CN114689272A - Device and method for measuring polarization-dependent loss of polarization-maintaining optical fiber device - Google Patents
Device and method for measuring polarization-dependent loss of polarization-maintaining optical fiber device Download PDFInfo
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- CN114689272A CN114689272A CN202011629706.6A CN202011629706A CN114689272A CN 114689272 A CN114689272 A CN 114689272A CN 202011629706 A CN202011629706 A CN 202011629706A CN 114689272 A CN114689272 A CN 114689272A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
- G01M11/337—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face by measuring polarization dependent loss [PDL]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0207—Details of measuring devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
- G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
- G01M11/333—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face using modulated input signals
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Abstract
A measurement device and method of polarization dependent loss of polarization maintaining optical fiber device belongs to the technical field of optical fiber communication, and solves the technical problem of how to accurately measure the polarization dependent loss of the device adopting the polarization maintaining optical fiber; through the built measuring device, the value of the polarization dependent loss PDL of the optical device with the input end being the polarization maintaining optical fiber is measured, the PDL is calculated only by recording the maximum value and the minimum value in the optical power meter, the difference between the two values is obtained, and the measuring method is simple; the waveform generator sends signals to the phase modulator, and the voltage value is changed, so that the polarization state of the light is changed, and the change of the polarization state of the light is more accurate than the change of the polarization state of the light by adjusting the polarization rotator.
Description
Technical Field
The invention belongs to the technical field of optical fiber communication, and relates to a device and a method for measuring polarization dependent loss of a polarization maintaining optical fiber device.
Background
Polarization Dependent Loss (PDL) is the maximum transmission difference of an optical device or system in all polarization states, which is the ratio of the maximum transmission to the minimum transmission of an optical device in all polarization states. Polarization dependent loss has now become a standard indicator for describing the characteristics of passive optical devices. Currently there are mainly two PDL measurement methods: polarization scanning methods and stationary methods. The polarization scanning method is a relative measurement method, and the actual measurement value reflects the deviation value of the optical power depending on the polarization state of the incident light, and the difference between the maximum value and the minimum value among the measured power values is the PDL. The fixed state method is a measurement method derived by using a mueller matrix and a Lagrange extremum method according to the transmission characteristics of polarized light.
In the prior art, the polarization-dependent loss of a measurement device is that the device to be measured is accessed into a measurement system by adopting a common optical fiber, the polarization state of incident light is changed by adjusting a polarization rotator to act on the common optical fiber, the deviation value of the polarization state of the incident light is recorded, and PDL is obtained by calculation.
The role of a Polarizing Beam Splitter (PBS) is to split a certain light Beam into two linearly polarized light beams with orthogonal Polarization directions, horizontally polarized and vertically polarized, and split them into two different propagation directions, usually perpendicular to each other.
The invention discloses a method for measuring Polarization Dependent Loss (PDL), which is disclosed in Chinese patent application (PDL) of 'PDL measurement method' with publication number 1988419A, the publication number of which is 06, 27 and 2007, the technical scheme is that an incident modulation optical signal enters a birefringent device, and then sequentially passes through an analyzer and 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.
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, because the power of the device to be measured is measured in sequence, the stability of the light source can generate great error influence on the measurement result.
Disclosure of Invention
The technical problem to be solved by the invention is how to accurately measure the polarization dependent loss of a device adopting the polarization maintaining optical fiber.
The invention solves the technical problems through the following technical scheme:
a polarization dependent loss measuring apparatus for measuring polarization dependent loss of a polarization maintaining fiber device, comprising: the device comprises a waveform generator (1), a laser (2), an optical power meter (3), a phase modulator (4) and a delay line (5); 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 the polarization-maintaining optical fiber device through a first tail fiber (P1); a second channel of the waveform generator (1) is connected with an input end of a phase modulator (4), one output port of the phase modulator (4) is connected with a 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 a delay line (5), and the other end of the delay line (5) is connected with the polarization-maintaining optical fiber device through a fourth tail fiber (P4); the optical power meter (3) is connected with the polarization-maintaining optical fiber device through a third tail fiber (P3).
The invention measures the value of the polarization dependent loss PDL of the optical device with the input end of the polarization maintaining optical fiber through the built measuring device, the PDL is calculated only by recording the maximum value and the minimum value in the optical power meter (3), the difference between the two values is the result, and the measuring method is simple.
As a further improvement of the technical scheme of the invention, the optical pulse emitted by the laser (2) enters from a first tail fiber (P1) of the polarization-maintaining optical fiber device, and is divided into two beams of polarized light after passing through the polarization-maintaining optical fiber device, wherein the path of one beam of polarized light is as follows: second pigtail (P2) → phase modulator (4) → delay line (5) → fourth pigtail (P4); the path of the other polarized light is: fourth pigtail (P4) → delay line (5) → phase modulator (4) → second pigtail (P2); the paths of the two beams of polarized light form a loop with equal path and opposite direction, and the loop returns to the polarization-maintaining optical fiber device for superposition to form a Sagnac ring; and adjusting the position of the delay line (5) to enable the phase modulator (4) to be placed at the asymmetric position of the Sagnac ring, wherein the Sagnac ring is divided into two sections of optical fibers by the phase modulator (4), and the time difference of the optical pulse passing through the two sections of optical fibers is larger than the rising time and the falling time of the voltage signal loaded by the waveform generator (1).
As a further improvement of the technical scheme of the invention, the polarization-maintaining optical fiber device is a Polarization Beam Splitter (PBS) or a circular polarization beam splitter (PCIR).
As a further improvement of the technical scheme of the invention, if the laser (2) is connected at the first tail fiber (P1), the optical power meter (3) is connected at the third tail fiber (P3); if an optical power meter (3) is connected at the first pigtail (P1), then a laser (2) is connected at the third pigtail (P3).
As a further improvement of the technical scheme of the invention, polarization-maintaining optical fibers are adopted in the first tail fiber (P1), the second tail fiber (P2), the third tail fiber (P3) and the fourth tail fiber (P4).
As a further improvement of the technical scheme of the invention, the phase modulator (4) is a polarization-maintaining phase modulator.
A measuring method adopting the measuring device comprises the following steps:
step 1): building a measuring device;
step 2): opening a first channel and a second channel of a waveform generator (1), respectively setting parameters of the two channels, and confirming that the waveforms of the two channels are normal;
step 3): adjusting the phase value of the voltage output by the second channel by rotating a knob of the waveform generator (1), thereby changing the polarization state of light, adjusting the polarization state from 0 to 360 degrees, observing the reading of the optical power meter (3), and recording the maximum value and the minimum value of the reading;
step 4): the polarization dependent loss PDL is calculated.
As a further improvement of the technical solution of the present invention, the parameters in step 2) include: waveform, frequency, time delay, high and low levels, duty cycle.
As a further improvement of the solution according to the invention, the adjustment step value from 0 ° to 360 ° in step 3) is set to 1 °.
As a further improvement of the technical solution of the present invention, the calculation formula for calculating the PDL according to the polarization dependent loss in step 4) is: PDL max (Power P3) -min (Power P3), max (Power P3) and min (Power P3) respectively represent the maximum value and the minimum value of the reading on the optical Power meter (3)
The invention has the advantages that:
(1) the invention measures the value of the polarization dependent loss PDL of the optical device with the input end of the polarization maintaining optical fiber through the built measuring device, the PDL is calculated only by recording the maximum value and the minimum value in the optical power meter (3), the difference between the two values is the result, and the measuring method is simple.
(2) The waveform generator (1) sends signals to the phase modulator (4), and the voltage value is changed, so that the polarization state of the light is changed, and the change of the polarization state of the light is more accurate than the change of the polarization state of the light by adjusting the polarization rotator.
Drawings
FIG. 1 is a structural diagram of a measurement apparatus for polarization dependent loss of a polarization maintaining fiber device according to a first embodiment of the present invention;
FIG. 2 is a structural diagram of a polarization dependent loss measurement apparatus for a polarization maintaining fiber device according to a second embodiment of the present invention;
fig. 3 is a flowchart of a method for measuring polarization dependent loss of a polarization maintaining fiber device according to the first and second embodiments of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical scheme of the invention is further described by combining the drawings and the specific embodiments in the specification:
example one
As shown in fig. 1, the apparatus for measuring polarization dependent loss of a polarization maintaining fiber device in this embodiment includes a waveform generator 1, a laser 2, an optical power meter 3, a phase modulator 4, and a delay line 5, and the device under test in this embodiment is a four-port polarization beam splitter PBS.
The four-port polarization beam splitter is provided with 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 optical power meter 3 and is used for measuring the optical power, 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.
The traditional scheme cannot measure the polarization maintaining fiber P1 at the input end of the PBS; connecting a tail fiber P2 of the PBS with an in port of a phase modulator 4, connecting a tail fiber P4 with a delay line 5, connecting the delay line 5 with an out port of the phase modulator 4, sending a signal to the phase modulator 4 through a waveform generator 1, and changing the voltage value of the phase modulator 4 so as to change the polarization state of light in the Sagnac ring; when the maximum value and the minimum value are read by the optical power meter 3, PDL is the difference between the maximum value and the minimum value.
In this embodiment, the positions of the laser 2 and the optical power meter 3 are interchangeable, i.e. if the laser 2 is connected at the pigtail P1, the optical power meter 3 is connected at the pigtail P3, and if the optical power meter 3 is connected at the pigtail P1, the laser 2 is connected at the pigtail P3.
Fig. 3 is a flow chart of a method for measuring polarization dependent loss of a polarization maintaining fiber device, the method comprising the steps of:
1. constructing a measuring device for polarization dependent loss of a polarization maintaining optical fiber device according to the figure 1;
2. turning on the waveform generator 1, respectively setting parameters such as waveform, frequency, time delay, high and low level, duty ratio and the like output by a CH1 port and a CH2 port of the waveform generator 1, and confirming that the pulse waveform output by a CH1 port and the sine waveform output by a CH2 port are normal;
3. adjusting the phase (delay) value of the voltage output by the port CH2 by rotating a knob of the waveform generator 1, thereby adjusting the polarization state of light from 0 degree to 360 degrees (step setting is 1 degree), wherein the optical Power changes, the reading on the optical Power meter 3 changes accordingly, the reading of the optical Power meter 3 is observed, and the maximum value max (Power P3) and the minimum value min (Power P3) of the reading are recorded;
4. calculating the PDL (polarization dependent loss), wherein the calculation formula is as follows: PDL max (Power P3) -min (Power P3).
Example two
As shown in fig. 2, unlike the first embodiment, the device under test in this embodiment is a ring polarization beam splitter (PCIR), in this embodiment, the PBS in the first embodiment is replaced by the ring polarization beam splitter (PCIR), light emitted by the laser 2 enters from a tail fiber P1 of the ring polarization beam splitter, is split into two polarized lights by the PBS in the PCIR, and is respectively overlapped by the tail fiber P2 and the tail fiber P4 through equal and opposite optical paths back to the PCIR to form a Sagnac ring. As shown in fig. 3, the measurement method of the present embodiment is the same as the measurement method of the first embodiment.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A polarization dependent loss measuring apparatus for measuring polarization dependent loss of a polarization maintaining fiber device, comprising: the device comprises a waveform generator (1), a laser (2), an optical power meter (3), a phase modulator (4) and a delay line (5); 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 the polarization-maintaining optical fiber device through a first tail fiber (P1); a second channel of the waveform generator (1) is connected with an input end of a phase modulator (4), one output port of the phase modulator (4) is connected with a 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 a delay line (5), and the other end of the delay line (5) is connected with the polarization-maintaining optical fiber device through a fourth tail fiber (P4); the optical power meter (3) is connected with the polarization-maintaining optical fiber device through a third tail fiber (P3).
2. A polarization dependent loss measuring device according to claim 1, wherein the optical pulse emitted from the laser (2) enters from the first pigtail (P1) of the polarization maintaining fiber device, and is split into two polarized lights after passing through the polarization maintaining fiber device, wherein the path of one polarized light is: second pigtail (P2) → phase modulator (4) → delay line (5) → fourth pigtail (P4); the path of the other polarized light is: fourth pigtail (P4) → delay line (5) → phase modulator (4) → second pigtail (P2); the paths of the two beams of polarized light form a loop with equal path and opposite direction, and the loops return to the polarization-maintaining optical fiber device for superposition to form a Sagnac loop; and adjusting the position of the delay line (5) to enable the phase modulator (4) to be placed at the asymmetric position of the Sagnac ring, wherein the Sagnac ring is divided into two sections of optical fibers by the phase modulator (4), and the time difference of the optical pulse passing through the two sections of optical fibers is larger than the rising time and the falling time of the voltage signal loaded by the waveform generator (1).
3. A polarization dependent loss measurement apparatus according to claim 1 or 2, wherein the polarization maintaining fiber device is a Polarization Beam Splitter (PBS) or a circular polarization beam splitter (PCIR).
4. A polarization dependent loss measuring device according to claim 1, characterized in that if the laser (2) is connected at the first pigtail (P1), then the optical power meter (3) is connected at the third pigtail (P3); if an optical power meter (3) is connected at the first pigtail (P1), then a laser (2) is connected at the third pigtail (P3).
5. A polarization dependent loss measuring device according to claim 1, wherein the first pigtail (P1), the second pigtail (P2), the third pigtail (P3) and the fourth pigtail (P4) are polarization maintaining fibers.
6. The polarization-maintaining fiber device polarization dependent loss measuring device according to claim 1, wherein the phase modulator (4) is a polarization-maintaining phase modulator.
7. A measuring method using the measuring apparatus according to any one of claims 1 to 6, characterized by comprising the steps of:
step 1): building a measuring device;
step 2): opening a first channel and a second channel of a waveform generator (1), respectively setting parameters of the two channels, and confirming that the waveforms of the two channels are normal;
step 3): adjusting the phase value of the voltage output by the second channel by rotating a knob of the waveform generator (1), thereby changing the polarization state of light, adjusting the polarization state from 0 to 360 degrees, observing the reading of the optical power meter (3), and recording the maximum value and the minimum value of the reading;
and step 4): the polarization dependent loss PDL is calculated.
8. The measurement method according to claim 7, wherein the parameters in step 2) include: waveform, frequency, time delay, high and low levels, duty cycle.
9. The measuring method according to claim 7, wherein the adjustment step value from 0 ° up to 360 ° in step 3) is set to 1 °.
10. The measurement method according to claim 7, wherein the calculation formula for calculating the PDL according to step 4) is: PDL, max (Power P3) -min (Power P3), max (Power P3), min (Power P3) represent the maximum and minimum readings on the optical Power meter (3), respectively.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117969043A (en) * | 2024-03-28 | 2024-05-03 | 德州振飞光纤技术有限公司 | Detection device for polarization axis of polarization maintaining optical fiber |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117969043A (en) * | 2024-03-28 | 2024-05-03 | 德州振飞光纤技术有限公司 | Detection device for polarization axis of polarization maintaining optical fiber |
| CN117969043B (en) * | 2024-03-28 | 2024-05-31 | 德州振飞光纤技术有限公司 | Detection device for polarization axis of polarization maintaining optical fiber |
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