JP2009047690A - Testing device for testing device under test, having switch for selecting different paths - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for testing an opto-electric device or an optical device, capable of periodically carrying out complete calibration without performing light measurement. <P>SOLUTION: This testing device for testing a DUT (Device Under Test) comprises a first electric terminal and a first optical terminal. The device has a first electric circuit port and a first optical circuit port. The first optical circuit port is connected to the first optical terminal by an optical line. The device comprises a first electric switch having first, second and third switch ports. The first switch is adapted to connect the first switch port selectively to the second switch port or the third switch port. Further, a first electric line is provided for connecting the second switch port to the first electric terminal, and a second electric line is provided for connecting the third switch port to the first electric circuit port. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to electronic testing, and more particularly to electronic instrumentation for measuring signals during testing performed on electro-optic systems or related optical systems and related components using electricity. The invention further relates to calibrating the test instrument to perform the corresponding test accurately.

  It is often required to determine the characteristics of a system or device that includes circuitry and interfaces using both light and electricity. These systems or devices are also referred to below as opto-electric (or electro-optic) systems or opto-electric (or electro-optic) devices. Such a system or device may have an optical input and an electrical output, hereinafter referred to as an optical-to-electrical system or optical / electrical device, or an electrical input and an optical output. In the following, it is referred to as an electrical-to-optical system or electrical / optical device.

  Modern optical transmission systems have core optoelectronic components, transmitters and receivers, and their subcomponents (lasers, modulators, modulators, etc.) to ensure performance in terms of modulation bandwidth, jitter, gain, and distortion. And high-speed, accurate and repeatable specialization of the detector).

  Various test systems have been developed to meet the measurement needs of testing such devices (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). One such test system is the TM Agilent N4373B Optical Component Analyzer (LCA) provided by the assignee Agilent Technologies, Inc. The analyzer comprises an internal light source and an internal optical receiver for performing electrical / optical (E / O) measurements, optical / electrical (O / E) measurements, and optical measurements.

  Test equipment is often affected by errors that can change more or less over time. Such errors are caused by incomplete test equipment and test setup. If these errors do not change during the measurement, they can be characterized by calibration and can be mathematically removed during the measurement process.

  Since some errors in the test equipment are not constant over time and vary with, for example, temperature and the particular interface cable being used, one prerequisite for accurate measurement is that calibration measurements are performed periodically. Is to do. This result (calibration data) is used to compensate for mismatch errors while testing the device under test (DUT). The above-mentioned patent document 3 further describes a set of calibration measurements that the user can perform to update the calibration data.

US Pat. No. 4,921,347 US Pat. No. 5,028,131 US Pat. No. 5,175,492

  It is an object of the present invention to provide an improved test. This object is solved by the independent claims. Further embodiments are indicated by the dependent claims.

Errors that occur in network measurements can be related to signal leakage, signal reflection, and frequency response. There are the following types of systematic errors.
Directivity error and crosstalk error related to signal leakage,
Source mismatch and load impedance mismatch related to reflection, and
Frequency response error caused by reflection / transmission tracking in the test receiver.

  Various error models and corresponding tests are known for determining test equipment errors. One model that characterizes the error of a test device having two ports connected to a two-port DUT is the so-called two-port error model. The two-port error model includes for all 12 error terms, all six of these terms for the forward direction and the corresponding six errors with different data in the reverse direction. Thus, two-port calibration is often referred to as 12-term error correction. Two-port error correction takes into account all of the major sources of systematic errors and therefore gives fairly accurate results. The two-port device error model reveals four S-parameters measured in the forward and reverse directions. Once the systematic error term has been characterized, the network analyzer uses four equations to derive the actual device S-parameters from the measured S-parameters.

  Systematic errors do not change over time, but drift errors occur when the performance of the test system changes after calibration is performed. These drift errors are first caused by environmental state variations, such as temperature variations, and can be eliminated by additional calibration. The rate of drift determines how often additional calibration is required.

  One insight is that in a test device with an opto-electric device or opto-electric circuit, the behavior of electrical components such as cables, switches or connectors can change over time. In contrast, for example, the relationship between the characteristics of the electrical signal of the modulated light source (eg, voltage) and the characteristics of the optical signal (eg, optical power), or the characteristics of the optical input signal of the photodetector and the electrical output signal The behavior of optoelectric components that can be expressed as a transfer function of the relationship between the input and output of an optoelectric circuit, such as the relationship between properties, may be relatively stable over time .

  Providing a test device for testing an opto-electrical device or an optical device, which makes it possible to perform a complete calibration periodically without taking any optical measurements, for example using the two-port electrical calibration measurement described above One idea is to do.

  According to an embodiment of the present invention, a test device for testing a DUT is provided that includes a first electrical terminal and a first optical terminal. The device comprises a first optoelectronic circuit having a first electrical circuit port and a first optical circuit port. The first optical circuit port is coupled to the first optical terminal by an optical line. The device further includes a first electrical switch having a first switch port, a second switch port, and a third switch port. The first switch selectively couples the first switch port with either the second switch port (first switch position) or the third switch port (second switch position). ing. In addition, a first electrical line is provided that connects the second switch port with the first electrical terminal, and a second electrical line is provided that connects the third switch port with the first electrical circuit port.

  Embodiments of the present invention make it possible to provide an optical electrical calibration for an optical terminal (eg, the first optical terminal) by performing an electrical calibration for the electrical terminal (eg, the first electrical terminal). . This is because the electrical behavior of the test device (eg, network analyzer) changes with time and / or temperature, while the opto-electrical behavior of the opto-electrical circuit varies with time and temperature. It is particularly advantageous because it is substantially stable.

  In one embodiment, the test device is adapted to store first calibration data describing the behavior of the first optoelectronic circuit with respect to the first electrical circuit port and the first optical circuit port; and Second calibration data describing the behavior of the test device with respect to the electrical calibration surface represented by the first electrical terminal and the second electrical terminal when the first switch is switched to the first switch position. It comes to memorize.

  As will be described in more detail below, the first calibration data can be determined by coupling the optoelectrical reference device to the test device, and the second calibration data can be an electrical reference device such as a so-called calibration kit, for example. Can be determined by coupling to a test device.

  In a further embodiment, the test device transmits a stimulus transmitted to the device under test along with the first calibration data and the second calibration data and response data when the switch is switched to the second switch position. The behavior of the device under test connected to the first optical terminal and the first electrical terminal is determined as a function of the data and the response data received from the device under test.

  In one embodiment, the first optoelectronic circuit comprises a light source, for example a modulated laser. In addition, the test device comprises a second opto-electrical circuit having a photodetector. This second opto-electrical circuit has a second electrical port and a second optical port. The second optical port is coupled to the second optical terminal. The test device further comprises a second electrical switch having a fourth switch port, a fifth switch port, and a sixth switch port. The second switch is configured to selectively couple the fourth switch port with the fifth switch port or the sixth switch port. A third line is provided that couples the fifth switch port to the second electrical terminal, and a fourth line that couples the sixth switch port to the second electrical circuit port. This embodiment tests optical devices under test including electrical / optical devices (eg, modulated light sources), optical / electrical devices (eg, photodetectors), and optical-to-optical devices. enable.

  In one embodiment, the test device further comprises a third electrical terminal coupled to the first switch port and a fourth electrical terminal coupled to the fourth switch port. The third electrical terminal is adapted to be coupled to a power source that provides an electrical stimulation signal, and the fourth electrical terminal is adapted to be coupled to an electrical detector that receives the electrical response signal. .

  In one embodiment, the calibration is performed with respect to a certain calibration layer that covers all circuits and connections of the test device. Thereby, it is not necessary to provide multiple calibrations of a single cable and circuit. Preferably, calibration is provided at the electrical interface terminal of the test device, for example with respect to the first electrical terminal and the second electrical terminal. On the other hand, it is possible to select other electrical interfaces such as cable ends of cables connected to the first electrical terminal and the second electrical terminal, respectively.

  An electrical calibration kit can be connected to the first electrical terminal and the second electrical terminal to provide calibration for the first electrical terminal and the second electrical terminal. The first switch is switched to connect the first electrical terminal to the third electrical terminal via the first line, and the second switch connects the second electrical terminal via the second line. To be connected to the fourth electrical terminal. A network analyzer can be connected to the third electrical terminal and the fourth electrical terminal to provide the stimulation signal to the third electrical terminal and receive the response signal at the fourth electrical terminal. Next, electrical calibration measurements can be performed on the first electrical terminal and the second electrical terminal, and the corresponding calibration data can be stored in the calibration data memory. If a previous optoelectrical calibration of the light source or photodetector is associated with these ports, such initial optoelectrical calibration reference data can be used for any new electrical calibration performed on the same calibration surface. Can be derived from calibration.

  In one embodiment, the test device has a first optical terminal when connected to either the first optical terminal and the second electrical terminal, or the first optical terminal and the second optical terminal. The behavior of the optoelectronic device under test is determined by evaluating the response signal along with the known characteristics of the electrical circuit and the electrical calibration data stored in the calibration data memory. Known properties here refer to opto-electrical calibration measurements made once, for example during the manufacture of the device, before entering operation. Electrical calibration data refers to calibration measurements that are made periodically to reduce drift errors.

  In one embodiment, a first line connecting one port of the first switch and the first electrical terminal, and another port of the first switch and the electrical of the first opto-electrical circuit. The second line connecting the ports is such that the electrical behavior of the first path between the first electrical terminal and the second switch port is within the third switch port and the first opto-electrical circuit. It is provided to be substantially similar to the behavior of the second pass between the electrical boundaries.

  In one embodiment, the difference in length between the first line and the second line is caused by environmental fluctuations, such as temperature fluctuations, that affect both lines as well, and as a result, calibration for the first electrical terminal. Are provided to compensate for (cover) variations in the second line. Here, the difference in length can be selected to be small, for example, 0 (zero) or substantially 0 (zero).

  In one embodiment, the difference in length between the first line and the second line is the electrical reflection behavior of the first path between the first electrical terminal and the second switch port. behavior) is provided that is substantially similar to the reflective behavior of the second path between the third switch port and the reflective terminal in the first opto-electrical circuit. Here, the first path includes a portion in the connector coupled to the first electrical terminal, and the second path includes a portion in the first opto-electrical circuit. By way of example, the path length portion of the connector is equal to 30 millimeters, and the path length portion of the first optoelectronic circuit is equal to 10 millimeters. Thereby, the difference in path length can be chosen to be 20 millimeters.

  In one embodiment, the remaining error (residual error) of the electrical calibration set can be further taken into account when selecting the lengths of the first line and the second line.

  In one embodiment, the calibration value or known characteristic of the first opto-electrical circuit includes a plurality of value sets. Each of these value sets corresponds to a different value of a parameter such as, for example, the optical power or wavelength of the optical signal, generated for example by an internal or external light source or received by an internal photodetector. In one embodiment, the transfer function of the internal light source is determined for a plurality of different optical power values and a plurality of at least one different wavelength value. In one embodiment, the transfer function of the internal optical receiver is determined for a plurality of different optical power values or a plurality of different wavelength values. In one embodiment, the calibration value of the internal light source or the internal optical receiver is determined according to the stimulus Rf (radio frequency) power of the network analyzer.

  In a further embodiment, for error correction, the actual output or wavelength of the light source is determined and a corresponding value set from the calibration values is selected to be used with the actual electrical calibration data. Correspondingly, for error correction, the transfer function of the internal photodetector can be determined for a plurality of different power values or a plurality of different wavelength values (for example, measured with an optical power meter). Depending on the actual measured power (or derived from internal parameters) or the actual measured wavelength (eg measured using a wavemeter), a corresponding set of values from the calibration values is used with the actual electrical calibration data Chosen to be.

  Embodiments of the invention can be implemented or supported in part or in whole by one or more suitable software programs. These software programs can be stored on any type of storage medium (or data carrier) or can be provided otherwise by any type of storage medium (or data carrier) It can be executed in or by a suitable data processing unit.

  Many of the other objects of the present invention and attendant advantages of embodiments of the present invention will be readily appreciated and better understood by referring to the following more detailed description of the preferred embodiment in conjunction with the accompanying drawings. . Features that are substantially or functionally equal or similar will be referred to with the same reference signs.

  In order to properly determine the characteristics of a device under test, it is important to be familiar with all relevant characteristics of the test device. Thus, calibration measurements are taken and the corresponding values are stored in the test device for consideration for subsequent test measurements. If these errors indicate that the characteristic is substantially invariant with time, these errors can be characterized by a single calibration. The corresponding calibration measurement result can be regarded as a known characteristic of the test device. On the other hand, such measurements may be repeated from time to time, for example, during the maintenance of the test device.

  For example, errors that indicate that characteristics change over time due to environmental fluctuations such as temperature, pressure, humidity, or due to wear that occurs during device use, such as wear on electrical connectors, can cause calibration measurements to occur quite frequently. It is also called drift characteristics that may be required. The frequency of the calibration measurement depends on the time characteristics of each drift. In general, such calibration may be performed, for example, daily or weekly, or before each new test is performed. Thus, calibration measurements must be performed directly by the user, often at the measurement location, and such calibration measurements should be as simple, reliable as possible.

  FIG. 1 shows the main calibration step and the DUT characterization step. Further, the left part of FIG. 1 shows that the test device 200 is connected to the electrical reference device 300, and the right part of FIG. 1 shows that the test device 200 is connected to the optical electrical device under test (DUT) 400. It shows that.

  The test device 200 includes a first electrical terminal T1, a second electrical terminal R1, a third electrical terminal T2, a fourth electrical terminal R2, and a first optical terminal O1. The test device further comprises a first electrical switch 210, a first optoelectronic circuit 220, a first line C1, a second line C2, and a fifth line C3. The first electrical switch 210 has a first switch port A1, a second switch port A2, and a third switch port A3. The first optoelectronic circuit 220 has a first electrical circuit port A4 and a first optical circuit port coupled to the first optical terminal O1. The first line C1 couples the second switch port A2 to the first electrical terminal T1. The second line C2 couples the third switch port A3 to the first electrical circuit port A4. The fifth line C3 couples the third electrical terminal T2 to the first switch port A1.

  The first switch 210 can be switched between a first state and a second state. In the first state, the first switch port A1 is electrically coupled to the second switch port A2, and in the second state, the switch port A1 is electrically coupled to the third switch port A3.

  For simplicity, the second electrical terminal R1 and the fourth electrical terminal R2 are shown directly coupled to each other via electrical wires. In the embodiment, such coupling can be realized by an arbitrary circuit, for example, by a circuit including a second switch as shown in FIG.

  The third electrical terminal T2 and the fourth electrical terminal R2 provide the electrical stimulation signal SG to the third electrical terminal T2 and the electrical network analyzer for receiving the electrical response signal RG at the fourth electrical terminal R2. Can be combined. For measurement in the reverse direction using this network analyzer, the electrical stimulation signal SG is provided to the fourth electrical terminal R2, and the electrical response signal RG is received from the third electrical terminal T2.

  As mentioned above, electrical components such as the test device shown in FIG. 1, such as lines C1, C2, and C3, electrical terminals T1, T2, R1, and R2, and the first switch 210, are May have changing characteristics. Since the test device comprises an optical component, for example a circuit provided in the first optoelectronic device terminated by the first optical terminal O1, it is not possible to perform an electrical calibration on this terminal. One possibility is to make a plurality of calibration measurements for each sub-device, for example, separate measurements for separate cables T1-T3 and the first switch, and calculate the resulting calibration values from those calibration measurements. It can be. However, such a technique involves a plurality of steps for calibrating and is thus cumbersome and prone to errors. Another possibility is to provide a reference optical device, for example a reference detector, connected to the optical terminal O1, and to provide a corresponding optical reference measurement similar to the measurements made during manufacture or in the course of initial calibration. It is to be. However, such a reference light device is expensive and sometimes difficult to handle.

  According to embodiments of the present invention, an alternative is proposed that allows the user to keep the calibration measurement simple and reliable. A test device for testing an opto-electrical device or an optical device that makes it possible to perform a complete calibration on a regular basis without having to provide an optical reference device or make separate measurements of several different components One idea is to provide Furthermore, embodiments of the present invention provide a first electrical terminal T1 for electrical calibration measurements. The first electrical terminal, and the first line connecting the first electrical terminal and the second switch port, the calibration for the first electrical terminal T1, the first switch and the first optical output. Designed to accommodate the calibration of the electrical part of the path between. Since the optical portion of the path between the first switch and the first optical output is considered to be fairly invariant with respect to time, the calibration with respect to the first electrical terminal and the known characteristics of the optoelectronic device are: This corresponds to the calibration for the first optical terminal.

  Referring to FIG. 1, the left side shows a test setup comprising a test device 200 and an electrical reference device 300. In this test setup, the input port of the reference device is connected to the first electrical terminal T1, and the output port of the reference device is connected to the second electrical terminal R1. The first switch 210 is switched to the first state. In this first state, the first switch port A1 is electrically coupled to the second switch port A2, thus providing a connection through the first path. This first path is delimited by the first electrical terminal T1 and the third electrical terminal T2, and together with the first electrical terminal T1 and the third electrical terminal T2, the fifth line C3, the first Switch 210 and a first line C1.

  The stimulation signal SG is provided to the input port of the reference device 300 via the third electrical terminal T2, and the response signal RG of the reference device is sent to the internal circuit via the second electrical terminal R1, It reaches the electric terminal R2. Corresponding measurements can be made in the opposite direction.

  The reference device 300 is also referred to as an electrical calibration kit 300 and can be considered as comprising a set of physical devices called standards. The electrical calibration standard provides a reference for error-corrected measurements in a network analyzer. Each standard has precisely known definitions including electrical delay, electrical impedance, and electrical loss. Measurements with different standards are used to calculate the network analyzer error correction term.

  A calibration measurement can then be performed on the first electrical terminal T1 and the second electrical terminal R1 by evaluating the response signal along with the stimulation signal for different states of the reference device 300. During calibration measurements, the analyzer measures standards and mathematically compares the results with their “ideal model”. From these comparison results, an error term of the network analyzer is derived. This error term can be stored in the calibration memory of the test device. Such terms are used later to provide error correction in the results of subsequent DUT measurements.

  Referring now to the right side of FIG. 1, a test setup comprising a test device 200 and an optical electrical device under test (DUT) 400 is shown. In this test setup, the optical input port of the DUT is connected to the first optical terminal O1, and the electrical output port of the DUT is connected to the second electrical terminal R1. Here, the first switch 210 is switched to the second state. In this second state, the first switch port A1 is electrically coupled to the third switch port A3, and therefore the first range delimited by the first electrical terminal T1 and the first optical terminal O1. A connection over the path is provided. This first path thus consists of a serial connection of the fifth line C 3, the first switch 210, the second line C 2, and the first optoelectronic circuit 220. The stimulus signal SG is provided to the input port of the reference device via the third electrical terminal T2, and the response signal RG of the reference device is provided via the second electrical terminal R1 to an internal circuit (shown in the form of a simple connection). To the fourth electrical terminal R2.

  The DUT can then be characterized by evaluating the response signal along with known characteristics of the opto-electrical device and the error term determined in the calibration step.

  Referring to FIG. 2, the test device 200 of FIG. 1 with both an internal light source and an internal photodetector is shown. Therefore, this test device can perform a pure electrical test when the electrical DUT is connected to the first electrical terminal T1 and the second electrical terminal R1, and the optical DUT is the first optical terminal O1. And when connected to the second optical terminal O2, a pure optical test can be performed, the input of the optical / electrical DUT is connected to the first optical terminal O1, and the electrical output of the DUT is the second When connected to the electrical terminal R1, the optical / electrical test can be performed, the electrical / optical DUT input is connected to the first electrical terminal T1, and the optical output of the DUT is the second optical terminal. When connected to O2, an electrical / optical test can be performed.

  Therefore, the direct connection between the second electrical terminal and the fourth electrical terminal in FIG. 1 is the second electrical switch 240, the second opto-electric circuit 230, the third line D1, and the fourth line D2. And a circuit comprising a second optical terminal O2.

  The first opto-electrical circuit 220 includes a light source, and the second opto-electrical circuit 230 includes a photodetector, and is optically coupled to the second electric circuit port B4 and the second optical terminal O2. 2 optical circuit ports.

  The second electrical switch 240 includes a fourth switch port B1, a fifth switch port B2, and a sixth switch port B3. Here, the second switch selectively couples the fourth switch port B1 to the fifth switch port B2 or the sixth switch port B3.

  The third line D1 is arranged to couple the fifth switch port B2 to the second electrical terminal R1, and the fourth line D2 connects the sixth switch port B3 to the second electrical circuit port B4. Arranged to join.

  Furthermore, an electrical analyzer (or network analyzer) 100 is provided. The electrical analyzer includes a first analyzer terminal P1 (also referred to as a first analyzer port P1) and a second analyzer terminal P2 (also referred to as a second analyzer port P2). The first analyzer port P1 is coupled to the third terminal T2 of the test device 200 via a first connection line to provide the electrical stimulation signal SG, and the second analyzer port P2 is connected to the electrical response signal. To receive RG, it is coupled to the fourth terminal R2 of the test device 200 via a second connection line.

  Corresponding to the description based on FIG. 1, a calibration measurement can be performed on the first electrical terminal T1 and the second electrical terminal R1 by evaluating the response signal together with the stimulation signal for different states of the reference device.

  In one embodiment, for example, the selection defined by the first electrical terminal T1 and the second electrical terminal R1 or by the terminals of the connecting cable connected to the first electrical terminal T1 and the second electrical terminal R1. Two-port electrical error correction is performed on the calibration surface.

  Two-port error correction targets the main causes of systematic errors in network analyzers. In addition, four so-called S-parameters are measured in the forward and reverse directions. The S-parameter test set also allows full 2-port error correction with the following 12 error terms:

Etf: Forward transmission error Erf: Forward reflection error Esf: Forward source matching Elf: Forward load matching Edf: Forward directivity Exf: Forward crosstalk Etr: Reverse transmission error Err: Reverse reflection error Esr: Reverse source matching Elr: Reverse load matching Edr: Reverse directivity Exr: Reverse crosstalk

  Depending on the type of DUT, a set with reduced error terms may be sufficient.

  Once the error terms are derived, the network analyzer 100 stores these error terms and uses these error terms to derive the actual DUT S-parameters (DUT behavior) from the measured S-parameters. .

  In subsequent figures, an exemplary calibration and test scenario using the test setup shown in FIG. 2 is shown. The test setup thereby comprises an internal light source 220 as the first opto-electrical circuit and an internal optical receiver 230 as the second opto-electrical circuit. In that regard, FIGS. 3-5 show the steps for initially determining the characteristics of the test setup, eg, stored in a calibration memory, and FIGS. 6-9 are for performing “latest” calibration measurements along with DUT measurements. Figure 6 illustrates exemplary calibration and measurement steps.

  FIG. 3 shows an electrical calibration kit E-cal as an electrical reference device for so-called short open load reciprocal (SOLT) or short open load reciprocal (SOLR) from left to right. The three calibration steps used are shown.

  On the left side of the figure, an electrical calibration kit E-cal is connected to the first terminal T1 to determine Esf (forward source alignment), Erf (forward reflection error), and Edf (forward directivity). ing.

  In the center of the figure, a calibration kit E-cal is connected to the second terminal R1 to determine Esr (reverse source match), Err (reverse reflection error), and Edr (reverse directivity). Yes.

  On the right side of the figure, the first electrical term is used to determine the remaining error terms Etf (forward transmission error), Etr (reverse transmission error), Elf (forward load matching), and Elr (reverse load matching). The terminal T1 is connected to the second electric terminal R1 via an electric line (RF cable). In addition, Exf (forward crosstalk) and Exr (reverse crosstalk) can be obtained. During this process, the electrical calibration surface is represented by a first electrical terminal T1 and a second electrical terminal R1.

  In addition to SOLT calibration or SOLR calibration, the TRL calibration method (through, reflection, line) can alternatively be used to determine the network analyzer error term.

  4 and 5 illustrate exemplary optical calibration measurement steps using the test device of FIG. These steps can be performed by a professional calibration service performed at a calibration laboratory, for example, before the user uses the test device.

  In the first step illustrated by FIG. 4, a reference optical receiver (or detector) NIST is connected between the first optical terminal O1 and the second electrical terminal R1. Next, the characteristics of the internal light source 220 can be determined based on the known reference data NISTrefdata of the reference detector NIST and the optical power measured in the reference detector. If S21NISTTXint corresponds to the result of the network analyzer measurement with error correction (representing transmission between the first analyzer terminal P1 and the second analyzer terminal P2 via the reference photodetector NIST), the internal light source The calibration data Tx_cal required for the above can be derived from dividing S21NISTTXint by the known reference data NISTrefdata.

  In the second step illustrated by FIG. 5, the first optical terminal O1 and the second optical terminal O2 are connected to each other by an optical line. Next, the internal optical receiver characteristic Rx_cal can be obtained based on the characteristic of the internal power supply 220 obtained in advance and the optical power measured in the internal receiver. S21TXRxint is the result of the network analyzer measurement with the error corrected (represents transmission between the first analyzer terminal P1 and the second analyzer terminal P2 via the internal optical transmitter circuit and the internal optical receiver circuit). The calibration data required for the internal optical receiver can be derived from dividing S21TXRxint by the reference data Tx_cal derived in the first step.

  The results Tx_cal and Rx_cal complete the optoelectrical calibration of the internal transmitter (T1 → O1) and the optoelectrical calibration of the internal receiver (O2 → R2), and the corresponding calibration data is (for example, in the electrical analyzer 100). It can be stored in memory and is not further modified during normal use of the test device.

  FIGS. 6-10 show measurements that can be made by the user of the test device of FIG. 2 after being calibrated according to previous figures.

  6 and 7 illustrate exemplary steps for measuring an electrical / optical DUT (eg, a modulated light source) using a test device.

  In the user calibration step illustrated by FIG. 6, it is preferably used for the initial calibration described with reference to FIG. 3 in order to update the electrical calibration data (first set of error terms) stored in the calibration memory. An electrical calibration kit E-cal, which is a calibration kit similar to the above, is connected between the first electrical terminal T1 and the second electrical terminal R1. Since the electrical behavior of the test device is considered to change in response to changes in ambient conditions (eg, temperature), such updates of electrical calibration data may be performed fairly frequently by the user.

  In the user measurement step illustrated by FIG. 7, the characterized electrical / optical DUT (eg optical transmitter) is electrically connected to the first electrical terminal T1 and optically connected to the second optical terminal. Measurement results can be corrected based on optical calibration data and updated electrical calibration data (eg, fixedly stored in calibration memory and changed only during test device maintenance).

  8 and 9 illustrate exemplary steps for measuring an optical / electrical DUT (eg, an optical receiver) using the test device of FIG. In the first step illustrated by FIG. 8, in order to update the electrical calibration data (second set of error terms) stored in the calibration memory, the electrical calibration kit E-cal has a first electrical terminal T1. And the second electrical terminal R1. In the next step, the characterized DUT is electrically connected to the second electrical terminal R1 and optically connected to the first optical terminal O1. Next, the measurement result can be corrected based on the optical calibration data and the updated electrical calibration data.

  FIG. 10 shows the steps for measuring the optical / optical DUT using the test device of FIG. In the first step, an electrical calibration can be performed as shown by FIG. 3, but this is not necessarily required here. Furthermore, the first optical terminal O1 and the second optical terminal O2 are connected using optical line means, and optical transmission is measured. Based on these measurements, the electrical calibration data (third set of error terms) can be updated and stored in the calibration memory. In the next step shown in FIG. 11, the characterized DUT is connected to both the first optical terminal O1 and the second optical terminal O2. Next, the measurement result can be corrected based on the optical calibration data and the updated electrical calibration data.

  Thus, the above-described embodiments enable electrical calibration measurements to be used to periodically perform full calibration of a test device for testing an optical device under test (eg, an optical receiver or optical transmitter). Become. Along with the results of such electrical calibration measurements (or updates of such electrical calibration measurements) and optical properties known in advance (eg, stored as optical calibration data required before use of the test device), The complete behavior of the test device relative to the device under test (or in other words to its optical interface and / or electrical interface) is actually required. Thus, the user can easily perform such calibration using an electrical reference device (eg, an electrical calibration kit).

  Although the present teachings have been described in detail with reference to specific embodiments, those skilled in the art to which the teachings pertain can make various changes and enhancements without departing from the spirit and scope of the claims. Will understand. In addition, the various devices and methods described herein are included by way of example only and are not intended to be limiting in any way. Finally, the embodiments of the present invention will be enumerated just in case.

(Embodiment 1)
A test device for testing a device under test (400),
A first optoelectronic circuit (220) having a first electrical circuit port (A4) and a first optical circuit port coupled to the first optical terminal (O1);
A first electrical switch (210) having a first switch port (A1), a second switch port (A2), and a third switch port (A3), wherein the first switch port ( A1) is selectively coupled to the second switch port (A2) at a first switch position or to the third switch port (A3) at a second switch position, 1 electrical switch,
A first line (C1) for coupling the second switch port (A2) to a first electrical terminal (T1); and a third switch port (A3) for the first electrical circuit port (A4). A second line (C2) coupled to
With
In a state where first calibration data describing the behavior of the first opto-electrical circuit (220) is stored, and the first switch is switched to the first switch position. Second calibration data describing the behavior of the test device with respect to the electrical calibration plane represented by the first electrical terminal (T1) and the second electrical terminal (R1) is stored. A test device characterized by a memory.
(Embodiment 2)
The test device of embodiment 1, wherein the first opto-electrical circuit (220) is one of an optical transmitter and a photodetector.
(Embodiment 3)
When the switch is switched to the second switch position, as a function of the first calibration data and the second calibration data, the first optical terminal (O1) and the first electrical terminal The test device according to any one of the first and second embodiments, comprising a processor that determines the behavior of the device under test (400) connected to (T1).
(Embodiment 4)
The first calibration data describing the behavior of the first optoelectronic circuit (220) includes a plurality of value sets, each of which is a parameter of an optical signal, preferably the first optoelectronic circuit. Corresponding to different values of the power or wavelength of the optical signal generated or received by the circuit, the test device is responsive to the set of values based on the value set selected corresponding to the actual value of the parameter of the optical signal. The test device of embodiment 3, wherein the behavior of the test device (400) is determined.
(Embodiment 5)
The first line (C1) and the second line (C2) are a first path of a first path between the first electrical terminal (T1) and the first switch port (A1). Electrical behavior and a second electrical behavior of a second path between the first switch port (A1) and the first opto-electrical circuit (220),
Temperature fluctuation has a substantially similar effect on the first electrical behavior and the second electrical behavior, so that the first line with respect to the first electrical terminal (T1). The calibration on (C1) is similar to compensate for variations in the second line (C2), or in an electrical calibration device (300) coupled to the first electrical terminal (T1) Considering at least one of an internal electrical path length and an internal electrical path length in the opto-electrical circuit (220), the first electrical terminal (T1) and the first optical terminal (O1). Different to minimize the modulation effect in the transmission behavior of the test device,
The test device according to any one of embodiments 1-4, selected as follows.
(Embodiment 6)
The difference between the first length of the first line (C1) and the second length of the second line (C2) is 0 (zero), less than 10 millimeters, less than 20 millimeters, less than 30 millimeters And 6. The test device of any one of embodiments 1-5, wherein the test device is one of less than 40 millimeters.
(Embodiment 7)
A second optoelectronic circuit (230) having a second electrical circuit port (B4) and a second optical circuit port optically coupled to the second optical terminal (O2);
A second electrical switch (240) having a fourth switch port (B1), a fifth switch port (B2), and a sixth switch port (B3), wherein the fourth switch port ( A second electrical switch adapted to selectively couple B1) to the fifth switch port (B2) or the sixth switch port (B3);
A third line (D1) for coupling the fifth switch port (B2) to a second electrical terminal (R1); and a sixth switch port (B3) for the second electrical circuit port (B4). A fourth line (D2) coupled to
The test device according to any one of Embodiments 1 to 6, further comprising:
(Embodiment 8)
The first optical electric circuit (220) is an optical transmitter, the first electric circuit port (A4) is an input of the optical transmitter, and is coupled to the first optical terminal (O1). The first optical circuit port is an output of the optical transmitter; the second opto-electric circuit (230) is a photodetector; and the second electric circuit port (B4) is the light The second optical circuit port coupled to the second optical terminal (O2), which is an output of the detector, is an input of the photodetector;
The test device of embodiment 7, comprising at least one of the following:
(Embodiment 9)
A third electrical terminal (T2) coupled to the first switch port (A1) and a fourth electrical terminal (R2) coupled to the fourth switch port (B1); The third electrical terminal (T2) and the fourth electrical terminal (R2) are electrically stimulated (SG) to one of the third electrical terminal (T2) and the fourth electrical terminal (R2). 9. The test device of embodiment 7 or 8, wherein the test device is coupled to an electrical analyzer (100) that provides an electrical response signal (RG) at the other of the terminals (T2, R2).
(Embodiment 10)
A method of using a test device, the test device having a first electrical circuit port (A4) and a first optical circuit port coupled to a first optical terminal (O1). A first electrical switch (210) having an opto-electrical circuit (220), a first switch port (A1), a second switch port (A2), and a third switch port (A3). The first switch port (A1) is selectively coupled to the second switch port (A2) at a first switch position or to the third switch port (A3) at a second switch position. A first electrical switch, a first line (C1) coupling the second switch port (A2) to a first electrical terminal (T1), and the third switch port ( A3) the first power A second line for coupling to a circuit port (A4) (C2), the method comprising,
Switching the first switch (210) to a first state in which the first switch port (A1) is coupled to the second switch port (A2), and the first electrical terminal (T1) and Performing electrical calibration on the electrical calibration surface represented by the second electrical terminal (R1), and a second state in which the first switch port (A1) is coupled to the third switch port (A3) Switching the first switch (210) to the first optical terminal (O1) and one of the first electrical terminal (T1) and the second optical terminal (O2). Testing the device under test (400)
A method comprising at least one of:
(Embodiment 11)
A software program or software product, preferably stored on a storage medium, for performing the method of embodiment 10 when executed on a data processing system such as a computer.

FIG. 2 is a block diagram of one exemplary test device in a first setup for performing calibration measurements and a second setup for performing test measurements. FIG. 2 is a block diagram of the test device of FIG. 1 comprising an internal light source and an internal photodetector. FIG. 3 illustrates an exemplary electrical calibration measurement step using the test device of FIG. FIG. 3 illustrates an exemplary optical calibration measurement step using the test device of FIG. FIG. 3 illustrates an exemplary optical calibration measurement step using the test device of FIG. It is a figure which shows the measurement of electrical / optical DUT. It is a figure which shows the measurement of electrical / optical DUT. It is a figure which shows the measurement of optical / electrical DUT. It is a figure which shows the measurement of optical / electrical DUT. It is a figure which shows the measurement of optical / optical DUT. It is a figure which shows the measurement of optical / optical DUT.

Explanation of symbols

100 electrical analyzer 200 test device 210 first switch 220 first opto-electric circuit 230 second opto-electric circuit 240 second switch 300 electrical reference device 400 opto-electrical device under test

Claims (11)

A test device for testing a device under test,
A first opto-electrical circuit having a first electrical circuit port and a first optical circuit port coupled to the first optical terminal;
A first electrical switch having a first switch port, a second switch port, and a third switch port, wherein the first switch port is at the first switch position and the second switch A first electrical switch adapted to selectively couple to a port or to the third switch port in a second switch position;
A first line coupling the second switch port to a first electrical terminal; and a second line coupling the third switch port to the first electrical circuit port;
With
The first calibration data describing the behavior of the first opto-electrical circuit is stored, and the first switch is switched to the first switch position when the first switch is switched to the first switch position. A test device characterized by a memory adapted to store second calibration data describing the behavior of the test device with respect to an electrical calibration plane represented by the electrical terminal and the second electrical terminal .   The test device of claim 1, wherein the first optoelectronic circuit is one of an optical transmitter and a photodetector.   When the switch is switched to the second switch position, it is connected to the first optical terminal and the first electrical terminal as a function of the first calibration data and the second calibration data. The test device according to claim 1, further comprising a processor for determining a behavior of the device under test.   The first calibration data describing the behavior of the first optoelectric circuit includes a plurality of value sets, each of which is generated by a parameter of an optical signal, preferably by the first optoelectric circuit. Or corresponding to different values of the power or wavelength of the received optical signal, and the test device is configured to determine whether the device under test is based on a value set selected corresponding to the actual value of the parameter of the optical signal. The test device according to claim 3, wherein the behavior is determined. The first line and the second line are a first electrical behavior of a first path between the first electrical terminal and the first switch port, and the first switch port. And the second electrical behavior of the second path between the first opto-electrical circuit and
Temperature variations have a substantially similar effect on the first electrical behavior and the second electrical behavior, so that calibration on the first line with respect to the first electrical terminal is achieved. Is similar to compensate for variations in the second line, or an internal electrical path length in an electrical calibration device coupled to the first electrical terminal, and an internal electrical path in the opto-electrical circuit. Taking into account at least one of the length and the first electrical terminal and the first optical terminal are different to minimize the modulation effect on the transmission behavior of the test device,
The test device according to claim 1, wherein the test device is selected as follows.   The difference between the first length of the first line and the second length of the second line is 0 (zero), less than 10 millimeters, less than 20 millimeters, less than 30 millimeters, and less than 40 millimeters. The test device according to claim 1, which is one of them. A second optoelectronic circuit having a second electrical circuit port and a second optical circuit port optically coupled to the second optical terminal;
A second electrical switch having a fourth switch port, a fifth switch port, and a sixth switch port, wherein the fourth switch port is connected to the fifth switch port or the sixth switch port. A second electrical switch adapted to selectively couple to the switch port;
A third line that couples the fifth switch port to a second electrical terminal; and a fourth line that couples the sixth switch port to the second electrical circuit port;
The test device according to claim 1, further comprising: The first optical electrical circuit is an optical transmitter, the first electrical circuit port is an input of the optical transmitter, and the first optical circuit port coupled to the first optical terminal is The output of the optical transmitter, and the second opto-electrical circuit is a photodetector, and the second electrical circuit port is the output of the photodetector, coupled to the second optical terminal The second optical circuit port being configured is an input of the photodetector;
The test device of claim 7, satisfying at least one of the following:   And a third electrical terminal coupled to the first switch port and a fourth electrical terminal coupled to the fourth switch port, the third electrical terminal and the fourth electrical terminal. Is coupled to an electrical analyzer that provides an electrical stimulation signal to one of the third electrical terminal and the fourth electrical terminal and receives an electrical response signal at the other of the terminals. The test device according to claim 7 or 8. A method of using a test device, the test device comprising: a first optoelectronic circuit having a first electrical circuit port and a first optical circuit port coupled to the first optical terminal; A first electrical switch having a first switch port, a second switch port, and a third switch port, wherein the first switch port is located at the first switch position and the second switch port; Or a first electrical switch adapted to selectively couple to the third switch port in a second switch position, a first electrical switch coupling the second switch port to the first electrical terminal. And a second line coupling the third switch port to the first electrical circuit port, the method comprising:
Switching the first switch to a first state where the first switch port is coupled to the second switch port, and an electrical calibration surface represented by the first electrical terminal and the second electrical terminal Performing electrical calibration with respect to the first switch port and switching the first switch to a second state in which the first switch port is coupled to the third switch port, and the first optical terminal and the first switch Testing the device under test coupled to one of the electrical terminal and the second optical terminal;
A method comprising at least one of:   A software program or software product, preferably stored on a storage medium, for performing the method of claim 10 when executed on a data processing system such as a computer.

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