CN111707361B - Method for measuring half-wave voltage of M-Z type light intensity modulator - Google Patents
Method for measuring half-wave voltage of M-Z type light intensity modulator Download PDFInfo
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- CN111707361B CN111707361B CN202010596711.5A CN202010596711A CN111707361B CN 111707361 B CN111707361 B CN 111707361B CN 202010596711 A CN202010596711 A CN 202010596711A CN 111707361 B CN111707361 B CN 111707361B
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- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
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Abstract
The invention discloses a method for measuring half-wave voltage of an M-Z type light intensity modulator, which comprises the steps of measuring the M-Z type light intensity modulator to be measured by adopting a light source, an optical power meter and a waveform generator, and firstly adjusting direct-current bias voltage to enable the output light power of the M-Z type light intensity modulator to be measured to be positioned in a maximum value area; and then, superposing a sine wave signal with a peak-to-peak value of 0 on the basis of the direct current bias voltage, gradually increasing the peak-to-peak value of the sine wave signal to reduce the display value of the optical power meter to a minimum value, and finally calculating the half-wave voltage of the M-Z type light intensity modulator to be measured according to the current peak-to-peak value of the sine wave signal. The sine wave is superposed on the direct current bias voltage to serve as the test signal, the influence of direct current drift is effectively avoided through innovation of a test method, the half-wave voltage of the M-Z type light intensity modulator can be accurately measured by using the optical power meter, a high-precision oscilloscope is not needed, the cost of a test system is low, and the test precision is high.
Description
Technical Field
The invention relates to the field of M-Z type light intensity modulators, in particular to a method for measuring half-wave voltage of an M-Z type light intensity modulator.
Background
An M-Z type optical intensity modulator (Mach Zehnder optical intensity modulator) is an important device in optical fiber communication and optical fiber sensing, and can be used for carrier suppression, pulse generation and pulse selection. The half-wave voltage is an important index of the M-Z type light intensity modulator, and the common test methods thereof include the following two methods:
1. connecting a test system according to figure 1, outputting sawtooth waves as test signals by a waveform generator, gradually increasing the voltage value of output signals of the waveform generator to enable the output waveform displayed by an oscilloscope to sequentially appear two maximum points, sequentially recording the voltage values of the output signals of the waveform generator corresponding to the two maximum points as V1 and V2, and calculating half-wave voltage V according to the following formula π ；
2. Connecting the test system according to FIG. 2, adjusting the alignmentA current regulator for gradually increasing output voltage from zero to maximize the reading of the optical power meter, and reading the voltage value of the current regulator and recording as V 1 (ii) a Regulating the DC voltage regulator, increasing output voltage gradually to make the reading of optical power meter decrease to minimum and then increase to maximum, reading the output voltage value of the DC voltage regulator and recording as V 2 (ii) a The half-wave voltage V is calculated as follows π 。
The first method has accurate test result, but needs an oscilloscope, and has higher test system price; in the second method, the optical power meter is used for replacing an oscilloscope, so that the test cost is low, but the direct-current voltage measurement is adopted, the drift is serious, and the accuracy is lower.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for measuring half-wave voltage of an M-Z type light intensity modulator, which is low in measurement cost and high in measurement precision.
The technical scheme of the invention is as follows:
a method for measuring half-wave voltage of an M-Z type light intensity modulator comprises the following steps:
s1, connecting an input port of an M-Z type light intensity modulator to be tested to a light source through an optical fiber, connecting an output port to an optical power meter through the optical fiber, and electrically connecting a voltage port to a waveform generator;
s2, applying a direct-current bias voltage to the M-Z type light intensity modulator to be tested through the waveform generator, and adjusting the direct-current bias voltage to enable the output light power of the M-Z type light intensity modulator to be tested to be located in a maximum value area;
s3, adjusting an output signal of the waveform generator to enable the output signal to be superposed with a sine wave signal with a peak-to-peak value of 0 on the basis of the current output direct current bias voltage;
s4, gradually increasing the peak value of the sine wave signal to gradually reduce the display value of the optical power meter, and recording the current peak value of the sine wave signal when the display value of the optical power meter is reduced to a minimum value;
and S5, calculating the half-wave voltage of the M-Z type light intensity modulator to be measured according to the current peak-to-peak value of the recorded sine wave signal.
Further, in the step S2, after applying a dc bias to the M-Z type optical intensity modulator to be measured, the phase difference θ generated by the two arm optical paths thereof satisfies the following condition:
cos(θ)≠0。
further, the frequency of the sine wave signal is greater than the sampling frequency of the optical power meter.
Further, in the step S5, a formula for calculating a half-wave voltage of the M-Z type light intensity modulator to be measured is as follows:
wherein, V π Representing half-wave voltage, V, of the M-Z type light intensity modulator to be measured ppπ Which represents the peak-to-peak value of the sine wave signal recorded when step S4 is performed.
A method for measuring half-wave voltage of an M-Z type light intensity modulator comprises the following steps:
step S1', an input light port of an M-Z type light intensity modulator to be tested is connected to a light source through an optical fiber, an output light port is connected to an optical power meter through the optical fiber, and a voltage port is electrically connected to a waveform generator;
s2', applying direct-current bias voltage to the device to be tested through a waveform generator, and adjusting the output optical power of the M-Z type light intensity modulator to be tested to be in a minimum value area;
s3', adjusting an output signal of a waveform generator to enable the output signal to be superposed with a sine wave signal with a peak-to-peak value of 0 on the basis of the current output direct current bias voltage;
step S4', gradually increasing the peak value of the sine wave signal to gradually increase the display value of the optical power meter, and recording the current peak value of the sine wave signal when the display value of the optical power meter is increased to the maximum value;
and S5', calculating the half-wave voltage of the M-Z type light intensity modulator to be measured according to the current peak-to-peak value of the recorded sine wave signal.
Further, in the step S2', after applying a bias voltage to the M-Z type optical intensity modulator to be measured, the phase difference θ generated by the two arm optical paths satisfies the following condition:
cos(θ)≠0。
further, the frequency of the sine wave signal is greater than the sampling frequency of the optical power meter.
Further, in the step S5', a formula for calculating a half-wave voltage of the M-Z type light intensity modulator to be measured is as follows:
wherein, V π Representing half-wave voltage, V, of the M-Z type light intensity modulator to be measured ppπ 'denotes a peak-to-peak value of the sine wave signal recorded when step S4' is performed.
Has the beneficial effects that: in the invention, the sine wave signal is superposed on the direct current bias voltage as the test signal, the influence of direct current drift is effectively avoided by innovating the test method, the half-wave voltage of the M-Z type light intensity modulator can be accurately measured by using the optical power meter, a high-precision oscilloscope is not required, the cost of the test system is low, and the test precision is high.
Drawings
FIG. 1 is a schematic diagram of a device connection in a first method for half-wave voltage testing of an M-Z type light intensity modulator in the prior art;
FIG. 2 is a schematic diagram of the connection of a second method for half-wave voltage testing of an M-Z type light intensity modulator in the prior art;
FIG. 3 is a flowchart of example 1 of the present invention;
fig. 4 is a schematic diagram of device connection during testing according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions in the embodiments of the present invention better understood and make the above objects, features and advantages of the embodiments of the present invention more comprehensible, the technical solutions in the embodiments of the present invention are described in further detail below with reference to the accompanying drawings.
In the description of the present invention, unless otherwise specified and limited, it is to be noted that the term "connected" is to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, or a communication between two elements, or may be a direct connection or an indirect connection through an intermediate medium, and a specific meaning of the term may be understood by those skilled in the art according to specific situations.
Example 1
As shown in fig. 3, embodiment 1 of the method for measuring the half-wave voltage of the M-Z type optical intensity modulator includes the steps of:
step S1, as shown in FIG. 4, connecting an input port of an M-Z type light intensity modulator to be tested to a light source through an optical fiber, connecting an output port to an optical power meter through the optical fiber, and electrically connecting a voltage port to a waveform generator;
s2, applying a direct-current bias voltage to the M-Z type light intensity modulator to be tested through the waveform generator, and adjusting the direct-current bias voltage to enable the output light power of the M-Z type light intensity modulator to be tested to be located in a maximum value area, wherein the maximum value area is an area with an output light power value larger than a half-power point, and is preferably a maximum value point or a vicinity of the maximum value point; after the direct current bias is applied to the M-Z type light intensity modulator to be tested, the phase difference theta generated by the two arm light paths meets the following condition:
cos(θ)≠0。
s3, adjusting an output signal of the waveform generator to superpose a sine wave signal with a peak-to-peak value of 0 on the basis of the current output direct current bias voltage, wherein the frequency of the sine wave signal is greater than the sampling frequency of the optical power meter;
s4, gradually increasing the peak value of the sine wave signal to gradually reduce the display value of the optical power meter, and recording the current peak value of the sine wave signal when the display value of the optical power meter is reduced to a minimum value;
s5, calculating the half-wave voltage of the M-Z type light intensity modulator to be detected according to the recorded peak-to-peak value of the sine wave signal, wherein the formula for calculating the half-wave voltage of the M-Z type light intensity modulator to be detected is as follows:
wherein, V π Indicating the half-wave voltage, V, of the M-Z type light intensity modulator to be measured ppπ Which represents the peak-to-peak value of the sine wave signal recorded when step S4 is performed.
The test principle of this embodiment is as follows:
when no signal is input, the M-Z type light intensity modulator outputs the light field E of the light signal out Can be expressed as
E out ＝A·exp(iω c t)
Where A is the optical field amplitude of the input light, ω c Is the angular frequency of the input light.
After the sine wave signal is input, the M-Z type optical intensity modulator outputs the optical field E of the optical signal out Can be expressed as
At this time, the output optical power P corresponding to the M-Z type optical intensity modulator out Is shown as
Wherein theta is the phase difference V generated by the bias voltage of the two-arm optical path of the M-Z interferometer pp For inputting peak-to-peak values, V, of a sine wave signal π Is half-wave voltage, ω e Is the angular frequency of the sine wave signal, E out * Is E out Conjugation of (1).
Since the measurement result of the optical power meter is the integral of the power in a period of time, when the frequency of the sine wave used is greater than the sampling frequency of the optical power meter (preferably, the frequency of the sine wave signal is greater than the sampling frequency of the power meter by about 2 orders of magnitude), the display value of the optical power meter is approximately the integral of the output optical power value in a single cycle of the sine wave signal.
The output optical power over a single period is integrated and the results can be discussed in three cases:
1、cos(θ)>at time 0, V pp Gradually increasing from 0, the value of P will gradually decrease until V pp ＝2.44V π The time is minimized.
2、cos(θ)<At time 0, V pp Gradually increasing from 0, the value of P will gradually increase until V pp ＝2.44V π Is maximized.
3. When cos (θ) =0, V is changed in any way pp The value of P does not change.
Therefore, only by avoiding the situation that cos (theta) =0, the half-wave voltage of the M-Z type light intensity modulator can be obtained through calculation of the peak-to-peak value of the sine wave signal output by the waveform generator when the display value of the optical power meter is reduced to the minimum value; when the output optical power of the M-Z type light intensity modulator to be measured is located in the maximum value region, cos (θ) =0, and when the output optical power of the M-Z type light intensity modulator to be measured is located at the maximum value point, cos (θ) =1, the case where cos (θ) =0 does not occur.
From the analysis, the half-wave voltage of the M-Z type light intensity modulator can be measured by using the light source, the optical power meter and the waveform generator, and meanwhile, the sine wave signal frequency of the measuring method has no upper limit, and only the fact that the sine wave signal frequency is greater than the sampling frequency of the power meter by about 2 orders of magnitude is required; because an oscilloscope is not used, the test method has lower cost; meanwhile, sine wave signals with certain frequency are adopted in the test, so that the influence of direct current drift is avoided, and the test result is more accurate.
Example 2
Embodiment 2 of the method for measuring the half-wave voltage of the M-Z type light intensity modulator comprises the following steps:
step S1' as shown in FIG. 4, an input port of the M-Z type light intensity modulator to be tested is connected to a light source through an optical fiber, an output port is connected to an optical power meter through an optical fiber, and a voltage port is electrically connected to a waveform generator;
s2', applying a direct-current bias voltage to the M-Z type light intensity modulator to be detected through the waveform generator, and adjusting the direct-current bias voltage to enable the output light power of the M-Z type light intensity modulator to be detected to be located in a minimum value area, wherein the minimum value area is an area where the output light power value is smaller than a half-power point, and is preferably an extremely small value point or a vicinity of the extremely small value point; after the direct current bias voltage is applied to the M-Z type light intensity modulator to be tested, the phase difference theta generated by the two arm light paths meets the following condition:
cos(θ)≠0。
s3', adjusting an output signal of a waveform generator to enable the output signal to be superposed with a sine wave signal with a peak-to-peak value of 0 on the basis of the current output direct current bias voltage, wherein the frequency of the sine wave signal is greater than the sampling frequency of an optical power meter;
step S4', gradually increasing the peak value of the sine wave signal to gradually increase the display value of the optical power meter, and recording the current peak value of the sine wave signal when the display value of the optical power meter is increased to the maximum value;
step S5', calculating the half-wave voltage of the M-Z type light intensity modulator to be detected according to the recorded peak-to-peak value of the sine wave signal, wherein the formula for calculating the half-wave voltage of the M-Z type light intensity modulator to be detected is as follows:
wherein, V π Representing half-wave voltage, V, of the M-Z type light intensity modulator to be measured ppπ 'denotes a peak-to-peak value of the sine wave signal recorded when step S4' is performed.
This example differs from example 1 only in that: example 1 the section of the test half-wave voltage is selected in such a way that the display value of the optical power meter is reduced from the maximum value region to the minimum value, while the section of the test half-wave voltage is selected in such a way that the display value of the optical power meter is increased from the minimum value region to the maximum value, i.e. only the selected test section is different, but the test principle is consistent with example 1, in which V is the case ppπ ' values and V in example 1 ppπ Should also be equal. At the same time, the user can select the desired position,in this embodiment, the half-wave voltage of the M-Z type light intensity modulator can be calculated by the peak-to-peak value of the sine wave signal output by the waveform generator when the display value of the optical power meter increases to the maximum value, as long as cos (θ) =0 is avoided; and when the output optical power of the M-Z type optical intensity modulator to be tested is positioned in the minimum value area, cos (theta)<And 0, when the output optical power of the M-Z type light intensity modulator to be tested is positioned at the minimum value point, cos (theta) = -1, and the condition that cos (theta) =0 cannot occur.
The undescribed parts of the present invention are consistent with the prior art, and are not described herein.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields, and are within the scope of the present invention.
Claims (6)
1. A method for measuring half-wave voltage of an M-Z type light intensity modulator is characterized by comprising the following steps:
the method comprises the following steps that S1, an input light port of an M-Z type light intensity modulator to be tested is connected to a light source through an optical fiber, an output light port is connected to an optical power meter through the optical fiber, and a voltage port is electrically connected to a waveform generator;
s2, applying a direct current bias voltage to the M-Z type light intensity modulator to be tested through a waveform generator, and adjusting the direct current bias voltage to enable the output light power of the M-Z type light intensity modulator to be tested to be located in a maximum value area, wherein the maximum value area is an area where the output light power value is larger than a half-power point; after the direct current bias is applied to the M-Z type light intensity modulator to be tested, the phase difference theta generated by the two arm light paths meets the following condition:
cos(θ)≠0；
s3, adjusting an output signal of the waveform generator to superpose a sine wave signal with a peak-to-peak value of 0 on the basis of the current output direct current bias voltage;
s4, gradually increasing the peak value of the sine wave signal to gradually reduce the display value of the optical power meter, and recording the current peak value of the sine wave signal when the display value of the optical power meter is reduced to a minimum value;
and S5, calculating the half-wave voltage of the M-Z type light intensity modulator to be detected according to the current peak-to-peak value of the recorded sine wave signal.
2. The method of measuring half-wave voltage of an M-Z type optical intensity modulator according to claim 1, wherein the frequency of the sine wave signal is greater than the sampling frequency of the optical power meter.
3. The method for measuring half-wave voltage of M-Z type light intensity modulator according to claim 1, wherein in the step S5, the formula for calculating the half-wave voltage of M-Z type light intensity modulator to be measured is as follows:
wherein, V π Indicating the half-wave voltage, V, of the M-Z type light intensity modulator to be measured ppπ Which represents the peak-to-peak value of the sine wave signal recorded when step S4 is performed.
4. A method for measuring half-wave voltage of an M-Z type light intensity modulator is characterized by comprising the following steps:
s1', connecting an input port of an M-Z type light intensity modulator to be tested to a light source through an optical fiber, connecting an output port to an optical power meter through the optical fiber, and electrically connecting a voltage port to a waveform generator;
s2', applying direct current bias voltage to a device to be tested through a waveform generator, and adjusting the output light power of the M-Z type light intensity modulator to be tested to be located in a minimum value area, wherein the minimum value area is an area where the output light power value is smaller than a half-power point; after bias voltage is applied to the M-Z type light intensity modulator to be tested, the phase difference theta generated by the two arm light paths meets the following condition:
cos(θ)≠0；
s3', adjusting an output signal of the waveform generator to superpose a sine wave signal with a peak-to-peak value of 0 on the basis of the current output direct current bias voltage;
step S4', gradually increasing the peak value of the sine wave signal to gradually increase the display value of the optical power meter, and recording the current peak value of the sine wave signal when the display value of the optical power meter is increased to the maximum value;
and S5', calculating the half-wave voltage of the M-Z type light intensity modulator to be measured according to the current peak-to-peak value of the recorded sine wave signal.
5. The method as claimed in claim 4, wherein the frequency of the sine wave signal is greater than the sampling frequency of the optical power meter.
6. The method for measuring half-wave voltage of M-Z type light intensity modulator according to claim 4, wherein in the step S5', the formula for calculating the half-wave voltage of M-Z type light intensity modulator under test is as follows:
wherein, V π Representing half-wave voltage, V, of the M-Z type light intensity modulator to be measured ppπ 'denotes a peak-to-peak value of the sine wave signal recorded when step S4' is performed.
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| JP3693872B2 (en) * | 1999-12-02 | 2005-09-14 | 住友大阪セメント株式会社 | Light modulation apparatus and method |
| JP4608149B2 (en) * | 2001-08-10 | 2011-01-05 | 住友大阪セメント株式会社 | Method and apparatus for measuring half-wave voltage of Mach-Zehnder type optical modulator |
| CN100498249C (en) * | 2007-04-19 | 2009-06-10 | 浙江大学 | Electrooptical phase modulation coefficient measing method for electrooptical phase modulator |
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