CN214040590U - Performance index measuring device of polarization maintaining optical fiber device - Google Patents
Performance index measuring device of polarization maintaining optical fiber device Download PDFInfo
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- CN214040590U CN214040590U CN202023341018.8U CN202023341018U CN214040590U CN 214040590 U CN214040590 U CN 214040590U CN 202023341018 U CN202023341018 U CN 202023341018U CN 214040590 U CN214040590 U CN 214040590U
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Abstract
A performance index measuring device of a polarization maintaining optical fiber device relates to the technical field of optical fiber communication and solves the problem of how to simply and efficiently measure the performance index of the polarization maintaining optical fiber device; the second channel of the waveform generator is connected with the input end of the phase modulator, one output port of the phase modulator is connected with the four-port polarization maintaining optical fiber device through a second tail fiber, the other output port of the phase modulator is connected with one end of a delay line, and the other end of the delay line is connected with the four-port polarization maintaining optical fiber device through a fourth tail fiber; the measuring instrument is connected with the four-port polarization maintaining optical fiber device through a third tail fiber; the measuring device can measure the polarization correlation loss and the half-wave voltage of the modulator, can measure another performance index only by replacing one device, does not need to build an environment again, and is simple to operate, time-saving, labor-saving, stable and efficient.
Description
Technical Field
The utility model belongs to the technical field of fiber communication, concretely relates to performance index measuring device of polarization maintaining fiber device.
Background
Polarization Dependent Loss (PDL) is a standard index for describing the characteristics of a passive optical device, and half-wave voltage is a very important physical quantity for representing the influence of voltage on phase difference during electro-optical modulation. These two indexes have respective measuring methods, and currently, there are two main PDL measuring methods: polarization scanning method and stationary method; there are three measurement methods for half-wave voltage: optical communication analog method, extreme value measurement method and frequency multiplication modulation method. That is to say, when the two indexes need to be measured, two appropriate schemes need to be selected from respective measuring methods to build two measuring systems.
The invention discloses a method for measuring polarization dependent loss PDL, which is disclosed in Chinese patent application 'PDL measuring method' with publication number 1988419A and publication date of 2007, 06, 27.A technical scheme is that an incident modulated light signal enters a birefringent device, then sequentially passes through an analyzer, a PDL device to be measured and finally enters a polarimeter; and rotating the polarization rotator for one circle along the polarization axis, recording the maximum value and the minimum value of DOP in the process respectively, and calculating the PDL value of the device according to the following formula:
although the technical scheme can quickly and effectively measure the PDL value in an optical device or system under the condition of single wavelength or multiple wavelengths; however, the above technical solution is not suitable for measuring the polarization dependent loss of the polarization maintaining fiber device.
Chinese patent application publication No. CN107121585A, published as 2017, 9/1, discloses a half-wave voltage measurement system and measurement method for an electro-optical phase modulator, which utilizes a port of a beam splitter, a first polarization controller, a polarization selection device, a phase modulator, a second polarization controller, and another port of the beam splitter to be sequentially connected to form a Sagnac loop structure, wherein the output of a power meter is maximized by adjusting the first polarization controller and the second polarization controller, a pulse voltage is applied to the phase modulator by an overvoltage source, the modulation voltage of the phase modulator is adjusted to maximize and minimize the readout output by the power meter, the half-wave voltage is the difference between the maximum value and the minimum value, and finally the half-wave voltage is measured by curve fitting to improve the measurement accuracy of the system. However, the measurement system has a complex structure, and requires adjusting the polarization controller and performing curve fitting, and the measurement method is cumbersome and prone to errors.
The polarization-dependent loss of a measurement device in the prior art needs to be measured by accessing a common optical fiber into a measurement system, adjusting a polarization rotator to act on the common optical fiber to change the polarization state of incident light, and recording the deviation value of the polarization state of the incident light to calculate PDL. If four-state measurement rules are adopted, four polarization states need to be generated to measure the PDL of the device, but 8 power values need to be measured to calculate the PDL, and the noise and measurement errors of the power meter can greatly influence the measurement errors of the PDL. Secondly, the power of the device to be measured is measured in sequence, so that the stability of the light source has little influence on the measurement result.
The prior art method for measuring half-wave voltage has the following defects: the minimum value of the sound volume appearing twice in the optical communication simulation method is difficult to judge, and the obtained result precision is not very high; the extreme value measurement method has the defects that the measurement precision of the method is limited due to the instability of factors such as a light source and the like, and in addition, the extreme value measurement method for measuring the half-wave voltage has the defects of sensitive and unstable optical path difference, complex system, high cost, easiness in being influenced by the outside and the like; the frequency multiplication modulation method has high requirements on adjustment and is difficult to adjust to an optimal state.
SUMMERY OF THE UTILITY MODEL
The utility model discloses the technical problem that will solve lies in how simple efficient measures the performance index of four port polarization maintaining optical fiber devices.
The utility model discloses a solve above-mentioned technical problem through following technical scheme:
a performance index measuring device of a polarization maintaining optical fiber device comprises: the device comprises a waveform generator (1), a laser (2), a measuring instrument (3), a phase modulator (4), a delay line (5) and a four-port polarization-maintaining optical fiber device; a first channel of the waveform generator (1) is connected with the input end of the laser (2), and the output end of the laser (2) is connected with a four-port polarization maintaining optical fiber device through a first tail fiber (P1); the second channel of the waveform generator (1) is connected with the input end of the phase modulator (4), one output port of the phase modulator (4) is connected with the four-port polarization maintaining optical fiber device through a second tail fiber (P2), the other output port of the phase modulator is connected with one end of the delay line (5), and the other end of the delay line (5) is connected with the four-port polarization maintaining optical fiber device through a fourth tail fiber (P4); the measuring instrument (3) is connected with the four-port polarization-maintaining optical fiber device through a third tail fiber (P3).
The measuring device can measure the polarization correlation loss and the half-wave voltage of the modulator, only one device in the system needs to be replaced to measure another performance index, the environment does not need to be built again, the operation is simple, time and labor are saved, and the measuring device is simple, stable and efficient.
As a further improvement of the technical scheme of the utility model, four-port polarization maintaining fiber device be Polarization Beam Splitter (PBS).
As the further improvement of the technical scheme of the utility model, four port polarization maintaining fiber device be annular polarization beam splitter (PCIR).
As the further improvement of the technical proposal of the utility model, the first tail fiber (P1) is connected with the laser (2), and the third tail fiber (P3) is connected with the measuring instrument (3).
As the further improvement of the technical proposal of the utility model, the first tail fiber (P1) is connected with the measuring instrument (3), and the third tail fiber (P3) is connected with the laser (2).
As the further improvement of the technical proposal of the utility model, the first tail fiber (P1), the second tail fiber (P2), the third tail fiber (P3) and the fourth tail fiber (P4) all adopt polarization maintaining optical fibers.
As the further improvement of the technical proposal of the utility model, the phase modulator (4) is a polarization maintaining phase modulator.
The utility model has the advantages that:
(1) the utility model discloses a measuring device both can measure the relevant loss of polarization and can measure the half-wave voltage of modulator again, only need just can survey another performance index with one of them device replacement in the system, need not build the environment again, easy operation and labour saving and time saving, and its measuring device is simple, stable and high-efficient.
(2) For the measurement of polarization dependent loss, the PDL of the optical device tail fiber as a polarization maintaining fiber can be measured; for the measurement of the half-wave voltage, the pole value does not need to be judged, the system is stable and is not easily influenced by the outside, only the time delay (phase) of the output voltage of the second channel of the waveform generator is needed to be adjusted, the change condition of the polarization state in the polarization analyzer is observed, and the half-wave voltage can be measured by measuring the polarization state by the polarization analyzer and rotating the polarization state on the Poincar sphere by a half circle.
Drawings
Fig. 1 is a structural diagram of a device for measuring PBS performance index according to a first embodiment of the present invention;
FIG. 2 is a structural diagram of a measurement apparatus for measuring PCIR performance index according to a second embodiment of the present invention;
FIG. 3 is a flow chart of a method of measuring PBS or PCIR polarization dependent loss;
fig. 4 is a flow chart of a method of measuring the half-wave voltage of a phase modulator.
Detailed Description
To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the embodiments of the present invention are combined to clearly and completely describe the technical solution in the embodiments of the present invention, and obviously, the described embodiments are some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
The technical solution of the present invention is further described below with reference to the drawings and specific embodiments of the specification:
example one
As shown in fig. 1, the performance index measuring apparatus of the polarization maintaining fiber device of the present embodiment includes a waveform generator 1, a laser 2, a measuring instrument 3, a phase modulator 4, a delay line 5, and a polarization beam splitter PBS.
The PBS has four tail fibers P1, P2, P3 and P4 which are polarization maintaining fibers, wherein the tail fiber P1 is connected with the laser 2, the tail fiber P2 is connected with the in port of the phase modulator 4, the tail fiber P3 is connected with the measuring instrument 3, and the tail fiber P4 is connected with one end of the delay line 5; the laser 2 is connected with a CH1 port of the waveform generator 1; the phase modulator 4 is connected with a port CH2 of the waveform generator 1, and a port out of the phase modulator 4 is connected with the other end of the delay line 5; the phase modulator 4 adopts a polarization maintaining phase modulator.
The optical pulse emitted by the laser 2 enters from the tail fiber P1 of the PBS, and is divided into two polarized lights after passing through the PBS, wherein the path of one polarized light is: PBS → pigtail P2 → phase modulator 4 → delay line 5 → pigtail P4 → PBS; the path of the other polarized light is: PBS → pigtail P4 → delay line 5 → phase modulator 4 → pigtail P2 → PBS; the paths of the two polarized lights form a loop with equal path length and opposite direction, and the two loops are superposed at the PBS to form a Sagnac loop.
The position of the delay line 5 is adjusted to enable the phase modulator 4 to be placed at the asymmetric position of the Sagnac loop, the time asymmetry degree of the phase modulator 4 must be larger than the rising and falling time of the voltage signal loaded by the waveform generator 1, namely the phase modulator 4 divides the Sagnac loop into two sections of optical fibers, and the time difference of the optical pulse passing through the two sections of optical fibers must be larger than the rising and falling time of the voltage signal loaded by the waveform generator 1, so that the accuracy of the measuring result is guaranteed.
A tail fiber P2 of the PBS is connected with an in port of the phase modulator 4, a tail fiber P4 is connected with a delay line 5, the delay line 5 is connected with an out port of the phase modulator 4, a signal is sent to the phase modulator 4 through the waveform generator 1, and the voltage value of the phase modulator 4 is changed, so that the polarization state of light in the Sagnac ring is changed.
In the present embodiment, the positions of the laser 2 and the measuring instrument 3 are interchangeable, that is, if the laser 2 is connected to the pigtail P1, the measuring instrument 3 is connected to the pigtail P3, and if the measuring instrument 3 is connected to the pigtail P1, the laser 2 is connected to the pigtail P3.
1. When the performance index measuring device of the polarization maintaining optical fiber device of the embodiment is used for measuring the polarization-dependent loss of the PBS, the measuring instrument 3 is set as an optical power meter; the specific measurement method is shown in fig. 3:
step (1): constructing a measuring device for polarization dependent loss of a four-port polarization-maintaining optical fiber device according to the diagram shown in FIG. 1;
step (2): turning on the waveform generator 1, respectively setting parameters such as waveforms, frequency, time delay, high and low levels, duty ratio and the like output by a CH1 port and a CH2 port of the waveform generator 1, and confirming that pulse waveforms output by a CH1 port and sine waveforms output by a CH2 port are normal;
and (3): adjusting the phase (delay) value of the voltage output by a CH2 port by rotating a knob of a waveform generator 1, thereby adjusting the polarization state of light from 0 degree to 360 degrees (step setting is 1 degree), changing the optical Power at the moment, changing the reading on an optical Power meter, observing the reading of the optical Power meter, and recording the maximum max (Power P3) and the minimum min (Power P3) of the reading;
and (4): calculating the PDL (polarization dependent loss), wherein the calculation formula is as follows: PDL max (Power P3) -min (Power P3).
2. When the performance index measuring device of the polarization maintaining optical fiber device of the embodiment is used for measuring the half-wave voltage of the phase modulator, the measuring instrument 3 is set as a polarization analyzer; the specific measurement method is shown in fig. 4:
step one, a waveform generator 1 sends a signal to a phase modulator 4, changes the voltage value of the phase modulator 4 so as to change the polarization state of light in a Sagnac ring, and measures the delay of the maximum light power;
and step two, setting the time delay of the waveform generator 1 as the time delay of the maximum optical power, adjusting the voltage value output by a port CH2 of the waveform generator by rotating a knob of the waveform generator 1, observing the change condition of the polarization state in the polarization analyzer, and when the polarization analyzer is observed to measure the rotation of the polarization state on the Poincare sphere by a half turn, the voltage value of the phase modulator 4 is the half-wave voltage value to be measured.
The method for measuring the time delay of the maximum optical power time in the first step comprises the following steps:
1. setting a measuring instrument 3 in the figure 1 as an optical power meter, and building a measuring device according to the figure 1;
2. turning on the waveform generator 1, respectively setting parameters such as waveforms, frequency, time delay, high and low levels, duty ratio and the like output by a CH1 port and a CH2 port of the waveform generator 1, and confirming that pulse waveforms output by a CH1 port and sine waveforms output by a CH2 port are normal;
3. by rotating the knob of the waveform generator 1, the phase (delay) value of the voltage output from the port CH2 is adjusted, so as to adjust the polarization state of the light from 0 ° to 360 ° (step by step is set to 1 °), at this time, the optical Power will change, the reading on the optical Power meter will change accordingly, the reading of the optical Power meter is observed, and the delay of the maximum value max (Power P3) of the reading is recorded.
Example two
As shown in fig. 2, different from the first embodiment, the device under test in the present embodiment is a circular polarization beam splitter (PCIR), light emitted by the laser 2 enters from a tail fiber P1 of the circular polarization beam splitter, is divided into two polarized lights by passing through a PBS in the PCIR, and returns to the PCIR through optical paths with equal paths and opposite directions by a tail fiber P2 and a tail fiber P4, and are superimposed to form a Sagnac loop.
1. When the performance index measuring device of the polarization maintaining optical fiber device of the embodiment is used for measuring the polarization-dependent loss of the PCIR, the measuring instrument 3 is set as an optical power meter; the specific measurement method is shown in fig. 3, which is the same as the method for measuring the polarization dependent loss of the PBS in the first embodiment.
2. When the performance index measuring device of the polarization maintaining optical fiber device of the embodiment is used for measuring the half-wave voltage of the phase modulator, the measuring instrument 3 is set as a polarization analyzer; the specific measurement method is shown in fig. 4, and is the same as that of the first embodiment.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.
Claims (5)
1. A performance index measuring device of a polarization maintaining optical fiber device is characterized by comprising: the device comprises a waveform generator (1), a laser (2), a measuring instrument (3), a phase modulator (4), a delay line (5) and a four-port polarization-maintaining optical fiber device; the first channel of the waveform generator (1) is connected with the input end of the laser (2), the positions of the laser (2) and the measuring instrument (3) can be interchanged, and if the output end of the laser (2) is connected with the four-port polarization-maintaining optical fiber device through the first tail fiber (P1), the measuring instrument (3) is connected with the four-port polarization-maintaining optical fiber device through the third tail fiber (P3); if a measuring instrument (3) is connected at the first tail fiber (P1), a laser (2) is connected at a third tail fiber (P3); the second channel of the waveform generator (1) is connected with the input end of the phase modulator (4), one output port of the phase modulator (4) is connected with the four-port polarization maintaining optical fiber device through a second tail fiber (P2), the other output port of the phase modulator is connected with one end of the delay line (5), and the other end of the delay line (5) is connected with the four-port polarization maintaining optical fiber device through a fourth tail fiber (P4).
2. The apparatus of claim 1, wherein the four-port polarization maintaining fiber device is a polarization beam splitter.
3. The apparatus of claim 1, wherein the four-port polarization maintaining fiber device is an annular polarization beam splitter.
4. The performance index measuring device of the polarization maintaining fiber device of claim 1, wherein the first pigtail (P1), the second pigtail (P2), the third pigtail (P3) and the fourth pigtail (P4) are all polarization maintaining fibers.
5. The apparatus for measuring performance index of a polarization maintaining fiber device according to claim 1, wherein the phase modulator (4) is a polarization maintaining phase modulator.
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