Method and device for testing common mode rejection ratio

Abstract

The embodiment of the invention provides a common-mode rejection ratio testing method and device, and the method comprises the steps: constructing a target interferometer through two same optical mixers to be tested; detecting the extinction ratio of the target interferometer; and determining the direct-current common-mode rejection ratio of the optical mixer to be detected according to the extinction ratio. According to the technical scheme, the detection steps of the direct-current common-mode rejection ratio can be well simplified, and the detection efficiency is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to but are not limited to the field of optical chip testing technology, and in particular to a common mode rejection ratio testing method and device thereof. Background Art

[0002] The mixer in the coherent optical receiver is an important component of the receiver. Its function is to make the local oscillator light and the signal light coherent at different phases and output them into four paths to the optical detector. Among them, one of the performance indicators of the coherent optical receiver is the common mode rejection ratio, which is divided into the DC common mode rejection ratio and the RF common mode rejection ratio; the DC common mode rejection ratio is mainly determined by the loss difference of different channels of the mixer and the consistency of the light detection responsivity of different channels of the mixer; in practical applications, since the consistency of the light detection responsivity of the mixer is good, the DC common mode rejection ratio of the mixer mainly depends on the loss difference of different channels of the mixer; however, in the process of testing the DC common mode rejection ratio of the mixer, the laser of the tunable laser needs to be coupled into the mixer chip through the optical fiber, and multiple probes are connected to the positive and negative poles of multiple light detectors at the same time to detect the photocurrent of multiple light detectors on the chip, scan the wavelength to detect multiple photocurrents, and perform needle puncture and optical coupling tests at the same time, which is more complicated, making the test efficiency low. Summary of the invention

[0003] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0004] The embodiments of the present application provide a common mode rejection ratio test method and device thereof, which solve the technical problem that the current DC common mode rejection ratio test process is relatively complicated.

[0005] In a first aspect, an embodiment of the present application provides a common mode rejection ratio testing method, comprising:

[0006] A target interferometer is constructed by two identical optical mixers to be measured;

[0007] detecting the extinction ratio of the target interferometer;

[0008] A direct current common mode rejection ratio of the optical mixer to be measured is determined according to the extinction ratio.

[0009] In a second aspect, an embodiment of the present application further provides a common mode rejection ratio testing device, comprising a target interferometer constructed by two identical optical mixers to be tested, wherein the common mode rejection ratio of the optical mixers to be tested is determined according to the extinction ratio of the target interferometer.

[0010] The embodiments of the present application include: in the process of testing the DC common mode rejection ratio, firstly, a target interferometer is constructed by two identical optical mixers to be tested; then, the extinction ratio of the target interferometer is detected; finally, the DC common mode rejection ratio of the optical mixer to be tested is determined according to the extinction ratio; by constructing a target interferometer by two identical optical mixers to be tested, then only the extinction ratio of the target interferometer needs to be measured to indirectly reflect the DC common mode rejection ratio of the optical mixer to be tested, and there is no need to detect the photocurrent of the multi-channel optical detector on the optical mixer chip as usual, which greatly simplifies the detection steps of the DC common mode rejection ratio and improves the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings are used to provide further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0012] Figure 1 is a flow chart of a common mode rejection ratio testing method provided by an embodiment of the present application;

[0013] Figure 2 This is a classic 2*4MMI mixer schematic;

[0014] Figure 3 is a flowchart of constructing a target interferometer provided by an implementation of the present application;

[0015] Figure 4 is a flowchart of constructing a target interferometer provided by another embodiment of the present application;

[0016] Figure 5 It is a schematic diagram of the application of the mixer CMRR test structure of the present application in a 2*4MMI mixer;

[0017] Figure 6 yes Figure 5 Schematic diagram of interference spectrum measured by CMRR test structure;

[0018] Figure 7 is based on Figure 6 Schematic diagram of the extinction ratio extracted from the interference spectrum;

[0019] Figure 8 is a flowchart of constructing a target interferometer provided by another embodiment of the present application;

[0020] Fig. 9 It is a classic mixer diagram consisting of a 2*2 beam splitter and a 1*2 beam splitter;

[0021] Fig.10 yes Fig. 9 Schematic diagram of the CMRR_LO test structure of the mixer;

[0022] Fig.11 yes Fig. 9 Schematic diagram of mixer CMRR_RX test structure;

[0023] Fig.12 yes Fig.10 Schematic diagram of the interference spectrum of the CMRR test structure;

[0024] Fig.13 is based on Fig.12 Schematic diagram of the extinction ratio extracted from the interference spectrum;

[0025] Fig.14 A flowchart for determining a DC common mode rejection ratio based on an extinction ratio is provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0027] In the description of this application, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0028] In addition, terms such as "upper", "above", "lower", "below", etc. used in this application to indicate spatial relative positions are used for the purpose of convenience to describe the relationship of one unit or feature relative to another unit or feature as shown in the accompanying drawings. Terms of spatial relative position may be intended to include different orientations of the device in use or operation other than the orientation shown in the figure. For example, if the device in the figure is turned over, the unit described as being "below" or "beneath" other units or features will be located "above" the other units or features. Therefore, the exemplary term "below" can encompass both the above and below orientations. The device can be oriented in other ways (rotated 90 degrees or other orientations), and the spatially related descriptors used in this article are interpreted accordingly.

[0029] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0030] The embodiment of the present application provides a common mode rejection ratio test method and a device thereof, and the common mode rejection ratio test method comprises: firstly, constructing a target interferometer by two identical optical mixers to be tested; then detecting the extinction ratio of the target interferometer; finally, determining the DC common mode rejection ratio of the optical mixer to be tested according to the extinction ratio; by constructing a target interferometer by two identical optical mixers to be tested, then only the extinction ratio of the target interferometer needs to be measured to indirectly reflect the DC common mode rejection ratio of the optical mixer to be tested, and there is no need to detect the photocurrent of the multi-channel optical detector on the optical mixer chip as usual, which greatly simplifies the detection steps of the DC common mode rejection ratio and improves the detection efficiency.

[0031] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0032] like Figure 1 As shown, a flowchart of a common mode rejection ratio test method provided by an embodiment of the first aspect of the present application is shown. The method includes but is not limited to step S100, step S200 and step S300.

[0033] Step S100, constructing a target interferometer by using two identical optical mixers to be measured;

[0034] Step S200, detecting the extinction ratio of the target interferometer;

[0035] Step S300: determining a DC common mode rejection ratio of the optical mixer to be measured according to the extinction ratio.

[0036] In an embodiment of the present application, firstly, a target interferometer is constructed by two identical optical mixers to be measured; then, the extinction ratio of the target interferometer is detected; finally, the DC common mode rejection ratio of the optical mixer to be measured is determined according to the extinction ratio; by constructing a target interferometer by two identical optical mixers to be measured, then only the extinction ratio of the target interferometer needs to be measured to indirectly reflect the DC common mode rejection ratio of the optical mixer to be measured, and there is no need to detect the photocurrent of the multi-channel optical detector on the optical mixer chip as usual, which greatly simplifies the detection steps of the DC common mode rejection ratio and improves the detection efficiency.

[0037] It is worth noting that Figure 2As shown in FIG. 1 , the optical mixer in the coherent optical receiver is an important part of the receiver. Its function is to make the local oscillator light and the signal light coherent at different phases, and output them into four paths, In, Ip, Qn, and Qp, to the optical detector PD for reception. The phase difference between the local oscillator LO and the signal RX light coherent in the four paths is different. Among them, In and Ip differ by 180° for differential amplification, Qn and Qp differ by 180° for differential amplification, and I and Q differ by 90°. One of the indicators of coherent receivers is the common mode rejection ratio (CMRR), which is divided into DC and RF. DC_CMRR is mainly determined by the consistency of the n-way and p-way insertion loss of the optical chip mixer and the consistency of the n-way and p-way PD responsivity, and is defined as CMRR = 20log (△I / (I n+I p)), where △I = |I nI p|, I n and I p are the DC state photocurrents of the n-way and p-way, and DC_CMRR is divided into two indicators: LO light input and RX light input. In CMRR_LO, this photocurrent is measured by only LO light input; in CMRR_RX, this photocurrent is measured by only RX light input. In practical applications, the consistency of PD responsivity is good, and the difference between the n-way and p-way photocurrents mainly comes from the difference in channel loss of the optical mixer. Therefore, when designing the optical mixer and testing and verifying the components, it is necessary to pay attention to its CMRR in the full working band. For a mixer, the general approach to testing its CMRR is to use waveguides to output to optical fibers at four outlets for testing or to connect to on-chip PDs at four outlets for photocurrent testing. This requires a tunable laser to couple into the chip through optical fibers, and multiple probes to simultaneously connect the positive and negative electrodes of multiple PDs to detect the photocurrents of multiple PDs on the chip. The wavelength is scanned to detect multiple photocurrents, and needle puncture and optical coupling tests are performed simultaneously, which makes the testing process more complicated and the test efficiency is low.

[0038] It is worth noting that the embodiment of the present application tests and obtains the DC common mode rejection ratio DC_CMRR of the optical mixer by equivalently converting it into the extinction ratio of the interferometer structure; taking the I-way CMRR of the test mixer as an example (the Q-way principle is similar), the output ends I n-way exit waveguides of two identical optical mixers a and b are connected, and the I p-way exit waveguides are connected. The two docking arms and the two mixers a and b constitute an asymmetric Mach-Zehnder interferometer AMZI as a whole. The free spectral range (FSR) of AMZI is determined by the length difference of the two pairs of connection waveguides. By setting a suitable length difference, a suitable free spectral range can be obtained to facilitate testing. Using passive testing (i.e., the laser of the tunable laser enters the chip through optical fiber coupling, passes through AMZI, is coupled from the chip output into the output optical fiber, and finally enters the optical power meter to detect the power, and the spectrum can be measured by scanning the wavelength), the extinction ratio (Extent ion Ratio, ER) of AMZI can be tested, and the DC_CMRR value of the mixer can be obtained.

[0039] In an embodiment of the present application, two optical mixers to be tested are combined into an interferometer, and a test optical signal is input into the combined interferometer, and a detection optical signal is obtained from an output branch of the combined interferometer. Finally, the extinction ratio of the interferometer is determined by the detection optical signal. Since the extinction ratio is related to the DC common-mode rejection ratio of the optical mixer, the DC common-mode rejection ratio of the optical mixer can be determined by the extinction ratio of the interferometer.

[0040] like Figure 3 As shown, the above step S100 may include but is not limited to step S110.

[0041] Step S110, connecting the first differential pair positive splitting branches of the two optical mixers to be measured through a first waveguide, and connecting the first differential pair negative splitting branches of the two optical mixers to be measured through a second waveguide, so that the two identical optical mixers to be measured form a target interferometer.

[0042] In an embodiment of the present application, in the process of constructing a target interferometer using two identical optical mixers to be measured, the first differential pair positive splitting branches of the two optical mixers to be measured can be connected through a first waveguide, and the first differential pair negative splitting branches of the two optical mixers to be measured can be connected through a second waveguide, thereby forming a target interferometer.

[0043] Exemplarily, in the process of measuring the DC common-mode rejection ratio of the in-phase path of an optical mixer, the differential pair of positive splitting branches of the in-phase path of one of the optical mixers can be connected to the differential pair of positive splitting branches of the in-phase path of another identical optical mixer, and the differential pair of negative splitting branches of the in-phase path of one of the optical mixers can be connected to the differential pair of negative splitting branches of the in-phase path of another identical optical mixer, and then two identical optical mixers can be used to construct an interferometer for measuring the extinction ratio of the in-phase path. In addition, in the process of measuring the DC common-mode rejection ratio of the orthogonal phase path of the optical mixer, the differential pair of positive light splitting branches of the orthogonal phase path of one of the optical mixers can be connected to the differential pair of positive light splitting branches of the orthogonal phase path of another identical optical mixer, and the differential pair of negative light splitting branches of the orthogonal phase path of one of the optical mixers can be connected to the differential pair of negative light splitting branches of the orthogonal phase path of another identical optical mixer, and then two identical optical mixers can be used to construct an interferometer for measuring the extinction ratio of the orthogonal phase path.

[0044] It is worth noting that the first waveguide and the second waveguide referred to in the embodiments of the present application are connecting lines of the same nature. They are distinguished by "first" and "second" mainly to make the explanation of the subsequent embodiments clearer and more unambiguous. It should not be assumed that the two are connecting lines of different natures.

[0045] like Figure 4 As shown, after the above step S110, connecting the first differential pair negative splitting branches of the two optical mixers to be measured through the second waveguide, the method may also include but is not limited to step S120.

[0046] Step S120, performing termination processing on the second differential pair positive light splitting branches and the second differential pair negative light splitting branches of the two optical mixers to be tested.

[0047] In some embodiments of the present application, the first differential pair positive splitting branches of two optical mixers to be measured are connected through a first waveguide, and the first differential pair negative splitting branches of the two optical mixers to be measured are connected through a second waveguide. In the process of constructing an interferometer, it is also necessary to terminate the second differential pair positive splitting branches and the second differential pair negative splitting branches of the two optical mixers to be measured, and use anti-reflection waveguide termination to eliminate the subsequent branch interference effects, so that the subsequent extinction ratio measurement can be more accurate.

[0048] For example, the test structure for testing the DC CMRR of the LO-to-I path is as follows: Figure 5 As shown, the I n waveguides of the two optical mixers are butted, and the I p waveguides are butted, wherein the connection length of the I p waveguide is longer than that of the I n waveguide by dL, forming an FSR of MZI, where λ 0is the central wavelength of the free spectral range, n g is the group refractive index of the waveguide. Figure 5 The crossed ones are Q-path exits, indicating that their waveguides use anti-reflection waveguide terminations to eliminate the impact. Similarly, the Q-path CMRR test structure connects the currently terminated Qn and Qp paths in pairs, and terminates the In and Ip paths with anti-reflection treatment. If you want to perform a CMRR test on the RX input light, just switch the In and Out on the left from LO to another entrance on the left. The In and Ip paths of the 2-input and 4-output MMI only receive half of the input light energy in total. Similarly, only half of the total energy of the In and Ip combined waves is output from the corresponding exits. Therefore, the highest point of the interference spectrum has a total system loss of 6dB. The MZI transmission spectrum of a channel test is obtained as follows Figure 6 However, this does not affect the highest and lowest point readings and the calculation of the extinction ratio. Figure 6 The extinction ratio can be read as a function of wavelength. Figure 7 As shown, the corresponding CMRR is the negative value of the measured ER. It can be seen that for this mixer, the CMRR degrades at the edge wavelength of the C-band, but the result is still better than -20dB.

[0049] In some embodiments of the present application, in the process of terminating the splitting branch, the termination can be performed by at least one of the following methods: doping absorption; germanium absorption; anti-reflection based on end coupler; bending and winding to generate loss. Through the above termination methods, the interference effect of other branches can be well eliminated, so that the extinction ratio measurement of the corresponding branch can be more accurate, and thus the measurement of the common mode rejection ratio can also be more accurate.

[0050] In some embodiments of the present application, in the process of constructing a target interferometer based on two identical optical mixers, the first differential pair of positive light-splitting branches are the differential pair of positive light-splitting branches of the in-phase path, the first differential pair of negative light-splitting branches are the differential pair of negative light-splitting branches of the in-phase path, the second differential pair of positive light-splitting branches are the differential pair of positive light-splitting branches of the quadrature phase path, and the second differential pair of negative light-splitting branches are the differential pair of negative light-splitting branches of the quadrature phase path. Alternatively, the first differential pair of positive light-splitting branches are the differential pair of positive light-splitting branches of the quadrature phase path, the first differential pair of negative light-splitting branches are the differential pair of negative light-splitting branches of the quadrature phase path, the second differential pair of positive light-splitting branches are the differential pair of positive light-splitting branches of the in-phase path, and the second differential pair of negative light-splitting branches are the differential pair of negative light-splitting branches of the in-phase path. Among them, the differential pair of positive splitting branches of the in-phase path is the I n path mentioned in the above embodiment, the differential pair of negative splitting branches of the in-phase path is the I p path mentioned in the above embodiment, the differential pair of positive splitting branches of the orthogonal phase path is the Qn path mentioned in the above embodiment, and the differential pair of negative splitting branches of the orthogonal phase path is the Qp path mentioned in the above embodiment.

[0051] like Figure 8 As shown, when the optical mixer to be measured is formed by cascading a 1×2 beam splitter and a 2×2 beam splitter, the above step S100 may include but is not limited to step S130.

[0052] Step S130, connecting the third differential pair positive splitting branches of the 2×2 beam splitters of the two optical mixers to be tested through the first waveguide, and connecting the third differential pair negative splitting branches of the 2×2 beam splitters of the two optical mixers to be tested through the second waveguide, so that the two 2×2 beam splitters form a target interferometer.

[0053] In some embodiments of the present application, when the optical mixer to be tested is formed by cascading a 1×2 beam splitter and a 2×2 beam splitter, in the process of constructing an interferometer using this type of optical mixer, the third differential pair of positive splitting branches of the 2×2 beam splitters of the two optical mixers to be tested can be connected through a first waveguide, and the third differential pair of negative splitting branches of the 2×2 beam splitters of the two optical mixers to be tested can be connected through a second waveguide, so that the two 2×2 beam splitters can form a target interferometer. In the process of testing the DC common mode rejection ratio of the optical mixer formed by cascading beam splitters, only part of the beam splitters need to be combined and tested, and the entire optical mixer does not need to be combined and tested, so that the process of DC common mode rejection ratio testing can be simpler and faster.

[0054] In the embodiment of the present application, for an optical mixer formed by cascading beam splitters, during the measurement process, only the beam splitter causing the n and P losses of the optical mixer may be concerned; for example, Fig. 9 As shown in the figure, a mixer with 1×2 and 2×2 beam splitters in cascade is used. It first divides the LO or RX light into I and Q paths, and then divides the RX or LO into n and p through the two 2×2 beam splitters on the left and right. The difference in n and p losses of this type of mixer is determined by the 2×2 beam splitters on the left and right sides. Therefore, Fig.10 and Fig.11 As shown, in the process of measuring the DC common mode rejection ratio of such optical mixers, it is only necessary to connect the third differential pair positive light splitting branches of the 2×2 beam splitters of the two optical mixers through a waveguide, and to connect the third differential pair negative light splitting branches of the 2×2 beam splitters of the two optical mixers through a waveguide; for example, in the process of testing the DC common mode rejection ratio of the I-channel of the two optical mixers, it is only necessary to combine and connect the 2×2 beam splitters for I-channel splitting in the two optical mixers, so as to realize the connection construction processing of the interferometer, and prepare for the measurement of the DC common mode rejection ratio of the I-channel of the optical mixer.

[0055] For a mixer using an adiabatic coupler as a 2×2 beam splitter, the spectrum of the tested MZI structure is as follows: Fig.12 As shown, the extracted ER Fig.13As shown in the figure, the wavelength dependence is small. The corresponding CMRR is the negative value of the measured ER, and the CMRR is better than -30dB in the entire C-band.

[0056] like Fig.14 As shown, the above step S300 may include but is not limited to step S310.

[0057] Step S310, performing an inversion operation on the extinction ratio to obtain a DC common mode rejection ratio of the optical mixer to be measured.

[0058] In some embodiments of the present application, after constructing a target interferometer by two identical optical mixers to be measured, the extinction ratio of the target interferometer is detected and processed, and finally the DC common mode rejection ratio of the optical mixer to be measured is obtained by performing an inverse operation on the measured extinction ratio.

[0059] It is worth noting that when testing CMRR_LO, the interferometer inputs light from the LO port of mixer a / b, and after MZI interference, the light is emitted from the LO port of mixer b / a. The wavelength is scanned, and the output light changes between coherent superposition and destructive, that is:

[0060]

[0061] Among them, Tab is the light entering from mixer a and exiting from mixer b, Tba is the light entering from mixer b and exiting from mixer a, the LO-In transmittance of mixers a and b is tn1 and tn2, and the LO-Ip transmittance is tp1 and tp2. When the two paths of light are coherently offset, the light output is the minimum value on the left side of the above formula, and when the two paths of light are coherently superimposed, the light output is the maximum value on the right side of the above formula. As the wavelength is scanned, a maximum and minimum value appear every time a FSR is passed, and an extinction ratio ER can be obtained. By scanning the entire required wavelength, an ER curve with an accuracy of one FSR per point can be obtained.

[0062] Because they are located in close proximity on the same chip, it can be assumed that the performance characteristics of mixers a and b are very similar, that is, t n1 =t n2 =t n ,t p1 =t p2 =t p ,but

[0063]

[0064] It can be concluded that the absolute value of the LO-in-LO-out ER of the interferometer structure is equal to CMRR_LO, but has the opposite sign (extinction ratio is generally defined as a positive value, and CMRR is defined as a negative value). In this way, the LO-input CMRR of path I can be measured by measuring ER. The entire process does not use multiple photodetectors or optical power comparisons of multiple channels, and the test process is relatively simple.

[0065] In some embodiments of the present application, the above-mentioned step S200 may include but is not limited to step S210, step S220 and step S230.

[0066] Step S210, inputting a test optical signal to a target interferometer;

[0067] Step S220, performing interference processing on the test optical signal based on the target interferometer and obtaining a detection optical signal from an output branch of the target interferometer;

[0068] Step S230: determining an extinction ratio based on the detected optical signal.

[0069] In some embodiments of the present application, in the process of measuring the extinction ratio of a target interferometer, a test optical signal can be first input into the target interferometer; then, interference processing is performed on the test optical signal based on the target interferometer and a detection optical signal is obtained from an output branch of the target interferometer; finally, the extinction ratio of the target interferometer is determined based on the detection optical signal.

[0070] In some embodiments of the present application, the test optical signal may be obtained through but not limited to step S211 , step S212 , and step S213 .

[0071] Step S211, determining a waveguide length difference based on the first waveguide and the second waveguide;

[0072] Step S212, determining the free spectrum range according to the waveguide length difference;

[0073] Step S213: generating a test optical signal according to the free spectrum range.

[0074] In some embodiments of the present application, in the process of determining the test optical signal input to the target interferometer, the waveguide length difference is first determined based on the first waveguide and the second waveguide; then the free spectrum range is determined according to the waveguide length difference; finally, the corresponding test optical signal can be generated according to the free spectrum range. Because the free spectrum range of the interferometer is determined by the length difference between the two pairs of waveguides, setting a suitable length difference can obtain a suitable free spectrum range to facilitate testing the extinction ratio of the interferometer.

[0075] In some embodiments of the present application, the above-mentioned step S212 may include but is not limited to step S2121 and step S2122.

[0076] Step S2121, obtaining the group refractive index of the first waveguide and the second waveguide and the center wavelength of the free spectral range;

[0077] Step S2122, calculating the free spectral range according to the group refractive index, the central wavelength and the waveguide length difference.

[0078] In some embodiments of the present application, in the process of determining the free spectral range, the group refractive index of the first waveguide and the second waveguide and the central wavelength of the free spectral range are first obtained; finally, the free spectral range can be determined based on the group refractive index, the central wavelength and the waveguide length difference.

[0079] For example, the group refractive index in the embodiment of the present application is the group refractive index of the waveguide, and the central wavelength is the central wavelength of the free spectrum range; the calculation formula of the free spectrum range FSR can be expressed as follows: Among them, λ 0 is the central wavelength, n g is the group refractive index of the waveguide, and dL is the length difference between the two waveguides.

[0080] In some embodiments of the present application, the above-mentioned step S230 may include but is not limited to step S231 and step S232.

[0081] Step S231, performing wavelength scanning processing on the detection light signal to obtain an output spectrum;

[0082] Step S232, obtaining the extinction ratio based on the output spectrum.

[0083] In some embodiments of the present application, in the process of determining the extinction ratio based on the detected light signal, the detected light signal is first subjected to wavelength scanning processing to obtain an output spectrum; and then the extinction ratio can be determined based on the output spectrum.

[0084] It is worth noting that the output spectrum can be obtained by measuring and processing the detection light signal based on the optical power meter and then performing wavelength scanning on the detection light signal; in the output spectrum, a maximum value and a minimum value will appear every time a free spectrum range is passed. Since the calculation formula of the extinction ratio ER can be shown as follows: ER=10log(Pmax / Pmin), where Pmax represents the maximum spectral power in a free spectrum range, and Pmin represents the minimum spectral power in a free spectrum range; therefore, the extinction ratio of the interferometer can be obtained based on the output spectrum.

[0085] In some embodiments of the present application, the above-mentioned step S232 may include but is not limited to step S2321 and step S2322.

[0086] Step S2321, determining the maximum output value and the minimum output value according to the output spectrum;

[0087] Step S2322, calculating the extinction ratio according to the maximum output value and the minimum output value.

[0088] In some embodiments of the present application, in the process of determining the extinction ratio based on the output spectrum, the maximum output value and the minimum output value are first determined according to the output spectrum; then the extinction ratio is calculated according to the maximum output value and the minimum output value.

[0089] It is worth noting that the calculation formula of the extinction ratio ER can be as follows: ER=10log(Pmax / Pmin), wherein Pmax represents the maximum spectral power in a free spectral range, and Pmin represents the minimum spectral power in a free spectral range; the maximum spectral power is the maximum output value in the embodiment of the present application, and the minimum spectral power is the minimum output value in the embodiment of the present application. The extinction ratio can be calculated based on the determined maximum output value and minimum output value.

[0090] In some embodiments of the present application, the above-mentioned step S213 may include but is not limited to step S2131 and step S2132.

[0091] Step S2131, generating a laser signal according to a free spectrum range by a tunable laser;

[0092] Step S2132: Use the laser signal as a test light signal.

[0093] In some embodiments of the present application, in the process of generating a test optical signal according to the free spectrum range, a laser signal is first generated according to the free spectrum range by a tunable laser; then the laser signal can be used as a test optical signal. In the embodiments of the present application, a test optical signal is generated based on a tunable laser.

[0094] A common mode rejection ratio test device provided by an embodiment of the second aspect of the present application includes a target interferometer constructed by two identical optical mixers to be tested, wherein the common mode rejection ratio of the optical mixer to be tested is determined according to the extinction ratio of the target interferometer.

[0095] In some embodiments of the present application, the first differential pair of positive light splitting branches of the two optical mixers to be measured are connected through a first waveguide, and the first differential pair of negative light splitting branches of the two optical mixers to be measured are connected through a second waveguide. In the embodiments of the present application, in the process of constructing a target interferometer using two identical optical mixers to be measured, the first differential pair of positive light splitting branches of the two optical mixers to be measured can be connected through the first waveguide, and the first differential pair of negative light splitting branches of the two optical mixers to be measured can be connected through the second waveguide, thereby forming a target interferometer.

[0096] In some embodiments of the present application, when both of the two optical mixers to be measured are formed by cascading a 1×2 beam splitter and a 2×2 beam splitter, the third differential pair of positive light splitting branches of the 2×2 beam splitters of the two optical mixers to be measured are connected through a first waveguide, and the third differential pair of negative light splitting branches of the 2×2 beam splitters of the two optical mixers to be measured are connected through a second waveguide. In some embodiments of the present application, when the optical mixer to be measured is formed by cascading a 1×2 beam splitter and a 2×2 beam splitter, in the process of constructing an interferometer using this type of optical mixer, the third differential pair of positive light splitting branches of the 2×2 beam splitters of the two optical mixers to be measured can be connected through the first waveguide, and the third differential pair of negative light splitting branches of the 2×2 beam splitters of the two optical mixers to be measured can be connected through the second waveguide, so that the two 2×2 beam splitters can form a target interferometer. In the process of testing the DC common mode rejection ratio of an optical mixer formed by cascading beam splitters, only part of the beam splitters need to be tested in combination, and the entire optical mixer does not need to be tested in combination, so the DC common mode rejection ratio test process can be simpler and faster.

[0097] The common mode rejection ratio test device in the embodiment of the present application and the common mode rejection ratio test method in the above embodiment are based on the same invention points, which will not be repeated here.

[0098] The above is a specific description of the preferred implementation of the present application, but the present application is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the present application. These equivalent deformations or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A common mode rejection ratio test method, comprising: A target interferometer is constructed by two identical optical mixers to be measured; detecting the extinction ratio of the target interferometer; A direct current common mode rejection ratio of the optical mixer to be measured is determined according to the extinction ratio.

2. The common mode rejection ratio test method according to claim 1, characterized in that: The target interferometer is constructed by using two identical optical mixers to be measured, comprising: The first differential pair positive light splitting branches of the two optical mixers to be measured are connected through a first waveguide, and the first differential pair negative light splitting branches of the two optical mixers to be measured are connected through a second waveguide, so that the two identical optical mixers to be measured form the target interferometer.

3. The common mode rejection ratio test method according to claim 2, characterized in that: After connecting the first differential pair negative splitting branches of the two optical mixers to be measured through the second waveguide, the method further includes: The second differential pair positive light splitting branches and the second differential pair negative light splitting branches of the two optical mixers to be tested are both terminated.

4. The common mode rejection ratio test method according to claim 3, characterized in that: The termination process includes at least one of the following: Doping absorption; Germanium absorption; Anti-reflection based on end coupler; Bend the windings to create losses.

5. The common mode rejection ratio test method according to claim 3, characterized in that: The first differential pair positive light splitting branch is a differential pair positive light splitting branch of an in-phase path, the first differential pair negative light splitting branch is a differential pair negative light splitting branch of an in-phase path, the second differential pair positive light splitting branch is a differential pair positive light splitting branch of an orthogonal phase path, and the second differential pair negative light splitting branch is a differential pair negative light splitting branch of an orthogonal phase path; Alternatively, the first differential pair positive optical splitting branch is a differential pair positive optical splitting branch of an orthogonal phase path, the first differential pair negative optical splitting branch is a differential pair negative optical splitting branch of an orthogonal phase path, the second differential pair positive optical splitting branch is a differential pair positive optical splitting branch of an in-phase path, and the second differential pair negative optical splitting branch is a differential pair negative optical splitting branch of an in-phase path.

6. The common mode rejection ratio test method according to claim 1, characterized in that: When the optical mixer to be measured is formed by cascading a 1×2 beam splitter and a 2×2 beam splitter, constructing a target interferometer by using two identical optical mixers to be measured includes: The third differential pair positive light splitting branches of the 2×2 beam splitters of the two optical mixers to be measured are connected through a first waveguide, and the third differential pair negative light splitting branches of the 2×2 beam splitters of the two optical mixers to be measured are connected through a second waveguide, so that the two 2×2 beam splitters form the target interferometer.

7. The common mode rejection ratio test method according to claim 1, characterized in that: The step of determining the DC common mode rejection ratio of the optical mixer to be measured according to the extinction ratio comprises: The extinction ratio is inverted to obtain the DC common mode rejection ratio of the optical mixer to be measured.

8. A common mode rejection ratio test device, comprising a target interferometer constructed by two identical optical mixers to be tested, wherein: The common mode rejection ratio of the optical mixer to be measured is determined according to the extinction ratio of the target interferometer.

9. The common mode rejection ratio test device according to claim 8, characterized in that: The first differential pair positive light splitting branches of the two optical mixers to be measured are connected through a first waveguide, and the first differential pair negative light splitting branches of the two optical mixers to be measured are connected through a second waveguide.

10. The common mode rejection ratio test device according to claim 8, characterized in that: When the two optical mixers to be tested are both composed of a cascade of a 1×2 beam splitter and a 2×2 beam splitter, the third differential pair of positive light splitting branches of the 2×2 beam splitters of the two optical mixers to be tested are connected through a first waveguide, and the third differential pair of negative light splitting branches of the 2×2 beam splitters of the two optical mixers to be tested are connected through a second waveguide.

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