonly used coupling methods generally employ an end-face horizontal coupling structure or an on-chip vertical coupling structure, wherein the vertical coupling generally employs a grating coupler. The grating coupler is characterized in that the diffraction light is coupled to the optical waveguide to be transmitted through the diffraction action of the grating, so that the real-time uploading and downloading of signals can be realized, and the flexibility of the system is greatly enhanced. The grating coupler can be manufactured at any position on the substrate, so that the input and the output of light can be carried out at any waveguide position needing to be tested, and the grating coupler has the advantages of easiness in on-line testing, no need of wafer or chip pretreatment, no strict space limitation and the like.

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

In a wafer factory, process errors exist in different wafers or different regions of the same wafer in wafer production, and the performance of devices also has differences.

In order to reduce the second-order reflection and improve the coupling efficiency, the diffraction direction of the grating coupler needs to be prevented from being completely perpendicular to the chip as much as possible, and usually forms a deflection angle of about 10 degrees (degrees). Similarly, the coupling angle during testing is also one of the important conditions affecting the testing accuracy, and the shift of the peak wavelength of the grating coupler due to process errors can be improved by adjusting the coupling angle during testing and packaging.

Usually, a grating design value of the coupling angle is used for testing (for example, commonly used 8 ° and 10 °), and when the process error is too large, the coupling efficiency at the operating wavelength is sharply reduced due to the drift of the peak wavelength, thereby increasing the insertion loss and the test error in the testing process. Even if the grating coupling angle is required to be adjusted, a blind tuning mode is usually adopted, the coupling angle is increased or reduced, no response reference value exists, the calibration efficiency is low, and the precision is low.

Meanwhile, most of the fiber coupling fixtures used in the coupling stations have no means for determining the coupling angle in the field. Even in the absence of process errors, it is not guaranteed before testing that the coupling angles are 8 ° (degrees), 10 °. It is necessary to calibrate the coupling angle of the fiber probe before the test. This is the most common function of the calibrator, and is not less important than correcting test errors caused by process errors.

Fig. 1 is a schematic diagram illustrating a vertical grating coupling test apparatus in the related art, as shown in fig. 1, an optical signal emitted by a light source 101 is incident on an incident grating 103 on a surface of a first grating coupler through an optical fiber 102, the incident grating 103 transmits the optical signal to an exit grating 105 on a surface of a second grating coupler through a waveguide 104, and the optical signal on the exit grating 105 is output to a power meter through an optical fiber 106. The optical power of the optical signal output from the optical fiber 106 can be calculated by a power meter.

In view of the above technical problem, an embodiment of the present invention provides a calibration structure of an optical fiber probe, as shown in fig. 2, the calibration structure 20 of the optical fiber probe includes: at least two grating couplers 201 having different desired coupling angles for a specific operating wavelength, at least one coupler 202, an optical detection device 203, and an optical waveguide 204 sequentially connecting gratings of the at least two grating couplers 201, the at least one coupler 202, and the optical detection device 203; the at least two grating couplers 201 comprise grating couplers to be calibrated;

each grating coupler is used for sequentially receiving the first optical signals output by the optical fiber probes according to a preset sequence and outputting second optical signals to the optical waveguide 204;

the at least one coupler 202 is configured to sequentially receive the second optical signals according to the preset sequence and output a third optical signal to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal;

the optical detection device 203 is configured to sequentially receive and respond to the third optical signals according to the preset sequence, and output an optical detection signal corresponding to each grating coupler, so that an actual coupling angle of the grating coupler to be calibrated can be determined based on the optical detection signals, and the calibration of the optical fiber probe is achieved.

Here, the fiber probe may be a preset initial angle, that is, the coupling angle of the grating coupler is a preset initial angle in performing calibration of the fiber probe.

It is understood that the desired coupling angle refers to a coupling angle determined based on preset parameters of an etching depth, a duty ratio, a period, etc. of the grating coupler in designing or manufacturing the grating coupler. Although the grating coupler is designed according to the preset parameters such as the etching depth, the duty ratio and the period of the grating coupler in the manufacturing process of the grating coupler, an error exists in actual manufacturing, for example, the etching depth of the preset grating coupler is 70nm, but the actual etching depth may be 65nm or 75nm, and the change of 1nm may affect the performance of the grating coupler, so the coupling angle is expected to be the coupling angle of the grating coupler determined according to theoretical parameter design, and is not the actual coupling angle.

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

In one possible embodiment, the preset rule may be any rule set in advance. For example, the preset rule may be that the coupling angles sequentially increase or sequentially decrease by a preset angle Δ θ, and in the case that at least two grating couplers are 1 st to nth grating couplers (N grating couplers) and the corresponding expected coupling angles are θ 1 to θ N, respectively, the preset rule may be that θ 1< θ 2< θ 3< … … < θ N; and Δ θ is not specifically limited, and Δ θ may be equal or unequal. If Δ θ is to be equal, the difficulty in designing the simulation is greatly increased. The predetermined order may be the 1 st grating coupler, the 2 nd grating coupler, the 3 rd grating coupler … … N-1 st grating coupler, the nth grating coupler.

It is understood that the grating coupler is insertion loss. The first optical signal outputs a 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.

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

In one embodiment, in the case that the at least two grating couplers 201 include N grating couplers, the at least one coupler 202 may include one 1 × N coupler (N inputs and 1 output), or may include a plurality of 1 × 2 couplers (two inputs and one output).

It will be appreciated that certain insertion losses also exist for couplers. The second optical signal input into the coupler outputs a third optical signal through the coupler; the optical power of the third optical signal and the second optical signal are different, the optical power of the second optical signal is greater than the optical power of the third optical signal, and a difference between the optical power of the second optical signal and the optical power of the third optical signal corresponds to a particular insertion loss.

In some possible embodiments, the optical detection signal may be an optical power signal or a photocurrent signal. Correspondingly, the light detecting device 203 may be a grating or a Photo Detector (PD).

It is understood that, in the case that the fiber probe is at the preset initial angle, in at least two grating couplers 201 having different desired coupling angles for a specific operating wavelength, the output optical power of each grating coupler is different, 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.

In some possible embodiments, the coupler comprises two input ports and one output port; the insertion loss of a first channel and a second channel formed by the two input ports and one output port is equal; the at least one coupler comprises at least two identical couplers.

In some possible embodiments, the coupler includes N input ports and one output port; the insertion loss of the 1 st channel to the Nth channel formed by the N input ports and one output port is equal; the at least one coupler comprises 1 of the couplers; n represents the number of the at least two grating couplers.

Fig. 3 is a schematic composition diagram of another calibration structure of an optical fiber probe according to an embodiment of the present disclosure, and as shown in fig. 3, the calibration structure 30 of the optical fiber probe includes: at least two grating couplers 301, at least one coupler 302, a PD303 having different desired coupling angles for a particular operating wavelength, and an optical waveguide 304 sequentially connecting gratings of the at least two grating couplers 301, the at least one coupler 302, and the PD 303; the at least two grating couplers 301 comprise grating couplers to be calibrated;

the at least one coupler 302 is configured to sequentially receive the second optical signals according to the preset sequence and output a third optical signal to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal;

the PD303 is configured to sequentially receive and respond to the third optical signals according to the preset sequence, and output the photocurrent signal corresponding to each grating coupler, so that an actual coupling angle of the grating coupler to be calibrated can be determined based on the photocurrent signal, and the calibration of the optical fiber probe is achieved.

In the embodiment of the application, the PD is more suitable for monitoring the photocurrent of the optical signal, so that the precision of the photocurrent signal corresponding to each grating coupler detected by the PD is higher, the coupling angle of the grating even coupler determined based on the photocurrent signal is more accurate, that is, the calibration precision is lower, and the calibration efficiency is higher without adopting blind tuning modes such as increasing or reducing the coupling angle.

Fig. 4 is a schematic composition diagram of a calibration structure of a fiber optic probe according to an embodiment of the present disclosure, and as shown in fig. 4, the calibration structure 40 of the fiber optic probe includes: at least two grating couplers 401 having different desired coupling angles for a particular operating wavelength, at least one coupler 402, a grating 403, and an optical waveguide 404 sequentially connecting the grating of the at least two grating couplers 401, the at least one coupler 402, and the grating 403; the at least two grating couplers 401 comprise grating couplers to be calibrated;

the at least one coupler 402 is configured to sequentially receive the second optical signals according to the preset sequence and output a third optical signal to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal;

the grating 403 is configured to sequentially receive and respond to the third optical signal according to the preset sequence to obtain the optical output power signal corresponding to each grating coupler, so that an actual coupling angle of the grating coupler to be calibrated can be determined based on the optical output power signal, and the calibration of the optical fiber probe is achieved.

In the embodiment of the application, because the optical output power signal corresponding to each grating coupler can be obtained through the grating, the precision of the optical output power signal corresponding to each grating coupler detected through the grating is higher, the coupling angle of the grating even coupler determined based on the optical power signal is more accurate, namely, the calibration precision is lower, blind tuning modes such as increasing or reducing the coupling angle are not adopted, and the calibration efficiency is higher.

In some possible embodiments, the at least two grating couplers include 1 st to nth grating couplers sequentially arranged in the preset order; and the expected coupling angles of the 1 st to Nth grating couplers accord with a preset rule.

In some possible embodiments, the desired coupling angle of each grating coupler is related to parameters such as grating etch depth, period, duty cycle, etc. of the grating coupler.

The purpose of the embodiment of the application is to be able to assist in calibrating and testing the angle of the optical fiber probe before large-scale testing, confirm the optimal coupling angle of the grating coupler, reduce insertion loss caused by the grating coupler during testing, reduce the difference between the insertion loss of two output ports, and improve the drift of the peak wavelength of the grating coupler caused by process errors. The method provides a coupling angle reference for the package, and can also be used for evaluating the process error of the grating coupler.

In order to achieve the above purpose, the embodiment of the present application adopts the following technical solutions: a fiber optic probe alignment structure for vertical grating coupling. The calibration structure comprises a plurality of grating couplers with different optimal coupling angles as light input ends, wherein one grating coupler is a standard grating coupler used by various devices in the batch; a plurality of 1 × 2 couplers (or one 1 × N coupler) for injecting light coupled in from the gratings of the respective grating couplers into the photodetectors with the same insertion loss; a photodetector for detecting the coupling efficiency of the grating coupler; a straight waveguide connecting the grating, a 1 × 2 coupler (or 1 × N coupler), and the photodetector, and the like.

The grating coupler, the 1 × 2 coupler, the 1 × N coupler, the photodetector, the optical waveguide and the like are manufactured ON an SOI (SilicoN-ON-INsulator, SilicoN ON an insulating substrate) wafer, and can be compatible with a SilicoN-based photonic process.

In some embodiments, the standard grating coupler is a standard grating coupler used as an optical input end of each type of grating coupler device in the batch of chips, and the standard grating coupler has parameters such as a fixed etching depth, a fixed period, and a fixed duty ratio.

In some embodiments, the plurality of 1 × 2 couplers are 1 × 2 couplers of the same specification, incident light enters through one of the 2 ports of the coupler, and is output from the 1 port, it is required to ensure that laser light with the same optical power enters from any one of the 2 ports, and the optical powers output from the 1 port are the same, that is, the insertion loss of the two ports is the same.

In some embodiments, in the 1 × N coupler, incident light enters through one of N ports of the coupler and is output from the 1 port, so that it is ensured that laser light with the same optical power enters through any one of the N ports, and the optical power output from the 1 port is the same, that is, the insertion loss of the N ports is uniform.

In some embodiments, one of the N grating couplers with different optimal coupling angles is consistent with all parameters of a standard input grating coupler, and is a standard grating coupler used as an optical output end of each type of grating coupler in the batch of chips; the other grating couplers are grating couplers with parameters such as grating etching depth, period, duty ratio and the like modified, so that the optimal coupling angle under incident light with the same wavelength is slightly different from that of a standard grating coupler and the difference is known (or the peak wavelength is slightly different and the difference is known under the same coupling angle); the N grating couplers are different in optimal coupling angle and are sequentially arranged from small to large in the optimal coupling angle.

In some embodiments, the optical fiber probe calibration structure coupled with the vertical grating may be divided into two types of calibrators, i.e., a left calibrator and a right calibrator, which are respectively used for calibrating the optical fiber probes on the left and right sides, and the photodetector may be one of the two calibrators, i.e., the left calibrator and the right calibrator, or may share one photodetector.

According to the embodiment of the application, the angle of the optical fiber probe can be calibrated and tested in an auxiliary mode before large-scale testing, the optimal coupling angle of the grating coupler is confirmed, insertion loss caused by the grating coupler in testing is reduced, the difference between the insertion loss of two output ports is reduced, and the drift of the peak wavelength of the grating coupler caused by process errors is improved.

The grating couplers are all equal period gratings.

In an embodiment, the grating coupler may include all grating couplers that need to be coupled at an inclined angle and that can determine that an optimal coupling angle is obtained and sort according to a preset rule, including but not limited to a uniform grating (unit period, duty ratio, and etching depth of the grating are all constant values), a non-uniform grating (variable period, variable duty ratio, and variable etching depth), a two-dimensional grating, a blazed grating, and the like.

In some embodiments, the plurality of 1 × 2 couplers are 1 × 2 couplers of the same specification, and the insertion loss incident from any one port is the same; the insertion loss incident from any port of the plurality of 1 × N couplers is the same.

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

In some embodiments, the standard grating coupler is designed with a fixed value of standard coupling angle, e.g., 10 °, where the peak wavelength is the design operating wavelength.

In some embodiments, the optimal coupling angle of the standard grating coupler is the angle of the fiber probe perpendicular to the SOI at which the coupling efficiency is highest at a particular wavelength.

Fig. 5 is a schematic composition diagram of a calibration structure including two types of left and right calibrators according to an embodiment of the present disclosure, and as shown in fig. 5, the left calibrator 50 and the right calibrator 51 may be completely the same, where the left calibrator 50 includes a 1 st to 4 th grating coupler 501, a 1 st to 3 rd coupler (1 × 2 coupler) 502, and an optical detection device 503, and a connection line in the drawing may be regarded as a connected optical waveguide.

It will be appreciated that in an actual alignment configuration, the left-hand aligner 50 and the right-hand aligner 51 may each include 8, 16 or more grating couplers.

Fig. 6 is a schematic diagram of another calibration structure including two types of left and right collimators according to an embodiment of the present disclosure, and as shown in fig. 6, the left collimator 60 and the right collimator 61 may be identical, where the left collimator 60 includes 1 st to nth grating couplers 601, 1 × N coupler 602, and PD 603, and a connecting line in the drawing may be regarded as a connected optical waveguide.

On the basis of the foregoing embodiments, the present application provides a calibration method for an optical fiber probe, which is applied to the above calibration structure for an optical fiber probe, as shown in fig. 7, and the method includes:

step S701: each grating coupler in the at least two grating couplers sequentially receives a first optical signal output by the optical fiber probe according to a preset sequence and outputs a second optical signal to the optical waveguide;

step S702: at least one coupler sequentially receives the second optical signals according to the preset sequence and outputs third optical signals to the optical waveguide; the difference of the optical power between each first optical signal and the corresponding third optical signal is equal;

step S703: and the optical detection device sequentially receives and responds to the third optical signals according to the preset sequence and outputs optical detection signals 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 signals, and the calibration of the optical fiber probe is realized.

Fig. 8 is a schematic implementation flowchart of another calibration method for an optical fiber probe according to an embodiment of the present application, and as shown in fig. 8, the flowchart includes:

step S801: under the condition of obtaining a specific working wavelength and a specific optical fiber probe angle, acquiring an optical detection signal corresponding to each grating coupler in at least two grating couplers arranged according to a preset sequence;

it will be appreciated that the magnitude of the optical probe signal for each grating coupler is different for a particular wavelength of operation and a particular fiber optic probe angle. The optical probe signal for each grating coupler is related to the desired coupling angle selected for each grating coupler.

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

Step S802: determining a first target optical detection signal with the maximum optical power or photocurrent from the optical detection signals corresponding to each grating coupler;

in some possible embodiments, the determining the first target optical detection signal with the maximum optical power or photocurrent from the optical detection signals corresponding to each grating coupler may be querying the optical detection signal with the maximum optical power or photocurrent in the optical detection signals corresponding to each grating coupler, and determining the queried optical detection signal with the maximum optical power or photocurrent as the first target optical detection signal.

Step S803: determining the specific optical fiber probe angle as an actual coupling angle of a first grating coupler corresponding to the first target optical detection signal;

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;

in some possible embodiments, determining the actual coupling angle range of the grating coupler to be tested based on the actual coupling angle of the first grating coupler comprises determining the actual coupling angle range of the grating coupler to be tested from an angle difference between the first target grating coupler and the desired coupling angle of the grating coupler to be tested and the actual coupling angle of the first grating coupler.

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

In one embodiment, 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 selected from the determined actual coupling angle range may be determined as the actual coupling angle of the grating coupler to be calibrated.

In another embodiment, the actual coupling angle of the grating coupler to be calibrated is determined based on the actual coupling angle range, which may be at least two grating couplers whose expected coupling angle ranges are reset based on the determined 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.

In practical applications, the steps S801 to S805 may be implemented by a control Unit, and the control Unit may 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.

In the embodiment of the present application, when the difference between the expected coupling angles of two adjacent grating couplers in the at least two grating couplers is the first angle precision, the precision of the actual grating coupling angle determined by the above method will be smaller than the first angle precision.

The embodiment of the present application further provides a calibration method for an optical fiber probe, which includes:

step 90: under the condition of obtaining a specific working wavelength and a specific optical fiber probe angle, acquiring an optical detection signal corresponding to each grating coupler in at least two grating couplers arranged according to a preset sequence; the expected coupling angle of each grating coupler accords with a preset rule;

step 91: determining a first target optical detection signal with the maximum optical power or photocurrent from the optical detection signals corresponding to each grating coupler;

and step 92: determining the specific optical fiber probe angle as an actual coupling angle of a first grating coupler corresponding to the first target optical detection signal;

step 93: acquiring the preset rule;

step 94: determining the 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;

step 95: determining an actual coupling angle of the grating coupler to be calibrated based on the actual coupling angle range.

In the embodiment of the application, because the expected coupling angle of each grating coupler in the at least two grating couplers accords with the preset rule, 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 under the condition of acquiring the preset rule.

In the embodiment of the present application, the at least two grating couplers include grating couplers GC1, GC2, GC3 to GCn, and GC1, GC2, GC3 to GCn are designed to have grating couplers with different optimal coupling angles (desired coupling angles) at a specified operating wavelength and the coupling efficiency of each grating coupler is nearly uniform when it is at the optimal coupling angle. At least one coupler is a 1 xn coupler; the light detection device is a PD.

The grating CGnorm between the middlemost of all gratings is a standard grating coupler used by various devices in the batch. All the optimal coupling angles of the grating under the specified working wavelength are theta 1, theta 2, theta 3 to theta n in sequence, the optimal coupling angles are designed to be theta 1< theta 2< theta 3< … … < theta n, and the difference value between two adjacent optimal coupling angles is delta theta and is a known value. And delta theta is the minimum resolution of the calibration structure, and the calibration precision can be improved by increasing the number of grating couplers and reducing delta theta.

Calibration of the left fiber optic probe is initiated with an initial angle θ of the fiber optic probe. Firstly, a reverse bias voltage is provided for PD, and a commercial laser tube device is adopted to input direct current light with fixed wavelength, wherein the wavelength is the working wavelength of various optical devices in the batch. The laser is sequentially coupled with the N grating couplers on the left side of the calibration structure through the optical fiber probe, the light coupled into the optical waveguide is injected into the photoelectric detector through the 1 XN couplers IN the same insertion loss, and the photoelectric detector records the optical power coupled into the photoelectric detector by the N grating couplers IN the form of photocurrent, namely I1, I2, I3 to IN. Since the insertion loss values of the 1 × N couplers incident on the ports are the same, the magnitude order of the photocurrent is considered to be the magnitude order of the coupling efficiency of each grating coupler.

After the test is finished, comparing the magnitude of each photocurrent, for example, where Im is the maximum photocurrent, that is, the fiber coupling angle θ at this time is considered to be the optimum coupling angle of GCm at the operating wavelength, which can be conveniently calculated, and θ + (norm-m) Δ θ is the optimum coupling angle of the standard grating coupler CGnorm, at this time, the coupling angle of the fiber coupler is only required to be increased by (norm-m) Δ θ, that is, the fiber probe is adjusted to the optimum coupling angle of the standard grating coupler. In order to avoid errors, the calibration process can be carried out once or for many times, Inorm is ensured to be calibrated to the maximum value, the calibration is completed, the optimal coupling small angle of the optical fiber probe is compared with a theoretical value, and the error is smaller than delta theta.

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

Fig. 9 is a schematic diagram illustrating an influence of a grating etching depth on a grating coupling efficiency spectrum according to an embodiment of the present disclosure, as shown in fig. 9, where an abscissa is a wavelength in nm, and an ordinate is a coupling efficiency in dimensionless units; the curves 900 to 909 correspond to curves representing grating coupling efficiency with a grating etching depth of 65 to 74nm, respectively. It can be seen that the curves of grating coupling efficiency for different grating etch depths (differing by 1nm) are quite different and the wavelength corresponding to the highest point of grating coupling efficiency increases with increasing grating etch depth.

Fig. 10 is a schematic diagram of a coupling efficiency spectrum of a grating under different duty ratios according to an embodiment of the present application, where, as shown in fig. 10, the abscissa is wavelength in nm, and the ordinate is coupling efficiency in dimensionless units; the curves 1000 to 1006 correspond to curves representing grating coupling efficiencies at duty ratios of 48%, 49%, 49.5%, 50%, 50.5%, 51%, and 52%, respectively. It can be seen that the curves of grating coupling efficiency for different light duty cycles (0.5% difference) are quite different and the wavelength corresponding to the highest point of grating coupling efficiency increases with increasing duty cycle.

Fig. 11 is a schematic diagram of a grating coupling efficiency spectrum at different coupling angles according to an embodiment of the present application, as shown in fig. 11, where the abscissa is wavelength in nm and the ordinate is coupling efficiency in dimensionless units; the curves 1100 to 1104 correspond to curves representing the grating coupling efficiency when the coupling angle is 8 to 12 degrees, respectively. It can be seen that the curves of grating coupling efficiency for different coupling angles (1 degree difference) are quite different and the highest point of grating coupling efficiency decreases with increasing coupling angle for the corresponding wavelength.

In some embodiments, functions of or modules included in the apparatus provided in the embodiments of the present application may be used to perform the method described in the above method embodiments, and the implementation thereof may refer to the description of the above method embodiments, and for brevity, will not be described again here.

The foregoing description of the various embodiments is intended to highlight various differences between the embodiments, and the same or similar parts may be referred to each other, and for brevity, will not be described again herein.

The methods disclosed in the method embodiments provided by the present application can be combined arbitrarily without conflict to obtain new method embodiments.

Features disclosed in various product embodiments provided by the application can be combined arbitrarily to obtain new product embodiments without conflict.

The features disclosed in the various method or apparatus embodiments provided herein may be combined in any combination to arrive at new method or apparatus embodiments without conflict.

Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solutions of the present application may be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk) and includes instructions for enabling a terminal (such as a mobile phone, a computer, a server, an air conditioner, or a network device) to execute the method according to the embodiments of the present application.

While the present embodiments have been described with reference to the accompanying drawings, the present embodiments are not limited to the above-described embodiments, which are merely illustrative and not restrictive, and it will be apparent to those of ordinary skill in the art that many more modifications and variations can be made in the present embodiments without departing from the spirit of the disclosure and the scope of the appended claims.

Claims

1. A calibration structure for a fiber optic probe, comprising: at least two grating couplers having different desired coupling angles for a particular operating wavelength, at least one coupler, an optical detection device, and an optical waveguide sequentially connecting a grating of the at least two grating couplers, the at least one coupler, and the optical detection device; the at least two grating couplers comprise grating couplers to be calibrated;

2. The calibration structure of the fiber optic probe according to claim 1, wherein the coupler comprises two input ports and one output port; the insertion loss of a first channel and a second channel formed by the two input ports and one output port is equal; the at least one coupler comprises at least two identical couplers.

3. The calibration structure of the fiber optic probe according to claim 1, wherein the coupler comprises N input ports and one output port; the insertion loss of the 1 st channel to the Nth channel formed by the N input ports and one output port is equal; the at least one coupler comprises 1 of the couplers; n represents the number of the at least two grating couplers.

4. The calibration structure of the fiber-optic probe according to any one of claims 1 to 3, wherein the light detection means comprises a photodetector PD; the optical detection signal comprises a photocurrent signal;

correspondingly, the PD is configured to sequentially receive and respond to the third optical signal according to the preset sequence, and output the photocurrent signal corresponding to each grating coupler, so that an actual coupling angle of the grating coupler to be calibrated can be determined based on the photocurrent signal, and the calibration of the optical fiber is achieved.

5. A calibration structure for a fiber optic probe according to any of claims 1 to 3, wherein said light detection means comprises a grating; the optical detection signal comprises an optical output power signal;

correspondingly, the grating is configured to sequentially receive and respond to the third optical signal according to the preset sequence to obtain the optical output power signal corresponding to each grating coupler, so that an actual coupling angle of the grating coupler to be calibrated can be determined based on the optical output power signal, and the calibration of the optical fiber is achieved.

6. The calibration structure of the fiber-optic probe according to any one of claims 1 to 3, wherein the at least two grating couplers comprise 1 st to Nth grating couplers arranged in sequence in the preset order; and the expected coupling angles of the 1 st to Nth grating couplers accord with a preset rule.

7. The calibration structure of the fiber-optic probe according to any one of claims 1 to 3, wherein the desired coupling angle of each grating coupler is related to parameters of grating etching depth, period, duty cycle, etc. of the grating coupler.

8. A method for calibrating an optical fiber probe, which is applied to the calibration structure for an optical fiber probe according to any one of the above items 1 to 7, the method comprising:

9. A method of calibrating a fiber optic probe, the method comprising:

10. The method of claim 9, wherein the desired coupling angle of each grating coupler conforms to a predetermined rule; the determining the actual coupling angle range of the grating coupler to be tested based on the actual coupling angle of the first grating coupler comprises:

acquiring the preset rule;

and determining the 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.